NOVEL REPLICATION COMPETENT HUMAN IMMUNODEFICIENCY VIRUS TYPE 2 (HIV-2) PROVIRAL CLONE DESIGNATED HIV-2KR

Abstract: A full-length infectious molecular clone, designated HIV-K, was obtained from a recombinant bacteriophage library constructed from HI-2PIE-infected MOLT-4/8 genomic DNA. Nucleotide sequence analysis of this clone demonstrated that the rev coding region extends for nearly 69 amino acid residues past the end of most other HIV-2/SIV rev genes. In addition, the long terminal repeat (LTR) contains a deletion of 9-10 bp, depending upon the nucleotide sequence alignment parameters, upstream from the SpI binding sites. This deletion is not present in other HIV-2/SIV isolates and is not similar to previously disclosed NFkB duplications in this region. The HIV-2KR LTR displays higher levels of basal transcriptional acitivty as compared to prototypical HIV-2 isolates. HIV-2KR is capable of infecting macaque peripheral blood lymphocytes (PBMCs) in vitro and produces a productive and persistant, albeit attenuated, infection in Macacca nemestrina. These proviral constructs are useful, inter alia, for the generation of in vitro diagnostic reagents, cell transcuction vectors, and the generation of HIV-2 based packaging cell lines.

Description: NOVEL REPLICATION COMPETENT HUMAN IMMUNODEFICIENCY VIRUS TYPE 2 (HIV-2) PROVIRAL CLONE DESIGNATED HIV-2KR. CROSS REFERENCE TO RELATED APPLICATIONS This application is a continuation-in-part of U.S. provisional application USSN 60/001,441 (Kraus et al.) filed July 26, 1995. BACKGROUND OF THE INVENTION Human immunodeficiency virus (HIV) type 1 (HIV-1) and HIV type 2 (HIV-2) are genetically related, antigenically cross reactive, and share a common cellular receptor (CD4). See, Rosenburg and Fauci (1993) in Fundamental Immunology, Third Edition Paul (ed) Raven Press, Ltd., New York (Rosenburg and Fauci I) and the references therein for an overview of HIV infection. HIV-1 infection is epidemic world wide, causing a variety of immune system-failure related phenomena commonly termed acquired immune deficiency syndrome (AIDS). HIV type 2 (HIV-2) has been isolated from both healthy individuals and patients with AIDS-like illnesses (Andreasson, et al. (1993) Aids 7, 989-93; Clavel, et al. (1986) Nature, 324, 691-695; Gao, et al. (1992) Nature 358, 495-9; Harrison, et al. (1991) Journal of Acquired Immune Deficiency Syndromes 4, 1155- 60; Kanki, et al. (1992) American Journal of Epidemiology 136, 895-907; Kanki, et al. (1991) Aids Clinical Review 1991, 17-38; Romieu, et al. (1990) Journal of Acquired Immune Deficiency Syndromes 3, 220-30; Naucler, et al. (1993) International Journal of STD and Aids 4, 217-21; Naucler, et al. (1991) Aids 5, 301-4). Although HIV-2 AIDS cases have been identified principally from West Africa, sporadic HIV-2 related AIDS cases have also been reported in the United States (O'Brien, et al. (1991) Aids 5, 85-8) and elsewhere. HIV-2 will likely become endemic in other regions over time, following routes of transmission similar to HIV-1 (Harrison, et al. (1991) Journal of Acquired Immune Deficiency Syndromes 4, 1155-60; Kanki, et al. (1992) American Journal of Epidemiology 136, 895-907; Romieu, et al. (1990) Journal of Acquired Immune Deficiency Syndromes 3, 220-30). Epidemiological studies suggest that HIV-2 produces human disease with lesser penetrance than HIV-1, and exhibits a considerably longer period of clinical latency (at least 25 years, and possibly longer, as opposed to less than a decade for HIV-1; see, Kanki, et al. (1991) Aids Clinical Review 1991, 17-38; Romieu, et al. (1990) Journal of Acquired Immune Deficiency Syndromes 3, 220-30, and Travers et al. (1995) Science 268: 1612-1615). The molecular receptor for HIV is the surface glycoprotein CD4 found mainly on a subset of T cells, monocytes, macrophage and some brain cells. HIV has a lipid envelope with viral antigens that bind the CD4 receptor, causing fusion of the viral membrane and the target cell membrane and release of the HIV capsid into the cytosol. HIV causes death of these immune cells, thereby disabling the immune system and eventually causing death of the patient due to complications associated with a disabled immune system. HIV infection also spreads directly from cell to cell, without an intermediate viral stage. During cell-cell transfer of HIV, a large amount of viral glycoprotein is expressed on the surface of an infected cell, which binds CD4 receptors on uninfected cells, causing cellular fusion. This typically produces an abnormal multinucleate syncytial cell in which HIV is replicated and normal cell functions are suppressed. Molecular analysis suggests that HIV-2 is more stable than HIV-1 in the human population, implying milder pathogenicity of the virus and introduction into the human population at a time earlier than HIV-1 (Clavel, et al. (1986) Nature, 324, 691-695; Gao, et al. (1992) Nature 358, 495-9; Naucler, et al. (1991) Aids 5, 301-4; O'Brien, et al. (1991) - t ' ώ 5, 85-8; Castro, et al. (1990) Virology 178, 527-34; Kirchhoff, et al. (1990) Aids 4, 847-57; Kuhnel, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2383-2387; Kumar, et al. (1990) Journal of Virology 64, 890-901; Zagury, et al. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 5941-5945; Franchini, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2433-2437). Overlap of HIV-2 sequences with those of related simian immunodeficiency virus (SIV) isolates also provides evidence indicating that HIV-2 infection of humans originated through introduction of these primate lentiviruses through environmental or occupational (e.g., hunting, or cooking) exposure (Gao, et al. (1992) Nature 358, 495-9). Several HIV-2 isolates, including three molecular clones of HIV-2 (HIV-2 ROD , HIV-2 SBL . ISY , and HIV-2 UC1 ), have been reported to infect macaques (M. mulatta and . nemestrina) or baboons (Franchini, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2433-2437; Barnett, et al. (1993) Journal of Virology 67 ' , 1006-14; Boeri, et al. (1992) Journal of Virology 66, 4546-50; Castro, et al. (1991) Virology 184, 219-26; Franchini, et al. (1990) Journal of Virology 64, 4462-7; Putkonen, et al. (1990) Aids 4, 783-9; Putkonen, et al. (1991) Nature 352, 436-8). As human pathogens capable of infection of small primates, HIV-2 molecular clones provide attractive models for studies of AIDS pathogenesis, and for drug and vaccine development against HIV-1 and HIV-2. Recently, HIV-2 was suggested as a possible vaccine candidate against the more virulent HIV-1 due to its long asymptomatic latency period, and its ability to protect against infection by HIV-1 (see, Travers et al. (1995) Science 268: 1612-1615 and related commentary by Cohen et al (1995) Science 268: 1566). In the nine-year study by Travers et al. (id) of West African prostitutes infected with HIV-2 it was determined that infection with HIV-2 caused a 70% reduction in infection by HIV-1. One notable characteristic of most HIV-2 isolates, in contrast to HIV-1, is their ability to readily infect primary monocyte-macrophages even after extensive passage on T-cell lines (Franchini, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2433-2437; Barnett, et al. (1993) Journal of Virology 67, 1006-14; Boeri, et al. (1992) Journal of Virology 66, 4546-50; Castro, et al. (1991) Virology 184, 219-26; Franchini, et al. (1990) Journal of Virology 64, 4462-7; Putkonen, et al. (1990) Aids 4, 783-9; Putkonen, et al. (1991) Nature 352, 436-81; Hattori, et al. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 8080-4). HIV-2, like SIV, encodes a vpx gene (Kappes, et al. (1991) Virology 184, 197-209; Marcon, et al. (1991) Journal of Virology 65, 3938-42), but lacks the vpu gene found in HIV-1. A consequence of the absence of vpu is that the HIV-2 envelope is not expressed as a bicistronic message. Other differences between HIV-1 and HIV-2 include differential sensitivity to non-nucleoside reverse transcriptase inhibitors (Bacolla, et al. (1993) Journal of Biological Chemistry 268, 16571-7), the variability and importance of the V3 region of envelope in neutralization (Bjorling, et al. (1994) Journal of Immunology 152, 1952-9; Chiodi, et al. (1993) Chemical Immunology 56, 61-77), the involvement of different transcriptional factors and T-cell signaling pathways in activation of the viral LTR (Hannibal, et al. (1993) Journal of Virology 67, 5035-40), and the specificity of the Tat and Rev transactivating proteins (Fenrick, et al. (1989) Journal of Virology 63, 5006-12; Malim, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 8222-6). The capacity to infect quiescent cells, which is not shared by oncoretroviruses or MoMLV-derived retroviral vectors, has spurred efforts to develop HIV-based gene therapy vectors. The goal of HIV-based vectors is stable transfer of genes to rarely dividing stem cells and post-mitotic cells in the hematopoietic, nervous, and other body systems. Progress has been made recently with vesicular stomatitis virus envelope glycoprotein (VSV-G)-pseudotyped HIV-1 vectors in this regard (Naldini et al. (1996) Science 272:263). Although high titers in the 10 5 range were achieved, this system relies upon transient transfection to generate vector supematants. Stable packaging cell lines were not developed. In addition, the vector is derived from HIV-1, a lentivirus with nearly uniform lethality in humans. Other HIV vector systems have been studied. See, Akkina et al. (1996) J Virol 70:2581; Poznansky et al. (1991) J Virol 65:532; Parolin et al. (1994) Journal of Virology 68:3888; Richardson et al. (1995) Journal of General Virology 76:691; Buchschacher et al. (1992) Journal of Virology 66:2731; and Marlink et al. (1994) Science 265: 1587. However, all are derived from HIV-1 and all evince a variety of limitations. Several use wild-type replication competent virus as the source of packaging proteins, and some represent simple pseudotyping of an env gene-mutated full-length provirus by VSV-G (t ' .e. , no packaging construct, lines or vector lacking other structural genes). In general, two problems have been most prominent in this field: (1) titers, with the exception of Naldini et al. (1996; supra), have been exceedingly low (lO'-lO 2 ) (Poznansky, 1991 and Parolin, 1994, supra) or not reported (Akkina, 1996, supra) and (2) stable packaging lines have not been developed. Accordingly, the isolation and development of non-pathogenic strains of HIV-2 as vaccines, in vitro diagnostic reagents, cell transduction and gene therapy vectors, and HIV-2 based packaging cell lines is needed. The present invention fulfills these and other needs. SUMMARY The molecular and biological properties of a full-length biologically active HIV-2 clone which is infectious for M. nemestrina are described. The clone causes asymptomatic infection, and protects against infection with more pathogenic strains of HIV. In addition, the clone provides a ready source of nucleic acid for the production of HIV-2 polypeptides and other immunogenic reagents, e.g., through cloning and expression of the relevant genes. In addition, the clone possesses many features which make it ideal for incorporation into gene therapy vectors, e.g., for the treatment and prevention of HIV infections, and more generally, as a source of components of retroviral vectors. For instance, HIV-2 KR has a strong basal promoter, removing the requirement for tαt and rev transactivation. Thus, retroviral vectors with the HIV-2,^ LTRs do not require tat or rev for transactivation. Furthermore, HIV-2, and HIV-2 KR in particular is useful for establishing HIV packaging cell lines, e.g., for use in retroviral vector construction. The present invention provides an isolated HIV-2 provirus with a full-length HIV-2 genome. The rev gene encoded by the provirus typically hybridizes to the second exon of the HIV-2 KR rev gene under stringent conditions, or more preferably under highly stringent conditions. In addition, the proviral HIV-2 LTR has an activating deletion, resulting in high basal activity. The rev gene is a particularly applicable marker for detecting full-length proviruses of the present invention because the second exon of the provirus encodes amino acid residues not found in other known HIV-2 proviruses. Similarly, the activating deletion in the LTR of the proviruses of this invention does not exist in other known HIV-2 strains. The HIV-2 proviruses of the invention exist as free nucleic acids (RNA or DNA), as a portion of a nucleic acid (e.g., incorporated into a nucleic acid vector (plasmid, virus, etc.), or cellular genome), or as a protein-nucleic acid complex (e.g., encapsidated in a retroviral viral particle such as an HIV-2 capsid/envelope, or as part of a cellular chromosome or episome). Because the proviruses of the invention are amphotropic (i.e., able to grow in multiple cell types outside of the host range of HIV), the proviruses of the invention exist in a variety of cell types (e.g., during replication), including human cells, M. nemistrina cells and murine cells. The amphotropic nature of the provirus makes it a suitable gene therapy vector, and suitable for the production of HIV packaging cell lines. The HIV-2 proviruses of the present invention are also amenable to cloning and subcloning. Accordingly, the provirus and regions of interest (t ' .e., nucleic acids encoding HIV-2 polypeptides and ris-active HIV-2 nucleic acids such as the 5' and 3' LTR regions, the MSD and the psi site) are optionally cloned or subcloned into known vectors. Thus, the HIV-2 provirus is optionally cloned or sub-cloned to produce a viral particle (e.g., a bacculovirus, pox virus, Adeno- associated virus or a retrovirus), a plasmid, a recombinant cell, a plant, or an animal (e.g., an insect, or a mammal). In one preferred embodiment, the HIV-2 provirus of the invention has the nucleic acid sequence described in SEQ ID NO: l (the full-length HIV-2 KR proviral nucleic acid sequence). One of skill will appreciate that many variations of SEQ ID NO: l yield an essentially identical virus. For example, due to the degeneracy of the genetic code, "silent substitutions" are an implied feature of every nucleic acid sequence which encodes an amino acid. Similarly, "conservative amino acid substitutions," in one or a few amino acids in an amino acid sequence are substituted with different amino acids with highly similar properties, are also readily identified as being highly similar to a particular amino acid sequence, or to a particular nucleic acid sequence which encodes an amino acid. Such conservatively substituted variations of a disclosed sequence are also a feature of the present invention. Subsequences of the HIV-2 KR provirus such as the HIV-2 KR 3' LTR, the HIV-2 KR 5' LTR, the HIV-2 KR env gene, the HIV-2 KR nef gene, the HIV-2 KR rev gene, the HIV-2 KR vpx gene, the HIV-2 KR tat gene, the HIV-2 KR gag gene, the HIV-2 KR pol gene, the HIV-2 KR vif gene, and the HIV-2 KR vpr gene are also a feature of the present invention. Any unique region of HIV-2 KR nucleic acid is useful as a molecular probe to identify the HIV-2 KR provirus, and to distinguish the provirus from other known strains of HIV-2. Unique HIV-2 KR regions are found by comparing HIV-2 KR nucleic acid sequences to other known HIV-2 clones and virus sequences, such as HIV-2 NIHZ . Typically, HIV-2 KR is about 80-90% identical to other known strains of HIV-2. Thus, comparison windows of 50, 60, 70, 80 and 90 nucleic acids reveal that no known strain of HIV-2 is completely identical to HIV-2 KR over a contiguous region of nucleic acid the size of the comparison window. Therefore, all contiguous nucleic acids of at least about 50 nucleic acids, and more preferably 60 nucleic acids, and still more preferably 70 nucleic acids, typically 80 nucleic acids and most typically 90 nucleic acids from the HIV-2 KR sequence described in SEQ ID NO: l are novel and useful, e.g., as molecular probes to detect HIV-2 KR , in biological samples. Polypeptides and nucleic acids encoded by the HIV-2 KR and other proviruses of the present invention are valuable for a variety of purposes, including as immunogens to generate antibodies against HIV viruses (e.g., HIV-1 and HIV- 2), as vaccines and other therapeutic compositions, as components of HIV packaging cells, as components of viral complementation assays, as diagnostic reagents for the diagnosis and monitoring of HIV infections, and as components of gene therapy vectors. When administered in a therapeutically effective amount to a mammal, the provirus of the present invention confers resistance to subsequent HIV infections. In a preferred embodiment, the HIV-2 provirus of the invention comprises a full-length HIV-2 genome and has the following characteristics. The provirus when encapsidated in an HIV viral particle encoded by the provirus, is replication competent in vitro in Molt-4/8 cells; the provirus is infectious in primary human and macaque lymphocytes when encapsidated in an HIV viral particle; the provirus, when encapsidated in an HIV viral particle encoded by the provirus, has reduced infectivity for macaque peripheral blood mononuclear cells compared to HIV-2 NIHZ and HIV-2 rod ; the provirus, when encapsitated in an HIV viral particle encoded by die provirus, produces an attenuated infection in M. nemestrina; the provirus, when encapsitated in an HIV viral particle encoded by the provirus, produces an infection in Hu-PBL-SCID mice; the second exon of the rev gene encoded by the provirus encodes an amino acid sequence 180 amino acids in length; the proviral LTR has an activating deletion; and, the proviral LTR has high basal activity. The invention provides high efficiency packaging vectors, packaging cells which express the vectors and nucleic acids which are packaged by the vectors. The high efficiency HIV-2 packaging vectors have a first high efficiency packaging vector nucleic acid, which encodes a first portion of an HIV-2 particle. The particle packages HIV-2 packagable nucleic acids (e.g., a nucleic acid encoding an HIV-2 packaging site). To increase safety, high efficiency packaging vectors are optionally present as multiple complementary nucleic acids, each of which encodes only a portion of the genes necessary for HIV packaging. When the complementary nucleic acids are co-expressed in a cell they provide all of the tra/zs-active factors necessary for HIV packaging. Thus, in one embodiment, the present invention provides a first high efficiency packaging vector nucleic acid, a second high efficiency vector nucleic acid, a third high efficiency vector nucleic acid, and so on. The high efficiency packaging vector nucleic acid lacks cis active sequences (e.g., the HIV-2 psi site) necessary for packaging the nucleic acid into an HIV viral particle; thus, the encoded HIV-2 particle is itself non- virulent (not capable of a productive infection which produces progeny virus; i.e., the particle is not replicative in the absence of a source of complementary viral components). The high efficiency packaging vector nucleic acid, when transfected into a population of cells, renders the cells competent to package HIV-2 packagable RNA with a cell supernatant titre of at least 1 X 10 3 transducing units per ml, and preferably 1 X IO 4 transducing units per ml. The HIV-2 packagable RNA comprises an HIV packaging site. Example high efficiency packaging nucleic acids include the plasmids pEP32, pEP40, pEP41, pEP42, and pEP43. The HIV-2 packaging cell lines express the high efficiency packaging vectors of the invention. In one class of embodiments, die host range of viral particles produced by the packaging cell is modified by pseudotyping the vector by expressing the vesicular stomatitis virus envelope glycoprotein in the cell. HIV-2 particles produced by the packaging cells of the invention typically include an HIV-2 packagable RNA which has the α ' s-active sequences necessary for packaging, but which lacks sequences encoding trans active HIV sequences which provide the structural components of the viral particle. A preferred the HIV-2 packaging site is derived from HIV-2 KR . Because the packaged nucleic acid does not comprise sequences necessary for HIV particle formation, the particle is non-virulent. Deletion of portions of complete HIV-2 genes from HIV-2 packagable nucleic acids can include deletion of some, or all of the genes for gag, pol, vif, vpx, vpr, env, rev, tat, and nef. The HIV-2 particles optionally comprise VSV-G envelope protein, which expands me infective range of the particle (e.g., to CD34 stem cells). In one class of embodiments, the packagable nucleic acid further comprises an HIV-2 LTR, pl7 subsequence, and HIV-2 RRE subsequence. These sequences aid in packaging, processing and integration of the packagable nucleic acid in a target cell (e.g., a CD4 + or CD34 + cell). The packagable nucleic acids of the invention optionally include marker genes which encode detectable markers. The inclusion of detectable markers provides a means of monitoring me infection and stable transduction of target cells. Markers include components of the beta-galactosidase gene and nucleic acid subsequences encoding the green fluorescence protein. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 provides a genetic analysis of HIV-2 KR . [A] Open reading frame analysis of HIV-2 KR produced from complete nucleotide sequence data obtained from double-stranded sequencing of the lambda proviral clone. Note the presence of long rev reading frame overlapping a substantial portion of nef, detailed in the alignment below, the presence of full length env (no truncation in transmembrane protein) and nef reading frames, and typical organization of vif, vpr, vpx, and odier frames, all full-length and open. The predicted amino acid sequence of HIV-2 KR REV protein and those of previously sequenced HIV-2 and SIV clones (Los Alamos database) were aligned and edited to show identity with the HIV-2 KR sequence (SEQ ID NOs:29-42) as [.], gaps as [-], and differences as die differing residue. Note that the HIV-2 KR sequence extends for nearly 69 residues past d e end of most other HIV-2 and SIV rev protein sequences. [B] Homology of HIV-2^ with other HIV-2 and SIV viruses was calculated for d e gag, pol, tat, rev, vif, vpr, vpx, env, and nef genes, using a hierarchical multiple alignment scoring program to obtain similarity scores (Maximum Match = 17, Minimum Gap=3, Mismatch = -8, Gap-Open Penalty = 8, Gap-Extension Penalty = 3). [C] Using Neighbor- Joining analysis to construct an unrooted Phylogenetic tree, HIV-2 KR grouped closely with all omer previously sequenced HIV-2 clones, except for HIV-2 UCI and HIV-2 EH0 , which grouped more closely with SIV AGM . Figure 2 shows the high basal activity of the HIV-2 KR LTR. [A] Alignments (SEQ ID NOs:43-50) were performed as in Figure IA and Figure IB. Predicted nuclear factor binding sites (TFD Data Base, David Gosh) are shown in d e top portion of this figure. Note the gap at position 429-430 in KR compared to other HIV-2 LTR sequences, suspected to be responsible for the increased basal activity. [B] Basal and stimulated activity of the HIV-2 KR , HIV-2 ST , and HIV-l πiB LTR promoters in U937 cells. CAT indicator plasmids were constructed as indicated in me Materials and Mediods section of die Examples. For the assay, 5 mg of the different LTR-CAT constructs were transfected into 1.5xl0 6 U937 cells using me cationic lipid technique (DoTAP™). Transfected cells were stimulated 20 hours later with either PHA (2 mg/ml) or GM-CSF (8 ng/ml), and incubated overnight. After harvesting the cells and extracting me cell lysate (See, Methods and Materials for Example 1), chloramphenicol transferase activity was quantitated using a commercial CAT-ELISA kit (Promega). Figure 3 shows the Kinetics of Macrophage Infection by HIV-2 KR . Replication kinetics of HIV-2 KR in human peripheral blood derived monocyte- macrophages were compared with those of other HIV-2 isolates and clones. Macrophages obtained from PBMC from normal donors were obtained by adherence onto fibronectin coated flasks, and cultured in die presence of 10% endothelial conditioned medium (containing M-CSF), 10% human serum, and 10% fetal calf serum (see, Materials and Mediods from Example 1). Infection of lOOOx TCID 50 of HIV-2 KR , HIV-2 R0D , or HIV-2 NIHz was performed after treatment of cells with polybrene (8 mg/ml) for 30 minutes at 37 °C. Cells were washed extensively with Hanks balanced salt solution after 3 hours of incubation with virus in media. Coulter SIV p26 EIA was used to quantify virus production at intervals after infection. Note the prompt rise in p26 production by HIV-2 KR infected monocytes, sustained over several weeks in culmre. WPI - Weeks Post Infection. The zero timepoint was obtained after extensive washing following initial infection (a 24 hour time point was also obtained and was comparable). Figure 4 shows the cytopathic effects of HIV-2 KR in vitro. The cytopathic effects of HIV-2 KR infection in on monocytes and lymphoblastoid cells were compared. Infection of lymphoblastoid Molt-4/Clone 8 cells [A,C,E] and primary human monocyte macrophages [B,D,F] with HIV-2 KR [A,B], HIV-2 R0D [C,D], and HIV-1 [E,F]. Approximately [A] Molt4/Clone 8 cells 5 days post- infection with 100xTCID 50 of HIV-2KR, [B] Monocytes 6 weeks after infection with 100xTCID 50 HIV-2 KR , [C] Molt4/Clone 8 cells 5 days post-infection with 100xTCID 50 HIV-2 R0D , [D] Monocytes 6 weeks after infection with an equivalent dose of HIV-2 R0D , [E] Molt-4/Clone 8 cells 5 days post-infection with 100xTCID 50 HIV-1 MN , and [F] Monocytes 6 weeks after infection with an equivalent infectious dose of HIV-1 IIIB . Note die distinct contrast between HIV-2 KR and HIV-2 R0D in antigen production (Figure 3) and production of multinucleate giant cells in infected monocyte-macrophage culmres. Figure 5 is a restriction map for the D53 plasmid deposited with the ATCC. Figure 6 shows the construction of infectious HIV-2 plasmid clone pEP32. Figure 7 shows the construction of HIV-2 protein expression vectors pEP40-pEP43. Figure 8 shows the construction of the Beta-galactosidase Vector 15.2; die pSPneo vector, and die CMV-G plasmid. Figure 9 shows the replication and expression of HIV-2 proviral constructs. IO 6 Molt 4 clone 8 cells lipofected (DOTAP, Boehringer-Mannheim) with 10 μg of CsCl-purified plasmid DNA and supematant was sampled at me indicated times for p26 antigen capture assay (Coulter). The pEP32Δpsi- and pEP40-transfected cultures were terminated at 7 months: at 200 days p26 levels remained undetectable. Figure 10 shows viral antigen expression by G418-selected cell lines. Figure 11 shows G418 stable viral producer and packaging cell lines , including viral antigen production. Stable cell lines were derived by selection and maintenance in G418 600 μg/ml after transfection of CsCl-purified plasmid DNA previously linearized in prokaryotic sequences. Adherent cell lines were derived using polybrene-DMSO transfection and suspension cell lines by lipofection. Single cell clones were obtained from 96-well plates seeded with limiting dilutions of cells resulting in less than 12 clones per plate. Viral titrations were carried out by end-point dilution infection of Molt4 clone 8 T cells in 96-well plates scored for syncytia at 10 days. p26 was assayed by die Coulter antigen capmre kit. Figure 12 shows a strategy for testing cell to cell spread of HIV-2 in producer cell lines. Figure 13 shows HIV-2 expression plasmid 40, wim Xbal and Pvul sites indicated. Figure 14 shows the construction of a GFP cell transduction vector. DEFINITIONS Unless defined odierwise, all technical and scientific terms used herein have me same meaning as commonly understood by one of ordinary skill in the art to which mis invention belongs. Singleton et al. (1994) Dictionary of Microbiology and Molecular Biology, second edition, John Wiley and Sons (New York) provides one of skill with a general dictionary of many of the terms