Quantitative detection of hepatitis E virus RNA and dynamics of viral replication in experimental infection

Hepatitis E Virus in Water Environments: A Systematic Review and Meta-analysis

Hepatitis E virus (HEV) is responsible for acute hepatitis in humans, through foodborne, zoonotic, and waterborne transmission routes. This study aimed to assess the prevalence of HEV in water matrices. Six categories were defined: untreated and treated wastewater, surface water (river, lake, and seawater), drinking water, groundwater, and other water environments (irrigation water, grey water, reservoir water, flood water, and effluent of pig slaughterhouse). We searched PubMed, Web of Science, Global Index Medicus, and Excerpta Medica Database. Study selection and data extraction were performed by at least two independent investigators. Heterogeneity (I²) was assessed using the χ² test on the Cochran Q statistic and H parameter. Sources of heterogeneity were explored by subgroup analysis. This study is registered with PROSPERO, number CRD42021289116. We included 87 prevalence studies from 58 papers, 66.4% of which performed in Europe. The overall prevalence of HEV in water was 9.8% (95% CI 6.4-13.7). The prevalence was higher in untreated wastewater (15.1%) and lower in treated wastewater (3.8%) and in drinking water (4.7%). In surface water, prevalence was 7.4%, and in groundwater, the percentage of positive samples, from only one study available, was 8.3%. Overall, only 36.8% of the studies reported the genotype of HEV, with genotype 3 (HEV-3) prevalent (168 samples), followed by HEV-1 (148 sample), and HEV-4 (2 samples). High-income countries were the most represented with 59/87 studies (67.8%), while only 3/87 (3.5%) of the studies were performed in low-income countries. The overall prevalence obtained of this study was generally higher in industrialized countries. Risk of bias was low in 14.9% of the studies and moderate in 85.1%. The results of this review showed the occurrence of HEV in different waters environments also in industrialized countries with sanitation and safe water supplies. While HEV transmission to humans through water has been widely demonstrated in developing countries, it is an issue still pending in industrialized countries. Better knowledge on the source of pollution, occurrence, survival in water, and removal by water treatment is needed to unravel this transmission path.

Dynamic of Hepatitis E Virus (HEV) Shedding in Pigs

Simple Summary

Hepatitis E virus (HEV) is an emerging pathogen, causing an increasing number of autochthonous cases in industrialized countries. In Europe, infections are associated with the zoonotic HEV-3 and HEV-4 genotypes and pigs and wild boars are the main reservoirs. A major concern of infections is linked to its foodborne transmission, due to consumption of raw or undercooked pork products infected by HEV-3 or HEV-4. HEV-3 is widespread in farmed pigs, mainly aged 3–4 months. Besides a decline with age, infected pigs have been observed at slaughterhouses, representing a risk for both the consumers and the workers of the pig industry. HEV is transmitted by the fecal–oral route and shed in feces in large amounts. The risk of viral spreading in farm and presence of infected pigs at slaughtering was evaluated by assessing the quantity and the duration of HEV-3 shedding in feces of infected pigs. Feces of 23 HEV-3 positive pigs were assayed during their fattening, shortly before their slaughtering. Results confirmed a long period of viral shedding in feces with a large amount of the virus released in the environment (mean 10⁵ GC/g). Prevalence and quantity of the virus declines with the age of animals. The study provides information on the dynamic of the infection in pigs, important to prevent HEV occurrence and circulation in farms.

