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González-Del Pino GL, Walsh RM, Atanasiu D, Cairns TM, Saw WT, Cohen GH, Heldwein EE. Allosteric mechanism of membrane fusion activation in a herpesvirus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.09.20.610514. [PMID: 39345478 PMCID: PMC11430019 DOI: 10.1101/2024.09.20.610514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 10/01/2024]
Abstract
Herpesviridae infect nearly all humans for life, causing diseases that range from painful to life-threatening1. These viruses penetrate cells by employing a complex apparatus composed of separate receptor-binding, signal-transmitting, and membrane-fusing components2. But how these components coordinate their functions is unknown. Here, we determined the 4.19-angstrom cryoEM reconstruction of the central signal-transmitting component from herpes simplex virus 2, the gH/gL complex, in its elusive pre-activation state. Analysis of the continuum of conformational ensembles observed in cryoEM data revealed a series of structural rearrangements in gH/gL that allosterically transmit the fusion-triggering signal from the receptor-binding glycoprotein gD to the membrane fusogen gB. Furthermore, we identified a structural "switch" element in gH/gL that refolds and flips 180 degrees during the transition from pre-activation to activated form. Conservation of this "switch" in gH/gL homologs suggests that the proposed fusion triggering mechanism may apply to all Herpesviridae and points to a new target for subunit-based vaccines and treatment efforts.
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Affiliation(s)
- Gonzalo L. González-Del Pino
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 0211
- Tufts NIH-IRACDA program, Tufts University School of Medicine, Boston, MA 02111
| | - Richard M. Walsh
- Harvard Medical School Cryoelectron Microscopy Center, Boston, MA 02115
| | - Doina Atanasiu
- University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
| | - Tina M. Cairns
- University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
| | - Wan Ting Saw
- University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
| | - Gary H. Cohen
- University of Pennsylvania School of Dental Medicine, Philadelphia, PA 19104
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, MA 0211
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2
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Liu X, Wang M, Cheng A, Yang Q, Tian B, Ou X, Sun D, He Y, Wu Z, Zhao X, Wu Y, Zhang S, Huang J, Jia R, Chen S, Liu M, Zhu D. Functions of the UL51 protein during the herpesvirus life cycle. Front Microbiol 2024; 15:1457582. [PMID: 39252835 PMCID: PMC11381400 DOI: 10.3389/fmicb.2024.1457582] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2024] [Accepted: 08/07/2024] [Indexed: 09/11/2024] Open
Abstract
The herpesvirus UL51 protein is a multifunctional tegument protein involved in the regulation of multiple aspects of the viral life cycle. This article reviews the biological characteristics of the UL51 protein and its functions in herpesviruses, including participating in the maintenance of the viral assembly complex (cVAC) during viral assembly, affecting the production of mature viral particles and promoting primary and secondary envelopment, as well as its positive impact on viral cell-to-cell spread (CCS) through interactions with multiple viral proteins and its key role in the proliferation and pathogenicity of the virus in the later stage of infection. This paper discusses how the UL51 protein participates in the life cycle of herpesviruses and provides new ideas for further research on UL51 protein function.
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Affiliation(s)
- Xiaolan Liu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Mingshu Wang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Anchun Cheng
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Qiao Yang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Bin Tian
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xumin Ou
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Di Sun
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Yu He
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Zhen Wu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Xinxin Zhao
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Ying Wu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Shaqiu Zhang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Juan Huang
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Renyong Jia
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Shun Chen
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Mafeng Liu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Institute of Veterinary Medicine and Immunology, Sichuan Agricultural University, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
| | - Dekang Zhu
- Engineering Research Center of Southwest Animal Disease Prevention and Control Technology, Ministry of Education of the People's Republic of China, Chengdu, China
- Key Laboratory of Animal Disease and Human Health of Sichuan Province, Chengdu, China
- International Joint Research Center for Animal Disease Prevention and Control of Sichuan Province, Chengdu, China
- Research Center of Avian Disease, College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, China
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Gianopulos KA, Makio AO, Pritchard SM, Cunha CW, Hull MA, Nicola AV. Herpes Simplex Virus 1 Glycoprotein B from a Hyperfusogenic Virus Mediates Enhanced Cell-Cell Fusion. Viruses 2024; 16:251. [PMID: 38400027 PMCID: PMC10892784 DOI: 10.3390/v16020251] [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: 12/05/2023] [Revised: 01/29/2024] [Accepted: 01/30/2024] [Indexed: 02/25/2024] Open
Abstract
Herpes simplex virus 1 (HSV-1) causes significant morbidity and death in humans worldwide. Herpes simplex virus 1 has a complex fusion mechanism that is incompletely understood. The HSV-1 strain ANG has notable fusion and entry activities that distinguish it from wild type. HSV-1 ANG virions fused with the Vero cell surface at 4 °C and also entered cells more efficiently at 15 °C, relative to wild type HSV-1 strain KOS virions, consistent with a hyperfusogenic phenotype. Understanding the molecular basis for the unique entry and fusion activities of HSV-1 strain ANG will help decipher the HSV fusion reaction and entry process. Sequencing of HSV-1 ANG genes revealed multiple changes in gB, gC, gD, gH, and gL proteins relative to wild type HSV-1 strains. The ANG UL45 gene sequence, which codes for a non-essential envelope protein, was identical to wild type KOS. HSV-1 ANG gB, gD, and gH/gL were necessary and sufficient to mediate cell-cell fusion in a virus-free reporter assay. ANG gB, when expressed with wild type KOS gD and gH/gL, increased membrane fusion, suggesting that ANG gB has hyperfusogenic cell-cell fusion activity. Replacing the KOS gD, gH, or gL with the corresponding ANG alleles did not enhance cell-cell fusion. The novel mutations in the ANG fusion and entry glycoproteins provide a platform for dissecting the cascade of interactions that culminate in HSV fusion and entry.
