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Zhou Y, Zhao C, Tian Y, Xu N, Wang Y. Characteristics and Functions of HEV Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2023; 1417:15-32. [PMID: 37223856 DOI: 10.1007/978-981-99-1304-6_2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Hepatitis E virus (HEV) is a non-enveloped virus containing a single-stranded, positive-sense RNA genome of 7.2 kb, which consists of a 5' non-coding region, three open reading frames (ORFs), and a 3' non-coding region. ORF1 is diverse between genotypes and encodes the nonstructural proteins, which include the enzymes needed for virus replication. In addition to its role in virus replication, the function of ORF1 is relevant to viral adaption in culture and may also relate to virus infection and HEV pathogenicity. ORF2 protein is the capsid protein, which is about 660 amino acids in length. It not only protects the integrity of the viral genome, but is also involved in many important physiological activities, such as virus assembly, infection, host interaction, and innate immune response. The main immune epitopes, especially neutralizing epitopes, are located on ORF2 protein, which is a candidate antigen for vaccine development. ORF3 protein is a phosphoprotein of 113 or 114 amino acids with a molecular weight of 13 kDa with multiple functions that can also induce strong immune reactivity. A novel ORF4 has been identified only in genotype 1 HEV and its translation promotes viral replication.
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Affiliation(s)
- Yan Zhou
- RegCMC, Great Regulatory Affairs, Sanofi (China) Investment Co., Ltd, Beijing, China
| | - Chenyan Zhao
- Division of HIV/AIDS and Sex-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Yabin Tian
- Division II of In Vitro Diagnostics for Infectious Diseases, National Institutes for Food and Drug Control, Beijing, China
| | - Nan Xu
- Division of HIV/AIDS and Sex-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, China
| | - Youchun Wang
- Institute of Medical Biology, Chinese Academy of Medical Science & Peking Union Medical College, Kunming, China.
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Mira C, Yepes JO, Henao LF, Montoya Guzmán M, Navas MC. EXPRESIÓN DE LA PROTEÍNA CORE DEL VIRUS DE LA HEPATITIS C EN CÉLULAS HEPG2 USANDO EL VIRUS DEL BOSQUE DE SEMLIKI. ACTA BIOLÓGICA COLOMBIANA 2020. [DOI: 10.15446/abc.v26n1.79365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
El Virus de la Hepatitis C (VHC) codifica la proteína Core. Core, además de ser la subunidad de la cápside, participa en diferentes mecanismos de patogénesis de la infección por VHC. Dado que el sistema de replicación in vitrodel VHC presenta limitaciones, el uso de vectores virales podría ser una herramienta útil para estudiar las propiedades de la proteína Core. Con el fin de validar el vector con el Virus del Bosque de Semliki (SFV) para el estudio de Core en células HepG2, se evaluó la expresión de la proteína verde fluorescente (GFP) y la proteína Core utilizando este vector viral. Las expresiones de GFP y Core se detectaron en células HepG2 transducidas con rSFV de 24 a 96 horas postransducción. La expresión de la proteína Core fue inferior a la expresión de GFP en las células HepG2. Teniendo en cuenta que la proteína Core del VHC puede regular la actividad del gen p53, se evaluó el nivel transcripcional de este gen. Se observó una disminución en el nivel de mARN de p53 en las células luego de la transducción, comparado con las células control. Aunque las células transducidas con rSFV-Core presentaron el menor nivel de mARN de p53,la diferencia no fue significativa comparada con las células transducidas con rSFV-GFP. Los resultados confirman que rSFV permite la expresión transitoria de proteínas heterólogas en líneas celulares de hepatoma humano. Se necesitan estudios adicionales para determinar si la expresión disminuida de Core puede deberse a degradación de la proteína viral.
