Takahashi Masaharu, Nishizawa Tsutomu, Miyajima Haruko, Gotanda Yuhko, Iita Teruhiko, Tsuda Fumio, Okamoto Hiroaki
Immunology Division and Division of Molecular Virology, Jichi Medical School, Tochigi-Ken 329-0498, Japan.
Japanese Red Cross Saitama Blood Center, Saitama-Ken 338-0001, Japan.
J Gen Virol. 2003 Apr;84(Pt 4):851-862. doi: 10.1099/vir.0.18918-0.
Japanese patients with sporadic acute hepatitis E are infected with polyphyletic strains of hepatitis E virus (HEV). Hepatitis E is considered a zoonotic disease. Thus far in Japan, only three strains of swine HEV have been identified and an antibody study for HEV antibodies has not been done on Japanese pigs. To determine the prevalence of swine HEV infection in Japan and the extent of genetic variation among Japanese swine HEV strains, we tested serum samples obtained from 2500 pigs from 2 to 6 months of age at 25 commercial swine farms in Japan for the presence of IgG antibodies to HEV and swine HEV RNA. Anti-HEV antibodies were detected in 1448 pigs (58 %). One-hundred-and-thirteen (15 %) of the 750 3-month-old pigs and 24 (13 %) of the 180 4-month-old pigs were positive for swine HEV RNA. The nucleotide sequence of a 412 bp region within open reading frame 2 of the 137 swine HEV isolates was determined. Sequence analyses revealed that the 137 isolates shared 76.6-100 % nucleotide sequence identities and were classifiable into genotype III (93 %) or IV (7 %) and that the isolates from the same farm were > or = 97.1 % similar to each other. Phylogenetic analysis showed that the Japanese swine and human HEV isolates segregated into four clusters, with the highest nucleotide identity being 94.4-100 % between swine and human isolates in each cluster. These results indicate that swine HEV is widespread in the Japanese swine population and further support the hypothesis that swine serve as reservoirs for HEV infection.
日本散发性急性戊型肝炎患者感染的是戊型肝炎病毒（HEV）的多系毒株。戊型肝炎被认为是一种人畜共患病。在日本，到目前为止仅鉴定出三株猪源HEV毒株，且尚未对日本猪进行过HEV抗体的血清学研究。为了确定日本猪源HEV感染的流行情况以及日本猪源HEV毒株间的遗传变异程度，我们检测了从日本25个商业养猪场采集的2500头2至6月龄猪的血清样本中HEV IgG抗体和猪源HEV RNA的存在情况。在1448头猪（58%）中检测到抗HEV抗体。750头3月龄猪中有113头（15%）以及180头4月龄猪中有24头（13%）猪源HEV RNA呈阳性。测定了137株猪源HEV分离株开放阅读框2内412 bp区域的核苷酸序列。序列分析显示，137株分离株的核苷酸序列同一性为76.6%至100%，可分为基因型III（93%）或IV（7%），且来自同一猪场的分离株彼此间相似度≥97.1%。系统发育分析表明，日本猪源和人源HEV分离株分为四个簇，每个簇中猪源和人源分离株之间的最高核苷酸同一性为94.4%至100%。这些结果表明猪源HEV在日本猪群中广泛存在，并进一步支持猪作为HEV感染宿主的假说。
