CROSS REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of priority from U.S. Provisional Application No. 62/565,438, filed September 29, 2017, the contents of which are incorporated herein by reference in its entirety.

INCORPORATION BY REFERENCE OF SEQUENCE LISTING

[0002] The Sequence Listing in the ASCII text file, named as

35342_10353US01_SequenceListing.txt of 50 KB, created on September 25, 2018 and submitted to the United States Patent and Trademark Office via EFS-Web, is incorporated herein by reference.

BACKGROUND

[0003] During preclinical drug development stage, candidate agents are typically studied based on their efficacy, toxicity, and other pharmacokinetic and pharmacodynamics properties. Candidate agents, such as antibodies, typically target a human antigen—as the end goal of investigation is to develop a human therapy. The ability to sequester the complement pathway provides a significant advantage to candidate therapeutic agents. The complement pathway is part of the innate immune response and assists humoral immune responses in the recruitment of marcrophage and phagocytes to the antigenic site.

Activation of the complement pathway results in cytokine release and the opsonization of the antibody-bound antigen by phagocytes. During development of therapeutic agents that are aimed at activation of complement pathway and innate immune response in order to combat human disease, a model non-human animal system that would allow studies into the mechanisms of action and/or therapeutic potential of the agent is invaluable; but such system is lacking.

SUMMARY

[0004] Disclosed herein are chimeric mammalian Clq polypeptides (such as, for example chimeric mammalian Clqa, Clqb and/or Clqc polypeptides), nucleic acid molecules encoding chimeric mammalian Clq polypeptides, and non-human animals (e.g., mammals such as rodents) comprising said nucleic acid molecules and expressing chimeric Clq polypeptides. [0005] In one aspect, disclosed herein is a genetically modified non-human animal comprising in its genome a nucleic acid encoding a chimeric Clq polypeptide (e.g., a chimeric Clqa polypeptide, a chimeric Clqb polypeptide, or a chimeric Clqc polypeptide), wherein the nucleic acid comprises a non-human nucleic acid sequence and a human nucleic acid sequence.

[0006] In some embodiments, the genetically modified non-human animal comprises in its genome more man one nucleic acid encoding a chimeric Clq polypeptide; for example, the non-human animal comprises in its genome a combination (e.g., two or all three) of a nucleic acid encoding a chimeric Clqa polypeptide, a nucleic acid encoding a chimeric Clqb polypeptide, and a nucleic acid encoding a chimeric Clqc polypeptide.

[0007] In some embodiments, the non-human animal is a mammal. In some embodiments, the non-human animal is a rodent, such as a rat or a mouse.

[0008] In some embodiments, the chimeric Clq polypeptide comprises a globular head domain that is substantially human (i.e., substantially identical to the globular head domain of a human Clq polypeptide), and an N-terminal stalk-stem region that is substantially non- human (i.e., substantially identical to the N-terminal stalk-stem region of a non-human Clq polypeptide such as an endogenous Clq polypeptide).

[0009] In some embodiments, the non-human animal comprises a nucleic acid encoding a chimeric Clq polypeptide that is a chimeric Clqa polypeptide. In some embodiments, the chimeric C 1 qa polypeptide comprises a globular head domain that is substantially identical to the globular head domain of a human Clqa polypeptide, and an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a non-human Clqa polypeptide such as an endogenous Clqa polypeptide. In some embodiments, the globular head domain of a human Clqa polypeptide comprises amino acids 108-245 of SEQ ID NO: 4.

[0010] In some embodiments, the non-human animal is a mouse which comprises a nucleic acid encoding a chimeric Clqa polypeptide that comprises a globular head domain that is substantially identical to the globular head domain of a human Clqa polypeptide, and an N- terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a mouse C 1 qa polypeptide such as an endogenous mouse C 1 qa polypeptide. In certain embodiments, the N-terminal stalk-stem region of the endogenous mouse Clqa polypeptide comprises amino acids 23-107 of SEQ ID NO: 1. In specific embodiments, the chimeric Clqa polypeptide comprises amino acids 23-245 of SEQ ID NO: 10 (mouse/human). In specific embodiments, the chimeric Clqa polypeptide comprises the amino acid sequence of SEQ ID NO: 10 (mouse/human).

[0011] In some embodiments, the genetically modified non-human animal is a rat, which comprises a nucleic acid encoding a chimeric Clqa polypeptide that comprises a globular head domain that is substantially identical to the globular head domain of a human Clqa polypeptide, and an N-terminal stalk-stem region that is substantially identical to the N- terminal stalk-stem region of a rat Clqa polypeptide such as an endogenous rat Clqa polypeptide. In some embodiments, the N-terminal stalk-stem region of the endogenous rat Clqa polypeptide comprises amino acids 23-107 of SEQ ID NO: 7. In specific

embodiments, the chimeric Clqa polypeptide comprises amino acids 23-245 of SEQ ID NO: 55 (rat/human). In specific embodiments, the chimeric Clqa polypeptide comprises the amino acid sequence of SEQ ID NO: 55 (rat/human).

[0012] In some embodiments, the non-human animal comprises a nucleic acid encoding a chimeric Clq polypeptide that is a chimeric Clqb polypeptide. In some embodiments, the chimeric Clqb polypeptide comprises a globular head domain that is substantially identical to the globular head domain of a human Clqb polypeptide, and an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a non-human Clqb polypeptide such as an endogenous Clqb polypeptide. In some embodiments, the globular head domain of a human Clqb polypeptide comprises amino acids 115-251 of SEQ ID NO: 5.

[0013] In some embodiments, the non-human animal is a mouse, which comprises a nucleic acid encoding a chimeric Clqb polypeptide that comprises an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a mouse Clqb polypeptide such as an endogenous mouse Clqb polypeptide. In some embodiments, the N- terminal stalk-stem region of the endogenous mouse Clqb polypeptide comprises amino acids 26-114 of SEQ ID NO: 2. In specific embodiments, the chimeric C lqb polypeptide comprises amino acids 26-251 of SEQ ID NO: 11 (mouse/human). In specific

embodiments, the chimeric Clqb polypeptide comprises the amino acid sequence of SEQ ID NO: 11 (mouse/human).

[0014] In some embodiments, the non-human animal is a rat, which comprises a nucleic acid encoding a chimeric Clqb polypeptide that comprises an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a rat Clqb polypeptide such as an endogenous rat Clqb polypeptide. In some embodiments, the N-terminal stalk- stem region of the endogenous rat Clqb polypeptide comprises amino acids 26-114 of SEQ ID NO: 8. In specific embodiments, the chimeric Clqb polypeptide comprises amino acids 26-251 of SEQ ID NO: 56 (rat/human). In specific embodiments, the chimeric Clqb polypeptide comprises the amino acid sequence of SEQ ID NO: 56 (rat/human).

[0015] In some embodiments, the non-human animal comprises a nucleic acid encoding a chimeric CI q polypeptide that is a chimeric Clqc polypeptide. In some embodiments, the chimeric Clqc polypeptide comprises a globular head domain that is substantially identical to the globular head domain of a human Clqc polypeptide, and an N -terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a non-human Clqc polypeptide such as an endogenous Clqc polypeptide. In some embodiments, the globular head domain of a human C lqc polypeptide comprises 113-245 of SEQ ID NO: 6.

[0016] In some embodiments, the non-human animal is a mouse which comprises a nucleic acid encoding a chimeric Clqc polypeptide that comprises a globular head domain that is substantially identical to the globular head domain of a human Clqc polypeptide, and an N- terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a mouse Clqc polypeptide such as an endogenous mouse Clqc polypeptide. In certain embodiments, the N-terminal stalk-stem region of the endogenous mouse Clqc polypeptide comprises amino acids 30-113 of SEQ ID NO: 3. In specific embodiments, the chimeric Clqc polypeptide comprises amino acids 30-246 of SEQ ID NO: 12 (mouse/human). In specific embodiments, the chimeric Clqc polypeptide comprises the amino acid sequence of SEQ ID NO: 12 (mouse/human).

[0017] In some embodiments, the genetically modified non-human animal is a rat, which comprises a nucleic acid encoding a chimeric Clqc polypeptide that comprises a globular head domain that is substantially identical to the globular head domain of a human Clqc polypeptide, and an N-terminal stalk-stem region that is substantially identical to the N- terminal stalk-stem region of a rat C lqc polypeptide such as an endogenous rat Clqc polypeptide. In some embodiments, the N-terminal stalk-stem region of the endogenous rat Clqc polypeptide comprises amino acids 32-115 of SEQ ID NO: 9. In specific

embodiments, the chimeric Clqc polypeptide comprises amino acids 32-248 of SEQ ID NO: 57 (rat/human). In specific embodiments, the chimeric Clqc polypeptide comprises the amino acid sequence of SEQ ID NO: 57 (rat/human).

[0018] In some embodiments, a chimeric Clq polypeptide is translated in the non-human animal to contain anon-human Clq signal peptide such as an endogenous non-human Clq signal peptide. In other words, the nucleic acid molecule encoding a chimeric Clq polypeptide also comprises a coding sequence for a non-human Clq signal peptide such as an endogenous Clq signal peptide. For example, a nucleic acid molecule encoding a chimeric Clqa polypeptide also comprises a coding sequence for a non-human Clqa signal peptide such as an endogenous Clqa signal peptide; a nucleic acid molecule encoding a chimeric Clqb polypeptide also comprises a coding sequence for a non-human Clqb signal peptide such as an endogenous Clqb signal peptide; and a nucleic acid molecule encoding a chimeric Clqc polypeptide also comprises a coding sequence for a non-human Clqc signal peptide such as an endogenous Clqc signal peptide. Examples of mouse and rat Clq signal peptides are disclosed herein (see, e.g., in Figures 3A-3C).

[0019] In some embodiments, the nucleic acid encoding a chimeric Clq polypeptide is at a locus other than an endogenous non-human Clq locus. In other embodiments, the nucleic acid encoding a chimeric Clq polypeptide is at an endogenous non-human Clq locus. For example, a nucleic acid encoding a chimeric Clqa polypeptide is at an endogenous non- human Clqa locus; a nucleic acid encoding a chimeric Clqb polypeptide is at an endogenous non-human Clqb locus; and/or a nucleic acid encoding a chimeric Clqc polypeptide is at an endogenous non-human Clqc locus.

[0020] In embodiments where the nucleic acid encoding a chimeric Clq polypeptide is at an endogenous non-human Clq locus, in some such embodiments, an endogenous genomic sequence at the endogenous non-human Clq locus has been replaced by a human nucleic acid sequence. In some embodiments, the human nucleic acid sequence, such as a genomic fragment of a human Clq gene, encodes substantially the globular head domain of a human Clq polypeptide. In some embodiments, the human nucleic acid sequence also includes the 3' UTR of the human Clq gene (including the polyadenylation signal and the

polyadenylation site of the human Clq gene).

[0021] In some embodiments, a genetically modified non-human animal comprises a nucleic acid encoding a chimeric Clqa polypeptide, wherein the nucleic acid comprises human and non-human nucleic acid sequences, and wherein the human nucleic acid sequence encodes substantially the globular head domain of a human Clqa polypeptide. In some embodiments, the globular head domain of the human Clqa polypeptide comprises amino acids 108-245 of SEQ ID NO: 4. In some embodiments, the human nucleic acid sequence encodes amino acids 112-245 of SEQ ID NO: 4. [0022] In some embodiments, a genetically modified non-human animal comprises a nucleic acid encoding a chimeric Clqb polypeptide, wherein the nucleic acid comprises human and non-human nucleic acid sequences, and wherein the human nucleic acid sequence encodes substantially the globular head domain of a human Clqb polypeptide. In some embodiments, the globular head domain of the human Clqb polypeptide comprises amino acids 115-251 of SEQ ID NO: 5. In some embodiments, the human nucleic acid sequence encodes amino acids 118-251 of SEQ ID NO: 5.

[0023] In some embodiments, a genetically modified non-human animal comprises a nucleic acid encoding a chimeric Clqc polypeptide, wherein the nucleic acid comprises human and non-human nucleic acid sequences, and wherein the human nucleic acid sequence encodes substantially the globular head domain of a human Clqc polypeptide. In some embodiments, the globular head domain of the human Clqc polypeptide comprises amino acids 113-245 of SEQ ID NO: 6. In some embodiments, the human nucleic acid sequence encodes amino acids 114-245 of SEQ ID NO: 6.

[0024] In embodiments of a genetically modified non-human animal comprising a nucleic acid encoding a chimeric Clq polypeptide, wherein the nucleic acid comprises human and non-human nucleic acid sequences, the non-human nucleic acid sequences encode substantially the N -terminal stalk-stem region of a non-human Clq polypeptide such as an endogenous non-human Clq polypeptide. In embodiments where an endogenous genomic sequence at the endogenous non-human Clq locus has been replaced by a human nucleic acid sequence, in some such embodiments, the endogenous genomic sequence remaining at the Clq locus encodes substantially the N-terminal stalk-stem region of the endogenous Clq polypeptide.

[0025] In some embodiments, the non-human animal is a mouse, and the N-terminal stalk- stem region of an endogenous Clq polypeptide comprises amino acids 23-107 of SEQ ID NO: 1 (for Clqa), amino acids 26-114 of SEQ ID NO: 2 (for Clqb), or amino acids 30-113 of SEQ ID NO: 3 (for C 1 qc). In some embodiments, the mouse comprises a nucleic acid encoding a chimeric Clqa polypeptide, wherein the nucleic acid comprises a mouse nucleic acid sequence and a human nucleic acid sequence, and wherein the mouse nucleic acid sequence encodes amino acids 23-111 of SEQ ID NO: 1. In some embodiments, the mouse comprises a nucleic acid encoding a chimeric Clqb polypeptide, wherein the nucleic acid comprises a mouse nucleic acid sequence and a human nucleic acid sequence, and wherein the mouse nucleic acid sequence encodes amino acids 26-117 of SEQ ID NO: 2. In some embodiments, the mouse comprises a nucleic acid encoding a chimeric Clqc polypeptide, wherein the nucleic acid comprises a mouse nucleic acid sequence and a human nucleic acid sequence, wherein the mouse nucleic acid sequence encodes amino acids 30-114 of SEQ ID NO: 3.

[0026] In some embodiments, the non-human animal is a rat, and the N-terminal stalk-stem region of the endogenous CI q polypeptides comprises amino acids 23-107 of SEQ ID NO: 7 (for Clqa), amino acids 26-114 of SEQ ID NO: 8 (for Clqb), or amino acids 32-115 of SEQ ID NO: 9 (for Clqc). In some embodiments, the rat comprises a nucleic acid encoding a chimeric Clqa polypeptide, wherein the nucleic acid comprises a rat nucleic acid sequence and a human nucleic acid sequence, wherein the rat nucleic acid sequence encodes amino acids 23-111 of SEQ ID NO: 7. In some embodiments, the rat comprises a nucleic acid encoding a chimeric Clqb polypeptide, wherein the nucleic acid comprises a rat nucleic acid sequence and a human nucleic acid sequence, wherein the rat nucleic acid sequence encodes amino acids 26-117 of SEQ ID NO: 8. In some embodiments, the rat comprises a nucleic acid encoding a chimeric Clqc polypeptide, wherein the nucleic acid comprises a rat nucleic acid sequence and a human nucleic acid sequence, wherein the rat nucleic acid sequence encodes amino acids 32-116 of SEQ ID NO: 9.

[0027] In a specific embodiment, the genetically modified non-human animal is a rat and comprises in its genome: (i) at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric rat/human Clqa polypeptide wherein the nucleic acid sequence comprises, 5'-3' and in operable linkage a first nucleotide sequence encoding amino acids 1 -111 of a rat Clqa polypeptide of SEQ ID NO: 7 and a second nucleotide sequence encoding amino acids 1 12-245 of a human C 1 qa polypeptide of SEQ ID NO: 4; (ii) at the endogenous C 1 qb locus a nucleic acid sequence encoding a chimeric rat/human Clqb polypeptide wherein the nucleic acid sequence comprises, 5' -3' and in operable linkage a third nucleotide sequence encoding amino acids 1-117 of a rat Clqb polypeptide of SEQ ID NO: 8 and a fourth nucleotide sequence encoding amino acids 118-251 of a human Clqb polypeptide of SEQ ID NO: 5; and (iii) at the endogenous Clqc locus a nucleic acid sequence encoding a chimeric rat/human Clqc polypeptide wherein the nucleic acid sequence comprises, 5 '-3' and in operable linkage a fifth nucleotide sequence encoding amino acids 1-116 of a rat Clqc polypeptide of SEQ ID NO: 9 and a sixth nucleotide sequence encoding amino acids 114-245 of a human Clqc polypeptide of SEQ ID NO: 6. In a particular embodiment, the genetically modified non-human animal is a rat which comprises in its genome: at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric rat/human Clqa polypeptide which comprises the amino acid sequence of SEQ ID NO: SS; at the endogenous Clqb locus a nucleic acid sequence encoding a chimeric rat/human Clqb polypeptide which comprises the amino acid sequence of SEQ ID NO: 56; and at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric rat/human Clqc polypeptide which comprises the amino acid sequence of SEQ ID NO: 57.

[0028] In another specific embodiment, the genetically modified non-human animal is a mouse and comprises in its genome: (i) at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric mouse/human Clqa polypeptide wherein the nucleic acid sequence comprises, 5 '-3' and in operable linkage a first nucleotide sequence encoding amino acids 1-111 of a mouse Clqa polypeptide of SEQ ID NO: 1 and a second nucleotide sequence encoding amino acids 112-245 of a human Clqa polypeptide of SEQ ID NO: 4; (ii) at the endogenous Clqb locus a nucleic acid sequence encoding a chimeric

mouse/human Clqb polypeptide wherein the nucleic acid sequence comprises, 5 '-3' and in operable linkage a third nucleotide sequence encoding amino acids 1-117 of a mouse Clqb polypeptide of SEQ ID NO: 2 and a fourth nucleotide sequence encoding amino acids 118- 251 of a human Clqb polypeptide of SEQ ID NO: 5; and (iii) at the endogenous Clqc locus a nucleic acid sequence encoding a chimeric mouse/human Clqc polypeptide wherein the nucleic acid sequence comprises, 5 '-3' and in operable linkage a fifth nucleotide sequence encoding amino acids 1-114 of a mouse Clqc polypeptide of SEQ ID NO: 3 and a sixth nucleotide sequence encoding amino acids 114-245 of a human Clqc polypeptide of SEQ ID NO: 6. In a particular embodiment, the genetically modified non-human animal is a mouse which omprises in its genome: at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric mouse/human Clqa polypeptide which comprises the amino acid sequence of SEQ ID NO: 10; at the endogenous Clqb locus a nucleic acid sequence encoding a chimeric mouse/human Clqb polypeptide which comprises the amino acid sequence of SEQ ID NO: 11; and at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric mouse/human Clqc polypeptide which comprises the amino acid sequence of SEQ ID NO: 12.

[0029] In some embodiments disclosed herein, the genetically modified non-human animal does not express a functional endogenous Clqa, Clqb, and/or Clqc polypeptides).

[0030] In another aspect, provided herein are methods of making a genetically modified non-human animal (such as, for example anon-human mammal such as a rodent including but not limited to a mouse or rat) comprising in its genome a chimeric Clq locus that includes a gene encoding a chimeric non-human/human Clqa polypeptide, a gene encoding a chimeric non-human/human Clqb polypeptide, and/or a gene encoding a chimeric non- human/human C1qc polypeptide, the method comprising introducing into the non-human animal genome a nucleic acid sequence(s) comprising a) a gene encoding a chimeric non- human/human Clqa polypeptide, b) a gene encoding a chimeric non-human/human Clqb polypeptide, and/or c) a gene encoding a chimeric non-human/human Clqc polypeptide. In some embodiments, the nucleic acid comprising a gene encoding a chimeric Clq polypeptide is at a location in the genome outside the endogenous locus. Thus, in some embodiments, the endogenous Clq gene(s) or a portion thereof may be silenced and/or deleted, such that the non-human animal does not express a functional endogenous Clq polypeptide (e.g., does not express afunctional endogenous Clqa, Clqb, and/or Clqc polypeptide). In other embodiments, the nucleic acid comprising a gene encoding a chimeric polypeptide is at the endogenous non-human Clq locus; and in one embodiment, the nucleic acid comprising a gene encoding a chimeric Clq polypeptide replaces the endogenous non-human Clq gene at the endogenous Clq locus.

[0031] Thus, provided herein are methods of making the genetically modified non-human animal described herein, wherein the nucleic acid sequence encoding a chimeric Clq polypeptide is introduced at the endogenous non-human mammal Clq locus. In a specific aspect, disclosed is a method of making a genetically modified non-human animal, wherein the nucleic acid sequence encoding a chimeric Clq polypeptide replaces a nucleotide sequence encoding an endogenous non-human mammal Clq polypeptide.

[0032] In some embodiments, the method of making a genetically modified non-human animal described herein, e.g., a genetically modified rat or mouse, comprises generating a targeting vector (e.g., a large targeting vector (LTVEC)) comprising nucleic acid sequences) encoding a chimeric Clqa, Clqb, and/or Clqc polypeptides), introducing said targeting vector into ES cells, and generating said non-human animal from said ES cell.

[0033] In another aspect, disclosed herein is a chimeric Clq polypeptide comprising a globular head domain that is substantially human and an N-terminal stalk-stem region that is substantially non-human, wherein the chimeric Clq polypeptide is selected from the group consisting of a chimeric Clqa polypeptide, a chimeric Clqb polypeptide, and a chimeric Clqc polypeptide. In some embodiments, such a chimeric Clq polypeptide is made from the genetically modified non-human animal disclosed herein. In other embodiments, a chimeric Clq polypeptide is made from an appropriate host cell.

[0034] In still another aspect, disclosed herein is a chimeric Clq protein comprising one or more of the chimeric Clq polypeptides disclosed herein. In some embodiments, the chimeric Clq protein comprises at least one chimeric Clqa, one chimeric Clqb, and one chimeric Clqc polypeptide. In some embodiments, the chimeric Clq protein comprises 6 each of a chimeric Clqa polypeptide, a chimeric Clqb polypeptide, and a chimeric Clqc polypeptide.

