Molecular biology and pathogenesis of hepatitis E virus

Hepatitis E outbreak in the health district of Bocaranga-Koui, Central African Republic, 2018-2019

BACKGROUND

Hepatitis E virus (HEV) is a major public health disease causing large outbreaks and sporadic cases of acute hepatitis. We investigated an outbreak of HEV infection that occurred in September 2018 in the health district (HD) of Bocaranga-Koui, located in the northwestern part of Central African Republic (CAR).

METHODS

Blood samples were collected from 352 patients aged 0-85 years suspected to be infected with yellow fever (YF), according to the World Health Organization YF case definition. The notification forms from recorded cases were used. Water consumed in the HD were also collected. Human samples found negative for anti-YF IgM were then tested by ELISA for anti-HEV IgM and IgG antibodies. Positive anti-HEV (IgM and/or IgG) samples and collected water were then subjected to molecular biology tests using a real time RT-PCR assay, followed by a nested RT-PCR assay for sequencing and phylogenetic analysis.

RESULTS

Of the 352 icterus patients included, anti-HEV IgM was found in 142 people (40.3%) and anti-HEV IgG in 175 (49.7%). Although HEV infection was detected in all age groups, there was a significant difference between the 0-10 age groups and others age groups (P = 0.001). Elevated levels of serum aminotransferase were observed in anti-HEV IgM-positive subjects. Phylogenetic analysis showed HEV genotype 1e in infected patients as well as in the contaminated water.

CONCLUSION

This epidemic showed that CAR remains an HEV-endemic area. The genotype 1e strain was responsible for the HEV outbreak in Bocaranga-Koui HD. It is necessary to implement basic conditions of hygiene and sanitation to prevent further outbreaks of a HEV epidemics, to facilitate access to clean drinking water for the population, to launch intensive health education for basic hygiene measures, to sett up targeted hygiene promotion activities and, finally, to ensure that formal health care is available.

Development of a HiBiT-tagged reporter hepatitis E virus and its utility as an antiviral drug screening platform

Previously, we developed an infectious hepatitis E virus (HEV) harboring the nanoKAZ gene in the hypervariable region of the open reading frame 1 (ORF1) of the HEV3b (JE03-1760F/P10) genome and demonstrated the usefulness for screening anti-HEV drugs that inhibit the early infection process. In the present study, we constructed another reporter HEV (HEV3b-HiBiT) by placing a minimized HiBiT tag derived from NanoLuc luciferase at the 3'-end of the viral capsid (ORF2) coding sequence. It replicated efficiently in PLC/PRF/5 cells, produced membrane-associated particles identical to those of the parental virus, and was genetically stable and infectious. The HiBiT tag was fused to both secreted ORF2s (ORF2s-HiBiT) and ORF2c capsid protein (ORF2c-HiBiT). The ORF2c-HiBiT formed membrane-associated HEV particles (eHEV3b-HiBiT). By treating these particles with digitonin, we demonstrated that the HiBiT tag was expressed on the surface of capsid and was present inside the lipid membrane. To simplify the measurement of luciferase activity and provide a more convenient screening platform, we constructed an ORF2s-defective mutant (HEV3b-HiBiT/ΔORF2s) in which the secreted ORF2s are suppressed. We used this system to evaluate the effects of introducing small interfering RNAs and treatment with an inhibitor or accelerator of exosomal release on HEV egress and demonstrated that the effects on virus release can readily be analyzed. Therefore, HEV3b-HiBiT and HEV3b-HiBiT/ΔORF2s reporters may be useful for investigating the virus life cycle and can serve as a more convenient screening platform to search for candidate drugs targeting the late stage of HEV infection such as particle formation and release. IMPORTANCE The construction of recombinant infectious viruses harboring a stable luminescence reporter gene is essential for investigations of the viral life cycle, such as viral replication and pathogenesis, and the development of novel antiviral drugs. However, it is difficult to maintain the stability of a large foreign gene inserted into the viral genome. In the present study, we successfully generated a recombinant HEV harboring the 11-amino acid HiBiT tag in the ORF2 coding region and demonstrated the infectivity, efficient virus growth, particle morphology, and genetic stability, suggesting that this recombinant HEV is useful for in vitro assays. Furthermore, this system can serve as a more convenient screening platform for anti-HEV drugs. Thus, an infectious recombinant HEV is a powerful approach not only for elucidating the molecular mechanisms of the viral life cycle but also for the screening and development of novel antiviral agents.

Hepatitis E Virus RNA Detection from Hunted Wild Boars in Central Italy: an Epidemiological Investigation

Every year, foodborne pathogens, including the hepatitis E virus (HEV), cause thousands of infections in different continents. Final consumers become infected through the ingestion of contaminated animal origin foodstuffs. Generally, in industrialized countries, HEV genotype 3 is involved in sporadic outbreaks. Infections have been described, in Europe and Japan as consequence of pork products and contaminated wild boar's primary or processed products (liver and muscle tissues) consumption. In Central Italy, hunting activities are largely practiced. In these small and rural communities, game meat and liver are ingested by hunters' families or at local and traditional restaurants. Therefore, these food chains can be considered critical HEV reservoirs. In this study, 506 liver and diaphragm tissues were collected from hunted wild boars in the Southern Marche region (Central Italy) and were screened for HEV RNA detection. From the 10.87% of liver and 2.76% of muscle samples, HEV3 subtype c was discovered. The observed prevalence values resulted in line with previous investigations performed in other Central Italian regions, but higher than Northern ones (3.7% and 1.9% from liver tissue). Therefore, the obtained epidemiological data highlighted the wide occurrence of HEV RNA circulation in a low-investigated area. Basing on results, a One-health approach was adopted due to the sanitary relevance of this Public Health concern.

Animal Models for Studying Congenital Transmission of Hepatitis E Virus

One of the most intriguing issues in the hepatitis E virus (HEV) field is the significant increase in mortality rates of the mother and fetus when infection occurs in the second and third trimesters of gestation. A virus that is normally self-limiting and has a mortality rate of less than one percent in otherwise healthy individuals steeply rises by up to 30% in these pregnant populations. Answering this pivotal question has not been a simple task. HEV, in general, has been a difficult pathogen to understand in the laboratory setting. A historical lack of ability to efficiently propagate the virus in tissue culture models has led to many molecular aspects of the viral lifecycle being understudied. Although great strides have been made in recent years to adapt viruses to cell culture, this field remains behind other viruses that are much easier to replicate efficiently in vitro. Some of the greatest discoveries regarding HEV have come from using animal models for which naturally occurring strains of HEV have been identified, including pigs and chickens, but key limitations have made animal models imperfect for studying all aspects of human HEV infections. In addition to the difficulties working with HEV, pregnancy is a very complicated biological process with an elaborate interplay between many different host systems, including hormones, cardiovascular, kidneys, respiratory, gastrointestinal, epithelial, liver, metabolic, immune, and others. Significant differences between the timing and interplay of these systems are notable between species, and making direct comparisons between animals and humans can be difficult at times. No simple answer exists as to how HEV enhances mortality in pregnant populations. One of the best approaches to studying HEV in pregnancy is likely a combinatorial approach that uses the best combination of emerging in vitro and in vivo systems while accounting for the deficiencies that are present in each model. This review describes many of the current HEV animal model systems and the strengths and weaknesses of each as they apply to HEV pregnancy-associated mortality. We consider factors that are critical to analyzing HEV infection within the host and how, despite no perfect animal model for human pregnancy mortality existing, recent developments in HEV models, both in vitro and in vivo, are advancing our overall understanding of HEV in the pregnant host.

