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

Hepatitis E Virus (HEV) Synopsis: General Aspects and Focus on Bangladesh

HEV is the most common cause of acute hepatitis globally. This review summarizes the latest knowledge on the epidemiology, clinical characteristics, testing, and treatment of HEV infection. We also focused on Bangladesh to highlight the distinct challenges and the possible remedies. In low-income settings, the virus is mainly transmitted between people by fecal contamination of drinking water causing large outbreaks, and sporadic cases. The disease is usually mild and self-limiting acute hepatitis. Still, pregnant women and their offspring in low-income countries are at particular risk for severe disease, with up to 20% maternal mortality. Despite the high burden of the disease, HEV remains a relatively neglected virus, with detection hampered by costly tests and a lack of suitable treatments. Molecular PCR diagnostics, together with ELISA antibody tests, remain the preferred methods for diagnosis of HEV; however, rapid bedside diagnostics are available and could offer a practical alternative, especially in low-income countries. One vaccine (HEV 239) is only available in China and Pakistan, as efficacy against the other genotypes remains uncertain. The effectiveness trial conducted in Bangladesh might lead the way in gathering more efficacy data and could, together with improved surveillance and raised awareness, dramatically reduce the global burden of HEV.

Molecular characterisation of Hepatitis E virus isolates from north India

PURPOSE

Hepatitis E virus (HEV) is responsible for >50% of acute viral hepatitis (AVH) in developing countries. It has 4 major genotypes and various subtypes which vary in geographical distribution, clinical manifestations and epidemiological patterns. This study was conducted to characterise HEV isolates from north India to study the effect of host and viral factors on HEV infection.

METHODS

Serum samples collected from 536 AVH patients admitted to Department of Medicine, King George's Medical University, Lucknow from July 2016 to June 2017 were screened for anti HEV IgM, anti HAV IgM, HBsAg and anti HCV antibodies using commercial ELISA kits. Samples either positive for anti HEV IgM antibodies (n ​= ​204) or negative for all 4 hepatotropic viruses (n ​= ​37) were enrolled and tested by real time PCR for HEV RNA. HEV RNA positive samples with high viral load were further subjected to nested PCR for amplification of capsid gene. Sequencing and phylogenetic analysis were performed. HEV strains isolated from this study were deposited to GenBank under accession numbers MG571274 to MG571283.

RESULTS

Anti HEV IgM positivity was observed among 38% clinically suspected AVH cases. HEV RNA was detected in 31.8% seropositive HEV cases and additional 3 seronegative cases. Males outnumbered females and the most affected age group was of young adults. Maximum number of cases were seen during the months of June to September. Phylogenetic analysis showed that HEV strains in our study belonged to genotype 1a. Mortality in HEV infected pregnant females was 23.5% as compared to 2.4% in non-pregnant females. Adverse fetal outcome was recorded in 51% of HEV infected pregnancies.

CONCLUSIONS

HEV genotype 1a is prevalent in our setting. HEV during pregnancy is associated with adverse maternal and fetal outcome.

Hepatitis E and Pregnancy: An Unholy Alliance Unmasked from Kashmir, India

The adverse relationship between viral hepatitis and pregnancy in developing countries had been interpreted as a reflection of retrospectively biased hospital-based data collection by the West. However, the discovery of hepatitis E virus (HEV) as the etiological agent of an epidemic of non-A, non-B hepatitis in Kashmir, and the documenting of the increased incidence and severity of hepatitis E in pregnancy via a house-to-house survey, unmasked this unholy alliance. In the Hepeviridae family, HEV-genotype (gt)1 from genus Orthohepevirus A has a unique open reading frame (ORF)4-encoded protein which enhances viral polymerase activity and viral replication. The epidemics caused by HEV-gt1, but not any other Orthohepevirus A genotype, show an adverse relationship with pregnancy in humans. The pathogenesis of the association is complex and at present not well understood. Possibly multiple factors play a role in causing severe liver disease in the pregnant women including infection and damage to the maternal-fetal interface by HEV-gt1; vertical transmission of HEV to fetus causing severe fetal/neonatal hepatitis; and combined viral and hormone related immune dysfunction of diverse nature in the pregnant women, promoting viral replication. Management is multidisciplinary and needs a close watch for the development and management of acute liver failure. (ALF). Preliminary data suggest beneficial maternal outcomes by early termination of pregnancy in patients with lower grades of encephalopathy.

Current Paradigm of Hepatitis E Virus Among Pediatric and Adult Patients

Hepatitis E virus (HEV) infection is a polymorphic condition, present throughout the world and involving children and adults. Multiple studies over the last decade have contributed to a better understanding of the natural evolution of this infection in various population groups, several reservoirs and transmission routes being identified. To date, acute or chronic HEV-induced hepatitis has in some cases remained underdiagnosed due to the lower accuracy of serological tests and due to the evolutionary possibility with extrahepatic manifestations. Implementation of diagnostic tests based on nucleic acid analysis has increased the detection rate of this disease. The epidemiological and clinical features of HEV hepatitis differ depending on the geographical areas studied. HEV infection is usually a self-limiting condition in immunocompetent patients, but in certain categories of vulnerable patients it can induce a sudden evolution toward acute liver failure (pregnant women) or chronicity (immunosuppressed patients, post-transplant, hematological, or malignant diseases). In acute HEV infections in most cases supportive treatment is sufficient. In patients who develop chronic hepatitis with HEV, dose reduction of immunosuppressive medication should be the first therapeutic step, especially in patients with transplant. In case of unfavorable response, the initiation of antiviral therapy is recommended. In this review, the authors summarized the essential published data related to the epidemiological, clinical, paraclinical, and therapeutic aspects of HEV infection in adult and pediatric patients.

The expression patterns of immune response genes in the Peripheral Blood Mononuclear cells of pregnant women presenting with subclinical or clinical HEV infection are different and trimester-dependent: A whole transcriptome analysis

Hepatitis E is an enteric disease highly prevalent in the developing countries. The basis for high mortality among pregnant hepatitis E patients remains unclear. Importantly, a large proportion of infected pregnant women present with subclinical infection as well. In order to understand the possible mechanisms influencing clinical presentation of hepatitis E in pregnant women, we explored a system biology approach. For this, PBMCs from various categories were subjected to RNAseq analysis. These included non-pregnant (NPR, acute and convalescent phases) and pregnant (PR, 2^nd and 3^rd trimesters, acute phase and subclinical HEV infections) patients and corresponding healthy controls. The current study deals with immune response genes.

In contrast to exclusive up-regulation of nonspecific, early immune response transcripts in the NPR patients, the PR patients exhibited broader and heightened expression of genes associated with innate as well as adaptive T and B cell responses. The study identified for the first time (1) inverse relationship of immunoglobulin (Ig) genes overexpression and (2) association of differential expression of S100 series genes with disease presentation. The data suggests possible involvement of TLR4 and NOD1 in pregnant patients and alpha defensins in all patient categories suggesting a role in protection. Induction of IFNγ gene was not detected during the acute phase irrespective of pregnancy. Association of response to vitamin D, transcripts related to NK/NKT and regulatory T cells during subclinical infection are noteworthy.

