Porcine Coronaviruses: Overview of the State of the Art

Prevalence and Genetic Characterization of Porcine Respiratory Coronavirus in Korean Pig Farms

Porcine respiratory coronavirus (PRCV) is a member of the species Alphacoronavirus 1 within the genus Alphacoronavirus of the family Coronaviridae. A few studies have been conducted on the prevalence of PRCV since its first identification in 1997, but there have been no recent studies on the prevalence and genetic characterization of the virus in Korea. In this study, the seroprevalence of PRCV was determined in Korean pig farms using a commercially available TGEV/PRCV differential enzyme-linked immunosorbent assay kit. The farm-level seroprevalence of PRCV was determined to be 68.6% (48/70), similar to previous reports in Korea, suggesting that PRCV is still circulating in Korean pig herds nationwide. Among the 20 PRCV-seropositive farms tested in this study, PRCV RNAs were detected in 17 oral fluid samples (28.3%) from nine farms (45.0%), while TGEV RNAs were not detected in any sample. To investigate the genetic characteristics of Korean PRCV strains, genetic and phylogenetic analyses were conducted on PRCV spike gene sequences obtained in this study. The three Korean PRCV strains (KPRCV2401, KPRCV2402, and KPRCV2403) shared 98.5-100% homology with each other and 96.2-96.6% and 91.6-94.5% homology with European and American strains, respectively. A 224-amino acid deletion was found in the S gene of both Korean and European PRCVs but not in that of American PRCVs, suggesting a European origin for Korean PRCVs. Phylogenetic analysis showed that Korean PRCVs are more closely related to European PRCVs than American PRCVs but clustered apart from both, suggesting that Korean PRCV has evolved independently since its emergence in Korean PRCVs. The results of this study will help expand knowledge on the epidemiology and molecular biology of PRCV currently circulating in Korea.

Dipeptidyl peptidase 4 interacts with porcine coronavirus PHEV spikes and mediates host range expansion

Porcine hemagglutinating encephalomyelitis virus (PHEV), a neurotropic betacoronavirus, is prevalent in natural reservoir pigs and infects mice. This raises concerns about host jumping or spillover, but little is known about the cause of occurrence. Here, we revealed that dipeptidyl peptidase 4 (DPP4) is a candidate binding target of PHEV spikes and works as a broad barrier to overcome. Investigations of the host breadth of PHEV confirmed that cells derived from pigs and mice are permissive to virus propagation. Both porcine DPP4 and murine DPP4 have high affinity for the viral spike receptor-binding domain (RBD), independent of their catalytic activity. Loss of DPP4 expression results in limited PHEV infection. Structurally, PHEV spike protein binds to the outer surface of blades IV and V of the DPP4 β-propeller domain, and the DPP4 residues N229 and N321 (relative to human DPP4 numbering) participate in RBD binding via its linked carbohydrate entities. Removal of these N-glycosylations profoundly enhanced the RBD-DPP4 interaction and viral invasion, suggesting they act as shielding in PHEV infection. Furthermore, we found that glycosylation, rather than structural differences or surface charges, is more responsible for DPP4 recognition and species barrier formation. Overall, our findings shed light on virus-receptor interactions and highlight that PHEV tolerance to DPP4 orthologs is a putative determinant of its cross-species transmission or host range expansion.IMPORTANCEPHEV is a neurotropic betacoronavirus that is circulating worldwide and has raised veterinary and economic concerns. In addition to being a reservoir species of pigs, PHEV can also infect wild-type mice, suggesting a "host jump" event. Understanding cross-species transmission is crucial for disease prevention and control but remains to be addressed. Herein, we show that the multifunctional receptor DPP4 plays a pivotal role in the host tropism of PHEV and identifies the conserved glycosylation sites in DPP4 responsible for this restriction. These findings highlight that the ability of PHEV to utilize DPP4 orthologs potentially affects its natural host expansion.

Establishment and application of a quadruplex real-time RT-qPCR assay for differentiation of TGEV, PEDV, PDCoV, and PoRVA

Porcine viral diarrhea is a common ailment in clinical settings, causing significant economic losses to the swine industry. Notable culprits behind porcine viral diarrhea encompass transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and porcine rotavirus-A (PoRVA). Co-infections involving the viruses are a common occurrence in clinical settings, thereby amplifying the complexities associated with differential diagnosis. As a consequence, it is therefore necessary to develop a method that can detect and differentiate all four porcine diarrhea viruses (TGEV, PEDV, PDCoV, and PoRVA) with a high sensitivity and specificity. Presently, polymerase chain reaction (PCR) is the go-to method for pathogen detection. In comparison to conventional PCR, TaqMan real-time PCR offers heightened sensitivity, superior specificity, and enhanced accuracy. This study aimed to develop a quadruplex real-time RT-qPCR assay, utilizing TaqMan probes, for the distinctive detection of TGEV, PEDV, PDCoV, and PoRVA. The quadruplex real-time RT-qPCR assay, as devised in this study, exhibited the capacity to avoid the detection of unrelated pathogens and demonstrated commendable specificity, sensitivity, repeatability, and reproducibility, boasting a limit of detection (LOD) of 27 copies/μL. In a comparative analysis involving 5483 clinical samples, the results from the commercial RT-qPCR kit and the quadruplex RT-qPCR for TGEV, PEDV, PDCoV, and PoRVA detection were entirely consistent. Following sample collection from October to March in Guangxi Zhuang Autonomous Region, we assessed the prevalence of TGEV, PEDV, PDCoV, and PoRVA in piglet diarrhea samples, revealing positive detection rates of 0.2 % (11/5483), 8.82 % (485/5483), 1.22 % (67/5483), and 4.94 % (271/5483), respectively. The co-infection rates of PEDV/PoRVA, PEDV/PDCoV, TGEV/PED/PoRVA, and PDCoV/PoRVA were 0.39 %, 0.11 %, 0.01 %, and 0.03 %, respectively, with no detection of other co-infections, as determined by the quadruplex real-time RT-qPCR. This research not only established a valuable tool for the simultaneous differentiation of TGEV, PEDV, PDCoV, and PoRVA in practical applications but also provided crucial insights into the prevalence of these viral pathogens causing diarrhea in Guangxi.

Inhibition of PEDV viral entry upon blocking N-glycan elaboration

Porcine Epidemic Diarrhea Virus (PEDV) poses a significant threat to the global swine industry, demanding a thorough understanding of its cellular invasion mechanism for effective interventions. This study meticulously investigates the impact of O- and N-linked glycans on PEDV proteins and host cell interaction, shedding light on their influence on the virus's invasion process. Utilizing CRISPR-Cas9 technology to inhibit cell surface O- and N-linked glycan synthesis demonstrated no discernible impact on virus infection. However, progeny PEDV strains lacking these glycans exhibited a minor effect of O-linked glycans on virus infection. Conversely, a notable 40% reduction in infectivity was observed when the virus surface lacked N-linked glycans, emphasizing their pivotal role in facilitating virus recognition and binding to host cells. Additionally, inhibition studies utilizing kifunensine, a natural glycosidase I inhibitor, reaffirmed the significant role of N-linked glycans in virus infection. Inhibiting N-linked glycan synthesis with kifunensine substantially decreased virus entry into cells and potentially influenced spike protein expression. Assessment of the stability and recovery potential of N-linked glycan-deficient strains underscored the critical importance of N-glycans at various stages of the virus lifecycle. In vivo experiments infecting piglets with N-glycan-deficient strains exhibited milder clinical symptoms, reduced virus excretion, and less severe pathological lesions compared to conventional strains. These findings offer promising translational applications, proposing N-glycosylation inhibitors as potential therapeutic interventions against PEDV. The utilization of these inhibitors might mitigate virus invasion and disease transmission, providing avenues for effective antiviral strategies and vaccine development. Nonetheless, further research is warranted to elucidate the precise mechanisms of N-linked glycans in PEDV infection for comprehensive clinical applications.

The N-glycosylation at positions 652 and 661 of viral spike protein negatively modulates porcine deltacoronavirus entry

N-glycosylation is a highly conserved glycan modification that plays crucial roles in various physiological processes, including protein folding, trafficking, and signal transduction. Porcine deltacoronavirus (PDCoV) poses a newly emerging threat to the global porcine industry. The spike protein of PDCoV exhibits a high level of N-glycosylation; however, its role in viral infection remains poorly understood. In this study, we applied a lentivirus-based entry reporter system to investigate the role of N-glycosylation on the viral spike protein during PDCoV entry stage. Our findings demonstrate that N-glycosylation at positions 652 and 661 of the viral spike protein significantly reduces the infectivity of PDCoV pseudotyped virus. Overall, our results unveil a novel function of N-glycosylation in PDCoV infection, highlighting its potential for facilitating the development of antiviral strategies.

Porcine lung tissue slices: a culture model for PRCV infection and innate immune response investigations

Respiratory coronaviruses (RCoVs) significantly threaten human health, necessitating the development of an ex vivo respiratory culture system for investigating RCoVs infection. Here, we successfully generated a porcine precision-cut lung slices (PCLSs) culture system, containing all resident lung cell types in their natural arrangement. Next, this culture system was inoculated with a porcine respiratory coronavirus (PRCV), exhibiting clinical features akin to humans who were infected by SARS-CoV-2. The results demonstrated that PRCV efficiently infected and replicated within PCLSs, targeting ciliated cells in the bronchioles, terminal bronchioles, respiratory bronchioles, and pulmonary alveoli. Additionally, through RNA-Seq analysis of the innate immune response in PCLSs following PRCV infection, expression levels of interferons, inflammatory cytokines and IFN stimulated genes were significantly upregulated. This ex vivo model may not only offer new insights into PRCV infection in the porcine respiratory tract but also serve as a valuable tool for studying human respiratory CoVs infection.