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Netzler NE, Enosi Tuipulotu D, Vasudevan SG, Mackenzie JM, White PA. Antiviral Candidates for Treating Hepatitis E Virus Infection. Antimicrob Agents Chemother 2019; 63:e00003-19. [PMID: 30885901 PMCID: PMC6535575 DOI: 10.1128/aac.00003-19] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2019] [Accepted: 03/04/2019] [Indexed: 12/14/2022] Open
Abstract
Globally, hepatitis E virus (HEV) causes significant morbidity and mortality each year. Despite this burden, there are no specific antivirals available to treat HEV patients, and the only licensed vaccine is not available outside China. Ribavirin and alpha interferon are used to treat chronic HEV infections; however, severe side effects and treatment failure are commonly reported. Therefore, this study aimed to identify potential antivirals for further development to combat HEV infection. We selected 16 compounds from the nucleoside and nonnucleoside antiviral classes that range in developmental status from late preclinical to FDA approved and evaluated them as potential antivirals for HEV infection, using genotype 1 replicon luminescence studies and replicon RNA quantification. Two potent inhibitors of HEV replication included NITD008 (half-maximal effective concentration [EC50], 0.03 μM; half-maximal cytotoxic concentration [CC50], >100 μM) and GPC-N114 (EC50, 1.07 μM, CC50, >100 μM), and both drugs reduced replicon RNA levels in cell culture (>50% reduction with either 10 μM GPC-N114 or 2.50 μM NITD008). Furthermore, GPC-N114 and NITD008 were synergistic in combinational treatment (combination index, 0.4) against HEV replication, allowing for dose reduction indices of 20.42 and 8.82 at 50% inhibition, respectively. Sofosbuvir has previously exhibited mixed results against HEV as an antiviral, both in vitro and in a few clinical applications; however, in this study it was effective against the HEV genotype 1 replicon (EC50, 1.97 μM; CC50, >100 μM) and reduced replicon RNA levels (47.2% reduction at 10 μM). Together these studies indicate drug repurposing may be a promising pathway for development of antivirals against HEV infection.
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Affiliation(s)
- Natalie E Netzler
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney, NSW, Australia
| | - Daniel Enosi Tuipulotu
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney, NSW, Australia
| | | | - Jason M Mackenzie
- Department of Microbiology and Immunology, The Peter Doherty Institute for Infection and Immunity, University of Melbourne, Melbourne, VIC, Australia
| | - Peter A White
- School of Biotechnology and Biomolecular Sciences, Faculty of Science, University of New South Wales, Sydney, NSW, Australia
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Life cycle and morphogenesis of the hepatitis E virus. Emerg Microbes Infect 2018; 7:196. [PMID: 30498191 PMCID: PMC6265337 DOI: 10.1038/s41426-018-0198-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2018] [Revised: 11/01/2018] [Accepted: 11/05/2018] [Indexed: 12/19/2022]
Abstract
Hepatitis E virus (HEV) is transmitted primarily via contaminated water and food by the fecal oral route and causes epidemics in developing countries. In industrialized countries, zoonotic transmission of HEV is prevalent. In addition, HEV is the major cause of acute hepatitis in healthy adults and can cause chronic hepatitis in immunocompromised patients, with pregnant HEV-infected women having increased mortality rates of approximately 25%. HEV was once an understudied and neglected virus. However, in recent years, the safety of blood products with respect to HEV has increasingly been considered to be a public health problem. The establishment of HEV infection models has enabled significant progress to be made in understanding its life cycle. HEV infects cells via a receptor (complex) that has yet to be identified. The HEV replication cycle is initiated immediately after the (+) stranded RNA genome is released into the cell cytosol. Subsequently, infectious viral particles are released by the ESCRT complex as quasi-enveloped viruses (eHEVs) into the serum, whereas feces and urine contain only nonenveloped infectious viral progeny. The uncoating of the viral envelope takes place in the biliary tract, resulting in the generation of a nonenveloped virus that is more resistant to environmental stress and possesses a higher infectivity than that of eHEV. This review summarizes the current knowledge regarding the HEV life cycle, viral morphogenesis, established model systems and vaccine development.
