Anti-IL-15 treatment reduces acute lentivirus inflammation and signaling in the brain.

HIV-associated neurocognitive disorder (HAND) remains a significant complication in people living with HIV, with inflammation playing a central role in its pathogenesis. Understanding how the brain's immune network responds to lentiviral infection is therefore critical. We show that acute simian immunodeficiency virus (SIV) infection elicits a robust resident brain immune response in control animals, marked by enhanced microglial ramification. In contrast, animals pretreated with anti-interleukin (IL)-15 antibodies (αIL-15) before SIVmac239X infection display reduced neuroinflammation without altering brain viral burden. Peripheral IL-15 blockade decreases brain-infiltrating T lymphocytes, alters their spatial dynamics, suppresses proinflammatory cytokine (IL-6) expression in microglia, and increases anti-inflammatory cytokine (TGF-β) expression in brain macrophages. Transcriptomic profiling reveals a global reduction in inflammatory signaling and an upregulation of genes associated with M1 macrophage pathways. Together, these findings demonstrate that peripheral IL-15 modulation attenuates neuroinflammation during acute lentiviral infection and highlight IL-15 as a potential therapeutic target for neuroinflammatory conditions of the brain.