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.

[Enteral viral hepatitis in monkeys]

Within the last decade, a large number of viruses genetically related to human hepatitis viruses have been identified in different animal species, including monkeys. Numerous viruses related to human hepatitis A virus (HAV, Picornaviridae: Hepatovirus: Hepatovirus A) were detected in various mammalian species in 2015-2018, predominantly in bats and rodents, but also in shrews, seals and marsupials. Zoonotic hepatitis E virus (HEV, Hepeviridae: Orthohepevirus: Orthohepevirus A) genotypes have been found in wild boars, deer, camels, and rabbits, as well as in non human primates. In addition, viruses that are genetically close to HEV have been described in bats, ferrets, rodents, birds, and fish. Nevertheless, monkeys remain important laboratory animals in HAV and HEV research. The study of spontaneous and experimental infection in these animals is an invaluable source of information about the biology and pathogenesis of these viruses and continues to be an indispensable tool for vaccine and drug testing. The purpose of this literature review was to summarize and analyze published data on the circulation of HAV and HEV among wild and captive primates, as well as the results of experimental studies of HAV and HEV infections in monkeys.

[Markers of viral hepatitis E (Hepeviridae, Orthohepevirus, Orthohepevirus A) in the imported Old World monkeys]

INTRODUCTION

Viral hepatitis E is a zooanthroponotic disease that occurs in humans and various animals, including monkeys. It is caused by hepatitis E virus (HEV) (Hepeviridae, Orthohepevirus: Orthohepevirus A), for which 8 genotypes have been described to date. Among them, strains of genotypes 1 and 2 have been isolated from humans, strains of genotypes 3 and 4 from humans and animals, and strains of genotypes 5-8 from animals only. The main threat of the disease is associated with the documented zoonotic transmission of HEV genotypes 3, 4, 7, and 8, to humans through infected meat, blood and milk. Thus, monkeys could be involved in the transmission of HEV.The aim of this work was to study serological and molecular genetic markers of HEV infection in strepsirrhines (Old World monkeys, Cercopithecoidea), imported to the Adler Primate Center from various regions of the world (Tanzania, Vietnam, Mauritius).

MATERIAL AND METHODS

Fecal (n = 224) and blood serum samples (n = 395) from cynomolgus (Macaca fascicularis) and vervet monkeys (Chlorocebus pygerythrus) were examined by the enzyme-linked immunosorbent assay (ELISA) and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS AND DISCUSSION

The data obtained show the high detection rate (51.8%) of IgG antibodies to HEV among 5 groups of cynomolgus monkeys imported from Vietnam, with a predominance of highly reactive sera (84%). High detection rate of IgM antibodies in these animals (10.4%) was observed, with the large number of IgM-reactive sera in one particular group of animals (36.8%). The fact of detection of HEV RNA in two groups of cynomolgus monkeys (11.9% and 5.7%) is of particular importance. All HEV sequences of isolated from monkeys belonged to genotype 4.

CONCLUSION

Our data indicate that monkeys (in particular, cynomolgus monkeys) can serve as a natural reservoir of HEV genotype 4 for humans. This requires an appropriate set of anti-epidemic measures in a number of situations.

Detection of hepatitis E virus antibodies among Cercopithecidae and Hominidae monkeys in Cameroon

We screened hepatitis E from 15 species of non-human primates. Anti-HEV IgG was detected in 11.1% (1/9) Mandrillus sphinx, 14.3% (2/14) Gorilla gorilla, 5.9% (4/67) pan troglodytes and 8.7% (2/23) Mandrillus leucophaeus, whereas anti-HEV IgM was detected in 1.5% (1/18) papio Anubis, 28.6% (2/7) Cercocebus agilis and 1.5% (1/67) pan troglodyte.

Survey for Hepatitis E virus infection in non-human primates in zoos in Spain

Hepatitis E virus (HEV) is an emerging zoonotic pathogen that has been detected in different animal species. A survey study was carried out to assess HEV infection in non-human primates (NHPs) housed in zoos in Spain. Anti-HEV antibodies were detected in eight of the 181 NHPs tested (4.4%; 95%CI: 1.4-7.4). At least one seropositive animal was detected in five of the 33 species sampled (15.2%). This is the first report of seropositivity in black-and-white ruffed lemurs (Varecia variegata), common chimpanzees (Pan troglodytes), and Barbary macaques (Macaca sylvanus). Anti-HEV antibodies were found in six of the eight zoos included in the study (75.0%). Seroconversion was detected in one chimpanzee, which confirms HEV circulation in one zoo between 2015 and 2016. Seropositivity was significantly higher in hominids than in other NHP families. HEV RNA was not detected in any of the serum samples tested. The results indicate susceptibility of NHPs to HEV infection. Further studies are required to elucidate the role of these species in the epidemiology of HEV.

