Extracellular MAVS associates with microvesicles that can actively trigger IFNβ production

Summary: Background: Type I interferons (IFN) are important in the pathogenesis of various autoimmune diseases, including lupus and dermatomyositis (DM). As mammalian cytoplasmic viral RNA sensors and mitochondrial adaptors, mitochondrial antiviral signaling (MAVS) protein can form aggregates that regulate IFNβ induction intracellularly. Recent evidence indicates that MAVS can be found in plasma. To explore how the extracellular MAVS exist and if they are bioactive for IFNβ induction, we investigated the potential association between MAVS and extracellular vesicles (EV), and the cellular mechanisms of EV-associated MAVS in IFNβ production. Methods: Human peripheral blood mononuclear cells (PBMCs) from healthy donors were treated without/with poly (I:C) (HMW)/LyoVec and TNFα for 24h, the supernatant were collected for EV isolation. MAVS-positive EVs released from PBMCs were also confirmed by confocal microscopy. Mouse bone marrow (BM) differentiated dendritic cells (DCs) were incubated for 24 h without/with EVs isolated from stimulated healthy PBMCs or from plasma of DM patients. The supernatant were collected for IFNβ detection, and the cells were lysed for IRF3 and NF-kB activation analysis. Results: Our study first detected that extracellular MAVS can be associated with EVs from MAVS-positive budding from Poly I:C/ TNFα-treated PBMCs. With SDD-AGE analysis of isolation EVs, we found the aggregated MAVS with EVs. Interestingly, MAVS aggregates preferentially accumulated in EVs isolated from stimulated PBMCs. Most importantly, these EV-associated MAVS are bioactive and can induce IFNβ production from mouse BM-DCs. Moreover, MAVS-associated EVs could trigger IRF3 and NF-κB activation, crucial upstream signals of IFNβ production. Conclusion: Extracellular MAVS can be harbored by EVs. EV-associated MAVS are bioactive and can enhance IFNβ production. These novel findings have advanced our understanding of type I IFN biology and provide insights into new therapeutic strategies for treatment of lupus and DM patients.