Abstract

The persistent threat of porcine epidemic diarrhea virus (PEDV) to the global swine industry is compounded by high neonatal piglet mortality and the absence of effective antiviral therapies. Host-directed strategies that reinforce immunity offer a promising avenue to counter viral immune evasion. Through screening of an FDA-approved compound library, we identify the small-molecule cyclocytidine hydrochloride (Cyclo-C) as a potent inhibitor of PEDV replication that acts by stabilizing the peroxisomal biogenesis factor PEX13, a previously unrecognized host restriction factor. The antiviral activity of Cyclo-C is strictly PEX13-dependent, as it is completely abrogated in PEX13 knockout cells. Mechanistically, Cyclo-C disrupts the interaction between PEX13 and the viral nonstructural protein 8 (NSP8), thereby preventing NSP8-mediated PEX13 degradation and the subsequent induction of PI3K/AKT/mTOR-driven pexophagy. Preservation of peroxisomal integrity stabilizes the peroxisome-localized pool of MAVS, leading to a robust enhancement of type III interferon (IFN-III) responses that suppress viral replication. Critically, this mechanism translates in vivo, where Cyclo-C treatment of PEDV-challenged piglets significantly reduces mortality, lowers viral loads, and protects intestinal villus architecture. Our findings establish Cyclo-C as a first-in-class host-directed therapeutic candidate and validate the concept that pharmacological preservation of peroxisome-mediated innate immunity represents an effective antiviral strategy against enteric coronaviruses.