Human class I MHC-restricted cytotoxic T-lymphocytes specific for human immunodeficiency virus envelope antigens

Vaccines incorporating HIV envelope antigens are being developed for the prevention of AIDS. To determine whether HIV envelope antigens are recognized by human cytotoxic T-lymphocytes (CTL), we assessed class I MHC-restricted, HIV envelope antigen-specific cytotoxic activity of peripheral blood mononuclear cells (PBMC) from HIV-infected individuals, following in vitro stimulation. The target cells were human skin fibroblasts of known tissue type, infected with recombinant vaccinia viruses, either containing or lacking the whole HIV envelope gene. Ten out of 17 (59%) asymptomatic HIV-seropositive individuals demonstrated HIV envelope antigen-specific cytotoxicity at levels that were above those seen in HIV-seronegative controls. MHC restriction of cytotoxicity was evident in that 13 out of 19 (68%) of the targets matched for the tissue type of the donor at one or more class I MHC loci were lysed, but only two out of 18 (11%) mismatched targets (P = 0.0004). Both partial purification of effector cells and evidence of MHC restriction indicated that T-lymphocytes were responsible for the observed cytotoxicity. HIV envelope antigen-specific CTL can be detected following in vitro stimulation of the PBMC in many asymptomatic HIV-seropositive individuals. HIV envelope antigens are recognized by human CTL and are, therefore, potentially relevant immunogens for induction of HIV-specific CTL responses.