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Chung CY, Sun CP, Tao MH, Wu HL, Wang SH, Yeh SH, Zheng QB, Yuan Q, Xia NS, Ogawa K, Nakashima K, Suzuki T, Chen PJ. Major HBV splice variant encoding a novel protein important for infection. J Hepatol 2024; 80:858-867. [PMID: 38336347 DOI: 10.1016/j.jhep.2024.01.037] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/04/2023] [Revised: 01/16/2024] [Accepted: 01/23/2024] [Indexed: 02/12/2024]
Abstract
BACKGROUND & AIMS HBV expresses more than 10 spliced RNAs from the viral pregenomic RNA, but their functions remain elusive and controversial. To address the function of HBV spliced RNAs, we generated splicing-deficient HBV mutants and conducted experiments to assess the impact of these mutants on HBV infection. METHODS HepG2-NTCP cells, human hepatocyte chimeric FRG mice (hu-FRG mice), and serum from patients with chronic hepatitis B were used for experiments on HBV infection. Additionally, SHifter assays and cryo-electron microscopy were performed. RESULTS We found the infectivity of splicing-deficient HBV was decreased 100-1,000-fold compared with that of wild-type HBV in hu-FRG mice. Another mutant, A487C, which loses the most abundant spliced RNA (SP1), also exhibits severely impaired infectivity. SP1 hypothetically encodes a novel protein HBcSP1 (HBc-Cys) that lacks the C-terminal cysteine from full-length HBc. In the SHifter assay, HBcSP1 was detected in wild-type viral particles at a ratio of about 20-100% vs. conventional HBc, as well as in the serum of patients with chronic hepatitis B, but not in A487C particles. When infection was conducted with a shorter incubation time of 4-8 h at lower PEG concentrations in HepG2-NTCP cells, the entry of the A487C mutant was significantly slower. SP1 cDNA complementation of the A487C mutant succeeded in rescuing its infectivity in hu-FRG mice and HepG2-NTCP cells. Moreover, cryo-electron microscopy revealed a disulfide bond between HBc cysteine 183 and 48 in the HBc intradimer of the A487C capsid, leading to a locked conformation that disfavored viral entry in contrast to the wild-type capsid. CONCLUSIONS Prior studies unveiled the potential integration of the HBc-Cys protein into the HBV capsid. We confirmed the proposal and validated its identity and function during infection. IMPACT AND IMPLICATIONS HBV SP1 RNA encodes a novel HBc protein (HBcSP1) that lacks the C-terminal cysteine from conventional HBc (HBc-Cys). HBcSP1 was detected in cell culture-derived HBV and confirmed in patients with chronic infection by both immunological and chemical modification assays at 10-50% of capsid. The splicing-deficient mutant HBV (A487C) impaired infectivity in human hepatocyte chimeric mice and viral entry in the HepG2-NTCP cell line. Furthermore, these deficiencies of the splicing-deficient mutant could be rescued by complementation with the SP1-encoded protein HBcSP1. We confirmed and validated the identity and function of HBcSP1 during infection, building on the current model of HBV particles.
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Affiliation(s)
- Chen-Yen Chung
- National Taiwan University College of Medicine, Taipei, Taiwan
| | - Cheng-Pu Sun
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Mi-Hua Tao
- Institute of Biomedical Sciences, Academia Sinica, Taipei, Taiwan
| | - Hui-Lin Wu
- Hepatitis Research Center, National Taiwan University Hospital, Taipei, Taiwan
| | - Sheng-Han Wang
- Hepatitis Research Center, National Taiwan University Hospital, Taipei, Taiwan
| | - Shiou-Hwei Yeh
- National Taiwan University College of Medicine, Taipei, Taiwan; Hepatitis Research Center, National Taiwan University Hospital, Taipei, Taiwan
| | - Qing-Bing Zheng
- National Institute of Diagnostics and Vaccine Development in Infectious Diseases, School of Life Sciences, Xiamen University, Xiamen, P.R. China
| | - Quan Yuan
- National Institute of Diagnostics and Vaccine Development in Infectious Diseases, School of Life Sciences, Xiamen University, Xiamen, P.R. China
| | - Ning-Shao Xia
- National Institute of Diagnostics and Vaccine Development in Infectious Diseases, School of Life Sciences, Xiamen University, Xiamen, P.R. China
| | - Kenji Ogawa
- RIKEN Center for Sustainable Resource Science (CSRS), RIKEN, Wako, Saitama, Japan
| | | | | | - Pei-Jer Chen
- National Taiwan University College of Medicine, Taipei, Taiwan.
