Nuclear receptor regulation of epigenetic mechanisms regulating HIV CNS latency - Background. This proposal entitled “ Nuclear receptor regulation of epigenetic mechanisms regulating HIV CNS latency is submitted in response to RFA-MH-22-280: Epigenetic Mechanisms Regulating HIV CNS Latency and Neuropathogenesis Using Novel Single Cell Technologies”. Microglial cells are the main target of HIV infection in the central nervous system (CNS) and form a reservoir of infection that persists despite antiviral treatment and contributes to HIV-associated neurocognitive disorder (HAND). Our goal. Using microglia cellular models, we demonstrated previously that the Nurr1 nuclear receptor, working in conjunction with ligand-activated nuclear receptors, plays a critical role in the regulation of HIV latency. We confirmed these observations in iPSC-derived human microglia (iMG), which provide the most informative primary cell model to study the interaction between HIV and this important target cell. Here, we will test the hypothesis that agonists of the Nurr1, RXR and RAR nuclear receptors lead to HIV silencing, suggesting a novel therapeutic strategy for HIV infections in the CNS. Underpinning this work are two key technical advances allowing the study of HIV in human microglia. First, we now have the capability to study HIV latency using iMG alone or in combination with iPSC-derived neurons and astrocytes - the first available model systems that do not rely on transformed cell lines. Second, in collaboration with the Cannon laboratory, we established a humanized mouse model of HIV latency in microglia based on the new NOG-hIL34 transgenic mouse, which is We demonstrated that the humanized mice support latent HIV infection of human microglia. We have been able to identify latently infected cells recovered from the humanized mice. In addition, we applied single cell RNA sequencing (scRNA-Seq) to confirm that the microglia have transcriptional characteristics that match reference human microglia and further identified subsets of reactive microglial cells that are associated with active HIV infections. the only humanized mouse model to support full human microglial cell maturation. Using these models, we will apply highly sensitive chromatin immunoprecipitation (ChIP) and single cell sequencing and epigenomics analyses to define nuclear receptor interactions with the HIV promoter region, and the mechanism of epigenetic silencing on the HIV LTR. How will we advance the field? Numerous clinically-effective, brain-penetrant drugs that regulate the nuclear receptors are available, many of which are now FDA approved, and will be evaluated using the iPSC derived cell models and in the humanized mouse model for their impact on HIV expression and latency in the context of an intact brain. We are undertaking these technically challenging studies because it is only by working within the context of authentic human microglial cells and an environment that better reflects the HIV-infected CNS, that the underlying physiology is accurately represented. We believe these studies will allow us to obtain a convincing proof-of-concept for this important therapeutic strategy to target HIV CNS Latency and Neuropathogenesis.
