Recombinant porcine interferon δ8 inhibited porcine deltacoronavirus infection in vitro and in vivo

Porcine deltacoronavirus (PDCoV) poses a significant threat to both the pig industry and public safety, and has recently been identified in humans. Currently, there are no commercially available vaccines or antiviral treatments for PDCoV. In this study, recombinant porcine interferon δ8 (rINF-δ8) expressed by the HEK 293F expression system was used to evaluated its antiviral activity against PDCoV both in vitro and in vivo. Results demonstrated that rIFN-δ8 displayed non-toxic to ST cells and primary PAMs, and effectively inhibited PDCoV replication in a dose-dependent manner in vitro, with complete suppression of virus replication at a concentration of 2 μg/ml. Treatment of piglets with two doses of 25 μg/kg of rIFN-δ8 reduced clinical symptoms, decreased virus shedding, alleviated intestinal damage, and lowered the viral load in the jejunum and ileum. Furthermore, the levels of interferon-stimulated genes (ISGs) such as Viper, Mx1, ISG15, IFIT1, OSA, and IFITM1 were significantly increased both in vitro and in vivo, with elevated ISG levels sustained for at least 3 days in vivo. These findings suggest that rIFN-δ8 has the potential to serve as an effective antiviral agent for preventing PDCoV in pigs in the future.