HIV invades the CNS during acute infection and persists in the brain despite combination antiretroviral therapy. The cellular and molecular mechanisms of HIV latency in the brain are not entirely clear. Data from our lab and that of others indicate that astrocytes, which constitute 50-70% of brain cells, are reservoirs for HIV exhibiting several important features defining HIV reservoirs. Yet little is known about the molecular mechanism(s) driving HIV latency in astrocytes and the extent of HIV compartmentalization within astrocytes. To address some of these knowledge gaps, we will define the epigenetic modifications of HIV DNA that drive latency in astrocytes and compare how these modifications are different or similar to those engaged by other HIV infected resident brain cells (macrophages/microglia) and within resting CD4+ T cells. Further, while there are extensive studies documenting HIV compartmentalization in the CNS, there is little evidence for the extent of HIV compartmentalization in astrocytes and its association with severity of HAND. We will assess the extent of HIV compartmentalization in astrocytes and its relationship to HIV from macrophages/microglia and correlation with various degrees of HAND. Finally, we will better define a novel dual role for astrocytes in NeuroAIDS that potentially regulates the extent of HIV latency in the CNS. We previously demonstrated that while astrocytes support HIV infection, they restrict virus output unless the Wnt/b-catenin signaling pathway is disrupted (e.g. inhibition of Wnt/b- catenin signaling in astrocytes leads to productive HIV replication). We provide preliminary data to indicate that astrocytes secrete specific Wnt ligands (soluble glycoproteins that initiate the Wnt/b-catenin pathway) to limit HIV replication in infiltrating peripheral blood mononuclear cells (PBMCs). We will define the role of Wnt ligands in suppression of HIV in leukocytes and establish the mechanism by which they do so. Collectively, these studies are critical to inform better therapeutic strategies to tackle the challenge of HIV latency in the CNS.
HIV establishes latency in the brain early on during infection and remains there despite current antiviral drugs. In the CNS, astrocytes constitute a cellular reservoir for HIV. How HIV remains latent in astrocytes in comparison to other brain and blood cells is not clear. Our studies will define mechanisms that drive HIV latency in astrocytes, establish extent of HIV compartmentalization within astrocytes, and define a unique role of astrocytes in balancing HIV latency and secreting factors that inhibit HIV replication in adjacent cells. Collectively these studies will help us understand HIV latency in the CNS to be in a better position to undertake the challenge of HIV latency in the CNS.
