A method for diagnosing an HIV-2 (LAV-II) infection and a kit containing reagents for the same is disclosed. These reagents include cDNA probes which are capable of hybridizing to at least a portion of the genome of HIV-2. In one embodiment, the DNA probes are capable of hybridizing to the entire genome of HIV-2. These reagents also include polypeptides encoded by some of these DNA sequences.

BACKGROUND OF THE INVENTION

The invention relates to cloned DNA sequences analogous to the genomic RNA of a virus known as Lymphadenopathy-Associated Virus II ("LAV-II"), a process for the preparation of these cloned DNA sequences, and their use as probes in diagnostic kits. In one embodiment, the invention relates to a cloned DNA sequence analogous to the entire genomic RNA of HIV-2 and its use as a probe. The invention also relates to polypeptides with amino acid sequences encoded by these cloned DNA sequences and the use of these polypeptides in diagnostic kits.

According to recently adopted nomenclature, as reported in Nature, May 1986, a substantially-identical group of retroviruses which has been identified as one causative agent of AIDS are now referred to as Human Immunodeficiency Viruses I (HIV-1). This previously-described group of retroviruses includes Lymphadenopathy-Associated Virus I (LAV-I), Human T-cell Lymphotropic Virus-III (HTLV-III), and AIDS-Related Virus (ARV).

Lymphadenopathy-Associated Virus II has been described in U.S. application Ser. No. 835,228, which was filed Mar. 3, 1986, and is specifically incorporated herein by reference. Because LAV-II is a second, distinct causative agent of AIDS, LAV-II properly is classifiable as a Human Immunodeficiency Virus II (HIV-2). Therefore, "LAV-II" as used hereinafter describes a particular genus of HIV-2 isolates.

While HIV-2 is related to HIV-1 by its morphology, its tropism and its in vitro cytopathic effect on CD4 (T4) positive cell lines and lymphocytes, HIV-2 differs from previously described human retroviruses known to be responsible for AIDS. Moreover, the proteins of HIV-1 and 2 have different sizes and their serological cross-reactivity is restricted mostly to the major core protein, as the envelope glycoproteins of HIV-2 are not immune precipitated by HIV-1-positive sera except in some cases where very faint cross-reactivity can be detected. Since a significant proportion of the HIV infected patients lack antibodies to the major core protein of their infecting virus, it is important to include antigens to both HIV-1 and HIV-2 in an effective serum test for the diagnosis of the infection by these viruses.

HIV-2 was first discovered in the course of serological research on patients native to Guinea-Bissau who exhibited clinical and immunological symptoms of AIDS and from whom sero-negative or weakly sero-positive reactions to tests using an HIV-1 lysate were obtained. Further clinical studies on these patients isolated viruses which were subsequently named "LAV-II."

One LAV-II isolate, subsequently referred to as LAV-II MIR, was deposited at the Collection Nationale des Cultures de Micro-Organismes (CNCM) at the Institut Pasteur in Paris, France on Dec. 19, 1985 under Accession No. I-502 and has also been deposited at the British ECA CC under No. 87.001.001 on Jan. 9, 1987. A second LAV-II isolate was deposited at CNCM on Feb. 21, 1986 under Accession No. I-532 and has also been deposited at the British ECA CC under No. 87.001.002 on Jan. 9, 1987. This second isolate has been subsequently referred to as LAV-II ROD. Other isolates deposited at the CNCM on Dec. 19, 1986 are HIV-2 IRMO (No. I-642) and HIV-2 EHO (No. I-643). Several additional isolates have been obtained from West African patients, some of whom have AIDS, others with AIDS-related conditions and others with no AIDS symptoms. All of these viruses have been isolated on normal human lymphocyte cultures and some of them were thereafter propagated on lymphoid tumor cell lines such as CEM and MOLT.

