Swine Acute Diarrhea Syndrome Coronavirus Research Articles

Identification of ZDHHC17 as a Potential Drug Target for Swine Acute Diarrhea Syndrome Coronavirus Infection.

ABSTRACTThe recent emergence and spread of zoonotic viruses highlights that animal-sourced viruses are the biggest threat to global public health. Swine acute diarrhea syndrome coronavirus (SADS-CoV) is an HKU2-related bat coronavirus that was spilled over from Rhinolophus bats to swine, causing large-scale outbreaks of severe diarrhea disease in piglets in China. Unlike other porcine coronaviruses, SADS-CoV possesses broad species tissue tropism, including primary human cells, implying a significant risk of cross-species spillover. To explore host dependency factors for SADS-CoV as therapeutic targets, we employed genome-wide CRISPR knockout library screening in HeLa cells. Consistent with two independent screens, we identified the zinc finger DHHC-type palmitoyltransferase 17 (ZDHHC17 or ZD17) as an important host factor for SADS-CoV infection. Through truncation mutagenesis, we demonstrated that the DHHC domain of ZD17 that is involved in palmitoylation is important for SADS-CoV infection. Mechanistic studies revealed that ZD17 is required for SADS-CoV genomic RNA replication. Treatment of infected cells with the palmitoylation inhibitor 2-bromopalmitate (2-BP) significantly suppressed SADS-CoV infection. Our findings provide insight on SADS-CoV-host interactions and a potential therapeutic application.

Update on the Phylodynamics of SADS-CoV.

Coronaviruses are known to be harmful and heterogeneous viruses, able to infect a large number of hosts. Among them, SADS-CoV (Swine Acute Diarrhea Syndrome Coronavirus), also known as PEAV (Porcine Enteric Alphacoronavirus), or SeA-CoV (Swine Enteric Alphacoronavirus), is the most recent Alphacoronavirus discovered, and caused several outbreaks reported in Chinese swine herds between late 2016 and 2019. We performed an upgraded phylodinamic reconstruction of SADS-CoV based on all whole genomes available on 21 June 2021. Results showed a very close relationship between SADS-CoV and HKU2-like CoV, which may represent the evolutionary intermediate step towards the present SADS-CoV. The direct progenitor of SADS-CoV is so far unknown and, although it is well known that horseshoe bats are reservoirs for Rhinolophus bat coronavirus HKU2-like (HKU2-like CoVs), the transmission path from bats to pigs is still unclear. The discrepancies in the phylogenetic position of rodent CoV, when different molecular markers were considered, corroborate the recombination hypothesis, suggesting that wild rats, which are frequent in farms, may have played a key role. The failure of the attempt at molecular dating, due to the lack of a clock signal, also corroborates the occurrence of a recombination event hypothesis. Zoonotic infections originating in wildlife can easily become a significant threat for human health. In such a context, due to the high recombination and cross-species capabilities of Coronavirus, SADS-CoV represents a possible high-risk pathogen for humans which needs a constant molecular monitoring.

The Characteristics of Spike Glycoprotein Gene of Swine Acute Diarrhea Syndrome Coronavirus Strain CH/FJWT/2018 Isolated in China.

Swine acute diarrhea syndrome (SADS) is a highly contagious infectious disease characterized by acute vomiting and watery diarrhea in neonatal piglets. The causative agent for SADS is the swine acute diarrhea syndrome coronavirus (SADS-CoV), an alphacoronavirus in the family Coronaviridae. Currently, SADS-CoV was identified only in Guangdong and Fujian provinces of China, not in any other regions or countries in the world. To explore the genetic diversity of SADS-CoV isolates, herein we comparatively analyzed 44 full-length genomes of viruses isolated in Guangdong and Fujian provinces during 2017–2019. The spike glycoprotein gene of SADS-CoV strain CH/FJWT/2018 isolated in Fujian province is distinct from that of other viral isolates in either spike glycoprotein gene-based phylogenetic analysis or whole genome-based gene similarity analysis. Moreover, at least 7 predicted linear B cell epitopes in the spike glycoprotein of CH/FJWT/2018 would be affected by amino acid variations when compared with a representative virus isolated in Guangdong province. The spike glycoprotein of coronaviruses determines viral host range and tissue tropism during virus infection via specific interactions with the cellular receptor and also plays critical roles in eliciting the production of neutralizing antibodies. Since SADS-CoVs have a broad cell tropism, the results in this report further emphasize that the spike glycoprotein gene is a pivotal target in the surveillance of SADS-CoV.