The data obtained here could be correlated with several studies reported earlier in hepatitis E patients suggesting utility of PBMCs as an alternate specimen. The extensive, informative data provided here for the first time should form basis for future studies that will help in understanding pathogenesis of fulminant hepatitis E.

In Silico Analysis of Hepatitis B Virus Genotype D Subgenotype D1 Circulating in Pakistan, China, and India

The focus of this study was the computational analysis of hepatitis B virus (HBV) genotype D subgenotype D1 in Pakistan, China, and India. In total, 54 complete genome sequences of HBV genotype D subgenotype D1 were downloaded from National Center for Biotechnology Information (NCBI). Of these, 6 complete genome sequences were from Pakistan, 14 were from China, and 34 were from India. Sequence alignment showed less than 4% divergence in these sequences. C and X genes showed divergence of less than 3%. Comparison over the S gene showed more than 97% similarity among the nucleotide sequences of genotype D subgenotype D1. The identity and similarity matrix of 54 nucleotide sequences of HBV genotype D subgenotype D1 from Pakistan, China, and India revealed more than 93% identity and 93% similarity. Phylogenetic analysis highlighted that complete genome isolates of HBV circulating in Pakistan had the closest evolutionary relationship with its neighboring countries China and India. China’s (HQ833466) and Pakistan’s (AB583680.1) isolates shared the same ancestor. Gene structure analysis showed that “P” gene exons were the longest, about three-fourth of the genome size, whereas gene “S” had the second longest coding regions with 2 exons and 1 intron. However, “C” and “X” genes had 1 smallest exon. X proteins had proven role in spreading of the HBV infection diseases. For HBx analysis, 1 X protein sequence of HBV genotype D subgenotype D1 belonging to each country was obtained. Homology models of the 3 X proteins generated using SWISS-MODEL revealed GMQE (Global Model Quality Estimation) = 0.1. Global and local quality estimate scores including Z-scores for Qualitative Model Energy Analysis (QMEAN) C-beta, all-atom, solvation, and torsion energy scores were similar indicating good quality, accuracy, and reliability of the predicted models. Three-dimensional (3D) visualization showed similar structures and Ramachandran plots showed a high percentage of protein residues into the favorable region for X protein models.

Seroprevalence of Hepatitis E Virus Infection in Pigs from Southern Bulgaria

Hepatitis E virus (HEV) has been isolated from humans and several animals' species. During the last years, the knowledge of HEV infection dramatically changed and enriched. The aim of this study was to estimate the seroprevalence of HEV in industrial pigs in different districts of Southern Bulgaria. Three hundred sixty swine serum samples were tested for anti-HEV IgG antibodies. The samples were collected from four industrial farms from three districts of Southern Bulgaria. HEV-specific antibodies in porcine serum were detected by enzyme-linked immunosorbent assay (PrioCHECK HEV Ab porcine). The overall HEV seroprevalence was 60.3%. The seropositivity varied widely depending on age groups and investigated farms. The overall prevalence in weaners was 25%, in fattening pigs 75.8%, and in group of sows was found the highest HEV positivity of 80%. The occurrence of HEV positivity in sows and fattening pigs presented odds ratio (OR) = 17.200 (95% confidence interval [CI]: 8.8-33.7) and OR = 11.342 (95% CI: 6.1-21.0), respectively, compared to weaners. The study indicated that HEV is widespread in industrial farms in Bulgaria and presented high seroprevalence in pigs. The results found that HEV seropositivity showed age dependency. The National Health Authorities should raise awareness of HEV and its zoonotic potential.

Classification and Genomic Diversity of Enterically Transmitted Hepatitis Viruses

Hepatitis A virus (HAV) and hepatitis E virus (HEV) are significant human pathogens and are responsible for a substantial proportion of cases of severe acute hepatitis worldwide. Genetically, both viruses are heterogeneous and are classified into several genotypes that differ in their geographical distribution and risk group association. There is, however, little evidence that variants of HAV or HEV differ antigenically or in their propensity to cause severe disease. Genetically more divergent but primarily hepatotropic variants of both HAV and HEV have been found in several mammalian species, those of HAV being classified into eight species within the genus Hepatovirus in the virus family Picornaviridae. HEV is classified as a member of the species Orthohepevirus A in the virus family Hepeviridae, a species that additionally contains viruses infecting pigs, rabbits, and a variety of other mammalian species. Other species (Orthohepevirus B-D) infect a wide range of other mammalian species including rodents and bats.

Detection of Genotype 1a and 1f of Hepatitis E Virus in Patients Treated at Tertiary Care Hospitals in Central India

BACKGROUND AND AIMS

An acute hepatitis, caused by hepatitis E virus (HEV), is a significant global health concern, especially in developing countries. HEV has 1 serotype and 8 genotypes, which are further divided into subtypes. Despite the availability of sporadic cases and outbreak data from India, specific information regarding HEV epidemiological data is lacking from central India. This study was conducted to understand epidemiological and molecular features of HEV in central India.

METHODS

In this 3-year study conducted from July 2012 to June 2015, IgM ELISA was used for the diagnosis of suspected HEV cases. For identifying the genotype, nRT PCR was conducted and the PCR products were sequenced and analysed. Clinical and demographic data were analysed using statistical tools to highlight the trends.

RESULT

Out of 1,369 suspected cases, 341 (24.9%) were positive for HEV. The positivity was significantly higher in males (69.2%) and in the age group of > 15-45 years (72.5%). The HEV cases peaked during the summer. Subtypes 1a and 1f of genotype 1 were detected in the area during the study period.

CONCLUSION

HEV is a major aetiological agent of viral hepatitis in central India with adults and males at higher risk of infection. Two subtypes of the virus were detected in the region. Continuous serological surveillance and molecular monitoring will help to understand the epidemiology of HEV infection, outbreak mitigation and aid in providing treatment.

The divergence of epidemiological, antigenic and immunogenic characteristics of hepatitis E virus of different genotypes

Hepatitis E virus (HEV) is an enterically transmitted pathogen that causes hepatitis E (HE). HEVs infecting mammals have been classified into four genotypes. Numerously diverse behaviors have been found among HEV genotypes; the first two genotypes are endemic in developing countries and only infect humans, whereas genotypes 3 and 4 infect other mammalian species as well. It is still unclear why only HEV genotypes 3 and 4 can infect across species. This article comprehensively: reviews the divergence of epidemiological and immunogenic characteristics of HEV infection derived from different genotypes; provides the current knowledge on the antigenic and immunogenic differences between different HEV genotypes; and will give useful information on serological diagnosis development and vaccines preparation.

