T-cell receptor-mediated anergy of a human immunodeficiency virus (HIV) gp120-specific CD4(+) cytotoxic T-cell clone, induced by a natural HIV type 1 variant peptide

Human immunodeficiency virus type 1 (HIV-1) infection triggers a cytotoxic T-lymphocyte (CTL) response mediated by CD8(+) and perhaps CD4(+) CTLs. The mechanisms by which HIV-1 escapes from this CTL response are only beginning to be understood. However, it is already clear that the extreme genetic variability of the virus is a major contributing factor. Because of the well-known ability of altered peptide ligands (APL) to induce a T-cell receptor (TCR)-mediated anergic state in CD4(+) helper T cells, we investigated the effects of HIV-1 sequence variations on the proliferation and cytotoxic activation of a human CD4(+) CTL clone (Een217) specific for an epitope composed of amino acids 410 to 429 of HIV-1 gp120. We report that a natural variant of this epitope induced a functional anergic state rendering the T cells unable to respond to their antigenic ligand and preventing the proliferation and cytotoxic activation normally induced by the original antigenic peptide. Furthermore, the stimulation of Een217 cells with this APL generated altered TCR-proximal signaling events that have been associated with the induction of T-cell anergy in CD4(+) T cells. Importantly, the APL-induced anergic state of the Een217 T cells could be prevented by the addition of interleukin 2, which restored their ability to respond to their nominal antigen. Our data therefore suggest that HIV-1 variants can induce a state of anergy in HIV-specific CD4(+) CTLs. Such a mechanism may allow a viral variant to not only escape the CTL response but also facilitate the persistence of other viral strains that may otherwise be recognized and eliminated by HIV-specific CTLs.     

Human immunodeficiency virus-specific CD8(+) T cells in human breast milk

Breast-feeding infants of human immunodeficiency virus (HIV)-infected women ingest large amounts of HIV, but most escape infection. While the factors affecting transmission risk are poorly understood, HIV-specific cytotoxic T-lymphocyte (CTL) responses play a critical role in controlling HIV levels in blood. We therefore investigated the ability of breast milk cells (BMC) from HIV-infected women from the United States and Zambia to respond to HIV-1 peptides in a gamma interferon enzyme-linked immunospot assay. All (n = 11) HIV-infected women had responses to pools of Gag peptide (range, 105 to 1,400 spot-forming cells/million; mean = 718), 8 of 11 reacted to Pol, 7 reacted to Nef, and 2 of 5 reacted to Env. Conversely, of four HIV-negative women, none responded to any of the tested HIV peptide pools. Depletion and tetramer staining studies demonstrated that CD8(+) T cells mediated these responses, and a chromium-release assay showed that these BMC were capable of lysing target cells in an HIV-specific manner. These data demonstrate the presence of HIV-specific major histocompatibility complex class I-restricted CD8(+) CTLs in breast milk. Their presence suggests a role in limiting transmission and provides a rationale for vaccine strategies to enhance these responses.     

CTL-mediated selective pressure influences dynamic evolution and pathogenic functions of HIV-1 Nef

HIV-1 Nef plays multiple roles in modulating immune responses, even though it is a dominant CTL target itself. How Nef accomplishes the balance between such conflicting selective pressures remains elusive. By genetic and functional studies, we found that Arg75Thr and Tyr85Phe mutations, located in a well-conserved proline-rich region in Nef, were differently associated with escape from CTL responses specific for two overlapping HLA-B35-restricted epitopes. CTLs specific for an epitope, that selected Tyr85Phe, were elicited earlier and had more potent functional avidities than did those that selected Arg75Thr. Although the double mutant could escape from both CTLs, the mutations are rarely observed in combination naturally. Introduction of both mutations reduced Nef's HLA class I down-regulation activity and increased the susceptibility of virus-infected cells to recognition by CTLs targeting other epitopes. Moreover, the mutant Nef was impaired in the association with activated cellular kinases and in the enhancement of viral replication. These results highlight CTL immunosurveillance as important modulators of Nef's biological activity in the infected host.     