used in mis invention. Al iough any methods and materials similar or equivalent to those described herein can be used in die practice or testing of the present invention, the preferred methods and materials are described. For purposes of the present invention, the following terms are defined below. An "HIV-2 provirus" includes nucleic acids encoded by me HIV-2 genome. The nucleic acid is typically a DNA or RNA encoding an entire HIV-2 genome incoφorated into a vector (e.g., a bacterial or eukaryotic plasmid, or a virus such as a λ-phage), or cell chromosome, but in the context of this invention also includes HIV-2 encoded DNA which is not incorporated into a vector (e.g., a restriction fragment) and RNA (e.g., HIV-2 genomic RNA which is to be incoφorated into an HIV capsid). An HIV-2 provirus also optionally includes nucleic acids unrelated to HIV (e.g. , vector or chromosomal sequences which flank HIV-2 encoded DNA). A "full-length HIV-2 genome" consists of a nucleic acid (RNA or DNA) encoded by an HIV-2 virus or viral clone which includes the 5' and 3' LTR regions and the genes between die LTR regions which are present in a typical wild- type HIV-2 virus (e.g., env, nef, rev, vpx, tat, gag, pol, vif, and vpr). An "activating deletion" in an HIV-2 LTR is a nucleic acid subsequence deletion, as compared to related HIV-2 strains, which increases the basal activity of the LTR promoter. "High basal activity" in the context of a particular HIV-2 LTR refers to an ability of the LTR to direct expression of die HIV-2 transcript in excess of a wild-type strain of HIV-2 such as HIV-2 ST (Kumar, et al. (1990) Journal of Virology 64, 890-901). Typically, die basal activity is at least about 1.5 times greater than HIV-2 ST , and preferably, d e basal activity is about twice that of the HIV-2 ST LTR. A "constitutive" promoter is a promoter which is active under most environmental and developmental conditions. "Encapsidation" generically refers to the process of incoφorating a nucleic acid sequence (e.g., a provirus) into a viral particle. In me context of HIV-2, the nucleic acid is typically an RNA. A "viral particle" is a generic term which includes a viral "shell", "particle" or "coat", including a protein "capsid", a "lipid enveloped strucmre", a "protein-nucleic acid capsid", or a combination thereof (e.g., a lipid-protein envelope surrounding a protein-nucleic acid particle). The term "identical" in me context of two nucleic acid or polypeptide sequences refers to the residues in the two sequences which are d e same when aligned for maximum correspondence. When percentage of sequence identity is used in reference to proteins or peptides it is recognized diat residue positions which are not identical often differ by conservative amino acid substimtions, where amino acids residues are substimted for otiier amino acid residues with similar chemical properties (e.g. charge or hydrophobicity) and therefore do not change the functional properties of the molecule. Where sequences differ in conservative substimtions, the percent sequence identity may be adjusted upwards to correct for the conservative namre of the substimtion. Means for making this adjustment are well known to those of skill in the art. Typically this involves scoring a conservative substimtion as a partial rather than a full mismatch, thereby increasing the percentage sequence identity. Thus, for example, where an identical amino acid is given a score of 1 and a non-conservative substimtion is given a score of zero, a conservative substimtion is given a score between zero and 1. The scoring of conservative substimtions is calculated, e.g., according to die algoridim of Meyers and Miller, Computer Applic. Biol. Sci., 4: 11-17 (1988) e.g., as implemented in the program PC/GENE (Intelligenetics, Mountain View, California, USA). A "comparison window", as used herein, refers to a segment of at least about 50 contiguous positions, usually about 50 to about 200, more usually about 100 to about 150 in which a sequence is compared to a reference sequence of the same number of contiguous positions after the two sequences are optimally aligned. Methods of alignment of sequences for comparison are well known in the art. Optimal alignment of sequences for comparison may be conducted by the local homology algoridim of Smith and Waterman (1981) Adv. Appl. Math. 2: 482; by the homology alignment algorithm of Needleman and Wunsch (1970) J. Mol. Biol. 48: 443; by the search for similarity method of Pearson and Lipman (1988) Proc. Natl. Acad. Sci. USA 85: 2444; by computerized implementations of these algorithms (including, but not limited to CLUSTAL in die PC/Gene program by Intelligenetics, Mountain View, California, GAP, BESTFIT, FASTA, and TFASTA in the Wisconsin Genetics Software Package, Genetics Computer Group (GCG), 575 Science Dr. , Madison, Wisconsin, USA); the CLUSTAL program is well described by Higgins and Shaφ (1988) Gene, 73: 237-244 and Higgins and Shaφ (1989) CABIOS 5: 151-153; Coφet, et al. (1988) Nucleic Acids Research 16, 10881-90; Huang, et al. (1992) Computer Applications in the Biosciences 8, 155-65, and Pearson, et al. (1994) Methods in Molecular Biology 24, 307-31. Alignment is also often performed by inspection and manual alignment. "Conservatively modified variations" of a particular nucleic acid sequence refers to those nucleic acids which encode identical or essentially identical amino acid sequences, or where me nucleic acid does not encode an amino acid sequence, to essentially identical sequences. Because of me degeneracy of d e genetic code, a large number of functionally identical nucleic acids encode any given polypeptide. For instance, me codons CGU, CGC, CGA, CGG, AGA, and AGG all encode die amino acid arginine. Thus, at every position where an arginine is specified by a codon, me codon can be altered to any of d e corresponding codons described without altering the encoded polypeptide. Such nucleic acid variations are "silent variations," which are one species of "conservatively modified variations." Every nucleic acid sequence herein which encodes a polypeptide also describes every possible silent variation. One of skill will recognize that each codon in a nucleic acid (except AUG, which is ordinarily die only codon for methionine) can be modified to yield a functionally identical molecule by standard techniques. Accordingly, each "silent variation" of a nucleic acid which encodes a polypeptide is implicit in each described sequence. Furthermore, one of skill will recognize that individual substimtions, deletions or additions which alter, add or delete a single amino acid or a small percentage of amino acids (typically less dian 5%, more typically less than 1 %) in an encoded sequence are "conservatively modified variations" where d e alterations result in the substimtion of an amino acid with a chemically similar amino acid. Conservative substimtion tables providing functionally similar amino acids are well known in the art. The following six groups each contain amino acids d at are conservative substimtions for one anodier: 1) Alanine (A), Serine (S), Threonine (T); 2) Aspartic acid (D), Glutamic acid (E); 3) Asparagine (N), Glutamine (Q); 4) Arginine (R), Lysine (K); 5) Isoleucine (I), Leucine (L), Methionine (M), Valine (V); and 6) Phenylalanine (F), Tyrosine (Y), Tryptophan (W). See also, Creighton (1984) Proteins W.H. Freeman and Company. An " inducible " promoter is a promoter which is under environmental or developmental regulation. The terms "isolated" or "biologically pure" refer to material which is substantially or essentially free from components which normally accompany it as found in its native state. The isolated nucleic acids of diis invention do not contain materials normally associated widi dieir in situ environment, in particular, nuclear, cytosolic or membrane associated proteins or nucleic acids odier than diose nucleic acids which are indicated. The term "labeled nucleic acid probe" refers to a nucleic acid probe that is bound, eidier covalently, dirough a linker, or dirough ionic, van der Waals or hydrogen "bonds" to a label such diat the presence of the probe may be detected by detecting the presence of die label bound to die probe. The term "label" refers to a composition detectable by spectroscopic, photochemical, biochemical, immunochemical, or chemical means. For example, useful labels include 32 P, 35 S, fluorescent dyes, electron-dense reagents, enzymes (e.g. , as commonly used in an ELISA), biotin, dioxigenin, or haptens and proteins for which antisera or monoclonal antibodies are available. The term "nucleic acid" refers to a deoxyribonucleotide or ribonucleotide polymer in either single- or double-stranded form, and unless odierwise limited, encompasses known analogues of namral nucleotides diat hybridize to nucleic acids in manner similar to namrally occurring nucleotides. Unless otherwise indicated, a particular nucleic acid sequence optionally includes the complementary sequence thereof. The term "operably linked" refers to functional linkage between a nucleic acid expression control sequence (such as a promoter, or array of transcription factor binding sites) and a second nucleic acid sequence, wherein die expression control sequence directs transcription of die nucleic acid corresponding to die second sequence. The term "recombinant" when used with reference to a cell indicates diat the cell replicates or expresses a nucleic acid, or expresses a peptide or protein encoded by nucleic acid whose origin is exogenous to d e cell. Recombinant cells can express genes that are not found within the native (non-recombinant) form of the cell. Recombinant cells can also express genes found in die native form of the cell wherein the genes are re-introduced into die cell or a progenitor of the cell by artificial means. The term "subsequence" in me context of a particular nucleic acid sequence refers to a region of the nucleic acid equal to or smaller than die specified nucleic acid. "Stringent conditions" in the context of nucleic acid hybridization are sequence dependent and are different under different environmental parameters. An extensive guide to die hybridization of nucleic acids is found in Tijssen (1993) Laboratory Techniques in biochemistry and molecular biology-hybridization with nucleic acid probes part I chapter 2 "overview of principles of hybridization and the strategy of nucleic acid probe assays", Elsevier, New York. Generally, stringent conditions are selected to be about 5° C lower dian the diermal melting point (T m ) for the specific sequence at a defined ionic strengdi and pH. The T m is the temperamre (under defined ionic strengdi and pH) at which 50% of the target sequence hybridizes to a perfectly matched probe. Highly stringent conditions are selected to be equal to die T m point for a particular probe. Nucleic acids which do not hybridize to each odier under stringent conditions are still substantially identical if die polypeptides which d ey encode are substantially identical. This occurs, e.g. , when a copy of a nucleic acid is created using the maximum codon degeneracy permitted by the genetic code. A "vector" is a composition which can transduce, transfect, transform or infect a cell, thereby causing die cell to express nucleic acids and/or proteins odier dian diose native to die cell, or in a manner not native to the cell. A cell is "transduced" by a nucleic acid when die nucleic acid is translocated into die cell from tiie extracellular environment. Any method of transferring a nucleic acid into die cell may be used; die term, unless odierwise indicated, does not imply any particular method of delivering a nucleic acid into a cell. A cell is "transformed" by a nucleic acid when die nucleic acid is transduced into d e cell and stably replicated. A vector includes a nucleic acid (ordinarily RNA or DNA) to be expressed by the cell. A vector optionally includes materials to aid in achieving entry of the nucleic acid into die cell, such as a viral particle, liposome, protein coating or die like. A "cell transduction vector" is a vector which encodes a nucleic acid capable of stable replication and expression in a cell once the nucleic acid is transduced into die cell. A "packaging vector" is a vector which encodes components necessary for production of HIV particles by a cell transduced by die packaging vector. The packaging vector optionally includes all of die components necessary for production of HIV particles, or optionally includes a subset of die components necessary for HIV packaging. For instance, in one preferred embodiment, a packaging cell is transduced with more dian one packaging vector nucleic acid, each of which has a complementary role in die production of an HIV particle. Two HIV-based packaging vectors are "complementary" when the two together encode die functions necessary for HIV packaging, and when each individually does not encode all of the functions necessary for packaging. Thus, when the two vectors transduce a single cell they togedier encode die information for production of HIV-based packaging particles. The use of such complementary vectors increases the safety of any packaging cell made by transduction with a packaging vector nucleic acid. Packaging vectors encode HIV particles. The HIV particles are competent to package target RNA which has an HIV packaging site. "High efficiency packaging vectors" package target RNAs such that packaging cells stably transduced with die packaging vector and transduced with a target packagable nucleic acid corresponding to the target packagable RNA produce packaged target RNA at a titer of at least about 10 3 to about IO 4 transducing units per ml of cell supematant or more, more preferably at least about 10 4 to about 10 5 transducing units per ml or more and often 10 5 to 10° transducing units or more. A "transducing unit" is a measure of the number of infective viral particles in a sample, typically as measured by an effect on a population of transducible cells. For example, where the cell population is exposed to a vimlent viral particle, cell death in a population of cells (e.g., TCID50/ml, or viral plaque forming units/ml) is a measurement of transduction. Where die viral particle is not vimlent, but carries a marker, the transfer of the marker (e.g. , neomycin resistance, or LacZ staining) is monitored. See, Examples 10 and 11. Transducing units can be correlated to the number of viral particles in a sample, e.g., using an ELISA assay to quantify the number of particles, and an activity assay (TCID50/ml, plaque formation assay, or marker detection) to measure the effect of the particles on a population of cells. DETAILED DESCRIPTION This invention provides HIV-2 nucleic acids, polypeptides, structural components (e.g., capsids and envelopes), whole vimses, subclones, immunogenic compositions, gene therapy vectors, cell systems and provimses. The compositions are useful as components of diagnostic assays, for the synthesis of diagnostic reagents, as vaccines against HIV infection, for die production of HIV-2 based retroviral packaging cells, and as components of cell transduction and gene therapy vectors. Provimses such as HIV-2 KR which are isolated from a particular library of HIV molecular clones generated from the viral infection of a single individual cannot be isolated using a molecular probe to a portion of die provims from a different molecular library. This is because the provims is unique to the specific molecular library. Accordingly, any prior art disclosure of a molecular probe directed to a particular unique provims cannot be used to isolate die unique provimses of the invention in the absence of a molecular library containing a clone of the provims. The present invention provides unique HIV-2 provimses including die HIV-2 KR provims. The complete sequence of the HIV-2 KR proviral clone is provided, enabling one of skill to generate die clone syntiietically, or by modification of otiier known HIV clones. In addition, d e clone was deposited as a plasmid ("D53") witii the ATCC on July 26, 1995. Making HIV-2 nucleic acids, provimses and provims fragments The present invention provides a variety of HIV-2 nucleic acids, including provimses and provims fragments such as provims subclones, PCR primers and molecular probes. In one preferred embodiment, the invention provides die HIV-2 proviral molecular clone HIV-2 KR . The complete sequence of die clone is given in SEQ. ID NO: l, and die sequence has been deposited witii GenBank (GenBank No. U22047). In addition, a plasmid (D53) with an HIV-2 KR provims containing die complete HIV-2 KR sequence was deposited widi die ATCC. Given the sequence of a provims of the present invention such as HIV-2 KR , one of skill can constmct a variety of clones containing derivative provimses and provims subsequences. Cloning methodologies to accomplish diese ends, and sequencing methods to verify die sequence of nucleic acids are well known in die art. Examples of appropriate cloning and sequencing techniques, and instmctions sufficient to direct persons of skill through many cloning exercises are found in Berger and Kimmel, Guide to Molecular Cloning Techniques, Methods in Enzymology volume 152 Academic Press, Inc. , San Diego, CA (Berger); Sambrook et al. (1989) Molecular Cloning - A Laboratory Manual (2nd ed.) Vol. 1-3, Cold Spring Harbor Laboratory, Cold Spring Harbor Press, NY, (Sambrook); and Current Protocols in Molecular Biology, F.M. Ausubel et al. , eds., Current Protocols, a joint venture between Greene Publishing Associates, Inc. and John Wiley & Sons, Inc., (1994 Supplement) (Ausubel). Product information from manufacmrers of biological reagents and experimental equipment also provide information useful in known biological methods. Such manufacmrers include the SIGMA chemical company (Saint Louis, MO), R&D systems (Minneapolis, MN), Pharmacia LKB Biotechnology (Piscataway, NJ), CLONTECH Laboratories, Inc. (Palo Alto, CA), Chem Genes Coφ., Aldrich Chemical Company (Milwaukee, WI), Glen Research, Inc., GIBCO BRL Life Technologies, Inc. (Gaithersberg, MD), Fluka Chemica-Biochemika Analytika (Fluka Chemie AG, Buchs, Switzerland), and Applied Biosystems (Foster City, CA), as well as many other commercial sources known to one of skill. The nucleic acid compositions of this invention, whether RNA, cDNA, genomic DNA, or a hybrid of the various combinations, are isolated from namral sources or synthesized in vitro. The nucleic acids claimed are present in transformed or transfected whole cells, in transformed or transfected cell lysates, or in a partially purified or substantially pure form. In vitro amplification techniques are suitable for amplifying provims sequences for use as molecular probes or generating proviral nucleic acid fragments for subsequent subcloning. Examples of techniques sufficient to direct persons of skill through such in vitro amplification methods, including die polymerase chain reaction (PCR) the ligase chain reaction (LCR), Q / 3-replicase amplification and other RNA polymerase mediated techniques (e.g., NASBA) are found in Berger, Sambrook, and Ausubel, as well as Mullis et al. , (1987) U.S. Patent No. 4,683,202; PCR Protocols A Guide to Methods and Applications (Innis et al. eds) Academic Press Inc. San Diego, CA (1990) (Innis); Arnheim & Levinson (October 1, 1990) C&EN 36-47; The Journal Of NIH Research (1991) 3, 81-94; (Kwoh et al. (1989) Proc. Natl. Acad. Sci. USA 86, 1173; Guatelli et al. (1990) Proc. Natl. Acad. Sci. USA 87, 1874; Lomell et al. (1989) J. Clin. Chem 35, 1826; Landegren et al , (1988) Science 241, 1077-1080; Van Brunt (1990) Biotechnology 8, 291-294; Wu and Wallace, (1989) Gene 4, 560; Barringer et al. (1990) Gene 89, 117, and Sooknanan and Malek (1995) Biotechnology 13: 563- 564. Improved methods of cloning in vitro amplified nucleic acids are described in Wallace et al. , U.S. Pat. No. 5,426,039. Improved mediods of amplifying large nucleic acids are summarized in Cheng et al. (1994) Namre 369: 684-685 and d e references therein. One of skill will appreciate tiiat essentially any RNA can be converted into a double stranded DNA suitable for restriction digestion, PCR expansion and sequencing using reverse transcriptase and a polymerase. See, Ausbel, Sambrook and Berger, all supra. Oligonucleotides for use as probes, e.g., in in vitro amplification methods, or for use as gene probes are typically chemically synthesized according to d e solid phase phosphoramidite triester method described by Beaucage and Caruthers (1981), Tetrahedron Letts. , 22(20): 1859- 1862, e.g., using an automated synthesizer, as described in Needham- VanDevanter et al. (1984) Nucleic Acids Res. , 12:6159-6168. Purification of oligonucleotides, where necessary, is typically performed by eidier native acrylamide gel electrophoresis or by anion-exchange HPLC as described in Pearson and Regnier (1983) J. Chrom. 255: 137-149. The sequence of the synthetic oligonucleotides can be verified using die chemical degradation method of Maxam and Gilbert (1980) in Grossman and Moldave (eds.) Academic Press, New York, Methods in Enzymology 65:499-560. The polypeptides of die invention can be syntiietically prepared in a wide variety of well-know ways. For instance, polypeptides of relatively short size, can be synthesized in solution or on a solid support in accordance widi conventional techniques. See, e.g., Merrifield (1963) J. Am. Chem. Soc. 85:2149-2154. Various automatic synthesizers are commercially available and can be used in accordance with known protocols. See, e.g., Stewart and Young (1984) Solid Phase Peptide Synthesis, 2d. ed., Pierce Chemical Co. Making Conservative Modifications of d e Nucleic Acids and Polypeptides of d e Invention. One of skill will appreciate tiiat many conservative variations of the proviral sequences disclosed yield an essentially identical vims. For example, due to the degeneracy of die genetic code, "silent substimtions" (i.e., substimtions of a nucleic acid sequence which do not result in an alteration in an encoded polypeptide) are an implied feature of every nucleic acid sequence which encodes an amino acid. Similarly, "conservative amino acid substimtions," in one or a few amino acids in an amino acid sequence are substimted with different amino acids with highly similar properties (see, the definitions section, supra), are also readily identified as being highly similar to a disclosed amino acid sequence, or to a disclosed nucleic acid sequence which encodes an amino acid. Such conservatively substimted variations of each explicitly disclosed sequence are a feature of the present invention. One of skill will recognize many ways of generating alterations in a given nucleic acid sequence. Such well-known methods include site-directed mutagenesis, PCR amplification using degenerate oligonucleotides, exposure of cells containing the nucleic acid to mutagenic agents or radiation, chemical synmesis of a desired oligonucleotide (e.g., in conjunction with ligation and/or cloning to generate large nucleic acids) and odier well-known techniques. See, Giliman and Smith (1979) Gene 8:81-97; Roberts etal. (1987) Nature 328:731-734 and Sambrook, Innis. Ausbel, Berger, Needham VanDevanter and Mullis (all supra). Most commonly, HIV-2 polypeptide sequences are altered by altering die corresponding nucleic acid sequence and expressing the polypeptide. However, HIV-2 polypeptide sequences are also optionally generated synthetically on commercially available peptide synthesizers to produce any desired polypeptide (see, Merrifield, and Stewart and Young, supra). One of skill can select a desired nucleic acid or polypeptide of die invention based upon d e sequences provided and upon knowledge in die art regarding HIV strains generally. The life-cycle, genomic organization, developmental regulation and associated molecular biology of HIVs have been d e focus of over a decade of intense research. The specific effects of many mutations in d e HIV genome are known. Moreover, general knowledge regarding die namre of proteins and nucleic acids allows one of skill to select appropriate sequences with activity similar or equivalent to the nucleic acids and polypeptides disclosed in d e sequence listings herein. The definitions section herein describes exemplar conservative amino acid substimtions. Finally, most modifications to nucleic acids and polypeptides are evaluated by routine screening techniques in suitable assays for the desired characteristic. For instance, changes in the immunological character of a polypeptide can be detected by an appropriate immunological assay. Modifications of other properties such as nucleic acid hybridization to a target nucleic acid, redox or diermal stability of a protein, hydrophobicity, susceptibility to proteolysis, or the tendency to aggregate are all assayed according. to standard techniques. Use of The Nucleic Acids of The Invention as Molecular Probes The nucleic acids of die invention are useful as molecular probes, in addition to dieir utility in encoding die polypeptides described herein. A wide variety of formats and labels are available and appropriate for nucleic acid hybridization, including those reviewed in Tijssen (1993) Laboratory Techniques in biochemistry and molecular biology— hybridization with nucleic acid probes parts I and II, Elsevier, New York and Choo (ed) (1994) Methods In Molecular Biology Volume 33- In Situ Hybridization Protocols Humana Press Inc. , New Jersey (see also, other books in die Methods in Molecular Biology series); see especially, Chapter 21 of Choo (id) "Detection of Vims Nucleic Acids by Radioactive and Nonisotopic in Situ Hybridization". For instance, PCR is routinely used to detect HIV nucleic acids in biological samples (see, Innis, supra for a general description of PCR techniques). Accordingly, in one class of embodiments, die nucleic acids of the invention are used as PCR primers, or as positive controls in PCR reactions for the detection of HIV in a biological sample such as human blood. Briefly, nucleic acids encoded by die nucleic acid constmcts of die invention are used as templates to syntiietically produce oligonucleotides of about 20-100 nucleotides witii sequences similar or identical to die selected nucleic acid. The oligonucleotides are tiien used as primers in PCR reactions to detect HIV nucleic acids in biological samples such as human blood. The nucleic acids of d e invention (i.e., a nucleic acid conesponding to die region to be amplified) are also used as amplification templates in separate reactions to determine mat the PCR reagents and hybridization conditions are appropriate. Otiier methods for the detection of HIV nucleic acids in biological samples using nucleic acids of the invention include Southern blots, northem blots, in situ hybridization (including Fluorescent in situ hybridization (FISH), reverse chromosome painting, FISH on DAPI stained chromosomes, generation of Alphoid DNA probes for FISH using PCR, PRINS labeling of DNA, free chromatin mapping and a variety of otiier techniques described in Choo (supra)). A variety of automated solid-phase detection techmques are also appropriate. For instance, very large scale immobilized polymer anays (VLSIPS™) are used for die detection of nucleic acids. See, Tijssen (supra), Fodor et al. (1991) Science, 251: 767- 777 and Sheldon et al. (1993) Clinical Chemistry 39(4): 718-719. Expression of HIV-2 polypeptides Once an HIV-2 provims nucleic acid or HIV-2 provims subsequence nucleic acid is isolated and cloned, one may express the nucleic acid in a variety of recombinantly engineered cells known to those of skill in the art. Examples of such cells include bacteria, yeast, filamentous fungi, insect (especially employing baculoviral vectors), and mammalian cells. It is expected d at diose of skill in die art are knowledgeable in the numerous expression systems available for cloning and expression of HIV-2 nucleic acids. In brief