CCR2 restricts IFN-γ production by hippocampal CD8 TRM cells that impair learning and memory during recovery from WNV...

Central nervous system (CNS) resident memory CD8 T cells (T_RM) that express IFN-γ contribute to neurodegenerative processes, including synapse loss, leading to memory impairment. Here, we show that CCR2 signaling in CD8 T_RM that persist within the hippocampus after recovery from CNS infection with West Nile virus (WNV) significantly prevents the development of memory impairments. Using CCR2-deficient mice, we determined that CCR2 expression is not essential for CNS T cell recruitment or virologic control during acute WNV infection. However, transcriptomic analyses of forebrain CCR2⁺ versus CCR2^- CD8 T_RM during WNV recovery reveal that CCR2 signaling significantly regulates hippocampal CD8 T_RM phenotype and function via extrinsic and intrinsic effects, limiting expression of CD103, granzyme A and IFN-γ, respectively, and increasing the percentages of virus-specific CD8 T cells. Consistent with this, WNV-recovered Cd8a^creCcr2^fl/fl mice exhibit decreased recognition memory. Overall, these data implicate CCR2 signaling in the regulation of CD8 T_RM phenotype, including antiviral specificity and IFN-γ expression, highlighing a neuroprotective role for CCR2 in limiting CD8 T cell-mediated neuroinflammation and cognitive deficits, providing insights into potential therapeutic targets for CNS infections.