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Montpellier C, Wychowski C, Sayed IM, Meunier JC, Saliou JM, Ankavay M, Bull A, Pillez A, Abravanel F, Helle F, Brochot E, Drobecq H, Farhat R, Aliouat-Denis CM, Haddad JG, Izopet J, Meuleman P, Goffard A, Dubuisson J, Cocquerel L. Hepatitis E Virus Lifecycle and Identification of 3 Forms of the ORF2 Capsid Protein. Gastroenterology 2018; 154:211-223.e8. [PMID: 28958858 DOI: 10.1053/j.gastro.2017.09.020] [Citation(s) in RCA: 128] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Revised: 09/08/2017] [Accepted: 09/14/2017] [Indexed: 12/11/2022]
Abstract
BACKGROUND & AIMS Hepatitis E virus (HEV) infection is a major cause of acute hepatitis worldwide. Approximately 2 billion people live in areas endemic for HEV and are at risk of infection. The HEV genome encodes 3 proteins, including the ORF2 capsid protein. Detailed analyses of the HEV life cycle has been hampered by the lack of an efficient viral culture system. METHODS We performed studies with gt3 HEV cell culture-produced particles and patient blood and stool samples. Samples were fractionated on iodixanol gradients and cushions. Infectivity assays were performed in vitro and in human liver chimeric mice. Proteins were analyzed by biochemical and proteomic approaches. Infectious particles were analyzed by transmission electron microscopy. HEV antigen levels were measured with the Wantaï enzyme-linked immunosorbent assay. RESULTS We developed an efficient cell culture system and isolated HEV particles that were infectious in vitro and in vivo. Using transmission electron microscopy, we defined the ultrastructure of HEV cell culture-produced particles and particles from patient sera and stool samples. We also identified the precise sequence of the infectious particle-associated ORF2 capsid protein. In cultured cells and in samples from patients, HEV produced 3 forms of the ORF2 capsid protein: infectious/intracellular ORF2 (ORF2i), glycosylated ORF2 (ORF2g), and cleaved ORF2 (ORF2c). The ORF2i protein associated with infectious particles, whereas the ORF2g and ORF2c proteins were massively secreted glycoproteins not associated with infectious particles. ORF2g and ORF2c were the most abundant antigens detected in sera from patients. CONCLUSIONS We developed a cell culture system and characterized HEV particles; we identified 3 ORF2 capsid proteins (ORF2i, ORF2g, and ORFc). These findings will advance our understanding of the HEV life cycle and improve diagnosis.
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Affiliation(s)
- Claire Montpellier
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Czeslaw Wychowski
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France.
| | - Ibrahim M Sayed
- Laboratory of Liver Infectious Diseases, Department of Clinical Chemistry, Microbiology and Immunology, Ghent University, Ghent, Belgium; Microbiology and Immunology Department, Faculty of Medicine, Assiut University, Assiut, Egypt
| | | | - Jean-Michel Saliou
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Maliki Ankavay
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Anne Bull
- Inserm-U966, University F. Rabelais, Tours, France
| | - André Pillez
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Florence Abravanel
- CHU Toulouse, Hôpital Purpan, Laboratoire de virologie, National Reference Center for Hepatitis E, Toulouse, France
| | - François Helle
- EA4294, Laboratoire de Virologie, Centre Universitaire de Recherche en Santé, Centre Hospitalier Universitaire et Université de Picardie Jules Verne, Amiens, France
| | - Etienne Brochot
- EA4294, Laboratoire de Virologie, Centre Universitaire de Recherche en Santé, Centre Hospitalier Universitaire et Université de Picardie Jules Verne, Amiens, France
| | - Hervé Drobecq
- University of Lille, CNRS, Institut Pasteur de Lille, UMR 8161-M3T-Mechanisms of Tumorigenesis and Target Therapies, Lille, France
| | - Rayan Farhat
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Cécile-Marie Aliouat-Denis
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Juliano G Haddad
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Jacques Izopet
- CHU Toulouse, Hôpital Purpan, Laboratoire de virologie, National Reference Center for Hepatitis E, Toulouse, France
| | - Philip Meuleman
- Laboratory of Liver Infectious Diseases, Department of Clinical Chemistry, Microbiology and Immunology, Ghent University, Ghent, Belgium
| | - Anne Goffard
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Jean Dubuisson
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France
| | - Laurence Cocquerel
- University of Lille, CNRS, INSERM, CHU Lille, Pasteur Institute of Lille, U1019-UMR8204-CIIL-Center for Infection and Immunity of Lille, Lille, France.
