Evolution, antigenicity and pathogenicity of global porcine epidemic diarrhea virus strains.

Four types of porcine epidemic diarrhea virus (PEDV) variants with a large deletion in the spike protein were detected, together with the original US PEDV, from pig fecal and oral fluid samples collected during 2016-2017 in the US. Two of the variants are similar to those identified in Japan: one contains a 194-aa deletion, the same as PEDV variant TTR-2/JPN/2014, while the other contains a 204-aa deletion, the same as PEDV variant JKa-292/CS1de204. Two new S1 NTD-del PEDV variants were found: one contains a 201-aa deletion located at residues 30-230 and the other contains a 202-aa deletion located at residues 24-225 of the S protein. This is the first report on coinfection of S1 NTD-del PEDV variants and the original US PEDV strain in US pigs, indicating that PEDV continues to evolve in pigs and might be responsible for disease pattern changes.

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New variants of porcine epidemic diarrhea virus with large deletions in the spike protein, identified in the United States, 2016-2017.

Cellular entry of the porcine epidemic diarrhea virus.

Porcine epidemic diarrhea virus (PEDV), a member of Alphacoronavirus, has caused huge economic losses for the global pork industry recently. The spike (S) protein mediates PEDV entry into host cells. Herein, we investigated the interactions between the S protein and its receptor porcine aminopeptidase N (pAPN) or co-receptor sugars. The C-terminal domain (CTD) of the S1 domain is bound to pAPN. The prototype strain demonstrated similar receptor-binding activity compared with the variant field isolate. Three loops at the tips of the β-barrel domains did not play crucial roles in the PEDV S-pAPN association, indicating that PEDV conforms to a different receptor recognition model compared with transmissible gastroenteritis virus (TGEV), porcine respiratory CoV (PRCV), and human coronavirus NL63 (HCoV-NL63). The N-terminal domain (NTD) of the PEDV S1 domain could bind sugar, a possible co-receptor for PEDV. The prototype strain exhibited weaker sugar-binding activity compared with the variant field isolate. Strategies targeting the receptor binding domain (RBD) may be helpful for developing vaccines or antiviral drugs for PEDV. Understanding the differences in receptor binding between the prototype and the variant strains may provide insight into PEDV pathogenesis.

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Identification and Comparison of Receptor Binding Characteristics of the Spike Protein of Two Porcine Epidemic Diarrhea Virus Strains

Porcine epidemic diarrhea virus (PEDV) is a worldwide-distributed alphacoronavirus, but the pathogenesis of PEDV infection is not fully characterized. During virus infection, type I interferon (IFN) is a key mediator of innate antiviral responses. Most coronaviruses develop some strategy for at least partially circumventing the IFN response by limiting the production of IFN and by delaying the activation of the IFN response. However, the molecular mechanisms by which PEDV antagonizes the antiviral effects of interferon have not been fully characterized. Especially, how PEDV impacts IFN signaling components has yet to be elucidated. In this study, we observed that PEDV was relatively resistant to treatment with type I IFN. Western blot analysis showed that STAT1 expression was markedly reduced in PEDV-infected cells and that this reduction was not due to inhibition of STAT1 transcription. STAT1 downregulation was blocked by a proteasome inhibitor but not by an autophagy inhibitor, strongly implicating the ubiquitin-proteasome targeting degradation system. Since PEDV infection-induced STAT1 degradation was evident in cells pretreated with the general tyrosine kinase inhibitor, we conclude that STAT1 degradation is independent of the IFN signaling pathway. Furthermore, we report that PEDV-induced STAT1 degradation inhibits IFN-α signal transduction pathways. Pharmacological inhibition of STAT1 degradation rescued the ability of the host to suppress virus replication. Collectively, these data show that PEDV is capable of subverting the type I interferon response by inducing STAT1 degradation.
 IMPORTANCE In this study, we show that PEDV is resistant to the antiviral effect of IFN. The molecular mechanism is the degradation of STAT1 by PEDV infection in a proteasome-dependent manner. This PEDV infection-induced STAT1 degradation contributes to PEDV replication. Our findings reveal a new mechanism evolved by PEDV to circumvent the host antiviral response.

Porcine Epidemic Diarrhea Virus Infection Inhibits Interferon Signaling by Targeted Degradation of STAT1

Molecular characterization of pig epidemic diarrhoea viruses isolated in Japan from 2013 to 2014.

From October 2013 to date, approximately 1,000 outbreaks of porcine epidemic diarrhoea virus (PEDV) have occurred in Japan. Porcine epidemic diarrhoea with non-lethal effects in piglets was identified in Tottori prefecture in October 2014. Complete genome analysis revealed that the causative pathogen, Tottori2, is a new PEDV variant with a large (582 nt) deletion in the spike gene. Phylogenetic analysis indicated that the Tottori2 PEDV strain might have been derived from the current PEDV strains circulating in domestic pigs. Moreover, the Tottori2 PEDV strain was successfully isolated in Vero cells by serial passage.

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New porcine epidemic diarrhoea virus variant with a large deletion in the spike gene identified in domestic pigs.

Porcine epidemic diarrhea virus (PEDV) is a cause of diarrhea outbreaks at swine farms, causing vomiting, severe diarrhea, and mortality in piglets. We sequenced and analyzed the complete genome of recently isolated strains. Tottori2/JPN/2014, one of the sequenced PEDV strains, had a unique large deletion in the S gene.

https://journals.asm.org/doi/pdf/10.1128/genomeA.00877-15

Osamu Takahashi

Papers

Molecular characterization of pig epidemic diarrhoea viruses isolated in Japan from 2013 to 2014.

New porcine epidemic diarrhoea virus variant with a large deletion in the spike gene identified in domestic pigs.

Complete Genome Sequence of the Porcine Epidemic Diarrhea Virus Variant Tottori2/JPN/2014.