Bioinformatics Analysis of Spike Proteins of Porcine Enteric Coronaviruses.

This article is aimed at analyzing the structure and function of the spike (S) proteins of porcine enteric coronaviruses, including transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV) by applying bioinformatics methods. The physical and chemical properties, hydrophilicity and hydrophobicity, transmembrane region, signal peptide, phosphorylation and glycosylation sites, epitope, functional domains, and motifs of S proteins of porcine enteric coronaviruses were predicted and analyzed through online software. The results showed that S proteins of TGEV, PEDV, SADS-CoV, and PDCoV all contained transmembrane regions and signal peptide. TGEV S protein contained 139 phosphorylation sites, 24 glycosylation sites, and 53 epitopes. PEDV S protein had 143 phosphorylation sites, 22 glycosylation sites, and 51 epitopes. SADS-CoV S protein had 109 phosphorylation sites, 20 glycosylation sites, and 43 epitopes. PDCoV S protein had 124 phosphorylation sites, 18 glycosylation sites, and 52 epitopes. Moreover, TGEV, PEDV, and PDCoV S proteins all contained two functional domains and two motifs, spike_rec_binding and corona_S2. The corona_S2 consisted of S2 subunit heptad repeat 1 (HR1) and S2 subunit heptad repeat 2 (HR2) region profiles. Additionally, SADS-CoV S protein was predicted to contain only one functional domain, the corona_S2. This analysis of the biological functions of porcine enteric coronavirus spike proteins can provide a theoretical basis for the design of antiviral drugs.

Use of dual priming oligonucleotide system-based multiplex RT-PCR assay to detect five diarrhea viruses in pig herds in South China

In this study, a specific and simple method based on the dual priming oligonucleotide (DPO) system was developed to simultaneously detect transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), porcine rotavirus A (PRV-A), porcine delta coronavirus (PDCoV), and swine acute diarrhea syndrome coronavirus (SADS-CoV), associated with the major enteric RNA viruses in pigs. The DPO system-based multiplex RT-PCR method simplified the primer design and did not require optimization of the annealing temperature. Specificity analysis revealed that the method could specifically detect TGEV, PEDV, PRV-A, PDCoV, and SADS-CoV without any cross-amplification of other circulating swine viruses. The limit of detection of the method was as low as 103–104 copies/μL plasmid of each virus. The method also had good repeatability, and obvious results were seen in three repeat experiments with an interval of 45 days. This optimized multiplex RT-PCR method was used to evaluate 181 clinical swine samples that were collected from four provinces of China between September 2016 and August 2018. The results showed that the positive detection rates of PEDV, PDCoV, SADS-CoV, PRV-A, and TGEV were 30.94% (56/181), 17.67% (32/181), 11.6% (21/181), 9.39% (17/181), and 0.55% (1/181), respectively. Mixed infection of two or more viruses was also common. The DPO system-based multiplex RT-PCR could be a useful tool for detecting enteric virus infections. This method has the advantages of easy operation, low cost, high detection efficiency, and short running time for early diagnosis in clinical cases.

Genetic characterization and phylogenetic analysis of porcine epidemic diarrhea virus in Guangdong, China, between 2018 and 2019.

