Investigation of variants in genetics and virulence of Porcine Epidemic Diarrhea Virus after serial passage on Vero cells

• Published in: Journal of virological methods 2023-08, Vol.318, p.114755-114755, Article 114755
• Main Authors: Nguyen, Tan-Liem, Le, Thu-Phuong Thi, Dinh, Thuan-Thien, Nguyen-Ho, Hai-Vy, Mai, Quoc-Gia, Vo-Nguyen, Hai-Vy, Tran, Thuoc Linh, Tran, Hanh Xuan, Tran-Van, Hieu
• Format: Article
• Language: English
• Subjects: 0 domain; Animals; Attenuation; Chlorocebus aethiops; Coronavirus Infections - epidemiology; Diarrhea - veterinary; Genetic variation; ORF3; Pathogenicity; Porcine epidemic diarrhea virus (PEDV); Porcine epidemic diarrhea virus - genetics; Serial Passage; Swine; Swine Diseases; Vaccines, Attenuated - genetics; Vero Cells; Virulence
• ISSN: 0166-0934; 1879-0984
• DOI: 10.1016/j.jviromet.2023.114755

Porcine epidemic diarrhea virus (PEDV) is a highly contagious intestinal virus. However, the current PEDV vaccine, which is produced from classical strain G1, offers low protection against recently emerged strain G2. This study aims to develop a better vaccine strain by propagating the PS6 strain, a G2b subgroup originating from Vietnam, on Vero cells until the 100th passage. As the virus was propagated, its titer increased, and its harvest time decreased. Analysis of the nucleotide and amino acid variation of the PS6 strain showed that the P100PS6 had 11, 4, and 2 amino acid variations in the 0 domain, B domain, and ORF3 protein, respectively, compared to the P7PS6 strain. Notably, the ORF3 gene was truncated due to a 16-nucleotide deletion mutation, resulting in a stop codon. The PS6 strain's virulence was evaluated in 5-day-old piglets, with P7PS6 and P100PS6 chosen for comparison. The results showed that P100PS6-inoculated piglets exhibited mild clinical symptoms and histopathological lesions, with a 100% survival rate. In contrast, P7PS6-inoculated piglets showed rapid and typical clinical symptoms of PEDV infection, and the survival rate was 0%. Additionally, the antibodies (IgG and IgA) produced from inoculated piglets with P100PS6 bound to both the P7PS6 and P100PS6 antigens. This finding suggested that the P100PS6 strain was attenuated and could be used to develop a live-attenuated vaccine against highly pathogenic and prevalent G2b-PEDV strains. [Display omitted] •NAVET/PED/PS6/2010 strain was continuously propagated on Vero cells until to the 100th passage.•Adapted PS6 strain had a high virus titer and decreased harvest time upon serial passage.•O domain, B domain (S gene), and ORF3 gene of the adapted strain accumulated mutations compared with the parent strain.•The adapted strain reduced virulence in piglet with mild clinical symptoms and histopathological lesions.•The P100PS6 strain potentiated live-attenuated vaccine development against highly pathogenic, prevalent G2b-PEDV strains.