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

Immunogenicity and protective efficacy in rhesus monkeys of a recombinant ORF2 protein from hepatitis E virus genotype 4

Several antigens derived from hepatitis E virus (HEV) genotype 1 strains have shown immunogenicity and efficacy against hepatitis E in primates and humans. However, the protective effect of a vaccine derived from HEV genotype 4 has not been studied. This study aimed to evaluate the immunogenicity and protective efficacy of the T1-ORF2 (56 kDa) capsid protein derived from HEV strain T1 (genotype 4) in rhesus monkeys. Two doses (40 microg) of alum-absorbed T1-ORF2 capsid protein were administered 4 weeks apart. Seroconversion occurred in all immunized monkeys 1-2 weeks after the first dose. The peak levels of anti-HEV IgG appeared at 2-3 weeks after the second dose and ranged from 5.7 to 196.0 U/ml. All monkeys showed an anamnestic antibody response to the second dose. Control monkeys immunized with saline remained negative for HEV antibodies throughout the pre-challenge period. The immunized monkeys were challenged intravenously with HEV genotypes 1 and 4. Monkeys immunized with T1-ORF2 were protected from infection and hepatitis after challenge with 5 x 10(4) genome equivalents of HEV, regardless of the genotype. After challenge with 5 x 10(5) genome equivalents of HEV genotype 4, the monkeys immunized with T1-ORF2 had a shorter period of raised alanine aminotransferase levels and a shorter duration of fecal shedding compared to control monkeys immunized with saline. In conclusion, these results suggest that, in rhesus monkeys, the T1-ORF2 capsid protein of HEV genotype 4 has similar cross-protective effects to other candidate vaccines derived from HEV genotype 1.

Hepatitis E: an emerging infection in developed countries

Hepatitis E is endemic in many developing countries where it causes substantial morbidity. In industrialised countries, it is considered rare, and largely confined to travellers returning from endemic areas. However, there is now a growing body of evidence that challenges this notion. Autochthonous hepatitis E in developed countries is far more common than previously recognised, and might be more common than hepatitis A. Hepatitis E has a predilection for older men in whom it causes substantial morbidity and mortality. The disease has a poor prognosis in the context of pre-existing chronic liver disease, and is frequently misdiagnosed as drug-induced liver injury. The source and route of infection remain uncertain, but it might be a porcine zoonosis. Patients with unexplained hepatitis should be tested for hepatitis E, whatever their age or travel history.

Swine hepatitis E virus in rural southern China: genetic characterization and experimental infection in rhesus monkeys (Macaca mulatta)

BACKGROUND

In rural areas of southern China, where hepatitis E is endemic, residents generally rear pigs in pigsties near their houses. The study was conducted to assess the possibility that hepatitis E virus (HEV) infections in this region are acquired primarily through contact with swine.

METHODS

One hundred twenty swine fecal samples collected from pigsties located in eight rural communities of southern China were tested for HEV RNA. The swine HEV isolates were analyzed genetically and were experimentally inoculated into rhesus monkeys to determine the potential risk of cross-species infection.

RESULTS

Twenty-nine of the 120 swine fecal samples were positive for HEV RNA. The nucleotide sequences of these swine HEV strains shared 85%-99% identities with the local human genotype 4 isolates and belonged to two subgroups of genotype 4. Importantly, swine HEV strains representing both subgroups induced hepatitis in rhesus monkeys by inoculation with the virus, evidenced by elevated serum alanine transaminase (ALT), viremia, fecal viral shedding, anti-HEV seroconversion, and liver histopathological changes.

CONCLUSIONS

Swine may be the principal reservoir for human HEV infection in rural southern China.

Hepatitis E: a complex and global disease

Thirty years after its discovery, the hepatitis E virus (HEV) continues to represent a major public health problem in developing countries. In developed countries, it has emerged as a significant cause of non-travel-associated acute hepatitis. HEV infects a wide range of mammalian species and a key reservoir worldwide appears to be swine. Genomic sequence similarity between some human HEV genotypes and swine HEV strains has been identified and we know that humans can acquire HEV infection from animals. Although for the most part the clinical course of HEV infection is asymptomatic or mild, significant risk of serious disease exists in pregnant women and those with chronic liver disease. In addition, there are data on the threat of chronic infections in immunocompromised patients. Beyond management of exposure by public health measures, recent data support that active immunisation can prevent hepatitis E, highlighting the need for vaccination programmes. Here we review the current knowledge on HEV, its epidemiology, and the management and prevention of human disease.