Porcine epidemic diarrhea virus (PEDV), a leading cause of piglet diarrhea outbreaks, poses a significant danger to the swine industry. The aim of this study was to investigate the epidemic characteristics of PEDV that was circulating in Guangdong province, one of China’s major pig producing provinces. Clinical samples were collected from eight pig farms in Guangdong province between 2018 and 2019 and tested for the major porcine enteric pathogens, including PEDV, transmissible gastroenteritis virus (TGEV), Swine enteric coronavirus (SeCoV), Swine acute diarrhea syndrome coronavirus (SADS-CoV), porcine deltacoronavirus (PDCoV), and porcine rotavirus (RV). As a result, only PEDV and RV were detected at a rate of 47.0% (16/34) and 18.6% (8/34), respectively. Coinfectoin with PEDV and RV occurred at a rate of PEDV 12.5% (2/16). Subsequently, the full-length S gene sequences of 13 PEDV strains were obtained, and phylogenetic analysis suggested the presence of GII-c group PEDV strains in this region (non-S-INDEL). Two novel common amino acid insertions (55T/IG56 and 551L) and one novel glycosylation site (1199G+) were detected when the CV777 and ZJ08 vaccine strains were compared. Furthermore, intragroup recombination events in the S gene regions 51–548 and 2478–4208 were observed in the PEDV strains studied. In summary, the observations provide current information on the incidence of viral agents causing swine diarrhea in southern China and detailed the genetic characteristics and evolutionary history of the dominant PEDV field strains. Our findings will aid in the development of an updated vaccine for the prevention and control of PEDV variant strains.

Comprehensive interactome analysis of the spike protein of swine acute diarrhea syndrome coronavirus

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a recently discovered coronavirus that causes severe and acute diarrhea and rapid weight loss in piglets. SADS-CoV was reported to be capable of infecting cell lines derived from diverse species, including bats, mice, hamsters, rats, chickens, pigs, nonhuman primates, and humans, implying its high risk of cross-species infection. However, its receptor is still unknown. In this study, the receptor-binding domain of the SADS-CoV spike (S) protein was purified and then subjected to affinity purification (AP)-coupled mass spectrometry (MS)-based proteomic analysis to identify the interactors of the SADS-CoV S protein. Forty-three host proteins were identified, and a Gene Ontology analysis indicated that these interactors can be grouped into categories such as “cell-cell adhesion”, “translation” “viral transcription”, suggesting that these processes may participate in the SADS-CoV life cycles. RNA interference-based screening of these interactors indicated that PPIB and vimentin can affect SADS-CoV replication. Our study provides an overarching view into the host interactome of the SADS-CoV S protein and highlights potential targets for the development of therapeutics against SADS-CoV.

Transcriptional Landscape of Vero E6 Cells during Early Swine Acute Diarrhea Syndrome Coronavirus Infection.

Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a newly emerged and highly pathogenic virus that is associated with fatal diarrhea disease in piglets, causing significant economic losses to the pig industry. At present, the research on the pathogenicity and molecular mechanisms of host-virus interactions of SADS-CoV are limited and remain poorly understood. Here, we investigated the global gene expression profiles of SADS-CoV-infected Vero E6 cells at 12, 18, and 24 h post-infection (hpi) using the RNA-sequencing. As a result, a total of 3324 differentially expressed genes (DEG) were identified, most of which showed a down-regulated expression pattern. Functional enrichment analyses indicated that the DEGs are mainly involved in signal transduction, cellular transcription, immune and inflammatory response, and autophagy. Collectively, our results provide insights into the changes in the cellular transcriptome during early infection of SADS-CoV and may provide information for further study of molecular mechanisms.

