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Molecular characterization of a novel hepatitis E virus (HEV) strain obtained from a wild boar in Japan that is highly divergent from the previously recognized HEV strains

Takahashi, Masaharu, Nishizawa, Tsutomu, Nagashima, Shigeo, Jirintai, Suljid, Kawakami, Manri, Sonoda, Yoshihide, Suzuki, Tadahiro, Yamamoto, Shogo, Shigemoto, Kazuhiro, Ashida, Kozo, Sato, Yukihiro, Okamoto, Hiroaki
Virus research 2014 v.180 pp. 59-69
rabbits, Orthohepevirus A, boars, humans, genome, Herpestidae, nucleotides, phylogeny, Sus scrofa, Chiroptera, ferrets, surveys, wild boars, genotype, genomics, rats, deer, birds, Japan
Although a consensus classification system for hepatitis E virus (HEV) genotypes is currently unavailable, HEV variants (JBOAR135-Shiz09 and wbJOY_06) from wild boars (Sus scrofa leucomystax) have provisionally been classified into two novel genotypes (5 and 6). While performing a survey of HEV infections among 566 wild boars that were captured in Japan between January 2010 and August 2013, we found 24 boars (4.2%) with ongoing HEV infections: 13 had genotype 3 HEV, 10 had genotype 4 HEV and the remaining boar possessed a novel HEV variant (designated wbJNN_13). The entire wbJNN_13 genome comprised 7247 nucleotides excluding the poly(A) tail, and was highly divergent from known genotype 1 to 4 HEV isolates derived from humans, swine, wild boars, deer, mongoose and rabbits by 22.4–28.2%, JBOAR135-Shiz09 and wbJOY_06 by 19.6−21.9% and rat, ferret, bat and avian HEV isolates by 40.9–46.1% over the entire genome. Phylogenetic trees confirmed that wbJNN_13 is distantly related to all known HEV isolates. A Simplot analysis revealed no significant recombination among the existing HEV strains. These results indicate the presence of at least three genetic lineages of presumably boar-indigenous HEV strains. Further studies to fully understand the extent of the genomic heterogeneity of HEV variants infecting wild boars are warranted.