PDCoV replication in enteroids is restricted by exogenous IFN. (A and B) PDCoV infection-induced IFN production in enteroids. Enteroid monolayers isolated from jejunal, duodenal, and colonic crypts were infected with PDCoV at an MOI of 2. Expression of IFN-β (A) or IFN-λ1 (B) was assessed by RT-qPCR. (C and D) Jejunal enteroid monolayers were mock inoculated or inoculated with PDCoV at an MOI of 2 for the indicated time points. The mRNA expression level of IFN-β (C) or IFN-λ1 (D) was assessed by RT-qPCR. (E and F) Inhibition of PDCoV replication in enteroids by IFN-λ1. Jejunal enteroid monolayers were pretreated with IFN-λ1 at the indicated concentrations for 24 h and then infected with PDCoV at an MOI of 1 for 24 h. The PDCoV genomes (E) and viral titers (F) were tested by RT-qPCR and titration, respectively. Data represent the means of results from three wells for each treatment and time point. Error bars denote deviations. *, P < 0.05; **, P < 0.01; ***, P < 0.005; ****, P < 0.001.