Transmission of a Novel Genotype of Hepatitis E Virus from Bactrian Camels to Cynomolgus Macaques

Current knowledge on the epidemiology and detection methods of hepatitis E virus in China

Hepatitis E is recognized as a significant zoonotic disease burden in China, with the hepatitis E virus (HEV) identified as the etiological agent responsible for this disease. HEV exhibits no specific host tropism, which facilitates its transmission among various mammalian species, including humans, pigs, cattle, goats, and others. Currently, the availability of effective therapeutic agents and vaccines for HEV infection is limited. Therefore, a comprehensive understanding of the epidemiological characteristics of HEV, and the existing detection methods, is crucial for disease prevention and control. In this review, we provide an overview of the current knowledge on HEV in China, mainly focusing on detection strategies, molecular characteristics, and the prevalence of this pathogen in the human population and other susceptible species. This review will be useful to enhance public awareness of HEV and to accelerate disease control efforts in the future.

Phosphorylation of Ser711 residue in the hypervariable region of zoonotic genotype 3 hepatitis E virus is important for virus replication

Hepatitis E virus (HEV) is distinct from other hepatotropic viruses because it is zoonotic. HEV-1 and HEV-2 exclusively infect humans, whereas HEV-3 and HEV-4 are zoonotic. However, the viral and/or host factors responsible for cross-species HEV transmission remain elusive. The hypervariable region (HVR) in HEV is extremely heterogenetic and is implicated in HEV adaptation. Here, we investigated the potential role of Serine phosphorylation in the HVR in HEV replication. We first analyzed HVR sequences across different HEV genotypes and identified a unique region at the N-terminus of the HVR, which is variable in the human-exclusive HEV genotypes but relatively conserved in zoonotic HEV genotypes. Using predictive tools, we identified four potential phosphorylation sites that are highly conserved in zoonotic HEV-3 and HEV-4 genomes but absent in human-exclusive HEV-1 strains. To explore the functional significance of these putative phosphorylation sites, we introduced mutations into the HEV-3 infectious clone and indicator replicon, replacing each Serine residue individually with alanine or aspartic acid, and assessed the impact of these substitutions on HEV-3 replication. We found that the phospho-blatant S711A mutant significantly reduced virus replication, whereas the phospho-mimetic S711D mutant modestly reduced virus replication. Conversely, mutations in the other three Serine residues did not significantly affect HEV-3 replication. Furthermore, we demonstrated that Ser711 phosphorylation did not alter host cell tropism of zoonotic HEV-3. In conclusion, our results showed that potential phosphorylation of the Ser711 residue significantly affects HEV-3 replication in vitro, providing new insights into the potential mechanisms of zoonotic HEV transmission.IMPORTANCEHEV is an important zoonotic pathogen, causing both acute and chronic hepatitis E and extrahepatic manifestation of diseases, such as neurological sequelae. The zoonotic HEV-3 is linked to chronic infection and neurological diseases. The specific viral and/or host factors facilitating cross-species HEV infection are unknown. The intrinsically disordered HVR in ORF1 is crucial for viral fitness and adaptation, both in vitro and in vivo. We hypothesized that phosphorylation of Serine residues in the HVR of zoonotic HEV by unknown host cellular kinases is associated with cross-species HEV transmission. In this study, we identified a conserved region within the HVR of zoonotic HEV strains but absent in the human-exclusive HEV-1 and HEV-2. We elucidated the important role of phosphorylation at the Ser711 residue in zoonotic HEV-3 replication, without altering the host cell tropism. These findings contribute to our understanding the mechanisms of cross-species HEV transmission.

Genomic characterization of Rocahepevirus ratti hepatitis E virus genotype C1 in Yunnan province of China

The Rocahepevirus ratti hepatitis E virus genotype C1 (HEV-C1) has been documented to infect humans. However, the understanding of HEV-C1 remains constrained. This study aims to determine the prevalence and genomic characteristics of HEV-C1 in small animals in Yunnan province of southwestern China. A total of 444 liver tissues were collected from animals covering the orders Rodentia, Soricomorpha, Scandentia and Erinaceomorpha in three regions in Yunnan. Then Paslahepevirus balayani and Rocahepevirus were examined using RT-qPCR. The detection rate of Rocahepevirus was 12.95 % (36/278) in animals of order Rodentia, with 14.77 % (35/237) in Rattus tanezumi and 33.33 % (1/3) in Niviventer fulvescens. No Paslahepevirus balayani was detected. Additionally, two full-length Rocahepevirus sequences (MSE-17 and LHK-54) and thirty-three partial ORF1 sequences were amplified and determined to be HEV-C1. MSE-17 and LHK-54 shared moderate nucleotide identity (78.9 %-80.3 %) with HEV-C1 isolated in rats and humans. The HEV-C1 isolated from Niviventer fulvescens demonstrated a 100 % nucleotide identity with that from Rattus tanezumi. The rat HEV-C1 sequences isolated in our study and other Asian HEV-C1 sequences were phylogenetically distant from those isolated in North America and Europe. Furthermore, the two full-length sequences isolated in our study had less amino acid substitutions in the motifs of RNA-dependent RNA polymerase domain (F204L and L238F), compared with other Asian sequences. In summary, HEV-C1 commonly spreads in rats in Yunnan province of China. Our findings suggest a spatially associated phylogeny, and potential cross-species transmission of HEV-C1.

Zoonotic diseases transmitted from the camels

Background

Zoonotic diseases, infections transmitted naturally from animals to humans, pose a significant public health challenge worldwide. After MERS-CoV was discovered, interest in camels was raised as potential intermediate hosts for zoonotic viruses. Most published review studies pay little attention to case reports or zoonotic epidemics where there is epidemiological proof of transmission from camels to humans. Accordingly, any pathogen found in camels known to cause zoonotic disease in other animals or humans is reported.

Methods

Here, zoonotic diseases linked to camels are reviewed in the literature, focusing on those with epidemiological or molecular evidence of spreading from camels to humans. This review examines the risks posed by camel diseases to human health, emphasizing the need for knowledge and awareness in mitigating these risks.

Results

A search of the literature revealed that eight (36.4%) of the 22 investigations that offered convincing evidence of camel-to-human transmission involved MERS, five (22.7%) Brucellosis, four (18.2%) plague caused by Yersinia pestis, three (13.6%) camelpox, one (4.5%) hepatitis E, and one (4.5%) anthrax. The reporting of these zoonotic diseases has been steadily increasing, with the most recent period, from 2010 to the present, accounting for 59% of the reports. Additionally, camels have been associated with several other zoonotic diseases, including toxoplasmosis, Rift Valley fever, TB, Crimean-Congo hemorrhagic fever, and Q fever, despite having no evidence of a transmission event. Transmission of human zoonotic diseases primarily occurs through camel milk, meat, and direct or indirect contact with camels. The above-mentioned diseases were discussed to determine risks to human health.

Conclusion

MERS, Brucellosis, plague caused by Y. pestis, camelpox, hepatitis E, and anthrax are the main zoonotic diseases associated with human disease events or outbreaks. Transmission to humans primarily occurs through camel milk, meat, and direct contact with camels. There is a need for comprehensive surveillance, preventive measures, and public health interventions based on a one-health approach to mitigate the risks of zoonotic infections linked to camels.

First serological and molecular investigation of hepatitis E virus infection in dromedary camels in Algeria

Hepatitis E is an acute self-limited or fulminant infection in humans, caused by the hepatitis E virus (HEV). This member of the Hepeviridae family has been identified in a wide range of domestic and wild animals all over the world, with a possible transmission to humans through fecal oral route, direct contact and ingestion of contaminated meat products, making it one of the global zoonotic and public health major concerns. Since there is no monitoring program and a lack of data on HEV in animals in Algeria, the current preliminary survey has been undertaken to elucidate the exposure to the virus in camels at abattoirs of six southern provinces of Algeria. Two-hundred and eight sera/plasma were collected and analyzed (by double antigen sandwich ELISA) for the presence of total anti-HEV antibodies, among which 35.1% were positive, but no HEV RNA could be isolated from them (by two pan-HEV nested RT-PCR and broad range real-time reverse transcription RT-PCR). The univariate analysis showed significant associations (p < 0.05) between HEV seroprevalence and province of origin, age, and sex of camels, whereas the multivariable logistic regression analysis revealed a negative impact of camels' age on it. The obtained results confirm that HEV infection is widespread established in the camelid population of Algeria.

