title: Progressive loss of IL-2-expandable HIV-1-specific cytotoxic T lymphocytes during asymptomatic HIV infection.
abstract: In HIV-1 infection, circulating HIV-1-specific cytotoxic T lymphocytes (CTL) exist in different states of activation, including activated cytotoxic cells and memory cells. We report that a subpopulation of HIV-1-specific CTL is capable of clonal expansion upon culture with IL-2 without exogenous antigen. The IL-2-expandable HIV-1-specific CTL precursor frequency was reduced in patients with advancing infection, although HIV-1-specific memory CTL could still be detected by stimulation in vitro with allele-specific HIV-1 peptide. Longitudinal analysis during advancing infection showed a progressive decline in the IL-2-expandable HIV-1-specific CTL precursor (CTLp) frequency without a decline in Epstein-Barr virus (EBV)-specific or allo-specific CTLp frequencies. To address mechanisms that may contribute to the decline in the IL-2-expandable HIV-specific CTL response, the requirements for in vitro generation of HIV-1-specific and EBV-specific effector CTL were examined. In the absence of exogenous IL-2 in limiting dilution, generation of EBV-specific CD8+ effector CTL was dependent upon help from CD4+ cells. CD4+ help for EBV-specific CD8+ CTL was observed in asymptomatic HIV infection but not in advanced infection. In the presence of exogenous IL-2, CD4+ cells could also provide help for the optimal generation of HIV-1 peptide-specific CD8+ CTL, because in vitro depletion of CD4+ cells prior to culture using stimulation with an MHC class I-restricted HIV-1 peptide reduced the peptide-specific CD8+ CTL response. We conclude that there is a decline in the IL-2-expandable HIV-1-specific CTL response during advancing infection. There are a number of possible mechanisms for this decline, including a reduction in CD4+ T cell help for in vivo antigen-activated CD8+ T cells.
authors.affiliation: Department of Medicine, University of Cambridge Clinical School, Addenbrookes Hospital, GB.
authors.forename: X
authors.initials: X
authors.lastname: Jin
authors.forename: M
authors.initials: M
authors.lastname: Wills
authors.forename: J G
authors.initials: JG
authors.lastname: Sissons
authors.forename: A
authors.initials: A
authors.lastname: Carmichael
mesh_terms: D000163:Acquired Immunodeficiency Syndrome / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D002478:Cells, Cultured; D015497:HIV-1 / Q000276:immunology*; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D007376:Interleukin-2 / Q000494:pharmacology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology*
chemical_list: D007376:Interleukin-2