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Affiliation(s)
- Katrina A. Gianopulos
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA; (K.A.G.); (A.O.M.); (C.W.C.)
- School of Molecular Biosciences, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA
- Protein Biotechnology Graduate Training Program, Washington State University, Pullman, WA 99164, USA
| | - Albina O. Makio
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA; (K.A.G.); (A.O.M.); (C.W.C.)
- Protein Biotechnology Graduate Training Program, Washington State University, Pullman, WA 99164, USA
| | - Suzanne M. Pritchard
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA; (K.A.G.); (A.O.M.); (C.W.C.)
| | - Cristina W. Cunha
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA; (K.A.G.); (A.O.M.); (C.W.C.)
- Animal Disease Research Unit, Agricultural Research Service, United States Department of Agriculture, Pullman, WA 99164, USA
| | - McKenna A. Hull
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA; (K.A.G.); (A.O.M.); (C.W.C.)
| | - Anthony V. Nicola
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164, USA; (K.A.G.); (A.O.M.); (C.W.C.)
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4
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Ingusci S, Hall BL, Goins WF, Cohen JB, Glorioso JC. Viral vectors for gene delivery to the central nervous system. HANDBOOK OF CLINICAL NEUROLOGY 2024; 205:59-81. [PMID: 39341663 DOI: 10.1016/b978-0-323-90120-8.00001-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/01/2024]
Abstract
Brain diseases with a known or suspected genetic basis represent an important frontier for advanced therapeutics. The central nervous system (CNS) is an intricate network in which diverse cell types with multiple functions communicate via complex signaling pathways, making therapeutic intervention in brain-related diseases challenging. Nevertheless, as more information on the molecular genetics of brain-related diseases becomes available, genetic intervention using gene therapeutic strategies should become more feasible. There remain, however, several significant hurdles to overcome that relate to (i) the development of appropriate gene vectors and (ii) methods to achieve local or broad vector delivery. Clearly, gene delivery tools must be engineered for distribution to the correct cell type in a specific brain region and to accomplish therapeutic transgene expression at an appropriate level and duration. They also must avoid all toxicity, including the induction of inflammatory responses. Over the last 40 years, various types of viral vectors have been developed as tools to introduce therapeutic genes into the brain, primarily targeting neurons. This review describes the most prominent vector systems currently approaching clinical application for CNS disorders and highlights both remaining challenges as well as improvements in vector designs that achieve greater safety, defined tropism, and therapeutic gene expression.
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Affiliation(s)
- Selene Ingusci
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, United States
| | - Bonnie L Hall
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, United States
| | - William F Goins
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, United States
| | - Justus B Cohen
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, United States
| | - Joseph C Glorioso
- Department of Microbiology and Molecular Genetics, University of Pittsburgh, Pittsburgh, PA, United States.
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Vallbracht M, Schnell M, Seyfarth A, Fuchs W, Küchler R, Mettenleiter TC, Klupp BG. A Single Amino Acid Substitution in the Transmembrane Domain of Glycoprotein H Functionally Compensates for the Absence of gL in Pseudorabies Virus. Viruses 2023; 16:26. [PMID: 38257727 PMCID: PMC10819001 DOI: 10.3390/v16010026] [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: 11/01/2023] [Revised: 12/12/2023] [Accepted: 12/20/2023] [Indexed: 01/24/2024] Open
Abstract
Herpesvirus entry requires the coordinated action of at least four viral glycoproteins. Virus-specific binding to a cellular receptor triggers a membrane fusion cascade involving the conserved gH/gL complex and gB. Although gB is the genuine herpesvirus fusogen, it requires gH/gL for fusion, but how activation occurs is still unclear. To study the underlying mechanism, we used a gL-deleted pseudorabies virus (PrV) mutant characterized by its limited capability to directly infect neighboring cells that was exploited for several independent serial passages in cell culture. Unlike previous revertants that acquired mutations in the gL-binding N-terminus of gH, we obtained a variant, PrV-ΔgLPassV99, that unexpectedly contained two amino acid substitutions in the gH transmembrane domain (TMD). One of these mutations, I662S, was sufficient to compensate for gL function in virus entry and in in vitro cell-cell fusion assays in presence of wild type gB, but barely for cell-to-cell spread. Additional expression of receptor-binding PrV gD, which is dispensable for cell-cell fusion mediated by native gB, gH and gL, resulted in hyperfusion in combination with gH V99. Overall, our results uncover a yet-underestimated role of the gH TMD in fusion regulation, further shedding light on the complexity of herpesvirus fusion involving all structural domains of the conserved entry glycoproteins.