First Detection of Hepatitis E Virus (Rocahepevirus ratti Genotype C1) in Synanthropic Norway Rats (Rattus norvegicus) in Romania

Hepatitis E virus (HEV) is an emerging zoonotic pathogen with different viral genera and species reported in a wide range of animals. Rodents, particularly rats, carry the specific genus rat HEV (Rocahepevirus genus, genotype C1) and are exposed occasionally to HEV-3 (Paslahepevirus genus, genotype 3), a zoonotic genotype identified in humans and widely distributed in domestic and feral pigs. In this study, the presence of HEV was investigated in synanthropic Norway rats from Eastern Romania, in areas where the presence of HEV-3 was previously reported in pigs, wild boars and humans. Using methods capable of detecting different HEV species, the presence of HEV RNA was investigated in 69 liver samples collected from 52 rats and other animal species. Nine rat liver samples were identified as being positive for rat HEV RNA (17.3%). High sequence identity (85-89% nt) was found with other European Rocahepevirus. All samples tested from other animal species, within the same environment, were negative for HEV. This is the first study to demonstrate the presence of HEV in rats from Romania. Since rat HEV has been reported to cause zoonotic infections in humans, this finding supports the need to extend the diagnosis of Rocahepevirus in humans with suspicion of hepatitis.

Animal reservoirs for hepatitis E virus within the Paslahepevirus genus

Hepatitis E virus (HEV) is responsible for acute hepatitis in humans. It is a single-stranded, positive-sense RNA virus that belongs to the Hepeviridae family. The majority of concerning HEV genotypes belong to the Paslahepevirus genus and are subsequently divided into eight genotypes. HEV genotypes 1 and 2 exclusively infect humans and primates while genotypes 3 and 4 infect both humans and other mammals. Whereas HEV genotypes 5 and 6 are isolated from wild boars and genotypes 7 and 8 were identified from camels in the United Arab Emirates and China, respectively. HEV mainly spreads from humans to humans via the fecal-oral route. However, some genotypes with the capability of zoonotic transmissions, such as 3 and 4 transmit from animals to humans through feces, direct contact, and ingestion of contaminated meat products. As we further continue to uncover novel HEV strains in various animal species, it is becoming clear that HEV has a broad host range. Therefore, understanding the potential animal reservoirs for this virus will allow for better risk management and risk mitigation of infection with HEV. In this review, we mainly focused on animal reservoirs for the members of the species Paslahepevirus balayani and provided a comprehensive list of the host animals identified to date.

Hepatitis E Virus (HEV) in Makkah, Saudi Arabia: A Population-Based Seroprevalence Study

BACKGROUND

The Hepatitis E virus (HEV) is a common cause of viral hepatitis worldwide. Little is known about the seroprevalence of HEV in the general population of Saudi Arabia.

METHODS

A community-based cross-sectional HEV seroprevalence study was conducted in Makkah, Saudi Arabia. Anti-HEV IgG antibodies were detected in sera using an in-house ELISA. The frequency of HEV sageerology and its correlation with demographic, and environmental factors were evaluated.

RESULTS

Enrollment consisted of 1329 individuals, ages ranged from 8 to 88 years, the mean age was 30.17 years, the median age was 28yrs, and the male: female ratio was 1.15. The overall seroprevalence was 23.8% (316/1329). Males had significantly higher seroprevalence than females (66.1 vs. 33.9%; p < 0.001). Seroprevalence had significant correlations with age, occupation, and lack of regular water supply and housing conditions.

CONCLUSIONS

This is the first HEV community-based seroprevalence study from Saudi Arabia. Results show that the HEV is endemic in Makkah and affects all age groups and occupations. HEV affects more males than females and those living in crowded accommodations without a regular supply of water. Further studies are required across all regions of Saudi Arabia to determine the country's seroprevalence of active or past infection using tests for HEV IgG, HEV IgM antibodies and/or HEV RNA and underlying determinants of transmission.

Puzzles for Hepatitis E Virus

Hepatitis E virus (HEV) is an important but understudied virus that has been the major cause of acute viral hepatitis worldwide. In recent decades, our understanding of this neglected virus has changed greatly: novel forms of viral proteins and their functions have been discovered; HEV can transmit via blood transfusion and organ transplantation; HEV can infect many animal species and the number is still increasing; HEV can induce chronic hepatitis and extra-hepatic manifestations. However, we are short of effective treatment measures to counter the virus. In this chapter we tend to briefly introduce the puzzles and major knowledge gaps existed in the field of HEV research.

Transmission of Hepatitis E Virus

Transmission of hepatitis E virus (HEV) occurs predominantly by the fecal-oral route. Large epidemics of hepatitis E in the developing countries of Asia and Africa are waterborne and spread through contaminated drinking water. The reservoir of HEV in developed countries is believed to be in animals with zoonotic transmission to humans, possibly through direct contact or the consumption of undercooked contaminated meat. And HEV transmission through blood transfusion, organ transplantation, and vertical transmission has been reported.

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.

Animal Models for Hepatitis E Virus

Animal models are one of the most important tools in the study of human hepatitis E virus (HEV) infection. They are particularly important in light of the major limitations of the cell culture system for HEV. Besides nonhuman primates, which are extremely valuable because of their susceptibility to HEV genotypes 1-4, animals like swine, rabbit, and humanized mice are also potential models for studies of pathogenesis, cross-species infection, and the molecular biology of HEV. Identification of a useful animal model for human HEV infection studies is crucial to further investigations into this ubiquitous yet poorly understood virus and facilitate the development of antiviral therapeutics and vaccines.

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

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

Current Knowledge of Hepatitis E Virus (HEV) Epidemiology in Ruminants

Hepatitis E virus (HEV) infection represents an emerging public health concern worldwide. In industrialized countries, increasing numbers of autochthonous cases of human HEV infection are caused by zoonotic transmission of genotypes 3 and 4, mainly through the consumption of contaminated raw or undercooked meat of infected pigs and wild boars, which are considered the main reservoirs of HEV. However, in the last few years, accumulating evidence seems to indicate that several other animals, including different ruminant species, may harbor HEV. Understanding the impact of HEV infection in ruminants and identifying the risk factors affecting transmission among animals and to humans is critical in order to determine their role in the epidemiological cycle of HEV. In this review, we provide a summary of current knowledge on HEV ecology in ruminants. A growing body of evidence has revealed that these animal species may be potential important hosts of HEV, raising concerns about the possible implications for public health.

Cross-Species Transmission of Rabbit Hepatitis E Virus to Pigs and Evaluation of the Protection of a Virus-like Particle Vaccine against Rabbit Hepatitis E Virus Infection in Pigs

We investigated the cross-species transmission of rabbit hepatitis E virus (rb HEV) to pigs and evaluated the cross-protection of a swine (sw) HEV-3 virus-like particle (VLP) vaccine against rb HEV infection in pigs. Twelve 4-week-old conventional pigs were divided into negative control (n = 3), positive control (rb HEV-infected, n = 4), and vaccinated (vaccinated and rb HEV-challenged, n = 5) groups. The vaccine was administered at weeks 0 and 2, and viral challenge was conducted at week 4. Serum HEV RNA, anti-HEV antibody, cytokine, and liver enzyme levels were determined. Histopathological lesions were examined in abdominal organs. Viral RNA was detected and increased anti-HEV antibody and alanine aminotransferase (ALT) levels were observed in positive control pigs; liver fibrosis, inflammatory cell infiltration in the lamina propria of the small intestine and shortened small intestine villi were also observed. In vaccinated pigs, anti-HEV antibody and Th1 cytokine level elevations were observed after the second vaccination; viral RNA was not detected, and ALT level elevations were not observed. The results verified the cross-species transmission of rb HEV to pigs and cross-protection of the sw HEV-3 VLP vaccine against rb HEV infection in pigs. This vaccine may be used for cross-protection against HEV infection in other species.

