Patent Publication Number: US-7220826-B1

Title: Expressing gp140 fragment of primary HIV-1 isolate

Description:
REFERENCE TO RELATED APPLICATIONS 
     This application is U.S. National Phase film under 35 USC 1.371 of PCT/CA00/00190 filed Feb. 24, 2000 which is a continuation-in-part of U.S. patent application Ser. No.: 09/256,194 filed Feb. 24, 1999 (now U.S. Pat. No. 6,395,741). 
    
    
     FIELD OF INVENTION 
     The present invention relates to the field of immunology, specifically HIV Vaccine Technology, and, in particular, is concerned with expressing the extracellular fragment of the envelope gene, gp140, of a primary human immunodeficiency virus type 1 (HIV-1) isolate. 
     BACKGROUND OF THE INVENTION 
     Acquired immunodeficiency syndrome (AIDS) is a disease which is the ultimate result of infection with human immunodeficiency virus (HIV). Currently, there is no effective vaccine which can protect the human population from HIV infection and hence the development of an efficacious HIV-vaccine and protocol for administering the same is urgently required. Previously, HIV-1 particles exhaustively inactivated by chemical treatments, a vaccinia vector encoding the whole envelope gene (gp140) of HIV-1, and purified recombinant gp120 have been evaluated as candidate HIV vaccines. Although inactivated HIV-1 virus preparations elicited a T-cell-mediated Delayed-Type Hypersensitivity (DTH) reaction in humans, and vaccinia/gp160 and gp120 recombinant vaccine candidates induced virus neutralizing antibodies, none of these immunogens have been shown to be efficacious human HIV vaccines (ref. 1, throughout this specification, various references are referred to in parenthesis to more fully describe the state of the art to which this invention pertains. Full bibliographic information for each citation is found at the end of the specification, immediately following the claims. The disclosures of these references are hereby incorporated by reference into the present disclosure). The inventors&#39; interest in HIV vaccinology is to develop immunogenic and cost-effective HIV-1 DNA vaccines and consider that their use alone or in conjunction with other forms of HIV-1 vaccine candidates will lead to the elicitation of more effective immune responses against HIV-1. 
     There has previously been described in granted European Patent No. 470,980 and U.S. Pat. No. 5,639,854, assigned to the assignee hereof, the disclosures of which are incorporated herein by reference, inter alia, the identification and characterization of a T-cell epitope of the core protein, p24E, of HIV-1. There has further been described in granted U.S. Pat. Nos. 5,759,769 and 5,795,955, assigned to the assignee hereof, and disclosures of which are incorporated by reference, the use of the T-cell epitope in the construction of immunogenic synthetic HIV-1 chimeric peptides comprising p24E linked to amino acid sequences of different B-cell epitopes of an envelope or core protein of HIV-1. 
     SUMMARY OF THE INVENTION 
     The present effort has turned to design and construction of HIV DNA-based immunogens capable of eliciting cell-mediated immunity (CMI). In this context, the inventors have focused interest on the extracellular envelope fragment, gp140, expressed in a primary HIV-1 isolate, HIV-1 (BX08), for the reason that this protein is rich in motifs restricted to both the murine and human Major Histocompatibility Complex (MHC) class 1 alleles. 
     Immunization with an appropriately constructed immunogen expressing the gp140 protein leads to the generation of peptides with class 1 binding capability to allow the induction of HIV-1-specific CTLs capable of killing virus infected cells to limit infection. 
     The invention described by the inventors is that they have found a plasmid designated, pCMV.gp140.BX08, expressing the gp140 gene under the control of a CMV promotor was immunogenic in BALB/c mice in the elicitation of CTL response directed against multiple epitopes of the gp140 protein that are restricted to different H-2 d  class 1 gene products. It was also found that plasmids based on Semliki Forest Virus (SFV) vectors, namely pMP83, pMP84 and pMP88, also requiring the gp140 gene under the control of a CMV promoter were similarly immunogenic. 
