Existing variations on the gene structure of hepatitis E virus strains from some regions of China

Hepatitis E Virus in Domestic Ruminants and Virus Excretion in Milk-A Potential Source of Zoonotic HEV Infection

The hepatitis E virus is a serious health concern worldwide, with 20 million cases each year. Growing numbers of autochthonous HEV infections in industrialized nations are brought on via the zoonotic transmission of HEV genotypes 3 and 4. Pigs and wild boars are the main animal reservoirs of HEV and play the primary role in HEV transmission. Consumption of raw or undercooked pork meat and close contact with infected animals are the most common causes of hepatitis E infection in industrialized countries. However, during the past few years, mounting data describing HEV distribution has led experts to believe that additional animals, particularly domestic ruminant species (cow, goat, sheep, deer, buffalo, and yak), may also play a role in the spreading of HEV. Up to now, there have not been enough studies focused on HEV infections associated with animal milk and the impact that they could have on the epidemiology of HEV. This critical analysis discusses the role of domestic ruminants in zoonotic HEV transmissions. More specifically, we focus on concerns related to milk safety, the role of mixed farming in cross-species HEV infections, and what potential consequences these may have on public health.

High Predictive Power of Meat Juice Serology on the Presence of Hepatitis E Virus in Slaughter Pigs

Hepatitis E virus (HEV) as a zoonotic agent can be responsible for an acute hepatitis in humans, which is usually self-limiting. Progression toward a chronic stage is possible, especially in immunocompromised patients. In the past decade, the number of hepatitis E cases in humans in Germany has increased enormously to 3491 cases in 2018. Domestic pigs have been identified as a main animal reservoir and the consumption of raw and undercooked pork products, that is, livers or liver products, meat or meat products, is known as a potential risk of foodborne HEV infection. The aim of this study was to determine whether serological tests are appropriate to predict the occurrence of HEV in the liver and muscle of domestic pigs in Germany. In 2018, samples of meat juice, liver, and ham muscle were collected from 250 fattening pigs at an abattoir in North West Germany. Samples were analyzed for the presence of HEV antibodies using enzyme-linked immunosorbent assay respectively for the presence of HEV RNA using real-time reverse transcription-polymerase chain reaction. In total, 62% (155/250) of the meat juice samples were positive for HEV antibodies at a single animal basis. At herd level, 72% (18/25) of the herds were seropositive. The HEV prevalence in the liver was 17.2% (43/250). Each positive liver sample originated from seropositive herds respectively from HEV seropositive pigs. This study demonstrates for the first time the significant correlation between a positive HEV serology and the occurrence of HEV RNA in the liver of slaughter pigs (χ² = 31.83; p < 0.001), highlighting the significant predictive power of positive serological results on the occurrence of HEV RNA in the liver.

Prevalence of hepatitis E virus infection among people and swine in mainland China: A systematic review and meta-analysis

Hepatitis E virus (HEV) infection remains an important public health problem, and it is endemic primarily in developing countries. This study aimed to evaluate the seroprevalence of HEV among the general population, occupational population and swine in mainland China and its risk factors based on a systematic review and meta-analysis. Systematic search from EMBASE, PubMed, Web of Science, Cochrane Library and several Chinese databases, such as Wanfang (WF) Data, China National Knowledge Infrastructure (CNKI), Chinese Science and Technology Periodical Database (VIP) and SINOMED, was searched from inception up to 25 April 2018. The overall seroprevalence of HEV and its corresponding 95% confidence interval (CI) as well as the correlation coefficients between different groups were estimated using stata 12.0 and r-3.4.1 software. Potential sources of heterogeneity were explored using subgroup and sensitivity analyses. Twenty-eight studies with 57,274 participants (including human and swine) were included. The seroprevalence of anti-HEV immunoglobulin G (IgG) among the general population, occupational population and swine was 27.3% (95% CI: 22.4-32.2), 47.4% (95% CI: 40.1-54.8) and 66.4% (95% CI: 61.7-71.1), respectively. The overall prevalence of IgM among the general population was 1.8% (95% CI: 0.7-2.9). The odds ratio for the occupational population, as compared to the general population, was 2.63. The highest anti-HEV IgG prevalence (59%) was observed in East China, whereas the lowest (34.8%) was noted in Northeast and North China. In the occupational population, the highest prevalence (77.0%) was observed among swine vendors. Seven studies included 30,392 participants (humans and swine); the correlation coefficient for the prevalence of anti-HEV IgG between the professional population and adult pigs was 0.88. Sensitivity analyses showed that the stability of results was not considered significant. This research found that HEV is common in China, and contact with pork or other pig products may be an important mode of HEV transmission.

Genetic heterogeneity and subtyping of human Hepatitis E virus isolates from Uruguay

Hepatitis E virus (HEV) infection is an important public health concern in many developing countries causing waterborne outbreaks, as well as sporadic autochthonous hepatitis. It is transmitted primarily by the fecal-oral route. However, zoonotic transmission from animal reservoirs to human has also been suggested. Genotype 3 is the most frequent genotype found in South America and the HEV epidemiology in this region seems to be very complex. However, data about the molecular characterization of HEV isolates of the region is still lacking and further investigation is needed. Our study characterized human HEV strains detected in a 1-year period in Uruguay, by extensive sequence analysis of three regions of the HEV genome. Uruguayan strains were closely related to a set of European strains and in turn, were dissimilar to Brazilian, Argentinean and Bolivian isolates. Additionally, the co-circulation of viral subtypes 3i and 3h was observed. Circulation of subtype 3i had been reported in Argentina and Bolivia whereas sequences of subtype 3h are rare and had never been reported in Latin America. In order to contribute to shedding light over the molecular epidemiology of this emergent infection in the region, we thoroughly analyzed the genetic variability of HEV strains detected in Uruguay, providing the largest dataset of sequences of HEV ever reported in a country in South America.

Phylogenetic analysis of hepatitis e virus in northwest India

Genotyping and subtyping are important to understand epidemiology of the hepatitis E virus so as to improve control measures to prevent transmission of virus in the community. Hence, the aim of the current study was to identify the prevalent HEV genotypes in Rajasthan in acute sporadic hepatitis E cases with varying degree of liver failure. We studied hepatitis E virus (HEV) isolates from hospitalized patients in Rajasthan, western India. In a total of seventeen HEV sequences, six acute viral hepatitis, seven acute liver failure, and 4 acute- on-chronic cases were analyzed. Subtypes 1a and 1c of HEV are prevalent in Northwest India.