summary, the expression of namral or synthetic nucleic acids encoding, e.g., HIV-2 KR polypeptides is typically achieved by operably linking a nucleic acid encoding die polypeptide of interest to a promoter (which is either constitutive or inducible), and incoφorating the constmct into an expression vector. The vectors can be suitable for replication and integration in prokaryotes, eukaryotes, or both. Typical cloning vectors contain transcription and translation terminators, transcription and translation initiation sequences, and promoters useful for regulation of the expression of the particular nucleic acid. The vectors optionally comprise generic expression cassettes containing at least one independent terminator sequence, sequences permitting replication of ti e cassette in eukaryotes, or prokaryotes, or both, (e.g. , shuttle vectors) and selection markers for bom prokaryotic and eukaryotic systems. See, e.g., Sambrook and Ausbel (both supra). To obtain high levels of expression of a cloned nucleic acid it is common to constmct expression plasmids which typically contain a strong promoter to direct transcription, a ribosome binding site for translational initiation, and a transcription/translation terminator. For example, as described herein, die polypeptides encoded by the HIV-2 provimses of the present invention (including HIV-2 KR ), which are useful as antigenic reagents and as components of diagnostic assays, are optionally expressed in bacterial cells such as E. coli. Examples of regulatory regions suitable for mis puφose in E. coli are the promoter and operator region of the E. coli tryptophan biosynthetic pathway as described by Yanofsky, C. , 1984, J. Bacteriol. , 158: 1018-1024 and the leftward promoter of phage lambda (P L ) as described by Herskowitz and Hagen, 1980, Ann. Rev. Genet. , 14:399-445. The inclusion of selection markers in DNA vectors transformed in bacteria such as E. coli is also useful. Examples of such markers include genes specifying resistance to ampicillin, tetracycline, or chloramphenicol. See, Sambrook, Ausbel, and Berger for details conceming selection markers, e.g., for use in E. coli. Expression systems for expressing polypeptides are available using E. coli, Bacillus sp. (Palva, I. et al , 1983, Gene 22:229-235; Mosbach, K. et al , Nature, 302:543- 545) and Salmonella. E. coli systems are the most common, and best defined prokaryotic expression systems and are, therefore, prefened when expression is performed in prokaryotes. Polypeptides produced by prokaryotic cells often require exposure to chaotropic agents for proper folding. During purification from, e.g., E. coli, the expressed protein is optionally denatured and tiien renamred. This is accomplished, e.g., by solubilizing die bacterially produced antibodies in a chaotropic agent such as guanidine HCl. The antibody is tiien renamred, either by slow dialysis or by gel filtration. See, U.S. Patent No. 4,511,503. Methods of transfecting and expressing genes in eukaryotic cells are also known in the art. For example, synthesis of heterologous proteins in yeast is well known and described. See, e.g., Sherman et al. (1982) Methods in Yeast Genetics, Cold Spring Harbor Laboratory. Examples of promoters for use in yeast include GAL1,10 (Johnson and Davies (1984) Mol. Cell. Biol. 4: 1440-1448) ADH2 (Russell et al. (1983) J. Biol. Chem. 258:2674-2682), PH05 (EMBO J. (1982) 6:675-680), and MFαl (Herskowitz and Oshima (1982) in The Molecular Biology of the Yeast Saccharomyces (eds. Strathern, Jones, and Broach) Cold Spring Harbor Lab., Cold Spring Harbor, N.Y., pp. 181-209). A multicopy plasmid with selective markers such as Leu-2, URA-3, Tφ-1, and His-3 is also commonly used. A number of yeast expression plasmids like YEp6, YEpl3, YEp4 can be used as expression vectors. An HIV-2 gene of interest can be fused to any of the promoters in various yeast vectors. The above-mentioned plasmids have been fully described in tiie literature (Botstein et al. (1979) Gene 8: 17-24; Broach, et al. (1979) Gene, 8: 121-133). Two procedures are commonly used in transforming yeast cells. In one case, yeast cells are first converted into protoplasts using zymolyase, lyticase or glusulase, followed by addition of DNA and polyethylene glycol (PEG). The PEG-treated protoplasts are then regenerated in a 3 % agar medium under selective conditions. Details of this procedure are given in Beggs (1978) Nature (London) 275: 104-109, and Hinnen et al. (1978) Proc. Natl. Acad. Sci. USA 75: 1929-1933. The second procedure does not involve removal of die cell wall. Instead d e cells are treated, e.g., with lithium chloride or acetate and PEG and put on selective plates (Ito, et al. (1983) J. Bact. 153: 163-168). The polypeptides of interest are isolated from yeast by lysing die cells and applying standard protein isolation techniques to die lysates. The polypeptides of tiiis invention are purified to substantial purity by standard techniques well known in the art, including selective precipitation with such substances as ammonium sulfate, column chromatography, immunopurification methods, and otiiers. See, for instance, Scopes (1982) Protein Purification: Principles and Practice Springer-Verlag New York. The monitoring of the purification process is accomplished by using Western blot techniques or radioimmunoassays or other standard immunoassay techniques, or by monitoring the protein directly, e.g., by coomassie blue or silver-stain polyacrylamide gel electrophoresis. Transducing cells with nucleic acids can involve, for example, incubating viral vectors (e.g., retroviral or adeno-associated viral vectors) containing nucleic acids which encode polypeptides of interest with cells within the host range of the vector. See, e.g., Methods in Enzymology, vol. 185, Academic Press, Inc. , San Diego, CA (D.V. Goeddel, ed.) (1990) or M. Krieger, Gene Transf er and Expression — A Laboratory Manual, Stockton Press, New York, NY, (1990) and d e references cited tiierein. The culmre of cells used in conjunction with the present invention, including cell lines and culmred cells from tissue or blood samples is well known in me art. Freshney (Culture of Animal Cells, a Manual of Basic Technique, third edition Wiley-Liss, New York (1994)) and d e references cited tiierein provides a general guide to the culmre of cells. Illustrative of cell culmres useful for the production of HIV-2 polypeptides are cells of insect or mammalian origin. Mammalian cell systems often will be in ti e form of monolayers of cells, although mammalian cell suspensions are also used. Illustrative examples of mammalian cell lines include VERO and HeLa cells, Chinese hamster ovary (CHO) cell lines, W138, BHK, Cos-7 or MDCK cell lines (see, e.g., Freshney, supra). As indicated above, die vector, e.g. , a plasmid, which is used to transform the host cell, preferably contains nucleic acid sequences to initiate transcription and sequences to control die translation of the encoded polypeptide. These sequences are refened to generally as expression control sequences. When the host cell is of insect or mammalian origin, illustrative expression control sequences are obtained from the SV-40 promoter (Science (1983) 222:524-527), the CMV I.E. Promoter (Proc. Natl. Acad. Sci. (1984) 81 :659-663) or the metallothionein promoter (Nature (1982) 296:39-42). The cloning vector containing the expression control sequences is cleaved using restriction enzymes and adjusted in size as necessary or desirable and ligated witii DNA coding for the HIV-2 polypeptide of interest by means well known in the art. As with yeast, when higher animal host cells are employed, polyadenlyation or transcription terminator sequences from known mammalian genes are typically incoφorated into die vector. An example of a terminator sequence is the polyadenlyation sequence from the bovine growth hormone gene. Sequences for accurate splicing of the transcript may also be included. An example of a splicing sequence is tiie VPI intron from SV40 (Sprague et al. (1983) J. Virol. 45: 773-781). Additionally, gene sequences to control replication in a particular host cell are incoφorated into me vector such as those found in bovine papilloma vims type-vectors. See, Saveria-Campo (1985), "Bovine Papilloma vims DNA a Eukaryotic Cloning Vector" in DNA Cloning Vol. II a Practical Approach Glover (ed) IRL Press, Arlington, Virginia pp. 213-238. Host cells are competent or rendered competent for transformation by various means. There are several well-known methods of introducing DNA into animal cells. These include: calcium phosphate precipitation, fusion of the recipient cells with bacterial protoplasts containing tiie DNA, treatment of the recipient cells witii liposomes containing the DNA, DEAE dextran, receptor- mediated endocytosis, electroporation and micro-injection of me DNA directly into the cells. Transformed cells are culmred by means well known in die art. See, Freshny (supra), Kuchler et al. (1977) Biochemical Methods in Cell Culture and Virology, Kuchler, R.J., Dowden, Hutchinson and Ross, Inc. The expressed polypeptides are isolated from cells grown as suspensions or as monolayers. The latter are recovered by well known mechanical, chemical or enzymatic means. See, Scopes, supra. Making Antibodies to HIV-2 provims polypeptides HIV-2 provims polypeptides (including HIV^ KR ) polypeptides are optionally bound by antibodies in one class of embodiments of die present invention. The polypeptides are used as diagnostic reagents as described herein, or are used as immunogens for the production of antibodies which are also useful, e.g., as diagnostic reagents. Mediods of producing polyclonal and monoclonal antibodies are known to those of skill in the art. See, e.g. , Coligan (1991) Current Protocols in Immunology Wiley/Greene, NY; and Harlow and Lane (1989) Antibodies: A Laboratory Manual Cold Spring Harbor Press, NY; Stites et al. (eds.) Basic and Clinical Immunology (4th ed.) Lange Medical Publications, Los Altos, CA, and references cited tiierein; Goding (1986) Monoclonal Antibodies: Principles and Practice (2d ed.) Academic Press, New York, NY; and Kohler and Milstein (1975) Namre 256: 495-497. Otiier suitable techniques for antibody preparation include selection of libraries of recombinant antibodies in phage or similar vectors. See, Hu? st al. (1989) Science 246: 1275-1281; and Ward, et al. (1989) Nature 341: 544-546. Specific monoclonal and polyclonal antibodies and antisera will usually bind witii a K D of at least about .1 mM, more usually at least about 1 μM, preferably at least about .1 μM or better, and most typically and preferably, .01 μM or better. Frequently, the polypeptides and their conesponding antibodies will be labeled by joining, eidier covalently or non covalently, a substance which provides for a detectable signal. A wide variety of labels and conjugation techniques are known and are reported extensively in both the scientific and patent literature. Suitable labels include radionucleotides, enzymes, substrates, cofactors, inhibitors , fluorescent moieties , chemiluminescent moieties , magnetic particles , and the like. Patents teaching the use of such labels include U.S. Patent Nos. 3,817,837; 3,850,752; 3,939,350; 3,996,345; 4,277,437; 4,275,149; and 4,366,241. Also, recombinant immunoglobulins may be produced. See, Cabilly, U.S. Patent No. 4,816,567; and Queen et al. (1989) Proc. Nat'l Acad. Sci. USA 86: 10029-10033. The immunogenic compositions of this invention (e.g., peptides, nucleic acids, viral particles, viral capsids, etc.) are also used for affinity chromatography in isolating and quantitating HIV-2 antibodies and anti-sera. Columns are prepared, e.g., with the antibodies linked to a solid support, e.g. , particles, such as agarose, Sephadex, or die like, where a cell lysate is passed dirough the column, washed, and treated widi increasing concentrations of a mild denaturant, whereby purified antibodies are released. Immunoassay formats In one prefened class of embodiments, the HIV-2 polypeptides of die present invention are used for the detection of HIV infection in human (or animal) patients. For instance, HIV-2 polypeptides (e.g., polypeptides encoded by HIV-2 KR ) are useful in western blots for die detection of antibodies to HIV in a patient's blood. Such tests are well known, and are presently a standard method by which HIV-1 and HIV-2 infections are detected in patient populations. The HIV-2 polypeptides of d e invention (individually or as part of an intact HIV-2 vims in a viral particle) can be used in known and standard immunoassay methods for the detection of HIV infections. A variety of immunoassay formats are known and available. A particular protein can be quantified by a variety of immunoassay methods. For a review of immunological and immunoassay procedures in general, see Stites and Ten (eds.) 1991 Basic and Clinical Immunology (7th ed.). Moreover, die immunoassays of the present invention can be performed in any of several configurations, e.g., those reviewed in Maggio (ed.) (1980) Enzyme Immunoassay CRC Press, Boca Raton, Florida; Tijan (1985) "Practice and Theory of Enzyme Immunoassays," Laboratory Techniques in Biochemistry and Molecular Biology, Elsevier Science Publishers B.V., Amsterdam; Harlow and Lane, supra; Chan (ed.) (1987) Immunoassay: A Practical Guide Academic Press, Orlando, FL; Price and Newman (eds.) (1991) Principles and Practice of Immunoassays Stockton Press, NY; and Ngo (ed.) (1988) Non isotopic Immunoassays Plenum Press, NY. Immunoassays often utilize a labeling agent to specifically bind to and label d e binding complex formed by die capmre agent and d e analyte (HIV-2 polypeptides are eitiier the capmre agent, or tiie analyte, depending on the format of the assay). The labeling agent may itself be one of the moieties comprising tiie capmre agent/analyte complex. Thus, tiie labeling agent is optionally a labeled HIV-2 polypeptide or a labeled HIV-2 antibody. Altematively, die labeling agent is optionally a tiiird moiety, such as another antibody, that specifically binds to the capmre agent/ polypeptide complex, or to a modified capmre group (e.g., biotin) which is covalently linked to die peptide or antibody. In one embodiment, the labeling agent is an antibody d at specifically binds to the capmre agent, which is an HIV-2 polypeptide antibody. Such agents are well known to those of skill in the art, and most typically comprise labeled antibodies tiiat specifically bind antibodies of d e particular animal species from which the capmre agent is derived (e.g., an anti-species antibody). Thus, for example, where die capmre agent is a mouse antibody, d e label agent may be a goat anti-mouse IgG, i.e., an antibody specific to die constant region of the mouse antibodies. Other proteins capable of specifically binding immunoglobulin constant regions, such as streptococcal protein A or protein G are also useful as labeling agents. These proteins are normal constiments of die cell walls of streptococcal bacteria. They exhibit a strong non-immunogenic reactivity with immunoglobulin constant regions from a variety of species. See, generally Kronval, et al. , (1973) J. Immunol. , 111: 1401-1406, and Akerstrom, et al. , (1985) J. Immunol. , 135:2589-2542. Alternatively, die HIV-2 polypeptide can be labeled directly, e.g., by producing die polypeptide in a cell culmre containing radioactive amino acids, or by radiolabeling purified HIV-2 polypeptide. In anodier embodiment, die capmre agent is an HIV-2 polypeptide and the analyte is an HIV-2 polypeptide analyte. In tiiis embodiment, die polypeptide is typically labeled directly (e.g., by radio labeling) or by using an antibody label distinct from d e analyte antibody. Throughout die assays, incubation and/or washing steps may be required after each combination of reagents. Incubation steps can vary from about 5 seconds to several hours, preferably from about 5 minutes to about 24 hours. However, e incubation time will depend upon the assay format, analyte, volume of solution, concentration of capmre agent and analyte, and die like. Usually, die assays are canied out at ambient temperamre, altiiough they can be conducted over a range of temperatures, such as 5°C to 45 °C. Non Competitive Assay Formats Immunoassays for detecting a polypeptide or antibody may be either competitive or noncompetitive. Noncompetitive immunoassays are assays in which the amount of capmred analyte is directly measured. In one prefened "sandwich" assay, for example, the capmre agent is bound directly to a solid substrate where it is immobilized. These immobilized capmre agents then "capmre" or "bind" analyte present in a test sample. The analyte thus immobilized is men bound by a labeling agent, such as an antibody bearing a label. Altematively, the labeling agent may lack a direct label, but it may, in mm, be bound by a labeled tiiird moiety such as an antibody specific to antibodies of die species from which the labeling agent is derived. Sandwich assays for an analyte are optionally constmcted. As described above, the immobilized capmre agent specifically binds to die analyte in die sample. The labeled anti-analyte (labeling agent) then binds to me capmre agent-analyte complex. Free labeling agent is washed away and the remaining bound labeled complex is detected (e.g., using a gamma detector where the label is radioactive). Competitive Assay Formats In competitive assays, the amount of analyte present in the test sample is measured indirectly by measuring the amount of an added (exogenous) analyte displaced (or competed away) from a capmre agent by the analyte present in the sample. In one competitive assay, a known amount of analyte is added to the sample and die sample is contacted with a capmre agent that specifically binds d e analyte. The amount of analyte bound to die capmre agent is inversely proportional to the concentration of analyte present in the sample. In a prefened embodiment, me capmre agent is immobilized on a solid substrate. The amount of analyte bound to the capmre agent is determined either by measuring me amount of analyte present in an analyte-capture agent complex, or altematively by measuring the amount of remaining uncomplexed analyte. The amount of analyte in a sample to be assayed may also be detected by providing exogenous labeled analyte to die assay. A hapten inhibition assay is another prefened competitive assay. In mis assay, a known analyte is immobilized on a solid substrate. A known amount of anti-analyte is added to die sample, and die sample is then contacted witii the capmre agent. In this case, the amount of anti-analyte bound to die immobilized capmre agent is proportional to the amount of analyte present in d e sample. Again, the amount of immobilized analyte is detected by quantitating eidier d e immobilized fraction of anti-analyte or the fraction of the anti-analyte that remains in solution. Detection is direct where the anti-analyte is labeled, or indirect where a labeled moiety is subsequently added which specifically binds to d e anti-analyte as described above. Assays for HIV-2 Proviral Genes and Gene Products Uses for HTV-2 Polypeptides and Nucleic Acids; Sample Collection and Processing An HIV-2 transcript, antibody or polypeptide is preferably quantified in a biological sample, such as a cell, or a tissue sample derived from a patient. In a prefened embodiment, antisera to HIV-2 polypeptides are quantified in semm (See, supra). In another prefened embodiment, HIV-2 nucleic acids are detected in an infected patient using gene probes derived from me nucleic acids of die invention. For instance, in one embodiment, HIV nucleic acids in a biological sample are amplified by an in vitro amplification technique (e.g., PCR or LCR) and detected using labeled HIV-2 KR nucleic acids. The HIV-2 nucleic acids of die invention are also useful as control reagents. For instance, the HIV-2 KR transcript or a portion thereof is useful as a control template to monitor the efficiency of in vitro amplification reactions. For instance, in a PCR reaction, in order to determine that all of the reagents are working properly (buffers, taq polymerase, etc.), one reaction (or a set of reactions at various concentrations of template) is set up using the HIV-2 KR nucleic acid as a template (e.g., with HIV-2 primers) and mn in parallel witii nucleic acid from biological samples taken from patients as PCR templates. The presence of such as "positive control" reaction is a straightforward way of showing tiiat a biological sample which tests "negative" (i.e. , the in vitro amplification method does not produce an amplification product) does so because diere is no template in die sample, and not because d e reagents are defective. Although die sample is typically taken from a human patient, the assays can be used to detect HIV-2 polypeptides or antibodies (including recombinant antibodies) in cells from eukaryotes in general, including plants, vertebrates and invertebrates, and in mammals in particular, such as dogs, cats, sheep, cattle and pigs, and most particularly primates such as humans, chimpanzees, gorillas, macaques, and baboons, and rodents such as mice, rats, and guinea pigs. As shown in the examples below, mice and macaques are bodi infected by HIV-2 KR . The sample is pretreated as necessary by dilution in an appropriate buffer solution or concentrated, if desired. Many standard aqueous buffer solutions employing one of a variety of buffers, such as phosphate, Tris, or the like, at physiological pH are appropriate. Quantification of Polypeptides, nucleic acids and Antibodies HIV-2 antibodies, and the polypeptides and nucleic acids of die invention are detected and quantified by any of a number of means well known to those of skill in die art. These include analytic biochemical methods such as spectrophotometry, radiography, electrophoresis, capillary electrophoresis, high performance liquid chromatography (HPLC), thin layer chromatography (TLC), hyperdif fusion chromatography, and d e like, and various immunological methods such as fluid or gel precipitin reactions, immunodiffusion (single or double), immunoelectrophoresis, radioimmunoassays (RIAs), enzyme-linked immunosorbent assays (ELISAs), immunofluorescent assays, and die like. The detection of nucleic acids proceeds by well known methods such as Soutiiern analysis, northem analysis, gel electrophoresis, PCR, radiolabeling and scintillation counting, and affinity chromatography. Reduction of Non Specific Binding One of skill will appreciate diat it is often desirable to reduce non specific binding in immunoassays and during analyte purification. Where the assay involves an HIV-2 polypeptide, antibody, or otiier capmre agent immobilized on a solid substrate, it is desirable to minimize the amount of non specific binding to die substrate. Means of reducing such non specific binding are well known to those of skill in the art. Typically, this involves coating the substrate with a proteinaceous composition. In particular, protein compositions such as bovine semm albumin (BSA), nonfat powdered milk, and gelatin are widely used. Other Assay Formats Western blot analysis can also be used to detect and quantify the presence of a polypeptide or antibody (peptide, transcript, or enzymatic digestion product) in the sample. The techmque generally comprises separating sample products by gel electrophoresis on die basis of molecular weight, transfening the separated proteins to a suitable solid support, (such as a nitrocellulose filter, a nylon filter, or derivatized nylon filter), and incubating the sample with labeling antibodies tiiat specifically bind to die analyte protein (antibody or HIV-2 polypeptide). The labeling antibodies specifically bind to analyte on die solid support. These antibodies are directly labeled, or altematively are subsequently detected using labeling agents such as antibodies (e.g., labeled sheep anti-mouse antibodies where die antibody to an analyte is a murine antibody) diat specifically bind to the labeling antibody. Other assay formats include liposome immunoassays (LIAs), which use liposomes designed to bind specific molecules (e.g., antibodies) and release encapsulated reagents or markers. The released chemicals are tiien detected according to standard techniques (see, Monroe et al. , (1986) Amer. Clin. Prod. Rev. 5:34-41). Labels Labeling agents include e.g. , monoclonal antibodies, polyclonal antibodies, proteins such as diose described herein, or otiier polymers such as affinity matricies, carbohydrates or lipids. Detection proceeds by any known method, such as immunoblotting, westem analysis, gel-mobility shift assays, fluorescent in situ hybridization analysis (FISH), tracking of radioactive or bioluminescent markers, nuclear magnetic resonance, electron paramagnetic resonance, stopped-flow spectroscopy, column chromatography, capillary electrophoresis, Southern blotting, northem blotting, southwestern blotting, northwestern blotting, or other methods which track a molecule based upon size, charge or affinity. The particular label or detectable group used and the particular assay are not critical aspects of d e invention. The detectable moeity can be any material having a detectable physical or chemical property. Such detectable labels have been well-developed in die field of gels, columns, solid substrates and immunoassays and, in general, any label useful in such methods can be applied to die present invention. Thus, a label is any composition detectable by spectroscopic, photochemical, biochemical, immunochemical, electrical, optical or chemical means. Useful labels in the present invention include magnetic beads (e.g. Dynabeads™), fluorescent dyes (e.g. , fluorescein isothiocyanate, Texas red, rhodamine, and die like), radiolabels (e.g. , 3 H, 125 I, 35 S, I C, or 32 P), enzymes (e.g. , LacZ, CAT, horse radish peroxidase, alkaline phosphatase and others, commonly used as detectable enzymes, either as marker gene products or in an ELISA), nucleic acid intercalators (e.g., ethidium bromide) and colorimetric labels such as colloidal gold or colored glass or plastic (e.g. polystyrene, polypropylene, latex, etc.) beads. The label is coupled directly or indirectly to the desired component of the assay according to methods well known in the art. As indicated above, a wide variety of labels are used, with the choice of label depending on die sensitivity required, ease of conjugation of the compound, stability requirements, available instrumentation, and disposal provisions. Non radioactive labels are often attached by indirect means. Generally, a ligand molecule (e.g., biotin) is covalently bound to a polymer. The ligand tiien binds to an anti-ligand (e.g. , streptavidin) molecule which is eidier inherently detectable or covalently bound to a signal system, such as a detectable enzyme, a fluorescent compound, or a chemiluminescent compound. A number of ligands and anti-ligands can be used. Where a ligand has a namral anti-ligand, for example, biotin, thyroxine, and cortisol, it can be used in conjunction witii labeled, anti-ligands. Alternatively, any haptenic or antigenic compound can be used in combination witii an antibody. Labels can also be conjugated directly to signal generating compounds, e.g. , by conjugation widi an enzyme or fluorophore. Enzymes of interest as labels will primarily be hydrolases, particularly phosphatases, esterases and glycosidases, or oxidoreductases, particularly peroxidases. Fluorescent compounds include fluorescein and its derivatives, rhodamine and its derivatives, dansyl, umbelliferone, etc. Chemiluminescent compounds include luciferin, and 2,3-dihydrophd alazinediones, e.g. , luminol. For a review of various labelling or signal producing systems which may be used, see, U.S. Patent No. 4,391,904, which is incoφorated herein by reference. Means of detecting labels are well known to those of skill in die art. Thus, for example, where the label is a radioactive