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1.
J Virol ; : e0003722, 2022 Apr 07.
Article in English | MEDLINE | ID: covidwho-1779311

ABSTRACT

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) continues to pose an enormous threat to economic activity and public health worldwide. Previous studies have shown that the nonstructural protein 5 (nsp5, also called 3C-like protease) of alpha- and deltacoronaviruses cleaves Q231 of the NF-κB essential modulator (NEMO), a key kinase in the RIG-I-like receptor pathway, to inhibit type I interferon (IFN) production. In this study, we found that both SARS-CoV-2 nsp5 and SARS-CoV nsp5 cleaved NEMO at multiple sites (E152, Q205, and Q231). Notably, SARS-CoV-2 nsp5 exhibited a stronger ability to cleave NEMO than SARS-CoV nsp5. Sequence and structural alignments suggested that an S/A polymorphism at position 46 of nsp5 in SARS-CoV versus SARS-CoV-2 may be responsible for this difference. Mutagenesis experiments showed that SARS-CoV-2 nsp5 (S46A) exhibited poorer cleavage of NEMO than SARS-CoV-2 nsp5 wild type (WT), while SARS-CoV nsp5 (A46S) showed enhanced NEMO cleavage compared with the WT protein. Purified recombinant SARS-CoV-2 nsp5 WT and SARS-CoV nsp5 (A46S) proteins exhibited higher hydrolysis efficiencies than SARS-CoV-2 nsp5 (S46A) and SARS-CoV nsp5 WT proteins in vitro. Furthermore, SARS-CoV-2 nsp5 exhibited stronger inhibition of Sendai virus (SEV)-induced interferon beta (IFN-ß) production than SARS-CoV-2 nsp5 (S46A), while introduction of the A46S substitution in SARS-CoV nsp5 enhanced suppression of SEV-induced IFN-ß production. Taken together, these data show that S46 is associated with the catalytic activity and IFN antagonism by SARS-CoV-2 nsp5. IMPORTANCE The nsp5-encoded 3C-like protease is the main coronavirus protease, playing a vital role in viral replication and immune evasion by cleaving viral polyproteins and host immune-related molecules. We showed that both SARS-CoV-2 nsp5 and SARS-CoV nsp5 cleave the NEMO at multiple sites (E152, Q205, and Q231). This specificity differs from NEMO cleavage by alpha- and deltacoronaviruses, demonstrating the distinct substrate recognition of SARS-CoV-2 and SARS-CoV nsp5. Compared with SARS-CoV nsp5, SARS-CoV-2 nsp5 encodes S instead of A at position 46. This substitution is associated with stronger catalytic activity, enhanced cleavage of NEMO, and increased interferon antagonism of SARS-CoV-2 nsp5. These data provide new insights into the pathogenesis and transmission of SARS-CoV-2.

3.
Viruses ; 13(10)2021 10 04.
Article in English | MEDLINE | ID: covidwho-1463827

ABSTRACT

Porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus, causes diarrhoea in suckling piglets and has the potential for cross-species transmission. No effective PDCoV vaccines or antiviral drugs are currently available. Here, we successfully generated an infectious clone of PDCoV strain CHN-HN-2014 using a combination of bacterial artificial chromosome (BAC)-based reverse genetics system with a one-step homologous recombination. The recued virus (rCHN-HN-2014) possesses similar growth characteristics to the parental virus in vitro. Based on the established infectious clone and CRISPR/Cas9 technology, a PDCoV reporter virus expressing nanoluciferase (Nluc) was constructed by replacing the NS6 gene. Using two drugs, lycorine and resveratrol, we found that the Nluc reporter virus exhibited high sensibility and easy quantification to rapid antiviral screening. We further used the Nluc reporter virus to test the susceptibility of different cell lines to PDCoV and found that cell lines derived from various host species, including human, swine, cattle and monkey enables PDCoV replication, broadening our understanding of the PDCoV cell tropism range. Taken together, our reporter viruses are available to high throughput screening for antiviral drugs and uncover the infectivity of PDCoV in various cells, which will accelerate our understanding of PDCoV.


Subject(s)
Coronavirus Infections/veterinary , Deltacoronavirus/genetics , Deltacoronavirus/metabolism , Genes, Reporter/genetics , Luciferases/genetics , A549 Cells , Animals , Cell Line , Chlorocebus aethiops , Chromosomes, Artificial, Bacterial/genetics , Coronavirus Infections/pathology , Deltacoronavirus/growth & development , Dogs , Genome, Viral/genetics , Humans , Luciferases/biosynthesis , Madin Darby Canine Kidney Cells , Nanostructures , Swine , Swine Diseases/virology , Vero Cells , Virus Replication/genetics
4.
J Virol ; 95(24): e0134521, 2021 11 23.
Article in English | MEDLINE | ID: covidwho-1441856