Modulation of cellular autophagy by genotype 1 hepatitis E virus ORF3 protein

Hepatitis E virus (HEV) egresses from infected hepatocytes as quasienveloped particles containing open reading frame 3 (ORF3) protein. HEV ORF3 (small phosphoprotein) interacts with host proteins to establish a favourable environment for virus replication. It is a functional viroporin that plays an important role during virus release. Our study provides evidence that pORF3 plays a pivotal role in inducing Beclin1-mediated autophagy that helps HEV-1 replication as well as its exit from cells. The ORF3 interacts with host proteins involved in regulation of transcriptional activity, immune response, cellular and molecular processes, and modulation of autophagy, by interacting with proteins, DAPK1, ATG2B, ATG16L2 and also several histone deacetylases (HDACs). For autophagy induction, the ORF3 utilizes non-canonical NF-κB2 pathway and sequesters p52NF-κB and HDAC2 to upregulate DAPK1 expression, leading to enhanced Beclin1 phosphorylation. By sequestering several HDACs, HEV may prevent histone deacetylation to maintain overall cellular transcription intact to promote cell survival. Our findings highlight a novel crosstalk between cell survival pathways participating in ORF3-mediated autophagy.

Hepatitis E as a Zoonosis

Hepatitis E viruses in the family of Hepeviridae have been classified into 2 genus, 5 species, and 13 genotypes, involving different animal hosts of different habitats. Among all these genotypes, four (genotypes 3, 4, 7, and C1) of them are confirmed zoonotic causing sporadic human diseases, two (genotypes 5 and 8) were likely zoonotic showing experimental animal infections, and the other seven were not zoonotic or unconfirmed. These zoonotic HEV carrying hosts include pig, boar, deer, rabbit, camel, and rat. Taxonomically, all the zoonotic HEVs belong to the genus Orthohepevirus, which include genotypes 3, 4, 5, 7, 8 HEV in the species A and genotype C1 HEV in the species C. In the chapter, information of zoonotic HEV such as swine HEV (genotype 3 and 4), wild boar HEV (genotypes 3-6), rabbit HEV (genotype 3), camel HEV (genotype 7 and 8), and rat HEV (HEV-C1) was provided in detail. At the same time, their prevalence characteristics, transmission route, phylogenetic relationship, and detection technology were discussed. Other animal hosts of HEVs were introduced briefly in the chapter. All these information help peer researchers have basic understanding of zoonotic HEV and adopt reasonable strategy of surveillance and prevention.

Regulatory Role of B Cells and Its Subsets in Hepatitis E Virus Infection

Antibodies as well as memory B cells are the potential correlates of a protective immune response against hepatitis E virus (HEV) infection. Literature on the role of B regulatory cells (Bregs) in acute viral infections is limited. We have evaluated the role of IL-10 expressing Bregs in HEV infection. A total of 108 acute hepatitis E patients, 55 hepatitis E recovered individuals and 128 HEV naïve healthy controls were enrolled. The percentages of peripheral CD19⁺, immature CD19⁺CD24^hiCD38^hi, mature CD19⁺CD24^intCD38^int and memory CD19⁺CD24^hiCD38⁻ B cells were analyzed by flowcytometry. Intracellular cytokine staining for IL-10 and TGF-β, HEV-rORF2p specific T cell response (IFN-γ expression) pre/post IL-10/IL-10R blocking and CD19⁺IL-10⁺ B cells-depletion based assays were carried out to assess the functionality of Bregs. The percentage of HEV-rORF2p specific immature B cell phenotype was significantly higher in acute hepatitis E patients compared to hepatitis E recovered individuals and controls. Significantly higher IL-10 expression on B and HEV-rORF2p stimulated immature B cells of acute hepatitis E patients compared to controls indicated that Bregs are functional and HEV-rORF2p specific. Enhanced IFN-γ expression on CD8⁺ T cells upon IL-10/IL-10R blocking and also post CD19⁺IL-10⁺ B cells depletion suggested that CD3⁺CD8⁺IFN-γ⁺ T cells corroborate the regulatory potential of Bregs via IL-10 dependent mechanism. We have identified HEV specific functional, immature CD19⁺CD24^hiCD38^hi B cells having IL-10 mediated regulatory activities and a potential to modulate IFN-γ mediated T cell response in Hepatitis E. The prognostic/pathogenic role of Bregs in recovery from severe hepatitis E needs evaluation.

Decoding the codon usage patterns in Y-domain region of hepatitis E viruses

Background

Hepatitis E virus (HEV) is a positive-sense RNA virus belonging to the family Hepeviridae. The genome of HEV is organized into three open-reading frames (ORFs): ORF1, ORF2, and ORF3. The ORF1 non-structural Y-domain region (YDR) has been demonstrated to play an important role in the HEV pathogenesis. The nucleotide composition, synonymous codon usage bias in conjunction with other factors influencing the viral YDR genes of HEV have not been studied. Codon usage represents a significant mechanism in establishing the host-pathogen relationship. The present study for the first time elucidates the detailed codon usage patterns of YDR among HEV and HEV-hosts (Human, Rabbit, Mongoose, Pig, Wild boar, Camel, Monkey).

Results

The overall nucleotide composition revealed the abundance of C and U nucleotides in YDR genomes. The relative synonymous codon usage (RSCU) analysis indicated biasness towards C and U over A and G ended codons in HEV across all hosts. Codon frequency comparative analyses among HEV-hosts showed both similarities and discrepancies in usage of preferred codons encoding amino acids, which revealed that HEV codon preference neither completely differed nor completely showed similarity with its hosts. Thus, our results clearly indicated that the synonymous codon usage of HEV is a mixture of the two types of codon usage: coincidence and antagonism. Mutation pressure from virus and natural selection from host seems to be accountable for shaping the codon usage patterns in YDR. The study emphasised that the influence of compositional constraints, codon usage biasness, mutational alongside the selective forces were reflected in the occurrence of YDR codon usage patterns.

Conclusions

Our study is the first in its kind to have reported the analysis of codon usage patterns on a total of seven different natural HEV hosts. Therefore, knowledge of preferred codons obtained from our study will not only augment our understanding towards molecular evolution but is also envisaged to provide insight into the efficient viral expression, viral adaptation, and host effects on the HEV YDR codon usage.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43141-022-00319-2.

Ecological Barrier Deterioration Driven by Human Activities Poses Fatal Threats to Public Health due to Emerging Infectious Diseases

The coronavirus disease 2019 (COVID-19) and concerns about several other pandemics in the 21st century have attracted extensive global attention. These emerging infectious diseases threaten global public health and raise urgent studies on unraveling the underlying mechanisms of their transmission from animals to humans. Although numerous works have intensively discussed the cross-species and endemic barriers to the occurrence and spread of emerging infectious diseases, both types of barriers play synergistic roles in wildlife habitats. Thus far, there is still a lack of a complete understanding of viral diffusion, migration, and transmission in ecosystems from a macro perspective. In this review, we conceptualize the ecological barrier that represents the combined effects of cross-species and endemic barriers for either the natural or intermediate hosts of viruses. We comprehensively discuss the key influential factors affecting the ecological barrier against viral transmission from virus hosts in their natural habitats into human society, including transmission routes, contact probability, contact frequency, and viral characteristics. Considering the significant impacts of human activities and global industrialization on the strength of the ecological barrier, ecological barrier deterioration driven by human activities is critically analyzed for potential mechanisms. Global climate change can trigger and expand the range of emerging infectious diseases, and human disturbances promote higher contact frequency and greater transmission possibility. In addition, globalization drives more transmission routes and produces new high-risk regions in city areas. This review aims to provide a new concept for and comprehensive evidence of the ecological barrier blocking the transmission and spread of emerging infectious diseases. It also offers new insights into potential strategies to protect the ecological barrier and reduce the wide-ranging risks of emerging infectious diseases to public health.

Biochemical and Biophysical Characterisation of the Hepatitis E Virus Guanine-7-Methyltransferase

Hepatitis E virus (HEV) is an understudied pathogen that causes infection through fecal contaminated drinking water and is prominently found in South Asian countries. The virus affects ~20 million people annually, leading to ~60,000 infections per year. The positive-stranded RNA genome of the HEV genotype 1 has four conserved open reading frames (ORFs), of which ORF1 encodes a polyprotein of 180 kDa in size, which is processed into four non-structural enzymes: methyltransferase (MTase), papain-like cysteine protease, RNA-dependent RNA polymerase, and RNA helicase. MTase is known to methylate guanosine triphosphate at the 5'-end of viral RNA, thereby preventing its degradation by host nucleases. In the present study, we cloned, expressed, and purified MTase spanning 33-353 amino acids of HEV genotype 1. The activity of the purified enzyme and the conformational changes were established through biochemical and biophysical studies. The binding affinity of MTase with magnesium ions (Mg2+) was studied by isothermal calorimetry (ITC), microscale thermophoresis (MST), far-UV CD analysis and, fluorescence quenching. In summary, a short stretch of nucleotides has been cloned, coding for the HEV MTase of 37 kDa, which binds Mg2+ and modulate its activity. The chelation of magnesium reversed the changes, confirming its role in enzyme activity.

