Evaluation of assays for antibody to hepatitis E virus by a serum panel. Hepatitis E Virus Antibody Serum Panel Evaluation Group

Acute sporadic hepatitis E in children: diagnostic relevance of specific immunoglobulin M and immunoglobulin G compared with nested reverse transcriptase PCR

This study was carried out to investigate the putative role played by the hepatitis E virus (HEV) in acute hepatic dysfunction in paediatric patients with acute non-A-C hepatitis. We also evaluated the diagnostic value for anti-HEV immunoglobulin G (IgG) and IgM enzyme-linked immunosorbent assays relative to nested reverse transcriptase PCR (RT-PCR) for HEV RNA detection. Sixty-four children with acute hepatitis were included in the study, in addition to sixteen healthy children with matched age and sex. All studied subjects were negative for IgM antibody to hepatitis A virus, hepatitis B virus surface antigen, IgM antibody to hepatitis B virus core antigen, antibody to hepatitis C virus, and by RT-PCR for HCV RNA. HEV RNA was detected in 23.4% of patients, followed by detection of specific IgM in 17.2% and IgG in 12.5% of patients. Two cases were positive for IgG in the control group (12.5%). The sensitivity, specificity and accuracy were 26.7%, 85.7%, 71.9%, respectively, for IgM, and 26.7%, 91.8%, and 76.6%, respectively, for IgG. From this study we can conclude that HEV is a frequent virus found sporadically with acute hepatitis among paediatric patients. We cannot depend upon serology alone for diagnosis; rather, both molecular and serological methods must be applied for accurate diagnosis.

Putative neutralization epitopes and broad cross-genotype neutralization of Hepatitis E virus confirmed by a quantitative cell-culture assay

Monolayers of Hep G2/C3A cells were inoculated with genotype 1 Hepatitis E virus (HEV) mixed with either anti-HEV or an appropriate control. After 5 or 6 days, cell monolayers were stained with anti-HEV and infected cells were identified by immunofluorescence microscopy and counted. Anti-HEV from vaccinated or infected rhesus monkeys neutralized the virus, as did mAbs that recognized epitopes on the C terminus of a recombinant vaccine protein. Antibodies were broadly cross-reactive, since convalescent serum from animals infected with any one of the four mammalian genotypes all neutralized the genotype 1 virus.

Hepatitis E antibody kinetics in Nepalese patients

A cohort of 62 Nepalese adults with acute hepatitis E was identified and total Ig as well as IgM levels to hepatitis E virus (HEV) capsid protein were determined using the Walter Reed Army Institute of Research (WRAIR) immunoassay. An antibody profile was constructed from serial serum specimens collected up to 14 months following the onset of illness. The decline in total Ig was rapid for the first 3 months. There followed a slow, sustained decline, but antibodies remained above the seropositive level of 20 WRAIR units. The decline of IgM was steeper than total Ig for the first 3 months, but IgM remained detectable after 14 months in 25% of cases. Study data contribute to an understanding of the pathophysiology of human hepatitis E and set an antibody response pattern to be targeted as a part of HEV vaccine development.

Seroprevalence of hepatitis E virus (HEV) antibody and the possible association with chronic liver disease: a case-control study in Albania

A case-control study involving 109 in-patients with chronic liver disease and 190 in-patients with no apparent liver disease was conducted to evaluate the seroprevalence of anti-HEV antibodies and the possible association with chronic liver disease. Among cases, the anti-HEV prevalence was 36.6% which increased significantly by age; among controls, the prevalence was 12.1% (P<0.05) and was similar among age groups <60 years. Among cases, aged >50 years (OR 4.0, 95% CI 1.4-11) and the presence of end stage liver disease (ESLD) (OR 4.3, 95% CI 1.4-12.8) were associated independently with anti-HEV positivity. The mean optical density, determined by anti-HEV immunoenzymatic test, was significantly higher among patients with ESLD, compared to the other patients. These results indicate that there is a high seroprevalence of anti-HEV in patients with chronic liver disease and a possible association between HEV infection and/or anti-HEV production and advanced stage chronic liver disease.

Hepatitis E antibody seroconversion without disease in highly endemic rural Egyptian communities

Hepatitis E virus (HEV) is enterically transmitted and causes self-limiting acute viral hepatitis (AVH) primarily in less developed countries. A prospective cohort study to assess incidence of, and risk factors for, seroconversion to HEV (anti-HEV) was conducted in two Egyptian villages with a 67.7% anti-HEV prevalence. Nine hundred and nineteen villagers who were initially anti-HEV-negative were followed for 10.7 months. Thirty-four (3.7%) had strong anti-HEV serologic responses at follow-up giving an estimated anti-HEV incidence of 41.6/1,000 person-years. No significant associations were found between anti-HEV seroincidence and demographic and socioeconomic factors, source of water, household plumbing or sanitation, hand and vegetable washing, ownership of animals, jaundice and many other variables. None of the seroconverting subjects gave a history compatible with AVH during the interval. We hypothesize that both zoonotic and anthroponotic transmission of avirulent (possibly genotype-3) HEV is occurring extensively in these rural villages. An alternative explanation for the lack of morbidity among anti-HEV incident cases could be initial asymptomatic infections occur during early childhood with subsequent antibody titer boosting without illness upon re-exposure to the virus.

Hepatitis E viruses in humans and animals

Hepatitis E virus (HEV) is an emerging pathogen belonging to a newly recognized family of RNA viruses (Hepeviridae). HEV is an important enterically transmitted human pathogen with a worldwide distribution. It can cause sporadic cases as well as large epidemics of acute hepatitis. Epidemics are primarily waterborne in areas where water supplies are contaminated with HEV of human origin. There is increasing evidence, however, that many animal species are infected with an antigenically similar virus. A recently isolated swine virus is the best candidate for causing a zoonotic form of hepatitis E. The virus is serologically cross-reactive with human HEV and genetically very similar, and the human and swine strains seem to be cross-infective. Very recent evidence has also shown that swine HEV, and possibly a deer strain of HEV, can be transmitted to humans by consumption of contaminated meat. In this review, we discuss the prevalence, pathogenicity, diagnosis and control of human HEV, swine HEV, the related avian HEV and HEV in other hosts and potential reservoirs.

