PRODUCTION OF VIRUSES IN AVIAN EGGS

FIELD OF THE INVENTION

The present invention relates to modified avian eggs which can be used to produce increased levels of virus. The present invention also relates to methods of producing viruses in avian eggs of the invention, as well as the use of the viruses obtained to prepare vaccine compositions.

BACKGROUND OF THE INVENTION

Viral infection remains an important health problem in both humans and in economically important livestock with adverse economic and social consequences.

One of the main approaches to protecting animals from viral disease is vaccination. Availability of sufficient quantities of virus, and the cost associated with virus production are limiting factors for the production of vaccines. Current virus production methods include cell culture and in ovo production systems. However, not all viruses replicate well in cell culture and/or in ovo production systems. For example, not all influenza viruses replicate well in eggs (Horimoto et al., 2006; Horimoto et al., 2007).

Thus, there is a need to develop improved methods for virus production. It is against this background that the present inventors have developed a method of increasing virus production in ovo.

SUMMARY OF THE INVENTION

The present inventors have demonstrated that reducing the expression of an antiviral gene, and/or the level of antiviral protein activity in an avian egg, can be used to increase viral production.

Thus, in one aspect the present invention provides an avian egg comprising; 1) a genetic modification which reduces the expression of an antiviral gene in the egg when compared to an isogenic egg lacking the genetic modification, and/or 2) an exogenous compound which reduces the expression of an antiviral gene and/or reduces the level of antiviral protein activity in the egg when compared to an isogenic egg lacking the compound,

wherein the egg is capable of producing more virus than the isogenic egg.

In an embodiment, the antiviral gene and/or protein is in the Type I, Type II or Type III interferon pathway. In an embodiment, the antiviral gene and/or protein is in the Type I interferon pathway. In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or more of: IFNAR1, IL-6, CNOT4, MDA5, IFNa, ΙΡΝβ, IFNy, ΙΡΝλ, IFNAR2, UBE1DC1, GNAZ, CDX2, LOC100859339, IL28RA, ZFPM2, TRIM50, DNASEIL2, PHF21A, GAPDH, BACE2, HSBP1, PCGF5, IL-1RA, DDI2, CAPN13, UBA5, NPR2, IFIH1 , LAMP1 , EFR3A, ARRDC3, ABI1 , SCAF4, GADL1 , ZKSCAN7, PLVAP, RPUSD1 , CYYR1 , UPF3A, ASAP1, NXF1 , TOP1MT, RALGAPB, SUCLA2, GORASP2, NSUN6, CELF1 , ANGPTL7, SLC26A6, WBSCR27, SIL1 , HTT, MYOC, TM9SF2,CEP250, F AMI 88 A, BCAR3, GOLPH3L, HN1 , ADCY7, AKAP10, ALX1, CBLN4, CRK, CXORF56, DDX10, EIF2S3, ESF1 , GBF1 , GCOM1 , GTPBP4, HOXB9, IFT43, IMP4, ISY1 , KIAA0586, KPN A3, LRRIQ1 , LUC7L, MECR, MRPL12, POLR3E, PWP2, RPL7A, SERPINH1 , SLC47A2, SMYD2, STAB 1 , TTK, WNT3, IFNGR1, IFNGR2, IL-10R2, IFNK, IFNQ, IL-1RB and XPOl.

In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or more of: IFNAR1, IL-6, CNOT4, MDA5, IFNa, IFN , IFNy, ΙΡΝλ, BACE2, UBA5, ZFPM2, TRIM50, DDI2, NPR2, CAPN13, DNASE1L2, PHF21A, PCGF5, IFIH1, IL-1RA, LAMP1, EFR3A, ABI1, GADL1, PLVAP, CYYR1, ASAP1, NXF1, NSUN6, ANGPTL7, SIL1, BCAR3, GOLPH3L, HN1, ADCY7, CBLN4, CXORF56, DDX10, EIF2S3, ESF1, GCOM1, GTPBP4, IFT43, KPN A3, LRRIQ1, LUC7L, MRPL12, POLR3E, PWP2, RPL7A, SMYD2, XPOl and ZKSCAN7.

In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or all of: IFNAR1, IL-6, CNOT4, MDA5, IFNa, IFN , IFNy, IFN and IL- 1RA.

In an embodiment, the antiviral gene and/or protein is IFNAR1. In an embodiment, the antiviral gene and/or protein is IL-6. In an embodiment, the antiviral gene and/or protein is MDA5. In an embodiment, the antiviral gene and/or protein is CNOT4. In another embodiment, the antiviral gene and/or protein is IFNa. In another embodiment, the antiviral gene and/or protein is IFN . In another embodiment, the antiviral gene and/or protein is IFNy. In another embodiment, the antiviral gene and/or protein is IFN . In another embodiment, the antiviral gene and/or protein is IL-1RA.

In an embodiment, the genetic modification is in the genome. In an embodiment, the genome is homozygous. In an embodiment, the genetic modification is in the mitochondrial DNA (mtDNA) or nuclear DNA of the embryo contained in the egg- The genetic modification can be any change to the naturally occurring avian egg or parent thereof that achieves the desired effect of reducing the expression of an antiviral gene, and/or the level of antiviral protein activity in the avian egg.

In an embodiment, the genetic modification is a deletion, substitution or an insertion into the antiviral gene or a regulatory region thereof. For example, the genetic modification can have been introduced by a programmable nuclease. In another example, the genetic modification can have been introduced by homologous recombination so that it no longer encodes a protein with antiviral activity such as by deleting part or all of the antiviral gene, inserting an exogenous polynucleotide into the antiviral gene, or rearranging the orientation of some of the antiviral gene (such as an exon). In another embodiment, the genetic modification was introduced by nonhomologous end joining. In yet a further embodiment, the genetic modification was introduced by a chemical mutagen.

In an embodiment, the genetic modification is a point mutation.

In an embodiment, the genetic modification was introduced by a transgene which encodes a polynucleotide which reduces the expression of an antiviral gene, and/or the level of antiviral protein activity in the avian egg. Examples of polynucleotides includes, but is not limited to, an antisense polynucleotide, a sense polynucleotide, a microRNA, a polynucleotide which encodes a polypeptide which binds a protein encoded by the antiviral gene, a transposon, an aptamer, a double stranded RNA molecule or a processed RNA molecule derived therefrom.

In an embodiment, the transgene comprises an open reading frame encoding the polynucleotide operably linked to a promoter which directs expression of the polynucleotide in the avian egg.

In an embodiment, the exogenous compound is a small carbon based molecule, a protein binding agent, a programmable nuclease, a polynucleotide or a combination of two or more thereof.

In an embodiment, the protein binding agent or the polynucleotide is expressed from a transgene administered to the egg.

In an embodiment, the transgene is present in a virus to be cultured in the egg.

In an embodiment, the protein binding agent is an antibody.

In an embodiment, the virus is an animal virus. In an embodiment, the animal is a human, chicken, pig, fish, sheep or cow. In an embodiment, the animal is a human.

In an embodiment, the virus is in a family selected from: Orthomyxoviridae, Herpesviridae, Paramyxoviridae, Flaviviridae and Coronaviridae. In an embodiment, the virus in selected from: Influenza virus, Canine distemper virus, Measles virus, Reovirus, Eastern equine encephalitis virus, Canine parainfluenza virus, Rabies virus, Fowlpox virus, Western equine encephalitis virus, Mumps virus, Equine encephalomyelitis, Rubella virus, Egg drop syndrome virus, Avian oncolytic viruses, Avian infectious laryngotracheitis Herpesvirus, Newcastle disease virus, Bovine parainfluenza virus, Smallpox virus, Infectious bursal disease, Bovine Ibaraki virus, Recombinant poxvirus, Avian adenovirus type I, II or III, Swine Japanese encephalitis virus, Yellow fever virus, Herpes virus, Sindbis virus, Infections bronchitis virus, Semliki forest virus, Encephalomyelitis virus, Venezuelan EEV virus, Chicken anaemia virus, Marek's disease virus, Parvovirus, Foot and mouth disease virus, Porcine reproductive and respiratory syndrome virus, Classical swine fever virus, Bluetongue virus, Kabane virus, Infectious salmon anaemia virus, Infectious hematopoietic necrosis virus, Viral haemorrhagic septicemia virus and Infectious pancreatic necrosis virus. In an embodiment, the virus is the Influenza virus.

In an embodiment, the avian egg is a chicken egg. In an embodiment, the avian egg is a duck egg.

In another aspect, the present invention provides an avian egg of the invention which comprises the virus. In an embodiment, the virus is the Influenza virus.

In a further aspect, the present invention provides a method of replicating a virus, the method comprising;

1) obtaining an avian egg of the invention which comprises the genetic modification,

2) inoculating the egg with the virus, and

3) incubating the egg for a predetermined period of time to replicate the virus. In an alternate aspect, the present invention provides a method of replicating a virus, the method comprising;

1) obtaining an avian egg,

2) administering a compound which reduces the expression of an antiviral gene and/or reduces the level of antiviral protein activity in the egg when compared to an isogenic egg lacking the compound,

3) inoculating the egg with the virus, and

4) incubating the egg for a predetermined period of time to replicate the virus.

In an embodiment, the methods as described herein further comprises harvesting the replicated virus or particles thereof from the egg.

In an embodiment, the harvesting comprises obtaining the allantoic fluid from the egg. As the skilled person will appreciate, methods of replicating a virus in an egg of the invention can be performed using standard techniques in the art.

In another aspect, the present invention provides a virus produced using an avian egg of the invention, and/or using a method of the invention.

In another aspect, the present invention provides a method of producing a vaccine composition, the method comprising;

1) replicating a virus using a method of the invention,

2) harvesting the replicated virus or particles thereof from the egg, and

3) preparing a vaccine composition from the harvested virus.

In an embodiment, step 2) or step 3) comprises inactivating the virus. In an embodiment, inactivating the virus comprises UV, heat or chemical inactivation.

In an embodiment, step 2) or step 3) comprises disruption of the virus to produce split virus particles or subunit virus particles.

As the skilled person will appreciate, methods of producing a vaccine composition in an egg of the invention can be performed using standard techniques in the art.

In an embodiment, harvesting the replicated virus or particles thereof comprises one or more of the following steps: 1) clarification, 2) concentration, 3) inactivation, 4) nuclease treatment, 5) separation/purification, 6) polishing; and/or 7) sterile filtration.

Also provided is a vaccine composition produced using a method of the invention.

In an embodiment, the vaccine composition is an attenuated vaccine. In an embodiment, the vaccine composition is an inactivated vaccine composition. In an embodiment, the vaccine composition is an Influenza vaccine composition.

In a further aspect, the present invention provides a transgenic avian comprising a genetic modification, wherein the genetic modification reduces expression of an antiviral gene in an egg produced by the avian compared to an egg produced by an isogenic avian lacking the genetic modification.

In an embodiment, the avian is a chicken.

In another aspect, the present invention provides a method of producing an avian of the invention, the method comprising;

1) introducing the genetic modification into an avian cell,

2) producing a female avian from the cell,

3) obtaining one or more eggs from the female avian and screening the egg(s) for the ability to produce more virus than an isogenic egg lacking the lacking the genetic modification, 4) selecting a female avian which produces eggs with a genetic modification which produces more virus than an isogenic egg lacking the lacking the genetic modification, and

5) optionally breeding more avians using the female avian.

In an embodiment, the genetic modification is in the genome of the cell.

In an embodiment, the genetic modification is introduced by a programmable nuclease.

In a further embodiment, the avian is a chicken.

Any embodiment herein shall be taken to apply mutatis mutandis to any other embodiment unless specifically stated otherwise. For instance, as the skilled person would understand examples of programmable nucleases outlined above for the avian egg of the invention equally apply to the methods of the invention.

The present invention is not to be limited in scope by the specific embodiments described herein, which are intended for the purpose of exemplification only. Functionally-equivalent products, compositions and methods are clearly within the scope of the invention, as described herein.

Throughout this specification, unless specifically stated otherwise or the context requires otherwise, reference to a single step, composition of matter, group of steps or group of compositions of matter shall be taken to encompass one and a plurality (i.e. one or more) of those steps, compositions of matter, groups of steps or group of compositions of matter.

The invention is hereinafter described by way of the following non-limiting Examples and with reference to the accompanying figures. BRIEF DESCRIPTION OF THE ACCOMPANING DRAWINGS

Figure 1. Antiviral activity of recombinant chicken (rch) IFNa, IFNP, IFNy and IFN in a virus neutralization assay. An increase in cell viability equates to an increase in the OD. Absorbance values are the means ± SE, duplicates from two independent experiments. Cells alone and cells + virus controls are shown as the means from 24 wells.

