Based on variation in nucleotide sequence within restricted regions in the putative C (core) gene of hepatitis C virus (HCV), four groups of HCV have been postulated in a panel of 44 HCV isolates. They were provisionally designated types I, II, III and IV. A method for typing HCV was developed, depending on the amplification of a C gene sequence by polymerase chain reaction using a universal primer (sense) and a mixture of four type-specific primers (antisense). HCV types were determined by the size of the products specific to each of them. Type II was found in HCV samples from 131 (82%) of 159 blood donors, more often than in those from 48 (60%) of 80 patients with non-A, non-B (NANB) liver disease in Japan (P< 0-01). In 11 haemophiliacs who had received imported coagulation factor concentrates, type I was found in five, as against type II in four. Double infection with two different HCV types was found in two patients with chronic NANB liver disease (types I and II; II and III) and two haemophiliacs (types I and II; I and III). HCV types were identical in mother and baby in each of two examples of perinatal transmission, and were also identical in donor and recipient in a case of accidental needle exposure.

, 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.

Carriers of HBV. Sera were obtained from 40 asymptomatic carriers of HBV, including 14 positive for HBeAg and 26 positive for anti-HBe, as well as from 42 patients with chronic 8102

The C gene of hepatitis B virus (HBV) codes for a nucleocapsid protein made of 183 amino acid residues and is preceded in phase by the precore (pre-C) region, encoding 29 residues. The pre-C-region product is required for the synthesis and secretion of hepatitis B e antigen (HBeAg), which is made of the C-terminal 10 amino acid residues of the pre-C-region product and the N-terminal 149 residues of the C-gene product. HBV mutants with pre-C-region defects prevailed in the circulation of three asymptomatic carriers as they seroconverted from HBeAg to the corresponding antibody (anti-HBe), and these mutants finally replaced nondefective HBV. HBV DNA clones were propagated from sera of an additional 15 carriers with anti-HBe and sequenced for the pre-C region. Essentially all HBV DNA clones (56 of 57 [98%]) revealed mutations that prohibited the translation of a functional pre-C-region product. A point mutation from G to A at nucleotide 83, converting Trp-28 (TGG) to a stop codon (TAG), was by far the commonest and was observed in HBV DNA clones from 16 (89%) of 18 carriers seropositive for anti-HBe. In addition, there were point mutations involving ATG codon to abort the translation initiation of the pre-C region, as well as deletion and insertion to induce frameshifts. Such mutations leading to pre-C-region defects were rarely observed in persistently infected individuals positive for HBeAg or in patients with type B acute hepatitis after they had seroconverted to anti-HBe. These results would indicate a selection of pre-C-defective mutants in persistently infected hosts, along with seroconversion to anti-HBe, by immune elimination of hepatocytes harboring nondefective HBV with the expression of HBeAg.

Hepatitis E, the major form of enterically transmitted non-A, non-B hepatitis, is caused by hepatitis E virus (HEV). HEV is transmitted primarily by the fecal-oral route. Waterborne epidemics are characteristic of hepatitis E in developing regions of Africa, the Middle East, and Southeast and Central Asia, where sanitation conditions are suboptimal; one epidemic has also been documented in North America (Mexico) (32). HEV-associated hepatitis also occurs among individuals in industrialized countries with no history of travel to areas where HEV is endemic (6,9,18,25,36,37,39,41,52,54). Recently, accumulating lines of evidence indicate that hepatitis E is a zoonosis, and pigs or other animals may act as reservoirs for HEV infection in humans (9, 15, 20-24, 27, 39, 42, 45, 56). A significant proportion of healthy individuals in industrialized countries where hepatitis E is not endemic are seropositive for HEV antibodies (8,19,46). Therefore, several epidemiological questions remain unanswered. The success of future studies on clinical and subclinical HEV infection not only in developing countries but also in industrialized countries will greatly depend on the availability of assays that are sensitive and specific.HEV was recently classified as the sole member of the genus Hepevirus in the family Hepeviridae. The genome of HEV is a 7.2-kb, positive-sense, single-stranded RNA. It contains a short 5Ј untranslated region, three open reading frames (ORFs; ORF1, ORF2 and ORF3), and a short 3Ј untranslated region terminated by a poly(A) tract (12,34,44,53). ORF1 encodes nonstructural proteins, ORF2 encodes the capsid protein, and ORF3 encodes a cytoskeleton-associated phosphoprotein. Extensive diversity has been noted among HEV isolates, and HEV sequences have been classified into four major genotypes (genotypes 1 to 4) (37). In Japan, polyphyletic HEV strains of genotype 3 or 4 or both have been isolated from patients with sporadic acute or fulminant hepatitis E who had no history of travel to countries where this virus is endemic (1,25,30,40,41,56).The immunoglobulin M (IgM) class of antibody against HEV (anti-HEV IgM) is used as a reliable and sensitive marker of recent HEV infection (2-4, 38). However, the specificity of the solid-phase assay for anti-HEV IgM has been questioned in some cases, particularly in patients with IgMrheumatoid factors in the serum, which have activity against the Fc portion of IgG directed to HEV antigen and may elicit