Investigators of the pathogenesis of HIV infection agree that one of the most critical questions in HIV disease is why immune responses do not control HIV replication in the vast majority of infected individuals. More specifically, the absence of large lymphocyte proliferation response (LPR) to HIV antigens in these individuals, and their presence in long-term nonprogressors (LTNPs) with a low viral load, requires an investigation of whether a causal relationship exists between LPR to HIV and control of HIV replication. Immunization with Remune has been shown to induce large LPR to HIV antigens when administered to patients in whom HIV replication has been suppressed with antiretroviral therapy (ART). A5120 will evaluate the abilities of immunization with HIV-1 Immunogen and of STIs to enhance immune responses that may control HIV replication in the absence of antiretroviral drugs.

Patients remain in the treatment arm (vaccine versus adjuvant placebo) to which they were randomized on entry to protocol A5057, and both the participant and investigator remain blinded as to the assignment. Patients may receive up to 3 injections of vaccine/adjuvant control in 1 of the following 2 groups.

Arm A: HIV-1 immunogen at study entry and at Week 9 in Step 3 and Step 5. Arm B: HIV-1 immunogen placebo at study entry and at Week 9 in Step 3 and Step 5.

ART is required during Steps 1, 3, 5, and 8 but is not provided by this study. The study is organized into the following series of steps.

Step 1 (ART and injection): receive injection of vaccine/adjuvant control. Patients remain on ART for 6 to 8 weeks.

Step 2 (first STI): all ART is stopped for up to 8 weeks with careful monitoring of viral load and CD4 T cells. Patients whose viral load is controlled may remain on Step 2 for an additional 6 weeks.

Step 3 (resumption of ART): restart ART for 14 weeks. Eligible patients receive an immunization with vaccine/adjuvant control at Week 9.

Step 4 (second STI): identical to Step 2. Step 5 (resumption of ART): identical to Step 3. Step 6 (analytical treatment interruption [ATI]): analytical "read-out" discontinuation of ART for up to 14 weeks.

Step 7 (long-term follow-up without ART): open only to patients with control of viral load who agree to participate in continued treatment withdrawal.

Step 8 (final resumption of ART): patients are followed for 8 weeks on ART to document the effect of restarting ART on suppression of viral load. Patients advance through steps as criteria for HIV RNA level, CD4 count, and treatment are met.

Patients have regular clinic visits for medical/medication histories, physical examinations, and laboratory tests for viral load and immunological parameters.