Figure 2. A. Indirect ELISA analysis reveals that purified anti-IFNs (IFNa, IFNP, IFNy and IFN ) sera recognise homologous protein. The graph shows that ammonium sulphate precipitated polyclonal anti-chlFN antisera detects homologous proteins in ELISA. The OD is a measure of antibody levels. Absorbance values shown are the means ± SE, duplicates from two independent experiments. B. Anti-chIFN-a antibodies do not appear to increase virus titre in ovo. Anti-chIFN-a antibodies co- inoculated with influenza vaccine virus (PR8 or NIBRG14) in ovo do not augment the haemagglutination (HA) titre measured by haemagglutination (HA) assay. The bar graph represents the mean of four experiments ± SE. C. Anti-chIFN-β antibodies do not appear to increase virus titre in ovo. The co-administration of purified anti- chIFN-β antibodies and influenza vaccine virus (PR8 or NIBRG14) does not affect the virus HA titres in ovo determined by HA assay. The bar graph represents the mean of up to three experiments ± SE. Figure 3. A. Anti-chIFN-λ antibodies increase virus titre in ovo. The inoculation of purified anti-chIFN-λ antibodies and influenza vaccine virus (PR8 or NIBRG14) results in an increased HA titre in ovo measured by HA assay. The bar graph represents the means of up to seven experiments ± SE. The statistical significance is represented as one asterisk (*) /?<0.05, two asterisks (**) /?<0.005 and three asterisks (***) represents /?=0.0001. B. Anti-chIFN-γ antibodies increase virus titre in ovo. The co-administration of anti-chIFN-γ antibodies and influenza vaccine virus (PR8 or NIBRG14) results in an increase on the virus HA titre in ovo measured by HA assay. The bar graph represents the means of 2 experiments ± SE. The statistical significance is represented as one asterisk (*) /?<0.05. C. Anti-chIL-6 antibodies increase virus titre in ovo. The effect of injecting both purified anti-chIL-6 antibodies and influenza vaccine virus (PR8 or NIBRG14) in ovo results in an increase in the HA virus titre measured by HA assay. The bar graph represents the mean of up to five experiments ± SE. The statistical significance is represented as one asterisk (*) /?<0.05, two asterisks (**) /?<0.005.

Figure 4. Screening and identification of antiviral genes for vaccine production of avian influenza. A. Viability of DF-1 cells transfected with a negative control siRNA (siNTl), or with siRNAs targeting the 21 candidate host genes. Viability was measured 72 h post transfection, at the time of virus infection. B. Titres of influenza A/WSN grown in the immortalized chicken fibroblast cell line, DF-1, in control cells (siNTl), or in cells transfected with siRNAs to silence expression of 21 host genes. A significant increase in viral titres measured as TCDI ₅₀ after knock down (KD) using siRNA was observed, with IFNRA1 shows the highest increase in viral titre. C. Immune staining of viral particles on DF1 cells show a significant increase in virus growth after inhibition of IFNAR1 expression by siRNA. Figure 5. siRNA down regulation of gene expression of the host increases viral growth in vitro. DF-1 cells were transfected with a negative control siRNA (siNTl), or siRNAs targeting CNOT4, IFNAR or MDA5, either as 4 siRNA duplexes pooled (smartpool), or as individual siRNA duplexes. */?<0.05 compared to mRNA levels in cells transfected with siNTl. mRNA levels were quantitated using Taqman probes 72 h post-transfection by quantitative real-time PCR. Each of the siRNA complexes were evaluated individually on its ability to KD the target gene (shown on the left) and increase viral titres (show on the right). Cells were infected with influenza A/WSN virus (MOI 0.1) for 48 h. Virus levels in the cell supernatant were quantitated by TCID ₅₀ assays. */?<0.05 compared to virus levels in cells transfected with siNTl.

Figure 6. TCID ₅₀ WSN from eggs. A. TCIDJO WSN from eggs after down regulation by siRNA delivered using ABA-21/117Q values are given as a single replicates. B. TCIDJO WSN from eggs after down regulation by siRNA delivered using ABA- 21/117Q. Values are given as Mean+2 SD.

Figure 7. TCID ₅₀ WSN from eggs. A. TCID ₅₀ PR8 vaccine strain from eggs after down regulation by siRNA delivered using ABA-21/117Q. Values are given as Mean + 2SD. B. Correlation between TCID ₅₀ titre and knockdown of IFNAR1. C. HA and TCID ₅₀ maximum values obtained by down regulation by siRNA delivered using ABA- 21/117Q it correspond to a 3 log increase compared with control. shIFNARl increases influenza growth in eggs. D. Expression of shIFNARl and levels of influenza RNA were measured in the heart of day 12 embryos following injection of RCAS-shlFNAl at day 0 and infection with influenza (PR8 strain) at day 10 of embryogenesis. The raw CT values from the real-time PCR shows a correlation between the expression of shIFNARl and influenza RNA levels. The higher the expression of shIFNARl and influenza RNA is indicated by a lower CT value (N=6).

Figure 8. Generation of IFNAR1 DF-1 KO cell lines. After transfection, the cells from the parental cell lines presented an alternative amplicon during the PCR screening in around 30% of the alleles. A. Deletion was confirmed by sequencing. Cells were sorted to obtain single clones presenting: biallelic (A136 and A142) mono-allelic (A13) or no apparent deletion (A143) when compared with the Wild Type (WT). B. IFNARIA gene expression was evaluated by qPCR. Results expressed as the mean of AAct value +/- 2 standard deviation (SD) against housekeeping WSN viral particles produced on the KO cell lines. Pfu and TCID ₅₀ were establish after infecting MDCK cells with the HlNl AAVSN/1933 growth on the different cell lines as an indicative of total virus yield. C. Gene KO at 0 and 48 h. D. WSN viral particles produced on the KO cell lines. Pfu and TCID5 ₀ were establish after infecting MDCK cells with the HlNl AAVSN/1933 growth on the different cell lines as an indicative of total virus yield.

Figure 9. Screening and identification of antiviral genes against Hendra Virus.

Hendra virus replication in the immortalized human cell line HeLa, in control cells (siNTl), or in cells transfected with siRNAs to silence expression listed. A significant increase in viral replication using siRNA was observed. LAMP1 shown the highest increase in viral titre.

DETAILED DESCRIPTION OF THE INVENTION

General Techniques and Selected Definitions

Unless specifically defined otherwise, all technical and scientific terms used herein shall be taken to have the same meaning as commonly understood by one of ordinary skill in the art (e.g., in cell culture, molecular genetics, transgenic avians, immunology, immunohistochemistry, precision genome engineering, protein chemistry, and biochemistry).

Unless otherwise indicated, the cell culture and immunological techniques utilized in the present invention are standard procedures, well known to those skilled in the art. Such techniques are described and explained throughout the literature in sources such as, J. Perbal, A Practical Guide to Molecular Cloning, John Wiley and Sons (1984), J. Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbour Laboratory Press (1989), T.A. Brown (editor), Essential Molecular Biology: A Practical Approach, Volumes 1 and 2, IRL Press (1991), D.M. Glover and B.D. Hames (editors), DNA Cloning: A Practical Approach, Volumes 1-4, IRL Press (1995 and 1996), and F.M. Ausubel et al. (editors), Current Protocols in Molecular Biology, Greene Pub. Associates and Wiley-Interscience (1988, including all updates until present), Ed Harlow and David Lane (editors) Antibodies: A Laboratory Manual, Cold Spring Harbour Laboratory, (1988), and J.E. Coligan et al. (editors) Current Protocols in Immunology, John Wiley & Sons (including all updates until present).

The term "and/or", e.g., "X and/or Y" shall be understood to mean either "X and Y" or "X or Y" and shall be taken to provide explicit support for both meanings or for either meaning. Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The term "avian" as used herein refers to any species, subspecies or race of organism of the taxonomic Class Aves, such as, but not limited to, such organisms as chicken, turkey, duck, goose, quail, pheasants, parrots, finches, hawks, crows and ratites including ostrich, emu and cassowary. The term includes the various known strains of Gallus gallus (chickens), for example, White Leghorn, Brown Leghorn, Barred-Rock, Sussex, New Hampshire, Rhode Island, Australorp, Cornish, Minorca, Amrox, California Gray, Italian Partidge-coloured, as well as strains of turkeys, pheasants, quails, duck, game hen, guinea fowl, squab, ostriches and other poultry commonly bred in commercial quantities.

As used herein, the term "genetic modification" is any man made alteration to the genetic material in the avian egg. The modification may have been made to the egg, one or both parents of the egg, or an ancestor of one of both parents. In one example, the genetic modification is a mutation to an endogenous gene in the genome introduced by a programmable nuclease. For instance, the mutation can be a frame- shift and/or deletion that results in the gene no longer encoding a functional protein. In another embodiment, homologous recombination is used to delete part of all of a target antiviral gene such that the antiviral protein is not produced. In an alternate embodiment, the genetic modification is the instruction of a transgene, for example in a nucleic acid construct, which expresses the desired polynucleotide in the egg. The transgene may be extrachromosomal or integrated into the genome of the egg.

As used herein, the "exogenous compound" can be any substance, such as a small carbon based molecule, protein or polynucleotide, administered to the egg to produce the desired result.

As used herein, the term "producing more virus than the isogenic egg" refers to the ability of an avian egg of the invention to be used to cultivate more virus than the isogenic egg. In an embodiment, the isogenic egg is from the same strain of avian as the avian egg of the invention. In an embodiment, the isogenic avian egg is genetically identical to the egg of the invention apart from the presence of the genetic modification and/or exogenous compound. In an embodiment, an avian of the invention produces at least 0.5 fold, or at least 1 fold, or at least 2 fold, or at least a 3 fold, or at least 5 fold, or at least 10 fold, or at least 15 fold, or at least 20 fold, or at least 50 fold, or at least 100 fold more virus when compared to an isogenic egg lacking the genetic modification and/or exogenous compound. Such an increase in virus production can readily be determined by the skilled person using routine techniques. For example, an egg of the invention and the isogenic egg can be inoculated with the same amount of the same virus and incubated under the same conditions for the same length of time and the amount of virus particles present in each egg can be determined using standard techniques, such as those outlined in the Examples.

As used herein, the term "virus or particles thereof refers to whole virus which may or may not be inactivated and to particles of such viruses. A virus particle can be any size suitable for use in a split virus vaccine or subunit virus vaccine. The whole virus or particles of the virus can be harvested form the allantoic fluid of the egg. A harvested whole virus may be disrupted during the preparation of a vaccine composition to form particles of a suitable size for a split virus vaccine or subunit virus vaccine.

As used herein, the term "reduces the expression of an antiviral gene" refers to the ability of the genetic modification and/or exogenous compound to down-regulate the level of RNA transcript and/or the level of translation from the RNA transcript in the egg when compared to the level(s) in the isogenic egg. In an embodiment, the isogenic egg is from the same strain of avian as the avian egg of the invention. In an embodiment, the isogenic avian egg is genetically identical to the egg of the invention apart from the presence of the genetic modification and/or exogenous compound. In an embodiment, the gene encodes an antiviral protein, and hence the level of antiviral protein activity in the egg will also be reduced when compared to the level in the isogenic egg. In an embodiment, the genetic modification and/or exogenous compound reduces expression of the antiviral gene in the egg by at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 98%, or at least 99%, or 100% when compared to the isogenic egg lacking the genetic modification and/or exogenous compound. Such a reduction can be identified using standard procedures.

As used herein, the term "reduces the level of antiviral protein activity" refers to the ability of the genetic modification and/or exogenous compound to down-regulate the level antiviral protein activity in the egg when compared to the level in the isogenic egg. In an embodiment, the isogenic egg is from the same strain of avian as the avian egg of the invention. In an embodiment, the isogenic avian egg is genetically identical to the egg of the invention apart from the presence of the genetic modification and/or exogenous compound. The activity of the protein can be reduced by, for example, reducing the amount of the protein in the egg and/or reducing the ability of the protein to perform its natural function (such as by binding an exogenous compound (for example an antibody) to its active site). In an embodiment, the genetic modification and/or exogenous compound reduces the level of antiviral protein activity in the egg by at least 10%, or at least 20%, or at least 30%, or at least 40%, or at least 50%, or at least 60%, or at least 70%, or at least 80%, or at least 90%, or at least 95%, or at least 98%, or at least 99%, or 100% when compared to the isogenic egg lacking the genetic modification and/or exogenous compound. Such a reduction can be identified using standard procedures.

A "transgene" as referred to herein has the normal meaning in the art of biotechnology and includes a genetic sequence which has been produced or altered by recombinant DNA or RNA technology and which has been introduced into an avian egg, or parent(s) of the egg or a predecessor thereof. The transgene may include genetic sequences derived from an avian cell. Typically, the transgene has been introduced into the avian, or egg thereof, by human manipulation such as, for example, by transformation but any method can be used as one of skill in the art recognizes. A transgene includes genetic sequences that are introduced into a chromosome as well as those that are extrachromosomal. The transgene will typically comprise an open reading frame encoding a polynucleotide of interest operably linked to a suitable promoter for expressing the polynucleotide in an avian egg. The transgene may be inserted by homologous recombination.

The term "small carbon based molecule," as used herein, refers to a chemical compound or molecule having a molecular weight below 2000 Daltons, preferably below 1500 Daltons, more preferably below 1000 Daltons, still more preferably below 750 Daltons, yet more preferably below 500 Daltons.