Acute hepatitis E in India appears to be caused exclusively by genotype 1 hepatitis E virus

BACKGROUND

Hepatitis E is caused by infection with hepatitis E virus (HEV), which has four well-known genotypes. Genotypes 1 and 2 HEV have been reported from human cases in areas where the disease is highly endemic. By contrast, genotypes 3 and 4 HEV, which primarily infect several animal species worldwide, have been reported mainly from sporadic human cases in non-endemic areas such as Japan and high-income countries of Europe and North America. To determine whether genotype 3/4 HEV cause sporadic disease in India, a disease-endemic area, we determined HEV genotype in a group of patients with such disease.

METHODS

A part of the HEV open reading frame (ORF) 1 was amplified and sequenced from sera of 74 patients with sporadic acute viral hepatitis E from four cities in India. The sequences were compared with prototype sequences for various HEV genotypes and subgenotypes and analyzed using phylogenetic tools to determine the genotype of the isolates. For 12 specimens, a part of HEV ORF2 was also similarly analyzed.

RESULTS

Partial ORF1 sequences of all the 74 isolates belonged to genotype 1 HEV, with 88.2% to 100% nucleotide identity with the prototype genotype 1 isolates. Partial ORF2 sequences for all the 12 isolates also belonged to genotype 1 HEV. On phylogenetic analysis, 71 isolates clustered with prototype genotype 1a HEV; the remaining three isolates were located between subgenotypes 1a and 1c but were closer to the former.

CONCLUSION

Human sporadic acute hepatitis E in India is caused almost exclusively by genotype 1 HEV.

Seroepidemiology and molecular characterization of hepatitis E virus infection in swine and occupationally exposed workers in Punjab, India

Hepatitis E virus (HEV) has two discrete epidemiological patterns: waterborne epidemics in developing countries only, caused by HEV genotype I, and sporadic zoonotic outbreaks in developing and developed countries caused by genotypes III and IV. This study was designed to investigate seroprevalence, molecular detection and the characterization of HEV by nested RT-PCR in swine as well as the occupational risk to exposed human population in Punjab state of north-western India. The occupational risk-exposed group comprised of swine farmers (organized - mixed feed feeders and unorganized - swill feeders), slaughterhouse workers, sewage workers and veterinary internes. During the study period, blood and faecal samples were collected from 320 swine and 360 humans with both high and low occupational exposure risks. The overall seroprevalence of swine HEV was 65.00%, with a significantly higher seropositivity in growing pigs (2-8 months of age). The prevalence of HEV RNA in swine faecal samples by nRT-PCR was 8.75% with a significantly higher detection in swill-fed pigs. With humans in the high occupational exposure risk population, significantly higher anti-HEV IgG seropositivity was observed (60.48%) as compared to control population (10.71%). Strong evidence of association between human anti-HEV IgG seropositivity and certain occupational exposure risk groups was observed (p < 0.05). This indicates that unorganized swine farmers, slaughterhouse workers and sewage workers have higher odds of HEV infection in this study region. Percentage of nucleotide similarity between swine and human HEV isolates was less than that found in countries with zoonotic HEV outbreaks. Molecular characterization revealed the circulation of G IV and G I genotypes among swine and human population in Punjab state, respectively.

Transmission of Hepatitis E Virus in Developing Countries

Hepatitis E virus (HEV), an RNA virus of the Hepeviridae family, has marked heterogeneity. While all five HEV genotypes can cause human infections, genotypes HEV-1 and -2 infect humans alone, genotypes HEV-3 and -4 primarily infect pigs, boars and deer, and genotype HEV-7 primarily infects dromedaries. The global distribution of HEV has distinct epidemiological patterns based on ecology and socioeconomic factors. In resource-poor countries, disease presents as large-scale waterborne epidemics, and few epidemics have spread through person-to-person contact; however, endemic diseases within these countries can potentially spread through person-to-person contact or fecally contaminated water and foods. Vertical transmission of HEV from infected mother to fetus causes high fetal and perinatal mortality. Other means of transmission, such as zoonotic transmission, can fluctuate depending upon the region and strain of the virus. For instance, zoonotic transmission can sometimes play an insignificant role in human infections, such as in India, where human and pig HEV infections are unrelated. However, recently China and Southeast Asia have experienced a zoonotic spread of HEV-4 from pigs to humans and this has become the dominant mode of transmission of hepatitis E in eastern China. Zoonotic HEV infections in humans occur by eating undercooked pig flesh, raw liver, and sausages; through vocational contact; or via pig slurry, which leads to environmental contamination of agricultural products and seafood. Lastly, blood transfusion-associated HEV infections occur in many countries and screening of donors for HEV RNA is currently under serious consideration. To summarize, HEV genotypes 1 and 2 cause epidemic and endemic diseases in resource poor countries, primarily spreading through contaminated drinking water. HEV genotypes 3 and 4 on the other hand, cause autochthonous infections in developed, and many developing countries, by means of a unique zoonotic food-borne transmission.

Advances in hepatitis E - II: Epidemiology, clinical manifestations, treatment and prevention

INTRODUCTION

Infection with hepatitis E virus (HEV) is the commonest cause of acute hepatitis worldwide. This infection, with fecal-oral transmission, was previously thought to be limited to humans residing in developing countries with poor sanitation, spreading via contaminated drinking water. In recent years, our understanding of epidemiology and clinical spectrum of this infection have changed markedly.

AREAS COVERED

This article reviews the epidemiology, including routes of transmission, and clinical manifestations of HEV infection around the world. In addition, recent findings on transmission-associated HEV infection, extrahepatic manifestations of hepatitis E and chronic infection with HEV, and treatment and prevention of this infection are discussed. Expert commentary: HEV infection has two distinct epidemiologic forms and clinical patterns of disease: (i) acute epidemic or sporadic hepatitis caused by fecal-oral (usually water-borne) transmission of genotype 1 and 2 HEV from a human reservoir in areas with poor hygiene and frequent water contamination, and (ii) infrequent sporadic hepatitis E caused by zoonotic infection, possibly from an animal source through ingestion of undercooked animal meal, of genotype 3 or 4 virus. In disease-endemic areas, pregnant women are at a particular risk of serious disease and high mortality. In less-endemic areas, chronic infection with HEV among immunosuppressed persons is observed. HEV can also be transmitted through Transfusion of blood and blood products. Ribivirin treatment is effective in chronic hepatitis E. Two efficacious vaccines have been tried in humans; one of these has received marketing approval in its country of origin.