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Affiliation(s)
- Melina Vallbracht
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
- Schaller Research Groups, Department of Infectious Diseases, Virology, Heidelberg University Hospital, 69120 Heidelberg, Germany
| | - Marina Schnell
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
| | - Annemarie Seyfarth
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
- Department of Hematology, Oncology and Tumor Immunology, CBF, Charité—Universitätsmedizin, Corporate Member of Freie Universität Berlin und Humboldt—Universität zu Berlin, 12200 Berlin, Germany
| | - Walter Fuchs
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
| | - Richard Küchler
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
| | - Thomas C. Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
| | - Barbara G. Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Federal Research Institute for Animal Health, 17493 Greifswald-Insel Riems, Germany; (M.V.); (R.K.)
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Rahangdale R, Tender T, Balireddy S, Goswami K, Pasupuleti M, Hariharapura RC. A critical review on antiviral peptides derived from viral glycoproteins and host receptors to decoy herpes simplex virus. Microb Biotechnol 2023; 16:2036-2052. [PMID: 37740682 PMCID: PMC10616652 DOI: 10.1111/1751-7915.14342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/09/2023] [Accepted: 09/12/2023] [Indexed: 09/25/2023] Open
Abstract
The health of the human population has been continuously challenged by viral infections. Herpes simplex virus (HSV) is one of the common causes of illness and can lead to death in immunocompromised patients. Existing anti-HSV therapies are not completely successful in eliminating the infection due to anti-viral drug resistance, ineffectiveness against the latent virus and high toxicity over prolonged use. There is a need to update our knowledge of the current challenges faced in anti-HSV therapeutics and realize the necessity of developing alternative treatment approaches. Protein therapeutics are now being explored as a novel approach due to their high specificity and low toxicity. This review highlights the significance of HSV viral glycoproteins and host receptors in the pathogenesis of HSV infection. Proteins or peptides derived from HSV glycoproteins gC, gB, gD, gH and host cell receptors (HSPG, nectin and HVEM) that act as decoys to inhibit HSV attachment, entry, or fusion have been discussed. Few researchers have tried to improve the efficacy and stability of the identified peptides by modifying them using a peptidomimetic approach. With these efforts, we think developing an alternative treatment option for immunocompromised patients and drug-resistant organisms is not far off.
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Affiliation(s)
- Rakesh Rahangdale
- Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical SciencesManipal Academy of Higher EducationManipalKarnatakaIndia
| | - Tenzin Tender
- Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical SciencesManipal Academy of Higher EducationManipalKarnatakaIndia
| | - Sridevi Balireddy
- Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical SciencesManipal Academy of Higher EducationManipalKarnatakaIndia
| | - Kamini Goswami
- Microbiology Division, Council of Scientific and Industrial ResearchCentral Drug Research InstituteLucknowUttar PradeshIndia
| | - Mukesh Pasupuleti
- Microbiology Division, Council of Scientific and Industrial ResearchCentral Drug Research InstituteLucknowUttar PradeshIndia
- Academy of Scientific and Innovative Research (AcSIR)GhaziabadIndia
| | - Raghu Chandrashekar Hariharapura
- Department of Pharmaceutical Biotechnology, Manipal College of Pharmaceutical SciencesManipal Academy of Higher EducationManipalKarnatakaIndia
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Khwaza V, Buyana B, Nqoro X, Peter S, Mbese Z, Feketshane Z, Alven S, Aderibigbe BA. Strategies for delivery of antiviral agents. VIRAL INFECTIONS AND ANTIVIRAL THERAPIES 2023:407-492. [DOI: 10.1016/b978-0-323-91814-5.00018-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/06/2025]
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8
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Role of Epitranscriptomic and Epigenetic Modifications during the Lytic and Latent Phases of Herpesvirus Infections. Microorganisms 2022; 10:microorganisms10091754. [PMID: 36144356 PMCID: PMC9503318 DOI: 10.3390/microorganisms10091754] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 08/27/2022] [Accepted: 08/27/2022] [Indexed: 11/24/2022] Open
Abstract
Herpesviruses are double-stranded DNA viruses occurring at a high prevalence in the human population and are responsible for a wide array of clinical manifestations and diseases, from mild to severe. These viruses are classified in three subfamilies (Alpha-, Beta- and Gammaherpesvirinae), with eight members currently known to infect humans. Importantly, all herpesviruses can establish lifelong latent infections with symptomatic or asymptomatic lytic reactivations. Accumulating evidence suggest that chemical modifications of viral RNA and DNA during the lytic and latent phases of the infections caused by these viruses, are likely to play relevant roles in key aspects of the life cycle of these viruses by modulating and regulating their replication, establishment of latency and evasion of the host antiviral response. Here, we review and discuss current evidence regarding epitranscriptomic and epigenetic modifications of herpesviruses and how these can influence their life cycles. While epitranscriptomic modifications such as m6A are the most studied to date and relate to positive effects over the replication of herpesviruses, epigenetic modifications of the viral genome are generally associated with defense mechanisms of the host cells to suppress viral gene transcription. However, herpesviruses can modulate these modifications to their own benefit to persist in the host, undergo latency and sporadically reactivate.