Abstract

Genotype 3 of hepatitis E virus (HEV-3) is the most common in Europe in both humans and pigs. HEV-3 strains are zoonotic, and foodborne cases associated with consumption of raw and undercooked pork products, mainly liver sausages, have been described. HEV-3 circulates largely in European pig farms, maybe due to its long persistence in the environment. Animals get infected around 3–4 months of age; shortly after, the infection starts to decline up to the age of slaughtering (8–9 months of age in Italy). With the purpose to understand the duration in farmed pigs of the shedding of the virus and its quantity, HEV-RNA detection was performed by Real-time RT-PCR from feces collected individually from two groups of 23 pigs. Sampling was conducted for 4 months shortly before slaughtering age. At 4-months-old, all animals were shedding HEV-3 to high load around 10⁵ genome copies per gram (GC/g). Prevalence was higher in growers than in fatteners, with most of the pigs still positive around 166 days of age. Beyond some difference among individual pigs, the amount of HEV in feces decreased with the age of animals. The longest fattening period should ensure a lower risk of HEV shedder animals at slaughter, reducing the risk of food contamination.

Study of Hepatitis E Virus-4 Infection in Human Liver-Chimeric, Immunodeficient, and Immunocompetent Mice

The hepatitis E virus (HEV) is responsible for 20 million infections worldwide per year. Although, HEV infection is mostly self-limiting, immunocompromised individuals may evolve toward chronicity. The lack of an efficient small animal model has hampered the study of HEV and the discovery of anti-HEV therapies. Furthermore, new HEV strains, infectious to humans, are being discovered. Human liver-chimeric mice have greatly aided in the understanding of HEV, but only two genotypes (HEV-1 and HEV-3) have been studied in this model. Moreover, the immunodeficient nature of this mouse model does not allow full investigation of the virus and all aspects of its interaction with the host. Recent studies have shown the susceptibility of regular and nude Balb/c mice to a HEV-4 strain (KM01). This model should allow the investigation of the interplay between HEV and the adaptive immune system of its host, and potential immune-mediated complications. Here, we assess the susceptibility of human liver-chimeric and non-humanised mice to a different HEV-4 strain (BeSW67HEV4-2008). We report that humanised mice could be readily infected with this isolate, resulting in an infection pattern comparable to HEV-3 infection. Despite these results and in contrast to KM01, non-humanised mice were not susceptible to infection with this viral strain. Further investigation, using other HEV-4 isolates, is needed to conclusively determine HEV-4 tropism and mouse susceptibility.

Seroprevalence of hepatitis E virus among blood donors on Corsica, France, 2017

Background

Hepatitis E virus (HEV) is an emerging zoonotic pathogen and an important cause of acute viral hepatitis in European countries. Corsica Island has been previously identified as a hyperendemic area for HEV.

Aim

Our aim was to characterise the prevalence and titres of IgG antibodies to HEV among blood donors on Corsica and establish a model of the annual force of infection.

Methods

Between September 2017 and January 2018, 2,705 blood donations were tested for anti-HEV IgG using the Wantai HEV IgG enzyme immunoassay.

Results

The overall seroprevalence was 56.1%. In multivariate analysis, seroprevalence was higher in men than in women (60.0% vs 52.2%; p < 0.01), increased with age and was significantly higher among donors born on Corsica (60.6% vs 53.2%; p < 0.01). No significant difference was observed between the five districts of the island. IgG anti-HEV titres were mostly low (70% of positive donors had titres < 3 IU/mL). In Corsican natives, increasing seroprevalence by age could be explained by models capturing a loss of immunity (annual probability of infection: 4.5%; duration of immunity: 55 years) or by age-specific probabilities of infection (3.8% for children, 1.3% for adults).

Conclusion

We confirmed the high HEV seroprevalence on Corsica and identified three aspects that should be further explored: (i) the epidemiology in those younger than 18 years, (ii) common sources of contamination, in particular drinking water, that may explain the wide exposure of the population, and (iii) the actual protection afforded by the low IgG titres observed and the potential susceptibility to secondary HEV infection.

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.

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.