Seroprevalence of the novel swine acute diarrhea syndrome coronavirus in China assessed by enzyme-linked immunosorbent assay

The endemic outbreak of SADS-CoV has resulted in economic losses and potentially threatened the safety of China's pig industry. The molecular epidemiology of SADS-CoV in pig herds has been investigated in many provinces in China. However, there are no data over a long-time span, and there is a lack of extensive serological surveys to assess the prevalence of SADS-CoV in Chinese swine herds since the discovery of SADS-CoV. In this study, an indirect anti-SADS-CoV IgG enzyme-linked immunosorbent assay (ELISA) based on the SADS-CoV S1 protein was established to investigate the seroprevalence of SADS-CoV in Chinese swine herds. Cross-reactivity assays, indirect immunofluorescence, and western blotting assays showed that the developed ELISA had excellent SADS-CoV specificity. In total, 12,978 pig serum samples from 29 provinces/municipalities/autonomous regions in China were tested from 2022 to 2023. The results showed that the general seroprevalence of SADS-CoV in China was 59.97%, with seroprevalence ranging from 16.7% to 77.12% in different provinces and from 42.61% to 68.45% in different months. SADS-CoV is widely prevalent in China, and its seroprevalence was higher in Northeast China, North China, and Central China than in other regions. Among the four seasons, the prevalence of SADS-CoV was the highest in spring and the lowest in autumn. The results of this study provide the general seroprevalence profile of SADS-CoV in China, facilitating the understanding of the prevalence of SADS-CoV in pigs. More importantly, this study is beneficial in formulating preventive and control measures for SADS-CoV and may provide directions for vaccine development.

Epidemiology, pathogenesis, immune evasion mechanism and vaccine development of porcine Deltacoronavirus

Coronaviruses have been identified as pathogens of gastrointestinal and respiratory diseases in humans and various animal species. In recent years, the global spread of new coronaviruses has had profound influences for global public health and economies worldwide. As highly pathogenic zoonotic viruses, coronaviruses have become the focus of current research. Porcine Deltacoronavirus (PDCoV), an enterovirus belonging to the family of coronaviruses, has emerged on a global scale in the past decade and significantly influenced the swine industry. Moreover, PDCoV infects not only pigs but also other species, including humans, chickens and cattles, exhibiting a broad host tropism. This emphasizes the need for in-depth studies on coronaviruses to mitigate their potential threats. In this review, we provided a comprehensive summary of the current studies on PDCoV. We first reviewed the epidemiological investigations on the global prevalence and distribution of PDCoV. Then, we delved into the studies on the pathogenesis of PDCoV to understand the mechanisms how the virus impacts its hosts. Furthermore, we also presented some exploration studies on the immune evasion mechanisms of the virus to enhance the understanding of host-virus interactions. Despite current limitations in vaccine development for PDCoV, we highlighted the inhibitory effects observed with certain substances, which offers a potential direction for future research endeavors. In conclusion, this review summarized the scientific findings in epidemiology, pathogenesis, immune evasion mechanisms and vaccine development of PDCoV. The ongoing exploration of potential vaccine candidates and the insights gained from inhibitory substances have provided a solid foundation for future vaccine development to prevent and control diseases associated with PDCoV.

Simultaneous Detection of Porcine Respiratory Coronavirus, Porcine Reproductive and Respiratory Syndrome Virus, Swine Influenza Virus, and Pseudorabies Virus via Quadruplex One-Step RT-qPCR

Porcine respiratory coronavirus (PRCoV), porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), and pseudorabies virus (PRV) are significant viruses causing respiratory diseases in pigs. Sick pigs exhibit similar clinical symptoms such as fever, cough, runny nose, and dyspnea, making it very difficult to accurately differentially diagnose these diseases on site. In this study, a quadruplex one-step reverse-transcription real-time quantitative PCR (RT-qPCR) for the detection of PRCoV, PRRSV, SIV, and PRV was established. The assay showed strong specificity, high sensitivity, and good repeatability. It could detect only PRCoV, PRRSV, SIV, and PRV, without cross-reactions with TGEV, PEDV, PRoV, ASFV, FMDV, PCV2, PDCoV, and CSFV. The limits of detection (LODs) for PRCoV, PRRSV, SIV, and PRV were 129.594, 133.205, 139.791, and 136.600 copies/reaction, respectively. The intra-assay and inter-assay coefficients of variation (CVs) ranged from 0.29% to 1.89%. The established quadruplex RT-qPCR was used to test 4909 clinical specimens, which were collected in Guangxi Province, China, from July 2022 to September 2023. PRCoV, PRRSV, SIV, and PRV showed positivity rates of 1.36%, 10.17%, 4.87%, and 0.84%, respectively. In addition, the previously reported RT-qPCR was also used to test these specimens, and the agreement between these methods was higher than 99.43%. The established quadruplex RT-qPCR can accurately detect these four porcine respiratory viruses simultaneously, providing an accurate and reliable detection technique for clinical diagnosis.

A one-step immunoassay based on switching peptides for diagnosis of porcine epidemic diarrhea virus (PEDV) using screened Fv-antibodies

In this study, a one-step immunoassay for porcine epidemic diarrhea virus (PEDV) based on Fv-antibodies and switching peptides was developed, and the assay results of PEDV were obtained by just mixing samples without any further reaction or washing steps. The Fv-antibodies with binding affinity to the spike protein of PEDV were screened from the Fv-antibody library using the receptor-binding domain (RBD) of the spike protein as a screening probe. Screened Fv-antibodies with binding affinities to the RBD antigen were expressed, and the binding constants (KD) were calculated to be 83-142 nM. The one-step immunoassay for the detection of PEDV was configured as a displacement immunoassay using a fluorescence-labeled switching peptide. The one-step immunoassay based on switching peptides was performed using PEDV, and the limit of detection (LOD) values for PEDV detection were estimated to be Ct = 39.7-36.4. Compared with the LOD value for a conventional lateral flow immunoassay (Ct = 33.0), the one-step immunoassay showed a remarkably improved LOD for the detection of PEDV. Finally, the interaction between the screened Fv-antibodies and the PEDV RBD was investigated using docking simulations and compared with the amino acid sequences of the receptors on host cells, such as aminopeptidase N (APN) and angiotensin-converting enzyme-2 (ACE-2).

Molecular characterization and phylogenetic analysis of porcine epidemic diarrhea virus in Xinjiang, China, from 2020 to 2022

In recent years, the pig industry in Xinjiang, China, has been severely impacted by outbreaks of porcine epidemic diarrhea (PED), despite vaccination efforts. In this study, we investigated the genetic characteristics of currently prevalent porcine epidemic diarrhea virus (PEDV) strains in the region. We collected 548 samples from animals with suspected PED on large-scale pig farms in Xinjiang. Of these, 258 tested positive for PEDV by RT-PCR, yielding an overall positivity rate of 47.08%. S1 gene sequencing and phylogenetic analysis were conducted on 23 randomly selected RT-PCR-positive samples. Three endemic strains of PEDV (PEDV/CH/XU/2020, PEDV/CH/XK/2020, and PEDV/CH/XA/2020) were isolated, and their complete genome sequences were analyzed for evidence of genetic recombination. Sequence comparison of the S gene indicated significant variations in the S1 gene of the Xinjiang strains compared to the vaccine strains CV777, AJ1102, and LWL, with 90.2%-98.5% nucleotide sequence identity. Notably, both the N-terminal and C-terminal domains of the S protein showed significant variation. Genetic evolutionary analysis identified the GIIa subtype as the dominant genotype among the epidemic strains in Xinjiang. Recombination analysis revealed inter-subtype recombination events in the PEDV/CH/XK/2020 and XJ1904-34 strains. These findings highlight the extensive genetic variation in the predominant GIIa genotype of PEDV in Xinjiang, which does not match the genotype of the currently used vaccine strains. These data may guide further efforts toward the development of effective vaccines for the control of PED.

Overview of the recent advances in porcine epidemic diarrhea vaccines

Vaccination is the most effective means of preventing and controlling porcine epidemic diarrhea (PED). Conventional vaccines developed from porcine epidemic diarrhea virus (PEDV) GI-a subtypes (CV777 and SM98) have played a vital role in preventing classical PED. However, with the emergence of PEDV mutants in 2010, conventional PEDV GI-a subtype-targeting vaccines no longer provide adequate protection against PEDV GII mutants, thereby making novel-type PED vaccine development an urgent concern to be addressed. Novel vaccines, including nucleic acid vaccines, genetically engineered subunit vaccines, and live vector vaccines, are associated with several advantages, such as high safety and stability, clear targeting, high yield, low cost, and convenient usage. These vaccines can be combined with corresponding ELISA kits to differentiate infected from vaccinated animals, which is beneficial for disease confirmation. This review provides a detailed overview of the recent advancements in PED vaccines, emphasizing on the research and application evaluation of novel PED vaccines. It also considers the future directions and challenges in advancing these vaccines to widespread use in clinics.

