The Role of Myeloid Cells in HIV Latency and Persistence in the Brain

Latently infected CD4+ T cells are considered to be the most important HIV reservoir preventing the implementation of an HIV cure. However, myeloid cells have been shown to be infected by HIV/SIV and to establish latency in animal models1-4. Therefore, elimination of the T cell reservoir alone is not likely to result in complete virus eradication. One of our long-term goals is to aid the development of effective HIV cure strategies by gaining a better understanding of the type and location of the cells that harbor replication competent HIV under ART suppression. HIV-associated neurological disorders or HAND affect up to 50% of people living with HIV (PLWH)5-7 suggesting that HIV-infected cells may persist in the brain of ART-suppressed individuals. HIV-DNA has been readily detected in the CSF of aviremic ART-suppressed PLWH and its presence is associated with poorer neurocognitive performance8. Analyses of brain tissue obtained postmortem from PLWH indicate that macrophages and microglia are major targets for HIV infection in the brain9-11 and demonstrate the presence of HIV-DNA+ cells in brain tissue from aviremic individuals10-12. Microglia are the predominant population of myeloid cells in the brain and in contrast to macrophages, are long lived and undergo cell division13,14. For these reasons, microglia are thought to represent a key cellular reservoir of HIV in the brain11. While there is a significant body of knowledge about the mechanisms of HIV latency and persistence in resting CD4+ T cells, there is significantly less known about HIV persistence in myeloid cells and therefore, a need to establish their possible role as a source of HIV reactivation after ART discontinuation. Specifically, in the brain the contribution of microglia is relatively unknown due in part to the difficulties in sampling cells in this compartment in PLWH. Our hypothesis is that HIV maintains a persistent reservoir in the brain under suppressive ART and our objective is to utilize an innovative humanized mouse model reconstituted with human brain microglia to increase the knowledge and understanding about how microglia contribute to HIV persistence and viral rebound by analyzing 1) HIV suppression by ART in human microglia in the brain, 2) the viral reservoir present in infected microglia, and 3) the development of HIV latency and rebound in human microglia in the brain after analytical therapy interruption. The new knowledge gained from the proposed experiments will contribute to a better understanding of HIV persistence in the brain, reactivation, and aid the development of novel HIV Cure approaches that target the CNS.