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Liu L, Wang H, Liu L, Cheng F, Aisa HA, Li C, Meng S. Rupestonic Acid Derivative YZH-106 Promotes Lysosomal Degradation of HBV L- and M-HBsAg via Direct Interaction with PreS2 Domain. Viruses 2024; 16:1151. [PMID: 39066313 PMCID: PMC11281537 DOI: 10.3390/v16071151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2024] [Revised: 07/13/2024] [Accepted: 07/16/2024] [Indexed: 07/28/2024] Open
Abstract
Hepatitis B surface antigen (HBsAg) is not only the biomarker of hepatitis B virus (HBV) infection and expression activity in hepatocytes, but it also contributes to viral specific T cell exhaustion and HBV persistent infection. Therefore, anti-HBV therapies targeting HBsAg to achieve HBsAg loss are key approaches for an HBV functional cure. In this study, we found that YZH-106, a rupestonic acid derivative, inhibited HBsAg secretion and viral replication. Further investigation demonstrated that YZH-106 promoted the lysosomal degradation of viral L- and M-HBs proteins. A mechanistic study using Biacore and docking analysis revealed that YZH-106 bound directly to the PreS2 domain of L- and M-HBsAg, thereby blocking their entry into the endoplasmic reticulum (ER) and promoting their degradation in cytoplasm. Our work thereby provides the basis for the design of a novel compound therapy to target HBsAg against HBV infection.
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Affiliation(s)
- Lanlan Liu
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; (L.L.); (H.W.); (L.L.)
| | - Haoyu Wang
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; (L.L.); (H.W.); (L.L.)
- University of Chinese Academy of Sciences, Beijing 100101, China
| | - Lulu Liu
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; (L.L.); (H.W.); (L.L.)
| | - Fang Cheng
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; (L.L.); (H.W.); (L.L.)
- University of Chinese Academy of Sciences, Beijing 100101, China
| | - Haji Akber Aisa
- State Key Laboratory Basis of Xinjiang Indigenous Medicinal Plants Resource Utilization, Xinjiang Technical Institute of Physics and Chemistry, Chinese Academy of Sciences, Urumqi 830011, China
| | - Changfei Li
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; (L.L.); (H.W.); (L.L.)
| | - Songdong Meng
- Key Laboratory of Pathogenic Microbiology and Immunology, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China; (L.L.); (H.W.); (L.L.)
- University of Chinese Academy of Sciences, Beijing 100101, China
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2
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Lok J, Dusheiko G, Carey I, Agarwal K. Review article: novel biomarkers in hepatitis B infection. Aliment Pharmacol Ther 2022; 56:760-776. [PMID: 35770458 DOI: 10.1111/apt.17105] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2022] [Revised: 06/08/2022] [Accepted: 06/12/2022] [Indexed: 12/09/2022]
Abstract
BACKGROUND Chronic hepatitis B remains a global health problem with an estimated 296 million people affected worldwide. Individuals are at risk of serious complications such as cirrhosis and hepatocellular carcinoma and accurately predicting these clinical endpoints has proven difficult. However, several viral biomarkers have recently been developed, including quantitative HBV surface antigen (qHBsAg), hepatitis B RNA (HBV RNA) and core-related antigen (HBcrAg), and shown promise in a range of clinical settings. AIMS To critically appraise these novel biomarkers, exploring their potential uses, availability of assays and areas for future development. METHODS We performed a literature search of PubMed, identifying articles published in the field of hepatitis B biomarkers between 2010 and 2022. RESULTS Novel biomarkers such as HBcrAg, HBV RNA and qHBsAg may be useful in predicting treatment outcomes, stratifying the risk of future complications and estimating off-treatment viral reactivation. Furthermore, HBV RNA and HBcrAg titres may accurately reflect cccDNA transcriptional activity, and this is particularly informative in the context of nucleoside analogue therapy. On a cautionary note, most studies have been performed in Caucasian or Asian populations, and methods for detecting HBV RNA lack standardisation. CONCLUSION Novel viral biomarkers have the potential to provide additional insights into the natural history of infection and allow a more bespoke, cost-effective framework of care. However, access remains limited, and further efforts are needed to validate their use in ethnically diverse populations, confirm predictive cut-off values, and establish their role in the era of novel antiviral therapies.
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Affiliation(s)
- James Lok
- Institute of Liver Studies, King's College Hospital, London, UK
| | | | - Ivana Carey
- Institute of Liver Studies, King's College Hospital, London, UK
| | - Kosh Agarwal
- Institute of Liver Studies, King's College Hospital, London, UK
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3
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Feng T, Zhang J, Chen Z, Pan W, Chen Z, Yan Y, Dai J. Glycosylation of viral proteins: Implication in virus-host interaction and virulence. Virulence 2022; 13:670-683. [PMID: 35436420 PMCID: PMC9037552 DOI: 10.1080/21505594.2022.2060464] [Citation(s) in RCA: 34] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Glycans are among the most important cell molecular components. However, given their structural diversity, their functions have not been fully explored. Glycosylation is a vital post-translational modification for various proteins. Many bacteria and viruses rely on N-linked and O-linked glycosylation to perform critical biological functions. The diverse functions of glycosylation on viral proteins during viral infections, including Dengue, Zika, influenza, and human immunodeficiency viruses as well as coronaviruses have been reported. N-linked glycosylation is the most common form of protein modification, and it modulates folding, transportation and receptor binding. Compared to N-linked glycosylation, the functions of O-linked viral protein glycosylation have not been comprehensively evaluated. In this review, we summarize findings on viral protein glycosylation, with particular attention to studies on N-linked glycosylation in viral life cycles. This review informs the development of virus-specific vaccines or inhibitors.
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Affiliation(s)
- Tingting Feng
- Jiangsu Key Laboratory of Infection and Immunity, Institute of Biology and Medical Sciences, Soochow University, Suzhou, China
| | - Jinyu Zhang
- Jiangsu Key Laboratory of Infection and Immunity, Institute of Biology and Medical Sciences, Soochow University, Suzhou, China
| | - Zhiqian Chen
- Jiangsu Key Laboratory of Infection and Immunity, Institute of Biology and Medical Sciences, Soochow University, Suzhou, China
| | - Wen Pan
- Jiangsu Key Laboratory of Infection and Immunity, Institute of Biology and Medical Sciences, Soochow University, Suzhou, China
| | - Zhengrong Chen
- Department of Respiratory Medicine, Children's Hospital of Soochow University, Soochow University, Suzhou, China
| | - Yongdong Yan
- Department of Respiratory Medicine, Children's Hospital of Soochow University, Soochow University, Suzhou, China
| | - Jianfeng Dai
- Jiangsu Key Laboratory of Infection and Immunity, Institute of Biology and Medical Sciences, Soochow University, Suzhou, China
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4
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Abstract
Hepatitis B virus (HBV) is a hepatotropic virus and an important human pathogen. There are an estimated 296 million people in the world that are chronically infected by this virus, and many of them will develop severe liver diseases including hepatitis, cirrhosis and hepatocellular carcinoma (HCC). HBV is a small DNA virus that replicates via the reverse transcription pathway. In this review, we summarize the molecular pathways that govern the replication of HBV and its interactions with host cells. We also discuss viral and non-viral factors that are associated with HBV-induced carcinogenesis and pathogenesis, as well as the role of host immune responses in HBV persistence and liver pathogenesis.
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Affiliation(s)
- Yu-Chen Chuang
- Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
| | - Kuen-Nan Tsai
- Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
| | - Jing-Hsiung James Ou
- Department of Molecular Microbiology and Immunology, University of Southern California Keck School of Medicine, Los Angeles, CA 90089, USA
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5
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Pfefferkorn M, Schott T, Böhm S, Deichsel D, Felkel C, Gerlich WH, Glebe D, Wat C, Pavlovic V, Heyne R, Berg T, van Bömmel F. Composition of HBsAg is predictive of HBsAg loss during treatment in patients with HBeAg-positive chronic hepatitis B. J Hepatol 2021; 74:283-292. [PMID: 32931877 DOI: 10.1016/j.jhep.2020.08.039] [Citation(s) in RCA: 34] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/03/2020] [Revised: 07/27/2020] [Accepted: 08/27/2020] [Indexed: 12/18/2022]
Abstract
BACKGROUND & AIMS During treatment of chronic HBV infections, loss or seroconversion of the HBV surface antigen (HBsAg) is considered a functional cure. HBsAg consists of the large (LHBs), middle (MHBs), and small surface protein (SHBs) and their relative proportions correlate strongly with disease stage. Our aim was to assess the association between HBsAg composition and functional cure during treatment. METHODS A total of 83 patients were retrospectively analyzed. HBsAg loss was achieved by 17/64 patients during nucleos(t)ide analogue (NA) treatment and 3/19 patients following treatment with pegylated interferon-alfa2a (PEG-IFN) for 48 weeks. Sixty-three patients without HBsAg loss were matched as controls. LHBs, MHBs and SHBs were quantified in sera collected before and during treatment. RESULTS Before treatment, median MHBs levels were significantly lower in patients with subsequent HBsAg loss than in those without (p = 0.005). During treatment, MHBs and LHBs proportions showed a fast decline in patients with HBsAg loss, but not in patients with HBV e antigen seroconversion only or patients without serologic response. MHBs became undetectable by month 6 of NA treatment in all patients with HBsAg loss, which occurred on average 12.8 ± 8.7 (0-52) months before loss of total HBsAg. Receiver-operating characteristic analyses revealed that the proportion of MHBs was the best early predictor of HBsAg loss before NA treatment (AUC = 0.726, p = 0.019). In patients achieving HBsAg loss with PEG-IFN, the proportions of MHBs and LHBs showed similar kinetics. CONCLUSION Quantification of HBsAg proteins shows promise as a novel tool to predict early treatment response. These assessments may help optimize individual antiviral treatment, increasing the rates of functional cure in chronically HBV-infected patients. LAY SUMMARY The hepatitis B surface antigen (HBsAg) is a key serum marker for viral replication. Loss of HBsAg is considered stable remission, which can be achieved with antiviral treatments. We have investigated whether the ratios of the different components of HBsAg, namely the large (LHBs) and medium (MHBs) HBsAg during different treatments are associated with the occurrence of HBsAg loss. We found that LHBs and MHBs decrease earlier than total HBsAg before HBsAg loss and we propose LHBs and MHBs as promising novel biomarker candidates for predicting cure of HBV infection.
