Characterization of an HLA-C-restricted CTL response in chronic HIV infection.

HIV-specific CTL play an important role in the host control of HIV infection. HIV-nef may facilitate escape of HIV-infected cells from CTL recognition by selectively downregulating the expression of HLA-A and HLA-B molecules, while surface expression of HLA-C is unaffected. The HLA-C-restricted CTL responses have previously been largely ignored and poorly characterized. We examined the frequency, function, and phenotype of HLA-C-restricted CTL in ten antiretroviral therapy-naïve Caucasian and African individuals with chronic HIV-1 infection (for at least 8 years; CD4 cell counts in the range of 50-350) who carried the HLA-Cw04 allele. HLA-Cw04-restricted CTL that recognize a conserved epitope within HIV-1 envelope (aa 375-383 SF9) were analyzed using IFN-gamma ELISPOT assays and phenotypic analysis was carried out by flow cytometry. HLA-C-restricted CTL play an important role in the HIV-specific response, and can account for as much as 54% of the total response. HLA-C-restricted CTL are functionally and phenotypically identical to HLA-A- and HLA-B-restricted CTL. HLA-C-restricted CTL in chronic HIV infection are memory cells of an intermediate phenotype, characterized by high CD27 and low CD28 expression and lack of perforin production.

Identification of a novel HLA B*57 restricted cytotoxic T-lymphocyte epitope within HIV-1 rev.

HLA-B5701 and its related allele B5703 have been shown to be strongly associated with slow HIV-1 disease progression. To elucidate the effect of these alleles fully on disease progression it is essential to identify key HIV-1 epitopes that are restricted by these alleles. Here we describe the identification of a novel HLA-B5701, B5703 restricted epitope within HIV-1 rev, which accounted for up to 25 and 40% of the total cytotoxic T-lymphocyte responses in two patients.

Elevated T cell counts and RANTES expression in the genital mucosa of HIV-1-resistant Kenyan commercial sex workers.

The initial site of exposure to human immunodeficiency virus (HIV)-1 during heterosexual transmission occurs in the genital tract. Although the majority of immunological studies have focused on the immune response to HIV-1 at the systemic level, our understanding of tissue-specific immunity is deficient. The goal of the present study was to characterize T cell populations found in the cervix of women shown to be resistant to infection by HIV-1. Levels of both systemic and cervical mucosal lymphocytes were compared between HIV-1-resistant, HIV-1-uninfected, and HIV-1-infected commercial sex workers (CSWs) as well as HIV-1-uninfected non-CSW control subjects at low risk for exposure. The HIV-1-resistant CSWs had increased cervical CD4+ and CD8+ T cell counts, compared with the HIV-1-uninfected CSWs; importantly, these increases were not reflected in the systemic lymphocyte compartment. There was a 2-fold increase in CD4+ T cell counts in the HIV-1-resistant CSWs, compared with both the HIV-1-infected and the HIV-1-uninfected CSWs. Expression of the HIV-1 coreceptors CCR5 and CXCR4 was also determined, and cytokine and beta chemokine levels in the genital mucosa were assessed. The HIV-1-resistant CSWs had a 10-fold increase in RANTES expression, compared with the HIV-1-uninfected CSWs. This is the first study to show elevated levels of beta chemokines and CD4+ T cells in the genital tracts of women who are exposed to HIV-1 and yet are uninfected.

Elevation of immune activation in kenyan women is associated with alterations in immune function: implications for vaccine development.

The infectious burden leading to immune activation can vary between different populations and lead to various immune dysfunctions. We compared the effect of immune activation on apoptosis and T cell function in HIV uninfected individuals from Nairobi, Kenya (n=34), and Winnipeg, Canada (n=10). Women from Nairobi had a significantly greater number of CD8+ T cells expressing the activation markers CD38 and HLA DR. Kenyan women also had significantly higher levels of CTLA-4+ CD4 and CD8+ T cells, and reduced levels of CD28+ CD8+ cells. Levels of CD95+ CD4+ T cells were higher in Kenyan women and, correspondingly, showed higher levels of spontaneous apoptosis. Kenyan women also demonstrated hyper-responsiveness to T cell activation as assessed by interferon gamma production. This study demonstrates that in a population of Kenyan women with high levels of T cell activation, there were also elevated levels of T cell apoptotic death and hyper-responsiveness. These differences may influence the efficacy of immune responses to pathogens and must be considered when testing candidate vaccines.

Quantitative ex vivo analysis of functional virus-specific CD8 T lymphocytes in the blood and genital tract of HIV-infected women.