Hepatitis E virus in Saudi Arabia: more surveillance needed

Hepatitis E virus (HEV) is a small quasi-enveloped ssRNA causing acute hepatitis. HEV is the leading cause of intermittent acute hepatitis and fulminant hepatic failure. Risk factors include drinking contaminated water in developing countries and consumption of infected animal products in developed countries. Previous reports on HEV prevalence in Saudi Arabia had small sample sizes. Nationwide systematic seroprevalence studies are needed to investigate risk factors and annual incidence. Camels play a cultural and economic role in the life of Saudi citizens with frequent human contact and potential role in zoonotic transmission. Future research needs to include larger sample-sizes and nationwide studies. Future studies should also focus on raising awareness of HEV infection and the need for wider population testing and screening.

Production of a Hepatitis E Vaccine Candidate Using the Pichia pastoris Expression System

Hepatitis E virus (HEV) is associated with acute hepatitis disease, which may lead to chronic disease in immunocompromised individuals. The disease is particularly severe among pregnant women (20-30% mortality). No vaccine is available to combat the HEV except Hecolin, which is available only in China. Virus-like particle (VLP) generated from the capsid protein (ORF2) of HEV is known to be a potent vaccine antigen against HEV. Hecolin consists of 368-606 amino acid (aa) region of the capsid protein of HEV, which forms a VLP. It is expressed and purified from the inclusion bodies of E. coli. Here, we describe a method to express the 112-608aa region of the capsid protein (ORF2) of genotype-1 HEV in Pichia pastoris (P. pastoris) and purify VLPs from the culture medium. 112-608aa ORF2 VLPs are secreted into the culture medium in a methanol inducible manner. The purified VLPs are glycosylated and induce robust immune response in Balb/c mice. Further, 112-608aa ORF2 VLPs are bigger than the 368-606 VLP present in Hecolin, which may help them in inducing a superior immune response. P. pastoris offers a robust and economical heterologous expression system to produce large quantities of glycosylated 112-608aa ORF2 VLP, which appears to be a promising vaccine candidate against the HEV.

Structural aspects of hepatitis E virus

Hepatitis E virus (HEV) is a leading cause of acute hepatitis worldwide. Hepatitis E is an enterically transmitted zoonotic disease that causes large waterborne epidemic outbreaks in developing countries and has become an increasing public-health concern in industrialized countries. In this setting, the infection is usually acute and self-limiting in immunocompetent individuals, although chronic cases in immunocompromised patients have been reported, frequently associated with several extrahepatic manifestations. Moreover, extrahepatic manifestations have also been reported in immunocompetent individuals with acute HEV infection. HEV belongs to the alphavirus-like supergroup III of single-stranded positive-sense RNA viruses, and its genome contains three partially overlapping open reading frames (ORFs). ORF1 encodes a nonstructural protein with eight domains, most of which have not been extensively characterized: methyltransferase, Y domain, papain-like cysteine protease, hypervariable region, proline-rich region, X domain, Hel domain, and RNA-dependent RNA polymerase. ORF2 and ORF3 encode the capsid protein and a multifunctional protein believed to be involved in virion release, respectively. The novel ORF4 is only expressed in HEV genotype 1 under endoplasmic reticulum stress conditions, and its exact function has not yet been elucidated. Despite important advances in recent years, the biological and molecular processes underlying HEV replication remain poorly understood, primarily due to a lack of detailed information about the functions of the viral proteins and the mechanisms involved in host-pathogen interactions. This review summarizes the current knowledge concerning HEV proteins and their biological properties, providing updated detailed data describing their function and focusing in detail on their structural characteristics. Furthermore, we review some unclear aspects of the four proteins encoded by the ORFs, highlighting the current key information gaps and discussing potential novel experimental strategies for shedding light on those issues.

Assessment of Knowledge, Attitude, and Practice among Saudi Residents Regarding Hepatitis E Virus

Global data, including those from Saudi Arabia, that examined public knowledge, attitudes, and practices (KAP) toward hepatitis E virus (HEV) are limited. This study examined KAP levels of the general population in Saudi Arabia toward HEV. A cross-sectional study was conducted among 768 participants. An Arabic electronic questionnaire that contained demographic data and had 35 questions was used to measure KAP of the participants concerning HEV. Collected data were analyzed at a significance level of 0.05. A total of 768 individuals participated in the study, of whom 16.3% (N = 125) were males and 83.7% (N = 643) were females. Study subjects were 18 years and above. Most of the participants were Saudi citizens (95.6%; N = 734), and from Western Saudi Arabia (76.4%; N = 587). Thirty-four percent (N = 261) of the participants had not heard of HEV, and 48% were aware that yellowish skin or eyes are the most important sign of hepatitis. The level of participants' knowledge about HEV was low (39.5%). However, positive attitudes and practices were apparent and tended to aim at how to avoid becoming infected with HEV. In conclusion, the level of HEV-related knowledge among the participants was low, and their practices and attitudes were aimed at avoiding HEV infection. Awareness campaigns are required to increase the public's HEV-related knowledge.

Role of "dual-personality" fragments in HEV adaptation-analysis of Y-domain region

BACKGROUND

Hepatitis E is a liver disease caused by the pathogen hepatitis E virus (HEV). The largest polyprotein open reading frame 1 (ORF1) contains a nonstructural Y-domain region (YDR) whose activity in HEV adaptation remains uncharted. The specific role of disordered regions in several nonstructural proteins has been demonstrated to participate in the multiplication and multiple regulatory functions of the viruses. Thus, intrinsic disorder of YDR including its structural and functional annotation was comprehensively studied by exploiting computational methodologies to delineate its role in viral adaptation.

RESULTS

Based on our findings, it was evident that YDR contains significantly higher levels of ordered regions with less prevalence of disordered residues. Sequence-based analysis of YDR revealed it as a "dual personality" (DP) protein due to the presence of both structured and unstructured (intrinsically disordered) regions. The evolution of YDR was shaped by pressures that lead towards predominance of both disordered and regularly folded amino acids (Ala, Arg, Gly, Ile, Leu, Phe, Pro, Ser, Tyr, Val). Additionally, the predominance of characteristic DP residues (Thr, Arg, Gly, and Pro) further showed the order as well as disorder characteristic possessed by YDR. The intrinsic disorder propensity analysis of YDR revealed it as a moderately disordered protein. All the YDR sequences consisted of molecular recognition features (MoRFs), i.e., intrinsic disorder-based protein-protein interaction (PPI) sites, in addition to several nucleotide-binding sites. Thus, the presence of molecular recognition (PPI, RNA binding, and DNA binding) signifies the YDR's interaction with specific partners, host membranes leading to further viral infection. The presence of various disordered-based phosphorylation sites further signifies the role of YDR in various biological processes. Furthermore, functional annotation of YDR revealed it as a multifunctional-associated protein, due to its susceptibility in binding to a wide range of ligands and involvement in various catalytic activities.

CONCLUSIONS

As DP are targets for regulation, thus, YDR contributes to cellular signaling processes through PPIs. As YDR is incompletely understood, therefore, our data on disorder-based function could help in better understanding its associated functions. Collectively, our novel data from this comprehensive investigation is the first attempt to delineate YDR role in the regulation and pathogenesis of HEV.