ABSTRACT

Porcine deltacoronavirus (PDCoV), an emerging enteropathogenic coronavirus, causes serious diarrhea in suckling piglets and has the potential for cross-species transmission. Although extensive studies have been reported on the biology and pathogenesis of PDCoV, the mechanisms by which PDCoV enters cells are not well characterized. In this study, we investigated how PDCoV enters IPI-2I cells, a line of porcine intestinal epithelial cells derived from pig ileum. Immunofluorescence assays, small interfering RNA (siRNA) interference, specific pharmacological inhibitors, and dominant negative mutation results revealed that PDCoV entry into IPI-2I cells depended on clathrin, dynamin, and a low-pH environment but was independent of caveolae. Specific inhibition of phosphatidylinositol 3-kinase (PI3K) and the Na+/H+ exchanger (NHE) revealed that PDCoV entry involves macropinocytosis and depends on NHE rather than on PI3K. Additionally, Rab5 and Rab7, but not Rab11, regulated PDCoV endocytosis. This is the first study to demonstrate that PDCoV uses clathrin-mediated endocytosis and macropinocytosis as alternative endocytic pathways to enter porcine intestinal epithelial cells. We also discussed the entry pathways of PDCoV into other porcine cell lines. Our findings reveal the entry mechanisms of PDCoV and provide new insight into the PDCoV life cycle. IMPORTANCE An emerging enteropathogenic coronavirus, PDCoV, has the potential for cross-species transmission, attracting extensive attenuation. Characterizing the detailed process of PDCoV entry into cells will deepen our understanding of the viral infection and pathogenesis and provide clues for therapeutic intervention against PDCoV. With the objective, we used complementary approaches to dissect the process in PDCoV-infected IPI-2I cells, a line of more physiologically relevant intestinal epithelial cells to PDCoV infection in vivo. Here, we demonstrate that PDCoV enters IPI-2I cells via macropinocytosis, which does not require a specific receptor, and clathrin-mediated endocytosis, which requires a low-pH environment and dynamin, while a caveola-mediated endocytic pathway is used by PDCoV to enter swine testicular (ST) cells and porcine kidney (LLC-PK1) cells. These findings provide a molecular detail of the cellular entry pathways of PDCoV and may direct us toward novel antiviral drug development.


Subject(s)
Coronavirus Infections/virology , Deltacoronavirus/physiology , Dynamins/metabolism , Endocytosis , Epithelial Cells/virology , Animals , Cell Line , Cell Survival , Clathrin/metabolism , Coronavirus/genetics , Hydrogen-Ion Concentration , Ileum/virology , Kidney/virology , Phosphatidylinositol 3-Kinases/metabolism , Pinocytosis , RNA, Small Interfering/metabolism , Swine , Swine Diseases/virology , Virus Internalization , rab5 GTP-Binding Proteins/metabolism
5.
Nat Commun ; 12(1): 141, 2021 01 08.
Article in English | MEDLINE | ID: covidwho-1387322

ABSTRACT

Coronaviruses spike (S) glycoproteins mediate viral entry into host cells by binding to host receptors. However, how the S1 subunit undergoes conformational changes for receptor recognition has not been elucidated in Alphacoronavirus. Here, we report the cryo-EM structures of the HCoV-229E S trimer in prefusion state with two conformations. The activated conformation may pose the potential exposure of the S1-RBDs by decreasing of the interaction area between the S1-RBDs and the surrounding S1-NTDs and S1-RBDs compared to the closed conformation. Furthermore, structural comparison of our structures with the previously reported HCoV-229E S structure showed that the S trimers trended to open the S2 subunit from the closed conformation to open conformation, which could promote the transition from pre- to postfusion. Our results provide insights into the mechanisms involved in S glycoprotein-mediated Alphacoronavirus entry and have implications for vaccine and therapeutic antibody design.


Subject(s)
CD13 Antigens/metabolism , Coronavirus 229E, Human/physiology , Spike Glycoprotein, Coronavirus/metabolism , Virus Internalization , Cell Line, Tumor , Coronavirus Infections/prevention & control , Coronavirus Infections/virology , Cryoelectron Microscopy , Humans , Models, Molecular , Protein Conformation, alpha-Helical , Protein Multimerization , Protein Structure, Quaternary , Protein Subunits/metabolism , Spike Glycoprotein, Coronavirus/ultrastructure
6.
J Virol ; 2021 Jan 07.
Article in English | MEDLINE | ID: covidwho-1376458