Hepatitis E virus RNA-dependent RNA polymerase: RNA template specificities, recruitment and synthesis

Hepatitis E virus (HEV) is a positive-sense RNA virus and member of the genus Orthohepevirus in the family Hepeviridae. Although HEV RNA-dependent RNA polymerase (HEV-RdRp) plays an important role in the HEV life cycle, its template specificities are not completely understood. We expressed HEV-RdRp protein with His-tag in a bacterial system and analysed template specificities using different putative cis-regulatory elements in the HEV genome. The enzyme showed highest affinity for the 3' non-coding region (NCR), then for the 5'NCR and least for the putative subgenomic promoter (SgP). The enzyme could co-bind to 3'NCR and putative SgP templates together, as evident from the supershift in binding assay, indicating presence of different binding sites for these elements. Proteomic analysis revealed that the RNA elements share two common peptides for binding, while a third peptide, which is highly conserved across different HEV genotypes, is specific for 3'NCR. We propose that, during the early phases of replication, as negative sense antigenome copies accumulate at the replication site, they probably initiate promoter swapping from 3'NCR to SgP, to favour synthesis of subgenomic RNA and to prevent synthesis of genomic RNA. The conserved site for 3'NCR binding could be potential antiviral target and needs further evaluation.

Detailed investigation of ongoing subclinical hepatitis E virus infections; occurring in outbreak settings of North India

BACKGROUND & AIMS

Every year globally WHO reports 20 million Hepatitis E virus (HEV) infections. The disease occurs as sporadic cases or focused outbreaks and has potentials to cause massive epidemics. The reservoir of HEV during inter-epidemic period is not well characterized. The sporadic cases usually lack history of contact with clinically overt HEV patients. In the present context we evaluated the occurrence of subclinical HEV as a possible reservoir in endemic region.

METHODS

Blood samples were collected from 67 apparently healthy individuals and 10 acute viral hepatitis (AVH) patients during two HEV outbreaks in North India. The serum samples were tested for anti-HEV IgM, IgG, HEV-IgG avidity index, HEV viral load and conventional-PCR followed by sequencing and phylogenetic analysis.

RESULTS

A total of 14 (20.89%) apparently healthy individuals showed the presence of anti-HEV IgM and IgG. Of 14 based on HEV-IgG avidity index, 9 (64.28%) had secondary-exposure, 4 (28.57%) had primary exposure, while one patient had intermediate avidity. Subclinical subjects with primary exposure had significantly higher anti-HEV IgM index as compared to secondary-exposure (P = 0.0028). Viral load in clinically jaundiced patients was significantly higher as compared to subclinical subjects (P < 0.0001). Phylogenetic analysis showed HEV sequences retrieved from subclinical individuals clustered along with AVH patients, suggesting matched source. The significantly low viral load in subclinical subjects hints towards the dose dependency for progression of clinical manifestation.

CONCLUSION

We document subclinical HEV with low level viremia occurs during outbreak settings and goes un-noticed, which helps maintaining the virus in nature possibly leading to its endemicity.

A scoping review of the evidence for public health risks of three emerging potentially zoonotic viruses: hepatitis E virus, norovirus, and rotavirus

Emerging zoonoses are defined as those newly recognized, or increasing in incidence or geographic range. Hepatitis E virus (HEV), norovirus (NoV), and rotavirus (RV), while well known to be transmitted person-person, have also been hypothesized to be emerging zoonoses. Our objective was to investigate their potential public health risks from animal reservoirs. Given the diversity of evidence sources, a scoping review incorporating a mixed methods synthesis approach was used. A broad search was conducted in five electronic databases. Each citation was appraised independently by two reviewers using screening tools designed and tested a priori. Level 1 relevance screening excluded irrelevant citations; level 2 confirmed relevance and categorized. At level 3 screening, data were extracted to support a risk profile. A stakeholder group provided input on study tools and knowledge translation and transfer. Level 1 screening captured 2471 citations, with 1270 advancing to level 2 screening, and 1094 to level 3. We defined criteria for case attribution to zoonosis for each virus. Using these criteria, we identified a small number of zoonotic cases (HEV n=3, NoV=0, RV=40 (zoonoses=3; human-animal re-assortants=37)) categorized as 'likely'. The available evidence suggests the following potential HEV human exposure sources: swine, other domestic animals, wildlife, surface waters, and asymptomatic human shedders. Possible at-risk groups include the immunocompromised and the elderly. Reports of NoV intergenogroup recombinants suggest potential for human-animal recombination. Greatest public health impact for RV zoonoses may be the potential effect of human-animal reassortants on vaccination efficacy.

Zoonotic origin of hepatitis E

The concept of zoonotic viral hepatitis E has emerged a few years ago following the discovery of animal strains of hepatitis E virus (HEV), closely related to human HEV, in countries where sporadic cases of hepatitis E were autochthonous. Recent advances in the identification of animal reservoirs of HEV have confirmed that strains circulating in domestic and wild pigs are genetically related to strains identified in indigenous human cases. The demonstration of HEV contamination in the food chain or pork products has indicated that HEV is frequently a foodborne zoonotic pathogen. Direct contacts with infected animals, consumption of contaminated animal meat or meat products are all potential means of zoonotic HEV transmission. The recent identification of numerous other genetically diverse HEV strains from various animal species poses additional potential concerns for HEV zoonotic infection.

Lack of persistent hepatitis E virus infection as a cause for unexplained transaminase elevation in renal transplant recipients in India

BACKGROUND

Hepatitis E virus (HEV) infection is highly endemic in India, being the most common cause of acute hepatitis; however, no case of chronic infection has been reported. All the human isolates of HEV from India till date have belonged to genotype 1. In contrast, in non-endemic areas, genotype 3 is the most prevalent, and persistent HEV infection has been reported among solid-organ transplant recipients. Whether persistent infection occurs with genotype 1 HEV is unclear. We therefore looked for evidence of HEV infection among renal transplant recipients with elevated alanine transaminase (ALT).

METHODS

Renal transplant recipients receiving immunosuppressive therapy were screened for ALT levels, irrespective of time duration since renal transplant. For those with ALT levels equal to or exceeding 50 IU/mL on at least two occasions ≥3 weeks apart, serum was tested for HEV RNA using a sensitive real-time reverse transcription polymerase chain reaction assay. For those testing positive, HEV genotyping and follow up for duration of viral persistence were planned.

RESULTS

Of the 275 patients studied, 49 (17.8 %, 44 male, median age = 39.5 years) had elevated ALT levels (median = 62 [range = 50-477] IU/L). None of these 49 patients had detectable HEV RNA in the serum using an assay with detection sensitivity of 300 copies of RNA/mL of specimen.

CONCLUSION

Our data indicate that persistent HEV infection is an infrequent cause of ALT elevation in Indian renal transplant recipients who are receiving immunosuppressive drugs. This suggests that infection with genotype 1 HEV may have either no or low potential to cause persistent infection.

Hepatitis E virus infection

Hepatitis E virus (HEV) infection is a worldwide disease. An improved understanding of the natural history of HEV infection has been achieved within the last decade. Several reservoirs and transmission modes have been identified. Hepatitis E is an underdiagnosed disease, in part due to the use of serological assays with low sensitivity. However, diagnostic tools, including nucleic acid-based tests, have been improved. The epidemiology and clinical features of hepatitis E differ between developing and developed countries. HEV infection is usually an acute self-limiting disease, but in developed countries it causes chronic infection with rapidly progressive cirrhosis in organ transplant recipients, patients with hematological malignancy requiring chemotherapy, and individuals with HIV. HEV also causes extrahepatic manifestations, including a number of neurological syndromes and renal injury. Acute infection usually requires no treatment, but chronic infection should be treated by reducing immunosuppression in transplant patients and/or the use of antiviral therapy. In this comprehensive review, we summarize the current knowledge about the virus itself, as well as the epidemiology, diagnostics, natural history, and management of HEV infection in developing and developed countries.