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Seitz S, Bartenschlager R. Cutting edges in the HBV genome: How RNA splicing is involved in modulating virus ultrastructure to promote infection. J Hepatol 2024; 80:832-833. [PMID: 38460792 DOI: 10.1016/j.jhep.2024.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/26/2024] [Accepted: 02/28/2024] [Indexed: 03/11/2024]
Affiliation(s)
- Stefan Seitz
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Heidelberg, Germany; Division Virus-Associated Carcinogenesis, German Cancer Research Center (DKFZ), Heidelberg, Germany.
| | - Ralf Bartenschlager
- Department of Infectious Diseases, Molecular Virology, Heidelberg University, Heidelberg, Germany; Division Virus-Associated Carcinogenesis, German Cancer Research Center (DKFZ), Heidelberg, Germany
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3
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Su J, Harati Taji Z, Kosinska AD, Ates Oz E, Xie Z, Bielytskyi P, Shein M, Hagen P, Esmaeili S, Steiger K, Protzer U, Schütz AK. Introducing adjuvant-loaded particulate hepatitis B core antigen as an alternative therapeutic hepatitis B vaccine component. JHEP Rep 2024; 6:100997. [PMID: 38425450 PMCID: PMC10904195 DOI: 10.1016/j.jhepr.2023.100997] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 11/27/2023] [Accepted: 12/19/2023] [Indexed: 03/02/2024] Open
Abstract
Background & Aims Particulate hepatitis B core antigen (HBcoreAg) is a potent immunogen used as a vaccine carrier platform. HBcoreAg produced in E. coli encapsidates random bacterial RNA (bRNA). Using the heterologous protein-prime, viral-vector-boost therapeutic hepatitis B vaccine TherVacB, we compared the properties of different HBcoreAg forms. We explored how the content of HBcoreAg modulates antigen stability, immunogenicity, and antiviral efficacy. Methods bRNA was removed from HBcoreAg by capsid disassembly, followed by reassembly in the absence or presence of specific nucleic acid-based adjuvants poly I:C or CpG. The morphology and structure of empty, bRNA-containing and adjuvant-loaded HBcoreAg were monitored by electron microscopy and nuclear magnetic resonance spectroscopy. Empty, bRNA-containing or adjuvant-loaded HBcoreAg were applied together with HBsAg and with or without nucleic acid-based external adjuvants within the TherVacB regimen in both wild-type and HBV-carrier mice. Results While HBcoreAg retained its structure upon bRNA removal, its stability and immunogenicity decreased significantly. Loading HBcoreAg with nucleic acid-based adjuvants re-established stability of the capsid-like antigen. Immunization with poly I:C- or CpG-loaded HBcoreAg induced high antibody titers against co-administered HBsAg. When applied within the TherVacB regimen, they activated vigorous HBcoreAg- and HBsAg-specific T-cell responses in wild-type and HBV-carrier mice, requiring a significantly lower dose of adjuvant compared to externally added adjuvant. Finally, immunization with adjuvant-loaded HBcoreAg mixed with HBsAg led to long-term control of persistent HBV replication in the HBV-carrier mice. Conclusion Adjuvant-loaded HBcoreAg retained capsid integrity and stability, was as immunogenic in vivo as externally adjuvanted HBcoreAg, requiring lower adjuvant levels, and supported immunity against co-administered, non-adjuvanted HBsAg. Thus, adjuvant-loaded HBcoreAg represents a promising novel platform for vaccine development. Impact and implications Hepatitis B core antigen (HBcoreAg) recapitulates the capsid of the HBV that hosts the viral genome. Produced recombinantly, it is not infectious but emerges as a potent immunogen in vaccine development. In this preclinical study, we show that loading HBcoreAg with defined nucleic-acid-based adjuvants on the one hand stabilizes the HBcoreAg with standardized capsid content and, on the other hand, efficiently promotes the immunity of HBcoreAg and a co-administered antigen, allowing for reduced adjuvant doses. Therefore, adjuvant-loaded HBcoreAg not only serves as an encouraging option for therapeutic hepatitis B vaccines, but could also act as an efficient adjuvant delivery system for other types of vaccine.