ABSTRACT

Coronaviruses that infect humans belong to the Alpha-coronavirus (including HCoV-229E) and Beta-coronavirus (including SARS-CoV and SARS-CoV-2) genera. In particular, SARS-CoV-2 is currently a major threat to public health worldwide. The spike (S) homotrimers bind to their receptors via the receptor-binding domain (RBD), which is a major target to block viral entry. In this study, we selected Alpha-coronavirus (HCoV-229E) and Beta-coronavirus (SARS-CoV and SARS-CoV-2) as models. Their RBDs exist two different conformational states (lying or standing) in the prefusion S-trimer structure. Then, the differences in the immune responses to RBDs from these coronaviruses were analyzed structurally and immunologically. Our results showed that more RBD-specific antibodies (antibody titers: 1.28×105; 2.75×105) were induced by the S-trimer with the RBD in the "standing" state (SARS-CoV and SARS-CoV-2) than the S-trimer with the RBD in the "lying" state (HCoV-229E, antibody titers: <500), and more S-trimer-specific antibodies were induced by the RBD in the SARS-CoV and SARS-CoV-2 (antibody titers: 6.72×105; 5×105) than HCoV-229E (antibody titers:1.125×103). Besides, we found that the ability of the HCoV-229E RBD to induce neutralizing antibodies was lower than S-trimer, and the intact and stable S1 subunit was essential for producing efficient neutralizing antibodies against HCoV-229E. Importantly, our results reveal different vaccine strategies for coronaviruses, and S-trimer is better than RBD as a target for vaccine development in Alpha-coronavirus Our findings will provide important implications for future development of coronavirus vaccines.Importance Outbreak of coronaviruses, especially SARS-CoV-2, poses a serious threat to global public health. Development of vaccines to prevent the coronaviruses that can infect humans has always been a top priority. Coronavirus spike (S) protein is considered as a major target for vaccine development. Currently, structural studies have shown that Alpha-coronavirus (HCoV-229E) and Beta-coronavirus (SARS-CoV and SARS-CoV-2) RBDs are in "lying" and "standing" states in the prefusion S-trimer structure. Here, we evaluated the ability of S-trimer and RBD to induce neutralizing antibodies among these coronaviruses. Our results showed that the S-trimer and RBD are both candidates for subunit vaccines in Beta-coronavirus (SARS-CoV and SARS-CoV-2) with a RBD "standing" state. However, for Alpha-coronavirus (HCoV-229E) with a RBD "lying" state, the S-trimer may be more suitable for subunit vaccines than the RBD. Our results will provide novel ideas for the development of vaccines targeting S protein in the future.

7.
J Virol ; 94(20)2020 09 29.
Article in English | MEDLINE | ID: covidwho-1271852

ABSTRACT

The 3C-like protease (3CLpro) of nidovirus plays an important role in viral replication and manipulation of host antiviral innate immunity, which makes it an ideal antiviral target. Here, we characterized that porcine torovirus (PToV; family Tobaniviridae, order Nidovirales) 3CLpro autocatalytically releases itself from the viral precursor protein by self-cleavage. Site-directed mutagenesis suggested that PToV 3CLpro, as a serine protease, employed His53 and Ser160 as the active-site residues. Interestingly, unlike most nidovirus 3CLpro, the P1 residue plays a less essential role in N-terminal self-cleavage of PToV 3CLpro Substituting either P1 or P4 residue of substrate alone has little discernible effect on N-terminal cleavage. Notably, replacement of the two residues together completely blocks N-terminal cleavage, suggesting that N-terminal self-cleavage of PToV 3CLpro is synergistically affected by both P1 and P4 residues. Using a cyclized luciferase-based biosensor, we systematically scanned the polyproteins for cleavage sites and identified (FXXQ↓A/S) as the main consensus sequences. Subsequent homology modeling and biochemical experiments suggested that the protease formed putative pockets S1 and S4 between the substrate. Indeed, mutants of both predicted S1 (D159A, H174A) and S4 (P62G/L185G) pockets completely lost the ability of cleavage activity of PToV 3CLpro In conclusion, the characterization of self-processing activities and substrate specificities of PToV 3CLpro will offer helpful information for the mechanism of nidovirus 3C-like proteinase's substrate specificities and the rational development of the antinidovirus drugs.IMPORTANCE Currently, the active-site residues and substrate specificities of 3C-like protease (3CLpro) differ among nidoviruses, and the detailed catalytic mechanism remains largely unknown. Here, porcine torovirus (PToV) 3CLpro cleaves 12 sites in the polyproteins, including its N- and C-terminal self-processing sites. Unlike coronaviruses and arteriviruses, PToV 3CLpro employed His53 and Ser160 as the active-site residues that recognize a glutamine (Gln) at the P1 position. Surprisingly, mutations of P1-Gln impaired the C-terminal self-processing but did not affect N-terminal self-processing. The "noncanonical" substrate specificity for its N-terminal self-processing was attributed to the phenylalanine (Phe) residue at the P4 position in the N-terminal site. Furthermore, a double glycine (neutral) substitution at the putative P4-Phe-binding residues (P62G/L185G) abolished the cleavage activity of PToV 3CLpro suggested the potential hydrophobic force between the PToV 3CLpro and P4-Phe side chains.


