HLA-A*3303-restricted cytotoxic T lymphocyte recognition for novel epitopes derived from the highly variable region of the HIV-1 Env protein

Epitope-dependent effect of long-term cART on maintenance and recovery of HIV-1-specific CD8+ T cells

IMPORTANCE

HIV-1-specific CD8+ T cells are anticipated to become effector cells for curative treatment using the "shock and kill" approach in people living with HIV-1 (PLWH) under combined antiretroviral therapy (cART). Previous studies demonstrated that the frequency of HIV-1-specific CD8+ T cells is reduced under cART and their functional ability remains impaired. These studies analyzed T-cell responses to a small number of HIV-1 epitopes or overlapping HIV-1 peptides. Therefore, the features of CD8+ T cells specific for HIV-1 epitopes under cART remain only partially clarified. Here, we analyzed CD8+ T cells specific for 63 well-characterized epitopes in 90 PLWH. We demonstrated that CD8+ T cells specific for large numbers of HIV-1 epitopes were maintained in an epitope-dependent fashion under long-term cART and that long-term cART enhanced or restored the ability of HIV-1-specific T cells to proliferate in vitro. This study implies that some HIV-1-specific T cells would be useful as effector cells for curative treatment.

Identification and characterization of HIV-1 epitopes presented by HLA-A*2603: comparison between HIV-1 epitopes presented by A*2601 and A*2603

Human leukocyte antigen (HLA)-A*26 is one of the alleles associated with a slow progression to AIDS. Identification and characterization of HIV-1-specific epitopes presented by this allele are necessary for studies on the immunopathogenesis of AIDS and vaccine development in Asia, where three HLA-A*26 subtypes are frequently found. In the present study, we sought to identify HLA-A*2603-restricted HIV-1 epitopes by using reverse immunogenetics and to compare them with HLA-A*2601-restricted ones recently identified. We found that 31 of 110 HIV-1 peptides bound to HLA-A*2603 and that only two peptides (Gag169-177 and Env63-72) induced specific CD8+T cells by stimulating peripheral blood mononuclear leukocytes from HIV-1-infected individuals carrying HLA-A*2603. The specific cytotoxic T lymphocyte clones killed HIV-1 recombinant vaccinia-infected cells, indicating that these two peptides were naturally occurring peptides presented by HLA-A*2603. Gag169-177-specific CD8+T cells were frequently detected in both HLA-A*2601+ and -A*2603+ individuals with chronic HIV-1 infection, whereas Env63-72-specific ones were frequently detected only in the HLA-A*2603+ individuals. Gag169-177 peptide bound equally to both HLA-A*26 antigens, whereas Env63-72 peptide bound to A*2603 much more strongly than to A*2601. These findings suggest that the relative affinity of these peptides for the HLA-A*26 subtypes determines whether these peptides are recognized as epitopes in HIV-1-infected individuals carrying these alleles.

Patterns of cytokine production in human immunodeficiency virus type 1 (HIV-1)-specific human CD8+ T cells after stimulation with HIV-1-infected CD4+ T cells

Although human immunodeficiency virus type 1 (HIV-1)-specific CD8+ T cells can produce various cytokines that suppress HIV-1 replication or modulate anti-HIV-1 immunity, the extent to which HIV-1-specific CD8+ T cells produce cytokines when they recognize HIV-1-infected CD4+ T cells in vivo still remains unclear. We first analyzed the abilities of 10 cytotoxic T-lymphocyte (CTL) clones specific for three HIV-1 epitopes to produce gamma interferon, macrophage inflammatory protein 1beta, and tumor necrosis factor alpha after stimulation with epitope peptide-pulsed cells. These CTL clones produced these cytokines in various combinations within the same specificity and among the different specificities, suggesting a functional heterogeneity of HIV-1-specific effector CD8+ T cells in cytokine production. In contrast, the HIV-1-specific CTL clones for the most part produced a single cytokine, without heterogeneity of cytokine production among the clones, after stimulation with HIV-1-infected CD4+ T cells. The loss of heterogeneity in cytokine production may be explained by low surface expression of HLA class I-epitope peptide complexes. Freshly isolated HIV-1-specific CD8+ T cells with an effector/memory or memory phenotype produced much more of the cytokines than the same epitope-specific CTL clones when stimulated with HIV-1-infected CD4+ T cells. Cytokine production from HIV-1-specific memory/effector and memory CD8+ T cells might be a critical event in the eradication of HIV-1 in HIV-1-infected individuals.