A multiplex real-time RT-qPCR assay for simultaneous detection of porcine epidemic diarrhea virus, porcine deltacoronavirus, and swine acute diarrhea syndrome coronavirus

Porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV) cause intestinal diseases with similar manifestations in suckling piglets. In this study, we developed a multiplex real-time PCR for differential diagnosis of PEDV, PDCoV, and SADS-CoV. The assay demonstrated high specificity with a detection limit of 5 copies/µl for each virus. The assay specifically detected PEDV, PDCoV, and SADS-CoV and excluded all other swine pathogens circulating in pigs. Furthermore, the assay exhibited satisfactory performance in analyzing clinical samples. The data indicate that the newly developed multiplex real-time PCR method can be applied for differential diagnosis of porcine enteric coronaviruses.

Hyperacetylated microtubules assist porcine deltacoronavirus nsp8 to degrade MDA5 via SQSTM1/p62-dependent selective autophagy

The microtubule (MT) is a highly dynamic polymer that functions in various cellular processes through MT hyperacetylation. Thus, many viruses have evolved mechanisms to hijack the MT network of the cytoskeleton to allow intracellular replication of viral genomic material. Coronavirus non-structural protein 8 (nsp8), a component of the viral replication transcriptional complex, is essential for viral survival. Here, we found that nsp8 of porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus with a zoonotic potential, inhibits interferon (IFN)-β production by targeting melanoma differentiation gene 5 (MDA5), the main pattern recognition receptor for coronaviruses in the cytoplasm. Mechanistically, PDCoV nsp8 interacted with MDA5 and induced autophagy to degrade MDA5 in wild-type cells, but not in autophagy-related (ATG)5 or ATG7 knockout cells. Further screening for autophagic degradation receptors revealed that nsp8 interacts with sequestosome 1/p62 and promotes p62-mediated selective autophagy to degrade MDA5. Importantly, PDCoV nsp8 induced hyperacetylation of MTs, which in turn triggered selective autophagic degradation of MDA5 and subsequent inhibition of IFN-β production. Overall, our study uncovers a novel mechanism employed by PDCoV nsp8 to evade host innate immune defenses. These findings offer new insights into the interplay among viruses, IFNs, and MTs, providing a promising target to develop anti-viral drugs against PDCoV.IMPORTANCECoronavirus nsp8, a component of the viral replication transcriptional complex, is well conserved and plays a crucial role in viral replication. Exploration of the role mechanism of nsp8 is conducive to the understanding of viral pathogenesis and development of anti-viral strategies against coronavirus. Here, we found that nsp8 of PDCoV, an emerging enteropathogenic coronavirus with a zoonotic potential, is an interferon antagonist. Further studies showed that PDCoV nsp8 interacted with MDA5 and sequestosome 1/p62, promoting p62-mediated selective autophagy to degrade MDA5. We further found that PDCoV nsp8 could induce hyperacetylation of MT, therefore triggering selective autophagic degradation of MDA5 and inhibiting IFN-β production. These findings reveal a novel immune evasion strategy used by PDCoV nsp8 and provide insights into potential therapeutic interventions.

Cleavage of HDAC6 to dampen its antiviral activity by nsp5 is a common strategy of swine enteric coronaviruses

HDAC6, a structurally and functionally unique member of the histone deacetylase (HDAC) family, is an important host factor that restricts viral infection. The broad-spectrum antiviral activity of HDAC6 makes it a potent antiviral agent. Previously, we found that HDAC6 functions to antagonize porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus with zoonotic potential. However, the final outcome is typically a productive infection that materializes as cells succumb to viral infection, indicating that the virus has evolved sophisticated mechanisms to combat the antiviral effect of HDAC6. Here, we demonstrate that PDCoV nonstructural protein 5 (nsp5) can cleave HDAC6 at glutamine 519 (Q519), and cleavage of HDAC6 was also detected in the context of PDCoV infection. More importantly, the anti-PDCoV activity of HDAC6 was damaged by nsp5 cleavage. Mechanistically, the cleaved HDAC6 fragments (amino acids 1-519 and 520-1159) lost the ability to degrade PDCoV nsp8 due to their impaired deacetylase activity. Furthermore, nsp5-mediated cleavage impaired the ability of HDAC6 to activate RIG-I-mediated interferon responses. We also tested three other swine enteric coronaviruses (transmissible gastroenteritis virus, porcine epidemic diarrhea virus, and swine acute diarrhea syndrome-coronavirus) and found that all these coronaviruses have adopted similar mechanisms to cleave HDAC6 in both an overexpression system and virus-infected cells, suggesting that cleavage of HDAC6 is a common strategy utilized by swine enteric coronaviruses to antagonize the host's antiviral capacity. Together, these data illustrate how swine enteric coronaviruses antagonize the antiviral function of HDAC6 to maintain their infection, providing new insights to the interaction between virus and host.IMPORTANCEViral infections and host defenses are in constant opposition. Once viruses combat or evade host restriction, productive infection is achieved. HDAC6 is a broad-spectrum antiviral protein that has been demonstrated to inhibit many viruses, including porcine deltacoronavirus (PDCoV). However, whether HDAC6 is reciprocally targeted and disabled by viruses remains unclear. In this study, we used PDCoV as a model and found that HDAC6 is targeted and cleaved by nsp5, a viral 3C-like protease. The cleaved HDAC6 loses its deacetylase activity as well as its ability to degrade viral proteins and activate interferon responses. Furthermore, this cleavage mechanism is shared among other swine enteric coronaviruses. These findings shed light on the intricate interplay between viruses and HDAC6, highlighting the strategies employed by viruses to evade host antiviral defenses.

Gut microbiota-derived butyrate promotes coronavirus TGEV infection through impairing RIG-I-triggered local type I interferon responses via class I HDAC inhibition

Gut microbiota-derived metabolites are important for the replication and pathogenesis of many viruses. However, the roles of bacterial metabolites in swine enteric coronavirus (SECoV) infection remain poorly understood. Recent studies show that SECoVs infection in vivo significantly alters the composition of short-chain fatty acids (SCFAs)-producing gut microbiota. This prompted us to investigate whether and how SCFAs impact SECoV infection. Employing alphacoronavirus transmissible gastroenteritis virus (TGEV), a major cause of diarrhea in piglets, as a model, we found that SCFAs, particularly butyrate, enhanced TGEV infection both in porcine intestinal epithelial cells and swine testicular (ST) cells at the late stage of viral infection. This effect depended on the inhibited productions of virus-induced type I interferon (IFN) and downstream antiviral IFN-stimulated genes (ISGs) by butyrate. Mechanistically, butyrate suppressed the expression of retinoic acid-inducible gene I (RIG-I), a key viral RNA sensor, and downstream mitochondrial antiviral-signaling (MAVS) aggregation, thereby impairing type I IFN responses and increasing TGEV replication. Using pharmacological and genetic approaches, we showed that butyrate inhibited RIG-I-induced type I IFN signaling by suppressing class I histone deacetylase (HDAC). In summary, we identified a novel mechanism where butyrate enhances TGEV infection by suppressing RIG-I-mediated type I IFN responses. Our findings highlight that gut microbiota-derived metabolites like butyrate can be exploited by SECoV to dampen innate antiviral immunity and establish infection in the intestine.IMPORTANCESwine enteric coronaviruses (SECoVs) infection in vivo alters the composition of short-chain fatty acids (SCFAs)-producing gut microbiota, but whether microbiota-derived SCFAs impact coronavirus gastrointestinal infection is largely unknown. Here, we demonstrated that SCFAs, particularly butyrate, substantially increased alphacoronavirus TGEV infection at the late stage of infection, without affecting viral attachment or internalization. Furthermore, enhancement of TGEV by butyrate depended on impeding virus-induced type I interferon (IFN) responses. Mechanistically, butyrate suppressed the cytoplasmic viral RNA sensor RIG-I expression and downstream type I IFN signaling activation by inhibiting class I HDAC, thereby promoting TGEV infection. Our work reveals novel functions of gut microbiota-derived SCFAs in enhancing enteric coronavirus infection by impairing RIG-I-dependent type I IFN responses. This implies that bacterial metabolites could be therapeutic targets against SECoV infection by modulating antiviral immunity in the intestine.

Pharmacodynamic, pharmacokinetic, toxicity, and recent advances in Eugenol's potential benefits against natural and chemical noxious agents: A mechanistic review

The active biological phytochemicals, crucial compounds employed in creating hundreds of medications, are derived from valuable and medicinally significant plants. These phytochemicals offer excellent protection from various illnesses, including inflammatory disorders and chronic conditions caused by oxidative stress. A phenolic monoterpenoid known as eugenol (EUG), it is typically found in the essential oils of many plant species from the Myristicaceae, Myrtaceae, Lamiaceae, and Lauraceae families. One of the main ingredients of clove oil (Syzygium aromaticum (L.), Myrtaceae), it has several applications in industry, including flavoring food, pharmaceutics, dentistry, agriculture, and cosmeceuticals. Due to its excellent potential for avoiding many chronic illnesses, it has lately attracted attention. EUG has been classified as a nonmutant, generally acknowledged as a safe (GRAS) chemical by the World Health Organization (WHO). According to the existing research, EUG possesses notable anti-inflammatory, antioxidant, analgesic, antibacterial, antispasmodic, and apoptosis-promoting properties, which have lately gained attention for its ability to control chronic inflammation, oxidative stress, and mitochondrial malfunction and dramatically impact human wellness. The purpose of this review is to evaluate the scientific evidence from the most significant research studies that have been published regarding the protective role and detoxifying effects of EUG against a wide range of toxins, including biological and chemical toxins, as well as different drugs and pesticides that produce a variety of toxicities, throughout view of the possible advantages of EUG.

