Sequence comparison of the capsid region of hepatitis E viruses isolated from Myanmar and China

Maternal-Fetal Hepatitis E Transmission: Is It Underestimated?

Hepatitis E virus (HEV) is an enterically transmitted virus; and several modes of transmission have been proposed, including blood transfusion, person to person transmission, and transplacental transmission. HEV during pregnancy is associated with an unfavorable prognosis for mothers and in severe cases can cause acute fulminate hepatitis and death. Transplacental transmission of HEV usually results in unfavorable outcomes of pregnancy, mainly fetal loss, preterm labor, and hepatic dysfunction in neonates. In this review, we will summarize the effects of HEV on maternal-fetal health in various clinical situations.

Hepatitis E: An emerging infection in high income countries

Hepatitis E virus (HEV) genotype 3 is the most recently characterized hepatotropic virus and is increasingly being recognized as the cause of unexplained liver disease in many western countries. Although asymptomatic in most cases, HEV GT3 may be responsible for a wide range of illnesses, from mild to fulminant acute hepatitis, and also chronic hepatitis in immunocompromised patients. Extrahepatic manifestations have been occasionally described. Anti-HEV antibody detection by immunoassays is hampered by moderate test accuracy particularly in immunocompromised hosts while a WHO international standard for molecular detection of HEV RNA by RT-PCR has recently been introduced. This review describes the basic virology, epidemiology, clinical virology and treatment of HEV GT3 infections in high income countries.

Hepatitis e: molecular virology and pathogenesis

Hepatitis E virus is a single, positive-sense, capped and poly A tailed RNA virus classified under the family Hepeviridae. Enteric transmission, acute self-limiting hepatitis, frequent epidemic and sporadic occurrence, high mortality in affected pregnants are hallmarks of hepatitis E infection. Lack of an efficient culture system and resulting reductionist approaches for the study of replication and pathogenesis of HEV made it to be a less understood agent. Early studies on animal models, sub-genomic expression of open reading frames (ORF) and infectious cDNA clones have helped in elucidating the genome organization, important stages in HEV replication and pathogenesis. The genome contains three ORF's and three untranslated regions (UTR). The 5' distal ORF, ORF1 is translated by host ribosomes in a cap dependent manner to form the non-structural polyprotein including the viral replicase. HEV replicates via a negative-sense RNA intermediate which helps in the formation of the positive-sense genomic RNA and a single bi-cistronic sub-genomic RNA. The 3' distal ORF's including the major structural protein pORF2 and the multifunctional host interacting protein pORF3 are translated from the sub-genomic RNA. Pathogenesis in HEV infections is not well articulated, and remains a concern due to the many aspects like host dependent and genotype specific variations. Animal HEV, zoonosis, chronicity in immunosuppressed patients, and rapid decompensation in affected chronic liver diseased patients warrants detailed investigation of the underlying pathogenesis. Recent advances about structure, entry, egress and functional characterization of ORF1 domains has furthered our understanding about HEV. This article is an effort to review our present understanding about molecular biology and pathogenesis of HEV.

Fusion of C3d molecule with neutralization epitope(s) of hepatitis E virus enhances antibody avidity maturation and neutralizing activity following DNA immunization

Previous studies have identified that a hepatits E virus peptide (HEV-p179), spanning amino acids (aa) 439-617 in the 660-aa protein encoded by open reading frame 2(ORF2) of the Chinese epidemic strain (genotype 4), is the minimal size fragment of conformation-dependent neutralization epitope(s). We report here the successful immunization of mice with DNA vaccines expressing the secreted form of HEV-p179 (fused with a human tissue plasminogen activator (tPA) signal sequence) and the tPA-p179-C3d fusion protein (fused with three tandem copies of the murine complement C3d). Analysis of antibody responses in vaccinated mice revealed that immunizations with tPA-p179-C3d3 DNA vaccine dramatically increased both the level and avidity maturation of antibodies against HEV-p179 compared to p179 and tPA-p179 DNA vaccines. In addition, this increased antibody response correlated with neutralizing titers in a PCR-based cell culture neutralization assay. These results indicate that vaccination with C3d conjugated p179 DNA vaccine enhances antibody responses to HEV, and this approach may be applied to overcome the poor immunogenicity of DNA vaccines to generate HEV neutralizing antibodies.