[0035] In another aspect, disclosed herein is an isolated nucleic acid encoding a chimeric Clq polypeptide (a C 1 qa polypeptide, a C 1 qb polypeptide, or a C 1 qc polypeptide), and comprising a non-human mammal nucleic acid sequence and a human nucleic acid sequence. In some embodiments, the human nucleic acid sequence encodes substantially the globular head domain of a human Clq polypeptide and the non-human nucleic acid sequence encodes substantially the N-terminal stalk-stem region of a cognate non-human Clq polypeptide. In some embodiments, the isolated nucleic acid encodes a chimeric Clq protein, and comprises one or more of a first, second or third nucleotide sequences, wherein the first nucleotide sequence encodes a chimeric Clqa polypeptide, the second nucleotide sequence encodes a chimeric Clqb polypeptide, and the third nucleotide sequence encodes a chimeric Clqc polypeptide.

[0036] In still another aspect, provided herein is a cell comprising an isolated nucleic acid disclosed herein. In some embodiments, the cell is an embryonic stem (ES) cell, e.g., a rodent (such as mouse or rat) ES cell.

[0037] In a further aspect, provided herein is a rodent model for testing a CI q-based bispecific antigen-binding protein, wherein the antigen-binding protein binds both human Clq and an antigen of interest, comprising a genetically modified rodent disclosed herein and further comprising the antigen of interest or a cell expressing the antigen of interest.

[0038] In another aspect, disclosed herein are methods of screening for a drug candidate that targets an antigen of interest comprising introducing the antigen of interest into the genetically modified non-human animal, e.g., the rodent, e.g., the rat or the mouse, provided herein, contacting said animal with a drug candidate of interest, wherein the drug candidate is directed against the human Clq and the antigen of interest, and assaying to determine whether the drug candidate is efficacious in preventing, reducing, or eliminating cells characterized by the presence or expression of the antigen of interest. In one embodiment, the step of introducing comprises expressing in the animal the antigen of interest (such as, for example, genetically modifying the rodent that expresses the antigen of interest) or introducing into said animal a cell or virus expressing the antigen of interest. In one specific aspect, the cell can be a tumor cell or bacterial cell. In a further aspect the antigen of interest can be a tumor associated antigen or a bacterial antigen. In another aspect, the cell can be a bacterial cell.

[0039] In another aspect, provided herein is a method of screening among therapeutic drug candidates that target an antigen of interest, the method comprising mixing a cell or virus expressing the antigen of interest with (i) a drug candidate of interest, wherein the drug candidate is directed against the human Clq and the antigen of interest, and (ii) a blood sample (e.g., a whole blood sample) of a genetically modified rodent described herein, and (b) assaying to determine whether the drug candidate is efficacious in reducing or eliminating the cell or virus characterized by the presence or expression of the antigen of interest. The determination can be made based on measuring, e.g., percentage survival of the cell or virus where a drug candidate is used as compared to a control drug or no drug at all. The antigen of interest may be a tumor-associated antigen or an infectious disease associated antigen, e.g., a bacterial or a viral antigen. In some embodiments, the antigen of interest is a bacterial antigen such as a Staphylococcus antigen. In some embodiments, the cell is a bacterial cell such as a Staphylococcus cell.

[0040] In some embodiments, provided is a method of screening for a drug candidate, wherein the step of introducing comprises infecting the animal (e.g., the rat or the mouse) with the antigen of interest (for example, a viral antigen or a bacterial antigen such as a Staphylococcus antigen). Thus, in one aspect, the step of introducing comprises infecting the animal with a virus or bacteria.

[0041] In some embodiments, the genetically modified non-human animal provided herein (e.g., the rodent, e.g., the rat or the mouse) is an immunocompetent animal (e.g., immunocompetent rat or mouse).

[0042] In another aspect, disclosed herein are methods of assessing whether an antibody comprising a human Fc region can activate classical complement pathway by utilizing a genetically engineered non-human animal (e.g., a rodent such as a mouse or rat) expressing a humanized Clq protein disclosed herein. In some embodiments, the method comprises (a) providing a cell expressing an antigen of interest on the cell surface, a candidate antibody comprising a human Fc region and directed to the antigen of interest, and a serum sample from a genetically engineered non-human animal expressing a humanized Clq protein; (b) mixing the cell with the candidate antibody to allow the antibody to bind to the antigen of interest expressed on the cell surface; (c) adding the serum sample to the cell-antibody mixture to permit binding of the humanized Clq proteins in the serum sample to antibodies bound to the antigen of interest on the cell; and (d) measuring cytotoxicity of the cell.

BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate several embodiments and together with the description illustrate the disclosed compositions and methods.

[0044] Unless specifically indicated (e.g., loxP, etc.), all human exon sequences are in empty boxes and all human intron sequences are in double lines. All mouse or rat sequences are either in filled boxes (exons) or single lines (introns).

[0045] Figure 1 A is a schematic representation (not to scale) of the exemplary method of deleting of the mouse Clq locus comprising all three mouse Clq genes (mouse genes are indicated with "m" before the gene label). Exons of the three Clq genes are labeled below the diagram (e.g., El, E2, and E3). Mouse BAC stands for bacterial artificial chromosome; BHR stands for bacterial homologous recombination; EP stands for electroporation.

HET=heterozygous; CM=chloramphenicol; lox = loxP site; pgk-Neo = neomycin selection cassette.

[0046] Figure IB shows a schematic representation (not to scale) of the creation of a humanized mouse Clq targeting vector, with chimeric human/mouse genes inserted by digestion/ligation and/or bacterial homologous recombination (BHR) into the mouse BAC genes (mouse genes are indicated with "m" before the gene label). Exons of the three Clq genes are labeled below the diagram (e.g., El, E2, and E3). Several restriction enzyme locations are indicated. CM=chloramphenicol; lox = loxP site; Ub-Hyg = hygromycin selection cassette; p=polyA tail; Spec=spectinomycin.

[0047] Figure 1C shows a schematic representation (not to scale) of the electroporation (EP) of a large targeting vector containing all three mouse/human chimeric Clq genes into mouse Clq KO HET ES cells. Exons of the three Clq genes are labeled below the diagram (e.g., El, E2, and E3). Lox = loxP site; Ub-Hyg = hygromycin selection cassette; pgk-Neo = neomycin selection cassette; p=polyA sequence. Sequence junctions between mouse, human, or cassette sequences are indicated with a line and a SEQ ID NO for that respective sequence below each junction.

[0048] Figure 2 A shows a schematic representation (not to scale) of the exemplary method of deleting of the rat Clq locus comprising all three rat Clq genes (rat genes are indicated with "r" before the gene label). Exons of the three Clq genes are labeled below the diagram (e.g., El, E2, and E3). Rat Clq BAC stands for rat bacterial artificial chromosome; BHR stands for bacterial homologous recombination; EP stands for electroporation.

HET=heterozygous; CM=chloramphenicol; loxP = loxP site; SDC-loxP-Hyg = self- deleting LoxP-Hygromycin selection cassette.

[0049] Figure 2B shows a schematic representation (not to scale) of the creation of a humanized rat Clq cassette, with chimeric human/rat genes inserted by digestion/Gibson assembly and/or CAS9/Gibson assembly into the rat BAC genes (rat genes are indicated with "r" before the gene label). Exons of the three Clq genes are labeled below the diagram (e.g., El, E2, and E3). Several restriction enzyme locations are indicated.

CM=chloramphenicol; SDC-loxp-puro= self-deleting loxp - puromycin cassette.

[0050] Figure 2C shows a schematic representation (not to scale) of the electroporation (EP) of a large targeting vector containing all three rat/human chimeric Clq genes into rat Clq KO HET ES cells. Exons of the three Clq genes are labeled below the diagram (e.g., El, E2, and E3). SDC-loxp-puro= self-deleting loxp - puromycin cassette; p=polyA sequence. Sequence junctions between rat, human, or cassette sequences are indicated with a line and a SEQ ID NO for that respective sequence below each junction.

[0051] Figure 3A shows Clqa amino acid alignments for rat (rClqa), human (hClQA), and mouse (mClqa) polypeptides, with similarities being outlined and mismatches shown in lower cases. Signal peptide sequences are boxed and labeled. The collagen triple helix repeat sequences are boxed and labeled. The Clqa globular head domain sequences are boxed with dashed lines, and the junction of mouse/human or rat/human sequence in the chimeric polypeptides is depicted with a dashed line and indicated with an arrow.

[0052] Figure 3B shows Clqb amino acid alignments for rat (rClqb), human (hClQB), and mouse (mClqb) polypeptides, with similarities being outlined and mismatches shown in lower cases. Signal peptide sequences are boxed and labeled. The collagen triple helix repeat sequences are boxed and labeled. The Clqb globular head domain sequences are boxed with dashed lines, and the junction of mouse/human or rat/human sequence in the chimeric polypeptides is depicted with a dashed line and indicated with an arrow. [0053] Figure 3C shows Clqc amino acid alignments for rat (rClqc), human (hClQC), and mouse (mClqc) polypeptides, with similarities being outlined and mismatches shown in lower cases. Signal peptide sequences are boxed and labeled. The collagen triple helix repeat sequences are boxed and labeled. The Clqc globular head domain sequences are boxed with dashed lines, and the junction of mouse/human or rat/human sequence in the chimeric polypeptides is depicted with a dashed line and indicated with an arrow.

[0054] Figure 4 top panel shows the presence chimeric Clq proteins in the serum of humanized Clq mice as detected by anti-human Clq antibody. Figure 4 bottom panel shows a hemolysis assay measuring complement activity comparing serum samples from wild-type littermate mouse (WT) and chimeric Clq mouse (1615 HO; HO=homozygous), and human serum

[0055] Figure 5 shows complement dependent cytotoxicity (CDC) activity mediated by a human anti-CD20 antibody at 2nM and a serum sample (normal human serum, humanized Clq mouse serum, or wild type mouse serum) on Raji cells.

[0056] Figure 6 shows results from a hemolysis assay measuring complement activity comparing serum samples from wild-type littermate rats ("WT"), humanized Clq rats ("Clq Humin" or 100015HO; HO=*omozygous), Clq knock-out rats ("Clq KO"), normal human serum ("NHS"), and Clq depleted human serum. Left panel: female rats; right panel, with the exception of Clq KO rats: male rats.

[0057] Figure 7 shows complement dependent cytotoxicity (CDC) activity mediated by a human anti-CD20 antibody at 20nM and a serum sample (normal human serum, humanized Clq rat serum, or wild type rat serum) on Raji cells.

DETAILED DESCRIPTION

[0058] Before the present compounds, compositions, articles, devices, and/or methods are disclosed and described, it is to be understood that they are not limited to specific synthetic methods or specific recombinant biotechnology methods unless otherwise specified, or to particular reagents unless otherwise specified, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

A. Definitions

[0059] As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "a pharmaceutical carrier" includes mixtures of two or more such carriers, and the like.

[0060] Ranges can be expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood mat the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.

[0061] In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings:

[0062] "Optional" or "optionally" means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0063] "Primers" are a subset of probes which are capable of supporting some type of enzymatic manipulation and which can hybridize with a target nucleic acid such that the enzymatic manipulation can occur. A primer can be made from any combination of nucleotides or nucleotide derivatives or analogs available in the art which do not interfere with the enzymatic manipulation.

[0064] "Probes" are molecules capable of interacting with a target nucleic acid, typically in a sequence specific manner, for example through hybridization. The hybridization of nucleic acids is well understood in the art and discussed herein. Typically a probe can be made from any combination of nucleotides or nucleotide derivatives or analogs available in the art.

[0065] "Functional" as used herein, e.g., in reference to a functional protein, includes a protein that retains at least one biological activity normally associated with the native protein. For example, in some embodiments, a replacement at an endogenous locus (e.g., replacement at endogenous non-human Clq loci) results in a locus that fails to express a functional endogenous protein.

[0066] The term "operably linked" includes a juxtaposition wherein the components so described are in a relationship permitting them to function in their intended manner. As such, a nucleic acid sequence encoding a protein may be operably linked to regulatory sequences (e.g., promoter, enhancer, silencer sequence, etc.) so as to retain proper transcriptional regulation. For example, by "operably linked" is meant a functional linkage between a nucleic acid expression control sequence (such as a promoter) and a second nucleic acid sequence, wherein the expression control sequence directs transcription of the nucleic acid corresponding to the second sequence. In addition, various portions of the humanized protein of the present disclosure may be operably linked or fused to retain proper folding, processing, targeting, expression, and other functional properties of the protein in the cell. Unless stated otherwise, various domains of the humanized protein of the present disclosure are operably linked to each other.

[0067] The term "humanized" as used in the phrases "humanized Clq allele," "humanized Clqa allele," "humanized Clqb allele," "humanized Clqc allele," "humanized Clq gene," "humanized Clqa gene," "humanized Clqb gene" or "humanized Clqc gene," includes, but is not limited to, embodiments wherein all or a portion of an endogenous non-human Clq, Clqa, Clqb, and/or Clqc gene or allele is replaced by a corresponding portion of the human Clq, Clqa, Clqb, and/or Clqc gene or allele. For example, in some embodiments, the term "humanized" refers to the complete replacement of the coding region (e.g., the exons) of the endogenous non-human Clq, Clqa, Clqb, and/or Clqc gene or allele with the

corresponding coding region of the human Clq, Clqa, Clqb, and/or Clqc gene or allele, while the endogenous non-coding region(s) (such as, but not limited to, the promoter, the 5' and/or 3' untranslated region(s), enhancer elements, etc.) of the non-human animal may not be replaced. In some embodiments, the humanized gene or allele are placed either randomly in the genome or targeted to a particular location within the genome. Thus, in some embodiments, the humanized gene or allele is placed in a location in the genome that is not the native location for corresponding endogenous gene or allele, i.e., it is placed at a location other than the endogenous locus. In other embodiments, the humanized gene or allele is placed at the endogenous locus; for example, the humanized gene or allele may replace the endogenous gene or allele at the endogenous locus. In some embodiments, the non-human animal is a rodent, such as a rat or mouse.

[0068] A "humanized protein" includes, but is not limited to, embodiments wherein all or a portion of the encoded endogenous non-human Clq, Clqa, Clqb, and/or Clqc protein is replaced by the corresponding portion of the human Clq, Clqa, CI qb, and/or Clqc protein. In some embodiments, a "humanized protein" can be encoded by a humanized Clq, Clqa, Clqb, and/or Clqc gene or allele but still is a fully human Clq, Clqa, Clqb, and/or Clqc protein (such as, but not limited to, the situation wherein all of the coding regions (e.g., the exons) of the endogenous non-human Clq, Clqa, Clqb, and/or Clqc gene or allele are replaced by the corresponding coding regions of the human Clq, Clqa, Clqb, and/or Clqc gene or allele but the endogenous non-coding region(s) (such as, but not limited to, the promoter, the 5' and/or 3' untranslated region(s), enhancer elements, etc.) of the non-human animal is not replaced). In some embodiments, the humanized protein is expressed from the humanized gene or allele that is not at its native location in the genome, e.g., it is not at the endogenous locus. In other embodiments, the humanized protein is expressed from the humanized gene or allele that is at the endogenous locus. In some embodiments, the humanized protein is expressed from the humanized gene or allele mat replaces the endogenous gene or allele at the endogenous locus. In some embodiments, the non-human animal is a rodent, such as a rat or mouse.

[0069] The present disclosure is directed to like-for-like humanization. For example, a nucleotide sequence of an endogenous non-human Clq gene is operably linked to a nucleotide sequence of a cognate human Clq gene to form a chimeric humanized gene. In some embodiments, a nucleotide sequence of an endogenous Clqa gene is operably linked to a nucleotide sequence of a human Clqa gene to form a humanized C 1 qa gene. In other embodiments, a nucleotide sequence of an endogenous Clqb gene is operably linked to a nucleotide sequence of a human Clqb gene to form a humanized Clqb gene. In still other embodiments, a nucleotide sequence of an endogenous Clqc gene is operably linked to a nucleotide sequence of a human Clqc gene to form a humanized Clqc gene.

[0070] The term "chimeric" as used herein includes a sequence, e.g., nucleic acid or polypeptide sequence, where a portion of the sequence is derived from one organism and a portion of the sequence is derived from a different organism. For example, a chimeric Clq polypeptide may comprise a sequence derived from a mouse or a rat, and another sequence derived from a human Clq protein. In one embodiment, a chimeric Clq polypeptide comprises a globular head domain or a fragment thereof of a human Clq polypeptide, and a stalk domain and a stem domain of a cognate mouse or rat Clq polypeptide.

[0071] The term "locus" as in "Clq locus" refers to the location of the genomic DNA comprising a Clq coding region. For example, a Clqa locus refers to the location of the genomic DNA comprising the Clqa coding region; a Clqb locus refers to the location of the genomic DNA comprising the Clqb coding region; and a Clqc locus refers to the location of the genomic DNA comprising the Clqc coding region. A reference to "a Clq locus" means any one of Clqa, Clqb or Clqc locus. Other sequences may be included in a Clq locus that have been introduced for the purposes of genetic manipulation, e.g., selection cassettes, restriction sites, etc.

[0072] Other definitions and meaning of various terms used throughout this specification and the claims are included throughout in the relevant sections.

[0073] Throughout mis application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application. The references disclosed are also individually and specifically incorporated by reference herein in their entireties for the material contained in them that is discussed in the sentence in which the reference is relied upon.

B. Compositions

[0074] Disclosed are the components to be used to prepare the disclosed compositions as well as the compositions themselves to be used within the methods disclosed herein. These and other materials are disclosed herein, and it is understood that when combinations, subsets, interactions, groups, etc. of these materials are disclosed, while specific reference to each various individual and collective combinations and permutations of these components may not be explicitly listed, each is specifically contemplated and described herein. For example, if a particular chimeric Clqa, Clqb, and/or Clqc nucleic acid or polypeptide is disclosed and discussed and a number of modifications that can be made to a number of molecules including the chimeric Clqa, Clqb, and/or Clqc nucleic acid or polypeptide are discussed, specifically contemplated is each and every combination and permutation of chimeric Clqa, Clqb, and/or Clqc nucleic acid or polypeptide and the modifications that are possible unless specifically indicated to the contrary. Thus, if a class of molecules A, B, and C are disclosed as well as a class of molecules D, E, and F and an example of a combination molecule, A-D is disclosed, then even if each is not individually recited each is individually and collectively contemplated meaning combinations, A-E, A-F, B-D, B-E, B-F, C-D, C-E, and C-F are considered disclosed. Likewise, any subset or combination of these is also disclosed. Thus, for example, the sub-group of A-E, B-F, and C-E would be considered disclosed. This concept applies to all aspects of this application including, but not limited to, steps in methods of making and using the disclosed compositions. Thus, if there are a variety of additional steps that can be performed it is understood that each of these additional steps can be performed with any specific embodiment or combination of embodiments of the disclosed methods. C. Polypeptides

[0075] The present disclosure provides novel chimeric mammalian Clq polypeptides, nucleic acids encoding said polypeptides, and genetically modified non-human mammals that comprise said nucleic acids and can express the chimeric Clq polypeptides.

[0076] As used herein, "Clq" (e.g., as in "Clq protein" or "Clq complex"), is one portion of the CI complex which, along with Clr and Cls, initiates activation of the complement pathway. Clq is the first component of the classical complement pathway, required for clearance of pathogens, apoptotic bodies and possibly tumor cells (Ghai R et al.,

Immunobiology. 2007;212(4-5):253-66; Lu JH et al., Cell Mol Immunol. 2008 Feb;5(l):9- 21). The complement pathway is a part of the innate immune system Activation of the complement pathway can result in direct lysis of antigen, recruitment of phagocytes and macrophages to the antigenic site, opsonization of the antigen by phagocytes, and cytokine secretion.

[0077] Human/mouse/rat Clq protein is composed of polypeptides encoded by three genes, Clqa, Clqc, and Clqb genes, which are arranged tandemly 5 '-3' in the order A-C-B (Petty F et al., Immunogenetics. 1996;43(6):370-6). These polypeptides are also referred to herein as a "Clq polypeptide", which can be a Clqa polypeptide, a Clqb polypeptide or a Clqc polypeptide. Each of the Clqa, Clqb and Clqc polypeptide chains has an N -terminus region that includes a stalk (or neck) domain containing a cysteine residue followed by a collagen-like domain (stem domain), and an C- terminus region (globular head domain). The N -terminal region is also referred to herein as "N-terminal stalk-stem region", and the C -terminal region is also referred to as the "globular head domain". Human Clq protein (approx. 410 kDa) resembles a bouqet-like structure assembled from six collagenous stems, each ending with a globular head. Each stem/globular head is made up of three polypeptide chains (ClqA, ClqB and ClqC) for a total of 18 polypeptides (six A-, six B-, and six C- chains making up one Clq molecule (Reid KB Biochem Soc Trans. 1983 Jan;ll(l):l-12)).

[0078] Clq is expressed by splenic macrophages and dendritic cells in both humans and rodents (Castellano G et al., Blood. 2004 May 15;103(10):3813-20). Clq is secreted and found in human circulation at approximately 100 ug/ml, and at similar levels in mice (Dillon SP et al., Biotechnol J. 2009 August ; 4(8): 1210-1214; Yonemasu K et al., Int Arch Allergy Appl Immunol. 1988;86(1):97-101). The protein belongs to a group of defense collagens which recognize pathogen-associated molecular patterns (PAMPs), where the C- terminus/globular head of Clq recognizes the CH3 domain of IgM; CH2 domain of IgG; beta-amyloid; poly-anions including DNA; C-reactive protein; serum amyloid P, as well as PAMPs associated with LPS, viruses, and prions (Dunkelberger JR, Song WC, Cell Res. 2010 Jan;20(l):34-50; Ghai R et al., Immunobiology. 2007;212(4-5):253-66). Clq spontaneously assembles with Cls-Clr-Clr-Cls tetramer to form CI macrocomplex. The CI macrocomplex is a pentamer of three proteins comprising one Clq complex, and two each of Clr and C1s, where Clr and Cls associate with the stalk-stem domains of Clq. Clr and Cls are regulated by serpin protease inhibitor family member CI inhibitor (C1INH) (Beinrohr L et al., Trends Mol Med. 2008 Dec;14(12):511-21). Clq also binds receptors including CD93, DC-SIGN and CR1/CD35 (Hosszu KK et al., Blood. 2012 Aug

9;120(6): 1228-36; Bohlson SS at al., Mol Immunol. 2007 Jan;44(l-3):33-43). By binding PAMPs, Clq opsonizes and facilitates pathogen clearance and can enhance phagocytosis of target particles sub-optimally opsonized with C3b/C4b or IgG, via CR1 or FcgR, respectively (Bobak DA et al., J Immunol. 1987 Feb 15;138(4): 1150-6). Thus, Clq activates the classical complement pathway, resulting in both formation of the membrane attack complex (target lysis) and also generation of activation fragments C3a and CSa (Bohlson SS at al., Mol Immunol. 2007 Jan;44(l-3):33-43). Lastly, Clq mediates clearance of immune complexes, as well as cells undergoing apoptosis and cells blebs by recognizing apoptotic cell-associated molecular patterns.

