Abstract

Mitochondrial antiviral signaling protein (MAVS) forms prion-like aggregates to activate innate immunity against RNA viruses, but the metabolic regulation of MAVS remains poorly understood. Here, we show that viral infection induces the formation of lipid droplets (LDs), which physically interact with mitochondria to promote the assembly of MAVS prion-like aggregates. Mechanistically, the LD-resident protein PLIN3 binds to the mitochondrial fusion protein MFN2, thereby relieving MFN2-mediated inhibition of MAVS and enabling its oligomerization. Furthermore, LD-mitochondria contact sites facilitate fatty acid transfer, sustaining mitochondrial membrane potential required for MAVS signaling. Oleic acid (OA)-enriched diets enhance LD formation and boost antiviral immunity in vivo, while myeloid-specific Seipin (an LD biogenesis regulator) deficiency attenuates MAVS activation and exacerbates viral susceptibility. These findings establish LDs as metabolic platforms that bridge cellular lipid metabolism with innate antiviral defense through organelle crosstalk, suggesting LD induction as a novel therapeutic strategy against viruses.