Hepatitis E virus

Hepatitis E virus (HEV) is the aetiological agent of non-HAV enterically transmitted hepatitis. It is the major cause of sporadic as well as epidemic hepatitis, which is no longer confined to Asia and developing countries but has also become a concern of the developed nations. In the Indian subcontinent, it accounts for 30-60% of sporadic hepatitis. It is generally accepted that hepatitis E is mostly self-limited and never progresses to chronicity. It has a higher mortality in pregnant women where the disease condition is accentuated with the development of fulminant liver disease. Currently, no antiviral drug or vaccine is licensed for HEV, although a vaccine candidate is in clinical trials. HEV genome is 7.2kb in size with three open reading frames (ORFs) and 5' and 3' cis acting elements, which have important roles to play in HEV replication and transcription. ORF1 codes for methyl transferase, protease, helicase and replicase; ORF2 codes for the capsid protein and ORF3 for a protein of undefined function. HEV has recently been classified in the genus Hepevirus of the family Hepeviridae. There are four major recognised genotypes with a single known serotype. The absence of a reliable in vitro propagation system is an obstacle to deciphering HEV biology. The genome of HEV has been cloned, sequenced and the infectious nature of these replicons has been established. However, questions related to replication, transcription, virus-host interactions and pathogenesis remain to be answered. This comprehensive review summarises the progress made so far in HEV research, and addresses some of the unanswered questions.

Seroprevalence of hepatitis E virus infection, rural southern People's Republic of China

HEV infection is thought to have been endemic in southern China for >60 years; swine are now the main source of human infection.

Genotype 4 hepatitis E virus (HEV) is the dominant cause of hepatitis E in the People's Republic of China; swine are the principal reservoir. Our study was conducted in 8 rural communities of southern China, where families keep pigs near their homes. Phylogenetic analysis showed that 23 of 24 concurrent virus isolates from this region are genotype 4 strains. Among the study populations, immunoglobulin G anti-HEV seroprevalence accumulated with age at ≈1% per year for persons >60 years of age. After age 30 years, seroprevalence increased at higher rates for male than for female study participants. The overall seroprevalence was 43% (range 25%–66%) among the communities. Infection rates were higher for participants between 25 and 29 years of age. The results suggest that HEV infection probably has been endemic in southern China for <60 years, with swine being the principal reservoir of human HEV infection in recent years.

Phylogenetic analysis of global hepatitis E virus sequences: genetic diversity, subtypes and zoonosis

Nucleotide sequences from a total of 421 HEV isolates were retrieved from Genbank and analysed. Phylogenetically, HEV was classified into four major genotypes. Genotype 1 was more conserved and classified into five subtypes. The number of genotype 2 sequences was limited but can be classified into two subtypes. Genotypes 3 and 4 were extremely diverse and can be subdivided into ten and seven subtypes. Geographically, genotype 1 was isolated from tropical and several subtropical countries in Asia and Africa, and genotype 2 was from Mexico, Nigeria, and Chad; whereas genotype 3 was identified almost worldwide including Asia, Europe, Oceania, North and South America. In contrast, genotype 4 was found exclusively in Asia. It is speculated that genotype 3 originated in the western hemisphere and was imported to several Asian countries such as Japan, Korea and Taiwan, while genotype 4 has been indigenous and likely restricted to Asia. Genotypes 3 and 4 were not only identified in swine but also in wild animals such as boar and a deer. Furthermore, in most areas where genotypes 3 and 4 were characterised, sequences from both humans and animals were highly conserved, indicating they originated from the same infectious sources. Based upon nucleotide differences from five phylogenies, it is proposed that five, two, ten and seven subtypes for HEV genotypes 1, 2, 3 and 4 be designated alphabetised subtypes. Accordingly, a total of 24 subtypes (1a, 1b, 1c, 1d, 1e, 2a, 2b, 3a, 3b, 3c, 3d, 3e, 3f, 3g, 3h, 3i, 3j, 4a, 4b, 4c, 4d, 4e, 4f and 4g) were given.

