Single-cell RNA sequencing study of brain-derived cells from two individuals with HIV-associated neurocognitive dysfunction
The high prevalence of cognitive alterations in persons with HIV (PWH)  despite effective antiretroviral therapy (ART) is associated with sustained neuroinflammation.  Here, we uncover the signaling pathways that are essential for persistent immune activation and might underly development of HIV associated Neurocognitive Disorder (HAND). We analyze the brain proteome from PWH on ART during HAND progression. We observe that 73.3% of the significantly upregulated proteins in brains from PWH and HAND (compared to PWH with normal cognition) belong to immune pathways. Among them, 36.4% of upregulated innate immune-related proteins are within the type I interferon (IFN-I) signaling, suggesting that persistent IFN-I activation is central to HAND-associated brain immune activation. Single cell (sc)RNA-seq analysis confirmed that FN-I occurs mainly in astrocytes during acute HIV infection in the microglia-containing organoid (MCO) model of HIV infection  and persistent in microglia in the brain of PLWH on ART. Of note, IFN-I persistence is independent of HIV status but associated with the induction of human endogenous retroviruses-W (HERV-W) Env during HAND progression after initial HIV infection and its associated immune activation. When induced, HERV-W Env directly activates IFN-I signaling in astrocytes, but not in microglia. Together, IFN-I signaling may be initiated directly in the astrocytes after acute HIV infection then sustained in the microglia during ART. IFN-I persists due to expression of HERV-W Env, thereby contributing to the persistent immune activation in the HAND brain on ART, independent of HIV and insensitive to ART.  Our data link the neuroinflammation of persistent IFN-I signaling to the HAND brain on ART. Overall design: Fresh human brain tissues were collected via established rapid research autopsy procedures from the donors enrolled in “the Last Gift” program (Donor1) and the National Disease Research Interchange (Donor2). Brain tissue was dissociated using a protocol established to preferentially isolate brain microglial cells. Single-cell suspensions were loaded into the 10x Genomics chromium device for 3' single-cell RNA sequencing.