A truncated ORF2 protein contains the most immunogenic site on ORF2: antibody responses to non-vaccine sequences following challenge of vaccinated and non-vaccinated macaques with hepatitis E virus

A candidate hepatitis E vaccine is composed of amino acids (aa) 112-607 of the 660-aa protein encoded by open reading frame 2 (ORF2) of hepatitis E virus (HEV). We have studied the antibody response to vaccine-associated epitopes and to epitopes excluded from the vaccine to determine if important epitopes were omitted from the vaccine and if antibody responses to these regions could be used to differentiate between infection and vaccination. ELISAs were developed based on genotype 1 ORF2 peptides, containing aa 112-607 (vaccine), 458-607 (minimum neutralization site), 1-111 (N-terminus) and 607-660 (C-terminus), as well as on ORF3 peptides, containing aa 1-123 (complete) and 91-123 (C-terminus). All naive macaques infected with HEV genotype 1, 2, 3 or 4 produced antibodies to all ORF2 peptides. Anti-ORF3 was detected in both monkeys infected with genotype 1 virus and in one of two infected with genotype 2 virus. These antibody responses were considerably weaker than those directed against the neutralization site. In contrast, vaccinated animals that were challenged with HEV had a diminished or absent immune response to the peptides not included in the vaccine. Thus, only minor epitopes were excluded from the vaccine; they had limited utility for distinguishing between vaccination and infection.

Age-specific antibody to hepatitis E virus has remained constant during the past 20 years in Japan

We investigated the presence of antibodies to hepatitis E virus (anti-HEV) and hepatitis A virus (anti-HAV) by enzyme immunoassays in sera from 1015 individuals collected in 1974, 1984 and 1994. Age-specific profiles of anti-HEV remained unchanged with a peak at 40-49 years, while those of anti-HAV started to increase in individuals aged 20-29 years in 1974, 30-39 years in 1984 and 40-49 years in 1994. These results suggest that a silent HEV infection has been taking place in the last 20 years or so in Japan, while HAV infection has been terminated at least since 1974.

Prevalence of antibodies to hepatitis E virus in residents of a district in Havana, Cuba

A seroepidemiological study of hepatitis E virus (HEV) infection was conducted in a district of Havana, where hepatitis A virus (HAV) is considered endemic. The levels of anti-HEV antibodies were evaluated by enzyme-linked immunosorbent assay (ELISA) based on the recombinant protein GST-ORF2.1. Anti-HEV antibodies were detected in 11 of 209 (5.3%) of serum samples, compared to 71.3% for anti-HAV antibodies. No risk factors reported previously for HEV infection showed a significant association with the presence of anti-HEV antibodies, whereas anti-HAV antibodies were strongly associated with increasing age. HEV may be considered endemic in this area and is likely to have a significant clinical impact.

An ELISA for putative neutralizing antibodies to hepatitis E virus detects antibodies to genotypes 1, 2, 3, and 4

Two monoclonal antibodies that neutralize hepatitis E virus (HEV) were used to identify a subregion of ORF2 capsid protein spanning amino acids 459-607 as the shortest peptide to form the corresponding neutralization epitopes. An enzyme-linked immunosorbent assay (ELISA) based on a purified recombinant protein covering amino acids 458-607 in ORF2 of the Sar-55 strain (genotype 1) efficiently detected anti-HEV in non-human primates which had been experimentally infected with the four known mammalian genotypes of HEV, respectively. However, anti-HEV in these animals did not react with a shorter ORF2 peptide spanning amino acids 475-607. The ELISA was highly specific and sensitive when human or non-human primate sera were tested in parallel with a previously established ELISA based on amino acids 112-607 in ORF2. The antibody titer to peptides 458-607 in two ORF2-vaccinated rhesus monkeys which had different HEV challenge outcomes differed at the time of challenge. Since the ELISA appeared to be specific for neutralizing antibodies against HEV, it should be especially useful for quantifying the humoral immune response in hepatitis E vaccine trials.

Hepatitis E is a cause of unexplained hepatitis in The Netherlands

BACKGROUND

Hepatitis E virus (HEV) is the major etiologic agent of enterically transmitted viral hepatitis in much of the developing world. Evidence provided in recent years shows that HEV is also prevalent in very low numbers in non-endemic countries. Recently, a cluster of three patients with acute hepatitis E but no history of travel to endemic countries was discovered in the geographical area provided with service by the Public Health Laboratory Groningen and Drenthe, The Netherlands.

OBJECTIVE

This lead to the question whether hepatitis E is a cause of unexplained hepatitis in this district.

STUDY DESIGN

The prevalence of anti-HEV IgG and IgM among 209 patients with clinical signs of hepatitis, negative test for hepatitis A-C, no history of foreign travel and no other cause of hepatocellular damage was compared with a matched control group of 209 individuals.

RESULTS

We found a significant difference in seroprevalence between the two groups for IgG anti-HEV as determined with the Abbot HEV EIA (6.2% versus 0.5%); however this difference could not be confirmed with the Genelabs Diagnostics HEV IgG ELISA (6.7% versus 3.8%). For confirmed cases of IgM anti-HEV we also detected a significant difference between the two groups (3.3% versus 0.5%). Remarkably, the combination of IgG and IgM anti-HEV was only found among hepatitis patients.

CONCLUSION

This study provides evidence of locally acquired hepatitis E in The Netherlands. Therefore, in cases of unexplained acute hepatitis, the diagnosis of hepatitis E should be considered even in the absence of foreign travel.

Hepatitis E in the south west of France in individuals who have never visited an endemic area

A total of 431 consecutive patients from the Midi Pyrenees area with acute hepatitis with unknown etiology in 2001-2002 were tested for the presence of immunoglobulin G-class (IgG) anti-hepatitis E virus (HEV) antibodies. Forty-six (10.7%) had anti-HEV IgG, and the results were questionable for a further 17 (3.9%). Real time PCR based on TaqMan detection was used to identify HEV genome fragments in the serum of patients with positive or questionable anti-HEV serology. HEV RNA was found in 25.4% of cases. All amplification products were sequenced and analyzed. Phylogenetic analysis revealed that all the strains were genotype 3. In conclusion, virological and epidemiological data indicate that genotype 3 viruses are circulating in the south west part of France (Midi-Pyrenees) in patients with acute hepatitis and who have not visited recently areas in which HEV is endemic.