Experimental Cross-Species Transmission of Rat Hepatitis E Virus to Rhesus and Cynomolgus Monkeys

Rat hepatitis E virus (rat HEV) was first identified in wild rats and was classified as the species Orthohepevirus C in the genera Orthohepevirus, which is genetically different from the genotypes HEV-1 to HEV-8, which are classified as the species Orthohepevirus A. Although recent reports suggest that rat HEV transmits to humans and causes hepatitis, the infectivity of rat HEV to non-human primates such as cynomolgus and rhesus monkeys remains controversial. To investigate whether rat HEV infects non-human primates, we inoculated one cynomolgus monkey and five rhesus monkeys with a V-105 strain of rat HEV via an intravenous injection. Although no significant elevation of alanine aminotransferase (ALT) was observed, rat HEV RNA was detected in fecal specimens, and seroconversion was observed in all six monkeys. The partial nucleotide sequences of the rat HEV recovered from the rat HEV-infected monkeys were identical to those of the V-105 strain, indicating that the infection was caused by the rat HEV. The rat HEV recovered from the cynomolgus and rhesus monkeys successfully infected both nude and Sprague-Dawley rats. The entire rat HEV genome recovered from nude rats was identical to that of the V-105 strain, suggesting that the rat HEV replicates in monkeys and infectious viruses were released into the fecal specimens. These results demonstrated that cynomolgus and rhesus monkeys are susceptible to rat HEV, and they indicate the possibility of a zoonotic infection of rat HEV. Cynomolgus and rhesus monkeys might be useful as animal models for vaccine development.

Identification of hepatitis E virus in wild sika deer in Japan

Hepatitis E virus (HEV) is a zoonotic agent mainly transmitted through the consumption of uncooked or undercooked meat products derived from infected animals. In Japan, domestic pigs and wild boars are the major animal reservoirs, and whether or not deer are an HEV reservoir remains controversial. We analyzed 395 serum and 199 liver samples from 405 sika deer (Cervus nippon) caught in the wild between 1997 and 2020 in 11 prefectures of Japan for markers of HEV infection. Overall, 17 deer had anti-HEV IgG (4.3%), while 1 (0.2%) had HEV RNA (genotype 3b), indicating the occurrence of ongoing HEV infection in wild deer in Japan. An analysis of the complete HEV genome (deJOI_14) recovered from a viremic deer in Oita Prefecture revealed only 88.8% identity with the first HEV strain in sika deer (JDEER-Hyo03L) in Japan, being closest (96.3%) to the HEV obtained from a hepatitis patient living in the same prefecture. Of note, the deJOI_14 strain was 8.7-9.0% different from the wild boar HEV strains obtained in the same habitat and the same year, suggesting that difference in infected HEV strains between boar and deer may be explained by the limited possibility of close contact with each other, although boars are a known source of HEV infection. Increased numbers of hepatitis E cases after consumption of raw or undercooked meat products of wild deer have been reported in Japan. These results suggest a low but nonnegligible zoonotic risk of HEV infection in wild deer in this country.

The Capsid (ORF2) Protein of Hepatitis E Virus in Feces Is C-Terminally Truncated

The hepatitis E virus (HEV) is a causative agent of hepatitis E. HEV virions in circulating blood and culture media are quasi-enveloped, while those in feces are nonenveloped. The capsid (ORF2) protein associated with an enveloped HEV virion is reported to comprise the translation product of leucine 14/methionine 16 to 660 (C-terminal end). However, the nature of the ORF2 protein associated with fecal HEV remains unclear. In the present study, we compared the molecular size of the ORF2 protein among fecal HEV, cell-culture-generated HEV (HEVcc), and detergent-treated protease-digested HEVcc. The ORF2 proteins associated with fecal HEV were C-terminally truncated and showed the same size as those of the detergent-treated protease-digested HEVcc virions (60 kDa), in contrast to those of the HEVcc (68 kDa). The structure prediction of the ORF2 protein (in line with previous studies) demonstrated that the C-terminal region (54 amino acids) of an ORF2 protein is in flux, suggesting that proteases target this region. The nonenveloped nondigested HEV structure prediction indicates that the C-terminal region of the ORF2 protein moves to the surface of the virion and is unnecessary for HEV infection. Our findings clarify the maturation of nonenveloped HEV and will be useful for studies on the HEV lifecycle.

A Cross-Species Transmission of a Camel-Derived Genotype 8 Hepatitis E Virus to Rabbits

Novel genotypes of hepatitis E virus (HEV), i.e., HEV-5, HEV-7, and HEV-8, have been identified in wild boar, dromedary camels, and Bactrian camels, respectively, and they transmit to cynomolgus monkeys in a trans-species manner, raising the potential for zoonotic infection. Rabbits are the natural reservoir for rabbit HEV, but they are also susceptible to HEV-3 and HEV-4. It has been unknown whether rabbits are susceptible to HEV-5, HEV-7, and HEV-8. To investigate the infectivity of novel HEVs in rabbits and to assess whether rabbits are appropriate animal models for these HEVs, we inoculated Japanese white rabbits with HEV-5, HEV-7, and HEV-8, respectively. We observed that viral RNA was present in the fecal specimens of the HEV-8-inoculated rabbits and anti-HEV IgG antibodies were present in its sera, although anti-HEV IgM was undetectable and no significant elevation of ALT was observed. These results indicated that HEV-8 crossed species and infected the rabbits. No evidence for replication was observed in HEV-5 and HEV-7, suggesting that rabbits are not susceptible to these genotypes. The antibodies elicited in the HEV-8-infected rabbits did not protect them from the rabbit HEV challenge, suggesting that the antigenicity differs between HEV-8 and rabbit HEV. Antigenic analyses demonstrated that anti-HEV-8 antibodies reacted more strongly with homologous HEV-8 virus-like particles (VLPs) compared to heterologous rabbit HEV VLPs, but anti-rabbit HEV antibody had similar reactivity to the VLPs of rabbit HEV and HEV-8, suggesting that HEV-8 lacks some epitope(s) that exist in rabbit HEV and induced the neutralizing antibodies against rabbit HEV.

Cellular Organelles Involved in Hepatitis E Virus Infection

Hepatitis E virus (HEV), a major cause of acute hepatitis worldwide, infects approximately 20 million individuals annually. HEV can infect a wide range of mammalian and avian species, and cause frequent zoonotic spillover, increasingly raising public health concerns. To establish a successful infection, HEV needs to usurp host machineries to accomplish its life cycle from initial attachment to egress. However, relatively little is known about the HEV life cycle, especially the functional role(s) of cellular organelles and their associated proteins at different stages of HEV infection. Here, we summarize current knowledge regarding the relation of HEV with the different cell organelles during HEV infection. Furthermore, we discuss the underlying mechanisms by which HEV infection is precisely regulated in infected cells and the modification of host cell organelles and their associated proteins upon HEV infection.

