Deciphering HAND Pathogenesis Using Single-Nucleotide Omics Approaches
Although antiretroviral therapy (ART) effectively suppresses HIV-1 replication to undetectable levels and restores many immune parameters in people living with HIV (PLWH), these individuals remain at elevated risk for HIV-associated comorbidities. Among the most prevalent is neurocognitive impairment—a mild form of HIV-associated neurocognitive disorders (HAND)—which affects up to 50% of PLWH. Despite extensive investigation, the precise mechanisms underlying HAND pathogenesis remain unclear, in part due to its multifactorial nature. To address this, we conducted a comparative single-nucleus multi-omics analysis—integrating RNA sequencing (RNA-seq) and chromatin accessibility profiling (ATAC-seq)—of post-mortem brain tissues from HIV-infected individuals with and without HAND, as well as uninfected controls. Our results reveal substantial dysregulation in genes involved in inflammation, innate immunity, glycosylation, and cholesterol metabolism in HIV-infected brains (HAND+ and HAND-) relative to uninfected controls. Notably, these changes were further accentuated in HAND+ samples compared to HAND-, with microglia and oligodendrocytes emerging as the most affected cell populations—highlighting their potential central role in sustaining neuroinflammation. Interestingly, we observed a disconnect between transcriptomic and epigenomic signals: many inflammation-related genes located in accessible chromatin regions in HAND+ brains were not transcriptionally upregulated. This epigenetic priming—particularly in microglia and astrocytes—is consistent with the concept of trained immunity (TRIM), wherein prior exposures epigenetically “train” innate immune cells to respond differently to subsequent stimuli. Our findings suggest that maladaptive TRIM may be a key contributor to persistent neuroinflammation and the pathogenesis of HAND in the ART era. Overall design: paired single-nuclei multiomic RNA and ATAC sequencing profiling of HAND and Non-HAND flash frozen brain tissue samples