Hepatitis E virus in lettuce and water samples: A method-comparison study

The hepatitis E virus (HEV), which is an increasing cause of acute viral hepatitis in Europe, is a zoonotic virus that is mainly transmitted through contaminated water, consumption of raw or undercooked meat from pigs or wild boar, blood transfusion, and organ transplantation. Although the role of HEV transmission through contaminated produce has not been confirmed, the presence of HEV has been reported in irrigation waters and in vegetables. The present study used a World Health Organization (WHO) international standard and clinical samples to evaluate the performance characteristics of three RT-qPCR assays for detection and quantification of HEV. Two of the evaluated assays provided good analytical sensitivity, as 250 international units (IU) per ml could be detected. Then, experiments focused on evaluating the elution conditions suitable for HEV release from vegetables, with the method proposed by the ISO 15216:2017 selected for evaluation in three types of fresh vegetables. The concentration method proposed by the ISO 15216:2017 combined with the RT-qPCR described by Schlosser et al. (2014) resulted in average HEV recoveries of 1.29%, 0.46%, and 3.95% in lettuce, spinach, and pepper, respectively, with an average detection limit of 1.47 × 105 IU/25 g. In naturally contaminated samples, HEV was detected in sewage only (10/14), while no detection was reported in lettuce (0/36) or in irrigation water samples (0/24).

Hepatitis E Virus: A New Foodborne Zoonotic Concern

Hepatitis E virus (HEV) is an enteric nonenveloped single-stranded RNA virus. Among the mammalian lineages, four genotypes are associated to human infection: genogroups 1 and 2 infect only humans and are mainly found in developing countries, while genogroups 3 and 4 are zoonotic, being found in a variety of animal species including pigs, and are autochthonous in developed countries. HEV infection can result in liver damage and with genotypes 1 and 2 symptoms can be particularly severe in pregnant women, with a high lethality ratio. Several cases of foodborne transmission of hepatitis E have been reported, often involving consumption of meat, especially raw or undercooked. Information is lacking on the exact extent of foodborne transmission of HEV.

Hepatitis E virus: advances and challenges

At least 20 million hepatitis E virus (HEV) infections occur annually, with >3 million symptomatic cases and ∼60,000 fatalities. Hepatitis E is generally self-limiting, with a case fatality rate of 0.5-3% in young adults. However, it can cause up to 30% mortality in pregnant women in the third trimester and can become chronic in immunocompromised individuals, such as those receiving organ transplants or chemotherapy and individuals with HIV infection. HEV is transmitted primarily via the faecal-oral route and was previously thought to be a public health concern only in developing countries. It is now also being frequently reported in industrialized countries, where it is transmitted zoonotically or through organ transplantation or blood transfusions. Although a vaccine for HEV has been developed, it is only licensed in China. Additionally, no effective, non-teratogenic and specific treatments against HEV infections are currently available. Although progress has been made in characterizing HEV biology, the scarcity of adequate experimental platforms has hampered further research. In this Review, we focus on providing an update on the HEV life cycle. We will further discuss existing cell culture and animal models and highlight platforms that have proven to be useful and/or are emerging for studying other hepatotropic (viral) pathogens.

Hepatitis E Virus in Industrialized Countries: The Silent Threat

Hepatitis E virus (HEV) is the main cause of acute viral hepatitis worldwide. Its presence in developing countries has been documented for decades. Developed countries were supposed to be virus-free and initially only imported cases were detected in those areas. However, sporadic and autochthonous cases of HEV infection have been identified and studies reveal that the virus is worldwide spread. Chronic hepatitis and multiple extrahepatic manifestations have also been associated with HEV. We review the data from European countries, where human, animal, and environmental data have been collected since the 90s. In Europe, autochthonous HEV strains were first detected in the late 90s and early 2000s. Since then, serological data have shown that the virus infects quite frequently the European population and that some species, such as pigs, wild boars, and deer, are reservoirs. HEV strains can be isolated from environmental samples and reach the food chain, as shown by the detection of the virus in mussels and in contaminated pork products as sausages or meat. All these data highlight the need of studies directed to control the sources of HEV to protect immunocompromised individuals that seem the weakest link of the HEV epidemiology in industrialized regions.

