Pathogenicity and pathogenesis of a United States porcine deltacoronavirus cell culture isolate in 5-day-old neonatal piglets

Abstract

Porcine deltacoronavirus (PDCoV) was first identified in Hong Kong in 2009-2010 and reported in United States swine for the first time in February 2014. However, diagnostic tools other than polymerase chain reaction for PDCoV detection were lacking and Koch's postulates had not been fulfilled to confirm the pathogenic potential of PDCoV. In the present study, PDCoV peptide-specific rabbit antisera were developed and used in immunofluorescence and immunohistochemistry assays to assist PDCoV diagnostics. The pathogenicity and pathogenesis of PDCoV was investigated following orogastric inoculation of 5-day-old piglets with a plaque-purified PDCoV cell culture isolate (3 × 10(4) TCID50 per pig). The PDCoV-inoculated piglets developed mild to moderate diarrhea, shed increasing amount of virus in rectal swabs from 2 to 7 days post inoculation, and developed macroscopic and microscopic lesions in small intestines with viral antigen confirmed by immunohistochemistry staining. This study experimentally confirmed PDCoV pathogenicity and characterized PDCoV pathogenesis in neonatal piglets.

Pathogenesis comparison between the United States porcine epidemic diarrhoea virus prototype and S-INDEL-variant strains in conventional neonatal piglets

“…Previous studies have demonstrated that neonatal piglets are more susceptible than weaned pigs to PEDV infection, and PEDV infection induces greater disease severity in neonates than in weaned pigs (Jung et al, 2015a;Thomas et al, 2015). Therefore, a sensitive 5-day-old neonatal piglet model was selected for pathogenesis comparisons in this study.…”

“…Five microlitres of each RNA template was used in a PCR setup in a 25 ml total reaction using the Path-ID Multiplex One-Step RT-PCR kit (Thermo Fisher Scientific). The primers, probes and in vitro-transcribed RNA used to generate standard curves of a quantitative PEDV N-gene-based real-time RT-PCR have been previously described (Lowe et al, 2014;Madson et al, 2014;Thomas et al, 2015). Based on standard curves, the virus concentration (expressed as genomic copies ml 21 ) in tested samples was calculated.…”

“…necropsy, IHC staining was only performed on serial sections of ileum. The IHC antigen detection was semi-quantitatively scored as previously described (Chen et al, 2015) with the following criteria: 0, no staining; 1, approximately 1-10% enterocytes with positive staining; 2, approximately 10-25% enterocytes with positive staining; 3, approximately 25-50% enterocytes with positive staining; 4, approximately 50-100% enterocytes with positive staining.…”

“…The pathogenicity of the US PEDV prototype strain has been evaluated in gnotobiotic (Jung et al, 2014) Caesarean-derived colostrum-deprived (Liu et al, 2015;Madson et al, 2016) and conventional pigs (Jung et al, 2015a;Madson et al, 2014;Thomas et al, 2015); these studies experimentally confirmed that the US PEDV prototype isolates are highly virulent. Evaluation of the pathogenicity of the US S-INDEL-variant strain in experimentally infected pigs has not been reported until recently (Lin et al, 2015a), when we were in the process of revising this manuscript.…”

Virulence factors in porcine coronaviruses and vaccine design

“…These clinical symptoms could lead to animal death. In general, PEDV and TGEV are considered more virulent than PDCoV (Chen et al, 2015), although after experimental inoculation of gnotobiotic piglets, PDCoV caused a severe disease (Jung et al, 2015b). Further analyses will be needed to determine whether the difference in viral strain, animal age, or other factors influence PDCoV pathogenesis.…”