Comparison of neutralizing antibody titers against Japanese encephalitis virus genotype V strain with those against genotype I and III strains in the sera of Japanese encephalitis patients in Japan in 2016

Abstract

Japanese encephalitis (JE) is an acute viral disease caused by the Japanese encephalitis virus (JEV). JEV strains are classified into five genotypes (I–V). JEV genotype V strains have never been detected in Japan to date, but they have been recently detected in South Korea. In the present analysis, we tried to determine if a JEV genotype V strain caused any JE case in Japan in 2016. The serum and cerebrospinal fluid samples were collected from 10 JE patients reported in Japan in 2016. JEV RNA was not detected in any of the samples. Although JEV is a single serotype virus, it can be expected that the neutralizing antibody titers against JEV genotype V strains are higher than those against genotype I and III strains in the sera of JE patients in Japan whose causative JEV was the genotype V strain. The neutralizing antibody titers against the JEV genotype V strain were not higher than those against the genotype I or III strain in any serum samples, indicating that the evidence that the JEV genotype V strain caused any JE case in Japan in 2016 was not shown.