Abstract
Japanese encephalitis virus (JEV), the prototype member of the JEV serocomplex, genus Flavivirus, family Flaviviridae, is the most significant arthropod-borne encephalitis worldwide in terms of morbidity and mortality. At least four genotypes (GI–GIV) of the virus have been identified; however, to date, the genomic nucleotide sequence of only one GII virus has been determined (FU strain, Australia, 1995). This study sequenced three additional GII strains of JEV isolated between 1951 and 1978 in Korea, Malaysia and Indonesia, respectively, and compared them with the FU strain, as well as with virus strains representing the other three genotypes. Based on nucleotide and amino acid composition, the genotype II strains were the most similar to GI strains; however, these two genotypes are epidemiologically distinct. Selection analyses revealed that the strains utilized in this study are under predominantly purifying selection, and evidence of positive selection was detected at aa 24 of the NS4B protein, a protein that functions as an alpha/beta interferon signalling inhibitor.
Highlights
Japanese encephalitis virus (JEV) is a member of the JEV serocomplex within the genus Flavivirus, family Flaviviridae
The nucleotide sequence of the ORF of the three additional strains of GII of JEV were determined [Bennett, (Korea, c.1951); WTP-70-22 (Malaysia, 1970); and JKT 654 (Indonesia, 1978)]. These were compared with 29 wildtype homologous JEV sequences and one sequence of Murray Valley encephalitis virus (MVEV) that were retrieved from GenBank for a final dataset comprising 33 virus strains, each of which was 10 308 nt (3436 aa) in length (Table 1)
Nine of the 32 JEV strains belonged to Genotype I (GI), four strains belonged to GII, 18 strains belonged to GIII and one strain belonged to GIV
Summary
Japanese encephalitis virus (JEV) is a member of the JEV serocomplex within the genus Flavivirus, family Flaviviridae. JEV is the most important arthropod-borne viral encephalitis, with 50 000 cases and 10 000 deaths reported yearly, this may be a significant underestimate due to a lack of surveillance and underreporting (Barrett, 2008). Whilst most human infections are asymptomatic, approximately 25 % of symptomatic infections are fatal, 50 % develop severe, often long-term, neurological and/or psychiatric sequelae, and 25 % resolve fully (Barrett, 2008). Humans and other non-avian vertebrates are only infected incidentally and are considered to be dead-end hosts because they fail to produce viraemias of sufficient titres to infect mosquitoes. The prototype strain of JEV was isolated in Japan in 1935 (Lewis et al, 1947) and the virus has since been found
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