A Study to Test the Safety of Three Experimental HIV Vaccines

Overview

The purpose of this study is to test three experimental HIV vaccines. This study will look at whether it is safe to give these vaccines together and how the immune system responds to the vaccines. There are a number of studies being performed to test HIV vaccines. The vaccines that seem to be the most promising are canarypox vaccines, known as ALVAC vaccines. The three experimental HIV vaccines used in this study are called ALVAC-HIV vCP205, HIV-1 SF-2 p24, and HIV-1 SF-2 rgp120. The HIV-1 SF-2 p24 and HIV-1 SF-2 rgp120 vaccines are mixed with an adjuvant, which is a substance that increases immune response.

There are currently several Phase I and II clinical trials being performed within AVEG to evaluate different HIV-1 vaccine candidates. The HIV-1 vaccination approach that is furthest along the clinical development pathway is the so-called prime-boost regimen of live recombinant canarypox priming (ALVAC-HIV vCP205) with recombinant subunit protein boosting (HIV-1 SF-2 rgp120 in MF59 adjuvant). The protein boost enhances neutralizing antibody responses against laboratory strains of HIV-1 in assays performed in vitro, as well as enhancing CD4 cell response and increasing the frequency of CD8 cytotoxic T lymphocytes (CTLs). In all of the ALVAC-HIV trials of the prime-boost regimen completed to date, the protein boost has been the HIV-1 SF-2 rgp120 subunit protein. This study is designed to explore whether boosting of live recombinant canarypox vaccination with a novel protein subunit, recombinant HIV-1 SF-2 p24, can enhance the CD4 and CD8 cell responses directed against HIV-1 antigens. Volunteers are randomized to 1 of 5 groups. All volunteers receive a total of 4 immunizations, administered at Months 0, 1, 3, and 6. Each group receives a different combination of vaccines as follows: Group 1: ALVAC-HIV vCP205 plus HIV-1 SF-2 p24. Group 2: ALVAC-HIV vCP205 plus MF59 adjuvant and citrate vehicle (control for HIV-1 SF-2 p24 and HIV-1 SF-2 rgp120) at Months 0 and 1; then ALVAC-HIV vCP205 plus HIV-1 SF-2 p24 at months 3 and 6. Group 3: ALVAC-HIV vCP205 plus control at Months 0 and 1; then ALVAC-HIV vCP205 plus HIV-1 SF-2 p24 combined with HIV-1 SF-2 rgp120 at Months 3 and 6. Group 4: ALVAC-HIV vCP205 plus control at Months 0 and 1; then ALVAC-HIV vCP205 plus HIV-1 SF-2 rgp 120 at Months 3 and 6. Group 5: ALVAC-RG vCP65 (control for ALVAC-HIV vCP205) plus control at Months 0,1,3, and 6. The study lasts for approximately 18 months; patients receive clinical evaluations to measure vaccine safety at 11 study visits at specified time intervals.