label, means for detection include a scintillation counter or photographic film as in autoradiography. Where die label is a fluorescent label, it may be detected by exciting the fluorochrome with the appropriate wavelengdi of light and detecting die resulting fluorescence, e.g., by microscopy, visual inspection, via photographic film, by the use of electronic detectors such as charge coupled devices (CCDs) or photomultipliers and the like. Similarly, enzymatic labels may be detected by providing appropriate substrates for the enzyme and detecting the resulting reaction product. Finally, simple colorimetric labels are often detected simply by observing die color associated with die label. Thus, in various dipstick assays, conjugated gold often appears pink, while various conjugated beads appear the color of the bead. Some assay formats do not require die use of labeled components. For instance, agglutination assays can be used to detect die presence of antibodies. In this case, antigen-coated (e.g., HIV-2 polypeptide-coated) particles are agglutinated by samples comprising d e target antibodies. In tiiis format, none of the components need be labeled and the presence of the target antibody is detected by simple visual inspection. Substrates As mentioned above, depending upon the assay, various components, including HIV-2 components, or anti-HIV-2 antibodies, are optionally bound to a solid surface. Many methods for immobilizing biomolecules to a variety of solid surfaces are known in tiie art. For instance, the solid surface may be a membrane (e.g. , nitrocellulose), a microtiter dish (e.g., PVC, polypropylene, or polystyrene), a test mbe (glass or plastic), a dipstick (e.g. glass, PVC, polypropylene, polystyrene, latex, and die like), a microcentrifuge mbe, or a glass, silica, plastic, metallic or polymer bead. The desired component may be covalently bound, or noncovalently attached dirough nonspecific bonding. A wide variety of organic and inorganic polymers, both namral and syntiietic may be employed as die material for the solid surface. Illustrative polymers include polyediylene, polypropylene, poly (4-methy Ibutene), polystyrene, polymethacrylate, poly(ethylene terephthalate), rayon, nylon, poly(vinyl butyrate), polyvinylidene difluoride (PVDF) , silicones , polyformaldehyde , cellulose , cellulose acetate, nitrocellulose, and the like. Other materials which are appropriate depending on the assay include paper, glasses, ceramics, metals, metalloids, semiconductive materials, cements and die like. In addition, substances tiiat form gels, such as proteins (e.g. , gelatins), lipopoly saccharides, silicates, agarose and polyacrylamides can be used. Polymers which form several aqueous phases, such as dextrans, polyalkylene glycols or surfactants, such as phospholipids, long chain (12-24 carbon atoms) alkyl ammonium salts and die like are also suitable. Where the solid surface is porous, various pore sizes may be employed depending upon die namre of the system. In preparing tiie surface, a plurality of different materials are optionally employed, e.g., as laminates, to obtain various properties. For example, protein coatings, such as gelatin can be used to avoid non specific binding, simplify covalent conjugation, enhance signal detection or the like. If covalent bonding between a compound and die surface is desired, die surface will usually be polyfunctional or be capable of being poly functionalized. Functional groups which may be present on the surface and used for linking can include carboxylic acids, aldehydes, amino groups, cyano groups, etiiylenic groups, hydroxyl groups, mercapto groups and d e like. The manner of linking a wide variety of compounds to various surfaces is well known and is amply illustrated in die literature. See, for example, Immobilized Enzymes, Ichiro Chibata, Halsted Press, New York, 1978, and Cuatrecasas, J. Biol. Chem. 245 3059 (1970) which are incoφorated herein by reference. In addition to covalent bonding, various methods for noncovalently binding an assay component can be used. Noncovalent binding is typically nonspecific absoφtion of a compound to the surface. Typically, the surface is blocked witii a second compound to prevent nonspecific binding of labeled assay components. Alternatively, the surface is designed such diat it nonspecifically binds one component but does not significantly bind anodier. For example, a surface bearing a lectin such as Concanavalin A will bind a carbohydrate containing compound but not a labeled protein diat lacks glycosylation. Various solid surfaces for use in noncovalent attachment of assay components are reviewed in U.S. Patent Nos. 4,447,576 and 4,254,082. Infectivity Assays, Trans-complementation and Packaging Cells The vimses of tiiis invention can be used to determine whedier cells have been infected with a particular vims. In one embodiment of mis method, one group of cells in a sample to be tested is transduced with a nucleic acid constmct containing a packagable or "encapsulateable" HIV-2 nucleic acid of the invention (e.g., an HIV-2 KR subsequence with ris-active sequences necessary for packaging the HIV-2 KR nucleic acid into an HIV-2 viral capsid) which does not encode trans¬ active sequences necessary for packaging the nucleic acid (e.g., viral particle proteins). Anodier group of cells serves as a control. Both groups of cells are incubated under appropriate conditions and for a sufficient time for viral replication. After incubation, each group is examined for evidence of packaging of the nucleic acid constmct into viral particles. Evidence of packaging of the test nucleic acid in die test group but not in die control group, indicates diat cells in die test group are infected by a retrovims (e.g., HIV-2). Packaging Cells The present invention provides stable HIV-2 based packaging cells. Prior art packaging systems are derived from HIV-1 and all evince a variety of limitations. Several use wild-type replication competent vims as the source of packaging proteins, and some represent simple pseudotyping of an env gene-mutated full-length provims by VSV-G (t ' .e. , they have no packaging constmct, lines or vector lacking other structural genes). In general, two problems have been most prominent in mis field: (1) titers have been exceedingly low (lO'-lO 2 ) and (2) stable packaging lines have not been developed. The packaging cell lines of the invention are different in two major ways. First, they are based upon HIV-2, a vims less pathogenic than HIV-1. In addition to diis serious safety issue, e.g., for delivery of anti-HIV- 1 genes to treat HIV disease, an HIV- 1 -based system is self- inactivating in direct proportion to the efficacy of the antiviral gene canied by gene ti erapy vectors directed against HIV- 1. HIV-2 KR and conservative modifications diereof, are a prefened source of material for constmcting packaging cell lines of the invention. HIV-2 KR replicates to high titers in T cell lymphoblastoid lines, primary human macrophages and peripheral blood lymphocytes. HIV-2 KR infects non-human primates and induces cell-mediated immunity against disease causation by a more pathogenic HIV-2 strain (HIV-2 EHO) but has itself proven completely apathogenic as well as unrecoverable by culmre even years following intravenous challenge of rhesus macaques. Although HIV-2 KR is prefened, otiier HIV-2 isolates, and components thereof can also be used in d e packaging cells of die invention. Such clones are known to persons of skill, and publicly available. Well-established repositories of sequence information include GenBank, EMBL, DDBJ and die NCBI. The invention provides stable packaging cell lines in addition to a transient transfection system for HIV-2. Stable cell lines have been difficult to make for HIV because of die genetic complexity of die vimses and because of die toxicity of HIV proteins in many cell lines. The HIV-2 envelope can be used for CD4-specific targeting from these lines. For transient packaging, the VSV-G protein, recently shown to have numerous advantages for virion particle stability and extended host range can be used. The establishment of stable cell lines producing high titers of fully characterized transducing particles is a major step forward in die utilization of HIV-2 derived constmcts for gene therapy. Suitable cells for transduction by die packaging nucleic acids of d e invention to make packaging cells include established mammalian cell lines, and primary cells isolated from patients. Example cells include HeLa cells, Molt 4 clone 8 cells, Cos cells, CV-1 cells, 293 cells and Daudi cells. High Efficiency Packaging Nucleic Acids Trans active genes rendered inactive in a vaccine or gene therapy vector as described herein are also capable of trans-complementation in order to render die constmct rescuable. This form of transcomplementation is used in creating HIV packaging cell lines and in performing co-infection assays and diagnostic mediods. For instance, cells transduced witii HIV-2 proviral sequences which lack the nucleic acid packaging site located in and around die major splice donor site and the gag initiator codon adjacent to die 5' LTR produce HIV trans active components, but do not specifically incoφorate HIV-2 nucleic acids into die capsids produced, and therefore produce little or no live vims. As described in die Examples below, a 61 base-pair psi region deletion (from nt 1007-1067 of HIV- 2 KR ) from an infective HIV-2 proviral clone was sufficient to completely block packaging of nucleic acids with die deletion. However, as shown in die examples, the deletion clone (e.g., pEP40) produced high levels of HIV-2 trans active components sufficient to package HIV-2 packagable nucleic acids. pEP40 is an example of a high efficiency packaging vector which produces high levels of trans active components in packaging cells. The high efficiency packaging vector nucleic acids of the invention encode some or all of the proteins needed to produce an HIV-2 particle. Typically, packaging vector nucleic acids are derived from an HIV viral genome, or a portion diereof. Packaging vector nucleic acids lack die nucleic acids necessary for packaging of an RNA conesponding to the packaging vector nucleic acid into an HIV capsid. That is, packaging vector nucleic acids are not diemselves encapsulated in tiie HIV particles which they encode, i.e., the high efficiency packaging vector nucleic acids are not diemselves vimlent. Typically, nucleic acids conesponding to a substantial portion of the HIV-2 psi site are deleted or altered in die packaging vector relative to the wild-type HIV genomic RNA nucleic acid. cis- and trans- active sequences are optionally deleted from a high efficiency packaging vector relative to a full-lengtii HIV-2 genome to increase the safety of the vector. Where the sequences are required for HIV-2 packaging of an HIV-2 packagable nucleic acid or particle formation, the missing components are encoded by a second vector nucleic acid. For example, high efficiency packaging vectors optionally comprise deletion of an LTR (reducing die ability of die vims to integrate into a packaging cell chromosome) and/or a deletion in the env gene, with env components being supplied in trans from a second vector nucleic acid. See also, the Examples. The particles encoded by the high efficiency packaging vector nucleic acids of tiie invention typically package the high efficiency packaging vector nucleic acid at a level less than 10%, and more typically less than 1 %, of die level that they package a nucleic acid which has a wild-type HIV packaging site. The level of nucleic acid incoφoration is optionally measured by RT-PCR. An altemative indication that the high efficiency packaging vector is not packaged into HIV particles is to co-culture cells transduced by die vector with permissive cells such as Molt-4 clone 8 cells, and test for transmission to the permissive cells. If no transmission is observed, die packaging vector nucleic acid is not packaged at a significant level. As described in the examples below, a deletion in die psi region from an HIV-2 KR genomic clone eliminated packaging as tested by co¬ culture of transduced cells witii permissive cell types. Packagable Nucleic Acids If packaging cells transduced witii the high efficiency packaging nucleic acids of die invention are subsequently transduced witii a vector nucleic acid which lacks coding sequences for HIV trans active functions, but includes an HIV packaging signal, die vector nucleic acid is packaged into an HIV capsid and envelope, which is capable of transducing a target cell. Packagable nucleic acids encode an RNA which is competent to be packaged by an HIV particle. Such nucleic acids can be constmcted by recombinantly combining an HIV packaging site with a nucleic acid of choice. The packaging site (psi site) is located adjacent to the 5' LTR, primarily between the MSD site and the gag initiator codon (AUG) in d e leader sequence of the gag gene. Thus, die minimal packaging site includes a majority of nucleic acids between the MSD and die gag initiator codon from either HIV-1 or HIV-2. Preferably, a complete packaging site includes sequences from the 5' LTR and the 5' region of gag gene for maximal packaging efficiency. When an HIV-2 packaging site is used, die first ATG of gag to the MSD is optionally included as die HIV-2 packaging site. The first 30 nucleotides of gag are optionally included as part of die HIV-2 packaging site. In some embodiments, the first 50 nucleotides of gag are included as part of d e HIV-2 packaging site. Optionally, die first 75 nucleotides of gag are also included as part of the HIV-2 packaging site. The first 100 nucleotides of gag can be included as part of the HIV-2 packaging site. Other functions of HIV replication not supplied by trans- complementation which are necessary for replication of the vector are present in the packagable vector nucleic acid. This optionally includes, e.g. , die TAR sequence, die sequences necessary for HIV packaging, die RRE sequence if the instability elements of me pl7 gene of gag is included, and sequences encoding die polypurine tract. HIV sequences that contain tiiese functions include a portion of tiie 5' long terminal repeat (LTR) and sequences downstream of the 5' LTR responsible for efficient packaging. See, Garzino-Demo et al. (1995) Hum. Gene Ther. 6(2): 177-184. For a general description of the structural elements of the HIV genome, see, Holmes et al. PCT/EP92/02787. The pl7 gene contains INS (instability) elements mat cause rapid degradation of the LTR promoter-mediated transcript in the absence of the Rev-RRE interaction. Therefore, if the INS sequences are included in die vector, d e RRE is also typically included. However, if die HIV portion does not contain the INS sequence of pl7, then the RRE sequence is optionally omitted. RRE is normally located in die envelope gene of HIV and is die sequence to which die rev protein binds. The TAR sequence is located in the R portion of d e 5' LTR. It is the sequence to which the tat protein binds. The sequences for packaging optionally include sequences from the U5 portion of the 5' LTR, and downstream of it into part of pl7, as well as die U3R portion of the 3' LTR. The polypurine tract is the sequence upstream from the 3' LTR site where RNAse H cleaves during plus (" + ") strand DNA synthesis. It mediates plus strand syndiesis. The complete LTRs are optionally included to facilitate packaging of die packagable nucleic acid, and to permit chromosomal integration of a DNA conesponding to the packagable nucleic acid in a target cell. The target cell is any cell within the host range of HIV particle, or where the particle is pseudotyped, in die host range of the pseudotyped HIV particle. The primate lenti vimses, including HIV-1, HIV-2 and SIV are structurally and functionally similar. Cognate portions of any of these vimses can be used in the vectors of the present invention, or in trans-complementation assays in a manner similar to that described for HIV-2. Cellular Transduction and Gene Therapy The present invention provides several features that allow one of skill to generate powerful retroviral cell transduction vectors. These vectors comprise an HIV-2 packagable nucleic acid packaged in an HIV-2 particle, typically using a packaging cell line of die invention. Cell transduction vectors have considerable commercial utility as a method of introducing genes into target cells. In particular, gene tiierapy procedures, in which die cell transduction vectors of the invention are used to transduce target cells with a therapeutic nucleic acid in an in vivo or ex vivo procedure are used to combat chronic illnesses such as HIV. Gene tiierapy provides a method for combating chronic infectious diseases such as HIV, as well as non-infectious diseases such as cancer. Yu et al. (1994) Gene Therapy 1:13-26 and d e references tiierein provides a general guide to gene tiierapy strategies for HIV infection. See also, Sodoski et al. PCT/US91/04335. One general limitation of common gene therapy vectors such as murine retrovimses is that they only infect actively dividing cells, and they are generally non-specific. In contrast, non-dividing cells are infected by HIV vimses (including HIV-2 KR ), and vectors which utilize an HIV particle. HIV based vectors are primarily used to transduce CD4 + cells and hematopoietic stem cells. HIV vimses also infect a few other cell-types in vitro which exhibit little or no CD4 expression, such as peripheral blood dendritic cells, follicular dendritic cells, epidermal Langerhans cells, megakaryocytes, microglia, astrocytes, oligodendroglia, CD8 + cells, retinal cells, renal epitiielial cells; cervical cells, rectal mucosa, trophoblastic cells, and cardiac myocytes (see, Rosenburg and Fauci I, supra); die infection of tiiese cell types by HIV in vivo, however, is rare. Lists of CD4 + and CD4 " cell types which are infectable by HIV have been compiled (see, Rosenburg and Fauci 1 supra; Rosenburg and Fauci (1989) Adv Immunol 47:377-431; and Connor and Ho (1992) in -4ZDS: etiology, diagnosis, treatment, and prevention, third edition Hellman and Rosenburg (eds) Lippincott, Philadelphia). The present invention provides HIV-2 nucleic acids and polypeptides. These nucleic acids and capsids are useful as components of gene therapy vectors. Retroviral vectors packaged into HIV envelopes primarily infect CD4 + cells, (i.e. , by interaction between the HIV envelope glycoprotein and the CD4 "receptor") including non-dividing CD4 + cells such as macrophage. For instance, the capsid polypeptides of die present invention package gene therapy vectors which include HIV packaging sequences. Thus, in one prefened embodiment, the nucleic acids of the present invention are used in cell transduction or gene therapy vectors to package therapeutic nucleic acids into an HIV-2 particle for delivery to CD4 + cells. This is accomplished by incoφorating cis active nucleic acids from the nucleic acids of die present invention (e.g., promoter sequences, packaging sequences, integration or cellular targeting sequences) into the vector, or by using trans active nucleic acids and polypeptides (capsid and envelope proteins and transcription factors) to replicate and package die gene tiierapy vector into an HIV particle. The cis active sequences of the invention are optionally used with non-retroviral gene tiierapy vectors such as adeno associated vims vectors to provide, e.g., promoter, integration or cellular targeting sequences. HIV cell transduction vectors are particularly desirable because of their ability to be pseudotyped to infect non-dividing hematopoietic stem cells (CD34 + ). This is done by transducing die packaging cell line used to package the vector with a nucleic acid which encodes the vesicular stomatitis vims (VSV) envelope glycoprotein, which is then expressed on die surface of die HIV vector. VSV infects CD34 + cells, and pseudotype HIV-2 vectors expressing VSV envelope proteins are competent to transduce diese cells. CD34 + cells are important target cells for ex vivo gene therapy, because tiiese cells differentiate into many different cell types, and because the cells are capable of re-engraftment into a patient undergoing ex vivo therapy. Stem cells differentiate in vivo into a variety of immune cells, including CD4 + cells which are the primary targets for HIV infection. HIV-2 vectors are pseudotyped by transducing packaging cell lines used to package the vector with a nucleic acid which encodes d e vesicular stomatitis vims (VSV) envelope glycoprotein protein, which is expressed on die surface of the HIV particle. VSV infects both dividing and non-dividing CD34 + cells, and pseudotype vectors expressing VSV envelope proteins are competent to transduce these cells. See, Naldini et al. (1996) Science 272:263; and Akkina et al. (1996) J Virol 70:2581. One class of embodiments utilizes me LTR sequences described herein as a component of a gene tiierapy vector. The LTR sequences described herein are particularly useful because they have a high level of basal promoter activity in CD4 cells, and have no tαt or rev requirement. The LTR sequences, in addition to binding tαt and rev are responsive to cellular cytokines (such as IL-2 and SP-1) which act to permit transcription of the viral genome. Thus, in one embodiment, a therapeutic gene of choice is placed under d e control of an LTR promoter of the present invention. See, e.g., Poznansky et al. (1991) Journal or Virology 65(1): 532-536 for a description of the region flanking the 5' LTR's ability to package vector nucleic acids. In one prefened embodiment, the HIV-2 provimses of the present invention are used to make retroviral vectors for gene tiierapy. Copending applications SN 08/245,742 (Wong-Staal et al., see also PCT application PCT/US94/05700 (WO 94/26877) and Chatterjee et al. (Science (1992), 258: 1485-1488, hereinafter Chatterjee et al. I) describe anti-sense inhibition of HIV-1 infectivity in target cells using viral vectors with a constitutive expression cassette expressing anti-TAR RNA. Chatterjee et al. (PCT application PCT/US91/03440 (1991), hereinafter Chatterjee et al. 2) describe viral vectors, including AAV-based vectors which express antisense TAR sequences. Chatterjee and Wong (Methods, A companion to Methods in Enzymology (1993), 5: 51- 59) further describe viral vectors for the delivery of antisense RNA. For a general review of gene therapy procedures, see Anderson, Science (1992) 256:808-813; Nabel and Feigner (1993) TIBTECH 11: 211-217; Mitani and Caskey (1993) TIBTECH 11 : 162-166; Mulligan (1993) Science 926-932; Dillon (1993) TIBTECH 11: 167-175; Miller (1992) Nature 357: 455-460; Van Brunt (1988) Biotechnology 6(10): 1149-1154; Vigne (1995) Restorative Neurology and Neuroscience 8: 35-36; Kremer and Penicaudet (1995) British Medical Bulletin 51(1) 31-44; Haddada et al. (1995) in Current Topics in Microbiology and Immunology Doerfler and Bδhm (eds) Springer-Verlag, Heidelberg Germany; and Yu et al. (1994) Gene Therapy 1 : 13- 26, and die references cited therein. Copending application SN 08/442,061, filed May 16, 1995 and PCT publication WO 94/26877 (PCT/US94/05700) describe a variety of anti-HIV therapy genes, and gene tiierapy strategies generally, including die use of suicide genes, trans-dominant genes, ribozymes, anti-sense genes, and decoy genes in gene tiierapy vectors. Ex Vivo Therapy Ex vivo methods for inhibiting viral replication in a cell in an organism involve transducing die cell ex vivo with a vector of this invention, and introducing the cell into tiie organism. The cells are CD4 + cells such as CD4 + T cells or macrophage isolated or culmred from a patient, or are CD34 + hematopoietic stem cells. T cells are used in some embodiments in ex vivo procedures. Several techniques are known for isolating T cells. One procedure for isolating T cells is described in Leavitt et al. Hum. Gene Ther. (1994) 5: 1115-1120. Wong- Staal et al. WO 94/26877 also describes methods of isolating and transducing T cells. HIV inhibitors are typically added to culmres of T-cells to inhibit HIV growth when the T cells are isolated from potentially HIV-positive sources. For example, delaviridine can be added to culmres of T cells to inhibit HIV growth. The expression of surface markers facilitates identification and purification of T cells. Methods of identification and isolation of T cells include FACS, incubation in flasks with fixed antibodies which bind d e particular cell type and panning with magnetic beads. In one embodiment, CD34 + stem cells are used in ex-vivo procedures for cell transduction and gene tiierapy. The advantage to using stem cells is that they can be differentiated into otiier cell types in vitro, or can be introduced into a mammal (such as the donor of die cells) where they will engraft in the bone manow. Methods for differentiating CD34 + cells in vitro into clinically important immune cell types using cytokines such a GM-CSF, IFN-γ and TNF-α are known (see, Inaba et al. (1992) J. Exp. Med. 176, 1693-1702, and Szabolcs et al. (1995) 154: 5851-5861). Methods of pseudotyping HIV-based vectors so diat they can transduce stem cells are described above. Stem cells are isolated for transduction and differentiation using known methods. For example, in mice, bone manow cells are isolated by sacrificing the mouse and cutting die leg bones with a pair of scissors. Stem cells are isolated from bone manow cells by panning the bone manow cells with antibodies which bind unwanted cells, such as CD4 + and CD8 + (T cells), CD45 + (panB cells), GR-1 (granulocytes), and Ia d (differentiated antigen presenting cells). For an example of this protocol see, Inaba et al. (1992) J. Exp. Med. 176, 1693- 1702. In humans, CD34 + hematopoietic stem cells can be obtained from a variety of sources including cord blood, bone manow, and mobilized peripheral blood. Purification of CD34 + cells can be accomplished by antibody affinity procedures. An affinity column isolation procedure for isolating CD34 + cells is described by Ho et al. (1995) Stem Cells 13 (suppl. 