Due to the sero-negative or weak sero-positive results obtained when using kits designed to identify HIV-1 infections in the diagnosis of these new patients with HIV-2 disease, it has been necessary to devise a new diagnostic kit capable of detecting HIV-2 infection, either by itself or in combination with an HIV-1 infection. The present inventors have, through the development of cloned DNA sequences analogous to at least a portion of the genomic RNA of LAV-II ROD viruses, created the materials necessary for the development of such kits.

SUMMARY OF THE INVENTION

As noted previously, the present invention relates to the cloned nucleotide sequences homologous or identical to at least a portion of the genomic RNA of HIV-2 viruses and to polypeptides encoded by the same. The present invention also relates to kits capable of diagnosing an HIV-2 infection.

Thus, a main object of the present invention is to provide a kit capable of diagnosing an infection caused by the HIV-2 virus. This kit may operate by detecting at least a portion of the RNA genome of the HIV-2 virus or the provirus present in the infected cells through hybridization with a DNA probe or it may operate through the immunodiagnostic detection of polypeptides unique to the HIV-2 virus.

Additional objects and advantages of the present invention will be set forth in part in the description which follows, or may be learned from practice of the invention. The objects and dvantages may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

To achieve these objects and in accordance with the purposes of the present invention, cloned DNA sequences related to the entire genomic RNA of the LAV-II virus are set forth. These sequences are analogous specifically to the entire genome of the LAV-II ROD strain.

To further achieve the objects and in accordance with the purposes of the present invention, a kit capable of diagnosing an HIV-2 infection is described. This kit, in one embodiment, contains the cloned DNA sequences of this invention which are capable of hybridizing to viral RNA or analogous DNA sequences to indicate the presence of an HIV-2 infection. Different diagnostic techniques can be used which include, but are not limited to: (1) Southern blot procedures to identify cellular DNA which may or may not be digested with restriction enzymes; (2) Northern blot techniques to identify RNA extracted from cells; and (3) dot blot techniques, i.e., direct filtration of the sample through an ad hoc membrane such as nitrocellulose or nylon without previous separation on agarose gel. Suitable material for dot blot technique could be obtained from body fluids including, but not limited to, serum and plasma, supernatants from culture cells, or cytoplasmic extracts obtained after cell lysis and removal of membranes and nuclei of the cells by centrifugation as accomplished in the "CYTODOT" procedure as described in a booklet published by Schleicher and Schull.

In an alternate embodiment, the kit contains the polypeptides created using these cloned DNA sequences. These polypeptides are capable of reacting with antibodies to the HIV-2 virus present in sera of infected individuals, thus yielding an immunodiagnostic complex.

It is understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate one embodiment of the invention and, together with the description, serve to explain the principles of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the presently preferred embodiments of the invention, which, together with the following examples, serve to explain the principles of the invention.

The genetic structure of the HIV-2 virus has been analyzed by molecular cloning according to the method set forth herein and in the Examples. A restriction map of the genome of this virus is included in FIG. 4 (see Original Patent). In addition, the partial sequence of a cDNA complementary to the genomic RNA of the virus has been determined. This cDNA sequence information is included in FIG. 1 (see Original Patent).

Also contained herein is data describing the molecular cloning of the complete 9.5 kb genome of HIV-2, data describing the observation of restriction map polymorphism between different isolates, and an analysis of the relationship between HIV-2 and other human and simian retroviruses. From the totality of these data, diagnostic probes can be discerned and prepared.

Generally, to practice one embodiment of the present invention, a series of filter hybridizations of the HIV-2 RNA genome with probes derived from the complete cloned HIV-1 genome and from the gag and pol genes were conducted. These hybridizations yielded only extremely weak signals even in conditions of very low stringency of hybrization and washing. Thus, it was found to be difficult to assess the amount of HIV-2 viral and proviral DNA in infected cells by Southern blot techniques.

