Cytotoxic T Cell and Neutralizing Antibody Responses to Human Immunodeficiency Virus Type 1 Envelope with a Combination Vaccine Regimen

Effective human immunodeficiency virus (HIV) vaccination may require induction of neutralizing antibodies (NAs) and CD8+ cytotoxic T lymphocytes (CTL) to prevent transmission and control early infection. Recombinant envelope proteins induce NAs but rarely CD8+ CTL responses, and vaccinia vectors containing HIV-1 envelope elicit CD8+ cytotoxicity but few NAs. To benefit from both approaches, 56 vaccinia-naive subjects were randomized to a regimen of priming with recombinant vaccinia gp160LAI and boosting with recombinant gp120SF-2, gp120LAI, gp120MN, or gp160MN. Of 51 persons for whom assays were done, 26 demonstrated envelope-specific CTL. Boosting with gp120, compared with gp160, elicited significantly more NAs and CD4-blocking antibodies. Neutralization of the homologous and heterologous HIV-1 laboratory strains occurred in all subjects receiving vac/env and gp120 and was detectable in 91% of the subjects for >6 months. Thus, vaccine regimens in which one component elicits primarily CTL and the other NAs offer promise for the development of an effective HIV-1 vaccine strategy.