Identification of genotype 4 Hepatitis E virus binding proteins on swine liver cells

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animal were reported as reservoirs. Swine stands out as the major reservoir for HEV infection in humans, as suggested by the close genetic relationship of swine and human virus and cross-species infection of HEV. Up to now, the mechanism of cross-species infection of HEV from swine to humans is still unclear. This study sought to identify receptor element for genotype 4 HEV on swine liver cells using the viral overlay protein binding assay (VOPBA) technique and Mass Spectrometry fingerprinting. A single virus binding band with natural molecular weight about 55 kDa was observed, and mass spectrometry revealed that this virus binding band contained 31 different proteins. Infection inhibition assay suggested that this 55 kDa protein could prevent HEV from infecting its susceptible A549 cell line, which was further confirmed by the HEV genome detecting in the inoculated cells. Further research should be performed to elucidate the accurate receptor of HEV on the swine liver cells.

Dynamics of HEV viremia, fecal shedding and its relationship with transaminases and antibody response in patients with sporadic acute hepatitis E

Background

There is paucity of data regarding duration of fecal excretion and viremia on sequential samples from individual patients and its correlation with serum transaminases and antibody responses in patients with acute hepatitis E. This prospective study was undertaken at a tertiary care center in Northern India over 15 months. Only those patients of sporadic acute hepatitis E who were in their first week of illness and followed up weekly for liver function tests, IgM anti HEV antibody and HEV RNA in sera and stool were included. HEV RNA was done by RT - nPCR using two pairs of primers from RdRp region of ORF 1 of the HEV genome.

Results

Over a period of 15 months 60 patients met the inclusion criterion and were enrolled for the final analysis. The mean age of the patients was 29.2 ± 8.92 years, there were 39 males. The positivity of IgM anti HEV was 80% at diagnosis and 18.3% at 7th week, HEV RNA 85% at diagnosis and 6.6% at 7th week and fecal RNA 70% at the time of diagnosis and 20% at 4th week. The maximum duration of viremia detected was 42 days and fecal viral shedding was 28 days after the onset of illness.

Conclusion

Present study reported HEV RNA positivity in sera after normalization of transaminases. Fecal shedding was not seen beyond normalization of transaminases. However, viremia lasted beyond normalization of transaminases suggesting that liver injury is independent of viral replication.

Hepatitis E virus infection in central China reveals no evidence of cross-species transmission between human and swine in this area

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animal were reported as reservoirs. Swine stands out as the major reservoir for HEV infection in humans, as suggested by the close genetic relationship of swine and human virus. Since 2000, Genotype 4 HEV has become the dominant cause of hepatitis E disease in China. Recent reports showed that genotype 4 HEV is freely transmitted between humans and swine in eastern and southern China. However, the infection status of HEV in human and swine populations in central China is still unclear. This study was conducted in a rural area of central China, where there are many commercial swine farms. A total of 1476 serum and 554 fecal specimens were collected from the general human and swine populations in this area, respectively. The seroepidemiological study was conducted by enzyme-linked immunosorbent assay. Conserved genomic sequences of open reading frame 2 were detected using reverse transcription-PCR. The results indicated that the overall viral burden of the general human subjects was 0.95% (14/1476), while 7.0% (39/554) of the swine excreted HEV in stool. The positive rate of anti-HEV IgG and IgM in the serum samples was 7.9% (117/1476) and 1.6% (24/1476), respectively. Phylogenetic analysis based on the 150 nt partial sequence of the capsid protein gene showed that the 53 swine and human HEV isolates in the current study all belonged to genotype 4, clustering into three major groups. However, the HEV isolates prevalent in the human and swine populations were classified into known distinct subgenotypes, which suggested that no cross-species transmission between swine and humans had taken place in this area. This result was confirmed by cloning and phylogenetic analysis of the complete capsid protein gene sequence of three representative HEV strains in the three major groups. The cross reactivity between anti-HEV IgG from human sera and the two representative strains from swine in central China was confirmed by Dot-blot assay. In conclusion, although all the HEV strains prevalent in central China belonged to genotype 4, there is no evidence of cross-species transmission between human and swine in this area.

Prevalence of antibody to hepatitis E virus among pet dogs in the Jiang-Zhe area of China

In order to investigate the prevalence of HEV infection and immunity in pet dogs in the Jiang-Zhe area of China, we examined 192 dog serum samples collected from 11 animal hospitals in this area for anti-HEV IgG and HEV RNA, using ELISA and RT-PCR assays, respectively. Two dogs were injected intravenously with swine HEV to obtain anti-HEV antibody positive serum for ELISA assay. After the ELISA assay, 26 samples showing OD values higher than 0.20 were selected and examined by Dot-blot assay, and 88.5% (23/26) were confirmed to be positive for anti-HEV IgG. Although our results indicated swine HEV could experimentally induce anti-HEV IgG in the serum, we failed to detect HEV RNA in the serum samples from either the 2 intravenously injected dogs or 192 serum samples collected from animal hospitals. This implied that dog may not be a reservoir of HEV in this area.

Molecular epidemiology of hepatitis E virus in Hong Kong

Hepatitis E virus (HEV) is one of the major causes of acute and self-limiting hepatitis in human. In Hong Kong, the number of notifications increased from 26 to 62 from year 2001 to 2007. This study describes the molecular epidemiology of HEV in Hong Kong in order to determine the movement and distribution of HEV. HEV in 171 serum samples from HEV IgM positive cases from year 2001 to 2007 were amplified using RT-PCR and subjected to nucleotide sequencing. Phylogenetic analysis showed 162 of 171 HEV detected cases (94.7%) belonged to genotype IV and 8 (4.7%) to genotype I. Interestingly, a cluster of 10 cases in year 2007 that had the same sequence of HEV was identified. Epidemiological data however did not detect any relationship between these cases. Since zoonotic transmission is a well known route of HEV infection, close monitoring of the circulating HEV strains in human and food source animals may help to provide additional information on the transmission of HEV and possible source of infection in Hong Kong.

Detection of hepatitis E virus RNA and genotype in Bangladesh

BACKGROUND/AIMS

Hepatitis E virus (HEV) in Bangladesh has not been adequately documented. We report HEV RNA and genotype detection in Bangladesh.

METHODS

In total, 82 samples were used; 36 sporadic acute hepatitis (AH), 12 fulminant hepatitis (FH), 14 chronic liver disease (CLD) and 20 from an apparently healthy population (HP) positive for both immunoglobulin (Ig) M and IgG specific anti-HEV antibodies (anti-HEV). The male/female ratio was 61/21, ages 12-67 (mean 30.4) years. RNA was extracted, transcribed to cDNA and amplified in nt 6345-6490 (ORF2) of HEV. Nucleic and amino acid sequences were determined. Homology comparison between Bangladesh clones and other representative HEV clones and phylogenetic tree analyses were done. Relations between HEV RNA-positivity and clinical factors were analyzed.

RESULTS

HEV RNA was positive in 9/36 (25.0%) of AH cases, 4/12 (33.3%) FH, 3/14 (21.4%) CLD and 0/20 (0%) HP samples; total 16/82 (19.5%). Four factors correlated significantly with HEV RNA-positivity (Mann-Whitney U test); alanine aminotransferase (ALT) (P = 0.0229), aspartate aminotransferase (AST) (P = 0.0448), and titers of IgG (P = 0.0208) and IgM (P = 0.0095) specific anti-HEV. The 16 HEV clones were divided mainly into two groups, A and B, including six different cDNA sub-groups.