Classification, replication, and transcription of Nidovirales

Nidovirales is one order of RNA virus, with the largest single-stranded positive sense RNA genome enwrapped with membrane envelope. It comprises four families (Arterividae, Mesoniviridae, Roniviridae, and Coronaviridae) and has been circulating in humans and animals for almost one century, posing great threat to livestock and poultry，as well as to public health. Nidovirales shares similar life cycle: attachment to cell surface, entry, primary translation of replicases, viral RNA replication in cytoplasm, translation of viral proteins, virion assembly, budding, and release. The viral RNA synthesis is the critical step during infection, including genomic RNA (gRNA) replication and subgenomic mRNAs (sg mRNAs) transcription. gRNA replication requires the synthesis of a negative sense full-length RNA intermediate, while the sg mRNAs transcription involves the synthesis of a nested set of negative sense subgenomic intermediates by a discontinuous strategy. This RNA synthesis process is mediated by the viral replication/transcription complex (RTC), which consists of several enzymatic replicases derived from the polyprotein 1a and polyprotein 1ab and several cellular proteins. These replicases and host factors represent the optimal potential therapeutic targets. Hereby, we summarize the Nidovirales classification, associated diseases, "replication organelle," replication and transcription mechanisms, as well as related regulatory factors.

The role of receptors in the cross-species spread of coronaviruses infecting humans and pigs

The pandemic caused by SARS-CoV-2, which has proven capable of infecting over 30 animal species, highlights the critical need for understanding the mechanisms of cross-species transmission and the emergence of novel coronavirus strains. The recent discovery of CCoV-HuPn-2018, a recombinant alphacoronavirus from canines and felines that can infect humans, along with evidence of SARS-CoV-2 infection in pig cells, underscores the potential for coronaviruses to overcome species barriers. This review investigates the origins and cross-species transmission of both human and porcine coronaviruses, with a specific emphasis on the instrumental role receptors play in this process.

Phylogenetically evolutionary analysis provides insights into the genetic diversity and adaptive evolution of porcine deltacoronavirus

BACKGROUND

Porcine deltacoronavirus (PDCoV) is one of the emerging swine enteric coronaviruses (SECoVs), which has been widely prevalent in the North America and Asia. In addition to causing severe diarrhea in piglets, PDCoV also shows the potential to infect diverse host species, including calves, chickens, turkey poults, and humans. However, the clinical pathogenicity and genetic evolution of PDCoV is still not fully understood.

RESULTS

Here, we recorded an outbreak of a novel recombinant PDCoV strain (CHN-HeN06-2022) in a large nursery fattening pig farm. Genomic analysis showed that the CHN-HeN06-2022 strain shared 98.3-98.7% sequence identities with the Chinese and American reference strains. To clarify the evolutionary relationships, phylogenetic analysis was performed using the PDCoV genome sequences available in the GenBank database. Based on genetic distance and geographical distribution, the phylogenetic tree clearly showed that all the PDCoV sequences could be divided into lineage 1 and lineage 2, which were further classified into sublineage 1.1 (Chinese strains), 1.2 (the North American strains), 2.1 (the Southeast Asian strains), and 2.2 (Chinese strains). Corresponding to the evolutionary tree, we found that, compared to lineage 1, lineage 2 strains usually contain a continuous 6-nt deletion in Nsp2 and a 9-nt deletion in Nsp3, respectively. Furthermore, recombination analysis suggested that the CHN-HeN06-2022 occurred segments exchange crossed Nsp2 and Nsp3 region between sublineage 1.1 and sublineage 2.1. Combined with previously reported recombinant strains, the highest recombination frequency occurred in Nsp2, Nsp3, and S gene. Additionally, we identified a total of 14 amino acid sites under positive selection in spike protein, most of which are located in the regions related with the viral attachment, receptor binding, and membrane fusion.

CONCLUSIONS

Taken together, our studies provide novel insights into the genetic diversity and adaptive evolution of PDCoV. It would be helpful to the development of vaccine and potential antiviral agent.

SARS-CoV-2 Outbreaks on Mink Farms-A Review of Current Knowledge on Virus Infection, Spread, Spillover, and Containment

Many studies have been conducted to explore outbreaks of SARS-CoV-2 in farmed mink and their intra-/inter-species spread and spillover to provide data to the scientific community, protecting human and animal health. Studies report anthropozoonotic introduction, which was initially documented in April 2020 in the Netherlands, and subsequent inter-/intra-species spread of SARS-CoV-2 in farmed mink, likely due to SARS-CoV-2 host tropism capable of establishing efficient interactions with host ACE2 and the mink hosts' ability to enhance swift viral transmission due to their density, housing status, and occupational contacts. Despite the rigorous prevention and control measures adopted, transmission of the virus within and between animal species was efficient, resulting in the development of mink-associated strains able to jump back and forth among the mink hosts and other animal/human contacts. Current knowledge recognizes the mink as a highly susceptible animal host harboring the virus with or without clinical manifestations, furthering infection transmission as a hidden animal reservoir. A One Health approach is, thus, recommended in SARS-CoV-2 surveillance and monitoring on mink farms and of their susceptible contact animals to identify and better understand these potential animal hosts.

Clinical, Pathological and Virological Outcomes of Tissue-Homogenate-Derived and Cell-Adapted Strains of Porcine Epidemic Diarrhea Virus (PEDV) in a Neonatal Pig Model

Porcine epidemic diarrhea virus (PEDV) is characterized by diarrhea, vomiting, dehydration, and high mortality rates in neonatal piglets. Two distinct genogroups, S-INDEL (G1a, G1b) and non-S INDEL (G2a, G2b, and G2c), circulate worldwide and are characterized by varying degrees of virulence. Here, we compared the early pathogenesis of a PEDV S-INDEL strain obtained from intestine homogenate (CALAF-HOMOG) or adapted to cell culture by 22 passages (CALAF-ADAP) and a virulent non-S INDEL strain (PEDV-USA) in newborn piglets. After orogastric inoculation of PEDV strains, body weight, temperature and clinical signs were monitored for 48 hpi. Pathological studies were performed at 48 hpi and RNA extracts from jejunal content (at 48 hpi) and rectal swabs (at 0 and 48 hpi) were tested for the presence of PEDV RNA as well as sequenced and compared to the inoculum. Piglets inoculated with PEDV-USA and CALAF-HOMOG isolates showed more severe weight loss, diarrhea, villi fusion and atrophy compared to CALAF-ADAP inoculated piglets. The viral load of rectal swabs was higher in the PEDV-USA inoculated group, followed by CALAF-HOMOG and CALAF-ADAP isolates. Similarly, viral RNA load in jejunal content was comparable among PEDV-USA and CALAF-HOMOG inoculated piglets and higher than that of CALAF-ADAP ones. The comparison of three full PEDV sequences of the inocula with the corresponding ones of pigs after 48 hpi yielded a nucleotide identity >99.9%. This study highlights variations in virulence among S-INDEL and non-S INDEL strains and between S-INDEL isolates obtained from homogenate and cell culture.

Cross-Reactivity of Human, Wild Boar, and Farm Animal Sera from Pre- and Post-Pandemic Periods with Alpha- and Βeta-Coronaviruses (CoV), including SARS-CoV-2

Panels of pre- and post-pandemic farm animals, wild boar and human sera, including human sera able to neutralize SARS-CoV-2 in vitro, were tested in serological tests to determine their cross-reactivity with β- and α-CoV originating from farm animals. Sera were tested in neutralization assays with high ascending concentrations (up to 1 × 104 TCID50 units/well) of β-CoV Bovine coronavirus (BCV), SARS-CoV-2, and porcine α-CoV-transmissible gastroenteritis virus (TGEV). In addition, sera were tested for immunostaining of cells infected with β-CoV porcine hemagglutinating encephalomyelitis (PHEV). Testing revealed a significantly higher percentage of BCV neutralization (78%) for sera of humans that had experienced a SARS-CoV-2 infection (SARS-CoV-2 convalescent sera) than was observed for human pre-pandemic sera (37%). Also, 46% of these human SARS-CoV-2 convalescent sera neutralized the highest concentration of BCV (5 × 103 TCID50/well) tested, whereas only 9.6% of the pre-pandemic sera did. Largely similar percentages were observed for staining of PHEV-infected cells by these panels of human sera. Furthermore, post-pandemic sera collected from wild boars living near a densely populated area in The Netherlands also showed a higher percentage (43%) and stronger BCV neutralization than was observed for pre-pandemic sera from this area (21%) and for pre- (28%) and post-pandemic (20%) sera collected from wild boars living in a nature reserve park with limited access for the public. High percentages of BCV neutralization were observed for pre- and post-pandemic sera of cows (100%), pigs (up to 45%), sheep (36%) and rabbits (60%). However, this cross-neutralization was restricted to sera collected from specific herds or farms. TGEV was neutralized only by sera of pigs (68%) and a few wild boar sera (4.6%). None of the BCV and PHEV cross-reacting human pre-pandemic, wild boar and farm animal sera effectively neutralized SARS-CoV-2 in vitro. Preexisting antibodies in human sera effectively neutralized the animal β-CoV BCV in vitro. This cross-neutralization was boosted after humans had experienced a SARS-CoV-2 infection, indicating that SARS-CoV-2 activated a "memory" antibody response against structurally related epitopes expressed on the surface of a broad range of heterologous CoV, including β-CoV isolated from farm animals. Further research is needed to elucidate if a symptomless infection or environmental exposure to SARS-CoV-2 or another β-CoV also triggers such a "memory" antibody response in wild boars and other free-living animals.