Antiviral Genes and/or Proteins

As used herein, an "antiviral gene" is any endogenous avian gene, the expression of which limits the production of the virus in the egg by any means. An antiviral gene may encode an antiviral protein.

As used herein, an "antiviral protein" is any endogenous avian protein, the presence of which limits the production of the virus in the egg.

The antiviral gene and/or protein may be involved in the ability of an adult avian to mount an immune response to a viral infection. In an embodiment, the antiviral gene and/or protein forms part of an interferon (IFN) pathway. In an embodiment, the antiviral gene and/or protein is in the Type I, Type II or Type III interferon pathway. In an embodiment, the antiviral gene and/or protein is in the Type I or Type III interferon pathway. In an embodiment, the antiviral gene and/or protein is the IFN-α/β receptor 1 (IFNAR1) chain. In another embodiment, the antiviral gene and/or protein is IL-6.

In an alternate embodiment, the antiviral gene and/or protein may be, or known to be, involved in the ability of an adult avian to mount an immune response to a viral infection. Examples of some previously known functions of such genes/proteins include being involved in cellular metabolism, embryonic development, cell signalling or nucleic acid synthesis.

In an alternate embodiment, reducing the expression of the antiviral gene and/or protein reduces apoptosis of cells of the avian egg infected with the virus.

In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or more of: IFNAR1, IL-6, CNOT4, MDA5, IFNa, ΙΡΝβ, IFNy, ΙΡΝλ, IFNAR2, UBE1DC1, GNAZ, CDX2, LOC100859339, IL28RA, ZFPM2, TRIM50, DNASEIL2, PHF21A, GAPDH, BACE2, HSBP1, PCGF5, IL-1RA, DDI2, CAPN13, UBA5, NPR2, IFIH1, LAMP1, EFR3A, ARRDC3, ABI1, SCAF4, GADL1, ZKSCAN7, PLVAP, RPUSD1, CYYR1, UPF3A, ASAP1, NXF1 , TOP1MT, RALGAPB, SUCLA2, GORASP2, NSUN6, CELF1, ANGPTL7, SLC26A6, WBSCR27, SIL1, HTT, MYOC, TM9SF2,CEP250, F AMI 88 A, BCAR3, GOLPH3L, HN1, ADCY7, AKAP10, ALX1, CBLN4, CRK, CXORF56, DDX10, EIF2S3, ESF1, GBF1, GCOM1, GTPBP4, HOXB9, IFT43, IMP4, ISY1, KIAA0586, KPN A3, LRRIQ1 , LUC7L, MECR, MRPL12, POLR3E, PWP2, RPL7A, SERPINH1 , SLC47A2, SMYD2, STAB 1 , TTK, WNT3, IFNGR1, IFNGR2, IL-10R2, IFNK, IFNQ, IL-1RB and XPOl or the corresponding receptor or agonist thereof. In an embodiment, IFNa is one or more of the following isoforms: IFNal, IFNa2, IFNa4, IFNa5, IFNa6, IFNa7, IFNA8, IFNalO, IFNal3, IFNal4, IFNal6, IFNal7 and IFNa21. In an embodiment, IFN is one or more of the following isoforms: IFN l, IFN 2, IFN 3, IFN 4.

In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or more of: IFNAR1, IL-6, CNOT4, MDA5, IFNa, ΙΡΝβ, IFNy, ΙΡΝλ, BACE2, UBA5, ZFPM2, TRIM50, DDI2, NPR2, CAPN13, DNASE1L2, PHF21A, PCGF5, IFIH1, IL-1RA, LAMP1, EFR3A, ABI1, GADL1, PLVAP, CYYR1, ASAP1, NXF1, NSUN6, ANGPTL7, SIL1, BCAR3, GOLPH3L, HN1, ADCY7, CBLN4, CXORF56, DDX10, EIF2S3, ESF1, GCOM1, GTPBP4, IFT43, KPN A3, LRRIQ1, LUC7L, MRPL12, POLR3E, PWP2, RPL7A, SMYD2, XPOl and ZKSCAN7 or the corresponding receptor or agonist thereof.

In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or more of: IL-6, CNOT4, MDA5, IFNa, ΙΡΝβ, IFNy, IFNAR2, UBE1DC1, GNAZ, CDX2, LOC100859339, IL28RA, ZFPM2, TRIM50, DNASEIL2, PHF21A, GAPDH, BACE2, HSBP1 , PCGF5, IL-1RA, DDI2, CAPN13, UBA5, NPR2, IFIH1 , LAMP1 , EFR3A, ARRDC3, ABI1 , SCAF4, GADL1 , ZKSCAN7, PLVAP, RPUSD1 , CYYR1 , UPF3A, AS API , NXF1 , TOP1MT, RALGAPB, SUCLA2, GORASP2, NSUN6, CELF1 , ANGPTL7, SLC26A6, WBSCR27, SIL1, HTT, MYOC, TM9SF2,CEP250, FAM188A, BCAR3, GOLPH3L, HN1 , ADCY7, AKAP10, ALX1 , CBLN4, CRK, CXORF56, DDX10, EIF2S3, ESF1 , GBF1 , GCOM1 , GTPBP4, HOXB9, IFT43, IMP4, ISY1 , KIAA0586, KPN A3, LRRIQ1 , LUC7L, MECR, MRPL12, POLR3E, PWP2, RPL7A, SERPINH1 , SLC47A2, SMYD2, STAB 1, TTK, WNT3, IFNGR1, IFNGR2, IL-10R2, IFNK, IFNQ, IL-IRB and XPOl or the corresponding receptor or agonist thereof.

In an embodiment, the antiviral gene and/or protein is selected from one, two, three, four or more of: IL-6, CNOT4, MDA5, IFNAR2, UBE1DC1, GNAZ, CDX2, LOC100859339, IL28RA, ZFPM2, TRIM50, DNASEIL2, PHF21A, GAPDH, BACE2, HSBP1 , PCGF5, IL-1RA, DDI2, CAPN13, UBA5, NPR2, IFIH1 , LAMP1 , EFR3A, ARRDC3, ABI1 , SCAF4, GADL1 , ZKSCAN7, PLVAP, RPUSD1 , CYYR1, UPF3A, ASAP1 , NXF1 , TOP1MT, RALGAPB, SUCLA2, GORASP2, NSUN6, CELF1 , ANGPTL7, SLC26A6, WBSCR27, SIL1 , HTT, MYOC, TM9SF2,CEP250, F AMI 88 A, BCAR3, GOLPH3L, HN1 , ADCY7, AKAP10, ALX1, CBLN4, CRK, CXORF56, DDX10, EIF2S3, ESF1 , GBF1 , GCOM1 , GTPBP4, HOXB9, IFT43, IMP4, ISY1 , KIAA0586, KPNA3, LRRIQ1 , LUC7L, MECR, MRPL12, POLR3E, PWP2, RPL7A, SERPINH1 , SLC47A2, SMYD2, STAB 1 , TTK, WNT3, IFNGR1 , IFNGR2, IL-10R2, IFNK, IFNQ, IL-IRB and XPOl or the corresponding receptor or agonist thereof.

In an embodiment, the antiviral gene and/or protein is IFNAR1. In an embodiment, the antiviral gene and/or protein is IL-6. In an embodiment, the antiviral gene and/or protein is MDA5. In an embodiment, the antiviral gene and/or protein is CNOT4. In another embodiment, the antiviral gene and/or protein is IFNa. In another embodiment, the antiviral gene and/or protein is IFN . In another embodiment, the antiviral gene and/or protein is IFNy. In another embodiment, the antiviral gene and/or protein is IFN . In another embodiment, the antiviral gene and/or protein is IL-1RA. In another embodiment, the antiviral gene and/or protein is IL-IRB.

Further details regarding the antiviral genes and/or proteins that can be targeted is provided below in Table 1. Table 1: Antiviral genes and/or proteins

Gene Name GENE ID Ref SeqID Pathway

mRNA

CDX2 caudal type homeobox 2 374205 NM_204311 Nucleic acid synthesis

HSBP1 heat shock factor binding 415813 NM_001112809 Embryo

protein 1 development

GAPDH glyceraldehyde-3-phosphate 374193 NM_204305 Metabolism dehydrogenase

ARRDC3 arrestin domain containing 3 427107 XM_424699.3 Metabolism

SCAF4 SR-related CTD-associated 418492 NM_001012822.1 Nucleic acid factor 4 synthesis

RPUSD1 RNA pseudouridylate 771031 XM 004945221.1 Nucleic acid synthase domain containing synthesis 1

UPF3A UPF3 regulator of nonsense 418734 XM_416933.4 Metabolism transcripts homolog A

TOP1MT topoisomerase (DNA) I, 408025 NM_001001300.1 Metabolism mitochondrial

RALGAPB Ral GTPase activating 419128 NM_001030846.1 Cell signalling protein, beta subunit

SUCLA2 succinate-CoA ligase, ADP- 418857 NM 001006271.2 Embryo

forming, beta subunit development

GORASP2 Golgi reassembly stacking 424156 NM_001012594.1 Immune response protein 2, 55kDa

CELF1 CUGBP, Elav-like family 373923 NM 001012521.1 Embryo

member 1 development

SLC26A6 solute carrier family 26 416012 NM_001252254.1 Metabolism

(anion exchanger), member

6

WBSCR27 Williams Beuren syndrome 770708 XM_001234037.3 Embryo

chromosome region 27 development

HTT huntingtin 422878 XM_420822.4 Metabolism

MYOC myocilin, trabecular 424391 XM_422235.4 Metabolism meshwork inducible

glucocorticoid response

TM9SF2 transmembrane 9 418777 XM_416972.4 Metabolism superfamily member 2

CEP250 centrosomal protein 250kDa 419138 XM_004946945.1 Nucleic acid synthesis

FAM188A family with sequence 420526 XM_418629.4 Nucleic acid similarity 188, member A synthesis

AKAP10 A kinase (PRKA) anchor 417612 XM_415856.4 Cell signalling protein 10

ALX1 ALX homeobox 1 427871 XM_425445.4 Embryo

development

CRK v-crk avian sarcoma virus 417553 L08168.1 Immune response

CT10 oncogene homolog

GBF1 Golgi brefeldin A resistant 423758 XM_421632.4 Cell signalling guanine nucleotide exchange

factor 1

HOXB9 homeobox B9 771865 XM_001233690.3 Metabolism IMP4 U3 small nucleolar 100857200 NM_001277715.1 Nucleic acid ribonucleoprotein synthesis

ISY1 Splicing factor homolog (S. 415968 XM_414311.2 Nucleic acid cerevisiae) synthesis

KIAA0586 TalpicB 423540 NM_001040707.1

SERPINH1 serpin peptidase inhibitor, 396228 NM_205291.1 Metabolism clade H (heat shock protein

47), member 1, (collagen

binding protein 1)

SLC47A2 solute carrier family 47, 417616 NM_001135679.1 Metabolism member 2

STAB 1 stabilin 1 415894 XM_414246.4 Embryo

development

TTK TTK protein kinase 421849 XM_419867.4 Cell signalling

WNT3 wingless-type MMTV 374142 NM_001081696.1 Cell signalling integration site family,

member 3

GNAZ guanine nucleotide binding 770226 XM_001232444 Metabolism protein (G protein), alpha z

polypeptide

MECR mitochondrial trans-2-enoyl- 419601 XM_417748.4 Metabolism

CoA reductase

BACE2 beta-site APP-cleaving 418526 XM_416735.4 Metabolism enzyme 2 (BACE2)

ZFPM2 zinc finger protein, FOG 420269 XM_418380 Nucleic acid family member 2 synthesis

TRIM50 tripartite motif containing 50 417461 XM_415709 Metabolism

DDI2 DNA-damage inducible 1 425541 XM_423293 Metabolism homolog 2 (S. cerevisiae)

NPR2 natriuretic peptide receptor 100859339 XMJX 642919 Metabolism

B/guanylate cyclase B

(atrionatriuretic peptide

receptor B)

CNOT4 CCR4-NOT transcription 417936 NM_001012811 Nucleic acid complex, subunit 4 synthesis

CAPN13 calpain 13 421304 XM_419369 Metabolism

DNASE1L2 deoxyribonuclease I-like 2 427682 XM_425256 Metabolism

PHF21A PHD finger protein 21A 423199 NM_001199647 Nucleic acid synthesis

PCGF5 polycomb group ring finger 423796 XM_421668 Nucleic acid

5 synthesis

IFN alpha interferon (alpha, beta and 395665 NM_204859 Immune response

Receptor omega) receptor 1

(IFNAR1)

IL-6 interleukin 6 395337 NM_204628 Immune response

IL- 1RA interleukin 1 receptor, type I 396481 NM_205485 Immune response

LAMP1 lysosomal-associated 396220 NM_205283.2 Immune response membrane protein 1

EFR3A EFR3 homolog A (S. 420327 NC_006089.3 Embryo

cerevisiae) development

ABI1 abl-interactor 1 420489 AJ720766.1 Immune response GADL1 glutamate decarboxylase- 100857134 XMJX 640735.2 Metabolism like 1