Detection of HEV-specific antibodies in four non-human primate species, including great apes, from different zoos in Germany

The hepatitis E virus (HEV) has been described in humans and various animal species in different regions of the world. However, the knowledge on natural HEV infection in non-human primates and the corresponding risk of zoonotic transmission is scarce. To determine whether primates in captivity are affected by HEV infection, we investigated 259 individual sera of clinically healthy non-human primates of 14 species from nine German zoos. Using a commercial double-antigen-sandwich ELISA and a commercial IgG ELISA, 10 animals (3·9%) reacted positive in at least one assay. Three ape species and one Old World monkey species were among the seropositive animals: bonobo (Pan paniscus), gorilla (Gorilla gorilla gorilla), lar gibbon (Hylobates lar) and drill (Mandrillus leucophaeus). Testing for anti-HEV-IgM antibodies by commercial ELISA and for viral RNA by reverse-transcription real-time polymerase chain reaction resulted in negative results for all animals indicating the absence of acute HEV infections. In the past, no clinical signs of hepatitis were recorded for the seropositive animals. The results suggest that non-human primates in zoos can get naturally and subclinically infected with HEV or related hepeviruses. Future studies should evaluate potential sources and transmission routes of these infections and their impact on human health.

Markers of hepatitis E among the population of the Greater Sochi and in monkeys of the Adler primate center

Serum from humans (n = 646) and monkeys (n = 1867) collected during the period 1999-2013 was tested by enzyme immunoassay. Anti-HEV IgG was detected significantly more frequently (P ≥ 0.001) in rhesus macaques (Macaca mulatta) - 45.1 ± 1.6% (n = 1001) than in cynomolgus macaques (M. fascicularis) 16.2 ± 1.8% (n = 426). Single seropositive individuals were found among M. nemestrina - 4.0±2.8% (n = 50). Anti-HEV was not detected in the sera of green monkeys (Chlorocebus aethiops) - n = 162, Papio hamadryas (n = 124), and Papio anubis - n = 104. The presence of the anti-HEV IgM indicating the cases of fresh infection in Macaca mulatta - 2.1 ± 0.5% (n = 717) and M. fascicularis - 3.5 ± 1.3% (n = 266) is of great significance. The overall frequency of detection of the anti-HEV IgG among the staff of the Adler Primate Center - 6.8 ± 2.3% (n = 118) was significantly lower (P ≤ 0.001) than among the population of the Greater Sochi - 15.9% ± 1.6 (n = 528). It is important that only in patients of medical institutions (clinic, hospital, cancer center), anti-HEV IgM were detected (2.7-11.8%) along with anti-HEV IgG (15-23.5%), thereby indicating the presence of acute cases of HEV infection among this population. HEV RNA was not detected in the serum of anti-HEV IgM-positive people and monkeys. Seroepidemiological data do not confirm the assumption on the ability of seropositive monkeys of Macaca genus to be a natural reservoir of HEV infection for humans.

Excretion of infectious hepatitis E virus into milk in cows imposes high risks of zoonosis

Hepatitis E virus (HEV) represents the main cause of acute hepatitis worldwide. HEV infection in immunocompromised patients involves a high risk for the development of chronic hepatitis. Because HEV is recognized as a zoonotic pathogen, it is currently believed that swine is the primary reservoir. However, this is not sufficient to justify the strikingly high seroprevalence of HEV in both developing and Western countries. Thus, this study aimed to identify new zoonotic sources that bear a high risk of transmission to humans. We collected fecal, blood, and milk samples of cows in a typical rural region of Yunnan Province in southwest China, where mixed farming of domestic animals is a common practice. HEV RNA was quantified by quantitative real-time polymerase chain reaction, and the whole genome was sequenced. HEV infectivity was assessed in rhesus macaques. We found a high prevalence of active HEV infection in cows as determined by viral RNA positivity in fecal samples. Surprisingly, we discovered that HEV is excreted into milk that is produced by infected cows. Phylogenetic analysis revealed that all HEV isolates from cow/milk belong to genotype 4 and subtype 4h. Gavage with HEV-contaminated raw and even pasteurized milk resulted in active infection in rhesus macaques. Importantly, a short period of boiling, but not pasteurization, could completely inactivate HEV.

CONCLUSION

Infectious HEV-contaminated cow milk is recognized as a new zoonotic source that bears a high risk of transmission to humans; these results call attention to understanding and establishing proper measurement and control of HEV zoonotic transmission, particularly in the setting of mixed farming of domestic animals. (Hepatology 2016;64:350-359).

Characterization of hepatitis E virus infection in tree shrew (Tupaia belangeri chinensis)

Background

Hepatitis E virus (HEV) is a major cause of hepatitis in developing countries and poses a threat to public health worldwide. Tree shrew (Tupaia belangeri chinensis) is a useful animal model in studies on hepatitis viruses, such as hepatitis B and C viruses. However, the use of this animal model for HEV research is yet to be developed.

