Enterically Transmitted Non-A, Non-B Hepatitis and the Discovery of Hepatitis E Virus

Isolation and characterization of a novel rodent hepevirus in long-tailed dwarf hamsters (Cricetulus longicaudatus) in China

Hepeviruses have been identified in a broad range of animal hosts, including mammals, birds, and fish. In this study, rodents (n=91) from seven different species and ten pikas (Ochotona curzoniae) were collected in Qinghai Province, China. Using transcriptomic sequencing and confirmatory molecular testing, hepeviruses were detected in 27 of 45 (60 %) long-tailed dwarf hamsters (Cricetulus longicaudatus) and were undetected in other rodents and pika. The complete genome sequences from 14 representative strains were subsequently obtained, and phylogenetic analyses suggested that they represent a novel species within the genus Rocahepevirus, which we tentatively designated as Cl-2018QH. The virus was successfully isolated in human hepatoma (Huh-7) and murine fibroblast (17 Cl-1) cell lines, though both exhibited limited replication as assayed by detection of negative-sense RNA intermediates. A129 immunodeficient mice were inoculated with Cl-2018QH and the virus was consistently detected in multiple organs, despite relatively low viral loads. In summary, this study has described a novel rodent hepevirus, which enhances our knowledge of the genetic diversity of rodent hepeviruses and highlights its potential for cross-species transmission.

Tracing the History of Hepatitis E Virus Infection in Mexico: From the Enigmatic Genotype 2 to the Current Disease Situation

Hepatitis E virus (HEV) is the major cause of acute viral hepatitis worldwide. This virus is responsible for waterborne outbreaks in low-income countries and zoonosis transmission in industrialized regions. Initially, considered self-limiting, HEV may also lead to chronic disease, and evidence supports that infection can be considered a systemic disease. In the late 1980s, Mexico became a hot spot in the study of HEV due to one of the first virus outbreaks in Latin America related to enterically transmitted viral non-A, non-B hepatitis. Viral stool particles recovered from Mexican viral hepatitis outbreaks represented the first identification of HEV genotype (Gt) 2 (Gt2) in the world. No new findings of HEV-Gt2 have been reported in the country, whereas this genotype has been found in countries on the African continent. Recent investigations in Mexico have identified other strains (HEV-Gt1 and -Gt3) and a high frequency of anti-HEV antibodies in animal and human populations. Herein, the potential reasons for the disappearance of HEV-Gt2 in Mexico and the advances in the study of HEV in the country are discussed along with challenges in studying this neglected pathogen. These pieces of information are expected to contribute to disease control in the entire Latin American region.

Discovery of Hepatitis E and Its Impact on Global Health: A Journey of 44 Years about an Incredible Human-Interest Story

The story of the discovery of hepatitis E originated in the late 1970s with my extreme belief that there was a hidden saga in the relationship between jaundice and pregnancy in developing countries and the opportunity for a massive epidemic of viral hepatitis, which hit the Gulmarg Kashmir region in November 1978. Based on data collected from a door-to-door survey, the existence of a new disease, epidemic non-A, non-B hepatitis, caused by a hitherto unknown hepatitis virus, was announced. This news was received by the world community with hype and skepticism. In the early 1980s, the world watched in awe as an extreme example of human self-experimentation led to the identification of VLP. In 1990, a cDNA clone from the virus responsible for epidemic non-A, non-B hepatitis was isolated. Over the years, we traversed three eras of ambiguity, hope, and hype of hepatitis E research and conducted several seminal studies to understand the biology of HEV and manifestations of hepatitis E. Many milestones have been reached on the long and winding road of hepatitis E research to understand the structure, biology, and diversity of the agent, changing the behavior of the pathogen in developed countries, and the discovery of a highly effective vaccine.

Hepatitis E Virus Infections: Epidemiology, Genetic Diversity, and Clinical Considerations

According to the World Health Organization, approximately 20 million people worldwide are infected annually with the hepatitis E virus (HEV). There are four main genotypes of HEV. Genotype 1 and genotype 2 are common in developing countries and are transmitted by contaminated water from a fecal-oral route. Genotype 3 and genotype 4 are common in developed countries and can lead to occasional transmission to humans via undercooked meat. Hepatitis E virus 1 and HEV3 can lead to fulminant hepatitis, and HEV3 can lead to chronic hepatitis and cirrhosis in immunocompromised patients. The majority of patients with HEV infection are asymptomatic and usually have spontaneous viral clearance without treatment. However, infection in immunocompromised individuals can lead to chronic HEV infection. Both acute and chronic HEV infections can have extrahepatic manifestations. No specific treatment is required for acute HEV infection, no treatment has been approved in chronic infection, and no HEV vaccine has been approved by the (United States) Food and Drug Administration. This review focuses on the molecular virology (HEV life cycle, genotypes, model systems, zoonosis), pathogenesis, clinical manifestation, and treatment of chronic HEV infection, especially in immunocompromised patients, to provide clinicians a better understanding of the global distribution of these infections and the significant effect they can have on immunocompromised patients.