Hepatitis E: Genotypes, strategies to prevent and manage, and the existing knowledge gaps

Hepatitis E virus (HEV) is considered an emergent source of viral hepatitis worldwide, with an increasing burden of jaundice, liver failure, extrahepatic illnesses, and deaths in developed countries. With the scarcity of data from efficient animal models, there are still open-ended questions about designing new models to study pathogenesis, types, virology, and evolution of these viruses. With an emphasis on available data and updates, there is still enough information to understand the HEV life cycle, pathogen interaction with the host, and the valuation of the role of vaccine and new anti-HEV therapies. However, the World Health Organization (WHO) and the European Association for the Study of the Liver (EASL) preferred to stress prevention and control measures of HEV infections in animals, zoonotic transmission, and foodborne transmission. It is being reviewed that with current knowledge on HEV and existing prevention tools, there is an excellent room for in-depth information about the virus strains, their replication, pathogenicity, and virulence. The current knowledge set also has gaps regarding standardized and validated diagnostic tools, efficacy and safety of the vaccine, and extrahepatic manifestations specifically in pregnant females, immunocompromised patients, and others. This review highlights the areas for more research exploration, focusing on enlisted research questions based on HEV infection to endorse the need for significant improvement in the current set of knowledge for this public health problem.

Epidemiology, diagnosis, vaccines, and bibliometric analysis of the 100 top-cited studies on Hepatitis E virus

INTRODUCTION

In low-income countries, Hepatitis E infection is a common cause of acute hepatitis. So far, only two recombinant vaccines (rHEV and HEV 239) have been developed against Hepatitis E virus (HEV). Of which HEV 239 is licensed in China, but is not yet available in any other country.

OBJECTIVE

This study aims to discuss epidemiology, diagnosis, available vaccines for HEV, and provides an overview of 100 top-cited studies on HEV.

METHODS

A bibliometric analysis was conducted on the topic "HEV" through a systematic search of the Web of Science. The keywords used were "Hepatitis E" and retrieved articles were assessed for number of attributes.

RESULTS

The search returned a total of 3,235 publications, cited 95,858 times with h-index 129. The main finding for the 100 top-cited articles on HEV showed: number of authors ranging from 1 to 23, cited references range from 4 to 304, global citations score per year range from 6.61 to 175, and global citations score range from 148 to 791. Of the 100 top-cited studies, the authors who published most articles are Purcell (n = 18), Meng (n = 17), and Emerson (n = 15). Most The largest share of articles on HEV was contributed by United States of America (n = 49) with 12,795 citations. The National Institute of Allergy andInfectious Diseases was leading institute with greatest number of publications (n = 16), cited 3,950 times.

CONCLUSIONS

The studies conducted on HEV have increased over time. The information presented would be very useful in decision making for policy makers providing health care, and for academicians in providing a reference point for future research.

Dissecting the potential role of hepatitis E virus ORF1 nonstructural gene in cross-species infection by using intergenotypic chimeric viruses

Hepatitis E virus (HEV) infects humans and more than a dozen other animal species. We previously showed that open reading frame 2 (ORF2) and ORF3 are apparently not involved in HEV cross-species infection, which infers that the ORF1 may contribute to host tropism. In this study, we utilize the genomic backbone of HEV-1 which only infects humans to construct a panel of intergenotypic chimeras in which the entire ORF1 gene or its functional domains were swapped with the corresponding regions from HEV-3 that infects both humans and pigs. We demonstrated that the chimeric HEVs were replication competent in human liver cells. Subsequently, we intrahepatically inoculated the RNA transcripts of chimeras into pigs to determine if the swapped ORF1 regions confer the chimeras' ability to infect pigs. We showed that there was no evidence of infectivity in pigs for any of the chimeras. We also investigated the role of human ribosome protein sequence S17, which expanded host range in cultured cells, in HEV cross-species infection. We demonstrated that S17 insertion in HEV ORF1 did not abolish HEV replication competency in vitro, but also did not expand HEV host tropism in vivo. The results highlight the complexity of the underlying mechanism of HEV cross-species infection.

Development of BacMam Induced Hepatitis E Virus Replication Model in Hepatoma Cells to Study the Polyprotein Processing

The processing of polyprotein(s) to form structural and non-structural components remains an enigma due to the non-existence of an efficient and robust Hepatitis E Virus (HEV) culture system. We used the BacMam approach to construct an HEV replication model in which the HEV genome was cloned in the BacMam vector under the CMV promoter. The recombinant BacMam was used to infect Huh7 cells to transfer the HEV genome. HEV replication was authenticated by the presence of RNAs of both the polarity (+) and (-) and formation of hybrid RNA, a replication intermediate. The presence of genes for Papain-like Cysteine Protease (PCP), methyltransferase (MeT), RNA dependent RNA polymerase (RdRp), and ORF2 was confirmed by PCR amplification. Further, the infectious nature of the culture system was established as evidenced by the cross-infection of uninfected cells using the cell lysate from the infected cells. The HEV replication model was validated by detection of the ORF1 (Open Reading Frame1) encoded proteins, identified by Western blotting and Immunofluorescence by using epitope-specific antibodies against each protein. Consequently, discrete bands of 18, 35, 37, and 56 kDa corresponding to PCP, MeT, RdRp, and ORF2, respectively, were seen. Besides demonstrating the presence of non-structural enzymes of HEV along with ORF2, activity of a key enzyme, HEV-methyltransferase has also been observed. A 20% decrease in the replicative forms of RNA could be seen in presence of 100 μM Ribavirin after 48 h of treatment. The inhibition gradually increased from 0 to 24 to 48 h post-treatment. Summarily, infectious HEV culture system has been established, which could demonstrate the presence of HEV replicative RNA forms, the structural and non-structural proteins and the methyltransferase in its active form. The system may also be used to study the mechanism of action of Ribavirin in inhibiting HEV replication and develop a therapy.

Antiviral Candidates for Treating Hepatitis E Virus Infection

Globally, hepatitis E virus (HEV) causes significant morbidity and mortality each year. Despite this burden, there are no specific antivirals available to treat HEV patients, and the only licensed vaccine is not available outside China. Ribavirin and alpha interferon are used to treat chronic HEV infections; however, severe side effects and treatment failure are commonly reported. Therefore, this study aimed to identify potential antivirals for further development to combat HEV infection. We selected 16 compounds from the nucleoside and nonnucleoside antiviral classes that range in developmental status from late preclinical to FDA approved and evaluated them as potential antivirals for HEV infection, using genotype 1 replicon luminescence studies and replicon RNA quantification. Two potent inhibitors of HEV replication included NITD008 (half-maximal effective concentration [EC50], 0.03 μM; half-maximal cytotoxic concentration [CC50], >100 μM) and GPC-N114 (EC50, 1.07 μM, CC50, >100 μM), and both drugs reduced replicon RNA levels in cell culture (>50% reduction with either 10 μM GPC-N114 or 2.50 μM NITD008). Furthermore, GPC-N114 and NITD008 were synergistic in combinational treatment (combination index, 0.4) against HEV replication, allowing for dose reduction indices of 20.42 and 8.82 at 50% inhibition, respectively. Sofosbuvir has previously exhibited mixed results against HEV as an antiviral, both in vitro and in a few clinical applications; however, in this study it was effective against the HEV genotype 1 replicon (EC50, 1.97 μM; CC50, >100 μM) and reduced replicon RNA levels (47.2% reduction at 10 μM). Together these studies indicate drug repurposing may be a promising pathway for development of antivirals against HEV infection.

Analysis of Hepatitis E virus (HEV) X-domain structural model

Hepatitis E viral infection is now emerging as a global health concern, which needs to be addressed. Mechanism of viral replication and release is attributed by the different genomic component of HEV. However, few proteins/domain like X and Y domain remain unexplored, so we aim to explore the physiochemical, structural and functional features of HEV ORF-1 X domain. Molecular modeling of the unknown X domain was carried out using Phyre2 and Swiss Model. Active ligand binding sites were predicted using Phyre2. The X-domain protein found to be stable and acidic in nature with high thermostability and better hydrophilic property. Twelve binding sites were predicted along with putative transferase and catalytic functional activity. Homology modeling showed 10 binding sites along with Mg2+ and Zn2+ as metallic heterogen ligands binding to predicted ligand-binding sites. This study may help to decipher the role of this unexplored X-domain of HEV, thereby improving our understanding of the pathogenesis of HEV infection.