Genetic host specificity of hepatitis E virus

Hepatitis E virus (HEV) causes epidemic and sporadic cases of hepatitis worldwide. HEV genotypes 3 (HEV3) and 4 (HEV4) infect humans and animals, with swine being the primary reservoir. The relevance of HEV genetic diversity to host adaptation is poorly understood. We employed a Bayesian network (BN) analysis of HEV3 and HEV4 to detect epistatic connectivity among protein sites and its association with the host specificity in each genotype. The data imply coevolution among ∼70% of polymorphic sites from all HEV proteins and association of numerous coevolving sites with adaptation to swine or humans. BN models for individual proteins and domains of the nonstructural polyprotein detected the host origin of HEV strains with accuracy of 74-93% and 63-87%, respectively. These findings, taken together with lack of phylogenetic association to host, suggest that the HEV host specificity is a heritable and convergent phenotypic trait achievable through variety of genetic pathways (abundance), and explain a broad host range for HEV3 and HEV4.

Hepatitis E: an emerging disease

Currently, the infection with the hepatitis E virus represents the most frequent cause for acute hepatitis and jaundice in the world. According to WHO estimations, around two billion people, representing one third of the world's population, live in endemic areas for HEV and, therefore, are at risk of infection. In developed countries, the circulation of the virus in both human and animal (swine, boar, deer) sewage has been confirmed; however, the incidence rate is low compared to that of developing countries where outbreaks of acute hepatitis transmitted via the fecal-oral route are originated, more frequently in the flooding season or after natural disasters, combined with deficient sanitary conditions. There are currently 4 known genotypes of HEV. Genotypes 1 and 2 are isolated in all human epidemic outbreaks in developing countries, while genotypes 3 and 4 are isolated not only in humans but also in animals, in both developing and industrialized countries. These data support genotypes 3 and 4 having zoonotic nature. The diagnosis of this disease is based in the detection of anti-HEV IgG and IgM in blood serum using enzyme-linked immunosorbent methods. However, the method that best confirms the diagnosis is the RT-PCR, which detects HEV RNA in blood serum and also provides the genotype. The clinical course is generally that of an acute hepatitis which in some cases may require hospitalization and that, in transplant patients or HIV infected individuals can become a chronic hepatitis. Furthermore, the virus constitutes an important risk for pregnant women. The hepatitis E can present a wide range of symptoms, from a subclinical case to chronic liver disease with extrahepatic manifestations. For this reason, the diagnostic is challenging if no differential diagnosis is included. There is no specific antiviral drug for hepatitis E, but satisfactory results have been observed in some patients treated with pegylated interferon alfa2a and/or ribavirin. This revision is an update of all the molecular, epidemiological, clinic and preventive knowledge on this emergent disease up to date.

Infections of the Liver

The portal vein carries blood from the gastrointestinal tract to the liver and in so doing carries microbes as well. The liver may therefore be involved in infections with a myriad number of microbial organisms. While some of these infections most commonly occur in the immunocompromised host, others affect the immune competence. Hepatic infections may be primary in nature or secondary, as part of systemic or contagious disease. The purpose of this chapter is to provide a brief overview of the various infections of the liver in the pediatric patient.

Host immune status and response to hepatitis E virus infection

Hepatitis E virus (HEV), identified over 30 years ago, remains a serious threat to life, health, and productivity in developing countries where access to clean water is limited. Recognition that HEV also circulates as a zoonotic and food-borne pathogen in developed countries is more recent. Even without treatment, most cases of HEV-related acute viral hepatitis (with or without jaundice) resolve within 1 to 2 months. However, HEV sometimes leads to acute liver failure, chronic infection, or extrahepatic symptoms. The mechanisms of pathogenesis appear to be substantially immune mediated. This review covers the epidemiology of HEV infection worldwide, the humoral and cellular immune responses to HEV, and the persistence and protection of antibodies produced in response to both natural infection and vaccines. We focus on the contributions of altered immune states (associated with pregnancy, human immunodeficiency virus [HIV], and immunosuppressive agents used in cancer and transplant medicine) to the elevated risks of chronic infection (in immunosuppressed/immunocompromised patients) and acute liver failure and mortality (among pregnant women). We conclude by discussing outstanding questions about the immune response to HEV and interactions with hormones and comorbid conditions. These questions take on heightened importance now that a vaccine is available.

Genotype-4 hepatitis E in a human after ingesting roe deer meat in South Korea

The recent increase in the number of cases of indigenous hepatitis E virus (HEV) infection highlights the importance of identifying the transmission routes for the prevention of such infections. Presented herein is the first case of acute HEV infection after ingesting wild roe deer meat in South Korea. A 43-year-old male presented with abdominal discomfort and jaundice. He had not recently traveled abroad, but had eaten raw roe-deer meat 6-8 weeks before the presentation. On the 7th day of hospitalization the patient was diagnosed with acute viral hepatitis E. Phylogenetic analysis of his serum revealed genotype-4 HEV. This case supports the possibility of zoonotic transmission of HEV because the patient appears to have been infected with genotype-4 HEV after ingesting raw deer meat.

Phylogenetic analysis of hepatitis e virus in northwest India

Genotyping and subtyping are important to understand epidemiology of the hepatitis E virus so as to improve control measures to prevent transmission of virus in the community. Hence, the aim of the current study was to identify the prevalent HEV genotypes in Rajasthan in acute sporadic hepatitis E cases with varying degree of liver failure. We studied hepatitis E virus (HEV) isolates from hospitalized patients in Rajasthan, western India. In a total of seventeen HEV sequences, six acute viral hepatitis, seven acute liver failure, and 4 acute- on-chronic cases were analyzed. Subtypes 1a and 1c of HEV are prevalent in Northwest India.

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.

