African swine fever virus pC147L inhibits retinoic acid-inducible gene I-like receptors pathway via targeting MAVS-TRAF6 complex.

African swine fever virus (ASFV) suppresses the host's innate immunity by interfering with pattern recognition receptors (PRRs) signaling pathways; however, the molecular mechanisms by which it inhibits PRR signaling remain poorly characterized. This study aimed to identify the ASFV-encoded protein pC147L. The pC147L, a subunit of the viral RNA polymerase, acts as a potent inhibitor of the Retinoic Acid-inducible Gene I (RIG-I)-like receptors (RLRs) pathway, which mediates the detection of viral double-stranded RNA. We used quantitative reverse transcription-polymerase chain reaction (qRT-PCR) and western blot assays, and demonstrated that pC147L specifically blocked RLRs-mediated interferon-β (IFN-β) production without affecting other antiviral pathways, such as TLR3 or cGAS-STING pathways. Mechanistically, pC147L targeted mitochondrial antiviral signaling protein (MAVS), the central adaptor of RLR signaling pathway, to disrupt downstream signal transduction. Co-immunoprecipitation assays revealed that pC147L physically interacted with both MAVS and TRAF6, preventing the formation of the MAVS-TRAF6 complex and subsequent TBK1 recruitment required for MAVS signalosome assembly. Furthermore, the overexpression and knockdown experiments demonstrated that pC147L enhanced ASFV replication by suppressing the type I IFN response in porcine alveolar macrophage (PAM) cells. Collectively, our findings revealed a positive role of pC147L during ASFV infection by promoting viral replication through suppressing innate immune response, presenting it as a potential target for vaccine development.