Use of Major Histocompatibility Complex Class I/Peptide/β2M Tetramers To Quantitate CD8+ Cytotoxic T Lymphocytes Specific for Dominant and Nondominant Viral Epitopes in Simian-Human Immunodeficiency Virus-Infected Rhesus Monkeys

To evaluate the impact of the diversity of antigen recognition by T lymphocytes on disease pathogenesis, we must be able to identify and analyze simultaneously cytotoxic T-lymphocyte (CTL) responses specific for multiple viral epitopes. Many of the studies of the role of CD8(+) CTLs in AIDS pathogenesis have been done with simian immunodeficiency virus (SIV)- and simian-human immunodeficiency virus (SHIV)-infected rhesus monkeys. These studies have frequently made use of the well-defined SIV Gag CTL epitope p11C,C-M presented to CTL by the HLA-A homologue molecule Mamu-A*01. In the present study we identified and fine mapped two novel Mamu-A*01-restricted CTL epitopes: the SIVmac Pol-derived epitope p68A (STPPLVRLV) and the human immunodeficiency virus type 1 (HIV-1) Env-derived p41A epitope (YAPPISGQI). The frequency of CD8(+) CTLs specific for the p11C,C-M, p68A, and p41A epitopes was quantitated in the same animals with a panel of tetrameric Mamu-A*01/peptide/beta2m complexes. All SHIV-infected Mamu-A*01(+) rhesus monkeys tested had a high frequency of SIVmac Gag-specific CTLs to the p11C,C-M epitope. In contrast, only a fraction of the monkeys tested had detectable CTLs specific for the SIVmac Pol p68A and HIV-1 Env p41A epitopes, and these responses were detected at very low frequencies. Thus, the p11C,C-M-specific CD8(+) CTL response is dominant and the p41A- and p68A-specific CD8(+) CTL responses are nondominant. These results indicate that CD8(+) CTL responses to dominant CTL epitopes can be readily quantitated with the tetramer technology; however, CD8(+) CTL responses to nondominant epitopes, due to the low frequency of these epitope-specific cells, may be difficult to detect and quantitate by this approach.     

HIV-specific cytotoxic cell frequencies measured directly ex vivo by the Lysispot assay can be higher or lower than the frequencies of IFN-gamma-secreting cells: anti-HIV cytotoxicity is not generally impaired relative to other chronic virus responses

CD8(+) T cells in HIV-infected patients are believed to contribute to the containment of the virus and the delay of disease progression. However, the frequencies of HIV-specific CD8(+) T cells, as measured by IFN-gamma secretion and tetramer binding, often do not correlate with a delay in disease progression during chronic infection. Using the Lysispot and ELISPOT assays, we measured the frequencies of cytotoxic and IFN-gamma-secreting T cells responding to overlapping peptides from Gag, Nef, Env, and Pol consensus HIV-1 clade B sequences. PBMC from the majority of HIV-infected subjects have significant frequencies of HIV-specific cells that killed targets within 5 h directly ex vivo. The relative frequencies of IFN-gamma-secreting and cytotoxic cells varied markedly between different HIV peptide pools within the same patient, and some T cells lysed targets without secreting IFN-gamma. These results indicate that measurement of IFN-gamma production alone may be insufficient to evaluate the breadth of the HIV-specific T cell response. Also, neither the CTL to IFN-gamma ratios nor the ex vivo CTL frequencies specific for different HIV proteins were consistently lower than responses specific for two other chronic viral infections, human CMV and EBV, within the same subjects. Thus ex vivo cytotoxic T cell frequencies do not provide evidence for a model of "preterminal differentiation" of HIV-specific CD8(+) T cells during chronic HIV infection. Analysis of the frequency of directly cytotoxic HIV-specific T cells may be of considerable value in the assessment of disease progression and the potential efficacy of HIV vaccines.     

Identification and characterization of HLA-B*5401-restricted HIV-1-Nef and Pol-specific CTL epitopes

The identification of HIV-1 cytotoxic T lymphocyte (CTL) epitopes presented by each HLA allele and the characterization of their CTL responses are important for the study of pathogenesis of AIDS and the development of a vaccine against it. In the present study, we focused on identification and characterization of HIV-1 epitopes presented by HLA-B*5401, which is frequently found in the Asian population, because these epitopes have not yet been reported. We identified these epitopes by using 17-mer overlapping peptides derived from HIV-1 Gag, Pol, and Nef. Seven of these 17-mer peptides induced HLA-B*5401-restricted CD8+ T cell responses. Only five HLA-B*5401-restricted Pol- or Nef-specific CD8+ T cell responses were detected in the analysis using 11-mer overlapping peptides. Three Pol and two Nef optimal peptides were identified by further analysis using truncated peptides. These epitope-specific CTLs effectively killed HLA-B*5401-expressing target cells infected with HIV-1 recombinant vaccinia virus, indicating that these peptides were naturally processed by HLA-B*5401 in HIV-1-infected cells. These epitope-specific CD8+ T cells were elicited in more than 25% of chronically HIV-1-infected individuals carrying HLA-B*5401. Therefore, these epitopes should prove useful for studying the pathogenesis of AIDS in Asia and developing a vaccine against HIV-1.     