Sporadic cases of acute autochthonous hepatitis E in Spain

BACKGROUND/AIMS

In industrialized countries hepatitis E virus (HEV) infection is rare and its diagnosis is difficult because the utility of available tests is not well established.

METHODS

We studied the presence of acute HEV infection markers in a cluster of 11 cases of acute hepatitis with IgG anti-HEV antibodies.

RESULTS

Three cases were confirmed as acute hepatitis E and 8 as presumptive hepatitis E, two as a past HEV infection and one could not be determined. Three different HEV strains were identified in serum from 3 patients. Two strains belonged to genotype 3, the predominant genotype found in local urban sewage and the other strain belonged to genotype 1 and was considered an imported strain.

CONCLUSIONS

Our findings demonstrate the presence of some autochthonous, sporadic acute hepatitis E cases as well as an imported case in our area and the transitory nature of virological and serological markers for HEV.

Detection and quantitation of hepatitis E virus in human faeces by real-time quantitative PCR

Hepatitis E Virus (HEV) is the causative agent of an acute and self-limited form of hepatitis. The virus is transmitted by the faecal-oral route and is a major cause of viral hepatitis in much of the developing world where it causes sporadic infections and large-scale epidemics. A simple and rapid protocol for the measurement of HEV faecal shedding by a real-time polymerase chain reaction (PCR) with the SYBR Green method on a LightCycler instrument, is described. After only 3h the real-time quantitative PCR method detected 10 molecules of HEV cDNA fragment per reaction tube and showed a high linear dynamic range of quantitation (10-10(6) molecules of cDNA/reaction) with a good correlation (r = -1.00). Its specificity was confirmed by assay in human faecal samples.

Immunohistochemistry for the detection of swine hepatitis E virus in the liver

Swine hepatitis E virus (HEV) antigen was detected immunohistochemically in formalin-fixed, paraffin-embedded hepatic tissue from 30 naturally infected pigs. Thirty pigs from 30 different herds were selected on the basis of positive results for reverse transcription-polymerase chain reaction. Positive cells typically exhibited a red reaction product in the cytoplasm without any observable background staining. Swine HEV antigen was consistently detected in liver from all 30 pigs tested. A strong immunohistochemical signal was seen within a variable number of hepatocytes in multifocal lobules. The signal involved the majority of hepatocytes diffusely or was confined to foci of liver cells. Positive immunohistochemical signals were also detected in small and large intestine, lymph node, tonsil, spleen, and kidney. The immunohistochemistry technique developed in this study proved useful for the detection of swine HEV in formalin-fixed, paraffin-embedded tissues taken from naturally infected pigs and may be a valuable tool in studying the pathogenesis of swine HEV infection.

Evaluation of antibody-based and nucleic acid-based assays for diagnosis of hepatitis E virus infection in a rhesus monkey model

We have evaluated four hepatitis E virus (HEV) specific antibody assays, using sequential samples taken from 86 rhesus monkeys at intervals for up to 86 weeks after they had been infected with different doses of HEV. The animals are a common experimental model of hepatitis E. The large collection of sequential samples used avoids uncertainties encountered in previous studies regarding the precise infection status of study subjects and minimizes bias due to the individuality of response to infection. One assay (YES IgG) was produced with synthetic peptides; the others (E2 IgM, E2 IgG, and GL IgG) were produced with recombinant antigens. The results were compared with the viral RNA contents of the serum and stool samples and the occurrence of these virological and immunological markers in the course of the infection was temporally related to the development of hepatitis. Diagnostic utility of the markers was assessed according to their response rates and prevalence at different times in the course of infection. All the animals produced E2 IgG and developed viremia and all but one also produced E2 IgM and excreted the virus in stool, whereas response rates for the other antibodies were lower and decreased with virus dose. Hepatitis occurred over a period of 4 weeks between 3 and 7 weeks after infection. Virological activity occurred mainly during the incubation period and the prevalence of viral markers declined rapidly after the onset of hepatitis. Production of the E2 antibodies immediately preceded the onset of hepatitis, and this was followed about one week later by production of the other antibodies. Seroprevalence E2 IgM reached a peak value 3 weeks after the onset of hepatitis, whereas seroprevalence of GL IgG and YES IgG peaked after the disease had subsided. E2 IgG persisted in all animals for the entire duration of the experiment of up to 86 weeks and possibly beyond and, thus, can serve as a useful epidemiological marker of HEV infection.

Hepatitis E Vaccines

Hepatitis E accounts for the major part of enterally transmitted non-A, non-B hepatitis worldwide. Its agent, the hepatitis E virus (HEV), is a small, single-stranded RNA virus. Only one serotype of HEV is recognised. Infection results in protective immunity with long-lived neutralising antibodies. In developing countries with poor sanitary conditions and high population density, hepatitis E causes water-borne epidemics with substantial mortality rates in pregnant women. In addition, more than 50% of cases of acute hepatic failure and sporadic acute hepatitis are due to hepatitis E. The overall prevalence rates of antibodies to the HEV in populations native to these areas rarely exceed 25%. Hence, many individuals remain susceptible to hepatitis E infection, making hepatitis E an important public health concern. In this context, the development of an HEV vaccine is warranted. Because HEV does not grow adequately in cell cultures the development of a vaccine based on inactivated or attenuated whole-virus particles is not feasible. HEV vaccines currently under study are based on recombinant proteins derived from immunogenic parts of the HEV capsid gene. Other approaches such as DNA-based vaccines or transgenic tomatoes have also been developed. Several recombinant protein-based vaccines elicited neutralising antibodies and protective immunity in vaccinated non-human primates. One such vaccine has passed phase I trial and is currently under further evaluation in field trials. Even so, several questions remain to be answered before vaccination programmes could be implemented.

