Using the unique resources of the ALIVE cohort of persons who inject drugs (PWID) led by study co- investigator Gregory Kirk and the extensive experience in reservoir biology provided by co-investigators Rafick Sekaly, Joel Blankson, Greg Laird, and study PI Robert Siliciano, we will investigate the effects of heroin and cocaine use on the latent reservoir for HIV-1 in CD4+ T cells, which is the major barrier to cure. We hypothesize that by affecting inflammatory and immune pathways, active heroin and/or cocaine may alter T cell homeostasis and the distribution of HIV-1 proviruses among memory cells subsets, thereby affecting the size, turnover, and inducibility of the latent reservoir. In addition, we hypothesize that past injection drug use and the associated unstructured treatment interruptions will permanently affect the size and inducibility of the latent reservoir. Active drug use and legacy effects of past drug use may also affect that ability of host effector cells to clear infected cells during curative interventions. Together these studies of the size, inducibility, and composition of the reservoir, and the ability of host effector cells to clear infected cells, should provide critical information for the design of cure strategies for PWID and guide longitudinal and mechanistic studies in the second phase of the grant.