CONCLUSION

HEV RNA was found in sporadic AH and FH and sub-clinical CLD cases, but not in HP. HEV RNA-positivity was significantly related to values of ALT and AST and titers of IgG and IgM specific anti-HEV, with IgM specific anti-HEV showing the most significant relationship. All clones were genotype I, which is prevalent in South Asia.

Isolation and characterization of a genotype 4 Hepatitis E virus strain from an infant in China

In the present study, a genotype 4 HEV strain was identified in the fecal specimen from a seven months old infant with no symptom of hepatitis in Shanghai Children's hospital. The full capsid protein gene (ORF2) sequence of this strain was determined by RT-PCR method. Sequence analysis based on the full ORF2 sequence indicated that this HEV strain shared the highest sequence identity (97.6%) with another human HEV strain isolated from a Japanese patient who was infected by genotype 4 HEV during traveling in Shanghai. Phylogenetic analysis showed that this genotype 4 HEV was phylogenetically far from the genotype 4 HEV strain that was commonly prevalent in Shanghai swine group, suggesting that this strain may not come from swine group and not involved in zoonotic transmission in this area.

Hepatitis E virus infection among domestic animals in eastern China

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animal were reported as reservoirs. Antibodies to HEV and HEV RNA have been detected in some Chinese population and swine groups but few other domestic animals. In this study, to investigate the HEV prevalence, we tested sera from 788 pigs, 100 cows, 50 goats, 49 horses, 101 pet dogs, 105 chickens, 47 duck and 45 pigeons in eastern China for anti-HEV immunoglobulin G (IgG). We also tested 50% of the swine sera, all of sera from the other domestic animals and 13 Shanghai human sera which were positive for anti-HEV immunoglobulin M (IgM) for HEV RNA using reverse transcriptase-polymerase chain reaction. Our results indicated that 82.5% (222/269) of the sows, 53.9% (104/193) of the 4- to 6-month-old swine, 63.4% (168/265) of the 1- to 3-month-old swine, 55.7% (34/61) of the slaughterhouse swine, 24% (12/50) of the goats, 16.3% (8/49) of the horses, 17.8% (21/101) of the pet dogs, 6% (6/100) of the cows, 12.8% (6/47) of the ducks, 4.4% (2/45) of the pigeons and 1.9% (2/105) of the chickens exhibited positive for anti-HEV IgG. Inhibition assay confirmed the infection with HEV or HEV-like viruses in these domestic animals except pigeons and chickens. From the sera, we isolated 18 swine HEV strains, one horse HEV strain and two human HEV strains. Sequence analysis showed that the horse HEV isolate and one swine isolate belonged to genotype 3. The other isolates belonged to genotype 4. The two human isolates were phylogenetically closely related to eight of the swine isolates. In short, the presence of anti-HEV antibody had been confirmed in several species of domestic animals in eastern China and HEV RNA has been identified in swine, human and horse. This suggested that the authorities should pay more attention to the prevalence of HEV in eastern China.

Comparison of a new synthetic, peptide-derived, polyclonal antibody-based, immunohistochemical test with in situ hybridisation for the detection of swine hepatitis E virus in formalin-fixed, paraffin-embedded tissues

A synthetic, peptide-derived, polyclonal antibody-based, immunohistochemical test was developed to detect swine hepatitis E virus (HEV) and was compared with in situ hybridisation for the detection of HEV in formalin-fixed, paraffin-embedded tissues from experimentally infected pigs. Solid-phase peptide synthesis was used to generate peptides from swine HEV open reading frame 2, and the purified peptides were injected into rabbits to produce polyclonal antibodies. The specificity and sensitivity of the test were both 100%. Liver was most consistently positive for swine HEV antigen and RNA by immunohistochemistry and in situ hybridisation, respectively, but both were detected much less frequently in extrahepatic tissues such as lymph node, tonsil, spleen, and intestine. Swine HEV antigen and RNA showed a similar distribution in virus-infected hepatocytes in serial sections. The novel test developed in this study is suitable for consistently detecting swine HEV antigen in formalin-fixed, paraffin-embedded tissues.

Prevalence of four different subgenotypes of genotype 4 hepatitis E virus among swine in the Shanghai area of China

Background

Hepatitis E virus (HEV) is a zoonotic pathogen of which swine was reported as major reservoirs. HEV has been divided into 4 different genotypes according to phylogenetic analysis. Recent reports showed that genotype 4 HEV is freely transmitted between humans and swine in eastern China, including Shanghai area. This paper investigated the recent infection status of HEV among swine population of Shanghai area in China.

Methods

480 swine faecal specimens were collected from 23 farms which distribute all over Shanghai from September to November, 2007 and tested for the presence of HEV RNA by the polymerase chain reaction (PCR).

Results

Our results showed that 26.1% (6/23) of the swine farms were positive for HEV RNA and the positive rate of the six farms were ranged from 9.1% to 33.3%. The HEV RNA positive rate for total samples were 5% (24/480). The resulted positive band specific for HEV was sequenced and sequence analysis indicated that all of these isolates belonged to genotype 4 HEV. Phylogenetic analysis showed that the 24 isolates clustered into 4 distinct subgroups, sharing 83.3–89.7% inter-subgroup and 97–99% intra-subgroup identities. More over, isolates in three of the four subgroups closely clustered with previous identified strains, sharing up high to 97% identity with them.

Conclusion

These results suggested that there were 4 different subgenotypes of HEV prevalent in Shanghai, and some of them may not be indigenous to Shanghai but introduced from other geographic regions.

Cross-species infection of hepatitis E virus in a zoo-like location, including birds

Hepatitis E virus (HEV) is a zoonotic pathogen of which several species of animals are considered to be reservoirs. Thirty-eight faecal samples, obtained from 22 species of animals including birds in a wildlife first-aid centre in Eastern China, were tested for HEV RNA. Our survey revealed that in total 28.9% (95% confidence interval 14.5-43.4) of the faecal samples from various mammals and birds were HEV RNA positive. Sequence and phylogenetic analyses of the 11 isolates demonstrated that all sequences clustered in genotype 4 with 96-100% identity to each other. In addition, serum samples from seven animal handlers have shown that five (71.4%) were seropositive. The findings imply that cross-species infection of HEV had probably occurred in this zoo-like location, and moreover, birds can be infected naturally with mammalian HEV.

