Efficacy of inactivated variant porcine epidemic diarrhea virus vaccines in growing pigs

Lee, Seung Heon; Yang, Dong-Kun; Kim, Ha-Hyun; Cho, In-Soo

To this end, we passaged the QIAP1401 isolate 70 times in Vero cells at 3-day intervals. A growth kinetics analysis showed and virus neutralization (VN) test (C and D) of PEDV-specific IgG and virus-neutralizing antibody titers, respectively. Bars represents the means standard deviation of five independent samples. *, **, and *** indicate significant differences from the non-vaccinated control (NVC) group (p < 0.05, p < 0.01, and p < 0.001, respectively, unpaired Student's t test). Different lower-case letters above the bars indicate significant differences among the groups (p < 0.05, Tukey's post hoc test). that the infectious titer of QIAP1401 increased significantly to 10 7.0 TCID50/mL after 70 passages [17] . This indicated that the virus had acquired adaptive mutations that enhanced production of infectious virus. To investigate the underlying mechanism, we analyzed the whole genome of QIAP1401-p70 by next-generation sequencing. Compared with reference G2b genogroup PEDVs, the adapted QIAP1401-p70 genome harbored mutations in genes encoding structural and nonstructural proteins. Among these mutations, the most remarkable was a 25 aa deletion in the ORF1a region of the nonstructural protein. We hypothesized that this 25 aa deletion reduced the duration of the replication cycle of QIAP1401-p70. This finding is supported by previous reports that the 5′ two-thirds of the coronavirus genome contains ORF1a and ORF 1b, which encode the viral RNA replicase [24, 25] .