Therefore, a complementary DNA (cDNA) to the HIV-2 genomic RNA initially was cloned in order to provide a specific hybridization probe. To construct this cDNA, an oligo (dT) primed cDNA first-strand was made in a detergent-activated endogenous reaction using HIV-2 reverse transcriptase with virions purified from supernatants of infected CEM cells. The CEM cell line is a lymphoblastoid CD4+ cell line described by G. E. Foley et al. in Cancer 18: 522-529 (1965), specifically incorporated herein by reference. The CEM cells used were infected with the isolate ROD and were continuously producing high amounts of HIV-2.

After second-strand synthesis, the cDNAs were inserted into the TG130 m13 bacteria phage vector. A collection of 10⁴ M13 recombinant phages was obtained and screened in situ with an HIV-1 probe spanning 1.5 kb. of the 3′ end of the LAV_BRU isolate (depicted in FIG. 1A (see Original Patent)). Some 50 positive plaques were detected, purified, and characterized by end sequencing and cross-hybridizing the inserts. This procedure is described in more detail in Example 1 (see Original Patent) and in FIG. 1 (see Original Patent).

The different clones were found to be complementary to the 3′ end of a polyadenylated RNA having the AATAAA signal about 20 nucleotides upstream of the poly A tail, as found in the long terminal repeat (LTR) of HIV-1. The LTR region of HIV-1 has been described by S. Wain Hobson et al. in Cell 40: 9-17 (1985), specifically incorporated herein by reference. The portion of the HIV-2 LTR that was sequenced was related only distantly to the homologous domain in HIV-1 as demonstrated in FIG. 1 B (see Original Patent). Indeed, only about 50% of the nucleotides could be aligned and about a hundred insertions/deletions need to be introduced. In comparison, the homology of the corresponding domains in HIV-1 isolates from USA and Africa is greater than 95% and no insertions or deletions are seen.

The largest insert of this group of M13 clones was a 2 kb. clone designated E2. Clone E2 was used as a probe to demonstrate its HIV-2 specificity in a series of filter hybridization experiments. Firstly, this probe could detect the genomic RNA of HIV-2 but not HIV-1 in stringent conditions as shown in FIG. 2, C and D (see Original Patent). Secondly, positive signals were detected in Southern blots of DNA from cells infected with the ROD isolate as well as other isolates of HIV-2 as shown in FIG. 2, A and FIG. 4 (see Original Patent), A. No signal was detected with DNA from uninfected cells or HIV-1 infected cells, confirming the exogenous nature of HIV-2. In undigested DNA from HIV-2 infected cells, an approximately 10 kb. species, probably corresponding to linear unintegrated viral DNA, was principally detected along with a species with an apparent size of 6 kb., likely to be the circular form of the viral DNA. Conversely, rehybridization of the same filter with an HIV-1 probe under stringent conditions showed hybridization to HIV-1 infected cells only as depicted in FIG. 2, B (see Original Patent).

To isolate the remainder of the genome of HIV-2, a genomic library in lambda phage L47.1 was constructed. Lambda phage L47.1 has been described by W. A. M. Loenen et al. in Gene 10: 249-259 (1980), specifically incorporated herein by reference. The genomic library was constructed with a partial Sau3AI restriction digest of the DNA from the CEM cell line infected with HIV-2_ROD.

About 2×10⁶ recombinant plaques were screened in situ with labelled insert from the E2 cDNA clone. Ten recombinant phages were detected and plaque purified. Of these phages, three were characterized by restriction mapping and Southern blot hybridization with the E2 insert and probes from its 3′ end (LTR) or 5′ end (envelope), as well as with HIV-1 subgenomic probes. In this instance, HIV-1 probes were used under non-stringent conditions.

A clone carrying a 9.5 kb. insert and derived from a circular viral DNA was identified as containing the complete genome and designated λROD 4. Two other clones, λROD 27 and λROD 35 were derived from integrated proviruses and found to carry an LTR and cellular flanking sequences and a portion of the viral coding sequences as shown in FIG. 3, A (see Original Patent).

Fragments of the lambda clones were subcloned into a plasmid vector p UC 18.