Hepatitis E virus

Hepatitis E virus (HEV) is the aetiological agent of non-HAV enterically transmitted hepatitis. It is the major cause of sporadic as well as epidemic hepatitis, which is no longer confined to Asia and developing countries but has also become a concern of the developed nations. In the Indian subcontinent, it accounts for 30-60% of sporadic hepatitis. It is generally accepted that hepatitis E is mostly self-limited and never progresses to chronicity. It has a higher mortality in pregnant women where the disease condition is accentuated with the development of fulminant liver disease. Currently, no antiviral drug or vaccine is licensed for HEV, although a vaccine candidate is in clinical trials. HEV genome is 7.2kb in size with three open reading frames (ORFs) and 5' and 3' cis acting elements, which have important roles to play in HEV replication and transcription. ORF1 codes for methyl transferase, protease, helicase and replicase; ORF2 codes for the capsid protein and ORF3 for a protein of undefined function. HEV has recently been classified in the genus Hepevirus of the family Hepeviridae. There are four major recognised genotypes with a single known serotype. The absence of a reliable in vitro propagation system is an obstacle to deciphering HEV biology. The genome of HEV has been cloned, sequenced and the infectious nature of these replicons has been established. However, questions related to replication, transcription, virus-host interactions and pathogenesis remain to be answered. This comprehensive review summarises the progress made so far in HEV research, and addresses some of the unanswered questions.

Seroprevalence of hepatitis E virus infection among institutionalized psychiatric patients in Taiwan

BACKGROUND

Hepatitis E virus infection (HEV) remains unclear in institutionalized psychiatric patients.

OBJECTIVES

To investigate the prevalence and risk factors of HEV infection in a psychiatric institution in Taiwan.

STUDY DESIGN

A total of 754 patients with psychiatric disorders were enrolled in the study. Clinical features, review of patient charts, and interviews with families were recorded for analysis. Antibody to HEV was tested using a commercial enzyme-linked immunosorbent assays.

RESULTS

The prevalence of HEV infection in institutionalized patients was as high as 14.5%. Males had higher prevalence than females. It was also found prevalence increased significantly by age group. When compared with patients 30 years old or less, those in the 31-40 year old age group had an odds ratio of 4.89 [95% confidence interval (CI), 1.15-20.82], 41-50 years old of 6.30 (95% CI, 1.48-26.83), and 50 years or older of 6.20 (95% CI, 1.44-26.74). In multivariate logistic regression analysis, age and male gender were the independent risk factors.

CONCLUSIONS

Institutionalized psychiatric patients had higher prevalence of HEV infection. In addition, there was an age-related increase in exposure to HEV with males that had a higher HEV seropositivity.

Molecular detection and sequence analysis of a new hepatitis E virus isolate from Pakistan

Sporadic and epidemic acute viral hepatitis E in many developing countries is caused by hepatitis E virus (HEV). The HEV genome has been classified into three major genotypes. However, extensive diversity has been noted among HEV isolates from patients with acute hepatitis in China and Taiwan. Some reports indicated that multiple genotypes of HEV could cocirculate in the same area; even distinct genotypes of HEV could exist in the same patient. Pakistan is a highly endemic area for hepatitis E. So far only two Pakistan HEV isolates Sar-55 (87-Pakistan-A) and Abb-2B (88-Pakistan-2B) have been characterized, and the nucleotide sequences of these two HEV isolates show only 90% homology. In this study, a third HEV isolate from Pakistan (87-Pakistan-B) is reported. The sequences of a 438-bp fragment from ORF-2 and a 259-bp fragment from the ORF-1-3 region of this new HEV isolate were obtained and sequenced. The sequence analysis showed that this new HEV isolate was very closely related to the Sar-55 but different from the Abb-2B HEV isolate. These results indicated that the Sar-55 (87-Pakistan-A) genotype is the main endemic HEV strain in the Sargodha area. These data will be useful for HEV epidemiological studies, diagnosis and vaccine development.

Phylogenetic analysis of hepatitis E virus isolates in southern China (1994-1998)

BACKGROUND

We have previously reported the identification of divergent hepatitis E virus (HEV) isolated (G9, G20 and 93G) in Guangzhou, a city in southern China. They are now recognised as a new HEV subgenotype in the world. However, the relatedness and significance of these novel isolates in sporadic HEV infection in southern China is still unclear.

OBJECTIVES

To perform phylogenetic analysis of nucleotide sequences from 41 HEV isolates in southern China from 1994 to 1998.

STUDY DESIGN

The partial nucleotide sequence of the HEV isolates were determined and compared with reported sequences in the GenBank. Their relatedness was analysed using computer software.

RESULTS

The majority of the HEV isolates, 39 out of 41, were found to belong to the Burmese-like isolates (genotype 1). The other two belonged to the Guangzhou-like isolates. The latter were only found in the samples collected in 1994. They, together with the G9 isolate, form a unique tree located between genotype 1 and genotype 4 (divergent HEV strains from northern China and Taiwan) on the phylogenetic tree.

CONCLUSION

Our results suggest that the Burmese-like isolates are the main causative agents of sporadic HEV infection in southern China. The Guangzhou-like isolates, which appeared transiently in 1994, did not seem to adapt to the environment and have caused no sporadic infection since.

Hepatitis E virus genotyping based on full-length genome and partial genomic regions

Some genomic regions for hepatitis E virus (HEV) genotyping have been reported to correlate well with the results from the phylogenetic analyses on the basis of the complete genome. However, few studies have systemically investigated the genomic regions for HEV genotyping using a combined phylogenetic and statistical approach. A consensus region for HEV genotyping has not been determined. In this study the nucleotide identities and genetic distances of 24 partial genomic regions and the complete genome sequences of 37 HEV strains were compared statistically. It was demonstrated with both one-way ANOVA and two-way ANOVA that only one genomic region in RNA-dependent RNA polymerase domain (4254-4560nt) for which there were no significant differences when compared with the full-length genome (P>0.05). The same four genotypes were identified by phylogenetic analysis based on this statistically predicted region identified as for the complete genome. RT-PCR amplification of HEV strains from all four genotypes confirmed conservation of the flanking primer sites of this region. Serum samples from 20 patients with a clinical diagnosis of hepatitis E were further analyzed by PCR using the same primers, 13 were positive and could be classified into genotype 4. These data strongly suggested that this newly identified region could be used for future HEV genotyping.

The 41-amino-acid C-terminal region of the hepatitis E virus ORF3 protein interacts with bikunin, a kunitz-type serine protease inhibitor

Hepatitis E virus (HEV), a human plus-stranded RNA virus, contains three open reading frames (ORF). Of these, ORF1 encodes the viral nonstructural polyprotein, ORF2 encodes the major capsid protein, and ORF3 codes for a phosphoprotein of undefined function. Recently, using the yeast two-hybrid system to screen a human cDNA liver library, we have isolated and characterized AMBP (alpha1-microglobulin/bikunin precursor), which specifically interacts with the ORF3 protein of HEV. The ORF3 protein expedites the processing and secretion of alpha1-microglobulin. When checked individually for interaction, the second processed protein from AMBP, bikunin, strongly interacted with the full-length ORF3 protein. This protein-protein interaction has been validated by immunoprecipitation in both COS-1 and Huh7 cells and by His6 pull-down assays. In dual-labeling immunofluorescent staining, followed by fluorescence microscopy of transfected human liver cells, ORF3 colocalized with endogenously expressed bikunin. Finally, a 41-amino-acid C-terminal region of ORF3 has been found to be responsible for interacting with bikunin. The importance of this virus-host protein-protein interaction, with reference to the viral life cycle, has been discussed.