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9
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Abstract
Herpesviruses—ubiquitous pathogens that cause persistent infections—have some of the most complex cell entry mechanisms. Entry of the prototypical herpes simplex virus 1 (HSV-1) requires coordinated efforts of 4 glycoproteins, gB, gD, gH, and gL. The current model posits that the glycoproteins do not interact before receptor engagement and that binding of gD to its receptor causes a “cascade” of sequential pairwise interactions, first activating the gH/gL complex and subsequently activating gB, the viral fusogen. But how these glycoproteins interact remains unresolved. Here, using a quantitative split-luciferase approach, we show that pairwise HSV-1 glycoprotein complexes form before fusion, interact at a steady level throughout fusion, and do not depend on the presence of the cellular receptor. Based on our findings, we propose a revised “conformational cascade” model of HSV-1 entry. We hypothesize that all 4 glycoproteins assemble into a complex before fusion, with gH/gL positioned between gD and gB. Once gD binds to a cognate receptor, the proximity of the glycoproteins within this complex allows for efficient transmission of the activating signal from the receptor-activated gD to gH/gL to gB through sequential conformational changes, ultimately triggering the fusogenic refolding of gB. Our results also highlight previously unappreciated contributions of the transmembrane and cytoplasmic domains to glycoprotein interactions and fusion. Similar principles could be at play in other multicomponent viral entry systems, and the split-luciferase approach used here is a powerful tool for investigating protein-protein interactions in these and a variety of other systems.
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10
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Using Split Luciferase Assay and anti-HSV Glycoprotein Monoclonal Antibodies to Predict a Functional Binding Site Between gD and gH/gL. J Virol 2021; 95:JVI.00053-21. [PMID: 33504603 PMCID: PMC8103690 DOI: 10.1128/jvi.00053-21] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Herpes simplex virus (HSV) entry and cell-cell fusion require glycoproteins gD, gH/gL, and gB. HSV entry begins with gD binding its receptor (nectin-1), which then activates gH/gL to enable the conversion of pre-fusion gB to its active form to promote membrane fusion. Virus-neutralizing monoclonal antibodies (Mabs) interfere with one or more of these steps and localization of their epitopes identifies functional sites on each protein. Utilizing this approach, we have identified the gH/gL binding face on gD and the corresponding gD binding site on gH/gL. Here, we used combinations of these Mabs to define the orientation of gD and gH/gL relative to each other. We reasoned that if two Mabs, one directed at gD and the other at gH/gL, block fusion more effectively than when either were used alone (additive), then their epitopes would be spatially distanced and binding of one would not directly interfere with binding of the other during fusion. However, if the two Mabs blocked fusion with equal or lesser efficacy that when either were used alone (indifferent), we propose that their epitopes would be in close proximity in the complex. Using a live cell fusion assay, we found that some Mab pairings blocked the fusion with different mechanisms while other had a similar mechanisms of action. Grouping the different combinations of antibodies into indifferent and additive groups, we present a model for the orientation of gD vis-à-vis gH/gL in the complex.Importance: Virus entry and cell-cell fusion mediated by HSV require four essential glycoproteins, gD, gH/gL, gB and a gD receptor. Virus-neutralizing antibodies directed against any of these proteins bind to residues within key functional sites and interfere with essential steps in the fusion pathway. Thus, the epitopes of these Mabs overlap and point to critical, functional sites on their target proteins. Here, we combined gD and gH/gL antibodies to determine whether they work in an additive or non-additive (indifferent) fashion to block specific events in glycoprotein-driven cell-cell fusion. Identifying combinations of antibodies that have additive effects will help in the rational design of an effective therapeutic "polyclonal antibody" to treat HSV disease. In addition, identification of the exact contact regions between gD and gH/gL can inform the design of small molecules that would interfere with the gD-gH/gL complex formation, thus preventing the virus from entering the host cell.
