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

Immunization against Hepatitis E

Soon after the 1991 molecular cloning of hepatitis E virus (HEV), recombinant viral capsid antigens were expressed and tested in nonhuman primates for protection against liver disease and infection. Two genotype 1 subunit vaccine candidates entered clinical development: a 56 kDA vaccine expressed in insect cells and HEV 239 vaccine expressed in Escherichia coli Both were highly protective against hepatitis E and acceptably safe. The HEV 239 vaccine was approved in China in 2011, but it is not yet prequalified by the World Health Organization, a necessary step for introduction into those low- and middle-income countries where the disease burden is highest. Nevertheless, the stage is set for the final act in the hepatitis E vaccine story-policymaking, advocacy, and pilot introduction of vaccine in at-risk populations, in which it is expected to be cost-effective.

Hepatitis E virus in rats, Los Angeles, California, USA

This virus is unlikely to be a zoonotic threat.

The role of rats in human hepatitis E virus (HEV) infections remains controversial. A genetically distinct HEV was recently isolated from rats in Germany, and its genome was sequenced. We have isolated a genetically similar HEV from urban rats in Los Angeles, California, USA, and characterized its ability to infect laboratory rats and nonhuman primates. Two strains of HEV were isolated from serum samples of 134 wild rats that had a seroprevalence of antibodies against HEV of ≈80%. Virus was transmissible to seronegative Sprague-Dawley rats, but transmission was spotty and magnitude and duration of infection were not robust. Viremia was higher in nude rats. Serologic analysis and reverse transcription PCR were comparably sensitive in detecting infection. The sequence of the Los Angeles virus was virtually identical to that of isolates from Germany. Rat HEV was not transmissible to rhesus monkeys, suggesting that it is not a source of human infection.

Molecular epidemiology of hepatitis E virus in Hong Kong

Hepatitis E virus (HEV) is one of the major causes of acute and self-limiting hepatitis in human. In Hong Kong, the number of notifications increased from 26 to 62 from year 2001 to 2007. This study describes the molecular epidemiology of HEV in Hong Kong in order to determine the movement and distribution of HEV. HEV in 171 serum samples from HEV IgM positive cases from year 2001 to 2007 were amplified using RT-PCR and subjected to nucleotide sequencing. Phylogenetic analysis showed 162 of 171 HEV detected cases (94.7%) belonged to genotype IV and 8 (4.7%) to genotype I. Interestingly, a cluster of 10 cases in year 2007 that had the same sequence of HEV was identified. Epidemiological data however did not detect any relationship between these cases. Since zoonotic transmission is a well known route of HEV infection, close monitoring of the circulating HEV strains in human and food source animals may help to provide additional information on the transmission of HEV and possible source of infection in Hong Kong.

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.

Epidemiology and genotypes of HEV in Wuhan

BACKGROUND

Understanding the genotype and clinical features of the hepatitis E virus (HEV) are important for understanding its characteristics, for evaluating region-specific diagnostic assays, and producing vaccines.

OBJECTIVES

To investigate the epidemiology and the genotypes of HEV among outpatients and inpatients in the Department of Infectious Diseases of Tongji Hospital in Wuhan, China.

METHODS

Clinical data were elicited from the hospital records of patients who were clinically diagnosed with acute hepatitis between January 2000 and August 2004 (4920 patients). Of these cases, 120 patients with anti-HEV-IgM, IgG-positive were selected to analysis. Conserved genomic sequences of open reading frame 2 (345 bp) in the HEV gene were detected using polymerase chain reaction, 25 of which were cloned and sequenced. Clustal X and Mega software were used for phylogenetic analysis of genotypes strains.

RESULTS

The HEV infection rate is gradually increasing in Wuhan. The number of male patients was 3.3-fold greater than the number of female patients found in clinical investigations. People aged 30-59 years are more susceptible to infection, and people are more susceptible in March-June. Twenty-five isolates shared the same genotype, genotype IV, with 82.61-98.55% nucleotide identity. This genotype had 76.52-81.74%, 70.43-73.04%, 76.52-81.16%, and 84.35-88.70% homology with the nucleotide sequence of HEV genotypes I-IV, respectively. Phylogenetic analysis suggested that these 25 isolates represented at least three different subtypes, but there were no significant differences found in the epidemiological features or liver function of patients with the three subtypes.

CONCLUSIONS

HEV sequences isolated from patients in Wuhan belong to different subtypes of HEV genotype IV.

