MODELING PRO-INFLAMMATORY CROSSTALK BETWEEN MICROGLIA AND ASTROCYTES DURING HIV INFECTION
HIV-Associated neurocognitive disorder (HAND) is a spectrum of cognitive deficits observed in 50% of people living with HIV (PWH). HAND is associated with viral transcription in the central nervous system (CNS) and neuroinflammation, though the mechanisms that drive this pathology remain poorly understood. The main cellular host for HIV in the CNS are microglia, which are difficult to model in vitro. We have developed an induced pluripotent stem cell (iPSC) based model of microglia (iMg) that reliably express key markers of microglia lineage and are transcriptomically similar to ex vivo microglia. We have shown that our iMg also support productive HIV infection, though at a reduced level compared to macrophages. Additionally, we show that iMg exhibit a weaker immune response to HIV challenge than macrophages. Based on this observation, we included iPSC-derived astrocytes (iAst) in coculture with iMg, attempting to improve the immune response to HIV infection and restrict viral replication. Surprisingly, we found that inclusion of iAst led to a robust increase in the rate of HIV replication in microglia. This increase in HIV replication was not due to replication in iAst themselves and was associated with production of TNFɑ by iAst. TNFɑ is associated with HAND and is known to increase transcription of HIV genomes in infected cells via NF-κB signaling. We thus hypothesized that iAst-derived TNFɑ drove the observed increase in HIV replication in iMg/iAst cocultures. Indeed, we showed that addition of exogenous TNFɑ to iMg led to increased HIV replication, whereas neutralization of TNFɑ in iMg/iAst cocultures reduced HIV replication. Further, we used a pharmacological inhibitor of NF-κB signaling to show that the increased HIV replication observed in iMg/iAst cocultures indeed depends on this signaling axis. Finally, we show that HIV infection in iMg leads to repositioning of lysosomes and release of lysosomal content into the extracellular space, which we propose leads to inflammatory activation of iAst. These results suggest a potential mechanism of non-resolving neuroinflammation in PWH and suggest targets for therapies designed to mitigate HAND.
Biology, Life Sciences, Neuroscience and Neurobiology
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