     Accordingly, in one aspect of the present invention, there is provided a vector, comprising a gene encoding the extracellular fragments of gp140 of a primary HIV-1 isolate, preferably BX08, under the control of a promotor for expression of the gene product in a host organism, thereby eliciting a cytotoxic T-cell response. 
     The promotor preferably is the cytomegalovirus promotor. The vector may preferably be a plasmid vector having the identifying characteristics of plasmid pCMV.gp140.BX08, as shown in  FIG. 1 . The vector also may preferably be a plasmid vector having the identifying characteristics of plasmids pMP88, pMP84 or pMP83. 
     The invention further includes an immunogenic composition containing the vector as well as a method of generating a cytotoxic T-cell response to HIV-1 in a host by administering to the host the immunogenic composition provided herein. Such immunogenic composition may be formulated for intramuscular immunization with a suitable carrier or may be formulated for gene gun delivery with gold particles. 
     The invention extends to the vector when used as an immunogen for generating a cytotoxic T-cell response to HIV-1 in a host and to the use of the vector in the manufacture of an immunogen for the generation of a cytotoxic T-cell response to the HIV-1 in a host. 
     The invention further includes certain novel peptides and nucleic acid molecules as set forth below. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  shows details of the elements of plasmid pCMV.gp140.BX08; 
         FIGS. 2A to 2E  show the nucleotide (SEQ ID No: 1) and deduced amino acid sequence (SEQ ID No: 2) of the gp140 open reading frame of the plasmid pCMV.gp140.BX08; 
         FIGS. 3A ,  3 B and  3 C show the effector responses elicited by intramuscular injection of the plasmid, pCMV.gp140.BX08, in BALB/c mice; 
         FIGS. 4A ,  4 B and  4 C show the effector responses elicited by gene gun delivery of the plasmid, pCMV.gp140.BX08, in BALB/c mice; and 
         FIG. 5  is a nucleotide sequence of a BamHI fragment (SEQ ID No: 15) containing the HIV-1, gp140 nucleotide sequence for incorporation into a BamHI site of alphavirus expression vectors. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A DNA immunogen is constructed using recombinant DNA technology to molecularly clone a gene of interest into a plasmid expression vector. A unique feature involving vaccination with a DNA-based immunogen is that, once delivered into a cell, the intracellular production of the immunogen favours the induction of MHC class 1-restricted cytotoxic T-cells as compared to other forms of vaccination involving the use of killed whole cell and formulated sub-unit immunogens, which tend to favour the elicitation of MHC class 2-restricted immuno-regulatory responses in the majority of cases studied (ref. 2). In this context, it is, therefore, favourable to use DNA technology to construct naked DNA immunogens for vaccination purposes in order to optimize the induction of cellular effector response against intracellular organisms, such as viruses as well as certain tumours. The other advantages DNA vaccines offer include: (i) the ease to produce them; and (ii) their stability over a wide temperature range. 
     A common model which has been used recently to predict murine and human CTL antigenic determinants has involved the identification of binding motifs for the respective MHC class 1 molecules from the primary sequences of the native protein molecules (see refs. 3 to 5). Thus, it has been proposed that motifs which are most favoured to bind and lodge into the peptide-binding groove of the H-2D d  gene product is usually 8 to 10 amino acids long. In the majority of cases, these peptides are found to contain anchor residues, such as glycine and proline (GP), at positions 2 and 3 near the amino- (N-) terminus, and either a leucine or phenylalanine at the carboxy- (C-) terminus, which serve to interact with the respective ‘pockets’ of the peptide-binding groove of a membrane-bound H-2D d  molecule. The motifs restricted to the other class 1 allele, K d , of the H-2 d  haplotype were reported to contain a tyrosine at position 2, and could be an isoleucine, valine or leucine at the C-terminus. Studies of the peptides isolated from the human MHC class 1 molecules, HLA-A0201, had similarly revealed that the anchor residues were leucine or methionine at position 2 and valine or leucine at the C-terminus in the majority of cases. 
