Isolation and characterization of the virulent porcine epidemic diarrhea virus strain CHGS20 in China.

Porcine epidemic diarrhea virus (PEDV) is the etiological agent of porcine epidemic diarrhea (PED), which threatens the swine industry worldwide. Although commercial PEDV vaccines are available, the disease continues to plague the swine industry in China. Therefore, isolating PEDV from clinical samples is beneficial for conducting molecular epidemiological investigations, developing effective vaccines and diagnostic methods, and investigating pathogenic mechanisms. In this study, a genotype II PEDV strain, CHGS20, was isolated from a small-intestine sample collected in 2020 from a PEDV-infected piglet and propagated in Vero cells. Virus production in cell culture was confirmed by cytopathology, immunofluorescence assay, and transmission electron microscopy. The infectious virus titers during the first 10 passages ranged from 10 to 10 TCID per mL. The inactivated CHGS20 virus was found to induce a potent neutralizing antibody response in immunized mice, with a mean neutralizing antibody titer of 1:136 against the homologous strain and 1:46 against the genotype I strain JX18. The dynamics of the cytopathic effect (CPE) induced by CHGS20 and JX18 were analyzed using an electric cell-substrate impedance sensing system. The results indicated that this CPE assay has the potential to be used to assess the neutralizing activity of antibodies and facilitate the development of antiviral agents. These findings will be helpful for future understanding, control, and prevention of PED.