Swine hepatitis E virus: cross-species infection and risk in xenotransplantation

Swine hepatitis E Virus (swine HEV), a ubiquitous agent recently discovered in pigs, is antigenically and genetically closely related to the human HEV. Swine HEV infection in pigs generally occurs at about 2-3 months of age, and about 80%-100% of the pigs in commercial farms in the USA were infected. Swine HEV infections have now been recognized in pigs in many other countries of the world. Interspecies transmission has been documented, as swine HEV infects non-human primates and some strains of human HEV infect pigs. Recent seroepidemiological studies showed that swine veterinarians and other pig handlers are at higher risk of HEV infection compared to normal blood donors. In addition, novel strains of human HEV recovered from hepatitis patients in the USA, Japan and Taiwan are genetically more closely related to strains of swine HEV from respective countries than to other strains of human HEV. The ubiquitous nature of the virus in pigs and the demonstrated ability of cross-species infection raise a potential concern for swine HEV infection in xenotransplantation with pig organs. This chapter discusses the recent advances in HEV research with emphases on potential zoonosis and xenozoonosis.

Influence of RNA secondary structure on HEV gene amplification using reverse-transcription and nested polymerase chain reaction

BACKGROUND

Single-stranded RNA has the potential to form secondary structures that may result in intrastrand misalignment of repeats and may be responsible for DNA mutation. Two amplicons obtained from amplification of hepatitis E virus (HEV) gene by reverse transcription and nested polymerase chain reaction (RT-nPCR) were of unexpected size and had the same misalignment. They did not contain the target region between the internal priming sites but contained two fragments flanking the target region joined by a 12-base sequence instead.

OBJECTIVES

To determine whether the unexpected amplicons obtained were due to secondary structures present in the HEV RNA.

STUDY DESIGN

HEV RNA sequences were obtained from the GenBank database and the software DNASIS was used to predict the presence of secondary structures within the amplification target regions. The free energy barriers of the secondary structures, which indicate their stability, were also calculated. Conventional RT-nPCR protocol was subsequently modified to eliminate RNA secondary structures.

RESULTS

An extensive stem-loop structure was predicted to exist between the two internal priming sites of the HEV RNA by the DNASIS software. Its free energy barrier was found to be significant and might have resulted in the deletion of the target region located between the internal priming sites. Increased temperature and addition of dimethyl sulphoxide (DMSO) in the reverse transcription step gave the expected amplicon after the nested polymerase chain reaction.

CONCLUSION

Spontaneous secondary structure formation can influence the outcome of RNA gene amplification and should be considered an important factor when designing primers and adopting protocols for RNA gene amplification.

Prevalence, isolation, and partial sequence analysis of hepatitis E virus from domestic animals in China

Evidence that hepatitis E is zoonotic is accumulating. Serum samples were collected from pigs, cattle, and goats from various regions of China to determine whether they had been infected with hepatitis E virus (HEV). An in-house enzyme immunoassay (EIA) and reverse transcriptase-polymerase chain reaction (RT-PCR) with primers from open reading frame (ORF) 2 were used to detect anti-HEV antibodies and HEV RNA. The mean positivity rates of anti-HEV antibody for pigs and cattle were 78.8% and 6.3% but none of the goat sera were positive. Pigs may be more susceptible to infection with HEV than cattle or goats. Five of 263 pig sera were positive for HEV RNA and four of these five were also positive for anti-HEV. The PCR products (nt 6007-6354) were cloned and sequenced and compared to other HEV sequences in the nucleotide databases. The five sequences shared 83-93% identity to each other at the nucleotide level and 74-79%, 73-74%, 73-78%, and 83-99% identity to HEV genotypes 1, 2, 3, and 4, respectively. They were closely related to human isolates of HEV genotype 4. Phylogenetic analyses also place these swine sequences in HEV genotype 4, resembling most closely viruses isolated from Chinese patients with acute hepatitis. These data support the hypothesis that sporadic hepatitis E in China is zoonotic.

Spread of hepatitis E virus among different-aged pigs: two-year survey in Taiwan

Swine are reservoirs of hepatitis E virus (HEV). In this study, a 2-year survey of HEV in feces and sera of swine was conducted to determine if: 1) HEV has circulated among pigs for some time in Taiwan; 2) the spread of HEV among different-aged pigs; and 3) there exists HEV strains possibly imported through trading. From 1998-2000, 521 serum samples and 54 fecal specimens from pigs were examined by reverse transcription polymerase chain reaction. None of the 11 pigs in suckling stage (< 2 months) were serum HEV RNA positive. The highest viremia rate (4.5%) was in pigs of 2 months age, followed by 1.2% and 1.8% in pigs of growing (3-4 months) and finishing stages (5-6 months), and none in pigs older than 6 months. Viremia showed little variation in different years and areas. None of the 20 fecal samples from pigs in suckling stage were HEV RNA positive, whereas 9% of the 34 samples from pigs in growing or finishing stages were positive. Most swine HEV isolates in Taiwan clustered within the genotype 4, whereas the three HEV isolates cloned from pigs imported recently from the U.S. belonged to the genotype 3 HEV in the U.S. The results suggest that HEV may infect pigs at an early growing stage and spread unnoticed among pigs and possibly across countries through trading.

Detection of sporadic cases of hepatitis E virus (HEV) infection in China using immunoassays based on recombinant open reading frame 2 and 3 polypeptides from HEV genotype 4

We reported previously on the complete sequence of hepatitis E virus (HEV) genotype 4, isolated from patients with sporadic cases of acute HEV infection in China. At least eight HEV genotypes have now been described worldwide, and further isolates await classification. Current immunoassays for the detection of anti-HEV antibodies are based on polypeptides from genotypes 1 and 2 only and may be inadequate for the reliable detection of other genotypes. Because genotypes 1 and 4 predominate in China, we wished to investigate the antigenic reactivities of HEV genotype 4 proteins. Four overlapping regions of open reading frame 2 (ORF2) (FB5, amino acids [aa] 1 to 130; E4, aa 67 to 308; F2-2, aa 288 to 461; E5, aa 414 to 672) and the entire ORF3 product were expressed in Escherichia coli as fusion proteins. Enzyme immunoassays based on each of the five purified polypeptides were evaluated with sera from patients with sporadic cases of acute HEV infection. Individual immunoassays derived from HEV genotype 4 detected more cases of acute hepatitis E than a commercial assay. Some serum samples, which were positive for anti-HEV immunoglobulin G only by assays based on HEV genotype 4, were positive for HEV RNA by reverse transcription-PCR. Polypeptide FB5, from the N terminus of ORF2, had the greatest immunoreactivity with sera from patients with acute hepatitis E. These data indicate that the N terminus of ORF2 may provide epitopes which are highly reactive with acute-phase sera and that assays based on genotypes 1 and 2 alone may be inadequate for the detection of HEV infection in China, where sporadic cases of HEV infection are caused predominantly by HEV genotypes 4 and 1.

