A Phase I Randomized Trial to Evaluate the Safety and Immunogenicity of Vaccinia-HIV Envelope Recombinant Vaccine (HIVAC-1e) in Combination With Soluble Recombinant Envelope Vaccine (VaxSyn)

Primary: To determine whether additional boosting with soluble recombinant gp160 vaccine (VaxSyn) after priming with a vaccinia-HIV envelope recombinant (HIVAC-1e) provides a significant advantage in the degree and duration of immunogenicity. Secondary: To learn more about the safety of the combination use of the two HIV envelope vaccines in the study (VaxSyn and HIVAC-1e). Recent Phase I trials conducted at the AIDS Vaccine Units have shown that antibodies have persisted in most recipients for 6 months after boosting, and responses seem significantly higher and more persistent than responses achieved by just two doses of soluble protein vaccine alone or two doses of HIVAC-1e alone. This study tests in a previously recruited cohort of volunteers whether additional boosting with soluble recombinant gp160 results in increased immunogenicity of longer duration.