Translation of HLA-HIV associations to the cellular level: HIV adapts to inflate CD8 T cell responses against Nef and HLA-adapted variant epitopes

Strong statistical associations between polymorphisms in HIV-1 population sequences and carriage of HLA class I alleles have been widely used to identify possible sites of CD8 T cell immune selection in vivo. However, there have been few attempts to prospectively and systematically test these genetic hypotheses arising from population-based studies at a cellular, functional level. We assayed CD8 T cell epitope-specific IFN-γ responses in 290 individuals from the same cohort, which gave rise to 874 HLA-HIV associations in genetic analyses, taking into account autologous viral sequences and individual HLA genotypes. We found immunological evidence for 58% of 374 associations tested as sites of primary immune selection and identified up to 50 novel HIV-1 epitopes using this reverse-genomics approach. Many HLA-adapted epitopes elicited equivalent or higher-magnitude IFN-γ responses than did the nonadapted epitopes, particularly in Nef. At a population level, inclusion of all of the immunoreactive variant CD8 T cell epitopes in Gag, Pol, Nef, and Env suggested that HIV adaptation leads to an inflation of Nef-directed immune responses relative to other proteins. We concluded that HLA-HIV associations mark viral epitopes subject to CD8 T cell selection. These results can be used to guide functional studies of specific epitopes and escape mutations, as well as to test, train, and evaluate analytical models of viral escape and fitness. The inflation of Nef and HLA-adapted variant responses may have negative effects on natural and vaccine immunity against HIV and, therefore, has implications for diversity coverage approaches in HIV vaccine design.     

Lack of Viral Escape and Defective In Vivo Activation of Human Immunodeficiency Virus Type 1-Specific Cytotoxic T Lymphocytes in Rapidly Progressive Infection

Human immunodeficiency virus type 1 (HIV-1)-specific immune responses over the course of rapidly progressive infection are not well defined. Detailed longitudinal analyses of neutralizing antibodies, lymphocyte proliferation, in vivo-activated and memory cytotoxic T-lymphocyte (CTL) responses, and viral sequence variation were performed on a patient who presented with acute HIV-1 infection, developed an AIDS-defining illness 13 months later, and died 45 months after presentation. Neutralizing-antibody responses remained weak throughout, and no HIV-1-specific lymphocyte proliferative responses were seen even early in the disease course. Strong in vivo-activated CTL directed against Env and Pol epitopes were present at the time of the initial drop in viremia but were quickly lost. Memory CTL against Env and Pol epitopes were detected throughout the course of infection; however, these CTL were not activated in vivo. Despite an initially narrow CTL response, new epitopes were not targeted as the disease progressed. Viral sequencing showed the emergence of variants within the two targeted CTL epitopes; however, viral variants within the immunodominant Env epitope were well recognized by CTL, and there was no evidence of viral escape from immune system detection within this epitope. These data demonstrate a narrowly directed, static CTL response in a patient with rapidly progressive disease. We also show that disease progression can occur in the presence of persistent memory CTL recognition of autologous epitopes and in the absence of detectable escape from CTL responses, consistent with an in vivo defect in activation of CTL.     