[0079] To activate the classical complement pathway, Clq binds to the pathogen surface or Fc domain of antibodies through its six globular heads, which results in activation of Clr and Cls serine proteases, leading to cleavage of downstream complement components and ultimately complement activation, deposition and cell lysis through the membrane attack complex (see Reid KB Biochem Soc Trans. 1983 Jan;ll(l):l-12)).

[0080] Exemplary sequences and GenBank Accession Numbers of human, mouse and rat Clqa, Clqb, and Clqc are presented in Tables 1, 2, and 8 below, and in FIG. 3 A (Clqa), FIG. 3B (Clqb), and FIG. 3C (Clqc).

[0081] As it is Clq that recognizes either the Fc domain of antibodies or antigen directly, it is Clq that is key to providing a humanized complement system. As the globular head domain of Clq (often abbreviated as gClq) is what recognizes the human antibody or the human pathogen, in certain embodiments provided herein, the globular head domain of Clq was engineered such mat it more readily recognizes these molecules. In certain

embodiments, the globular head domain of Clq is human while the remainder of the protein is non-human. In such embodiment, the non-human animals provided herein retain the portion of the protein that is known to interact with the Clr/Cls and the remainder of the complement system (e.g., the stem and stalk portion of the protein). Thus, in the embodiments provided herein, the non-human animal expressing Clq harboring a globular head domain that is substantially human and an N-terminal stalk-stem region that is substantially non-human is useful in assessing the requirement for complement system as an effector mechanism of action of a therapeutic molecule, e.g., an antibody. In embodiments provided, said non-human animal is also useful to study the effectiveness of the therapeutic treatment if the complement system is engaged by the antibody. In embodiments provided, said non-human animals are also useful as an in vivo model to test the efficacy of fully human therapeutic antibodies, e.g., bispecific antibodies, designed for infectious disease indications.

[0082] Thus, in one aspect, disclosed herein are chimeric mammalian Clq polypeptides (such as, for example chimeric mammalian Clqa, Clqb and/or Clqc polypeptides).

[0083] In some embodiments, the chimeric Clq polypeptide provided herein comprises a human C terminal region that is responsible for recognition of immunoglobulin Fc domain, or responsible for recognizing pathogen-associated molecular patterns (PAMPs).

[0084] In some embodiments, the chimeric Clq polypeptide provided herein comprises a human globular head domain or a fragment thereof.

[0085] In some embodiments, a chimeric Clq polypeptide provided herein comprises a globular head domain that is substantially human. By "a globular head domain that is substantially human", it is meant that the globular head domain in a chimeric (humanized) Clq polypeptide is substantially identical to the globular head domain of a human Clq polypeptide. By "substantially identical", it refers to, (i) in some embodiments, a globular head domain that is at least 90%, 95%, 98%, 99% or 100% identical in sequence to the globular head domain of a human Clq polypeptide; (ii) in other embodiments, a globular head domain that differs from the globular head domain of a human Clq polypeptide by not more man S, 4, 3, 2 or 1 amino acid(s); (iii) in still other embodiments, a globular head domain that differs from the globular head domain of a human Clq polypeptide only at the N- or C- terminal portion of the domain, e.g., by having the same length but with one or more (e.g., 1, 2, 3, 4, or 5, but not more than 5) amino acid substitutions (such as a conservative substitution) within the N- or C- terminal portion of the globular head domain (e.g., within the 5-10 amino acids at the N- or C- terminus of the globular head domain); and/or (iv) in other embodiments, a globular head domain that is shorter or longer than the globular head domain of a human Clq polypeptide by 1, 2, 3, 4, 5 but not more than S amino acids at either the N- or C- terminus of the domain. In some embodiments, a globular head domain substantially identical to the globular head domain of a human Clq polypeptide differs from the human globular head domain by not more than 1, 2, or 3 amino acids within the N-terminal portion (e.g., within the 5-10 amino acids from the N-terminus) of the domain; and in certain such embodiments, the difference comprises a substitution(s) of an amino acid in the human globular head domain with the amino acid at the

corresponding position from a cognate non-human (e.g., a mouse or rat) globular head domain. For example, disclosed herein in Figure 3 A is a chimeric C lqa polypeptide that has a globular head domain that is substantially human - the globular domain of this chimeric Clqa polypeptide differs from the globular head domain of a human C lqa of SEQ ID NO: 4 by only one amino acid at the third position from the N-terminus of the globular head domain ("K" in human, and "R" in the chimeric, mouse and rat Clqa polypeptides).

[0086] In some embodiments, the chimeric Clq polypeptide comprises an N terminal stalk- stem region that is responsible for recognizing non-human (e.g., endogenous rodent ) Cls and Clr and/or other non-human (e.g., endogenous rodent) components of the complement pathway.

[0087] In some embodiments, the chimeric Clq polypeptide comprises a non-human stalk- stem region. In some embodiments, the chimeric Clq polypeptide comprises a non-human stalk domain. In some embodiments, the chimeric Clq polypeptide comprises a non-human collagen triple helix domain. In some embodiments, the chimeric Clq polypeptide comprises a non-human N terminal region comprising non-human stem and non-human stalk domains.

[0088] In some embodiments, a chimeric Clq polypeptide provided herein comprises an N- terminal stalk-stem region that is substantially non-human. By "an N-terminal stalk-stem region that is substantially non-human", it is meant that the N-terminal stalk-stem region of a chimeric Clq polypeptide is substantially identical to the corresponding N-terminal stalk- stem region of a non-human (e.g., a rodent) Clq polypeptide. By "substantially identical", it is meant (i) in some embodiments, an N-terminal stalk-stem region that is at least 90%, 95%, 95%, 99% or 100% identical in sequence with the N-terminal stalk-stem region of a non-human Clq polypeptide; (ii) in other embodiments, an N-terminal stalk-stem region that differs from the N-terminal stalk-stem region of a non-human Clq polypeptide by not more than 5, 4, 3, 2 or 1 amino acid(s); (iii) in still other embodiments, an N-terminal stalk- stem region that differs from the N -terminal stalk-stem region of a non-human Clq polypeptide only at the C- terminus, e.g., by having the same length but with one or more amino acid substitutions of the 5-10 amino acids from the C- terminus of the stalk-stem region; and/or (iv) in other embodiments, an N-terminal stalk-stem region that is shorter or longer than the N-terminal stalk-stem region of a non-human Clq polypeptide by 1, 2, 3, 4, or 5 but not more than 5 amino acids at the N- or C-terminus of the region. In specific embodiments, the N-terminal stalk-stem region of a chimeric Clq polypeptide is identical to the N-terminal stalk-stem region of a non-human (e.g., rodent) Clq polypeptide.

[0089] In one embodiment, a human Clqa polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 4. In another embodiment, a human Clqa polypeptide comprises the amino acid sequence as set forth in GenBank Accession No.

NP 001334394.1. In one embodiment, a human Clqb polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 5. In another embodiment, a human Clqb polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP 000482.3. In one embodiment, a human Clqc polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 6. In another embodiment, a human Clqc polypeptide comprises the amino acid sequence as set forth in GenBank Accession No.

NP_001334548.1.

[0090] In one embodiment, a mouse C lqa polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 1. In another embodiment, a mouse Clqa polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP_031598.2. In one embodiment, a mouse Clqb polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 2. In another embodiment, a mouse Clqb polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP 033907.1. In one embodiment, a mouse Clqc polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 3. In another embodiment, a mouse Clqc polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP 031600.2.

[0091] In one embodiment, a rat Clqa polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 7. In another embodiment, a rat Clqa polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP_001008515.1. In one embodiment, a rat Clqb polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 8. In another embodiment, a rat Clqb polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP 062135.1. In one embodiment, a rat Clqc polypeptide comprises the amino acid sequence as set forth in SEQ ID NO: 9. In another embodiment, a rat Clqc polypeptide comprises the amino acid sequence as set forth in GenBank Accession No. NP OO 1008524.1.

[0092] Thus, in one aspect, the chimeric mammalian Clq polypeptide is a chimeric Clqa polypeptide.

[0093] In some embodiments, the chimeric Clqa polypeptide comprises a human globular head domain or a fragment thereof. In one embodiment, the polypeptide is a chimeric Clqa polypeptide comprising amino acids 122-222 of the human Clqa polypeptide as set forth in SEQ ID NO: 4 (for example, a chimeric mammalian C lqa polypeptide comprising amino acids 122-235 or 112-245 of the human Clqa polypeptide).

[0094] In some embodiments, the chimeric Clqa polypeptide comprises a globular head domain that is substantially human (i.e., a globular head domain substantially identical to the globular head domain of a human Clqa polypeptide). In one embodiment, a human Clqa polypeptide comprises the amino acid sequence of SEQ ID NO: 4, and amino acids 108-245 of SEQ ID NO: 4 constitute the globular head domain of the human Clqa polypeptide of SEQ ID NO: 4 (see Figure 3 A). Thus, in some embodiments, a chimeric Clqa polypeptide comprises a globular head domain that is substantially identical to the human Clqa globular head domain represented by amino acids 108-245 of SEQ ID NO: 4. In a specific embodiment, the globular head domain of a chimeric Clqa polypeptide is represented by amino acids 108-245 of SEQ ID NO: 10, such domain differing from the human Clqa globular head domain represented by amino acids 108-245 of SEQ ID NO: 4 in one amino acid (the third amino acid residue being "R" as in mouse and rat Clqa, instead of "K" in human Clqa). In another specific embodiment, a chimeric Clqa polypeptide comprises a globular head domain mat is identical to the human Clqa globular head domain represented by amino acids 108-245 of SEQ ID NO: 4.

[0095] In some embodiments, a chimeric Clqa polypeptide comprises non-human Clqa stalk and/or stem domains. Thus, in some embodiments, a chimeric mammalian Clqa polypeptide comprises a non-human sequence which is a mouse sequence comprising at least amino acids 33-102, 30-102, 25-105, 23-107 or 23-111 of the mouse Clqa polypeptide set forth in SEQ ID NO: 1. In other embodiments, the chimeric mammalian Clqa polypeptide comprises a non-human sequence which is a rat sequence comprising at least amino acids 33-102, 30-102, 25-105, 23-107 or 23-111 of the rat Clqa polypeptide set forth in SEQ ID NO: 7. [0096] In some embodiments, the chimeric Clqa polypeptide comprises an N -terminal stalk-stem region that is substantially non-human, i.e., an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a non-human Clqa polypeptide. In certain embodiments, the chimeric C lqa polypeptide comprises an N- terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a mouse Clqa polypeptide. In one embodiment, the mouse Clqa polypeptide comprises the amino acid sequence of SEQ ID NO: 1 (Figure 3 A), and amino acids 23-107 of SEQ ID NO: 1 constitute the N-terminal stalk-stem region of the mouse Clqa polypeptide of SEQ ID NO: 1 (Figure 3 A). Thus, in some embodiments, a chimeric Clqa polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the mouse Clqa N-terminal stalk-stem region represented by amino acids 23-107 of SEQ ID NO: 1. In a specific embodiment, the N-terminal stalk-stem region of a chimeric Clqa polypeptide is represented by amino acids 23-107 of SEQ ID NO: 1. In some embodiments, the chimeric Clqa polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a rat Clqa polypeptide. In one embodiment, the rat Clqa polypeptide comprises the amino acid sequence of SEQ ID NO: 7 (Figure 3 A), and amino acids 23-107 of SEQ ID NO: 7 constitute the N-terminal stalk-stem region of the rat Clqa polypeptide of SEQ ID NO: 7 (Figure 3A). Thus, in some embodiments, a chimeric Clqa polypeptide comprises an N-terminal stalk-stem region mat is substantially identical to the rat Clqa N-terminal stalk-stem region represented by amino acids 23-107 of SEQ ID NO: 7. In a specific embodiment, the N-terminal stalk-stem region of a chimeric Clqa polypeptide is represented by amino acids 23-107 of SEQ ID NO: 7.

[0097] In some embodiments, the chimeric Clqa polypeptide comprises a globular head domain mat is substantially human and an N-terminal stalk-stem region mat is substantially non-human. For example, disclosed herein is a chimeric mammalian Clqa polypeptide, wherein the chimeric mammalian Clqa polypeptide comprises at least amino acids 23-245 of the polypeptide set forth in SEQ ID NO: 10 (mouse/human) or at least amino acids 23- 245 of the polypeptide set forth in SEQ ID NO:55 (rat/human). In one aspect, the chimeric Clqa polypeptide is or comprises SEQ ID NO: 10 or SEQ ID NO: 55.

[0098] In another aspect, the chimeric mammalian Clq polypeptide is a CI qb polypeptide.

[0099] In some embodiments, the chimeric Clqb polypeptide comprises a human Clqb globular head or a fragment thereof. In one embodiment, the polypeptide is a chimeric Clqb polypeptide comprising amino acids 125-233 of the human Clqb polypeptide as set forth in SEQ ID NO: S (such as, for example, amino acids 120-250 or 118-251 of the human Clqb polypeptide).

[00100] In some embodiments, the chimeric Clqb polypeptide comprises a globular head domain mat is substantially human (i.e., a globular head domain substantially identical to the globular head domain of a human C lqb polypeptide). In one embodiment, a human Clqb polypeptide comprises the amino acid sequence of SEQ ID NO: 5 (Figure 3B), and amino acids 115-251 of SEQ ID NO: 5 constitute the globular head domain of the human Clqb polypeptide of SEQ ID NO: 5 (Figure 3B). Thus, in some embodiments, a chimeric Clqb polypeptide comprises a globular head domain that is substantially identical to the human globular head domain represented by amino acids 115-251 of SEQ ID NO: 5. In a specific embodiment, the globular head domain of a chimeric Clqb polypeptide is represented by amino acids 115-251 of SEQ ID NO: 11, such domain differing from the human Clqb globular head domain represented by amino acids 115-251 of SEQ ID NO: 5 in one amino acid (the first amino acid residue being "G" as in mouse Clqb, instead of "K" in human Clqb). In another specific embodiment, a chimeric Clqb polypeptide comprises a globular head domain that is identical to the human Clqb globular head domain represented by amino acids 115-251 of SEQ ID NO: 5.

[00101] In some embodiments, a chimeric Clqb polypeptide comprises non-human Clqb stalk and/or stem domains. In some embodiments, the chimeric mammalian Clqb polypeptide comprises a non-human mammal sequence which is a mouse sequence comprising at least amino acids 32-105, 27-105, 27-110, 26-114, or 26-117 of the mouse Clqb polypeptide set forth in SEQ ID NO: 2. In other embodiments, the chimeric mammalian Clqb polypeptide comprises anon-human mammal sequence which is a rat sequence comprising at least amino acids 32-105, 27-105, 27-110, 26-114, or 26-117 of the rat Clqb polypeptide set forth in SEQ ID NO: 8.

[00102] In some embodiments, the chimeric Clqb polypeptide comprises an N-terminal stalk-stem region that is substantially non-human, i.e., an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a non-human Clqb polypeptide. In certain embodiments, the chimeric Clqb polypeptide comprises an N- terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a mouse Clqb polypeptide. In one embodiment, the mouse Clqb polypeptide comprises the amino acid sequence of SEQ ID NO: 2 (Figure 3B), and amino acids 26-114 of SEQ ID NO: 2 constitute the N-terminal stalk-stem region of the mouse Clqb polypeptide of SEQ ID NO: 2 (Figure 3B). Thus, in some embodiments, a chimeric Clqb polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the mouse Clqb N-terminal stalk-stem region represented by amino acids 26-114 of SEQ ID NO: 2. In a specific embodiment, the N-terminal stalk-stem region of a chimeric Clqb polypeptide is represented by amino acids 26-114 of SEQ ID NO: 2. In some embodiments, the chimeric Clqb polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a rat Clqb polypeptide. In one embodiment, the rat Clqb polypeptide comprises the amino acid sequence of SEQ ID NO: 8 (Figure 3B), and amino acids 26-114 of SEQ ID NO: 8 constitute the N-terminal stalk-stem region of the rat Clqb polypeptide of SEQ ID NO: 8 (Figure 3B). Thus, in some embodiments, a chimeric Clqb polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the rat Clqb N-terminal stalk-stem region represented by amino acids 26-114 of SEQ ID NO: 8. In a specific embodiment, the N-terminal stalk-stem region of a chimeric C 1 qb polypeptide is represented by amino acids 26-114 of SEQ ID NO: 8.

[00103] In some embodiments, the chimeric Clqb polypeptide comprises a globular head domain that is substantially human and an N-terminal stalk-stem region that is substantially non-human. For example, disclosed herein is a chimeric mammalian Clqb polypeptide, wherein the polypeptide comprises at least amino acids 26-251 of the polypeptide set forth in SEQ ID NO: 11 (mouse/human) or at least amino acids 26-251 of the polypeptide set forth in SEQ ID NO: 56 (rat/human). In one aspect, the chimeric Clqb polypeptide is or comprises SEQ ID NO: 11 or SEQ ID NO: 56.

[00104] In another aspect, the chimeric mammalian Clq polypeptide is a chimeric Clqc polypeptide.

[00105] In some embodiments, the chimeric Clqc polypeptide comprises a human Clqc globular head or a fragment thereof. In one embodiment, the polypeptide is a chimeric Clqc polypeptide comprising amino acids 118-234 of the human Clqc polypeptide as set forth in SEQ ID NO: 6 (for example, a chimeric mammalian Clqc polypeptide comprising amino acids 114-245 of the human Clqc polypeptide set forth in SEQ ID NO:6).

[00106] In some embodiments, the chimeric Clqc polypeptide comprises a globular head domain that is substantially human (i.e., a globular head domain substantially identical to the globular head domain of a human C lqc polypeptide). In one embodiment, the human Clqc polypeptide comprises the amino acid sequence of SEQ ID NO: 6 (Figure 3C), and amino acids 113-245 of SEQ ID NO: 6 constitute the globular head domain of the human Clqc polypeptide of SEQ ID NO: 6 (Figure 3C). Thus, in some embodiments, a chimeric Clqc polypeptide comprises a globular head domain mat is substantially identical to the human Clqc globular head domain represented by amino acids 113-245 of SEQ ID NO: 6. In a specific embodiment, the globular head domain of a chimeric Clqc polypeptide is identical to the human Clqc globular head domain represented by amino acids 113-245 of SEQ ID NO: 6.

[00107] In some embodiments, a chimeric Clqc polypeptide comprises non-human Clqc stalk and/or stem domains. For example, disclosed herein is a chimeric mammalian Clqc polypeptide wherein the non-human mammal sequence is a mouse sequence comprising at least amino acids 31-111, 30-113, or 30-114 of the mouse Clqc polypeptide set forth in SEQ ID NO: 3; or the chimeric mammalian Clqc polypeptide wherein the non-human mammal sequence is a rat sequence comprising at least amino acids 33-113, 32-115, or 32- 1 16 of the rat CI qc polypeptide set forth in SEQ ID NO: 9.

[00108] In some embodiments, the chimeric Clqc polypeptide comprises an N-terminal stalk-stem region that is substantially non-human, i.e., an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a non-human Clqc polypeptide. In certain embodiments, the chimeric Clqc polypeptide comprises an N- terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a mouse Clqc polypeptide. In one embodiment, the mouse Clqc polypeptide comprises the amino acid sequence of SEQ ID NO: 3 (Figure 3C), and amino acids 30-113 of SEQ ID NO: 3 constitute the N-terminal stalk-stem region of the mouse Clqc polypeptide of SEQ ID NO: 3 (Figure 3C). Thus, in some embodiments, a chimeric Clqc polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the mouse Clqc N-terminal stalk-stem region represented by amino acids 30-113 of SEQ ID NO: 3. In a specific embodiment, the N-terminal stalk-stem region of a chimeric Clqc polypeptide is represented by amino acids 30-113 of SEQ ID NO: 3. In some embodiments, the chimeric Clqc polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the N-terminal stalk-stem region of a rat Clqc polypeptide. In one embodiment, the rat Clqc polypeptide comprises the amino acid sequence of SEQ ID NO: 9 (Figure 3C), and amino acids 32-115 of SEQ ID NO: 9 constitute the N-terminal stalk-stem region of the rat Clqc polypeptide of SEQ ID NO: 9 (Figure 3C). Thus, in some embodiments, a chimeric Clqc polypeptide comprises an N-terminal stalk-stem region that is substantially identical to the rat C 1 qc N-terminal stalk-stem region represented by amino acids 32-115 of SEQ ID NO: 9. In a specific embodiment, the N-terminal stalk-stem region of a chimeric Clqc polypeptide is represented by amino acids 32-115 of SEQ ID NO: 9.

[00109] In some embodiments, the chimeric Clqc polypeptide comprises a globular head domain that is substantially human and an N-terminal stalk-stem region mat is substantially non-human. For example, also disclosed herein is a chimeric mammalian Clqc polypeptide, wherein the polypeptide comprises at least amino acids 30-246 of the polypeptide set forth in SEQ ID NO: 12 (mouse/human) or at least amino acids 32-248 of the polypeptide set forth in SEQ ID NO: 57 (rat/human). In one aspect, the chimeric Clqc polypeptide is or comprises SEQ ID NO: 12 or SEQ ID NO: 57.

[00110] In one particular aspect, disclosed herein is a chimeric CI q protein comprising one or more of the chimeric Clq polypeptides described herein. For example, disclosed herein is a chimeric Clq protein, wherein the protein comprises at least one, two, three, four, five, or six chimeric Clqa, one, two, three, four, five, or six chimeric Clqb, and/or one, two, three, four, five, or six chimeric Clqc polypeptide. Thus, in some embodiments, the chimeric protein comprises six of each chimeric Clqa polypeptide, chimeric Clqb polypeptide, and chimeric Clqc polypeptide.

