Respiratory Syncytial Virus Nonstructural Protein NS1 Colocalizes with Mitochondrial Antiviral Signaling (MAVS)Protein Following Infection

Abstract

Respiratory Syncytial Virus Nonstructural Protein NS1 Colocalizes with Mitochondrial Antiviral Signaling (MAVS) Protein Following Infection. Sandhya Boyapalle1, Terianne Wong1, Byeong Cha1, Subhra Mohapatra1 and Shyam Mohapatra1,2. University of South Florida College of Medicine1 and James A. Haley VA Medical Center2, Tampa, FL. RATIONALE: RSV NS1 protein plays a direct role in inhibiting the innate immune response by attenuating type-I IFN production during RSV infection. We investigated the role of NS1 in early infection and found that RSV replication and transcription occur near mitochondria. In this study, we examined colocalization of NS1 with antiviral mitochondrial protein, MAVS. METHODS: Human alveolar epithelial A549 cells or normal human bronchial epithelial cells were infected with wt RSV or RSV with an NS1 deletion. Colocalization and interaction of NS1 with MAVS on mitochondria was assessed by confocal microscopy and immuno-electron microscopy. Immunoprecipitation and western blotting were used to show NS1 interaction with MAVS, 12 and 24 h after RSV infection. RESULTS: Confocal microscopy showed NS1 localized to mitochondria and bound to the mitochondrial antiviral protein MAVS by 12 h postinfection. NS1 associated with MAVS at the mitochondria and was also found in the nucleus 24 h after infection. NS1 binding to MAVS was independent of NS2. Immunoelectron microscopy showed direct association of NS1 with MAVS. CONCLUSIONS: These results demonstrate that NS1 associates with MAVS early in infection. Since MAVS has been implicated in suppressing antiviral immune responses by interacting with RIG-I, the finding that NS1is associated with MAVS, could be exploited to develop novel therapeutics for RSV-induced lung diseases.