PLVAP plasmalemma vesicle 100857417 XM_004950319.1 Immune response associated protein

CYYR1 cysteine/tyrosine -rich 1 770067 XM_001233378.3 Cell signalling

ASAP1 ArfGAP with SH3 domain, 428385 XM_425945.4 Immune response ankyrin repeat and PH

domain 1

NXF1 nuclear RNA export factor 1 769691 XM_001232980.3 Nucleic acid synthesis

NSUN6 NOP2/Sun domain family, 428419 XM_004939249.1 Nucleic acid member 6 synthesis

ANGPTL7 angiopoietin-like 7 101750033 XM_004947467.1 Embryo

development

SIL1 SIL1 nucleotide exchange 416185 XM_004944772.1 Embryo

factor development

BCAR3 breast cancer anti-estrogen 424494 XM_004936593.1 Immune response resistance 3

GOLPH3L Golgi phosphoprotein 3-like 425072 XM_004948290.1 Nucleic acid synthesis

HN1 hematological and 422119 NM_001006425.1 Embryo

neurological expressed 1 development

ADCY7 adenylate cyclase 7 415732 XM_414097.4 Immune response

CBLN4 cerebellin 4 precursor 769254 NM_001079487.1 Metabolism

CXORF56 chromosome 4 open reading 428719 XM_003641123.2

frame, human CXorf56

DDX10 DEAD (Asp-Glu-Ala-Asp) 418965 AJ720478.1 Metabolism box polypeptide 10

EIF2S3 Putative eukaryotic 418597 NM_001006260.2 Metabolism translation initiation factor 2

subunit 3-like protein

ESF1 nucleolar pre-rRNA 428551 NM_001031519.1 Nucleic acid processing protein homolog synthesis

GC0M1 GRINL1A complex locus 1 415404 XM_413789.4 Nucleic acid synthesis

GTPBP4 GTP binding protein 4 420458 NM_001006354.1 Nucleic acid synthesis

KPNA3 karyopherin alpha 3 418870 CN232780.1 Cell signalling

LRRIQ1 Leucine-rich repeats and IQ 417882 XM_416125.4 Embryo

motif containing 1 development

LUC7L LUC7-like (S. cerevisiae) 416654 XR_213192.1 Nucleic acid synthesis

MRPL12 mitochondrial ribosomal 769031 XM_001232213.3 Metabolism protein L12

POLR3E polymerase (RNA) III (DNA 416620 XM_414921.4 Nucleic acid directed) polypeptide E synthesis

PWP2 PWP2 periodic tryptophan 418551 XM_416757.4 Nucleic acid protein homolog (yeast) synthesis

RPL7A ribosomal protein L7a 417158 NM_001004379.1 Nucleic acid synthesis

SMYD2 SET and MYND domain 421361 NM_001277571.1 Nucleic acid containing 2 synthesis

XPOl exportin 1 (CRM1 homolog, 421192 NM_001290134.1 Cell signalling

yeast)

ZKSCAN7/ zinc finger with KRAB and 416664 XM 004945381.1

ZNF436 SCAN domains 7

IFT43 intraflagellar transport 43 771922 XM_004941812.1 Embryo

homolog (Chlamydomonas) development

IFNa IFNA3 interferon 396398 NM_205427.1 Immune response

IFN Interferon, beta 554219 NM_001024836.1 Immune response

IFN interleukin 28B (interferon, 770778 NM_001 128496.1 Immune response

(IFNL3) lambda 3)

IFNy interferon gamma 396054 NM_205149.1 Immune response

MDA5/IF1 interferon induced with 424185 NM_001 193638.1 Immune response

HI helicase C domain 1

UBE1DC1/ ubiquitin-like modifier 414879 NM_001001765.1 Immune response

UBA5 activating enzyme 5

IFN alpha interferon (alpha, beta and 395664 NM_204858.1 Immune response

Receptor omega) receptor 2

(IFNAR2)

IFNGR1 Interferon Gamma Receptor 421685 NM_001 130387.1 Immune response

1

IFNGR2 Interferon Gamma Receptor 418502 NM_001008676.2 Immune response

2 (Interferon Gamma

Transducer 1)

IL10R2 interleukin 10 receptor 395663 NM_204857.1 Immune response subunit beta

IL1RB Interleukin 1 receptor type 2 418715 XM_416914.5 Immune response

IFNK/ interferon kappa 56832 NM_020124.2 Immune response

IFNK/IFN

Kappa

IFNn/IFN Interferon omega 3467 NM_002177.2 Immune response omega

LOCI 00859 natriuretic peptide receptor 100859339 XMJX 642919.2 Immune response

339/ NPR2 B/guanylate cyclase B

(atrionatriuretic peptide

receptor B)

IL28RA/ interferon, lambda receptor 1 419694 XM_004947908.1 Immune response

IFNLR1

Reducing Expression of an Antiviral Gene and/or Level of Antiviral Protein Activitv in an Avian Egg

Increased viral production can be achieved through the use of genetically modified avian eggs and/or avian eggs treated with exogenous compounds as defined herein.

In some embodiments the expression of the antiviral gene in the avian egg is reduced by introduction of a genetic modification. In one example, the genetic modification is introduced directly into the egg of the avian. In an alternate example, the genetic modification is introduced into the parental maternal and/or paternal germ line of the egg. Introduction of the genetic modification into the parental maternal and/or paternal germ line of the egg results in the creation of a transgenic avian. In such instances, the egg would inherit the genetic modification from the maternal and/or paternal parent.

In some embodiments, the expression of the antiviral gene and/or protein activity in the avian egg is reduced by an exogenous compound. Examples of methods of exogenous compounds, include but are not limited to, a small carbon based molecule, a protein binding agent, a programmable nuclease, a polynucleotide or a combination of two or more thereof.

Genetic modification

The genetic modification can be any man made change to a naturally occurring avian egg or the parent thereof that achieves the desired effect, that being reduced expression of an antiviral gene and/or level of antiviral protein activity in the avian egg. Methods of genetically modifying cells are well known in the art. In an embodiment, the genetic modifications is a mutation of an endogenous gene which partially or completely inactivates the gene, such as a point mutation, an insertion, or a deletion (or a combination of one or more thereof). The point mutation may be a premature stop codon (a nonsense mutation), a splice-site mutation, a deletion, a frame-shift mutation or an amino acid substitution mutation that reduces activity of the gene or the encoded polypeptide.

In an embodiment, the genetic modification is introduced by a programmable nuclease. In an embodiment, the genetic modification is introduced by homologous recombination. In an embodiment, the genetic modification is introduced by non- homologous end joining. In an embodiment, the genetic modification is introduced by a chemical mutagen. In an alternative embodiment, the genetic modification is introduced by a transgene encoded by an exogenous polynucleotide. In an embodiment, the exogenous polynucleotide is encoded by a DNA molecule, a RNA molecule or a DNA/RNA hybrid molecule. Examples of exogenous polynucleotide which reduces expression of an endogenous gene are selected from the group consisting of an antisense polynucleotide, a sense polynucleotide, a microRNA, a polynucleotide which encodes a polypeptide which binds the endogenous enzyme, a transposon, an aptamer, a double stranded RNA molecule and a processed RNA molecule derived therefrom. In an embodiment, the transgene comprises an open reading frame encoding the polynucleotide operably linked to a promoter which directs expression of the polynucleotide in the avian egg. Programmable nucleases

In some embodiments, the genetic modification which reduces the expression of an antiviral gene in the egg when compared to an isogenic egg lacking the genetic modification is introduced into the avian egg or the parental maternal and/or paternal germ line of the egg via a programmable nuclease. In some embodiments, the exogenous compound which reduces the expression of an antiviral gene and/or reduces the level of antiviral protein activity in the egg when compared to an isogenic egg lacking the compound is a programmable nuclease.

As used herein, the term "programmable nuclease" relates to nucleases that is

"targeted" ("programed") to recognize and edit a pre-determined site in a genome of an avian egg or in the parental maternal and/or paternal germ line of an avian egg.

In an embodiment, the programmable nuclease can induce site specific DNA cleavage at a pre-determined site in a genome. In an embodiment, the programmable nuclease may be programmed to recognize a genomic location with a DNA binding protein domain, or combination of DNA binding protein domains. In an embodiment, the nuclease introduces a deletion, substitution or an insertion into the antiviral gene or a regulatory region thereof.

In an embodiment, the programmable nuclease may be programmed to recognize a genomic location by a combination of DNA-binding zinc-finger protein (ZFP) domains. ZFPs recognize a specific 3-bp in a DNA sequence, a combination of ZFPs can be used to recognize a specific a specific genomic location.

In an embodiment, the programmable nuclease may be programmed to recognize a genomic location by transcription activator-like effectors (TALEs) DNA binding domains.

In an alternate embodiment, the programmable nuclease may be programmed to recognize a genomic location by one or more RNA sequences. In an alternate embodiment, the programmable nuclease may be programmed by one or more DNA sequences. In an alternate embodiment, the programmable nuclease may be programmed by one or more hybrid DNA/RNA sequences. In an alternate embodiment, the programmable nuclease may be programmed by one or more of an RNA sequence, a DNA sequences and a hybrid DNA/RNA sequence.

In an alternate embodiment, the programmable nuclease can be used for multiplex silencing i.e. delivery of programmable nuclease with more than one "targeting" or "programming sequence" (i.e. two, three, four, five or more programming sequences) such that two, three, four, five or more antiviral genes can be targeted simultaneously (Kim et al., 2014).

Programmable nucleases that can be used in accordance with the present disclosure include, but are not limited to, RNA-guided engineered nuclease (RGEN) derived from the bacterial clustered regularly interspaced short palindromic repeat (CRISPR)-cas (CRISPR-associated) system, zinc-finger nuclease (ZFN), transcription activator-like nuclease (TALEN), and argonautes.

(CRISPR)-cas (CRISPR-associated) system is a microbial nuclease system involved in defence against invading phages and plasmids. CRISPR loci in microbial hosts contain a combination of CRISPR-associated (Cas) genes as well as non-coding RNA elements capable of programming the specificity of the CRISPR-mediated nucleic acid cleavage. Three types (I-III) of CRISPR systems have been identified across a wide range of bacterial hosts with II RGEN classes (Makarova et al., 2015). One key feature of each CRISPR locus is the presence of an array of repetitive sequences (direct repeats) interspaced by short stretches of non-repetitive sequences (spacers). The non-coding CRISPR array is transcribed and cleaved within direct repeats into short crRNAs containing individual spacer sequences, which direct Cas nucleases to the target site (protospacer).

The Type II CRISPR carries out targeted DNA double-strand break in four sequential steps (for example, see Cong et al., 2013). First, two non-coding RNA, the pre-crRNA array and tracrRNA, are transcribed from the CRISPR locus. Second, tracrRNA hybridizes to the repeat regions of the pre-crRNA and mediates the processing of pre-crRNA into mature crRNAs containing individual spacer sequences. Third, the mature crRNA: tracrRNA complex directs Cas9 to the target DNA via Watson-Crick base-pairing between the spacer on the crRNA and the protospacer on the target DNA next to the protospacer adjacent motif (PAM), an additional requirement for target recognition. Finally, Cas9 mediates cleavage of target DNA to create a double-stranded break within the protospacer. The CRISPR system can also be used to generate single-stranded breaks in the genome. Thus, the CRISPR system can be used for RNA guided (or RNA programmed) site specific genome editing.

In an embodiment, the nuclease is a RNA-guided engineered nuclease (RGEN). In an embodiment, the RGEN is from an archaeal genome or is a recombinant version thereof. In an embodiment, the RGEN is from a bacterial genome or is a recombinant version thereof. In an embodiment, the RGEN is from a Type I (CRISPR)-cas (CRISPR-associated) system. In an embodiment, the RGEN is from a Type II (CRISPR)-cas (CRISPR-associated) system. In an embodiment, the RGEN is from a Type III (CRISPR)-cas (CRISPR-associated) system. In an embodiment, the nuclease is a class I RGEN. In an embodiment, the nuclease is a class II RGEN. In an embodiment, the RGEN is a multi-component enzyme. In an embodiment, the RGEN is a single component enzyme. In an embodiment, the RGEN is CAS3. In an embodiment, the RGEN is CASIO. In an embodiment, the RGEN is CAS9. In an embodiment, the RGEN is Cpfl (Zetsche et al., 2015). In an embodiment, the RGEN is targeted by a single RNA or DNA. In an embodiment, the RGEN is targeted by more than one RNA and/or DNA. In an embodiment, the CAS9 is from Steptococcus pyogenes.

In an embodiment, the programmable nuclease may be a transcription activatorlike effector (TALE) nuclease (see, e.g., Zhang et al., 2011). TALEs are transcription factors from the plant pathogen Xanthomonas that can be readily engineered to bind new DNA targets. TALEs or truncated versions thereof may be linked to the catalytic domain of endonucleases such as Fokl to create targeting endonuclease called TALE nucleases or TALENs.