The 41-amino-acid C-terminal region of the hepatitis E virus ORF3 protein interacts with bikunin, a kunitz-type serine protease inhibitor

Hepatitis E virus (HEV), a human plus-stranded RNA virus, contains three open reading frames (ORF). Of these, ORF1 encodes the viral nonstructural polyprotein, ORF2 encodes the major capsid protein, and ORF3 codes for a phosphoprotein of undefined function. Recently, using the yeast two-hybrid system to screen a human cDNA liver library, we have isolated and characterized AMBP (alpha1-microglobulin/bikunin precursor), which specifically interacts with the ORF3 protein of HEV. The ORF3 protein expedites the processing and secretion of alpha1-microglobulin. When checked individually for interaction, the second processed protein from AMBP, bikunin, strongly interacted with the full-length ORF3 protein. This protein-protein interaction has been validated by immunoprecipitation in both COS-1 and Huh7 cells and by His6 pull-down assays. In dual-labeling immunofluorescent staining, followed by fluorescence microscopy of transfected human liver cells, ORF3 colocalized with endogenously expressed bikunin. Finally, a 41-amino-acid C-terminal region of ORF3 has been found to be responsible for interacting with bikunin. The importance of this virus-host protein-protein interaction, with reference to the viral life cycle, has been discussed.

Evidence of recombination between divergent hepatitis E viruses

Phylogenetic and recombination analysis was performed on 32 complete hepatitis E virus (HEV) genomes from infected humans and pigs. For the first time, evidence for recombination between divergent HEV strains was obtained, with at least two strains being found to have discordant phylogenetic relationships consistent with the occurrence of intragenotype recombination. This finding confirms that humans can be dually infected with divergent HEV strains and has implications for the emergence and evolution of new HEV epidemics.

Phylogenetic analysis of the first complete hepatitis E virus (HEV) genome from Africa

Hepatitis E virus (HEV) is globally distributed, transmitted enterically and between humans and animals. Phylogenetic analysis has identified five distinct HEV genotypes. The first full-length sequence of an African strain (Chad) is presented and compared to 31 complete HEV genomes available, including the fulminant hepatitis strain from India, swine strains and a strain from Morocco. The two African strains are more closely related to genotype 1 than to any other genotypes and together they possibly form a sub-genotype or sixth genotype. The first evidence for recombination between divergent HEV strains is presented.

Emerging and re-emerging infectious diseases

Microbial pathogens discovered as aetiological agents of human disease over the last 25 years are reviewed. Strengthening of laboratory and public health surveillance is of paramount importance for early detection and management of emerging infectious diseases.

Antigenic domains of the open reading frame 2-encoded protein of hepatitis E virus

The antigenic composition of the hepatitis E virus (HEV) protein encoded by open reading frame 2 (ORF2) was determined by using synthetic peptides. Three sets of overlapping 18-, 25-, and 30-mer peptides, with each set spanning the entire ORF2 protein of the HEV Burma strain, were synthesized. All synthetic peptides were tested by enzyme immunoassay against a panel of 32 anti-HEV-positive serum specimens obtained from acutely HEV-infected persons. Six antigenic domains within the ORF2 protein were identified. Domains 1 and 6 located at the N and C termini of the ORF2 protein, respectively, contain strong immunoglobulin G (IgG) and IgM antigenic epitopes that can be efficiently modeled with peptides of different sizes. In contrast, antigenic epitopes identified within the two central domains (3 and 4) were modeled more efficiently with 30-mer peptides than with either 18- or 25-mers. Domain 2 located at amino acids (aa) 143 to 222 was modeled best with 25-mer peptides. A few 30-mer synthetic peptides derived from domain 5 identified at aa 490 to 579 demonstrated strong IgM antigenic reactivity. Several 30-mer synthetic peptides derived from domains 1, 4, and 6 immunoreacted with IgG or IgM with more than 70% of anti-HEV-positive serum specimens. Thus, the results of this study demonstrate the existence of six diagnostically relevant antigenic domains within the HEV ORF2 protein.

