Abstract
Base on the sequence of S genes, which encode spike proteins, we previously identified three different types (North American, S INDEL, and S large-DEL types) of porcine epidemic diarrhea virus (PEDV) that have re-emerged in Japan since 2013. Based on experimental infections with the North American and S large-DEL types, we also hypothesized that PEDV virulence may be linked to the S1 subunit of the S protein. To test this hypothesis, we have now assayed in gnotobiotic piglets various recombinant PEDVs generated by reverse genetics. Piglets inoculated with CV777 maintained in National Institute of Animal Health, along with piglets infected with a recombinant form of the same virus, developed subclinical to mild diarrhea. In contrast, severe watery diarrhea, dehydration, weight loss, astasia, and high mortality were observed in piglets inoculated with recombinant strains in which the S gene was partially or fully replaced with corresponding sequences from the highly virulent Japanese PEDV isolate OKN-1/JPN/2013. Indeed, symptoms resembled those in piglets inoculated with the OKN-1/JPN/2013, and were especially pronounced in younger piglets. Collectively, the data demonstrate that the S1 subunit of the S protein is an important determinant of PEDV virulence, and advance development of new vaccine candidate.
Highlights
Porcine epidemic diarrhea is characterized by severe watery diarrhea which causes dehydration and high mortality among piglets
The disease is due to porcine epidemic diarrhea virus (PEDV), which belongs to the family Coronaviridae and genus Alphacoronavirus, and has an envelope surrounding a single-stranded positive-sense RNA genome [1]
There were mainly two different types of PEDV strains in the US based on analysis of the S genes: the original highly virulent strain (North American type), which is genetically closely related to strains that emerged in China since
Summary
Porcine epidemic diarrhea is characterized by severe watery diarrhea which causes dehydration and high mortality among piglets. The disease is due to porcine epidemic diarrhea virus (PEDV), which belongs to the family Coronaviridae and genus Alphacoronavirus, and has an envelope surrounding a single-stranded positive-sense RNA genome [1]. Severe outbreaks caused by a strain genetically distinct from the prototype strain CV777 based on analysis of S genes, which encode spike proteins, have been reported in China since late 2010, with considerable morbidity and mortality among suckling piglets [9,10,11,12]. There were mainly two different types of PEDV strains in the US based on analysis of the S genes: the original highly virulent strain (North American type), which is genetically closely related to strains that emerged in China since
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