Plasmid pROD 27-5′ is derived from λROD 27 and contains the 5′ 2 Kb of the HIV-2 genome and cellular flanking sequences (5′ LTR and 5′ viral coding sequences to the EcoRI site)

Plasmid pROD 4.8 is dervied from λROD 4 and contains the about 5 kb HindIII fragments that is the central part of the HIV-2 genome.

Plasmid pROD 27-5′ and p ROD 4.8 inserts overlap.

Plasmid pROD 4.7 contains a HindIII 1.8 Kb fragment from λROD 4. This fragment is located 3′ to the fragment subcloned into pROD 4.8 and contains about 0.8 Kb of viral coding sequences and the part of the lambda phage (λL47.1) left arm located between the BamHI and HindIII cloning sites.

Plasmid pROD 35 contains all the HIV-2 coding sequences 3′ to the EcoRI site, the 3′ LTR and about 4 Kb of cellular flanking sequences.

Plasmid pROD 27-5′ and pROD 35 in E. coli strain HB 101 are deposited respectively under No. 1-626 and 1-633 at the CNCM, and have also been deposited at the NCIB (British Collection). These plasmids are depicted in FIG. 5 (see Original Patent). Plasmid pROD 4.7 and PROD 4.8 in E. coli strain TG1 are deposited respectively under No. 1-627 and 1-628 at the CNCM.

To reconstitute the complete HIV-2 ROD genome, pROD 35 is linearized with EcoRI and the EcoRI insert of pROD 27-5′ is ligated in the correct orientation into this site.

The relationship of HIV-2 to other human and simian retroviruses was surmised from hybridization experiments. The relative homology of the different regions of the HIV-1 and 2 genomes was determined by hybridization of fragments of the cloned HIV-1 genome with the labelled λROD 4 expected to contain the complete HIV-2 genome. Even in very low stringency conditions (Tm-42° C.), the hybridization of HIV-1 and 2 was restricted to a fraction of their genomes, principally the gag gene (dots 1 and 2), the reverse transcriptase domain in pol (dot 3), the end of pol and the Q (or sor) genes (dot 5) and the F gene (or 3′ orf) and 3′ LTR (dot 11). The HIV-1 fragment used to detect the HIV-2 cDNA clones contained the dot 11 subclone, which hybridized well to HIV-2 under non-stringent conditions. Only the signal from dot 5 persisted after stringent washing. The envelope gene, the region of the tat gene and a part of pol thus seemed very divergent. These data, along with the LTR sequence obtained, indicated that HIV-2 is not an envelope variant of HIV-1 as described by Alizon et al., Cell 40:63-74 (1986).

It was observed that HIV-2 is related more closely to the Simian Immunodeficiency Virus (SIV) than it is to HIV-1. This correlation has been described by F. Clavel et al. in C.R. Acad. Sci. (Paris) 302: 485-488 (1986) and F. Clavel et al. in Science 233: 343-346 (1986), both of which are specifically incorporated herein by reference. Simian Immunodeficiency Virus (also designated Simian T-cell Lymphotropic Virus Type 3, STLV-3) is a retrovirus first isolated from captive macaques with an AIDS-like disease in the USA. This simian virus has been described by M. D. Daniel et al. in Science 228: 1201-1204 (1985), specifically incorporated herein by reference.

All the SIV proteins, including the envelope, are immune precipitated by sera from HIV-2 infected patients, whereas the serological cross-reactivity of HIV-1 to 2 is restricted to the core proteins. However SIV and HIV-2 can be distinguished by slight differences in the apparent molecular weight of their proteins.

In terms of nucleotide sequence, it also appears that HIV-2 is closely related to SIV. The genomic RNA of SIV can be detected in stringent conditions as shown in FIG. 2 (see Original Patent), C by HIV-2 probes corresponding to the LTR and 3′ end of the genome (E2) or to the gag or pol genes. Under the same conditions, HIV-1 derived probes do not detect the SIV genome as shown in FIG. 2, D (see Original Patent).

