Impaired interferon response in senecavirus A infection and identification of 3C as an antagonist.

Senecavirus A (SVA), a picornavirus, causes vesicular diseases and epidemic transient neonatal losses in swine, resulting in a multifaceted economic impact on the swine industry. SVA counteracts host antiviral response through multiple strategies facilitatng viral infection and transmission. However, the mechanism of how SVA modulates interferon (IFN) response remains elusive. Here, we demonstrate that SVA 3C protease (3C) blocks the transduction of Janus kinase-signal transducer and activator of transcription (JAK-STAT) signaling pathway to antagonize type I IFN response. Mechanistically, 3C selectively cleaves and degrades STAT1 and STAT2 while does not target JAK1, JAK2, and IRF9, through its protease activity. Notably, SVA 3C cleaves human and porcine STAT1 on a Leucine (L)-Aspartic acid (D) motif, specifically L693/D694. In the case of STAT2, two cleavage sites were identified: glutamine (Q) 707 was identified in both human and porcine, while the second cleavage pattern differed, with residues 754-757 (Valine-Leucine-Glutamine-Serine motifs) in human STAT2 and Q758 in porcine STAT2. These cleavage patterns by SVA 3C partially differ from previously reported classical motifs recognized by other picornaviral 3C, highlighting the distinct characteristics of SVA 3C. Together, these results reveal a mechanism by which SVA 3C antagonizes IFN-induced antiviral response but also expands our knowledge about the substrate recognition patterns for picornaviral 3C.IMPORTANCESenecavirus A (SVA), the only member in the genus within the family, causes vesicular diseases in pigs that are clinically indistinguishable from foot-and-mouth disease (FMD), a highly contagious viral disease listed by the World Organization for Animal Health (WOAH). Interferon (IFN)-mediated antiviral response plays a pivotal role in restricting and controlling viral infection. Picornaviruses evolved numerous strategies to antagonize host antiviral response. However, how SVA modulates the JAK-STAT signaling pathway, influencing the type I IFN response, remains elusive. Here, we identify that 3C, a protease of SVA, functions as an antagonist for the IFN response. 3C utilizes its protease activity to cleave STAT1 and STAT2, thereby diminishing the host IFN response to promote SVA infection. Our findings underscore the significance of 3C as a key virulence factor in the antagonism of the type I signaling pathway during SVA infection.