Development of new hepatitis E vaccines

Hepatitis E virus (HEV) infection is an emerging zoonotic disease posing a severe threat to public health in the world, especially to pregnant women. Currently, no specific treatments are available for HEV infection. Therefore, it is crucial to develop vaccine to prevent this infection. Although several potential candidate vaccines against HEV have been studied for their immunogenicity and efficacy, only Hecolin® which is developed by Xiamen Innovax Biotech Co., Ltd. and approved by China Food and Drug Administration (CFDA) in 2012, is the licensed HEV vaccine in the world so far. Extensive studies on safety, immunogenicity and efficacy in phase III clinical trials have shown that Hecolin® is a promising vaccine for HEV prevention and control. In this article, the advances on HEV vaccine development and research are briefly reviewed.

Seroprevalence and risk factors of Hepatitis E virus infection among pregnant women attending antenatal care in health facilities of Tigray, Northern Ethiopia

Existing literatures from developing countries show an increased mortality and morbidity related to hepatitis E virus during pregnancy as compared to the general population. Studies focusing on pregnant women are required for policy makers to improve maternal and child health. Therefore this study is aimed at determining the prevalence and associated risk factors of hepatitis E virus infection among pregnant women attending the health facilities of Tigray region, Northern Ethiopia. In this cross sectional study 846 pregnant women were included consecutively from April 2014 to February 2016. Clinical and sociodemographic were collected using structured questionnaire and blood was collected for laboratory analysis of Hepatitis E virus using IgG and IgM HEV ELISA. The data were analyzed using SPSS software version 21.0. Association with variables with the risk factors was determined using bivariate and multivariate analysis. The overall sero-prevalence of hepatitis E virus using anti-HEV IgG and anti-HEV IgM antibody among pregnant women were 367 (43.4%). From this 359 (42.4%) and 8 (0.9%) were tested positive for anti-HEV IgG and anti-HEV IgM antibody, respectively. Then finally age, rural residence, not washing after toilet use and lack of prevention aspects to minimize contamination were associated with HEV infection. This study shows the significant public health impact of HEV during pregnancy in low income countries.

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.

Knowledge gaps and research priorities in the prevention and control of hepatitis E virus infection

Hepatitis E virus (HEV), family Hepeviridae, is a main cause of epidemic hepatitis in developing countries and sporadic and cluster cases of hepatitis in industrialized countries. There are an increasing number of reported cases in humans especially in industrialized countries, and there is a high potential for transboundary spread of zoonotic genotypes of the virus through the transport of pigs, pig products and by-products. Bloodborne transmission of the virus has been reported with a significant medical concern. To better coordinate HEV research and design better control measures of HEV infections in animals, a group of HEV experts reviewed the current knowledge on the disease and considered the existing disease control tools. It was concluded that there is a lack of in-depth information about the spread of the virus from pigs to humans. The role of animals other than pigs in the zoonotic transmission of the virus to humans and the extent of foodborne transmission are poorly understood. Factors involved in development of clinical disease such as infectious dose, susceptibility and virulence of virus strains need to be studied more extensively. However, such studies are greatly hindered by the absence of a broadly applicable, efficient and sensitive in vitro cell culture system for HEV. Diagnostic tools for HEV are available but need to be further validated, harmonized and standardized. Commercially available HEV vaccines for the control of HEV infection in animal populations are needed as such vaccines can minimize the zoonotic risk for humans. Anti-HEV drugs for treatment of HEV-infected patients need to be studied more extensively. The detailed expert review can be downloaded from the project website at http://www.discontools.eu/.

Characterization of the Quasi-Enveloped Hepatitis E Virus Particles Released by the Cellular Exosomal Pathway

Our previous studies demonstrated that membrane-associated hepatitis E virus (HEV) particles-now considered "quasi-enveloped particles"-are present in the multivesicular body with intraluminal vesicles (exosomes) in infected cells and that the release of HEV virions is related to the exosomal pathway. In this study, we characterized exosomes purified from the culture supernatants of HEV-infected PLC/PRF/5 cells. Purified CD63-, CD9-, or CD81-positive exosomes derived from the culture supernatants of HEV-infected cells that had been cultivated in serum-free medium were found to contain HEV RNA and the viral capsid (ORF2) and ORF3 proteins, as determined by reverse transcription-PCR (RT-PCR) and Western blotting, respectively. Furthermore, immunoelectron microscopy, with or without prior detergent and protease treatment, revealed the presence of virus-like particles in the exosome fraction. These particles were 39.6 ± 1.0 nm in diameter and were covered with a lipid membrane. After treatment with detergent and protease, the diameter of these virus-like particles was 26.9 ± 0.9 nm, and the treated particles became accessible with an anti-HEV ORF2 monoclonal antibody (MAb). The HEV particles in the exosome fraction were capable of infecting naive PLC/PRF/5 cells but were not neutralized by an anti-HEV ORF2 MAb which efficiently neutralizes nonenveloped HEV particles in cell culture. These results indicate that the membrane-wrapped HEV particles released by the exosomal pathway are copurified with the exosomes in the exosome fraction and suggest that the capsids of HEV particles are individually covered by lipid membranes resembling those of exosomes, similar to enveloped viruses.IMPORTANCE Hepatitis E, caused by HEV, is an important infectious disease that is spreading worldwide. HEV infection can cause acute or fulminant hepatitis and can become chronic in immunocompromised hosts, including patients after organ transplantation. The HEV particles present in feces and bile are nonenveloped, while those in circulating blood and culture supernatants are covered with a cellular membrane, similar to enveloped viruses. Furthermore, these membrane-associated and -unassociated HEV particles can be propagated in cultured cells. The significance of our research is that the capsids of HEV particles are individually covered by a lipid membrane that resembles the membrane of exosomes, similar to enveloped viruses, and are released from infected cells via the exosomal pathway. These data will help to elucidate the entry mechanisms and receptors for HEV infection in the future. This is the first report to characterize the detailed morphological features of membrane-associated HEV particles.

Classification of human and zoonotic group hepatitis E virus (HEV) using antigen detection

Hepatitis E virus (HEV) is one of the major pathogens that cause acute viral hepatitis. The human (genotypes 1 and 2) and zoonotic (genotypes 3 and 4) groups of HEV present different epidemiology and clinical features. In this study, we developed a classification method for rapidly classifying HEV into human or zoonotic groups that combines a general antigen test with a zoonotic group-specific antigen test. Evaluation of serial samples from HEV-infected rhesus monkeys indicated that HEV antigen-positive samples can be classified using the antigen-based classification method. The antigen-based classification method was evaluated further on 55 genotyped samples from acute hepatitis E patients, including 9 human and 46 zoonotic groups. The novel method was completely consistent with the sequencing results: 9/9 for the human groups (100%, 95% confidence interval [CI] 66.4-100%) and 46/46 for the zoonotic groups (100%, 95% CI 92.3-100%). This method was also successfully used for the clustering of some samples that could not be clustered by sequencing. Compared with the sequencing-based method, this method is less time-consuming, less expensive, and less technically complex and is therefore ideal for large numbers of samples. In conclusion, this study provides a convenient and sensitive method for classifying different groups of HEV, and it has potentially important public health applications, especially in underdeveloped areas that cannot afford the high cost of nucleic acid testing.

Identification and characterization of two linear epitope motifs in hepatitis E virus ORF2 protein

Hepatitis E virus (HEV) is responsible for hepatitis E, which represents a global public health problem. HEV genotypes 3 and 4 are reported to be zoonotic, and animals are monitored for HEV infection in the interests of public hygiene and food safety. The development of novel diagnostic methods and vaccines for HEV in humans is thus important topics of research. Opening reading frame (ORF) 2 of HEV includes both linear and conformational epitopes and is regarded as the primary candidate for vaccines and diagnostic tests. We investigated the precise location of the HEV epitopes in the ORF2 protein. We prepared four monoclonal antibodies (mAbs) against genotype 4 ORF2 protein and identified two linear epitopes, G438IVIPHD444 and Y457DNQH461, corresponding to two of these mAbs using phage display biopanning technology. Both these epitopes were speculated to be universal to genotypes 1, 2, 3, 4, and avian HEVs. We also used two 12-mer fragments of ORF2 protein including these two epitopes to develop a peptide-based enzyme-linked immunosorbent assay (ELISA) to detect HEV in serum. This assay demonstrated good specificity but low sensitivity compared with the commercial method, indicating that these two epitopes could serve as potential candidate targets for diagnosis. Overall, these results further our understanding of the epitope distribution of HEV ORF2, and provide important information for the development of peptide-based immunodiagnostic tests to detect HEV in serum.