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Hilterbrand AT, Daly RE, Heldwein EE. Contributions of the Four Essential Entry Glycoproteins to HSV-1 Tropism and the Selection of Entry Routes. mBio 2021; 12:e00143-21. [PMID: 33653890 PMCID: PMC8092210 DOI: 10.1128/mbio.00143-21] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2021] [Accepted: 01/22/2021] [Indexed: 01/02/2023] Open
Abstract
Herpes simplex viruses (HSV-1 and HSV-2) encode up to 16 envelope proteins, four of which are essential for entry. However, whether these four proteins alone are sufficient to dictate the broad cellular tropism of HSV-1 and the selection of different cell type-dependent entry routes is unknown. To begin addressing this, we previously pseudotyped vesicular stomatitis virus (VSV), lacking its native glycoprotein G, with only the four essential entry glycoproteins of HSV-1: gB, gH, gL, and gD. This novel VSVΔG-BHLD pseudotype recapitulated several important features of HSV-1 entry: the requirement for gB, gH, gL, gD, and a cellular receptor and sensitivity to anti-gB and anti-gH/gL neutralizing antibodies. However, due to the use of a single cell type in that study, the tropism of the VSVΔG-BHLD pseudotype was not investigated. Here, we show that the cellular tropism of the pseudotype is severely limited compared to that of wild-type HSV-1 and that its entry pathways differ from the native HSV-1 entry pathways. To test the hypothesis that other HSV-1 envelope proteins may contribute to HSV-1 tropism, we generated a derivative pseudotype containing the HSV-1 glycoprotein C (VSVΔG-BHLD-gC) and observed a gC-dependent increase in entry efficiency in two cell types. We propose that the pseudotyping platform developed here has the potential to uncover functional contributions of HSV-1 envelope proteins to entry in a gain-of-function manner.IMPORTANCE Herpes simplex viruses (HSV-1 and HSV-2) contain up to 16 different proteins in their envelopes. Four of these, glycoproteins gB, gD, gH, and gL, are termed essential with regard to entry, whereas the rest are typically referred to as nonessential based on the entry phenotypes of the respective single genetic deletions. However, the single-gene deletion approach, which relies on robust loss-of-function phenotypes, may be confounded by functional redundancies among the many HSV-1 envelope proteins. We have developed a pseudotyping platform in which the essential four entry glycoproteins are isolated from the rest, which can be added back individually for systematic gain-of-function entry experiments. Here, we show the utility of this platform for dissecting the contributions of HSV envelope proteins, both the essential four and the remaining dozen (using gC as an example), to HSV entry.
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Affiliation(s)
- Adam T Hilterbrand
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Raecliffe E Daly
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Cellular, Molecular, and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
| | - Ekaterina E Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, USA
- Graduate Program in Cellular, Molecular, and Developmental Biology, Tufts University School of Medicine, Boston, Massachusetts, USA
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12
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Madavaraju K, Koganti R, Volety I, Yadavalli T, Shukla D. Herpes Simplex Virus Cell Entry Mechanisms: An Update. Front Cell Infect Microbiol 2021; 10:617578. [PMID: 33537244 PMCID: PMC7848091 DOI: 10.3389/fcimb.2020.617578] [Citation(s) in RCA: 69] [Impact Index Per Article: 17.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Accepted: 12/02/2020] [Indexed: 12/17/2022] Open
Abstract
Herpes simplex virus (HSV) can infect a broad host range and cause mild to life threating infections in humans. The surface glycoproteins of HSV are evolutionarily conserved and show an extraordinary ability to bind more than one receptor on the host cell surface. Following attachment, the virus fuses its lipid envelope with the host cell membrane and releases its nucleocapsid along with tegument proteins into the cytosol. With the help of tegument proteins and host cell factors, the nucleocapsid is then docked into the nuclear pore. The viral double stranded DNA is then released into the host cell’s nucleus. Released viral DNA either replicates rapidly (more commonly in non-neuronal cells) or stays latent inside the nucleus (in sensory neurons). The fusion of the viral envelope with host cell membrane is a key step. Blocking this step can prevent entry of HSV into the host cell and the subsequent interactions that ultimately lead to production of viral progeny and cell death or latency. In this review, we have discussed viral entry mechanisms including the pH-independent as well as pH-dependent endocytic entry, cell to cell spread of HSV and use of viral glycoproteins as an antiviral target.
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Affiliation(s)
- Krishnaraju Madavaraju
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Raghuram Koganti
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Ipsita Volety
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Tejabhiram Yadavalli
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States
| | - Deepak Shukla
- Shukla Lab, Department of Ophthalmology and Visual Sciences, University of Illinois at Chicago, Chicago, IL, United States.,Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL, United States
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13
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Menotti L, Avitabile E. Herpes Simplex Virus Oncolytic Immunovirotherapy: The Blossoming Branch of Multimodal Therapy. Int J Mol Sci 2020; 21:ijms21218310. [PMID: 33167582 PMCID: PMC7664223 DOI: 10.3390/ijms21218310] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2020] [Revised: 10/30/2020] [Accepted: 11/02/2020] [Indexed: 02/06/2023] Open
Abstract
Oncolytic viruses are smart therapeutics against cancer due to their potential to replicate and produce the needed therapeutic dose in the tumor, and to their ability to self-exhaust upon tumor clearance. Oncolytic virotherapy strategies based on the herpes simplex virus are reaching their thirties, and a wide variety of approaches has been envisioned and tested in many different models, and on a range of tumor targets. This huge effort has culminated in the primacy of an oncolytic HSV (oHSV) being the first oncolytic virus to be approved by the FDA and EMA for clinical use, for the treatment of advanced melanoma. The path has just been opened; many more cancer types with poor prognosis await effective and innovative therapies, and oHSVs could provide a promising solution, especially as combination therapies and immunovirotherapies. In this review, we analyze the most recent advances in this field, and try to envision the future ahead of oHSVs.