Subject(s)
Coronavirus 3C Proteases/metabolism , Protein Processing, Post-Translational , Proteolysis , Torovirus Infections/embryology , Torovirus/enzymology , Animals , Coronavirus 3C Proteases/genetics , HEK293 Cells , Humans , Substrate Specificity , Swine , Torovirus/genetics , Torovirus Infections/genetics
8.
Viruses ; 13(6)2021 06 13.
Article in English | MEDLINE | ID: covidwho-1270126

ABSTRACT

Coronavirus accessory proteins are a unique set of proteins whose genes are interspersed among or within the genes encoding structural proteins. Different coronavirus genera, or even different species within the same coronavirus genus, encode varying amounts of accessory proteins, leading to genus- or species-specificity. Though accessory proteins are dispensable for the replication of coronavirus in vitro, they play important roles in regulating innate immunity, viral proliferation, and pathogenicity. The function of accessory proteins on virus infection and pathogenesis is an area of particular interest. In this review, we summarize the current knowledge on accessory proteins of several representative coronaviruses that infect humans or animals, including the emerging severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), with an emphasis on their roles in interaction between virus and host, mainly involving stress response, innate immunity, autophagy, and apoptosis. The cross-talking among these pathways is also discussed.


Subject(s)
Immunity, Innate , SARS-CoV-2/immunology , SARS-CoV-2/metabolism , Viral Regulatory and Accessory Proteins/metabolism , COVID-19/immunology , COVID-19/virology , Host-Pathogen Interactions , Humans , Immune Evasion , Open Reading Frames , SARS-CoV-2/chemistry , SARS-CoV-2/genetics , Viral Regulatory and Accessory Proteins/genetics , Virus Replication
9.
Arch Virol ; 166(3): 935-941, 2021 Mar.
Article in English | MEDLINE | ID: covidwho-1045234

ABSTRACT

Enteric coronaviruses (CoVs) are major pathogens that cause diarrhea in piglets. To date, four porcine enteric CoVs have been identified: transmissible gastroenteritis virus (TGEV), porcine epidemic diarrhea virus (PEDV), porcine deltacoronavirus (PDCoV), and HKU2-like porcine enteric alphacoronavirus (PEAV). In this study, we investigated the replicative capacity of these four enteric CoVs in LLC-PK1 cells, a porcine kidney cell line. The results showed that LLC-PK1 cells are susceptible to all four enteric CoVs, particularly to TGEV and PDCoV infections, indicating that LLC-PK1 cells can be applied to porcine enteric CoV research in vitro, particularly for coinfection studies.


Subject(s)
Deltacoronavirus/growth & development , Gastroenteritis, Transmissible, of Swine/virology , Porcine epidemic diarrhea virus/growth & development , Transmissible gastroenteritis virus/growth & development , Virus Replication/physiology , Animals , Cell Line , Chlorocebus aethiops , Disease Susceptibility , Fluorescent Antibody Technique, Indirect , Intestine, Small/virology , LLC-PK1 Cells , Swine , Swine Diseases/virology , Vero Cells
10.
Virus Res ; 295: 198306, 2021 04 02.
Article in English | MEDLINE | ID: covidwho-1031553

ABSTRACT

Cholesterol 25-hydroxylase (CH25 H) is a key enzyme regulating cholesterol metabolism and also acts as a broad antiviral host restriction factor. Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus that can cause vomiting, diarrhea, dehydration and even death in newborn piglets. In this study, we found that PDCoV infection significantly upregulated the expression of CH25H in IPI-FX cells, a cell line of porcine ileum epithelium. Overexpression of CH25H inhibited PDCoV replication, whereas CH25H silencing using RNA interference promoted PDCoV infection. Treatment with 25-hydroxycholesterol (25HC), the catalysate of cholesterol via CH25H, inhibited PDCoV proliferation by impairing viral invasion of IPI-FX cells. Furthermore, a mutant CH25H (CH25H-M) lacking hydroxylase activity also inhibited PDCoV infection to a lesser extent. Taken together, our data suggest that CH25H acts as a host restriction factor to inhibit the proliferation of PDCoV but this inhibitory effect is not completely dependent on its enzymatic activity.


Subject(s)
Coronavirus Infections/prevention & control , Deltacoronavirus , Steroid Hydroxylases/physiology , Virus Internalization , Animals , Cells, Cultured , Coronavirus Infections/enzymology , Steroid Hydroxylases/antagonists & inhibitors , Swine , Virus Replication
11.
Emerg Microbes Infect ; 10(1): 66-80, 2021 Dec.
Article in English | MEDLINE | ID: covidwho-979439