Autochthonous hepatitis E in Southwest England: natural history, complications and seasonal variation, and hepatitis E virus IgG seroprevalence in blood donors, the elderly and patients with chronic liver disease

AIMS

To report the natural history of autochthonous hepatitis E and hepatitis E virus (HEV) IgG seroprevalence in Southwest England.

METHODS

Patients with unexplained hepatitis were tested for hepatitis E and cases followed until recovery or death. Five hundred blood donors, 336 individuals over the age of 60 years and 126 patients with chronic liver disease were tested for HEV IgG.

RESULTS

Forty cases of autochthonous hepatitis E (genotype 3) were identified. Hepatitis E was anicteric in 25% of cases and usually caused a self-limiting hepatitis predominantly in elderly Caucasian males. Six of 40 had a significant complication and three patients died, two of who had previously undiagnosed cirrhosis. Hepatitis E shows a seasonal variation with peaks in the spring and summer and no cases in November and December. HEV IgG prevalence increases with age, is more common in men and is 16% in blood donors, 13% in patients with chronic liver disease and 25% in individuals over 60 years.

CONCLUSION

Autochthonous hepatitis E is more common than previously recognized, and should be considered in the differential diagnosis in patients with hepatitis, whatever their age or travel history. It carries a significant morbidity and when seen in the context of chronic liver disease carries an adverse prognosis.

Cross-protection of hepatitis E virus genotypes 1 and 4 in rhesus macaques

The purpose of this study was to determine cross-protection between HEV genotypes 1 and 4, which are prevalent in China. Fecal suspensions of genotypes 1 and 4 from patients, as well as genotype 4 from swine, were inoculated intravenously into rhesus macaques. Each inoculum contained 5 x 10(4) genome equivalents of HEV. After infection, serum and fecal samples were collected serially and the levels of alanine aminotransferase (ALT) and anti-HEV IgG and IgM in sera, and HEV RNA in fecal samples, were measured. Liver biopsies were carried out. All the infected monkeys (12/12) developed anti-HEV IgG and exhibited fecal shedding of virus. IgM was detected in 11 of 12, and ALT elevation occurred about 2-6 weeks post-inoculation in 10 of 12, infected monkeys. Hepatic histopathology was consistent with acute viral hepatitis and the ORF2 antigen of HEV was detected in the granular cytoplasm of hepatocytes by immunohistochemistry. After recovery from their initial HEV infection, the monkeys were challenged with a heterologous genotype or heterologous source of HEV and monitored for hepatitis and fecal shedding. Previous infection with HEV completely or partially protected against subsequent challenge with a heterologous virus, because 7 of 11 monkeys did not develop HEV infection or shed virus in the feces, and none of them developed hepatitis or exhibited ALT elevation or liver biopsy findings of hepatitis. In conclusion, previous HEV infection may give rise to cross-genotype and cross-host-species protection.

Seroepidemiology and molecular characterization of hepatitis E virus in Jilin, China

BACKGROUND

In order to develop region-specific diagnostic assays and prevent hepatitis E virus (HEV), it is essential to understand epidemiology and genotypic variation within different populations. However, the epidemiological data of HEV infections in Jilin is shortage.

METHODS

The seroepidemiological study was conducted by enzyme-linked immunosorbent assay, and the conserved genomic sequences of open reading frame 2 (348 bp) was detected using reverse transcription-PCR.

RESULTS

Overall, 1,289 serum samples were positive to HEV-specific immunoglobulin G (IgG), and 180 serum samples were positive to HEV-specific immunoglobulin M (IgM). The seroprevalence of HEV-specific IgG was 26.3%, 27.9%, 25.3%, 32.7% in 2003, 2004, 2005, 2006, respectively. Acute HEV infection mainly occurred in male, people aged from 20 to 69 were more susceptible to infection, and cases with IgM anti-HEV reaction mainly occurred from July to November. HEV RNA was detectable in the serum samples or stool suspension of 15 patients with HEV-specific IgM, and all of these belonged to genotype IV.