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14
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Abstract
Herpesviruses are ubiquitous, double-stranded DNA, enveloped viruses that establish lifelong infections and cause a range of diseases. Entry into host cells requires binding of the virus to specific receptors, followed by the coordinated action of multiple viral entry glycoproteins to trigger membrane fusion. Although the core fusion machinery is conserved for all herpesviruses, each species uses distinct receptors and receptor-binding glycoproteins. Structural studies of the prototypical herpesviruses herpes simplex virus 1 (HSV-1), HSV-2, human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) entry glycoproteins have defined the interaction sites for glycoprotein complexes and receptors, and have revealed conformational changes that occur on receptor binding. Recent crystallography and electron microscopy studies have refined our model of herpesvirus entry into cells, clarifying both the conserved features and the unique features. In this Review, we discuss recent insights into herpesvirus entry by analysing the structures of entry glycoproteins, including the diverse receptor-binding glycoproteins (HSV-1 glycoprotein D (gD), EBV glycoprotein 42 (gp42) and HCMV gH-gL-gO trimer and gH-gL-UL128-UL130-UL131A pentamer), as well gH-gL and the fusion protein gB, which are conserved in all herpesviruses.
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15
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Localization of the Interaction Site of Herpes Simplex Virus Glycoprotein D (gD) on the Membrane Fusion Regulator, gH/gL. J Virol 2020; 94:JVI.00983-20. [PMID: 32759318 DOI: 10.1128/jvi.00983-20] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Accepted: 07/27/2020] [Indexed: 12/12/2022] Open
Abstract
A cascade of protein-protein interactions between four herpes simplex virus (HSV) glycoproteins (gD, gH/gL, and gB) drive fusion between the HSV envelope and host membrane, thereby allowing for virus entry and infection. Specifically, binding of gD to one of its receptors induces a conformational change that allows gD to bind to the regulatory complex gH/gL, which then activates the fusogen gB, resulting in membrane fusion. Using surface plasmon resonance and a panel of anti-gD monoclonal antibodies (MAbs) that sterically blocked the interaction, we previously showed that gH/gL binds directly to gD at sites distinct from the gD receptor binding site. Here, using an analogous strategy, we first evaluated the ability of a panel of uncharacterized anti-gH/gL MAbs to block binding to gD and/or inhibit fusion. We found that the epitopes of four gD-gH/gL-blocking MAbs were located within flexible regions of the gH N terminus and the gL C terminus, while the fifth was placed around gL residue 77. Taken together, our data localized the gD binding region on gH/gL to a group of gH and gL residues at the membrane distal region of the heterodimer. Surprisingly, a second set of MAbs did not block gD-gH/gL binding but instead stabilized the complex by altering the kinetic binding. However, despite this prolonged gD-gH/gL interaction, "stabilizing" MAbs also inhibited cell-cell fusion, suggesting a unique mechanism by which the fusion process is halted. Our findings support targeting the gD-gH/gL interaction to prevent fusion in both therapeutic and vaccine strategies against HSV.IMPORTANCE Key to developing a human HSV vaccine is an understanding of the virion glycoproteins involved in entry. HSV employs multiple glycoproteins for attachment, receptor interaction, and membrane fusion. Determining how these proteins function was resolved, in part, by structural biology coupled with immunological and biologic evidence. After binding, virion gD interacts with a receptor to activate the regulator gH/gL complex, triggering gB to drive fusion. Multiple questions remain, one being the physical location of each glycoprotein interaction site. Using protective antibodies with known epitopes, we documented the long-sought interaction between gD and gH/gL, detailing the region on gD important to create the gD-gH/gL triplex. Now, we have identified the corresponding gD contact sites on gH/gL. Concurrently we discovered a novel mechanism whereby gH/gL antibodies stabilize the complex and inhibit fusion progression. Our model for the gD-gH/gL triplex provides a new framework for studying fusion, which identifies targets for vaccine development.
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16
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Vollmer B, Grünewald K. Herpesvirus membrane fusion - a team effort. Curr Opin Struct Biol 2020; 62:112-120. [PMID: 31935542 DOI: 10.1016/j.sbi.2019.12.004] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 11/18/2019] [Accepted: 12/02/2019] [Indexed: 12/01/2022]
Abstract
One of the essential steps in every viral 'life' cycle is entry into the host cell. Membrane-enveloped viruses carry dedicated proteins to catalyse the fusion of the viral and cellular membrane. Herpesviruses feature a set of essential, structurally diverse glycoproteins on the viral surface that form a multicomponent fusion machinery, necessary for the entry mechanism. For Herpes simplex virus 1, these essential glycoproteins are gD, gH, gL and gB. In this review we describe the functions of the individual components, the potential interactions between them as well as the influence of post-translational modifications on the fusion mechanism.