Zoonotic Hepatitis E Virus: Classification, Animal Reservoirs and Transmission Routes

During the past ten years, several new hepatitis E viruses (HEVs) have been identified in various animal species. In parallel, the number of reports of autochthonous hepatitis E in Western countries has increased as well, raising the question of what role these possible animal reservoirs play in human infections. The aim of this review is to present the recent discoveries of animal HEVs and their classification within the Hepeviridae family, their zoonotic and species barrier crossing potential, and possible use as models to study hepatitis E pathogenesis. Lastly, this review describes the transmission pathways identified from animal sources.

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.

Zoonotic origin of hepatitis E

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

Hepatitis E virus genotypes 1 and 3 in wastewater samples in Tunisia

Hepatitis E represents an important public-health concern throughout the world. It is one of the leading causes of hepatitis in North Africa, Asia and the Middle East. In Tunisia, the true burden of HEV infection is still unknown. The objectives of the present study were to assess the occurrence of hepatitis E virus in Tunisia through the monitoring of urban sewage and to characterize the strains identified using molecular assays. A total of 150 sewage samples (raw and treated) were collected from three wastewater treatment plants located in the regions of Monastir and Mahdia and analyzed by nested RT-PCR using a qualitative assay targeting the methyltransferase gene in ORF1. Of these, only three samples (2 %) were found to be positive for HEV, one belonging to genotype 1 and two to genotype 3. The results of the present study indicate a low level of virus excretion among the Tunisian population. Both genotypes 1 and 3 are circulating in this country, however, possibly causing sporadic infections. The presence of the zoonotic genotype 3, known to be transmitted to humans mainly by swine and demonstrated in Tunisia for the first time in this work, raises the question of possible reservoir species, since pork products are not consumed in this country, pigs are not bred, and wild boar is not endemic. Further studies will be needed to gather information on the occurrence and diversity of HEV strains circulating among humans and animals in Tunisia, and on possible animal reservoirs.

[Hepatitis E: molecular virology, epidemiology and pathogenesis]

Hepatitis E represents a significant proportion of enteric transmitted liver diseases and poses a major public health problem, mainly associated with epidemics due to contamination of water supplies, especially in developing countries. Hepatitis E virus (HEV) is responsible for self-limiting acute liver oral-faecal infections. In industrialised countries, acute hepatitis E is sporadic, detected in travellers from endemic areas but also in sporadic cases with no risk factors. HEV is a non-enveloped virus with a single-stranded RNA genome classified into 4 genotypes and a single serotype. Genotypes 1 and 2 only infect humans, and are predominant in the developing countries, while 3 and 4 are predominant in industrialised countries, and also infect other species of mammals, especially pigs, and multiple evidence classifies HEV as a zoonotic agent. Some HEV chronic infections have recently been reported in kidney and liver transplant patients. The mortality rate of HEV infection is greater than hepatitis A. In addition to faecal-oral transmission, parenteral transmission of HEV has also been reported. Several vaccines are currently in development. The severity of this infection in some groups of patients, especially pregnant women, and the occurrence of chronic hepatitis, even with progression to cirrhosis, have raised interest in the application of interferon and/or ribavirin therapy.

Pathogenetic elements of hepatitis E and animal models of HEV infection

The pathogenesis of HEV infection responsible for liver pathology and clinical disease is not well understood. The main target for the virus is the hepatocyte, where it replicates and is released to bile and gastrointestinal tract. Viremia is regularly seen during the virus replication. The exact mechanism of hepatocytic death is uncertain. In experimentally infected non-human primates, the peak of liver lesions, measured by alanine aminotransferase activity elevation, is concordant with the virus disappearance from stool at the time of dynamic humoral immune response; the role of cellular immunity has not been researched adequately, especially HEV-specific immune response in the liver. Non-human primates (chimpanzees, rhesus and cynomolgus macaques) are most widely used animal models for the study of HEV infection, its pathogenesis and vaccine trials. Several other animal models including pigs, rabbits and chickens have recently been established for the study of various aspects of HEV infection. Infectivity studies in susceptible primates were of significance in molecular studies of the virus itself. Preclinical vaccine trials with the use of various recombinant HEV capsid proteins and viral DNA established basic platform for formulation of HEV vaccine applied in HEV-endemic regions (China, Nepal).

