Search

Japanese encephalitis is caused by Japanese encephalitis virus (JEV), a mosquitoborne virus of the family Flaviviridae, genus Flavivirus (1). The JEV genome is composed of a single-stranded, positive-sense RNA of [...]

We isolated Japanese encephalitis virus genotype 5 from human specimens in South Korea. Whole-genome analysis showed 90.4% identity with other genotype 5 viruses from humans. This virus had a unique insertion in the NS4A gene. However, the envelope protein contained Lys 84, which was specific to strains of genotype 5 viruses from South Korea. [ABSTRACT FROM AUTHOR]

Background: Japanese encephalitis (JE) has been predominantly controlled through vaccination. However, the isolation of JE virus (JEV) genotype V (GV) in China in 2009, and the subsequent alarming increase in JE cases in the Republic of Korea since 2010, present a new challenge., Methods: Serum samples from individuals vaccinated with genotype III (GIII)-based JE vaccines were analyzed for neutralizing seroresponse to GV isolates., Results: Serum from immunocompromised pediatric patients vaccinated with an inactivated JE vaccine showed higher 50% plaque reduction neutralization test (PRNT50) geometric mean titer (GMT) against GIII Nakayama (11,358; 95% CI = 1,790, 29,658), but lower GMTs against GV isolates: GV Muar (499; 95% CI = 0, 2,437), GV 43279 (308; 95% CI = 159, 582), and GV 43413 (231; 95% CI = 108, 738). Similarly, 32 healthy volunteers receiving a live attenuated JE vaccine achieved 100% seroprotection against GIII Nakayama with GMT of 338 (95% CI = 304, 651) at 1 month post-vaccination. However, GMTs against GV isolates were 123 (95% CI = 102, 446) for GV Muar, 81 (95% CI = 63, 168) for GV 43279, and 107 (95% CI = 100, 322) for GV 43413, not achieving 100% seroprotection against these isolates. At 6 months post-vaccination, GMT against Nakayama increased to 696 (95% CI = 409, 2,353), while remaining similar for GV isolates., Conclusions: Our study underscores that current GIII-based vaccines do not provide comparable protection against GV JEVs, impacting individuals in both current and potential endemic regions, as well as travelers to these regions., (© The Author(s) 2024. Published by Oxford University Press on behalf of Infectious Diseases Society of America. All rights reserved. For commercial re-use, please contact reprints@oup.com for reprints and translation rights for reprints. All other permissions can be obtained through our RightsLink service via the Permissions link on the article page on our site—for further information please contact journals.permissions@oup.com.)

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.