Hepatitis E

Hepatitis E refers to liver disease caused by the hepatitis E virus (HEV), a small, nonenveloped virus with a single-stranded RNA genome. The virus has four genotypes, but only one serotype. Genotypes 1 and 2 exclusively infect humans, whereas genotypes 3 and 4 also infect pigs and several other mammalian species. Though HEV does not grow well in cell culture, several aspects of its biology and pathogenesis have been worked out using animal models and cell transfection studies, and by analogy with other related viruses. HEV itself appears noncytopathic, and the liver injury during hepatitis E may be mediated by the host immune response. In areas with poor sanitation, HEV infection is common and presents as outbreaks and also as sporadic cases with acute self-limited hepatitis. The transmission is feco-oral, usually through contaminated drinking water. The disease often affects young adults and is particularly severe among pregnant women and persons with preexisting liver cirrhosis. In the developed world, the disease is being increasingly recognized. It occurs as occasional sporadic cases, most often among elderly men with coexisting illnesses. These appear to be related to zoonotic transmission. Chronic infection is known among immunosuppressed persons in these regions and may progress to liver cirrhosis. Serological tests for diagnosis of HEV exposure and recent infection, namely immunoglobulin (Ig)G and IgM anti-HEV, respectively, need further improvement in sensitivity and specificity, particularly when used in developed countries. Two recombinant protein vaccines have undergone successful human trials, but are not yet commercially available. Recent development of cell-culture methods for HEV should allow a better understanding of this enigmatic agent.

Infection dynamics of hepatitis E virus in naturally infected pigs in a Chinese farrow-to-finish farm

To analyze the changes that occur in pigs during hepatitis E virus (HEV) infection, 256 serial serum samples were obtained from 32 pigs from one pig farm at ages 0 (cord blood), 15, 30, 60, 75, 90, 120, and 150 days. All HEV markers were assayed in these samples and showed that total anti-HEV antibodies and IgG formed two peaks. The first peak occurred at 0-60 days and the second after 75 days. No markers of infection, such as HEV RNA, antigen and anti-HEV IgM, were detectable during the first peak. Most newborn piglets (< 24 h of age) were negative for total anti-HEV and IgG. However, colostrum from all of the sows had evidence of these antibodies. Thus, the anti-HEV in the first peak was assumed to be acquired from maternal milk. Some infectious markers were positive at the beginning of second peak. PCR products were cloned and sequenced and the results indicated those sequences belonged to HEV genotype 4. The antibody present during the second peak may be induced by natural infection with HEV. In conclusion, pigs are susceptible to HEV infection and may remain infectious after the first peak of anti-HEV antibody.

Hepatitis E virus infections in swine and swine handlers in Vellore, Southern India

Hepatitis E virus (HEV) in industrialized countries is zoonotically transmitted, and swine act as a major reservoir of HEV. Serum samples from 102 swine and plasma from 34 swine handlers in Vellore, India were tested by using a reverse transcription-polymerase chain reaction to detect and genotype HEV. We measured levels of IgG against HEV in swine handlers and in age and geographically matched controls from rural and urban populations in Vellore. HEV was amplified from two pigs and both viruses belonged to genotype 4. No HEV RNA was amplified from any swine handler, but 94.1% of swine handlers were positive for antibodies against HEV, a seroprevalence rate significantly higher than in rural and urban controls. The HEV genotype circulating in swine in India is different from that of humans, but the higher antibody levels in swine handlers support the possibility that zoonotic infections may occur.

The molecular epidemiology of hepatitis E virus infection

Molecular characterization of various hepatitis E virus (HEV) strains circulating among humans and animals (particularly swine, deer and boars) in different countries has revealed substantial genetic heterogeneity. The distinctive four-genotype distribution worldwide of mammalian HEV and varying degrees of genetic relatedness among local strains suggest a long and complex evolution of HEV in different geographic regions. The population expansion likely experienced by mammalian HEV in the second half of the 20th century is consistent with an extensive genetic divergence of HEV strains and high prevalence of HEV infections in many parts of the world, including developed countries. The rate and mechanisms of human-to-human transmission and zoonotic transmission to humans vary geographically, thus contributing to the complexity of HEV molecular evolution.

Differences in capabilities of different enzyme immunoassays to detect anti-hepatitis E virus immunoglobulin G in pigs infected experimentally with hepatitis E virus genotype 3 or 4 and in pigs with unknown exposure

Hepatitis E virus (HEV), a major cause of acute viral hepatitis in humans in many developing countries, is highly prevalent in the pig population worldwide. The objective of this study was to assess the capability of three porcine prototypes of a human enzyme-linked immunosorbent assay (ELISA), an in-house ELISA and a line-immunoassay (LIA) to detect anti-HEV antibodies in pigs infected experimentally with HEV (n = 57), known to be negative for HEV infection (n = 27), or with unknown exposure to HEV infection (field samples, n = 90). All 27 samples from non-infected pigs were negative with all five assays. The earliest detection of anti-HEV antibodies occurred at 14 days post-inoculation (dpi) with four of five assays. From 42 dpi, all samples from infected pigs were detected correctly as anti-HEV positive. Kappa analysis demonstrated substantial agreement among tests (0.62-1.00) at 14 dpi and complete agreement (1.00) at 56 dpi. The overall area under the curve for all quantitative tests as determined by receiver operator characteristic analysis ranged from 0.794 to 0.831 indicating moderate accuracy. The results showed that all five assays can detect anti-HEV IgG antibodies accurately in pigs infected experimentally with HEV. In field samples, a higher prevalence of anti-HEV IgG was found in breeding herds than in growing pigs (100% versus 66.7-93.9%). These serological assays should be very useful in veterinary diagnostic labs for HEV diagnosis in swine.

Animal sentinels for environmental and public health

Studies of the effects of environmental exposures on domestic and wild animals can corroborate or inform epidemiologic studies in humans. Animals may be sensitive indicators of environmental hazards and provide an early warning system for public health intervention, as exemplified by the iconic canary in the coal mine. This article illustrates the application of animal sentinel research to elucidate the effects of exposure to traditional and emerging contaminants on human health. Focusing on environmental issues at the forefront of current public health research, the article describes exposures to community air pollution, environmental tobacco smoke, and pesticides and associations with cancer, reproductive outcomes, and infectious diseases. Finally, it covers the role of marine mammals in monitoring the health of the oceans and humans.

A systematic review/meta-analysis of primary research investigating swine, pork or pork products as a source of zoonotic hepatitis E virus

The objectives of our study were to identify and categorize primary research investigating swine/pork as a source of zoonotic hepatitis E virus (HEV) using the relatively new technique of scoping study, and to investigate the potential association between human exposure to swine/pork and HEV infection quantitatively using systematic review/meta-analysis methodology. From 1890 initially identified abstracts, 327 were considered for the review. Five study design types (cross-sectional, prevalence, genotyping, case-report and experimental transmission studies) were identified. A significant association between occupational exposure to swine and human HEV IgG seropositivity was reported in 10/13 cross-sectional studies. The association reported between pork consumption and HEV IgG seropositivity was inconsistent. The quantification of viral load in swine and retail pork, viral load required for infection in primates, cohort and case-control studies in humans, and formal risk assessment are recommended before specific public-health policy actions are taken.