     The suitability of the HIV-1(BX08) gp140 gene product as a CTL-inducing imnunogen was assessed by prediction algorithms to determine the number of both the murine and human MHC class 1-restricted binding motifs it contained. The amino acid sequences of the binding motifs and the designation of the peptides representing them are shown in Table 1 below. Such peptides are novel and are claimed herein. The presence of binding motifs towards the different H-2 d  restricted class 1 alleles, i.e. D d  and K d , allows the immunogenicity of plasmids, pCMV.gp140.BX08, pMP83, pMP84 and pMP88, expressing gp140 of HIV-1 of the primary isolate, BX08, and constructed as described in the Examples below, to be studied in the inbred mouse strain BALB/c of the H-2 d  haplotype. The elements and restriction sites of plasmid pCMV.gp140.BX08 are shown in  FIG. 1 . The construction of the plasmids pMP83, pMP84 and pMP88 is described in Example 5 below. The nucleotide sequence (SEQ ID No: 1) and the deduced amino acid sequence (SEQ ID No: 2) of the gp140 open reading frame of the plasmid pCMV.gp140.BX08, pMP83, pMP84 and pMP88, is shown in  FIG. 2 , which appear to be unique sequences and are claimed herein along with their complements. 
     The location of several binding motifs against the human MHC class 1 allele, HLA-A0201, as seen in Table 1, implied that, under an appropriate immunization regimen, the plasmid has the potential to elicit CTL response directed to these epitopes in the context of this class 1 molecule in human subjects. 
     The immunogenicity of the plasmid pCMV.gp140.BX08 was studied in BALB/c mice. The results of the study involving three injections of the plasmid at 100.0 μg per dose using the intramuscular route are shown in  FIG. 3 . Upon in vitro re-stimulation of the spleenocytes of the plasmid-immunized animals with irradiated autologous LPS blasts pulsed individually with the D d - and K d -restricted motif containing peptides, namely, CLP-501 and CLP-504 (SEQ ID Nos.: 3, 5), respectively, it was found that CTLs were generated that killed P815 targets presented with the respective peptides ( FIGS. 3A and 3B ). The amino acid sequences of the peptides are shown in Table 1. A comparison of the magnitude of the responses at the same effector to target (E:T) ratio revealed that the D d -restricted response to the CLP-501 peptide is immuno-dominant and that the K d -restricted response to the CLP-504 peptide is sub-dominant. The in vitro re-stimulation leading to the expansion of the effectors was specific because the addition of the same number of irradiated LPS blasts alone (not treated with peptide) did not lead to any generation of effectors in the bulk culture able to kill either of the specific targets tested. The findings that the control group of mice injected with the pCMV vector without the gp140 insert alone failed to generate any of the two sub-populations of CTLs ( FIG. 3C ) confirmed that the plasmid, pCMV.gp 140.BX08, was indeed immunogenic. 
     The pCMV.gp140.BX08 plasmid, when delivered with the gene gun, was similarly found to be immunogenic. The results shown in  FIG. 4  show that following two injections at a dose of 0.7 μg of the plasmid, and using the same in vitro re-stimulation condition described above that CTLs recognizing the CLP-501 and CLP-504 peptides were detected ( FIGS. 4A and 4B ), while no effector response was elicited by the group of animals given the vector, pCMV, alone ( FIG. 4C ). 
     The immunogenicity of the plasmids pMP83, pMP84 and pMP88 was separately studied, delivered intramuscularly, in BALB/c mice, in comparison to pCMV.gp140.BX08, at three different dosage levels, namely 1.0, 10.0 and 100.0 μg of DNA following the above described procedures. The results obtained are contained in Tables II and III below. CTL activation is achieved at significantly lower doses of the alphavirus vectors than with pCMV.gp140.BX08. 
     It is clearly apparent to one skilled in the art, that the various embodiments of the present invention have many applications in the fields of vaccination, diagnosis and treatment of HIV infections. A further non-limiting discussion of such uses is further presented below. 