Porcine Coronaviruses: Overview of the State of the Art

Like RNA viruses in general, coronaviruses (CoV) exhibit high mutation rates which, in combination with their strong tendency to recombine, enable them to overcome the host species barrier and adapt to new hosts. It is currently known that six CoV are able to infect pigs. Four of them belong to the genus Alphacoronavirus [transmissible gastroenteritis coronavirus (TEGV), porcine respiratory coronavirus (PRCV), porcine epidemic diarrhea virus (PEDV), swine acute diarrhea syndrome coronavirus (SADS-CoV)], one of them to the genus Betacoronavirus [porcine hemagglutinating encephalomyelitis virus (PHEV)] and the last one to the genus Deltacoronavirus (PDCoV). PHEV was one of the first identified swine CoV and is still widespread, causing subclinical infections in pigs in several countries. PRCV, a spike deletion mutant of TGEV associated with respiratory tract infection, appeared in the 1980s. PRCV is considered non-pathogenic since its infection course is mild or subclinical. Since its appearance, pig populations have become immune to both PRCV and TGEV, leading to a significant reduction in the clinical and economic importance of TGEV. TGEV, PEDV and PDCoV are enteropathogenic CoV and cause clinically indistinguishable acute gastroenteritis in all age groups of pigs. PDCoV and SADS-CoV have emerged in 2014 (US) and in 2017 (China), respectively. Rapid diagnosis is crucial for controlling CoV infections and preventing them from spreading. Since vaccines are available only for some porcine CoV, prevention should focus mainly on a high level of biosecurity. In view of the diversity of CoV and the potential risk factors associated with zoonotic emergence, updating the knowledge concerning this area is essential.

Swine Acute Diarrhea Syndrome Coronavirus Nucleocapsid Protein Antagonizes Interferon-β Production via Blocking the Interaction Between TRAF3 and TBK1.

Swine acute diarrhea syndrome coronavirus (SADS-CoV), first discovered in 2017, is a porcine enteric coronavirus that can cause acute diarrhea syndrome (SADS) in piglets. Here, we studied the role of SADS-CoV nucleocapsid (N) protein in innate immunity. Our results showed that SADS-CoV N protein could inhibit type I interferon (IFN) production mediated by Sendai virus (Sev) and could block the phosphorylation and nuclear translocation of interferon regulatory factor 3 (IRF3). Simultaneously, the IFN-β promoter activity mediated by TANK binding kinase 1 (TBK1) or its upstream molecules in the RLRs signal pathway was inhibited by SADS-CoV N protein. Further investigations revealed that SADS-CoV N protein could counteract interaction between TNF receptor-associated factor 3 (TRAF3) and TBK1, which led to reduced TBK1 activation and IFN-β production. Our study is the first report of the interaction between SADS-CoV N protein and the host antiviral innate immune responses, and the mechanism utilized by SADS-CoV N protein provides a new insight of coronaviruses evading host antiviral innate immunity.

The Roles of Apoptosis in Swine Response to Viral Infection and Pathogenesis of Swine Enteropathogenic Coronaviruses.

Apoptosis is a tightly regulated mechanism of cell death that plays important roles in various biological processes including biological evolution, multiple system development, anticancer, and viral infections. Swine enteropathogenic coronaviruses invade and damage villous epithelial cells of the small intestine causing severe diarrhea with high mortality rate in suckling piglets. Transmissible gastroenteritis virus (TGEV), Porcine epidemic diarrhea virus (PEDV), Porcine deltacoronavirus (PDCoV), and Swine acute diarrhea syndrome coronavirus (SADS-CoV) are on the top list of commonly-seen swine coronaviruses with a feature of diarrhea, resulting in significant economic losses to the swine industry worldwide. Apoptosis has been shown to be involved in the pathogenesis process of animal virus infectious diseases. Understanding the roles of apoptosis in host responses against swine enteropathogenic coronaviruses infection contribute to disease prevention and control. Here we summarize the recent findings that focus on the apoptosis during swine coronaviruses infection, in particular, TGEV, PEDV, PDCoV, and SADS-CoV.

Molecular diversity of coronavirus host cell entry receptors.

ABSTRACTCoronaviruses are a group of viruses causing disease in a wide range of animals, and humans. Since 2002, the successive emergence of bat-borne severe acute respiratory syndrome coronavirus (SARS-CoV), Middle East respiratory syndrome coronavirus (MERS-CoV), swine acute diarrhea syndrome coronavirus (SADS-CoV) and SARS-CoV-2 has reinforced efforts in uncovering the molecular and evolutionary mechanisms governing coronavirus cell tropism and interspecies transmission. Decades of studies have led to the discovery of a broad set of carbohydrate and protein receptors for many animal and human coronaviruses. As the main determinant of coronavirus entry, the spike protein binds to these receptors and mediates membrane fusion. Prone to mutations and recombination, spike evolution has been studied extensively. The interactions between spike proteins and their receptors are often complex and despite many advances in the field, there remains many unresolved questions concerning coronavirus tropism modification and cross-species transmission, potentially leading to delays in outbreak responses. The emergence of SARS-CoV-2 underscores the need to address these outstanding issues in order to better anticipate new outbreaks. In this review, we discuss the latest advances in the field of coronavirus receptors emphasizing on the molecular and evolutionary processes that underlie coronavirus receptor usage and host range expansion.