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Zhou Y, Zhao C, Tian Y, Xu N, Wang Y. Characteristics and Functions of HEV Proteins. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2016; 948:17-38. [PMID: 27738977 DOI: 10.1007/978-94-024-0942-0_2] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hepatitis E virus (HEV) is a non-enveloped virus containing a single-stranded, positive-sense RNA genome of 7.2 kb, which consists of a 5' noncoding region, three open reading frames (ORFs), and a 3' noncoding region. ORF1 is diverse between genotypes and encodes the nonstructural proteins, which include the enzymes needed for virus replication. In addition to its role in virus replication, the function of ORF1 is relevant to viral adaption in cultured cells and may also relate to virus infection and HEV pathogenicity. ORF2 protein is the capsid protein, which is about 660 amino acids in length. It not only protects the integrity of the viral genome but is also involved in many important physiological activities, such as virus assembly, infection, and host interaction. The main immune epitopes, especially neutralizing epitopes, are located on ORF2 protein, which is a candidate antigen for vaccine development. ORF3 protein is a phosphoprotein of 113 or 114 amino acids with a molecular weight of 13 kDa with multiple functions that can also induce strong immune reactivity.
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Affiliation(s)
- Yan Zhou
- Division of Drug and Cosmetics Inspection, Center for Food and Drug Inspection, China Food and Drug Administration, No.11 Fa Hua Nan Li, Dongcheng District, Beijing, 100061, China
| | - Chenyan Zhao
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, National Institutes for Food and Drug Control, No. 2 Tiantanxili, Dongcheng District, Beijing, 100050, China
| | - Yabin Tian
- Division of Diagnosis, National Institutes for Food and Drug Control, No. 2 Tiantanxili, Dongcheng District, Beijing, 100050, China
| | - Nan Xu
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, National Institutes for Food and Drug Control, No. 2 Tiantanxili, Dongcheng District, Beijing, 100050, China
| | - Youchun Wang
- Division of HIV/AIDS and Sex-transmitted Virus Vaccines, National Institutes for Food and Drug Control, No. 2 Tiantanxili, Dongcheng District, Beijing, 100050, China.
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Qi Y, Zhang F, Zhang L, Harrison TJ, Huang W, Zhao C, Kong W, Jiang C, Wang Y. Hepatitis E Virus Produced from Cell Culture Has a Lipid Envelope. PLoS One 2015; 10:e0132503. [PMID: 26161670 PMCID: PMC4498737 DOI: 10.1371/journal.pone.0132503] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 06/15/2015] [Indexed: 01/10/2023] Open
Abstract
The absence of a productive cell culture system hampered detailed analysis of the structure and protein composition of the hepatitis E virion. In this study, hepatitis E virus from a robust HEV cell culture system and from the feces of infected monkeys at the peak of virus excretion was purified by ultra-centrifugation. The common feature of the two samples after ultracentrifugation was that the ORF2 protein mainly remained in the top fractions. The ORF2 protein from cell culture system was glycosylated, with an apparent molecular weight of 88 kDa, and was not infectious in PLC/PRF/5 cells. The ORF2 protein in this fraction can bind to and protect HEV RNA from digestion by RNase A. The RNA-ORF2 product has a similar sedimentation coefficient to the virus from feces. The viral RNA in the cell culture supernatant was mainly in the fraction of 1.15 g/cm3 but that from the feces was mainly in the fraction of 1.21 g/cm3. Both were infectious in PLC/PRF/5 cells. And the fraction in the middle of the gradient (1.06 g/cm3) from the cell culture supernatant,but not that from the feces, also has ORF2 protein and HEV RNA but was not infectious in PLC/PRF/5.The infectious RNA-rich fraction from the cell culture contained ORF3 protein and lipid but the corresponding fraction from feces had no lipid and little ORF3 protein. The lipid on the surface of the virus has no effect on its binding to cells but the ORF3 protein interferes with binding. The result suggests that most of the secreted ORF2 protein is not associated with HEV RNA and that hepatitis E virus produced in cell culture differs in structure from the virus found in feces in that it has a lipid envelope.