Generation of a Bactrian camel hepatitis E virus by a reverse genetics system

Bactrian camel hepatitis E virus (HEV) is a novel HEV belonging to genotype 8 (HEV-8) in the Orthohepevirus A species of the genus Hepevirus in the family Hepeviridae. HEV-8 cross-transmits to cynomolgus monkeys and has a potential risk for zoonotic infection. Until now, neither a cell-culture system to grow the virus nor a reverse genetics system to generate the virus has been developed. To generate replication-competent HEV-8 and to establish a cell-culture system, we synthesized capped genomic HEV-8 RNAs by in vitro transcription and used them to transfect into PLC/PRF/5 cells. A HEV-8 strain, HEV-8M2, was recovered from the capped HEV-8 RNA-transfected cell-culture supernatants and subsequently passaged in the cells, demonstrating that PLC/PRF/5 cells were capable of supporting the replication of the HEV-8, and that a cell-culture system for HEV-8 was successfully established. In addition to PLC/PRF/5 cells, A549 and Caco-2 cells appeared to be competent for the replication, but HepG2 C3/A, Vero, Hela S3, HEp-2C, 293T and GL37 cells were incompetent. The HEV-8M2 strain was capable of infecting cynomolgus monkeys by an intravenous inoculation, indicating that HEV-8 was infectious and again carried a risk for zoonotic infection. In contrast, HEV-8 did not infect nude rats and BALB/c nude mice, suggesting that the reservoir of HEV-8 was limited. In addition, the replication of the HEV-8M2 strain was efficiently abrogated by ribavirin but not by favipiravir, suggesting that ribavirin is a drug candidate for therapeutic treatment of HEV-8-induced hepatitis. The infectious HEV-8 produced by a reverse genetics system would be useful to elucidate the mechanisms of HEV replication and the pathogenesis of type E hepatitis.

Immunogenicity and Antigenicity of Rabbit Hepatitis E Virus-Like Particles Produced by Recombinant Baculoviruses

Rabbit hepatitis E virus (HEV) is a novel HEV belonging to genotype 3 (HEV-3) in the Orthohepevirus A species of the genus Hepevirus, family Hepeviridae. Rabbit HEV was originally isolated from rabbits and found to cause zoonotic infection. Although rabbit HEV can be successfully grown in culture with several cell lines, including the human carcinoma cell line PLC/PRF/5, it is difficult to obtain the large amounts of viral antigen required for diagnosis and vaccine development. In this study, we expressed N-terminal 13 and 111 aa-truncated rabbit HEV ORF2 proteins using recombinant baculoviruses and obtained two types of virus-like particles (VLPs), RnVLPs and RsVLPs with ~35 and 24 nm diameter, respectively. Anti-rabbit HEV IgG antibodies were induced in high titer by immunizing rabbits with RnVLPs or RsVLPs. The antibody secretion in the serum persisted more than three years. RsVLPs showed stronger antigenic cross-reactivity against HEV-1, HEV-3 and HEV-4 than rat HEV. Moreover, anti-RsVLPs antibodies neutralized not only the cognate virus but also HEV-1, HEV-3 and HEV-4 ex vivo, indicating that rabbit HEV had the same serotype as human HEVs. In contrast, the antibody did not block rat HEV infection, demonstrating that rat HEV belonged to a different serotype. Animal experiments indicated that immunization with either RnVLPs or RsVLPs completely protected the rabbits from challenge by rabbit HEV, suggesting that the VLPs are candidates for rabbit HEV vaccine development.

Hepatitis E: An update on One Health and clinical medicine

The hepatitis E virus (HEV) is one of the main causes of acute hepatitis and the de facto global burden is underestimated. HEV-related clinical complications are often undetected and are not considered in the differential diagnosis. Convincing findings from studies suggest that HEV is clinically relevant not only in developing countries but also in industrialized countries. Eight HEV genotypes (HEV-1 to HEV-8) with different human and animal hosts and other HEV-related viruses are in circulation. Transmission routes vary by genotype and location, with large waterborne outbreaks in developing countries and zoonotic food-borne infections in developed countries. An acute infection can be aggravated in pregnant women, organ transplant recipients, patients with pre-existing liver disease and immunosuppressed patients. HEV during pregnancy affects the fetus and newborn with an increased risk of vertical transmission, preterm and stillbirth, neonatal jaundice and miscarriage. Hepatitis E is associated with extrahepatic manifestations that include neurological disorders such as neuralgic amyotrophy, Guillain-Barré syndrome and encephalitis, renal injury and haematological disorders. The risk of transfusion-transmitted HEV is increasingly recognized in Western countries where the risk may be because of a zoonosis. RNA testing of blood components is essential to determine the risk of transfusion-transmitted HEV. There are currently no approved drugs or vaccines for HEV infections. This review focuses on updating the latest developments in zoonoses, screening and diagnostics, drugs in use and under development, and vaccines.

Infectivity and pathogenicity of different hepatitis E virus genotypes/subtypes in rabbit model

The pathogenicity of each hepatitis E virus (HEV) genotypes/subtypes may be different. This study aimed to investigate the infectivity and pathogenicity of different HEV genotypes/subtypes from different mammalian sources especially human in rabbits, and to assess whether rabbits are an appropriate animal model to study different HEV genotypes/subtypes. Thirty-seven rabbits were randomly divided into nine groups and inoculated with eight different HEV strains, including human-derived HEV3b (hHEV-3b), hHEV-4a, hHEV-4d and hHEV-4h, swine-derived HEV4d (sHEV-4d) and sHEV-4h, rabbit-derived HEV3 (HEV-3ra) and camel-derived HEV8. HEV RNA, antigen, anti-HEV and alanine aminotransferase (ALT) in serum or/and feces were monitored weekly. One rabbit from each group was euthanized at seven weeks post inoculation and the liver specimens were taken for histopathological analysis and immunofluorescence staining of HEV ORF2 proteins. hHEV-4d, sHEV-4d and HEV-3ra infections were successfully established in rabbits and typical acute hepatitis symptoms were observed, including viraemia/antigenemia, fecal virus/antigen shedding, elevated ALT level and liver histopathological changes. One rabbit infected with HEV-3ra showed chronic infection. hHEV-4d and sHEV-4d are less infectious and pathogenic than HEV-3ra in rabbits. hHEV-3b and HEV8 only caused inapparent infection in rabbits as 60% (3/5) and 20% (1/5) of the rabbits seroconverted to anti-HEV, respectively. No obvious signs of HEV infection in rabbits inoculated with hHEV-4a, hHEV-4h and sHEV-4h. The infectivity and pathogenicity of different HEV genotypes/subtypes in rabbits is different, which may be related to the species specificity of HEV. Rabbit can be used as an animal model for the study of HEV-3ra and more importantly human HEV-4d.

Prevalence of Hepatitis E Virus Infection among Laboratory Rabbits in China

Hepatitis E virus (HEV) is zoonotic and the leading cause of acute viral hepatitis worldwide. Rabbit HEV can infect humans and is prevalent globally. It is reported that laboratory rabbits are also naturally infected with HEV. Therefore, it is important to investigate in a large scale the prevalence of HEV in laboratory rabbits. Serum samples were collected from 649 laboratory rabbits of 13 different commercial vendors in Beijing, China, from 2017 to 2019, and anti-HEV and HEV antigen (Ag) were tested. Fecal samples were collected from 50 laboratory rabbits from one of the vendors for HEV RNA detection. Six laboratory rabbits with natural HEV infection were euthanized and their liver, kidney, bile and urine samples were collected for HEV RNA quantification. Liver tissues were subjected to histopathology analysis. The overall positive rates of anti-HEV antibodies and HEV-Ag are 2.6% (15/588) and 7.9% (51/649), respectively. HEV RNA was detected in 12.0% (6/50) of the rabbits. High viral load of HEV RNA was detected in liver and bile samples. Liver inflammation was observed. HEV is circulating in laboratory rabbit population in China. Strict screening is crucial to ensure experimental accuracy and prevent zoonotic transmission to research personnel.

