Correlation between the barrier function of the intestinal epithelium and susceptibility to PEDV infection in piglets at different ages.

Porcine epidemic diarrhoea (PED) results in vomiting, diarrhoea, dehydration, and death in pigs. To analyse the relationship between intestinal development and susceptibility to porcine epidemic diarrhoea virus (PEDV), six new-born, 1-, 2-, 3-, 4-, and 8-week-old piglets were orally inoculated with 2 × 107 copies of the PEDV strain LJX01/2014 and sacrificed 48 h after infection. The results demonstrated that PEDV infection elicits diarrhoea of diverse severity across piglets of distinct ages. Moreover, viral shedding and villous atrophy were most pronounced in neonatal piglets. With increasing age, the shedding of villi gradually decreased, resulting in significantly lower villi/crypt ratios in the duodenum of newborn, 1-week-old, and 3-week-old piglets and significantly lower villi/crypt ratios in the jejunum and ileum of newborn and 1-week-old piglets than in the control. Indirect immunofluorescence and immunohistochemistry revealed a positive correlation between intraepithelial lymphocyte counts and epithelial cells and piglet age. PEDV infection led to a significant increase in intraepithelial lymphocytes and a decrease in epithelial cells, with the most severe effects observed in newborn piglets. The numbers of goblet cells, absorptive enterocytes, and enteroendocrine cells significantly decreased, whereas the numbers of Paneth cells, stem cells, and proliferating cells significantly increased with increasing piglet age. Overall, the results indicate that intestinal tissue repair increases with increasing age. Consequently, this results in a more robust intestinal epithelial barrier and reduced PEDV-induced damage to the small intestine.