Highly active antiretroviral therapy effectively targets viral replication but fails to eliminate proviruses in long-lived cell populations. Our knowledge of HIV persistence in the human brain remains limited. Microglia are the resident innate immune cells of the central nervous system. Our preliminary data indicate that HIV infection of primary human microglia cells results in proliferation (termed microgliosis). Our reporter HIV vector toolkit termed pMorpheus allows examination of latency establishment at the single cell level using microscopy and flow cytometry approaches. We hypothesize that HIV infection induces microgliosis by clonal expansion of latently infected microglia cells. This proposal leverages our pMorpheus based primary human microglia model system to experimentally test this hypothesis. We propose to investigate productive and latent HIV infections in depth in human primary microglia cells isolated from post-mortem brain tissues (Aim 1) and to identify biomarkers and cellular rewiring characteristic of HIV associated microgliosis (Aim 2). The experiments outlined in this high risk/high reward R21 application will not only fill critical knowledge gaps in our understanding of HIV latency establishment in primary human microglia cells but also inform on biomarkers of microgliosis and neuro-degeneration.