ABSTRACT

Coronaviruses (CoVs) are potential pandemic pathogens that can infect a variety of hosts and cause respiratory, enteric, hepatic and neurological diseases. Nonstructural protein 3 (nsp3), an essential component of the replication/transcription complex, is one of the most important antiviral targets. Here, we report the first crystal structure of multiple functional domains from porcine delta-coronavirus (PDCoV) nsp3, including the macro domain (Macro), ubiquitin-like domain 2 (Ubl2) and papain-like protease (PLpro) catalytic domain. In the asymmetric unit, two of the subunits form the head-to-tail homodimer with an interaction interface between Macro and PLpro. However, PDCoV Macro-Ubl2-PLpro mainly exists as a monomer in solution. Then, we conducted fluorescent resonance energy transfer-based protease assays and found that PDCoV PLpro can cleave a peptide by mimicking the cognate nsp2/nsp3 cleavage site in peptide substrates and exhibits deubiquitinating and de-interferon stimulated gene(deISGylating) activities by hydrolysing ubiquitin-7-amino-4-methylcoumarin (Ub-AMC) and ISG15-AMC substrates. Moreover, the deletion of Macro or Macro-Ubl2 decreased the enzyme activity of PLpro, indicating that Macro and Ubl2 play important roles in maintaining the stability of the PLpro domain. Two active sites of PLpro, Cys260 and His398, were determined; unexpectedly, the conserved site Asp412 was not the third active site. Furthermore, the motif "NGYDT" (amino acids 409-413) was important for stabilizing the enzyme activity of PLpro, and the N409A mutant significantly decreased the enzyme activity of PLpro. These results provide novel insights into the replication mechanism of CoV and new clues for future drug design.


Subject(s)
Coronavirus Papain-Like Proteases/chemistry , Catalytic Domain , Coronavirus Papain-Like Proteases/physiology , Crystallization , HeLa Cells , Humans , Protein Domains , Protein Multimerization , Ubiquitination
12.
J Virol ; 94(15)2020 07 16.
Article in English | MEDLINE | ID: covidwho-831394

ABSTRACT

Currently, an effective therapeutic treatment for porcine reproductive and respiratory syndrome virus (PRRSV) remains elusive. PRRSV helicase nsp10 is an important component of the replication transcription complex that plays a crucial role in viral replication, making nsp10 an important target for drug development. Here, we report the first crystal structure of full-length nsp10 from the arterivirus PRRSV, which has multiple domains: an N-terminal zinc-binding domain (ZBD), a 1B domain, and helicase core domains 1A and 2A. Importantly, our structural analyses indicate that the conformation of the 1B domain from arterivirus nsp10 undergoes a dynamic transition. The polynucleotide substrate channel formed by domains 1A and 1B adopts an open state, which may create enough space to accommodate and bind double-stranded RNA (dsRNA) during unwinding. Moreover, we report a unique C-terminal domain structure that participates in stabilizing the overall helicase structure. Our biochemical experiments also showed that deletion of the 1B domain and C-terminal domain significantly reduced the helicase activity of nsp10, indicating that the four domains must cooperate to contribute to helicase function. In addition, our results indicate that nidoviruses contain a conserved helicase core domain and key amino acid sites affecting helicase function, which share a common mechanism of helicase translocation and unwinding activity. These findings will help to further our understanding of the mechanism of helicase function and provide new targets for the development of antiviral drugs.IMPORTANCE Porcine reproductive and respiratory syndrome virus (PRRSV) is a major respiratory disease agent in pigs that causes enormous economic losses to the global swine industry. PRRSV helicase nsp10 is a multifunctional protein with translocation and unwinding activities and plays a vital role in viral RNA synthesis. Here, we report the first structure of full-length nsp10 from the arterivirus PRRSV at 3.0-Å resolution. Our results show that the 1B domain of PRRSV nsp10 adopts a novel open state and has a unique C-terminal domain structure, which plays a crucial role in nsp10 helicase activity. Furthermore, mutagenesis and structural analysis revealed conservation of the helicase catalytic domain across the order Nidovirales (families Arteriviridae and Coronaviridae). Importantly, our results will provide a structural basis for further understanding the function of helicases in the order Nidovirales.


Subject(s)
Porcine respiratory and reproductive syndrome virus/enzymology , RNA Helicases/chemistry , RNA, Double-Stranded/chemistry , RNA, Viral/chemistry , Viral Proteins/chemistry , Porcine respiratory and reproductive syndrome virus/genetics , Protein Domains , RNA Helicases/genetics , RNA, Double-Stranded/genetics , RNA, Viral/genetics , Viral Proteins/genetics
13.
J Virol Methods ; 276: 113772, 2020 02.
Article in English | MEDLINE | ID: covidwho-829838

ABSTRACT

Porcine epidemic diarrhea virus (PEDV) is a highly pathogenic enteric coronavirus causing lethal watery diarrhea in suckling piglets. Reverse genetics is a valuable tool to study the functions of viral genes and to generate vaccine candidates. In this study, a full-length infectious cDNA clone of the highly virulent PEDV strain AJ1102 was assembled in a bacterial artificial chromosome (BAC). The rescued virus (rAJ1102) exhibited similar proliferation characteristics in vitro to the wildtype AJ1102. Using CRISPR/Cas9 technology, a recombinant virus rAJ1102-ΔORF3-EGFP in which the ORF3 gene was replaced with an EGFP gene, was successfully generated, and its proliferation characteristics were compared with the parental rAJ1102. Importantly, it just took one week to construct the recombinant PEDV rAJ1102-ΔORF3-EGFP using this method, providing a more efficient platform for PEDV genome manipulation, which could also be applied to other RNA viruses.