Antiretroviral drug resistance mutations sustain or enhance CTL recognition of common HIV-1 Pol epitopes

Antiretroviral drug resistance and escape from CTL are major obstacles to effective control of HIV replication. To investigate the possibility of combining drug and immune-based selective pressures against HIV, we studied the effects of antiretroviral drug resistance mutations on CTL recognition of five HIV-1 Pol epitopes presented by common HLA molecules. We found that these common drug resistance mutations sustain or even enhance the antigenicity and immunogenicity of HIV-1 Pol CTL epitopes. Variable patterns of cross-reactive and selective recognition of wild-type and corresponding variant epitopes demonstrate a relatively diverse population of CD8(+) T cells reactive against these epitopes. Variant peptides with multiple drug resistance mutations still sustained CTL recognition, and some HIV-infected individuals demonstrated strong CD8(+) T cell responses against multiple CTL epitopes incorporating drug resistance mutations. Selective reactivity against variant peptides with drug resistance mutations reflected ongoing or previous exposure to the indicated drug, but was not dependent upon the predominance of the mutated sequence in endogenous virus. The frequency and diversity of CTL reactivity against the variant peptides incorporating drug resistance mutations and the ability of these peptides to activate and expand CTL precursors in vitro indicate a significant functional interface between the immune system and antiretroviral therapy. Thus, drug-resistant variants of HIV are susceptible to immune selective pressure that could be applied to combat transmission or emergence of antiretroviral drug-resistant HIV strains and to enhance the immune response against HIV.     

HIV-1 Gag Cytotoxic T Lymphocyte Epitopes Vary in Presentation Kinetics Relative to HLA Class I Downregulation

Although CD8⁺ cytotoxic T lymphocytes (CTLs) are protective in HIV-1 infection, the factors determining their antiviral efficiency are poorly defined. It is proposed that Gag targeting is superior because of very early Gag epitope presentation, allowing early killing of infected cells before Nef-mediated downregulation of human leukocyte antigen class I (HLA-I). To study Gag epitope presentation kinetics, three epitopes (SL9_77-85, KF11_162-172, and TW10_240-249) were genetically translocated from their endogenous location in the Rev-dependent (late) gag gene into the Rev-independent (early) nef gene with concomitant mutation of the corresponding endogenous epitopes to nonrecognized sequences. These viruses were compared to the index virus for CTL-mediated suppression of replication and the susceptibility of this antiviral activity to Nef-mediated HLA-I downregulation. SL9-specific CTLs gained activity after SL9 translocation to Nef, going from Nef sensitive to Nef insensitive, indicating that translocation accelerated infected cell recognition from after to before HLA-I downregulation. KF11-specific CTL antiviral activity was unchanged and insensitive to HLA-I downregulation before and after KF11 translocation, suggesting that already rapid recognition of infected cells was not accelerated. However, TW10-specific CTLs that were insensitive to Nef at the baseline became sensitive with reduced antiviral activity after translocation, indicating that translocation retarded epitope expression. Cytosolic peptide processing assays suggested that TW10 was inefficiently generated after translocation to Nef, compared to SL9 and KF11. As a whole, these data demonstrate that epitope presentation kinetics play an important role in CTL antiviral efficiency, that Gag epitopes are not uniformly presented early, and that the epitope context can play a major role in presentation kinetics.     

Fitness costs and diversity of the cytotoxic T lymphocyte (CTL) response determine the rate of CTL escape during acute and chronic phases of HIV infection

HIV-1 often evades cytotoxic T cell (CTL) responses by generating variants that are not recognized by CTLs. We used single-genome amplification and sequencing of complete HIV genomes to identify longitudinal changes in the transmitted/founder virus from the establishment of infection to the viral set point at 1 year after the infection. We found that the rate of viral escape from CTL responses in a given patient decreases dramatically from acute infection to the viral set point. Using a novel mathematical model that tracks the dynamics of viral escape at multiple epitopes, we show that a number of factors could potentially contribute to a slower escape in the chronic phase of infection, such as a decreased magnitude of epitope-specific CTL responses, an increased fitness cost of escape mutations, or an increased diversity of the CTL response. In the model, an increase in the number of epitope-specific CTL responses can reduce the rate of viral escape from a given epitope-specific CTL response, particularly if CD8+ T cells compete for killing of infected cells or control virus replication nonlytically. Our mathematical framework of viral escape from multiple CTL responses can be used to predict the breadth and magnitude of HIV-specific CTL responses that need to be induced by vaccination to reduce (or even prevent) viral escape following HIV infection.     

