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Phylogenetic analysis of two new complete genomes of the hepatitis E virus (HEV) genotype 3 from Thailand.

ABSTRACT: Hepatitis E virus (HEV) is a causative agent of acute viral hepatitis globally. Evolutionary phylogeny classifies the HEV into eight genotypes that correlate with the viral transmission. Only four genotypes have been proven to be responsible for transmission in humans. However, there has been no report on the genomics and genotyping of HEV in Thailand during the past ten years. Here, we identified the genotype distributions of the Thai isolates of HEV and we sequenced two HEV genomes. We screened for 18 Thai isolates of HEV from Siriraj Hospital in Bangkok, from 2014-2016. The HEV genomes were sequenced from the serum and feces of a patient. The results showed that all Thai isolates of HEV were identified as genotype 3 (HEV-3). The ORF2 and genome phylogenies suggested two subgenotypes, called 3.1 and 3.2. The Thai isolates of HEV were frequently found in the subgenotype 3.1. The genome sequences of the two Thai isolates of HEV from the serum and fecal samples of the same patient showed 91% nucleotide similarity with the HEV genotype 3. Comparisons between the HEV genome and the ORF2 phylogenies illustrated that the ORF2 tree can be used to identify HEV genotypes, but it has less phylogenetic power for the HEV evolution. The two new genome sequences of HEV-3 from Thailand could contribute valuable information to the HEV genome study. (226 words).

SUBMITTER: Chanmanee T

PROVIDER: S-EPMC7674359 | biostudies-literature | 2020 Nov

REPOSITORIES: biostudies-literature

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Phylogenetic analysis of two new complete genomes of the hepatitis E virus (HEV) genotype 3 from Thailand.

Chanmanee Tipsuda T Ajawatanawong Pravech P Louisirirotchanakul Suda S Chotiyaputta Watcharasak W Chainuvati Siwaporn S Wongprompitak Patimaporn P

Molecular biology reports 20201014 11

Hepatitis E virus (HEV) is a causative agent of acute viral hepatitis globally. Evolutionary phylogeny classifies the HEV into eight genotypes that correlate with the viral transmission. Only four genotypes have been proven to be responsible for transmission in humans. However, there has been no report on the genomics and genotyping of HEV in Thailand during the past ten years. Here, we identified the genotype distributions of the Thai isolates of HEV and we sequenced two HEV genomes. We screene ...[more]

PMID: 33058031

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Project description:Hepatitis E virus (HEV) is a viral pathogen transmitted by the fecal-oral route and is a major cause of waterborne acute hepatitis in many developing countries. In addition to infecting humans, HEV has been identified in swine, wild boars, rabbits and other mammals; with swine and wild boars being main reservoirs for zoonotic transmission of HEV. There are four major HEV genotypes known to infect humans; genotypes 1 (HEV-1) and 2 (HEV-2) are restricted to humans, and genotypes 3 (HEV-3) and 4 (HEV-4) are zoonotic. Herein, three human HEV strains originating in France were sequenced and near full-length genomes were characterized. Phylogenetic analysis showed that two strains were genotype 3 and closely grouped (a 100% bootstrap value) with subtype 3i reference strains. In percent nucleotide identities, these two strains were 94% identical to each other, 90-93% identical to subtype 3i strains, 82-86% identical to other HEV-3, and 77-79% identical to rabbit HEV strains excluding the two divergent strains KJ013414 and KJ013415 (74%); these two strains were less than 77% identical to strains of HEV genotypes 1, 2 and 4. The third strain was found distinct from any known HEV strains in the database, and located between the clusters of HEV-3 and rabbit HEV strains. This unique strain was 74-75% identical to HEV-1, 73% to HEV-2, 81-82% to HEV-3, 77-79% to rabbit HEV again excluding the two divergent strains KJ013414 and KJ013415 (74%), and 74-75% to HEV-4, suggesting a novel unclassified strain associated with HEV-3 and rabbit HEV. SimPlot and BootScan analyses revealed a putative recombination of HEV-3 and rabbit HEV sequences at four breakpoints. Phylogenetic trees of the five fragments of the genome confirmed the presence of two HEV-3 derived and three unclassified sequences. Analyses of the amino acid sequences of the three open reading frames (ORF1-3) encoded proteins of these three novel strains showed that some amino acid residues specific to rabbit HEV strains were found solely in this unclassified strain but not in the two newly identified genotype 3i strains. The results obtained by SimPlots, BootScans, phylogenetic analyses, and amino acid sequence comparisons in this study all together appear to suggest that this novel unclassified strain is likely carrying a mosaic genome derived from HEV-3 and rabbit HEV sequences, and is thus designated as a putative genotype 3/rabbit HEV recombinant.