[00111] The disclosed Clq polypeptides are chimeric polypeptides comprising part human and part non-human amino acid structure. It is understood and herein contemplated that the human and non-human portions of the disclosed chimeric polypeptides are linked, fused, or otherwise chemically joined in such a manner as to retain functionality of the C 1 q polypeptide. As used herein, "function" and "functionality" refer to the ability to carry out the duties of the native molecule. For Clqa, Clqb and Clqc, functionality includes the ability to form dimers (for Clqa and Clqb heterodimers and for Clqc homodimers), the ability for each portion of the chimeric polypeptide to assume proper folding, the ability to assemble as a trimer of dimers (two Clqa and Clqb heterodimers and 1 Clqc homodimer per trimer) forming a Clq complex, the ability to form a pentamer CI complex with Clr and C Is, the ability to recognize an Fc domain of an antibody or PAMPs, and the ability initiate the classical complement pathway. The assembly of a Clq protein has been described (see, e.g., Lu et al. (Cellular & Mol. Immunol. 2008, 5(1): 9-21), especially Figure 1). Clqa and Clqb polypeptide chains dimerize through a disulphide bond at the N- terminal end and two Clqc chains form homodimers through similar disulphide bonding. A Clqa-Clqb dimer and a single Clqc chain form a triple helix and the other Clqc-chain in a Clqc-Clqc dimer trimerizes with another Clqa-Clqb dimer forming two triple helices linked by the disulphide bond between the two Clqc chains. Three such structures form a Clq protein molecule through N -terminal association.

[00112] In a particular aspect, disclosed herein is a chimeric mammalian Clqa, Clqb, and/or Clqc polypeptides, wherein the polypeptide disclosed herein further comprises a human, a mouse, or a rat Clqa, Clqb, and/or Clqc signal sequence, respectively.

Exemplary human, mouse, and rat CI qa, Clqb, and Clqc signal sequence are shown in Figures 3A, 3B, and 3C, respectively.

[00113] It is understood and herein contemplated that any of the disclosed chimeric polypeptides can be expressed in anon-human animal. Thus, encompassed by the disclosure is a genetically modified non-human animal, e.g., rodent, e.g., mouse or rat, expressing a chimeric Clq protein(s) described herein or chimeric Clq protein(s) comprising variants, e.g., conservative amino acid substitutions, of the amino acid sequence(s) described herein.

[00114] Thus, the chimeric polypeptide can be one of the numerous variants of the chimeric Clqa, Clqb, and/or Clqc polypeptide that are known and herein contemplated. In addition to the known functional Clqa, Clqb, and/or Clqc species and strain variants, there are derivatives of the Clqa, Clqb, and/or Clqc polypeptides which also function in the disclosed methods and compositions. Protein variants and derivatives are well understood to those of skill in the art and can involve amino acid sequence modifications. For example, amino acid sequence modifications typically fall into one or more of three classes:

substitutional, insertional or deletional variants. These types of modifications and molecular techniques to achieve them are known in the art. Substitutions, deletions, insertions or any combination thereof may be combined to arrive at a final construct. These modifications must not place the sequence out of reading frame and preferably will not create complementary regions that could produce secondary mRNA structure. The term "conservative," when used to describe a conservative amino acid substitution, includes substitution of an amino acid residue by another amino acid residue having a side chain R group with similar chemical properties (e.g., charge or hydrophobicity). Conservative amino acid substitutions may be achieved by modifying a nucleotide sequence so as to introduce a nucleotide change that will encode the conservative substitution. In general, a conservative amino acid substitution will not substantially change the functional properties of interest of a protein, for example, the ability of Clq complex to bind immunoglobulin or activate the complement pathway. Examples of groups of amino acids that have side chains with similar chemical properties include aliphatic side chains such as glycine, alanine, valine, leucine, and isoleucine; aliphatic-hydroxyl side chains such as serine and threonine; amide-containing side chains such as asparagine and glutamine; aromatic side chains such as phenylalanine, tyrosine, and tryptophan; basic side chains such as lysine, arginine, and histidine; acidic side chains such as aspartic acid and glutamic acid; and, sulfur-containing side chains such as cysteine and methionine. Conservative amino acids substitution groups include, for example, valine/leucine/isoleucine, phenylalanine/tyrosine, lysine/arginine, alanine/valine, glutamate/aspartate, and asparagine/glutamine. In some embodiments, a conservative amino acid substitution can be a substitution of any native residue in a protein with alanine, as used in, for example, alanine scanning mutagenesis. In some embodiments, a conservative substitution is made that has a positive value in the PAM250 log-likelihood matrix disclosed in Gonnet et al. ((1992) Exhaustive Matching of the Entire Protein Sequence Database, Science 256: 1443-45), hereby incorporated by reference. In some embodiments, the substitution is a moderately conservative substitution wherein the substitution has a nonnegative value in the PAM250 log-likelihood matrix.

[00115] Substantial changes in function are made by selecting substitutions that are less conservative man those listed above, i.e., selecting residues mat differ more significantly in their effect on maintaining (a) the structure of the polypeptide backbone in the area of the substitution, for example as a sheet or helical conformation, (b) the charge or

hydrophobicity of the molecule at the target site or (c) the bulk of the side chain. The substitutions which in general are expected to produce the greatest changes in the protein properties will be those in which (a) a hydrophilic residue, e.g. seryl or threonyl, is substituted for (or by) a hydrophobic residue, e.g. leucyl, isoleucyl, phenylalanyl, valyl or alanyl; (b) a cysteine or proline is substituted for (or by) any other residue; (c) a residue having an electropositive side chain, e.g., lysyl, arginyl, or histidyl, is substituted for (or by) an electronegative residue, e.g., glutamyl or aspartyl; or (d) a residue having a bulky side chain, e.g., phenylalanine, is substituted for (or by) one not having a side chain, e.g., glycine, (e) by increasing the number of sites for sulfation and/or glycosylation.

[00116] Substitutional or deletional mutagenesis can be employed to insert sites for N- glycosylation (Asn-X-Thr/Ser) or 0-glycosylation (Ser or Thr). Deletions of cysteine or other labile residues also may be desirable. Deletions or substitutions of potential proteolysis sites, e.g. Arg, is accomplished for example by deleting one of the basic residues or substituting one by glutaminyl or histidyl residues. [00117] It is understood that one way to define the variants and derivatives of the disclosed proteins herein is through defining the variants and derivatives in terms of

homology/identity to specific known sequences. For example, SEQ ID NO: 1 sets forth a particular sequence of mouse Clqa polypeptide, SEQ ID NO: 2 sets forth a particular sequence of mouse Clqb polypeptide, SEQ ID NO: 3 sets forth a particular sequence of mouse Clqc polypeptide, SEQ ID NO: 4 sets forth a particular sequence of human Clqa polypeptide, SEQ ID NO: 5 sets forth a particular sequence of human Clqb polypeptide, SEQ ID NO: 6 sets forth a particular sequence of human Clqc polypeptide, SEQ ID NO: 7 sets forth a particular sequence of rat Clqa polypeptide, SEQ ID NO: 8 sets forth a particular sequence of rat Clqb polypeptide and SEQ ID NO: 9 sets forth a particular sequence of a rat Clqc polypeptide. Specifically disclosed are variants of these and other proteins herein disclosed which have at least 90%, 95%, 98%, or 99% homology to the stated sequence. In some embodiments, the homologous sequences are those represented by GenBank Accession Numbers listed in Tables 1, 2, and 8. Those of skill in the art readily understand how to determine the homology of two proteins. For example, the homology can be calculated after aligning the two sequences so that the homology is at its highest level.

[00118] Another way of calculating homology can be performed by published algorithms. Optimal alignment of sequences for comparison may be conducted by the local homology algorithm of Smith and Waterman Adv. Appl. Math. 2: 482 (1981), by the homology' alignment algorithm of Needleman and Wunsch, J. MoL Biol. 48: 443 (1970), by the search for similarity method of Pearson and Lipman, Proc. Natl. Acad Sci. U.S.A. 85: 2444 (1988), by computerized implementations of these algorithms (GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group, 575 Science Dr., Madison, Wl), or by inspection.

[00119] The same types of homology can be obtained for nucleic acids by for example the algorithms disclosed in Zuker, M. Science 244:48-52, 1989, Jaeger et al. Proc. Natl. Acad Sci. USA 86:7706-7710, 1989, Jaeger d. Methods Enzymol. 183:281-306, 1989.

[00120] It is understood that the description of conservative mutations and homology can be combined together in any combination, such as embodiments that have at least 70, 71, 72, 73, 74,75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, or 99 % homology to a particular sequence wherein the variants are conservative mutations. [00121] As this specification discusses various proteins and protein sequences it is understood that the nucleic acids that can encode those protein sequences are also disclosed. This would include all degenerate sequences related to a specific protein sequence, i.e., all nucleic acids having a sequence that encodes one particular protein sequence as well as all nucleic acids, including degenerate nucleic acids, encoding the disclosed variants and derivatives of the protein sequences. Thus, while each particular nucleic acid sequence may not be written out herein, it is understood that each and every sequence is in fact disclosed and described herein through the disclosed protein sequence.

D. Nucleic acids

[00122] There are a variety of molecules disclosed herein that are nucleic acid based, including for example the nucleic acids that encode, for example the chimeric Clqa, Clqb, Clqc, or any of the nucleic acids disclosed herein for making Clqa, Clqb, and/or Clqc genetically modified non-human animals, as well as various functional nucleic acids.

[00123] Disclosed herein are isolated nucleic acids encoding a chimeric mammalian Clqa, Clqb, and/or Clqc polypeptides comprising non-human and human nucleic acid sequences. In some embodiments, the isolated nucleic acid sequences described herein are large targeting vectors including entire regions of the genome, and include exons, introns, and/or intergenic sequences. These may include 5' and 3' untranslated regions, enhancers, promoters, and other regulatory regions. In some embodiments, these regulatory elements are non-human regulatory elements, e.g., regulatory elements of an endogenous non-human Clq gene. In other embodiments, these regulatory elements are human regulator}' elements, e.g., regulatory elements of a human Clq gene. In other embodiments, the isolated nucleic acid sequences described herein are cDNA sequences. In some embodiments, the isolated nucleic acids, e.g., a large targeting vector, described herein may include more than a single Clq gene, e.g., two or three genes (e.g., it may encode all three chimeric Clqa, Clqb, and Clqc genes described herein).

[00124] In one aspect, disclosed herein is an isolated nucleic acid comprising non-human and human nucleic acid sequences, wherein the nucleic acid encodes a chimeric mammalian Clq polypeptide (e.g., Clqa, Clqb, or Clqc polypeptide) described hereinabove, e.g., a chimeric Clq polypeptide comprising an N-terminal stalk-stem region that is substantially non-human and a globular head domain that is substantially human.

[00125] In some embodiments, an isolated nucleic acid encoding a chimeric mammalian Clqa polypeptide comprises non-human and human nucleic acid sequences, wherein the human nucleic acid sequence encodes substantially the globular head domain of a human Clq polypeptide, and the non-human nucleic acid sequence encodes substantially the N- terminal stalk-stem region of a cognate non-human Clq polypeptide.

[00126] By "a human Clq nucleic acid sequence encoding substantially the globular head domain of a human Clq polypeptide", it means a fragment of a human Clq gene that encodes the globular head domain or a polypeptide fragment that is slightly longer or shorter than the globular domain of the human Clq polypeptide. By "slightly longer or shorter" is meant a difference in length of not more than 5, 4, 3, 2, or 1 amino acid.

Similarly, by "a non-human Clq nucleic acid sequence encoding substantially the N- terminal stalk-stem region of anon-human Clq polypeptide", it means a fragment of anon- human Clq gene that encodes the N-terminal stalk-stem region or a polypeptide fragment that is slightly longer or shorter than the N-terminal stalk-stem region of the non-human Clq polypeptide.

[00127] In circumstances where a non-human Clq polypeptide and a cognate human Clq polypeptide share common amino acids near the junction between the stalk-stem region and the globular head domain, it may not be necessary to utilize a human Clq nucleic acid sequence that encodes precisely the globular head domain of the human Clq polypeptide. It is possible to use a nucleic acid sequence of a human Clq gene that encodes substantially the globular head domain of the human Clq polypeptide, in operable linkage to a nucleic acid that encodes substantially the stalk-stem region of the non-human animal Clq polypeptide, such that the chimeric Clq polypeptide includes a globular head domain that is substantially or fully identical to the globular head domain of the human Clq polypeptide, and a stalk-stem region that is substantially or fully identical to stalk-stem region of the non-human Clq polypeptide. Similarly, in circumstances where a non-human Clq polypeptide and a human Clq polypeptide share common amino acids near the C -terminus of the globular head domain, it may not be necessary to utilize a human Clq nucleic acid that encodes precisely the globular head domain of the human Clq polypeptide. It is possible to insert a slightly shorter nucleic acid of a human Clq gene that encodes a polypeptide slightly shorter than the globular head domain of the human Clq polypeptide, in operable linkage to a non-human nucleic acid that encodes the remainder amino acids at the C -terminus of the globular head domain, such mat the chimeric Clq polypeptide includes a globular head domain that is still substantially or fully identical to the globular head domain of the human Clq polypeptide. [00128] In one aspect, disclosed herein is an isolated nucleic acid encoding a chimeric mammalian Clqa polypeptide, wherein the human nucleic acid sequence encodes substantially the globular head domain of a human Clqa polypeptide, e.g., encodes the globular head domain of a human C lqa polypeptide or a fragment thereof. For example, in one aspect, disclosed herein is an isolated nucleic acid encoding a chimeric mammalian C 1 qa polypeptide, wherein the nucleic acid comprises at least a nucleic acid sequence encoding amino acids 122-222 of the human Clqa polypeptide as set forth in SEQ ID NO: 4. For example, the nucleic acid can comprise a nucleic acid sequence (e.g., a portion of human Clqa exon 3) encoding amino acids 122-235 or 112-245 of the human Clqa polypeptide as set forth in SEQ ID NO: 4.

[00129] The disclosed nucleic acid encoding chimeric mammalian Clqa polypeptide may further comprise non-human nucleic acid sequences (such as, for example, a nucleic acid sequence encoding substantially the N -terminal stalk-stem region of a non-human C 1 qa polypeptide). Thus, also disclosed herein are isolated nucleic acids, wherein the nucleic acid sequence comprises at least a nucleotide sequence encoding amino acids 33-102, 30- 102, 25-105, 23-107 or 23-111 of the mouse Clqa polypeptide set forth in SEQ ID NO: 1, or at least a nucleotide sequence encoding amino acids 33-102, 30-102, 25-105, 23-107 or 23-111 of the rat Clqa polypeptide set forth in SEQ ID NO: 7. In a particular aspect, disclosed herein is an isolated nucleic acid, wherein the isolated nucleic acid encodes at least amino acids 23-245 of the polypeptide set forth in SEQ ID NO: 10 (mouse/human) or at least amino acids 23-245 of the polypeptide set forth in SEQ ID NO: 55 (rat/human). In one aspect, the isolated nucleic acid encodes a functional chimeric mammalian Clqa polypeptide which is or comprises SEQ ID NO: 10 or SEQ ID NO: 55.

[00130] Also disclosed herein is an isolated nucleic acid encoding a chimeric mammalian Clqb polypeptide comprising a nucleic acid sequence encoding substantially the globular head domain of a human Clqb polypeptide, e.g., encoding the globular head domain of a human Clqb polypeptide or a fragment thereof. For example, the nucleic acid encoding the chimeric mammalian Clqb polypeptide comprises at least a nucleic acid sequence encoding amino acids 125-233 of the human Clqb polypeptide as set forth in SEQ ID NO: 5. For example, the nucleic acid can comprise a nucleic acid sequence (e.g., a portion of human Clqb exon 3) encoding amino acids 118-251 of human Clqb polypeptide as set form in SEQ ID NO: 5. [00131] The disclosed nucleic acid encoding chimeric mammalian Clqb polypeptide may further comprise non-human nucleic acid sequences (such as, for example, a nucleic acid sequence encoding substantially the N -terminal stalk-stem region of a non-human Clqb polypeptide). Thus, also disclosed herein is an isolated nucleic acid, wherein the nucleic acid sequence comprises at least a nucleotide sequence encoding amino acids 32-105, 27- 105, 27-110, 26-114, or 26-117 of the mouse Clqb polypeptide set forth in SEQ ID NO: 2, or wherein the nucleic acid sequence comprises at least a nucleotide sequence encoding amino acids 32-105, 27-105, 27-110, 26-114, or 26-117 of the rat Clqb polypeptide set forth in SEQ ID NO: 8. In a particular aspect, disclosed herein is an isolated nucleic acid, wherein the isolated nucleic acid encodes at least amino acids 26-251 of the polypeptide set forth in SEQ ID NO: 11 (mouse/human) or wherein the isolated nucleic acid encodes at least amino acids 26-251 of the polypeptide set forth in SEQ ID NO: 56 (rat/human). In one aspect, the isolated nucleic acid encodes a functional chimeric mammalian Clqb polypeptide which is or comprises SEQ ID NO: 11 or SEQ ID NO: 56.

[00132] Also disclosed herein is an isolated nucleic acid encoding a chimeric mammalian Clqc polypeptide comprising a nucleic acid sequence encoding substantially the globular head domain of a human Clqc polypeptide, e.g., encoding the globular head domain of a human Clqc polypeptide or a fragment thereof. In one aspect, the isolated nucleic acid encoding chimeric mammalian Clqc polypeptide, wherein the nucleic acid encoding the chimeric mammalian Clqc polypeptide comprises at least a nucleic acid sequence encoding amino acids 118-234 of human Clqc polypeptide set forth in SEQ ID NO: 6. For example, the nucleic acid can comprise a nucleic acid sequence (e.g., a portion of human Clqa exon 3) encoding amino acids 114-245 of human Clqc polypeptide as set forth in SEQ ID NO: 6.

[00133] The nucleic acids encoding chimeric mammalian Clqc polypeptide may further comprise non-human nucleic acid sequences (such as, for example, a nucleic acid sequence encoding the substantially the N-terminal stalk-stem region of anon-human Clqc polypeptide). Thus, also disclosed herein is an isolated nucleic acid, wherein the nucleic acid sequence comprises at least a nucleotide sequence encoding amino acids 31-111, 30- 113, or 30-114 of the mouse Clqc polypeptide set forth in SEQ ID NO: 3, or wherein the nucleic acid sequence comprises at least a nucleotide sequence encoding amino acids 33- 113, 32-115, or 32-116 of the rat Clqc polypeptide set forth in SEQ ID NO: 9. In a particular aspect, disclosed herein is an isolated nucleic acid, wherein the isolated nucleic acid encodes at least amino acids 30-246 of the polypeptide set forth in SEQ ID NO: 12 (mouse/human) or wherein the isolated nucleic acid encodes at least amino acids 32-248 of the polypeptide set forth in SEQ ID NO: 57 (rat/human). In one aspect, the isolated nucleic acid encodes a functional chimeric mammalian Clqc polypeptide which is or comprises SEQ ID NO: 12 or SEQ ID NO: 57.

[00134] In some embodiments, the non-human nucleic acid sequence in an isolated nucleic acid encoding a chimeric Clq polypeptide also encodes a non-human signal peptide, e.g., the signal peptide of an endogenous non-human Clq polypeptide.

[00135] In some embodiments, the non-human nucleic acid sequence in an isolated nucleic acid encoding a chimeric Clq polypeptide also comprises a non-human 5' UTR region, e.g., the 5' UTR region of an endogenous non-human Clq gene.

[00136] In some embodiments, the human nucleic acid sequence in an isolated nucleic acid encoding a chimeric Clq polypeptide also comprises a human 3' UTR region, e.g., the 3' UTR region of a human Clq gene.

[00137] In some embodiments, the non-human nucleic acid sequence is a genomic fragment of a non-human C lq gene which comprises a coding portion of exon 2 (e.g., the portion that encodes amino acids of the mature form of the non-human Clq polypeptide) and a portion of exon 3 (e.g., the portion that encodes amino acids of the N-terminal stalk-stem region). In some embodiments, the non-human nucleic acid sequence is a genomic fragment of a non-human C lq gene comprising the entire coding portion of exon 2 which encodes both the signal peptide and amino acids of the mature form of the non-human Clq polypeptide, and the portion of exon 3 that encodes amino acids of the N-terminal stalk-stem region. In some embodiments, the non-human nucleic acid sequence is a genomic fragment of a non- human Clq gene comprising exon 1, exon 2, and the portion of exon 3 that encodes amino acids of the N-terminal stalk-stem region, thereby encompassing the 5' UTR of the non- human Clq gene.

[00138] In some embodiments, the human nucleic acid sequence is a genomic fragment of a human Clq gene which comprises a portion of exon 3 that encodes the globular head domain or a fragment thereof of a human Clq polypeptide. The human nucleic acid sequence is operably linked to the non-human nucleic acid sequence such that the encoded chimeric Clq polypeptide comprises an N-terminal stalk-stem region that is substantially non-human and a globular head domain that is substantially human and is a functional Clq polypeptide. [00139] In some embodiments, the human nucleic acid sequence is a genomic fragment of a human Clq gene comprising a 3' portion of exon 3 that encodes the globular head domain or a fragment thereof and includes the entire 3' UTR of the human Clq gene.

[00140] In one particular aspect, disclosed herein is an isolated nucleic acid encoding a chimeric non-human Clq protein, wherein the nucleic acid comprises a sequence encoding a chimeric CI qa, a chimeric Clqb, and/or a chimeric Clqc. In some embodiments, one or more of the sequence(s) encoding the chimeric Clqa, Clqb, and/or Clqc comprise a sequence encoding a human globular head domain or a fragment thereof. In some embodiments, one or more of the sequences) encoding the chimeric Clqa, Clqb, and/or Clqc comprise a sequence encoding non-human (e.g., rodent, e.g., rat or mouse) stem and/or stalk. In some embodiments, one or more of the sequence(s) encoding the chimeric Clqa, Clqb, and/or Clqc comprise a sequence encoding non-human (e.g., rodent, e.g., rat or mouse) collagen triple helix domain.

[00141] Thus, in some embodiments, disclosed herein is an isolated nucleic acid, wherein the isolated nucleic acid encodes a chimeric non-human mammal Clq protein, comprising one or more of a first, second or third nucleotide sequences, wherein the first nucleotide sequence encodes a chimeric non-human mammalian Clqa polypeptide, the second nucleotide sequence encodes a chimeric non-human mammalian Clqb polypeptide, and the third nucleotide sequence encodes a chimeric non-human mammalian Clqc polypeptide.