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Affiliation(s)
- Jinpeng Su
- Institute of Virology, Technical University of Munich / Helmholtz Munich, 81675, Munich, Germany
- German Center for Infection Research (DZIF), Munich partner site, Germany
| | - Zahra Harati Taji
- Ludwig Maximilians University of Munich, 81377, Munich, Germany
- Bavarian NMR Center, Technical University of Munich, 85748, Garching, Germany
- Institute of Structural Biology, Helmholtz Munich, 85764, Neuherberg, Germany
| | - Anna D. Kosinska
- Institute of Virology, Technical University of Munich / Helmholtz Munich, 81675, Munich, Germany
- German Center for Infection Research (DZIF), Munich partner site, Germany
| | - Edanur Ates Oz
- Institute of Virology, Technical University of Munich / Helmholtz Munich, 81675, Munich, Germany
| | - Zhe Xie
- Institute of Virology, Technical University of Munich / Helmholtz Munich, 81675, Munich, Germany
| | - Pavlo Bielytskyi
- Bavarian NMR Center, Technical University of Munich, 85748, Garching, Germany
- Institute of Structural Biology, Helmholtz Munich, 85764, Neuherberg, Germany
| | - Mikhail Shein
- Ludwig Maximilians University of Munich, 81377, Munich, Germany
- Bavarian NMR Center, Technical University of Munich, 85748, Garching, Germany
- Institute of Structural Biology, Helmholtz Munich, 85764, Neuherberg, Germany
| | - Philipp Hagen
- Institute of Virology, Technical University of Munich / Helmholtz Munich, 81675, Munich, Germany
| | - Shohreh Esmaeili
- Ludwig Maximilians University of Munich, 81377, Munich, Germany
- Bavarian NMR Center, Technical University of Munich, 85748, Garching, Germany
- Institute of Structural Biology, Helmholtz Munich, 85764, Neuherberg, Germany
| | - Katja Steiger
- Comparative Experimental Pathology, Institute of Pathology, School of Medicine and Health, Technical University Munich, 81675, Munich, Germany
| | - Ulrike Protzer
- Institute of Virology, Technical University of Munich / Helmholtz Munich, 81675, Munich, Germany
- German Center for Infection Research (DZIF), Munich partner site, Germany
| | - Anne K. Schütz
- Ludwig Maximilians University of Munich, 81377, Munich, Germany
- Bavarian NMR Center, Technical University of Munich, 85748, Garching, Germany
- Institute of Structural Biology, Helmholtz Munich, 85764, Neuherberg, Germany
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Kim C, Schlicksup CJ, Pérez-Segura C, Hadden-Perilla JA, Wang JCY, Zlotnick A. Structure of the Hepatitis B virus capsid quasi-6-fold with a trapped C-terminal domain reveals capsid movements associated with domain exit. J Biol Chem 2023; 299:105104. [PMID: 37517693 PMCID: PMC10463254 DOI: 10.1016/j.jbc.2023.105104] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2023] [Revised: 07/08/2023] [Accepted: 07/11/2023] [Indexed: 08/01/2023] Open
Abstract
Many viruses undergo transient conformational change to surveil their environments for receptors and host factors. In Hepatitis B virus (HBV) infection, after the virus enters the cell, it is transported to the nucleus by interaction of the HBV capsid with an importin α/β complex. The interaction between virus and importins is mediated by nuclear localization signals on the capsid protein's C-terminal domain (CTD). However, CTDs are located inside the capsid. In this study, we asked where does a CTD exit the capsid, are all quasi-equivalent CTDs created equal, and does the capsid structure deform to facilitate CTD egress from the capsid? Here, we used Impβ as a tool to trap transiently exposed CTDs and examined this complex by cryo-electron microscopy. We examined an asymmetric reconstruction of a T = 4 icosahedral capsid and a focused reconstruction of a quasi-6-fold vertex (3.8 and 4.0 Å resolution, respectively). Both approaches showed that a subset of CTDs extended through a pore in the center of the quasi-6-fold complex. CTD egress was accompanied by enlargement of the pore and subtle changes in quaternary and tertiary structure of the quasi-6-fold. When compared to molecular dynamics simulations, structural changes were within the normal range of capsid flexibility. Although pore diameter was enlarged in the Impβ-bound reconstruction, simulations indicate that CTD egress does not exclusively depend on enlarged pores. In summary, we find that HBV surveillance of its environment by transient exposure of its CTD requires only modest conformational change of the capsid.
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Affiliation(s)
- Christine Kim
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, Indiana, USA
| | | | - Carolina Pérez-Segura
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA
| | - Jodi A Hadden-Perilla
- Department of Chemistry and Biochemistry, University of Delaware, Newark, Delaware, USA
| | - Joseph Che-Yen Wang
- Department of Microbiology & Immunology, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA
| | - Adam Zlotnick
- Molecular and Cellular Biochemistry Department, Indiana University, Bloomington, Indiana, USA.
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Molecular elucidation of drug-induced abnormal assemblies of the hepatitis B virus capsid protein by solid-state NMR. Nat Commun 2023; 14:471. [PMID: 36709212 PMCID: PMC9884277 DOI: 10.1038/s41467-023-36219-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 01/18/2023] [Indexed: 01/29/2023] Open
Abstract
Hepatitis B virus (HBV) capsid assembly modulators (CAMs) represent a recent class of anti-HBV antivirals. CAMs disturb proper nucleocapsid assembly, by inducing formation of either aberrant assemblies (CAM-A) or of apparently normal but genome-less empty capsids (CAM-E). Classical structural approaches have revealed the CAM binding sites on the capsid protein (Cp), but conformational information on the CAM-induced off-path aberrant assemblies is lacking. Here we show that solid-state NMR can provide such information, including for wild-type full-length Cp183, and we find that in these assemblies, the asymmetric unit comprises a single Cp molecule rather than the four quasi-equivalent conformers typical for the icosahedral T = 4 symmetry of the normal HBV capsids. Furthermore, while in contrast to truncated Cp149, full-length Cp183 assemblies appear, on the mesoscopic level, unaffected by CAM-A, NMR reveals that on the molecular level, Cp183 assemblies are equally aberrant. Finally, we use a eukaryotic cell-free system to reveal how CAMs modulate capsid-RNA interactions and capsid phosphorylation. Our results establish a structural view on assembly modulation of the HBV capsid, and they provide a rationale for recently observed differences between in-cell versus in vitro capsid assembly modulation.
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