Hepatitis Virus Infections in Poultry

Viral hepatitis in poultry is a complex disease syndrome caused by several viruses belonging to different families including avian hepatitis E virus (HEV), duck hepatitis B virus (DHBV), duck hepatitis A virus (DHAV-1, -2, -3), duck hepatitis virus Types 2 and 3, fowl adenoviruses (FAdV), and turkey hepatitis virus (THV). While these hepatitis viruses share the same target organ, the liver, they each possess unique clinical and biological features. In this article, we aim to review the common and unique features of major poultry hepatitis viruses in an effort to identify the knowledge gaps and aid the prevention and control of poultry viral hepatitis. Avian HEV is an Orthohepevirus B in the family Hepeviridae that naturally infects chickens and consists of three distinct genotypes worldwide. Avian HEV is associated with hepatitis-splenomegaly syndrome or big liver and spleen disease in chickens, although the majority of the infected birds are subclinical. Avihepadnaviruses in the family of Hepadnaviridae have been isolated from ducks, snow geese, white storks, grey herons, cranes, and parrots. DHBV evolved with the host as a noncytopathic form without clinical signs and rarely progressed to chronicity. The outcome for DHBV infection varies by the host's ability to elicit an immune response and is dose and age dependent in ducks, thus mimicking the pathogenesis of human hepatitis B virus (HBV) infections and providing an excellent animal model for human HBV. DHAV is a picornavirus that causes a highly contagious virus infection in ducks with up to 100% flock mortality in ducklings under 6 wk of age, while older birds remain unaffected. The high morbidity and mortality has an economic impact on intensive duck production farming. Duck hepatitis virus Types 2 and 3 are astroviruses in the family of Astroviridae with similarity phylogenetically to turkey astroviruses, implicating the potential for cross-species infections between strains. Duck astrovirus (DAstV) causes acute, fatal infections in ducklings with a rapid decline within 1-2 hr and clinical and pathologic signs virtually indistinguishable from DHAV. DAstV-1 has only been recognized in the United Kingdom and recently in China, while DAstV-2 has been reported in ducks in the United States. FAdV, the causative agent of inclusion body hepatitis, is a Group I avian adenovirus in the genus Aviadenovirus. The affected birds have a swollen, friable, and discolored liver, sometimes with necrotic or hemorrhagic foci. Histologic lesions include multifocal necrosis of hepatocytes and acute hepatitis with intranuclear inclusion bodies in the nuclei of the hepatocytes. THV is a picornavirus that is likely the causative agent of turkey viral hepatitis. Currently there are more questions than answers about THV, and the pathogenesis and clinical impacts remain largely unknown. Future research in viral hepatic diseases of poultry is warranted to develop specific diagnostic assays, identify suitable cell culture systems for virus propagation, and develop effective vaccines.

Molecular and structural changes related to hepatitis E virus antigen and its expression in testis inducing apoptosis in Mongolian gerbil model

Hepatitis E virus (HEV) infection has been associated with a wide range of extrahepatic manifestations, so this study was designed to examine the effect and role of HEV on structural and molecular changes in the testicular tissues of Mongolian gerbils experimentally infected with swine HEV. HEV RNA was first detected in testis at 14 days post-inoculation and reached a peak between 28 and 42 days later with viral load between 3.12 and 6.23 logs/g by PCR assays. Changes including vacuolation, sloughing of germ cells, formation of multinuclear giant cells, degeneration, necrosis of tubules and damaged blood-testis barrier were observed through transmission electron microscopy. HEV ORF2 antigen was detected in the sperm cell cytoplasm along with decrease in relative protein of zonula occludens-1 through immunohistochemistry. HEV ORF3 antigen and ZO-1 protein were detectable by Western blotting. Lower (P<.05) serum testosterone and higher (P<.05) blood urea nitrogen level was observed in inoculated Mongolian gerbils. Likewise, increased (P<.05) germ cell apoptosis rate was detected with significant increased expression of Fas-L and Fas in HEV-inoculated groups at each time points. Up-regulation (P<.05 or P<.01) in mRNA level of Fas-L, Fas, Bax, Bcl-2 and caspase-3 was observed in HEV RNA-positive testes. Our study demonstrated that after experimental inoculation, HEV can be detected in testis tissues and viral proteins produce structural and molecular changes that in turn disrupt the blood-testis barrier and induce germ cell apoptosis.

The hepatitis E virus nonstructural polyprotein

Hepatitis E virus (HEV) is a globally important pathogen of acute and chronic hepatitis in humans. The HEV ORF1 gene encodes a nonstructural polyprotein, essential for RNA replication and virus infectivity. Expression and processing of ORF1 polyprotein are shown in prokaryotic and eukaryotic systems, however, its proteolysis into individual proteins is still debated. While molecular or biochemical characterization of methyltransferase, protease, hypervariable region, helicase and RNA polymerase domains in ORF1 has been achieved, the role of the X and Y domains in the HEV life cycle has only been demonstrated very recently. Clinically, detection of a number of ORF1 mutants in infected patients is implicated in disease severity, mortality and drug nonresponse. Moreover, several artificial lethal mutations in ORF1 offer a potential basis for developing live-attenuated vaccines for HEV. This article intends to present the molecular and clinical updates on the HEV ORF1 polyprotein.

Transcriptome Analysis of HepG2 Cells Expressing ORF3 from Swine Hepatitis E Virus to Determine the Effects of ORF3 on Host Cells

Hepatitis E virus- (HEV-) mediated hepatitis has become a global public health problem. An important regulatory protein of HEV, ORF3, influences multiple signal pathways in host cells. In this study, to investigate the function of ORF3 from the swine form of HEV (SHEV), high-throughput RNA-Seq-based screening was performed to identify the differentially expressed genes in ORF3-expressing HepG2 cells. The results were validated with quantitative real-time PCR and gene ontology was employed to assign differentially expressed genes to functional categories. The results indicated that, in the established ORF3-expressing HepG2 cells, the mRNA levels of CLDN6, YLPM1, APOC3, NLRP1, SCARA3, FGA, FGG, FGB, and FREM1 were upregulated, whereas the mRNA levels of SLC2A3, DKK1, BPIFB2, and PTGR1 were downregulated. The deregulated expression of CLDN6 and FREM1 might contribute to changes in integral membrane protein and basement membrane protein expression, expression changes for NLRP1 might affect the apoptosis of HepG2 cells, and the altered expression of APOC3, SCARA3, and DKK1 may affect lipid metabolism in HepG2 cells. In conclusion, ORF3 plays a functional role in virus-cell interactions by affecting the expression of integral membrane protein and basement membrane proteins and by altering the process of apoptosis and lipid metabolism in host cells. These findings provide important insight into the pathogenic mechanism of HEV.

The Bama miniature swine is susceptible to experimental HEV infection

The hepatitis E virus (HEV) is one of the main causes of enterically transmitted hepatitis worldwide. Although the mortality rates associated with HEV are generally low, they can be up to 28% in HEV-infected pregnant women, and the elderly are more susceptible. The reasons for this selective severity are unclear, partially because there is no suitable, easy-to-use model in which to study HEV infection. Non-human primates and standard swine have been identified as being sensitive to infection with HEV and have been used for HEV infection studies. However, studies in these animals have been limited by high housing costs and the difficulty of manipulating these animals. In the current study, we established a model of HEV infection using Bama miniature swine. The model is easy to use and is sensitive to infections with HEV genotypes 3 and 4, which are classified as zoonotic HEVs. In this model, infection of Bama miniature swine with HEV genotypes 3 and 4 caused the typical features. All Bama miniature swine that were infected with HEV genotypes 3 and 4 exhibited significant HEV viremia, shedding, anti-HEV antibody responses and partial liver inflammation. Bama miniature swine may serve as an alternative to standard swine models for the study of zoonotic HEV infection and HEV genotype specificity research.