Much meat, much malady: changing perceptions of the epidemiology of hepatitis E

Hepatitis E, which is caused by hepatitis E virus (HEV), may now be considered a zoonosis as well as an anthroponosis. Pigs, boars and deer have been identified as reservoirs, and their flesh and entrails--as meat and offal--as vehicles of HEV transmission. Shellfish also act as vehicles. Dietary, gastronomic and culinary preferences influence how extensively HEV conveyed by these vehicles can be inactivated before their ingestion by the host. Another route of infection is paved by HEV that is enterically shed by humans and by live animals into the environment. Although anthroponotic transmission of HEV is primarily environmental, zoonotic transmission may proceed along both foodborne and environmental routes.

RNA interference inhibits hepatitis E virus mRNA accumulation and protein synthesis in vitro

Hepatitis E virus (HEV) is a zoonotic pathogen to which several species, including human beings, pigs and rodents, are reported to be susceptible. To date, vaccines developed against HEV still need to be improved and a structural gene (ORF2), which encodes a capsid protein with high sequence conservation found across HEV genotypes, is a potential candidate. To exploit the possibility of using RNA interference (RNAi) as a strategy against HEV infection, four small interference RNA (siRNA) duplex targeting ORF2 gene were constructed. A challenge against HEV infection by RNAi was performed in A549 cells. Real-Time quantitative polymerase chain reaction (Real-Time qPCR) and Western blot assay demonstrated that four HEV specific siRNAs (si-ORF2-1, si-ORF2-2, si-ORF2-3 and si-ORF2-4) were capable of protecting cells against HEV infection with very high specificity and efficiency. The results suggest that RNAi is a potent anti-HEV infection prophylaxis strategy.

Full-genome nucleotide sequence and analysis of a Chinese swine hepatitis E virus isolate of genotype 4 identified in the Guangxi Zhuang autonomous region: evidence of zoonotic risk from swine to human in South China

BACKGROUND

Hepatitis E virus (HEV) is one of the leading causes of the enteric-transmitted acute hepatitis. Many studies have found high identities between human and animal HEV isolates using partial sequence comparison analysis.

AIMS

To determine and phylogenetically analyse the complete genome of the swGX40 isolate from the Guangxi Zhuang autonomous region.

METHODS

The overlapping fragments of HEV isolate swGX40 were amplified with reverse transcription-nested polymerase chain reaction (PCR) and the 5' and 3' ends of viral genome were amplified with rapid amplification of cDNA ends. The PCR products were cloned and sequenced. The sequence and phylogenetic analysis of swGX40 were performed.

RESULTS

The full genome of the swGX40 strain consisted of 7233 nucleotides, excluding the poly (A) tail of 36 residues. There are three open reading frames (ORFs), encoding 1705, 674 and 114 amino acids (aa) respectively. The full-genomic sequencing showed that the swGX40 strain shared similarity with all known HEV genotype 1, 2 and 3 isolates by 73.4-76.5% and with an identity of 83.1-91.2% among genotype 4 HEV isolates. The partial ORF2 sequencing (249 nt) showed that swGX40 shared a high nucleotide identity of 94 and 97% with the Chinese human strain LZ-105 and the Vietnamese human strain HE-JVN-1 respectively.

CONCLUSIONS

The swine isolate swGX40 was closely related to the human isolate LZ-105, both of which were collected from Liuzhou, the same district in the Guangxi Zhuang autonomous region. This molecular biological evidence strongly supported the zoonosis hypothesis of hepatitis E.

Experimental infection of Balb/c nude mice with Hepatitis E virus

BACKGROUND

Several animal species can reportedly act as reservoirs for Hepatitis E virus (HEV), a zoonotic pathogen. HEV and antibody to the virus have been detected in a variety of animals including rodents. Pig and rat models for HEV have been established for HEV, but a nude mouse has not yet been developed.