In an embodiment, the programmable nuclease is a zinc-finger nuclease (ZFN). In one embodiment, each monomer of the ZFN comprises 3 or more zinc finger-based DNA binding domains, wherein each zinc finger-based DNA binding domain binds to a 3 bp subsite. In other embodiments, the ZFN is a chimeric protein comprising a zinc finger-based DNA binding domain operably linked to an independent nuclease. In one embodiment, the independent endonuclease is a Fokl endonuclease. In one embodiment, the nuclease agent comprises a first ZFN and a second ZFN, wherein each of the first ZFN and the second ZFN is operably linked to a Fokl nuclease, wherein the first and the second ZFN recognize two contiguous target DNA sequences in each strand of the target DNA sequence separated by about 6 bp to about 40 bp cleavage site or about a 5 bp to about 6 bp cleavage site, and wherein the Fokl nucleases dimerize and make a double strand break (see, for example, US20060246567, US20080182332, US20020081614, US20030021776, WO/2002/057308, US20130123484, US20100291048 and WO 11/017293).

In an embodiment, the programmable nuclease may be a DNA programmed argonaute (WO 14/189628). Prokaryotic and eukaryotic argonautes are enzymes involved in RNA interference pathways. An argonaute can bind and cleave a target nucleic acid by forming a complex with a designed nucleic acid-targeting acid. Cleavage can introduce double stranded breaks in the target nucleic acid which can be repaired by non-homologous end joining machinery. A DNA "guided" or "programmed" argonaute can be directed to introducing double stranded DNA breaks in predetermined locations in DNA. In an embodiment, the argonaute is from Natronobacterium gregoryi.

Homologous recombination

In an embodiment, the genetic modification is introduced by homologous recombination. Homologous recombination is a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA which can involve the use of the double-strand break repair (DSBR) pathway and the synthesis-dependent strands annealing (SDSA pathway) (Lodish et al., 2000; Weaver, 2002). Homologues recombination can be used to a delete a gene or portion thereof, or to introduce a substitution or an insertion into the antiviral gene or a regulatory region thereof. In addition, homologous recombination can be used to insert a transgene. Homologous recombination can be used to introduce a genetic modification into the DNA of a host cell by any method known to a person skilled in the art. In an embodiment, homologous recombination may be triggered by a programmable nuclease. Double-stranded RNA

In one embodiment, the genetic modification is a transgene which encodes a dsRNA molecule for RNAi, preferably integrated into the genome of the avian. In another embodiment, the exogenous compound is a dsRNA molecule for RNAi, or a transgene encoding the dsRNA (for instance provided in a suitable expression vector such as a virus).

The terms "RNA interference", "RNAi" or "gene silencing" refer generally to a process in which a dsRNA molecule reduces the expression of a nucleic acid sequence with which the double-stranded RNA molecule shares substantial or total homology. However, it has been shown that RNA interference can be achieved using non-RNA double stranded molecules (see, for example, US 20070004667).

The present invention includes nucleic acid molecules comprising and/or encoding double-stranded regions for RNA interference for use in the invention. The nucleic acid molecules are typically RNA but may comprise chemically-modified nucleotides and non-nucleotides.

The double-stranded regions should be at least 19 contiguous nucleotides, for example about 19 to 23 nucleotides, or may be longer, for example 30 or 50 nucleotides, or 100 nucleotides or more. The full-length sequence corresponding to the entire gene transcript may be used. Preferably, they are about 19 to about 23 nucleotides in length.

The degree of identity of a double-stranded region of a nucleic acid molecule to the targeted transcript should be at least 90% and more preferably 95-100%. The nucleic acid molecule may of course comprise unrelated sequences which may function to stabilize the molecule.

The term "short interfering RNA" or "siRNA" as used herein refers to a nucleic acid molecule which comprises ribonucleotides capable of inhibiting or down regulating gene expression, for example by mediating RNAi in a sequence-specific manner, wherein the double stranded portion is less than 50 nucleotides in length, preferably about 19 to about 23 nucleotides in length. For example the siRNA can be a nucleic acid molecule comprising self-complementary sense and antisense regions, wherein the antisense region comprises nucleotide sequence that is complementary to nucleotide sequence in a target nucleic acid molecule or a portion thereof and the sense region having nucleotide sequence corresponding to the target nucleic acid sequence or a portion thereof. The siRNA can be assembled from two separate oligonucleotides, where one strand is the sense strand and the other is the antisense strand, wherein the antisense and sense strands are self-complementary.

As used herein, the term siRNA is meant to be equivalent to other terms used to describe nucleic acid molecules that are capable of mediating sequence specific RNAi, for example micro-RNA (miRNA), short hairpin RNA (shRNA), short interfering oligonucleotide, short interfering nucleic acid (siNA), short interfering modified oligonucleotide, chemically-modified siRNA, post-transcriptional gene silencing RNA (ptgsRNA), and others. In addition, as used herein, the term RNAi is meant to be equivalent to other terms used to describe sequence specific RNA interference, such as post transcriptional gene silencing, translational inhibition, or epigenetics. For example, siRNA molecules of the invention can be used to epigenetically silence genes at both the post-transcriptional level or the pre-transcriptional level. In a non-limiting example, epigenetic regulation of gene expression by siRNA molecules of the invention can result from siRNA mediated modification of chromatin structure to alter gene expression.

By "shRNA" or "short-hairpin RNA" is meant an RNA molecule where less than about 50 nucleotides, preferably about 19 to about 23 nucleotides, is base paired with a complementary sequence located on the same RNA molecule, and where said sequence and complementary sequence are separated by an unpaired region of at least about 4 to about 15 nucleotides which forms a single-stranded loop above the stem structure created by the two regions of base complementarity. An Example of a sequence of a single-stranded loop includes: 5' UUCAAGAGA 3' .

Included shRNAs are dual or bi-finger and multi-finger hairpin dsRNAs, in which the RNA molecule comprises two or more of such stem-loop structures separated by single-stranded spacer regions.

Once designed, the nucleic acid molecules comprising a double-stranded region can be generated by any method known in the art, for example, by in vitro transcription, recombinantly, or by synthetic means.

Modifications or analogues of nucleotides can be introduced to improve the properties of the nucleic acid molecules of the invention. Improved properties include increased nuclease resistance and/or increased ability to permeate cell membranes. Accordingly, the terms "nucleic acid molecule" and "double-stranded RNA molecule" includes synthetically modified bases such as, but not limited to, inosine, xanthine, hypoxanthine, 2-aminoadenine, 6-methyl-, 2-propyl- and other alkyl- adenines, 5-halo uracil, 5-halo cytosine, 6-aza cytosine and 6-aza thymine, pseudo uracil, 4-thiuracil, 8- halo adenine, 8-aminoadenine, 8-thiol adenine, 8-thiolalkyl adenines, 8-hydroxyl adenine and other 8-substituted adenines, 8-halo guanines, 8-amino guanine, 8-thiol guanine, 8-thioalkyl guanines, 8-hydroxyl guanine and other substituted guanines, other aza and deaza adenines, other aza and deaza guanines, 5-trifluoromethyl uracil and 5- trifluoro cytosine.

Small molecules

In some embodiments, the exogenous compound is a small molecule. In an embodiment, the small molecule binds the antiviral protein thereby reducing the ability of the protein to perform its normal function in a virally infected avian egg.

In an embodiment, the compound that is administered may be a precursor compound which is inactive or comparatively poorly active, but which following administration is converted (e.g. metabolised) to a compound reduces the expression of an antiviral gene and/or protein activity in the egg when compared to an isogenic egg lacking the compound. In those embodiments, the compound that is administered may be referred to as a prodrug. Alternatively or in addition, the compounds that are administered may be metabolized to produce active metabolites which have activity in reducing the expression of an antiviral gene and/or protein activity in the egg when compared to an isogenic egg lacking the compound. The use of such active metabolites is also within the scope of the present disclosure. Depending on the substituents present in the exogenous compound, the compound may optionally be present in the form of a salt. Salts of compounds which are suitable for use in in the invention are those in which a counter ion is pharmaceutically acceptable. Suitable salts include those formed with organic or inorganic acids or bases. In particular, suitable salts formed with acids include those formed with mineral acids, strong organic carboxylic acids, such as alkane carboxylic acids of 1 to 4 carbon atoms which are unsubstituted or substituted, for example, by halogen, such as saturated or unsaturated dicarboxylic acids, such as hydroxycarboxylic acids, such as amino acids, or with organic sulfonic acids, such as (Ci_4)-alkyl- or aryl- sulfonic acids which are substituted or unsubstituted, for example by halogen. Pharmaceutically acceptable acid addition salts include those formed from hydrochloric, hydrobromic, sulphuric, nitric, citric, tartaric, acetic, phosphoric, lactic, pyruvic, acetic, trifluoroacetic, succinic, perchloric, fumaric, maleic, glycolic, lactic, salicylic, oxaloacetic, methanesulfonic, ethanesulfonic, p-toluenesulfonic, formic, benzoic, malonic, naphthalene-2-sulfonic, benzenesulfonic, isethionic, ascorbic, malic, phthalic, aspartic, and glutamic acids, lysine and arginine. Pharmaceutically acceptable base salts include ammonium salts, alkali metal salts, for example those of potassium and sodium, alkaline earth metal salts, for example those of calcium and magnesium, and salts with organic bases, for example dicyclohexylamine, N-methyl-D-glucomine, morpholine, thiomorpholine, piperidien, pyrrolidine, a mono-, di- or tri-lower alkylamine, for example ethyl-, t-butyl-, diethyl-, diisopropyl-, triethyl-, tributyl- or dimethyl-propylamine, or a mono-, di- or trihydroxy lower alkylamine, for example mono-, di- or triethanolamine. Corresponding internal salts may also be formed.

Those skilled in the art of organic and/or medicinal chemistry will appreciate that many organic compounds can form complexes with solvents in which they are reacted or from which they are precipitated or crystallised. These complexes are known as "solvates". For example, a complex with water is known as a "hydrate". Solvates, such as hydrates, exist when the drug substance incorporates solvent, such as water, in the crystal lattice in either stoichiometric or non-stoichiometric amounts. Drug substances are routinely screened for the existence of solvates such as hydrates since these may be encountered at any stage. Accordingly it will be understood that the compounds useful for the present invention may be present in the form of solvates, such as hydrates. Solvated forms of the compounds which are suitable for use in the invention are those wherein the associated solvent is pharmaceutically acceptable. For example, a hydrate is an example of a pharmaceutically acceptable solvate. The compounds useful for the present invention may be present in amorphous form or crystalline form. Many compounds exist in multiple polymorphic forms, and the use of the compounds in all such forms is encompassed by the present disclosure.

Small molecules useful for the present disclosure can be identified using standard procedures such as screening a library of candidate compounds for binding to an antiviral target protein of the invention, and then determining if any of the compounds which bind reduce protein activity. For example, a small molecule useful for reducing activity of the chicken IFN-α/β receptor 1 would bind the receptor and inhibit the ability of a ligand of the receptor (such as IFNoc) to induce a cellular signal.

Binding agents

In an embodiment, the exogenous compound is a protein which binds and reduces the activity of the antiviral protein. In an embodiment, the binding agent is an antibody or a fragment thereof. In some embodiments, the antibody is directed at and/or reduces the expression or activity of the IFNAR1, IL-6, CNOT4, MDA5, IFNa, ΙΡΝβ, IFNy, IFN , IFNAR2, UBE1DC1, GNAZ, CDX2, LOC100859339, IL28RA, ZFPM2, TRIM50, DNASEIL2, PHF21A, GAPDH, BACE2, HSBP1, PCGF5, IL-1RA, DDI2, CAPN13, UBA5, NPR2, IFIH1, LAMP1, EFR3A, ARRDC3, ABI1, SCAF4, GADL1, ZKSCAN7, PLVAP, RPUSD1, CYYR1, UPF3A, ASAP1, NXF1, TOP1MT, RALGAPB, SUCLA2, GORASP2, NSUN6, CELF1, ANGPTL7, SLC26A6, WBSCR27, SIL1, HTT, MYOC, TM9SF2,CEP250, F AMI 88 A, BCAR3, GOLPH3L, HN1, ADCY7, AKAP10, ALX1, CBLN4, CRK, CXORF56, DDX10, EIF2S3, ESF1, GBF1, GCOM1, GTPBP4, HOXB9, IFT43, IMP4, ISY1, KIAA0586, KPN A3, LRRIQ1, LUC7L, MECR, MRPL12, POLR3E, PWP2, RPL7A, SERPINH1, SLC47A2, SMYD2, STAB 1 , TTK, WNT3, IFNGR1, IFNGR2, IL-10R2, IFNK, IFNQ, IL-1RB and XPOl gene and/or protein or the corresponding receptor or agonist thereof. In some embodiments the binding agent is a bispecific antibody directed at any combination of two or more of: IFNAR1 , IL-6, CNOT4, MDA5, IFNa, IFN , IFNy, ΙΡΝλ, IFNAR2, UBE1DC1, GNAZ, CDX2, LOC100859339, IL28RA, ZFPM2, TRIM50, DNASEIL2, PHF21A, GAPDH, BACE2, HSBP1, PCGF5, IL-1RA, DDI2, CAPN13, UBA5, NPR2, IFIH1, LAMP1, EFR3A, ARRDC3, ABI1, SCAF4, GADL1, ZKSCAN7, PLVAP, RPUSD1, CYYR1, UPF3A, ASAP1, NXF1 , TOP1MT, RALGAPB, SUCLA2, GORASP2, NSUN6, CELF1, ANGPTL7, SLC26A6, WBSCR27, SIL1, HTT, MYOC, TM9SF2,CEP250, F AMI 88 A, BCAR3, GOLPH3L, HN1, ADCY7, AKAP10, ALX1, CBLN4, CRK, CXORF56, DDX10, EIF2S3, ESF1, GBF1, GCOM1, GTPBP4, HOXB9, IFT43, IMP4, ISY1, KIAA0586, KPN A3, LRRIQ1, LUC7L, MECR, MRPL12, POLR3E, PWP2, RPL7A, SERPINH1, SLC47A2, SMYD2, STAB 1 , TTK, WNT3, IFNGR1, IFNGR2, IL-10R2, IFNK, IFNQ, IL-1RB and XPOl or a receptor or agonist thereof. In an embodiment, the antibody is an antibody modified to penetrate or be taken up (passively or actively) by a cell of the avian egg. In an embodiment, the binding agent is not B 18R.

