Although recent advances have been made in antiviral therapy for AIDS, there is no cure for HIV-1 infection or AIDS, and drug therapy is too expensive for most affected populations. The development of safe, effective vaccines to prevent HIV-1 infection and AIDS worldwide is a global priority. One promising approach in the development of HIV-1 vaccines utilizes live vaccines as vectors to express HIV-1 antigens. The potential advantages of the live vector approach include the ability of live vector recombinants to induce long-lasting humoral and cell-mediated immunity (particularly neutralizing antibody and CD8+ cytotoxic T-cell activity) and the relatively low cost of production. Moreover, live vector recombinant vaccines administered orally might be able to stimulate the production of secretory IgA vaccine-specific antibodies locally at relevant mucosal sites.

Part I of this study is conducted as an open-label, dose-escalation trial. The first 5 volunteers (Group A) receive a single oral dose of Salmonella typhi CVD 908-HIV-1 LAI gp 120 (VVG203). If no typhoid fever-like illness is seen in these volunteers during at least 14 days of follow-up, the next 5 patients (Group B) receive a single dose of VVG203. If this higher dose is well-tolerated, Phase II of the study is initiated once all Phase I volunteers have been assessed for safety for at least 21 days. [AS PER AMENDMENT 11/07/97: Groups A and B are expanded to 10 patients each.] Part II of this study is a randomized, placebo-controlled, double-blind trial. Nine volunteers are randomized to each of treatment groups, with oral VVG203 given alone or sequentially with HIV-1 SF-2 rgp 120 in MF59 (SF) given intramuscularly. [AS PER AMENDMENT 11/07/97: Randomization is to VVG 203 alone or sequentially with HIV-1 MN rgp120 in alum (MN).] A total of 3 vaccinations are administered within each 9-person cohort, 1 volunteer serves as a control and receives a sodium bicarbonate buffer rather than VVG203 or a vaccine placebo rather than SF. Group C receives VVG at Month 0 and SF at Months 2 and 6. Group D receives VVG at Months 0, 2, and 6. Group E receives SF at Months 0 and 2 and VVG at Month 6. [AS PER AMENDMENT 11/07/97: MN is given in place of SF in all Groups C, D, and E.]