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Affiliation(s)
- Maria Pfefferkorn
- Division of Hepatology, Department of Medicine II, Leipzig University Medical Center, Leipzig, Germany
| | - Tina Schott
- Division of Hepatology, Department of Medicine II, Leipzig University Medical Center, Leipzig, Germany
| | - Stephan Böhm
- Ludwig Maximilians-University, Max von Pettenkofer-Institute for Hygiene and Clinical Microbiology, Munich, Germany
| | - Danilo Deichsel
- Division of Hepatology, Department of Medicine II, Leipzig University Medical Center, Leipzig, Germany
| | - Christin Felkel
- Division of Hepatology, Department of Medicine II, Leipzig University Medical Center, Leipzig, Germany
| | - Wolfram H Gerlich
- Justus Liebig University Giessen, National Reference Centre for Hepatitis B Viruses and Hepatitis D Viruses, Institute of Medical Virology, Giessen, Germany, German Centre for Infection Research (DZIF)
| | - Dieter Glebe
- Justus Liebig University Giessen, National Reference Centre for Hepatitis B Viruses and Hepatitis D Viruses, Institute of Medical Virology, Giessen, Germany, German Centre for Infection Research (DZIF)
| | | | | | - Renate Heyne
- Liver and Study Center Checkpoint, Berlin, Germany
| | - Thomas Berg
- Division of Hepatology, Department of Medicine II, Leipzig University Medical Center, Leipzig, Germany
| | - Florian van Bömmel
- Division of Hepatology, Department of Medicine II, Leipzig University Medical Center, Leipzig, Germany.
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6
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Intracellular Trafficking of HBV Particles. Cells 2020; 9:cells9092023. [PMID: 32887393 PMCID: PMC7563130 DOI: 10.3390/cells9092023] [Citation(s) in RCA: 45] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2020] [Revised: 08/31/2020] [Accepted: 09/02/2020] [Indexed: 12/15/2022] Open
Abstract
The human hepatitis B virus (HBV), that is causative for more than 240 million cases of chronic liver inflammation (hepatitis), is an enveloped virus with a partially double-stranded DNA genome. After virion uptake by receptor-mediated endocytosis, the viral nucleocapsid is transported towards the nuclear pore complex. In the nuclear basket, the nucleocapsid disassembles. The viral genome that is covalently linked to the viral polymerase, which harbors a bipartite NLS, is imported into the nucleus. Here, the partially double-stranded DNA genome is converted in a minichromosome-like structure, the covalently closed circular DNA (cccDNA). The DNA virus HBV replicates via a pregenomic RNA (pgRNA)-intermediate that is reverse transcribed into DNA. HBV-infected cells release apart from the infectious viral parrticle two forms of non-infectious subviral particles (spheres and filaments), which are assembled by the surface proteins but lack any capsid and nucleic acid. In addition, naked capsids are released by HBV replicating cells. Infectious viral particles and filaments are released via multivesicular bodies; spheres are secreted by the classic constitutive secretory pathway. The release of naked capsids is still not fully understood, autophagosomal processes are discussed. This review describes intracellular trafficking pathways involved in virus entry, morphogenesis and release of (sub)viral particles.
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7
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Jiang B, Wen X, Wu Q, Bender D, Carra G, Basic M, Kubesch A, Peiffer KH, Boller K, Hildt E. The N-Terminus Makes the Difference: Impact of Genotype-Specific Disparities in the N-Terminal Part of The Hepatitis B Virus Large Surface Protein on Morphogenesis of Viral and Subviral Particles. Cells 2020; 9:cells9081898. [PMID: 32823751 PMCID: PMC7463600 DOI: 10.3390/cells9081898] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2020] [Revised: 07/27/2020] [Accepted: 08/11/2020] [Indexed: 12/12/2022] Open
Abstract
The N-terminus of the hepatitis B virus (HBV) large surface protein (LHB) differs with respect to genotypes. Compared to the amino terminus of genotype (Gt)D, in GtA, GtB and GtC, an additional identical 11 amino acids (aa) are found, while GtE and GtG share another similar 10 aa. Variants of GtB and GtC affecting this N-terminal part are associated with hepatoma formation. Deletion of these amino-terminal 11 aa in GtA reduces the amount of LHBs and changes subcellular accumulation (GtA-like pattern) to a dispersed distribution (GtD-like pattern). Vice versa, the fusion of the GtA-derived N-terminal 11 aa to GtD causes a GtA-like phenotype. However, insertion of the corresponding GtE-derived 10 aa to GtD has no effect. Deletion of these 11aa decreases filament size while neither the number of released viral genomes nor virion size and infectivity are affected. A negative regulatory element (aa 2–8) and a dominant positive regulatory element (aa 9–11) affecting the amount of LHBs were identified. The fusion of this motif to eGFP revealed that the effect on protein amount and subcellular distribution is not restricted to LHBs. These data identify a novel region in the N-terminus of LHBs affecting the amount and subcellular distribution of LHBs and identify release-promoting and -inhibiting aa residues within this motive.
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Affiliation(s)
- Bingfu Jiang
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
| | - Xingjian Wen
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
| | - Qingyan Wu
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
| | - Daniela Bender
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
| | - Gert Carra
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
| | - Michael Basic
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
- Department of Gastroenterology and Hepatology, J. W. Goethe University, D-60590 Frankfurt, Germany
| | - Alica Kubesch
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
- Department of Gastroenterology and Hepatology, J. W. Goethe University, D-60590 Frankfurt, Germany
| | - Kai-Henrik Peiffer
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
- Department of Gastroenterology and Hepatology, J. W. Goethe University, D-60590 Frankfurt, Germany
| | - Klaus Boller
- Department of Immunology, Paul-Ehrlich-Institut, D-63225 Langen, Germany;
| | - Eberhard Hildt
- Division of Virology, Paul-Ehrlich-Institut, D-63225 Langen, Germany; (B.J.); (X.W.); (Q.W.); (D.B.); (G.C.); (M.B.); (A.K.); (K.-H.P.)
- TTU Hepatitis, German Center for Infection Research (DZIF), 38124 Braunschweig, Germany
- Correspondence: ; Tel.: +496103772140
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8
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Seitz S, Habjanič J, Schütz AK, Bartenschlager R. The Hepatitis B Virus Envelope Proteins: Molecular Gymnastics Throughout the Viral Life Cycle. Annu Rev Virol 2020; 7:263-288. [PMID: 32600157 DOI: 10.1146/annurev-virology-092818-015508] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
New hepatitis B virions released from infected hepatocytes are the result of an intricate maturation process that starts with the formation of the nucleocapsid providing a confined space where the viral DNA genome is synthesized via reverse transcription. Virion assembly is finalized by the enclosure of the icosahedral nucleocapsid within a heterogeneous envelope. The latter contains integral membrane proteins of three sizes, collectively known as hepatitis B surface antigen, and adopts multiple conformations in the course of the viral life cycle. The nucleocapsid conformation depends on the reverse transcription status of the genome, which in turn controls nucleocapsid interaction with the envelope proteins for virus exit. In addition, after secretion the virions undergo a distinct maturation step during which a topological switch of the large envelope protein confers infectivity. Here we review molecular determinants for envelopment and models that postulate molecular signals encoded in the capsid scaffold conducive or adverse to the recruitment of envelope proteins.
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Affiliation(s)
- Stefan Seitz
- Department of Infectious Diseases, University of Heidelberg, 69120 Heidelberg, Germany;
| | - Jelena Habjanič
- Bavarian NMR Center, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Anne K Schütz
- Bavarian NMR Center, Department of Chemistry, Technical University of Munich, 85748 Garching, Germany.,Institute of Structural Biology, Helmholtz Zentrum München, 85764 Neuherberg, Germany
| | - Ralf Bartenschlager
- Department of Infectious Diseases, University of Heidelberg, 69120 Heidelberg, Germany; .,Division of Virus-Associated Carcinogenesis, German Cancer Research Center (DKFZ), 69120 Heidelberg, Germany
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9
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N-Glycosylation and N-Glycan Processing in HBV Biology and Pathogenesis. Cells 2020; 9:cells9061404. [PMID: 32512942 PMCID: PMC7349502 DOI: 10.3390/cells9061404] [Citation(s) in RCA: 24] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2020] [Revised: 05/29/2020] [Accepted: 06/03/2020] [Indexed: 12/17/2022] Open
Abstract
Hepatitis B Virus (HBV) glycobiology has been an area of intensive research in the last decades and continues to be an attractive topic due to the multiple roles that N-glycosylation in particular plays in the virus life-cycle and its interaction with the host that are still being discovered. The three HBV envelope glycoproteins, small (S), medium (M) and large (L) share a very peculiar N-glycosylation pattern, which distinctly regulates their folding, degradation, assembly, intracellular trafficking and antigenic properties. In addition, recent findings indicate important roles of N-linked oligosaccharides in viral pathogenesis and evasion of the immune system surveillance. This review focuses on N-glycosylation’s contribution to HBV infection and disease, with implications for development of improved vaccines and antiviral therapies.
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10
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Aviner R, Frydman J. Proteostasis in Viral Infection: Unfolding the Complex Virus-Chaperone Interplay. Cold Spring Harb Perspect Biol 2020; 12:cshperspect.a034090. [PMID: 30858229 DOI: 10.1101/cshperspect.a034090] [Citation(s) in RCA: 31] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Viruses are obligate intracellular parasites that rely on their hosts for protein synthesis, genome replication, and viral particle production. As such, they have evolved mechanisms to divert host resources, including molecular chaperones, facilitate folding and assembly of viral proteins, stabilize complex structures under constant mutational pressure, and modulate signaling pathways to dampen antiviral responses and prevent premature host death. Biogenesis of viral proteins often presents unique challenges to the proteostasis network, as it requires the rapid and orchestrated production of high levels of a limited number of multifunctional, multidomain, and aggregation-prone proteins. To overcome such challenges, viruses interact with the folding machinery not only as clients but also as regulators of chaperone expression, function, and subcellular localization. In this review, we summarize the main types of interactions between viral proteins and chaperones during infection, examine evolutionary aspects of this relationship, and discuss the potential of using chaperone inhibitors as broad-spectrum antivirals.