Structural and molecular biology of hepatitis E virus

Hepatitis E virus (HEV) is one of the most common causes of acute viral hepatitis, mainly transmitted by fecal-oral route but has also been linked to fulminant hepatic failure, chronic hepatitis, and extrahepatic neurological and renal diseases. HEV is an emerging zoonotic pathogen with a broad host range, and strains of HEV from numerous animal species are known to cross species barriers and infect humans. HEV is a single-stranded, positive-sense RNA virus in the family Hepeviridae. The genome typically contains three open reading frames (ORFs): ORF1 encodes a nonstructural polyprotein for virus replication and transcription, ORF2 encodes the capsid protein that elicits neutralizing antibodies, and ORF3, which partially overlaps ORF2, encodes a multifunctional protein involved in virion morphogenesis and pathogenesis. HEV virions are non-enveloped spherical particles in feces but exist as quasi-enveloped particles in circulating blood. Two types of HEV virus-like particles (VLPs), small T = 1 (270 Å) and native virion-sized T = 3 (320-340 Å) have been reported. There exist two distinct forms of capsid protein, the secreted form (ORF2S) inhibits antibody neutralization, whereas the capsid-associated form (ORF2C) self-assembles to VLPs. Four cis-reactive elements (CREs) containing stem-loops from secondary RNA structures have been identified in the non-coding regions and are critical for virus replication. This mini-review discusses the current knowledge and gaps regarding the structural and molecular biology of HEV with emphasis on the virion structure, genomic organization, secondary RNA structures, viral proteins and their functions, and life cycle of HEV.

Hepatitis E should be a global public health priority: recommendations for improving surveillance and prevention

INTRODUCTION

Hepatitis E virus (HEV) is an important cause of enterically transmitted viral hepatitis and a significant contributor to maternal mortality in endemic regions around the world, yet the global response has been limited. HEV is a disease of poverty, and the populations experiencing the greatest burden of HEV-associated illness are not benefitting from existing interventions, including WASH strategies and immunization.

AREAS COVERED

Though a vaccine exists (HEV 239, Hecolin®, Xiamen Innovax Biotech, China), it is only licensed and available in the private market in China and has yet to be prequalified by the WHO for use in endemic settings and outbreaks. This review of the current state of HEV disease and subsequent recommendations for a coordinated public health response are intended to guide the global health community towards breaking the current 'vicious cycle,' in which a lack of data prevents actions that would improve health outcomes.

EXPERT OPINION

Vaccine implementation in future outbreaks, targeted studies assessing vaccine effectiveness and immunogenicity in endemic regions and populations, improved understanding of the global burden, and improvements in diagnostic and epidemiologic tools are urgently needed. Strategies for implementing routine vaccination programs, improving water, sanitation, and hygiene in endemic regions.

Hepatitis E Virus Infection: Circulation, Molecular Epidemiology, and Impact on Global Health

Infection with hepatitis E virus (HEV) represents the most common source of viral hepatitis globally. Although infecting over 20 million people annually in endemic regions, with major outbreaks described since the 1950s, hepatitis E remains an underestimated disease. This review gives a current view of the global circulation and epidemiology of this emerging virus. The history of HEV, from the first reported enteric non-A non-B hepatitis outbreaks, to the discovery of the viral agent and the molecular characterization of the different human pathogenic genotypes, is discussed. Furthermore, the current state of research regarding the virology of HEV is critically assessed, and the challenges towards prevention and diagnosis, as well as clinical risks of the disease described. Together, these points aim to underline the significant impact of hepatitis E on global health and the need for further in-depth research to better understand the pathophysiology and its role in the complex disease manifestations of HEV infection.

Hepatitis E virus: host tropism and zoonotic infection

Hepatitis E virus (HEV), the causative agent of hepatitis E, is an understudied but important pathogen. HEV typically causes self-limiting acute viral hepatitis, however chronic infection with neurological and other extrahepatic manifestations has increasingly become a significant clinical problem. The discovery of swine HEV from pigs and demonstration of its zoonotic potential led to the genetic identification of very diverse HEV strains from more than a dozen other animal species. HEV strains from pig, rabbit, deer, camel, and rat have been shown to cross species barriers and infect humans. Zoonotic HEV infections through consumption of raw or undercooked animal meat or direct contact with infected animals have been reported. The discovery of a large number of animal HEV variants does provide an opportunity to develop useful animal models for HEV. In this mini-review, we discuss recent advances in HEV host range, and cross-species and zoonotic transmission.