3): 100-105. See also, Brenner (1993) Journal of Hematotherapy 2: 7-17. Yu et al. (1995) N S 92: 699-703 describe a method of transducing CD34 + cells from human fetal cord blood using retroviral vectors. Freshney et al. , supra and the references cited therein provide a general discussion of how to isolate and culmre cells from patients. Altematively, the cells used for ex vivo procedures can be those stored in a cell bank (e.g., a blood bank). In one class of prefened embodiments, the gene therapy vector utilizes an anti-viral therapeutic agent (e.g., suicide gene, trans-dominant gene, anti-HIV ribozyme, anti-sense gene, or decoy gene) which inhibits die growth or replication of an HIV vims, under die control of an activated HIV-2 LTR of the invention (e.g., an LTR such as the HIV-2 KR LTR which has high basal activity). The gene therapy vector inhibits viral replication in any of those cells already infected with HIV vims, in addition to confening a protective effect to cells which are not infected by HIV. In addition, in prefened embodiments, the vector is replicated and packaged into HIV capsids using die HIV replication machinery, thereby causing the anti-HIV therapeutic gene to propagate in conjunction with the replication of an HIV vims. Thus, an organism infected with HIV can be treated for the infection by transducing a population of its cells with a vector of the invention and introducing die transduced cells back into die organism as described herein. Thus, die present invention provides a method of protecting cells in vitro, ex vivo or in vivo, even when die cells are already infected witii the vims against which protection is sought. Vaccines and Immunogenic Compositions A variety of vaccine constmcts confening resistance by an organism to HIV-1 and pathogenic forms of HIV-2 are provided by die present invention. In one embodiment, die HIV-2 RR clone herein is packaged into an HIV-2 particle (capsid/envelope) and used to infect an organism. As described in d e examples below, this strategy confened resistance in live M. nemistrina to highly pathogenic strains of HIV-2. Moreover, resistance to HIV-1 is confened upon infection of humans with HIV-2 (see, Travers et al. (1995) Science 268: 1612-1615 and related commentary by Cohen et al (1995) Science 268: 1566). Thus, die present invention provides a provims which confers resistance to HIV-1 and HIV-2 when administered as a vaccine. Furthermore, HIV particles which lack nucleic acids, e.g., produced using a high efficiency packaging vector and a packaging cell, can be used as immunogenic compositions and vaccines. In addition to full length clones, deletion mutants of the full-length constmcts provided herein produce attenuated forms of HIV-2 which are less pathogenic than the full-length constmcts. For instance, Looney and Wong-Staal 51 (PCT/US93/ 12088) describe multiple gene mutants of HIV and provide strategies for attenuating HIV clones. These strategies can be applied to die clones of d e present invention to produce attenuated forms of HIV-2, including attenuated forms of HIV-2 KR . In addition to HIV-based vaccines, die present invention provides a variety of vaccines which incoφorate an immunogenic fragment of an HIV polypeptide into a vaccine vector. Many vaccine vectors are known in the art. For instance, HIV sequences of the invention can be used to modify vimses that transfect host cells in the patient. Live attenuated vimses, such as vaccinia or adenovims, are convenient altematives for vaccines because they are inexpensive to produce and are easily transported and administered. Vaccinia vaccine vectors and methods useful in immunization protocols are described, for example, in U.S. Patent No. 4,722,848. Suitable vimses for use in the present invention include, but are not limited to, pox vimses, such as canarypox and cowpox vimses, and vaccinia vimses, alpha vimses, adenovimses, adeno associated vimses and otiier animal vimses. The recombinant vimses can be produced by methods well known in die art, for example, using homologous recombination or ligating two plasmids to form a vaccine provims. A recombinant canarypox or cowpox vims can be made, for example, by inserting the nucleic acids encoding HIV env polypeptides into plasmids so that diey are flanked by vaccine viral vector sequences. The nucleic acids encoding d e HIV env are tiien inserted into the vims genome through homologous recombination or by using standard cloning techmques. A recombinant adenovims can be produced, for example, by ligating together two plasmids each containing about 50% of the adeno vims viral sequence and the a DNA sequence encoding env. Recombinant RNA vimses such as die alpha vims can be made via a cDNA intermediate using cloning methods known in the art. In the case of vaccinia vims (for example, strain WR), ti e nucleic acid sequence encoding an HIV polypeptide can be inserted in die genome by a number of methods including homologous recombination using a transfer vector, e.g., pTKgpt-OFIS as described in Kaslow et al. (1991) Science 252:1310-1313. Alternately the nucleic acid encoding an HIV polypeptide can be inserted into anomer plasmid designed for producing recombinant vaccinia, such as pGS62, Langford et al. (1986) Mol. Cell. Biol. 6:3191-3199. This plasmid consists of a cloning site for insertion of foreign genes, the P7.5 promoter of vaccinia to direct syndiesis of die inserted gene, and die vaccinia TK gene flanking bom ends of the foreign gene. Confirmation of production of recombinant vims can be achieved by DNA hybridization using cDNA encoding the polypeptide, by PCR (or other in vitro technique as described above), and by immunodetection techniques using antibodies specific for d e expressed polypeptide. Vims stocks are prepared, e.g., by infection of cells such as HELA S3 spinner cells and harvesting of vims progeny. A recombinant vaccine vims of me present invention can be used to induce antibodies to HIV polypeptides in mammals, such as mice, rabbits or humans, useful in a variety of in vitro assays as described above. In addition, a recombinant vims can be used to produce die polypeptide by infecting host cells in vitro, which in mm express the polypeptide (see, above). The present invention also provides a variety of immunogenic compositions, including intact vimses, polypeptides, viral capsids, viral envelopes, viral particles and nucleic acids, all of which are encoded by d e provimses of die invention. For instance, die present invention describes the provims HIV-2 KR , which is optionally encapsidated in a viral capsid and/or a viral envelope. HIV-2 KR also encodes peptides and nucleic acids which are diemselves immunogenic. These immunogenic peptides and nucleic acids are optionally incoφorated into immunogenic vectors as described above, or are optionally used as immunogenic or immunodetective reagents. Any of these compositions encoded by die provims HIV-2 KR can be admimstered, preferably with an immunogenic adjuvant to raise antibodies and antisera in mice, rabbits, humans, macaques and otiier mammals. Many methods for d e generation of antibodies and antisera are known. See, Coligan, Harlow and Lane, Stites et al. , Goding, Kohler and Milstein, Huse et al. and Ward (all supra). These antibodies are useful as diagnostic reagents to detect HIV in biological samples. In Vivo Therapy and Vaccination Gene therapy vectors containing nucleic acid or polypeptide sequences of die invention can be administered directly to die organism for transduction of cells in vivo. In addition, die vimses of the present invention, or immunogenic or recombinant forms thereof can also be administered directly to an organism to confer resistance to HIV infection. As discussed herein, HIV-2 infection dramatically reduces die infection rate of an organism by HIV-1. As discussed in the examples herein, infection of an organism with the non-pathogenic HIV strains provided in this invention prevent infection of die organism by pathogenic strains of HIV. Examples of retroviral packaging cells, HIV-2 packagable nucleic acids and packaging systems for making pseudotype vectors are provided. Administration of gene tiierapy vectors, cells transduced ex vivo, and HIV vaccines can be by any of die routes normally used for introducing a cell or molecule into ultimate contact with blood or tissue cells. As described herein, prefened vectors and vaccines utilize HIV viral particles, but other anangements are also feasible, such as adeno-associated capsids (see, SN 08/442,061), polypeptides, and any of the numerous vaccine vectors known in the art (see, supra). Gene therapy vectors and vaccines of die present invention can be used to treat and prevent virally-mediated diseases such as AIDS in patients. The vectors, transduced cells, or vaccines are administered in any suitable manner, preferably with pharmaceutically acceptable caniers. Suitable methods of administering such vectors and vaccines in die context of die present invention to a patient are available, and, although more than one route can be used to administer a particular composition, a particular route can often provide a more immediate and more effective reaction than another route. Pharmaceutically acceptable caniers are determined in part by d e particular composition being administered, as well as by die particular method used to administer the composition. Accordingly, diere is a wide variety of suitable formulations of pharmaceutical compositions of the present invention. Formulations suitable for oral administration can consist of (a) liquid solutions, such as an effective amount of the vector dissolved in diluents, such as water, saline or PEG 400; (b) capsules, sachets or tablets, each containing a predetermined amount of me active ingredient, as liquids, solids, granules or gelatin; (c) suspensions in an appropriate liquid; and (d) suitable emulsions. Tablet forms can include one or more of lactose, sucrose, mannitol, sorbitol, calcium phosphates, com starch, potato starch, tragacantii, microcrystalline cellulose, acacia, gelatin, colloidal silicon dioxide, croscarmellose sodium, talc, magnesium stearate, stearic acid, and other excipients, colorants, fillers, binders, diluents, buffering agents, moistening agents, preservatives, flavoring agents, dyes, disintegrating agents, and pharmaceutically compatible caniers. Lozenge forms can comprise the active ingredient in a flavor, usually sucrose and acacia or tragacanth, as well as pastilles comprising the active ingredient in an inert base, such as gelatin and glycerin or sucrose and acacia emulsions, gels, and the like containing, in addition to the active ingredient, caniers known in the art. The vectors and vaccines, alone or in combination with other suitable components, can be made into aerosol formulations to be administered via inhalation. Aerosol formulations can be placed into pressurized acceptable propellants, such as dichlorodifluoromethane, propane, nitrogen, and die like. Suitable formulations for rectal administration include, for example, suppositories, which consist of the vector with a suppository base. Suitable suppository bases include namral or syntiietic triglycerides or paraffin hydrocarbons. In addition, it is also possible to use gelatin rectal capsules which consist of a combination of the vector with a base, including, for example, liquid triglyercides, polyethylene glycols, and paraffin hydrocarbons. Formulations suitable for parenteral administration, such as, for example, by intraarticular (in die joints), intravenous, intramuscular, intradermal, intraperitoneal, and subcutaneous routes, include aqueous and non-aqueous, isotonic sterile injection solutions, which can contain antioxidants, buffers, bacteriostats, and solutes tiiat render d e formulation isotonic with the blood of die intended recipient, and aqueous and non-aqueous sterile suspensions that can include suspending agents, solubilizers, thickening agents, stabilizers, and preservatives. Parenteral administration the prefened method of administration. The formulations of vector can be presented in unit-dose or multi-dose sealed containers, such as ampules and vials, and in some embodiments, can be stored in a freeze-dried (lyophilized) condition requiring only the addition of the sterile liquid canier, for example, water, for injections, immediately prior to use. For many vectors, this mode of administration will not be appropriate, because many virions are destroyed by lyophilization. Otiier vectors (e.g., vectors utilizing an AAV capsid) tolerate lyophilization well. Extemporaneous injection solutions and suspensions can be prepared from sterile powders, granules, and tablets of the kind previously described. Cells transduced by die vector as described above in die context of ex vivo therapy can also be administered parenterally as described above, except tiiat lyophilization is not generally appropriate, since cells are destroyed by lyophilization. The dose administered to a patient, in die context of die present invention should be sufficient to effect a beneficial therapeutic response in the patient over time, or to inhibit infection by a pathogenic strain of HIV. The dose will be determined by die efficacy of die particular vector employed and the condition of the patient, as well as die body weight or surface area of the patient to be treated. The size of die dose also will be determined by d e existence, namre, and extent of any adverse side-effects tiiat accompany the administration of a particular vector, vaccine, or transduced cell type in a particular patient. In determining the effective amount of me vector to be administered in d e treatment or prophylaxis of virally-mediated diseases such as AIDS, the physician needs to evaluate circulating plasma levels, vector toxicities, progression of die disease, and, in the case of vaccine compositions, the production of anti-HIV antibodies. In general, the dose of a naked nucleic acid composition such as a DNA vaccine or gene therapy vector is from about 1 μg to 100 μg for a typical 70 kilogram patient. In ex vivo procedures, prior to infusion of transduced cells, blood samples are obtained and saved for analysis. Between 1 X IO 6 and 1 X 10 10 transduced cells are typically infused intravenously over 60- 200 minutes. Vital signs and oxygen saturation by pulse oximetry are closely monitored. Leukopheresis, transduction and reinfusion may be repeated every 2 to 3 months for a total of 4 to 6 treatments in a one year period. After d e first treatment, infusions can be performed on a outpatient basis at die discretion of die clinician. If die reinfusion is given as an outpatient, the participant is generally monitored for 4 to 8 hours or more following the therapy. Transduced cells are prepared for reinfusion according to established methods. See, Abrahamsen et al. (1991) J. Clin. Apheresis 6:48-53; Carter et al. (1988) J. Clin. Apheresis 4: 113-117; Aebersold et al. (1988), J. Immunol. Methods 112: 1-7; Muul et al. (1987) J. Immunol. Methods 101: 171-181 and Carter et al. (1987) Transfusion 27:362-365. After a period of about 2-4 weeks in culmre, die cells may number between 1 X 10° and 1 X 10 10 . In this regard, the growth characteristics of cells vary from patient to patient and from cell type to cell type. About 72 hours prior to reinfusion of the transduced cells, an aliquot is taken for analysis of phenotype, and percentage of cells expressing the therapeutic agent. If a patient undergoing infusion of a vector or transduced cell develops fevers, chills, or muscle aches, he/she receives the appropriate dose of aspirin, ibuprofen or acetaminophen. Patients who experience reactions to tiie infusion such as fever, muscle aches, and chills are premedicated 30 minutes prior to die future infusions with either aspirin, acetaminophen, or diphenhydramine. Meperidine is used for more severe chills and muscle aches tiiat do not quickly respond to antipyretics and antihistamines. Cell infusion is slowed or discontinued depending upon die severity of the reaction. In the practice of this invention, compositions can be administered, for example, by intravenous infusion, orally, topically, intraperitoneally, intravesically or intrathecally. The prefened method of administration will often be oral, rectal or intravenous, but the vectors can be applied in a suitable vehicle for the local and topical treatment of virally-mediated conditions. The vectors of this invention can supplement treatment of virally-mediated conditions by any known conventional therapy, including cytotoxic agents, nucleotide analogues and biologic response modifiers. For administration, vectors, vaccines and transduced cell types of the present invention can be administered at a rate determined by die LD-50 of d e vector, vaccine, or transduced cell type, and die side-effects of d e vector or cell type at various concentrations, as applied to die mass and overall healdi of the patient. Administration can be accomplished via single or divided doses. . Anti-viral Agents The gene therapy vectors of this invention typically include at least one "anti-viral agent" or "viral inhibitor" operably linked to an expression control sequence (such as an LTR of die invention). As used herein the terms "anti-viral agent" and "viral inhibitor" refer to any nucleic acid whose product, upon transcription or translation, inhibits die replication of a specified vims. Anti-viral agents are known in the art. The literamre describes such genes and dieir use. See, for example, Yu et ai , (1994) Gene Therapy, 1: 13; Herskowitz (1987) Nature, 329:212 and Baltimore (1988) Nature, 335:395. Anti-viral agents useful in this invention include, widiout limitation, anti-sense genes, ribozymes, decoy genes, transdominant genes/proteins and suicide genes. (i) Antisense genes An antisense nucleic acid is a nucleic acid tiiat, upon expression, hybridizes to a particular mRNA molecule, to a transcriptional promoter or to the sense strand of a gene. By hybridizing, die antisense nucleic acid interferes with the transcription of a complementary nucleic acid, d e translation of an mRNA, or the function of a catalytic RNA. Antisense molecules useful in tiiis invention include tiiose that hybridize to HIV genes and gene transcripts. Two target sequences for antisense molecules are me first and second exons of die HIV genes tat and rev. Chatterjee and Wong, supra, and Marcus-Sekura (Analytical Biochemistry (1988) 172, 289-285) describe d e use of anti-sense genes to block or modify gene expression. (ii). Ribozymes A ribozyme is a catalytic RNA molecule that cleaves other RNA molecules having particular nucleic acid sequences. Ribozymes useful in diis invention are those that cleave HIV gene transcripts. Ojwang et al. (1992) Proc. Nat'l. Acad. Sci., U.S.A. 89: 10802-10806 provide an example of an HIV-1 pol-specific haiφin ribozyme. Wong-Staal et al. PCT/US94/05700 (WO 94/26877) provide examples of haiφin and hammerhead ribozymes (e.g. , those which cut at me sequence GUX). A hammerhead ribozyme directed against d e sequence 5' - CAGGAAGTCA GCCTAAGA - 3' (SEQ ID NO:27) in the first exon of tαr has the sequence: 5' - UCUUAGGCU [CUGAUGAGUC CGUGAGGACG AA] GACUUCCUG - 3' (SEQ ID NO:28). (iii). Decoy Nucleic Acids A decoy nucleic acid is a nucleic acid having a sequence recognized by a regulatory nucleic acid binding protein (i.e., a transcription factor). Upon expression, the transcription factor binds to die decoy nucleic acid, ratiier than to its namral target in the genome. Useful decoy nucleic acid sequences include any sequence to which a viral transcription factor binds. For instance, the TAR sequence, to which the tat protein binds, and HIV RRE sequence, to which the rev proteins binds are suitable sequences to use as decoy nucleic acids. Thus, most gene tiierapy vectors containing the HIV LTRs of the present invention serve as decoy nucleic acids. (iv). Transdominant Proteins A transdominant protein is a protein whose phenotype, when supplied by transcomplementation, will overcome the effect of the native form of the protein. For example, tat and rev can be mutated to retain the ability to bind to TAR and RRE, respectively, but to lack the proper regulatory function of those proteins. In particular, rev can be made transdominant by eliminating the leucine- rich domain close to the C terminus which is essential for proper normal regulation of transcription. Tat transdominant proteins can be generated by mutations in die RNA binding/nuclear localization domain. (v). Suicide Genes A suicide gene produces a product which is cytotoxic. In die gene tiierapy vectors of the present invention, a suicide gene is operably linked to an expression control sequence in die vector which is stimulated upon infection by HIV (e.g., an LTR which requires tat for activation in a vector which does not encode tat). Upon infection of the cell by competent vims, the suicide gene product is produced, tiiereby killing the cell and blocking replication of the vims. Examples of antisense molecules, ribozymes and decoy nucleic acids and dieir use can be found in Weintraub (Jan. 1990) S . Am. 262:40-46; Marcus-Sekura (1988) Anal. Biochem. 172:289-95; and Hasselhoff et al. (1988) Nature 334:585-591. Discussion of the Accompanying Sequence Listing SEQ ID NO: 1 provides d e complete sequence of die HIV-2 provims HIV-2 KR . The information is presented as a DNA sequence (i.e., the sequence of die HIV-2 KR provims as it appears, e.g., cloned in a bacterial plasmid). One of skill will readily understand diat die sequence also describes die full-length genomic RNA of HIV-2 KR (i.e., by substimtion of the T residues witii U residues) and a variety of conservatively modified variations of die sequence provided. SEQ ID NO: 10 and SEQ ID NO: 11 provide subsequences of the full-length HIV-2 KR sequence comprising the nucleic acid sequences encoding the HIV genes nef, and vif, respectively. SEQ ID NO: 12 provides the sequence of the 5' HIV-2 KR LTR. SEQ ID NOs: 13-15 provide subsequences of die full-lengtii HIV-2 KR sequence comprising the nucleic acid sequences encoding die HIV genes env, pol, and rev. SEQ ID NO: 16 provides d e HIV revl subsequence. One of skill will readily understand tiiat each of the subsequences of the HIV-2 KR sequence also describe die full-length genomic RNA of HIV-2 KR (t ' .e., by substimtion of the T residues with U residues) and a variety of conservatively modified variations of the sequences provided. SEQ ID NO: 2 provides ti e amino acid sequence of d e env protein encoded by HIV-2 KR . SEQ ID NO: 3 provides the amino acid sequence of the gag protein encoded by HIV-2 KR . SEQ ID NO:4 provides die amino acid sequence of die nef protein encoded by HIV-2 KR . SEQ ID NO: 5 provides die amino acid sequence of die pol protein encoded by HIV-2 KR . SEQ ID NO:6 provides die amino acid sequence of die rev protein encoded by HIV-2 KR . SEQ ID NO: 7 provides the amino acid sequence of die tαt protein encoded by HIV-2 KR . SEQ ID NO: 8 provides d e amino acid sequence of die vif protein encoded by HIV-2 KR . SEQ ID NO: 9 provides die amino acid sequence of die vpr protein encoded by HIV-2 KR . A variety of conservatively modified variations of the amino acid sequences provided will be apparent to one of skill, and one of skill will recognize that a variety of nucleic acid sequences encode each of the polypeptides due to the codon degeneracy present in the genetic code. SEQ ID NOs: 17-26 describe exemplar oligonucleotides derived from die HIV-2 provimses of the invention. EXAMPLES The following examples are provided by way of illustration only and not by way of limitation. Those of skill will readily recognize a variety of noncritical parameters which can be changed or modified to yield essentially similar results. Example 1: Isolation and Characterization of HIV-2 KR A lambda-phage clone containing a full-length HIV-2 provims, designated HIV^ KR , was obtained from the genomic DNA of Molt 4 Clone 8 (Molt-4/8) lymphoblastic cells infected widi die HIV-2 PEI2 strain, isolated from the peripheral blood mononuclear cells of a single HIV-2 seropositive AIDS patient. HIV-2 KR is distinct from all known HIV-2 isolates, possessing, inter alia, both a unique deletion in the LTR promoter region, and a long rev reading frame uncommon among HIV-2 sequences. HIV-2 KR is replication competent in vitro, producing p26 protein and infectious progeny virions after direct transfection into Molt-4/8 cells, and in vivo in Macaques. Like the parental HIV-2 PEI2 isolate, HIV- 2 KR replicated in a variety of established human T-cell (Molt-4/8, SupTl, H9, C8166) and myelomonocytic (U937) cell lines, and displayed cytopathic effects upon infection of Molt-4/8 cells. In addition, HIV-2 KR was found to be infectious for primary human and macaque lymphocytes, and primary human monocyte- macrophage culmres. Intravenous inoculation of cell-free HIV-2 KR into Macaca nemestrina resulted in persistent low-level infection, with transient viremia and a transient decline in CD4 lymphocyte numbers. HIV-2 KR also provided protection against more pathogenic strains of HIV-2 in M. nemestrina. Growing Plasmid D53 Deposited with the ATCC The HIV-2 KR genome was deposited witii the ATCC on July 26, 1995. The form of the deposit is as a plasmid (D53) which contains die complete HIV-2 KR genome, as well as an ampicillin selectable marker gene. An aliquot of the plasmid can be obtained from the ATCC. The plasmid can be transformed into DH5α E. Coli and plated onto LB-Amp agar plates. Colonies are then picked and grown in standard LB-amp media at 37 °C through late log phase growth (.6 to .7 OD at 600 mn ), harvested, and d e plasmid DNA is purified. The plasmid is verified, e.g. , by restriction analysis (See, Figure 5 for a restriction map of the D53 plasmid, see also, SΕQ ID NO: l for d e sequence of die HIV-2 KR proviral portion of the plasmid) . See, Sambrook for a description of experimental protocols suitable for growing and harvesting cells, plasmid DNA purification, and restriction analysis. Materials and Methods The following materials and mediods were used in Example 1. Molecular cloning of proviral HIV-2 DNA. Genomic DNA was extracted from Molt-4/8 cells from a patient chronically infected with HIV-2 PEI2 (see, Kirchhoff, et al. (1990) Aids 4, 847-57 for a general description of the method). After partial digestion witii Sau3A, 9-20 kb fragments were ligated to EMBL-4 arms. The ligated DNA was packaged into phage using Stratagene Gigapack™ Gold extract. The genomic library was screened by using a pol probe derived from HIV-2 ISY . One hybridization positive λ-phage clone was found to contain a complete provims (designated HIV-2 KR ). The insert DNA was subcloned into two plasmids. Plasmid pRTsac, containing the 3' portion of die provims, was created by cloning a Sac I fragment extending from a site in HIV-2 KR tat to a site in the 3' cellular flank into the Sac I site of pUC19c. Plasmid pKTM, containing tiie 5' portion of the provims, was created by first cloning a proviral EcoRI - Sacl fragment into pSVL opened witii EcoRI and Sacl, and dien cloning a EcoRI fragment containing a fragment extending from the 5' cellular flank to die proviral EcoRI site into die EcoRI site of the first plasmid (only the conect orientation was observed after ligation). The viral sequence was obtained by dideoxynucleotide chain termination double-strand sequencing (BioRad DNA sequencing kit). Sequences were read and entered manually. Sequence data was analyzed using hierarchical multiple sequence alignment and FASTA similarity comparisons (Coφet, et al. (1988) Nucleic Acids Research 16, 10881-90; Huang, et al. (1992) Computer Applications in the Biosciences 8, 155-65; Pearson, et al. (1994) Methods in Molecular Biology 24, 307-31). HIV-2 and HIV-1 LTR Reporter Plasmids. Plasmid pC15CAT (Arya, et al. (1985) Science 229, 69-73) contains a Hind III fragment of the HIV-1 IIIB LTR driving the bacterial chloramphenicol acetyl transferase (CAT) gene. Plasmid HIV2CAT (Kumar, et al. (1990) Journal of Virology 64, 890-901) contains the U3 and R portions of the HIV-2 ST LTR upstream of the CAT. Reporter constmct pCV- KRLTR was created by cloning an 840 bp PCR amplified fragment (including d e complete U3 & R regions and all but 104 bp of die U5 region of die HIV-2 KR LTR, sequences -534 to +288 from the transcription start site) of the HIV-2 RR LTR into the Hind III site of pCV-LTR-basic (Promega). Primers used were (Left) 5'-gca-agc-ttg-gga-tgg-gat-gta-tta-cag-3' (SEQ ID NO: 17) and (Right) 5'-cca- agc-ttc-tgc-tag-gta-ttt-tcc-cgc-t-3' (SEQ ID NO: 18). Choramphenicol Acetyl Transferase - ss--y. This assay was performed according to standard techniques (Arya, et al. (1985) Science 229, 69-73). Briefly, 48 hours after cationic lipid (DoTap™, Boehringer Mannheim) transfection of 1.5 x 10° cells with 5 mg of reporter plasmid, cells were washed tiiree times in phosphate buffered saline, pelleted at 4°C, resuspended in 150 ml 0.25M Tris pH 7.8, subjected to three cycles of freeze thawing in dry ice - ethanol bath and vortexed for 30 seconds. The extract was cleared of. debris by low speed centrifugation (15 minutes, 12000 RPM, 4°C). For EIA determination of CAT activity, 75 ml of extract was serially diluted and tested according to the manufacmrers directions (Promega). To determine the effect of various stimuli on promoter activity, cells were treated immediately after transfection with GM-CSF (8 ng/ml, Genzyme) and LPS (10 ng/ml Salmonella typhimurium lipopolysaccharide, Sigma), PHA-P and PMA (2 mg/ml and 10 "8 M respectively). Virus Propagation In Human Primary Cells And Permanent Cell Lines. Human T- lymphocytic cell lines were propagated in RPMI 1640 supplemented witii 10% fetal calf semm (FCS), 200 mM L-glutamine, and penicillin/ streptomycin. Human peripheral blood lymphocytes (PBMCs) and human monocyte macrophages were isolated from healthy donors as previously described (Fisher, et al. (1988) Nature 334, 444-447). The PBMCs were stimulated with 2.5 μg of phytohemagglutamin per ml in RPMI 1640 supplemented with 10% FCS three days before infection. Monocytes were prepared from heparinized peripheral blood by Ficoll-Hypaque separation, low-speed centrifugation through heat- inactivated FCS, and separation of adherent cells in fibronectin coated (2 mg/ml) 162 cm 2 flasks for one hour. Adherent cells were detached at 4°C using calcium-free phosphate-buffered saline witii ImM EDTA, and replated at a density of 10° cells/cm 2 in 24-well tissue culmre plates coated with autologous semm in medium containing 10% FCS, 10% autologous semm, 10% endodielial cell conditioned medium. DNA Transfection In Permanent T Cells Lines. Molt4/8 cells (3 x 10°) were used for transfections. Phage DNA or ligated KTM-RTsac proviral DNA (1-2 μg viral DNA) was transfected into using cationic lipid transfection (DOTAP™). The cells were culmred in 10 ml RPMI 1640 medium. Every two days 50% of die medium was replaced. Viral production was monitored by testing for p26 in the cell supematant (Coulter™ SIV EIA). Immunoprecipitation Of Viral Proteins. HIV-2 KR infected cells were starved in methionine and cysteine free medium. After one hour die cells were incubated in medium supplemented with 200 mCi/ml each 35 S-Methionine and 35 S-Cysteine for six hours. The cells were washed tiiree times in PBS and lysed in RIPA buffer (5 mM Tris-HCl/50 mM NaCl/0.1 % SDS/1 % TritonX- 100/1 % deoxycholic acid/1 mM pheny Imethylsulfonyl fluoride). The cell lysate was centrifuged at 12000 x g, 4°C, for 30 min. and d e supematant was transfened to a new mbe. Aliquots of the supematant were incubated witii sera from HIV-1 and HIV-2 infected patients and die immune complexes were isolated witii S. aureus protein A bound to Sepharose. After incubation, the samples were washed five times with RIPA- buffer and electrophoresed on a 11.5% SDS/polyacrylamide gel. The gel was dried and immunoprecipitated bands visualized using autoradiography. Western Blotting. Supematant from Molt 4/Clone 8 cells infected witii HIV-2KR was cleared by low-speed centrifugation (2000 x g for 20 minutes) and vims pelleted at 100,000 x g for one hour at 4°C (45Ti rotor). The pellet was resuspended in Hank's balanced salt solution and centrifuged over a discontinuous RNAase free sucrose gradient (20% -40% w/v) at 100,000 x g for one hour (50Ti rotor). The inteφhase was collected, resuspended in sample buffer (5x sample buffer: 325 mM Tris, 10% SDS, 50% glycerol, 0.05% bromphenol blue, 20% β- mercaptoethanol) and samples mn on a 10.5% polyacrylamide gel. After electrophoretic transfer to nitrocellulose, strips were blocked witii 0.65% Tween 20, and incubated overnight with pooled HIV-1 (9 donors) or HIV-2 (courtesy P. Kanki) seropositive sera at a 1: 100 dilution. Strips were tiien incubated with goat antihuman horseradish peroxidase conjugate and blots developed widi diaminobenzidine . Viral Quantitation and Infection of M. nemestrina. Infectious vims supematant was harvested from transfected Molt-4/8 cells, cleared by low speed centrifugation, aliquoted, and stored in liquid nitrogen. Concentrated viral stocks were made by ultracentrifugation of cleared vims supematant (200x). Viral pools were titered on HeLa CD4 (HT4-6C), Molt 4/Clone 8 cells, and human and M. nemestrina PBMC. Coulter™ SIV p26 EIA kits were used to quantitate viral antigen in infection experiments. Juvenile M. nemestrina were infected witii 1000 HT4-6C syncytia forming units (SFU) by intravenous injection, unless otiierwise stated. Polymerase Chain Reaction. Integrated provims was detected in DNA extracted from the PBMC of infected M. nemestrina using nested PCR. Amplification was canied out for 35 cycles (30" at 94°C, 60" at 55°C, 60" at 74°C) for each primer- pair. Primer pairs used for HIV-2 env were GR72 (outside, left) 5'-ATG-TGG- ACT-AAC-TGC-AGA-GGA-GAA-T-3' (SEQ ID NO: 19), GR81 (outside, right): 5'-ATC-CAG-GAG-GTT-AAA-TCA-AAC-CAG-T-3' (SEQ ID NO:20), GR7 (inside, left): 5'-GGG-ATC-GAT-TGA-AAT-AAC-ACC-AAT-TGG-CTT-CG-3' (SEQ ID NO:21), and GR8 (inside, right): 5'-GGG-ATC-GAT-CAT-AGT-ACA- GTG-GTG-TAG-CAG-AC -3' (SEQ ID NO:22). Primer pairs used for HIV-2 ne/were NEF9216 (outside, left): 5'-CCA-GCT-GAT-TCG-CCT-CTT-G-3' (SEQ ID NO:23), NEF10018 (outside, right): 5'-CCT-TCT-GGA- AAG-TCC-CTG-C-3 ' (SEQ ID NO:24), NEF253 (inside, left): 5'-AAC-AAA-ATA-TGG -ATG-ATG- TAG-ATG-C-3' (SEQ ID NO:25), and NEF360 (inside, right): 5'-TAG-AAA- ATG-TGA-TAT-ATC-TAC-TGC-C-3' (SEQ ID NO:26). Molecular Cloning And DNA Sequence Of The Complete HIV-2^ Provirus A recombinant λ-phage containing a complete provims was obtained from a genomic library constmcted from die DNA of Molt-4/Clone 8 cells from a patient infected witii HIV-2 PEI2 using a 32 P labelled probe derived from the HIV- 2 SBL . IS γ pol region. One positive clone containing the full length viral DNA was selected and designated HIV^ KR . This clone contained bod LTR's as well as 5' and 3' cellular flanking sequences. Restriction enzyme analysis demonstrated tiiat HIV-2 KR was distinct previously described HIV-2 isolates. The complete nucleotide sequence of die proviral DNA was obtained, and compared widi those of odier HIV-2 isolates. Analysis of the open reading frames (orfs) of HIV-2 KR revealed a genetic organization similar to that of previously characterized HIV-2 isolates (Figure IA). Open reading frames conesponding to die nine previously identified HIV-2 viral genes were all present. The sequences of the HIV-2 KR env and nef genes do not show premature stop codons. Alignments of predicted amino acid sequences of viral proteins were performed using a hierarchical multiple alignment technique (Coφet, et al. (1988) Nucleic Acids Research 16, 10881-90; Huang, et al. (1992) Computer Applications in the Biosciences 8, 155-65), and the homology of HIV-2 KR to other HIV-2 vimses (Andreasson, et al. (1993) Aids 1, 989-93; Clavel, et al. (1986) Nature, 324, 691- 695; Gao, et al. (1992) Nature 358, 495-9; Naucler, et al. (1991) Aids 5, 301-4; O'Brien, et al. (1991) Aids 5, 85-8; Castro, et al. (1990) Virology 178, 527-34; Kirchhoff, et al. (1990) Aids 4, 847-57; Kuhnel, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2383-2387; Kumar, et al. (1990) Journal of Virology 64, 890-901; Zagury, et al. (1988) Proc. Natl. Acad. Sci. U.S.A. 85, 5941-5945; Franchini, et al. (1989) Proc. Natl. Acad. Sci. U.S.A. 86, 2433-2437; Barnett, et al. (1993) Journal of Virology 67, 1006-14) was calculated using die FASTA algorithm (Pearson, et al. (1994) Methods in Molecular Biology 24, 307-31) (Figure IB). For comparison, SIV AGM and HIV-1 BRU sequences were also included. The nucleotide sequence of HIV-2 KR is more similar to that of other HIV-2 sequences (89-94% homology) than to SIV AGM (70% homology), or HIV-1 (59% homology.) The greatest similarity with other HIV-2 vimses was present in the gag gene (93- 98%), while the greatest average divergence was suφrisingly seen in the nef and pol genes. Phylogenetic analysis of gag coding sequences using d e neighbor- joining method (Felsenstein, et αl. (1988) Annual Review of Genetics 22, 521-65) (Figure IC) revealed that HIV-2 KR clustered closely with HIV-2 R0D , HIV-2 NIHz , and HIV-2 ST (1-2 map units), moderately closely to HIV-2 ISY (3 map units), less closely to HIV-2 D194 , HIV-2 BEN and HIV-2 GH1 (5-6 map units), and least closely with HIV- 2 UC1 (8 map units). Several distinctive molecular feamres were identified. First, as for HIV- 2 Isy (SEQ ID NO:30), (HIV-2 UC1 (SEQ ID NO:32), HIV-2 EH0 (SEQ ID NO:31), the second coding exon of d e KR rev gene is considerably larger than other HIV-2 rev reading frames (471 bp, 180 amino acid residues), extending an additional 72 residues further than the rev proteins of HIV-2 R0D (SEQ ID NO: 33), HIV-2 BEN (SEQ ID NO:34), HIV-2 GH1 (SEQ ID NO:35), HIV-2 D194 (SEQ ID NO:36), HIV- 2 NIHZ (SEQ ID NO:37), HIV-2 ST (SEQ ID NO:38), SIV MM239 (SEQ ID NO:39), SIV MM251 (SEQ ID NO:40), or SIV MNE (SEQ ID NO:41) (see Figure IA, lower section). Secondly, a deletion of 9-10bp (depending on alignment parameters) conesponding to approximately a single mm of the DNA helix is noted in die LTR (Figure 2 A) just before the Spl binding sites. This deletion is not seen in other HIV-2 isolates, and is not similar to the NFkB duplication (Novembre, et al. (1991) Journal of Medical Primatology 20, 188-92) previously described in the SIV MMpbj LTR. Transcriptional Activity of the HIV-2^ LTR. To determine if the unique deletion in die HIV-2 KR LTR affected transcriptional activity, a reporter plasmid was constmcted using a promoterless pCV based constmct containing the chloramphenicol acetyltransferase gene (see, Material and Methods). The basal and stimulated transcriptional activity of the HIV-2 KR plasmid was en compared with tiiat of similar reporter constmcts (Arya, et al. (1985) Science 229, 69-73; Kumar, et al. (1990) Journal of Virology 64, 890-901) containing the HIV-1 IIIB LTR and the HIV-2 ST LTR in a transient transfection assay using U937 cells. As seen in Figure 2B, the basal activity of the HIV-2 KR LTR was twofold that of HIV-2 ST , and 3-fold that of the HIV-1 IIIB LTR. This increased activity was also evident after stimulation with PHA and PMA (Figure 2B, second panel). Only die HIV-2 KR LTR exhibited significant transactivation after simulation with GM-CSF and LPS (Figure 2B, tiiird panel). The U3 promoter regions of the HIV-2 KR and HIV-2 ST LTR included in die reporter plasmids are essentially identical except for a 24 bp region containing is 9 bp deletion (see Figure 2 A.) The biological significance of die greater basal activity of the HIV-2 KR LTR was demonstrated by the constmction of a fully replicative HIV-2 KR mutant deleted of die first coding exon of tat. Replication and Biological Activity OfHIV-2,^. The recombinant λ-phage DNA, containing the complete HIV-2 KR provims was transfected into Molt-4/8 cells. The supematant of die transfected cells were monitored for p26 core antigen. Giant multinucleated cells appeared in die transfected Molt-4/8 culmres about 7-10 days post transfection concunent with the detection of p26 antigen in the supematant. Radioimmunoprecipitation of 35 S- Cysteine and methionine labeled HIV-2 KR infected cells and westem blotting of single-banded HIV^ KR viral pellets performed using human sera from HIV-1 and HIV-2 seropositive individuals revealed production of all structural viral proteins (Castro, et al. (1990) Virology 178, 527-34). A typical pattern of cross-reactivity was demonstrated by die HIV-1 positive sera, which detected only the HIV-2 KR p26 protein. Infected Molt-4/8 culmres producing HIV-2 KR were expanded and supematants harvested to obtain characterized pools of cell free vims and vims antigen (see, Material and Mediods), for further experiments. The infectivity of HIV-2 KR was compared to tiiat of HIV-2 SBL.ISY and two uncloned HIV-2 isolates, HIV-2 NIHz and HIV-2 R0D on a variety of cell lines and primary human cells (see Table I.) HIV-2 KR readily infected Molt 4/Clone 8 lymphoblastoid cells and HeLa T4 cells, as well as a number of other permanent human T cell lines (Molt-3, Molt-4, SupTl, H9, and C8166). The greatest cytopatiiic effect by HIV-2 KR was evident in Molt-4/8 and SupTl cells. Both molecular clones (HIV-2 KR and HIV-2, SY ) exhibited reduced infectivity for primary macaque PBMC compared to uncloned isolates (HIV-2 R0D , HIV-2 NIHz ), requiring 10-lOOx more viral antigen for each tissue culmre infectious unit. As for other previously described HIV-2 isolates and clones (Romieu, et al. (1990) Journal of Acquired Immune Deficiency Syndromes 3, 220-30; Naucler, et al. (1993) International Journal of STD and Aids 4, 217-21; Naucler, et al. (1991) Aids 5, 301-4; O'Brien, et al. (1991) Aids 5, 85-8; Castro, et al. (1990) Virology 178, 527-34; Kirchhoff, et al. (1990) Aids 4, 847-57), HIV^ was also infectious for human monocytes, and produced markedly higher levels of vims after infection of monocyte-macrophages than did HIV-2 R0D or HIV-2 NIHz , when inocula were adjusted to represent equivalent amounts of infectious vims on T-lymphocytes (Figure 3). Altiiough HIV-2 KR replicated efficientiy in monocytes and macrophages and was highly cytopathic in T-cell lines, few multinucleate giant cells were observed in HIV-2 KR infected monocyte-macrophage culmres (Figure 4). In contrast, HIV-2 ROD and HIV^^- produced numerous large syncytia in both lymphoblastoid and monocytic cell culmres (Figure 4). Infection ofM. nemestrina with HlΥ-2^ Eight juvenile M. nemestrina were inoculated widi HIV-2 KR at four infectious dose levels, as determined by in vitro titration (IO 4 , 10 3 , 10 2 , and 10 1 SFU). Every four weeks blood was obtained from the inoculated animals, and infection monitored by cocultivation with Molt4/Clone8 cells for vims reisolation, PCR on DNA obtained from PBMC of each animal, EIA seroreactivity to transmembrane protein, and quantitation of plasma antigen (Coulter™ SIV EIA). The course of infection in two animals infected widi 10 3 SFU are shown in Table 2. Both animals became PCR positive by week 4, and remained positive for over 19 weeks. However, vims was reisolated from peripheral blood mononuclear cells only during a brief period, usually from 4-8 weeks after inoculation, concomitant with detection of viral antigen in plasma. Vims was not reisolated from animals receiving less than 10 3 SFU, though evidence of infection was detected by PCR amplification of proviral DNA from peripheral blood lymphocytes in M. nemestrina receiving as little as 10 1 SFU. Clinical illness after intravenous inoculation of up to 10 5 SFU HIV-2 KR was not observed. Numbers of CD4 + lymphocytes decreased to as low as 50% of the baseline values following inoculation, returning to normal levels within 20 weeks following infection. Animal F90407, which received an inoculum of 10 3 SFU, displayed transient seropositivity to transmembrane peptide antigen at weeks 6-8, when vims was no longer recoverable (Table 2). Both animals recognized multiple vims-specific bands on westem blots up to one year after infection. Prior exposure to HIV-2 KR was found to protect infected animals against disease produced upon challenge with highly pathogenic strains of HIV-2, demonstrating mat the vims in its present form is an effective vaccine against HIV-2 infection. Features of HIV-2^. While genotypically similar to previously described HIV-2 isolates, HIV-2 KR possesses several unique feamres. For instance, the increased basal and stimulated activity of the HIV-2 KR promoter is unique, and provides for the development of tat deleted vimses as attenuated vaccine candidates, a desirable option in light of die immunosuppressive and paracrine effects of tat (Subramanyam, et al. (1993) Journal of Immunology 150, 2544-53; Ensoli, et al. (1990) Nature 345, 84-6). The presence of a substantial deletion in an otherwise highly conserved LTR promoter region indicates tiiat the deleted region is recognized by inhibitory factor(s), for example, via a mechanism similar to the reported YYl mediated inhibition (Margolis, et al. (1994) Journal of Virology 68, 905-10) of HIV-1. HIV-2 KR also has a unique long rev reading frame. Like other HIV-2 isolates and clones, HIV-2 KR is dual-tropic, infecting both primary blood lymphocytes and monocyte-macrophages as well as established T-cell lines cells. HIV-2 KR is also capable of infecting macaque peripheral blood lymphocytes in vitro, and produces a productive and persistent, though namrally "attenuated" infection in live M. nemestrina (Table 2). Efficient infection of Hu- PBL-SCID mice was also observed, providing, inter alia, a small animal model for use of this molecular clone in addition to die M. nemestrina model discussed herein. Example 2: Construction of a stable infectious TV-2^ clone containing a selectable marker cassette An HIV-2 high efficiency packaging vector project was initiated by constmcting a stable HIV-2 plasmid clone (pEP32) from lambda phage-derived subgenomic viral plasmids. This plasmid, pEP32, (Figure 6) and its derivatives, contain all HIV-2 KR genes as well as a selectable marker gene (neoR initially and subsequently die phleomycin resistance marker). The plasmids have remained stable through numerous modifications and allow antibiotic-selection of stable cell lines containing them. Example 3: Modifications to the Selecteable HIV-2^ clone A series of modifications to pEP32 were made to achieve tiiree goals: (1) expression of the HIV-2 stmcmral proteins in trans; (2) abrogation of viral replication and genomic RNA packaging and (3) reduction of die probability of replication- competent retrovimses (RCR) occuning in packaging cell lines. 61 (out of a total of 75) base pairs were deleted from the "psi" (putative packaging signal region) between the major 5' splice donor and die gag gene start codon (see, Figure 7). Next, the 3' R repeat, U5 and a portion of U3 were replaced with the bovine growth hormone (BGH) polyadenylation signal (plasmid pEP40). As illustrated in Figure 7, pEP 41-43 in tiiis series terminate viral sequences precisely with the stop codon of nef, which is adjoined to the BGH poly A signal. The psi-deleted pEP40-43 series include four permutations of the HIV-2 KR LTR and die heterologous HCMV promoter with env-intact and env-deleted genomes. Plasmids pEP40 and pEP43 express the HIV-2 envelope, while pEP41 and pEP42 have a 776 bp deletion in the envelope gene (from nt 6780 to 7555; numbered according to convention with nucleotide 1 conesponding to die T of TGGATGGG at the start of the 5' LTR; see, the sequence listing herein and GenBank No. U22047) which renders the Env protein non-functional, but does not interfere with Tat and Rev regulation. Only env expression is abrogated. pEP41 and pEP42 can be used as first high efficiency packaging nucleic acids in which a second high efficiency nucleic acid supplies env in trans, decreasing the possibility that a recombinatorial event will produce a vimlent vims. The constmcts can also be used for VSV-G pseudotyping, in which a second constmct supplies VSV envelope in trans. pEP42 and pEP43 express d e HIV stmcmral proteins from the human cytomegalovims promoter, eliminating both LTRs. The hCMV promoter is joined to the HIV-2 genome just after U5, at nucleotide 864 numbered according to convention with nucleotide 1 conesponding to the T of TGGATGGG at d e start of the 5' LTR; see, the sequence listings herein and GenBank No. U22047). While the 776 bp deletion is conveniently constmcted (die deletion spans two Nsi sites, and can be generated by cleavage with Nsi and ligation of the resulting ends of die env gene), one of skill will recognize diat larger or smaller deletions of die env gene have similar effects on env expression. Example 4: HIV-2 based Retroviral Vectors As illustrated in Fig. 3, HIV-2 based retroviral vectors were constmcted to have bodi LTRs, the psi region and, since the packaging signal is predicted by analogy to otiier retrovimses to extend into gag, a portion of tiiat gene's pl7 region. As expression of the pl7 gag mRNA is Rev-dependent, d e rev-response element (RRE) is placed downstream of this pl7 fragment to confer stability and nuclear export upon d e vector transcript in die presence of Rev. Therefore, both vector and internally-promoted (sv40 promoter) marker gene mRNAs can be expressed in the packaging cell, but only the sv40 promoted transcript was appreciably expressed in die target cell. For transient pseudotyping experiments with pEP 41 and 42, a third plasmid phCMV-G , is included to express the VSV-G protein. Example 5: Replication and Expression of HIV-2 based Retroviral Vectors Altiiough the packaging plasmid LTR modifications illustrated in Example 4 were incoφorated to increase safety, d e 61 bp deletion in the psi region of HIV-2 RR (from nt 1007 to 1067, numbered according to convention witii nucleotide 1 conesponding to the T of TGGATGGG at the start of the 5' LTR; see, the sequence listings herein and GenBank No. U22047) was alone sufficient to abrogate replication of die vims. As shown in Figure 9, lipofection of pEP32 into the highly permissive T cell line Molt 4/clone 8 resulted in lytic infection, while lipofection of die psi-deleted (and otherwise wild-type) clone or psi+3'LTR-deleted clone (pEP40) resulted in botii transient p26 production and transient syncytia formation (die latter being Env-mediated); however in die case of die psi-deleted clone, both p26 and syncytia disappeared from the culmre by two weeks. Six month follow-up of these experiments revealed no detectable p26 by an antigen capmre assay sensitive to 10 picomoles per ml. 10° Molt 4 clone 8 cells lipofected (DOTAP, Boehringer-Mannheim) with 10 μg of CsCl-purified plasmid DNA and supematant was sampled at die indicated times in Figure 9 for a p26 antigen capmre assay (Coulter). The pEP32Δpsi- and pEP40-transfected culmres were terminated at 7 monti s. At 200 days, p26 levels remained undetectable. Example 6: Viral antigen Expression bv g418 Selected Cell Lines Stably transformed lines were derived by G418-selection for pEP32 (wild-type), pEP34 (a wild-type plasmid lacking only the downstream BGH polyA signal) and pEP40 for a number of cell types. Stable cell lines were derived by selection and maintenance in G418 600 μg/ml after transfection of CsCl-purified plasmid DNA previously linearized in prokaryotic sequences. Adherent cell lines were derived using polybrene-DMSO transfection and suspension cell lines by lipofection. Single cell clones were obtained from 96-well plates seeded with limiting dilutions of cells resulting in less tiian 12 clones per plate. Viral titrations were canied out by end-point dilution infection of Molt4 clone 8 T cells in 96-well plates scored for syncytia at 10 days. p26 was assayed by the Coulter antigen capmre kit. Initially, levels of p26 expression were low in HeLa, Daudi, U937, T lymphoblastoid and odier cell lines (Figure 10). However, CD4-negative monkey kidney epithelial cell lines (CVI and COS) were readily selectable, clone well and express very high levels of viral proteins that were equal to or in excess of that produced by lytic T-cell line infection witii wild type vims. As illustrated in Figure 11, cells selected for bodi psi+3'LTR-deleted ("C4" series) and full-length infectious provimses ("C5" series) expressed over 100 ng/ml of p26 and over 700 ng/ml in some clones. Single cell clones routinely expressing 300-500 ng p26/ml were derived. Both COS-1 and CV-1 cells expressed high levels of p26, however, vims from COS-1 cells was a log more infectious per unit of p26. Clones selected for die wild-type provims produced 5 x IO 6 TCID50/ml of HIV-2 (limiting dilution titer on Molt-4/clone-8 T cells) indicating normal processing and virion maturation from these cells. Example 7: Safetv of Packaging Cell Lines Since numerous CD4-negative cell types have been shown to be infectable by HIV, it was important to document that these producer and packaging lines produced particles from the transfected DNA only (i. e. , that replication or spread did not occur in diese lines either in a cell-free or cell to cell manner). To that end, two experiments were performed. First, passage of filtered wild-type HIV-2 supernatant widi a titer of 10° TCID50/ml to fresh COS-1 cells resulted in no detectable infection by p26 antigen capmre assay or by PCR following trypsinization and cell passage. Second, cell-cell spread was mled out by die co-culture experiment illustrated in Figure 12. A hygromycin-stable COS-1 cell line was generated and co-culmred at high density in a 1: 1 ration with a G418-stable COS-1 clone (C5.8) selected for an infectious provims and producing > 300,000 pg/ml of p26 antigen as well as > 10° TCID50/ml of vims. After several weeks of passage in co-culture, the mixed cells were tiien selected in hygromycin. 50% of the cells (the G418 stable producers) were observed to die. The remaining hygromycin-stable cell line was negative for p26 by antigen capmre. Furthermore, no vims was rescuable by high volume co-culture with highly permissive T-lymphoblastoid lines such as Molt-4/clone-8, H9 and Jurkat. Thus, particles produced by diese cell lines do not reinfect or spread widiin die culmre and diat expression is from die introduced plasmid DNA only. Example 8: Packazinε Cell Lines Express and Properly Process HIV-2 Product To assess the ability of packaging cell lines to produce properly processed HIV-2 proteins, radioimmunoprecipitation using combined 35S-methionine and 35 S-cysteine labeling was performed. 35 S Met and 35 S Cys labeling was canied out for six hours following an initial tiiree hour semm starvation. Following six-hour labeling, single cell- cloned and polyclonal lines were immunoprecipitated using a pooled human semm from five HIV-2-positive donors. Each cell line was simultaneously immunoprecipitated with an uninfected human control semm. No specific bands were precipitated from COS-1 cells alone or uninfected U937 cells, or in any cells precipitated with HIV-2-negative semm. However, cells selected for bodi the wild-type pEP34 (lines designated C5, single cell clones C5.X) and die psi/LTR-deleted packaging plasmid pEP40 (lines designated C4, single cell clones C4.X) revealed identical prominent bands specific for fully-processed HIV-2 stmcmral proteins, including pl7, p26, gp41, p55, and gp 140. The results showed tiiat the packaging signal deletion, extending to 10 bases downstream of the major 5' splice donor, and 3 bases upstream of the gag start codon, abrogated replication but did not interfere with proper viral mRNA processing and protein expression. Single cell cloning resulted in die selection of high-producers, as illustrated in a comparison of the C4 polyclonal cell immunoprecipitation experiments versus 8 C4 single cell clones. Example 9: Packaging Cell Line Expression Plasmid Copy Number Although the tested HIV-2 packaging plasmids contain the sv40 promoter driving selectable marker expression, the high levels of expression obtained in G418-stable cell lines was not the result of either T-antigen driven amplification or episomal maintenance, as demonstrated by the following six lines of evidence. First, Southern blotting revealed one or two proviral insertions for all of the cell line clones examined. 