Detection of immunoglobulin M antibodies to hepatitis E virus by class capture enzyme immunoassay

The measurement of antibodies to hepatitis E virus (anti-HEV) has been essential for understanding the epidemiology of hepatitis E. Studies to determine the prevalence of HEV infections require a reliable serologic assay that is sensitive and specific. It is also important to distinguish the acute from the convalescent phase of an infection; this usually requires the detection of the immunoglobulin M (IgM) class of antibody. Few enzyme immunoassays (EIAs) that measure IgM anti-HEV have been described, and most have utilized the sandwich method. The present study describes an EIA that detects IgM anti-HEV by antibody class capture methodology. The assay was validated by using serum and/or plasma panels from experimentally infected nonhuman primates. It was used to demonstrate an anamnestic response and the reappearance of IgM anti-HEV in a chimpanzee experimentally challenged with HEV at two different times 45 months apart. The class capture method was more sensitive than the sandwich EIA when used to test clinical samples from two hepatitis E epidemics in Pakistan; it also had the advantage of distinguishing IgM anti-HEV in the presence of high titers of IgG anti-HEV.

Hepatitis E virus

Hepatitis E virus (HEV) is a positive-stranded RNA virus with a 7.2 kb genome that is capped and polyadenylated. The virus is currently unclassified: the organisation of the genome resembles that of the Caliciviridae but sequence analyses suggest it is more closely related to the Togaviridae. Hepatitis E virus is an enterically transmitted virus that causes both epidemics and sporadic cases of acute hepatitis in many countries of Asia and Africa but only rarely causes disease in more industrialised countries. Initially the virus was believed to have a limited geographical distribution. However, serological studies suggest that HEV may be endemic also in the United States and Europe even though it infrequently causes overt disease in these countries. Many different animal species worldwide recently have been shown to have antibodies to HEV suggesting that hepatitis E may be zoonotic. Although two related strains have been experimentally transmitted between species, direct transmission from an animal to a human has not been documented. There are four currently recognised genotypes and two of the four contain viruses isolated from swine as well as from humans. Regardless of country of origin or genotype of the virus, most, if not all, strains belong to a single serotype. A promising recombinant vaccine candidate comprised of a truncated capsid protein is currently under evaluation in Nepal.

Hepatitis E virus epidemiology in industrialized countries

To determine the prevalence of Hepatitis E virus (HEV) in industrialized nations, we analyzed the excretion of HEV strains by the populations of Spain, France, Greece, Sweden, and the United States. Twenty of 46 (43.5%) urban sewage samples collected in Barcelona from 1994 to 2002 tested positive for HEV. We identified 15 HEV strains, which were similar to two HEV isolates previously described in Barcelona in clinical samples and to strains from diverse geographic HEV-nonendemic areas. We also identified two HEV strains in sewage samples from Washington, D.C., and Nancy, France; these samples were also positive for Hepatitis A virus. In addition, we studied the role of pigs as a reservoir for HEV and identified one new swine HEV strain. Our results suggest that HEV may be more prevalent than previously considered in industrialized countries and that variants of the virus circulate simultaneously in one region.

Hepatitis E virus (HEV) capsid antigens derived from viruses of human and swine origin are equally efficient for detecting anti-HEV by enzyme immunoassay

The recombinant truncated ORF2 (capsid) antigen derived from the Meng strain of swine hepatitis E virus (HEV) differs from that of the Sar-55 strain of human HEV by approximately 5% at the amino acid level. Serial serum samples from two chimpanzees and six rhesus monkeys experimentally infected with HEV were tested with one enzyme immunoassay (EIA) based on the Sar-55 antigen and with a second EIA based on the Meng antigen. We obtained 98% agreement (kappa = 0.952) by direct comparison. The virtually identical results obtained with these antigens in detecting seroconversion following infection with HEV suggests that they were reacting with antibodies that detect the same or very similar epitopes of HEV. We then tested human and swine serum samples for anti-HEV in EIAs that utilized one or the other of the two ORF2 antigens and showed that these results were also virtually identical. The specimens tested included swine sera from the United States, Canada, China, Korea, and Thailand and sera from veterinarians, U.S. and non-U.S. volunteer blood donors, and U.S. and non-U.S. animal handlers. We tested 792 swine sera and obtained 93% agreement (kappa = 0.839). We similarly tested 882 human sera and obtained 99% agreement (kappa = 0.938). Moreover, we found virtually no difference in the levels of prevalence of anti-HEV as measured by the two tests, again suggesting that the antigens derived from human and swine HEV contain the same immunodominant epitopes.

A new enzyme immunoassay for the detection of antibody to hepatitis E virus

BACKGROUND AND AIM

The purpose of the present study was to develop enzyme immunoassay (EIA) for the detection of IgG anti-hepatitis E virus (HEV) activity using two new recombinant proteins as antigenic targets, and to evaluate these EIA with the aid of statistical methods.

METHODS

Two proteins, a mosaic protein and pB166 containing region 452-617 aa of the ORF2 of the HEV Burma strain, were used to develop the new HEV EIA. This EIA was evaluated using several panels of serum specimens obtained from: (i) acutely HEV-infected patients; (ii) patients with non-A, non-C hepatitis; (iii) normal blood donors (NBD) from non-endemic countries; and (iv) experimentally infected chimpanzees.

RESULTS

A new HEV EIA was developed using two new recombinant proteins. This assay was able to detect anti-HEV activity in all specimens from acutely HEV-infected patients. When NBD were tested, more than 15% of specimens were found to be IgG anti-HEV positive. All NBD anti-HEV-positive specimens were tested with overlapping synthetic peptides spanning the entire HEV ORF2-encoded protein. More than 90% of the anti-HEV-positive NBD specimens immunoreacted with an average of 15 synthetic peptides derived from different regions of the HEV ORF2 protein. These data suggest that the HEV EIA is at least 90% specific in detecting remote HEV infections.

CONCLUSION

The new HEV EIA developed in the present study is a highly specific diagnostic assay for the detection of anti-HEV activity in serum specimens obtained from different epidemiologic settings.