In Southern blots of DNA from SIV-infected cells, a restriction pattern clearly different from HIV-2_ROD and other isolates is seen. All the bands persist after a stringent washing, even though the signal is considerably weakened, indicating a sequence homology throughout the genomes of HIV-2 and SIV. It has recently been shown that baboons and macaques could be infected experimentally by HIV-2, thereby providing an interesting animal model for the study of the HIV infection and its preventive therapy. Indeed, attempts to infect non-human primates with HIV-1 have been successful only in chimpanzees, which are not a convenient model.

From an initial survey of the restriction maps for certain of the HIV-2 isolates obtained according to the methods described herein, it is already apparent that HIV-2, like HIV-1, undergoes restriction site polymorphism. FIG. 4 A (see Original Patent) depicts examples of such differences for three isolates, all different one from another and from the cloned HIV-2_ROD. It is very likely that these differences at the nucleotide level are accompanied by variations in the amino-acid sequence of the viral proteins, as evidenced in the case of HIV-1 and described by M. Alizon et al. in Cell 46: 63-74 (1986), specifically incorporated herein by reference. It is also to be expected that the various isolates of HIV-2 will exhibit other minor amino acid heterogeneities. See, for example, Clavel et al., Nature 324 (18):691-695 (1986), specifically incorporated herein by reference.

Further, the chacterization of HIV-2 will also delineate the domain of the envelope glycoprotein that is responsible for the binding of the surface of the target cells and the subsequent internalization of the virus. This interaction was shown to be mediated by the CD4 molecule itself in the case of HIV-1 and similar studies tend to indicate that HIV-2 uses the same receptor. Thus, although there is wide divergence between the env genes of HIV-1 and 2, small homologous domains of the envelopes of the two HIV could represent a candidate receptor binding site. This site could constitute a target for use to raise a protective immune response against this group of retroviruses.

From the data discussed herein, certain nucleotide sequences have been identified which are capable of being used as probes in diagnostic methods to obtain the immunological reagents necessary to diagnose an HIV-2 infection. In particular, these sequences may be used as probes in hybridization reactions with the genetic material of infected patients to indicate whether the RNA of the HIV-2 virus is present in these patient's lymphocytes or whether an analogous DNA is present. In this embodiment, the test methods which may be utilized include Northern blots, Southern blots and dot blots. One particular nucleotide sequence which may be useful as a probe is the combination of the 5 kb. HindIII fragment of ROD 4 and the E2 cDNA used in FIG. 4 (see Original Patent).

In addition, the genetic sequences of the HIV-2 virus may be used to create the polypeptides encoded by these sequences. Specifically, these polypeptides may be created by expression of the cDNA obtained according to the teachings herein in hosts such as bacteria, yeast or animal cells. These polypeptides may be used in diagnostic tests such as immunofluorescence assays (IFA), radioimmunoassays (RIA) and Western Blot tests.

Moreover, it is also contemplated that additional diagnostic tests, including additional immunodiagnostic tests, may be developed in which the DNA probes or the polypeptides of this invention may serve as one of the diagnostic reagents. The invention described herein includes these additional test methods.

In addition, monoclonal antibodies to these polypeptides or fragments thereof may be created. The monoclonal antibodies may be used in immunodiagnostic tests in an analogous manner as the polypeptides described above.

The polypeptides of the present invention may also be used as immunogenic reagents to induce protection against infection by HIV-2 viruses. In this embodiment, the polypeptides produced by recombinant-DNA techniques would function as vaccine agents.

Also, the polypeptides of this invention may be used in competitive assays to test the ability of various antiviral agents to determine their ability to prevent the virus from fixing on its target.
 

Claim 1 of 9 Claims

1. A recombinant or synthetic peptide consisting of the following amino acid sequence:

Ser Lys Ser Leu Glu Gln Ala Gln Ile Gln Gln Glu Lys Asn Met Tyr Glu Leu Gln Lys Leu Asn Ser Trp,

wherein said peptide constitutes an env2 peptide of HIV-2.

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