Genetic heterogeneity of hepatitis E virus

Hepatitis E virus (HEV) infection has been considered a disease associated with developing regions and attributed to oral-fecal transmission due to inadequate sanitation. Several recent findings, however, have led to a new understanding of this virus. A number of novel isolates have been identified in patients with acute hepatitis from regions not considered endemic for HEV, and these individuals reported no recent travel to HEV endemic areas. In addition, a number of HEV-like sequences have also been isolated from swine worldwide, suggesting the potential of an animal reservoir. Although full-length sequence is available for some strains, the majority of HEV isolates have only been sequenced partially. Sequence comparisons and phylogenetic analyses were performed to determine the genotypic distribution of HEV isolates, based on the partial sequence data available. It has been suggested that HEV isolates segregate into four major genotypes based on full-length comparisons. These analyses, however, indicate that HEV may be distributed into at least nine different groups.

Acute hepatitis caused by a novel strain of hepatitis E virus most closely related to United States strains

A unique hepatitis E virus (HEV) strain was identified as the aetiological agent of acute hepatitis in a United States (US) patient who had recently returned from vacation in Thailand, a country in which HEV is endemic. Sequence comparison showed that this HEV strain was most similar, but not identical, to the swine and human HEV strains recovered in the US. Phylogenetic analysis revealed that this new HEV isolate was closer to genotype 3 strains than to the genotype 1 strains common in Asia. The fact that this HEV was closely related to strains recovered in countries where HEV is not endemic and was highly divergent from Asian HEV strains raises the questions of where the patient's infection was acquired and of whether strains are geographically as localized as once thought.

Comparative pathogenesis of infection of pigs with hepatitis E viruses recovered from a pig and a human

Specific-pathogen-free pigs were inoculated with one of two hepatitis E viruses (HEV) (one recovered from a pig and the other from a human) to study the relative pathogenesis of the two viruses in swine. Fifty-four pigs were randomly assigned to three groups. Seventeen pigs in group 1 served as uninoculated controls, 18 pigs in group 2 were intravenously inoculated with the swine HEV recovered from a pig in the United States, and 19 pigs in group 3 were intravenously inoculated with the US-2 strain of human HEV recovered from a hepatitis patient in the United States. Two to four pigs from each group were necropsied at 3, 7, 14, 20, 27, or 55 days postinoculation (DPI). Evidence of clinical disease or elevation of liver enzymes or bilirubin was not found in pigs from any of the three groups. Enlarged hepatic and mesenteric lymph nodes were observed in both HEV-inoculated groups. Multifocal lymphoplasmacytic hepatitis was observed in 9 of 17, 15 of 18, and 16 of 19 pigs in groups 1 to 3, respectively. Focal hepatocellular necrosis was observed in 5 of 17, 10 of 18, and 13 of 19 pigs in groups 1 to 3, respectively. Hepatitis lesions were very mild in group 1 pigs, mild to moderate in group 2 pigs, and moderate to severe in group 3 pigs. Hepatic inflammation and hepatocellular necrosis peaked in severity at 20 DPI and were still moderately severe at 55 DPI in the group inoculated with human HEV. Hepatitis lesions were absent or nearly resolved by 55 DPI in the swine-HEV-inoculated pigs. All HEV-inoculated pigs seroconverted to anti-HEV immunoglobulin G. HEV RNA was detected by reverse transcriptase PCR in feces, liver tissue, and bile of pigs in both HEV-inoculated groups from 3 to 27 DPI. Based on evaluation of microscopic lesions, the US-2 strain of human HEV induced more severe and persistent hepatic lesions in pigs than did swine HEV. Pig livers or cells from the livers of HEV-infected pigs may represent a risk for transmission of HEV from pigs to human xenograft recipients. Since HEV was shed in the feces of infected pigs, exposure to feces from infected pigs represents a risk for transmission of HEV, and pigs should be considered a reservoir for HEV.

Diagnostic value of immunoglobulin G (IgG) and IgM anti-hepatitis E virus (HEV) tests based on HEV RNA in an area where hepatitis E is not endemic

Acute hepatitis E (AHE) has rarely been reported in industrialized countries, but the rate of seroprevalence of hepatitis E virus (HEV) antibodies (anti-HEV) is inappropriately high. The sensitivity and specificity of the assay used to test for immunoglobulin G (IgG) and IgM anti-HEV have not been well established in areas where hepatitis E is not endemic (hereafter referred to as "nonendemic areas"). We collected serum samples from 13 AHE patients, 271 healthy subjects, and 160 other liver disease patients in Taiwan to test for HEV RNA by reverse transcription (RT)-PCR and for IgG and IgM anti-HEV by enzyme-linked immunosorbent assays. The sensitivities of IgG and IgM anti-HEV (relative to RT-PCR) were 86.7 and 53.3%, respectively. The specificities of IgG and IgM anti-HEV assays for diagnosing AHE were 92.1 and 98.6%, respectively. The rate of seroprevalence of IgG anti-HEV was 11% among healthy subjects in this nonendemic area, and it increased with age. In summary, IgG anti-HEV is a good diagnostic test for screening for AHE in nonendemic areas. The high rate of prevalence of anti-HEV in healthy subjects indicates that subclinical infection may exist.

The complete sequence of hepatitis E virus genotype 4 reveals an alternative strategy for translation of open reading frames 2 and 3

Isolates of hepatitis E virus (HEV) have recently been described from China that are distinct from Burmese, Mexican and US viruses and constitute a novel genotype (genotype 4). Here, the complete genomic sequence of a representative isolate of genotype 4 HEV, amplified directly from the stool of an acutely infected patient, is presented. Analysis of the entire sequence confirms our previous conclusion, based upon partial sequence data, that these Chinese isolates belong to a novel genotype. Typical of genetic variation in HEV, most nucleotide substitutions occur in the third base of the codon and do not affect the amino acid sequence. The genotype 4 virus is unusual in that a single nucleotide insertion in the ORF 3 region changes the initiation of ORF 3, and perhaps also ORF 2. The consequences of these changes are discussed.