The term "antibody" as used herein includes polyclonal antibodies, monoclonal antibodies, bispecific antibodies, fusion diabodies, triabodies, heteroconjugate antibodies, chimeric antibodies including intact molecules as well as fragments thereof, and other antibody-like molecules. Antibodies include modifications in a variety of forms including, for example, but not limited to, domain antibodies including either the VH or VL domain, a dimer of the heavy chain variable region (VHH, as described for a camelid), a dimer of the light chain variable region (VLL), Fv fragments containing only the light (VL) and heavy chain (VH) variable regions which may be joined directly or through a linker, or Fd fragments containing the heavy chain variable region and the CHI domain.

A scFv consisting of the variable regions of the heavy and light chains linked together to form a single-chain antibody (Bird et al. , 1988; Huston et al. , 1988) and oligomers of scFvs such as diabodies and triabodies are also encompassed by the term "antibody". Also encompassed are fragments of antibodies such as Fab, (Fab')2 and FabFc2 fragments which contain the variable regions and parts of the constant regions. Complementarity determining region (CDR)-grafted antibody fragments and oligomers of antibody fragments are also encompassed. The heavy and light chain components of an Fv may be derived from the same antibody or different antibodies thereby producing a chimeric Fv region. The antibody may be of animal (for example mouse, rabbit or rat) or may be chimeric (Morrison et al., 1984). The antibody may be produced by any method known in the art.

Using the guidelines provided herein and those methods well known to those skilled in the art which are described in the references cited above and in such publications as Harlow & Lane, Antibodies: a Laboratory Manual, Cold Spring Harbor Laboratory, (1988) the antibodies for use in the methods of the present invention can be readily made.

The antibodies may be Fv regions comprising a variable light (VL) and a variable heavy (VH) chain in which the light and heavy chains may be joined directly or through a linker. As used herein a linker refers to a molecule that is covalently linked to the light and heavy chain and provides enough spacing and flexibility between the two chains such that they are able to achieve a conformation in which they are capable of specifically binding the epitope to which they are directed. Protein linkers are particularly preferred as they may be expressed as an intrinsic component of the Ig portion of the fusion polypeptide.

In one embodiment, the antibodies have the capacity for intracellular transmission. Antibodies which have the capacity for intracellular transmission include antibodies such as camelids and llama antibodies, shark antibodies (IgNARs), scFv antibodies, intrabodies or nanobodies, for example, scFv intrabodies and VHH intrabodies. Such antigen binding agents can be made as described by Harmsen and De Haard (2007), Tibary et al. (2007) and Muyldermans et al. (2001). Yeast SPLINT antibody libraries are available for testing for intrabodies which are able to disrupt protein-protein interactions (see for example, Visintin et al. (2008) for methods for their production). Such agents may comprise a cell-penetrating peptide sequence or nuclear-localizing peptide sequence such as those disclosed in Constantini et al. (2008). Also useful for in vivo delivery are Vectocell or Diato peptide vectors such as those disclosed in De Coupade et al. (2005) and Meyer-Losic et al. (2006).

In addition, the antibodies may be fused to a cell penetrating agent, for example a cell-penetrating peptide. Cell penetrating peptides include Tat peptides, Penetratin, short amphipathic peptides such as those from the Pep-and MPG-families, oligoarginine and oligolysine. In one example, the cell penetrating peptide is also conjugated to a lipid (C6-C18 fatty acid) domain to improve intracellular delivery (Koppelhus et al., 2008). Examples of cell penetrating peptides can be found in Howl et al. (2007) and Deshayes et al. (2008). Thus, the invention also provides the use of antibodies fused via a covalent bond (e.g. a peptide bond), at optionally the N-terminus or the C-terminus, to a cell-penetrating peptide sequence.

Nucleic acid constructs

Introduction of a genetic modification into an avian and/or into an egg of an avian may involve the use of nucleic acid construct. In an embodiment, the nucleic acid construct may comprise a transgene. As used herein, "nucleic acid construct" refers to any nucleic acid molecule that encodes, for example, a double-stranded RNA molecule as defined herein, a RNA, DNA or RNA/DNA hybrid sequences which "guides" or "targets" a programmable nuclease, or a polynucleotide of interest in a vector. Typically, the nucleic acid construct will be double stranded DNA or double-stranded RNA, or a combination thereof. Furthermore, the nucleic acid construct will typically comprise a suitable promoter operably linked to an open reading frame encoding the polynucleotide. The nucleic acid construct may comprise, for example, a first open reading frame encoding a first single strand of the double-stranded RNA molecule, with the complementary (second) strand being encoded by a second open reading frame by a different, or preferably the same, nucleic acid construct. The nucleic acid construct may be a linear fragment or a circular molecule and it may or may not be capable of replication. The skilled person will understand that the nucleic acid construct of the invention may be included within a suitable vector. Transfection or transformation of the nucleic acid construct into a recipient cell allows the cell to express an RNA or DNA molecule encoded by the nucleic acid construct.

In another example, the nucleic acid construct may express multiple copies of the same, and/or one or more (e.g. 1, 2, 3, 4, 5, or more) including multiple different, RNA molecules comprising a double-stranded region, for example a short hairpin RNA. In another example, the nucleic acid construct may be a gene targeting cassette as described in Schusser et al. (2013)

The nucleic acid construct also may contain additional genetic elements. The types of elements that may be included in the construct are not limited in any way and may be chosen by one with skill in the art. In some embodiments, the nucleic acid construct is inserted into a host cell as a transgene. In such instances it may be desirable to include "stuffer" fragments in the construct which are designed to protect the sequences encoding the RNA molecule from the transgene insertion process and to reduce the risk of external transcription read through. Stuffer fragments may also be included in the construct to increase the distance between, e.g., a promoter and a coding sequence and/or terminator component. The stuffer fragment can be any length from 5- 5000 or more nucleotides. There can be one or more stuffer fragments between promoters. In the case of multiple stuffer fragments, they can be the same or different lengths. The stuffer DNA fragments are preferably different sequences. Preferably, the stuffer sequences comprise a sequence identical to that found within a cell, or progeny thereof, in which they have been inserted. In a further embodiment, the nucleic acid construct comprises stuffer regions flanking the open reading frame(s) encoding the double stranded RNA(s).

Alternatively, the nucleic acid construct may include a transposable element, for example a transposon characterized by terminal inverted repeat sequences flanking the open reading frames encoding the double stranded RNA(s). Examples of suitable transposons include Tol2, mini-Tol, Sleeping Beauty, Mariner and Galluhop.

Other examples of an additional genetic element which may be included in the nucleic acid construct include a reporter gene, such as one or more genes for a fluorescent marker protein such as GFP or RFP; an easily assayed enzyme such as beta- galactosidase, luciferase, beta-glucuronidase, chloramphenical acetyl transferase or secreted embryonic alkaline phosphatase; or proteins for which immunoassays are readily available such as hormones or cytokines. Other genetic elements that may find use in embodiments of the present invention include those coding for proteins which confer a selective growth advantage on cells such as adenosine deaminase, aminoglycodic phosphotransferase, dihydrofolate reductase, hygromycin-B- phosphotransferase, or drug resistance.

Where the nucleic acid construct is to be transfected into an avian, it is desirable that the promoter and any additional genetic elements consist of nucleotide sequences that naturally occur in the avian's genome.

In some instances it may be desirable to insert the nucleic acid construct into a vector. The vector may be, e.g., a plasmid, virus or artificial chromosome derived from, for example, a bacteriophage, adenovirus, adeno-associated virus, retrovirus, poxvirus or herpesvirus. Such vectors include chromosomal, episomal and virus- derived vectors, e.g., vectors derived from bacterial plasmids, bacteriophages, and viruses, vectors derived from combinations thereof, such as those derived from plasmid and bacteriophage genetic elements, cosmids and phagemids.

In an embodiment, the nucleic acid construct comprises a promoter. The skilled person will appreciate that a promoter such as a constitutive promoter, tissue specific or development stage specific promoter or an inducible promoter can be used in the present invention. In an embodiment, the promoter is an avian promoter. In an embodiment, the promoter is a Pol I, Pol II or Pol II promoter. Examples of avian promoters include the 7sK RNA polymerase III Promoter, U6 RNA polymerase II promoter (Bannister et al., 2007; Massine et al., 2005).

Transgenic avians

A "transgenic avian" refers to an avian in which one or more, or all, of the cells contain a genetic modification. Examples of "genetic modification" include, but are not limited to deletion, substitution or insertion in a gene and/or regulator region thereof. "Insertion" can include, but is not limited to insertion of a single nucleotide or insertion of a nucleic acid construct ("transgene"). In an embodiment, the genetic modification is in the germ line of the transgenic avian. In an embodiment, the genetic modification produced using a programmable nuclease alters the coding region of an endogenous avian antiviral gene such that a functional protein is not produced, or the encoded protein has reduced activity. The genetic modification may be extrachromasomal or integrated into the nuclear or mitochondrial genome of the egg. Transgenic avians comprising a genetic modification in the germ line can be used for the production of avians and/or eggs comprising the germline genetic modification. Transgenic avians of the present invention can be used for the production of eggs comprising a genetic modification wherein the genetic modification reduces the expression of an antiviral gene and/or protein in the egg when compared to an isogenic egg lacking the genetic modification. In one embodiment, the genetic modification results in reduced expression of one or more genes and/or proteins in the animal and/or progeny thereof and/or eggs produced by the avian or progeny thereof. In an embodiment, a gene knockout animal can be produced. In an embodiment, the targeted germline genetic modification is in a sex chromosome. In an alternate embodiment, the targeted germ line genetic modification is a somatic chromosome. In another embodiment, the genetic modification is at least introduced into the DNA of the fertilized ovum (at the single cell stage). As the skilled person will appreciate, in this embodiment the genetic modification may be introduced into either the maternal or paternal derived DNA, or both.

Techniques for producing transgenic animals are well known in the art. A useful general textbook on this subject is Houdebine, Transgenic animals - Generation and Use (Harwood Academic, 1997).

Heterologous DNA can be introduced, for example, into fertilized ova. For instance, totipotent or pluripotent stem cells can be transformed by microinjection, calcium phosphate mediated precipitation, liposome fusion, retroviral infection or other means, the transformed cells are then introduced into the embryo, and the embryo then develops into a transgenic animal. In one method, developing embryos are infected with a retrovirus containing the desired DNA, and transgenic animals produced from the infected embryo. In an alternative method, however, the appropriate DNAs are coinjected into the pronucleus or cytoplasm of embryos, preferably at the single cell stage, and the embryos allowed to develop into mature transgenic animals.

Another method used to produce a transgenic avian involves microinjecting a nucleic acid into pro-nuclear stage eggs by standard methods. Injected eggs are then cultured before transfer into the oviducts of pseudopregnant recipients.

Transgenic avians may also be produced by nuclear transfer technology. Using this method, fibroblasts from donor animals are stably transfected with a plasmid incorporating the coding sequences for a binding domain or binding partner of interest under the control of regulatory sequences. Stable transfectants are then fused to enucleated oocytes, cultured and transferred into female recipients. Sperm-mediated gene transfer (SMGT) is another method that may be used to generate transgenic animals. This method was first described by Lavitrano et al. (1989).