Prevention and Control of Swine Enteric Coronaviruses in China: A Review of Vaccine Development and Application

Swine enteric coronaviruses (SECs) cause significant economic losses to the pig industry in China. Although many commercialized vaccines against transmissible gastroenteritis virus (TGEV) and porcine epidemic diarrhea virus (PEDV) are available, viruses are still widespread. The recent emergence of porcine deltacoronavirus (PDCoV) and swine acute diarrhea syndrome coronavirus (SADS-CoV), for which no vaccines are available, increases the disease burden. In this review, we first introduced the genomic organization and epidemiology of SECs in China. Then, we discussed the current vaccine development and application in China, aiming to provide suggestions for better prevention and control of SECs in China and other countries.

HSP90AB1 Is a Host Factor Required for Transmissible Gastroenteritis Virus Infection

Transmissible gastroenteritis virus (TGEV) is an important swine enteric coronavirus causing viral diarrhea in pigs of all ages. Currently, the development of antiviral agents targeting host proteins to combat viral infection has received great attention. The heat shock protein 90 (HSP90) is a critical host factor and has important regulatory effects on the infection of various viruses. However, its roles in porcine coronavirus infection remain unclear. In this study, the effect of HSP90 on TGEV infection was evaluated. In addition, the influence of its inhibitor VER-82576 on proinflammatory cytokine (IL-6, IL-12, TNF-α, CXCL10, and CXCL11) production induced by TGEV infection was further analyzed. The results showed that the knockdown of HSP90AB1 and HSP90 inhibitor VER-82576 treatment resulted in a reduction in TGEV M gene mRNA levels, the N protein level, and virus titers in a dose-dependent manner, while the knockdown of HSP90AA1 and KW-2478 treatment had no significant effect on TGEV infection. A time-of-addition assay indicated that the inhibitory effect of VER-82576 on TGEV infection mainly occurred at the early stage of viral replication. Moreover, the TGEV-induced upregulation of proinflammatory cytokine (IL-6, IL-12, TNF-α, CXCL10, and CXCL11) expression was significantly inhibited by VER-82576. In summary, these findings indicated that HSP90AB1 is a host factor enhancing TGEV infection, and the HSP90 inhibitor VER-82576 could reduce TGEV infection and proinflammatory cytokine production, providing a new perspective for TGEV antiviral drug target design.

Airborne transmission of common swine viruses

The transmission of viral aerosols poses a vulnerable aspect in the biosecurity measures aimed at preventing and controlling swine virus in pig production. Consequently, comprehending and mitigating the spread of aerosols holds paramount significance for the overall well-being of pig populations. This paper offers a comprehensive review of transmission characteristics, influential factors and preventive strategies of common swine viral aerosols. Firstly, certain viruses such as foot-and-mouth disease virus (FMDV), porcine reproductive and respiratory syndrome virus (PRRSV), influenza A viruses (IAV), porcine epidemic diarrhea virus (PEDV) and pseudorabies virus (PRV) have the potential to be transmitted over long distances (exceeding 150 m) through aerosols, thereby posing a substantial risk primarily to inter-farm transmission. Additionally, other viruses like classical swine fever virus (CSFV) and African swine fever virus (ASFV) can be transmitted over short distances (ranging from 0 to 150 m) through aerosols, posing a threat primarily to intra-farm transmission. Secondly, various significant factors, including aerosol particle sizes, viral strains, the host sensitivity to viruses, weather conditions, geographical conditions, as well as environmental conditions, exert a considerable influence on the transmission of viral aerosols. Researches on these factors serve as a foundation for the development of strategies to combat viral aerosol transmission in pig farms. Finally, we propose several preventive and control strategies that can be implemented in pig farms, primarily encompassing the implementation of early warning models, viral aerosol detection, and air pretreatment. This comprehensive review aims to provide a valuable reference for the formulation of efficient measures targeted at mitigating the transmission of viral aerosols among swine populations.

Development of a quadruplex real-time quantitative RT-PCR for detection and differentiation of PHEV, PRV, CSFV, and JEV

Porcine hemagglutinating encephalomyelitis virus (PHEV), porcine pseudorabies virus (PRV), classical swine fever virus (CSFV), and Japanese encephalitis virus (JEV) cause similar neurological symptoms in the infected pigs, and their differential diagnosis depends on laboratory testing. Four pairs of specific primers and probes were designed targeting the PHEV N gene, PRV gB gene, CSFV 5' untranslated region (5'UTR), and JEV NS1 gene, respectively, and a quadruplex real-time quantitative RT-PCR (qRT-PCR) was developed to detect and differentiate PHEV, PRV, CSFV, and JEV. The assay showed high sensitivity, with the limit of detection (LOD) of 1.5 × 101 copies/μL for each pathogen. The assay specifically detected only PHEV, PRV, CSFV, and JEV, without cross-reaction with other swine viruses. The coefficients of variation (CVs) of the intra-assay and the inter-assay were less than 1.84%, with great repeatability. A total of 1,977 clinical samples, including tissue samples, and whole blood samples collected from Guangxi province in China, were tested by the developed quadruplex qRT-PCR, and the positivity rates of PHEV, PRV, CSFV, and JEV were 1.57% (31/1,977), 0.35% (7/1,977), 1.06% (21/1,977), and 0.10% (2/1,977), respectively. These 1,977 samples were also tested by the previously reported qRT-PCR assays, and the coincidence rates of these methods were more than 99.90%. The developed assay is demonstrated to be rapid, sensitive, and accurate for detection and differentiation of PHEV, PRV, CSFV, and JEV.

Computationally-driven epitope identification of PEDV N-protein and its application in development of immunoassay for PEDV detection

The nucleocapsid (N) protein is a suitable candidate for early diagnosis of porcine epidemic diarrhea virus (PEDV). Here, we identified the linear B-cell epitopes of the PEDV N-protein by integrating a computational-experimental framework and constructed three-dimensional (3D) structure model of the N protein using the ColabFold program in Google Colaboratory. Furthermore, we prepared the monoclonal antibodies against the predicted epitopes and recombinant N protein, respectively, and selected pairing mAbs (named 9C4 and 3C5) to develop a double-antibody sandwich immunochromatographic test strip using CdSe/ZnS quantum dots (QDs)-labelled 9C4 and 3C5 as capture and detection antibodies, respectively. This strip can specifically detect PEDV within 10 min with a detection limit of less than 6.25 × 103 TCID50/mL. In comparison with RT-PCR for testing 90 clinical samples, the relative sensitivity and specificity of the strip were found to be 98.0% and 100%, respectively, with a concordance rate of 98.9% and a kappa value of 0.978, indicating that QDs-ICTS is a reliable method for the application of PEDV detection in clinical samples.

Identification of a receptor tyrosine kinase inhibitor CP-724714 inhibits SADS-CoV related swine diarrhea coronaviruses infection in vitro

The outbreak of the COVID-19 epidemic in 2020 has caused unprecedented panic among all mankind, pointing the major importance of effective treatment. Since the emergence of the swine acute diarrhea syndrome coronavirus (SADS-CoV) at the end of 2017, multiple reports have indicated that the bat-related SADS-CoV possesses a potential threat for cross-species transmission. Vaccines and antiviral drugs development deserve more attention. In this study, we found that the HER2 phosphorylation inhibitor (CP-724714) inhibited SADS-CoV infection in a dose-dependent manner. Further validation demonstrated that CP-724714 affected at the post-entry stage of SADS-CoV infection cycle. Also, efficient SADS-CoV infection required the activation of HER2 and its cascade Ras-Raf-Mek-Erk signaling pathway. In addition, CP-724714 has a broad-spectrum anti-swine diarrhea coronaviruses activity, and can dose-dependently combat SADS-CoV, porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV) and transmissible gastroenteritis virus (TGEV) infection in vitro with a specificity index of greater than 21.98, 9.38, 95.23 and 31.62, respectively. These results highlight the potential utility of CP-724714 or antiviral drugs targeting with HER2 and its cascade Ras-Raf-Mek-Erk signaling pathway as host-targeted SADS-CoV and other related coronaviruses therapeutics.

Identification of a Monoclonal Antibody against Porcine Deltacoronavirus Membrane Protein

Porcine deltacoronavirus (PDCoV) is an emerging virus that poses a significant threat to the global swine industry. Its membrane (M) protein is crucial for virion assembly and virus-host interactions. We selected the hydrophilic region of M protein for prokaryotic expression, purification, and recombinant protein production. Utilizing hybridoma technology, we prepared the monoclonal antibody (mAb) 24-A6 against M protein. The mAb 24-A6 was shown to be suitable for use in immunofluorescence assays, western blotting, and immunoprecipitation, with specificity for PDCoV and no cross-reactivity with other five porcine viruses. The M protein was observed to be expressed as early as 3 h after PDCoV infection, increasing its expression over the duration of infection. Notably, the antigenic epitope of the M protein identified as 103SPESRL108 recognized by mAb 24-A6 was found within a conserved structural domain (SWWSFNPETNNL) of the coronavirus M protein, indicating a crucial overlap between a functionally important viral assembly region and a region recognized by the immune system. Our findings provide valuable insights into mAb 24-A6 targeting the antigenic epitope of M protein and may contribute to the development of diagnostic tools for PDCoV infection and fundamental research into the function of PDCoV M protein.

