Genotype V (GV) StrainsJEV is currently subdivided into five genotypes mainly based on premembrane (prM) and envelope (E) gene sequences [11,12]. In 1952, a serologically distinct JEV, Muar, was isolated from the brain of a JE patient in Malaysia [13]. Based on a series of serologic studies using monoclonal antibodies, it was confirmed that Muar belongs to a separate antigenic group [14,15]. Early phylogenetic analysis also determined the Muar as a distinct GV [12,16]. An evolutionary study revealed that GV is the ancestor of other genotypes (i.e., GI~GIV) [17]. A follow-up study with phylogenetic simulation using whole genome sequence of all JEV genotypes also suggested that GV is nearest to the common ancestor and that GIV, GIII, GII, and GI evolved sequentially from GV [18].Because GV and GIV strains are relatively older, it seems natural to find GIII and GI more frequently from recent isolates. Indeed, GIII strains were common in early JEV studies but were gradually replaced by GI strains in most endemic areas [19,20]. In 2009, 57 years after isolation of the GV Muar, GV XZ0934 was isolated from Cx. tritaeniorhynchus in China [21]. When compared the whole genome between GV Muar and GV XZ0934, the similarity was 90.6% and 98.3% for nucleotide and amino acid sequences, respectively, reflecting a temporal gap between these two GV isolates [22].
Japanese encephalitis (JE) is a vaccine-preventable mosquito-borne disease caused by infection with the Japanese encephalitis virus (JEV). JEV has five genotypes, including genotype V (GV), which is considered ancestral to the other genotypes. The first GV strain, GV Muar, was isolated from a Malayan patient in 1952 and GV did not reappear for 57 years until GV XZ0934 was isolated from a mosquito sample in China. Since 2010, 21 GV strains have been identified in Republic of Korea (ROK). Both GV Muar and GV XZ0934 are more pathogenic than other GI/GIII strains and are serologically distinct. However, because the ROK's GV strains have not been experimentally tested, their characteristics are not known. Characterization of the ROK's isolates is needed to enable development of effective GV strain-based vaccines to protect against GV infections.