Molecular characterization of a hepatitis E virus isolate from Namibia

Hepatitis E virus (HEV) causes sporadic and epidemic acute viral hepatitis in many developing countries. In Africa, hepatitis E has been documented by virus detection (reverse transcriptase polymerase chain reaction, RT-PCR) in Egypt, Chad, Algeria, Morocco and Tunisia. Cases of presumptive hepatitis E also have been documented by detection of antibody to HEV in the Sudan, Kenya, Ethiopia, Somalia, Djibouti and South Africa. Recently, we reported the recovery of 9 isolates of HEV from feces collected during an outbreak of jaundice in Namibia. These specimens were stored frozen for many years at the South African Institute for Medical Research awaiting new methods to determine the etiology of jaundice. HEV genomic sequences were detected by antigen-capture RT-PCR with primers that amplified 2 independent regions of the HEV genome (ORF-2 and ORF-3). To further characterize the HEV 83-Namibia isolates, we determined the nucleotide (nt) sequence of the 3' end of the capsid gene (296 of 1, 980 nt in ORF-2) and ORF-3 for 1 isolate. The capsid gene sequence shared 86% identity with the prototype Burma strain and up to 96% identity with other African strains at the (nt) level, and 99% identity with Burma or other Africa strains at the amino acid level. A 188 (nt) fragment amplified from ORF-3 was also highly homologous to other HEV but was too short for meaningful comparison. Phylogenetic analysis indicated that HEV 83-Namibia is closely related to other African isolates, and differs from Burmese, Mexican and Chinese HEV. These data link the HEV causing the 1983 Namibia outbreak to more recent HEV transmission in northern and sub-Saharan Africa, suggesting this subgenotype of HEV is firmly established throughout the continent.

93G, a novel sporadic strain of hepatitis E virus in South China isolated by cell culture

The nucleotide sequence of Hepatitis E virus (HEV) serous isolates (G-9 and G-20) from Guangzhou, South China, which has been reported previously, are divergent significantly from those of other reported HEV isolates. In order to investigate more extensively the Guangzhou isolate, the 93G strain was isolated from the faecal sample of the same individual as G-9 by A549 cell culture and identified immunologically and by molecular biological techniques. The results showed that strain 93G could be propagated in an A549 cell line causing cytopathic effects. The viral particles were aggregated by a specific antibody to HEV Chinese Xinjiang strain (87A) observed using immunoelectron microscopy and were similar morphologically to HEV from other sources. In this study, an indirect fluorescent antibody assay was first developed to examine HEV antigen in the infected cells, by immunofluorescence in the cytoplasm and on the surface membrane of the cells. The 58-kDa and 82-kDa native structural proteins of HEV were also identified in this study by Western blotting. The 93G genome showed high homology (93%) with G-9 previously reported but was also as divergent from the Burmese, Mexican, Chinese Xinjiang isolates and the recently reported US-1 isolate, as was G-9. The data presented indicate that 93G propagated in A549 cells, together with its related serum isolate G-9, represents another HEV strain circulating in China and is responsible for some sporadic hepatitis E infections.

Identification of a novel hepatitis E virus in Nigeria

Sporadic cases of acute hepatitis E among ten native Nigerian adults were reported in Port-Harcourt (Nigeria). Hepatitis E virus (HEV) was detected in serum and/or faecal samples of seven patients by RT-PCR of the open reading frame (ORF)-1 polymerase region and the 3'-end of ORF2. Restriction analysis widely used to distinguish genotypes I and III showed that all Nigerian strains have a pattern similar to the Mexican strain (NotI, nt 286; SmaI, nt 397; no KpnI restriction site) but displayed a BsmI restriction site at nt 213 as do most African HEV strains sequenced so far. Sequence analysis performed from internal ORF1 and ORF2 PCR products displayed strong homogeneity between the HEV isolates, determining a regional cluster. Phylogenetic analysis of nucleotide sequences revealed that these strains were more related to the Mexican prototype genotype III (87% homology in ORF1, 80% homology in ORF2) than to either the African strain genotype I (74% homology in ORF1, 77% homology in ORF2) or the USA strain genotype II (75% homology in ORF1, 77% homology in ORF2). Genetic divergence up to 15% in ORF2 with the Mexican genotype clearly defined a new subgenotype within genotype III. At the amino acid level, Nigerian strains showed more homology with genotype III (96%) than with genotype I (92%). This study clearly determined the co-existence of genotypes I and III in Africa. These Nigerian HEV strains belonging to genotype III, but sharing some properties with genotype I, could be one of the missing links between African and Latin American HEV and could help us to determine the phylogenetic evolution of HEV from the ancestral virus.

Cell culture of sporadic hepatitis E virus in China

The isolation and identification of the 87A strain of epidemic hepatitis E virus (HEV) by means of cell culturing have been described previously. This paper reports the successful isolation of a sporadic HEV strain (G93-2) in human lung carcinoma cell (A549) cultures. The etiology, molecular and biological properties, and serological relationship of this new strain to other, epidemic HEV strains are described. The propagation of both sporadic and epidemic HEV strains in a cell culture system will facilitate vaccine research.

Novel hepatitis E virus (HEV) isolates from Europe: evidence for additional genotypes of HEV

Hepatitis E infection is associated with areas in which hepatitis E virus (HEV) infection is endemic. Acute infections in industrialized nations are usually linked to travel to endemic areas. Recently, an acute hepatitis infection in a patient from the United States (US), with no recent foreign travel history, was linked to a novel strain of HEV. Although a few additional cases have been reported from patients who have not traveled to endemic areas, the source of these infections has not been determined. The objective of this study was to identify additional HEV isolates from patients with acute infection who had no recent history of travel to areas where HEV is considered endemic, and to determine the genetic relationship between these and other HEV isolates. Viral RNA was isolated from serum and polymerase chain reaction (PCR) was performed using consensus primers based on a number of HEV isolates. HEV sequence in open reading frame (ORF) 1 and ORF2 was identified in three patients from nonendemic areas, one from Italy and two from Greece. Comparative and phylogenetic analyses were performed. The Greek and Italian isolates were significantly divergent from two isolates from the US and isolates identified previously from HEV-endemic regions. The Italian isolate was distinct from the two Greek isolates. In addition, the two Greek isolates were significantly divergent from each other. Phylogenetic analysis indicated that the Italian and two Greek isolates represent three new genotypes of HEV, distinct from the Burmese, Mexican, and US genotypes.

Phylogenetic analysis of hepatitis E virus isolates from Egypt

Hepatitis E virus (HEV) genome was detected by reverse transcriptase-polymerase chain reaction (RT-PCR) in fecal samples of two sporadic cases of hepatitis E in Cairo Egypt. Sequence of the complete putative structural region [open reading frame (ORF)-2] and complete region of unknown function (ORF-3) was determined for the two HEV isolates. Phylogenetic analysis of the nucleotide sequences was performed using neighbor joining or maximum parsimony methods of tree reconstruction. Direct correspondence between the HEV evolutionary trees and geographic origin of the HEV isolates was observed. Three genotypes of HEV were identified: genotype I (Asia-Africa), genotype II (US), and genotype III (Mexico). Genotype I was further divided into two subgenotypes (Asia and Africa). In the Asian subgenotype, three smaller genetic clusters were observed (China-like sequences, Burma-like sequences, and sequence from a fulminant case of HEV). The segregation of all these genetic clusters was supported by the high level of bootstrap probabilities. Four regions of the HEV genome were used for phylogenetic analysis. In all four regions, Egyptian HEV isolates were grouped in a separate African clade.