Polyphyletic strains of hepatitis E virus are responsible for sporadic cases of acute hepatitis in Japan

Among 87 patients who were previously treated for acute hepatitis of unknown etiology between 1992 and 2001 at five hospitals in Japan, 11 (13%) patients were positive for immunoglobulin M-class antibodies to hepatitis E virus (HEV) by enzyme immunoassay and had detectable HEV RNA by reverse transcription-PCR with two independent sets of primers derived from well-conserved genomic areas in open reading frames 1 and 2. Clinical HEV infection was significantly associated with male sex (9 of 11 versus 29 of 76 patients [P < 0.01]) and older age (52 +/- 11 [mean +/- standard deviation] versus 41 +/- 17 years [P < 0.05]), 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.

Prevalence, isolation, and partial sequence analysis of hepatitis E virus from domestic animals in China

Evidence that hepatitis E is zoonotic is accumulating. Serum samples were collected from pigs, cattle, and goats from various regions of China to determine whether they had been infected with hepatitis E virus (HEV). An in-house enzyme immunoassay (EIA) and reverse transcriptase-polymerase chain reaction (RT-PCR) with primers from open reading frame (ORF) 2 were used to detect anti-HEV antibodies and HEV RNA. The mean positivity rates of anti-HEV antibody for pigs and cattle were 78.8% and 6.3% but none of the goat sera were positive. Pigs may be more susceptible to infection with HEV than cattle or goats. Five of 263 pig sera were positive for HEV RNA and four of these five were also positive for anti-HEV. The PCR products (nt 6007-6354) were cloned and sequenced and compared to other HEV sequences in the nucleotide databases. The five sequences shared 83-93% identity to each other at the nucleotide level and 74-79%, 73-74%, 73-78%, and 83-99% identity to HEV genotypes 1, 2, 3, and 4, respectively. They were closely related to human isolates of HEV genotype 4. Phylogenetic analyses also place these swine sequences in HEV genotype 4, resembling most closely viruses isolated from Chinese patients with acute hepatitis. These data support the hypothesis that sporadic hepatitis E in China is zoonotic.

Identification of two distinct genotypes of hepatitis E virus in a Japanese patient with acute hepatitis who had not travelled abroad

Two distinct hepatitis E virus (HEV) isolates, designated HE-JI3 and HE-JI4, were identified in a single patient with acute hepatitis in Japan, who had not travelled abroad. The HEV load of HE-JI3 at admission was 10(2) copies/ml, but that of HE-JI4 was tenfold higher at 10(3) copies/ml. The viraemia of HE-JI4 persisted for up to 16 days from admission, whereas HE-JI3 disappeared at 9 days after admission. The entire nucleotide sequence of the HE-JI4 isolate and partial nucleotide sequences of open reading frames (ORFs) 1 and 2 of the HE-JI3 isolate were determined. The full-length nucleotide sequence of HE-JI4 consisted of 7171 nucleotides excluding the poly(A) tail and contained ORF1 encoding 1684 amino acids, ORF2 encoding 671 amino acids and ORF3 encoding 114 amino acids. Sequence and phylogenetic analyses of the HEV genomes indicated that HE-JI4 was most closely related to an HEV isolate (T1) of genotype IV with the same strategy for translation of ORF2 and ORF3, but which differed from it by 16.5% over the entire genome. The HE-JI3 isolate showed the highest nucleotide identity (88.6-95.1%) to the genotype III HEVs, having higher identity to human and swine HEV isolates from the United States (US1, US2 and swUS1) than to those reported thus far from Japan (JRA1 and swJ570). The two co-infecting strains of HE-JI3 and HE-JI4 identified from the single patient shared only 80.1% nucleotide identity. These results indicate that multiple genotypes of HEV co-circulate in Japan, and that genotype IV comprises a remarkably heterogeneous group of HEVs.