Cryo-electron Microscopy Structure of the Swine Acute Diarrhea Syndrome Coronavirus Spike Glycoprotein Provides Insights into Evolution of Unique Coronavirus Spike Proteins.

Coronaviruses (CoV) have caused a number of major epidemics in humans and animals, including the current pandemic of coronavirus disease 2019 (COVID-19), which has brought a renewed focus on the evolution and interspecies transmission of coronaviruses. Swine acute diarrhea syndrome coronavirus (SADS-CoV), which was recently identified in piglets in southern China, is an alphacoronavirus that originates from the same genus of horseshoe bats as severe acute respiratory syndrome CoV (SARS-CoV) and that was reported to be capable of infecting cells from a broad range of species, suggesting a considerable potential for interspecies transmission. Given the importance of the coronavirus spike (S) glycoprotein in host range determination and viral entry, we report a cryo-electron microscopy (cryo-EM) structure of the SADS-CoV S trimer in the prefusion conformation at a 3.55-Å resolution. Our structure reveals that the SADS-CoV S trimer assumes an intrasubunit quaternary packing mode in which the S1 subunit N-terminal domain (S1-NTD) and the S1 subunit C-terminal domain (S1-CTD) of the same protomer pack together by facing each other in the lying-down state. SADS-CoV S has several distinctive structural features that may facilitate immune escape, such as a relatively compact architecture of the S trimer and epitope masking by glycan shielding. Comparison of SADS-CoV S with the spike proteins of the other coronavirus genera suggested that the structural features of SADS-CoV S are evolutionarily related to those of the spike proteins of the other genera rather than to the spike protein of a typical alphacoronavirus. These data provide new insights into the evolutionary relationship between spike glycoproteins of SADS-CoV and those of other coronaviruses and extend our understanding of their structural and functional diversity.IMPORTANCE In this article, we report the atomic-resolution prefusion structure of the spike protein from swine acute diarrhea syndrome coronavirus (SADS-CoV). SADS-CoV is a pathogenic alphacoronavirus that was responsible for a large-scale outbreak of fatal disease in pigs and that was reported to be capable of interspecies transmission. We describe the overall structure of the SADS-CoV spike protein and conducted a detailed analysis of its main structural elements. Our results and analyses are consistent with those of previous phylogenetic studies and suggest that the SADS-CoV spike protein is evolutionarily related to the spike proteins of betacoronaviruses, with a strong similarity in S1-NTDs and a marked divergence in S1-CTDs. Moreover, we discuss the possible immune evasion strategies used by the SADS-CoV spike protein. Our study provides insights into the structure and immune evasion strategies of the SADS-CoV spike protein and broadens the understanding of the evolutionary relationships between coronavirus spike proteins of different genera.

Swine acute diarrhea syndrome coronavirus replication in primary human cells reveals potential susceptibility to infection