CONCLUSIONS

Our results indicate that HEV is widely spread in Jilin and confined to genotype IV.

Putative receptor-binding sites of hepatitis E virus

A truncated structural protein of hepatitis E virus (HEV), p239, occurs as 23 nm particles consisting of partial homodimers. As the latter resemble the HEV capsomere structurally and antigenically, it was postulated that the recombinant protein may serve as a probe for the HEV receptor. This hypothesis was supported by findings that purified p239 bound and penetrated different cell lines that are susceptible to HEV, and inhibited HEV infection of these cells. The binding was blocked by four of six monoclonal antibodies (mAbs) reactive against the dimeric domain of p239, and by two of three mAbs reactive against its monomeric domain, suggesting that binding may involve a portion of each domain. Mutation affecting the monomeric domain had no effect on binding or capacity to block HEV infection, whereas that affecting the dimeric domain diminished binding of the mutant peptide markedly and abrogated its capacity to block HEV infection. These results suggest that HEV infection might involve distinct receptor-binding sites.

Difference of T cell and B cell activation in two homologous proteins with similar antigenicity but great distinct immunogenicity

The candidate particulate hepatitis E vaccine, HEV 239, has been shown to be an efficacious vaccine in primates, and clinical study to date shows it to be safe and immunogenic for humans. The antigenicity of HEV 239 is virtually identical to its N-terminal 26 amino acids truncated protein, E2, which is not particulate but soluble. However, HEV 239 is over 200 times more immunogenic than E2. In present study, several events underlying this dramatic immunogenicity difference have been addressed. (1) HEV 239 can efficiently evoke a vigorous and predominant T cell response while E2 cannot induce detectable T cell response; (2) the dominant T cell epitopes in HEV 239 are identified, and both are also contained integrally in E2; (3) priming mice with Th epitope peptide can partially rescue the weak immunogenicity of E2 in alum adjuvant and (4) HEV 239 but not E2 can induce significant antibody response in athymic mice, which indicates that HEV 239 can directly activate B cell more efficiently. These results contribute to a better understanding of the mechanisms involved in the significant high immunogenicity of particulate antigen and may provide knowledge for the rational design and development of future vaccines.

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

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

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

Significance of serum IgA in patients with acute hepatitis E virus infection

AIM: To study the significance of serum anti-hepatitis E virus (HEV) IgA in patients with hepatitis E.

METHODS: A new method was established to assay anti-HEV IgA, which could be detected in the middle phase of the infection. We compared anti-HEV IgA assay with anti-HEV IgM and anti-HEV IgG assay in sera from 60 patients with positive HEV-RNA.

RESULTS: The 60 patients with positive HEV-RNA had both anti-HEV IgA and anti-HEV IgM and 410 patients with negative HEV-RNA were used as control. Periodic serum samples obtained from 60 patients with hepatitis E were tested for HEV RNA, anti-HEV IgM, anti-HEV IgA and anti-HEV IgG. Their HEV-RNA was detectable in the serum until 20 ± 11 d. We used anti-HEV IgM and anti-HEV IgA assay to detect HEV infection and positive results were found in 90 ± 15 d and 120 ± 23 d respectively, the positive rate of anti-HEV IgA was higher than that of anti-HEV IgM and HEV-RNA (P <0.05).

CONCLUSION: The duration of anti-HEV IgA in serum is longer than that of anti-HEV IgM, and anti-HEV IgA assay is a good method to detect HEV infection.

Epidemiology and clinical features of sporadic hepatitis E as compared with hepatitis A

OBJECTIVES

To compare the epidemiology and clinical features of two enterically transmitted hepatitis, namely hepatitis E and hepatitis A.

METHODS

We analyzed clinical features and risk factors of 105 cases of hepatitis A and 24 cases of hepatitis E admitted in 2002. All patients were tested positive for IgM antibody against either hepatitis A virus (HAV) or hepatitis E virus (HEV), and all patients were tested to be negative for IgM anti-HBV or IgG anti-HCV.