     Immunogenic compositions, including vaccines, containing the DNA vector may be prepared as injectables, in physiologically-acceptable liquid solutions or emulsions for polynucleotide administration. The DNA vector may be associated with liposomes, such as lecithin liposomes or other liposomes known in the art, as a nucleic acid liposome (for example, as described in WO 93/24640) or the DNA vector may be associated with an adjuvant, as described in more detail below. 
     Liposomes comprising cationic lipids interact spontaneously and rapidly with polyanions, such as DNA and RNA, resulting in liposome/nucleic acid complexes that capture up to 100% of the polynucleotide. In addition, the polycationic complexes fuse with cell membranes, resulting in an intracellular delivery of polynucleotide that bypasses the degradative enzymes of the lysosomal compartment. Published PCT application WO 94/27435 describes compositions for genetic immunization comprising cationic lipids and polynucleotides. 
     Agents which assist in the cellular uptake of nucleic acid, such as calcium ions, viral proteins and other transfection facilitating agents, may advantageously be used with the vector. 
     Polynucleotide immunogenic preparations may also be formulated as microcapsules, including biodegradable time-release particles. Thus, U.S. Pat. No. 5,151,264 describes a particular carrier of a phospholipid/glycolipid/polysaccharide nature that has been termed Bio Vecteurs Supra Moléculaires (BVSM). The particulate carriers are intended to transport a variety of molecules having biological activity in one of the layers thereof. 
     U.S. Pat. No. 5,075,109 describes encapsulation of the antigens trinitrophenylated keyhole limpet hemocyanin and staphylococcal enterotoxin B in 50:50 poly (DL-lactideco-glycolide). Other polymers for encapsulation are suggested, such as poly(glycolide), poly(DL-lactide-co-glycolide), copolyoxalates, polycaprolactone, poly(lactide-co-caprolactone), poly(esteramides), polyorthoesters and poly(8-hydroxybutyric acid), and polyanhydrides. 
     Published PCT application WO 91/06282 describes a delivery vehicle comprising a plurality of bioadhesive microspheres and antigens. The microspheres being of starch, gelatin, dextran, collagen or albumin. This delivery vehicle is particularly intended for the uptake of vaccine across the nasal mucosa. The delivery vehicle may additionally contain and absorption enhancer. 
     In particular embodiments of the present invention, the vector may be delivered in conjunction with a targeting molecule to target the vector to selected cells including cells of the immune system. 
     The vectors may be delivered to the host by a variety of procedures, for example, Tang et al (ref. 6) discloses that introduction of gold microprojectiles coated with DNA encoding bovine growth hormone (BGH) into the skin of mice resulted in production of anti-BGH antibodies in the mice, while Furth et al. (ref. 7) showed that a jet injector could be used to transfect skin, muscle, fat and mammary tissues of living animals. 
     Biological Deposits 
     Certain vectors that contain nucleic acid coding for an extracellular fragment of gp140 of a primary isolate that are described and referred to herein as well as precursor alphavirus vectors have been deposited with the America Type Culture Collection (ATCC) located at 10801 University Boulevard, Manassas, Va. 20110-2209, USA, pursuant the Budapest Treaty and prior to the filing of this application. Samples of the deposited vectors will become available to the public and all restrictions imposed or access to the deposits will be received upon grant of a patent based on this United States patent application. In addition, the deposit will be replaced if viable samples cannot be dispensed by the Depository. The invention described and claimed herein is not limited in scope by the biological materials deposited, since the deposited embodiment is intended only as an illustration of the invention. Any equivalent or similar vectors that contain nucleic acid which encodes equivalent or similar antigens as described in this application are within the scope of the invention. 
     Deposit Summary 
     