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Affiliation(s)
- Benjamin Vollmer
- Centre for Structural Systems Biology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, University of Hamburg, Hamburg, Germany; Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK
| | - Kay Grünewald
- Centre for Structural Systems Biology, Heinrich Pette Institute, Leibniz Institute for Experimental Virology, University of Hamburg, Hamburg, Germany; Division of Structural Biology, Wellcome Centre for Human Genetics, University of Oxford, Oxford, UK.
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17
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Banerjee A, Kulkarni S, Mukherjee A. Herpes Simplex Virus: The Hostile Guest That Takes Over Your Home. Front Microbiol 2020; 11:733. [PMID: 32457704 PMCID: PMC7221137 DOI: 10.3389/fmicb.2020.00733] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2020] [Accepted: 03/30/2020] [Indexed: 12/15/2022] Open
Abstract
Alpha (α)-herpesviruses (HSV-1 and HSV-2), like other viruses, are obligate intracellular parasites. They hijack the cellular machinery to survive and replicate through evading the defensive responses by the host. The viral genome of herpes simplex viruses (HSVs) contains viral genes, the products of which are destined to exploit the host apparatus for their own existence. Cellular modulations begin from the entry point itself. The two main gateways that the virus has to penetrate are the cell membrane and the nuclear membrane. Changes in the cell membrane are triggered when the glycoproteins of HSV interact with the surface receptors of the host cell, and from here, the components of the cytoskeleton take over. The rearrangement in the cytoskeleton components help the virus to enter as well as transport to the nucleus and back to the cell membrane to spread out to the other cells. The entire carriage process is also mediated by the motor proteins of the kinesin and dynein superfamily and is directed by the viral tegument proteins. Also, the virus captures the cell’s most efficient cargo carrying system, the endoplasmic reticulum (ER)–Golgi vesicular transport machinery for egress to the cell membrane. For these reasons, the host cell has its own checkpoints where the normal functions are halted once a danger is sensed. However, a cell may be prepared for the adversities from an invading virus, and it is simply commendable that the virus has the antidote to these cellular strategies as well. The HSV viral proteins are capable of limiting the use of the transcriptional and translational tools for the cell itself, so that its own transcription and translation pathways remain unhindered. HSV prefers to constrain any self-destruction process of the cell—be it autophagy in the lysosome or apoptosis by the mitochondria, so that it can continue to parasitize the cell for its own survival. This review gives a detailed account of the significance of compartmentalization during HSV pathogenesis. It also highlights the undiscovered areas in the HSV cell biology research which demand attention for devising improved therapeutics against the infection.
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Affiliation(s)
- Anwesha Banerjee
- Division of Virology, Indian Council of Medical Research-National AIDS Research Institute, Pune, India
| | - Smita Kulkarni
- Division of Virology, Indian Council of Medical Research-National AIDS Research Institute, Pune, India
| | - Anupam Mukherjee
- Division of Virology, Indian Council of Medical Research-National AIDS Research Institute, Pune, India
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18
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Monteiro AFM, de Oliveira Viana J, Muratov E, Scotti MT, Scotti L. In Silico Studies against Viral Sexually Transmitted Diseases. Curr Protein Pept Sci 2020; 20:1135-1150. [PMID: 30854957 DOI: 10.2174/1389203720666190311142747] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Revised: 01/17/2019] [Accepted: 01/18/2019] [Indexed: 01/02/2023]
Abstract
Sexually Transmitted Diseases (STDs) refer to a variety of clinical syndromes and infections caused by pathogens that can be acquired and transmitted through sexual activity. Among STDs widely reported in the literature, viral sexual diseases have been increasing in a number of cases globally. This emphasizes the need for prevention and treatment. Among the methods widely used in drug planning are Computer-Aided Drug Design (CADD) studies and molecular docking which have the objective of investigating molecular interactions between two molecules to better understand the three -dimensional structural characteristics of the compounds. This review will discuss molecular docking studies applied to viral STDs, such as Ebola virus, Herpes virus and HIV, and reveal promising new drug candidates with high levels of specificity to their respective targets.
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Affiliation(s)
- Alex F M Monteiro
- Program of Natural and Synthetic Bioactive Products (PgPNSB), Health Sciences Center, Federal University of Paraíba, Joao Pessoa-PB, Brazil
| | - Jessika de Oliveira Viana
- Program of Natural and Synthetic Bioactive Products (PgPNSB), Health Sciences Center, Federal University of Paraíba, Joao Pessoa-PB, Brazil
| | - Engene Muratov
- Laboratory for Molecular Modeling, Division of Medicinal Chemistry and Natural Products, Eshelman School of Pharmacy, University of North Carolina, Beard Hall 301, CB#7568, Chapel Hill, NC, 27599, United States
| | - Marcus T Scotti
- Program of Natural and Synthetic Bioactive Products (PgPNSB), Health Sciences Center, Federal University of Paraíba, Joao Pessoa-PB, Brazil
| | - Luciana Scotti
- Program of Natural and Synthetic Bioactive Products (PgPNSB), Health Sciences Center, Federal University of Paraíba, Joao Pessoa-PB, Brazil.,Teaching and Research Management - University Hospital, Federal University of Paraíba, Campus I, 58051-900, João Pessoa-PB, Brazil
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19
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White EM, Stampfer SD, Heldwein EE. Expression, Purification, and Crystallization of HSV-1 Glycoproteins for Structure Determination. Methods Mol Biol 2020; 2060:377-393. [PMID: 31617192 PMCID: PMC9903252 DOI: 10.1007/978-1-4939-9814-2_23] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
Herpes simplex viruses utilize glycoproteins displayed on the viral envelope to perform a variety of functions in the viral infectious cycle. Structural and functional studies of these viral glycoproteins can benefit from biochemical, biophysical, and structural analysis of purified proteins. Here, we describe a general protocol for expression and purification of viral glycoproteins from insect cells based on those developed for the HSV-1 gB and HSV-2 gH/gL ectodomains as well as the protocol for crystallization of these glycoproteins. This protocol can be used for generating milligram amounts of wild-type (WT) or mutant gB and gH/gL ectodomains or can be adapted to produce purified ectodomains of glycoproteins from HSV or other herpesviruses for biochemical and structural studies.