Another method of producing transgenic animals is linker based sperm-mediated gene transfer technology (LB-SMGT). This procedure is described in US 7067308. Briefly, freshly harvested semen is washed and incubated with murine monoclonal antibody mAbC (secreted by the hybridoma assigned ATCC accession number PTA- 6723) and then the construct DNA. The monoclonal antibody aids in the binding of the DNA to the semen. The sperm/DNA complex is then artificially inseminated into a female.

Another method used to produce a transgenic avian is homologous recombination. One example of this procedure is provided in Schusser et al. (2013). Schusser et al describes gene targeting by homologous recombination in cultured primordial germ cells to generate gene specific knockout birds. In one example, the transgenic avian is produced using the gene silencing cassette described in Schusser et al. (2013).

Germ line transgenic chickens may be produced by injecting replication- defective retrovirus into the subgerminal cavity of chick blastoderms in freshly laid eggs (US 5,162,215; Bosselman et al., 1989; Thoraval et al., 1995). The retroviral nucleic acid carrying a foreign gene randomly inserts into a chromosome of the embryonic cells, generating transgenic animals, some of which bear the transgene in their germ line. Use of insulator elements inserted at the 5' or 3' region of the fused gene construct to overcome position effects at the site of insertion has been described (Chim et al, 1993).

Another method for generating germ line transgenic animals is by using a transposon, for example the Tol2 transposon, to integrate a nucleic acid construct of the invention into the genome of an animal. The Tol2 transposon which was first isolated from the medaka fish Oryzias latipes and belongs to the hAT family of transposons is described in Koga et al. (1996) and Kawakami et al. (2000). Mini-Tol2 is a variant of Tol2 and is described in Balciunas et al. (2006). The Tol2 and Mini-Tol2 transposons facilitate integration of a transgene into the genome of an organism when co-acting with the Tol2 transposase. By delivering the Tol2 transposase on a separate non- replicating plasmid, only the Tol2 or Mini-Tol2 transposon and transgene is integrated into the genome and the plasmid containing the Tol2 transposase is lost within a limited number of cell divisions. Thus, an integrated Tol2 or Mini-Tol2 transposon will no longer have the ability to undergo a subsequent transposition event. Additionally, as Tol2 is not known to be a naturally occurring avian transposon, there is no endogenous transposase activity in an avian cell, for example a chicken cell, to cause further transposition events.

Any other suitable transposon system may be used in the methods of the present invention. For example, the transposon system may be a Sleeping Beauty, Frog Prince or Mosl transposon system, or any transposon belonging to the tcl /mariner or hAT family of transposons may be used.

The injection of avian embryonic stem cells into recipient embryos to yield chimeric birds is described in US 7,145,057. Breeding the resulting chimera yields transgenic birds whose genome is comprised of exogenous DNA.

Methods of obtaining transgenic chickens from long-term cultures of avian primordial germ cells (PGCs) are described in US 20060206952. When combined with a host avian embryo by known procedures, those modified PGCs are transmitted through the germ line to yield transgenic offspring.

A viral delivery system based on any appropriate virus may be used to deliver the nucleic acid constructs of the present invention to a cell. In addition, hybrid viral systems may be of use. The choice of viral delivery system will depend on various parameters, such as efficiency of delivery into the cell, tissue, or organ of interest, transduction efficiency of the system, pathogenicity, immunological and toxicity concerns, and the like. It is clear that there is no single viral system that is suitable for all applications. When selecting a viral delivery system to use in the present invention, it is important to choose a system where nucleic acid construct-containing viral particles are preferably: 1) reproducibly and stably propagated; 2) able to be purified to high titers; and 3) able to mediate targeted delivery (delivery of the nucleic acid expression construct to the cell, tissue, or organ of interest, without widespread dissemination).

In one embodiment, transfection reagents can be mixed with an isolated nucleic acid molecule, polynucleotide or nucleic acid construct as described herein and injected directly into the blood of developing avian embryos as described in WO 2013/155572. This method is referred to herein as "direct injection". Using such a method the transgene is introduced into primordial germ cells (PGCs) in the embryo and inserted into the genome of the avian. Direct injection can additional be used to administer a programmable nuclease.

Accordingly, a polynucleotide, such as transgene and/or nucleic acid construct as defined herein, can be complexed or mixed with a suitable transfection reagent. The term "transfection reagent" as used herein refers to a composition added to the polynucleotide for enhancing the uptake of the polynucleotide into a eukaryotic cell including, but not limited to, an avian cell such as a primordial germ cell. While any transfection reagent known in the art to be suitable for transfecting eukaryotic cells may be used, transfection reagents comprising a cationic lipid are particularly useful. Non- limiting examples of suitable commercially available transfection reagents comprising cationic lipids include Lipofectamine (Life Technologies) and Lipofectamine 2000 (Life Technologies).

The polynucleotide may be mixed (or "complexed") with the transfection reagent according to the manufacturer's instructions or known protocols. By way of example, when transfecting plasmid DNA with Lipofectamine 2000 transfection reagent (Invitrogen, Life Technologies), DNA may be diluted in 50 Opit-MEM medium and mixed gently. The Lipofectamine 2000 reagent is mixed gently and an appropriate amount diluted in 50 μL· Opti-MEM medium. After a 5 minute incubation, the diluted DNA and transfection reagent are combined and mixed gently at room temperature for 20 minutes.

A suitable volume of the transfection mixture may then be directly injected into an avian embryo in accordance with the method of the invention. Typically, a suitable volume for injection into an avian embryo is about 1 μL· to about 3 μί, although suitable volumes may be determined by factors such as the stage of the embryo and species of avian being injected. The skilled person will appreciate that the protocols for mixing the transfection reagent and DNA, as well as the volume to be injected into the avian embryo, may be optimised in light of the teachings of the present specification.

Prior to injection, eggs are incubated at a suitable temperature for embryonic development, for example around 37.5 to 38°C, with the pointy end upward for approximately 2.5 days (Stages 12-17), or until such time as the blood vessels in the embryo are of sufficient size to allow injection. The optimal time for injection of the transfection mixture is the time of PGC migration that typically occurs around Stages 12-17, but more preferably Stages 13-14. As the skilled person will appreciate, broiler line chickens typically have faster growing embryos, and so injection should preferably occur early in Stages 13-14 so as to introduce the transfection mixture into the bloodstream at the time of PGC migration.

To access a blood vessel of the avian embryo, a hole is made in the egg shell. For example, an approximately 10 mm hole may be made in the pointy end of the egg using a suitable implement such as forceps. The section of shell and associated membranes are carefully removed while avoiding injury to the embryo and it's membranes. Following injection of the transfection mixture into the blood vessel of the avian embryo, the egg is sealed using a sufficient quantity of parafilm, or other suitable sealant film as known in the art. For example, where a 10 mm hole has been made in the shell, an approximately 20 mm square piece of parafilm may be used to cover the hole. A warm scalpel blade may then be used to affix the parafilm to the outer egg surface. Eggs are then turned over to the pointy-end down position and incubated at a temperature sufficient for the embryo to develop, such as until later analysis or hatch. The direct injection technique is further described in WO 2013/155572 which claims priority from US 61/636,331.

Animals and/or eggs produced using the methods of the invention can be screened for the presence of the genetic modification. This can step can be performed using any suitable procedure known in the art. For instance, a nucleic acid sample, such as a genomic DNA sample, can be analysed using standard DNA amplification and sequencing procedures to determine if the genetic modification is present at the targeted site (locus) in the genome. In an embodiment, the screening also determines whether the animal and/or egg is homozygous or heterozygous for the genetic modification. In another embodiment, the avian is screened to identify whether the genetic modification can be found in germ line cells such that it can be passed on to its offspring.

Viruses

Viruses which can be produced in avian eggs of the invention include any virus capable of replicating and producing new viral particles in an avian egg. Such viruses include DNA and RNA viruses. In an embodiment, the virus is an animal virus. In an embodiment, the animal virus is a human virus. In an embodiment, the virus is a non- human virus. In an embodiment, the virus is an avian virus.

Examples of viruses for use in the present invention include, but are not limited to, viruses in a family selected from: Orthomyxoviridae, Herpesviridae, Paramyxoviridae, Flaviviridae and Coronaviridae. In an embodiment, the virus is a member of the Orthomyxoviridae family.

The Orthomyxoviridae virus may be, for example, Influenza A virus, Influenza B virus, Influenza C virus, Isavirus, Thogotovirus and/or Quaranjavirus. The influenza virus may be an Influenza A virus. The Influenza A virus may be selected from Influenza A viruses isolated from an animal. In an embodiment, the animal is a human or an avian. In particular, the Influenza A virus may be selected from H1N1, H1N2, H1N3, H1N4, H1N5, H1N6, H1N7, H1N9, H2N1, H2N2, H2N3, H2N4, H2N5, H2N7, H2N8, H2N9, H3N1, H3N2, H3N3, H3N4, H3N5, H3N6, H3N8, H4N1, H4N2, H4N3, H4N4, H4N5, H4N6, H4N8, H4N9, H5N1, H5N2, H5N3, H5N6, H5N7, H5N8, H5N9, H6N1, H6N2, H6N3, H6N4, H6N5, H6N6, H6N7, H6N8, H6N9, H7N1, H7N2, H7N3, H7N4, H7N5, H7N7, H7N8, H7N9, H9N1, H9N2, H9N3, H9N5, H9N6, H9N7, H9N8, H10N1, H10N3, H10N4, H10N6, H10N7, H10N8, H10N9, H11N2, H11N3, H11N6, H11N9, H12N1, H12N4, H12N5, H12N9, H13N2, H13N6, H13N8, H13N9, H14N5, H15N2, H15N8, H15N9 and H16N3. In one embodiment, the Influenza A virus is selected from H1N1, H3N2, H7N7, and/or H5N1.

The Herpesviridae virus may be, for example, a HSV-1, HSV-2, varicella zoster virus, Epstein-barr virus or Cytomegalovirus.

The Paramyxoviridae virus may be, for example, a Paramyxovirinae or Pneumovirinae. In an embodiment, the Paramyxoviridae is Newcastle disease virus.

The Flaviviridae may be, for example, a Flavivirus, Hepacivirus, Pegivirus, Pestivirus. In an embodiment, the Flaviviridae may be the Apoi virus, Aroa virus, Bagaza virus, Banzi virus, Bouboui virus, Bukalasa bat virus, Cacipacore virus, Carey Island virus, Cowbone Ridge virus, Dakar bat virus, Dengue virus, Edge Hill virus, Entebbe bat virus, Gadgets Gully virus, Ilheus virus, Israel turkey meningoencephalomyelitis virus, Japanese encephalitis virus, Jugra virus, Jutiapa virus, Kadam virus, Kedougou virus, Kokobera virus, Koutango virus, Kyasanur Forest disease virus, Langat virus, Louping ill virus, Meaban virus, Modoc virus, Montana myotis leukoencephalitis virus, Murray Valley encephalitis virus, Ntaya virus, Omsk hemorrhagic fever virus, Phnom Penh bat virus, Powassan virus, Rio Bravo virus, Royal Farm virus, Saboya virus, Sal Vieja virus, San Perlita virus, Saumarez Reef virus, Sepik virus, St. Louis encephalitis virus, Tembusu virus, Tick-borne encephalitis virus, Tyuleniy virus, Uganda S virus, Usutu virus, Wesselsbron virus, West Nile virus, Yaounde virus, Yellow fever virus, Yokose virus, Zika virus

The Coronaviradae virus may be, for example, a Coronavirinae or a Corovirinae. The Coronavirinae may be a Alphacoronavirus, Betacoronavirus, Deltacoronavirus, or Gammacoronavirus. The Torovirinae may be a Alphacoronavirus or Betacoronavirus. In on embodiment, the Coronaviradae may be the SARS (severe acute respiratory syndrome) coronavirus.

In an embodiment, the virus in selected from: Influenza virus, Canine distemper virus, Measles virus, Reovirus, Eastern equine encephalitis virus, Canine parainfluenza virus, Rabies virus, Fowlpox virus, Western equine encephalitis virus, Mumps virus, Equine encephalomyelitis, Rubella virus, Egg drop syndrome virus, Avian oncolytic viruses, Avian infectious laryngotracheitis Herpesvirus, Newcastle disease virus, Bovine parainfluenza virus, Smallpox virus, Infectious bursal disease, Bovine Ibaraki virus, Recombinant poxvirus, Avian adenovirus type I, II or III, Swine Japanese encephalitis virus, Yellow fever virus, Herpes virus, Sindbis virus, Infections bronchitis virus, Semliki forest virus, Encephalomyelitis virus, Venezuelan EEV virus, Chicken anaemia virus, Marek's disease virus, Parvovirus, Foot and mouth disease virus, Porcine reproductive and respiratory syndrome virus, Classical swine fever virus, Bluetongue virus, Kabane virus, Infectious salmon anaemia virus, Infectious hematopoietic necrosis virus, Viral haemorrhagic septicemia virus and Infectious pancreatic necrosis virus.