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Affiliation(s)
- Ying Qi
- National Engineering Laboratory for AIDS Vaccine, Jilin University, Changchun, 130012, China
- Division of HIV/AIDS and Sexually-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, 100050, China
| | - Feng Zhang
- Division of HIV/AIDS and Sexually-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, 100050, China
| | - Li Zhang
- Division of HIV/AIDS and Sexually-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, 100050, China
| | - Tim J. Harrison
- Division of Medicine, University College London Medical School, London, WC1E 6BT, United Kingdom
| | - Weijin Huang
- Division of HIV/AIDS and Sexually-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, 100050, China
| | - Chenyan Zhao
- Division of HIV/AIDS and Sexually-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, 100050, China
| | - Wei Kong
- National Engineering Laboratory for AIDS Vaccine, Jilin University, Changchun, 130012, China
| | - Chunlai Jiang
- National Engineering Laboratory for AIDS Vaccine, Jilin University, Changchun, 130012, China
| | - Youchun Wang
- Division of HIV/AIDS and Sexually-Transmitted Virus Vaccines, National Institutes for Food and Drug Control, Beijing, 100050, China
- * E-mail:
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Osterman A, Vizoso-Pinto MG, Jung J, Jaeger G, Eberle J, Nitschko H, Baiker A. A novel indirect immunofluorescence test for the detection of IgG and IgA antibodies for diagnosis of Hepatitis E Virus infections. J Virol Methods 2013; 191:48-54. [PMID: 23557668 DOI: 10.1016/j.jviromet.2013.03.022] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2012] [Revised: 03/07/2013] [Accepted: 03/14/2013] [Indexed: 12/27/2022]
Abstract
Hepatitis E Virus (HEV) causes epidemic infections in regions of poor hygiene in the developing world. Over the last years, however, increasing numbers of autochthonous infections in industrialized countries have been described, leading to new interest in this pathogen. Currently available serological test formats to detect IgG and IgM antibodies are mainly based on bacterially expressed ORF2 and ORF3 antigens and often give ambiguous results. The objective of this study was the development of a different assay format for HEV diagnosis--a HEV immunofluorescence test (HEV-IFT) based on mammalian cells transiently expressing recombinant HEV ORF2 protein with a simple production and staining protocol and the investigation of its performance and methodical feasibility under diagnostic laboratory conditions. 31 sera of patients at different phases of HEV infection and 40 control sera from a non-endemic region were analyzed for anti-HEV IgG, IgM, and IgA antibodies. The HEV-IFT detected successfully anti-HEV IgG and IgA, but not anti-HEV IgM antibodies. In the study group the HEV-IFT was able to confirm HEV infections and to support diagnosis when ambiguous results were obtained by commercial assays. Signal localization and staining patterns helped to gather additional information about reactive antibodies present in patient sera. In conclusion the developed IFT for the detection of anti-HEV IgG and IgA antibodies can be used for diagnosis and for the serological confirmation of HEV infections.
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Affiliation(s)
- Andreas Osterman
- Max von Pettenkofer-Institute, Virology, Ludwig-Maximilians-University of Munich, Pettenkoferstrasse 9a, D-80336 Munich, Germany.
