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.~Twelve volunteers who have previously received two doses of HIVAC-1e (or DryVax) and two doses of gp160 receive an additional boost of gp160 at 12-20 months after the last boost and an additional dose of HIVAC-1e at least 9 months after the final gp160 boost.
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.