Memory Cytotoxic T Lymphocyte Responses in Human Immunodeficiency Virus Type 1 (HIV-1)-Negative Volunteers Immunized with a Recombinant Canarypox Expressing gp160 of HIV-1 and Boosted with a Recombinant gp160

A vaccine against human immunodeficiency virus (HIV) should induce virus-specific cytotoxic T lymphocyte (CTL) activity. Immunization of uninfected volunteers with a canarypox virus expressing HIV envelope was carried out in a phase I trial. Two injections of canarypox expressing HIV-1MN gp 160 (months 0 and 1) were followed by two boosts of recombinant envelope protein (months 3 and 6). HIV envelope-specific CTL were detected in peripheral blood mononuclear cells stimulated with autologous HIV-1-infected blast cells. T cell lines were obtained from 18 of 20 donors: CTL were detected at least once following immunization in 7 (39%) of these 18. This activity was mediated by major histocompatibility complex class I-restricted CD3+CD8+ T cells. For two subjects, this activity was still present 2 years after the initial immunization. The CTL responses with this prime-boost regimen are the best observed with any HIV vaccine tested in humans.