METHODS

Balb/c nude mice were inoculated with swine HEV, both orally and via intravenous injection to insure infection. Negative control and experimental contact-exposed groups of mice were also included in the study. The liver, spleen, kidney, jejunum, ileum, cecum and colon of each mouse from all three groups were collected for reverse transcription nested polymerase chain reaction (RT-nPCR) detection, indirect immunofluorescence observation and histopathologic examination. The sera from nude mice were tested for anti-HEV IgG by enzyme linked immunosorbent assay (ELISA). Activities of liver enzymes, including alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP), as well as total bilirubin (TBIL) were also measured in the sera of the nude mice.

RESULTS

HEV antigens and HEV RNA were detected in liver, spleen, kidney, jejunum, ileum and colon both by indirect immunofluorescence and by RT-nPCR in all of the inoculated and in one of the contact-exposed nude mice. Histopathological changes were observed in the liver and spleen of these mice. Infected mice showed increased levels of AST, ALP, and anti-HEV IgG in sera. The livers of contact-exposed mice showed obvious histopathological damage.

CONCLUSION

Nude mice could be readily infected by HEV isolated from pigs. The nude mouse may therefore be a useful animal model for studying the pathogenesis of HEV.

Widespread diffusion of genotype 3 hepatitis E virus among farming swine in Northern Italy

Hepatitis E virus (HEV) causes acute hepatitis in humans, and infects several animal species, mostly asymptomatically. Swine and human HEV strains are genetically related suggesting both a zoonotic and a possible foodborne transmission. The prevalence of swine HEV was investigated in 274 randomly selected pigs from six different swine farms of Northern Italy, testing viral RNA in stools by nested reverse-transcription-polymerase chain reaction. HEV genome was detected in 115 stools (42%). All farms resulted positive for HEV, with a prevalence ranging between 12.8% and 72.5%. HEV-positive pigs were detected in all age groups and production stages tested, although infection was more prevalent in weaners than in the older fatteners (42.2% vs. 27.0%). Genetic characterization of swine strains identified was performed by sequencing and database alignment. Phylogenetic analysis on the nucleotide sequences from 16 positive PCR products indicated that all strains belonged to genotype 3. In particular, one group of seven Italian strains clustered close (91.6-96.2% identity) to human and swine European HEV strains.

Comparison of real-time fluorescent RT-PCR and conventional RT-PCR for the detection of hepatitis E virus genotypes prevalent in China

To compare the specificity and sensitivity of a real-time fluorescent RT-PCR assay with conventional RT-PCR, sera from 110 healthy blood donors, 120 patients with a clinical diagnosis of chronic hepatitis B, and 416 patients with non-A-C acute hepatitis, as well as serial dilutions of HEV genotypes 1 and 4, were tested with both assays. All samples from healthy blood donors and patients with chronic hepatitis B were negative by both assays. Real-time RT-PCR could detect the same final dilution of genotype 1 as conventional RT-PCR but could detect a 10-fold lower concentration of genotype 4 than conventional RT-PCR. Of 416 samples from patients with a clinical diagnosis of non-A-C acute hepatitis, 127 (30.5%) and 83 (20.0%) were positive for HEV by real-time and conventional RT-PCR, respectively. The concordance of real-time and conventional RT-PCR was 80.8%. Furthermore, 96 and 57 of 171 samples were positive for anti-HEV IgM by real-time and conventional RT-PCR, respectively, and 31 and 26 of 245 samples negative for anti-HEV IgM, were positive by real-time and conventional RT-PCR, respectively. All amplicons positive by conventional RT-PCR were sequenced. Of 83 isolates, 7 and 76 belonged to genotypes 1 and 4, respectively. Thus, both assays have a high specificity, but the real-time RT-PCR assay is more sensitive than conventional RT-PCR. Furthermore, HEV genotype 4 is responsible for most sporadic cases of hepatitis E in the north of China.