Discovery of hepatitis E: the epidemic non-A, non-B hepatitis 30 years down the memory lane

Hepatitis E was first recognised during an epidemic of hepatitis, which occurred in Kashmir Valley in 1978. The epidemic involved an estimated 52,000 cases of icteric hepatitis with 1700 deaths. The disease had unique clinical and epidemiological features. The epidemic was water-borne with highly compressed epidemic curve. Following the epidemic, secondary waves of hepatitis did not occur. Clinical profile was characterized by cholestasis in around 20% of patients. The disease predominantly occurred in young adults. There was increased incidence and severity of the disease in pregnant women. A subset of patients had distinctive liver histology with bile plugs in the canaliculi and formation of pseudo-ductules by hepatocytes around the bile plugs. All surviving patients had self limiting disease. Sera lacked serological markers of acute hepatitis A and hepatitis B. Based on these data, the possibility of another human hepatitis virus distinct from post-transfusion non-A, non-B hepatitis was postulated. Balayan et al. (1983) successfully transmitted the disease into himself by oral administration of pooled stool extracts of 9 patients from a non-A, non-B hepatitis outbreak which had occurred in a Soviet military camp located in Afghanistan. Reyes et al. (1990) cloned and sequenced hepatitis E virus genome. Over the years, hepatitis E was identified as a major health problem in developing countries with unsafe water supplies and poor sanitary disposal. Data from sero-surveys forced re-evaluation of the epidemiology of hepatitis E and gave an indirect indication to vocationally acquired HEV infections in industrialized countries. Soon, autochthonous hepatitis E was recognised as a clinical problem in such countries. Several animal species especially domestic swine, wild boar and wild deer were found to be reservoirs of hepatitis E virus genotype 3 & 4 in these countries. Human infections occur through intake of uncooked or undercooked meat of the infected animals and pig livers or sausages made from these livers and sold in supermarkets. Chronic hepatitis E resulting in rapidly progressive liver cirrhosis and end stage liver disease was described in organ transplant patients and those with other immunodeficiency states from many European countries. Two recombinant hepatitis E virus vaccines have successfully undergone phase 3 trials.

Hepatitis E in Italy: a long-term prospective study

BACKGROUND & AIMS

In developed countries, hepatitis E is usually associated with travelling to endemic areas, but a growing number of sporadic cases are also seen in patients with no travel history. The aim of this study was to assess the impact and the molecular epidemiology of hepatitis E in Italy.

METHODS

Between January 1994 and October 2009, we analyzed 651 patients with acute non-A-C hepatitis. Diagnosis of hepatitis E was based on the presence of IgM anti-HEV and/or the detection of HEV RNA by RT-PCR. Viral isolates were sequenced and phylogenetically characterized.

RESULTS

A total of 134 out of 651 (20.6%) patients tested had acute hepatitis E. All were anti-HEV IgM and IgG positive and 96 (71.6%) were also positive for HEV RNA. Moreover, 39 (6%) patients were anti-HEV IgG positive but negative for both IgM anti-HEV and HEV RNA. A total of 109 (81.3%) patients developed hepatitis E travelling to endemic areas, 3 (2.3%) acquired intra-familial infection from relatives who developed travel-related disease, while 22 (16.4%) patients denied having travelled abroad. In all patients, acute disease had a self-limited course with ALT normalization within 3-6 weeks. Phylogenetic analysis of 39 isolates from patients with a travel-related disease showed that they belonged to genotype 1, while sequences from five patients with autochthonous hepatitis E belonged to genotype 3.

CONCLUSIONS

In Italy, most cases of hepatitis E are travel related, caused by viral genotype 1, while autochthonous cases are caused by genotype 3. The prevalence of genotype 3 among pigs and boars suggests that HEV infection may have zoonotic origins in non-endemic countries.

Hepatitis E: Historical, contemporary and future perspectives

Hepatitis E was suspected for the first time in 1980 during a waterborne epidemic of acute hepatitis in Kashmir, India. In the 30 years since then, a small virus with single-stranded RNA genome has been identified as the cause of this disease and named as hepatitis E virus (HEV). The virus has four genotypes; of these, genotypes 1 and 2 are known to infect only humans, whereas genotypes 3 and 4 primarily infect other mammals, particularly pigs, but occasionally cause human disease. In highly-endemic areas, the disease occurs in epidemic and sporadic forms, caused mainly by infection with genotype 1 or 2 virus, acquired through the fecal-oral route, usually through contaminated water supplies. The disease is characterized by particularly severe course and high mortality among pregnant women. In persons with pre-existing chronic liver disease, HEV superinfection can present as acute-on-chronic liver disease. In low-endemic regions, sporadic cases of locally-acquired HEV infection are reported; these are caused mainly by genotype 3 or 4 HEV acquired possibly through zoonotic transmission from pigs, wild boars or deer. In these areas, chronic infection with genotype 3 HEV, which may progress to liver cirrhosis, has been reported among immunosuppressed persons. Two subunit vaccines containing recombinant truncated capsid proteins of HEV have been shown to be highly effective in preventing the disease; however, these are not yet commercially available. These vaccines should be of particular use in groups that are at high risk of HEV infection and/or of poor outcome.

The nucleotides on the stem-loop RNA structure in the junction region of the hepatitis E virus genome are critical for virus replication

The roles of conserved nucleotides on the stem-loop (SL) structure in the intergenic region of the hepatitis E virus (HEV) genome in virus replication were determined by using Huh7 cells transfected with HEV SL mutant replicons containing reporter genes. One or two nucleotide mutations of the AGA motif on the loop significantly reduced HEV replication, and three or more nucleotide mutations on the loop abolished HEV replication. Mutations on the stem and of the subgenome start sequence also significantly inhibited HEV replication. The results indicated that both the sequence and the SL structure in the junction region play important roles in HEV replication.

Hepatitis E virus infection among animals and humans in Xinjiang, China: possibility of swine to human transmission of sporadic hepatitis E in an endemic area

Hepatitis E is a worldwide public health problem, especially in areas with poor sanitation. This study examines the potential hepatitis E virus (HEV) animal reservoirs and the current status of HEV infection among animals and humans in an endemic area of Xinjiang, China. One thousand five hundred twenty-one serum samples from 12 different animal species and 296 sera from humans were detected for anti-HEV with an in-house enzyme immunoassay, and partial HEV RNA was amplified with a reverse transcription-nested polymerase chain reaction (RT-nPCR). All these distinct animal species, except jerboa and hoptoad, were positive for anti-HEV. However, HEV RNA was only amplified from pigs and a sporadic hepatitis E case in humans. The human HEV strain (CHN-XJ-HE29) shared 100% nucleotide identity with the swine HEV strain (CHN-XJ-SW50), both of which were collected from the same district; this indicates the possibility of HEV transmission from swine to humans in an endemic area.