Hepatitis E Virus Mutations: Functional and Clinical Relevance

Hepatitis E virus (HEV) infection is a major cause of acute hepatitis and affects more than 20 million individuals, with three million symptomatic cases and 56,000 recognized HEV-related deaths worldwide. HEV is endemic in developing countries and is gaining importance in developed countries, due to increased number of autochthone cases. Although HEV replication is controlled by the host immune system, viral factors (especially specific viral genotypes and mutants) can modulate HEV replication, infection and pathogenesis. Limited knowledge exists on the contribution of HEV genome variants towards pathogenesis, susceptibility and to therapeutic response. Nonsynonymous substitutions can modulate viral proteins structurally and thus dysregulate virus-host interactions. This review aims to compile knowledge and discuss recent advances on the casual role of HEV heterogeneity and its variants on viral morphogenesis, pathogenesis, clinical outcome and antiviral resistance.

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HEV causes acute hepatitis and recently comes into focus because of persistent infection in immunocompromised patients.

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HEV variability can be associated with clinical pathogenesis and transmission dynamics.

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Mutations in the HEV genome can influence HEV physiology and virus-host interaction.

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HEV mutations and variability are likely associated with fulminant hepatic failure and chronic hepatitis E.

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The Y1320H and G1634R/K mutations in the RdRp domain contribute to antiviral resistance through enhancing HEV replication.

We searched MEDLINE database and PubMed for articles from 1980 through June 30, 2016. Search terms used in various combinations were “hepatitis E”, “hepatitis E virus”, “hepatitis E virus infection”, “hepatitis E virus mutation”, “HEV variability”, “HEV genotype”, “HEV drug resistance”, “HEV replication” and “ribavirin”. Articles resulting from these searches and relevant references cited in those articles were selected based on their related topics and were reviewed. Abstracts and reports from meetings were also included. Articles published in English were included.

Detection of Hepatitis E Virus Genotype 1 Among Blood Donors From Southwest of Iran

BACKGROUND

Infection with hepatitis E virus (HEV) is endemic in developing countries and reveals significant regional differences. Several studies have reported virus transmission via blood transfusion. To date, however, no cases of HEV RNA detection in blood donors have been reported from Iran.

OBJECTIVES

The aim of this study was to determine the presence of HEV RNA in plasma samples of blood donors referred to a blood transfusion center in Shiraz in the southwest of Iran. The HEV genotypes were also investigated using nucleotide sequencing.

PATIENTS AND METHODS

Blood samples were collected from 700 blood donors who were referred to Fars blood transfusion organization from January to March 2014. Plasma samples were screened for the presence of HEV IgG and IgM antibodies by standard enzyme immunoassay. Samples seroreactive to anti-HEV were further tested for the presence of HEV RNA using nested polymerase chain reaction (PCR) with universal primers for detection of all four HEV genotypes. Positive PCR samples were then subjected to DNA sequencing for further analysis.

RESULTS

Fifty (50, 7.1%) out of 700 plasma samples tested positive for anti-HEV antibodies. HEV RNA was detected in 7/50 (12%) of the antibody-positive samples, the majority of which were IgM positive. Sequence analysis of seven isolates of the HEV RNA ORF 2 gene region revealed > 80% similarity with genotype 1.

CONCLUSIONS

The analysis indicates that the HEV isolated from blood donors in the southwest of Iran belongs to genotype 1. However, more samples from other geographic regions of Iran are needed to confirm these findings. Because transmission of HEV by administration of blood or blood components is likely to occur, it may be sensible to screen donor blood for HEV to eliminate transfusion-transmitted HEV infection when the recipient is immunocompromised.

Production and characterization of a Brazilian candidate antigen for Hepatitis E Virus genotype 3 diagnosis

Hepatitis E, caused by hepatitis E virus (HEV), is a viral infectious pathology of great importance in the public health. Hepatitis E outbreaks were registered in developing countries with poor or no sanitation, where drinking water was contaminated with fecal material, but also in many industrialized countries probably due to consumption of HEV-positive swine meat. In this study, we present the development and characterization of a recombinant antigen from ORF2 HEV genotype 3. Viral RNA was extracted from swine feces infected with the native virus. A total of 267 residues from the C-terminal ORF2((394-661)) coding sequence were cloned into the pET20a vector and expressed in Escherichia coli ER2566. Recombinant protein was purified by liquid chromatography and the fragment obtained a 98% homology against other human or swine HEV genotype 3 ORF2 sequences. Wistar rats were inoculated with ORF2p, developing antibodies able to recognize both the homologous antigen and the native HEV genotype 3 ORF2 present in infected stool. In parallel, HEV-negative swine were experimentally challenged with HEV genotype 3. ORF2 was detected by PCR 14 days post-inoculation in three-fourth piglets' feces and one week later by dot blot. In conclusion, this study proved the immunogenic and antigenic properties of the recombinant protein ORF2p.

Full coding hepatitis E virus genotype 3 genome amplification method

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A new amplification method for the complete HEV coding genome was described.

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HEV genome organization and function were reviewed.

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Polymorphic amino acids of each HEV genome region were analyzed in reference sequences.

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Complete coding HEV sequence of an immunocompromised patient with acute infection was analyzed.

Hepatitis E virus (HEV) genotype 3 produces zoonotic infection associated with the consumption of infected animals. HEV infections can become chronic in immunocompromised (IC) patients. The viral genome has three well defined open reading frames (ORF1, ORF2 and ORF3) within which various domains and functions have been described. This paper (i) describes a new method of complete sequencing of the HEV coding region through overlapping PCR systems, (ii) establishes a consensus sequence and polymorphic positions (PP) for each domain, and (iii) analyzes the complete coding sequence of an IC patient. With regard to the consensus, a high percentage of PP was observed in protease (PP = 19%) and the X domain (PP = 22%) within ORF1, the N-terminal region of the S domain (PP = 22%) in ORF2, and the P1 (PP = 35%) and P2 (PP = 25%) domains in ORF3. In contrast, the ORF1 Y, ORF2 S, ORF2 M and ORF3 D1 domains were conserved in the reference sequences (0.40, 1, 0.70 and 0% of PP, respectively). The sequence from the IC patient had more mutations in the RpRp (D1235G, Q1242R, S1454T, V1480I, I1502 V, K1511R, G1373 V, E1442D, V1693 M), the terminal ORF2 S- domain (F10L, S26T, G36S, S70P, A105 V, I113 V), the X domain (T938 M, T856 V, S898A) and the helicase (S1014N, S975T, Q1133 K).

ORF3 of Hepatitis E Virus Inhibits the Expression of Proinflammatory Cytokines and Chemotactic Factors in LPS-Stimulated Human PMA-THP1 Cells by Inhibiting NF-κB Pathway

Hepatitis E virus (HEV) is one of the primary causative agents of acute hepatitis. It is noteworthy that HEV can develop chronic infection and even lead to liver cirrhosis; however, the mechanism has not been revealed. In this study, the ELISA assay was used to detect protein levels, and we found that HEV open reading frame 3 (ORF3) protein inhibited the expression of proinflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interleukin [IL]-1β, IL-6, IL-8, IL-12p40, and IL-18) and chemotactic factors (nitric oxide [NO], interferon-inducible protein-10 (IP-10), macrophage inflammatory protein (MIP)-1α, monocyte chemoattractant protein-1 (MCP-1), granulocyte colony-stimulating factor (G-CSF), granulocyte macrophage colony-stimulating factor (GM-CSF)] in lipopolysaccharide (LPS)-stimulated human PMA-THP1 cells. Further study showed that mRNA and protein levels of pattern recognition receptors (PRRs), such as Toll-like receptor 4 (TLR4), TNF receptor-associated factor 6 (TRAF6), and nucleotide-binding oligomerization domain containing 2 (NOD2), decreased after infection of pLL3.7-ORF3 (pORF3); moreover, the inhibition produced corresponding upregulation of IκBα and downregulation of phosphorylated IκB kinase IKKɛ (p-IKKɛ) and phosphorylated nuclear factor (NF)-κB (p-NF-κB), but little variation was found in the concentration of IKKɛ and NF-κB. Taken together, our results demonstrated that HEV ORF3 attenuated LPS-induced cytokine production and chemotactic factors, predominantly by inhibiting various PRRs-mediated NF-κB signaling pathways. The anti-inflammatory properties might be of great importance to clarify the role and mechanism of macrophages in chronic HEV infection and cirrhosis.