Subject(s)
CRISPR-Cas Systems , Coronavirus Infections/virology , Porcine epidemic diarrhea virus/genetics , Swine Diseases/virology , Animals , Coronavirus Infections/prevention & control , Genome, Viral , Recombination, Genetic , Swine , Viral Vaccines/genetics
14.
Vet Microbiol ; 247: 108785, 2020 Aug.
Article in English | MEDLINE | ID: covidwho-827867

ABSTRACT

Porcine deltacoronavirus (PDCoV) is a novel swine enteropathogenic coronavirus that causes watery diarrhea, vomiting and mortality in nursing piglets. Type III interferons (IFN-λs) are the major antiviral cytokines in intestinal epithelial cells, the target cells in vivo for PDCoV. In this study, we found that PDCoV infection remarkably inhibited Sendai virus-induced IFN-λ1 production by suppressing transcription factors IRF and NF-κB in IPI-2I cells, a line of porcine intestinal mucosal epithelial cells. We also confirmed that PDCoV infection impeded the activation of IFN-λ1 promoter stimulated by RIG-I, MDA5 and MAVS, but not by TBK1 and IRF1. Although the expression levels of IRF1 and MAVS were not changed, PDCoV infection resulted in reduction of the number of peroxisomes, the platform for MAVS to activate IRF1, and subsequent type III IFN production. Taken together, our study demonstrates that PDCoV suppresses type III IFN responses to circumvent the host's antiviral immunity.


Subject(s)
Coronavirus Infections/veterinary , Epithelial Cells/immunology , Epithelial Cells/virology , Host-Pathogen Interactions/immunology , Interferons/antagonists & inhibitors , Animals , Cell Line , Coronavirus , Coronavirus Infections/immunology , Coronavirus Infections/virology , Interferon Regulatory Factor-1/antagonists & inhibitors , Interferon Regulatory Factor-1/immunology , Interferons/immunology , Intestines/cytology , Intestines/virology , Kidney/cytology , Kidney/virology , NF-kappa B/antagonists & inhibitors , NF-kappa B/immunology , Sendai virus/immunology , Signal Transduction/immunology , Swine/virology , Swine Diseases/immunology , Swine Diseases/virology
15.
ACS Appl Bio Mater ; 3(8): 4809-4819, 2020 08 17.
Article in English | MEDLINE | ID: covidwho-833523

ABSTRACT

Despite the good biocompatibility and antibacterial activity of zinc sulfide nanoparticles (ZnS NPs), whether they possess antiviral activity is still unclear. Here, GSH-modified ZnS NPs (GSH-ZnS NPs) were synthesized and their significant antiviral activity was demonstrated using the Arteriviridae family RNA virus, porcine reproductive and respiratory syndrome virus (PRRSV), as a model. Mechanistically, GSH-ZnS NPs were shown to reduce PRRSV-induced ROS production to prevent PRRSV multiplication, with no activating effect on the interferon (IFN) signal pathway, the first defense line against virus infection. Furthermore, isobaric tags for relative and absolute quantification (iTRAQ)-based quantitative proteomic analysis of GSH-ZnS NP-treated cells revealed the involvement of numerous crucial proteins in virus proliferation, with vitronectin (VTN) being confirmed as an efficient PRRSV antagonist here. Furthermore, GSH-ZnS NPs were found to have potent antiviral effects on the Herpesviridae family DNA virus, pseudorabies virus (PRV), the Coronaviridae family positive-sense RNA virus, porcine epidemic diarrhea virus (PEDV), and the Rhabdoviridae family negative-stranded RNA virus, vesicular stomatitis virus (VSV), indicating their broad-spectrum antiviral activity against viruses from different families with various genome types. Overall, GSH-ZnS NP is a prospective candidate for the development of antiviral nanomaterials and may serve as a model for investigation of potential host restriction factors in combination with proteomics.


Subject(s)
Antiviral Agents/pharmacology , Glutathione/chemistry , Nanoparticles/chemistry , Sulfides/chemistry , Viruses/drug effects , Zinc Compounds/chemistry , Animals , Cell Line , Chlorocebus aethiops , Microbial Sensitivity Tests , Reactive Oxygen Species/metabolism , Viruses/classification
16.
Virology ; 539: 38-48, 2020 01 02.
Article in English | MEDLINE | ID: covidwho-822398

ABSTRACT

Ionic calcium (Ca2+) is a versatile intracellular second messenger that plays important roles in cellular physiological and pathological processes. Porcine deltacoronavirus (PDCoV) is an emerging enteropathogenic coronavirus that causes serious vomiting and diarrhea in suckling piglets. In this study, the role of Ca2+ to PDCoV infection was investigated. PDCoV infection was found to upregulate intracellular Ca2+ concentrations of IPI-2I cells. Chelating extracellular Ca2+ by EGTA inhibited PDCoV replication, and this inhibitory effect was overcome by replenishment with CaCl2. Treatment with Ca2+ channel blockers, particularly the L-type Ca2+ channel blocker diltiazem hydrochloride, inhibited PDCoV infection significantly. Mechanistically, diltiazem hydrochloride reduces PDCoV infection by inhibiting the replication step of the viral replication cycle. Additionally, knockdown of CACNA1S, the L-type Ca2+ voltage-gated channel subunit, inhibited PDCoV replication. The combined results demonstrate that PDCoV modulates calcium influx to favor its replication.