[00142] In one embodiment, the disclosed isolated nucleic acids can further comprise a nucleotide sequence that encodes a human, a mouse or a rat Clqa, Clqb, and/or Clqc signal peptide as set forth in Figures 3 A, 3B, and/or 3C.

[00143] Also disclosed herein is an isolated nucleic acid encoding a chimeric mammalian Clq polypeptide, wherein the non-human mammal nucleic acid sequence comprises exons 1 and 2 of the non-human mammal Clqa, Clqb, and/or Clqc gene.

[00144] It is understood and herein contemplated mat the disclosed nucleic acids can be incorporated into a cell to be translated and expressed. Thus, any of the disclosed nucleic acids can be cloned into the genome of a cell for expression of the chimeric Clq polypeptide. Therefore, provided herein is a genetically modified cell comprising one or more isolated nucleic acids of any preceding aspect.

[00145] The term "cell" includes any cell mat is suitable for expressing a recombinant nucleic acid sequence. Cells include those of prokaryotes and eukary otes (single-cell or multiple-cell), bacterial cells (e.g., strains of E. coli, Bacillus spp., Streptomyces spp., etc.), mycobacteria cells, fungal cells, yeast cells (e.g., S. cerevisiae, S. pombe, P. pastoris, P. methanolica, etc.), plant cells, insect cells (e.g., SF-9, SF-21, baculovirus-infected insect cells, Trichoplusiani, etc.), non-human animal cells, human cells, or cell fusions such as, for example, hybridomas or quadromas. In some embodiments, the cell is a human, monkey, ape, hamster, rat, or mouse cell. In some embodiments, the cell is eukaryotic and is selected from the following cells: CHO (e.g., CHO Kl, DXB-11 CHO, Veggie-CHO), COS (e.g., COS-7), retinal cell, Vera, CV1, kidney (e.g., HEK293, 293 EBNA, MSR 293, MDCK, HaK, BHK), HeLa, HepG2, WI38, MRC 5, Colo205, HB 8065, HL-60, (e.g., BHK21), Jurkat, Daudi, A431 (epidermal), CV-1, U937, 3T3, L cell, C127 cell, SP2/0, NS- 0, MMT 060562, Sertoli cell, BRL 3 A cell, HT1080 cell, myeloma cell, tumor cell, and a cell line derived from an aforementioned cell. In some embodiments, the cell comprises one or more viral genes, e.g. a retinal cell that expresses a viral gene (e.g., a PER.C6™ cell). In some embodiments, the cell is an ES cell. In other embodiments, the cell is a dendritic cell, a fibroblast, a epithelial cell, or a primary cell. In some embodiments, the cell is used to produce genetically modified non-human animals. It is further understood that some said cells can be incorporated into and used to develop a genetically modified non-human animal comprising any of the disclosed nucleic acids which at least encode one or more chimeric Clqa, Clqb, and/or Clqc polypeptides, and can express said polypeptides. In some embodiments, a cell is obtained from the genetically modified non-human animal provided herein. In some such embodiments, the cell may be a primary cell. In some embodiments, the cell may be a macrophage or a dendritic cell.

[00146] One skilled in the art would understand that in addition to the nucleic acid residues encoding humanized Clq proteins described herein, due to the degeneracy' of the genetic code, other nucleic acids may encode the polypeptides of the present disclosure. Therefore, in addition to a genetically modified non-human animal that comprises in its genome nucleotide sequences encoding humanized Clq proteins described herein, a non-human animal that comprises in its genome nucleotide sequences that differ from those described herein due to the degeneracy of the genetic code are also provided.

[00147] There are a variety of sequences related to the protein Clq, for example the polypeptides Clqa, Clqb, and/or Clqc as well as chimeric Clqa, , Clqb, and/or Clqc, or any of the nucleic acids disclosed herein for making chimeric Clqa, Clqb, and/or Clqc polypeptides, all of which are encoded by nucleic acids or are nucleic acids. The sequences for the human analogs of these genes, as well as other analogs, and alleles of these genes, and splice variants and other types of variants, are available in a variety of protein and gene databases, including Genbank. Those of skill in the art understand how to resolve sequence discrepancies and differences and to adjust the compositions and methods relating to a particular sequence to other related sequences.

E. Genetically Modified Humanized Clq Animals

[00148] In a further aspect, provided herein is a genetically modified non-human animal (e.g., rodent such as mouse or rat) that expresses a chimeric, humanized Clq polypeptide (e.g., a chimeric Clqa, Clqb or Clqc) as described hereinabove. Such non-human animal expresses a humanized Clq complex comprising the humanized Clq polypeptide.

[00149] In one aspect, disclosed herein are non-human animals (e.g., rodent such as mouse or rat) that comprise in their genome a nucleic acid molecule encoding a chimeric Clq polypeptide described hereinabove, e.g., a chimeric Clq polypeptide (Clqa, Clqb, or Clqc) comprising an N-terminal stalk-stem region that is substantially non-human (endogenous) and a globular head domain that is substantially human.

[00150] In some embodiments, the animal disclosed herein comprises a nucleic acid molecule encoding a chimeric Clq polypeptide (e.g., Clqa, Clqb or Clqc polypeptide) as described hereinabove, wherein the nucleic acid molecule comprises non-human (e.g., endogenous) and human nucleic acid sequences.

[00151] In some embodiments, the nucleic acid molecule encoding a chimeric Clq polypeptide includes anon-human (e.g., endogenous) Clq nucleic acid sequence and a cognate human Clq nucleic acid sequence, operably linked to each other such that the nucleic acid molecule encodes a functional Clq polypeptide. The term "cognate" is used herein in the context of a chimeric molecule to indicate that the sequences in the chimeric molecule that are of different origins correspond to the same gene. For example, a mouse or rat Clqa sequence is linked to a human Clqa sequence to form a chimeric Clqa molecule, a mouse or rat Clqb sequence is linked to a human Clqb sequence to form a chimeric Clqb molecule, a mouse or rat Clqc sequence is linked to a human Clqc sequence to form a chimeric Clqc molecule. In some embodiments, the chimeric Clq polypeptide comprises an N-terminal stalk-stem region mat is substantially non-human and a globular head domain that is substantially human.

[00152] In some embodiments, the nucleic acid molecule encoding a chimeric Clq polypeptide in the genome of a genetically modified non-human animal includes a non- human Clq nucleic acid sequence (e.g., an endogenous non-human Clq nucleic acid sequence) and a human Clq nucleic acid sequence, wherein the human Clq nucleic acid sequence encodes substantially the globular head domain of a human Clq polypeptide.

[00153] In some embodiments, the nucleic acid molecule encoding a chimeric Clq polypeptide in the genome of a genetically modified non-human animal includes a non- human (e.g., endogenous) Clq nucleic acid sequence and a human Clq nucleic acid sequence, wherein the non-human Clq nucleic acid sequence encodes substantially die N- terminal stalk-stem region of anon-human (e.g., endogenous) Clq polypeptide.

[00154] In some embodiments, the nucleic acid molecule encoding a chimeric Clq polypeptide is operably linked to a 5' regulatory element(s), such as the promoter and/or enhancer(s), of anon-human (e.g., endogenous) Clq gene.

[00155] In some embodiments, the nucleic acid molecule encoding a chimeric Clq polypeptide in the genome is at a locus other than an endogenous Clq locus.

[00156] In some embodiments, the chimeric Clq nucleic acid molecule in the genome is at an endogenous Clq locus. In some such embodiments, the chimeric Clq nucleic acid molecule in the genome can result from a replacement of a nucleotide sequence of an endogenous Clq gene at its endogenous locus with a nucleotide sequence of a cognate human Clq gene.

[00157] In some embodiments, a contiguous genomic sequence of a non-human Clq gene at an endogenous C lq locus has been replaced with a contiguous genomic sequence of a cognate human Clq gene to form a chimeric, humanized Clq gene.

[00158] In some embodiments, a contiguous genomic sequence of a human Clq gene inserted into an endogenous non-human Clq gene includes a portion of exon 3 of the human Clq gene such that the resulting chimeric, humanized Clq gene encodes a chimeric Clq polypeptide comprising a globular head domain that is substantially human. In some embodiments, a contiguous genomic sequence of a human Clq gene inserted into an endogenous non-human Clq gene includes a portion of exon 3 of the human Clq gene that encodes substantially the globular head domain the human Clq polypeptide.

[00159] In some embodiments, the genomic sequence of an endogenous Clq gene that remains at an endogenous locus after the humanization and is operably linked to the inserted contiguous human Clq genomic sequence, includes a 3' portion of exon 2 and a 5' portion of exon 3, and encodes substantially the N-terminal stalk-stem region of the endogenous Clq polypeptide. [00160] In circumstances where a non-human Clq polypeptide and a cognate human Clq polypeptide share common amino acids near the junction between the stalk-stem region and the globular head domain, it may not be necessary to insert a human Clq nucleic acid that encodes precisely the globular head domain of the human Clq polypeptide. It is possible to insert a slightly longer or shorter nucleic acid of a human Clq gene that encodes substantially the globular head domain of the human Clq polypeptide, in operable linkage to a nucleic acid that encodes substantially the stalk-stem region of the non-human animal Clq polypeptide, such that the chimeric Clq polypeptide includes a globular head domain that is substantially or fully identical to the globular head domain of the human Clq polypeptide, and a stalk-stem region that is substantially or fully identical to stalk-stem region of the non-human Clq polypeptide. Similarly, in circumstances where anon-human Clq polypeptide and a human Clq polypeptide share common amino acids near the C- terminus of the globular head domain, it may not be necessary- to utilize a human Clq nucleic acid that encodes precisely the globular head domain of the human Clq polypeptide. It is possible to insert a slightly shorter nucleic acid of a human Clq gene that encodes substantially (i.e., slightly shorter than) the globular head domain of the human Clq polypeptide, in operable linkage to a non-human nucleic acid that encodes the remainder of amino acids at the C -terminus of the globular head domain, such that the chimeric Clq polypeptide includes a globular head domain that is still substantially or fully identical to the globular head domain of the human Clq polypeptide.

[00161] In some embodiments, the human Clq nucleotide sequence included in a humanized, chimeric Clq gene also includes the 3' untranslated region ("UTR") of the human Clq gene, which is the last part of exon 3 in all Clq genes (i.e., Clqa, Clqb and Clqc genes). In certain embodiments, in addition to the 3' UTR of a human Clq gene, an additional human genomic sequence from the human Clq gene locus can also be included. The additional human genomic sequence can consist of at least 10-200 bp, e.g., SO bp, 75 bp, 100 bp, 125 bp, 150 bp, 175 bp, 200 bp, or more, found in the human Clq gene locus immediately downstream of the 3' UTR of the human Clq gene. In other embodiments, the human Clq nucleotide sequence included in a humanized Clq gene does not include the 3' UTR of the human Clq gene; instead, the 3' UTR of an endogenous Clq gene is included and follows immediately the stop codon of the humanized Clq gene.

[00162] In some embodiments, the endogenous non-human Clq nucleic acid sequence included in a humanized, chimeric Clq gene (e.g., the endogenous genomic Clq sequence remaining at an endogenous locus after humanization) includes the 5' UTR of endogenous Clq gene (which may include exon 1 and in most cases a 5' portion of exon 2). In some embodiments, the endogenous non-human Clq nucleotide sequence included in a humanized, chimeric Clq gene also includes a nucleotide sequence (e.g., a 5' portion of exon 2) coding for the signal peptide of the endogenous Clq polypeptide.

[00163] In some embodiments, a non-human animal provided herein is heterozygous for a humanized Clq gene in its genome. In other embodiments, a non-human animal provided herein is homozygous for a humanized Clq gene in its genome.

[00164] In certain embodiments, a non-human animal includes multiple, i.e., two or more, chimeric Clq genes in its genome, each at an endogenous Clq locus or a different locus. In some embodiments, the multiple chimeric Clq genes are on a contiguous nucleic acid fragment at a non-endogenous Clq locus. In some embodiments, the multiple chimeric Clq genes are each at its endogenous Clq locus. For example, two or all three endogenous Clq genes (Clqa, Clqb and Clqc) in anon-human animal have been humanized using nucleotide sequences of cognate human Clq genes.

[00165] In various embodiments provided, the genetically modified non-human animal expresses the polypeptide(s) encoded by the chimeric non-human/human Clq nucleic acid molecules. Thus, disclosed herein is a genetically modified non-human animal, wherein the non-human animal expresses one or more chimeric non-human/human Clqa, Clqb, and/or Clqc polypeptides. In such an aspect, the genetically modified non-human animals can express one, two, three, four, five, or six chimeric non-human/human Clqa polypeptides, one, two, three, four, five, or six chimeric non-human/human Clqb polypeptides, and/or one, two, three, four, five, or six chimeric non-human/human Clqc polypeptides. In various embodiments, the expressed chimeric Clq polypeptides are functional Clq polypeptides. In various embodiments, the Clq polypeptides provided herein arrange in a typical Clq bouquet structure to form a functional Clq protein comprising 18 polypeptide chains.

[00166] In some embodiments, the non-human animal does not express a functional endogenous Clq polypeptide (e.g., an endogenous Clqa, Clqb or Clqc polypeptide). In some embodiments, the non-human animal does not express a functional endogenous Clqa polypeptide, afunctional endogenous Clqb polypeptide, or a functional endogenous Clqc polypeptide. The lack of expression of a functional endogenous Clq polypeptide(s) can be a result of inactivation, deletion, and/or humanization of the endogenous Clq gene(s). [00167] In some aspects, the non-human animal expresses one or more chimeric Clqa, Clqb, and/or Clqc polypeptides comprising the globular head domains of human Clqa, Clqb, and/or Clqc polypeptides. In some aspects, the non-human animal expresses a chimeric Clqa polypeptide comprising an globular head domain of human Clqa set forth in SEQ ID NO: 4 or a fragment thereof (for example, amino acids 112-245, 122-235 or 122- 222 as set forth in SEQ ID NO: 4). In some aspects, the non-human animal expresses a chimeric Clqb polypeptide comprising a globular head domain of human Clqb set forth in SEQ ID NO: 5 or a fragment thereof (for example, amino acids 118-251, 120-251 or 125- 233 as set forth in SEQ ID NO: 5). In some aspects, the non-human animal expresses a chimeric Clqc polypeptide comprising a globular head domain of human Clqc set forth in SEQ ID NO: 6 or a fragment thereof (for example, amino acids 118-234 or amino acids 114-245 as set forth in SEQ ID NO: 6). In some aspects, the non-human animal expresses the chimeric Clqa as set forth in SEQ ID NOs: 10 or 55, Clqb as set forth in SEQ ID NOs: 11 or 56, and/or Clqc polypeptide as set form in SEQ ID NOs: 12 or 57.

[00168] In one aspect, it is understood and herein contemplated that the disclosed genetically modified non-human animals comprise nucleic acids encoding Clq polypeptides that comprise non-human amino acid sequences and human amino acid sequences. It is further understood that all or a portion of the globular head domain of chimeric Clq is comprised of human amino acid sequences. In one aspect, disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat), wherein the nucleic acid sequence encoding the globular head of a human Clqa polypeptide or a fragment thereof encodes at least amino acids 122-222 of the human Clqa polypeptide as set forth in SEQ ID NO: 4 (for example, a nucleic acid sequence encoding amino acids 122- 235 or 112-245 of the human Clqa polypeptide as set forth in SEQ ID NO: 4). In one aspect, the genetically modified non-human animal is a rat and further comprises, operably linked to the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human Clqa polypeptide, a nucleotide sequence encoding at least amino acids 33-102, 30-102, 25-105, 23-107 or 23-111 of the rat Clqa polypeptide set forth in SEQ ID NO: 7, or the genetically modified non-human animal is a mouse and further comprises, operably linked to the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human C 1 qa polypeptide, a nucleotide sequence encoding at least amino acids 33-102, 30-102, 25-105, 23-107 or 23-111 of the mouse Clqa polypeptide set forth in SEQ ID NO: 1. In one aspect, the genetically modified non-human animals comprise one or more nucleic acid sequences encoding at least amino acids 23-245 of a Clqa polypeptide as set forth in SEQ ID NO: 10 or SEQ ID NO: 55. In a specific aspect, disclosed herein are genetically modified non-human animals (such as, for example a rodent such as a mouse or rat), wherein the non-human animal comprises one or more nucleic acid sequences encoding a Clqa polypeptide as set forth in SEQ ID NO: 10 or SEQ ID NO: 55. In some embodiments, a genetically modified non-human animal is a mouse that comprises a nucleic acid encoding a Clqa polypeptide as set forth in SEQ ID NO: 10. In some embodiments, a genetically modified non-human animal is a rat that comprises a nucleic acid encoding a Clqa polypeptide as set forth in SEQ ID NO: 55.

[00169] In another aspect, disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat), wherein the nucleic acid sequence encoding the globular head of a human Clqb polypeptide or a fragment thereof encodes at least amino acids 125-233 of the human Clqb polypeptide as set forth in SEQ ID NO: 5 (for example, a nucleic acid sequence encoding amino acids 120-250 or 118-251 of the human Clqb polypeptide).

[00170] Also disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat) wherein the genetically modified non-human animal is a rat and comprises, operably linked to the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human Clqb polypeptide, a nucleotide sequence encoding at least amino acids 32-105, 27-105, 27-110, 26-114, or 26-117 of the rat Clqb polypeptide set forth in SEQ ID NO: 8, or wherein the genetically modified non- human animal is a mouse and further comprises, operably linked to the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human Clqb polypeptide, a nucleotide sequence encoding at least amino acids 32-105, 27-105, 27-110, 26-114, or 26-117 of the mouse Clqb polypeptide set forth in SEQ ID NO: 2.

[00171] In one aspect, the genetically modified non-human animal comprises one or more nucleic acid sequences encoding at least amino acids 26-251 of a Clqb polypeptide as set forth in SEQ ID NO: 11 or SEQ ID NO: 56. In a specific aspect, disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat), wherein the non-human animal comprises one or more nucleic acid sequences encoding a Clqb polypeptide as set forth in SEQ ID NO: 11 or SEQ ID NO: 56. In some embodiments, a genetically modified non-human animal is a mouse that comprises a nucleic acid encoding a Clqb polypeptide as set forth in SEQ ID NO: 1 1. In some embodiments, a genetically modified non-human animal is a rat that comprises a nucleic acid encoding a Clqb polypeptide as set forth in SEQ ID NO: 56.

[00172] In one aspect, the genetically modified non-human animal (such as, for example a rodent such as a mouse or rat) comprises a nucleic acid, wherein the nucleic acid sequence encoding the globular head of a human Clqc polypeptide or a fragment thereof encodes at least amino acids 1 18-234 of the human Clqc polypeptide as set forth in SEQ ID NO: 6 (for example, a nucleic acid sequence encoding amino acids 114-245 of the human Clqc polypeptide).

[00173] Also disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat), wherein the non-human animal is a rat and further comprises, operably linked to the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human Clqc polypeptide, a nucleotide sequence encoding at least amino acids 33-113, 32-115, or 32-116 of the rat Clqc polypeptide set forth in SEQ ID NO: 9, or wherein the non-human animal is a mouse and further comprises, operably linked to the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human Clqc polypeptide, a nucleotide sequence encoding at least amino acids 31-111, 30-113, or 30-114 of the mouse Clqc polypeptide set forth in SEQ ID NO: 3.

[00174] In one aspect, the genetically modified non-human animal comprises one or more nucleic acid sequences encoding at least amino acids 30-246 of a Clqc polypeptide as set forth in SEQ ID NO: 12 or one or more nucleic acid sequences encoding at least amino acids 32-248 of a Clqc polypeptide as set forth in SEQ ID NO: 57. In a specific aspect, disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat), wherein the non-human animal comprises one or more nucleic acid sequences encoding a Clqc polypeptide as set forth in SEQ ID NO: 12 or SEQ ID NO: 57. In some embodiments, a genetically modified non-human animal is a mouse that comprises a nucleic acid encoding a Clqc polypeptide as set forth in SEQ ID NO: 12. In some embodiments, a genetically modified non-human animal is a rat that comprises a nucleic acid encoding a Clqb polypeptide as set forth in SEQ ID NO: 57.

[00175] In some aspect, it is beneficial for the expression of a polypeptide for a signal sequence to be present. The disclosed polypeptides and disclosed nucleic acids encoding said polypeptides can comprise signal sequences or have signal sequences absent. Thus, in one aspect, disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat) wherein the non-human animal further comprises, in operable linkage, a nucleotide sequence encoding a rat, a mouse or a human Clqa, Clqb, and/or Clqc signal peptide. Examples of signal peptides from rat, mouse and human Clqa, Clqb, and Clqc polypeptides are shown in Figures 3A-3C. For example, disclosed herein is a non-human animal comprising, in operable linkage, a nucleic acid sequence comprising a signal peptide-encoding portion of the rat or mouse Clqa, Clqb, and/or Clqc gene, and at least the nucleic acid sequence encoding the globular head domain or the fragment thereof of the human Clqa, Clqb, and/or Clqc polypeptide, respectively.

[00176] In one aspect, disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat) comprising in its genome a) at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric rat/human Clqa polypeptide wherein the nucleic acid sequence comprises, 5 '-3' and in operable linkage a first nucleotide sequence encoding amino acids 1 - 111 of a rat C 1 qa polypeptide of SEQ ID NO: 7 and a second nucleotide sequence encoding amino acids 112-245 of a human Clqa polypeptide of SEQ ID NO: 4; b) at the endogenous Clqb locus a nucleic acid sequence encoding a chimeric rat/human Clqb polypeptide wherein the nucleic acid sequence comprises, 5'-3' and in operable linkage a third nucleotide sequence encoding amino acids 1-117 of a rat Clqb polypeptide of SEQ ID NO: 8 and a fourth nucleotide sequence encoding amino acids 118-251 of a human Clqb polypeptide of SEQ ID NO: 5; and c) at the endogenous Clqc locus a nucleic acid sequence encoding a chimeric rat/human Clqc polypeptide wherein the nucleic acid sequence comprises, 5'-3' and in operable linkage a fifth nucleotide sequence encoding amino acids 1-116 of a rat Clqc polypeptide of SEQ ID NO: 9 and a sixth nucleotide sequence encoding amino acids 114-245 of a human Clqc polypeptide of SEQ ID NO: 6. In one embodiment, such genetically modified non-human animal is a rat.

