Technical Field

This invention relates to Lyme disease.

Background Art

Lyme disease is a systemic tick-borne illness generally characterized as a reddish or purplish target rash radiating around the tick bite. Lyme disease is generally characterized as being caused by a spirochete bacteria Borrelia burgdorferi. Various sub-species and strains of this organism have been identified, but their inter-relationship is not finally determined.

The diagnostic acumen for Lyme Disease is poor. The ability to quickly and reliably detect the presence of Borrelia burgdorferi in patients suspected of having Lyme Disease is of great medical importance. The in-vitro culture of Borrelia burgdorferi is current¬ ly the most effective technique but is an impractical method of diagnosis.

A technique for detecting the presence of the organism Borrelia burgdorferi by utilizing antibodies specific for at least one antigen of the organism is described in U.S. Patent No. 4,888,276. The use of other monoclonal and polyclonal antibody tests for detection of Borrelia burgdorferi antigens is described in the JOURNAL OF CLINICAL MICROBIOLOGY, June 1991, page 1162-1170. However, immunological methods are neither

sufficiently sensitive nor reliable for diagnostic screening.

Molecular biological techniques have also been attempted. PCR (Polymerase Chain Reaction) amplifica- tion and subsequent hybridization of amplified material with radiolabeled probe has been reported in the JOURNAL OF CLINICAL MICROBIOLOGY, June 1990, page 1089-1093 and in the JOURNAL OF CLINICAL MICROBIOLOGY, April 1991, page 731- 737. However, this PCR work was not done on clinical samples. In general, the PCR technique works best when amplifying nucleic acid materials present in pure culture or in joint or cerebrospinal fluid. The PCR technique has limited utility in whole blood or plasma samples. Therefore, the amplification technique does not provide an adequate diagnostic method for detection of Borrelia burgdorferi in individuals suspected of having Lyme Disease.

Summary Of The Invention

The present invention provides a quick and reliable diagnostic technique suitable for use with whole blood or plasma samples taken from patients suspected of having Lyme disease.

The present invention is concerned with a method for detecting the presence of an organism associ- ated with Lyme disease, such as, B. burgdorferi compris¬ ing the steps: a) . combining a sample with an oligonucleo- tide probe for the organism; b) . hybridizing the probe with the organism; and

c) . determining the presence of the organism hybridized with the probe.

It is an object of the present invention to use an oligonucleotide that has the ability to hybridize with the organism in clinical or experimental samples without amplification.

It is also an object of the present invention to describe a oligonucleotide that has the ability to act as a hybridizing probe with the nucleic acids of the organism. The oligonucleotide can be characterized as containing the following formula:

5 ^» NH2 GTT CGC CTT CGC CTC CGG TAT TC or 5 ¹ GTT CGC CTT CGC CTC CGG TAT TC NH ₂

Brief Description of the Drawings

FIGURE 1 is an exploded sectional view of the apparatus employed in the Lyme disease detection method;

FIGURE 2 is the assembled structure of Figure

1;

FIGURE 3 is a top view of the filter used in the apparatus of Figure 1;

FIGURE 4 is a top view of another filter used in the apparatus of Figure 1; and

FIGURE 5 is a top view of the filter support used in the apparatus of Figure 1.

Detailed Description

The term "oligonucleotide" is generally taken to mean oligo-deoxyribonucleotide. Oligonucleotide lengths are usually stated as numbers: e.g., 18 "mer", 35 "mer", etc. Sequences are given using the accepted abbreviations. Correctly, the component nucleotides are abbreviated 'dA ¹ (deoxyadenylate) 'dG ¹ (deoxyguanylate) •dC ¹ (deoxycytidylate) and 'dT' (deoxythy idylate) . In the present application, the most preferred oligonucleo- tide is as follows:

5' NH2 GTT CGC CTT CGC CTC CGG TAT TC.

The most preferred is that the oligonucleotide has a primary amine bound to the terminal 5* or 3* phosphoribosyl moiety.

It is to be appreciated that for an oligonu¬ cleotide to be a probe for the organism burgdorferi, it is not necessary that a 23 "mer" be utilized. It may be that only an effective portion of the aforementioned oligonucleotide need be used. For example, the first nine oligonucleotides or the last nine oligonucleotides or the nine in the middle may be useful. Also, the 23 "mer" oligonucleotide may be a part of a larger sequence of bases and still be functional as a hybridizing agent for B. burgdorferi. Therefore, when utilizing the terminology oligonucleotide probe of the present appli¬ cation it includes the 23 "mer" and all effective portions thereof, sufficient to hybridize with B. burg¬ dorferi organism.

