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At least two genetically different porcine epidemic diarrhea virus (PEDV) strains have been identified in the United States: U.S. PEDV prototype and S-INDEL-variant strains. The objective of this study was to compare the pathogenicity differences of the U.S. PEDV prototype and S-INDEL-variant strains in conventional neonatal piglets under experimental infections. Fifty PEDV-negative 5-day-old pigs were divided into 5 groups of 10 pigs each and were inoculated orogastrically with three U.S. PEDV prototype isolates (IN19338/2013, NC35140/2013, and NC49469/2013), an S-INDEL-variant isolate (IL20697/2014), and virus-negative culture medium, respectively, with virus titers of 104 TCID50/ml, 10 ml per pig.
All three PEDV prototype isolates tested in this study, regardless of their phylogenetic clades, had similar pathogenicity and caused severe enteric disease in 5-day-old pigs as evidenced by clinical signs, fecal virus shedding, and gross and histopathological lesions. Compared to pigs inoculated with the three U.S. PEDV prototype isolates, pigs inoculated with the S-INDEL-variant isolate had significantly diminished clinical signs, virus shedding in feces, gross lesions in small intestines, ceca and colons, histopathological lesions in small intestines and immunohistochemistry staining in ileum. However, the U.S. PEDV prototype and the S-INDEL-variant strains induced similar viremia levels in inoculated pigs. Whole genome sequences of the PEDV prototype and S-INDEL-variant strains were determined but the molecular basis of virulence differences between these PEDV strains remains to be elucidated using reverse genetics approach.
Chen Q, Gauger PC, Stafne MR, Thomas JT, Madson DM, Huang H, Zheng Y, Li G, Zhang J. Pathogenesis comparison between the United States porcine epidemic diarrhea virus prototype and S-INDEL-variant strains in conventional neonatal piglets.J Gen Virol. 2016 Feb 3. doi: 10.1099/jgv.0.000419. [Epub ahead of print]