Neutralization of different geographic strains of the hepatitis E virus with anti-hepatitis E virus-positive serum samples obtained from different sources

A recently developed polymerase chain reaction (PCR)-based cell culture neutralization assay was used to investigate cross-neutralization of known hepatitis E virus (HEV) strains obtained from various HEV-endemic regions of the world with different anti-HEV-positive serum samples. Serum specimens obtained from cynomolgus macaques experimentally infected with strains from Burma, Mexico, or Pakistan cross-neutralized the infectivity of each strain as well as an isolate from Morocco. Serum samples obtained either from infected patients who reside in HEV-endemic regions of the world or from U.S. residents who became infected while traveling to such regions also neutralized all four strains. In contrast, antibodies obtained from rabbits immunized with full-length Burma strain ORF2 protein neutralized only the Burma and Pakistan strains, not the Mexico or Morocco strains. In addition, antibodies obtained from guinea pigs immunized with an N-terminal truncated Burma strain ORF2 protein neutralized each strain except the Morocco strain. These data strongly suggest that antibodies elicited during an HEV infection demonstrate broad HEV neutralizing activity, whereas antibodies elicited after immunization with recombinant Burma ORF2 protein demonstrate a more limited ability to neutralize various HEV strains obtained from different regions of the world endemic for the disease.

Identification of a novel strain of hepatitis E virus responsible for sporadic acute hepatitis in Taiwan

Hepatitis caused by the hepatitis E virus (HEV) is a self-limited disease and occurs most frequently as epidemic or sporadic hepatitis in developing countries. The role of HEV in sporadic acute hepatitis in areas without a history of hepatitis E epidemics is obscure. Recently, it was found that more than 10% of the patients with acute non-A, non-B, non-C hepatitis in Taiwan were associated with an acute HEV infection. Nucleotide sequences of the regions within the first open reading frame of HEV were determined in four cases and were 96.7-100% identical to each other. As compared to the isolates from China, Pakistan, Burma, India, Africa, and Mexico, the similarities were, however, only 71.7-79.3%. Phylogenetic analysis revealed that the four Taiwan isolates were categorized as a novel HEV group (the Taiwan strain), which was distinct from all of the strains isolated from other parts of the world. In addition, the isolates from China, Burma, India, and Pakistan were catalogued as the second genotype of HEV (the Asian strain), and the Mexican isolate as the third (the Mexican strain). The African isolate was more related to the Asian type and might be a subtype of the Asian strain. A simple genotyping method by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) is described. The findings also support the hypothesis that HEV may be responsible for some sporadic acute non-A, non-B, non-C hepatitis in other developed countries.

Genotyping of hepatitis E virus in clinical specimens by restriction endonuclease analysis

The genomic variability of hepatitis E virus (HEV) was examined by restriction endonuclease analysis (REA) of four genomic cDNA copies comprising a 499 bp segment of the putative polymerase gene, a 264 bp segment of the helicase gene, and two, 680 bp and 448 bp, segments of the capsid gene. Analysis of the deduced restriction sites of all 27 HEV sequences currently available in the GenBank, and digestion of reverse-transcribed and nested PCR amplified segments obtained from six Nepali isolates were used to devise and test a REA genotyping assay. The assay allowed easy discrimination between the Mexico and Asian genotypes, and the classification of the Asian genotypes into three, or perhaps four subgenotypes. In addition, endonucleases identifiers of individual isolate or clusters of isolates were found. This assay permits rapid identification of a large number of HEV isolates directly from clinical specimens for studies on the molecular epidemiology and evolution of HEV.

Hepatitis E virus in Nepal: similarities with the Burmese and Indian variants

Hepatitis E has been the predominant type of acute hepatitis in Nepal both in adults and children, in sporadic and epidemic forms. We examined six hepatitis E virus (HEV) isolates obtained during an 8-year period, from 1987 to 1995, in the Kathmandu valley of Nepal. Analysis of portions of the putative helicase, polymerase and capsid genes demonstrated close genetic relatedness among themselves (> 96.4% identity) and with the Burmese (> 95.5%) and Indian (> 95.3%) isolates, and less so with the African (> 94.4%) and the Chinese (> 91%) isolates within the Asian genotype. Phylogenetic analysis placed the Nepali isolates in the Burma-India evolutionary branch and showed that the oldest isolate, TK78/87 was more similar to the Burmese isolates whereas the most recent isolates were closer to the Indian ones. Assuming no frameshifts, the Nepali isolates showed high amino acid conservation, but also unique changes when compared to other HEV isolates. Amino acid residue 614 of the capsid protein was identified as a possible marker to distinguish the Burma-Nepal-India from the China-Central Asian Republics subgenotype, and the Mexico genotype.

