STING1 negatively regulates translation and replication of Foot-and-Mouth Disease Virus independently of interferon and is antagonized by the viral proteins 3C and 2B

Foot-and-mouth disease virus (FMDV), a highly contagious picornavirus, employs multifaceted strategies to evade host innate immunity, with viral proteins 3C protease (3C pro ) and 2B serving as key immune antagonists. The stimulator of interferon genes 1 (STING1) is a critical innate immune adaptor; however, its role and regulatory mechanisms during FMDV infection remain incompletely understood. Here, we report that STING1 inhibits FMDV replication through an interferon (IFN)-independent mechanism, while FMDV counteracts this antiviral effect by degrading STING1 via 3C pro and 2B. Mechanistically, FMDV 3C pro mediates STING1 degradation in a protease activity-dependent manner; this STING1-degrading activity is conserved among 3C pro proteins of poliovirus, enterovirus 71, and coxsackievirus, but not senecavirus A. In contrast, FMDV 2B suppresses STING1 expression at the mRNA level, and neither proteasomal, lysosomal, nor caspase pathways are involved in 3C pro /2B-mediated STING1 downregulation. Furthermore, the STING1 stabilizer SB24011 enhances endogenous STING1 expression, dose-dependently inhibits FMDV replication by targeting viral internal ribosome entry site (IRES)-mediated translation, and exhibits broad-spectrum antiviral activity against multiple picornaviruses. In vivo , SB24011 treatment alleviates virus-induced histopathological lesions. Collectively, our findings reveal a novel IFN-independent antiviral role of STING1 against FMDV, identify 3C pro and 2B as FMDV-encoded STING1 antagonists, and highlight the potential of SB24011 as a broad-spectrum anti-picornavirus therapeutic agent. • FMDV infection leads to the downregulation of STING1 protein expression, a process primarily mediated by the viral proteins. • STING1 inhibits FMDV replication through an interferon-independent pathway. • The STING1 stabilizer SB24011 effectively suppresses FMDV replication by inhibiting viral translation. • SB24011 also demonstrates broad-spectrum antiviral efficacy against a variety of picornaviruses.