Characterization of Norwalk-like virus associated with gastroenteritis in Indonesia

Norwalk Virus and Norwalk-like viruses (NLVs) are reportedly responsible for 2.5-4.0% of nonbacterial acute gastroenteritis (NBAG) worldwide. To help clarify the impact of NLVs on NBAG in Indonesia, stool specimens from 102 patients, 74 with NBAG and 28 with BAG, were screened for the presence of NLVs, using a reverse transcription-polymerase chain reaction (RT-PCR) assay. The specimens were subtyped using prototype-specific oligonucleotide probes and were sequenced and compared with published NLV sequences. Of the 102 specimens examined, 31 (30%) were found to be positive for NLVs. Type-specific probe analysis of the RT-PCR products indicated that 31 isolates hybridized to UK1 (Taunton agent) and UK3/4 (Hawaii agent/Snow Mountain agent) prototype strains. The results of this study indicate that prototype strains of NV or NLVs co-circulate in Indonesia and contribute to the overall level of acute gastroenteritis throughout the region.

Human and swine hepatitis E viruses from Western India belong to different genotypes

BACKGROUND/AIMS

Hepatitis E is endemic in India. Earlier, we showed prevalence of IgG antibodies to hepatitis E virus (IgG-anti-HEV) in different animal species and inability of at least one human hepatitis E virus (HEV) strain to infect pigs. In the US where hepatitis E is not endemic in humans, zoonotic spread of HEV was suspected as swine and human HEV were closely related and cross-species infection was documented. The present study attempts to identify and partially characterize swine HEV from India.

METHODS

Serum samples from 284 pigs were screened for the presence of HEV-RNA (nested polymerase chain reaction; PCR) and IgG-anti-HEV (enzyme-linked immunosorbent assay; ELISA). PCR products (Open Reading Frame-2 region) were sequenced and subjected to phylogenetic analysis. Two sero-negative pigs were inoculated with swine HEV-positive serum pool.

RESULTS

ELISA and PCR positivity were 42.9 and 4.6%, respectively. All Indian swine HEV sequences clustered with genotype IV. Pigs could be experimentally infected with swine HEV.

CONCLUSIONS

Swine HEV circulates in Indian pigs. In contrast to US and Taiwan wherein both human and swine HEV isolates belong to same genotype, Indian human HEV isolates belong to genotype I whereas genotype IV circulates in swine. Though experimental infection with Indian swine HEV was possible, at least one human HEV strain could not infect pigs.

Detection of sporadic cases of hepatitis E virus (HEV) infection in China using immunoassays based on recombinant open reading frame 2 and 3 polypeptides from HEV genotype 4

We reported previously on the complete sequence of hepatitis E virus (HEV) genotype 4, isolated from patients with sporadic cases of acute HEV infection in China. At least eight HEV genotypes have now been described worldwide, and further isolates await classification. Current immunoassays for the detection of anti-HEV antibodies are based on polypeptides from genotypes 1 and 2 only and may be inadequate for the reliable detection of other genotypes. Because genotypes 1 and 4 predominate in China, we wished to investigate the antigenic reactivities of HEV genotype 4 proteins. Four overlapping regions of open reading frame 2 (ORF2) (FB5, amino acids [aa] 1 to 130; E4, aa 67 to 308; F2-2, aa 288 to 461; E5, aa 414 to 672) and the entire ORF3 product were expressed in Escherichia coli as fusion proteins. Enzyme immunoassays based on each of the five purified polypeptides were evaluated with sera from patients with sporadic cases of acute HEV infection. Individual immunoassays derived from HEV genotype 4 detected more cases of acute hepatitis E than a commercial assay. Some serum samples, which were positive for anti-HEV immunoglobulin G only by assays based on HEV genotype 4, were positive for HEV RNA by reverse transcription-PCR. Polypeptide FB5, from the N terminus of ORF2, had the greatest immunoreactivity with sera from patients with acute hepatitis E. These data indicate that the N terminus of ORF2 may provide epitopes which are highly reactive with acute-phase sera and that assays based on genotypes 1 and 2 alone may be inadequate for the detection of HEV infection in China, where sporadic cases of HEV infection are caused predominantly by HEV genotypes 4 and 1.

Hepatitis E virus sequences in swine related to sequences in humans, The Netherlands

Hepatitis E virus (HEV), a major cause of viral hepatitis in much of the developing world, has recently been detected in swine in North America and Asia, raising concern about potential for zoonotic transmission. To investigate if HEV is commonly present in swine in the Netherlands, pooled stool samples from 115 swine farms and nine individual pigs with diarrhea were assayed by reverse transcription-polymerase chain reaction (RT-PCR) amplification. HEV RNA was detected by RT-PCR and hybridization in 25 (22%) of the pooled specimens, but in none of the individual samples. RT-PCR amplification products of open reading frames 1 and 2 were sequenced, and the results were compared with published sequences of HEV genotypes from humans and swine. HEV strains from swine in the Netherlands were clustered in at least two groups, together with European and American isolates from swine and humans. Our data show that HEV in swine in the Netherlands are genetically closely related to HEV isolates from humans. Although zoonotic transmission has not been proven, these findings suggest that swine may be reservoir hosts of HEV.

