HIV-1 evolves rapidly and multiple genetic subtypes have been isolated from a number of geographic locations. There are limited data on the distribution of subtypes in the Southern African HIVNET sites. Data suggest subtype C HIV-1 predominates and this study is designed to substantiate and extend these observations to understand the biological relationship between HIV-1 subtypes, genetic variability, and immune responses. Earlier studies were conducted using individuals who had been seropositive for 3 to 9 years with advanced disease status; this study will test reactivity during the early stage of infection. This will assist in the rational selection of prototypic isolates for inclusion in either a single universal vaccine or vaccines tailored for specific subtypes/geographical regions.

Volunteers are recruited from Malawi, South Africa, Zambia, and Zimbabwe. The earliest possible cases of seroconversion are included. At enrollment, participants are counseled appropriately for their HIV status and demographic information is obtained. Participants are followed quarterly up to 12 months. Epidemiological, clinical, and laboratory data are collected during physical exams and blood draws at each visit. Blood samples are used to assess CD4 counts, plasma viral load, genetic parameters, and individual immune responses. Participants who are seronegative or whose status is unknown are tested for HIV at each visit, with post-test counseling when participants return to the clinic for test results.

In addition to enrolling the HIV-infected and uninfected volunteers, each site contributes a 5-ml blood sample from 50 seronegative individuals for DNA extraction and HLA genotyping.