[00177] Also disclosed herein is a genetically modified non-human animal (such as, for example a rodent such as a mouse or rat) comprising in its genome a) at the endogenous Clqa locus a nucleic acid sequence encoding a chimeric mouse/human Clqa polypeptide wherein the nucleic acid sequence comprises, 5' -3' and in operable linkage a first nucleotide sequence encoding amino acids 1-111 of a mouse Clqa polypeptide of SEQ ID NO: 1 and a second nucleotide sequence encoding amino acids 112-245 of a human C 1 qa polypeptide of SEQ ID NO: 4; b) at the endogenous Clqb locus a nucleic acid sequence encoding a chimeric mouse/human Clqb polypeptide wherein the nucleic acid sequence comprises, 5'-3' and in operable linkage a third nucleotide sequence encoding amino acids 1-117 of a mouse Clqb polypeptide of SEQ ID NO: 2 and a fourth nucleotide sequence encoding amino acids 118-251 of a human Clqb polypeptide of SEQ ID NO: 5; and c) at the endogenous Clqc locus a nucleic acid sequence encoding a chimeric mouse/human Clqc polypeptide wherein the nucleic acid sequence comprises, S'-3' and in operable linkage a fifth nucleotide sequence encoding amino acids 1-114 of a mouse Clqc polypeptide of SEQ ID NO: 3 and a sixth nucleotide sequence encoding amino acids 114- 245 of a human Clqc polypeptide of SEQ ID NO: 6. In one embodiment, such genetically modified non-human animal is a mouse.

[00178] In one aspect disclosed herein is a genetically modified non-human animal, wherein the non-human animal, e.g., the rat or the mouse, does not express a functional endogenous Clqa, Clqb, and/or Clqc polypeptide(s).

[00179] In some embodiments, the non-human animal is a mammal. In one aspect, the non- human animal is a small mammal, e.g., of the superfamily Dipodoidea or Muroidea In one embodiment, the genetically modified animal is a rodent. In one embodiment, the rodent is selected from a mouse, a rat, and a hamster. In one embodiment, the rodent is selected from the superfamily Muroidea. In one embodiment, the genetically modified animal is from a family selected from Calomyscidae (e.g., mouse-like hamsters), Cricetidae (e.g., hamster, New World rats and mice, voles), Muridae (true mice and rats, gerbils, spiny mice, crested rats), Nesomyidae (climbing mice, rock mice, white-tailed rats, Malagasy rats and mice), Platacanthomyidae (e.g., spiny dormice), and Spalacidae (e.g., mole rats, bamboo rats, and zokors). In a specific embodiment, the genetically modified rodent is selected from a true mouse or rat (family Muridae), a gerbil, a spiny mouse, and a crested rat. In one embodiment, the genetically modified mouse is from a member of the family Muridae. In one embodiment, the animal is a rodent. In a specific embodiment, the rodent is selected from a mouse and a rat. In one embodiment, the non-human animal is a mouse.

[00180] In one embodiment, the non-human animal is a rodent that is a mouse of a C57BL strain selected from C57BL/A, C57BL/An, C57BL/GrFa, C57BL/KaLwN, C57BI76, C57BL/6J, C57BL/6ByJ, C57BL/6NJ, C57BL/10, C57BL/10ScSn, C57BL/10Cr, and C57BL/01& In another embodiment, the mouse is a 129 strain selected from the group consisting of a strain that is 129P1, 129P2, 129P3, 129X1, 129S1 (e.g., 12951/SV,

129Sl/SvIm), 129S2, 129S4, 129S5, 129S9/SvEvH, 129S6 (129/SvEvTac), 129S7, 129S8, 129T1, 129T2 (see, e.g., Festing et al. (1999) Revised nomenclature for strain 129 mice, Mammalian Genome 10:836, see also, Auerbach et al (2000) Establishment and Chimera Analysis of 129/SvEv- and C57BIJ6-Derived Mouse Embryonic Stem Cell Lines). In a specific embodiment, the genetically modified mouse is a mix of an aforementioned 129 strain and an aforementioned C57BL/6 strain. In another specific embodiment, the mouse is a mix of aforementioned 129 strains, or a mix of aforementioned BL/6 strains. In a specific embodiment, the 129 strain of the mix is a 129S6 (129/SvEvTac) strain. In another embodiment, the mouse is a BALB strain, e.g., BALB/c strain. In yet another embodiment, the mouse is a mix of a BALB strain and another aforementioned strain.

[00181] In one embodiment, the non-human animal is a rat. In one embodiment, the rat is selected from a Wistar rat, an LEA strain, a Sprague Dawley strain, a Fischer strain, F344, F6, and Dark Agouti. In one embodiment, the rat strain is a mix of two or more strains selected from the group consisting of Wistar, LEA, Sprague Dawley, Fischer, F344, F6, and Dark Agouti.

[00182] In some embodiments, a genetically engineered animal disclosed herein expresses in its serum a humanized Clq protein comprising one or more chimeric Clq polypeptides. In specific embodiments, the animal expresses in its serum a Clq protein composed of chimeric Clqa, Clqb and Clqc polypeptides, each of which comprises a globular head domain mat is substantially human. In some embodiments, the level of a humanized Clq protein in the serum of a genetically engineered animal is comparable to the level of the Clq protein in a control animal without the humanization, as detected by any of conventional assays such as Western Blot or ELISA. By "comparable" it is meant to refer to level and values within a variation of e.g., 10%, 20%, 30%, or 40%.

[00183] In some embodiments, a genetically engineered animal expressing a humanized Clq protein in its serum displays complement activity. In some embodiments, the complement activity is detectable by a classical hemolysis assay, as further illustrated in the examples below. In specific embodiments, the genetically engineered animal displays classical hemolytic activity in its serum at a level comparable to the level in a control animal without the humanization. In other embodiments, the complement activity is detectable in an in vitro complement-dependent cytotoxicity (CDC) assay. In specific embodiments, the serum of a genetically engineered animal comprising a humanized Clq protein displays CDC activity at a level comparable to that of normal human serum.

[00184] In a further aspect, provided herein are methods of making the genetically modified non-human animal described herein. [00185] In some embodiments, the method comprises modifying the genome of a non- human animal such that the modified genome comprises a nucleic acid molecule encoding a humanized Clq polypeptide (i.e., a humanized Clqa, Clqb, and/or Clqc polypeptide).

[00186] In some embodiments, the modified genome comprises a nucleic acid encoding a chimeric Clq polypeptide, wherein the nucleic acid is located at a locus different from an endogenous Clq locus. In certain embodiments, a contiguous nucleic acid fragment comprising multiple nucleic acid molecules encoding different humanized Clq polypeptides is located at a locus different from an endogenous Clq locus. For example, a contiguous nucleic acid fragment comprising a nucleic acid sequence encoding a humanized Clqa polypeptide, a nucleic acid sequence encoding a humanized Clqb polypeptide, and a nucleic acid sequence encoding a humanized Clqc polypeptide, is located at a locus different from the endogenous Clq locus.

[00187] In some embodiments, the modified genome comprises a nucleic acid encoding a chimeric Clq polypeptide wherein the nucleic acid is located at an endogenous Clq locus. In certain embodiments, a contiguous nucleic acid fragment comprising a nucleic acid sequence encoding a humanized Clqa polypeptide, a nucleic acid sequence encoding a humanized Clqb polypeptide, and a nucleic acid sequence encoding a humanized Clqc polypeptide, is located at an endogenous Clq locus.

[00188] The modification to introduce a nucleic acid encoding a chimeric C lq polypeptide into an endogenous Clq locus can, in some embodiments, result in replacement of an endogenous Clq nucleotide sequence with a human Clq nucleotide sequence. In one embodiment, the replacement comprises the replacement of sequences of Clqa, Clqb, and Clqc.

[00189] Humanization may be accomplished by creating a large targeting vector that incorporates a genetic modification, e.g., a genetic modification in one, two or all three Clq loci and then introducing the large targeting vector into non-human (e.g., rodent such as mouse or rat) ES cells to make a non-human animal such as a mouse, e.g., as described in Example 1, or a rat, e.g., as described in Example 2.

[00190] Thus, in one embodiment, provided herein is a large targeting vector for making a genetically modified animal of the present disclosure. In an exemplary embodiment, the large targeting vector comprises 5' and 3' mouse homology arms; a DNA fragment comprising the Clqa gene which comprises a replacement of partial sequence of mouse Clqa coding exon 3 with partial sequence of human Clqa coding exon 3; a DNA fragment comprising the Clqb gene which comprises a replacement of partial sequence of mouse Clqb coding exon 3 with partial sequence of human Clqb coding exon 3; a DNA fragment comprising the Clqc gene which comprises a replacement of partial sequence of mouse Clqc coding exon 3 with partial sequence of human Clqc coding exon 3; and a selection cassette. In another exemplary' embodiment, the large targeting vector comprises 5' and 3' rat homology' arms; a DNA fragment comprising the CI qa gene which comprises a replacement of partial sequence of rat Clqa coding exon 3 with partial sequence of human Clqa coding exon 3; a DNA fragment comprising the Clqb gene which comprises a replacement of partial sequence of rat Clqb coding exon 3 with partial sequence of human Clqb coding exon 3; a DNA fragment comprising the Clqc gene which comprises a replacement of partial sequence of rat Clqc coding exon 3 with partial sequence of human Clqc coding exon 3; and a selection cassette.

[00191] In some embodiments, a large targeting vector is a genetically modified bacterial artificial chromosome (BAC) clone. A BAC clone carrying one or more of non-human (e.g., rodent) Clqa, Clqb and Clqc genes can be modified and humanized using bacterial homologous recombination and VELOCIGENE® technology (see, e.g., U.S. 6,586,251 and Valenzuela et al. #003), High-throughput engineering of the mouse genome coupled with high-resolution expression analysis. Nature Biotech. 21(6): 652-659). In embodiments where the BAC clone comprises more than one non-human Clq gene (e.g., a combination of non-human Clqa, Clqb and Clqc genes), the multiple non-human Clq genes can be sequentially modified through serial bacterial homologous recombination. As a result, a non-human Clq nucleotide sequence has been deleted from the original BAC clone, and a human Clq nucleotide sequence has been inserted, resulting in a modified BAC clone carrying one or more humanized Clq genes, flanked by 5' and 3' non-human homology arms.

[00192] A selection cassette is a nucleotide sequence inserted into a targeting construct to facilitate selection of cells (e.g., bacterial cells, ES cells) mat have integrated the construct of interest. A number of suitable selection cassettes are known in the art (Neo, Hyg, Pur, CM, SPEC, etc.). In addition, a selection cassette may be flanked by recombination sites, which allow deletion of the selection cassette upon treatment with recombinase enzymes. Commonly used recombination sites are loxP and Fit, recognized by Cre and Flp enzymes, respectively, but others are known in the art. A selection cassette may be located anywhere in the construct outside the coding region. In one embodiment, the selection cassette is inserted upstream of an inserted human Clqa sequence.

[00193] The large targeting vector, such as a modified BAC clone can be introduced into non-human (e.g., rodent) embryonic stem (ES) cells by known techniques, e.g.,

electroporation. Bom mouse ES cells and rat ES cells have been described in the art. See, e.g., US 7,576,259, US 7,659,442, US 7,294,754, and US 2008-0078000 Al (all of which are incorporated herein by reference) describe mouse ES cells and the VELOCIMOUSE® method for making a genetically modified mouse; US 2014/0235933 Al, US 2014/0310828 Al, Tong etal. (2010) Nafure 467:211-215, and Tong et al. (2011) Nat Protoc. 6(6):

doi: 10.1038/nprot.2011.338 (all of which are incorporated herein by reference) describe rat ES cells and methods for making a genetically modified rat. In some embodiments, the recipient ES cell to which a modified BAC clone is to be introduced comprises a deletion of a nucleotide sequence at an endogenous Clq locus. In some embodiments, the deletion comprises the coding region of one or more of the Clqa, CI qb and Clqc genes. In specific embodiments, the deletion comprises the coding regions of all of the Clqa, CI qb and Clqc genes; for example, a deletion that comprises the start codon of Clqa through the stop codon of Clqb. In some embodiments, the recipient ES cell is heterozygous for a deletion at an endogenous Clq locus. In other embodiments, the recipient ES cell is homozygous for a deletion at an endogenous Clq locus.

[00194] Upon completion of gene targeting, ES cells or genetically modified non-human animals are screened to confirm successful incorporation of exogenous nucleotide sequence of interest or expression of exogenous polypeptide. Numerous techniques are known to those skilled in the art, and include (but are not limited to) Southern blotting, long PCR, quantitative PCR (e.g., real-time PCR using TAQMAN™), fluorescence in situ

hybridization, Northern blotting, flow cytometry, Western analysis, immunocytochemistry, immunohistochemistry, etc. In one example, non-human animals (e.g., mice) bearing the genetic modification of interest can be identified by screening for loss of mouse allele and/or gain of human allele using a modification of allele assay described in Valenzuela et al. (2003) High-throughput engineering of the mouse genome coupled with high-resolution expression analysis, Nature Biotech. 21(6):652-659. Other assays that identify a specific nucleotide or amino acid sequence in the genetically modified animals are known to those skilled in the art. Selected ES cells are then used as donor ES cells for injection into a pre- morula stage embryo (e.g., 8-cell stage embryo) by using the VELOCIMOUSE® method (see, e.g., US 7,576,259, US 7,659,442, US 7,294,754, and US 2008-0078000 Al), or methods described in US 2014/0235933 Al and US 2014/0310828 Al. The embryo comprising the donor ES cells is incubated until blastocyst stage and then implanted into a surrogate mother to produce an F0 rodent. Pups bearing the humanized Clq gene can be identified by genotyping of DNA isolated from tail snips using loss of non-human allele and/or gain of human allele assays. Non-human animals heterozygous for a humanized Clq gene can be crossed to generated homozygous offersprings.

[00195] In one aspect, a method for making a chimeric human/non-human Clq molecule is provided, comprising expressing in a single cell a chimeric Clq protein from a nucleotide construct as described herein. In one embodiment, the nucleotide construct is a viral vector; in a specific embodiment, the viral vector is a lentiviral vector. In one embodiment, the cell is selected from a CHO, COS, 293, HeLa, and a retinal cell expressing a viral nucleic acid sequence (e.g., a PERC.6™ cell).

[00196] In one aspect, a cell that expresses a chimeric human/non-human Clq protein is provided. In one embodiment, the cell comprises an expression vector comprising a chimeric Clq sequence as described herein. In one embodiment, the cell is selected from CHO, COS, 293, HeLa, and a retinal cell expressing a viral nucleic acid sequence (e.g., a PERC.6™ cell).

[00197] A chimeric Clq molecule made by a non-human animal as described herein is also provided, wherein, in one embodiment, the chimeric Clq molecule comprises an amino acid sequence of all or substantially all of a globular head domain of a human Clqa, Clqb, and/or Clqc polypeptides, and at least stem and/or stalk domains from a non-human Clq protein, e.g., mouse Clq protein.

[00198] In addition to a genetically engineered non-human animal, anon-human embryo (e.g., a rodent, e.g., a mouse or a rat embryo) is also provided, wherein the embryo comprises a donor ES cell that is made as disclosed hereinabove or is derived from a non- human animal (e.g., a rodent, e.g., a mouse or a rat) as described herein. In one aspect, the embryo comprises an ES donor cell that comprises a chimeric Clq gene, and host embryo cells.

[00199] Also provided is a tissue, wherein the tissue is derived from anon-human animal (e.g., a rodent, e.g., a mouse or a rat) as described herein, and expresses a chimeric Clq protein. In some embodiments, a tissue is selected from blood, plasma, serum, bone marrow, spleen, lymph nodes, brain, and a combination thereof. [00200] In addition, a non-human cell isolated from a non-human animal as described herein is provided. In one embodiment, the cell is an ES cell. In one embodiment, the cell is a dendritic cell.

F. Rodent Model for Testing Human Therapies

[00201] Clq molecules are being studied as targets for bispecific agents, e.g., bispecific antibodies, with one arm binding human Clq and another binding an antigen of interest.

[00202] During preclinical drug development stage, candidate agents are typically studied based on their efficacy, toxicity, and other pharmacokinetic and pharmacodynamics properties. Candidate agents, such as antibodies, typically target a human antigen—as the end goal of investigation is to develop a human therapy. Many preclinical studies are conducted in large animals such as primates as their physiology and drug metabolism are most similar to humans. To conduct effective preclinical investigations relating to efficacy, toxicity, and other parameters of a drug candidate, first, the drug candidate must be determined to recognize primate Clq molecule.

[00203] However, a separate factor complicating development of anti-Clq therapy is that large primates such as chimpanzees are endangered and in many countries studies in chimpanzees are prohibited; while studies in other primates, e.g., cynomolgus monkeys (Macaca fascicularis), may raise ethical concerns. Thus, any preliminary data on a specific therapeutic candidate that can be obtained in a smaller animal model, such as a rodent, e.g., a mouse, can be helpful in determining further progress of preclinical investigations in large primates.

[00204] The most useful small animal model to conduct preliminary studies is a non- human animal, e.g., a rodent, that expresses a human or humanized Clq protein, and allows the testing of anti-Clq drug candidates that also target, for example a tumor antigen, viral antigen, or bacterial antigen (such, as for example, a Staphylococcus antigen).

[00205] Accordingly, in some aspects, provided herein is a rodent model (such as, for example, a mouse or rat model) for testing C lq-targeted ("anti-Clq") therapeutic agents. In some embodiments, provided herein is a rodent model (such as, for example, a mouse or rat model) for testing anti-Clq antigen-binding proteins. In some embodiments, provided herein is a rodent model (such as, for example, a mouse or rat model) for testing anti-Clq antibodies. In some such embodiments, provided is a rodent model for testing anti-Clq multi-specific, e.g. bispecific, antigen-binding proteins or anti-Clq bispecific antibodies. As such, an anti-Clq multi-specific antigen-binding protein, e.g. an anti-Clq bispecific antigen-binding protein, targets or specifically binds said humanized Clq polypeptide or humanized Clq complex and at least one other antigen of interest. In various aspects, the rodent model for testing anti-Clq bispecific antigen-binding proteins wherein the antigen- binding protein is capable of binding both a humanized Clq complex (with one or more Clqa, Clqb, and/or Clqc polypeptides of the complex being humanized) and the antigen of interest comprises a nucleic acid sequence encoding a humanized Clq complex, wherein the humanized Clq polypeptide is selected from the group consisting of Clqa, Clqb, Clqc, and/or a combination thereof, and a cell expressing or comprising the antigen of interest. In one embodiment, the rodent comprises a dendritic cell expressing said humanized Clq protein(s).

[00206] The term "germline" in reference to an immunoglobulin nucleic acid sequence includes a nucleic acid sequence mat can be passed to progeny.

[00207] The phrase "immunoglobulin molecule" includes two immunoglobulin heavy chains and two immunoglobulin light chains. The heavy chains may be identical or different, and the light chains may be identical or different.

[00208] The term "antigen-binding protein" as used herein includes antibodies and various naturally produced and engineered molecules capable of binding the antigen of interest. Such include, e.g., domain-specific antibodies, single domain antibodies (e.g., derived from camelids and fish, etc.), domain-deleted antibodies, chimeric antibodies, CDR-grafted antibodies, diabodies, triabodies, tetrabodies, minibodies, nanabodies (e.g., monovalent nanobodies, bivalent nanobodies, etc.), small modular immunopharmaceuticals (SMEPs), shark variable IgNAR domains, T cell receptor molecules and molecules comprising T cell receptor variable domains and fragments thereof, etc. Antigen-binding protein may also include antigen-binding fragments such as, e.g., (i) Fab fragments; (ii) F(ab')2 fragments; (iii) Fd fragments; (iv) Fv fragments; (v) single-chain Fv (scFv) molecules; (vi) dAb fragments; and (vii) minimal recognition units consisting of the amino acid residues that mimic the hypervariable region of an antibody (e.g., an isolated complementarity determining region (CDR) such as a CDR3 peptide), etc.

[00209] The term "antibody", as used herein, includes immunoglobulin molecules comprising four polypeptide chains, two heavy (H) chains and two light (L) chains interconnected by disulfide bonds. Each heavy chain comprises a heavy chain variable domain and a heavy chain constant region (CH). The heavy chain constant region comprises three domains, CHI, CH2 and CH3. Each light chain comprises a light chain variable domain and a light chain constant region (CL). The heavy chain and light chain variable domains can be further subdivided into regions of hypervariability, termed complementarity determining regions (CDR), interspersed with regions that are more conserved, termed framework regions (FR). Each heavy and light chain variable domain comprises three CDRs and four FRs, arranged from amino-terminus to carboxy-terminus in the following order: FR1, CDR1, FR2, CDR2, FR3, CDR3, FR4 (heavy chain CDRs may be abbreviated as HCDR1, HCDR2 and HCDR3; light chain CDRs may be abbreviated as LCDR1, LCDR2 and LCDR3).

[00210] As used herein, "an antibody that binds Clq" or an "anti-Clq antibody" includes antibodies and antigen-binding fragments thereof that specifically recognize a single Clq subunit (e.g., Clqa, Clqb, and/or Clqc), as well as antibodies and antigen-binding fragments thereof that specifically recognize a dimeric complex of two Clq subunits (e.g., Clqa/Clqb, and Clqc/Clqc dimers) as well as trimers of dimers. The antibodies and antigen-binding fragments can also bind soluble Clq and/or IgM or IgG bound Clq.

[00211] The term "high affinity" antibody or antigen-binding protein refers to an antibody that has a KD with respect to its target epitope about of 10 ^"9 M or lower (e.g., about lxlO ^"9 M, lxlO ^"10 M, lxlO ^"11 M, or about lxlO ^"12 M).

[00212] The phrase "bispecific antibody" or "bispecific antigen-binding protein" includes an antibody or antigen-binding protein capable of selectively binding two epitopes.