       
         
           
               
               
               
               
             
               
                   
                   
               
               
                   
                 Plasmid 
                 ATCC 
                 Deposited Date 
               
               
                   
                   
               
             
            
               
                   
                 pCMV.gp140.BX08 
                 203839 
                 Mar. 9, 1999 
               
               
                   
                 pMP42 
                 203461 
                 Nov. 12, 1998 
               
               
                   
                 pMP76 
                 203462 
                 Nov. 12, 1998 
               
               
                   
                   
               
            
           
         
       
     
     EXAMPLES 
     The above disclosure generally describes the present invention. A more complete understanding can be obtained by reference to the following specific Examples. These Examples are described solely for purposes of illustration and are not intended to limit the scope of the invention. Changes in form and substitution of equivalents are contemplated as circumstances may suggest or render expedient. Although specific terms have been employed herein, such terms are intended in a descriptive sense and not for purposes of limitation. 
     Methods of plasmid construction, peptide synthesis, cell culture, CTL assay and other testing procedures that are not explicitly described in this disclosure are amply reported in the scientific literature and are well within the scope of those skilled in the art. 
     Example 1 
     This Example illustrates the construction of the plasmid, pCMV.gp140.BX08. 
     The plasmid, pCMV.gp140.BX08, contains sequence segments from various sources, and the elements of construction are depicted in  FIG. 1 . The nucleotide (SEQ ID No: 1) and derived amino acid sequences (SEQ ID No: 2) of the gp140 open reading frame of the plasmid are shown in  FIG. 2 . 
     The prokaryotic vector pBluescript SK (Stratagene) is the backbone of the plasmid pCMV.gp140.BX08 and was modified by the replacement of the Amp R  with Kan R  gene and the deletion of the fl and the LacZ regions. To achieve the desired modifications, the sequence between Ahdl (nucleotide 2,041) and Sacl (nucleotide 759) of pBluescript SK, which contains the AmP R , fl origin and the LacZ, was deleted. A 1.2 kb Pstl fragment from the plasmid pUC-4K (Pharmacia) containing the Kan R  gene, was blunt end ligated to the Ahdl site of pBluescript SK in a counter-clockwise orientation relative to it&#39;s transcription. A 1.6 kb Ss/stl DNA fragment containing the human cytomegalovirus immediate-early gene promotor, enhancer and intron A sequences (CMV) was ligated to the other end of the Kan R  gene so that the transcription from the CMV promotor proceeds in the clockwise orientation. A synthetic oligonucleotide segment containing translation initiation sequence and sequences encoding the human tissue plasminogen activator signal peptide (TPA) was used to link the CMV promotor and the sequences encoding the gp140 of the primary isolate HIV-1 BX08 . The gp140 sequence encodes a portion of the envelope protein between amino acid 33 and 666 which ends before the transmembrane domain of gp41 (see  FIG. 2 ). A translation termination codon was placed at the end of the gp140 coding sequence. Next to the gp140 coding region is a 0.2 kb fragment containing the bovine growth hormone (BGH) polyadenylation signal sequence that is PCR amplified from pRC/CMV (Invitrogen). A remnant 80 bp DNA segment from the SV40 polyadenylation signal remained between the BGH poly A sequence and the Sacl site of pbluescript SK due to DNA manipulation and it serves no purpose in this plasmid. 