Identification of cross-clade CTL epitopes in HIV-1 clade A/E-infected individuals by using the clade B overlapping peptides

Identification of cross-clade T cell epitopes is one of key factors for the development of a widely applicable AIDS vaccine. We here investigated cross-clade CD8⁺ T cell responses between clade B and A/E viruses in chronically HIV-1 clade A/E-infected Japanese individuals. CD8⁺ T cell responses to 11-mer overlapping peptides derived from Nef, Gag, and Pol clade B consensus sequences were at a similar level to those to the same peptides found in clade B-infected individuals. Fifteen cross-clade CTL epitopes were identified from 13 regions where the frequency of responders was high in the clade A/E-infected individuals. The sequences of 6 epitopes were conserved between the clade B and clade A/E viruses whereas 9 epitopes had different amino acid sequences between the 2 viruses. CD8⁺ T cells specific for the 6 conserved epitopes recognized cells infected with the clade A/E virus, whereas those for 8 diverse epitopes recognized both the clade A/E virus-infected and clade B-infected cells. All of the cross-clade CD8⁺ T cells specific for conserved and diverse epitopes were detected in chronically HIV-1 clade A/E-infected individuals. These results show that in addition to conserved regions polymorphic ones across the clades can be targets for cross-clade CTLs.     

Naturally arising HIV-1 Nef variants conferring escape from cytotoxic T lymphocytes influence viral entry co-receptor expression and susceptibility to superinfection

HIV-1 Nef is a key factor for pathogenesis and is known to down-regulate functionally important molecules, including viral entry co-receptor CCR5 and CXCR4, from the surface of HIV-infected cells. Some of these Nef activities are mediated by the well-conserved proline-rich region of Nef, and this region is highly targeted by cytotoxic T lymphocytes (CTLs). In the present study, we asked whether Nef variants selected under CTL-mediated selective pressure in vivo may constrain these important Nef activities. The analysis of autologous nef sequences isolated from a cohort of total 235 subjects in Japan revealed that the subjects showing amino acid variations, such as Arg75Thr and Tyr85Phe, located within the proline-rich region were significantly over-represented by those having HLA-B*3501. CTL assays corroborated that these mutations conferred escape from HLA-B(?)3501-restricted CTLs. The Arg75Thr variant Nef selectively impaired CCR5, but not CXCR4, down-regulation activity from the cell surface; whereas the Tyr85Phe variant Nef affected neither CCR5 nor CXCR4 down-regulation activity. Moreover, the cells expressing the Arg75Thr variant Nef significantly impaired protection from superinfection by CCR5-tropic, but not CXCR4-tropic, viruses. These results highlighted the importance of certain Nef-specific CTLs in modulation of viral co-receptor down-regulation activity and protection from HIV-1 superinfection, providing us with additional insight into vaccine design.     

Dynamics of viral evolution and CTL responses in HIV-1 infection

Improved understanding of the dynamics of host immune responses and viral evolution is critical for effective HIV-1 vaccine design. We comprehensively analyzed Cytotoxic T-lymphocyte (CTL)-viral epitope dynamics in an antiretroviral therapy-naïve subject over the first four years of HIV-1 infection. We found that CTL responses developed sequentially and required constant antigenic stimulation for maintenance. CTL responses exerting strong selective pressure emerged early and led to rapid escape, proliferated rapidly and were predominant during acute/early infection. Although CTL responses to a few persistent epitopes developed over the first two months of infection, they proliferated slowly. As CTL epitopes were replaced by mutational variants, the corresponding responses immediately declined, most rapidly in the cases of strongly selected epitopes. CTL recognition of epitope variants, via cross-reactivity and de novo responses, was common throughout the period of study. Our data demonstrate that HIV-specific CTL responses, especially in the critical acute/early stage, were focused on regions that are prone to escape. Failure of CTL responses to strongly target functional or structurally critical regions of the virus, as well as the sequential cascade of CTL responses, followed closely by viral escape and decline of the corresponding responses, likely contribute to a lack of sustainable viral suppression. Focusing early and rapidly proliferating CTL on persistent epitopes may be essential for durable viral control in HIV-1 infection.     

HIV: current opinion in escapology

Much recent work strongly supports the hypothesis that CD8(+) T lymphocytes (CTLs) exert important immune control over HIV and so are a major selective force in its evolution. We analyse this host-pathogen interplay and focus on new data that describe the overall 'effectiveness' of CTL responses (strength, spread, specificity and 'stamina') and the mechanisms by which HIV may evade this suppressive activity. CTLs directed against HIV recognise very large numbers of distinct epitopes across the genome, are largely functional, turn over rapidly, and possess a phenotype that is distinct from CD8(+) lymphocytes specific for other viruses. Mutation of HIV epitopes that alters or abolishes CTL recognition altogether appears to be the most important immune escape mechanism, as the variation that HIV generates defies the limits of the T cell repertoire. However, this immune evasion is still only well-studied in a few patients. The rules that govern immune escape, and the ultimate limits of CTL capacity to deal with the variant epitopes that currently circulate, are not understood. This information will determine the feasibility of current vaccine approaches that, so far, make no provision for the enormous antigenic plasticity of HIV.     