Hepatitis E as a Zoonosis

Hepatitis E (HE) virus infection is not limited to spread from human to human but also occurs between animals and more importantly as zoonotic spread from animals to humans. Genotyping of strains from hepatitis E virus-infected patients has revealed that these infections are not all caused by genotypes 1 or 2 but often by genotypes 3 or 4. Therefore, it is important to understand the striking difference between the spread of genotypes 1 and 2 in countries with poor sanitary standards and the spread of genotypes 3 and 4 in countries with good sanitary standards. The number of animal species known to be infected with HEV is expanding rapidly. The finding of HEV in new host species always raises the question regarding the zoonotic potential of these newfound strains. However, as new strains are found, the complexity increases.Certain genotypes are known to have the ability of zoonotic spread from certain animal species and these animals may even constitute an infection reservoir. Some animal species may contribute to zoonotic infections albeit on a smaller scale, while others are believed to be of minor or no importance at all. This chapter reviews possible sources of zoonotic hepatitis E virus infection.

Antigen detection and apoptosis in Mongolian gerbil's kidney experimentally intraperitoneally infected by swine hepatitis E virus

We examined the effect of hepatitis E virus (HEV) on the renal tissue pathogenesis, morphological damages and related molecular mechanisms following swine HEV suspension intraperitoneally inoculation in Mongolian gerbils. The microscopic and ultramicroscopic analyses of kidney tissue structure were carried out at different points after inoculation of HEV. The immunohistochemistry, real-time PCR and Western blot were performed to explore the molecular mechanisms associated with HEV presence in the renal tissues. Real-time PCR revealed that the copies of HEV RNA in the kidney were detected at 7 dpi, and peaked at 14 dpi at a concentration was 7.18 logs g(-1), with detection of HEV ORF2 antigen by immunohistochemistry. Hematoxylin and eosin (HE) staining showed pathological lesions including glomerular atrophy, degeneration, edema and necrosis of renal tubular epithelial cells and Mallory and Sirius red staining indicated the presence of collagen fibers and fibrosis in kidney tissues of inoculated gerbils. Ultrastructural studies of basal membrane of renal tubules demonstrated the rough and uneven with mitochondria swelling and vacuolation in the tissues of HEV inoculated animals. Similarly, significantly higher number of (TUNEL)-positive cells were seen in renal tubule tissues compared to control group. Moreover, immuno histochemical results indicated that significant increase expression of the B-cell lymphoma 2 (Bcl-2), Bcl-2 associated X protein (Bax), FAS and Caspase-3 in HEV inoculated Mongolian gerbils at each time points. Relative mRNA expression by real-time PCR revealed a significantly higher (P<0.05) mRNA level of BAX, Bcl-2 and caspase-3 transcription in HEV inoculated Mongolian gerbils. Our results demonstrates that activation of mitochondria and Caspase-3 protease might be induced the apoptosis which subsequently cause the necrosis and cell death of renal epithelial cells during acute phase of HEV infection in HEV inoculated Mongolian gerbils.

Establishment of hepatitis E virus infection-permissive and -non-permissive human hepatoma PLC/PRF/5 subclones

PLC/PRF/5 cells show limited permissiveness, meaning that almost all subclones are permissive; however, some subclones do not exhibit permissiveness for hepatitis E virus (HEV) infection. In this study, the single-cell cloning of PLC/PRF/5 was performed and heterogeneous subclones characterized. Notably, the efficiency of intracellular virus replication did not correlate with the permissiveness for HEV infection. However, as well as binding permissive subclones, virus-like particles bound non-permissive subclones on various levels, suggesting that these subclones have some deficiencies in the attachment and entry steps of infection. Our data would be useful for investigating the HEV life cycle.

NMR study on the interaction of the conserved CREX 'stem-loop' in the Hepatitis E virus genome with a naphthyridine-based ligand

A 2-amino-1,8-naphthyridine derivative that is described to bind single guanine bulges in RNA-DNA and RNA-RNA duplexes was synthesized and its interaction with the single G bulge in the conserved CREX of the Hepatitis E Virus (HEV) genome was explored by NMR and molecular modeling. Results indicate that the ligand intercalates in the internal loop, though none of the expected hydrogen bonds with the single G in the bulge could be demonstrated.

Experimental infection of pregnant rabbits with hepatitis E virus demonstrating high mortality and vertical transmission

A high mortality rate of approximately 20% in pregnant women with hepatitis E has been reported in previous studies. However, other studies showed no difference between pregnant and nonpregnant women in the severity of hepatitis E. To determine the effects of HEV infection on pregnancy, we successfully established HEV infection in six pregnant rabbits (PR) and six nonpregnant rabbits (NPR) with a rabbit HEV isolate, taking three PR and one NPR without HEV infection as controls. Tests for HEV RNA by RT-PCR, anti-HEV antibodies by ELISA and HEV antigen via immunohistochemistry and histopathology were carried out. Two of six infected PR miscarried and three of the remaining four PR died which may be attributed to severe liver necrosis caused by HEV infection. Moreover, vertical transmission was found to be associated with the replication of HEV in placenta, indicated by the presence of HEV RNA and antigen in placenta from the infected PR. Our findings strongly suggest that HEV infection could lead to adverse outcomes in pregnancy and vertical transmission, suggesting the necessity for pregnant women at risk of HEV infection to be vaccinated.

Distribution and Molecular Characterization of Hepatitis E virus in Domestic Animals and Wildlife in Croatia

Hepatitis E is becoming a growing health concern in European countries as an increase of sporadic human cases of unknown origin has been recorded lately. Its causative agent, Hepatitis E virus (HEV), is known to have zoonotic potential and thus the role of domestic and wild animals in the chain of viral spread should be considered when investigating risk factors and the epidemiology of the disease. A comprehensive survey based on viral RNA detection was carried out in Croatia including blood, spleen and liver samples originating from 1816 different domestic and wild animals and digestive gland samples from 538 molluscs. A high HEV prevalence was detected in domestic pigs (24.5%) and wild boars (12.3%), whereas cattle, molluscs, ruminant and carnivore wildlife samples tested negative. Molecular characterization of both ORF1 and ORF2 genomic regions confirmed the phylogenetic clustering of the obtained sequences into genotype 3, previously reported in Europe. Furthermore, our results proved the presence of identical sequence variants in different samples, regardless of their origin, age or habitat of the host, suggesting transmission events between domestic swine, as well as between domestic swine and wild boars in the country. Moreover, a close genetic relationship of Croatian animal strains and known human HEV strains from GenBank opens the question of possible cross-species HEV transmission in Croatia, especially in the areas with an intensive swine production.

Seroprevalence of Hepatitis A and E Virus Infections Among Healthy Population in Shiraz, Southern Iran

Background:

Enterically-transmitted acute viral hepatitis is caused predominantly by hepatitis A virus (HAV) and hepatitis E virus (HEV). The prevalence of HEV and HAV infections varies in different geographical regions.

Objectives:

This study was conducted to determine the prevalence of HEV and HAV infections among Iranian healthy individuals in southern Iran.

Patients and Methods:

Totally, 1030 samples were collected from healthy subjects in schools, those referred to tertiary outpatient clinics and health centers in Shiraz between November 2011 and May 2012. Their ages ranged between six months and 95 years. The presence of total anti-HAV and anti-HEV immunoglobulin M (IgM) in plasma was assessed by ELISA.

Results:

The results showed that 66.2% and 0.6% of the general population in this area were positive for total anti-HAV and IgM antibodies by ELISA, respectively. As seen, 13.4% and 0.9% were positive for total anti-HEV and IgM antibodies, respectively. The difference in total anti-HAV and anti-HEV antibodies was significant among the age groups (P < 0.001).

Conclusions:

This study showed that the prevalence rates of HAV and HEV antibodies were positively correlated with age. The results demonstrated that the infection with these two viruses in the region was high and some high-risk individuals including females at child-bearing age were more susceptible. HAV vaccination could be recommended for antibody-negative adults.