     The pCMV.gp140.BX08 construct was introduced into HB101 competent cells according to manufacturer&#39;s recommendations (GibcoBRL). Correct molecular clones were identified by restriction and sequencing analysis and their expression of gp140 was examined in transient transfections followed by Western blot analysis. 
     All DNAs used for immunizations were prepared using EndoFree Plasmid Kit (Qiagen). For intramuscular immunizations in mice, 100 μg of pCMV.gp140.BX08, in 100 μl PBS was injected into the tibialis anterior muscles at 4 weeks intervals. Gene gun immunizations were accomplished with the Helios Gene Gun System (Biorad). Cartridges were prepared according to manufacturer&#39;s recommendations. Specifically, each cartridge was made to contain 0.7 μg of the DNA and 0.5 mg gold. Immunizations were carried out by applying two cartridges to each animal onto the shaved abdominal area at 4 week intervals. 
     Example 2 
     This Example illustrates the synthesis of peptides. 
     Solid phase peptide synthesis of peptide CLP-501 and CLP-504 were conducted on an ABI 430A automated peptide synthesizer according to the manufacturer&#39;s standard protocols. The peptides were cleaved from solid support by treatment with liquid hydrogen fluoride in the presence of thiocresole, anisole, and methyl sulfide. The crude products were extracted with trifluoroacetic acid (TFA) and precipitated with diethyl ether. 
     The amino acid sequences of these peptides are shown in Table 1. 
     Example 3 
     This Example illustrates in vitro cell culture protocols to re-stimulate and expand CTLs and assay for their effector functions. 
     Spleens of BALB/c mice injected with the plasmid, pCMV.gp140.BX08, prepared and formulated as described in Example 1, using the intramuscular route or gene gun delivery method, were removed 10 to 11 days post final booster injection. Spleenocytes at 3.0×10 7  were co-cultured with 1.3×10 7  autogolous LPS blasts which had been pulsed with the test peptide for 5 hr at 37° C. and irradiated at 3000 rads in 10.0 ml of complete medium (RPMI 1640 supplemented with 10.0% 56° C. heat-inactivated bovine serum, 120.0 units per ml of penicillin G sodium, 120.0 μg per ml of streptomycin sulphate and 0.35 mg per ml of L-glutamine) in a 25 cm 2  tissue culture flask. The cultures were kept at 37° C. in a humidified CO 2  incubator for days, and the responders were then tested against peptide-pulsed P815 target cells in a standard in vitro 4 hr CTL assay as follows: 
     The responders were harvested from the 7-day cultures and washed once with RPMI 1640 medium without added bovine serum. The positive target was created by incubating 3 to 5×10 6  P815 cells with 100.0 μg of the specified peptide overnight in a 26° C. water bath. The target cells were then labeled with  51 Cr at 250.0 uCi per 1×10 6  cells in the presence of 25.0 μg of the same test peptides for 60 to 75 minutes at 26° C. After washing twice with complete medium to remove excess  51 Cr, the targets were incubated at 2.5×10 3  with different numbers of the responders per well in a V-bottomed 96 will tissue culture plates for 4 hr in a 37° C. CO 2  incubator. Half amount of the supernatant from each micro-assay culture was then removed and counted for radioactivity. Results were expressed as % which was calculated using the equation: % lysis=(spontaneous lysis in cpm of experimental sample−spontaneous lysis in cpm of labeled target cells alone) divided by (total lysis in cpm of target cells alone−spontaneous lysis in cpm of target cells alone)×100. 
     The results obtained employing intramuscular injection are shown in  FIGS. 3A ,  3 B and  3 C while those obtained employing the gene gun delivery are shown in  FIGS. 4A ,  4 B and  4 C. 
     Example 4 
     This Example illustrates the construction of alphavirus expression vectors pMP83, pMP84 and pMP88. 
     DNA vector pCMV.gp140.BX08, prepared as described in Example 1, was digested with restriction endonucleases NbeI and BamHI to release the HIV-1 gp140 sequence. The NheI/BamHI fragment was gel purified and ligated to a synthetic oligonucleotide linker made from the following annealed oligonucleotides: Oligo 1-TPA-1 
     