Bispecific antibodies generally comprise two arms, each binding a different epitope (e.g., two heavy chains with different specificities) - either on two different molecules (e.g., different epitopes on two different immunogens) or on the same molecule (e.g., different epitopes on the same immunogen). If a bispecific antibody or antigen-binding protein is capable of selectively binding two different epitopes (a first epitope and a second epitope), the affinity of the first antibody arm for the first epitope will generally be at least one to two or three or four or more orders of magnitude lower than the affinity of the first antibody arm for the second epitope, and vice versa. Epitopes specifically bound by the bispecific antibody can be on the same or a different target (e.g., on the same or a different protein). Exemplary bispecific antibodies include those with a first antibody arm specific for Clq, and a second antibody arm specific for an antigen of interest (e.g., an antigen of an infectious agent). Bispecific antibodies can be made, for example, by combining heavy chains that recognize different epitopes of the same immunogen. For example, nucleic acid sequences encoding heavy chain variable sequences that recognize different epitopes of the same immunogen can be fused to nucleic acid sequences encoding the same or different heavy chain constant regions, and such sequences can be expressed in a cell that expresses an immunoglobulin light chain. A typical bispecific antibody has two heavy chains each having three heavy chain CDRs, followed by (N-terminal to C -terminal) a CHI domain, a hinge, a CH2 domain, and a CH3 domain, and an immunoglobulin light chain that either does not confer epitope-binding specificity but that can associate with each heavy chain, or that can associate with each heavy chain and that can bind one or more of the epitopes bound by the heavy chain epitope-binding regions, or that can associate with each heavy chain and enable binding of one or both of the heavy chains to one or both epitopes. Similarly, the phrase "multispecific antibody" includes an antibody capable of selectively binding multiple epitopes (e.g., two, three, four epitopes).

[00213] The phrase "complementarity determining region," or the term "CDR," includes an amino acid sequence encoded by a nucleic acid sequence of an organism's

immunoglobulin genes that normally (i.e., in a wild-type animal) appears between two framework regions in a variable region of a light or a heavy chain of an immunoglobulin molecule. A CDR can be encoded by, for example, a germline sequence or a rearranged or unrearranged sequence, and, for example, by a naive or a mature B cell. A CDR can be somatically mutated (e.g., vary from a sequence encoded in an animal's germline), humanized, and/or modified with amino acid substitutions, additions, or deletions. In some circumstances (e.g., for a CDR3), CDRs can be encoded by two or more sequences (e.g., germline sequences) that are not contiguous (e.g., in an unrearranged nucleic acid sequence) but are contiguous in a B cell nucleic acid sequence, e.g., as the result of splicing or connecting the sequences (e.g., V-D-J recombination to form a heavy chain CDR3).

[00214] The phrase "functional fragment" includes fragments of antigen-binding proteins such as antibodies that can be expressed, secreted, and specifically bind to an epitope with a KD in the micromolar, nanomolar, or picomolar range. Specific recognition includes having a KD that is at least in the micromolar range, the nanomolar range, or the picomolar range.

[00215] The phrase "heavy chain," as in "immunoglobulin heavy chain", includes an immunoglobulin heavy chain sequence, including immunoglobulin heavy chain constant region sequence, from any organism. Heavy chain variable domains include three heavy chain CDRs and four FR regions, unless otherwise specified. Fragments of heavy chains include CDRs, CDRs and FRs, and combinations thereof. A typical heavy chain has, following the variable domain (from N-terminal to C-terminal), a CRI domain, a hinge, a CH2 domain, and a CH3 domain. A functional fragment of a heavy chain includes a fragment that is capable of specifically recognizing an epitope (e.g., recognizing the epitope with a KD in the micromolar, nanomolar, or picomolar range), that is capable of expressing and secreting from a cell, and that comprises at least one CDR. A heavy chain variable domain is encoded by a variable region gene sequence, which generally comprises VH, DH, and JH segments derived from a repertoire of VH, DH, and ½ segments present in the germline. Sequences, locations and nomenclature for V, D, and J heavy chain segments for various organisms can be found on the website for the International Immunogenetics Information System (IMGT database).

[00216] The phrase "light chain", as in "immunoglobulin light chain", includes an immunoglobulin light chain sequence from any organism, and unless otherwise specified includes human kappa and lambda light chains and a VpreB, as well as surrogate light chains. Light chain variable domains typically include three light chain CDRs and four framework (FR) regions, unless otherwise specified. Generally, a full-length light chain includes, from amino terminus to carboxyl terminus, a variable domain that includes FR1- CDR1 -FR2-CDR2-FR3-CDR3-FR4, and a light chain constant region. A light chain variable domain is encoded by a light chain variable region gene sequence, which generally comprises V _L and J _L segments, derived from a repertoire of V and J segments present in the germline. Sequences, locations and nomenclature for V and J light chain segments for various organisms can be found on the website for the International Immunogenetics Information System (IMGT database). Light chains include those, e.g., that do not selectively bind any epitopes recognized by antigen-binding protein (e.g., antibody) in which they appear. Light chains also include those that bind and recognize, or assist the heavy chain with binding and recognizing, one or more epitopes selectively bound by the antigen-binding protein (e.g., an antibody) in which they appear.

[00217] In various embodiments, the antigen-binding protein binds both Clq and an antigen of interest.

[00218] In another embodiment, the rodent model is used to determine if a candidate bispecific antigen-binding protein is capable of blocking or affecting an antigen of interest which is an infectious disease associated antigen. In one embodiment, the rodent is infected with an infectious agent. In one embodiment, the infectious disease associated antigen is a viral antigen. [00219] In another embodiment, wherein the antigen of interest is an infectious disease associated antigen, the antigen of interest is a bacterial antigen. In some aspects, the bacterial antigen is a Staphylococcus antigen.

[00220] In some aspects, the Clq-based bispecific antigen binding protein is a human Clq based antigen binding protein. In one embodiment, the antigen binding protein is an antibody, e.g., a human antibody, or an antigen-binding fragment thereof.

[00221] In some embodiments, the testing of a bispecific antibody with one arm targeting human Clq and another arm targeting an infectious disease associated antigen (such as S. aureus), is done in vivo using a genetically engineered animal disclosed herein that expresses a humanized Clq having a human or substantially human globular head domain in each of its Clqa, Clqb and Clqc polypeptide chains. The animal can be infected with the infectious disease associated antigen (such as S. aureus), and the bispecific antibody can be evaluated in such animal, e.g., in its ability to reduce bacterial burden and/or improve survival.

G. Use of Genetically Modified Non-Human Animals

[00222] Further disclosed are various methods of using the genetically modified non- human animals described herein.

[00223] In one embodiment, provided herein is a method of screening therapeutic drug candidates that target an antigen of interest comprising (a) providing or receiving a genetically modified rodent (such as a mouse or rat) comprising at its endogenous rodent Clq locus a nucleic acid sequence encoding a chimeric, humanized Clqa polypeptide, Clqb polypeptide and/or Clqc polypeptide and/or any combination thereof, (b) introducing into said genetically modified rodent an antigen of interest, (c) contacting said rodent with a drug candidate of interest, wherein the drug candidate is directed against the human Clq and the antigen of interest, and (d) assaying if the drug candidate is efficacious in preventing, reducing or eliminating cells or viruses characterized by the presence or expression of the antigen of interest. In various embodiments, the rodent expresses a functional humanized Clq complex. In one embodiment of the method, the genetically modified rodent comprises at the endogenous rodent Clq locus a nucleic acid sequence encoding a chimeric Clqa polypeptide comprising a globular head domain that is substantially human, a chimeric Clqb polypeptide comprising a globular head domain that is substantially human, and a chimeric Clqc polypeptide comprising a globular head domain that is substantially human. In one embodiment of the method described herein, the rodent does not comprise a nucleic acid sequence encoding a functional globular head domain of the corresponding rodent protein.

[00224] In various embodiments of the method described herein, introduction of the antigen of interest into the genetically modified rodent described herein may be

accomplished by any methods known to those skilled in the art, which may include, without limitation, transgenesis, injection, infection, tissue or cell transplantation. As such, introduction may be achieved by expressing in the rodent the antigen of interest, which can comprise genetically modifying said rodent to express the antigen of interest. Alternatively, introduction may comprise introduction into said rodent a cell expressing the antigen of interest, e.g., as in cell or tissue transplantation. Introduction may also comprise infecting said rodent with the antigen of interest, e.g., as in bacterial or viral infection. In one embodiment, the antigen of interest may be a human antigen of interest. In another embodiment, it may be a bacterial or a viral antigen of interest. The antigen of interest may be a tumor-associated antigen or an infectious disease associated antigen, e.g., a bacterial or a viral antigen, as described in detail above.

[00225] In another embodiment, provided herein is a method of assessing or screening therapeutic drug candidates that target an antigen of interest comprising mixing a cell or virus expressing the antigen of interest with (i) a drug candidate of interest, wherein the drug candidate is directed against the human Clq and the antigen of interest, and (ii) a blood sample (e.g., a whole blood sample) of a genetically modified rodent described herein, and (b) assaying to determine whether the drug candidate is efficacious in reducing or eliminating the cell or virus characterized by the presence or expression of the antigen of interest. The determination can be made based on measuring, e.g., percentage survival of the cell or virus where a drug candidate is used as compared to a control drug or no drug at all. The antigen of interest may be a tumor-associated antigen or an infectious disease associated antigen, e.g., a bacterial or a viral antigen, as described in detail above. In some embodiments, the antigen of interest is a bacterial antigen such as a Staphylococcus antigen. In some embodiments, the cell is a bacterial cell such as a Staphylococcus cell.

[00226] In various embodiments of the methods of screening a therapeutic drug candidate, the drug candidate may be an antigen-binding protein, e.g., an antibody, e.g., a bispecific antibody. In various aspects, such drug candidate is capable of binding both human Clq and the antigen of interest. The antigen of interest may be a human antigen. The antigen of interest may also be a primate, e.g., a monkey, antigen. Thus, the drug candidate used for screening may be capable of binding both a human antigen and a corresponding primate antigen, in addition to binding human Clq. The drug candidate may also be capable of binding primate, e.g., monkey, Clq. Thus, the drug candidate may be capable of binding both human and primate, e.g., monkey, Clq; and also, in one embodiment, be capable of binding a human antigen of interest. In another embodiment, the antigen of interest may be a bacterial or a viral antigen, and the drug candidate may be capable of binding both the human and primate, e.g., monkey, Clq and the antigen of interest (e.g., a viral or bacterial antigen).

[00227] In various embodiments of the methods described herein, the therapeutic candidate is capable of reducing, eliminating, or preventing a disease. In one embodiment, the disease is a tumor, and the therapeutic candidate is capable of reducing, eliminating, or preventing tumor growth as compared to an agent that does not target the antigen of interest. In such an embodiment of the method, determination whether the drug candidate is efficacious in preventing, reducing or eliminating cells characterized by the presence or expression of the antigen of interest can be performed using a tumor volume assay, a tumor cell killing assay, induction of apoptotic markers in tumors, reduction in blood vessel growth in tumors, infiltration of immune cells into tumors, etc. In another embodiment, the disease is an infectious disease, and a therapeutic candidate is capable reducing, eliminating, or preventing a bacterial or a viral infection as compared to an agent that does not target the antigen of interest. In such an embodiment of the method, determination whether the drug candidate is efficacious in preventing, reducing or eliminating cells or viruses characterized by the presence or expression of the antigen of interest can be performed using a measure of bacterial or viral titers, induction of apoptotic markers in infected cells, etc., or by measuring survival of bacterial cells or viruses using a blood sample (e.g., a whole blood sample).

[00228] In addition to evaluating bispecific antibodies with one arm targeting a humanized Clq protein and the other arm targeting an antigen of interest, the genetically engineered non-human animals expressing a humanized Clq protein disclosed herein are useful for evaluating the effects of other antibodies, e.g., monospecific antibodies having a human Fc region (such as a human antibody). The binding of a humanized C 1 q to the human Fc region of an antibody can activate classical complement pathway, which leads to complement-dependent cytotoxicity (CDC). There had been a difficulty in assessing whether an antibody has an effect on the complement system of a recipient, or whether or how much of the efficacy of a therapeutic antibody is attributable to the action of the complement system. The genetically engineered non-human animals expressing a humanized Clq disclosed herein will permit assessment of whether an antibody having a human Fc region (e.g., a human antibody) will be capable of activating classical complement pathway, and the results of such assessment will more accurately reflect whether such antibody will activate classical complement pathway when given to human patients.

[00229] Therefore, in a further aspect, disclosed herein is a method of assessing whether an antibody comprising a human Fc region can activate classical complement pathway by utilizing a genetically engineered non-human animal (e.g., a rodent such as a mouse or rat) expressing a humanized Clq protein disclosed herein.

[00230] In some embodiments, the method utilizes a cell expressing an antigen of interest on the cell surface, a candidate antibody comprising a human Fc region and directed to the antigen of interest, and a serum sample from a genetically engineered non-human animal expressing a humanized Clq protein, and is designed to evaluate in vitro complement- dependent cytotoxicity of the cell expressing the antigen of interest. In specific

embodiments, the cell is first mixed with the candidate antibody to allow the antibody to bind to the antigen of interest expressed on the cell surface; then a serum sample is added to the cell-antibody mixture to permit binding of the Clq proteins in the serum sample to antibodies bound to the antigen of interest on the cell. Cytotoxicity (i.e., killing of said cell) can then be measured using reagents readily available, including those from commercial sources (e.g., CytoTox-Cflo™ reagent from Promega), using flow cytometry methods or release of pre-loaded radioisotopes from target cells. Cytotoxicity using a serum sample from a humanized non-human animal expressing a humanized Clq protein can be compared with a serum sample from a control non-human animal without the humanization (negative control), and with a human serum sample (positive control).

[00231] In some embodiments, cells suitable for use in this method include Raji cells, Ramos cells, Daudi cells, HEK293 cells, and A431 cells. In some embodiments, Raji cells, Ramos cells, or Daudi cells are used in the present methods. The cells can naturally express an antigen of interest on the cell surface, or can be modified to recombinantly express an antigen of interest on the cell surface. [00232] In some embodiments, the candidate antibody is a human antibody directed to a tumor antigen, a bacterial or viral antigen, etc. Examples of candidate antibodies include, e.g., anti-CD20, etc.

[00233] In some embodiments, the methods of assessing whether an antibody comprising a human Fc region can activate classical complement pathway is performed in vivo by comparing the effects of a candidate antibody in a Clq humanized animal with a Clq knockout animal. To rule out that the effect is due to ADCC (as opposed to CDC), NK cells, neutrophils and macrophages in the animals could be depleted, leaving the complement system intact.

EXAMPLES

[00234] The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds, compositions, articles, devices and/or methods claimed herein are made and evaluated, and are intended to be purely exemplary and are not intended to limit the disclosure. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.), but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, temperature is in °C or is at ambient temperature, and pressure is at or near atmospheric.

Example 1. Generation of Humanized Clq Mouse

[00235] Mouse genomic sequence of C 1 q genes can be found under NCBI Accession Number NC_000070.6, and Clq loci are located at mouse chromosome 4D3 (Reference GRCm38.p4 C57BL/6J). Human genomic sequence of Clq genes can be found under NCBI Accession Numbers NG_007281.1, NG_007283.1 and NG_007565.1, and Clq loci are located at human chromosome lp36.1. Some examples of genomic and amino acid sequences for human and mouse Clq are listed below in Tables 1 and 2. Predicted signal peptide in the listed SEQ ID NOs boundaries are indicated. The signal peptide boundaries are also boxed in Figures 3A-3C.

Table 1: GeneBank Accession Numbers for Mouse Clq sequences

Table 2: GeneBank Accession Numbers for Human Clq Sequences

[00236] Briefly, to generate chimeric Clq mice, the mouse C 1 q locus was humanized by construction of a unique targeting vector from human and mouse bacterial artificial chromosomes (BAG) DNA using VELOCIGENE® technology (see, e.g., US Patent No. 6,586,251 and Valenzuela et al. (2003) High-throughput engineering of the mouse genome couple with high-resolution expression analysis. Nat. Biotech. 21(6): 652-659, both incorporated herein by reference) using the mouse BAC library Mouse BAC ES release 2 (Incyte Genomics, 129/SvJ in pBeloBACl 1). DNA from mouse BAC clone 302p21 was modified to replace genomic DNA encoding portions of mouse Clqa, Clqb, and Clqc (mouse Clq genes are located in close proximity to one another on the reverse strand of mouse chromosome 4) with corresponding portions of human Clqa, Clqb, and Clqc, respectively (human Clq genes are located in close proximity to one another on the forward strand of human chromosome 1).

[00237] The mouse Clq BAC was modified by introduction of human Clq sequences, to generate a BAC comprising humanized Clqa, CI qb, and Clqc genes. The sequences encoding substantially the mouse Clqa, Clqb, and Clqc globular domains were replaced, respectively, with the corresponding sequences encoding substantially the human Clqa, Clqb, and Clqc globular domains. Alignments of human and mouse Clq (and rat) protein sequences are depicted in Figures 3 A, B, and C, where the boundaries for globular heads are as indicated, and the boundaries of mouse/human genes are indicated with arrows. The amino acid sequences of the humanized mouse Clqa, Clqb, and Clqc proteins are set forth in SEQ ID NOs: 10, 11, and 12, respectively, and are listed in Table 3 below, with mouse sequences italicized.

Table 3: Amino Acid Sequences of the Chimeric Mouse/Human Clq proteins

Example 1.1. Generation of Clq Knock Out Mouse

[00238] In detail, first, a mouse Clq locus comprising all three Clq genes was modified to delete the 17.6 kB nucleotide sequence comprising genes encoding mouse Clq (see Figure 1 A). A targeting vector comprising LacZ-neo cassette, 20 Kb 5' homology' arm and 55 kb 3' homology arm was introduced into mouse BAC 302p21 by bacterial homologous recombination such that 17.6 Kb of nucleotide sequence comprising all three mouse Clq genes from Clqa ATG to Clqb stop codon was deleted. The deletion spanned Clqa exon 2 just after the start ATG through Clqb exon 3 past the stop codon including 19 bp into the Clqb 3 ^' UTR. The cassette was inserted such that the LacZ coding sequence was in frame with the Clqa ATG codon. LacZ coding sequence is followed by an SV40 polyadenylation site, then a floxed neomycin resistance cassette under control of the mouse phosphoglycerate kinase 1 (Pgkl) promoter with Pgkl polyadenylation signal. The resultant vector was used to electroporate mouse ES cells to create modified ES cells for generating a mouse that lacked the endogenous Clq locus. The sequences of the various junctions in the deleted locus are labeled in the second schematic diagram in Figure 1C, with corresponding nucleic acid sequences listed in Table 4 below. The junctions shown in Tables in this example only list short nucleotide sequences, but direct one skilled in the art to the location where the sequences were inserted into the mouse genome.

Table 4: Junction Sequences of the mouse CI q Knock Out Locus

[00239] ES cells containing deletion of mouse Clq sequences were identified by a quantitative TAQMAN™ assay (see, e.g., Lie and Petropoulos, 1998. Curr. Opin.

Biotechnology 9:43-48, incorporated herein by reference), modification of allele assay (MO A). Specific primer sets and probes were designed for detecting insertion of the cassette sequences (gain-of-allele, GO A) and deletion of mouse sequences (loss-of-allele, LOA). Table 5 identifies the names and locations of each of primers/probe sets used in the quantitative PCR assays.

Table 5: Primer and Probes Used in a MOA Assay to Confirm Deletion of mouse Clq locus

[00240] Targeted ES cells described above were used as donor ES cells and introduced into an 8-cell stage mouse embryo by the VELOCIMOUSE® method (see, e.g., US Pat. No. 7,294,754 and Poueymirou et al. (2007) FO generation mice that are essentially fully derived from the donor gene-targeted ES cells allowing immediate phenotypic analyses Nature Biotech. 25(1 ):91-99). VELOCIMICE® (FO mice fully derived from the donor ES cell) independently bearing a mouse Clq deletion were identified by genotyping using a modification of allele assay (see above) that detects the absence of mouse Clq gene sequences. Modified mouse ES cells comprising the deleted mouse Clq locus (mouse Clq KO HET ES cells) were used for humanized Clq construction as described below.

[00241] The selection cassette used in this method may be removed by methods known by the skilled artisan. For example, ES cells bearing the Clq knock out locus may be transfected with a construct that expresses Cre in order to remove the floxed cassette. The selection cassette may optionally be removed by breeding to mice that express Cre recombinase. Optionally, the selection cassette is retained in the mice.

Example 1.2. Generation of Humanized Clq Mouse

[00242] To generate humanized mouse Clq, donor plasmids were generated by In-Fusion HD Cloning Kits™ (Clontech) using sequences for Clq globular head domains (the same sequences as used for the humanized Clq rat in the Example below) and overlapping mouse sequences. For Clqb humanization construct, a loxP-Ub-Hyg selection cassette was inserted by restriction digest downstream of the human Clqb polyA sequence. For both Clqa and Clqc constructs, a spectinomycin (Spec) selection cassette was inserted by restriction digest downstream of each Clqa and Clqc poly A sequences. The resultant constructs were introduced sequentially into the mouse Clq BAC (302p21) through bacterial homologous recombination followed by selection and/or digestion steps to remove the selection cassettes, as demonstrated in Figure IB. In this particular embodiment, the chimeric nucleic acid sequence for Clqb was introduced first (1 in the figure), followed by introduction of chimeric Clqc DNA (2 in the figure), and then chimeric Clqa DNA (3 in the figure).

[00243] The large targeting vector containing all three chimeric C 1 q genes was electroporated into mouse Clq KO HET ES cells as depicted in Figure 1C, and successful integration was confirmed by a TAQMAN® real-time PCT-based modification of allele (MO A) assay described above. Primers and probes used for the MOA assay, and their locations, are described in Table 6.

Table 6: Primer and Probes Used in MOA Assay to Confirm Presence of Chimeric

Mouse/Human C1 enes

[00244] Junction sequences between various genetically engineered components at the chimeric locus are depicted in Table 7 below, and are indicated on the bottom schematic diagram in Figure 1C. The junctions shown in Tables in this Example only list short nucleotide sequences, but direct one skilled in the art to the location where the sequences were inserted into the mouse genome.

Tabic 7: Junction Se uences of the Chimeric Human/Mouse Cl Locus

[00245] Targeted ES cells described above are used as donor ES cells and introduced into an 8-cell stage mouse embryo by the VELOCIMOUSE® method described above.

VELOCIMICE® independently bearing a humanized Clq genes are identified by genotyping using a modification of allele assay (see above) mat detects the presence of the unique human Clq gene sequences. Mice comprising a heterozygous modification of the Clq genes are bred to homozygousity.

[00246] To generate ES cells without the hygromycin resistance cassette, a pi as mid containing ere recombinase coding sequence was electroporated into mouse Clq KO HET ES cells and resulting ES cell clones were screened for loss of the hygromycin resistance cassette by TaqMan assay using primers and probe depicted in Table 6. Selected clones were men microinjected into 8-cell stage mouse embryos as described above and resulting mice were bred to homozygosity. The resulting expressed chimeric proteins are shown above in Table 3 and the Sequence Listing.

