Recent studies at the AIDS vaccine units have shown the safety of two candidate HIV vaccines, HIVAC-1e and gp160. Specific questions to be addressed in this part of the study include: Does combination vaccination result in a synergistic (added) response not predicted by just the addition of a second vaccination, and does this synergism depend on the unique priming effect of a vaccinia recombinant, or will any combination do?~Volunteers will be randomized to one of four groups. Group A (20 volunteers) will receive gp160 (VaxSyn) followed two months later by a repeat dose. Group B (20 volunteers) will receive VaxSyn followed two months later by HIVAC-1e. Group C (20 volunteers) will receive HIVAC-1e followed two months later by VaxSyn. Group D (10 volunteers) will receive HIVAC-1e followed two months later by HIVAC-1e. For volunteers in Groups A, B, and C who do not react to the initial vaccination, a second attempt to obtain a reaction may be made 7 or more days following the initial inoculation. Per addendum, two additional booster inoculations are given: one at 6 months or later post initial inoculation (Groups A, C, and D receive VaxSyn and Group B receives HIVAC-1e) and another at 12 months or later (all Groups receive VaxSyn).
To determine if priming (giving the first vaccination) with a vaccinia recombinant (HIVAC-1e) provides a significant advantage in immunogenicity (production of antibodies) compared to priming with a soluble recombinant protein (gp160); to learn more about the safety of the combination use of the two HIV envelope vaccines utilized in the study.~Recent studies at the AIDS vaccine units have shown the safety of two candidate HIV vaccines, HIVAC-1e and gp160. Specific questions to be addressed in this part of the study include: Does combination vaccination result in a synergistic (added) response not predicted by just the addition of a second vaccination, and does this synergism depend on the unique priming effect of a vaccinia recombinant, or will any combination do?