HEV identified in serum from humans with acute hepatitis and in sewage of animal origin in Spain

BACKGROUND/AIMS

Hepatitis E virus (HEV) is an enterically transmitted pathogen that appears sporadically in non-endemic countries. We studied HEV as a causal agent of acute hepatitis cases in the Spanish population, and the role of pigs as an animal reservoir.

METHODS

The presence of HEV-RNA was analysed by nested polymerase chain reaction in 37 serum samples from patients with acute viral hepatitis, 48 porcine serum samples, 6 pig faecal samples and 12 slaughter-house sewage samples. Presence of antibodies was also tested in porcine sera.

RESULTS

HEV-RNA was found in 3 human serum samples from patients presenting IgG anti-HEV antibodies. Nucleotide sequence analysis identified 2 strains with 93.4% identity, phylogenetically most closely related to the Greece1 isolate, and more closely related to North American and other European strains than to those from endemic regions. HEV-RNA was also detected in slaughterhouse sewage mainly from pigs, presenting 92-94% nucleotide similarity compared to the strains detected in the human sera. Twenty-five per cent of the pigs tested presented IgG anti-HEV antibodies.

CONCLUSIONS

These data suggest that the HEV could be more widespread than previously thought, and present new evidence of the close relationship between HEV strains detected in pigs and those from acute hepatitis patients.

Hepatitis E

Hepatitis E, previously known as enterically transmitted non-A, non-B hepatitis, is an infectious viral disease with clinical and morphologic features of acute hepatitis. Its causative agent, hepatitis E virus, consists of small, 32- to 34-nm diameter, icosahedral, nonenveloped particles with a single-stranded, positive-sense, 7.5-kb RNA. The virus has two main geographically distinct strains, Asian and Mexican; recently, novel isolates from nonendemic areas and a genetically related swine HEV have been described. HEV is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in the Indian subcontinent, southeast and central Asia, the Middle East, parts of Africa, and Mexico. The virus is excreted in feces and is transmitted predominantly by fecal-oral route, usually through contaminated water. Person-to-person transmission is uncommon. Clinical attack rates are the highest among young adults. Recent evidence suggests that humans with subclinical HEV infection and animals may represent reservoirs of HEV; however, further data are needed. Diagnosis of hepatitis E is usually made by detection of specific IgM antibody, which disappears rapidly over a few months; IgG anti-HEV persists for at least a few years. Clinical illness is similar to other forms of acute viral hepatitis except in pregnant women, in whom illness is particularly severe with a high mortality rate. Subclinical and unapparent infections may occur; however, chronic infection is unknown. No specific treatment is yet available. Use of clean drinking water and proper sanitation is currently the most effective method of prevention. Passive immunization has not been proved to be effective, and recombinant vaccines for travelers to disease-endemic areas and for pregnant women currently are being developed.

93G, a novel sporadic strain of hepatitis E virus in South China isolated by cell culture

The nucleotide sequence of Hepatitis E virus (HEV) serous isolates (G-9 and G-20) from Guangzhou, South China, which has been reported previously, are divergent significantly from those of other reported HEV isolates. In order to investigate more extensively the Guangzhou isolate, the 93G strain was isolated from the faecal sample of the same individual as G-9 by A549 cell culture and identified immunologically and by molecular biological techniques. The results showed that strain 93G could be propagated in an A549 cell line causing cytopathic effects. The viral particles were aggregated by a specific antibody to HEV Chinese Xinjiang strain (87A) observed using immunoelectron microscopy and were similar morphologically to HEV from other sources. In this study, an indirect fluorescent antibody assay was first developed to examine HEV antigen in the infected cells, by immunofluorescence in the cytoplasm and on the surface membrane of the cells. The 58-kDa and 82-kDa native structural proteins of HEV were also identified in this study by Western blotting. The 93G genome showed high homology (93%) with G-9 previously reported but was also as divergent from the Burmese, Mexican, Chinese Xinjiang isolates and the recently reported US-1 isolate, as was G-9. The data presented indicate that 93G propagated in A549 cells, together with its related serum isolate G-9, represents another HEV strain circulating in China and is responsible for some sporadic hepatitis E infections.