Comparison of clinical manifestations and epidemiology between acute hepatitis A and acute hepatitis E in Taiwan

BACKGROUND AND AIMS

Acute hepatitis A (AHA) and acute hepatitis E (AHE) are endemic in developing countries. They share similar transmission routes and clinical manifestations. To compare the differences in epidemiology, clinical picture and prognosis between these two enterically transmitted forms of hepatitis, we enrolled 58 consecutive AHA or AHE patients (42 men and 16 women; age 16-74 years) from January 1990 to April 2001.

RESULTS

In comparison to AHA, patients with AHE were older (56.2 +/- 15.4 vs 30.7 +/- 11.0 years, P < 0.0001), and more frequently had a history of travel within 3 months before onset of illness (68.8 vs 30.8%, P = 0.003). In laboratory data, AHE patients had lower serum levels of albumin (3.4 +/- 0.4 vs 3.8 +/- 0.4 g/dL, P = 0.016), alanine aminotransferase (1912 +/- 1587 vs 3023 +/- 1959 U/L, P = 0.015), and aspartate aminotransferase (1681 +/- 1444 vs 2374 +/- 2869 U/L, P = 0.24), but a higher serum bilirubin level (17.8 +/- 12.3 vs 8.7 +/- 5.0 mg/dL, P = 0.003) than AHA patients. Moreover, five (15.6%) patients with AHE compared with none with AHA died. This probably indicates that AHE had a worse outcome than AHA in our study. In analysis of epidemiological factors, older age of onset of illness was the only significant predicator of outcome. From an epidemiological survey, most AHE patients were imported while most AHA patients were not. However, native AHE and imported AHA did occur in Taiwan.

CONCLUSION

Patients with AHE in Taiwan had older age of onset, more records of traveling history, and poorer clinical manifestations than those with AHA, and age seemed to be the most important factor to influence outcome.

New perspectives on hepatitis E

The infectious agent causing epidemic non-A, non-B hepatitis was identified in 1983 from a human challenge experiment. The novel hepatitis E virus (HEV) subsequently was cloned in 1990 and the genome sequenced. HEV transmission is highly endemic in Asia, the Middle East, and Africa. Fecal contamination of drinking water is the most common mode of spread. Although usually asymptomatic, HEV infection can cause fulminant hepatitis. Recent studies indicate that hepatitis E may be a zoonotic disease, with pigs and possibly rats serving as reservoirs for human infection. A recombinant HEV vaccine is currently in phase III clinical trials. The characterization of the major types of viral hepatitis during the last 20 years illustrates how modern genetic technology has revolutionized research in infectious diseases. Within less than two decades of the discovery of HEV, its epidemiology has been described, serologic tests have been developed, and a candidate vaccine has been evaluated in clinical trials.

Hepatitis E: an overview

The hepatitis E virus (HEV) is a non-enveloped, positive-sense, single-stranded RNA virus with icosahedral symmetry. Although it is related to the alpha-virus superfamily, the HEV is classified as a separate Hepatitis E-like viruses genus. Infection in humans occurs in sporadic and epidemic forms and can cause an acute, self-limited, icteric hepatitis. Recent studies indicate the existence of a reservoir in animals.

Hepatitis C-Z: recent advances

In this review, recently identified hepatitis viruses (hepatitis C, hepatitis D, hepatitis E, hepatitis F, hepatitis G, transfusion transmissible virus) are described, and the implications for paediatric liver disease discussed.

Quantitation of immunoglobulin to hepatitis E virus by enzyme immunoassay

We developed a quantitative enzyme immunoassay (EIA) for antibody to hepatitis E virus (HEV) by using truncated HEV capsid protein expressed in the baculovirus system to improve seroepidemiology, to contribute to hepatitis E diagnosis, and to enable vaccine evaluations. Five antigen lots were characterized; we used a reference antiserum to standardize antigen potency. We defined Walter Reed antibody units (WR U) with a reference antiserum by using the four-parameter logistic model, established other reference pools as assay standards, and determined the conversion factor: 1 WR U/ml = 0.125 World Health Organization unit (WHO U) per ml. The EIA performed consistently; median intra- and inter-test coefficients of variation were 9 and 12%, respectively. The accurate minimum detection limit with serum diluted 1:1,000 was 5.6 WR U/ml; the test could detect reliably a fourfold antibody change. In six people followed from health to onset of hepatitis E, the geometric mean antibody level rose from 7.1 WR U/ml to 1,924.6 WR U/ml. We used the presence of 56- and 180-kDa bands by Western blotting as a confirmatory test and to define true-negative and -positive serum specimens. A receiver-operating characteristics plot identified 30 WR U/ml as an optimum cut-point (sensitivity, 86%; specificity, 89%). The EIA detected antibody more sensitively than a commercially available test. The EIA was transferred to another laboratory, where four operators matched reference laboratory results for a panel of unknowns. Quantitation of antibody to HEV and confirmation of its specificity by Western blotting make HEV serology more meaningful.

Hepatitis E virus infection in haemodialysis patients: a case-control study in Saudi Arabia

To determine the prevalence of antibody to hepatitis E virus (IgM anti-HEV) among haemodialysis patients and evaluate whether there was an increased risk of infection and exposure to HEV in an area of endemic viral hepatitis, serum samples obtained from 83 Saudi patients on chronic haemodialysis (group 1), 400 sex- and age-matched healthy subjects (group 2) and hospital patients (group 3) were tested for the IgM anti-HEV and IgG anti-HEV. The prevalence of anti-HEV among the patients (group 1) and the healthy controls were 4.8% and 0.3%, respectively. The difference (4.5%) was statistically significant, with a calculated odds ratio (OR) of 20.2 (95% CI = 2.1-481.0; P = 0.0002). In contrast, there was no significant difference in the prevalence rates of IgG anti-HEV (7.2% vs 10.8%) in both groups. In nonhaemodialysis patients with various diseases, 1.6% (1 of 64) of outpatients (group 3) and none (0 of 113) of the ward patients (group 4) was positive for IgM anti-HEV. Thus, the prevalence (4 of 83) of IgM anti-HEV in the haemodialysis patients was significantly higher than the rate (1 of 177) in the combined groups of nonhaemodialysis hospital patients. The calculated OR was 8.9 (95% CI = 0.92, 212.8; P = 0.037). IgM antibody to hepatitis A virus (IgM anti-HAV) was not detected in any subjects, and the prevalence rates of IgG anti-HAV were similar in the patients and controls (72.3% and 74.3% in groups 1 and 2, respectively, and 75.7% combined groups 3 and 4). The study indicated a significantly higher risk of acute HEV infection among patients on chronic haemodialysis. It is possible that these were nosocomial infections acquired by person-to-person transmission in the haemodialysis unit. However, it is more probable that the infections were community acquired, a conclusion supported albeit indirectly by the lack of a significant difference between the prevalence in haemodialysis patients (4.8%) and outpatients (1.6%). In areas of endemic HEV, appropriate strategies should be adopted to prevent the risk of HEV among haemodialysis patients.

