Location: Virus and Prion ResearchTitle: Isolation and characterization of porcine epidemic diarrhea viruses associated with the 2013 disease outbreak in US swine) Author
Submitted to: Journal of Clinical Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2013
Publication Date: 1/1/2014
Citation: Chen, Q., Li, G., Stasko, J., Thomas, J.T., Stensland, W.R., Pillatzki, A.E., Gauger, P.C., Schwartz, K.J., Madson, D., Yoon, K.J., Stevenson, G.W., Burrough, E.R., Harmon, K.M., Main, R.G., Zhang, J. 2014. Isolation and characterization of porcine epidemic diarrhea viruses associated with the 2013 disease outbreak among swine in the United States. Journal of Clinical Microbiology. 52(1):234-243. Interpretive Summary: Porcine epidemic diarrhea virus (PEDV) has been confined to Asia and Europe until April of 2013. For the first time, it was detected in US swine making it a concern to the pork producer. Electron microscopy was utilized to find the virus. PEDV is a virus belonging to the family Coronaviridae. With the virus family identified, it could now be characterized by real-time PCR and immunofluorescence. This is the first report of having the virus isolated and characterized. PEDV is an acute, highly contagious and devastating disease which will have a significant economic loss to US swine. Having a US PEDV isolate is critical for PEDV pathogenesis study, diagnostic assays and vaccine development.
Technical Abstract: Porcine epidemic diarrhea virus (PEDV) was detected for the first time in US swine in April 2013 and has caused significant economic loss. Obtaining a US PEDV isolate that can grow efficiently in cell culture is critical for PEDV pathogenesis study, diagnostic assays and vaccine development. It was also unclear which gene of PEDV is suitable for determining the genetic relatedness of viruses. Here we describe that two PEDV isolates (ISU13-19338E and ISU13-22038) were successfully obtained from the small intestines of pigs from sow farms in Indiana and Iowa, respectively. The two isolates had been serially propagated on cell cultures for over 10 passages. Virus production in cell cultures was confirmed by PEDV N gene-based real-time RT-PCR, immunofluorescence assay and electron microscopy. The infectious titers of the viruses during the first 10 passages ranged from 6×102 to 2×105 TCID50/ml. In addition, the full-length genome sequences of six viruses (ISU13-19338E homogenate, P3, P9; ISU13-22038 homogenate, P3, P9) were determined. The two PEDV isolates were genetically relatively stable during at least the first 10 passages in cell culture. Sequences were also compared to the available sequences of other 4 US PEDV strains and 23 strains outside of the US. All US PEDV strains were genetically closely related to each other (=99.7% nucleotide identity), and most closely related to some Chinese strains reported in 2011-2012. Phylogenetic analyses using different genes of PEDV suggested that the full-length spike gene or the S1 portion is appropriate for sequencing to study the genetic relatedness of viruses.