The 23 "mer" oligonucleotide can be synthe- sized by any well known technique for oligonucleotide sequences. A number of references describe synthesis of

synthetic oligonucleotides such as Oligonucleotide Synthesis, H. A. White; MOLECULAR BIOLOGY AND BIOTECHNOLOGY, edited by Walker, J.M. , Gingold, E.B.; ROYAL SOCIETY OF CHEMISTRY, London, Chapter 16, pages 349-371. Also, R. Frank et al., Simultaneous Synthesis and Biological Applications of DNA Fragments : An Efficient and Complete Methodology. METHODS IN ENZYMOLOGY, Volume 154, pages 221- 249, M. H. Caruthers et al., Chemical Synthesis of Deoxyoligonucleotides by the Phosphor amidite Method, METHODS IN ENZYMOLOGY, Vol. 154, pp. 287-313; S. J. Horvath et al., An Automated DNA Synthesizer Employing Deoxynu- cleotide 3 ' -Phosphoramiditeε, METHODS IN ENZYMOLOGY, Vol. 154, pp. 314-326. Commercial machines are likewise available for producing the desired oligonucleotide. Such machines are generally available from Beckman Instruments or Applied Biosystems.

The present application is likewise concerned with a method for detecting the presence of the organism B. burgdorferi. The sample that is to be analyzed can be a human sample or animal sample. The sample may be a biological fluid such as blood, plasma, serum, sputum, spinal fluids, tissue extracts, animal fluids, culture medium, urine, and the like. The sample may also be portions of the above biological fluid including plasma from blood and the like. The preferred sample is whole blood as extracted from a human or an animal. The test is a non-invasive in-vitro test, but rather is made on a specimen taken from the human or animal.

The mechanism for detecting the presence of the organism is to hybridize the oligonucleotide with the organism. By hybridization is meant a process whereby single-stranded DNA or RNA molecules are com-

bined and double-stranded molecules formed if complemen¬ tary sequences exist in the specimen to be tested.

To assist in the determination of the product of hybridization, the oligonucleotide probe is marked or treated with a label to facilitate the subsequent detection.

Any number of convenient labels may be placed on the probe. The probe could be radioactively labeled or covalently bonded with other labels such as a fluo- rescent label or other appropriate label that would make the probe susceptible to detection, such as being bound to an enzyme. The probe could be reacted with an radioactive marker such as ¹²⁵ I or ¹³¹ I or ³² P. Radioactive labels such as ³ H, ¹⁴ C, and the like may also be used. The most preferred technique is radiolabeling with ¹²⁵ I which, because of its half-life, is the most practical for use in a clinical setting.

A radioactive iodine conjugate may be reacted with the oligonucleotide using standard techniques, heretofore used in the biochemical arts to label pro¬ tein. Specifically, the probe bearing a 5' or 3' primary amine could be reacted with Bolton Hunter (BH) reagent followed by a borate solution. See Preparation of Radiolabelled Antigens. MOLECULAR IMMUNOLOGY, (1984) edited by Atassi, VanOss, and Absolom, Dekker, 1984, pages 410-411. The labeled probe could be subsequently purified on a BioRad spin column followed by final purification on polyacrylamide gel or by reverse phase High Performance Liquid Chromatography (HPLC) .

The oligonucleotide probe could also be reacted with the fluorescing agent such as fluorescein

isothiocyanate (FITC) , tetramethylrhodamine isothiocyan- ate (TRITAC) , texas red, phycoerythrin (PE) , allophyco- cyanin (APC) , and the like. For varying lengths of the nucleotide probe, different reagents could be utilized and therefore detected in a fluorometer or in a multi¬ color fluorescent system by using a flow cytometer, NATIONAL ACADEMY OF SCIENCES U.S.A., Volume 83, pages 8361- 8365, November 1986.

If an Elisa technique were to be utilized, then the nucleotide probe could be reacted with an enzyme which enzyme could then be detected as in a commercially available enzyme linked immunosorbent assay. Suitable enzymes may be horse radish peroxidase, alkaline phosphatase, urease, and the like. Commercial- ly available Elisa are readily available.

Other markers may likewise be used such s chemiluminescers such as luciferin, 2,3-dihydrophthal- azinediones, e.g., luminol, and the like.

