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, and its prevalence differed by geographic region (6 to 25%), with a higher rate in the northern part of Japan. At admission, the 11 patients with HEV-associated hepatitis had elevated alanine aminotransferase levels of 914 to 4,850 IU/liter, and all but 1 had elevated bilirubin levels of 1.5 to 24.0 mg/dl. The 11 HEV isolates were of genotype III or IV and were segregated into three groups with intergroup nucleotide differences of 9.5 to 22.0%. Phylogenetic analysis revealed that four isolates of genotype III were closely related to a Japanese isolate, while the other four isolates of the same genotype were nearest those from the United States. The remaining three isolates were close to known isolates of genotype IV in China and Taiwan but shared less than 88% identity with them. These results indicate that multiple genotypes of HEV cocirculate in Japan and contribute to the development of sporadic acute hepatitis, with the prevalence differing by age, sex, and geographic region.

A nonenveloped, single-stranded, and circular DNA virus designated TT virus (TTV) has been reported in association with hepatitis of unknown etiology. TTV has a wide sequence divergence (approximately 52%), by which it is classified into at least 16 genotypes separated by an evolutionary distance of >0.30. Therefore, the detection of TTV DNA by polymerase chain reaction would be influenced by primers deduced from conserved or divergent regions of the genome. Of the 30 sera from healthy individuals, up to 17% tested positive with primers deduced from coding region, much less frequently than up to 93% testing positive with primers from noncoding region. These differences were not attributable to the sensitivity of detection, because a cloned TTV DNA of genotype 1a was detected sensitively (up to 1 copy per test) with primers deduced from either the coding or the noncoding region of the same genotype. Sera testing positive only with noncoding region primers, or those showing higher titers with noncoding than coding region primers, contained TTV DNA strains with sequence divergence of 47-53% from the TA278 isolate of genotype 1a within the N22 region spanning 222-231 nucleotides. Some of the sera contained two or three TTV DNA strains of distinct genotypes. These results indicate TTV strains with extremely high sequence divergence prevailing in healthy individuals and frequent mixed infection with TTV strains of distinct genotypes.

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-monthold 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 ¢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. INTRODUCTIONHepatitis E virus (HEV) is an unclassified virus that is the major causative pathogen of enterically transmitted non-A, non-B hepatitis in many developing countries in Asia, Africa and Latin America (Purcell & Emerson, 2001a). There is a growing consensus that HEV-associated hepatitis also occurs among individuals in industrialized nations who have no history of travel to areas endemic for HEV (Harrison, 1999;Purcell & Emerson, 2001a;Schlauder & Mushahwar, 2001).The genome of HEV is a single-stranded, positive-sense RNA of approximately 7?2 kb and contains a short 59 untranslated region (59UTR), three open reading frames (ORF1, ORF2 and ORF3) and a short 39UTR terminated by a poly(A) tract (Reyes et al., 1990;Tam et al., 1991). HEV sequences have tentatively been classified into four major genetic groups (genotypes I-IV) (Schlauder & Mushahwar, 2001). The majority of HEV infections in several countries in Asia and Africa are caused by genotype I and the majority of HEV infections in Mexico and Nigeria are caused by genotype II, while only isolated cases of infection with HEV of genotype III or IV have been described in the US, European countries, Argentina, Taiwan and China (Hsieh et al., 1999;Pina et al., 2000;Schlauder et al., 1998Schlauder et al., , 1999Schlauder et al., , 2000Wang et al., 1999Wang et al., , 2000Wang et al., , 2001Worm et al., 2000;Zanetti et al., 1999). In Japan, 13 % (11/87) of the cases of acute non-A, non-B, non-C hepatitis were caused by HEV infection (Mizuo et al., 20...

We recently developed a cell culture system for hepatitis E virus (HEV) in PLC/PRF/5 and A549 cells, using fecal specimens from HEV-infected patients. Since transfusion-associated hepatitis E has been reported, we examined PLC/PRF/5 and A549 cells for the ability to support replication of HEV in various serum samples obtained from 23 patients with genotype 1, 3, or 4 HEV. HEV progenies emerged in culture media of PLC/PRF/5 cells, regardless of the coexistence of HEV antibodies in serum but dependent on the load of HEV inoculated (31% at 2.0 ؋ 10 4 copies per well and 100% at >3.5 ؋ 10 4 copies per well), and were successfully passaged in A549 cells. HEV particles in serum, with or without HEV antibodies, banded at a sucrose density of 1.15 to 1.16 g/ml, which was markedly lower than that for HEV particles in feces, at 1.27 to 1.28 g/ml, and were nonneutralizable by immune sera in this cell culture system. An immuno-capture PCR assay of HEV virions treated with or without detergent indicated that HEV particles in serum are associated with lipids and HEV ORF3 protein, similar to those in culture supernatant. By immunoprecipitation, it was found that >90% of HEV particles in the circulation exist as free virions not complexed with immunoglobulins, despite the coexistence of HEV antibodies. These results suggest that our in vitro cell culture system can be used for propagation of a wide variety of HEV strains in sera from various infected patients, allowing extended studies on viral replication specific to different HEV strains.Hepatitis E, an acute viral hepatitis caused by infection with hepatitis E virus (HEV), is a globally distributed human disease. In developing countries of Asia, Africa, and Latin America, where sanitation conditions are not well maintained, HEV infection is transmitted via the fecal-oral route through viruscontaminated water or food, with substantial mortality in pregnant women (7, 33). In industrialized countries, autochthonous hepatitis E is far more common than previously recognized and has a predilection for older men, in whom it causes substantial morbidity and mortality (5,13,31,36,44). HEV is the sole member of the genus Hepevirus within the family Hepeviridae (6). It is a single-stranded, positive-sense, polyadenylated RNA molecule of approximately 7.2 kb in size, with short 5Ј-and 3Ј-untranslated regions (53). The genomic RNA contains three open reading frames (ORFs). ORF1 encodes nonstructural proteins involved in virus replication and virus protein processing. ORF2 and ORF3 overlap, and the ORF2 and ORF3