Characterization of a Small Plaque Variant Derived from Genotype V Japanese Encephalitis Virus Clinical Isolate K15P38.

Genotype V (GV) Japanese encephalitis virus (JEV) has been predominantly reported in the Republic of Korea (ROK) since 2010. GV JEV exhibits higher virulence and distinct antigenicity compared to other genotypes, which results in reduced efficacy of existing vaccines. Research on GV JEV is essential to minimize its clinical impact, but the only available clinical strain in the ROK is K15P38, isolated from the cerebrospinal fluid of a patient in 2015. We obtained this virus from National Culture Collection for Pathogens (NCCP) and isolated a variant forming small plaques during our research. We identified that this variant has one amino acid substitution each in the PrM and NS5 proteins compared to the reported K15P38. Additionally, we confirmed that this virus exhibits delayed propagation in vitro and an attenuated phenotype in mice. The isolation of this variant is a critical reference for researchers intending to study K15P38 obtained from NCCP, and the mutations in the small plaque-forming virus are expected to be useful for studying the pathology of GV JEV.