Exosomes mediate the antibody-resistant intercellular transmission of porcine epidemic diarrhea virus

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic enteric coronavirus that causes severe enteritis and lethal watery diarrhea in suckling piglets, leading to tremendous economic losses. Exosomes have been reported to participate in intercellular communication by the transportation of a variety of biological materials, including RNAs, lipids, and proteins. However, PEDV transmission routes have not yet been fully elucidated, and whether exosomes function in PEDV transmission remains unclear. In this study, we extracted and purified exosomes from PEDV-infected Vero cells using a stringent isolation method with a combination of chemical precipitation, ultracentrifugation, and incubation with CD63-labeled magnetic beads. We found that exosomes from PEDV-infected Vero cells contain viral genomic RNA and viral nucleocapsid protein. Furthermore, we demonstrated that the purified exosomes from PEDV-infected cells are capable of transmitting the virus to both PEDV-susceptible and non-susceptible cells. Importantly, exosome-mediated PEDV infection was resistant to neutralization by PEDV-specific neutralizing antibodies that potently neutralized free PEDV. Our study reveals a potential immune evasion mechanism utilized by PEDV and provides new insight into the transmission and infection of this important pathogen.

mLST8 is essential for coronavirus replication and regulates its replication through the mTORC1 pathway

Coronaviruses (CoVs), which pose a serious threat to human and animal health worldwide, need to hijack host factors to complete their replicative cycles. However, the current study of host factors involved in CoV replication remains unknown. Here, we identified a novel host factor, mammalian lethal with sec-13 protein 8 (mLST8), which is a common subunit of mTOR complex 1 (mTORC1) and mTOR complex 2 (mTORC2), and is critical for CoV replication. Inhibitor and knockout (KO) experiments revealed that mTORC1, but not mTORC2, is essential for transmissible gastroenteritis virus replication. Furthermore, mLST8 KO reduced the phosphorylation of unc-51-like kinase 1 (ULK1), a factor downstream of the mTORC1 signaling pathway, and mechanistic studies revealed that decreased phosphorylation of the mTORC1 downstream factor ULK1 promoted the activation of autophagy, which is responsible for antiviral replication in mLST8 KO cells. Then, transmission electron microscopy indicated that both mLST8 KO and autophagy activator inhibited the formation of double-membrane vesicles in early viral replication. Finally, mLST8 KO and autophagy activator treatment could also inhibit the replication of other CoVs, indicating a conserved relationship between autophagy activation and CoV replication. In summary, our work reveals that mLST8 is a novel host regulator of CoV replication, which provides new insights into the mechanism of CoV replication and can facilitate the development of broad-spectrum antiviral drugs. IMPORTANCE CoVs are highly variable, and existing CoV vaccines are still limited in their ability to address mutations in CoVs. Therefore, the need to improve our understanding of the interaction of CoVs with the host during viral replication and to find targets for drugs against CoVs is urgent. Here, we found that a novel host factor, mLST8, is critical for CoV infection. Further studies showed that mLST8 KO inhibited the mTORC1 signaling pathway, and we found that autophagy activation downstream of mTORC1 was the main cause of antiviral replication in mLST8 KO cells. Autophagy activation impaired the formation of DMVs and inhibited early viral replication. These findings deepen our understanding of the CoV replication process and provide insights into potential therapeutic applications.

Characterization of monoclonal antibodies against porcine epidemic diarrhea virus S1/S2 junction protein

Pig producers have faced considerable economic losses due to porcine epidemic diarrhea virus (PEDV) infection, emphasizing the need for PEDV antibody development. The S1/S2 junction (S1S2J) cleavage site of the S protein of PEDV is one of the major determinants of coronavirus infection success. In this study, we specifically selected the S1S2J protein of PEDV-AJ1102 (a representative strain of the G2 type) as a target protein to immunize mice and generated monoclonal antibodies (mAbs) using hybridoma technology. Three mAbs with high-binding activities to the S1S2J protein and were obtained and further analyzed. To reveal the characterization of these mAbs, variable region genes of antibodies were studied by using DNA sequencing, thereby revealing differences in their CDR3 amino acid sequences. We then developed a new method to identify the isotypes of these three mAbs. Results showed that these three antibodies were of the IgM type. As for the functions of these three mAbs, indirect immunofluorescence assay confirmed their good binding ability to Vero E6 cells infected with the PEDV-SP-C strain (G1 type). Epitope analysis showed linear epitopes for all three mAbs. These antibodies were also used to detect infected cells via flow cytometry analysis. In summary, we prepared and examined three mAbs against PEDV-S1S2J. These mAbs can be employed as detection antibodies for diagnostic reagents and further developed for other applications. We also designed a novel technique for easy and cost-saving identification of isotypes of mouse mAbs. Our results lay a good foundation for the development of research on PEDV.

Development of a Multiplex Quantitative PCR for Detecting Porcine Epidemic Diarrhea Virus, Transmissible Gastroenteritis Virus, and Porcine Deltacoronavirus Simultaneously in China

Porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), and porcine deltacoronavirus (PDCoV) belong to the category of swine enteric coronavirus that cause acute diarrhea in piglets, which has resulted in massive losses to the pig husbandry. Therefore, a sensitive and rapid detection method which can differentially detect these viruses that lead to mixed infections in clinical cases, is urgently needed. According to the conserved regions of the PEDV M gene, TGEV S gene, and PDCoV N gene, and the reference gene of porcine (β-Actin), we designed new specific primers and probes for the multiplex qPCR assay capable of simultaneously detecting three RNA viruses. This method, with a great specificity, did not cross-react with the common porcine virus. Moreover, the limit of detection of the method we developed could reach 10 copies/μL ,and the intra- and inter-group coefficients of variation of it below 3%. Applying this assay to detect 462 clinical samples which were collected in 2022-2023, indicated that the discrete positive rates of PEDV, TGEV, and PDCoV were 19.70%, 0.87%, and 10.17%, respectively. The mixed infection rates of PEDV/TGEV, PEDV/PDCoV, TGEV/PDCoV, and PEDV/TGEV/PDCoV were 3.25%, 23.16%, 0.22%, and 11.90%, respectively. All in all, the multiplex qPCR assay we developed as a tool for differential and rapid diagnosing can be put on the active prevention and control of PEDV, TGEV, and PDCoV, , which can create great value in the diagnosis of swine diarrhea diseases.

HDAC6 Degrades nsp8 of Porcine Deltacoronavirus through Deacetylation and Ubiquitination to Inhibit Viral Replication

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that has the potential to infect humans. Histone deacetylase 6 (HDAC6) is a unique type IIb cytoplasmic deacetylase with both deacetylase activity and ubiquitin E3 ligase activity, which mediates a variety of cellular processes by deacetylating histone and nonhistone substrates. In this study, we found that ectopic expression of HDAC6 significantly inhibited PDCoV replication, while the reverse effects could be observed after treatment with an HDAC6-specific inhibitor (tubacin) or knockdown of HDAC6 expression by specific small interfering RNA. Furthermore, we demonstrated that HDAC6 interacted with viral nonstructural protein 8 (nsp8) in the context of PDCoV infection, resulting in its proteasomal degradation, which was dependent on the deacetylation activity of HDAC6. We further identified the key amino acid residues lysine 46 (K46) and K58 of nsp8 as acetylation and ubiquitination sites, respectively, which were required for HDAC6-mediated degradation. Through a PDCoV reverse genetics system, we confirmed that recombinant PDCoV with a mutation at either K46 or K58 exhibited resistance to the antiviral activity of HDAC6, thereby exhibiting higher replication compared with wild-type PDCoV. Collectively, these findings contribute to a better understanding of the function of HDAC6 in regulating PDCoV infection and provide new strategies for the development of anti-PDCoV drugs. IMPORTANCE As an emerging enteropathogenic coronavirus with zoonotic potential, porcine deltacoronavirus (PDCoV) has sparked tremendous attention. Histone deacetylase 6 (HDAC6) is a critical deacetylase with both deacetylase activity and ubiquitin E3 ligase activity and is extensively involved in many important physiological processes. However, little is known about the role of HDAC6 in the infection and pathogenesis of coronaviruses. Our present study demonstrates that HDAC6 targets PDCoV-encoded nonstructural protein 8 (nsp8) for proteasomal degradation through the deacetylation at the lysine 46 (K46) and the ubiquitination at K58, suppressing viral replication. Recombinant PDCoV with a mutation at K46 and/or K58 of nsp8 displayed resistance to the antiviral activity of HDAC6. Our work provides significant insights into the role of HDAC6 in regulating PDCoV infection, opening avenues for the development of novel anti-PDCoV drugs.

Establishment and Application of a Triplex Real-Time RT-PCR Assay for Differentiation of PEDV, PoRV, and PDCoV

Porcine viral diarrhea is very common in clinical practice and has caused huge losses to the pig industry. Porcine epidemic diarrhea virus (PEDV), porcine rotavirus (PoRV), and porcine deltacoronavirus (PDCoV) are important pathogens of porcine viral diarrhea. Co-infection situations among these three viruses in clinics are common, which increases the difficulty of differential diagnosis. Currently, polymerase chain reaction (PCR) is commonly used to detect pathogens. TaqMan real-time PCR is more sensitive than conventional PCR and has better specificity and accuracy. In this study, a triplex real-time RT-PCR assay based on TaqMan probes was developed for differential detection of PEDV, PoRV, and PDCoV. The triplex real-time RT-PCR assay developed in this study could not detect unrelated pathogens and showed satisfactory specificity, sensitivity, repeatability, and reproducibility with a limit of detection (LOD) of 6.0 × 10¹ copies/μL. Sixteen clinical samples were used to compare the results of the commercial RT-PCR kit and the triplex RT-PCR for PEDV, PoRV, and PDCoV detection, and the results were completely consistent. A total of 112 piglet diarrhea samples collected from Jiangsu province were next used to study the local prevalence of PEDV, PoRV, and PDCoV. The positive rates of PEDV, PoRV, and PDCoV detected by the triplex real-time RT-PCR were 51.79% (58/112), 59.82% (67/112), and 2.68% (3/112), respectively. The co-infections of PEDV and PoRV were frequent (26/112, 23.21%), followed by the co-infections of PDCoV and PoRV (2/112, 1.79%). This study established a useful tool for simultaneous differentiation of PEDV, PoRV, and PDCoV in practice and provided valuable information on the prevalence of these diarrhea viral pathogens in Jiangsu province.

