Swine GBP1 restricts PDCoV replication via disrupting the replication and transcription complex formation.

Porcine deltacoronavirus (PDCoV) has been prevalent worldwide for over a decade, causing considerable economic damage to the pig industry and posing a potential threat to public biosecurity. In this study, we found that one of the interferon-stimulated genes (ISGs), swine guanylate-binding proteins 1 (sGBP1), was induced by PDCoV. In the experiments we describe below, we demonstrate that sGBP1 is an antiviral gene inhibiting PDCoV infection by utilizing the sGBP1 stable expression cell line and sGBP1 knockout cell line. Both the large GTPase domain and the α-helical domain are responsible for sGBP1 anti-PDCoV replication. Notably, sGBP1 directly interacts with the scaffold protein NSP8 of the PDCoV replication and transcription complex (RTC). Moreover, the large GTPase domain of sGBP1 interacts with the NTD domain of NSP8, which disrupts the interaction between NSP8 and NSP12 in RTC. In addition, sGBP1 is able to bind with the RNA of PDCoV and inhibits RTC from binding with virus RNA. Here, our research uncovers a new mechanism through which sGBP1 inhibits PDCoV replication. This finding not only deepens our comprehension of the antiviral roles of ISG molecules but also offers a promising target for the prevention of PDCoV infections.IMPORTANCEPDCoV is an enteric coronavirus that has garnered significant global attention due to its current prevalence in causing diarrhea and even mortality in pigs, as well as its broad host range encompassing poultry, rodents, ruminants, and even humans. Understanding the mechanism by which host factors inhibit viral replication is critical for developing effective antiviral strategies. Here, we found that PDCoV induced swine guanylate-binding proteins 1 (sGBP1) to inhibit viral replication. Our study first reveals that sGBP1 impairs the replication and transcription complex (RTC) formation through two ways: (i) competes with the RNA-dependent RNA polymerase (RdRp) NSP12 to bind with NSP8; (ii) sGBP1 binds with PDCoV RNA to inhibit the RNA binding of RTC. Our results uncover a previously unknown antiviral mechanism of GBP1, offering a promising target for the prevention of viral infections.