Hepatitis E: an overview and recent advances in clinical and laboratory research

Hepatitis E virus (HEV) is a non-enveloped RNA (7.5 kb) virus that is responsible for large epidemics of acute hepatitis and a proportion of sporadic hepatitis cases in southeast and central Asia, the Middle East, parts of Africa and Mexico. Hepatitis E virus infection spreads by the faecal-oral route (usually through contaminated water) and presents after an incubation period of 8-10 weeks with a clinical illness resembling other forms of acute viral hepatitis. Clinical attack rates are the highest among young adults. Asymptomatic and anicteric infections are known to occur. Chronic HEV infection is not observed. Although the mortality rate is usually low (0.07-0.6%), the illness may be particularly severe among pregnant women, with mortality rates reaching as high as 25%. Recent isolation of a swine virus resembling human HEV has opened the possibility of zoonotic HEV infection. Studies of pathogenetic events in humans and experimental animals reveal that viral excretion begins approximately 1 week prior to the onset of illness and persists for nearly 2 weks; viraemia can be detected during the late phase of the incubation period. Immunoglobulin M antibody to HEV (anti-HEV) appears early during clinical illness but disappears rapidly over a few months. Immunoglobulin G anti-HEV appears a few days later and persists for at least a few years. There is no specific treatment available for hepatitis E virus infection. Ensuring a clean drinking water supply remains the best preventive strategy. Recombinant vaccines are being developed that may be particularly useful for travellers to disease-endemic areas and for pregnant women.

Antiserum generated by DNA vaccine binds to hepatitis E virus (HEV) as determined by PCR and immune electron microscopy (IEM): application for HEV detection by affinity-capture RT-PCR

Previously, we have described that injection of an expression vector containing hepatitis E virus (HEV) open reading frame 2 (HEV-ORF-2) generated a strong antibody response in mice. To characterize the reaction of this antiserum with native HEV and to evaluate its potential diagnostic application, we tested the antiserum's ability to bind HEV using immune electron microscope (IEM) and affinity-capture reverse transcription polymerase chain reaction (RT-PCR) amplification. Antiserum to ORF-2 aggregated HEV virions as seen by electron microscopy, providing direct evidence that ORF-2 encodes a structural protein. Antiserum also captured HEV for RT-PCR amplification. This antiserum bound HEV from diverse origins (Asia, Africa, Mexico) at virus concentrations found in patient fecal specimens and bile from inoculated non-human primates. The specificity of the affinity binding was demonstrated when pre-immune sera or sera collected from mice injected with control DNA vector (lacking the HEV ORF-2 gene) failed to bind HEV for RT-PCR amplification and IEM. Specific RT-PCR amplification was confirmed by restriction enzyme digestion of PCR products. The sensitivity of the binding was evaluated by RT-PCR amplification of serially diluted bile containing a genetically divergent HEV, Mexico'86. HEV was detected in a 10(-8) dilution of this bile. This is the first report that antibodies elicited by a DNA vaccine recognize native HEV. Our results indicate that ORF-2 encodes a structural protein and that antiserum to this protein enables simple, sensitive, and specific HEV detection by affinity-capture RT-PCR.

Genetic variability of hepatitis E virus within and between three epidemics in India

Hepatitis E virus (HEV) is an important cause of epidemic and sporadic acute viral hepatitis in many developing countries, including India. We evaluated the genetic variability within two regions (a 476-nt long ORF1 segment and a 304-nt long ORF2 segment) from specimens collected during three outbreaks in the cities of Karnal (1987), Yamunanagar (1989), and Meerut (1996), India, and from one patient, residing in Lucknow, India, who had a case of sporadic hepatitis (1996). Within an outbreak, sequences in the ORF1 and ORF2 regions were 99.3-100.0% identical. However, when strains were compared between outbreaks, identity in the ORF1 and ORF2 region was 97.1-99.2 and 96.4-100.0%, respectively. A comparison of these sequences to previously published Indian ORF1 and ORF2 sequences revealed even lower similarities, 95.2-98.5 and 95.1-98.7%, respectively. One patient in the Meerut outbreak had genomic sequences that differed substantially from the other patients affected during this outbreak and probably reflected a sporadic infection. The sporadic hepatitis E strain from Lucknow clustered with a previously described HEV strain from a patient with fulminant hepatic failure (FHF). Our data suggest that the ORF1 and ORF2 segments can be used to study the molecular epidemiology of HEV infection and indicate that much remains to be determined about the genetic variability of Indian HEV strains.