After the appropriately labeled probe is prepared, it can then be hybridized with the specimen. The nucleic acid material is placed in contact with a physical support on which the denatured nucleic acids adhere. In general, the Borrelia burgdorferi spiro- chetes or vesicles containing nucleic acid material shed by Borrelia burgdorferi contained in the specimen will be lysed and their nucleic acids denatured in the presence of heat and hybridization buffer. Thereafter, the labeled probe is contacted with the nucleic acid material and incubated. Subsequently, the support on which the hybridization reaction has taken place can then be utilized to detect the presence of the hybrid¬ ized product.

Most preferably, the solid support on which the nucleic acids are immobilized is a nitrocellulose filter resting on a blotter filter and filter support as contained within the plastic tube of the diagnostic unit described below. Any nonbrittle plastic to which sample materials and reagents will not adhere, such as polypro¬ pylene, may be used.

Number 10 of Figure 1 consists of the compo¬ nents comprising the preferred diagnostic unit to be employed in the detection of Borrelia burgdorferi from clinical samples of whole blood or plasma.

Figure 2 shows the components assembled and ready to accept a diagnostic sample. Specifically, a cylindrical plastic upper chamber 12, having a height of 7 centimeters and an outer diameter of 0.98 centimeters bears exteriorly protruding snap-lock connectors 16 separated by a vertical distance of 0.9 centimeters. A plastic lower chamber 14, having a height of 4 centime¬ ters and an inner diameter of 1.00 centimeters contains an interiorly protruding snap-lock connector 18 and a ridge 20 separated by a vertical distance of 1.0 centi¬ meters. A plastic filter support 26 of 0.1 centimeter thickness rests on the ridge 20 of lower chamber 14. On the filter support 26 rests filter paper 24, such as Whatman No. 3 quality. Above filter paper 24 rests 22 which is a filter, such as nitrocellulose, nylon, or other suitable hybridization materials, on which nucleic acid material is retained for hybridization with labeled probe. Filters 24 and 22 have an outer diameter of 0.97 centimeters. The filter support 26 and filters 22 and 24 are to be placed within the lower chamber 14 as the first step in assembly of the diagnostic unit 10. Next, the lower portion of upper chamber 12 is placed into the

upper portion of lower chamber 14 such that the lower snap-lock, connector 16 rests upon ridge 20 and the upper snap-lock connector 16 fits securely immediately below snap-lock connector 18. The snap-lock connection serves to hold the sandwich of filter support 26 and filters 24 and 22 securely in place, such that the entire blood sample is passed through the filters 24 and 22.

Figure 3 is a top view of 22 which is a filter of nitrocellulose or other suitable material on which nucleic acid material is retained for hybridization with the labeled probe.

Figure 4 is a top view of 24 and is filter paper, such as Whatman No. 3 quality, which, being located below the filter 22 of Figure 3, serves to draw away excess fluid from the filter 22.

Figure 5 is a top view of the plastic support unit 26 which functions to hold the filters in place in the assembled diagnostic unit 10, as shown in Figure 2.

It is to be appreciated that any technique for permitting the contact of the hybridization product would be satisfactory. While a physical support such as a nitrocellulose filter may be utilized, obviously, other physical medium may likewise be used such as a coated tube, resin beads, a sandwich assay technique, a plastic strip, a microtiter well, and the like.

It may also be desired to va."y how the detec¬ tion could take place depending upon the label that would be utilized.

In the most preferred embodiment, the hybridi¬ zation fluid that is utilized is a buffer of Denhardt's solution and of saline citrate medium further containing dodecylsulfate together with salmon sperm DNA. The latter acts as a medium to prevent interference by non¬ specific DNA binding.

Due to the uniqueness of the technique as described herein, the present invention is also con¬ cerned with a Lyme disease kit which contains a hybrid- ization buffer, the labeled probe, and filter assemblies on which the hybridized product may be placed during the hybridization reaction. The kit may also contain positive and negative control filters to assist in the evaluation of unknown specimens.

Having described the invention, listed below are preferred embodiments wherein all temperatures are in degrees Centigrade and all parts are parts by weight, unless otherwise indicated.