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Cao D, Meng XJ. Molecular biology and replication of hepatitis E virus. Emerg Microbes Infect 2012; 1:e17. [PMID: 26038426 PMCID: PMC3630916 DOI: 10.1038/emi.2012.7] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2011] [Revised: 03/21/2012] [Accepted: 04/08/2012] [Indexed: 02/07/2023]
Abstract
Hepatitis E virus (HEV), a single-stranded, positive-sense RNA virus, is responsible for acute hepatitis E epidemics in many developing countries, and the virus is also endemic in some industrialized countries. Hepatitis E is a recognized zoonotic disease, and several animal species, including pigs, are potential reservoirs for HEV. The genome of HEV contains three open reading frames (ORFs). ORF1 encodes the nonstructural proteins, ORF2 encodes the capsid protein, and ORF3 encodes a small multifunctional protein. The ORF2 and ORF3 proteins are translated from a single, bicistronic mRNA. The coding sequences for these two ORFs overlap each other, but neither overlaps with ORF1. Whereas the mechanisms underlying HEV replication are poorly understood, the construction of infectious viral clones, the identification of cell lines that support HEV replication, and the development of small animal models have allowed for more detailed study of the virus. As result of these advances, recently, our understanding of viral entry, genomic replication and viral egress has improved. Furthermore, the determination of the T=1 and T=3 structure of HEV virus-like particles has furthered our understanding of the replication of HEV. This article reviews the latest developments in the molecular biology of HEV with an emphasis on the genomic organization, the expression and function of genes, and the structure and replication of HEV.
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Affiliation(s)
- Dianjun Cao
- Center for Molecular Medicine and Infectious Diseases, Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University (Virginia Tech) , Blacksburg, VA 24061-0913, USA
| | - Xiang-Jin Meng
- Center for Molecular Medicine and Infectious Diseases, Department of Biomedical Sciences and Pathobiology, Virginia Polytechnic Institute and State University (Virginia Tech) , Blacksburg, VA 24061-0913, USA
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Kapur N, Thakral D, Durgapal H, Panda SK. Hepatitis E virus enters liver cells through receptor-dependent clathrin-mediated endocytosis. J Viral Hepat 2012; 19:436-48. [PMID: 22571906 DOI: 10.1111/j.1365-2893.2011.01559.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
We investigated the virus-host interaction for hepatitis E virus (HEV) by performing competitive binding assays using in vitro assembled virus-like particles (VLPs). We used Escherichia coli expressed native capsid protein (pORF2) and its mutants with an attached Gly((5))-Ala (linker) reporter [enhanced green fluorescent protein (EGFP)/firefly luciferase (Fluc)]. Transmission electron microscopy and nanoparticle tracking showed near uniform particles of approximately 30-35 nm in diameter for pORF2 VLPs and 60-100 nm for reporter-linked VLPs. Binding of reporter-linked full-length (1-660aa) and N-terminal truncated (Δ1-112aa) pORF2 VLPs to Huh7 cell surfaces was found to be specific with 1.92 ± 0.065 × 10(5) sites per cell. Saturation binding indicated an equilibrium dissociation constant (K(d)) of 121.1 ± 23.83 and 123.8 ± 16.15 nm for pORF2-linker-EGFP and pORF2-linker-Fluc VLPs respectively. A similar binding pattern was observed for Δ1-112aa pORF2-linker-EGFP and Δ1-112aa pORF2-linker-Fluc VLPs with K(d) values of 123.6 ± 10.60 and 135.6 ± 16.19 nm respectively. The affinity (log K(i)) of pORF2 binding on Huh7 cells in the presence of EGFP-tagged and Fluc-tagged pORF2 VLPs was found to be approximately 2.0. However, no VLP formation or binding was observed with refolded C-terminal truncated (Δ458-660aa) pORF2. We investigated HEV internalization using fluorescent VLPs (EGFP-VLPs), which showed vesicle-mediated uptake starting at 5 min post-incubation. The uptake of VLPs could be stopped by inhibitors for clathrin-dependent endocytosis, but not by caveosome inhibitors. No binding and uptake of EGFP-VLPs were observed on non-hepatic cell lines (HeLa and SiHa). These findings suggest that HEV attaches to the host cell via a specific high affinity receptor and enters the cytoplasm by clathrin-mediated endocytosis.