Methods

Tree shrews were intravenously (IV) injected with swine genotype 4 HEV or infected by contact-exposure to IV infected tree shrews. RT-nPCR was performed to detect HEV RNA in the feces, tissues, and blood. HEV capsid protein in the different tissues was detected by Western blot and estimated by quantitative RT-PCR. Anti-HEV antibodies were determined by ELISA. Liver damages were evaluated by histopathologic examination and analysis of liver-specific enzymes activities.

Results

Both negative and positive strands of HEV RNA were detected in the feces of the HEV-infected or contact-exposed tree shrews 3–4 days post-inoculation. HEV RNA was detectable in the liver, spleen, kidneys, and bile. Virusemia developed in all the HEV-infected tree shrews. HEV capsid protein was expressed in the liver, spleen, and kidneys. The histological examination and analysis of liver-specific enzymes activities showed that HEV caused acute liver lesions in the tree shrews. Meanwhile, the infected tree shrews showed positive IgG and IgM antibodies.

Conclusions

Tree shrews are susceptible to HEV and may be useful animal models for HEV experimental infection studies on pathogenesis or preclinical drug development.

Pregnancy serum facilitates hepatitis E virus replication in vitro

Hepatitis E virus (HEV) infection causes high mortality in pregnant women. However, the pathogenic mechanisms of HEV infection in pregnant women remain unknown. In this study, the roles of pregnancy serum in HEV infection were investigated using an efficient cell culture system. HEV infection was exacerbated by supplementing with pregnancy serum, especially theat in third trimester of pregnancy. Oestrogen receptors (ER-α and ER-β) were activated in cells supplemented with pregnancy serum and were significantly inhibited during HEV infection. Type I IFN, especially IFN-β, showed delayed upregulation in HEV-infected cells supplemented with the serum in the third trimester of pregnancy, which indicated that delayed IFN-β expression may facilitate viral replication. Results suggested that pregnancy serum accelerated HEV replication by suppressing oestrogen receptors and type I IFN in the early stage of infection.

Infection by Brazilian and Dutch swine hepatitis E virus strains induces haematological changes in Macaca fascicularis

BACKGROUND

Hepatitis E virus (HEV) has been described as an emerging pathogen in Brazil and seems to be widely disseminated among swine herds. An autochthonous human case of acute hepatitis E was recently reported. To obtain a better understanding of the phenotypic profiles of both human and swine HEV strains, a experimental study was conducted using the animal model, Macaca fascicularis.

METHODS

Six cynomolgus monkeys (Macaca fascicularis) were inoculated intravenously with swine HEV genotype 3 that was isolated from naturally and experimentally infected pigs in Brazil and the Netherlands. Two other monkeys were inoculated with HEV genotype 3 that was recovered from Brazilian and Argentinean patients with locally acquired acute and fulminant hepatitis E. The haematological, biochemical, and virological parameters of all animals were monitored for 67 days.

RESULTS

Subclinical hepatitis was observed in all monkeys after inoculation with HEV genotype 3 that was recovered from the infected swine and human patients. HEV RNA was detected in the serum and/or faeces of 6 out of the 8 cynomolgus monkeys between 5 and 53 days after inoculation. The mild inflammation of liver tissues and elevations of discrete liver enzymes were observed. Seroconversions to anti-HEV IgM and/or IgG were detected in 7 animals. Reactivities to anti-HEV IgA were also detected in the salivary samples of 3 animals. Interestingly, all of the infected monkeys showed severe lymphopenia and a trend toward monocytosis, which coincided with elevations in alanine aminotransferase and antibody titres.

CONCLUSIONS

The ability of HEV to cross the species barrier was confirmed for both the swine (Brazilian and Dutch) and human (Argentinean) strains, thus reinforcing the zoonotic risk of hepatitis E in South America. Cynomolgus monkeys that were infected with HEV genotype 3 developed subclinical hepatitis that was associated with haematological changes. Haematological approaches should be considered in future studies of HEV infection.

Hepatitis E virus infection in Latin America: a review

Data reported during recent years reveal the complex picture of the epidemiology of hepatitis E virus (HEV) infection in Latin America. Whereas in countries like Argentina and Brazil is almost identical to the characteristic of most countries from North America and Europe, HEV in the Caribbean and Mexico involves the water-borne, non-zoonotic viral genotypes responsible for epidemics in Asia and Africa. Nevertheless, Latin America has been considered a highly endemic region for hepatitis E in the scientific literature, a generalization that ignores the above complexity. In addition, reports from isolated Amerindian communities, which display well known, important and very specific epidemiological features for hepatitis B and D virus infections are neither taken into account when considering the epidemiology of hepatitis E in the region. This review updates compilation of the available information for the HEV infection, both among humans and other mammals, in Latin America, discusses the strengths and the weaknesses of our current knowledge, and identifies future areas of research.