DNA-PK impact on HIV reservoir in the CNS

About This Grant

Project Summary: Although the resting memory CD4+ T cells are the best-recognized long-lived reservoirs of latent HIV provirus, it is now well accepted that the myeloid cells, especially of the central nervous system (CNS), including perivascular macrophages and microglial cells are the major target of HIV. The molecular mechanisms relevant to HIV latency are primarily defined by analyzing HIV latency in latently infected CD4+ lymphoid cells. However, very little is known about HIV latency/persistence in myeloid cells. Notably, the presence of HIV-harboring myeloid cells in the CNS is documented to be the key factor contributing to CNS inflammation and promoting HIV-associated neurocognitive disorder (HAND) in HIV patients. Microglial cells are the main HIV reservoir in the CNS, yet there is a gap in the knowledge regarding our understanding of the molecular mechanisms that maintain HIV reservoirs in those cells. Our long-term goal is to identify and characterize the underlying molecular mechanisms that regulate HIV latency in the CNS. We have shown the vital role of DNA-PK in supporting HIV transcription and latency-reactivation in both lymphoid and myeloid cells. Recently, we published one more article, bringing a total of 3 articles on this subject. The objective of this grant is to characterize the role of DNA-PK during HIV latency and define the molecular mechanisms by which DNA-PK supports HIV transcription in the main CNS reservoir, microglial cells. Based on our published and preliminary findings, we have hypothesized that DNA-PK modulates HIV transcription in microglial cells by reducing RNAPII pausing during HIV transcription. For testing our hypothesis, in Aim 1, we will establish the role of DNA-PK in relieving RNAPII pausing during HIV transcription and latency- reactivation in microglial cells, by Stimulating RNAPII processivity (elongation capability) and Relieving restrictions exerted by negative elongation factors to HIV transcription. In Aim 2, we will characterize the role of DNA-PK-induced chromatin modifications in regulating HIV gene expression and latent reservoir in microglial cells. Our rationale is that since HIV latency is primarily regulated at the transcriptional level, defining the precise and all mechanism(s) that regulate HIV transcription in microglial cells will offer novel therapeutic opportunities to target HIV reservoirs in the CNS. These studies will also provide a well-defined therapeutic target in the form of DNA-PK, and this new knowledge will be valuable for both basic and translational research. The proposed research is innovative because, besides iPSCs-derived human microglial cells (IDMs), it uses a novel ex vivo model system for HIV latency in microglia, that for the first time, allows the studies of the molecular correlates for HIV entry and exit into latency in microglial cells, which is otherwise an impossible task due to insufficient availability of brain autopsy specimens. This contribution is significant since the identified mechanisms, which regulate HIV transcription and latency in microglial cells, will facilitate the designing of optimized therapies targeting CNS reservoirs of HIV, and contributing towards cure approaches.