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Affiliation(s)
- Ranen Aviner
- Department of Biology, Stanford University, Stanford, California 94305
| | - Judith Frydman
- Department of Biology, Stanford University, Stanford, California 94305.,Department of Genetics, Stanford University, Stanford, California 94305
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11
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Ho JKT, Jeevan-Raj B, Netter HJ. Hepatitis B Virus (HBV) Subviral Particles as Protective Vaccines and Vaccine Platforms. Viruses 2020; 12:v12020126. [PMID: 31973017 PMCID: PMC7077199 DOI: 10.3390/v12020126] [Citation(s) in RCA: 56] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2019] [Revised: 01/13/2020] [Accepted: 01/13/2020] [Indexed: 12/15/2022] Open
Abstract
Hepatitis B remains one of the major global health problems more than 40 years after the identification of human hepatitis B virus (HBV) as the causative agent. A critical turning point in combating this virus was the development of a preventative vaccine composed of the HBV surface (envelope) protein (HBsAg) to reduce the risk of new infections. The isolation of HBsAg sub-viral particles (SVPs) from the blood of asymptomatic HBV carriers as antigens for the first-generation vaccines, followed by the development of recombinant HBsAg SVPs produced in yeast as the antigenic components of the second-generation vaccines, represent landmark advancements in biotechnology and medicine. The ability of the HBsAg SVPs to accept and present foreign antigenic sequences provides the basis of a chimeric particulate delivery platform, and resulted in the development of a vaccine against malaria (RTS,S/AS01, MosquirixTM), and various preclinical vaccine candidates to overcome infectious diseases for which there are no effective vaccines. Biomedical modifications of the HBsAg subunits allowed the identification of strategies to enhance the HBsAg SVP immunogenicity to build potent vaccines for preventative and possibly therapeutic applications. The review provides an overview of the formation and assembly of the HBsAg SVPs and highlights the utilization of the particles in key effective vaccines.
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Affiliation(s)
- Joan Kha-Tu Ho
- Victorian Infectious Diseases Reference Laboratory (VIDRL), Melbourne Health, The Peter Doherty Institute, Melbourne, Victoria 3000, Australia; (J.K.-T.H.); (B.J.-R.)
| | - Beena Jeevan-Raj
- Victorian Infectious Diseases Reference Laboratory (VIDRL), Melbourne Health, The Peter Doherty Institute, Melbourne, Victoria 3000, Australia; (J.K.-T.H.); (B.J.-R.)
| | - Hans-Jürgen Netter
- Victorian Infectious Diseases Reference Laboratory (VIDRL), Melbourne Health, The Peter Doherty Institute, Melbourne, Victoria 3000, Australia; (J.K.-T.H.); (B.J.-R.)
- Royal Melbourne Institute of Technology (RMIT) University, School of Science, Melbourne, Victoria 3001, Australia
- Correspondence:
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12
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Jiang B, Wu Q, Kuhnhenn L, Akhras S, Spengler C, Boller K, Peiffer KH, Hildt E. Formation of semi-enveloped particles as a unique feature of a hepatitis B virus PreS1 deletion mutant. Aliment Pharmacol Ther 2019; 50:940-954. [PMID: 31240738 DOI: 10.1111/apt.15381] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/24/2019] [Revised: 04/29/2019] [Accepted: 05/29/2019] [Indexed: 12/12/2022]
Abstract
BACKGROUND Naturally occurring variants with deletions or mutations in the C-terminal PreS1 domain from hepatitis B virus (HBV) chronically infected patients have been shown to promote HBsAg retention, inhibit HBsAg secretion and change the extracellular appearance of PreS1-containing HBV particles (filaments and virions). AIMS To study the impact of N-terminal deletion in preS1 domain on viral secretion and morphogenesis. METHODS An HBV mutant with 15 amino acids (aa 25-39) deletion in N-terminal preS1 was isolated. Intracellular and extracellular HBsAg were quantified by Western blot. Subcellular HBsAg distribution was analysed by confocal laser scanning microscopy. The viral morphology was characterised by sucrose density gradient ultracentrifugation, Western blot, electron microscopy, HBV mixed ELISA and HBV particle gel essay. RESULTS Expression of this mutant genome released higher amounts of HBsAg in the form of shorter filaments. A significant fraction of semi-enveloped virions was observed in the supernatant that has been unprecedented so far. Stepwise insertion of aa 25-31, aa 32-39 and aa 25-39 increased the length of filaments. The rescue of aa 25-31 and aa 25-39 drastically reduced the amounts of extracellular HBsAg and semi-enveloped virions, while such effects could not be observed after insertion of aa 32-39, arguing against a simple spacer function of this region. The deletion and rescued mutants do not differ in subcellular HBsAg distribution and colocalisation with ER, Golgi and multivesicular bodies markers arguing against differences in release pathways. CONCLUSION N-terminal PreS1-domain (aa 25-31) determines HBsAg secretion and triggers proper assembly of PreS1-containing particles.
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Affiliation(s)
- Bingfu Jiang
- Division of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | - Qingyan Wu
- Division of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | - Lisa Kuhnhenn
- Division of Virology, Paul-Ehrlich-Institut, Langen, Germany.,Department of Gastroenterology and Hepatology, J. W. Goethe University, Frankfurt, Germany
| | - Sami Akhras
- Division of Virology, Paul-Ehrlich-Institut, Langen, Germany
| | | | - Klaus Boller
- Department of Immunology, Paul-Ehrlich-Institut, Langen, Germany
| | - Kai-Henrik Peiffer
- Division of Virology, Paul-Ehrlich-Institut, Langen, Germany.,Department of Gastroenterology and Hepatology, J. W. Goethe University, Frankfurt, Germany
| | - Eberhard Hildt
- Division of Virology, Paul-Ehrlich-Institut, Langen, Germany.,German Center for Infection Research (DZIF), Germany
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13
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Liu K, Hu J. Secretion of empty or complete hepatitis B virions: envelopment of empty capsids versus mature nucleocapsids. Future Virol 2019. [DOI: 10.2217/fvl-2018-0128] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
HBV replicates its DNA genome, a partially double-stranded, relaxed circular DNA, via reverse transcription of an RNA intermediate called pre-genomic RNA by its reverse transcriptase. A major characteristic of HBV replication is the selective envelopment and secretion of relaxed circular DNA-containing mature capsids and empty capsids with no DNA or RNA, but not those containing pre-genomic RNA or the single-stranded DNA replication intermediate. In this review, the potential mechanisms of HBV virion morphogenesis will be discussed, with a focus on key determinants of both the capsid and envelope proteins for the selective secretion of complete and empty virions.
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Affiliation(s)
- Kuancheng Liu
- Department of Biochemistry & Molecular Biology, College of Life Sciences, Zhejiang Sci-Tech University, Hangzhou, 310018 China
| | - Jianming Hu
- Department of Microbiology & Immunology, Penn State University College of Medicine, Hershey, PA 17033, USA
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14
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Common and Distinct Capsid and Surface Protein Requirements for Secretion of Complete and Genome-Free Hepatitis B Virions. J Virol 2018; 92:JVI.00272-18. [PMID: 29743374 DOI: 10.1128/jvi.00272-18] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2018] [Accepted: 05/04/2018] [Indexed: 02/06/2023] Open
Abstract
During the morphogenesis of hepatitis B virus (HBV), an enveloped virus, two types of virions are secreted: (i) a minor population of complete virions containing a mature nucleocapsid with the characteristic, partially double-stranded, relaxed circular DNA genome and (ii) a major population containing an empty capsid with no DNA or RNA (empty virions). Secretion of both types of virions requires interactions between the HBV capsid or core protein (HBc) and the viral surface or envelope proteins. We have studied the requirements from both HBc and envelope proteins for empty virion secretion in comparison with those for secretion of complete virions. Substitutions within the N-terminal domain of HBc that block secretion of DNA-containing virions reduced but did not prevent secretion of empty virions. The HBc C-terminal domain was not essential for empty virion secretion. Among the three viral envelope proteins, the smallest, S, alone was sufficient for empty virion secretion at a basal level. The largest protein, L, essential for complete virion secretion, was not required but could stimulate empty virion secretion. Also, substitutions in L that eliminated secretion of complete virions reduced but did not eliminate empty virion secretion. S mutations that blocked secretion of the hepatitis D virus (HDV), an HBV satellite, did not block secretion of either empty or complete HBV virions. Together, these results indicate that both common and distinct signals on empty capsids and mature nucleocapsids interact with the S and L proteins during the formation of complete and empty virions.IMPORTANCE Hepatitis B virus (HBV) is a major cause of severe liver diseases, including cirrhosis and cancer. In addition to the complete infectious virion particle, which contains an outer envelope layer and an interior capsid that, in turn, encloses a DNA genome, HBV-infected cells also secrete noninfectious, incomplete viral particles in large excess over the number of complete virions. In particular, the empty (or genome-free) virion shares with the complete virion the outer envelope and interior capsid but contains no genome. We have carried out a comparative study on the capsid and envelope requirements for the secretion of these two types of virion particles and uncovered both shared and distinct determinants on the capsid and envelope for their secretion. These results provide new information on HBV morphogenesis and have implications for efforts to develop empty HBV virions as novel biomarkers and a new generation of HBV vaccine.
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15
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Zhao K, Wu C, Yao Y, Cao L, Zhang Z, Yuan Y, Wang Y, Pei R, Chen J, Hu X, Zhou Y, Lu M, Chen X. Ceruloplasmin inhibits the production of extracellular hepatitis B virions by targeting its middle surface protein. J Gen Virol 2017; 98:1410-1421. [PMID: 28678687 DOI: 10.1099/jgv.0.000794] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Ceruloplasmin (CP) is mainly synthesized by hepatocytes and plays an essential role in iron metabolism. Previous reports have shown that CP levels correlate negatively with disease progression in patients with chronic hepatitis B. However, the function of CP in the hepatitis B virus (HBV) life cycle and the mechanism underlying the above correlation remain unclear. Here, we report that CP can selectively inhibit the production of extracellular HBV virions without altering intracellular viral replication. HBV expression can also downregulate the expression of CP. Knockdown of CP using small interfering RNA significantly increased the level of extracellular HBV virions in both Huh7 and HepG2.2.15 cells, while overexpression of CP decreased this level. Mechanistically, CP could specifically interact with the HBV middle surface protein (MHB). Using an HBV replication-competent clone unable to express MHBs, we demonstrated that the overexpression of CP did not affect the production of extracellular HBV virions in the absence of MHBs. Furthermore, introduction of an MHB expression construct could rescue the impairment in virion production caused by CP. Taken together, our results suggest that CP may be an important host factor that targets MHBs during the envelopment and/or release of virions.
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Affiliation(s)
- Kaitao Zhao
- University of Chinese Academy of Sciences, Beijing, PR China.,State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Chunchen Wu
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Yongxuan Yao
- University of Chinese Academy of Sciences, Beijing, PR China.,State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Liang Cao
- University of Chinese Academy of Sciences, Beijing, PR China.,State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Zhenhua Zhang
- School of Pharmacy, Anhui Medical University, Hefei 230022, PR China.,Department of Infectious Diseases, The First Affiliated Hospital, Anhui Medical University, Hefei 230022, PR China
| | - Yifei Yuan
- University of Chinese Academy of Sciences, Beijing, PR China.,State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Yun Wang
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Rongjuan Pei
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Jizheng Chen
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Xue Hu
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Yuan Zhou
- State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Mengji Lu
- Institute of Virology, University Hospital of Essen, Essen, Germany.,State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
| | - Xinwen Chen
- University of Chinese Academy of Sciences, Beijing, PR China.,State Key Lab of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, PR China
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16
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Watashi K. HBV Slow Maturation Process Leads to Infection. Trends Microbiol 2016; 24:597-599. [PMID: 27345260 DOI: 10.1016/j.tim.2016.06.007] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2016] [Accepted: 06/16/2016] [Indexed: 11/29/2022]
Abstract
Initial hepatitis B virus (HBV) attachment occurs via heparan sulfate proteoglycans (HSPGs), which then trigger receptor-mediated internalization. Although HSPGs express in many tissues, HBV is destined for hepatotropic infection. A recent paper by Seitz et al. proposed that the slow viral maturation process plays a critical role in liver-specific distribution.