RESULTS

Hepatitis A patients were significantly younger (median age = 27 yr) and most had a recent history of shellfish consumption, whereas hepatitis E patients were older (median age = 53 yr) and most had a recent travel history. Whereas hepatitis A was milder and recovery was uneventful, hepatitis E was more severe, associated with significant mortality and frequently complicated by protracted coagulopathy and cholestasis.

CONCLUSIONS

Hepatitis E is a more severe disease entity as compared with hepatitis A and significant proportion of them are imported cases from an endemic area.

A bacterially expressed particulate hepatitis E vaccine: antigenicity, immunogenicity and protectivity on primates

It was evaluated its antigenicity, immunogenicity and efficacy of a candidate recombinant hepatitis E virus (HEV) vaccine, referred hitherto as HEV 239 vaccine. The vaccine peptide has a 26 amino acids extension from the N terminal of another peptide, E2, of the HEV capsid protein, which has been shown to protect monkeys against HEV infection previously. The vaccine peptide is similar as E2 in that: first, the vaccine peptide migrates predominantly as dimer in SDS-PAGE and it is dissociated into monomers by heating; second, its dimeric form of which predominantly recognized by HEV reactive human serum; and third, it shows the same pattern of reaction as E2 with a panel of eight monoclonal antibodies that had been raised against E2. In contrast to E2, the vaccine peptide aggregates to form particles of 13 nm mean radius, and consequently, it is more than 240 times more immunogenic than E2. Using alum as adjuvant, immunizing dose determined in mice was 80-250 ng for the vaccine and >60 microg for E2. Rhesus monkeys twice vaccinated with a 10 microg or a 20 microg formulation of this vaccine showed essentially the same antibody response, whereas the response to a 5 microg formulation was delayed but reached similar antibody levels. All the three vaccine formulations afford complete protection against infection with 10(4) genome equivalent dose of the homologous genotype 1 virus. At higher virus dose of 10(7), the same vaccine formulation partially protected against the infection and completely protected against hepatitis. The efficacy of the vaccine was essentially the same for the homologous genotype 1 virus and heterologous genotype 4 virus.

Analysis of hepatitis E virus neutralization sites using monoclonal antibodies directed against a virus capsid protein

The dimeric form of the recombinant peptide (E2), comprising amino acid 394-606 of the capsid protein of hepatitis E virus (HEV), is strongly recognized by HEV reactive human serum, and when used as a vaccine, it protects rhesus monkeys against experimental HEV infection. In this work, the relationship of E2 to HEV has been probed using three murine monoclonal antibodies, 8C11, 13D8 and 8H3, all of which react predominantly against the E2 dimer, and can effect immune capture of the virus as well. 8C11 and 8H3 were further found to neutralize HEV infectivity in animals. Cross-blocking patterns between these antibodies discerned two spatially separate antigenic domains, one identified by 8C11 and 13D8, and the other, by 8H3. Kinetic studies using BIAcore biosensor suggest that the epitope to which 8H3 is directed is partially masked, and thus has limited access by the native antibody. However, this is not the case with the smaller Fab. Access to the 8H3 epitope was enhanced by the binding of 8C11, and inhibited by the binding of 13D8 to a distal site on the peptide. Similar to the effects of binding 8H3 to E2, 8C11 was found to enhance immune capture by 8H3, while 13D8 was inhibitory. Moreover, 8C11 and 8H3 act synergistically to neutralize HEV infectivity. The parallel cross-reaction patterns that these antibodies exhibit against the peptide and the virus, respectively, implicate two interacting conformationally dependent neutralization sites on the HEV particle. These sites might cooperate in the adsorption and penetration of the HEV virus.

