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

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

The complete genome of the QIAP1401-p70 isolate, comprising 27,920 nucleotides, was determined by next-generation sequencing. The whole genome of the PEDV USA/Minneso-ta250/2014 strain was used as a reference for sequencing because of its close genetic relationship to QIAP1401 isolates. To assess whether the PEDV QIAP1401 variant had emerged after sequential passaging, the genome sequence was compared with that of U.S. PEDV strains. The PEDV QIAP1401-p70 isolate had > 99.4% sequence homology to the USA/Iowa303/ 2014, USA/Minnesota250/2014 and OH1414 U.S. PEDV strains. However, we identified 42 amino acid (aa) mutations, including a 25 aa deletion, in the ORF1a gene of the QIAP1401-p70 isolate (Fig. 1A) . To determine at which passage the deletion arose, viral RNA isolated from each passage was screened by reverse transcription polymerase chain reaction using OR-F1a-specific PCR primers. The results show ed that the deletion mutant emerged after 41 passages (Fig. 1B) . The deletion mutation detected at passage 37 was present during the following three passages. Moreover, viral stock at passages 37 to 40 contained both parental and mutant viruses.