Seroprevalence and distribution of hepatitis E virus in various ethnic groups in Gansu province, China

Gansu province is located in northwestern China and is home to 45 ethnic groups including Han, Hui, Zang and others. Different ethnic groups have varying involvement with livestock and meat consumption, especially pork. To investigate the prevalence of hepatitis E virus (HEV) infection and the distribution of HEV genotypes among the major ethnic groups in Gansu province, 2090 serum samples were collected from individuals from four regions and three ethnic groups, the Han, Hui and Zang. All serum samples were tested for anti-HEV IgG and IgM antibodies, as well as HEV antigen, and selected samples were then tested for HEV RNA. The data showed that the seroprevalence of anti-HEV IgG in the Hui, Han and Zang ethnic groups from the four regions was 8.9%, 18.7% and 32.9%, respectively, and these differed significantly (P<0.05). The seroprevalence of anti-HEV antibody for each ethnic group varied among the different regions. In general, within the same region, the three ethnic groups also show differences. Genomic analysis indicated that HEV isolated from humans belonged to genotype 4, and resembled closely swine HEV isolates from Gansu province. The seroprevalence of anti-HEV antibodies was in accordance with the amount of contact with pigs in the different regions. Pigs are the primary host for HEV, so people in frequent contact with pigs may be at risk of zoonotic infection. However, populations that have rare contact with pigs are more likely to be susceptible to HEV when exposed, suggesting that should be the target of vaccination.

First case of genotype 4 human hepatitis E virus infection acquired in India

This report describes a case of severe hepatitis in an individual returning from India which was found to be the result of infection with HEV genotype 4. HEV was diagnosed using a novel RT-PCR assay (with internal control) for HEV RNA detection/quantitation, described herein. This is the first documented report of zoonotic transmission of HEV genotype 4 infection acquired in India.

Hepatitis E virus infection in central China reveals no evidence of cross-species transmission between human and swine in this area

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animal were reported as reservoirs. Swine stands out as the major reservoir for HEV infection in humans, as suggested by the close genetic relationship of swine and human virus. Since 2000, Genotype 4 HEV has become the dominant cause of hepatitis E disease in China. Recent reports showed that genotype 4 HEV is freely transmitted between humans and swine in eastern and southern China. However, the infection status of HEV in human and swine populations in central China is still unclear. This study was conducted in a rural area of central China, where there are many commercial swine farms. A total of 1476 serum and 554 fecal specimens were collected from the general human and swine populations in this area, respectively. The seroepidemiological study was conducted by enzyme-linked immunosorbent assay. Conserved genomic sequences of open reading frame 2 were detected using reverse transcription-PCR. The results indicated that the overall viral burden of the general human subjects was 0.95% (14/1476), while 7.0% (39/554) of the swine excreted HEV in stool. The positive rate of anti-HEV IgG and IgM in the serum samples was 7.9% (117/1476) and 1.6% (24/1476), respectively. Phylogenetic analysis based on the 150 nt partial sequence of the capsid protein gene showed that the 53 swine and human HEV isolates in the current study all belonged to genotype 4, clustering into three major groups. However, the HEV isolates prevalent in the human and swine populations were classified into known distinct subgenotypes, which suggested that no cross-species transmission between swine and humans had taken place in this area. This result was confirmed by cloning and phylogenetic analysis of the complete capsid protein gene sequence of three representative HEV strains in the three major groups. The cross reactivity between anti-HEV IgG from human sera and the two representative strains from swine in central China was confirmed by Dot-blot assay. In conclusion, although all the HEV strains prevalent in central China belonged to genotype 4, there is no evidence of cross-species transmission between human and swine in this area.

Zoonotic risk of hepatitis E virus (HEV): A study of HEV infection in animals and humans in suburbs of Beijing

AIM

To investigate hepatitis E virus (HEV) infection among different animals and workers in pig farms and slaughterhouses, and analyze the genotype of HEV isolated in this study.

METHODS

Serum samples were collected from adult swine, cows, sheep, younger swine (< 3 months), and workers in pig farms and slaughterhouses (professional group). Fecal samples were collected from younger swine in the south suburbs of Beijing. Anti-HEV antibody was evaluated by direct sandwich enzyme immunoassay. HEV RNA was extracted from fecal samples and amplified by nested reverse transcription polymerase chain reaction (RT-nPCR). The PCR products were sequenced, and the sequence homology and phylogenetics of the HEV strains isolated from swine were analyzed.

RESULTS

The anti-HEV positivity rates in adult swine, cows, sheep, younger swine, professional group and general population were 98.23% (222/226), 29.35% (54/184), 9.80% (20/207), 60.73% (99/164), 42.51% (105/247) and 20.29% (522/2572), respectively. The HEV RNA positivity rate of fecal samples was 22.89% (19/83) and 16/19 samples were positive for HEV RNA amplified with both primers, HEV open reading frame (ORF)1 and HEV ORF2. Sequence analysis of these 16 samples showed that there were two groups, designated BJ-1 and BJ-2. The nucleotide homology of BJ-1 and BJ-2 was 99%. Phylogenetic analysis indicated that both of these groups belonged to genotype 4d.

CONCLUSION

Workers in pig farms and slaughterhouses were more likely to contract HEV infection than the general population because of close contact with swine with a high prevalence of anti-HEV.

Epidemiology of hepatitis E: current status

Hepatitis E, caused by infection with hepatitis E virus (HEV), is a common cause of acute hepatitis in areas with poor sanitation. The virus has four genotypes with one serotype: genotypes 1 and 2 exclusively infect humans, whereas genotypes 3 and 4 also infect other animals, particularly pigs. In endemic areas, both large outbreaks of acute hepatitis as well as sporadic cases occur frequently. These cases are usually due to genotype 1 or 2 HEV and are predominantly caused by fecal-oral transmission, usually through contamination of drinking water; contaminated food, materno-fetal (vertical spread) and parenteral routes are less common modes of infection. The acute hepatitis caused by this virus has the highest attack rates in young adults and the disease is particularly severe among pregnant women. HEV superinfection can occur among persons with pre-existing chronic liver disease. In non-endemic regions, locally acquired disease was believed to be extremely uncommon. However, in recent years, an increasing number of cases, due mostly due to genotype 3 or 4 HEV, have been recognized. These are more often elderly men who have other coexisting illnesses, and appear to be related to zoonotic transmission from pigs, wild boars and deer, either food-borne or otherwise. Also, chronic infection with genotype 3 HEV has been reported among immunosuppressed persons in these regions. A subunit vaccine has been shown to be effective in preventing clinical disease, but is not yet commercially available. Our understanding of hepatitis E epidemiology has undergone major changes in recent years, and the future may hold even more surprises.

Molecular biology and pathogenesis of hepatitis E virus

The hepatitis E virus (HEV) is a small RNA virus and the etiological agent for hepatitis E, a form of acute viral hepatitis. The virus has a feco-oral transmission cycle and is transmitted through environmental contamination, mainly through drinking water. Recent studies on the isolation of HEV-like viruses from animal species also suggest zoonotic transfer of the virus. The absence of small animal models of infection and efficient cell culture systems has precluded virological studies on the replication cycle and pathogenesis of HEV. A vaccine against HEV has undergone successful clinical testing and diagnostic tests are available. This review describes HEV epidemiology, clinical presentation, pathogenesis, molecular virology and the host response to HEV infection. The focus is on published literature in the past decade.