20 μg of Genomic DNA were digested witii Xbal, which cleaves once within the introduced plasmid DNA upstream of neoR (Figure 13). Cleavage in flanking genomic DNA outside die site of linearization (Pvul) produced a single, uniquely sized band for each plasmid copy insertion. Xbal-digested DNA was electrophoresed in 0.8% agarose, transfened to a nylon membrane and probed with a 32 P-labeled probe randomly primed from a gel-purified 0.6 kb fragment of die neoR gene. The results showed tiiat the cells had one or two proviral insertions. Single cell clones C4.2 and C4.4 each have a single proviral insertion and have been used for subsequent stable packaging line work. Second, mutation of die T-antigen binding site widiin d e Sv40 promoter resulted in equally high (> 100 ng/ml) levels of expression in G418-selected lines. Third, a plasmid substimting an hCMV promoter-phleomycin resistance marker for the sv40-neoR cassette (thereby eliminating all sv40 and T-antigen binding site sequences) was constmcted and also gave high ( > 100 ng/ml p26) when used to derive stable COS-1 lines. Fourth, > 95% (32/33) of G418-stable single cell clones derived for pEP32 or pEP34 produced infectious vims (although levels varied by orders of magnitude), indicating tiiat gross reanangements and deletions leading to selection for only the neoR encoding portion of d e plasmid was uncommon. Fifth, G418-selected CV-1 cell clones, which were parental to COS cells, also produced > 30 ng p26/ml. Sixtii, Hirt DNA extracts were negative for plasmids, as tested by Southern blot and bacterial transformation. To further characterize these cloned lines, electron microscopy was performed on several single cell clones. A transmission electron micrograph of C4.2 at 50,000 X magnification showed the full range of normal virion particle maturation, from electron dense circular budding circular forms to fully mamre, condensed conical cores. Numerous intracellular particles were also seen. Example 10: Packaging of HIV-2 packagable RNAs C4.4 was transfected with linearized pSPneo (see, Figure 8) and selected in phleomycin (200 4g/ml). Filtered supematant was collected from d e resulting G418+ phleomycin-stable cell line and serial dilutions (without polybrene) were used to transduce U937 cells, which were then selected in 400 μg/ml G418. Results are shown in Table 1 below. Cells transduced wid heat- inactivated supematant gave a titer of zero. Table 1 : NeoR titers obtained by transducing U937 cells with filtered supematant from C4.4 spneo stable producer cell line HIV-2 Vector Stable Producer Cell Line NeoR Titre Mean Experiments (HIV-2 Envelope-mediated) C4.4sPneo Stable Cell line Exp. 1 ; 1.3 X IO 4 1.8 X IO 4 Transduction of U937 Cells C4.4sPneo Stable Cell line Exp. 2; 8.5 X 10 3 Transduction of U937 Cells C4.4sPneo Stable Cell line Exp. 3; 3.2 X IO 4 Transduction of U937 Cells C4.4sPneo Stable Cell line Exp. 1-3; Heat 0 Inactivated Example 11: Pseudotype Vectors Transient co-transfection of the VSV-G protein (see, Lin et al. (1994) Science 265:666) was used for transient pseudotyping of HIV-2 based vectors. Table 2 below describes the methods used to generated pseudotyped vector using triple transfection of pEP41 , PEP15.2 and hCMV-G (see, Figures 7 and 8 for illustrations of plasmid stmcmre). Omission of the VSV-G expression plasmid or heat inactivation abrogated gene transfer. Titers generated by calcium phosphate transfection of 293T cells and by COS-1 cell coelectroporation of these plasmids are shown in Table 2. Table 2: Transduction of HeLa cells with VSV-g pseudotyped HIV-2 LacZ vector. Three plasmids: pEP41, pEP15.2 and CMV-G (15 μg each) were cotransfected by calcium phosphate co-precipitation into 293 T cells or co-electroporated into COS-1 cells plated a day earlier in 162 cm 2 flasks. 10-18 hours after transfection, transfected cells were washed and fresh medium was added. 48-72 hours later, the supernatant was collected and subjected to low-speed centrifugation and filtration (45μm). HeLa cells plated the day before were incubated 36-48 hours further, with fresh medium. Titers represent number of blue-staining cells after 1-4 hours of X-gal staining divided by the dilution factor. No background was seen in control cells even after overnight staining. Heat inactivated (H.I.) supernatant (56°C, for 10 min) and transfections omitting the CMV-G plasmid yielded no positive cells. VSV-G Pseudotyped HTV-2 Vector Experiments LacV Titer Mean 293 T cells; plasmids 41 + 15.2 +CMV-G; Exp. 1 8.6 X IO 6 3.8 X 10 5 293 T cells; plasmids 41 + 15.2 +CMV-G; Exp. 2 5.3 X IO 5 293 T cells; plasmids 41 + 15.2 +CMV-G; Exp. 3 5.1 X 10 5 293 T cells; plasmids 41 + 15.2; Exp. 1-3 0 293 T cells; plasmids 41 + 15.2 +CMV-G; Exp. 1- 0 3 (H.I) Cos-1 cells; plasmids 41 + 15.2 +CMV-G; Exp. 1 4.2 X 10 4 2.7 X 10" Cos-1 cells; plasmids 41 + 15.2 +CMV-G; Exp. 2 1.5 X 10 3 Cos-1 cells; plasmids 41 + 15.2 +CMV-G; Exp. 3 3.8 X 10" Cos-1 cells; plasmids 41 + 15.2; Exp. 1-3 0 Cos-1 cells; plasmids 41 + 15.2 +CMV-G; Exp. 1- 0 3 (H.I.) Example 12: A Bioluminescent Marker For Retroviral Gene Transfer The green fluorescent protein (GFP; see, Chalfie et al. (1994) Science 263:802) of the bioluminescent jellyfish Aequoria victoria was used as a marker for retroviral vector gene transfer. The principal advantages of this namrally fluorescent protein are its small size and the ability to detect it in living cells by simple UV-illumination (through either microscopy or flow cytometry). Shown in Figure 14 is an HIV-2 based retroviral vector constmcted by insertion of the s65t mutant of GFP (see, Helm et al (1995) Nature 373:663; Cubitt et al. (1995) Trends in Biochemical Sciences 20:448) in-frame in the nef gene. The resulting chimeric Nef/GFP fusion protein retains properties of both Nef and GFP (myristoylation-modulated confinement to intracellular membranous structures, and fluorescence respectively). Full-lengti infectious HIV-2 bearing this insertion transfers GFP to T cells with a low detectable transduction efficiency (approximately 2%). However, vector LXRTG, which is illustrated in figure 14, was also packaged with HIV-2 stmcmral proteins from pEP41 and pseudotyped with VSV-G. The experimental design is illustrated in Figure 14. Photomicrographs 15 showed that when this supematant (generated by calcium phosphate co-transfection into 293T cells according to the experimental design illustrated in Figure 14) was used to transduce the monocytoid cell line U937, a transduction efficiency of > 50% was achieved. A titer of 4 x 10 5 was obtained. Further modifications of this vector, which also expresses HIV-2 Tat, Rev, Vpr and Vpx, include deletion of these sequences. Although isolated stable expression of non-structural HIV-2 proteins is useful for a variety of basic experiments, clinically useful vectors preferably include substimtion of HIV-2 coding sequences with an intemal promoter such as SV4O or the murine SL3-3 promoter. All publications and patent applications cited in this specification are herein incoφorated by reference for all puφoses as if each individual publication or patent application were specifically and individually indicated to be incoφorated by reference. Although the foregoing invention has been described in some detail by way of illustration and example for puφoses of clarity of understanding, it will be readily apparent to those of ordinary skill in the art in light of the teachings of this invention that certain changes and modifications may be made thereto without departing from the spirit or scope of the appended claims. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: THE REGENTS OF THE UNIVERSITY OF CALIFORNIA (ii) TITLE OF INVENTION: ISOLATION OF NOVEL HIV-2 PROVIRUSES (iii) NUMBER OF SEQUENCES: 16 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: Robbins, Berliner & Carson (B) STREET: 201 N. Figueroa Street, 5th Floor (C) CITY: Los Angeles (D) STATE: California (E) COUNTRY: USA (F) ZIP: 90012-2628 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Floppy disk (B) COMPUTER: IBM PC compatible (C) OPERATING SYSTEM: PC-DOS/MS-DOS (D) SOFTWARE: Patentin Release #1.0, Version #1.30 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: (B) FILING DATE: (C) CLASSIFICATION: (vii) ATTORNEY/AGENT INFORMATION: (A) NAME: Robert Berliner (B) REGISTRATION NUMBER: 20,121 (C) REFERENCE/DOCKET NUMBER: 5555-399C1 (viii) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: 213-977-1001 (B) TELEFAX: 213-977-1003 (2) INFORMATION FOR SEQ ID NO:1: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 10163 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..10163 (D) OTHER INFORMATION: /note= "HIV-2KR" (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1: TGGATGGGAT GTATTACAGT GAGAGAAGGA CATAGAATCT TAGACATATA CATGGAAAAG 60 GAAGAAGGGA TAATTCCAGA TTGGCAGAAC TATACTCATG GGCCAGGAGT AAGGTACCCA 120 AAGTTCTTTG GGTGGCTATG GAAGCTAGTA CCAGTAGACG TCCCACAAGG TGAAGAGGAC 180 CACTGCTTAC TACACCCAGC ACAAACAAGC GGGTCTGATG ACCCTCATGG GGAAACATTA 240 ATGTGGAGGT TTGACCCTAG GCTGGCCTAT GAGTATACGG CTTTTAATCG ATACCCAGAA 300 GAATTTGGGT ATAAGTCAGG CCTGCCAGAA GAAGAGTGGA AGGCAAAACT GAAAGCAAGA 360 GGGATACCAT TTAGTTAAAG ACAGGAACAG CTATATTTGG TCAGAACAGG AAGTAGATGA 420 TGAAACTGCA GGGACTTTCC AGAAGGGGCT GTAACCAGGG GAGGGACGTG GGAGGAACCG 480 GTGGGGAACG CCCTCATACT TCTGTATAAA TGTACCCGCT GCTTGCATTG TATTCAGTCG 540 CTCTGCGGAG AGGCTGGCAG ATCGAGCCCT GGGAGGTTCT CTCCAGCACT AGCAGGTAGA 600 GCCTGGGTGT TCCCTGCTAG ACTCTCACCA GTACTTGGCC GGTACTGGGC AGACGGCTCC 660 ACGCTTGCTT GCTTAAAGAC CTCTTAATAA AGCTGCCAGT TAGAAGCAAG TTAAGTGTGT 720 GTTCCCATCT CTCCTAGTCG CCGCCTGGTC ATTCGGTGTT CACCTAAGTG ACAAGACCCT 780 GGTCTGTTAG GACCCTTCTT GCTTTGGGGA ACCGAAGCGG GAAAATACCT AGCAGATTGG 840 CGCCCGAACA GGACTTGAAG GAGACTGGAA CACGGCTGAG TGAAGGCAGT AAGGGCGGCA 900 GGAACAAACC ACGACGGAGT GCTCCTAGAA AGGCGCGGGC CGAGGTACCA AAGGCGGCGT 960 GTGGAGCGGG AGTAAAGAGG CCTCCGGGTG AAGGTAAGTA CCTACACCAA AAACTGTAGC 1020 CAGAAAAAGG CTTGTTATCC TACCTTTAGA CAGGTAGAAG ATTGTGGGAG ATGGGCGCGA 1080 GAAGCTCCGT CTTGAGAGGG AAAAAAGTAG ATGAATTAGA AAAAATTAGG TTACGGCCCG 1140 GCGGGAAGAA AAAATATAGA CTAAAGCATA TTGTGTGGGC AGCGAATGAA TTGGGCAAAT 1200 TCGGATTGGC AGAAAGCCTG TTGGAGTCAA AAGAAGGTTG CCAAAAAATT ATTACAGTTT 1260 TAGATCCATT AGTGCCAACA GGATCAGAAA ATTTAAAAAG CCTTTTTAAT ACTGTCTGCG 1320 TCATTTGGTG CTTGCACGCA GAAGAGAAAG TGAAAGATAC TGAAGGAGCA AAACAAATAG 1380 TACAGAGACA TCTAGTGGCA GAAACAGGAA CTGCAGACAA AATGCCAAGC ACAAGTAGAC 1440 CAGCAGCACC ACCTAGCGGG AGAGGGGGAA ATTACCCCGT GCAACAAATA GCTGGCAACT 1500 ATTCCCATGT GCCGTTGAGC CCCCGAACCC TAAATGCTTG GGTAAAGTTA GTGGAAGAAA 1560 AGAAGTTCGG GGCAGAAGTA GTGCCAGGGT TTCAGGCACT CTCAGAAGGC TGCACGCCCT 1620 ATGATATTAA TCAAATGCTT AATTGTGTGG GCGACCATCA AGCAGCTATG CAAATAATCA 1680 GAGAGATTAT TAATGAAGAA GCAGCAGATT GGGATGTGCA ACACCCAATA CCAGGCCCCT 1740 TGCCAGCGGG GCAGCTTAGA GAACCAAGAG GGTCTGATAT AGCAGGGACA ACAAGCACAG 1800 TAGAAGAACA GATCCAGTGG ATGTTTAGAG CACAAAATCC TATACCAGTA GGGAACATCT 1860 ATAGGAGATG GATCCAGATA GGACTGCAGA AGTGCGTCAG GATGTACAAT CCAACCAACA 1920 TCCTAGACGT AAAACAGGGA CCAAAGGAGC CGTTCCAAAG CTATGTAGAT AGATTCTACA 1980 AAAGCCTAAG GGCAGAACAA ACAGACCCAG CAGTAAAAAA TTGGATGACC CAAACACTGC 2040 TGGTACAGAA TGCCAACCCA GACTGTAAAT TAGTACTAAA AGGACTGGGG ATGAATCCTA 2100 CCTTAGAGGA GATGCTGACC GCCTGTCAGG GAATAGGAGG ACCAGGCCAG AAAGCCAGAT 2160 TAATGGCAGA AGCCTTAAAG GAGGCCCTAG CACCAGCCCC TATCCCATTT GCAGCAGCCC 2220 AACAGAGAAG GACAATTAAG TGCTGGAATT GTGGAAAGGA TGGGCACTCG GCAAGACAAT 2280 GCCGAGCACC TAGAAGACAG GGCTGCTGGA AATGTGGCAA ATCAGGACAT GTCATGGCAA 2340 ACTGCCCAGA AAGACAGGCT GGTTTTTTAG GGATTGGCCC ATGGGGAAAG AAGCCTCGCA 2400 ACTTCCCCGT GACCCGAGTC CCGCAGGGGC TGACACCAAC AGCACCCCCA GCAGACCCAG 2460 CAGCAGACCT GCTAGAGAAG TACTTGCAGC AAGGGAGGAA GCAGAAAGAG CAGAAAATGA 2520 GACCATACAA GGAGGTGACA GAGGACTTAC TGCACCTCGA ACAAGGAGAG ACACCACACA 2580 AAGAGGCGAC AGAGGATTTG CTGCACCTCA ATTCTCTCTT TGGAAAAGAC CAGTAGTCAC 2640 AGCATATGTT GAGGGTCAGC CAGTAGAAGT CTTACTAGAC ACAGGGGCTG ACGACTCAAT 2700 AGTAGCAGGA ATAGAGTTGG GGAGCAATTA TAGTCCAAAA ATAGTAGGGG GAATAGGGGG 2760 ATTCATAAAC ACCAAGGAAT ATAAAAATGT AGAAATAAAA GTACTAAATA AAAAGGTAAA 2820 AGCCACCATA ATGACAGGTG ATACCCCAAT CAACATTTTT GGCAGAAACA TTCTGACAGC 2880 CTTAGGCATG TCATTAAATC TACCAGTCGC CAAGGTAGAC CCGATAAAAG TAATACTGAA 2940 ACCAGGAAAA GATGGACCAA AAGTAAGACA ATGGCCTCTA ACAAAAGAAA AGATAGAGGC 3000 ACTAAAAGAA ATCTGTGAAA AAATGGAAAG AGAAGGCCAG CTAGAGGAAG CTCCCCCAAC 3060 TAATCCTTAT AATACCCCCA CATTTGCAAT TAAGAAAAAG GACAAAAACA AATGGAGAAT 3120 GCTAATAGAT TTTAGAGAAC TAAATAAGGT AACTCAAGAG TTCACAGAAA TTCAGTTAGG 3180 AATTCCACAC CCAGCAGGAT TAGCCAAGAA AAGAAGAATT ACTGTACTAG ATATAGGGGA 3240 TGCCTACTTT TCCATACCAC TACATGAGGA CTTTAGACAA TATACTGCAT TTACTCTACC 3300 AACAGTGAAC AATGCAGAAC CAGGAAAGAG ATATATATAT AAAGTCCTAC CACAGGGATG 3360 GAAAGGATCG CCAGCAATTT TTCAACACAC AATGAGGCAG GTCTTAGAGC CATTCAGAAA 3420 AGCAAACCCA GACGTCATTC TCGTCCAATA TATGGATGAT ATCTTAATAG CTAGCGACAG 3480 GACAGACTTA GAGCATGACA GAACGGTCCT GCAGTTAAAA GAACTTTTAA ATGGCCTAGG 3540 ATTCTCCACC CCAGATGAGA AGTTCCAAAA AGACCCCCCA TACAAATGGA TGGGCTATGA 3600 ACTATGGCCA ACCAAATGGA AGCTGCAAAA AATACAATTG CCCCAAAAAG AAGTATGGAC 3660 AGTCAATGAC ATCCAAAAGC TAGTAGGTGT CCTAAATTGG GCAGCACAAA TCTACCCAGG 3720 GATAAAGACC AAACACTTAT GTAGGCTAAT TAGAGGAAAA ATGACACTCA CGGAAGAAGT 3780 ACAGTGGACA GAACTAGCAG AGGCAGAACT AGAAGAGAAC AAAATTATCT TGAGCCAGGA 3840 ACAGGAGGGA TGCTATTACC AAGAAGAAAA GGAATTAGAA GCAACAGTCC AAAAGGATCA 3900 AGACAATCAG TGGACATATA AAATACACCA AGGAGAGAAA ATCCTAAAAG TAGGAAAATA 3960 TGCAAAGATA AAAAATACCC ATACCAATGG GGTCAGATTG TTAGCACATG TAGTTCAAAA 4020 AATAGGAAAA GAAGCACTAG TCATTTGGGG ACGAATACCA AAATTTCACC TACCAGTAGA 4080 AAGAGAAACC TGGGAGCAGT GGTGGGATAA CTATTGGCAA GTGACATGGA TCCCAGACTG 4140 GGACTTCGTA TCTACTCCAC CACTGGTCAG GTTAGCATTT AACCTAGTAA AAGATCCCAT 4200 ACCAGGTGAA GAGACCTTCT ACACAGATGG ATCCTGTAAT AGGCAATCAA AAGAGGGAAA 4260 AGCAGGATAT ATAACAGATA GAGGGAGAGA CAAGGTAAGG ATATTGGAGC AAACTACCAA 4320 TCAGCAAGCA GAATTAGAAG CCTTCGCAAT GGCATTAACA GACTCAGGTC CAAAAGCCAA 4380 TATTATAGTA GACTCACAGT ATGTAATGGG AATAGTAGCG GGCCAGCCAA CAGAATCAGA 4440 GAGTAAACTA GTAAACCAAA TCATAGAAGA AATGATAAAA AAGGAAACAC TCTATGTTGC 4500 ATGGGTCCCA GCCCACAAAG GCATAGGAGG AAATCAGGAA GTAGATCATT TAGTAAGTCA 4560 GGGCATTAGA CAAGTATTAT TCCTAGAAAA AATAGAGCCC GCTCAGGAAG AACATGAGAA 4620 ATATCATAGC AATGTAAAAG AATTATCCCA TAAATTTGGA CTGCCCAAAC TAGTGGCAAG 4680 ACAAATAGTA AACACATGTG CCCAATGTCA ACAGAAAGGG GAAGCTATAC ATGGGCAAGT 4740 82 AGATGCAGAA CTGGGCACTT GGCAAATGGA CTGCACACAC TTAGAGGGAA AAATCATTAT 4800 AGTAGCAGTA CATGTTGCAA GCGGGTTTAT AGAAGCAGAA GTTATCCCAC AGGAAACGGG 4860 AAGGCAAACA GCACTCTTCC TATTAAAACT GGCCAGTAGG TGGCCAATAA CACACCTGCA 4920 CACAGATAAT GGTGCCAACT TCΛCCTCACA GGAAGTAAAG ATGGTAGCGT GGTGGACAGG 4980 TATAGAACAA TCCTTTGGAG TACCTTACAA TCCACAAAGC CAAGGAGTAG TAGAAGCAAT 5040 GAATCACCAC TTAAAAAACC AGATAAGCAG AATTAGAGAG CAGGCAAATA CAATGGAAAC 5100 AATAGTATTA ATGGCAGTTC ATTGCATGAA TTTTAAAAGA AGGGGAGGAA TAGGGGATAT 5160 GACCCCAGCA GAAAGACTAA TCAATATGAT CACCACAGAA CAAGAAATAC AATTCCTCCA 5220 CGCAAAAAAT TCAAAATTAA AAAATTTCCG GGTCTATTTC AGAGAAGGCA GAGATCAGCT 5280 GTGGAAAGGA CCTGGGGAAC TACTGTGGAA GGGAGATGGA GCAGTCATAG TCAAGGTAGG 5340 GACAGACATA AAAATAGTGC CAAGAAGGAA AGCTAAGATC ATCAGAGACT ATGGAGGAAG 5400 GCGAGAGGTG GATAGTAGTT CCCACTTGGA GGGTACCAGG GAGGATGGAG AAGTGGCATA 5460 GCCTTGTCAA GTATCTAAAA CACAGAACAA AAGATCTGGA AGGGGTGTGC TATGTTCCCC 5520 ACCATAAGGT GGGATGGGCA TGGTGGACTT GCAGCAGGGT AATATTCCCA TTACAAGGAA 5580 ATAGTCACCT AGAGATACAG GCATATTGGA ACCTAACACC AGAAAAAGGA TGGCTCTCCT 5640 CTTATGCAGT AAGAATAACC TGGTATACAG AGAGGTTCTG GACAGATGTT ACCCCAGACT 5700 GTGCAGACTC CCTAATACAT AGCACTTATT TCTCTTGTTT TACGGCGGGT GAAGTAAGAA 5760 GAGCCATCAG AGGGGAAAAG TTACTGTCCT GCTGCAATTA CCCCCAAGCC CATAGATCTA 5820 AGGTACCGTT ACTCCAATTT CTGGCCTTAG TAGTAGTGCA ACAAAATGGC AGACCCCAGA 5880 AAAACAGTAC CACCAGGAAA CGGTGGCGAA GTAACTATTG GAGAGGCTTT CGCTTGGCTA 5940 GAAAGGATGG TAGAGGCCAT AAACAGAGAG GCAGTGAACC ACCTGCCTCG GGAGCTTATT 6000 TTCCAGGTGT GGCAAAGGTC CTGGAGATAC TGGCATGATG ACCTAGGGAT GTCACAAAGT 6060 TACACAAAGT ATAGATATTT GCGCTTAATG CAGTATGCTA TGTTCATACA TGTTAAGAAA 6120 GGGTGCACTT GCCTGGGGGG AGGACATGGG CCGGGAGGGT GGAGACCAGG ACCTCCCCCT 6180 CCTCCCCCAG GCCTAGTCTA ATGACTGAAG CACCAGCAGA GTTTCCCCCG GAGGATGAAA 6240 CCCCACCGAG GGGGCCAGGG GATGAGTGGG TAATAGGAAT CCTGAGAGAA TTAAGAGAAG 6300 AAGCTTTAAA GCATTTTGAC CCTCGCTTGC TAACTACTCT TGGCAACTAT ATCTGTGCTA 6360 GACATGGAGA CACCCTCGAA AGCGCCAGAG AGCTCATTAA TGTCCTGCAA CGAGCCCTCT 6420 TCGTGCACTT CAGAGCAGGA TGTAAAATCT CAAGAATTGG CCAAACAAGG GGAGAGACTC 6480 CTTTCTCAGC TATACCAACC CCTAGAGGCA TGCAATAACC CATGTTATTG TAAGAAATGT 6540 TGTTACCATT GCCAGCTATG TTTTTTAAAA AAGGGACTCG GGATATGTTA TGAACGGAAG 6600 GGCAGACGAA GAAGGACTCC AAGGGCTCAT TCGTCTTCTG CATCAGACAA GTGAGTATAA 6660 TGGATAGTAG AAATCAGCTA ATTGTTGCCA TTTTACTAAC TAGTGCTTGC TTAATATATT 6720 GCGCCCAATA TGTGACTGTT TTCTATGGCA TACCCGCGTG GAAGAATGCA TCCATTCCCC 6780 TCTTTTGTGC AACCAGAAAT AGAGATACTT GGGGAACCAT ACAGTGCTTG CCAGACAATG 6840 ATGATTATCA GGAAATACCT TTAAATGTGA CAGAGGCTTT TGACGCATGG AACAATACAG 6900 TAACAGAACA AGCAGTAGAA GATGTCTGGA ATCTATTTGA GACATCAGTA AAACCATGTG 6960 TCAAATTAAC ACCCTTATGT GTGCAAATGG AATGTAACAG CACAAGTACA GAGAGCAGTA 7020 ACAGCACAAG TGAGGGGAGC ACAGTCCCAG AGATATTAAA CGAAACTACT TCATGCATAA 7080 CCAACAACAG CTGCTCAGAT TTΛGGGAGTG AAGAGGTAGT CGATTGTCGG TTCAATATGA 7140 CAGGACTACA ACTAGATAAG CCACAGCAAT ATAGTGAAAC ATGGTACTCA AAGGATGTAG 7200 TTTGTGACAC AACTAATGGG ACCAGCCGCA AATGTTACAT GAACCATTGC AACACATCAG 7260 TCATCACAGA GTCATGTGAT AAGCACTATT GGGATGCTAT GAGGTTTAGA TACTGTGCAC 7320 CACCGGGTTT ATGCTTGCTA AGATGCAATG ATACCAATTA TTCAGGCTTT GAGCCCAAGT 7380 GTCCTAAAGT AGTAGCTGCT ACATGCACAA GAATGATGGA AACGCAAACT TCTACTTGGT 7440 TTGGCTTTAA TGGCACTAGG GCAGAAAATA GAACATATAT CTATTGGCAT GGTAGAGATA 7500 ATAGGACTAT TATCAGCTTA AATACACATT ATAATCTCAC AATGCATTGT AAGAGGCCAG 7560 GAAATAAGTC AGTTTTGCCA ATAACACTTA GGTCAGGGAG AGTGTTTCAC TCCCGACCGA 7620 TCATCAATGA AAGACCCAAG CAGGCATGGT GCTGGTTCGG AGGTGATTGG AAGAAAGCCA 7680 TGCAGGAGGT GAAACAAACC CTTGTGAAAC ATCCCAGGTA TAGAGGAACC AACGACACAC 7740 AGAAAATTAA CTTTACACAA CCAGGAAAAG GTTCAGATGC AGAAGTGGTA TACATGTGGA 7800 CTAACTGCAG AGGAGAATTT CTATACTGCA ACATGACTCG GTTCCTCAAT TGGATAGAAA 7860 ACAGGGCACA CCCACAGCGC AATTATGCAC CGTGCCATAT AAGGCAAATA ATTAATACCT 7920 GGCATAGAGT AGGCCAAAAT ATATATTTGC CTCCTAGGGA AGGGGAATTG GTCTGCAACT 7980 CAACAGTAAC CAGCATAATT GCTAACATTG ACATGTTTGA TAACCAGACA AGCATTACCT 8040 TTAGTGCAGA GGTGGCAGAA CTATACCGAT TGGAATTGGG AGATTACAAA TTAGTAGAAA 8100 TAACACCAAT TGGCTTCGCA CCTACATCAG AAAAAAGGTA TTCCTCTGCT CCACAGAGGA 8160 ATAAAAGAGG TGTGTTTGTG CTAGGAGTCT TGGGTTTTCT CGCAACAGCA GGTTCTGCAA 8220 TGGGCGCGGC GTCCTTGACG CTGTCGGCTC ATCCCGGACT TTACTGGGCT GGGATAGTGC 8280 AGCAACAGCA ACAGCTGTTG GACGTGGTCA AGAGACAACA AGAAATGTTG CGACTGACCG 8340 TCTGGGGAAC AAAAAATCTC CAGACAAGAG TCACTGCTAT CGAGAAATAC CTAAGGGACC 8400 AGGCGCGGCT AAATTCATGG GGATGTGCAT TTAGACAAGT CTGCTACACC ACTGTACTAT 8460 GGGAAAATAA CAGCATAGTA CCTGATTGGA ACAACATGAC GTGGCAGGAA TGGGAACAAC 8520 AAACCCGCGA CCTAGAGGCA AATATCAGTA GATCGTTAGA GCAGGCACAA ATCCAACAAG 8580 AGAAAAATAT GTATGAGCTA CAAAAATTAA ATAGCTGGGA TGTTTTTGGC AACTGGTTTG 8640 ATTTAACCTC CTGGATTAAG TATATTCAGT ATGGAGTTTA TGTAATAATA GGAATAATAG 8700 CTTTAAGAAT AGTAATATAT GTAGTACAAT TACTAAGTAG ACTTAGAAAG GGCTATAGGC 8760 CTGTTTTCTC TTCCCCCCCC GGTTATATCC AACAGATCCA TATCCACAAG GACTGGGAAC 8820 AGCCAGACAG AGAAGAAACA GACGAAGACG CCGGAAACAG CATTGGAGAC AGCTCGTGGC 8880 CTTGGCCAAT AGCATATATA CATTTCCTGA TCCGCCAGCT GATTCGCCTC TTGACCGGGC 8940 TATACAGCGT CTGCAAGGAC TTACTATCCA GGAGCTTCCC GACCCTCCAA CTAATCTTCC 9000 AGAGTCTTCA GAGAGCACTA ACAACAATCA GGGACTGGCT GAGACTTACA ATAGCCTACC 9060 TGCAATATGG GTGCGAGTGG ATCCAAGAAG TGCTCCAGGT CCTTGCAAGG ACTACGAGAG 9120 AGACTCTTGC GAGCGCGTGG AGAGACTTGT GGGGGGCAAT GGGACGGATC GGCAGGGGAA 9180 TACTTGCAGT TCCAAGAAGG ATCAGGCAGG GGGCAGAACT TGCCCTCCTG TGAGGGGCAG 9240 CGGTATCAAC AGGGAGACTT TΛTGAACACC CCATGGAGAA CTCCAGCAGC AGGAAGGGAG 9300 GGAACATTGT ACAAGCAACA AAATATGGAT GATGTAGATG CAGATAATGA TAACCTAATA 9360 GGGGTCCCTG TCACACCAAG AGTACCATTA AGGGCAATGA CATATAAGTT GGCAGTAGAT 9420 ATATCACATT TTCTAAATGA AAAGGGGGGA CTGGATGGGA TGTATTACAG TGAGAGAAGA 9480 CATAGAATCT TAGACATATA CATGGAAAAG GAAGAAGGGA TAATTCCAGA TTGGCAGAAC 9540 TATACTCATG GGCCAGGAGT AAGGTACCCA AAGTTCTTTG GGTGGCTATG GAAGCTAGTA 9600 CCAGTAGACG TCCCACAAGG TGAAGAGGAC CACTGCTTAC TACACCCAGC ACAAACAAGC 9660 GGGTCTGATG ACCCTCATGG GGAAACATTA ATGTGGAGGT TTGACCCTAG GCTGGCCTAT 9720 GAGTATACGG CTTTTAATCG ATACCCAGAA GAATTTGGGT ATAAGTCAGG CCTGCCAGAA 9780 GAAGAGTGGA AGGCAAAACT GAAAGCAAGA GGGATACCAT TTAGTTAAAG ACAGGAACAG 9840 CTATATTTGG TCAGAACAGG AAGTAGATGA TGAAACTGCA GGGACTTTCC AGAAGGGGCT 9900 GTAACCAGGG GAGGGACGTG GGAGGAACCG GTGGGGAACG CCCTCATACT TCTGTATAAA 9960 TGTACCCGCT GCTTGCATTG TATTCAGTCG CTCTGCGGAG AGGCTGGCAG ATCGAGCCCT 10020 GGGAGGTTCT CTCCAGCACT AGCAGGTAGA GCCTGGGTGT TCCCTGCTAG ACTCTCACCA 10080 GTACTTGGCC GGTACTGGGC AGACGGCTCC ACGCTTGCTT GCTTAAAGAC CTCTTAATAA 10140 AGCTGCCAGT TAGAAGCAAG TTA 10163 (2) INFORMATION FOR SEQ ID NO:2: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 857 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear ( i i ) MOLECULE TYPE : protein ( ix) FEATURE : (A) NAME/KEY: Protein (B) LOCATION: 1..857 (D) OTHER INFORMATION: /note= "HIV2ENVP" (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: Met Asp Ser Arg Asn Gin Leu Ile Val Ala Ile Leu Leu Thr Ser Ala 1 5 10 15 Cys Leu Ile Tyr Cys Ala Gin Tyr Val Thr Val Phe Tyr Gly lie Pro 20 25 30 Ala Trp Lys Asn Ala Ser Ile Pro Leu Phe Cys Ala Thr Arg Asn Arg 35 40 45 Asp Thr Trp Gly Thr Ile Gin Cys Leu Pro Asp Asn Asp Asp Tyr Gin 50 55 60 Glu Ile Pro Leu Asn Val Thr Glu Ala Phe Asp Ala Trp Asn Asn Thr 65 70 75 80 Val Thr Glu Gin Ala Val Glu Asp Val Trp Asn Leu Phe Glu Thr Ser 85 90 95 Val Lys Pro Cys Val Lys Leu Thr Pro Leu Cys Val Gin Met Glu Cys 100 105 110 Asn Ser Thr Ser Thr Glu Ser Ser Asn Ser Thr Ser Glu Gly Ser Thr 115 120 125 Val Pro Glu Ile Leu Asn Glu Thr Thr Ser Cys Ile Thr Asn Asn Ser 130 135 140 Cys Ser Asp Leu Gly Ser Glu Glu Val Val Asp Cys Arg Phe Asn Met 145 150 155 160 Thr Gly Leu Gin Leu Asp Lys Pro Gin Gin Tyr Ser Glu Thr Trp Tyr 165 170 175 Ser Lys Asp Vat Val Cys Asp Thr Thr Asn Gly Thr Ser Arg Lys Cys 180 185 190 Tyr Met Asn His Cys Asn Thr Ser Val Ile Thr Glu Ser Cys Asp Lys 195 200 205 His Tyr Trp Asp Ala Met Arg Phe Arg Tyr Cys Ala Pro Pro Gly Leu 210 215 220 Cys Leu Leu Arg Cys Asn Asp Thr Asn Tyr Ser Gly Phe Glu Pro Lys 225 230 235 240 Cys Pro Lys Val Val Ala Ala Thr Cys Thr Arg Met Met Glu Thr Gin 245 250 255 Thr Ser Thr Trp Phe Gly Phe Asn Gly Thr Arg Ala Glu Asn Arg Thr 260 265 270 Tyr Ile Tyr Trp His Gly Arg Asp Asn Arg Thr Ile Ile Ser Leu Asn 275 280 285 Thr His Tyr Asn Leu Thr Met His Cys Lys Arg Pro Gly Asn Lys Ser 290 295 300 Val Leu Pro Ile Thr Leu Arg Ser Gly Arg Val Phe His Ser Arg Pro 305 310 315 320 Ile Ile Asn Glu Arg Pro Lys Gin Ala Trp Cys Trp Phe Gly Gly Asp 325 330 335 Trp Lys Lys Ala Met Gin Glu Val Lys Gin Thr Leu Val Lys His Pro 340 345 350 Arg Tyr Arg Gly Thr Asn Asp Thr Gin Lys Ile Asn Phe Thr Gin Pro 355 360 365 Gly Lys Gly Ser Asp Ala Glu Val Val Tyr Met Trp Thr Asn Cys Arg 370 375 380 Gly Glu Phe Leu Tyr Cys Asn Met Thr Arg Phe Leu Asn Trp Ile Glu 385 390 395 400 Asn Arg Ala His Pro Gin Arg Asn Tyr Ala Pro Cys His Ile Arg Gin 405 410 415 Ile Ile Asn Thr Trp His Arg Val Gly Gin Asn Ile Tyr Leu Pro Pro 420 425 430 Arg Glu Gly Glu Leu Val Cys Asn Ser Thr Val Thr Ser Ile Ile Ala 435 440 445 Asn Ile Asp Met Phe Asp Asn Gin Thr Ser Ile Thr Phe Ser Ala Glu 450 455 460 Val Ala Glu Leu Tyr Arg Leu Glu Leu Gly Asp Tyr Lys Leu Val Glu 465 470 475 480 lie Thr Pro Ile Gly Phe Ala Pro Thr Ser Glu Lys Arg Tyr Ser Ser 485 490 495 Ala Pro Gin Arg Asn Lys Arg Gly Val Phe Val Leu Gly Val Leu Gly 500 505 510 Phe Leu Ala Thr Ala Gly Ser Ala Met Gly Ala Ala Ser Leu Thr Leu 515 520 525 Ser Ala His Pro Gly Leu Tyr Trp Ala Gly Ile Val Gin Gin Gin Gin 530 535 540 Gin Leu Leu Asp Val Val Lys Arg Gin Gin Glu Met Leu Arg Leu Thr 545 550 555 560 Val Trp Gly Thr Lys Asn Leu Gin Thr Arg Val Thr Ala Ile Glu Lys 565 570 575 Tyr Leu Arg Asp Gin Ala Arg Leu Asn Ser Trp Gly Cys Ala Phe Arg 580 585 590 Gin Val Cys Tyr Thr Thr Val Leu Trp Glu Asn Asn Ser Ile Val Pro 595 600 605 Asp Trp Asn Asn Met Thr Trp Gin Glu Trp Glu Gin Gin Thr Arg Asp 610 615 620 Leu Glu Ala Asn Ile Ser Arg Ser Leu Glu Gin Ala Gin Ile Gin Gin 625 630 635 640 Glu Lys Asn Met Tyr Glu Leu Gin Lys Leu Asn Ser Trp Asp Val Phe 645 650 655 Gly Asn Trp Phe Asp Leu Thr Ser Trp Ile Lys Tyr Ile Gin Tyr Gly 660 665 670 Val Tyr Val Ile lie Gly Ile Ile Ala Leu Arg Ile Val Ile Tyr Val 675 680 685 Val Gin Leu Leu Ser Arg Leu Arg Lys Gly Tyr Arg Pro Val Phe Ser 690 695 700 Ser Pro Pro Gly Tyr Ile Gin Gin Ile His Ile His Lys Asp Trp Glu 705 710 715 720 Gin Pro Asp Arg Glu Glu Thr Asp Glu Asp Ala Gly Asn Ser Ile Gly 725 730 735 Asp Ser Ser Trp Pro Trp Pro Ile Ala Tyr lie His Phe Leu I e Arg 740 745 750 Gin Leu Ile Arg Leu Leu Thr Gly Leu Tyr Ser Val Cys Lys Asp Leu 755 760 765 Leu Ser Arg Ser Phe Pro Thr Leu Gin Leu Ile Phe Gin Ser Leu Gin 770 775 780 Arg Ala Leu Thr Thr Ile Arg Asp Trp Leu Arg Leu Thr Ile Ala Tyr 785 790 795 800 Leu Gin Tyr Gly Cys Glu Trp Ile Gin Glu Val Leu Gin Val Leu Ala 805 810 815 Arg Thr Thr Arg Glu Thr Leu Ala Ser Ala Trp Arg Asp Leu Trp Gly 820 825 830 Ala Met Gly Arg Ile Gly Arg Gly Ile Leu Ala Val Pro Arg Arg Ile 835 840 845 Arg Gin Gly Ala Glu Leu Ala Leu Leu 850 855 (2) INFORMATION FOR SEQ'ID NO:3: (i) SEQUENCE CHARACTE ISTICS: (A) LENGTH: 521 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..521 (D) OTHER INFORMATION: /note= "HIVGAGP" (xi) SEQUENCE DESCRIPTION: SEQ ID N0:3: Met Gly Ala Arg Ser Ser Val Leu Arg Gly Lys Lys Val Asp Glu Leu 1 5 10 15 Glu Lys Ile Arg Leu Arg Pro Gly Gly Lys Lys Lys Tyr Arg Leu Lys 20 25 30 His Ile Val Trp Ala Ala Asn Glu Leu Gly Lys Phe Gly Leu Ala Glu 35 40 45 Ser Leu Leu Glu Ser Lys Glu Gly Cys Gin Lys Ile Ile Thr Val Leu 50 55 60 Asp Pro Leu Val Pro Thr Gly Ser Glu Asn Leu Lys Ser Leu Phe Asn 65 70 75 80 Thr Val Cys Val Ile Trp Cys Leu His Ala Glu Glu Lys Val Lys Asp 85 90 95 Thr Glu Gly Ala Lys Gin Ile Val Gin Arg His Leu Val Ala Glu Thr 100 105 110 Gly Thr Ala Asp Lys Met Pro Ser Thr Ser Arg Pro Ala Ala Pro Pro 115 120 125 Ser Gly Arg Gly Gly Asn Tyr Pro Val Gin Gin Ile Ala Gly Asn Tyr 130 135 140 Ser His Val Pro Leu Ser Pro Arg Thr Leu Asn Ala Trp Val Lys Leu 145 150 155 160 Val Glu Glu Lys Lys Phe Gly Ala Glu Val Val Pro Gly Phe Gin Ala 165 170 175 Leu Ser Glu Gly Cys Thr Pro Tyr Asp Ile Asn Gin Met Leu Asn Cys 180 185 190 Val Gly Asp His Gin Ala Ala Met Gin Ile Ile Arg Glu Ile Ile Asn 195 200 205 Glu Glu Ala Ala Asp Trp Asp Val Gin His Pro Ile Pro Gly Pro Leu 210 215 220 Pro Ala Gly Gin Leu Arg Glu Pro Arg Gly Ser Asp Ile Ala Gly Thr 225 230 235 240 Thr Ser Thr Val Glu Glu Gin Ile Gin Trp Met Phe Arg Ala Gin Asn 245 250 255 Pro Ile Pro Val Gly Asn Ile Tyr Arg Arg Trp Ile Gin Ile Gly Leu 260 265 270 Gin Lys Cys Val Arg Met Tyr Asn Pro Thr Asn Ile Leu Asp Val Lys 275 280 285 Gin Gly Pro Lys Glu Pro Phe Gin Ser Tyr Val Asp Arg Phe Tyr Lys 290 295 300 Ser Leu Arg Ala Glu Gin Thr Asp Pro Ala Val Lys Asn Trp Met Thr 305 310 315 320 Gin Thr Leu Leu Val Gin Asn Ala Asn Pro Asp Cys Lys Leu Val Leu 325 330 335 Lys Gly Leu Gly Met Asn Pro Thr Leu Glu Glu Met Leu Thr Ala Cys 340 345 350 Gin Gly Ile Gly Gly Pro Gly Gin Lys Ala Arg Leu Met Ala Glu Ala 355 360 365 Leu Lys Glu Ala Leu Ala Pro Ala Pro Ile Pro Phe Ala Ala Ala Gin 370 375 380 Gin Arg Arg Thr Ile Lys Cys Trp Asn Cys Gly Lys Asp Gly His Ser 385 390 395 400 Ala Arg Gin Cys Arg Ala Pro Arg Arg Gin Gly Cys Trp Lys Cys Gly 405 410 415 Lys Ser Gly His Val Met Ala Asn Cys Pro Glu Arg Gin Ala Gly Phe 420 425 430 Leu Gly Ile Gly Pro Trp Gly Lys Lys Pro Arg Asn Phe Pro Val Thr 435 440 445 Arg Val Pro Gin Gly Leu Thr Pro Thr Ala Pro Pro Ala Asp Pro Ala 450 455 460 Ala Asp Leu Leu Glu Lys Tyr Leu Gin Gin Gly Arg Lys Gin Lys Glu 465 470 475 480 Gin Lys Met Arg Pro Tyr Lys Glu Val Thr Glu Asp Leu Leu His Leu 485 490 495 Glu Gin Gly Glu Thr Pro His Lys Glu Ala Thr Glu Asp Leu Leu His 500 505 510 Leu Asn Ser Leu Phe Gly Lys Asp Gin 515 520 (2) INFORMATION FOR SEQ ID N0:4: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 253 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..253 (D) OTHER INFORMATION: /note= "HIV2NEFP" (xi) SEQUENCE DESCRIPTION: SEQ ID N0:4: Met Gly Ala Ser Gly Ser Lys Lys Cys Ser Arg Ser Leu Gin Gly Leu 1 5 10 15 Arg Glu Arg Leu Leu Arg Ala Arg Gly Glu Thr Cys Gly Gly Gin Trp 20 25 30 Asp Gly Ser Ala Gly Glu Tyr Leu Gin Phe Gin Glu Gly Ser Gly Arg 35 40 45 Gly Gin Asn Leu Pro Ser Cys Glu Gly Gin Arg Tyr Gin Gin Gly Asp 50 55 60 Phe Met Asn Thr Pro Trp Arg Thr Pro Ala Ala Gly Arg Glu Gly Thr 65 70 75 80 Leu Tyr Lys Gin Gin Asn Met Asp Asp Val Asp Ala Asp Asn Asp Asn 85 90 95 Leu Ile Gly Val Pro Val Thr Pro Arg Val Pro Leu Arg Ala Met Thr 100 105 110 Tyr Lys Leu Ala Val Asp Ile Ser His Phe Leu Asn Glu Lys Gly Gly 115 120 125 Leu Asp Gly Met Tyr Tyr Ser Glu Arg Arg His Arg Ile Leu Asp lie 130 135 140 Tyr Met Glu Lys Glu Glu Gly Ile Ile Pro Asp Trp Gin Asn Tyr Thr 145 150 155 160 His Gly Pro Gly Val Arg Tyr Pro Lys Phe Phe Gly Trp Leu Trp Lys 165 170 175 Leu Val Pro Val Asp Val Pro Gin Gly Glu Glu Asp His Cys Leu Leu 180 185 190 His Pro Ala Gin Thr Ser Gly Ser Asp Asp Pro His Gly Glu Thr Leu 195 200 205 Met Trp Arg Phe Asp Pro Arg Leu Ala Tyr Glu Tyr Thr Ala Phe Asn 210 215 220 Arg Tyr Pro Glu Glu Phe Gly Tyr Lys Ser Gly Leu Pro Glu Glu Glu 225 230 235 240 Trp Lys Ala Lys Leu Lys Ala Arg Gly Ile Pro Phe Ser 245 250 (2) INFORMATION FOR SEQ ID NO:5: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 1055 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..1055 (D) OTHER INFORMATION: /note= "HIV2POLP" (xi) SEQUENCE DESCRIPTION: SEQ ID N0:5: Lys Thr Gly Leu Leu Glu Met Trp Gin Ile Arg Thr Cys His Gly Lys 1 5 10 15 Leu Pro Arg Lys Thr