Production of capsid proteins of rat hepatitis E virus in Escherichia coli and characterization of self-assembled virus-like particles

Rat hepatitis E virus (HEV) has been isolated from wild rats worldwide and the potential of zoonotic transmission has been documented. Escherichia coli (E. coli) is utilized as an effective system for producing HEV-like particles. However, the production of rat HEV ORF2 proteins in E. coli forming virus-like particles (VLPs) has not yet been reported. In this study, nine rat HEV ORF2 proteins of the ratELOMB-131L strain with truncated N- and C-termini (amino acids 339-594, 349-594, 351-594, 354-594, 357-594, 357-599, 357-604, 357-609, and 357-614 of ORF2 protein) were expressed in E. coli and the 357-614 protein self-assembled most efficiently. A bioanalyzer showed that the purified 357-614 protein has a molecular weight of 33.5 kDa and a purity of 93.2%. Electron microscopy revealed that the purified 33.5 kDa protein formed VLPs with a diameter of 21-52 (average 32) nm, and immunoelectron microscopy using an anti-rat HEV ORF2 monoclonal antibody (TA7014) indicated that the observed VLPs were derived from rat HEV ORF2. The VLPs attached to and entered the PLC/PRF/5 cells and blocked the neutralization of rat HEV by TA7014, suggesting that the VLPs possess the antigenic structure of infectious rat HEV particles. In addition, rat HEV VLPs showed high immunogenicity in mice. The present results would be useful for future studies on the development of VLP-based vaccines for HEV prevention in a rat model and for the prevention of rat HEV infection in humans.

Mechanism of Cross-Species Transmission, Adaptive Evolution and Pathogenesis of Hepatitis E Virus

Hepatitis E virus (HEV) is the leading cause of acute hepatitis worldwide. While the transmission in developing countries is dominated by fecal-oral route via drinking contaminated water, the zoonotic transmission is the major route of HEV infection in industrialized countries. The discovery of new HEV strains in a growing number of animal species poses a risk to zoonotic infection. However, the exact mechanism and the determinant factors of zoonotic infection are not completely understood. This review will discuss the current knowledge on the mechanism of cross-species transmission of HEV infection, including viral determinants, such as the open reading frames (ORFs), codon usage and adaptive evolution, as well as host determinants, such as host cellular factors and the host immune status, which possibly play pivotal roles during this event. The pathogenesis of hepatitis E infection will be briefly discussed, including the special forms of this disease, including extrahepatic manifestations, chronic infection, and fulminant hepatitis in pregnant women.

Mitochondrial dysfunction and mitophagy pathway activation in hepatitis E virus-infected livers of Mongolian gerbils

Recently, hepatitis E virus (HEV) has caused large outbreaks and presented a significant public health problem. Thus, the mechanism of HEV has attracted increasing research attention. Previous studies revealed that HEV infection induced hepatocyte injuries and structural and functional changes in mitochondria. These pathological changes affected the life cycle of hepatocytes. However, the precise underlying mechanism and the effector protein responsible for this process remain unclear. In the present study, mitochondrial function and the expression of mitophagy-associated mRNA transcripts and proteins were detected in an HEV- infected Mongolian gerbil model. Observation of ultrastructural changes in the liver of the inoculated group revealed the disappearance of mitochondrial cristae of mitochondrion, blurring of the bilayer structure and cavitation in the cytoplasm. The results showed that the mitochondrial transmembrane potential of decreased, mitochondrial transition pore (MPTP) opening increased, reactive oxygen species (ROS) production increased, and glutathione peroxidase (GSH-Px) activity decreased in the HEV-inoculated group. Moreover, the LC3, Beclin1, BNIP3L, Parkin, PINK1 and P62 mRNA levels were significantly increased (p < 0.05 and p < 0.01) in the inoculated group. Western blot and immunohistochemistry assay analyses detected the upregulation of the mitophagy-associated proteins LC3, Beclin1, BNIP3L, Parkin, PINK1 and P62 (p < 0.05 and p < 0.01) in HEV-infected gerbils. All these data demonstrated that HEV infection in vivo induced mitochondrial dysfunction and the activation of the mitophagy pathway, which might be one of the key factors in hepatocyte injury.

Identification and a full genome analysis of novel camel hepatitis E virus strains obtained from Bactrian camels in Mongolia

Hepatitis E virus (HEV) infects humans and a wide variety of other mammalian hosts. Recently, HEV strains belonging to genotype 8 (G8) within the Orthohepevirus A species of the Hepeviridae family, were identified in Bactrian camels (Camelus bactrianus) in China. The Bactrian camel (also known as the Mongolian camel) is native to the steppes of Central Asia. However, the HEV strains of Mongolian camels have not been examined. Among 200 serum samples from domestic Bactrian camels raised on 6 farms, in 6 soums in 3 provinces; 71 (35.5 %) were positive for anti-HEV IgG, with prevalence differing by farm (soum) (4.2-75.0 %); and 2 camels (1.0 %) that had been raised in Bogd, Bayankhongor Province, which had the highest seroprevalence among the six studied areas, were positive for HEV RNA. The two HEV strains (BcHEV-MNG140 and BcHEV-MNG146) obtained from the viremic camels in the present study shared 97.7 % nucleotide identity. They were closest to the reported G8 Chinese camel HEV strains but differed from them by 13.9-14.3 % over the entire genome, with a nucleotide difference of 24.0-26.5 % from the reported G1-G7 HEV strains. A phylogenetic tree indicated that the BcHEV-MNG140 and BcHEV-MNG146 strains were located upstream of a clade consisting of the Chinese camel HEV strains and formed a cluster with them, with a bootstrap value of 100 %, suggesting that they may represent a novel subtype within G8. These results indicate a high prevalence of HEV infection in Mongolian camels and suggest that the variability of camel HEV genomes is markedly high.

Development and Clinical Validation of a Pangenotypic PCR-Based Assay for the Detection and Quantification of Hepatitis E Virus (Orthohepevirus A Genus)

The objective of this study was to design a pangenotypic PCR-based assay for the detection and quantification of hepatitis E virus (HEV) RNA from across the entire spectrum of described genotypes belonging to the Orthohepevirus A genus. The optimal conditions and the performance of the assay were determined by testing the WHO standard strain (6219/10) and the WHO HEV panel (8578/13). Similarly, performance comparisons were made with two commercial assays (Real Star HEV RT-PCR 2.0 and ampliCube HEV 2.0 Quant) to detect HEV RNA at concentrations below 1,000 IU/ml with viral strains from the WHO and to test samples from 54 patients with acute hepatitis. The assay presented in this study was able to detect the entire spectrum of described genotypes belonging to the Orthohepevirus A genus, demonstrating better performance than both commercial kits. This procedure may represent a significant improvement in the molecular diagnosis of HEV infection.

Model systems for studying extrahepatic pathogenesis of hepatitis E virus. Current knowledge and future directions

Hepatitis E Virus is the most common cause of acute viral hepatitis globally. HEV infection is endemic in developing countries. Also, autochthonous and sporadic cases are reported in developed countries. HEV causes acute and chronic infections. Besides, extrahepatic manifestations including neurological, renal, haematological, acute pancreatitis and complications during pregnancy are associated with HEV infections. The pathogenesis of HEV in the extrahepatic tissues is either due to direct cytopathic effect mediated by the virus replication, or immunological mechanisms caused by an uncontrollable host response. Researchers have used different in vivo and in vitro models to study the pathogenesis of HEV in the extrahepatic tissues and analyse the host immune response against HEV infection. This review highlights the extrahepatic disorders associated with HEV infection. We focused on the in vivo and in vitro models as a tool for elucidating the HEV infection beyond the liver and studying the mechanisms of HEV induced tissue damages.

The global trends and regional differences in incidence of HEV infection from 1990 to 2017 and implications for HEV prevention

BACKGROUND/AIMS

Hepatitis E virus (HEV) infection is an important cause of acute viral hepatitis worldwide, but it is long-neglected. We aimed to understand the global trends and regional differences in the incidence of HEV infection, thereby making global tailored prevention strategies.

METHODS

This study is a post-hoc analysis of the data from Global Burden of Disease Study 2017. Annual HEV incident cases and incidence rates from 1990 to 2017 were collected. Changes in incident cases and estimated annual percentage changes (EAPCs) of age-standardized incidence rates (ASRs) were calculated to quantify the temporal trends of HEV infection.

