SPECIFIC AIM 1) To determine the relative long-term benefits of immediate vs. early vs. delayed initiation of ART. Initiation of ART during Fiebig I-II, while theoretically appealing, is infeasible in clinical practice because the duration of FI-II is very short (10 days) and because antibody-based tests, used almost world-wide, are unable to diagnose FI-II. Six months of ART initiated shortly after seroconversion (FIII) can improve many immune parameters, although not to the near normal level seen when ART is initiated during FI-II (4). Longer-term follow-up of seropositive participants who started ART ~2-8 months after HIV acquisition compared to those initiating ART during FI-II is needed to see whether markers of inflammation and residual viral load might continue to improve after 6 months, decreasing the difference between the groups. Methods: the investigators will evaluate the 3 groups using specimens from equivalent times after ART initiation for a total of 3.5 years of ART, comparing CD4 counts, time to reach undetectable VL, the GI microbiota, and inflammatory markers. The size of the replication-competent reservoir in PBMCs will be compared using measurements of multiply spliced viral RNA (msRNA) and the degree of low-level infection of new cells by assessing the production of circular viral DNA (2LTR HIV DNA). They will model the size and persistence of the viral reservoir across all ART-compliant study subjects. In a subset of individuals from each group, the proviral integration sites will be defined at ART initiation and after 1.5 and 3.5 years to assess the maintenance of the reservoir by proliferating CD4 cells.