Report of a collaborative study to assess the suitability of a reference reagent for antibodies to hepatitis E virus

Several commercial and "in-house" assays have been developed for the detection of antibodies to hepatitis E virus, a major causative agent of enterically transmitted non-A non-B hepatitis. As these kits contain a variety of synthetic peptides or recombinant proteins, greater standardisation is required. A collaborative study was therefore carried out to assess the suitability of a freeze dried preparation designated 95/584 to serve as a reference reagent for hepatitis E virus serum IgG. Preparation 95/584, which is a serum from a previously infected individual, was assayed along with four coded samples, one of which D, was a coded duplicate of 95/584, and three individual sera, coded A, B and C. These preparations were sent to seven laboratories in five countries who tested them in eight different enzyme immunoassays. In most laboratories the coded duplicate gave a mean potency of within 20% of the candidate reference reagent despite the wide range of assays used. However, the potencies of the coded samples which were from different individuals gave somewhat variable potencies relative to the candidate reference reagent. This is not surprising as each sample will have varying proportions of antibodies against individual viral proteins and result in the variation in results observed. Nevertheless, this material will be of use in the standardisation of diagnostic tests for use in sero-prevalence studies and for assessing immunity. Preparation 95/584 was found to be suitable to serve as a reference reagent for hepatitis E serum IgG and has been established as an interim Reference Reagent for Human anti-hepatitis E serum. Each ampoule contains 50 Units per ampoule.

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.

High prevalence of hepatitis E antibodies among Danish prisoners and drug users

Injecting drug users and prisoners have high prevalences of antibodies to hepatitis A-C. The aim of this study was to determine the prevalence of antibodies to hepatitis E virus (anti-HEV) in two Danish high-risk populations and correlate anti-HEV with risk factors for transmission. Three hundred thirty male prisoners and 137 patients at a drug treatment center were tested for anti-HEV with an in-house enzyme-linked immunoassay (EIA) utilizing antigens derived from open reading frame 2 (ORF2). This was compared with a commercial test with antigens derived from ORF2 and ORF3 (Abbott HEV EIA). In addition the samples were tested for antibodies against hepatitis A-C viruses, human immunodeficiency virus (HIV) 1 and 2, human T lymphotropic virus (HTLV) I and II and herpes simplex virus type 2 (HSV2). The participants were interviewed about risk factors for transmission. The anti-HEV prevalence was 16.9% (95% CI 14-21) for the in-house assay compared to 4.1% (95% CI 2.5-6.3) with the commercial assay. The correlation between the two assays was low (87% overall agreement; kappa value 0.32). One sample was strongly anti-HEV IgM positive, suggesting recent HEV infection inside Denmark. The presence of anti-HEV was associated significantly with anti-HAV among prisoners and increased with age in both groups. In contrast, associations were not found with injecting drug use or sexual risk factors. With the commercial assay an increased prevalence of anti-HEV was found among participants who had spent more than 5 years outside Northern Europe. In conclusion, anti-HEV was highly prevalent among Danish prisoners and drug users but not related to risk factors for blood-borne or sexual transmission.

Recombinant hepatitis E virus genomes infectious for primates: importance of capping and discovery of a cis-reactive element

Hepatitis E virus recombinant genomes transcribed in vitro from two cDNA clones differing by two nucleotides were infectious for chimpanzees. However, one cDNA clone encoded a virus that was attenuated for chimpanzees and unable to infect rhesus monkeys. The second cDNA clone encoded a virus that infected both chimpanzees and rhesus monkeys and caused acute hepatitis in both. One mutation differentiating the two clones identified a cis-reactive element that appeared to overlap the 3' end of the capsid gene and part of the 3' noncoding region. Capping of the RNA transcripts was essential for infectivity.

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.

Prevalence of hepatitis E virus antibodies in Canadian swine herds and identification of a novel variant of swine hepatitis E virus

Swine hepatitis E virus is a newly identified potentially zoonotic virus from pigs of particular concern for possible direct transmission to a human xenotransplant recipient by organ transplantation. In the present study, prevalence of serum antibodies to hepatitis E virus was examined in Canadian swine herds. A total of 998 serum samples collected from 6-month-old healthy slaughter hogs were examined by enzyme immunoassay and Western blot analysis for antibodies to the recombinant open reading frame 3 (ORF3) protein of hepatitis E virus expressed in Escherichia coli. These samples represented more than 80 different swine production units from five major swine-producing provinces across Canada. From this study, 594 samples (59.4%) were found to be positive for hepatitis E virus antibody. The seroprevalence was higher in Quebec (88.8%) and Ontario (80.1%) than in Alberta and Saskatchewan (38.3%). By PCR using a pair of oligonucleotide primers deduced from the ORF2 sequence of human hepatitis E virus, a specific hepatitis E virus sequence was recovered from feces of pigs. The nucleotide sequence identity between the U.S. swine hepatitis E virus and the Canadian isolate (SK3) was only 85.8%, suggesting that genotypic variations may exist in swine hepatitis E virus in North America. Among 165 serum samples collected from humans in Saskatchewan, 2.4% were found to be positive for antibodies to the hepatitis E virus ORF3 protein. Our data indicate that hepatitis E virus is highly prevalent in commercial swine populations in Canada and support the suggestion that the swine hepatitis E virus may be an important zoonotic agent for humans.