Gly Trp Phe Phe Arg Asp Trp Pro Met Gly Lys 20 25 30 Glu Ala Ser Gin Leu Pro Arg Asp Pro Ser Pro Ala Gly Ala Asp Thr 35 40 45 Asn Ser Thr Pro Ser Arg Pro Ser Ser Arg Pro Ala Arg Glu Val Leu 50 55 60 Ala Ala Arg Glu Glu Ala Glu Arg Ala Glu Asn Glu Thr Ile Gin Gly 65 70 75 80 Gly Asp Arg Gly Leu * Thr Ala Pro Arg Thr Arg Arg Asp Thr Thr Gin 85 90 95 Arg Gly Asp Arg Gly Phe Ala Ala Pro Gin Phe Ser Leu Trp Lys Arg 100 105 110 Pro Val Val Thr Ala Tyr Val Glu Gly Gin Pro Val Glu Val Leu Leu 115 120 125 Asp Thr Gly Ala Asp Asp Ser Ile Val Ala Gly Ile Glu Leu Gly Ser 130 135 140 Asn Tyr Ser Pro Lys Ile Val Gly Gly Ile Gly Gly Phe Ile Asn Thr 145 150 155 160 Lys Glu Tyr Lys Asn Val Glu Ile Lys Val Leu Asn Lys Lys Val Lys 165 170 175 Ala Thr Ile Met Thr Gly Asp Thr Pro Ile Asn Ile Phe Gly Arg Asn 180 185 190 Ile Leu Thr Ala Leu Gly Met Ser Leu Asn Leu Pro Val Ala Lys Val 195 200 205 Asp Pro Ile Lys Val Ile Leu Lys Pro Gly Lys Asp Gly Pro Lys Val 210 215 220 Arg Gin Trp Pro Leu Thr Lys Glu Lys Ile Glu Ala Leu Lys Glu Ile 225 230 235 240 Cys Glu Lys Met Glu Arg Glu Gly Gin Leu Glu Glu Ala Pro Pro Thr 245 250 255 Asn Pro Tyr Asn Thr Pro Thr Phe Ala Ile Lys Lys Lys Asp Lys Asn 260 265 270 Lys Trp Arg Met Leu Ile Asp Phe Arg Glu Leu Asn Lys Val Thr Gin 275 280 285 Glu Phe Thr Glu Ile Gin Leu Gly Ile Pro His Pro Ala Gly Leu Ala 290 295 300 Lys Lys Arg Arg Ile Thr Val Leu Asp Ile Gly Asp Ala Tyr Phe Ser 305 310 315 320 Ile Pro Leu His Glu Asp Phe Arg Gin Tyr Thr Ala Phe Thr Leu Pro 325 330 335 Thr Val Asn Asn Ala Glu Pro Gly Lys Arg Tyr Ile Tyr Lys Val Leu 340 345 350 Pro Gin Gty Trp Lys Gly Ser Pro Ala Ile Phe Gin His Thr Met Arg 355 360 365 Gin Val Leu Glu Pro Phe Arg Lys Ala Asn Pro Asp Val Ile Leu Val 370 375 380 Gin Tyr Met Asp Asp Ile Leu Ile Ala Ser Asp Arg Thr Asp Leu Glu 385 390 395 400 His Asp Arg Thr Val Leu Gin Leu Lys Glu Leu Leu Asn Gly Leu Gly 405 410 415 Phe Ser Thr Pro Asp Glu Lys Phe Gin Lys Asp Pro Pro Tyr Lys Trp 420 425 430 Met Gly Tyr Glu Leu Trp Pro Thr Lys Trp Lys Leu Gin Lys Ile Gin 435 440 445 Leu Pro Gin Lys Glu Val Trp Thr Val Asn Asp Ile Gin Lys Leu Val 450 455 460 Gly Val Leu Asn Trp Ala Ala Gin Ile Tyr Pro Gly Ile Lys Thr Lys 465 470 475 480 His Leu Cys Arg Leu Ile Arg Gly Lys Met Thr Leu Thr Glu Glu Val 485 490 495 Gin Trp Thr Glu Leu Ala Glu Ala Glu Leu Glu Glu Asn Lys Ile Ile 500 505 510 Leu Ser Gin Glu Gin Glu Gly Cys Tyr Tyr Gin Glu Glu Lys Glu Leu 515 520 525 Glu Ala Thr Val Gin Lys Asp Gin Asp Asn Gin Trp Thr Tyr Lys Ile 530 535 540 His Gin Gly Glu Lys Ile Leu Lys Val Gly Lys Tyr Ala Lys Ile Lys 545 550 555 560 Asn Thr His Thr Asn Gly Val Arg Leu Leu Ala His Val Val Gin Lys 565 570 575 Ile Gly Lys Glu Ala Leu Vat Ile Trp Gly Arg Ile Pro Lys Phe His 580 585 590 Leu Pro Val Glu Arg Glu Thr Trp Glu Gin Trp Trp Asp Asn Tyr Trp 595 600 605 Gin Val Thr Trp Ile Pro Asp Trp Asp Phe Val Ser Thr Pro Pro Leu 610 615 620 Val Arg Leu Ala Phe Asn Leu Val Lys Asp Pro Ile Pro Gly Glu Glu 625 630 635 640 Thr Phe Tyr Thr Asp Gly Ser Cys Asn Arg Gin Ser Lys Glu Gly Lys 645 650 655 Ala Gly Tyr Ile Thr Asp Arg Gly Arg Asp Lys Val Arg Ile Leu Glu 660 665 670 Gin Thr Thr Asn Gin Gin Ala Glu Leu Glu Ala Phe Ala Met Ala Leu 675 680 685 Thr Asp Ser Gly Pro Lys Ala Asn Ile Ile Val Asp Ser Gin Tyr Val 690 695 700 Met Gty Ile Val Ala Gty Gin Pro Thr Glu Ser Glu Ser Lys Leu Val 705 710 715 720 Asn Gin Ile Ile Glu Glu Met Ile Lys Lys Gtu Thr Leu Tyr Val Ala 725 730 735 Trp Val Pro Ala His Lys Gly Ile Gly Gly Asn Gin Glu Val Asp His 740 745 750 Leu Val Ser Gin Gly Ile Arg Gin Vat Leu Phe Leu Glu Lys Ile Glu 755 760 765 Pro Ala Gin Glu Glu His Glu Lys Tyr His Ser Asn Val Lys Glu Leu 770 775 780 Ser His Lys Phe Gly Leu Pro Lys Leu Val Ala Arg Gin Ile Val Asn 785 790 795 800 Thr Cys Ala Gin Cys Gin Gin Lys Gly Glu Ala Ile His Gly Gin Val 805 810 815 Asp Ala Glu Leu Gly Thr Trp Gin Met Asp Cys Thr His Leu Glu Gly 820 825 830 Lys Ile Ile Ile Val Ala Val His Val Ala Ser Gly Phe Ile Glu Ala 835 840 845 Glu Val Ile Pro Gin Glu Thr Gly Arg Gin Thr Ala Leu Phe Leu Leu 850 855 860 Lys Leu Ala Ser Arg Trp Pro Ile Thr His Leu His Thr Asp Asn Gty 865 870 875 880 Ala Asn Phe Thr Ser Gin Glu Val Lys Met Vat Ala Trp Trp Thr Gly 885 890 895 Ile Glu Gin Ser Phe Gly Val Pro Tyr Asn Pro Gin Ser Gtn Gly Val 900 905 910 Vat Glu Ala Met Asn His His Leu Lys Asn Gin Ile Ser Arg Ile Arg 915 920 925 Glu Gin Ala Asn Thr Met Glu Thr Ile Val Leu Met Ala Val His Cys 930 935 940 Met Asn Phe Lys Arg Arg Gly Gly Ile Gly Asp Met Thr Pro Ala Glu 945 950 955 960 Arg Leu Ile Asn Met Ile Thr Thr Glu Gin Glu Ile Gin Phe Leu His 965 970 975 Ala Lys Asn Ser Lys Leu Lys Asn Phe Arg Val Tyr Phe Arg Glu Gly 980 985 990 Arg Asp Gin Leu Trp Lys Gly Pro Gly Glu Leu Leu Trp Lys Gly Asp 995 1000 1005 Gly Ala Val Ile Val Lys Val Gly Thr Asp Ile Lys Ile Val Pro Arg 1010 1015 1020 Arg Lys Ala Lys lie Ile Arg Asp Tyr Gly Gty Arg Arg Glu Val Asp 1025 1030 1035 1040 Ser Ser Ser His Leu Glu Gly Thr Arg Glu Asp Gly Glu Val Ala 1045 1050 1055 (2) INFORMATION FOR SEQ ID NO:6: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 176 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..176 (D) OTHER INFORMATION: /note= "HIV2REVP" (xi) SEQUENCE DESCRIPTION: SEQ ID N0:6: Met Asn Gly Arg Ala Asp Glu Glu Gly Leu Gin Gly Leu Ile Arg Leu 1 5 10 15 Leu His Gin Thr Asp Pro Tyr Pro Gin Gly Leu Gly Thr Ala Arg Gin 20 25 30 Arg Arg Asn Arg Arg Arg Arg Arg Lys Gin His Trp Arg Gin Leu Val 35 40 45 Ala Leu Ala Asn Ser Ile Tyr Thr Phe Pro Asp Pro Pro Ala Asp Ser 50 55 60 Pro Leu Asp Arg Ala Ile Gin Arg Leu Gin Gly Leu Thr Ile Gin Glu 65 70 75 80 Leu Pro Asp Pro Pro Thr Asn Leu Pro Glu Ser Ser Glu Ser Thr Asn 85 90 95 Asn Asn Gin Gly Leu Ala Glu Thr Tyr Asn Ser Leu Pro Ala Ile Trp 100 105 110 Val Arg Val Asp Pro Arg Ser Ala Pro Gly Pro Cys Lys Asp Tyr Glu 115 120 125 Arg Asp Ser Cys Glu Arg Val Gtu Arg Leu Val Gly Gly Asn Gty Thr 130 135 140 Asp Arg Gin Gly Asn Thr Cys Ser Ser Lys Lys Asp Gin Ala Gly Gly 145 150 155 160 Arg Thr Cys Pro Pro Val Arg Gly Ser Gly Ile Asn Arg Glu Thr Leu 165 170 175 (2) INFORMATION FOR SEQ ID N0:7: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 127 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..127 (D) OTHER INFORMATION: /note= "HIV2TATP" (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7: Met Glu Thr Pro Ser Lys Ala Pro Glu Ser Ser Leu Met Ser Cys Asn 1 5 10 15 Glu Pro Ser Ser Cys Thr Ser Glu Gin Asp Val Lys Ser Gin Glu Leu 20 25 30 Ala Lys Gin Gly Glu Arg Leu Leu Ser Gin Leu Tyr Gin Pro Leu Glu 35 40 45 Ala Cys Asn Asn Pro Cys Tyr Cys Lys Lys Cys Cys Tyr His Cys Gin 50 55 60 Leu Cys Phe Leu Lys Lys Gty Leu Gly Ile Cys Tyr Glu Arg Lys Gly 65 70 75 80 Arg Arg Arg Arg Thr Pro Arg Ala His Ser Ser Ser Ala Ser Asp Lys 85 90 95 Ser Ile Ser Thr Arg Thr Gly Asn Ser Gin Thr Gtu Lys Lys Gin Thr 100 105 110 Lys Thr Pro Glu Thr Ala Leu Glu Thr Ala Arg Gly Leu Gly Gin 115 120 125 (2) INFORMATION FOR SEQ ID NO:8: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 215 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..215 (D) OTHER INFORMATION: /note= "HIV2VIFP" (xi) SEQUENCE DESCRIPTION: SEQ ID N0:8: Met Glu Glu Gly Glu Arg Trp Ile Val Val Pro Thr Trp Arg Val Pro 1 5 10 15 Gly Arg Met Glu Lys Trp His Ser Leu Val Lys Tyr Leu Lys His Arg 20 25 30 Thr Lys Asp Leu Glu Gly Val Cys Tyr Val Pro His His Lys Val Gly 35 40 45 Trp Ala Trp Trp Thr Cys Ser Arg Val Ile Phe Pro Leu Gtn Gty Asn 50 55 60 Ser His Leu Glu Ile Gin Ala Tyr Trp Asn Leu Thr Pro Glu Lys Gly 65 70 75 80 Trp Leu Ser Ser Tyr Ala Val Arg Ile Thr Trp Tyr Thr Glu Arg Phe 85 90 95 Trp Thr Asp Val Thr Pro Asp Cys Ala Asp Ser Leu Ile His Ser Thr 100 105 110 Tyr Phe Ser Cys Phe Thr Ala Gly Glu Val Arg Arg Ala Ile Arg Gly 115 120 125 Glu Lys Leu Leu Ser Cys Cys Asn Tyr Pro Gin Ala His Arg Ser Lys 130 135 140 Val Pro Leu Leu Gin Phe Leu Ala Leu Vat Vat Val Gin Gin Asn Gly 145 150 155 160 Arg Pro Gin Lys Asn Ser Thr Thr Arg Lys Arg Trp Arg Ser Asn Tyr 165 170 175 Trp Arg Gly Phe Arg Leu Ala Arg Lys Asp Gly Arg Gly His Lys Gin 180 185 190 Arg Gly Ser Glu Pro Pro Ala Ser Gly Ala Tyr Phe Pro Gly Val Ala 195 200 205 Lys Val Leu Glu Ile Leu Ala 210 215 (2) INFORMATION FOR SEQ ID N0:9: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 105 amino acids (B) TYPE: amino acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: protein (ix) FEATURE: (A) NAME/KEY: Protein (B) LOCATION: 1..105 (D) OTHER INFORMATION: /note= "HIV2VPRP" (xi) SEQUENCE DESCRIPTION: SEQ ID N0:9: Met Thr Glu Ala Pro Ala Glu Phe Pro Pro Glu Asp Glu Thr Pro Pro 1 5 10 15 Arg Gly Pro Gly Asp Glu Trp Val Ile Gly Ile Leu Arg Glu Leu Arg 20 25 30 Glu Glu Ala Leu Lys His Phe Asp Pro Arg Leu Leu Thr Thr Leu Gly 35 40 45 Asn Tyr Ile Cys Ala Arg His Gly Asp Thr Leu Glu Ser Ala Arg Glu 50 55 60 Leu Ile Asn Val Leu Gtn Arg Ala Leu Phe Val His Phe Arg Ala Gly 65 70 75 80 Cys Lys Ile Ser Arg Ile Gly Gin Thr Arg Gly Glu Thr Pro Phe Ser 85 90 95 Ala Ile Pro Thr Pro Arg Gly Met Gin 100 105 (2) INFORMATION FOR SEQ ID NO:10: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 762 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..762 (D) OTHER INFORMATION: /note= "HIV-2NEF." (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10: ATGGGTGCGA GTGGATCCAA GAAGTGCTCC AGGTCCTTGC AAGGACTACG AGAGAGACTC 60 TTGCGAGCGC GTGGAGAGAC TTGTGGGGGG CAATGGGACG GATCGGCAGG GGAATACTTG 120 CAGTTCCAAG AAGGATCAGG CAGGGGGCAG AACTTGCCCT CCTGTGAGGG GCAGCGGTAT 180 CAACAGGGAG ACTTTATGAA CACCCCATGG AGAACTCCAG CAGCAGGAAG GGAGGGAACA 240 TTGTACAAGC AACAAAATAT GGATGATGTA GATGCAGATA ATGATAACCT AATAGGGGTC 300 CCTGTCACAC CAAGAGTACC ATTAAGGGCA ATGACATATA AGTTGGCAGT AGATATATCA 360 CATTTTCTAA ATGAAAAGGG GGGACTGGAT GGGATGTATT ACAGTGAGAG AAGACATAGA 420 ATCTTAGACA TATACATGGA AAAGGAAGAA GGGATAATTC CAGATTGGCA GAACTATACT 480 CATGGGCCAG GAGTAAGGTA CCCAAAGTTC TTTGGGTGGC TATGGAAGCT AGTACCAGTA 540 GACGTCCCAC AAGGTGAAGA GGACCACTGC TTACTACACC CAGCACAAAC AAGCGGGTCT 600 GATGACCCTC ATGGGGAAAC ATTAATGTGG AGGTTTGACC CTAGGCTGGC CTATGAGTAT 660 ACGGCTTTTA ATCGATACCC AGAAGAATTT GGGTATAAGT CAGGCCTGCC AGAAGAAGAG 720 TGGAAGGCAA AACTGAAAGC AAGAGGGATA CCATTTAGTT AA 762 (2) INFORMATION FOR SEQ ID NO:11: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 648 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..648 (D) OTHER INFORMATION: /note= "HIV-2VIF." (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11: ATGGAGGAAG GCGAGAGGTG GATAGTAGTT CCCACTTGGA GGGTACCAGG GAGGATGGAG 60 AAGTGGCATA GCCTTGTCAA GTATCTAAAA CACAGAACAA AAGATCTGGA AGGGGTGTGC 120 TATGTTCCCC ACCATAAGGT GGGATGGGCA TGGTGGACTT GCAGCAGGGT AATATTCCCA 180 TTACAAGGAA ATAGTCACCT AGAGATACAG GCATATTGGA ACCTAACACC AGAAAAAGGA 240 TGGCTCTCCT CTTATGCAGT AAGAATAACC TGGTATACAG AGAGGTTCTG GACAGATGTT 300 ACCCCAGACT GTGCAGACTC CCTAATACAT AGCACTTATT TCTCTTGTTT TACGGCGGGT 360 GAAGTAAGAA GAGCCATCAG AGGGGAAAAG TTACTGTCCT GCTGCAATTA CCCCCAAGCC 420 CATAGATCTA AGGTACCGTT ACTCCAATTT CTGGCCTTAG TAGTAGTGCA ACAAAATGGC 480 AGACCCCAGA AAAACAGTAC CACCAGGAAA CGGTGGCGAA GTAACTATTG GAGAGGCTTT 540 CGCTTGGCTA GAAAGGATGG TAGAGGCCAT AAACAGAGAG GCAGTGAACC ACCTGCCTCG 600 GGAGCTTATT TTCCAGGTGT GGCAAAGGTC CTGGAGATAC TGGCATGA 648 (2) INFORMATION FOR SEQ ID NO:12: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 1070 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..1070 (D) OTHER INFORMATION: /note= "HIV25LTR." (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12: TGGATGGGAT GTATTACAGT GAGAGAAGGA CATAGAATCT TAGACATATA CATGGAAAAG 60 GAAGAAGGGA TAATTCCAGA TTGGCAGAAC TATACTCATG GGCCAGGAGT AAGGTACCCA 120 AAGTTCTTTG GGTGGCTATG GAAGCTAGTA CCAGTAGACG TCCCACAAGG TGAAGAGGAC 180 CACTGCTTAC TACACCCAGC ACAAACAAGC GGGTCTGATG ACCCTCATGG GGAAACATTA 240 ATGTGGAGGT TTGACCCTAG GCTGGCCTAT GAGTATACGG CTTTTAATCG ATACCCAGAA 300 GAATTTGGGT ATAAGTCAGG CCTGCCAGAA GAAGAGTGGA AGGCAAAACT GAAAGCAAGA 360 GGGATACCAT TTAGTTAAAG ACAGGAACAG CTATATTTGG TCAGAACAGG AAGTAGATGA 420 TGAAACTGCA GGGACTTTCC AGAAGGGGCT GTAACCAGGG GAGGGACGTG GGAGGAACCG 480 GTGGGGAACG CCCTCATACT TCTGTATAAA TGTACCCGCT GCTTGCATTG TATTCAGTCG 540 CTCTGCGGAG AGGCTGGCAG ATCGAGCCCT GGGAGGTTCT CTCCAGCACT AGCAGGTAGA 600 GCCTGGGTGT TCCCTGCTAG ACTCTCACCA GTACTTGGCC GGTACTGGGC AGACGGCTCC 660 ACGCTTGCTT GCTTAAAGAC CTCTTAATAA AGCTGCCAGT TAGAAGCAAG TTAAGTGTGT 720 GTTCCCATCT CTCCTAGTCG CCGCCTGGTC ATTCGGTGTT CACCTAAGTG ACAAGACCCT 780 GGTCTGTTAG GACCCTTCTT GCTTTGGGGA ACCGAAGCGG GAAAATACCT AGCAGATTGG 840 CGCCCGAACA GGACTTGAAG GAGACTGGAA CACGGCTGAG TGAAGGCAGT AAGGGCGGCA 900 GGAACAAACC ACGACGGAGT GCTCCTAGAA AGGCGCGGGC CGAGGTACCA AAGGCGGCGT 960 GTGGAGCGGG AGTAAAGAGG CCTCCGGGTG AAGGTAAGTA CCTACACCAA AAACTGTAGC 1020 CAGAAAAAGG CTTGTTATCC TACCTTTAGA CAGGTAGAAG ATTGTGGGAG 1070 (2) INFORMATION FOR SEQ ID NO:13: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 2574 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..2574 (D) OTHER INFORMATION: /note= "HIV2ENV." (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13: ATGGATAGTA GAAATCAGCT AATTGTTGCC ATTTTACTAA CTAGTGCTTG CTTAATATAT 60 TGCGCCCAAT ATGTGACTGT TTTCTATGGC ATACCCGCGT GGAAGAATGC ATCCATTCCC 120 CTCTTTTGTG CAACCAGAAA TAGAGATACT TGGGGAACCA TACAGTGCTT GCCAGACAAT 180 GATGATTATC AGGAAATACC TTTAAATGTG ACAGAGGCTT TTGACGCATG GAACAATACA 240 GTAACAGAAC AAGCAGTAGA AGATGTCTGG AATCTATTTG AGACATCAGT AAAACCATGT 300 GTCAAATTAA CACCCTTATG TGTGCAAATG GAATGTAACA GCACAAGTAC AGAGAGCAGT 360 AACAGCACAA GTGAGGGGAG CACAGTCCCA GAGATATTAA ACGAAACTAC TTCATGCATA 420 ACCAACAACA GCTGCTCAGA TTTAGGGAGT GAAGAGGTAG TCGATTGTCG GTTCAATATG 480 ACAGGACTAC AACTAGATAA GCCACAGCAA TATAGTGAAA CATGGTACTC AAAGGATGTA 540 GTTTGTGACA CAACTAATGG GACCAGCCGC AAATGTTACA TGAACCATTG CAACACATCA 600 GTCATCACAG AGTCATGTGA TAAGCACTAT TGGGATGCTA TGAGGTTTAG ATACTGTGCA 660 CCACCGGGTT TATGCTTGCT AAGATGCAAT GATACCAATT ATTCAGGCTT TGAGCCCAAG 720 TGTCCTAAAG TAGTAGCTGC TACATGCACA AGAATGATGG AAACGCAAAC TTCTACTTGG 780 TTTGGCTTTA ATGGCACTAG GGCAGAAAAT AGAACATATA TCTATTGGCA TGGTAGAGAT 840 AATAGGACTA TTATCAGCTT AAATACACAT TATAATCTCA CAATGCATTG TAAGAGGCCA 900 GGAAATAAGT CAGTTTTGCC AATAACACTT AGGTCAGGGA GAGTGTTTCA CTCCCGACCG 960 ATCATCAATG AAAGACCCAA GCAGGCATGG TGCTGGTTCG GAGGTGATTG GAAGAAAGCC 1020 ATGCAGGAGG TGAAACAAAC CCTTGTGAAA CATCCCAGGT ATAGAGGAAC CAACGACACA 1080 CAGAAAATTA ACTTTACACA ACCAGGAAAA GGTTCAGATG CAGAAGTGGT ATACATGTGG 1140 ACTAACTGCA GAGGAGAATT TCTATACTGC AACATGACTC GGTTCCTCAA TTGGATAGAA 1200 AACAGGGCAC ACCCACAGCG CAATTATGCA CCGTGCCATA TAAGGCAAAT AATTAATACC 1260 TGGCATAGAG TAGGCCAAAA TATATTTG CCTCCTAGGG AAGGGGAATT GGTCTGCAAC 1320 TCAACAGTAA CCAGCATAAT TGCTAACATT GACATGTTTG ATAACCAGAC AAGCATTACC 1380 TTTAGTGCAG AGGTGGCAGA ACTATACCGA TTGGAATTGG GAGATTACAA ATTAGTAGAA 1440 ATAACACCAA TTGGCTTCGC ACCTACATCA GAAAAAAGGT ATTCCTCTGC TCCACAGAGG 1500 AATAAAAGAG GTGTGTTTGT GCTAGGAGTC TTGGGTTTTC TCGCAACAGC AGGTTCTGCA 1560 ATGGGCGCGG CGTCCTTGAC GCTGTCGGCT CATCCCGGAC TTTACTGGGC TGGGATAGTG 1620 CAGCAACAGC AACAGCTGTT GGACGTGGTC AAGAGACAAC AAGAAATGTT GCGACTGACC 1680 GTCTGGGGAA CAAAAAATCT CCAGACAAGA GTCACTGCTA TCGAGAAATA CCTAAGGGAC 1740 CAGGCGCGGC TAAATTCATG GGGATGTGCA TTTAGACAAG TCTGCTACAC CACTGTACTA 1800 TGGGAAAATA ACAGCATAGT ACCTGATTGG AACAACATGA CGTGGCAGGA ATGGGAACAA 1860 CAAACCCGCG ACCTAGAGGC AAATATCAGT AGATCGTTAG AGCAGGCACA AATCCAACAA 1920 GAGAAAAATA TGTATGAGCT ACAAAAATTA AATAGCTGGG ATGTTTTTGG CAACTGGTTT 1980 GATTTAACCT CCTGGATTAA GTATATTCAG TATGGAGTTT ATGTAATAAT AGGAATAATA 2040 GCTTTAAGAA TAGTAATATA TGTAGTACAA TTACTAAGTA GACTTAGAAA GGGCTATAGG 2100 CCTGTTTTCT CTTCCCCCCC CGGTTATATC CAACAGATCC ATATCCACAA GGACTGGGAA 2160 CAGCCAGACA GAGAAGAAAC AGACGAAGAC GCCGGAAACA GCATTGGAGA CAGCTCGTGG 2220 CCTTGGCCAA TAGCATATAT ACATTTCCTG ATCCGCCAGC TGATTCGCCT CTTGACCGGG 2280 CTATACAGCG TCTGCAAGGA CTTACTATCC AGGAGCTTCC CGACCCTCCA ACTAATCTTC 2340 CAGAGTCTTC AGAGAGCACT AACAACAATC AGGGACTGGC TGAGACTTAC AATAGCCTAC 2400 CTGCAATATG GGTGCGAGTG GATCCAAGAA GTGCTCCAGG TCCTTGCAAG GACTACGAGA 2460 GAGACTCTTG CGAGCGCGTG GAGAGACTTG TGGGGGGCAA TGGGACGGAT CGGCAGGGGA 2520 ATACTTGCAG TTCCAAGAAG GATCAGGCAG GGGGCAGAAC TTGCCCTCCT GTGA 2574 (2) INFORMATION FOR SEQ ID NO:14: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 3168 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..3168 (D) OTHER INFORMATION: /note= "HIV2POL." (xi) SEQUENCE DESCRIPTION: SEQ ID NO:14: AAGACAGGGC TGCTGGAAAT GTGGCAAATC AGGACATGTC ATGGCAAACT GCCCAGAAAG 60 ACAGGCTGGT TTTTTAGGGA TTGGCCCATG GGGAAAGAAG CCTCGCAACT TCCCCGTGAC 120 CCGAGTCCCG CAGGGGCTGA CACCAACAGC ACCCCCAGCA GACCCAGCAG CAGACCTGCT 180 AGAGAAGTAC TTGCAGCAAG GGAGGAAGCA GAAAGAGCAG AAAATGAGAC CATACAAGGA 240 GGTGACAGAG GACTTACTGC ACCTCGAACA AGGAGAGACA CCACACAAAG AGGCGACAGA 300 GGATTTGCTG CACCTCAATT C7CTCTTTGG AAAAGACCAG TAGTCACAGC ATATGTTGAG 360 GGTCAGCCAG TAGAAGTCTT ACTAGACACA GGGGCTGACG ACTCAATAGT AGCAGGAATA 420 GAGTTGGGGA GCAATTATAG TCCAAAAATA GTAGGGGGAA TAGGGGGATT CATAAACACC 480 AAGGAATATA AAAATGTAGA AATAAAAGTA CTAAATAAAA AGGTAAAAGC CACCATAATG 540 ACAGGTGATA CCCCAATCAA CATTTTTGGC AGAAACATTC TGACAGCCTT AGGCATGTCA 600 TTAAATCTAC CAGTCGCCAA GGTAGACCCG ATAAAAGTAA TACTGAAACC AGGAAAAGAT 660 GGACCAAAAG TAAGACAATG GCCTCTAACA AAAGAAAAGA TAGAGGCACT AAAAGAAATC 720 TGTGAAAAAA TGGAAAGAGA AGGCCAGCTA GAGGAAGCTC CCCCAACTAA TCCTTATAAT 780 ACCCCCACAT TTGCAATTAA GAAAAAGGAC AAAAACAAAT GGAGAATGCT AATAGATTTT 840 AGAGAACTAA ATAAGGTAAC TCAAGAGTTC ACAGAAATTC AGTTAGGAAT TCCACACCCA 900 GCAGGATTAG CCAAGAAAAG AAGAATTACT GTACTAGATA TAGGGGATGC CTACTTTTCC 960 ATACCACTAC ATGAGGACTT TAGACAATAT ACTGCATTTA CTCTACCAAC AGTGAACAAT 1020 GCAGAACCAG GAAAGAGATA TATATATAAA GTCCTACCAC AGGGATGGAA AGGATCGCCA 1080 GCAATTTTTC AACACACAAT GAGGCAGGTC TTAGAGCCAT TCAGAAAAGC AAACCCAGAC 1140 GTCATTCTCG TCCAATATAT GGATGATATC TTAATAGCTA GCGACAGGAC AGACTTAGAG 1200 CATGACAGAA CGGTCCTGCA GTTAAAAGAA CTTTTAAATG GCCTAGGATT CTCCACCCCA 1260 GATGAGAAGT TCCAAAAAGA CCCCCCATAC AAATGGATGG GCTATGAACT ATGGCCAACC 1320 AAATGGAAGC TGCAAAAAAT ACAATTGCCC CAAAAAGAAG TATGGACAGT CAATGACATC 1380 CAAAAGCTAG TAGGTGTCCT AAATTGGGCA GCACAAATCT ACCCAGGGAT AAAGACCAAA 1440 CACTTATGTA GGCTAATTAG AGGAAAAATG ACACTCACGG AAGAAGTACA GTGGACAGAA 1500 CTAGCAGAGG CAGAACTAGA AGAGAACAAA ATTATCTTGA GCCAGGAACA GGAGGGATGC 1560 TATTACCAAG AAGAAAAGGA ATTAGAAGCA ACAGTCCAAA AGGATCAAGA CAATCAGTGG 1620 ACATATAAAA TACACCAAGG AGAGAAAATC CTAAAAGTAG GAAAATATGC AAAGATAAAA 1680 AATACCCATA CCAATGGGGT CAGATTGTTA GCACATGTAG TTCAAAAAAT AGGAAAAGAA 1740 GCACTAGTCA TTTGGGGACG AATACCAAAA TTTCACCTAC CAGTAGAAAG AGAAACCTGG 1800 GAGCAGTGGT GGGATAACTA TTGGCAAGTG ACATGGATCC CAGACTGGGA CTTCGTATCT 1860 ACTCCACCAC TGGTCAGGTT AGCATTTAAC CTAGTAAAAG ATCCCATACC AGGTGAAGAG 1920 ACCTTCTACA CAGATGGATC CTGTAATAGG CAATCAAAAG AGGGAAAAGC AGGATATATA 1980 ACAGATAGAG GGAGAGACAA GGTAAGGATA TTGGAGCAAA CTACCAATCA GCAAGCAGAA 2040 TTAGAAGCCT TCGCAATGGC ATTAACAGAC TCAGGTCCAA AAGCCAATAT TATAGTAGAC 2100 TCACAGTATG TAATGGGAAT AGTAGCGGGC CAGCCAACAG AATCAGAGAG TAAACTAGTA 2160 AACCAAATCA TAGAAGAAAT GATAAAAAAG GAAACACTCT ATGTTGCATG GGTCCCAGCC 2220 CACAAAGGCA TAGGAGGAAA TCAGGAAGTA GATCATTTAG TAAGTCAGGG CATTAGACAA 2280 GTATTATTCC TAGAAAAAAT AGAGCCCGCT CAGGAAGAAC ATGAGAAATA TCATAGCAAT 2340 GTAAAAGAAT TATCCCATAA ATTTGGACTG CCCAAACTAG TGGCAAGACA AATAGTAAAC 2400 ACATGTGCCC AATGTCAACA GAAAGGGGAA GCTATACATG GGCAAGTAGA TGCAGAACTG 2460 GGCACTTGGC AAATGGACTG CACACACTTA GAGGGAAAAA TCATTATAGT AGCAGTACAT 2520 GTTGCAAGCG GGTTTATAGA AGCAGAAGTT ATCCCACAGG AAACGGGAAG GCAAACAGCA 2580 CTCTTCCTAT TAAAACTGGC CAGTAGGTGG CCAATAACAC ACCTGCACAC AGATAATGGT 2640 GCCAACTTCA CCTCACAGGA AGTAAAGATG GTAGCGTGGT GGACAGGTAT AGAACAATCC 2700 TTTGGAGTAC CTTACAATCC ACAAAGCCAA GGAGTAGTAG AAGCAATGAA TCACCACTTA 2760 AAAAACCAGA TAAGCAGAAT TAGAGAGCAG GCAAATACAA TGGAAACAAT AGTATTAATG 2820 GCAGTTCATT GCATGAATTT TAAAAGAAGG GGAGGAATAG GGGATATGAC CCCAGCAGAA 2880 AGACTAATCA ATATGATCAC CACAGAACAA GAAATACAAT TCCTCCACGC AAAAAATTCA 2940 AAATTAAAAA ATTTCCGGGT CTATTTCAGA GAAGGCAGAG ATCAGCTGTG GAAAGGACCT 3000 GGGGAACTAC TGTGGAAGGG AGATGGAGCA GTCATAGTCA AGGTAGGGAC AGACATAAAA 3060 ATAGTGCCAA GAAGGAAAGC TAAGATCATC AGAGACTATG GAGGAAGGCG AGAGGTGGAT 3120 AGTAGTTCCC ACTTGGAGGG TACCAGGGAG GATGGAGAAG TGGCATAG 3168 (2) INFORMATION FOR SEQ ID NO:15: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 531 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..531 (D) OTHER INFORMATION: /note= "HIV2REV." (xi) SEQUENCE DESCRIPTION: SEQ ID NO:15: ATGAACGGAA GGGCAGACGA AGAAGGACTC CAAGGGCTCA TTCGTCTTCT GCATCAGACA 60 GATCCATATC CACAAGGACT GGGAACAGCC AGACAGAGAA GAAACAGACG AAGACGCCGG 120 AAACAGCATT GGAGACAGCT CGTGGCCTTG GCCAATAGCA TATATACATT TCCTGATCCG 180 CCAGCTGATT CGCCTCTTGA CCGGGCTATA CAGCGTCTGC AAGGACTTAC TATCCAGGAG 240 CTTCCCGACC CTCCAACTAA TCTTCCAGAG TCTTCAGAGA GCACTAACAA CAATCAGGGA 300 CTGGCTGAGA CTTACAATAG CCTACCTGCA ATATGGGTGC GAGTGGATCC AAGAAGTGCT 360 CCAGGTCCTT GCAAGGACTA CGAGAGAGAC TCTTGCGAGC GCGTGGAGAG ACTTGTGGGG 420 GGCAATGGGA CGGATCGGCA GGGGAATACT TGCAGTTCCA AGAAGGATCA GGCAGGGGGC 480 AGAACTTGCC CTCCTGTGAG GGGCAGCGGT ATCAACAGGG AGACTTTATG A 531 (2) INFORMATION FOR SEQ ID N0:16: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 78 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single (D) TOPOLOGY: linear (ii) MOLECULE TYPE: DNA (genomic) (ix) FEATURE: (A) NAME/KEY: - (B) LOCATION: 1..78 (D) OTHER INFORMATION: /note= "HIV2REV1." (xi) SEQUENCE DESCRIPTION: SEQ ID N0:16: ATGAACGGAA GGGCAGACGA AGAAGGACTC CAAGGGCTCA TTCGTCTTCT GCATCAGACA 60 AGTGAGTATA ATGGATAG 78 Sequence Id No. 17 -gca-agc-ttg-gga-tgg-gat-gta-tta-cag- Sequence Id No. 18 -cca-agc-ttc-tgc-tag-gta-ttt-tcc-cgc-t- Sequence Id No. 19 GR72 (outside, left) 5'-ATG-TGG- ACT-AAC-TGC-AGA-GGA-GAA-T-3' , Sequence Id No. 20. GR81 (outside, right): 5'-ATC-CAG-GAG-GTT-AAA-TCA-AAC-CAG-T-3' , Sequence Id No. 21 GR7 (inside, left): 5'-GGG-ATC-GAT-TGA-AAT-AAC-ACC-AAT-TGG-CTT-CG-3', Sequence Id No. 22 GR8 (inside, right): 5'-GGG-ATC-GAT-CAT-AGT-ACA-GTG-GTG-TAG-CAG-AC-3' Sequence Id. No. 23 NEF9216 (outside, left): 5'-CCA-GCT-GAT-TCG-CCT-CTT-G-3' , Sequence Id No. 24 NEF10018 (outside, right): 5'-CCT-TCT-GGA- AAG-TCC-CTG-C-3' , Sequence Id No. 25 NEF253 (inside, left): 5'-AAC-AAA-ATA-TGG -ATG-ATG-TAG-ATG-C-3' Sequence Id No. 26 NEF360 (inside, right): 5'-TAG-AAA-ATG-TGA-TAT-ATC-TAC-TGC-C-3' .

Claims: WHAT IS CLAIMED IS: 1. An isolated HIV-2 provims comprising a full-length HIV-2 genome, wherein: the rev gene encoded by the provims hybridizes to the second exon of the HIV-2 KR rev gene as described in SEQ ID NO: l under stringent conditions; the proviral LTR has an activating deletion; and, the proviral LTR has high basal activity. 2. The HIV-2 provims of claim 1 , wherein the provims is encapsidated in an HIV viral particle. 3. The HIV-2 provims of claim 1 , wherein the HIV-2 provims comprises a sequence selected from the sequence of SEQ ID NO: l and conservatively modified variations thereof. 4. An isolated polypeptide encoded by the provims of claim 1. 5. A polypeptide encoded by the HIV-2 KR provims of claim 3. 6. A recombinant cell which comprises the provims of claim 1. 7. A mammal which comprises the provims of claim 1. 8. An immunogenic composition comprising the provims of claim 1. 9. A pharmaceutical composition comprising the HIV-2 provims of claim 1. 10. A vaccine comprising the HIV-2 provims of claim 1 , wherein said vaccine, when administered in a therapeutically effective amount, prevents infection of a mammal by an HIV vims. 11. An HIV-2 provims comprising a full-length HIV-2 genome, wherein: the provims when encapsidated in an HIV viral particle encoded by the provims, is replication competent in vitro in Molt-4/8 cells; the provims is infectious in primary human and macaque lymphocytes when encapsidated in an HIV viral particle; the provims, when encapsidated in an HIV viral particle encoded by the provims, has reduced infectivity for macaque peripheral blood mononuclear cells compared to HIV-2 NIHZ and HIV-2 rod ; the provims, when encapsitated in an HIV viral particle encoded by the provims, produces an attenuated infection in M. nemestrina; the provims, when encapsitated in an HIV viral particle encoded by the provims, produces an infection in Hu-PBL-SCID mice; the second exon of the rev gene encoded by the provims encodes an amino acid sequence 180 amino acids in length; the proviral LTR has an activating deletion; and, the proviral LTR has high basal activity. 12. An isolated nucleic acid comprising a subsequence of the HIV- 2 KR provims, wherein said subsequence is selected from the group of HIV-2 KR nucleic acid sequences consisting of 30 contiguous nucleotides from the HIV-2 KR genome, wherein the isolated nucleic acid binds to an HIV-2 KR proviral nucleic acid under highly stringent conditions. 13. The isolated nucleic acid of claim 11 , wherein said subsequence encodes a region of the HIV-2 KR provims selected from the group consisting of the HIV-2 KR 3' LTR, the HIV-2 KR 5' LTR, the HIV-2 KR env gene, the HIV-2 KR nef gene, the HIV-2 KR rev gene, the HIV-2 KR vpx gene, the HIV-2 KR tat gene, the HIV- 2 KR gag gene, the HIV-2 KR /?Ø/ gene, the HIV-2 KR vt/gene, the HIV-2 KR packaging site, and the HIV-2 KR vpr gene. 14. A recombinant nucleic acid comprising the sequence of SEQ ID NO: 12. 15. A high efficiency HIV-2 packaging vector comprising a first high efficiency packaging vector nucleic acid, which first high efficiency packaging vector nucleic acid encodes a first portion of an HIV-2 particle, wherein the encoded HIV-2 particle is non-vimlent; the first high efficiency packaging vector nucleic acid, when transfected into a cell, renders the cell competent to package HIV-2 packagable RNA with a titre of at least 1 X 10" transducing units per ml, wherein the HIV-2 packagable RNA comprises an HIV packaging site; and, the first high efficiency packaging vector nucleic acid comprises a deletion in the HIV-2 psi region as compared to a wild-type genomic HIV-2 nucleic acid. 16. The high efficiency packaging vector of claim 15, wherein the vector is derived from HIV-2 KR . 17. The high efficiency packaging vector of claim 15, wherein the vector is derived from HIV-2 KR by deleting 61 bp from the HIV-2 KR psi site. 18. The high efficiency packaging vector of claim 15, wherein the high efficiency packaging vector is selected from the group of packaging vectors consisting of pEP32, pEP40, pEP41, pEP42, and pEP43. 19. The vector of claim 15, wherein the cell transduced by the high efficiency packaging vector comprises a second high efficiency packaging vector nucleic acid, which second high efficiency packaging vector nucleic acid encodes a second portion of an HIV-2 particle, wherein the first and second high efficiency packaging vector nucleic acids are complementary. 20. An HIV-2 packaging cell line comprising tiie recombinant packaging vector of claim 15, wherein the packaging cell line is stable and non- virulent. 21. The packaging cell line of claim 21 , wherein the recombinant packaging vector is derived from HIV-2 KR . 22. The packaging cell line of claim 21 , wherein the cell further comprises a nucleic acid encoding a VSV-G protein. 23. The packaging cell line of claim 21, wherein the cell further comprises an HIV-2 packagable nucleic acid. 24. An HIV-2 particle comprising an HIV-2 packagable RNA, wherein the packagable RNA encodes an HIV-2 packaging sequence and does not encode one or more complete HIV-2 genes selected from the group of trans- active HIV-2 genes consisting of gag, pol, vif, vpx, vpr, env, rev, tat, and nef. 25. The HIV-2 particle of claim 24, wherein the particle further comprises a VSV-G envelope protein. 26. The HIV-2 particle of claim 24, wherein the HIV-2 packaging site is derived from HIV-2 KR . 27. The HIV-2 particle of claim 24, wherein the packagable nucleic acid further comprises an HIV-2 LTR, pl7 subsequence, and HIV-2 RRE subsequence. 28. The HIV-2 particle of claim 27, wherein the HIV-2 LTR, pl7 subsequence and HIV-2 RRE subsequence are derived from HIV-2 KR . 29. The HIV-2 particle of claim 28, wherein the packagable nucleic acid is selected from the group consisting of Beta galactosidase 15.2, and pSPneo. 30. The HIV-2 particle of claim 24, wherein the packagable nucleic acid comprises a nucleic acid which encodes a detectable label.

Inventors: KRAUS GUNTER, POESCHLA ERIC, TALBOTT RANDY, WONG-STAAL FLOSSIE, KRAUS, GUNTER, POESCHLA, ERIC, TALBOTT, RANDY, WONG-STAAL, FLOSSIE
Applicants: UNIV CALIFORNIA, THE REGENTS OF THE UNIVERSITY OF CALIFORNIA
Application year: 1996
Main classification: C12N7
IPC codes: A61K38, C07K14, C12N7