Perfluorooctanoic acid disrupts splenic immunity and antiviral responses in the LCMV model: Insights from single-cell transcriptomics

Per- and poly-fluoroalkyl substances (PFAS) are widely used chemicals and frequently detected in drinking water supplies worldwide and linked to a variety of adverse health outcomes. Accumulating evidence suggests that PFAS exposure might be associated with immune dysregulation and inflammatory disorders. However, impact on the immune system and cell type-specific mechanisms during viral infection remain unclear. We treated female C57BL/6J mice with perfluorooctanoic acid (PFOA; 2.5 or 7.5 mg/kg/day, oral gavage, 14 days), yielding serum PFOA concentrations of 83 μg/mL (low dose) and 141 μg/mL (high dose). Flow cytometry demonstrated broad immunosuppression, with significant reductions in multiple lymphoid and myeloid populations, including plasma cells and neutrophils even at the low dose, indicating sensitivity of humoral and innate compartments to PFOA exposure. Single-cell RNA-sequencing on pooled spleens (control vs. high-dose PFOA; 5522 vs. 4741 cells; 13 annotated clusters) revealed decreased proportions of macrophages, dendritic cells (DCs), NK cells, activated CD8⁺ T cells, follicular and transitional B cells, with increased naïve CD4⁺/CD8⁺ T cells, Tregs, TH1, marginal zone B cells, and VCAM1⁺ B cells. Challenging mice with LCMV Clone 13 after high-dose PFOA treatment (7.5 mg/kg/day, 14 days) increased viral RNA in the liver and lungs and reduced multifunctional virus-specific T-cell responses, including fewer LCMV GP33-tetramer⁺ CD8⁺ T cells. In the DCs, downregulated pathways included complement/coagulation, IL-6/JAK/STAT3, and IL-2/STAT5, while CCL5hiCD8⁺ T cells exhibited suppressed TNF-α/NF-κB and KRAS signaling. Overall, PFOA remodels splenic cellularity and weakens antiviral defense, reprograms inflammation and metabolism in DC, providing cell type specific mechanisms for PFAS-associated immunosuppression.