Project description:UnlabelledGenotype 3 (gt3) hepatitis E virus (HEV) infections are emerging in Western countries. Immunosuppressed patients are at risk of chronic HEV infection and progressive liver damage, but no adequate model system currently mimics this disease course. Here we explore the possibilities of in vivo HEV studies in a human liver chimeric mouse model (uPA(+/+)Nod-SCID-IL2Rγ(-/-)) next to the A549 cell culture system, using HEV RNA-positive EDTA-plasma, feces, or liver biopsy specimens from 8 immunocompromised patients with chronic gt3 HEV. HEV from feces- or liver-derived inocula showed clear virus propagation within 2 weeks after inoculation onto A549 cells, compared to slow or no HEV propagation of HEV RNA-positive, EDTA-plasma samples. These in vitro HEV infectivity differences were mirrored in human-liver chimeric mice after intravenous (i.v.) inoculation of selected samples. HEV RNA levels of up to 8 log IU HEV RNA/gram were consistently present in 100% of chimeric mouse livers from week 2 to week 14 after inoculation with human feces- or liver-derived HEV. Feces and bile of infected mice contained moderate to large amounts of HEV RNA, while HEV viremia was low and inconsistently detected. Mouse-passaged HEV could subsequently be propagated for up to 100 days in vitro In contrast, cell culture-derived or seronegative EDTA-plasma-derived HEV was not infectious in inoculated animals. In conclusion, the infectivity of feces-derived human HEV is higher than that of EDTA-plasma-derived HEV both in vitro and in vivo Persistent HEV gt3 infections in chimeric mice show preferential viral shedding toward mouse bile and feces, paralleling the course of infection in humans.ImportanceHepatitis E virus (HEV) genotype 3 infections are emerging in Western countries and are of great concern for immunosuppressed patients at risk for developing chronic HEV infection. Lack of adequate model systems for chronic HEV infection hampers studies on HEV infectivity and transmission and antiviral drugs. We compared the in vivo infectivity of clinical samples from chronic HEV patients in human liver chimeric mice to an in vitro virus culture system. Efficient in vivo HEV infection is observed after inoculation with feces- and liver-derived HEV but not with HEV RNA-containing plasma or cell culture supernatant. HEV in chimeric mice is preferentially shed toward bile and feces, mimicking the HEV infection course in humans. The observed in vivo infectivity differences may be relevant for the epidemiology of HEV in humans. This novel small-animal model therefore offers new avenues to unravel HEV's pathobiology.

Project description:Hepatitis E virus (HEV) can account for up to a 30% mortality rate in pregnant women, with highest incidences reported for genotype 1 (gt1) HEV. Reasons contributing to adverse maternal-fetal outcome during pregnancy in HEV-infected pregnant women remain elusive in part due to the lack of a robust tissue culture model for some strains. Open reading frame (ORF4) was discovered overlapping ORF1 in gt1 HEV whose protein expression is regulated via an IRES-like RNA element. To experimentally determine whether gt3 HEV contains an ORF4-like gt1, gt1 and gt3 sequence comparisons were performed between the gt1 and the homologous gt3 sequence. To assess whether ORF4 protein could enhance gt3 replication, Huh7 cell lines constitutively expressing ORF4 were created and used to assess the replication of the Kernow-C1 gt3 and sar55 gt1 HEV. Virus stocks from transfected Huh7 cells with or without ORF4 were harvested and infectivity assessed via infection of HepG2/C3A cells. We also studied the replication of gt1 HEV in the ORF4-expressing tunicamycin-treated cell line. To directly show that HEV transcripts have productively replicated in the target cells, we assessed events at the single-cell level using indirect immunofluorescence and flow cytometry. Despite not naturally encoding ORF4, replication of gt3 HEV was enhanced by the presence of gt1 ORF4 protein. These results suggest that the function of ORF4 protein from gt1 HEV is transferrable, enhancing the replication of gt3 HEV. ORF4 may be utilized to enhance replication of difficult to propagate HEV genotypes in cell culture. IMPORTANCE: HEV is a leading cause of acute viral hepatitis (AVH) around the world. The virus is a threat to pregnant women, particularly during the second and third trimester of pregnancy. The factors enhancing virulence to pregnant populations are understudied. Additionally, field strains of HEV remain difficult to culture in vitro. ORF4 was recently discovered in gt1 HEV and is purported to play a role in pregnancy related pathology and enhanced replication. We present evidence that ORF4 protein provided in trans enhances the viral replication of gt3 HEV even though it does not encode ORF4 naturally in its genome. These data will aid in the development of cell lines capable of supporting replication of non-cell culture adapted HEV field strains, allowing viral titers sufficient for studying these strains in vitro. Furthermore, development of gt1/gt3 ORF4 chimeric virus may shed light on the role that ORF4 plays during pregnancy.

Dataset Information

Phylogenetic analysis of two new complete genomes of the hepatitis E virus (HEV) genotype 3 from Thailand.

Publications

Phylogenetic analysis of two new complete genomes of the hepatitis E virus (HEV) genotype 3 from Thailand.

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