Recombinant vaccines for hepatitis E

Hepatitis E virus causes epidemics of acute hepatitis in many developing countries. It infrequently causes disease in developed countries, but avirulent strains might circulate. Some evidence suggests that hepatitis E might be a zoonosis. There is probably only a single serotype. A candidate vaccine consisting of baculovirus-expressed recombinant capsid protein protected macaques from hepatitis E--it passed phase I clinical trials and is currently scheduled for phase II/III clinical trials.

Evidence of extrahepatic sites of replication of the hepatitis E virus in a swine model

Hepatitis E virus (HEV) is the major cause of enterically transmitted non-A, non-B hepatitis in many developing countries and is also endemic in many industrialized countries. Due to the lack of an effective cell culture system and a practical animal model, the mechanisms of HEV pathogenesis and replication are poorly understood. Our recent identification of swine HEV from pigs affords us an opportunity to systematically study HEV replication and pathogenesis in a swine model. In an early study, we experimentally infected specific-pathogen-free pigs with two strains of HEV: swine HEV and the US-2 strain of human HEV. Eighteen pigs (group 1) were inoculated intravenously with swine HEV, 19 pigs (group 2) were inoculated with the US-2 strain of human HEV, and 17 pigs (group 3) were used as uninoculated controls. The clinical and pathological findings have been previously reported. In this expanded study, we aim to identify the potential extrahepatic sites of HEV replication using the swine model. Two pigs from each group were necropsied at 3, 7, 14, 20, 27, and 55 days postinoculation (DPI). Thirteen different types of tissues and organs were collected from each necropsied animal. Reverse transcriptase PCR (RT-PCR) was used to detect the presence of positive-strand HEV RNA in each tissue collected during necropsy at different DPI. A negative-strand-specific RT-PCR was standardized and used to detect the replicative, negative strand of HEV RNA from tissues that tested positive for the positive-strand RNA. As expected, positive-strand HEV RNA was detected in almost every type of tissue at some time point during the viremic period between 3 and 27 DPI. Positive-strand HEV RNA was still detectable in some tissues in the absence of serum HEV RNA from both swine HEV- and human HEV-inoculated pigs. However, replicative, negative-strand HEV RNA was detected primarily in the small intestines, lymph nodes, colons, and livers. Our results indicate that HEV replicates in tissues other than the liver. The data from this study may have important implications for HEV pathogenesis, xenotransplantation, and the development of an in vitro cell culture system for HEV.

Empty virus-like particle-based enzyme-linked immunosorbent assay for antibodies to hepatitis E virus

Hepatitis E, an enterically transmitted non-A, non-B hepatitis, is a serious viral infection that occasionally causes large epidemics in developing countries. In developed countries, the disease only appears sporadically due to the transmission routes, and it is considered to be less important. The hepatitis E virus (HEV) cannot grow in cultured cells and no reliable assay system has ever been developed. In addition, the present diagnostic are not perfect, and actual rates of HEV infection may be underestimated. Highly purified empty virus-like particles (VLPs) of HEV have been produced by the use of a recombinant baculovirus vector in insect cells. Using these VLPs as an antigen, an enzyme-linked immunosorbent assay (ELISA) for antibodies to HEV was developed. A panel of 164 sera that were randomized and coded, and sera collected periodically from three patients with hepatitis E were used for the evaluation. The sensitivity of the assay was shown to be equal to or better than that obtained in previous research that used the same serum panel. The ELISA demonstrated that the serum IgM level of the patients was highest at the onset of the clinical illness and then rapidly decreased. In contrast, a high level of circulating IgG antibody titers lasted for more than 4 years. In Japan, a non-endemic country, the prevalence of the IgG class antibody to HEV in healthy individuals was found to range from 1.9% to 14.1%, depending on the geographical area. Only one out of 900 (0.1%) serum samples was IgM-positive. The IgM class antibody to HEV was detected in 10.8% of non-A, non-B, and non-C acute hepatitis patients in northeast China, whereas none of the patients in Korea had the IgM antibody. The ELISA utilizing the VLPs is sensitive and specific in its detection of the IgM and IgG antibodies to HEV. The ELISA is therefore useful for diagnosing HEV infection and for seroepidemiological study of hepatitis E.

Diagnosis and monitoring of hepatic injury. II. Recommendations for use of laboratory tests in screening, diagnosis, and monitoring

Purpose: To review information on the use of laboratory tests in screening, diagnosis, and monitoring of acute and chronic hepatic injury.

Data Sources and Study Selection: A MEDLINE search was performed for key words related to hepatic diseases, including acute hepatitis, chronic hepatitis, alcoholic hepatitis, cirrhosis, hepatocellular carcinoma, and etiologic causes. Abstracts were reviewed, and articles discussing use of laboratory tests selected for review. Additional articles were selected from the references.

Guideline Preparation and Review: Drafts of the guidelines were posted on the Internet, presented at the AACC Annual Meeting in 1999, and reviewed by experts. Areas requiring further amplification or literature review were identified for further analysis. Specific recommendations were made based on analysis of published data and evaluated for strength of evidence and clinical impact.

Recommendations: Although many specific recommendations are made in the guidelines, only some summary recommendations are listed here. In acute hepatic injury, prothrombin time and, to a lesser extent, total bilirubin are the best indicators of severity of disease. Although ALT is useful for detecting acute and chronic hepatic injury, it is not related to severity of acute hepatic injury and only weakly related to severity of chronic hepatic injury. Specific tests of viral markers should be the initial differential tests in both acute and chronic hepatic injury; when positive, they are also useful for monitoring recovery from hepatitis B and C.

Identification of a novel variant of hepatitis E virus in Austria: sequence, phylogenetic and serological analysis

We isolated a novel hepatitis E virus (HEV-Au1) variant from a patient in Austria suffering from acute viral hepatitis, who had no known risk factors for acquiring hepatitis E. The clinical presentation and initial serological findings have been reported previously. In this paper we report the results of sequence and phylogenetic analysis of HEV products from viral RNA isolated from acute phase serum. The results show that HEV-Au1 is significantly divergent from other HEV isolates. The nucleotide identity of analysed fragments from the novel isolate ranges from 76.6 to 78.4% when compared to isolates from endemic regions and 84.6 to 87.9% when compared to isolates from non-endemic regions. Divergent results were obtained when serum samples taken from the convalescent phase of disease were tested with three different immunoassays (EIAs). An EIA based on United States isolate-specific peptides showed enhanced reactivity whereas EIAs based on recombinant proteins derived from prototype HEV strains from Burma and Mexico were unable to detect antibodies to HEV (anti-HEV) in late phase serum. The findings verify the presence of an additional HEV variant in an industrialized country and provide information about possible problems in detecting anti-HEV.