Systematic pathogenesis and replication of avian hepatitis E virus in specific-pathogen-free adult chickens

Hepatitis E virus (HEV) is an important human pathogen. Due to the lack of a cell culture system and a practical animal model for HEV, little is known about its pathogenesis and replication. The discovery of a strain of HEV in chickens, designated avian HEV, prompted us to evaluate chickens as a model for the study of HEV. Eighty-five 60-week-old specific-pathogen-free chickens were randomly divided into three groups. Group 1 chickens (n=28) were each inoculated with 5 x 10(4.5) 50% chicken infectious doses of avian HEV by the oronasal route, group 2 chickens (n=29) were each inoculated with the same dose by the intravenous (i.v.) route, and group 3 chickens (n=28) were not inoculated and were used as controls. Two chickens from each group were necropsied at 1, 3, 5, 7, 10, 13, 16, 20, 24, 28, 35, and 42 days postinoculation (dpi), and the remaining chickens were necropsied at 56 dpi. Serum, fecal, and various tissue samples, including liver and spleen samples, were collected at each necropsy for pathological and virological testing. By 21 dpi, all oronasally and i.v. inoculated chickens had seroconverted. Fecal virus shedding was detected variably from 1 to 20 dpi for the i.v. group and from 10 to 56 dpi for the oronasal group. Avian HEV RNA was detected in serum, bile, and liver samples from both i.v. and oronasally inoculated chickens. Gross liver lesions, characterized by subcapsular hemorrhages or enlargement of the right intermediate lobe, were observed in 7 of 28 oronasally and 7 of 29 i.v. inoculated chickens. Microscopic liver lesions were mainly lymphocytic periphlebitis and phlebitis. The lesion scores were higher for oronasal (P=0.0008) and i.v. (P=0.0029) group birds than for control birds. Slight elevations of the plasma liver enzyme lactate dehydrogenase were observed in infected chickens. The results indicated that chickens are a useful model for studying HEV replication and pathogenesis. This is the first report of HEV transmission via its natural route in a homologous animal model.

Mutational analysis of essential interactions involved in the assembly of hepatitis E virus capsid

The hepatitis E virus (HEV) capsid consists of a single structural protein, a portion of which is engaged in isosahedral contact to form a basal shell, and another portion in dimeric contact to form the homodimers protruding from the shell. Previous studies revealed that homodimers of the truncated HEV capsid proteins, E2 (amino acids 394-606) and p239 (amino acids 368-606), model dominant antigenic determinants of HEV. Immunization with these proteins protected rhesus monkeys against the virus, and three monoclonal antibodies against the homodimers could neutralize HEV infectivity and/or immune-capture of the virus. Furthermore, homodimers of p239 further interact to form particles of 23 nm diameter, rendering it an efficacious candidate vaccine. In light of this we postulate that the interactions involved in the formation of the homodimers and particles might be similar to those involved in assembly of the virus capsid. Presently, mutational analysis was carried out to identify these sites of interactions. The site of dimeric interactions was located to a cluster of six hydrophobic amino acids residues, Ala597, Val598, Ala599, Leu601, and Ala602; furthermore, the site involved in particle formation was located at amino acids 368-394. The possibility that these sites are also involved in assembly of the virus capsid is supported by the fact that they are located at two major and highly conserved hydrophobic regions of the HEV structural protein.

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.

Hepatitis E: An overview and recent advances in vaccine research

Hepatitis E virus (HEV) is an unclassified, small, non-enveloped RNA virus, as a causative agent of acute hepatitis E that is transmitted principally via the fecal-oral route. The virus can cause large water-born epidemics of the disease and sporadic cases as well. Hepatitis E occurs predominantly in developing countries, usually affecting young adults, with a high fatality rate up to 15%-20% in pregnant women. However, no effective treatment currently exists for hepatitis E, and the only cure is prevention. But so far there are no commercial vaccines for hepatitis E available in the world. Although at least four major genotypes of HEV have been identified to date, only one serotype of HEV is recognized. So there is a possibility to produce a broadly protective vaccine. Several studies for the development of an effective vaccine against hepatitis E are in progress and the best candidate at present for a hepatitis E vaccine is a recombinant HEV capsid antigen expressed in insect cells from a baculovirus vector. In this article, the recent advances of hepatitis E and the development of vaccine research for HEV including recombinant protein vaccine, DNA vaccine and the recombinant hepatitis E virus like particles (rHEV VLPs) are briefly reviewed.