Recombinant human adenovirus type 5 based vaccine candidates against GIIa- and GIIb-genotype porcine epidemic diarrhea virus induce robust humoral and cellular response in mice

Porcine epidemic diarrhea virus (PEDV) is a porcine enteropathogenic coronavirus causing severe watery diarrhea, vomiting, dehydration, and death in piglets. However, most commercial vaccines are developed based on the GI genotype strains, and have poor immune protection against the currently dominant GII genotype strains. Therefore, four novel replication-deficient human adenovirus 5-vectored vaccines expressing codon-optimized forms of the GIIa and GIIb strain spike and S1 glycoproteins were constructed, and their immunogenicity was evaluated in mice by intramuscular (IM) injection. All the recombinant adenoviruses generated robust immune responses, and the immunogenicity of recombinant adenoviruses against the GIIa strain was stronger than that of recombinant adenoviruses against the GIIb strain. Moreover, Ad-XT-tPA-Sopt-vaccinated mice elicited optimal immune effects. In contrast, mice immunized with Ad-XT-tPA-Sopt by oral gavage did not induce strong immune responses. Overall, IM administration of Ad-XT-tPA-Sopt is a promising strategy against PEDV, and this study provides useful information for developing viral vector-based vaccines.

Genomic Characterizations of Porcine Epidemic Diarrhea Viruses (PEDV) in Diarrheic Piglets and Clinically Healthy Adult Pigs from 2019 to 2022 in China

Porcine epidemic diarrhea virus (PEDV) is a major causative pathogen of diarrheic disease. In this study, the prevalence and evolution of PEDV was evaluated using intestinal samples collected from six provinces of China in 2019-2022. PEDV could not only be detected in diarrheic piglets but also in adult pigs without enteric diseases. The complete genomes of five temporal and geographical representative PEDV strains were determined. Genome-based phylogenetic analysis indicated that XJ1904-700 belongs to the G2-a subgroup, while the other strains are clustered within the S-INDEL subgroup. Recombination analyses supported that JSNJ2004-919 is an inter-subgroup recombinant from SD2014-like (G2-b), CHZ-2013-like (G2-b) and CV777-like (G1-b) isolates, while FJFZ2004-1017 is an intra-subgroup recombinant from XM1-2-like (S-INDEL) and LYG-2014-like (S-INDEL) isolates. Both JSNJ2004-919 and FJFZ2004-1017 were from adult pigs, providing evidence that adult pigs may also serve as the host of PEDV reservoirs for virus evolution. Overall, this study provides new insights into PEDV's prevalence and evolution in both diseased piglets and clinically healthy adult pigs.

Porcine Epidemic Diarrhea Virus Replication in Human Intestinal Cells Reveals Potential Susceptibility to Cross-Species Infection

Various coronaviruses have emerged as a result of cross-species transmission among humans and domestic animals. Porcine epidemic diarrhea virus (PEDV; family Coronaviridae, genus Alphacoronavirus) causes acute diarrhea, vomiting, dehydration, and high mortality in neonatal piglets. Porcine small intestinal epithelial cells (IPEC-J2 cells) can be used as target cells for PEDV infection. However, the origin of PEDV in pigs, the host range, and cross-species infection of PEDV remain unclear. To determine whether PEDV has the ability to infect human cells in vitro, human small intestinal epithelial cells (FHs 74 Int cells) were inoculated with PEDV LJX and PEDV CV777 strains. The results indicated that PEDV LJX, but not PEDV CV777, could infect FHs 74 Int cells. Furthermore, we observed M gene mRNA transcripts and N protein expression in infected FHs 74 Int cells. A one-step growth curve showed that the highest viral titer of PEDV occurred at 12 h post infection. Viral particles in vacuoles were observed in FHs 74 Int cells at 24 h post infection. The results proved that human small intestinal epithelial cells are susceptible to PEDV infection, suggesting the possibility of cross-species transmission of PEDV.

Metavirome Analysis Reveals a High Prevalence of Porcine Hemagglutination Encephalomyelitis Virus in Clinically Healthy Pigs in China

Six swine coronaviruses (SCoVs), which include porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine hemagglutination encephalomyelitis virus (PHEV), porcine respiratory coronavirus (PRCV), swine acute diarrhea syndrome coronavirus (SADS-CoV), and porcine delta coronavirus (PDCoV), have been reported as infecting and causing serious diseases in pigs. To investigate the genetic diversity and spatial distribution of SCoVs in clinically healthy pigs in China, we collected 6400 nasal swabs and 1245 serum samples from clinically healthy pigs at slaughterhouses in 13 provinces in 2017 and pooled them into 17 libraries by type and region for next-generation sequencing (NGS) and metavirome analyses. In total, we identified five species of SCoVs, including PEDV, PDCoV, PHEV, PRCV, and TGEV. Strikingly, PHEV was detected from all the samples in high abundance and its genome sequences accounted for 75.28% of all coronaviruses, while those belonging to TGEV (including PRCV), PEDV, and PDCoV were 20.4%, 2.66%, and 2.37%, respectively. The phylogenetic analysis showed that two lineages of PHEV have been circulating in pig populations in China. We also recognized two PRCVs which lack 672 nucleotides at the N-terminus of the S gene compared with that of TGEV. Together, we disclose preliminarily the genetic diversities of SCoVs in clinically healthy pigs in China and provide new insights into two SCoVs, PHEV and PRCV, that have been somewhat overlooked in previous studies in China.

Nonsteroidal anti-inflammatory drugs (NSAIDs) and nucleotide analog GS-441524 conjugates with potent in vivo efficacy against coronaviruses

Coronaviruses (CoVs) infect a broad range of hosts, including humans and various animals, with a tendency to cross the species barrier, causing severe harm to human society and fostering the need for effective anti-coronaviral drugs. GS-441524 is a broad-spectrum antiviral nucleoside with potent anti-CoVs activities. However, its application is limited by poor oral bioavailability. Herein, we designed and synthesized several conjugates via covalently binding NSAIDs to 5'-OH of GS-441524 through ester bonds. The ibuprofen conjugate, ATV041, exhibited potent in vitro anti-coronaviral efficacy against four zoonotic coronaviruses in the alpha- and beta-genera. Oral-dosed ATV041 resulted in favorable bioavailability and rapid tissue distribution of GS-441524 and ibuprofen. In MHV-A59 infected mice, ATV041 dose-dependently decreased viral RNA replication and significantly reduced the proinflammatory cytokines in the liver and the lung at 3 dpi. As a result, the MHV-A59-induced lung and liver inflammatory injury was significantly alleviated. Taken together, this work provides a novel drug conjugate strategy to improve oral PK and offers a potent anti-coronaviral lead compound for further studies.

Transmissible Gastroenteritis Virus: An Update Review and Perspective

Transmissible gastroenteritis virus (TGEV) is a member of the alphacoronavirus genus, which has caused huge threats and losses to pig husbandry with a 100% mortality in infected piglets. TGEV is observed to be recombining and evolving unstoppably in recent years, with some of these recombinant strains spreading across species, which makes the detection and prevention of TGEV more complex. This paper reviews and discusses the basic biological properties of TGEV, factors affecting virulence, viral receptors, and the latest research advances in TGEV infection-induced apoptosis and autophagy to improve understanding of the current status of TGEV and related research processes. We also highlight a possible risk of TGEV being zoonotic, which could be evidenced by the detection of CCoV-HuPn-2018 in humans.

Butyrate limits the replication of porcine epidemic diarrhea virus in intestine epithelial cells by enhancing GPR43-mediated IFN-III production

Porcine epidemic diarrhea virus (PEDV) is a threat to the health of newborn piglets and has a significant impact on the swine industry. Short-chain fatty acids (SCFAs) are gut microbial metabolites that regulate intestinal function through different mechanisms to enhance the intestinal barrier and immune function. In this study, we aimed to determine whether butyrate displayed a better effect than other SCFAs on limiting PEDV replication in porcine intestinal epithelial cells. Mechanistically, butyrate treatment activated the interferon (IFN) response and interferon-stimulated gene (ISG) expression. Further experiments showed that inhibition of GPR43 (free fatty acid receptor 2) in intestinal epithelial cells increased virus infection and reduced antiviral effects through IFN λ response. Our findings revealed that butyrate exerts its antiviral effects by inducing GPR43-mediated IFN production in intestinal epithelial cells.