Diagnosis and Monitoring of Hepatic Injury. I. Performance Characteristics of Laboratory Tests

Purpose: To review information on performance characteristics for tests that are commonly used to identify acute and chronic hepatic injury.

Data Sources and Study Selection: A MEDLINE search was performed for key words related to hepatic tests, including quality specifications, aminotransferases, alkaline phosphatase, γ-glutamyltransferase, bilirubin, albumin, ammonia, and viral markers. Abstracts were reviewed, and articles discussing performance of laboratory tests were selected for review. Additional articles were selected from the references.

Guideline Preparation and Review: Drafts of the guidelines were posted on the Internet, presented at the AACC Annual Meeting in 1999, and reviewed by experts. Areas requiring further amplification or literature review were identified for further analysis. Specific recommendations were made based on analysis of published data and evaluated for strength of evidence and clinical impact. The drafts were also reviewed by the Practice Guidelines Committee of the American Association for the Study of Liver Diseases and approved by the committee and the Association’s Council.

Recommendations: Although many specific recommendations are made in the guidelines, some summary recommendations are discussed here. Alanine aminotransferase is the most important test for recognition of acute and chronic hepatic injury. Performance goals should aim for total error of &lt;10% at the upper reference limit to meet clinical needs in monitoring patients with chronic hepatic injury. Laboratories should have age-adjusted reference limits for enzymes in children, and gender-adjusted reference limits for aminotransferases, γ-glutamyltransferase, and total bilirubin in adults. The international normalized ratio should not be the sole method for reporting results of prothrombin time in liver disease; additional research is needed to determine the reporting mechanism that best correlates with functional impairment. Harmonization is needed for alanine aminotransferase activity, and improved standardization for hepatitis C viral RNA measurements.

Diagnostic value of immunoglobulin G (IgG) and IgM anti-hepatitis E virus (HEV) tests based on HEV RNA in an area where hepatitis E is not endemic

Acute hepatitis E (AHE) has rarely been reported in industrialized countries, but the rate of seroprevalence of hepatitis E virus (HEV) antibodies (anti-HEV) is inappropriately high. The sensitivity and specificity of the assay used to test for immunoglobulin G (IgG) and IgM anti-HEV have not been well established in areas where hepatitis E is not endemic (hereafter referred to as "nonendemic areas"). We collected serum samples from 13 AHE patients, 271 healthy subjects, and 160 other liver disease patients in Taiwan to test for HEV RNA by reverse transcription (RT)-PCR and for IgG and IgM anti-HEV by enzyme-linked immunosorbent assays. The sensitivities of IgG and IgM anti-HEV (relative to RT-PCR) were 86.7 and 53.3%, respectively. The specificities of IgG and IgM anti-HEV assays for diagnosing AHE were 92.1 and 98.6%, respectively. The rate of seroprevalence of IgG anti-HEV was 11% among healthy subjects in this nonendemic area, and it increased with age. In summary, IgG anti-HEV is a good diagnostic test for screening for AHE in nonendemic areas. The high rate of prevalence of anti-HEV in healthy subjects indicates that subclinical infection may exist.

Empty virus-like particle-based enzyme-linked immunosorbent assay for antibodies to hepatitis E virus

Hepatitis E, an enterically transmitted non-A, non-B hepatitis, is a serious viral infection that occasionally causes large epidemics in developing countries. In developed countries, the disease only appears sporadically due to the transmission routes, and it is considered to be less important. The hepatitis E virus (HEV) cannot grow in cultured cells and no reliable assay system has ever been developed. In addition, the present diagnostic are not perfect, and actual rates of HEV infection may be underestimated. Highly purified empty virus-like particles (VLPs) of HEV have been produced by the use of a recombinant baculovirus vector in insect cells. Using these VLPs as an antigen, an enzyme-linked immunosorbent assay (ELISA) for antibodies to HEV was developed. A panel of 164 sera that were randomized and coded, and sera collected periodically from three patients with hepatitis E were used for the evaluation. The sensitivity of the assay was shown to be equal to or better than that obtained in previous research that used the same serum panel. The ELISA demonstrated that the serum IgM level of the patients was highest at the onset of the clinical illness and then rapidly decreased. In contrast, a high level of circulating IgG antibody titers lasted for more than 4 years. In Japan, a non-endemic country, the prevalence of the IgG class antibody to HEV in healthy individuals was found to range from 1.9% to 14.1%, depending on the geographical area. Only one out of 900 (0.1%) serum samples was IgM-positive. The IgM class antibody to HEV was detected in 10.8% of non-A, non-B, and non-C acute hepatitis patients in northeast China, whereas none of the patients in Korea had the IgM antibody. The ELISA utilizing the VLPs is sensitive and specific in its detection of the IgM and IgG antibodies to HEV. The ELISA is therefore useful for diagnosing HEV infection and for seroepidemiological study of hepatitis E.

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.

The complete sequence of hepatitis E virus genotype 4 reveals an alternative strategy for translation of open reading frames 2 and 3

Isolates of hepatitis E virus (HEV) have recently been described from China that are distinct from Burmese, Mexican and US viruses and constitute a novel genotype (genotype 4). Here, the complete genomic sequence of a representative isolate of genotype 4 HEV, amplified directly from the stool of an acutely infected patient, is presented. Analysis of the entire sequence confirms our previous conclusion, based upon partial sequence data, that these Chinese isolates belong to a novel genotype. Typical of genetic variation in HEV, most nucleotide substitutions occur in the third base of the codon and do not affect the amino acid sequence. The genotype 4 virus is unusual in that a single nucleotide insertion in the ORF 3 region changes the initiation of ORF 3, and perhaps also ORF 2. The consequences of these changes are discussed.

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.