Julia Barilo, Queen's University

Andra Banete1,3, Julia Barilo1, Michael J. Rauh2, Bruce W. Banfield1, and Sameh Basta1,2* 1 Department of Biomedical and Molecular Sciences, Queen's University 2 Department of Pathology and Molecular Medicine, Queen's University 3 Department of Laboratory Medicine and Pathobiology, University of Toronto

Fighting & Responding

Arenaviruses such as lymphocytic choriomeningitis virus (LCMV) evade host innate immune signaling to establish infection. While classically activated macrophages (Mφ) are known to restrict viral replication, the antiviral capacity of alternatively activated Mφ remains poorly defined. Here, we examined how prolonged IL-4 priming alters Mφ susceptibility to LCMV and modulates antiviral signaling pathways. Spleen-derived Mφ were polarized with IL-4 (24-48h) and infected with LCMV-WE. Prolonged IL-4 stimulation significantly reduced viral nucleoprotein expression and progeny virus production compared to non-activated Mφ. Viral entry was not impaired, indicating restriction at post-entry stages of the viral life cycle. Unlike M1 Mφ, which upregulated RIG-I and MDA5, IL-4 primed Mφ, restricted LCMV independently of increased RLR expression. In response to infection, IL-4 primed Mφ exhibited enhanced IFN-α induction and increased secretion of pro-inflammatory cytokines. Confocal microscopy revealed infection-associated mitochondrial remodeling and reduced MAVS co-localization with mitochondria. Notably, prolonged IL-4 stimulation increased MAVS localization to peroxisomes, suggesting a shift in antiviral signaling platforms. Together, these findings demonstrate that Mφ activation state critically shapes arenavirus replication and identify peroxisome-associated MAVS signaling as a potential mechanism limiting LCMV infection.