Example 2. Generation of Humanized Clq Rat

[00247] Rat genomic sequence of C lq genes can be found under NCBI Accession Number NC_005104.4, and Clq loci are located at Rat chromosome 5 (Reference Rnor_6.0 Primary Assembly). Human genomic sequence of Clq genes can be found under NCBI Accession Numbers NG_007283.1, NG_007282.1 andNG_007565.1, and Clq loci are located at human chromosome lp36.1. Some examples of genomic and amino acid sequences for rat and human Clq are listed in Tables 8 and 2, respectively. Predicted signal peptide boundaries in the listed SEQ ID NOs are indicated. The signal peptide boundaries are also boxed in Figures 3A-3C. Table 8: GeneBank Accession Numbers for Rat Clq sequences

[00248] To generate chimeric C 1 q rat, briefly, the rat C 1 q locus was humanized by construction of a unique targeting vector from synthesized human sequences and rat bacterial artificial chromosomes (BACs) DNA using the rat BAC library generated for Regeneron by LUCIGEN® from rat Dark Agouti ES cells, and the rat targeting technology described in US 2014/0310828, incorporated herein in its entirety by reference. The BAC sequences were confirmed and updated based on the data from Next Generation

Sequencing. DNA from rat BAC (rat Clq BAC, LUCIGEN®) was modified to replace genomic DNA encoding portions of rat Clqa, Clqb, and Clqc (rat Clq genes are located in close proximity to one another on the reverse strand of rat chromosome 5) with

corresponding portions of human Clqa, Clqb, and Clqc, respectively (human Clq genes are located in close proximity to one another on the forward strand of human chromosome 1)·

[00249] The rat C 1 q BAC generated in-house and described above was modified by introduction of human Clq sequences, to generate a vector comprising humanized Clqa, Clqb, and Clqc genes. The sequences encoding the majority of rat Clqa, Clqb, and Clqc globular domains were replaced, respectively, with the corresponding sequences of human Clqa, Clqb, and Clqc. Alignments of human and rat Clq (and mouse) protein sequences are depicted in Figures 3 A, B, and C, where the boundaries for globular heads are as indicated, and the boundaries of rat/human genes are indicated with arrows. The amino acid sequences of the humanized rat Clqa, Clqb, and Clqc proteins are set form in SEQ ID NOs: 55, 56, and 57, respectively, and are listed in Table 9, with rat sequences italicized.

Example 2.1 Generation of Clq Knock Out Rat

[00250] In detail, first, a rat Clq locus comprising all three Clq genes was modified to delete a 17.6Kb nucleotide sequence comprising genes encoding rat Clq (see Figure 2A). A targeting vector was synthesized to comprise a LacZ gene and a self-deleting hygromycin selection cassette, and the vector contained 5' and 3' homology arms allowing deletion of all three rat Clq genes from Clqa ATG to Clqb stop codon. The vector comprising the Clq sequence deletion was introduced into rat Clq BAC via bacterial homologous recombination (BHR), and the resultant BAC DNA was used to electroporate rat ES cells to create modified ES cells for generating a rat that lacked the endogenous Clq locus. The sequences of the various junctions in the deleted locus are labeled in the second schematic diagram in Figure 2C, with corresponding nucleic acid sequences listed in Table 10 below. The junctions shown in Tables in this example only list short nucleotide sequences, but direct one skilled in the art to the location where the sequences were inserted into the rat genome.

Table 10: Junction Sequences of the deletion of Rat Clq Locus

[00252] Targeted chimeric Clq Dark Agouti ES cells are implanted into Sprague Dawley rat embryos to generate F0 pups bearing deletion of Clq locus. F0 chimeric pups are bred to wild type rats to create Fl pups mat are heterozygous for the genetic manipulation; the presence of the modified allele is confirmed by TAQMAN® assay as described above. Fl pups are subsequently bred to homozygosity.

Example 2.2. Generation of Humanized Clq Rat

[00253] To generate humanized C 1 q rat, plasmids were synthesized by Blue Heron using sequences for human Clq globular head domains (the same sequences as used for the humanized Clq mouse in Example 1 above) and overlapping rat sequences. For Clqb humanization construct, a self-deleting loxP-puromycin (SDC-loxp-Puro) selection cassette was inserted by restriction digest downstream of the human Clqb polyA sequence. For both Clqa and Clqc constructs, a spectinomycin (Spec) selection cassette was inserted by restriction digest downstream of each C 1 qa and C 1 qc poly A sequences. The resultant constructs are introduced sequentially into the Rat Clq BAC from LUCIGEN® through either a combination CRISPR/CAS9 technology and Gibson Assembly or bacterial homologous recombination (BHR) followed by selection and/or digestion steps to remove the selection cassettes, as demonstrated in Figure 2B. In this particular embodiment, the chimeric nucleic acid sequence for Clqb was introduced by BHR first (1 in the figure), followed by BHR of chimeric Clqc DNA (2 in the figure), and then introduction by BHR of chimeric Clqa DNA (3 in the figure).

[00254] The large targeting vector containing all three chimeric Clq genes was electroporated into Rat Clq KO HET ES cells as depicted in Figure 2C, and successful integration was confirmed by a TAQMAN® real-time PCT-based modification of allele (MO A) assay. Primers and probes used for the MOA assay are described in Table 12. Table 12: Primer and Probes Used in MOA Assay to Confirm Presence of Chimeric Human/Rat Clq genes

[00255] Junction sequences between various genetically engineered components at the chimeric locus are depicted in Table 13 below, and are indicated on the bottom schematic diagram in Figure 2C. The junctions shown in Tables in this example only list short nucleotide sequences, but direct one skilled in the art to the location where the sequences were inserted into the rat genome.

Table 13: Junction Sequences of the Chimeric Human/Rat Clq Locus

[00256] Targeted chimeric Clq Dark Agouti ES cells are implanted into Sprague Dawley rat embryos to generate F0 pups bearing the chimeric human/rat Clq locus. F0 chimeric pups are bred to wild type rats to create Fl pups that are heterozygous for the genetic manipulation; the presence of the modified allele is confirmed by TAQMAN® assay as described above. Fl pups are subsequently bred to homozygosity.

Example 3: Characterization of Humanized Clq Mouse

Example 3.1: Chimeric Clq Is Present and Functional in Mouse Serum

[00257] In order to determine if chimeric Clq was expressed and functional in mouse serum, humanized Clq mice were phenotyped by Western blot and classical complement hemolysis assay. All mice were housed and bred in the specific pathogen-free facility at Regeneron Pharmaceuticals. All animal experiments were approved by IACUC and Regeneron Pharmaceuticals. (1) Western blot:

[00258] Serum Clq concentrations were assayed in 1615 HO mice (mice homozygous for humanized Clq as described above) using Western blot, as follows: mouse or normal human serum (NHS) were diluted in PBS. Normal human serum (Quidel) was used as a positive control. Serum was added to electorophoresis sample loading buffer containing mercaptoethanol and SDS and run on a polyacrylamide gel under reducing/denaturing conditions, then transferred onto nitrocellulose membrane. Blots were blocked, then probed with goat anti-human Clq primary antibody (Quidel), followed by detection with donkey anti-goat IgG HRP (Santa Cruz). ThermoScientific Super Signal West Pico

Chemiluminescent Subtrate was used to develop the blot. GE Image Quant LAS4000 was used for imaging.

(2) Classical pathway hemolysis assay:

[00259] Desired number of SRBC (sheep red blood cells) were washed in GVB++ buffer and re suspended at lxlO ⁹ cells/mL and opsonized with rabbit anti-sheep hemolysin.

Sensitized SRBC were diluted to 2xl0 ⁸ cells/mL in GVB++ buffer prior to using in hemolysis assay. Serum from WT littermates (n=5) and 1615HO (n=4) mice was collected at seven to nine weeks of age. Mouse serum was serially diluted in a 6 point, 2-fold dilution series from 1/5 to 1/160 with GVB++ buffer (100 ul diluted serum/well). Immediately, 100 uL of sensitized SRBCs (at 2xl0 ⁸ cells/mL) were added, for a total volume of 200 uL, and incubated 1 hr at 37°C. After the incubation time, cells were spun down by centrifugation at 1250 xg at 4°C. A total of lOOuL of the supernatant was transferred to a fresh 96- well flat bottom plate and read at 541 nm on a Molecular Devices Spectramax M5 microplate reader and SoftMax Pro software. The hemolytic activity was calculated: OD541 of all experimental samples was divided by the OD541 at Maximum cell lysis (cells treated with 100 uL water) and then multiplied by 100. Data represented are single points (duplicates not run).

[00260] As demonstrated in Figure 4, top panel, chimeric Clq proteins, as detected by anti-human Clq antibody, were detected in the serum of humanized Clq mice, albeit less Clq protein was detected in humanized Clq mouse serum than in human serum. The chimeric Clq protein obtained from the humanized mouse displayed similar classical complement activity as measured by hemolysis assay to that observed in the mice comprising wild type mouse Clq (Figure 4, bottom panel). [00261] The concentration of chimeric human/mouse C 1 q in mouse serum was also determined using a sandwich ELISA format with antibodies specific for human head of Clq. The standard curve was generated using a known concentration of human Clq protein, and the concentration of chimeric Clq in mouse serum was determined to be in the range of about 10-30 ug/mL.

Example 4: Humanized Clq Mouse as a Model for Testing Human Therapeutics

[00262] To confirm whether the humanized Clq mouse can serve as a model for testing human therapeutics, we first developed an in vitro assay to assess the ability of humanized Clq to activate complement dependent cytotoxicity (CDC) of Raj i cells (B cells expressing cell-surface antigen CD20) by binding to human anti-CD20 antibody. Therapeutic anti- CD20 antibodies against the B-cell specific cell-surface antigen CD20 have been shown to lead to CDC of B-cells (Glennie et al. 2007, Mechanisms of killing by anti-CD20 monoclonal antibodies, Mol. Immunol., Vol. 44(16) pp.3823-37) and CDC assay using cell lines expressing CD20 has been described previously (Flieger et al. 2000, Mechanisms of Cytotoxicity Induced by Chimeric Mouse Human Monoclonal Antibody IDEC-C2BB in CD20-Expressing Lymphoma Lines, Cell Immunol., Vol. 204(1) pp. 55-63).

[00263] For the CDC bioassay, Raji cells were seeded onto a 96-well assay plates at 10,000 cells/well in 1% BSA containing RPM1 1640. To measure CDC with human or mouse serum (from either humanized Clq or WT mice), the human anti-CD20 antibody was diluted 1 :4 from 2nM to 0.007nM and incubated with cells for 10 minutes at 25°C. At the conclusion of the incubation with the anti-CD20 antibody, the serum was added to cells at a final concentration of 1%. Cytotoxicity was measured after 1 hour of incubation at 37°C and in 5% C02, followed by a 30 minute incubation at 25°C, and addition of CytoTox-Glo™ reagent (Promega, # G9291). CytoTox-Glo™ is a luminescence-based reagent that measures cell killing such that increased luminescence is observed with increased cytotoxicity (measured in relative light units, RLUs). Untreated cells in control wells were lysed by treatment with digitonin 10 minutes before addition of CytoTox-Glo™ reagent to determine maximal killing of cells. Plates were read for luminescence by a Victor X instrument (Perkin Elmer) 10-15 minutes following the addition of CytoTox- Glo™. Where calculated, the percentage of cytotoxicity was calculated with the RLU values by using the following equation:

[00264] In this equation "background cell lysis" is the luminescence from the cells treated with media and serum alone without any anti-CD20 antibody and the "maximum cell lysis" is the luminescence from the cells treated with digitonin. The results, expressed as % cy totoxicity or RLUs, were analyzed using nonlinear regression (4-parameter logistics) with Prism 7 software (GraphPad).

[00265] Complement dependent cytotoxicity (CDC) activity mediated by 2nM human anti-CD20 antibody and normal human serum resulted in 83% of maximum lysis, while CDC mediated by 2nM human CD20 antibody and serum from humanized C 1 q mice was 55-58% of maximum lysis (Figure 5). No cell lysis was detected using wild type mouse serum. Thus, serum containing humanized Clq globular head led to more efficient complement dependent lysis of Raj i cells mediated by the human anti-CD20 antibody compared to the serum containing wild-type mouse Clq protein.

[00266] For in vivo testing, S. aureus infection model was chosen. S. aureus is a major cause of bacteremia in patients, and these infections are often fatal. Mouse models of bacteremia have been developed by many laboratories using a variety of laboratory-adapted and clinical S. aureus isolates and in a variety of mouse backgrounds (O'Keeffe KM, et al, Infect Immun. 2015 Sep;83(9):3445-57. Manipulation of Autophagy in Phagocytes Facilitates Staphylococcus aureus Bloodstream Infection.; Rauch et al, Infect Immun. 2012 Oct;80(10):3721-32. Abscess formation and alpha-hemolysin induced toxicity in a mouse model of Staphylococcus aureus peritoneal infection) to study the infection dynamics and effect of potential therapeutics. A bacteremia model was established to evaluate the activity of bispecific antibodies (bisAbs), with one arm targeting Clq and another arm targeting an antigen expressed on S. aureus, in both reducing bacterial burden and improving survival.

[00267] Humanized Clq mice and control wild type mice were infected intraperitoneally with 1.7 x 10 ⁸ colony forming units (CFUs) per mouse in a 200ul volume of S. aureus Newman grown to log phase, ODmo≤ 1, in TSB at 37°C and washed 3 times in PBS.

Immediately following infection, mice were dosed with lOOug of each bisAb and isotype- matched antibody in a 1 OOul volume, intraperitoneally. Mice were euthanized on Day 3 and kidneys were collected to determine organ burden. Briefly, kidney's were homogenized in 5.0mL PBS using gentleMACS Octo Dissociator (Miltenyi Biotec). Tissue homogenate was diluted in PBS and multiples of 10-fold serial dilutions were plated on LB agar plates and incubated at 37°C overnight. Next day individual colonies were counted to determine bacterial burden at that time point post-infection and results were reported as CFUs/gram tissue.

[00268] BisAbs were tested alongside an isotype control antibody for efficacy in reducing bacterial kidney burden in female humanized Clq mice and WT control mice. Compared to mice treated with isotype control Ab, on day 3 after treatment, 2-4 log reduction of bacterial CFUs was detected in kidneys of bisAbs treated humanized Clq mice; however, similar to results obtained with isotype control antibody, no reduction in bacterial burden was observed in WT mice expressing endogenous mouse Clq treated with BisAbs (data not shown).

[00269] To examine the effect of the bisAbs on survival, humanized Clq mice were infected with 1.5 x 10 ⁸ CFUs per mouse of S. aureus Newman and treated with test antibodies as described above. Instead of sacrificing the mice on Day 3, they were monitored until Day 18. Mice that lost 20% of their starting body weight were sacrificed and recorded as a death. The percentage of surviving animals was reported at the end of the study.

[00270] BisAb was tested alongside an isotype control antibody for efficacy in a survival study in humanized Clq female mice (n=9). As shown in Table 14, at the end of the study, on Day 18 post infection, 100% of the mice treated with BisAb survived, in comparison to 78% of the isotype control treated mice.

Table 14: Survival of Humanized Clq Mice in Bacteremia Model

[00271] In conclusion, this study demonstrates that humanized Clq mice are a valuable model for testing therapeutic agents, such as antibodies (e.g., bispecific antibodies), which are directed against human Clq protein. Example 5: Characterization of Humanized Clq Rat

[00272] In order to determine if chimeric Clq was functional in rat serum, humanized Clq rats described in Example 2 were phenotyped by classical complement hemolysis assay. Results were compared to Clq knock-out (KO) rats and normal human serum All rats were 50% Dark Agouti 50% Sprague Dawley background. All rats were housed and bred in the specific pathogen-free facility at Regeneron Pharmaceuticals. All animal experiments were approved by IACUC and Regeneron Pharmaceuticals.

(1) Classical pathway hemolysis assay

[00273] Desired number of SRBCs (sheep red blood cells) were washed in GVB++ buffer and re suspended at lxl 0 ⁹ cells/mL and opsonized with rabbit anti-sheep hemolysin. Sensitized SRBCs were diluted to 2x10 ⁸ cells/mL in GVB++ buffer prior to using in hemolysis assay. Serum from WT (n=3 females and n=4 males), 100015 HO (homozygous humanized Clq rats) (n=5 females and n=6 males) and homozygous Clq knock-out rats (n=2 females) was collected at ten to seventeen weeks of age. Normal human serum (Qui del) was used as a positive control, while Clq depleted human serum (Qui del) was used as a negative control. Rat and human serum was serially diluted in a 12 point, 2-fold dilution series from 1/5 to 1/10240 with GVB++ buffer (100 ul diluted serum/well).

Immediately, 100 uL of sensitized SRBCs (at 2xl0 ⁸ cells/mL) were added, for a total volume of 200 uL, and incubated 1 hr at 37°C. After the incubation time, cells were spun down by centrifugation at 1250 xg at 4°C. A total of lOOuL of the supernatant was transferred to a fresh 96 -well flat bottom plate and read at 412 nm on a Molecular Devices Spectramax M5 microplate reader and SoftMax Pro software. The hemolytic activity was calculated: OD541 of all experimental samples was divided by the OD541 at Maximum cell lysis (cells treated with 100 uL water) and then multiplied by 100. Data represented are single points (duplicates not run).

[00274] As shown in Figure 6, the chimeric Clq protein obtained from humanized rats displayed similar classical complement activity as measured by hemolysis assay to that observed in the rats comprising wild type rat Clq, and to that observed with normal human serum. No differences were observed between male and female rats.

Example 6: Humanized Clq Rat as a Model for Testing Human Therapeutics

[00275] To confirm whether a humanized Clq rat can serve as a model for testing human therapeutics, an in vitro complement dependent cytotoxicity assay and a whole blood bacterial survival assay were performed. (1) Complement dependent cytotoxicity (CDC) assay

[00276] For the CDC bioassay, Raji cells (a human B cell line expressing CD20), a serum sample (complement preserved human serum, WT rat serum, or serum from a homozygous Clq humanized rat as described in Example 2), and an anti-CD20 antibody, were used.

[00277] Raji cells were seeded onto a 96-well assay plates at 10,000 cells/well in 1% BSA containing RPMI 1640. To measure CDC with human or rat serum, the anti-CD20 antibody was diluted 1 :4 from 20nM to 0.019nM (including a control sample containing no antibody) and incubated with cells for 10 minutes at 25°C followed by addition of 0.5% serum Cytotoxicity was measured after 1 hour of incubation at 37 °C and in 5% C02, followed by 30 minute incubation at 25°C, and addition of CytoTox-CHo™ reagent (Promega, # G9291). CytoTox-Glo™ is a luminescence-based reagent that measures cell killing such that increased luminescence is observed with increased cytotoxicity (measured in relative light units, RLUs). Untreated cells in control wells were lysed by treatment with digitonin immediately after addition of CytoTox-do™ reagent to determine maximal killing of cells. Plates were read for luminescence by a Victor X instrument (Perkin Elmer) 10-15 minutes following the addition of CytoTox-do™. Where calculated, the percentage of cytotoxicity was calculated with the RLU values by using the following equation:

[00278] In this equation "background cell lysis" is the luminescence from the cells treated with media and serum alone without any anti-CD20 antibody and the "maximum cell lysis" is the luminescence from the cells treated with digitonin. The results, expressed as % cytotoxicity or RLUs, were analyzed using nonlinear regression (4-parameter logistics) with Prism 7 software (GraphPad).

[00279] As shown in Figure 7, complement dependent cytotoxicity activity mediated by 20nM CD20 antibody and the humanized Clq rat (MAID10015) serum resulted in 85-90% maximum lysis of Raji cells, which was similar to lysis using wild type rat serum (93-112% lysis) and normal human serum (83% lysis). Humanization of the Clq molecule did not alter the complement dependent lysis of Raji cells mediated by the CD20 antibody as compared to the rat Clq. (2) S. aureus survival in Clq humanized rat blood and die effects of a bisperific antibody

[00280] S. aureus survival in whole human blood can be assessed in an ex vivo assay to explore the role of complement and immune effector cells in modulating bacterial growth (Thammavongsa et al., J Exp Med. 2009 Oct26;206(l l):2417-27). In this assay, the activity of a bisperific antibody targeting Clq and a S. aureus antigen in modulating S. aureus survival is measured where the bispecific antibody is added into whole blood and survival is assessed after 24 hours. This assay has been adapted in this Example to use Clq humanized rat blood and examine the functionality of the humanized chimeric Clq protein in mediating the effects of a bispecific antibody that specifically recognizes a S. aureus antigen and the human or humanized Clq protein but not the rat Clq protein. A bivalent monospecific antibody against the same S. aureus antigen was used as a control.

[00281] Briefly, a culture of <S aureus Newman was grown in RPMI overnight, washed in PBS, and resuspended to a concentration of 1.25 x 10 ⁸ colony forming units (CFU)/mL in PBS and serially diluted to a concentration of 10 ⁵ CFU/mL. In duplicates, 10 ⁴ CFU of the S. aureus suspension was mixed with lOOug/mL bispecific antibody, control antibody or no antibody and lOOuL of humanized Clq or wild type (WT) rat blood (in sodium citrate as anti-coagulant with additional SOOnM dabigatran to prevent clot formation). The samples were incubated in 96 well plates at 37°C with shaking (lOOrpm) for 24 hours. After incubation, lOOul of agglutination lysis buffer (PBS supplemented with 200U Streptokinase, 2ug/mL RNase, lOug/mL DNase, 0.5% saponin, lOOug trypsin per ml of PBS) was added to the samples and vigorously vortexed until the pellet disappeared. A total of 50uL from each sample was serially diluted in PBS and plated onto LB agar plates for enumeration of CFUs.

[00282] In this assay, freshly drawn blood samples from 11 humanized Clq and 10 WT rats were tested. Percent survival of S. aureus after treatment with the bispecific or control antibodies was determined. The overall growth in rat blood in the absence of test antibody is normalized to 100%. Survival of <S aureus in the WT rat blood with the bispecific antibody treatment ranged from 58-131%, while the bispecific antibody treatment in Clq humanized rat blood resulted in 7-49% survival. Survival of S. aureus in the WT rat blood with the control antibody treatment ranged from 40-139%, and the control antibody treatment in Clq humanized rat blood resulted in 61-114% survival.