       
         
           
               
               
               
            
               
                 5′- TCC GGA TCC ACC ATG GAT GCA ATG AAG AGA GGG CTC TGC TGT 
                 (SEQ ID No: 16) 
                   
               
               
                   
               
               
                 GTG CTG CTG CTG TGT GGA GCA GTC TTC GTT TCG G -3′ 
               
               
                   
               
               
                 Oligo 2 - TPA-2 
               
            
           
         
       
     
                            5′- CTA GTC GAA ACG AAG ACT GCT CCA CAC AGC AGC AGC ACA CAG   (SEQ ID No: 17)                   CAG AGC CCT CTC TTC ATT GCA TCC ATG GTG GAT CCG GA -3′            
This ligation restrored the TPA signal sequence. The resulting fragment was restricted with BamHI and the resulting BamHI fragment was gel purified. The nucleotide sequence of the BamHI fragment is shown in  FIG. 5  (SEQ ID No: 15).
 
     After the DNA sequence verification, the BamHI fragment was cut out of the pUC19 vector and ligated into BamHI restricted plasmids pMP42, pMP74 and pMP76 to make plasmids pMP88, pMP84 and pMP83 respectively. 
     Plasmid pMP42, containing the SFV replicon, is described in WO 99/25858 (1038–864), assigned to the applicants and the disclosure of which is incorporated herein by reference and has been deposited with ATCC (203461). The construction of pMP42 is shown in  FIGS. 2A and 2B  of WO 99/25858. 
     Plasmid pMP76, containing the SFV replicon, is described in WO 99/25859 (1038–862), assigned to the applicants and the disclosure of which is incorporated herein by reference and has been deposited with ATCC (203462). The construction of pMP76 is shown in  FIGS. 8A to 8D  of WO 99/25859. 
     Plasmid pMP74, containing the SFV replicon, is identical to pMP76 except that it lacks the rabbit β-globin intron II insertion into the SFV replicon. This plasmid may be constructed by suitable modification to the scheme shown in  FIGS. 8A to 8D  of WO 99/25859. 
     Example 5 
     This Example shows the results of immunizations using the alphavirus vectors. 
     The recombinant alphavirus vectors pMP88, pMP84 and pMP83, prepared as described in Example 4, were employed in comparative immunogenicity studies with plasmid pCMV.gp140.BX08, prepared as described in Example 1, in BALB/c mice following the procedure outlines in Example 1 for intramuscular immunization in mice using pCMV.gp140.BX08 and the CTL assay of Example 3, with unmodified pMP76 and pCMV being employed as negative controls. The results obtained are shown in Table II below. 
     Comparative analysis of the alphavirus constructs and the DNA construct of Example 1 showed similar results in the CTL assay. As expected, the negative control vectors that did not contain the gp140 sequences from HIV-1 BX08 showed no specific lysis in the CTL assay. All three alphavirus replicons, pMP83, pMP84 and pMP88, showed specific lysis as did the vector pCMV.gp140.BX08. The difference between the two types of vector was the amount of immunizing nucleic acid needed to elicit the same response. At 1 μg dose, the alphavirus vectors pMP83 and pMP88 showed comparable responses to pCMV.gp140.BX08 at a much higher dose of 100 μg. 
     These results were confirmed by an vector from a interferon-gamma (IFN-γ) assay, the results of which are shown in Table III. The assay is well known, as the measure of IFN-γ secreted from the spleenocytes indicated activation of the CTLs. Again, the alphavirus vectors showed comparable activation at an approximately 100 fold lower dose than the pCMV.gp140.BX08 vector. Overall these results indicate that immunization with nucleic acid vector expressing the gp140 sequence from the primary isolate BX08 generated MHC Class I restricted cytotoxic T-cells and that the alphavirus expression system used was approximately 100-fold more effective at the lower dose. 
     SUMMARY OF DISCLOSURE 
     In summary of this disclosure, the present invention provides a novel plasmid expressing, in vitro and in vivo, the gp140 protein of the primary HIV-1 isolate BX08 and the generation of MHC class 1-restricted cytotoxic T-cells in animals. Modifications are possible within the scope of this invention. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 MHC class 1-restricted motifs of the extracellular envelope fragment, 
               
               
                 gp140, of HIV-1(BX08) 
               
            
           
           
               
               
            
               
                 H-2 d -restricted* 
                 HLA-A0201-restricted** 
               
            
           
           
               
               
               
               
            
               
                 Pep- 
                   
                 Pep- 
                   
               
               
                 tide*** 
                 D d - 
                 tide*** 
                 K d - 
               
               
                   
               
            
           
           
               
               
               
               
               
            
               
                 CLP- 
                 IGPGRAFYTT 
                 CLP- 
                 AYDTEVHNV 
                 KLTPLCVTL 
               
               
                 501 
                 (274–283) 
                 503 
                 (29–37) 
                 (91–98) 
               
               
                   
                 (SEQ ID No:3) 
                   
                 (SEQ ID No:4) 
                 (SEQ ID No:10) 
               
               
                   
                   
                 CLP- 
                 FYSLKIVPI 
                 TLFRVAIKL 
               
               
                   
                   
                 504 
                 (141–149) 
                 (305–313) 
               
               
                   
                   
                   
                 (SEQ ID No:5) 
                 (SEQ ID No:11) 
               
               
                   
                   
                 CLP- 
                 LYKYKVVKI 
                 TLTVQARQL 
               
               
                   
                   
                 505 
                 (443–451) 
                 (403–411) 
               
               
                   
                   
                   
                 (SEQ ID No:6) 
                 (SEQ ID No:12) 
               
               
                   
                   
                 CLP- 
                 KYKVVKTEPL 
                 TLTVQARAL 
               
               
                   
                   
                 506 
                 (445–454) 
                 (496–504) 
               
               
                   
                   
                   
                 (SEQ ID No:7) 
                 (SEQ ID No:13) 
               
               
                   
                   
                 CLP- 
                 RYLQDQRFL 
                 QLQARVLAL 
               
               
                   
                   
                 507 
                 (545–553) 
                 (535–543) 
               
               
                   
                   
                   
                 (SEQ ID No:8) 
                 (SEQ ID No:14) 
               
               
                   
                   
                 CLP- 
                 NYTEIIYSL 
               
               
                   
                   
                 508 
                 (597–605) 
               
               
                   
                   
                   
                 (SEQ ID No:9) 
               
               
                   
               
               
                 *or **Anchors residues were typed in bolded letters. 
               
