Immunogenicity of a Vero cell-adapted Japanese encephalitis attenuated virus strain SA14-14-2 VC₆

To develop a Vero cell-adapted Japanese encephalitis (JE) SA14-14-2 strain for the production of JE SA14-14-2 live attenuated vaccine (LAV) using Vero cells as the substrate, the SA14-14-2 PHKC strain was adapted to Vero cells and subjected to plaque purification followed by clone selection. A highly attenuated strain, SA14-14-2 VC₆, was isolated, whose phenotypic and genotypic characteristics were highly consistent with those of its parental strain SA14-14-2 PHKC. Immunogenicity assays demonstrated that the VC₆ strain exhibited comparable immunogenicity to the parental SA14-14-2 strain. Under the experimental conditions used in this study, the VC₆ strain induced stronger neutralizing antibody (NAb) responses, protection against intraperitoneal (i.p.) or intracerebral (i.c.) challenge with wild-type JE virus (JEV), viremia inhibition, and cellular immune responses than the chimeric JE-CV vaccine. Collectively, these findings indicate that the SA14-14-2 VC₆ retains the immunogenic properties of the parental SA14-14-2 strain after adaptation to Vero cells and warrants further preclinical evaluation before its potential use in Vero cell-based JE vaccine development.