Existing variations on the gene structure of hepatitis E virus strains from some regions of China

The isolation and identification of the 87A strain of hepatitis E virus (HEV) by means of cell culture have been described previously. This paper reports the nucleotide sequence of a portion of this HEV strain. The RNA extracted from the supernatants of the different passages of the 87A strain cultured in the A549 cell line was reverse-transcribed (RT) to cDNA, and then the polymerase chain reaction (PCR) amplification was carried out using the primers of HEV ET1.1 region. The PCR products from 1) the supernatant of the infected cells at the fourth passage, 2) the virus concentrated by polyethylene glycol (PEG) precipitation at the tenth passage, and 3) the virus purified by a sucrose gradient at the tenth passage were sequenced. In addition, three other PCR products obtained from sera of acute hepatitis E patients in Beijing (B-9) and Guangzhou (G-9 and G-20) were also sequenced. The nucleotide sequences of the above four strains of HEV (located in the genome from positions 4545-4754) were compared to those of some reported HEV strains. The nucleotide sequences of the B-9 strain and the 87A strain were similar to the Burmese strain and may belong to the same branch of HEV. The nucleotide sequences of the G-9 strain and the G-20 strain were a novel and unique branch. The Chinese HEV strains are multiplex and variable in gene structure.

Synthesis and application of hepatitis E virus peptides to diagnosis

Based on computer analysis of hydrophobicity and prediction of secondary structures for the full-length putative proteins encoded by open reading frame-1 (ORF-1), ORF-2 and ORF-3 of hepatitis E virus (HEV), we selected antigenic regions with hydrophilicity, beta-turn, and beta-sheet, and synthesized 7 peptides of possible epitope-containing regions of the polypeptide encoded by all 3 ORFs of HEV genomic RNA by Merrifield's method of solid-phase synthesis. The synthetic peptides were screened and identified by solid-phase enzyme-linked immunosorbent assay (ELISA). Three of the peptides (EH174 from ORF-1, EH286 from ORF-2 and EH362 from ORF-3) showed antigenic activity and possible application for the development of anti-HEV test kits (the peptide-based ELISA). The laboratory experiments and clinical trials showed that the kits, using a set of 3 synthetic HEV peptides as coating antigens, were of high specificity and exhibited good reproducibility. The small-scale seroepidemiological survey indicated high seroprevalence (14.3%) of anti-HEV in Tibetan populations. Additionally, the results also demonstrated good agreement with clinical findings, suggesting that the test kits will be of major use for immunodiagnosis and seroepidemiological surveys of HEV infection.

Hepatitis E probably contracted via a Chinese herbal medicine, demonstrated by nucleotide sequencing

Hepatitis E is endemic in developing countries and may occur as imported hepatitis in industrialized countries. A 46-year-old Japanese man developed immunoserologically diagnosed acute hepatitis E in Japan 4 months after he had made a trip to China. He had bought a Chinese herbal medicine there, taking it occasionally until approximately 6 weeks prior to the onset of acute hepatitis. Nucleotide sequencing of the 3' terminal region of the viral cDNA amplified from the patient's serum by polymerase chain reaction revealed a high degree of homology (99.8% of 752 nucleotides) with the Chinese strain. Thus, the results of sequencing suggest that his hepatitis E was caused by infection with the Chinese strain, via the Chinese herbal medicine.

Persistent and transient antibody responses to hepatitis E virus detected by western immunoblot using open reading frame 2 and 3 and glutathione S-transferase fusion proteins

Recombinant proteins containing amino acid sequences from open reading frame (ORF) 2 and ORF3 of a Chinese strain of hepatitis E virus (HEV) were constructed as fusions with glutathione S-transferase (GST). Stable fusion proteins were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the proteins were transferred to nitrocellulose membranes, and the immobilized proteins were probed with sera from hepatitis E patients from various regions or from rhesus monkeys (Macaca mulatta) experimentally infected with the Chinese strain of HEV. Immunoglobulin G-class antibodies were detected with chemiluminescence and anti-human immunoglobulin G conjugated to horseradish peroxidase. Anti-ORF3 antibodies were detected in most patients and monkeys within 17 days of exposure, but this humoral response declined with time and was usually undetectable by approximately 100 days. Anti-ORF2.1 antibody was usually detected as early as anti-ORF3 but persisted in all animals and many patients, whereas reactivity to the larger GST-ORF2.2 fusion protein was more transient, even though all sequences present in GST-ORF2.1 are present in GST-ORF2.2. Rechallenge of these monkeys with HEV suggested that immunity to reinfection was incomplete, as levels of anti-ORF2.1 (but not anti-ORF2.2) were boosted after each rechallenge. The results demonstrate that the carboxy-terminal region of HEV ORF2 contains epitopes which are recognized by convalescent-phase antibody and are likely to be associated with limited immunity to infection, but these epitopes may be masked when larger portions of ORF2 are expressed as recombinant proteins.

