Porcine reproductive and respiratory syndrome virus (PRRVS) is a major swine viral pathogen that affects the pig industry worldwide. Control of early PRRSV infection is essential, and different types of PRRSV-positive samples can reflect the time point of PRRSV infection. This study aims to investigate the epidemiological characteristics of PRRSV in China from Q4 2021 to Q4 2022, which will be beneficial for porcine reproductive and respiratory syndrome virus (PRRSV)control in the swine production industry in the future. A total of 7518 samples (of processing fluid, weaning serum, and oral fluid) were collected from 100 intensive pig farms in 21 provinces, which covered all five pig production regions in China, on a quarterly basis starting from the fourth quarter of 2021 and ending on the fourth quarter of 2022. Independent of sample type, 32.1% (2416/7518) of the total samples were PCR-positive for PRRSV, including 73.6% (1780/2416) samples that were positive for wild PRRSV, and the remaining were positive for PRRSV vaccine strains. On the basis of the time of infection, 58.9% suckling piglets (processing fluid) and 30.8% weaning piglets (weaning serum) showed PRRSV infection at an early stage (approximately 90% of the farms). The sequencing analysis results indicate a wide range of diverse PRRSV wild strains in China, with lineage 1 as the dominant strain. Our study clearly demonstrates the prevalence, infection stage, and diversity of PRRSV in China. This study provides useful data for the epidemiological understanding of PRRSV, which can contribute to the strategic and systematic prevention and control of PRRSV in China.

This study aimed to evaluate the effectiveness of combining load–close–homogenize (LCH), test and removal (T&R), and rollover strategies for PRRSV elimination in breeding herds using PRRSV-positive weaned gilts. Here, a novel strategy was explored for PRRSV elimination from more than 1500 weaned gilts, and we documented the process from PRRSV natural infection to elimination at the herd level. With LCH implementation, the herd achieved PRRSV-positive stability within 8 months. Consequently, by rolling in self-breeding PRRSV-naive gilts to replace PRRSV-positive weaned sows batch by batch, the time from being positive stable to negative was 13 months. A PRRSV-positive farm intending to retain its genes in its repopulate farrow to become a finished breeding farm can initiate PRRSV elimination from its weaned gilts; this will result in the first farrowing batch of piglets aged 8–10 weeks becoming PRRSV-negative after 8 months of herd closure. This approach offers a viable pathway for genetic retention and PRRSV elimination in breeding farms.

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. IMPORTANCE: PDCoV 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.

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.