RESULTS

Globally, HEV ASRs decreased by an average 0.16% (95% CI: 0.14%-0.17%) per year from 279.79 per 100 000 in 1990 to 269.70 per 100 000 in 2017; however, the number of HEV incident cases increased by 17.63% from 16.53 million in 1990 to 19.44 million in 2017. Against the global trend of ASR falling, an increasing trend was reported in Oceania (EAPC = 0.03; 95% CI: 0.03-0.04) and Western Europe (EAPC = 0.02; 95% CI: 0.01-0.03). The number of HEV incident cases increased remarkably in low (63.07%) and low-middle (37.46%) Socio-Demographic Index (SDI) regions between 1990 and 2017. Additionally, the number of HEV incident cases increased by 4.63% in high SDI regions, mainly in 40 plus age group. Surprisingly, more than 40% of HEV incident cases in Western Europe in 2017 were over 40 years old.

CONCLUSIONS

HEV is still pending in hyperendemic regions, and it is emerging in low endemic regions, suggesting more efforts should be done to make targeted prevention strategies.

Influenza A virus infection-induced macroautophagy facilitates MHC class II-restricted endogenous presentation of an immunodominant viral epitope

CD4⁺ T cells recognize peptides presented by major histocompatibility complex class II molecules (MHC-II). These peptides are generally derived from exogenous antigens. Macroautophagy has been reported to promote endogenous antigen presentation in viral infections. However, whether influenza A virus (IAV) infection-induced macroautophagy also leads to endogenous antigen presentation through MHC-II is still debated. In this study, we show that IAV infection leads to endogenous presentation of an immunodominant viral epitope NP_311-325 by MHC-II to CD4⁺ T cells. Mechanistically, such MHC-II-restricted endogenous IAV antigen presentation requires de novo protein synthesis as it is inhibited by the protein synthesis inhibitor cycloheximide, and a functional ER-Golgi network as it is totally blocked by Brefeldin A. These results indicate that MHC-II-restricted endogenous IAV antigen presentation is dependent on de novo antigen and/or MHC-II synthesis, and transportation through the ER-Golgi network. Furthermore, such endogenous IAV antigen presentation by MHC-II is enhanced by TAP deficiency, indicating some antigenic peptides are of cytosolic origin. Most importantly, the bulk of such MHC-II-restricted endogenous IAV antigen presentation is blocked by autophagy inhibitors (3-MA and E64d) and deletion of autophagy-related genes, such as Beclin1 and Atg7. We have further demonstrated that in dendritic cells, IAV infection prevents autophagosome-lysosome fusion and promotes autophagosome fusion with MHC class II compartment (MIIC), which likely promotes endogenous IAV antigen presentation by MHC-II. Our results provide strong evidence that IAV infection-induced autophagosome formation facilitates endogenous IAV antigen presentation by MHC-II to CD4⁺ T cells. The implication for influenza vaccine design is discussed.

Surveillance Study of Hepatitis E Virus (HEV) in Domestic and Wild Ruminants in Northwestern Italy

Simple Summary

Hepatitis E virus (HEV) infection can cause both acute and chronic hepatitis in humans and represents an emerging public health concern worldwide. In developed countries, zoonotic transmission of HEV genotypes 3 and 4 is caused by ingestion of raw or undercooked meat of infected swine or wild boars, the main reservoirs of HEV. However, in the last few years, molecular and serological evidence seem to indicate that several other animal species may act as HEV host, including domestic and wild ruminants. In this study, serum and fecal specimens from sheep, goats, red deer, roe deer, chamois, and Alpine ibex collected in two northwestern Italian regions (Piemonte and Valle d’Aosta) were screened molecularly and serologically. With the exception of chamois, HEV antibodies were found both in the domestic and wild ruminant species investigated with the highest rates in sheep and goats. These findings demonstrate that wild also domestic ruminants may be implicated in the viral cycle transmission.

Abstract

In industrialized countries, increasing autochthonous infections of hepatitis E virus (HEV) are caused by zoonotic transmission of genotypes (Gts) 3 and 4, mainly through consumption of contaminated raw or undercooked pork meat. Although swine and wild boar are recognized as the main reservoir for Gt3 and Gt4, accumulating evidence indicates that other animal species, including domestic and wild ruminants, may harbor HEV. Herein, we screened molecularly and serologically serum and fecal samples from two domestic and four wild ruminant species collected in Valle d’Aosta and Piemonte regions (northwestern Italy. HEV antibodies were found in sheep (21.6%), goats (11.4%), red deer (2.6%), roe deer (3.1%), and in Alpine ibex (6.3%). Molecular screening was performed using different primer sets targeting highly conserved regions of hepeviruses and HEV RNA, although at low viral loads, was detected in four fecal specimens (3.0%, 4/134) collected from two HEV seropositive sheep herds. Taken together, the data obtained document the circulation of HEV in the geographical area assessed both in wild and domestic ruminants, but with the highest seroprevalence in sheep and goats. Consistently with results from other studies conducted in southern Italy, circulation of HEV among small domestic ruminants seems to occur more frequently than expected.

Presence and persistence of hepatitis E virus RNA and proteins in human bone marrow

Hepatitis E virus (HEV) infection is primarily manifesting as acute hepatitis, but extra-hepatic replication and injury are frequently reported. During the study period, we discovered two acute myeloid leukaemia (AML) patients infected with HEV genotype 3 and 4, respectively, and HEV RNA and/or viral proteins were persistently detected in the bone marrow of both patients. The finding suggests that HEV can replicate in human bone marrow as it may serve as a new target site and reservoir of HEV persistence.

Review of Hepatitis E Virus in Rats: Evident Risk of Species Orthohepevirus C to Human Zoonotic Infection and Disease

Hepatitis E virus (HEV) (family Hepeviridae) is one of the most common human pathogens, causing acute hepatitis and an increasingly recognized etiological agent in chronic hepatitis and extrahepatic manifestations. Recent studies reported that not only are the classical members of the species Orthohepevirus A (HEV-A) pathogenic to humans but a genetically highly divergent rat origin hepevirus (HEV-C1) in species Orthohepevirus C (HEV-C) is also able to cause zoonotic infection and symptomatic disease (hepatitis) in humans. This review summarizes the current knowledge of hepeviruses in rodents with special focus of rat origin HEV-C1. Cross-species transmission and genetic diversity of HEV-C1 and confirmation of HEV-C1 infections and symptomatic disease in humans re-opened the long-lasting and full of surprises story of HEV in human. This novel knowledge has a consequence to the epidemiology, clinical aspects, laboratory diagnosis, and prevention of HEV infection in humans.

Viral Hepatitis E and Chronicity: A Growing Public Health Concern

Hepatitis E viral infection recently emerges as a global health concern. Over the last decade, the understanding of hepatitis E virus (HEV) had changed with the discovery of new genotypes like genotype-7 and genotype-8 with associated host and mode of infection. Diversification in the mode of hepatitis E infection transmission through blood transfusion, and organ transplants in contrast to classical feco-oral and zoonotic mode is the recent medical concern. The wide spectrum of infection ranging from self-limiting to acute liver failure is now overpowered by HEV genotype-specific chronic infection especially in transplant patients. This concern is further escalated by the extra-hepatic manifestations of HEV targeting the central nervous system (CNS), kidney, heart, and pancreas. However, with the development of advanced efficient cell culture systems and animal models simulating the infection, much clarity toward understanding the pathogenetic mechanism of HEV has been developed. Also this facilitates the development of vaccines research or therapeutics. In this review, we highlight all the novel findings in every aspect of HEV with special emphasis on recently emerging chronic mode of infection with specific diagnosis and treatment regime with an optimistic hope to help virologists and/or liver specialists working in the field of viral hepatitis.

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.

