Preparation and characterization of an attenuated porcine epidemic diarrhea virus strain by serial passaging

Abstract

Porcine epidemic diarrhea virus (PEDV) is prevalent in most parts of the world. Owing to its antigenic variation, prevention of the diseases caused by this virus is difficult. In this study, two PEDV isolates with similar growth kinetics were successfully propagated in Vero cells. Complete genome sequence analysis showed that they have a 49nt deletion in the ORF3 gene and were classified into Group 1, the same group that includes the classical CV777 strain. Recombination analysis revealed that the event had occurred in the ORF1a gene, at 3596-6819 nt, among the two PEDV isolates and the CV777 and DR13 strains. During their continuous propagation, 14 nonsynonymous mutations occurred in the spike (S) gene of strain JS-2/2014 between generations G5 and G90, but there were no changes between G90 and G100. We assumed that strain JS-2/2014 might be attenuated by the 90th generation. Piglets orally fed with JS-2/2014 G90 showed no clinical symptoms, and no virus was detected in the feces and nasal fluid. In conclusion, JS-2/2014 was successfully identified by screening, was attenuated after propagation in Vero cells, and may serve as a candidate virus for vaccine preparations.

Engineering a Live Attenuated Porcine Epidemic Diarrhea Virus Vaccine Candidate via Inactivation of the Viral 2'-O-Methyltransferase and the Endocytosis Signal of the Spike Protein

“…PEDV LAVs based on classical (G1) strains have been applied in Asian countries ( 11 ), but their efficacies against the emerging highly virulent (G2) strains were minimal, probably due to the antigenic difference between the S proteins of G1 and G2 strains ( 12 ). To develop G2 PEDV LAVs, we and other research groups have previously applied the traditional method of attenuation via serially passaging virulent G2 isolates in Vero cells ( 13 – 20 ). Although these LAV candidates were attenuated sufficiently in pigs, they usually failed to consistently induce adequate protective immunity against challenge with the virulent G2 strains ( 16 , 20 ).…”

Regulatory Effect of Methylation of the Porcine AQP3 Gene Promoter Region on Its Expression Level and Porcine Epidemic Diarrhea Virus Resistance

“…Porcine epidemic diarrhea virus (PEDV), transmissible gastroenteritis virus (TGEV), and rotavirus (PoRV) are the main causes of porcine viral diarrheal disease through individual or mixed infections [ 1 ]. PEDV is a single-stranded positive-strand alpha coronavirus with a length of approximately 28 kb.…”

A porcine epidemic diarrhea virus strain with distinct characteristics of four amino acid insertion in the COE region of spike protein

“…Recombination in PEDV is also a widespread phenomenon. Several reports have identified recombinant sequences (Supplementary Table S3) in the PEDV S gene ( Qin et al, 2019 ), ORF1a ( Jie et al, 2018 ), and ORF1b ( Chen et al, 2017 ); recombination across multiple genes has also been shown ( Jarvis et al, 2016 ). Among CoVs, homologous RNA recombination is a major factor underlying genetic evolution and diversity ( Ntafis et al, 2011 ; Woo et al, 2009 ).…”