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Affiliation(s)
- Koichi Watashi
- Department of Virology II, National Institute of Infectious Diseases, Tokyo, Japan; Department of Applied Biological Science, Tokyo University of Science, Noda, Japan; CREST, JST, Saitama, Japan.
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17
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Peiffer KH, Akhras S, Himmelsbach K, Hassemer M, Finkernagel M, Carra G, Nuebling M, Chudy M, Niekamp H, Glebe D, Sarrazin C, Zeuzem S, Hildt E. Intracellular accumulation of subviral HBsAg particles and diminished Nrf2 activation in HBV genotype G expressing cells lead to an increased ROI level. J Hepatol 2015; 62:791-8. [PMID: 25445396 DOI: 10.1016/j.jhep.2014.11.028] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 10/06/2014] [Accepted: 11/23/2014] [Indexed: 12/15/2022]
Abstract
BACKGROUND & AIMS Hepatitis B virus genotype G (HBV/G) is characterized by a lack of HBeAg secretion and very low HBsAg secretion. This study aimed at (1) comparing HBV genotype G and A2 with respect to morphogenesis and release of HBV-derived particles, (2) characterizing factors contributing to HBV/G-associated pathogenesis. METHODS HBV/G- and HBV/A-expressing hepatoma cells and infected HepaRG cells were analyzed by confocal laser scanning microscopy, Western blot, real-time PCR, density gradient centrifugation, and electron microscopy. Modulation of the transcription factors Nrf2 and AP-1 was analyzed. RESULTS While the release of viral particles is not affected in HBV/G replicating cells, the secretion of subviral particles is impaired, although they are produced in high amounts. These subviral particles, which display an increased density and a predominantly filamentous morphology, accumulate at the endoplasmic reticulum. The PreS1PreS2 domain of genotype G, which forms aggregates, causes the block of HBsAg-secretion at the ER and leads to decreased transcriptional activator function of LHBs. Intracellular accumulation of HBsAg and impaired induction of the cytoprotective transcription factor Nrf2 lead to an elevated level of ROIs. This results in activation of JNK and as a consequence in Ser-phosphorylation of IRS-1, which is known to impair insulin signaling, a key factor for liver regeneration. CONCLUSIONS Although competent for release of viral particles, secretion of subviral particles is impaired in HBV/G expressing cells leading to ER-stress. In parallel, HBV-induced Nrf2 activation diminishes, which causes a decrease of the capacity to inactivate ROIs. This might be related to genotype-specific pathogenesis.
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Affiliation(s)
- Kai-Henrik Peiffer
- Goethe-University Hospital Frankfurt, Department of Gastroenterology and Hepatology, D-60590 Frankfurt am Main, Germany; Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany.
| | - Sami Akhras
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany
| | | | - Matthias Hassemer
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany
| | - Malin Finkernagel
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany
| | - Gert Carra
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany
| | - Michael Nuebling
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany
| | - Michael Chudy
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany
| | - Hauke Niekamp
- Justus-Liebig University, Institute of Medical Virology, National Reference Centre for Hepatitis B and D Viruses, D-35392 Giessen, Germany; DZIF, German Center for Infection Research, Germany
| | - Dieter Glebe
- Justus-Liebig University, Institute of Medical Virology, National Reference Centre for Hepatitis B and D Viruses, D-35392 Giessen, Germany; DZIF, German Center for Infection Research, Germany
| | - Christoph Sarrazin
- Goethe-University Hospital Frankfurt, Department of Gastroenterology and Hepatology, D-60590 Frankfurt am Main, Germany
| | - Stefan Zeuzem
- Goethe-University Hospital Frankfurt, Department of Gastroenterology and Hepatology, D-60590 Frankfurt am Main, Germany
| | - Eberhard Hildt
- Paul Ehrlich Institut, Division of Virology, D-63325 Langen, Germany; DZIF, German Center for Infection Research, Germany.
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18
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Hu Z, Li M, Liu J, Yu L, Xue Y, Chen Y. Detection of Hepatitis B Virus Large Surface Protein Using a Time-Resolved Immunofluorometric Assay. J Clin Lab Anal 2014; 29:498-504. [PMID: 25277704 DOI: 10.1002/jcla.21800] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Revised: 06/17/2014] [Accepted: 08/07/2014] [Indexed: 01/28/2023] Open
Abstract
BACKGROUND To establish a novel method based on time-resolved immunofluorometric assay (TR-IFMA) with higher sensitivity and a broader detection range for detecting serum hepatitis B virus large surface protein (L protein). METHODS The precision, sensitivity, specificity, coefficient of recovery, and stability of the assay were evaluated and comparison with the classical enzyme-linked immunosorbent assay (ELISA) was also executed. RESULTS The precision, specificity, and sensitivity of the TR-IFMA were clearly better than ELISA. Particularly, the sensitivity was 0.1 ng/ml; moreover, the specificity was 100%, 96%, 92.5%, 96.9%, 97.8%, and 100% in the sera of healthy blood donors, systemic lupus erythematosus (SLE) patients, rheumatoid arthritis (RA) patients, hepatitis C virus (HCV) patients, cytomegalovirus (CMV) infection patients, and pregnant patients, respectively. Meanwhile, we observed that the established TR-IFMA kit has a wider acceptable linear range of 0.63-10,367 ng/ml rather than the regular commercial ELISA kit having range of only 10.12-1095.9 ng/ml. Subsequently, correlation coefficient between the TR-IFMA and ELISA was 0.8009. The intra- and interassay precision rates were less than 5% for three different concentrations. The average recovery rate for L protein was 101.17%. In sum, the established assay kit performed better in terms of stability than the commercial ELISA kit. CONCLUSION The TR-IFMA that we developed for L protein presented a higher sensitivity and wider detecting range than regular commercial ELISA. Therefore, this TR-IFMA has promising value both in the screening of HBV and monitoring of antiviral therapy.
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Affiliation(s)
- Zhigang Hu
- Department of Laboratory Medicine, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China.,Department of Laboratory Medicine, Affiliated Wuxi people's Hospital of Nanjing Medical University, Wuxi, China
| | - Mei Li
- Department of Laboratory Medicine, Affiliated Wuxi people's Hospital of Nanjing Medical University, Wuxi, China
| | - Jie Liu
- Department of Laboratory Medicine, Affiliated Wuxi people's Hospital of Nanjing Medical University, Wuxi, China
| | - Lei Yu
- Department of Laboratory Medicine, Affiliated Wuxi people's Hospital of Nanjing Medical University, Wuxi, China
| | - Yifeng Xue
- Department of Laboratory Medicine, Affiliated Wuxi people's Hospital of Nanjing Medical University, Wuxi, China
| | - Yu Chen
- Department of Laboratory Medicine, The First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, China
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19
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Endmann A, Klünder K, Kapp K, Riede O, Oswald D, Talman EG, Schroff M, Kleuss C, Ruiters MHJ, Juhls C. Cationic lipid-formulated DNA vaccine against hepatitis B virus: immunogenicity of MIDGE-Th1 vectors encoding small and large surface antigen in comparison to a licensed protein vaccine. PLoS One 2014; 9:e101715. [PMID: 24992038 PMCID: PMC4081723 DOI: 10.1371/journal.pone.0101715] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2014] [Accepted: 06/11/2014] [Indexed: 12/19/2022] Open
Abstract
Currently marketed vaccines against hepatitis B virus (HBV) based on the small (S) hepatitis B surface antigen (HBsAg) fail to induce a protective immune response in about 10% of vaccinees. DNA vaccination and the inclusion of PreS1 and PreS2 domains of HBsAg have been reported to represent feasible strategies to improve the efficacy of HBV vaccines. Here, we evaluated the immunogenicity of SAINT-18-formulated MIDGE-Th1 vectors encoding the S or the large (L) protein of HBsAg in mice and pigs. In both animal models, vectors encoding the secretion-competent S protein induced stronger humoral responses than vectors encoding the L protein, which was shown to be retained mainly intracellularly despite the presence of a heterologous secretion signal. In pigs, SAINT-18-formulated MIDGE-Th1 vectors encoding the S protein elicited an immune response of the same magnitude as the licensed protein vaccine Engerix-B, with S protein-specific antibody levels significantly higher than those considered protective in humans, and lasting for at least six months after the third immunization. Thus, our results provide not only the proof of concept for the SAINT-18-formulated MIDGE-Th1 vector approach but also confirm that with a cationic-lipid formulation, a DNA vaccine at a relatively low dose can elicit an immune response similar to a human dose of an aluminum hydroxide-adjuvanted protein vaccine in large animals.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Marcel H. J. Ruiters
- Synvolux Therapeutics B.V., Groningen, The Netherlands
- Department of Pathology and Medical Biology, University of Groningen, Groningen, The Netherlands
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20
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Schittl B, Bruss V. Mutational profiling of the variability of individual amino acid positions in the hepatitis B virus matrix domain. Virology 2014; 458-459:183-9. [PMID: 24928050 DOI: 10.1016/j.virol.2014.04.030] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2014] [Revised: 02/12/2014] [Accepted: 04/22/2014] [Indexed: 01/20/2023]
Abstract
The hepatitis B virus (HBV) is formed by budding. A stretch of 22 amino acids (aa) (matrix domain, MD, R103 - S124) in the large envelope protein L is crucial for virion formation and probably establishes contact to the nucleocapsid. Here, we assess the impact of sequence variations at numerous individual aa positions within the MD on virion formation. We generated panels of L mutants covering all 19 possible aa for 11 positions and tested the capacity of these mutants to rescue virus production by an L-defective HBV genome. At four positions (L112, R113, P117, W122), any replacement of the wild type (WT) aa reduced virus assembly to undetectable levels. Virus production was strongly diminished by substitutions at five other positions (R103, T106, S115, H116, A119). Only two tested positions (D114, Q118) tolerated several substitutions. The restricted positions may represent promising targets for the development of novel antiviral strategies.
