After 3-day acclimation, pigs in the challenged group were inoculated with a prototype US PEDV isolate US/Iowa/18984/ 2013 (GenBank accession #KF804028) (Hoang et al., 2013), 10 3 plaque-forming units/pig, via oro-gastric gavage as previously described (Madson et al., 2014). Pigs in the control group received virus-free cell culture media. Some of these pigs were inoculated again with the same strain in the identical manner at day 56 post-inoculation (PI).