Porcine ISG20 Restricts PEDV Replication Independent of Its Exonuclease Activity and Is Associated with Enhanced IRF3 Activation

Porcine epidemic diarrhea virus (PEDV) causes severe enteric disease in swine and remains a major threat to the global pig industry. Interferon-stimulated gene 20 (ISG20) is a well-characterized antiviral effector; however, its specific role against PEDV remains poorly understood. This study investigated the antiviral function and underlying mechanism of ISG20 during PEDV infection. We observed that PEDV infection significantly induced ISG20 expression at both mRNA and protein levels in porcine intestinal epithelial cells (IPEC-J2). Functional assays demonstrated that ectopic expression of ISG20 potently suppressed PEDV proliferation, whereas shRNA-mediated knockdown facilitated viral replication. An exonuclease mutant of ISG20 (D94G) retained antiviral activity comparable to the wild-type ISG20 protein. Further investigation revealed that ISG20 overexpression was associated with increased IRF3 phosphorylation and nuclear accumulation and with elevated IFN-β mRNA abundance. These findings suggested that ISG20 may restrict PEDV by enhancing the IFN-β signaling pathway through phosphorylation of IRF3, rather than through direct viral RNA degradation, providing new insights into antiviral strategies against coronaviruses.