Genetic and experimental evidence for cross-species infection by swine hepatitis E virus

Prior to the recent discovery of the swine hepatitis E virus (swine HEV) in pigs from the midwestern United States, HEV was not considered endemic to this country. Since swine HEV is antigenically and genetically related to human strains of HEV, it was important to characterize this new virus further. The infectivity titer of a pool of swine HEV in pigs was determined in order to prepare a standardized reagent and to evaluate the dose response in pigs. Although the sequence of swine HEV varied extensively from those of most human strains of HEV, it was very closely related to the two strains of human HEV (US-1 and US-2) isolated in the United States. The U.S. strains which were recently recovered from two patients with clinical hepatitis E in the United States shared >/=97% amino acid identity with swine HEV in open reading frames 1 and 2. Phylogenetic analyses of different regions of the genome revealed that swine HEV and the U.S. strains grouped together and formed a distinct branch. These results suggested that swine HEV may infect humans. When we inoculated rhesus monkeys and a chimpanzee, experimental surrogates of humans, with swine HEV, the primates became infected. Furthermore, in a reciprocal experiment, specific-pathogen-free pigs were experimentally infected with the US-2 strain of human HEV that is genetically similar to swine HEV. These results provided experimental evidence for cross-species infection by the swine virus. Thus, humans appear to be at risk of infection with swine HEV or closely related viruses.

Neutralization of different geographic strains of the hepatitis E virus with anti-hepatitis E virus-positive serum samples obtained from different sources

A recently developed polymerase chain reaction (PCR)-based cell culture neutralization assay was used to investigate cross-neutralization of known hepatitis E virus (HEV) strains obtained from various HEV-endemic regions of the world with different anti-HEV-positive serum samples. Serum specimens obtained from cynomolgus macaques experimentally infected with strains from Burma, Mexico, or Pakistan cross-neutralized the infectivity of each strain as well as an isolate from Morocco. Serum samples obtained either from infected patients who reside in HEV-endemic regions of the world or from U.S. residents who became infected while traveling to such regions also neutralized all four strains. In contrast, antibodies obtained from rabbits immunized with full-length Burma strain ORF2 protein neutralized only the Burma and Pakistan strains, not the Mexico or Morocco strains. In addition, antibodies obtained from guinea pigs immunized with an N-terminal truncated Burma strain ORF2 protein neutralized each strain except the Morocco strain. These data strongly suggest that antibodies elicited during an HEV infection demonstrate broad HEV neutralizing activity, whereas antibodies elicited after immunization with recombinant Burma ORF2 protein demonstrate a more limited ability to neutralize various HEV strains obtained from different regions of the world endemic for the disease.

The impact of traveling to endemic areas on the spread of hepatitis E virus infection: epidemiological and molecular analyses

Traveling to endemic areas carries a risk of hepatitis E virus (HEV) infection, but no molecular analysis to document sources of infection is available. Eighteen (38%) of 47 patients with acute non-A, non-B, non-C hepatitis were positive for antibody to HEV (anti-HEV), and 9 (50%) of these were also positive for serum HEV RNA by polymerase chain reaction following reverse transcription. Only 1 (5%) of the 21 patients with acute hepatitis A was positive for HEV RNA. Travel to endemic areas (mostly to China; odds ratio, 22.2; 95% confidence interval, 4.7-105.8) and deeper jaundice (odds ratio, 5.2; 95% confidence interval, 1.01-27.2) were the only factors associated with HEV infection in multivariate analysis. The two HEV isolates from two patients who had traveled to China and the HEV isolate from a patient whose travel history was obscure formed a monophyletic group with the isolates from Guangzhou. The HEV isolates from our patients show a homology of 72% to 78% in nucleotide sequence with the Burma, Beijing, India, Pakistan, and Xiangjiang strains; a homology of 81% to 91% with the Guangzhou strains; and a homology of 76% with the Mexico strain. The close relationship between the Taiwan isolates and the Guangzhou strains was further supported by the short Kimura's two-parameter distances among them. In summary, HEV infection does occur in this area. Epidemiological and molecular analyses strongly indicate that most cases of HEV infection originated from travel to HEV-endemic areas.

Genotyping of hepatitis E virus in clinical specimens by restriction endonuclease analysis

The genomic variability of hepatitis E virus (HEV) was examined by restriction endonuclease analysis (REA) of four genomic cDNA copies comprising a 499 bp segment of the putative polymerase gene, a 264 bp segment of the helicase gene, and two, 680 bp and 448 bp, segments of the capsid gene. Analysis of the deduced restriction sites of all 27 HEV sequences currently available in the GenBank, and digestion of reverse-transcribed and nested PCR amplified segments obtained from six Nepali isolates were used to devise and test a REA genotyping assay. The assay allowed easy discrimination between the Mexico and Asian genotypes, and the classification of the Asian genotypes into three, or perhaps four subgenotypes. In addition, endonucleases identifiers of individual isolate or clusters of isolates were found. This assay permits rapid identification of a large number of HEV isolates directly from clinical specimens for studies on the molecular epidemiology and evolution of HEV.

Identification of hepatitis E virus in clinical specimens: amplification of hydroxyapatite-purified virus RNA and restriction endonuclease analysis

A multi-site nested reverse transcription and polymerase chain reaction (RT-PCR) followed by restriction endonuclease analysis (REA) was developed to identify hepatitis E virus (HEV) in clinical specimens. Four sets of primers were selected to amplify regions in the HEV genome supposed to encode the helicase, polymerase, and parts of the viral capsid protein. Digestion of the nested PCR products with HinfI, HaeII, AvaII, BglI, KpnI, SmaI, or EcoRI generated readily recognizable profiles that confirm the HEV sequences and/or distinguish the unique Mexico genotype (our positive control) from all other isolates (Asian genotype). In addition, the hydroxyapatite (HA) adsorption method was compared to other adsorption and extraction methods widely used to purify viral RNA from clinical specimens for RT-PCR. All methods presented the same sensitivity of recovery of HEV RNA, but only the adsorption methods efficiently removed fecal enzymatic inhibitors. The HA method gave the best results and was the most economic in terms of time, cost, manipulations and reagents. The method was validated by screening a small number of serum and fecal specimens available from patients with acute non-A,B,C hepatitis in Nepal. HEV RNA was identified in half (5/11) of the fecal specimens obtained from patients with evidence of recent HEV infection, but in none of the 14 patients without a serological marker for hepatitis E.