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.

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.

Cross-challenge studies in rhesus monkeys employing different Indian isolates of hepatitis E virus

The aim of this study was to determine if rhesus monkeys infected with one isolate of hepatitis E virus (HEV) were immune to subsequent challenge with other isolates of the virus. Three epidemic and one sporadic Indian HEV isolates were employed in the study. The interval between primary inoculation and challenge varied from 1 year and 6 months to 2 years and 9 months. Evidence of HEV infection was ascertained by rise in serum alanine transaminase (ALT) levels and/or seroconversion to antibodies to HEV (anti-HEV), and the presence of HEV-RNA in the bile or faeces of the infected monkeys. No evidence for multiplication of virus in monkeys challenged with different HEV isolates was obtained. These results show that immunity generated by one isolate of HEV protects against different isolates of hepatitis E virus.

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.

Successful passive and active immunization of cynomolgus monkeys against hepatitis E

Virtually full protection against hepatitis E and partial or complete protection against infection with hepatitis E virus (HEV) were achieved in passively or actively immunized cynomolgus monkeys. Hepatitis, viremia, and shedding of the virus in feces were detected in all nonimmunized animals that were challenged with HEV. HEV titers detected by reverse transcriptase PCR were higher in feces than in serum of nonimmunized animals. Anti-HEV antibody titers at the time of challenge ranged between 1:40 and 1:200 in animals passively immunized with convalescent plasma from a cynomolgus monkey previously infected with HEV and between 1:100 and 1:10,000 in animals actively immunized with a recombinant 55-kDa open reading frame 2 protein. The estimated 50% protective titer of passively acquired anti-HEV antibodies was 1:40. Although only one of four passively immunized animals showed histopathologic evidence of hepatitis, all four were infected after challenge; however, the titers of HEV in serum and feces were lower in the passively immunized animals than in the nonimmunized group. The actively immunized animals developed neither hepatitis nor viremia when challenged with HEV and virus was either not detected or was present in low titer in feces. The protective response was a function of the ELISA anti-HEV antibody titer at the time of challenge and the immunization schedule.

A new Chinese isolate of hepatitis E virus: comparison with strains recovered from different geographical regions

The full-length cDNA of a new Chinese strain (KS2-87) of Hepatitis E virus (HEV) has been constructed and sequenced. The 5' noncoding region of KS2-87 is 26 nucleotides in length, which is one nucleotide shorter than that of HEV (B1) (Burma) and 23 nucleotides longer than that of HEV (Mexico). Comparison of the nucleotide and amino acid sequences of KS2-87 with all other published HEV sequences showed that KS2-87 was closer to two other Chinese strains (CHT-88, CHT-87) and SAR-55 (Pakistan) than to HEV (B1) and HEV (B2) (Burma) or HEV (Mexico). Comparisons of partial sequences of genes encoding a nonstructural and a structural protein revealed the existence of genetically related groups of HEV within geographical regions, whereas larger nucleotide differences were seen among isolates that were more geographically and epidemiologically distant.

Infectivity titration of a prototype strain of hepatitis E virus in cynomolgus monkeys

The infectivity titer of a standard stock of the SAR-55 strain of hepatitis E virus (HEV) was determined in cynomolgus macaques (Macaca fascicularis) and the effect of dose on the course of the infection was examined by weekly monitoring of alanine aminotransferase (ALT) and anti-HEV levels. Antibody to HEV (anti-HEV) was measured with ELISAs based on ORF-2 recombinant antigens consisting of either a 55 kDa region expressed in insect cells or shorter regions expressed as fusion proteins in bacteria. The ELISA based on the 55 kDa antigen was generally more sensitive. The infectivity titer of SAR-55 was 10(6) cynomolgus 50% infectious doses per gram of feces. The infectivity titer corresponded to the HEV genome titer of the inoculum as determined by reverse transcriptase-polymerase chain reaction (RT-PCR). Anti-HEV IgM was detected in only a portion of the animals that had an anti-HEV IgG response. Biochemical evidence of hepatitis was most prominent in animals that were inoculated with the higher concentrations of virus and the incubation period to seroconversion was prolonged in animals that received the lower doses.