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Affiliation(s)
- Beate Schittl
- Institute of Virology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany
| | - Volker Bruss
- Institute of Virology, Helmholtz Zentrum München, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
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21
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Roose K, De Baets S, Schepens B, Saelens X. Hepatitis B core-based virus-like particles to present heterologous epitopes. Expert Rev Vaccines 2013; 12:183-98. [PMID: 23414409 DOI: 10.1586/erv.12.150] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Since the first effort to recombinantly express the hepatitis B core protein (HBc) in bacteria, the remarkable virion-like structure has fuelled interest in unraveling the structural and antigenic properties of this protein. Initial studies proved HBc virus-like particles to possess strong immunogenic properties, which can be conveyed to linked antigens. More than 35 years later, numerous studies have been performed using HBc as a carrier protein for antigens derived from over a dozen different pathogens and diseases. In this review, the authors highlight the intriguing features of HBc as carrier and antigen, illustrated by some examples and experimental results that underscore the value of HBc as an antigen-presenting platform. Two of these HBc fusions, targeting influenza A and malaria, have even progressed into clinical testing. In the future, the HBc-based virus-like particles platform will probably continue to be used for the display of poorly immunogenic antigens, mainly because virus-like particle formation by HBc capsomers is compatible with nearly any available recombinant gene expression system.
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Affiliation(s)
- Kenny Roose
- Department for Molecular Biomedical Research, VIB, 9052 Ghent, Belgium
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22
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Niedre-Otomere B, Bogdanova A, Bruvere R, Ose V, Gerlich WH, Pumpens P, Glebe D, Kozlovska T. Posttranslational modifications and secretion efficiency of immunogenic hepatitis B virus L protein deletion variants. Virol J 2013; 10:63. [PMID: 23442390 PMCID: PMC3598826 DOI: 10.1186/1743-422x-10-63] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2012] [Accepted: 02/20/2013] [Indexed: 12/23/2022] Open
Abstract
BACKGROUND Subviral particles of hepatitis B virus (HBV) composed of L protein deletion variants with the 48 N-terminal amino acids of preS joined to the N-terminus of S protein (1-48preS/S) induced broadly neutralizing antibodies after immunization of mice with a Semliki Forest virus vector. A practical limitation for use as vaccine is the suboptimal secretion of such particles. The role of the N-terminal preS myristoylation in the cellular retention of full-length L protein is described controversially in the literature and the relation of these data to the truncated L protein was unknown. Thus, we studied the effect of preS myristoylation signal suppression on 1-48preS/S secretion efficiency, glycosylation and subcellular distribution. FINDINGS The findings are that 1-48preS/S is secreted, and that removal of the N-terminal myristoylation signal in its G2A variant reduced secretion slightly, but significantly. The glycosylation pattern of 1-48preS/S was not affected by the removal of the myristoylation signal (G2A mutant) but was different than natural L protein, whereby N4 of the preS and N3 of the S domain were ectopically glycosylated. This suggested cotranslational translocation of 1-48preS in contrast to natural L protein. The 1-48preS/S bearing a myristoylation signal was localized in a compact, perinuclear pattern with strong colocalization of preS and S epitopes, while the non-myristoylated mutants demonstrated a dispersed, granular cytoplasmic distribution with weaker colocalization. CONCLUSIONS The large deletion in 1-48preS/S in presence of the myristoylation site facilitated formation and secretion of protein particles with neutralizing preS1 epitopes at their surface and could be a useful feature for future hepatitis B vaccines.
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23
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Jung HM, Jun DW, Min JY, Doo EY, Nam KW, Kwon YI, Kwon OW. A Case of Acute Hepatitis B by Occult HBV Infection without HbsAg Seroconversion. ACTA ACUST UNITED AC 2012. [DOI: 10.3904/kjm.2012.83.5.619] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- Hye Mi Jung
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
| | - Dae Won Jun
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
| | - Ji Yeon Min
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
| | - Eun Young Doo
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
| | - Kil Woo Nam
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
| | - Young Il Kwon
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
| | - Oh Wan Kwon
- Department of Internal Medicine, Hanyang University School of Medicine, Seoul, Korea
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24
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Cholesterol depletion of hepatoma cells impairs hepatitis B virus envelopment by altering the topology of the large envelope protein. J Virol 2011; 85:13373-83. [PMID: 21994451 DOI: 10.1128/jvi.05423-11] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous reports have shown that cholesterol depletion of the membrane envelope of the hepatitis B virus (HBV) impairs viral infection of target cells. A potential function of this lipid in later steps of the viral life cycle remained controversial, with secretion of virions and subviral particles (SVP) being either inhibited or not affected, depending on the experimental approach employed to decrease the intracellular cholesterol level. This work addressed the role of host cell cholesterol on HBV replication, assembly, and secretion, using an alternative method to inhibition of the enzymes involved in the biosynthesis pathway. Growing HBV-producing cells with lipoprotein-depleted serum (LPDS) resulted in an important reduction of the amount of cholesterol within 24 h of treatment (about 40%). Cell exposure to chlorpromazine, an inhibitor of the clathrin-mediated pathway used by the low-density lipoprotein receptor for endocytosis, also impacted the cholesterol level; however, this level of inhibition was not achievable when the synthesis inhibitor lovastatin was used. HBV secretion was significantly inhibited in cholesterol-depleted cells (by ∼80%), while SVP release remained unaffected. The viral DNA genome accumulated in LPDS-treated cells in a time-dependent manner. Specific immunoprecipitation of nucleocapsids and mature virions revealed an increased amount of naked nucleocapsids, while synthesis of the envelope proteins occurred as normally. Following analysis of the large envelope protein conformation in purified microsomes, we concluded that cholesterol is important in maintaining the dual topology of this polypeptide, which is critical for viral envelopment.
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25
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26
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Occult hepatitis B: clinical implications and treatment decisions. Dig Dis Sci 2010; 55:3328-35. [PMID: 20927592 PMCID: PMC3001399 DOI: 10.1007/s10620-010-1413-0] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/10/2010] [Accepted: 08/26/2010] [Indexed: 01/27/2023]
Abstract
First reported in 1978, occult hepatitis B is a term used to describe the presence of hepatitis B virus (HBV) DNA without hepatitis B surface antigenemia. The prevalence of occult HBV is unclear and depends in part on the sensitivity of the hepatitis B surface antigen (HBsAg) and DNA assays used as well as the prevalence of HBV infection in the study population. The origin of occult HBV also remains in question. Several mechanisms have been hypothesized including mutations in the regulatory regions of the HBV genome, persistence of Ig-bound HBV immune complexes, viral interference, and blockage of free HBsAg secretion. Occult HBV has important clinical implications such as transmission through blood transfusion, reactivation in the setting of immunosuppression, and interference with hepatitis C treatment. To date, there is little data pertaining to the treatment of occult HBV outside of the setting of chemotherapy-induced HBV reactivation.
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27
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Schaedler S, Krause J, Himmelsbach K, Carvajal-Yepes M, Lieder F, Klingel K, Nassal M, Weiss TS, Werner S, Hildt E. Hepatitis B virus induces expression of antioxidant response element-regulated genes by activation of Nrf2. J Biol Chem 2010; 285:41074-86. [PMID: 20956535 DOI: 10.1074/jbc.m110.145862] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
The expression of a variety of cytoprotective genes is regulated by short cis-acting elements in their promoters, called antioxidant response elements (AREs). A central regulator of ARE-mediated gene expression is the NF-E2-related factor 2 (Nrf2). Human hepatitis B virus (HBV) induces a strong activation of Nrf2/ARE-regulated genes in vitro and in vivo. This is triggered by the HBV-regulatory proteins (HBx and LHBs) via c-Raf and MEK. The Nrf2/ARE-mediated induction of cytoprotective genes by HBV results in a better protection of HBV-positive cells against oxidative damage as compared with control cells. Furthermore, there is a significantly increased expression of the Nrf2/ARE-regulated proteasomal subunit PSMB5 in HBV-positive cells that is associated with a decreased level of the immunoproteasome subunit PSMB5i. In accordance with this finding, HBV-positive cells display a higher constitutive proteasome activity and a decreased activity of the immunoproteasome as compared with control cells even after interferon α/γ treatment. The HBV-dependent induction of Nrf2/ARE-regulated genes might ensure survival of the infected cell, shape the immune response to HBV, and thereby promote establishment of the infection.
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Affiliation(s)
- Stephanie Schaedler
- Institute of Infection Medicine, Molecular Medical Virology, University of Kiel, D-24105 Kiel, Germany
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Huang HP, Hsu HY, Chen CL, Ni YH, Wang HY, Tsuei DJ, Chiang CL, Tsai YC, Chen HL, Chang MH. Pre-S2 deletions of hepatitis B virus and hepatocellular carcinoma in children. Pediatr Res 2010; 67:90-4. [PMID: 19816238 DOI: 10.1203/pdr.0b013e3181c1b0b7] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The cause of early oncogenesis in hepatitis B virus (HBV)-related childhood hepatocellular carcinoma (HCC) remains unclear. This study investigated whether pre-S deletion of HBV is related to childhood HCC. By using nested polymerase chain reaction, we compared the pre-S sequence of HBV from sera of children with HCC against control children with similar chronic HBV infection. The HBV in sera of children with HCC had a significantly higher rate of pre-S deletion than that of children with chronic HBV infection (p = 0.008). All except one of the pre-S deletions from the HCC group involved the pre-S2 region, whereas no pre-S2 deletion was found in the chronic HBV group (p = 0.003). There was a trend whereby genotype-C sera had a higher rate of pre-S2 deletion than genotype-B sera (p = 0.11). A multivariate logistic regression model revealed that pre-S deletion was an independent risk factor for HCC in children (odds ratio: 36.69, p = 0.015). In conclusion, pre-S2 deletion does not need to take decades to occur; its presence in nearly half of children with HCC, in contrast to its absence in children with chronic HBV infection, suggests a link between pre-S2 deletion and HCC development in children.
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Affiliation(s)
- Hsiang-Po Huang
- Department of Medical Research, National Taiwan University Hospital, Taipei 100, Taiwan
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29
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The first transmembrane domain of the hepatitis B virus large envelope protein is crucial for infectivity. J Virol 2009; 83:11819-29. [PMID: 19740987 DOI: 10.1128/jvi.01026-09] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The early steps of the hepatitis B virus (HBV) life cycle are still poorly understood. Indeed, neither the virus receptor at the cell surface nor the mechanism by which nucleocapsids are delivered to the cytosol of infected cells has been identified. Extensive mutagenesis studies in pre-S1, pre-S2, and most of the S domain of envelope proteins revealed the presence of two regions essential for HBV infectivity: the 77 first residues of the pre-S1 domain and a conformational motif in the antigenic loop of the S domain. In addition, at the N-terminal extremity of the S domain, a putative fusion peptide, partially overlapping the first transmembrane (TM1) domain and preceded by a PEST sequence likely containing several proteolytic cleavage sites, was identified. Since no mutational analysis of these two motifs potentially implicated in the fusion process was performed, we decided to investigate the ability of viruses bearing contiguous deletions or substitutions in the putative fusion peptide and PEST sequence to infect HepaRG cells. By introducing the mutations either in the L and M proteins or in the S protein, we demonstrated the following: (i) that in the TM1 domain of the L protein, three hydrophobic clusters of four residues were necessary for infectivity; (ii) that the same clusters were critical for S protein expression; and, finally, (iii) that the PEST sequence was dispensable for both assembly and infection processes.