Variations of hepatitis B virus precore/core gene sequence in acute and fulminant hepatitis B

Variations of the hepatitis B virus (HBV) precore/core sequence has been shown to play a role in the development of active liver disease in chronic hepatitis B. Whether this is also an important viral factor in the pathogenesis of acute and fulminant hepatitis B is unknown. To determine the precore/core gene sequence in patients with acute and fulminant hepatitis B, 11 patients with fulminant hepatitis B and seven patients with acute hepatitis B were studied. The sequences of precore/core gene were determined by direct sequencing of the polymerase chain reaction amplicons generated from the HBV isolated from patients' serum. For the 11 patients with fulminant hepatitis B, the precore/core regions were successfully amplified in 10 patients. Eight patients exhibited precore stop codon mutations. In addition, nine of the 10 fulminant hepatitis B patients had frequent nucleotide substitutions with corresponding changes in the predicted amino acid sequences in the mid-core and the 5' terminus region of the core gene. In contrast, precore stop codon mutants were not detected, and variations of the HBV core gene were minimal in patients with acute hepatitis B. The association of HBV precore mutants and HBV core gene variations with fulminant hepatitis B and not acute hepatitis B suggested that these variations may be important in modulating the clinical course of HBV infection.

Rolling review--the pathogenesis, diagnosis and management of viral hepatitis

Five major hepatotrophic viruses have been identified. The pathogenesis, diagnosis and treatment of chronic viral hepatitis continues to be intensely researched. Experimental evidence suggests that HLA restricted virus-specific T cells play a role in hepatocellular injury in type A hepatitis. The absence of chronic infection indicates the effectiveness of the host immune response to hepatitis A virus (HAV). It is postulated that HAV may rarely trigger an autoimmune chronic hepatitis. Active prophylaxis of hepatitis A is possible. The elimination of hepatitis B is dependent on the recognition of viral determinants in association with HLA proteins on infected hepatocytes by cytotoxic T cells. The specific epitopes recognized by B and T cells are being mapped. Polymerase chain reaction (PCR) amplification and sequencing of genomic DNA in patients with chronic hepatitis B has indicated that nucleotide substitutions in the genome are not uncommon. Their pathogenicity is being explored. Antiviral therapy for hepatitis B remains difficult. Interferon is effective in a proportion of patients. Thymosin may prove to be more effective immunomodulatory therapy. New nucleoside analogues suppress HBV replication, but the safety of these drugs has been questioned after the appearance of severe liver toxicity with fialuridine. The data that hepatitis D virus is pathogenic has recently been challenged with the observation that HDV re-occurs in transplanted liver after engrafting, but without signs of HBV recurrence or evidence of liver damage. Treatment of hepatitis D virus remains difficult. Several isolates of hepatitis C virus have been cloned, and the sequence divergence of these isolates indicates that there are several major genotypes and component subtypes of this polymorphic virus.(ABSTRACT TRUNCATED AT 250 WORDS)

Partial sequence comparison of eight new Chinese strains of hepatitis E virus suggests the genome sequence is relatively stable

Partial genomic sequences representing 420 nucleotides of a nonstructional region, 480 nucleotides of the putative RNA polymerase region, and 540 nucleotides of the structural region of epidemic-associated Chinese strains of hepatitis E virus (HEV) were obtained by direct sequencing of PCR-amplified DNA. Comparison with previously published HEV sequences showed a clear relatedness of all Chinese strains to each other and to a Pakistani strain (Sar-55). All eight Chinese strains examined had very similar sequences (98.5-99.8% homology) in the regions examined and were much closer to the Pakistani strain (Sar-55) (97.9-98.4% homology) than to the Burmese strain (92.5-93.3% homology). Sequence comparisons of the three genomic regions in the Chinese strains indicated that the RNA polymerase region was much more conserved than the other nonstructural region or the structural region. HEV isolates from three remote geographic regions of China had sequences closely related to each other.