Subject(s)
Calcium/metabolism , Coronavirus Infections/metabolism , Coronavirus Infections/virology , Coronavirus/physiology , Swine Diseases/metabolism , Swine Diseases/virology , Virus Replication , Animals , Calcium Signaling , Swine , Swine, Miniature
17.
Elife ; 92020 09 02.
Article in English | MEDLINE | ID: covidwho-740561

ABSTRACT

Porcine reproductive and respiratory syndrome virus (PRRSV) and transmissible gastroenteritis virus (TGEV) are two highly infectious and lethal viruses causing major economic losses to pig production. Here, we report generation of double-gene-knockout (DKO) pigs harboring edited knockout alleles for known receptor proteins CD163 and pAPN and show that DKO pigs are completely resistant to genotype 2 PRRSV and TGEV. We found no differences in meat-production or reproductive-performance traits between wild-type and DKO pigs, but detected increased iron in DKO muscle. Additional infection challenge experiments showed that DKO pigs exhibited decreased susceptibility to porcine deltacoronavirus (PDCoV), thus offering unprecedented in vivo evidence of pAPN as one of PDCoV receptors. Beyond showing that multiple gene edits can be combined in a livestock animal to achieve simultaneous resistance to two major viruses, our study introduces a valuable model for investigating infection mechanisms of porcine pathogenic viruses that exploit pAPN or CD163 for entry.


Pig epidemics are the biggest threat to the pork industry. In 2019 alone, hundreds of billions of dollars worldwide were lost due to various pig diseases, many of them caused by viruses. The porcine reproductive and respiratory virus (PRRS virus for short), for instance, leads to reproductive disorders such as stillbirths and premature labor. Two coronaviruses ­ the transmissible gastroenteritis virus (or TGEV) and the porcine delta coronavirus ­ cause deadly diarrhea and could potentially cross over into humans. Unfortunately, there are still no safe and effective methods to prevent or control these pig illnesses, but growing disease-resistant pigs could reduce both financial and animal losses. Traditionally, breeding pigs to have a particular trait is a slow process that can take many years. But with gene editing technology, it is possible to change or remove specific genes in a single generation of animals. When viruses infect a host, they use certain proteins on the surface of the host's cells to find their inside: the PRRS virus relies a protein called CD163, and TGEV uses pAPN. Xu, Zhou, Mu et al. used gene editing technology to delete the genes that encode the CD163 and pAPN proteins in pigs. When the animals were infected with PRRS virus or TGEV, the non-edited pigs got sick but the gene-edited animals remained healthy. Unexpectedly, pigs without CD163 and pAPN also coped better with porcine delta coronavirus infections, suggesting that CD163 and pAPN may also help this coronavirus infect cells. Finally, the gene-edited pigs reproduced and produced meat as well as the control pigs. These experiments show that gene editing can be a powerful technology for producing animals with desirable traits. The gene-edited pigs also provide new knowledge about how porcine viruses infect pigs, and may offer a starting point to breed disease-resistant animals on a larger scale.


Subject(s)
CD13 Antigens/deficiency , Coronavirus Infections/prevention & control , Coronavirus/pathogenicity , Gastroenteritis, Transmissible, of Swine/prevention & control , Porcine Reproductive and Respiratory Syndrome/prevention & control , Porcine respiratory and reproductive syndrome virus/pathogenicity , Receptors, Cell Surface/deficiency , Transmissible gastroenteritis virus/pathogenicity , Animals , Animals, Genetically Modified , Antigens, CD/genetics , Antigens, CD/immunology , Antigens, Differentiation, Myelomonocytic/genetics , Antigens, Differentiation, Myelomonocytic/immunology , Body Composition , CD13 Antigens/genetics , CD13 Antigens/immunology , Coronavirus/immunology , Coronavirus Infections/genetics , Coronavirus Infections/immunology , Coronavirus Infections/virology , Disease Susceptibility , Gastroenteritis, Transmissible, of Swine/genetics , Gastroenteritis, Transmissible, of Swine/immunology , Gastroenteritis, Transmissible, of Swine/virology , Gene Knockdown Techniques , Host Microbial Interactions , Meat-Packing Industry , Phenotype , Porcine Reproductive and Respiratory Syndrome/genetics , Porcine Reproductive and Respiratory Syndrome/immunology , Porcine Reproductive and Respiratory Syndrome/virology , Porcine respiratory and reproductive syndrome virus/immunology , Receptors, Cell Surface/genetics , Receptors, Cell Surface/immunology , Sus scrofa/genetics , Swine , Transmissible gastroenteritis virus/immunology , Weight Gain
18.
J Virol ; 94(15)2020 07 16.
Article in English | MEDLINE | ID: covidwho-382053