BACKGROUND: CD8 T lymphocytes are important in HIV-1 control and mediate virus-specific immunity in the blood and genital tract. The induction and monitoring of mucosal CD8 cell responses will be an important component of HIV-1 vaccine trials, but information regarding the frequency, phenotype and function of genital tract CD8 cell responses is lacking. METHODS: Simultaneous blood and cervical cytobrush samples were obtained from 16 HIV-1-infected Kenyan sex workers. Epitope-specific CD8 T lymphocyte frequencies in the blood and genital tract were analysed after short-term peptide incubation and intracellular cytokine staining for interferon-gamma (IFN gamma). RESULTS: Cervical sampling resulted in adequate cell numbers for analysis in 10/16 women. Background IFN gamma production was higher in CD3+/CD8+ lymphocytes from the genital tract than from blood (0.48% versus 0.1%; P < 0.01). Responses to staphylococcal enterotoxin B were detected in cervical CD8 lymphocytes from 10/10 women, at a similar frequency to blood (16.7% in cervix and 13.3% in blood; P = 0.4). HIV-1-specific responses were detected the cervix of 8/10 women, with a trend to higher response frequencies in the genital tract than blood (2.1% versus 0.8%; P = 0.09). Co-expression of integrin CD103 (alpha E beta 7), a mucosal marker, was used to confirm the mucosal origin of cervical responses. CONCLUSIONS: Cytobrush sampling and intracellular cytokine staining is well suited to the analysis of cervical CD8 cell responses. The frequency of functional virus-specific CD3+/CD8+ T cells is similar in the genital tract and blood of HIV-1-infected women. The role of genital tract CD8 cell responses in HIV-1 control warrants further investigation.

Cross-clade HIV-1-specific neutralizing IgA in mucosal and systemic compartments of HIV-1-exposed, persistently seronegative subjects.

There is an urgent need for a universally effective HIV-1 vaccine, but whether a vaccine will be able to protect against HIV-1 of different clades is a significant concern. IgA from HIV-1-exposed, persistently seronegative (HEPS) subjects has been shown to neutralize HIV-1 and to block epithelial HIV-1 transcytosis, and it may target novel HIV-1 epitopes. We have tested the ability of plasma and mucosal IgA purified from HEPS subjects to neutralize HIV-1 primary isolates of different viral clades and phenotypes. IgA from two groups of HEPS subjects was tested: sex workers from Nairobi, Kenya, where clades A and D predominate, and the heterosexual partners of individuals infected by clade B virus. HIV-1-infected and low-risk uninfected individuals were included as controls. IgA purified from the blood, genital tract, and saliva of most HEPS sex workers demonstrated significant cross-clade HIV-1 neutralization, whereas a more clade-restricted pattern of neutralization was found in partners of clade B-infected individuals. IgA purified from HIV-1-infected individuals also mediated cross-clade neutralization, whereas IgA from uninfected controls lacked neutralizing activity. In conclusion, mucosal and plasma IgA from HEPS subjects neutralizes HIV-1 of different clades. This ability to induce HIV-1-specific systemic and mucosal IgA may be an important feature of an effective prophylactic HIV-1 vaccine.

Gonococcal cervicitis is associated with reduced systemic CD8+ T cell responses in human immunodeficiency virus type 1-infected and exposed, uninfected sex workers.

Neisseria gonorrhoeae cervicitis and human immunodeficiency virus (HIV) type 1 frequently coinfect core transmitter populations, such as female sex workers. Gonococcal cervicitis is associated with increased viral shedding and plasma viremia in HIV-1-infected women and increased HIV-1 susceptibility in uninfected women. We studied the influence of gonococcal cervicitis on CD8(+) interferon (IFN)-gamma responses to HIV-1 and cytomegalovirus (CMV) epitopes in HIV-1-infected and in highly-exposed, persistently seronegative (HEPS) female sex workers. In HIV-1-infected women, gonococcal cervicitis was associated with reduced IFN-gamma responses in bulk CD8(+) lymphocyte populations, and intracellular cytokine staining, combined with class I major histocompatibility complex (MHC)-peptide tetramer studies, demonstrated reduced IFN-gamma production by HIV-1 epitope-specific CD8(+) lymphocytes. In HEPS sex workers, cervicitis was associated with the transient loss of systemic HIV-1-specific CD8(+) responses and with reduced function of CMV-specific CD8(+) lymphocytes. Impaired function of virus-specific CD8(+) lymphocytes may partly explain the deleterious effects of gonococcal cervicitis on HIV-1 immune control and susceptibility.

Cross-reactive cytotoxic T lymphocytes against a HIV-1 p24 epitope in slow progressors with B*57.

OBJECTIVES: To determine whether CD8 T lymphocytes from HIV-1-infected patients expressing B*5701 and B*5703 show broad cross-reactivity against different variants of a conserved p24 epitope, which might account for the good prognosis of HIV-1-infected individuals with HLA-B*57. DESIGN: B*5701+ and B*5703+ were recruited from Nairobi, Kenya and from Oxford, UK. All patients had been HIV positive for at least 8 years and could be categorized as slow progressors. METHODS: CD8 cytotoxic T cell clones were generated from B*5701+ and B*5703+ donors and tested for their ability to recognize clade variants of an index p24 epitope in standard cytolytic assays. Cross-reactive responses in freshly isolated peripheral blood mononuclear cells (PBMC) were assessed by interferon-gamma (IFNgamma) production and tetramer binding. RESULTS: Broad cross-clade reactivity for both cytolysis and tetramer binding was observed in CD8 T cell clones from patients harbouring the index epitope sequence. Patterns of cross-reactivity were similar in freshly isolated PBMC but varied between individuals in terms of strength and breath of responses generated. One common variant induced an unusual response with tetramer binding but often failed to induce IFNgamma production, and another was a weak stimulator of both IFNgamma and cytolytic activity. CONCLUSION: B*5701+ and B5703+ donors demonstrate broad functional cross-reactivity to both common and rare variants of a dominant p24 epitope, which could be relevant to the association of B*57 alleles with slow progression to AIDS.