Example1

A diagnostic unit made of polypropylene and containing filters, which is substantially comparable to that described in Figure 1, is placed in a centrifuge tube. Fresh human EDTA (ethylene diamine tetraacetic acid) plasma is placed in the unit in the amount of 2.0 ml and centrifuged for 10 minutes. Centrifugation causes the material to pass through the filter assembly within the diagnostic unit. Nucleic acid material is retained on filter 22 and the effluent is captured for disposal in the centrifuge tube. The two components of the diagnostic unit are then separated and the nitrocel¬ lulose filter is transferred to an appropriately labeled

second nonadherent plastic tube suitable for use in a gamma counter. The tube is then heated for 30 minutes at 80"Centigrade. A warm hybridization buffer at 65"Centigrade in the amount 500 μl (microliter) is added to the specimen tube as well as the positive and nega¬ tive control tubes. The material is incubated for two hours at 65"Centigrade in a shaking water bath. There¬ after, 25 microliters of the iodinated probe is added to each specimen and the material is then incubated for two hours at 65"Centigrade. Thereafter, the buffer is decanted, washed with one milliliter of a wash solution, shaken for five minutes and then decanted. The filters are then counted in a gamma counter. Thereafter, one can determine from the positive and negative controls and the active specimen the presence of the B. burgdor¬ feri organism.

The procedure was followed and found to have an 89% clinical sensitivity and 94% clinical specificity as indicated by the following result of a blind study of 45 donor samples. Twenty-seven of the 45 samples were taken from people clinically judged to be positive for Lyme Disease based on 2 or more criteria accepted as diagnostic for Lyme Disease. These criteria include tick bite, musculo-skeletal involvement, cardiac in- volvement, neurological involvement, flu, or positive in-vitro culture of Borrelia burgdorferi. The other 18 donors were clinically judged to be negative for Lyme Disease. Of the 27 Lyme Disease positive donors, 24 were positive in the gene probe assay of the present invention and 3 were negative. Of the Lyme Disease negative donors, 17 were judged negative and 1 positive. Positive and negative gene probe results were based upon cpm (counts per minute) scoring as compared to positive

and negative controlled samples as illustrated in Table 1.

Table 1

Scoring

+ + + + + +

+ + + +

+ + + + + + + + + +

The solutions that were utilized in the above experiment are described as follows. The hybridization buffer is prepared by blending the following materials to make 100 ml:

Hybridization Buffer per 100 ml 5 ml of lOOx (fold) Denhardt's solution 25 ml of 2Ox Standard Saline Citrate

200 μl dodecylsulfate solution 10 ml salmon sperm DNA solution bring to 100 ml after pHing to 8.0

The Denhardt's solution is made from the following solution:

lOOx Denhardt's Solution (500 ml) lOg Ficoll 400 lOg polyvinylpyrrolidone lOg bovine serum albumin (Fraction V) bring to 500 ml (can be stored frozen)

The standard saline citrate solution is prepared from the following materials:

2Ox Standard Saline Citrate (11) 175g sodium chloride 88g trisodium citrate dissolve in 500 ml water adjust to pH 7.0 with 1 MCH1 bring to 1000 ml

The dodecylsulfate solution is prepared as follows:

Sodium dodecylsulfate solution (SDS) 5 g SDS/ l Tris-EDTA buffer Tris-EDTA buffer pH 8.0 10 mM Tris-Cl pH 8.0 lmM EDTA pH 9.0

The salmon sperm DNA solution is prepared as follows:

Salmon Sperm DNA solution Dilute 1 ml Tris EDTA buffer to 100 ml with deionized water add - 100 mg salmon sperm to 100 ml of water diluted Tris EDTA buf er

The probe is prepared by iodinating the 23 "mer" as follows:

To 250 μg probe add 50 μl of deionized water.

Dry 500 μC± of Bolton Hunter reagent (BH) in its reac¬ tion vessel under a slow stream of nitrogen in an appropriate hood and behind a lead glass shield. To the reaction vessel add 45 μl of probe solution, followed by 4.5 μl of 1M borate (final borate concentration 0.1M) mix and incubate for 30 minutes.

Set 1 μl of reaction mixture aside for counting and run the balance of the mixture through a Bio Rad spin column. Take 1 μl of the purified probe and count it and the 1 μl of reaction mixture set aside before purification.

Radioactive incorporation in the probe should be 40 to 50%.

Final purification of probe is performed on polyacryl¬ amide gel (20%) or on reverse phase HPLC.

To detect the presence of B. burgdorferi, a culture strain was obtained from American Type Culture Collection (ATCC 35 210) from which the positive con¬ trols were prepared.

While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. It is not intended herein to mention all of the possible equivalent forms or ramifi¬ cations of the invention. It is understood that the terms used herein are merely descriptive rather than limiting, and that various changes may be made without departing from the spirit or scope of the invention.