Zoonotic coronaviruses represent an ongoing threat, yet the myriads of circulating animal viruses complicate the identification of higher-risk isolates that threaten human health. Swine acute diarrhea syndrome coronavirus (SADS-CoV) is a newly discovered, highly pathogenic virus that likely evolved from closely related HKU2 bat coronaviruses, circulating in Rhinolophus spp. bats in China and elsewhere. As coronaviruses cause severe economic losses in the pork industry and swine are key intermediate hosts of human disease outbreaks, we synthetically resurrected a recombinant virus (rSADS-CoV) as well as a derivative encoding tomato red fluorescent protein (tRFP) in place of ORF3. rSADS-CoV replicated efficiently in a variety of continuous animal and primate cell lines, including human liver and rectal carcinoma cell lines. Of concern, rSADS-CoV also replicated efficiently in several different primary human lung cell types, as well as primary human intestinal cells. rSADS-CoV did not use human coronavirus ACE-2, DPP4, or CD13 receptors for docking and entry. Contemporary human donor sera neutralized the group I human coronavirus NL63, but not rSADS-CoV, suggesting limited human group I coronavirus cross protective herd immunity. Importantly, remdesivir, a broad-spectrum nucleoside analog that is effective against other group 1 and 2 coronaviruses, efficiently blocked rSADS-CoV replication in vitro. rSADS-CoV demonstrated little, if any, replicative capacity in either immune-competent or immunodeficient mice, indicating a critical need for improved animal models. Efficient growth in primary human lung and intestinal cells implicate SADS-CoV as a potential higher-risk emerging coronavirus pathogen that could negatively impact the global economy and human health.

Bat-related coronavirus

The outbreak of coronavirus disease 2019 (COVID-19) in Dec 2019 sounded another alarm for humanbeing, with the first being the outbreak of severe acute respiratory syndrome (SARS) in 2003 Researchers found that the natural host of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen of COVID-19, may be the Rhinolophus sinicus There have been four outbreaks of coronaviruses (severe acute respiratory syndrome coronavirus [SARS-CoV], Middle East respiratory syndrome coronavirus [MERS-CoV], swine acute diarrhea syndrome coronavirus [SADS-CoV] and SARS-CoV-2) worldwide since the beginning of 21st century, and they have caused huge threats and losses to human health, public health, economic development, and social stability A large amount of evidence suggests that the natural host of all these four coronaviruses may be bats This article reviews the species and global geographic distribution of bat-related coronaviruses, and the above-metioned four coronaviruses causing severe outbreaks

RNA-Seq-Based Whole Transcriptome Analysis of IPEC-J2 Cells During Swine Acute Diarrhea Syndrome Coronavirus Infection.

The new emergence of swine acute diarrhea syndrome coronavirus (SADS-CoV) has resulted in high mortality in suckling pigs in China. To date, the transcriptional expression of host cells during SADS-CoV infection has not been documented. In this study, by means of RNA-Seq technology, we investigated the whole genomic expression profiles of intestinal porcine epithelial cells (IPEC-J2) infected with a SADS-CoV strain SADS-CoV-CH-FJWT-2018. A total of 24,676 genes were identified: 23,677 were known genes, and 999 were novel genes. A total of 1,897 differentially expressed genes (DEGs) were identified between SADS-CoV-infected and uninfected cells at 6, 24, and 48 h post infection (hpi). Of these, 1,260 genes were upregulated and 637 downregulated. A Gene Ontology enrichment analysis revealed that DEGs in samples from 6, 24, and 48 hpi were enriched in 79, 383, and 233 GO terms, respectively, which were mainly involved in immune system process, response to stimulus, signal transduction, and cytokine–cytokine receptor interactions. The 1,897 DEGs were mapped to 109 KEGG Ontology (KO) pathways classified into four main categories. Most of the DEGs annotated in the KEGG pathways were related to the immune system, infectious viral disease, and signal transduction. The mRNA of porcine serum amyloid A-3 protein (SAA3), an acute phase response protein, was significantly upregulated during the infection. Over-expressed SAA3 in IPEC-J2 cells drastically inhibited the replication of SADS-CoV, while under-expressed SAA3 promoted virus replication. To our knowledge, this is the first report on the profiles of gene expression of IPEC-J2 cells infected by SADS-CoV by means of RNA-Seq technology. Our results indicate that SADS-CoV infection significantly modified the host cell gene expression patterns, and the host cells responded in highly specific manners, including immune response, signal and cytokine transduction, and antiviral response. The findings provide important insights into the transcriptome of IPEC-J2 in SADS-CoV infection.