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Affiliation(s)
- N Kapur
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India
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Mutations within potential glycosylation sites in the capsid protein of hepatitis E virus prevent the formation of infectious virus particles. J Virol 2007; 82:1185-94. [PMID: 18032496 DOI: 10.1128/jvi.01219-07] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Hepatitis E virus is a nonenveloped RNA virus. However, the single capsid protein resembles a typical glycoprotein in that it contains a signal sequence and potential glycosylation sites that are utilized when recombinant capsid protein is overexpressed in cell culture. In order to determine whether these unexpected observations were biologically relevant or were artifacts of overexpression, we analyzed capsid protein produced during a normal viral replication cycle. In vitro transcripts from an infectious cDNA clone mutated to eliminate potential glycosylation sites were transfected into cultured Huh-7 cells and into the livers of rhesus macaques. The mutations did not detectably affect genome replication or capsid protein synthesis in cell culture. However, none of the mutants infected rhesus macaques. Velocity sedimentation analyses of transfected cell lysates revealed that mutation of the first two glycosylation sites prevented virion assembly, whereas mutation of the third site permitted particle formation and RNA encapsidation, but the particles were not infectious. However, conservative mutations that did not destroy glycosylation motifs also prevented infection. Overall, the data suggested that the mutations were lethal because they perturbed protein structure rather than because they eliminated glycosylation.
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Abstract
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.
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Affiliation(s)
- Subrat Kumar Panda
- Department of Pathology, All India Institute of Medical Sciences, Ansari Nagar, New Delhi, India.
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Zafrullah M, Khursheed Z, Yadav S, Sahgal D, Jameel S, Ahmad F. Acidic pH enhances structure and structural stability of the capsid protein of hepatitis E virus. Biochem Biophys Res Commun 2004; 313:67-73. [PMID: 14672699 DOI: 10.1016/j.bbrc.2003.11.088] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Hepatitis E virus (HEV) is enterically transmitted and endemic to tropical areas of the world. The major capsid protein of HEV is pORF2 ( approximately 74 kDa), encoded by open reading frame 2 (ORF2). When expressed in insect cells, it is processed into a approximately 55 kDa form (n-pORF2). We also generated a mutant, m-pORF2, lacking a C-terminal hydrophobic region shown earlier to be required for its homo-oligomerization. Circular dichroism was used to measure the secondary structure and stability of these proteins as a function of pH and temperature. With decreasing pH both proteins acquired increasing alpha-helicity and thermal stability in terms of midpoint of denaturation and the Gibbs energy change.
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Affiliation(s)
- Mohammad Zafrullah
- Department of Biosciences, Jamia Millia Islamia, Jamia Nagar, New Delhi 110025, India
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14
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Magden J, Takeda N, Li T, Auvinen P, Ahola T, Miyamura T, Merits A, Kääriäinen L. Virus-specific mRNA capping enzyme encoded by hepatitis E virus. J Virol 2001; 75:6249-55. [PMID: 11413290 PMCID: PMC114346 DOI: 10.1128/jvi.75.14.6249-6255.2001] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Hepatitis E virus (HEV), a positive-strand RNA virus, is an important causative agent of waterborne hepatitis. Expression of cDNA (encoding amino acids 1 to 979 of HEV nonstructural open reading frame 1) in insect cells resulted in synthesis of a 110-kDa protein (P110), a fraction of which was proteolytically processed to an 80-kDa protein. P110 was tightly bound to cytoplasmic membranes, from which it could be released by detergents. Immunopurified P110 catalyzed transfer of a methyl group from S-adenosylmethionine (AdoMet) to GTP and GDP to yield m(7)GTP or m(7)GDP. GMP, GpppG, and GpppA were poor substrates for the P110 methyltransferase. There was no evidence for further methylation of m(7)GTP when it was used as a substrate for the methyltransferase. P110 was also a guanylyltransferase, which formed a covalent complex, P110-m(7)GMP, in the presence of AdoMet and GTP, because radioactivity from both [alpha-(32)P]GTP and [(3)H-methyl]AdoMet was found in the covalent guanylate complex. Since both methyltransferase and guanylyltransferase reactions are strictly virus specific, they should offer optimal targets for development of antiviral drugs. Cap analogs such as m(7)GTP, m(7)GDP, et(2)m(7)GMP, and m(2)et(7)GMP inhibited the methyltransferase reaction. HEV P110 capping enzyme has similar properties to the methyltransferase and guanylyltransferase of alphavirus nsP1, tobacco mosaic virus P126, brome mosaic virus replicase protein 1a, and bamboo mosaic virus (a potexvirus) nonstructural protein, indicating there is a common evolutionary origin of these distantly related plant and animal virus families.
