The efficiency of the immune response to HIV antigens is the critical feature that allows some individuals with chronic HIV infection to maintain low level viremia (less than 3000 copies/ml). The fundamental measurement of this response is the steady state level of viremia in the absence of antiretroviral drugs. However, using this clinical endpoint in vaccine and drug trials is time-consuming. Several laboratory assays of HIV T cell function have been developed to measure the key characteristics of an efficient immune response. This study will evaluate these assays in two distinct patient populations.

Two patient cohorts will be followed in this study. Cohort A will enroll patients who are stable on highly active antiretroviral therapy (HAART). These patients will have been on the same HAART regimen for at least 9 months prior to study entry. Cohort B will enroll patients with chronic HIV infection and efficient immune control. These patients will have not been on any antiretroviral drugs for at least 6 months and will have viral loads less than 3,000 copies/ml. Participants in both cohorts will have blood drawn at study entry and Weeks 12 and 24. Blood samples will be used for CD4/CD8 cell count, plasma HIV-1 RNA, and immunologic assays.