ABSTRACT

Porcine deltacoronavirus (PDCoV) is an emerging swine enteropathogenic coronavirus. The nonstructural protein nsp5, also called 3C-like protease, is responsible for processing viral polyprotein precursors in coronavirus (CoV) replication. Previous studies have shown that PDCoV nsp5 cleaves the NF-κB essential modulator and the signal transducer and activator of transcription 2 to disrupt interferon (IFN) production and signaling, respectively. Whether PDCoV nsp5 also cleaves IFN-stimulated genes (ISGs), IFN-induced antiviral effector molecules, remains unclear. In this study, we screened 14 classical ISGs and found that PDCoV nsp5 cleaved the porcine mRNA-decapping enzyme 1a (pDCP1A) through its protease activity. Similar cleavage of endogenous pDCP1A was also observed in PDCoV-infected cells. PDCoV nsp5 cleaved pDCP1A at glutamine 343 (Q343), and the cleaved pDCP1A fragments, pDCP1A1-343 and pDCP1A344-580, were unable to inhibit PDCoV infection. Mutant pDCP1A-Q343A, which resists nsp5-mediated cleavage, exhibited a stronger ability to inhibit PDCoV infection than wild-type pDCP1A. Interestingly, the Q343 cleavage site is highly conserved in DCP1A homologs from other mammalian species. Further analyses demonstrated that nsp5 encoded by seven tested CoVs that can infect human or pig also cleaved pDCP1A and human DCP1A, suggesting that DCP1A may be the common target for cleavage by nsp5 of mammalian CoVs.IMPORTANCE Interferon (IFN)-stimulated gene (ISG) induction through IFN signaling is important to create an antiviral state and usually directly inhibits virus infection. The present study first demonstrated that PDCoV nsp5 can cleave mRNA-decapping enzyme 1a (DCP1A) to attenuate its antiviral activity. Furthermore, cleaving DCP1A is a common characteristic of nsp5 proteins from different coronaviruses (CoVs), which represents a common immune evasion mechanism of CoVs. Previous evidence showed that CoV nsp5 cleaves the NF-κB essential modulator and signal transducer and activator of transcription 2. Taken together, CoV nsp5 is a potent IFN antagonist because it can simultaneously target different aspects of the host IFN system, including IFN production and signaling and effector molecules.


Subject(s)
Antiviral Agents/pharmacology , Coronavirus/drug effects , Coronavirus/metabolism , Cysteine Endopeptidases/metabolism , Endoribonucleases/metabolism , Trans-Activators/metabolism , Viral Nonstructural Proteins/metabolism , Animals , Coronavirus 3C Proteases , Coronavirus Infections/veterinary , Coronavirus Infections/virology , Cysteine Endopeptidases/chemistry , Exoribonucleases/metabolism , HEK293 Cells , Host-Pathogen Interactions , Humans , Immune Evasion , Interferons/metabolism , STAT2 Transcription Factor/metabolism , Signal Transduction , Swine , Swine Diseases/virology
19.
Evol Appl ; 2020 May 13.
Article in English | MEDLINE | ID: covidwho-245726

ABSTRACT

Deltacoronavirus is the last identified Coronaviridae subfamily genus. Differing from other coronavirus (CoV) genera, which mainly infect birds or mammals, deltacoronaviruses (δ-CoVs) reportedly infect both animal types. Recent studies show that a novel δ-CoV, porcine deltacoronavirus (PDCoV), can also infect calves and chickens with the potential to infect humans, raising the possibility of cross-species transmission of δ-CoVs. Here, we explored the deep phylogenetic history and cross-species transmission of δ-CoVs. Virus-host co-phylogenetic analyses showed that δ-CoVs have undergone frequent host switches in birds, and sparrows may serve as the unappreciated hubs for avian to mammal transmission. Our molecular clock analyses show that PDCoV possibly originated in Southeast Asia in the 1990s, and that the PDCoV cluster shares a common ancestor with Sparrow-CoV of around 1810. Our findings contribute valuable insights into the diversification, evolution, and interspecies transmission of δ-CoVs and the origin of PDCoV, providing a model for exploring the relationships of δ-CoVs in birds and mammals.

20.
ACS Appl Nano Mater ; 3(5): 4913, 2020 May 22.
Article in English | MEDLINE | ID: covidwho-115616

ABSTRACT

[This corrects the article DOI: 10.1021/acsanm.8b00779.].

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