A phase II study of two HIV type 1 envelope vaccines, comparing their immunogenicity in populations at risk for acquiring HIV type 1 infection

Several immunogens induce HIV-specific neutralization and in vitro lymphopr oliferation in adults at low HIV-1 risk, but responses in persons at high H IV-1 risk are not known, We performed a multicenter. double-blinded, adjuva nt-controlled trial with two gp120 vaccines in 296 HIV-1-uninfected volunte ers, including 176 reporting higher HIV-1 risk activities. The immunogens w ere remarkably well tolerated, After three immunizations, 210 of 241 vaccin ees (87%) developed neutralizing antibodies, which persisted in 59% after 2 years. The injection drug users receiving SF-2/gp120 had decreased antibod y responses relative to the lower risk groups. Envelope-specific lymphoprol iferation peaked after two immunizations, and 54% of vaccinees. mounted a D TH reaction to gp120 after 4 years. In summary, these immunogens have low a dverse reactogenicity and induce durable antibody and T cell responses to t he prototype strains, Unexpected differences in antibody responses among di verse HIV-1 risk strata lend support to the conduct of expanded phase II tr ials in populations other than low-risk volunteers.