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30
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HBV life cycle: entry and morphogenesis. Viruses 2009; 1:185-209. [PMID: 21994545 PMCID: PMC3185491 DOI: 10.3390/v1020185] [Citation(s) in RCA: 77] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2009] [Revised: 07/31/2009] [Accepted: 08/13/2009] [Indexed: 02/07/2023] Open
Abstract
Hepatitis B virus (HBV) is a major cause of liver disease. HBV primarily infects hepatocytes by a still poorly understood mechanism. After an endocytotic process, the nucleocapsids are released into the cytoplasm and the relaxed circular rcDNA genome is transported towards the nucleus where it is converted into covalently closed circular cccDNA. Replication of the viral genome occurs via an RNA pregenome (pgRNA) that binds to HBV polymerase (P). P initiates pgRNA encapsidation and reverse transcription inside the capsid. Matured, rcDNA containing nucleocapsids can re-deliver the RC-DNA to the nucleus, or be secreted via interaction with the envelope proteins as progeny virions.
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31
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Patient R, Hourioux C, Roingeard P. Morphogenesis of hepatitis B virus and its subviral envelope particles. Cell Microbiol 2009; 11:1561-70. [PMID: 19673892 DOI: 10.1111/j.1462-5822.2009.01363.x] [Citation(s) in RCA: 105] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
After cell hijacking and intracellular amplification, non-lytic enveloped viruses are usually released from the infected cell by budding across internal membranes or through the plasma membrane. The enveloped human hepatitis B virus (HBV) is an example of virus using an intracellular compartment to form new virions. Four decades after its discovery, HBV is still the primary cause of death by cancer due to a viral infection worldwide. Despite numerous studies on HBV genome replication little is known about its morphogenesis process. In addition to viral neogenesis, the HBV envelope proteins have the capability without any other viral component to form empty subviral envelope particles (SVPs), which are secreted into the blood of infected patients. A better knowledge of this process may be critical for future antiviral strategies. Previous studies have speculated that the morphogenesis of HBV and its SVPs occur through the same mechanisms. However, recent data clearly suggest that two different processes, including constitutive Golgi pathway or cellular machinery that generates internal vesicles of multivesicular bodies (MVB), independently form these two viral entities.
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32
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Warner N, Locarnini S. The antiviral drug selected hepatitis B virus rtA181T/sW172* mutant has a dominant negative secretion defect and alters the typical profile of viral rebound. Hepatology 2008; 48:88-98. [PMID: 18537180 DOI: 10.1002/hep.22295] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
UNLABELLED The hepatitis B virus (HBV) mutation that encodes rtA181T is selected in the viral polymerase during antiviral drug therapy and can also encode a stop codon in the overlapping surface gene at amino acid 172 (sW172*) resulting in truncation of the last 55 amino acids of the C-terminal hydrophobic region of the surface proteins. This mutation is usually detected as a mixed population with wild-type HBV. In vitro analysis revealed that the rtA181T/sW172* variant is not only defective in secretion of viral particles causing intracellular retention of surface proteins, it also has a dominant negative effect on virion but not subviral particle secretion when coexpressed with the wild type. This dominant negative effect was attributed to the truncated S protein alone. Furthermore, these truncated surface proteins were less glycosylated, and the truncated L protein was able to support virion secretion. Examination of sequential HBV DNA levels in patients failing lamivudine or adefovir therapy where only the rtA181T change was detected via polymerase chain reaction sequencing revealed that viral load rebound did not occur or was not as large as usually observed with drug-resistant HBV. CONCLUSION The rtA181T/sW172* variant has a secretory defect and exerts a dominant negative effect on wild-type HBV virion secretion. The selection of rtA181T/sW172* reduced the typical extent of virological breakthrough, resulting in a missed diagnosis of drug resistance if viral load was used as the only criterion for drug failure, necessitating HBV polymerase chain reaction sequencing or other genotypic methods to diagnose antiviral drug resistance in these cases.
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Affiliation(s)
- Nadia Warner
- Victorian Infectious Diseases Reference Laboratory, North Melbourne, Victoria, Australia
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33
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Abstract
In the sera of patients infected with hepatitis B virus (HBV), in addition to infectious particles, there is an excess (typically 1,000- to 100,000-fold) of empty subviral particles (SVP) composed solely of HBV envelope proteins in the form of relatively smaller spheres and filaments of variable length. Hepatitis delta virus (HDV) assembly also uses the envelope proteins of HBV to produce an infectious particle. Rate-zonal sedimentation was used to study the particles released from liver cell lines that produced SVP only, HDV plus SVP, and HBV plus SVP. The SVP made in the absence of HBV or HDV were further examined by electron microscopy. They bound efficiently to heparin columns, consistent with an ability to bind cell surface glycosaminoglycans. However, unlike soluble forms of HBV envelope protein that were potent inhibitors, the SVP did not inhibit the ability of HBV and HDV to infect primary human hepatocytes.
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34
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Abou-Jaoudé G, Molina S, Maurel P, Sureau C. Myristoylation signal transfer from the large to the middle or the small HBV envelope protein leads to a loss of HDV particles infectivity. Virology 2007; 365:204-9. [PMID: 17462692 DOI: 10.1016/j.virol.2007.03.030] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2007] [Revised: 03/07/2007] [Accepted: 03/16/2007] [Indexed: 02/07/2023]
Abstract
A myristate linked to the N-terminus of the large hepatitis B virus (HBV) envelope protein was found to be required for infectivity of the hepatitis delta virus (HDV). Myristoylation of the large HBV envelope protein being known as indispensable for HBV infectivity, this result further demonstrates the similarities between the HBV and HDV entry pathways. In addition, the transfer of the N-myristoylation signal from the large to the middle or the small HBV envelope protein led in both cases to a loss of HDV infectivity. Hence, it is suggested that viral entry could depend on a physical link, or a spatial association, between the N-terminal receptor-binding polypeptide of the large protein and the myristoyl anchor linked to glycine-2.
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35
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Mhamdi M, Funk A, Hohenberg H, Will H, Sirma H. Assembly and budding of a hepatitis B virus is mediated by a novel type of intracellular vesicles. Hepatology 2007; 46:95-106. [PMID: 17567837 DOI: 10.1002/hep.21666] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
UNLABELLED Formation of enveloped viruses involves assembly and budding at cellular membranes. In this study, we elucidated the morphogenesis of hepadnaviruses on the ultrastructural and biochemical level using duck hepatitis B virus (DHBV) as a model system. Formation of virus progeny initiates at the endoplasmic reticulum (ER) and is conserved both in vitro and in vivo. The morphogenesis proceeds via membrane-surrounded vesicles containing both virions and subviral particles, indicating a common morphogenetic pathway. The virus particle-containing vesicles (VCVs) are generated and maintained by reorganization of endomembranes accompanied by a striking disorganization of the rough ER (rER). VCVs are novel organelles with unique identity and properties of ER, intermediate compartment, endosomes, and multivesicular bodies. VCVs are dynamic structures whose size and shape are regulated by both membrane fusion and fission. CONCLUSION Our data indicate a strong reorganization of endomembranes during DHBV infection, resulting in the biogenesis of novel organelles serving as multifunctional platforms for assembly and budding of virus progeny.
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Affiliation(s)
- Mouna Mhamdi
- Heinrich-Pette-Institut für experimentelle Virologie und Immunologie an der Universität Hamburg, Hamburg, Germany
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36
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Lambert C, Prange R. Posttranslational N-glycosylation of the hepatitis B virus large envelope protein. Virol J 2007; 4:45. [PMID: 17537250 PMCID: PMC1891283 DOI: 10.1186/1743-422x-4-45] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 05/30/2007] [Indexed: 11/25/2022] Open
Abstract
Background The addition of N-linked glycans to proteins is normally a cotranslational process that occurs during translocation of the nascent protein to the endoplasmic reticulum. Here, we report on an exception to this rule occurring on the hepatitis B virus (HBV) large L envelope protein that is a subject to co-plus posttranslational N-glycosylation. Results By using an improved detection system, we identified so far unrecognized, novel isoforms of L. Based on mutational analyses, the use of N-glycosylation inhibitors, and pulse-chase studies, we showed that these isoforms are due to posttranslational N-glycan addition to the asparagines 4 and 112 within the preS domain of L. While an inhibition of N-glycosylation and glycan trimming profoundly blocked virus assembly and release, the posttranslational N-glycosylation of L itself was found to be dispensable for HBV morphogenesis. Conclusion These data together with previous results implicate that the N-glycosylation requirements of virion release are due to functional inhibition of cell glycoproteins engaged by HBV.
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Affiliation(s)
- Carsten Lambert
- Institute for Medical Microbiology and Hygiene, University of Mainz, Augustusplatz, D-55101 Mainz, Germany
| | - Reinhild Prange
- Institute for Medical Microbiology and Hygiene, University of Mainz, Augustusplatz, D-55101 Mainz, Germany
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37
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Lepère C, Régeard M, Le Seyec J, Gripon P. The translocation motif of hepatitis B virus envelope proteins is dispensable for infectivity. J Virol 2007; 81:7816-8. [PMID: 17494068 PMCID: PMC1933348 DOI: 10.1128/jvi.00224-07] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The early events of hepatitis B virus (HBV) infection remain unclear. In 2006, Stoeckl et al. proposed a new entry mechanism involving a translocation motif (TLM) present in the pre-S2 domain of envelope proteins (L. Stoeckl, A. Funk, A. Kopitzki, B. Brandenburg, S. Oess, H. Will, H. Sirma, and E. Hildt, Proc. Natl. Acad. Sci. USA 103:6730-6734, 2006). After receptor binding and internalization into the endosomal compartment, this motif would allow the translocation of HBV particles through the endosomal membrane into the cytosol. In this study we have used two different mutated viruses containing a truncated TLM and showed their ability to infect human hepatocytes in primary culture, thus demonstrating the dispensability of the TLM for HBV infectivity.