Development of a TaqMan-probe-based multiplex real-time PCR for the simultaneous detection of emerging and reemerging swine coronaviruses

ABSTRACT With the outbreak of the recent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in 2019, coronaviruses have become a global research hotspot in the field of virology. Coronaviruses mainly cause respiratory and digestive tract diseases, several coronaviruses are responsible for porcine diarrhea, such as porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and emerging swine acute diarrhea syndrome coronavirus (SADS-CoV). Those viruses have caused huge economic losses and are considered as potential public health threats. Porcine torovirus (PToV) and coronaviruses, sharing similar genomic structure and replication strategy, belong to the same order Nidovirales. Here, we developed a multiplex TaqMan-probe-based real-time PCR for the simultaneous detection of PEDV, PDCoV, PToV, and SADS-CoV for the first time. Specific primers and TaqMan fluorescent probes were designed targeting the ORF1a region of PDEV, PToV, and SADS-CoV and the ORF1b region of PDCoV. The method showed high sensitivity and specificity, with a detection limit of 1 × 102 copies/μL for each pathogen. A total of 101 clinical swine samples with signs of diarrhea were analyzed using this method, and the result showed good consistency with conventional reverse transcription PCR (RT-PCR). This method improves the efficiency for surveillance of these emerging and reemerging swine enteric viruses and can help reduce economic losses to the pig industry, which also benefits animal and public health.

Microfluidic-RT-LAMP chip for the point-of-care detection of emerging and re-emerging enteric coronaviruses in swine

Porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and swine acute diarrhea syndrome-coronavirus (SADS-CoV) are three emerging and re-emerging coronaviruses (CoVs). Symptoms caused by these three viruses are extremely similar, including acute diarrhea, vomiting and even death in piglets. To date, strict biosecurity is still the most effective disease prevention and control measures, and the early detection of pathogens is the most important link. Here, we developed a microfluidic-RT-LAMP chip detection system for the first time, which could detected PEDV, PDCoV and SADS-CoV simultaneously, and had advantages of rapid, simple, sensitive, high-throughput, and accurate at point-of-care settings. The lowest detection limits of the microfluidic-RT-LAMP chip method are 101 copies/μL, 102 copies/μL and 102 copies/μL for PEDV, PDCoV and SADS-CoV, respectively. The whole detection procedure can be finished rapidly in 40 min without any cross-reaction with other common swine viruses. A total of 173 clinical swine fecal samples characterized with diarrheal symptoms were used to evaluate the performance of the newly developed system, which presented good stabilities (C.V.s<5%) and specificities (100%), and possessed sensitivities of 92.24%, 92.19% and 91.23% for PEDV, PDCoV and SADS-CoV respectively. In summary, the established microfluidic-RT-LAMP chip detection system could satisfy the demanding in field diagnoses, which was suitable for promotion in remote areas due to its fast, portable and cost-effective characters.

Structural and biochemical characterization of SADS-CoV papain-like protease 2.

Swine acute diarrhea syndrome coronavirus (SADS‐CoV) is a novel coronavirus that is involved in severe diarrhea disease in piglets, causing considerable agricultural and economic loss in China. The emergence of this new coronavirus increases the importance of understanding SADS‐CoV as well as antivirals. Coronaviral proteases, including main proteases and papain‐like proteases (PLP), are attractive antiviral targets because of their essential roles in polyprotein processing and thus viral maturation. Here, we describe the biochemical and structural identification of recombinant SADS papain‐like protease 2 (PLP2) domain of nsp3. The SADS‐CoV PLP2 was shown to cleave nsp1 proteins and also peptides mimicking the nsp2|nsp3 cleavage site and also had deubiquitinating and deISGynating activity by in vitro assays. The crystal structure adopts an architecture resembling that of PLPs from other coronaviruses. We characterize both conserved and unique structural features likely directing the interaction of PLP2 with the substrates, including the tentative mapping of active site and other essential residues. These results provide a foundation for understanding the molecular basis of coronaviral PLPs' catalytic mechanism and for the screening and design of therapeutics to combat infection by SADS coronavirus.

Coronavirus disease 2019 (COVID-19) outbreak: Could pigs be vectors for human infections?

Coronavirus disease 2019 (COVID-19) outbreak: Could pigs be vectors for human infections?