Diagnostic Approach to Enteric Disorders in Pigs

The diagnosis of enteric disorders in pigs is extremely challenging, at any age. Outbreaks of enteric disease in pigs are frequently multifactorial and multiple microorganisms can co-exist and interact. Furthermore, several pathogens, such as Clostridium perfrigens type A, Rotavirus and Lawsonia intracellularis, may be present in the gut in the absence of clinical signs. Thus, diagnosis must be based on a differential approach in order to develop a tailored control strategy, considering that treatment and control programs for enteric diseases are pathogen-specific. Correct sampling for laboratory analyses is fundamental for the diagnostic work-up of enteric disease in pigs. For example, histology is the diagnostic gold standard for several enteric disorders, and sampling must ensure the collection of representative and optimal intestinal samples. The aim of this paper is to focus on the diagnostic approach, from sampling to the aetiological diagnosis, of enteric disorders in pigs due to different pathogens during the different phases of production.

Genetic comparison of transmissible gastroenteritis coronaviruses

Transmissible gastroenteritis virus (TGEV) is a porcine coronavirus that threatens animal health and remains elusive despite years of research efforts. The systematical analysis of all available full-length genomes of TGEVs (a total of 43) and porcine respiratory coronaviruses PRCVs (a total of 7) showed that TGEVs fell into two independent evolutionary phylogenetic clades, GI and GII. Viruses circulating in China (until 2021) clustered with the traditional or attenuated vaccine strains within the same evolutionary clades (GI). In contrast, viruses latterly isolated in the USA fell into GII clade. The viruses circulating in China have a lower similarity with that isolated latterly in the USA all through the viral genome. In addition, at least four potential genomic recombination events were identified, three of which occurred in GI clade and one in GII clade. TGEVs circulating in China are distinct from the viruses latterly isolated in the USA at either genomic nucleotide or antigenic levels. Genomic recombination serves as a factor driving the expansion of TGEV genomic diversity.

Co-infection of porcine deltacoronavirus and porcine epidemic diarrhoea virus alters gut microbiota diversity and composition in the colon of piglets

Porcine deltacoronavirus (PDCoV) and porcine epidemic diarrhoea virus (PEDV) are the main porcine enteric coronaviruses that cause severe diarrhoea in piglets, posing huge threat to the swine industry. Our previous study verified that the co-infection of PDCoV and PEDV is common in natural swine infections and obviously enhances the disease severity in piglets. However, the effects of co-infection of PDCoV and PEDV on intestinal microbial community are unknown. In current study, the microbial composition and diversity in the colon of piglets were analyzed. Our results showed that both of PDCoV and PEDV were mainly distributed in the small intestines and caused severe damage of ileum but not colon in the co-inoculated piglets. Furthermore, we observed that PDCoV and PEDV co-infection alters the gut microbiota composition at the phylum, family and genus levels. The abundance of Mitsuokella and Collinsella at genus level were significantly increased in PDCoV-PEDV co-infection piglets. Spearman's correlation analysis further suggested that there existed strong positive correlation between Mitsuokella and TNF-α, IL-6 and IL-8 secretion, these two factors may together aggravating the small intestine pathological lesions. These results proved there existed obvious correlation between the disease severity caused by PDCoV-PEDV co-infection and intestinal microbial community.

A Quadruplex qRT-PCR for Differential Detection of Four Porcine Enteric Coronaviruses

Porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV) are four identified porcine enteric coronaviruses. Pigs infected with these viruses show similar manifestations of diarrhea, vomiting, and dehydration. Here, a quadruplex real-time quantitative PCR (qRT-PCR) assay was established for the differential detection of PEDV, TGEV, PDCoV, and SADS-CoV from swine fecal samples. The assay showed extreme specificity, high sensitivity, and excellent reproducibility, with the limit of detection (LOD) of 121 copies/μL (final reaction concentration of 12.1 copies/μL) for each virus. The 3236 clinical fecal samples from Guangxi province in China collected between October 2020 and October 2022 were evaluated by the quadruplex qRT-PCR, and the positive rates of PEDV, TGEV, PDCoV, and SADS-CoV were 18.26% (591/3236), 0.46% (15/3236), 13.16% (426/3236), and 0.15% (5/3236), respectively. The samples were also evaluated by the multiplex qRT-PCR reported previously by other scientists, and the compliance rate between the two methods was more than 99%. This illustrated that the developed quadruplex qRT-PCR assay can provide an accurate method for the differential detection of four porcine enteric coronaviruses.

Development of a multiplex RT-PCR method for the detection of four porcine enteric coronaviruses

Porcine enteric coronaviruses are pathogens that cause viral diarrhea in pigs and are widely prevalent worldwide. Moreover, studies have shown that some porcine enteric coronaviruses can infect humans and poultry. In order to effectively monitor these viruses, it is necessary to establish a multiple detection method to understand their prevalence and conduct in-depth research. Common porcine enteric coronaviruses include Porcine epidemic diarrhea virus (PEDV), Porcine transmissible gastroenteritis virus (TGEV), Porcine delta coronavirus (PDCoV), and Swine acute diarrhea syndrome coronavirus (SADS-CoV). Pigs infected with these viruses have the common clinical symptoms that are difficult to distinguish. A quadruplex RT-PCR (reverse transcription-polymerase chain reaction) method for the simultaneous detection of PEDV, PDCoV, TGEV and SADS-CoV was developed. Four pairs of specific primers were designed for the PEDV M gene, PDCoV N gene, TGEV S gene and SADS-CoV RdRp gene. Multiplex RT-PCR results showed that the target fragments of PDCoV, SADS-CoV, PEDV and TGEV could be amplified by this method. and the specific fragments with sizes of 250 bp, 368 bp, 616 bp and 801 bp were amplified, respectively. This method cannot amplify any fragment of nucleic acids of Seneca Valley virus (SVV), Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) and Atypical Porcine Pestivirus (APPV), and has good specificity. The lowest detection limits of PDCoV, PEDV, TGEV and SADS-CoV were 5.66 × 105 copies/μL, 6.48 × 105 copies/μL, 8.54 × 105 copies/μL and 7.79 × 106 copies/μL, respectively. A total of 94 samples were collected from pig farms were analyzed using this method. There were 15 positive samples for PEDV, 3 positive samples for mixed infection of PEDV and PDCoV, 2 positive samples for mixed infection of PEDV and TGEV, and 1 positive sample for mixed infection of PEDV, TGEV, and PDCoV. Multiplex RT-PCR method could detect four intestinal coronaviruses (PEDV, PDCoV, TGEV, and SADS-CoV) in pigs efficiently, cheaply and accurately, which can be used for clinical large-scale epidemiological investigation and diagnosis.

Molecular epidemiological survey of porcine epidemic diarrhea in some areas of Shandong and genetic evolutionary analysis of S gene

Responsible for the acute infectious disease porcine epidemic diarrhea (PED), PED virus (PEDV) induces severe diarrhea and high mortality in infected piglets and thus severely harms the productivity and economic efficiency of pig farms. In our study, we aimed to investigate and analyze the recent status and incidence pattern of PEDV infection in some areas of Shandong Province, China. We collected 176 clinical samples of PED from pig farms in different regions of Shandong Province during 2019–2021. PEDV, TGEV, and PORV were detected using RT-PCR. The full-length sequences of positive PEDV S genes were amplified, the sequences were analyzed with MEGA X and DNAStar, and a histopathological examination of typical PEDV-positive cases was performed. RT-PCR revealed positivity rates of 37.5% (66/176) for PEDV, 6.82% (12/176) for transmissible gastroenteritis virus, and 3.98% (7/176) for pig rotavirus. The test results for the years 2019, 2020, and 2021 were counted separately, PEDV positivity rates for the years were 34.88% (15/43), 39.33% (35/89), and 36.36% (16/44), respectively. Histopathological examination revealed atrophied, broken, and detached duodenal and jejunal intestinal villi, as typical of PED, and severe congestion of the intestinal submucosa. Moreover, the results of our study clearly indicate that the G2 subtype is prevalent as the dominant strain of PEDV in Shandong Province, where its rates of morbidity and mortality continue to be high. Based on a systematic investigation and analysis of PEDV's molecular epidemiology across Shandong Province, our results enrich current epidemiological data regarding PEDV and provide some scientific basis for preventing and controlling the disease.

Retrospective Serosurvey of Three Porcine Coronaviruses among the Wild Boar (Sus scrofa) Population in the Campania Region of Italy

The growing interest in porcine coronaviruses (CoVs) is due to both their negative effect on the swine industry and their propensity to mutate and overcome host barriers. Since information on CoVs in wild boar (Sus scrofa) is limited, especially in Italy, a serosurvey was conducted to assess the epidemiologic situation in the Campania region and to clarify the role of wild boar as reservoirs for enteric (porcine epidemic diarrhea virus [PEDV], transmissible gastroenteritis virus [TGEV]) and respiratory (respiratory coronavirus [PRCV]) swine CoVs. During the 2016-17 hunting season, serum samples were collected from 444 wild boars and tested for antibodies to enteric (PEDV, TGEV) and respiratory (PRCV) porcine CoVs by enzyme-linked immunosorbent assay. The highest seroprevalence in wild boars was for PEDV, with a positivity of 3.83% (95% confidence interval [CI] 2.05-5.6), whereas very low seroprevalences were found for TGEV and PRCV (0.67% positivity; 95% CI 0-1.44 in both cases). There was no statistical association between seropositivity to CoVs, sex, and location, whereas the prevalence of seropositive animals was positively correlated with young age (0-12 mo old). Our data confirm the presence of CoVs in wild boars in the Campania region. Our data are in agreement with the results of similar studies from other European countries, which attribute a minor role to wild boar in the transmission of these infections to domestic pigs. Our results suggest that continuous serologic surveys are necessary to monitor wild animals and detect emerging threats to livestock and humans.