Enhancement of the Molecular and Serological Assessment of Hepatitis E Virus in Milk Samples

Hepatitis E virus (HEV) infection is endemic in developing and developed countries. HEV was reported to be excreted in the milk of ruminants, raising the possibility of transmission of HEV infection through the ingestion of contaminated milk. Therefore, the detection of HEV markers in milk samples becomes pivotal. However, milk includes inhibitory components that affect HEV detection assays. Previously it was reported that dilution of milk matrix improves the performance of HEV molecular assay, however, the dilution of milk samples is not the best strategy especially when the contaminated milk sample has a low HEV load. Therefore, the objective of this study is to compare the effect of extraction procedures on the efficiency of HEV RNA detection in undiluted milk samples. In addition, we assessed the effect of the removal of milk components such as fats and casein on the performance of the molecular and serological assays of HEV. Phosphate buffered saline (PBS) and different milk matrices (such as whole milk, skim milk, and milk serum) were inoculated with different HEV inoculums and subjected to two different extraction procedures. Method A includes manual extraction using spin column-based extraction, while method B includes silica-based automated extraction. Method A was more sensitive than method B in the whole milk and skim milk matrices with a LoD_95% of 300 IU/mL, and virus recovery yield of 47%. While the sensitivity and performance of method B were significantly improved using the milk serum matrix, with LoD_95% of 96 IU/mL. Interestingly, retesting HEV positive milk samples using the high sensitivity assay based on method B extraction and milk serum matrix increased the HEV RNA detection rate to 2-fold. Additionally, the performance of HEV serological assays such as anti-HEV IgG and HEV Ag in the milk samples was improved after the removal of the fat globules from the milk matrix. In conclusion, HEV RNA assay is affected by the components of milk and the extraction procedure. Removal of inhibitory substances, such as fat and casein from the milk sample increased the performance of HEV molecular and serological assays which will be suitable for the low load HEV milk with no further dilutions.

Prevalence and genotype/subtype distribution of hepatitis E virus (HEV) among wild boars in Japan: Identification of a genotype 5 HEV strain

To further investigate the prevalence of hepatitis E virus (HEV) infection and characterize HEV genomes among Japanese wild boars (Sus scrofa leucomystax), 1880 boars captured in 17 prefectures in Japan from 2013 to 2019 were studied. Overall, anti-HEV IgG was detected in 8.9 % and HEV RNA was detected in 3.9 % of boars, which was comparable with our previous studies during 2003-2013 (10.3 % and 3.5 %, respectively). Among 74 boar HEV strains obtained from infected boars in the present study, 50 (68 %) were classified into genotype 3 (3a and 3b), 23 (31 %) were classified into genotype 4 (4i), and the remaining strain (wbJGF_19-1) was classified into genotype 5. The wbGF_19-1 strain shared 92.7 % identity over the entire genome with the prototype genotype 5 strain (JBOAR135-Shiz09). The identification of the second genotype 5 HEV strain in a place that is located only 100 km from the site at which JBOAR135-Shiz09 was identified, suggests that genotype 5 HEV circulates within a relatively close range in Japan. Genetically similar HEV strains forming a clade were identified from wild boars living in each area during the observation period of 11-13 years, although the nucleotide sequence changed gradually, accounting for up to 3.4-3.6 % within the 412-nucleotide ORF2 sequence. Eight groups of boars with a cluster of HEV infections were observed, consisting of two, three or four infected offspring, presumably born to the same mother or offspring with their mother. These results suggest that wild boars continue to be important reservoirs for HEV infection in humans in Japan.

Persistent infection with a rabbit hepatitis E virus created by a reverse genetics system

Rabbit hepatitis E virus (HEV) is a novel zoonotic infectious agent. Although a cell culture system to grow the virus has been established, there is currently no reverse genetics system for generating the virus. In this study, capped genomic rabbit HEV RNAs generated by in vitro transcription were transfected into PLC/PRF/5 cells, and the recovered viruses were subsequently passaged in the cells. The cell culture supernatant was capable of infecting rabbits negative for anti-HEV antibody by intravenous and oral inoculation, indicating that rabbit HEV generated by the reverse genetics system is infectious. Genome-wide analyses indicated that no nucleotide sequence change occurred in the virus genomes that were recovered from the cell culture supernatant after transfection and passaged one time or in the virus genomes recovered from faecal specimens of the infected rabbits. Ribavirin, a broad-spectrum anti-viral inhibitor, efficiently abrogated virus replication ex vivo and transiently suppressed the virus growth in the virus-infected rabbits, suggesting that this reagent is a candidate for therapeutic treatment. In addition, transmission of rabbit HEV to rabbits caused persistent infection, suggesting that the virus-infected rabbit could be an animal model for virus-induced hepatitis. The infectious rabbit HEV produced by a reverse genetics system would be useful to elucidate the mechanisms of HEV replication and the pathogenesis of viral hepatitis.

Update: proposed reference sequences for subtypes of hepatitis E virus (species Orthohepevirus A)

In this recommendation, we update our 2016 table of reference sequences of subtypes of hepatitis E virus (HEV; species Orthohepevirus A, family Hepeviridae) for which complete genome sequences are available (Smith et al., 2016). This takes into account subsequent publications describing novel viruses and additional proposals for subtype names; there are now eight genotypes and 36 subtypes. Although it remains difficult to define strict criteria for distinguishing between virus subtypes, and is not within the remit of the International Committee on Taxonomy of Viruses (ICTV), the use of agreed reference sequences will bring clarity and stability to researchers, epidemiologists and clinicians working with HEV.

Swine hepatitis E virus: Cross-species infection, pork safety and chronic infection

Swine hepatitis E virus (swine HEV) belongs to the species Orthohepevirus A within the genus Orthohepevirus in the family Hepeviridae. Four different genotypes of swine HEV within the species Orthohepevirus A have been identified so far from domesticated and wild swine population: genotypes 3 (HEV-3) and 4 (HEV-4) swine HEVs are zoonotic and infect humans, whereas HEV-5 and HEV-6 are only identified from swine. As a zoonotic agent, swine HEV is an emerging public health concern in many industrialized countries. Pigs are natural reservoir for HEV, consumption of raw or undercooked pork is an important route of foodborne HEV transmission. Occupational risks such as direct contact with infected pigs also increase the risk of HEV transmission in humans. Cross-species infection of HEV-3 and HEV-4 have been documented under experimental and natural conditions. Both swine HEV-3 and swine HEV-4 infect non-human primates, the surrogates of man. Swine HEV, predominantly HEV-3, can establish chronic infection in immunocompromised patients especially in solid organ transplant recipients. The zoonotic HEV-3, and to lesser extent HEV-4, have also been shown to cause neurological diseases and kidney injury. In this review, we focus on the epidemiology of swine HEV, host and viral determinants influencing cross-species HEV infection, zoonotic infection and its associated pork safety concern, as well as swine HEV-associated chronic infection and neurological diseases.

Orthohepevirus C: An Expanding Species of Emerging Hepatitis E Virus Variants

Hepatitis E virus (HEV) is an emerging zoonotic pathogen that has received an increasing amount of attention from virologists, clinicians, veterinarians, and epidemiologists over the past decade. The host range and animal reservoirs of HEV are rapidly expanding and a plethora of emerging HEV variants have been recently identified, some of which have the potential for interspecies infection. In this review, the detection of genetically diverse HEV variants, classified into and presumably associated with the species Orthohepevirus C, currently comprising HEV genotypes C1 and C2, by either serological or molecular approach is summarized. The distribution, genomic variability, and evolution of Orthohepevirus C are analyzed. Moreover, the potential risk of cross-species infection and zoonotic transmission of Orthohepevirus C are discussed.

Clinical Manifestations, Pathogenesis and Treatment of Hepatitis E Virus Infections

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis throughout the world. Most infections are acute but they can become chronic in immunocompromised patients, such as solid organ transplant patients, patients with hematologic malignancy undergoing chemotherapy and those with a human immunodeficiency virus (HIV) infection. Extra-hepatic manifestations, especially neurological and renal diseases, have also been described. To date, four main genotypes of HEV (HEV1-4) were described. HEV1 and HEV2 only infect humans, while HEV3 and HEV4 can infect both humans and animals, like pigs, wild boar, deer and rabbits. The real epidemiology of HEV has been underestimated because most infections are asymptomatic. This review focuses on the recent advances in our understanding of the pathophysiology of acute HEV infections, including severe hepatitis in patients with pre-existing liver disease and pregnant women. It also examines the mechanisms leading to chronic infection in immunocompromised patients and extra-hepatic manifestations. Acute infections are usually self-limiting and do not require antiviral treatment. Conversely, a chronic HEV infection can be cleared by decreasing the dose of immunosuppressive drugs or by treating with ribavirin for 3 months. Nevertheless, new drugs are needed for those cases in which ribavirin treatment fails.