Detection of precore/core-mutant hepatitis B virus genome in patients with acute or fulminant hepatitis without serological markers for recent HBV infection

To confirm the possibility that some hepatitis B virus (HBV) variants do not induce HB s antigen (HBsAg), anti-HB core antibody (anti-HBc) and anti-HBc IgM in a transient infection, polymerase chain reaction (PCR) was performed in 20 patients with acute hepatitis and 7 patients with fulminant hepatitis. Patients were diagnosed with non-A, non-B hepatitis by serological markers at admission. PCR successfully amplified the precore/core gene in 5 (25%) of the patients with acute hepatitis and 2 (29%) of the patients with fulminant hepatitis. Subsequent sequencing revealed frequent mutations including precore-defects in the precore/core gene.

An epidemic outbreak of hepatitis E in Yangon of Myanmar: antibody assay and animal transmission of the virus

An epidemic outbreak of hepatitis E occurred in an army recruit camp of Yangon, Myanmar, in October 1989. One hundred and eleven patients among 600 residents were hospitalized. As high as 83.7% of these patients were positive for the acute phase antibody against hepatitis E virus by an enzyme-linked immunosorbent assay developed in our laboratory. Also, 30.6% of 49 symptom-free residents examined were positive for the antibody. We prepared a stool extract from six patients and inoculated it into 10 rhesus monkeys for a series of three sub-passages. All of them developed acute biochemical hepatitis along with an elevation of antibody levels. A rechallenge with viruses of the present outbreak failed to provoke hepatitis in two monkeys that had previously recovered from acute hepatitis caused by an isolate of sporadic hepatitis E of the same area. Similarly, the rechallenge of the sporadic strain did not induce hepatitis in two monkeys that had been previously infected with the epidemic virus. These data suggested that the subjects would obtain neutralizing antibodies against the hepatitis E virus once infected, and many adult inhabitants of the endemic area had no protective antibodies and were still susceptible to hepatitis E infection.

Sequence and gene structure of the hepatitis E virus isolated from Myanmar

Hepatitis E virus (HEV) is a causative agent of enterically transmitted non-A, non-B hepatitis. Hepatitis E occurs not only in sporadic forms but also in epidemic outbreaks in the developing world. We have revealed the nucleotide and predicted amino acid sequences of full cDNA of HEV isolated from sporadic hepatitis E of Myanmar. The genome is 7194 nucleotides long, followed by a poly(A) tail, and has three open reading frames. The nonstructural gene is located in the 5' terminus, while the structural gene is situated in the 3' terminus. Our HEV strain has 98.5% nucleic acid identity with the HEV strain cloned by workers at Genelabs Incorporated from Myanmar. The difference is point nucleotide substitutions. There is a high degree of nucleotide relatedness among HEVs isolated from the same geographical location.

Hepatitis E: review

Hepatitis E is endemic, often provoking epidemics in many developing countries. It resembles hepatitis A clinically and epidemiologically but show a higher mortality rate and less infectiousness. Several lines of evidence strongly support the assumption that humans become immunized once they contract hepatitis E. Because of the low infectiousness, most of the adult population of endemic areas are susceptible to hepatitis E until an epidemic occurs, although they are almost always infected with hepatitis A during infancy. Epidemics are caused by accidental contamination by the hepatitis E virus (HEV) in feces of water provided to these people. The liver change reveals necroinflammation related to the immune-mediated mechanism. The HEV is molecularly cloned and sequenced and has a single-stranded, positive-sense RNA genome, 7,194 nucleotides followed by a poly (A) tail. There are three open reading frames. The non-structural gene, approximately 5 kb is located at the 5' end, while the structural gene, approximately 2 kb is located at the 3' end of the genome. There is a low level of nucleotide variations among HEV strains isolated from Myanmar and China and a single serotype appears to exist. The HEV may be a new RNA virus or belong to Caliciviridae family. Further investigation include in vitro propagation, elucidation of the gene replication, global seroepidemiology and vaccination of the HEV.