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Affiliation(s)
- Charlotte Lepère
- INSERM U522, Hôpital de Pontchaillou, Avenue Henri le Guilloux, Rennes Cedex 35033, France
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38
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Blanchet M, Sureau C. Infectivity determinants of the hepatitis B virus pre-S domain are confined to the N-terminal 75 amino acid residues. J Virol 2007; 81:5841-9. [PMID: 17376925 PMCID: PMC1900317 DOI: 10.1128/jvi.00096-07] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022] Open
Abstract
The N-terminal pre-S domain of the large hepatitis B virus (HBV) envelope protein plays a pivotal role at the initial step of the viral entry pathway. In the present study, the entire pre-S domain was mapped for infectivity determinants, following a reverse-genetics approach and using in vitro infection assays with hepatitis delta virus (HDV) or HBV particles. The results demonstrate that lesions created within the N-terminal 75 amino acids of the pre-S region abrogate infectivity, whereas mutations between amino acids 76 and 113, overlapping the matrix domain, had no effect. In contrast to the results of a recent study (L. Stoeckl, A. Funk, A. Kopitzki, B. Brandenburg, S. Oess, H. Will, H. Sirma, and E. Hildt, Proc. Natl. Acad. Sci. 103:6730-6734, 2006), the deletion of a cell membrane translocation motif (TLM) located between amino acids 148 and 161 at the C terminus of pre-S2 did not interfere with the infectivity of the resulting HDV or HBV mutants. Furthermore, a series of large deletions overlapping the pre-S2 domain were compatible with infectivity, although the efficiency of infection was reduced when the deletions extended to the pre-S1 domain. Overall, the results demonstrate that the activity of the pre-S domain at viral entry solely depends on the integrity of its first 75 amino acids and thus excludes any function of the matrix domain or TLM.
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Affiliation(s)
- Matthieu Blanchet
- Laboratoire de Virologie Moléculaire, Institut National de la Transfusion Sanguine, 6 Rue Alexandre-Cabanel, 75739 Paris, France
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39
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Chai N, Gudima S, Chang J, Taylor J. Immunoadhesins containing pre-S domains of hepatitis B virus large envelope protein are secreted and inhibit virus infection. J Virol 2007; 81:4912-8. [PMID: 17329331 PMCID: PMC1900235 DOI: 10.1128/jvi.02865-06] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Hepatitis B virus (HBV) replication produces three envelope proteins (L, M, and S) that have a common C terminus. L, the largest, contains a domain, pre-S1, not present on M. Similarly M contains a domain, pre-S2, not present on S. The pre-S1 region has important functions in the HBV life cycle. Thus, as an approach to studying these roles, the pre-S1 and/or pre-S2 sequences of HBV (serotype adw2, genotype A) were expressed as N-terminal fusions to the Fc domain of a rabbit immunoglobulin G chain. Such proteins, known as immunoadhesins (IA), were highly expressed following transfection of cultured cells and, when the pre-S1 region was present, >80% were secreted. The IA were myristoylated at a glycine penultimate to the N terminus, although mutation studies showed that this modification was not needed for secretion. As few as 30 amino acids from the N terminus of pre-S1 were both necessary and sufficient to drive secretion of IA. Even expression of pre-S1 plus pre-S2, in the absence of an immunoglobulin chain, led to efficient secretion. Overall, these studies demonstrate an unexpected ability of the N terminus of pre-S1 to promote protein secretion. In addition, some of these secreted IA, at nanomolar concentrations, inhibited infection of primary human hepatocytes either by hepatitis delta virus (HDV), a subviral agent that uses HBV envelope proteins, or HBV. These IA have potential to be part of antiviral therapies against chronic HDV and HBV, and may help understand the attachment and entry mechanisms used by these important human pathogens.
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Affiliation(s)
- Ning Chai
- Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA 19111-2497, USA
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40
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Patient R, Hourioux C, Sizaret PY, Trassard S, Sureau C, Roingeard P. Hepatitis B virus subviral envelope particle morphogenesis and intracellular trafficking. J Virol 2007; 81:3842-51. [PMID: 17267490 PMCID: PMC1866106 DOI: 10.1128/jvi.02741-06] [Citation(s) in RCA: 96] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
Hepatitis B virus (HBV) is unusual in that its surface proteins (small [S], medium, and large [L]) are not only incorporated into the virion envelope but they also bud into empty subviral particles in great excess over virions. The morphogenesis of these subviral envelope particles remains unclear, but the S protein is essential and sufficient for budding. We show here that, in contrast to the presumed model, the HBV subviral particle formed by the S protein self-assembles into branched filaments in the lumen of the endoplasmic reticulum (ER). These long filaments are then folded and bridged for packing into crystal-like structures, which are then transported by ER-derived vesicles to the ER-Golgi intermediate compartment (ERGIC). Within the ERGIC, they are unpacked and relaxed, and their size and shape probably limits further progression through the secretory pathway. Such progression requires their conversion into spherical particles, which occurred spontaneously during the purification of these filaments by affinity chromatography. Small branched filaments are also formed by the L protein in the ER lumen, but these filaments are not packed into transport vesicles. They are transported less efficiently to the ERGIC, potentially accounting for the retention of the L protein within cells. These findings shed light on an important step in the HBV infectious cycle, as the intracellular accumulation of HBV subviral filaments may be directly linked to viral pathogenesis.
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Affiliation(s)
- Romuald Patient
- Université François Rabelais, INSERM ERI 19, Laboratoire de Biologie Cellulaire, Faculté de Médecine de Tours, 10 boulevard Tonnellé, F-37032 Tours Cedex, France
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41
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Abstract
The hepatitis B virus (HBV) particle consists of an envelope containing three related surface proteins and probably lipid and an icosahedral nucleocapsid of approximately 30 nm diameter enclosing the viral DNA genome and DNA polymerase. The capsid is formed in the cytosol of the infected cell during packaging of an RNA pregenome replication complex by multiple copies of a 21-kDa C protein. The capsid gains the ability to bud during synthesis of the viral DNA genome by reverse transcription of the pregenome in the lumen of the particle. The three envelope proteins S, M, and L shape a complex transmembrane fold at the endoplasmic reticulum, and form disulfide-linked homo- and heterodimers. The transmembrane topology of a fraction of the large envelope protein L changes post-translationally, therefore, the N terminal domain of L (preS) finally appears on both sides of the membrane. During budding at an intracellular membrane, a short linear domain in the cytosolic preS region interacts with binding sites on the capsid surface. The virions are subsequently secreted into the blood. In addition, the surface proteins can bud in the absence of capsids and form subviral lipoprotein particles of 20 nm diameter which are also secreted.
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Affiliation(s)
- Volker Bruss
- Department of Virology, University of Göttingen, Kreuzbergring 57, Göttingen 37075, Germany.
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42
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Lundin M, Lindström H, Grönwall C, Persson MAA. Dual topology of the processed hepatitis C virus protein NS4B is influenced by the NS5A protein. J Gen Virol 2006; 87:3263-3272. [PMID: 17030859 DOI: 10.1099/vir.0.82211-0] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Among the least-known hepatitis C virus proteins is the non-structural protein 4B (NS4B). It localizes to the endoplasmic reticulum (ER) membrane and induces membrane changes, resulting in a membranous web that is reported to be the locale for virus replication. A model was presented previously for the topology of recombinant HCV NS4B of the 1a genotype based on in vitro data. In this model, the N-terminal tail of a considerable fraction of the NS4B molecules was translocated into the ER lumen via a post-translational process, giving the protein a dual transmembrane topology. It is now reported that translocation of the N terminus also occurs for processed NS4B expressed in cells in the context of the polyprotein. In the presence of NS5A, however, a lower degree of translocation was observed, which may indicate that NS5A influences the topology of NS4B. In vitro expression studies of NS4B from all major genotypes demonstrated that translocation of the N terminus to the ER lumen is conserved across genotypes. This clearly suggests an important function for this feature. Furthermore, when disrupting a previously reported amphipathic helix (AH) in the N terminus of NS4B, translocation was inhibited. As a disrupted AH also abolished the ability of NS4B to rearrange membranes, these data indicate for the first time an association between translocation of the N terminus and membrane rearrangement. Finally, the present experiments also confirm the predicted location of the first luminal loop to be around aa 112.
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Affiliation(s)
- Marika Lundin
- Karolinska Institutet, Department of Medicine at Center for Molecular Medicine (L8 : 01), Karolinska University Hospital Solna, S-171 76 Stockholm, Sweden
| | - Hannah Lindström
- Karolinska Institutet, Department of Medicine at Center for Molecular Medicine (L8 : 01), Karolinska University Hospital Solna, S-171 76 Stockholm, Sweden
| | - Caroline Grönwall
- The Royal Institute of Technology, Department of Biotechnology, Alba Nova University Centre, Stockholm, Sweden
| | - Mats A A Persson
- Karolinska Institutet, Department of Medicine at Center for Molecular Medicine (L8 : 01), Karolinska University Hospital Solna, S-171 76 Stockholm, Sweden
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43
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Blanchet M, Sureau C. Analysis of the cytosolic domains of the hepatitis B virus envelope proteins for their function in viral particle assembly and infectivity. J Virol 2006; 80:11935-45. [PMID: 17020942 PMCID: PMC1676254 DOI: 10.1128/jvi.00621-06] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The hepatitis B virus (HBV) envelope proteins have the ability to assemble three types of viral particles, (i) the empty subviral particles (SVPs), (ii) the mature HBV virions, and (iii) the hepatitis delta virus (HDV) particles, in cells that are coinfected with HBV and HDV. To gain insight into the function of the HBV envelope proteins in morphogenesis of HBV or HDV virions, we have investigated subdomains of the envelope proteins that have been shown or predicted to lie at the cytosolic face of the endoplasmic reticulum membrane during synthesis, a position prone to interaction with the inner core structure. These domains, referred to here as cytosolic loops I and II (CYL-I and -II, respectively), were subjected to mutagenesis. The mutations were introduced in the three HBV envelope proteins, designated small, middle, and large (S-HBsAg, M-HBsAg, and L-HBsAg, respectively). The mutants were expressed in HuH-7 cells to evaluate their capacity for self-assembly and formation of HBV or HDV virions when HBV nucleocapsid or HDV ribonucleoprotein, respectively, was provided. We found that SVP-competent CYL-I mutations between positions 23 and 78 of the S domain were permissive to HBV or HDV virion assembly. One mutation (P29A) was permissive for synthesis of the S- and M-HBsAg but adversely affected the synthesis or stability of L-HBsAg, thereby preventing the assembly of HBV virions. Furthermore, using an in vitro infection assay based on the HepaRG cells and the HDV model, we have shown that particles coated with envelope proteins bearing CYL-I mutations were fully infectious, hence indicating the absence of an infectivity determinant in this region. Finally, we demonstrated that the tryptophan residues at positions 196, 199, and 201 in CYL-II, which were shown to exert a matrix function for assembly of HDV particles (I. Komla-Soukha and C. Sureau, J. Virol. 80:4648-4655, 2006), were dispensable for both assembly and infectivity of HBV virions.