Middle East Respiratory Syndrome Coronavirus Antibodies in Bactrian and Hybrid Camels from Dubai

So far, dromedary camels are the only known animal reservoir for Middle East respiratory syndrome (MERS) coronavirus (MERS-CoV). Previous published serological studies showed that sera of Bactrian camels were all negative for MERS-CoV antibodies. However, a recent study revealed that direct inoculation of Bactrian camels intranasally with MERS-CoV can lead to infection with abundant virus shedding and seroconversion. In this study, we examined the presence of MERS-CoV antibodies in Bactrian and hybrid camels in Dubai, the United Arab Emirates (where dromedaries are also present), and Bactrian camels in Xinjiang, China (where dromedaries are absent). For the 29 serum samples from Bactrian camels in Dubai tested by the MERS-CoV spike (S) protein-based enzyme-linked immunosorbent assay (S-ELISA) and neutralization antibody test, 14 (48%) and 12 (41%), respectively, were positive for MERS-CoV antibodies. All the 12 serum samples that were positive with the neutralization antibody test were also positive for the S-ELISA. For the 11 sera from hybrid camels in Dubai tested with the S-ELISA and neutralization antibody test, 6 (55%) and 9 (82%), respectively, were positive for MERS-CoV antibodies. All the 6 serum samples that were positive for the S-ELISA were also positive with the neutralization antibody test. There was a strong correlation between the antibody levels detected by S-ELISA and neutralizing antibody titers, with a Spearman coefficient of 0.6262 (P < 0.0001; 95% confidence interval, 0.5062 to 0.7225). All 92 Bactrian camel serum samples from Xinjiang were negative for MERS-CoV antibodies tested using both S-ELISA and the neutralization antibody test. Bactrian and hybrid camels are potential sources of MERS-CoV infection.IMPORTANCE Since its first appearance in 2012, Middle East respiratory syndrome (MERS) has affected >25 countries, with >2,400 cases and an extremely high fatality rate of >30%. The total number of mortalities due to MERS is already greater than that due to severe acute respiratory syndrome. MERS coronavirus (MERS-CoV) has been confirmed to be the etiological agent. So far, dromedaries are the only known animal reservoir for MERS-CoV. Previously published serological studies showed that sera of Bactrian camels were all negative for MERS-CoV antibodies. In this study, we observed that 41% of the Bactrian camel sera and 55% of the hybrid camel sera from Dubai (where dromedaries are also present), but none of the sera from Bactrian camels in Xinjiang (where dromedaries are absent), were positive for MERS-CoV antibodies. Based on these results, we conclude that in addition to dromedaries, Bactrian and hybrid camels are also potential sources of MERS-CoV infection.

Hepatitis E Virus Induces Brain Injury Probably Associated With Mitochondrial Apoptosis

Hepatitis E virus (HEV) infection has been associated with extrahepatic manifestations, particularly neurological disorders. Although it has been reported that HEV infection induced hepatocyte apoptosis associated with mitochondria injury, activation of mitochondrial apoptotic pathway in the central nervous system during HEV infection was not clearly understood. In this study, the induction of mitochondrial apoptosis-associated proteins and pro-inflammatory cytokines were detected in HEV infected Mongolian gerbil model and primary human brain microvascular endothelial cells (HBMVECs). Mitochondrial exhibited fragments with loss of cristae and matrix in HEV infected brain tissue by transmission electron microscope (TEM). In vitro studies showed that expression of NADPH oxidase 4 (NOX4) was significantly increased in HEV infected HBMVECs (p < 0.05), while ATP5A1 was significantly decreased (p < 0.01). Expressions of pro-apoptotic proteins were further evaluated. Bax was significantly increased in both HEV infected brain tissues and HBMVECs (p < 0.01). In vivo studies showed that caspase-9 and caspase-3 were activated after HEV inoculation (p < 0.01), associated with PCNA overexpression as response to apoptosis. Cytokines were measured to evaluate tissue inflammatory levels. Results showed that the release of TNFα and IL-1β were significantly increased after HEV infection (p < 0.01), which might be attributed to microglia activation characterized by high level of IBA1 expression (p < 0.01). Taken together, these data support that HEV infection induces high levels of pro-inflammatory cytokines, associated with mitochondria-mediated apoptosis. The results provide new insight into mechanisms of extra-hepatic injury of HEV infection, especially in the central nervous system.

Updates in Hepatitis E virus (HEV) field; lessons learned from human liver chimeric mice

Hepatitis E virus (HEV) is the most common cause of viral hepatitis globally, and it is an emerging pathogen in developed countries. In vivo studies of HEV have long been hindered due to the lack of an efficient small animal model. Recently, human liver chimeric mice were described as an elegant model to study chronic HEV infection. HEV infection was established in mice with humanized liver that were challenged with stool preparations containing HEV genotype (gt)1 and/or gt3. An increase in viral load and the level of HEV Ag in mouse samples were markers of active infection. Plasma-derived HEV preparations were less infectious. The kinetics of HEV ORF2 Ag during HEV infection and its impact on HEV diagnosis were described in this model. In addition, the nature of HEV particles and HEV ORF2 Ag were characterized. Moreover, humanized mice were used to study the impact of HEV infection on the hepatic innate transcriptome and evaluation of anti-HEV therapies. This review highlights recent advances in the HEV field gathered from well-established experimental mouse models, with an emphasis on this model as a tool for elucidating the course of HEV infection, the study of the HEV life cycle, the interaction of the virus with the host, and the evaluation of new anti-HEV therapies.

Human Immunodeficiency Virus Infected Patients are Not at Higher Risk for Hepatitis E Virus Infection: A Systematic Review and Meta-Analysis

Hepatitis E virus (HEV) infection is the most common cause of acute hepatitis in the world. It is not well established whether people infected with the human immunodeficiency virus (HIV) are more susceptible to infection with HEV than people not infected with HIV. Many studies have evaluated this relationship, although none are conclusive. The aim of this systematic review and meta-analysis was to assess whether patients with HIV infection constitute a risk group for HEV infection. A systematic review and meta-analysis was performed in line with Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA), to find publications comparing HEV seroprevalences among HIV infected and uninfected populations. The analysis was matched by sex, age and geographical area, and compared patients who live with HIV and HIV-negative individuals. The odds ratio (OR) for patients with HIV was 0.87 (95% CI: 0.74-1.03) in the fixed effects meta-analysis and 0.88 (95% CI: 0.70-1.11) in random effects, with I² = 47%. This study did not show that HIV infection was a risk factor for HEV infection when compared with those who are HIV-negative.

In vivo models for studying Hepatitis E virus infection; Updates and applications

Hepatitis E virus (HEV) is the most common cause of acute viral hepatitis globally. HEV belongs to the Hepeviridae family and at least five genotypes (gt) infect humans. Several animal species are reservoirs for different HEV strains, and they are the source of infection for humans. Some HEV strains are species specific, but other strains could cross species and infect many hosts. The study of HEV infection and pathogenesis was hampered due to the lack of an in vitro and in vivo robust model system. The cell culture system has been established for certain HEV strains, especially gt3 and 4, but gt1 strains replicate poorly in vitro. To date, animal models are the best tool for studying HEV infection. Non-human primates (NHPs) and pigs are the main animal models used for studying HEV infection, but ethical and financial concerns restrict the use of NHPs in research. Therefore, new small animal models have been developed which help more progress in HEV research. In this review, we give updates on the animal models used for studying HEV infection, focusing on the applicability of each model in studying different HEV infections, cross-species infection, virus-host interaction, evaluation of anti-HEV therapies and testing potential HEV vaccines.