Identification and characterization of HIV-1-specific CD8+ T cell epitopes presented by HLA-A*2601

Since HLA-A*26 is one of the most common alleles in Asia, where approximately 20% of people have this allele, identification of HIV-1-specific epitopes presented by HLA-A*26 is necessary for studies on the immunopathogenesis of AIDS and vaccine development in Asia. As presented herein, we used the reverse immunogenetics approach to identify HIV-1 epitopes presented by HLA-A*2601, one of the major HLA-A*26 subtypes. We selected 24 HLA-A*2601-binding peptides out of 110 HIV-1 peptides by using a HLA-A*2601 stabilization assay. The ability of these HLA-A*2601-binding peptides to induce peptide-specific CD8(+) T cells was tested by stimulating PBMCs from HIV-1-infected individuals having HLA-A*2601 with these peptides. Four HLA-A*2601-binding peptides induced peptide-specific CD8 T cells. Analysis using HIV-1 recombinant vaccinia-infected C1R-A*2601 cells indicated that these four peptides were HIV-1 epitopes endogenously presented by HLA-A*2601. Two epitope-specific CD8(+) T cells were predominantly detected in HIV-1 infected individuals, suggesting that these epitopes may be useful for vaccine development.

HLA class I serotypes and cytotoxic T-lymphocyte responses among human immunodeficiency virus-1-uninfected Thai volunteers immunized with ALVAC-HIV in combination with monomeric gp120 or oligomeric gp160 protein boosting

Antigen-induced cellular immunogenicity may vary between populations due to differences in human leukocyte antigen (HLA) diversity and, hence, may play a critical role in the protection afforded by vaccines. In the setting of two, phase I/II human immunodeficiency virus-1 vaccine trials of a recombinant canarypox prime, and boosting with either recombinant monomeric gp120 or oligomeric gp160, we assessed the association between specific human leukocyte antigen (HLA) class I serotypes and the presence of cytotoxic T-lymphocyte response measured by 51Cr-release assay. HLA class I serotypes A11, A24, A33, B46, and B75 were the most common, present in 10% or more of 245 individuals studied. Forty of 187 (21.4%) Thai adults who received either ALVAC-HIV with gp120 or oligomeric gp160 or ALVAC alone had a precursor cytolytic CD8 T-cell response (pCTL). HLA-B44 was positively and significantly associated with a pCTL response (odds ratio 7.6, 95% CI: 2.7-21.2), whereas B46 was negatively associated but not robust when adjusted for multiple comparisons. Responses to Env proteins accounted for the majority (nine of 11) of pCTL activity among those persons with B44. This HLA class I serotype occurred in 9.4% of participants overall (including the placebo group), less commonly than what is reported from populations of European ancestry. These results strengthen the importance of assessing HLA class I distributions in conjunction with studies of vaccines designed to elicit cellular immunity in different populations.

Identification and characterization of HLA-A*3303-restricted, HIV type 1 Pol- and Gag-derived cytotoxic T cell epitopes

HLA-A*3303 is one of the common HLA alleles in East and Southeast Asia. Identification of HLA-A*3303-restricted HIV-1 cytotoxic T lymphocyte (CTL) epitopes is therefore required to investigate the immunopathogenesis of AIDS and vaccine development in these areas, where AIDS is rapidly expanding. We attempted to identify HLA-A*3303-restricted CTL epitopes derived from relatively conserved proteins Pol, Gag, and Nef of HIV-1 clade B, using reverse immunogenetics. Ninety-nine 8-mer to 11-mer peptides corresponding to the HLA-A*3303-binding peptide motif were selected from the HIV-1 SF2 sequence. Fifty-two of these 99 peptides bound to HLA-A*3303. Six of these binding peptides induced peptide-specific CTLs in PBMCs from at least one of two HIV-1-seropositive individuals. CTL clones specific for three Pol peptides and one Gag peptide killed HLA-A*3303-restricted target cells infected with HIV-1 recombinant vaccinia, indicating that these peptides were naturally processed HLA-A*3303-restricted CTL epitopes. SF2-Pol 594-602 (FYVDGAANR) and SF2-Gag 144-152 (MVHQAISPR) induced specific CTLs in 5 and 4 of 10 chronically HIV-1-infected individuals, respectively, whereas SF2-Pol 60-70 (TLWQRPLVTIR) and SF2-Pol 934-943 (KIQNFRVYYR) induced specific CTLs in 2 and 1 of 10 chronically HIV-1-infected individuals, respectively. Thus, the former are immunodominant epitopes whereas the latter are not. These epitopes are useful for studies of AIDS immunopathogenesis and vaccine development.

HIV-1 Vpu represents a minor target for cytotoxic T lymphocytes in HIV-1-infection

We have previously shown that Vpu is rarely targeted by HIV-1-specific cytotoxic T lymphocytes (CTL). The present report extends these findings and describes the characterization of the first CTL epitope within HIV-1 Vpu, identified in an individual with long-term non-progressive HIV-1 infection. The epitope was shown to be highly conserved among HIV clade B sequences and is restricted by HLA-A*3303, an HLA allele commonly seen in Asian and west-African populations.