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Affiliation(s)
- Matthieu Blanchet
- Laboratoire de Virologie, Institut National de la Transfusion Sanguine, 6 rue Alexandre Cabanel, 75739 Paris, France
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44
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Abstract
The hepatitis delta virus (HDV) is a subviral agent that utilizes the envelope proteins of the hepatitis B virus (HBV) for propagation. When introduced into permissive cells, the HDV RNA genome replicates and associates with multiple copies of the HDV-encoded proteins to assemble a ribonucleoprotein (RNP) complex. The mechanism necessary to export the RNP from the cell is provided by the HBV envelope proteins, which have the capacity to assemble lipoprotein vesicles that bud into the lumen of a pre-Golgi compartment before being secreted. In addition to allowing the release of the HDV RNP, the HBV envelope proteins also provide a means for its targeting to an uninfected cell, thereby ensuring the spread of HDV. This chapter covers the molecular aspects of the HBV envelope protein functions in the HDV replication cycle, in particular the activity of the small envelope protein in RNP export and the function of the large envelope protein at viral entry.
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Affiliation(s)
- C Sureau
- Laboratoire de Virologie Moléculaire, Institut National de la Transfusion Sanguine, Paris, France.
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45
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Yu D, Fukuda T, Kuroda S, Tanizawa K, Kondo A, Ueda M, Yamada T, Tada H, Seno M. Engineered bio-nanocapsules, the selective vector for drug delivery system. IUBMB Life 2006; 58:1-6. [PMID: 16596748 DOI: 10.1080/15216540500484368] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The bio-nanocapsule (BNC) is our concept of artificial hollow nanoparticles that have been designed and produced through biotechnological procedures. We proposed an empty virus-like particle, which consists of a recombinant L envelope protein of hepatitis B virus (HBV) and a lipid derived from the host cell, as an engineered BNC. Although this BNC was first developed as an immunogen of hepatitis B vaccine, the pre-S1 region in N-terminus of L envelope protein confers hepatocyte specific infectivity of HBV on the BNC. This recombinant BNC is now being developed as a novel platform of drug delivery system (DDS) vector for selective delivery.
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Affiliation(s)
- Dongwei Yu
- Graduate School of Natural Science and Technology, Okayama University, 3.1.1 Tsushima-Naka, Okayama 700-8530, Japan
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Friedrich B, Wollersheim M, Brandenburg B, Foerste R, Will H, Hildt E. Induction of anti-proliferative mechanisms in hepatitis B virus producing cells. J Hepatol 2005; 43:696-703. [PMID: 15922479 DOI: 10.1016/j.jhep.2005.02.026] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2004] [Revised: 12/10/2004] [Accepted: 02/02/2005] [Indexed: 12/04/2022]
Abstract
BACKGROUND/AIMS Hepatitis B virus (HBV) preferentially replicates in quiescent cells. It was analyzed whether HBV affects cell cycle control. METHODS The amount of EGF-receptor (EGFR) and the binding capacity for 125I-EGF was determined. Expression of mdm2 and p21 and relevance of p53 for it were analyzed by reporter gene assays and western blotting. Cyclin A/E associated cdk2 activities were determined by immunocomplex assays. Cell proliferation was quantified by measurement of BrdU incorporation. RESULTS In HBV producing cells a significant reduction of EGFR expression, diminished 125I-EGF-binding capacity and insensitivity to EGF-stimulation were observed as compared to the control. Moreover, c-Raf-1-dependent induction of mdm2-P2 and p21cip1/waf1-promoter and elevated amounts of the respective proteins were observed in HBV producing cells. Whereas activation of mdm2-P2-promoter requires p53, activation of p21cip1/waf1-promoter is mediated partially by a p53-independent process. Induction of p21cip1/waf1 is reflected by a reduction of cyclin A associated cdk2 activity and an increase of cyclin E associated cdk2 activity. In accordance with this proliferation rate of HBV-producing hepatocytes is reduced as compared to control cells. CONCLUSIONS These results describe novel cell-cycle inhibitory functions of HBV that correlate well with the general concept of enhanced HBV replication in quiescent cells.
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Kluge B, Schläger M, Pairan A, Bruss V. Determination of the minimal distance between the matrix and transmembrane domains of the large hepatitis B virus envelope protein. J Virol 2005; 79:7918-21. [PMID: 15919948 PMCID: PMC1143687 DOI: 10.1128/jvi.79.12.7918-7921.2005] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
The cytosolic matrix domain (MD) located between amino acids (aa) 103 and 124 of the large hepatitis B virus envelope protein L is essential for virion formation. We reduced the distance between MD and the transmembrane domain (TD; aa 254 to 272) by deletions starting at aa 132. Six mutants with deletions of up to aa 234 were wild type, and four mutants with slightly larger deletions were blocked with respect to virion morphogenesis. Thus, the minimal distance between MD and TD was around 26 aa. This spacer might be required by MD to reach contact sites on the capsid.
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Affiliation(s)
- Britta Kluge
- University of Göttingen, Department of Virology, Kreuzbergring 57, D-37075 Göttingen, Germany.
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Abstract
AIM: To express the complete PreS region of HBV in E.coli with good solubility and stability, and to establish an effective method for purification of the recombinant PreS protein.
METHODS: The complete PreS region (PreS1 and PreS2) was fused into a series of tags including glutathione S-transferase (GST), dihydrofolate reductase (DHFR), maltose binding protein (MBP), 6×histidine, chitin binding domain (CBD), and thioredoxin, respectively. Expression of recombinant PreS fusion proteins was examined by SDS-PAGE analysis and confirmed by Western blot. Two fusion proteins, thio-PreS, and PreS-CBD, with desirable solubility and stability, were subjected to affinity purification and further characterization.
RESULTS: Recombinant PreS fusion proteins could be synthesized with good yields in E.coli. However, most of these proteins except for thio-PreS and PreS-CBD were vulnerable to degradation or insoluble as revealed by SDS-PAGE and Western blot. Thio-PreS could be purified by affinity chromatography with nickel-chelating sepharose as the matrix. However, some impurities were also co-purified. A simple freeze-thaw treatment yielded most of the thio-PreS proteins in solution while the impurities were in the precipitate. Purified thio-PreS protein was capable of inhibiting the binding of HBV virion to a specific monoclonal antibody against an epitope within the PreS1 domain.
CONCLUSION: Increased solubility and stability of the complete PreS region synthesized in E.coli can be achieved by fusion with the thioredoxin or the CBD tag. A simple yet highly effective method has been established for the purification of the thio-PreS protein. Purified thio-PreS protein likely assumes a native conformation, which makes it an ideal candidate for studying the structure of the PreS region as well as for screening antivirals.
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Affiliation(s)
- Qiang Deng
- State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Chinese Academy of Sciences, Shanghai 200031, China
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Wang HC, Chang WT, Chang WW, Wu HC, Huang W, Lei HY, Lai MD, Fausto N, Su IJ. Hepatitis B virus pre-S2 mutant upregulates cyclin A expression and induces nodular proliferation of hepatocytes. Hepatology 2005; 41:761-70. [PMID: 15726643 DOI: 10.1002/hep.20615] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Naturally occurring mutants with a deletion in the pre-S2 region of the large surface protein (Delta S2-LHBs) are prevalent in serum and livers of patients with chronic hepatitis B virus (HBV) infection associated with cirrhosis. The Delta S2-LHBs protein is retained in the endoplasmic reticulum (ER) and may induce ER stress. One interesting observation is the consistently clustered distribution of hepatocytes expressing Delta S2-LHBs. In this study, complementary DNA microarray analysis identified cyclin A and several groups of genes as being significantly upregulated by Delta S2-LHBs in the HuH-7 cell line. This observation was confirmed in liver tissues. The induction of cyclin A expression may occur via the specific transactivator function of Delta S2-LHBs independent of ER stress. In the presence of Delta S2-LHBs, hepatocytes sustained cyclin A expression and cell cycle progression under ER stress and displayed increased BrdU incorporation with multinuclear formation. Furthermore, Delta S2-LHBs could enhance anchorage-independent cell growth in a nontransformed human hepatocyte line and induced nodular proliferation of hepatocytes in transgenic mice. In conclusion, these in vitro and in vivo data support a role for Delta S2-LHBs in the hepatocyte hyperplasia and a likely role in the process of HBV-related tumorigenesis.
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Affiliation(s)
- Hui-Ching Wang
- Division of Clinical Research, National Health Research Institutes, Tainan, Taiwan
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Utsumi T, Ohta H, Kayano Y, Sakurai N, Ozoe Y. The N-terminus of B96Bom, a Bombyx mori G-protein-coupled receptor, is N-myristoylated and translocated across the membrane. FEBS J 2005; 272:472-81. [PMID: 15654885 DOI: 10.1111/j.1742-4658.2004.04487.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In eukaryotic cellular proteins, protein N-myristoylation has been recognized as a protein modification that occurs mainly on cytoplasmic or nucleoplasmic proteins. In this study, to search for a eukaryotic N-myristoylated transmembrane protein, the susceptibility of the N-terminus of several G-protein-coupled receptors (GPCRs) to protein N-myristoylation was evaluated by in vitro and in vivo metabolic labeling. It was found that the N-terminal 10 residues of B96Bom, a Bombyx mori GPCR, efficiently directed the protein N-myristoylation. Analysis of a tumor necrosis factor (TNF) fusion protein with the N-terminal 90 residues of B96Bom at its N-terminus revealed that (a) transmembrane domain 1 of B96Bom functioned as a type I signal anchor sequence, (b) the N-myristoylated N-terminal domain (58 residues) was translocated across the membrane, and (c) two N-glycosylation motifs located in this domain were efficiently N-glycosylated. In addition, when Ala4 in the N-myristoylation motif of B96Bom90-TNF, Met-Gly-Gln-Ala-Ala-Thr(1-6), was replaced with Asn to generate a new N-glycosylation motif, Asn-Ala-Thr(4-6), efficient N-glycosylation was observed on this newly introduced N-glycosylation site in the expressed protein. These results indicate that the N-myristoylated N-terminus of B96Bom is translocated across the membrane and exposed to the extracellular surface. To our knowledge, this is the first report showing that a eukaryotic transmembrane protein can be N-myristoylated and that the N-myristoylated N-terminus of the protein can be translocated across the membrane.
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Affiliation(s)
- Toshihiko Utsumi
- Department of Biological Chemistry, Faculty of Agriculture, Yamaguchi University, Yamaguchi 753-8515, Japan.
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