Vaccine Production in Eggs

Methods of replicating viruses in avian eggs, and producing vaccines from these eggs, have been around for more than 70 years and thus are well known in the art. For example, conventional methods for producing influenza vaccine compositions have typically involved the growth of the viruses in embryonated chicken eggs. Viruses grown by this method are then used for producing, for example, live attenuated virus, killed whole virus or subunit vaccines compositions. One method for producing influenza vaccine composition is by inoculation of live influenza virus into 10-11 day old embryonated chicken eggs. This inoculated vaccine virus is incubated for a predetermined period of time e.g. 2 or more days to allow for virus replication before harvesting of the virus-rich allantoic fluid (Hoffmann et al., 2002). In one example, the predetermined time is at least 12 hours, or at least 24 hours, or at least 18 hours, or at least 24 hours, or a t least 48 hours, or at least 72 hours, or at least 4 days, or at least 5 days, or at least 6 days, or at least 7 days, or at least 8 days, or at least 9 days, or at least 10 days.

In a typical operation, eggs must be candled, the shells must be sterilized and each egg must be inoculated by injection of a small volume of virus into the allantoic cavity. The injected eggs then are incubated for 48-72 hours at 33°-37°C, candled again, refrigerated overnight and opened to allow harvesting of the allantoic fluid. The harvested fluid can then be clarified by filtration and/or centrifugation before processing for further purification. Requirements For Inactivated Influenza Vaccine, World Health Organization Technical Report Series, 384 (1966). Many commercially available influenza vaccines in the United States have been propagated in embryonated hen eggs. In an embodiment, the egg is a chicken egg and the virus is harvested day 8 to day 11. In an embodiment, the egg is a chicken egg and the virus is harvested about day 10. Harvesting the Replicated Virus or Particles thereof from the Egg

The replicated virus or particles thereof (such as split virus particles or subunit virus particles) can be harvested from the egg, preferably the allantoic fluid of the egg by any method known to the skilled person. For example, harvesting of replicated virus or particles thereof can involve one or more of the following steps: clarification, concentration, inactivation, nuclease treatment, separation/purification, polishing and sterile filtration (Wolf et al, 2008; Wolf et al., 2011; Kalbfuss et al, 2006; Josefsberg et al., 2012). In one example, clarification is performed by centrifugation, microfiltration and/or depth filtration. In one example, concentration is performed by centrifugation, ultrafiltration, precipitation, monoliths and/or membrane adsorber. In one example, inactivation is performed by UV, heat or chemical treatment. Chemical forms of inactivation include formalin, binary ethyleneimine and β-propiolactone or any other method known to the skilled person. In an embodiment, the nuclease treatment is treatment with benzonase. In one example, separation/purification is performed by ultracentrifugation (for example density gradient), bead chromatography (for example size exclusion chromatography, ion exchange chromatography or affinity chromatography), and/or membrane adsorber (for example ion exchange chromatography or affinity chromatography). In one example, polishing is performed by ultrafiltration and/or diafiltration. In one example, virus or virus particles can be concentrated by alcohol or polyethylene glycol precipitation. In one example, harvesting the replicated virus or particles thereof comprises the use of a membrane as described in Grein et al. (2013).

In another example, harvesting the replicated virus may include a virus disruption step to produce virus particles of a suitable size for a split vaccine composition or a subunit vaccine composition (Wolf et al., 2008; Josefsberg et al., 2012). Such a step can be any method that produces virus particles of a suitable size for a split vaccine composition or subunit vaccine composition. In one example, the disruption step is detergent solubilisation.

A skilled person would understand that harvested virus (whole attenuated or inactivated) or harvested virus particles (split virus particles or subunit virus particles) can be formulated into vaccine compositions. Such compositions can comprise one or more of: an adjuvant, an excipient, a binder, a preservative, a carrier coupling, a buffering agent, a stabilizing agent, an emulsifying agents, a wetting agent, a non-viral vector and a transfection facilitating compound (Josefsberg et al., 2011 ; Jones, 2008). A skilled person would further understand that such vaccine compositions can be lyophilized. In one example, the vaccine composition produced is suitable for human use. In one example, the vaccine composition produced is suitable for veterinary use.

EXAMPLES

Example 1 - Disruption of Interferon Response by Neutralizing Antibodies Increases Viral Yield in ovo

The ORF of ChlFNa, ChlFN , ChlFNy and ChlFN were expressed in Top F' 10 Escherichia coli (E. coli) competent cells using a pQE50 expression system and after induction with IPTG. Recombinant protein was solubilised and purified using Ni- NTA-Agarose. Biological activities of rchlFNs were measured using a virus neutralization assay (Lowenthal et al., 1995). rchlFNs protected cells over a range of concentrations and therefore are biologically active (Figure 1).

The rchlFNs were used as immunogens to generate rabbit antiserum against the homologous recombinant protein. New Zealand female white rabbits were immunized subcutaneously with the rchlFN protein in Quilaja saponaria (Quil A) cocktail adjuvant up to 7 times. Ammonium sulphate was used to enrich the globular serum proteins in the rabbit anti-chlFN antiserum. Enriched antisera were quantified using a Spectrophotometer (NanoDrop® ND-1000, NanoDrop Technologies, USA) prior to 0.2 μπι filter sterilization (Sartorius, Germany) of the antibodies for in ovo injection. Reactivity of the sera and polyclonal antibody recognition was tested using and Indirect ELISA analysis. In brief, purified rchlFNs were diluted to 5 μg/mL in coating buffer in 96-well ELISA plates read at 450nm on a Titertek Multiscan Plus plate reader. The analysis showed a dose-effect reactivity of the serum against the corresponding protein (Figure 2A).

Next, Hyline brown eggs (Hy-Line, Australia) at embryonic age day 10-11 were inoculated via allantoic fluid with antibody and/or virus. Stocks of influenza virus (provided by CSL Pty Ltd) were diluted to 10-5 in virus diluent containing 1% neomycin/polymyxin. PR8 (H1N1) or H5N1 vaccine virus (NIBRG-14) (CSL, Australia) inoculations of eggs were performed separately. Purified anti-chlFN and anti-chIL-6 antibodies were also diluted in virus diluent solution for inoculation into eggs at either 1000 μg, 200 μg or 20 μg per egg. After inoculation eggs were incubated at 35°C for 48 h.

The eggs were candled after incubation to check viability prior to being chilled

O/N at 4°C in preparation for harvesting. Allantoic fluid (5 mL) was removed from each egg for further analysis. HA assays were performed on the same day as harvest. Briefly, allantoic fluid samples were serial diluted 1/25 in PBS and added in duplicate to the last row of round bottomed 96 well plates (ICN Biochemicals, USA). 50 μL· of 0.5% of washed chicken RBC was added to all wells, gently tapped to mix and left at RT for at least 40 min and HA end point was determined. Experiments in ovo indicated that the anti-chIFN-a antibodies (Figure 2B) and anti-chIFN-β antibodies (Figure 2C) at all concentrations did not have a significant effect on the HA titre of either PR8 or NIBRG-14 virus in the eggs. However, the anti-chIFN-λ antibodies (Figure 3A) were shown to statistically improve the titre of PR8 virus when administered at 200 μg/egg (p=0.04). The H5N1 vaccine virus titre was statistically improved, up to 1.5 fold, when the antibodies were injected at both 1000 μg/egg (p=0.0045) and at 20 μg/egg (p=0.0001). Similarly, anti-chIFN-γ antibodies (Figure 3B), when inoculated at 1000 μg/egg (p=0.015), were capable of improving the HA titre of the H5N1 vaccine virus. Furthermore, the anti-chIL-6 antibodies (Figure 3C) also statistically enhanced H5N1 vaccine virus titres in eggs.

Example 2 - Disruption of Numerous Genes by siRNA in vitro Increases Viral Titres

In order to identify gene candidates with an antiviral function a set of genes were evaluated by small interference RNA (siRNA) assay. DF-1 cells were transfected with a multiplex (smartpool) of siRNA against each gene prior infection with avian influenza (AI) virus. The results show an increase in viral titres after KD without any apparent toxic effect on the cells (Figure 4). At least in some instances no apparent affect was observed but this may be due to the siRNA not being administered early enough to produce efficient KD (for example, considering the anti-IL6 antibody data this will most likely explain the IL-6 siRNA data in Figure 4). For CNOT4, IFNAR or MDA5 the effect of individual smartpool siRNAs on cell viability and gene silencing was assessed (Figure 5). Example 3 - Down-regulation of Numerous Genes by shRNA in ovo Increases Viral Titres

For in ovo analysis, siRNA was delivered as complexes with ABA-21/117Q/PF polymer (ABA-21/117Q; polymer without PolyFluor 570 dye labels) at molar ratios of 4: 1 of polymer to 2 nmol siRNA in a total of 200 μΐ. Complexes were formed in aqueous solution in the presence of phosphate-buffered saline (PBS). The required amount of polymer (316 μg), resuspended in water, was added to the tubes and mixed by vortexing. A total of 2 nmol, equivalent to 30 μg of siControl or 24.5 μg of siAntilFNARl was then added to the tubes and the sample vortexed. Complexion was allowed to continue for 1 h at room temperature. Complexes were injected directly into the corioallantoic fluid. After 48 hours virus was injected as previously described and samples were collected 24 hours after virus infection. Results show an increase of virus growth after KD of IFNAR1 (Figure 6 and Figure 7).

Example 4 - Deletion of the IFNAR1 Gene in Chickens Increases Viral Titres in vitro

To probe that permanent deletion of the chicken interferon (alpha, beta and omega) receptor 1, IFNAR1 (Gene ID: 395665) have an effect on viral yield; KO cell lines from the continuous cell line of chicken embryo fibroblasts (DF-1) were generated. Using the RNA-guided Cas9 nuclease from the microbial clustered regularly interspaced short palindromic repeats (CRISPR/Cas9) system, two different single guides RNA (sgRNA) were designed in order to produce a dual double-strand break by duplexing. sgRNA were cloned according to (Ran et al., 2013) and the corresponding constructs were transfected into DF-1 cells using encoding the deletion of around 200 bb removed entirely the transcription start site (TSS) and exon one of the IFNAR1 precursor. Single cells were isolated after sorting using a BD FACS Aria II™ cell sorter. The deletion in each clone was identified after genomic PCR screening to distinguish between wild type and monoallelic and biallelic targeted cell lines.

After transfection around 30% of the alleles presented a deletion of more than 200 bp that was confirmed by cloning and sequencing of the amplicom. Following cell sorting to single clones, cells were screened by gDNA PCR, and monoallelic and biallelic cell lines were isolated. Furthermore, the induced deletion proved to interrupt the expression of the gene at the transcriptional level in a gene-dosage dependent manner where mono-allelic cell lines showed half level of expression compared to wild-type and bi-allelic cell lines showed levels close to zero. This effect lasted even after challenging with the virus or poly(I:C) the latter, a strong inductor of the innate response (Figure 8A, B and C).

To evaluate the impact of the deletion on vaccine production the H1N1 strain A/WSN/1933 was used at high and low multiplicity of infection (1 and 0.1 MOI respectively). Using this approach viral yield increases significantly in biallelic cell lines after ten hours of infection, around three times those levels found in the wild-type cell lines when measured in a plaque-forming units (PFU) assay. Virus isolated also showed five times higher TCID50s from biallelic cell lines when compared to the parental cell line (Figure 8D).

Example 5 - Screening and identification of antiviral genes against Hendra Virus

A number of genes relevant for virus production were identified in an siRNA screen investigating proteins required for Hendra virus (HeV) infection in human HeLa cells. HeLa cells (ATCC CCL-2) were maintained in growth medium (Eagles Modified Eagle Medium; EMEM) supplemented with 10% v/v foetal bovine serum (FBS), 10 mM HEPES, 2 mM L-glutamine and 100 U/ml penicillin, and 100 μg/mL streptomycin (P/S; Life Technologies). HeLa cells (7 x 104) were reverse-transfected with siRNA pools (GE Life Sciences) using Dharmafect-1 (GE Life Sciences) in Opti- MEM (Life Technologies) overnight, after which media was removed and replaced with transfection media (growth media minus antibiotics) and cells incubated for a further 24 hours. Media was replaced ~6 hours post transfection (h.p.t.) and incubated for a further 18 hours. Cells were then infected with the Hendra Virus (HeV) (Hendra virus/ Australia/Horse/1994/Hendra). For the 50% tissue culture infective dose (TCID50), 10-fold dilutions of tissue culture supernatants were made in medium in a 96-well tissue culture. Plates were incubated for 3 days (HeV) at 37°C and 5% C02 and scored for cytopathic effect. The infectious titer was calculated by the method of Reed and Muench (1938). Viral replication for silenced genes was compared to a non- targeting siRNA control (siNT). A significant increase in viral replication was observed with silencing of a number of genes (see Figure 9 and Table 2). Silencing of ADCY7 demonstrated the highest increase in viral titre (see Table 2).

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

This application claims priority from Australian Provisional Application No. 2015904854 entitled "Production of viruses in avian eggs" filed on 24 November 2015, the entire contents of that application are hereby incorporated by reference.

All publications discussed and/or referenced herein are incorporated herein in their entirety.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

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