               
                 ***Peptides chosen for the study reported herein are bolded. 
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE II 
               
             
            
               
                   
               
               
                 A comparative immunogenicity study of recombinant alpha viruses and 
               
               
                 pCMV.gp140.BX08 expressing gp140 of HIV-1 BX08  in BALB/c mice 
               
            
           
           
               
               
               
            
               
                   
                   
                 % CLP-501 
               
               
                 Immunization 
                   
                 specific lysis 
               
               
                 (3 injections, im) 
                 Dose (μg) 
                 at E:T ratio of 75:1 
               
               
                   
               
            
           
           
               
               
               
            
               
                 pMP76 
                 100.0 
                 0.6 
               
               
                   
                 10.0 
                 0.02 
               
               
                   
                 1.0 
                 0 
               
               
                 pMP83 
                 100.0 
                 23.4 
               
               
                   
                 10.0 
                 38.5 
               
               
                   
                 1.0 
                 42.7 
               
               
                 pMP84 
                 100.0 
                 37.2 
               
               
                   
                 10.0 
                 18.6 
               
               
                   
                 1.0 
                 12.4 
               
               
                 pMP88 
                 100.0 (not done, mice died) 
               
               
                   
                 10.0 
                 39.6 
               
               
                   
                 1.0 
                 49.6 
               
               
                 pCMV3 
                 100.0 
                 0 
               
               
                   
                 10.0 
                 0.06 
               
               
                   
                 1.0 
                 0 
               
               
                 PCMV.gp140.BX08 
                 100.0 
                 59.7 
               
               
                   
                 10.0 
                 29.3 
               
               
                   
                 1.0 
                 0 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
             
               
                 TABLE III 
               
             
            
               
                   
               
               
                 Frequencies of spleenic CLP-501-specific effectors induced by 
               
               
                 recombinant vectors expressing HIV-1 BX08  gp 140 determined by IFN- 
               
               
                 gamma ELISPOT 
               
            
           
           
               
               
               
            
               
                   
                   
                 Number 
               
               
                   
                   
                 of spots scored 
               
               
                 Immunization 
                   
                 per 5 × 10 5  responders 
               
               
                 (3 injections, im) 
                 Dose (μg) 
                 In duplicate cultures 
               
               
                   
               
            
           
           
               
               
               
            
               
                 pMP76 
                 100.0 
                 0, 0 
               
               
                   
                 10.0 
                 0, 0 
               
               
                   
                 1.0 
                 0, 0 
               
               
                 pMP83 
                 100.0 
                 10, 14 
               
               
                   
                 10.0 
                 14, 19 
               
               
                   
                 1.0 
                 18, 13 
               
               
                 pMP84 
                 100.0 
                 7, 12 
               
               
                   
                 10.0 
                 4, 7 
               
               
                   
                 1.0 
                 2, 6 
               
               
                 pMP88 
                 100.0 (not done, mice died) 
               
               
                   
                 10.0 
                 20, 13 
               
               
                   
                 1.0 
                 24, 17 
               
               
                 pCMV3 
                 100.0 
                 0 
               
               
                   
                 10.0 
                 0 
               
               
                   
                 1.0 
                 0 
               
               
                 PCMV.gp140.BX08 
                 100.0 
                 17, 13 
               
               
                   
                 10.0 
                 6, 9 
               
               
                   
                 1.0 
                 0 
               
               
                   
               
            
           
         
       
     
     REFERENCES 
     
         
         1. B. J. Spalding. Biotechnology, vol. 10, pp 24–28, 1992 
         2. H. L. Robinson and C. A. T. Torres. Seminars in Immunology, vol. 9, pp 271–283, 1997. 
         3. Ian A. Wilson and Daved H. Fremont. Seminars in Immunology, vol. 5, pp 75–80, 1993. 
         4. Kristen Falk and Olaf Rotzschke. Seminars in Immunology. Vol. 5, pp 81–94, 1993. 
         5. Victor H. Englefard. Current Opinion in Immunology, Vol. 6, pp 13–23, 1994. 
         6. Tang et al, Nature, 1992, 356:152–154. 
         7. Furth et al, Analytical Biochemistry, 1992, 205:365–368.