Recognition of variant HIV-1 epitopes from diverse viral subtypes by vaccine-induced CTL

Recognition by CD8(+) T lymphocytes (CTL) of epitopes that are derived from conserved gene products, such as Gag and Pol, is well documented and conceptually supports the development of epitope-based vaccines for use against diverse HIV-1 subtypes. However, many CTL epitopes from highly conserved regions within the HIV-1 genome are highly variable, when assessed by comparison of amino acid sequences. The TCR is somewhat promiscuous with respect to peptide binding, and, as such, CTL can often recognize related epitopes. In these studies, we evaluated CTL recognition of five sets of variant HIV-1 epitopes restricted to HLA-A*0201 and HLA-A*1101 using HLA transgenic mice. We found that numerous different amino acid substitutions can be introduced into epitopes without abrogating their recognition by CTL. Based on our findings, we constructed an algorithm to predict those CTL epitopes capable of inducing responses in the HLA transgenic mice to the greatest numbers of variant epitopes. Similarity of CTL specificity for variant epitopes was demonstrated for humans using PBMC from HIV-1-infected individuals and CTL lines produced in vitro using PBMC from HIV-1-uninfected donors. We believe the ability to predict CTL epitope immunogenicity and recognition patterns of variant epitopes can be useful for designing vaccines against multiple subtypes and circulating recombinant forms of HIV-1.     

Rapid T cell receptor delineation reveals clonal expansion limitation of the magnitude of the HIV-1-specific CD8+ T cell response

TCRs mediate CTL specificity, but TCRs recognizing the same epitope often differ between persons due to their stochastic derivation. The role of this variability in the pathogenesis of virus infections and malignancies has been technically difficult to study. We apply an adaptation of TCR spectratyping to study HIV-specific CTLs, defining the clonal breadth and sequences of epitope-specific TCRs from PBMCs without cellular sorting or molecular cloning. Examining 48 CTL responses in 12 persons reveals a mean of 4.5 ± 2.7 clones per response, of both public and private clonotypes. The number of identified epitope-specific TCRs correlates with CTL frequency across epitopes, suggesting that clonal breadth limits the magnitude of the CTL response against HIV-1 in vivo. HLA A- and B-restricted CTLs are similar in their TCR breadth in this small cohort, preliminarily suggesting that qualitative differences may account for their disparate impacts on pathogenesis. Overall, these findings demonstrate that the magnitude of the CTL response in chronic HIV-1 infection is constrained by TCR clonal breadth, suggesting maximal expansion of CTLs in response to chronic antigenic stimulation.     

Results of phase I clinical trials of a combined vaccine against HIV-1 based on synthetic polyepitope immunogens

The CombiHIVvac candidate vaccine against HIV-1/AIDS containing two synthetic polyepitope immunogens such as TBI and TCI to stimulate the humoral and cellular response is described. The recombinant TBI protein is constructed as a polypeptide with predetermined tertiary structure and contains epitopes of Env and Gag proteins of HIV-1. TCI contains CD8⁺ CTL and CD4⁺ Th epitopes of the major viral proteins such as Env, Gag, Pol and Nef which are highly conserved among subtypes A, B and C of HIV-1. A gene encoding the polyepitope TCI immunogen is inserted into a pcDNA-3.1 plasmid vector. The CombiHIVvac vaccine was designed as virus-like particles containing the pcDNA-TCI plasmid in their cores (DNA vaccine) and the TBI protein conjugated with polyglucin on their surfaces. Immunogenicity and safety of CombiHIVvac has been shown in preclinical studies in several animal species. Phase I clinical trials of the vaccine have been completed and the results obtained in human volunteers confirmed that the CombiHIVvac candidate vaccine was safe and did not cause side effects, at the same time, inducing the HIV-specific humoral and cellular immune response. The phase II clinical trials have been approved by the Ministry of Health and Social Development of the Russian Federation.