MAVS Orchestrates a Potent IFN-independent Antiviral Immunity by 2 Preserving Mitochondrial Integrity
Viruses target mitochondria, critical for antiviral defense and metabolism, to evade immunity. While mitochondrial antiviral-signaling protein (MAVS) is known for its regulation of type I interferon (IFN) signaling, we discover that its overarching primary role is safeguarding mitochondrial integrity against virus- and toxin-induced mitophagy. This function is critical in enacting a potent, IFN/NF-?B-independent antiviral response. Using SARS-CoV-2 (CoV-2) infection model, where disruption of MAVS aggregation and induction of mitophagy were observed, we demonstrate that functional MAVS prevents CoV-2-induced mitophagy and restricts viral replication without engaging type I or III interferon (IFN), and NF-?B pathways. Employing MAVS-knockout and MAVS:IFNAR1 double-knockout cells, and inhibition studies, our results further establish MAVS as a critical protector against virus- and chemical mitotoxin-induced mitophagy. Loss of MAVS results in increased mitochondrial membrane depolarization, reduced oxidative potential, and increased PINK1-dependent mitophagy leading to elevated viral replication-all reversed by MAVS supplementation. The IFN-independent antiviral immunity generated by MAVS-driven mitochondrial safeguarding conferred robust protection against mitophagy-inducing viruses, such as CoV-2 and JEV, but not DENV, which does not trigger mitophagy. By facilitating the mitochondrial integrity, MAVS governs the overall innate antiviral immunity- integrating IFN-dependent and IFN-independent mechanisms- and energy metabolism in the host cells. Thus, the regulation of these central functions makes MAVS a prime target for subverting host defenses and cellular energy homeostasis. These insights underscoring MAVS's wider role in sustaining mitochondrial homeostasis positions it as a promising target for antiviral strategies. Overall design: Experiment 1: RNA-Seq profiling of Huh7 cells upon overexpression of MAVS or Interferon alpha (IFN-a), in uninfected or CoV-2 infected conditions for 24 hours at an MOI of 1. Appropriate  Empty Vector and Vehicle controls are included.  Experiment 2: RNA-Seq profiling of Mouse Embryonic Fibroblasts (MEFs) isolated from WT and MAVS KO mice in uninfected and CoV-2 infected conditions at an MOI of 1 for 12, 24 and 48 hours.