A Porcine Epidemic Diarrhea Virus Isolated from a Sow Farm Vaccinated with CV777 Strain in Yinchuan, China: Characterization, Antigenicity, and Pathogenicity

Abstract

Porcine epidemic diarrhea virus (PEDV) is a porcine enteric coronavirus globally, causing serious economic losses to the global pig industry since 2010. Here, a PEDV CH/Yinchuan/2021 strain was isolated in a CV777-vaccinated sow farm which experienced a large-scale PEDV invasion in Yinchuan, China, in 2021. Our results demonstrated that the CH/Yinchuan/2021 isolate could efficiently propagate in Vero cells, and its proliferation ability was weaker than that of CV777 at 10 passages (P10). Phylogenetic analysis of the S gene revealed that CH/Yinchuan/2021 was clustered into subgroup GIIa, forming an independent branch with 2020-2021 isolates in China. Moreover, GII was obviously allocated into four clades, showing regional and temporal differences in PEDV global isolates. Notably, CH/Yinchuan/2021 was analyzed as a recombinant originated from an American isolate and a Chinese isolate, with a big recombinant region spanning ORF1a and S1. Importantly, we found that CH/Yinchuan/2021 harbored multiple mutations relative to CV777 in neutralizing epitopes (S10, S1A, COE, and SS6). Homology modelling showed that these amino acid differences in S protein occur on the surface of its structure, especially the insertion and deletion of multiple consecutive residues at the S10 epitope. In addition, cross-neutralization analysis confirmed that the differences in the S protein of CH/Yinchuan/2021 changed its antigenicity compared with the CV777 strain, resulting in a different neutralization profile. Animal pathogenicity test showed that CH/Yinchuan/2021 caused PEDV-typified symptoms and 100% mortality in 3-day-old piglets. These data will provide valuable information to understand the epidemiology, molecular characteristics, evolution, and antigenicity of PEDV circulating in China.

Porcine Epidemic Diarrhea Virus: Etiology, Epidemiology, Antigenicity, and Control Strategies in China

“…Additionally, another study reported that the non-S-INDEL PEDV HM2017 strain caused clinical symptoms in piglets at 12 hpi, and they all died at 84 hpi [43]. In our lab, the PEDV CH/Yinchuan/2021 strain infected pig populations of all ages and caused 100% mortality in 3-day-old piglets [42]. Moreover, we found that 13-week-old growing pigs infected with PEDV experienced watery diarrhea and vomiting and significantly reduced weight gain despite low mortality (unpublished data).…”

“…The emerging non-S-INDEL PEDV strains harbor some novel pathogenic features, such as rapid onset, rapid transmission, rapid death, and high mortality. In our investigation, 3-day-old piglets were infected with the identified novel non-S-INDEL strain PEDV CH/Yinchuan/2021, which caused vomiting and diarrhea at 18 hpi, and all the piglets died at 96 hpi (Table 1) [42]. Additionally, another study reported that the non-S-INDEL PEDV HM2017 strain caused clinical symptoms in piglets at 12 hpi, and they all died at 84 hpi [43].…”

“…Of note, the vaccine-immunized farms were not spared, and the mortality rate was close to 100% in neonatal piglets [10,11,38]. It has been confirmed by some investigations that PEDV has mutated in China, and the traditional vaccine PEDV CV777 cannot completely protect against highly pathogenic variants [9,10,42]. These variants have higher virulence and cause clinical symptoms in pigs of all ages, with 80-100% mortality in piglets [41,42].…”

“…It has been confirmed by some investigations that PEDV has mutated in China, and the traditional vaccine PEDV CV777 cannot completely protect against highly pathogenic variants [9,10,42]. These variants have higher virulence and cause clinical symptoms in pigs of all ages, with 80-100% mortality in piglets [41,42]. In 29 Chinese provinces, excluding Tibet and Hainan, an epidemiological survey carried out between February 2011 and March 2014 found that the rate of PEDV-positive samples ranged from 61.10% to 78.49%, while the rate of PEDVpositive pig farms was 71.43% to 83.47% [9].…”

“…The main clinical symptoms of 1-to 7-day-old newborn piglets infected with PEDV were acute watery diarrhea, dehydration, vomiting, and marked emaciation, with 80-100% mortality. Adult pigs infected with PEDV had comparatively low mortality, which was characterized by watery diarrhea, anorexia, agalactia, depression, and impaired reproductive function [41,42].…”