A possible risk of environmental exposure to HEV in Ibadan, Oyo State, Nigeria

Hepatitis E virus (HEV) infection is both a major public health concern and emerging global health concern, with a documented incidence of 20 million, 3.4 million clinical cases, 70,000 deaths, and 3,000 stillbirths. The aetiologic agent, HEV is a primarily enterally transmitted hepatotropic virus. Fecal samples were collected from three selected pig farms across Ibadan, South-west Nigeria. Randomly picked samples were pooled per unit pen and fecal suspensions prepared were subjected to HEV Antigen (Ag) enzyme-linked immunosorbent assay. Molecular probing was done by Reverse Transcription and nested polymerase reaction (RT-nPCR) and deep sequencing. Sequencing was done paired-end for 300 cycles using the HiSeq system. Overall farm prevalence of 66.7% (2/3) and prevalence at individual level of 13.2% (9/68) were recorded. All nine samples positive for the ELISA screen were negative when subjected to RT-nPCR assays. Further, on deep sequencing, no HEV genomic fragment was found in the sample using de-novo assembly. Findings suggest possibly inapparent HEV in the pigs studied or a yet to be identified protein with HEV-Ag cross-reactivity ability on ELISA, thus constituting a possible risk of exposure to HEV infection in the population. Consequently, we recommend prompt intervention to unravel the mystery and break the chain of transmission.

The Discovery of Hepatitis Viruses: Agents and Disease

Discovery of five hepatitis viruses A to E has followed distinctive definable phases. Human experiments at Willowbrook identified two forms of hepatitis namely infectious hepatitis and serum hepatitis. The discovery of Australia antigen in 1965 led to rapid scientific developments in viral hepatitis. SH antigen was detected in sera of patients with serum hepatitis and soon SH antigen and Australia antigen were found to be identical and selectively associated with serum hepatitis. In 1970, 42-nm Dane particles were detected in Australia antigen positive sera and linked to the virus of serum hepatitis. Subsequently, a new antigen-antibody system (e-antigen/antibody) was detected in such patients and associated with infectivity. Then, DNA polymerase was found in concentrated pellets containing Australia antigen. Hepatitis B virus (HBV) DNA cloning and sequencing of HBV followed these developments. In 1973, 27 nm hepatitis A virus (HAV)-like particles were visualized in stool samples obtained during acute phase of illness after inoculation of MS-1 strain in volunteers. Cloning and sequencing of HAV followed. In 1977, a new antigen-antibody system (δ antigen-antibody system) was identified by chance associated with HBV. Based on animal transmission studies, δ agent was found to be another virus called hepatitis D virus that is defective, requires the helper functions of HBV and interferes with HBV replication. The search for hepatitis C virus started when non-A, non-B hepatitis was recognised in multiply transfused patients with subsequent successful animal transmission. HCV was identified by a novel immunoscreening approach involving screening of cDNA libraries from infectious sera. The story of hepatitis E is historically linked to discovery of waterborne epidemic non-A, non-B hepatitis from Kashmir, India. Virus-like-particles of the agent were identified in stool samples of a human volunteer after a self-experimentation. HEV cDNA was detected in bile-enriched infectious samples and full-length HEV RNA genome was subsequently cloned and sequenced.

Emerging hepatitis E virus compared with hepatitis A virus: A new sanitary challenge

Hepatitis A (HAV) and E (HEV) viruses are able to cause liver disease in humans. Among the five classical hepatotropic viruses, they are mainly transmitted via the fecal-oral route. Historically, many similarities have thus been described between them according to their incidence and their pathogenicity, especially in countries with poor sanitary conditions. However, recent advances have provided new insights, and the gap is widening between them. Indeed, while HAV infection incidence tends to decrease in developed countries along with public health improvement, HEV is currently considered as an underdiagnosed emerging pathogen. HEV autochthonous infections are increasingly observed and are mainly associated with zoonotic transmissions. Extra hepatic signs resulting in neurological or renal impairments have also been reported for HEV, as well as a chronic carrier state in immunocompromised patients, arguing in favor of differential pathogenesis between those two viruses. Recent molecular tools have allowed studies of viral genome variability and investigation of links between viral plasticity and clinical evolution. The identification of key functional mutations in viral genomes may improve the knowledge of their clinical impact and is analyzed in depth in the present review.