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Affiliation(s)
- J Magden
- Program in Cellular Biotechnology, Institute of Biotechnology, Viikki Biocenter, Viikinkaari 9, 00014 University of Helsinki, Finland
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Xiaofang L, Zafrullah M, Ahmad F, Jameel S. A C-Terminal Hydrophobic Region is Required for Homo-Oligomerization of the Hepatitis E Virus Capsid (ORF2) Protein. J Biomed Biotechnol 2001; 1:122-128. [PMID: 12488605 PMCID: PMC129057 DOI: 10.1155/s1110724301000262] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Hepatitis E virus (HEV) is the causative agent of hepatitis E, an acute form of viral hepatitis. The open reading frame 2 (ORF2) of HEV encodes the viral capsid protein, which can self-oligomerize into virus-like particles. To understand the domains within this protein important for capsid biogenesis, we have carried out in vitro analyses of association and folding patterns of wild type and mutant ORF2 proteins. When expressed in vitro or in transfected cells, the ORF2 protein assembled as dimers, trimers and higher order forms.While N-terminal deletions upto 111 amino acids had no effect, the deletion of amino acids 585-610 led to reduced homo-oligomerization. This deletion also resulted in aberrant folding of the protein, as determined by its sensitivity to trypsin. This study suggests that a C-terminal hydrophobic region encompassing amino acids 585-610 of the ORF2 protein might be critical for capsid biogenesis.
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Affiliation(s)
- Li Xiaofang
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Mohammad Zafrullah
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Faizan Ahmad
- Department of Biosciences, Jamia Millia Islamia, New Delhi, India
| | - Shahid Jameel
- Virology Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi-110067, India
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Riddell MA, Li F, Anderson DA. Identification of immunodominant and conformational epitopes in the capsid protein of hepatitis E virus by using monoclonal antibodies. J Virol 2000; 74:8011-7. [PMID: 10933710 PMCID: PMC112333 DOI: 10.1128/jvi.74.17.8011-8017.2000] [Citation(s) in RCA: 74] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibody to the capsid (PORF2) protein of hepatitis E virus (HEV) is sufficient to confer immunity, but knowledge of B-cell epitopes in the intact capsid is limited. A panel of murine monoclonal antibodies (MAbs) was generated following immunization with recombinant ORF2.1 protein, representing the C-terminal 267 amino acids (aa) of the 660-aa capsid protein. Two MAbs reacted exclusively with the conformational ORF2.1 epitope (F. Li, J. Torresi, S. A. Locarnini, H. Zhuang, W. Zhu, X. Guo, and D. A. Anderson, J. Med. Virol. 52:289-300, 1997), while the remaining five demonstrated reactivity with epitopes in the regions aa 394 to 414, 414 to 434, and 434 to 457. The antigenic structures of both the ORF2.1 protein expressed in Escherichia coli and the virus-like particles (VLPs) expressed using the baculovirus system were examined by competitive enzyme-linked immunosorbent assays (ELISAs) using five of these MAbs and HEV patient sera. Despite the wide separation of epitopes within the primary sequence, all the MAbs demonstrated some degree of cross-inhibition with each other in ORF2. 1 and/or VLP ELISAs, suggesting a complex antigenic structure. MAbs specific for the conformational ORF2.1 epitope and a linear epitope within aa 434 to 457 blocked convalescent patient antibody reactivity against VLPs by approximately 60 and 35%, respectively, while MAbs against epitopes within aa 394 to 414 and 414 to 434 were unable to block patient serum reactivity. These results suggest that sequences spanning aa 394 to 457 of the capsid protein participate in the formation of strongly immunodominant epitopes on the surface of HEV particles which may be important in immunity to HEV infection.
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Affiliation(s)
- M A Riddell
- Hepatitis Research Unit and Australian Centre for Hepatitis Virology, Macfarlane Burnet Centre for Medical Research, Fairfield 3078, Victoria, Australia
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