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20
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Surface Plasmon Resonance Reveals Direct Binding of Herpes Simplex Virus Glycoproteins gH/gL to gD and Locates a gH/gL Binding Site on gD. J Virol 2019; 93:JVI.00289-19. [PMID: 31092568 DOI: 10.1128/jvi.00289-19] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2019] [Accepted: 05/04/2019] [Indexed: 12/23/2022] Open
Abstract
Herpes simplex virus (HSV) requires fusion between the viral envelope and host membrane. Four glycoproteins, gD, gH/gL, and gB, are essential for this process. To initiate fusion, gD binds its receptor and undergoes a conformational change that hypothetically leads to activation of gH/gL, which in turn triggers the fusion protein gB to undergo rearrangements leading to membrane fusion. Our model predicts that gD must interact with both its receptor and gH/gL to promote fusion. In support of this, we have shown that gD is structurally divided into two "faces": one for the binding receptor and the other for its presumed interaction with gH/gL. However, until now, we have been unable to demonstrate a direct interaction between gD and gH/gL. Here, we used surface plasmon resonance to show that the ectodomain of gH/gL binds directly to the ectodomain of gD when (i) gD is captured by certain anti-gD monoclonal antibodies (MAbs) that are bound to a biosensor chip, (ii) gD is bound to either one of its receptors on a chip, and (iii) gD is covalently bound to the chip surface. To localize the gH/gL binding site on gD, we used multiple anti-gD MAbs from six antigenic communities and determined which ones interfered with this interaction. MAbs from three separate communities block gD-gH/gL binding, and their epitopes encircle a geographical area on gD that we propose comprises the gH/gL binding domain. Together, our results show that gH/gL interacts directly with gD, supporting a role for this step in HSV entry.IMPORTANCE HSV entry is a multistep process that requires the actions of four glycoproteins, gD, gH/gL, and gB. Our current model predicts that gD must interact with both its receptor and gH/gL to promote viral entry. Although we know a great deal about how gD binds its receptors, until now we have been unable to demonstrate a direct interaction between gD and gH/gL. Here, we used a highly sensitive surface plasmon resonance technique to clearly demonstrate that gD and gH/gL interact. Furthermore, using multiple MAbs with defined epitopes, we have delineated a domain on gD that is independent of that used for receptor binding and which likely represents the gH/gL interaction domain. Targeting this interaction to prevent fusion may enhance both therapeutic and vaccine strategies.
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21
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Vallbracht M, Backovic M, Klupp BG, Rey FA, Mettenleiter TC. Common characteristics and unique features: A comparison of the fusion machinery of the alphaherpesviruses Pseudorabies virus and Herpes simplex virus. Adv Virus Res 2019; 104:225-281. [PMID: 31439150 DOI: 10.1016/bs.aivir.2019.05.007] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Membrane fusion is a fundamental biological process that allows different cellular compartments delimited by a lipid membrane to release or exchange their respective contents. Similarly, enveloped viruses such as alphaherpesviruses exploit membrane fusion to enter and infect their host cells. For infectious entry the prototypic human Herpes simplex viruses 1 and 2 (HSV-1 and -2, collectively termed HSVs) and the porcine Pseudorabies virus (PrV) utilize four different essential envelope glycoproteins (g): the bona fide fusion protein gB and the regulatory heterodimeric gH/gL complex that constitute the "core fusion machinery" conserved in all members of the Herpesviridae; and the subfamily specific receptor binding protein gD. These four components mediate attachment and fusion of the virion envelope with the host cell plasma membrane through a tightly regulated sequential activation process. Although PrV and the HSVs are closely related and employ the same set of glycoproteins for entry, they show remarkable differences in the requirements for fusion. Whereas the HSVs strictly require all four components for membrane fusion, PrV can mediate cell-cell fusion without gD. Moreover, in contrast to the HSVs, PrV provides a unique opportunity for reversion analyses of gL-negative mutants by serial cell culture passaging, due to a limited cell-cell spread capacity of gL-negative PrV not observed in the HSVs. This allows a more direct analysis of the function of gH/gL during membrane fusion. Unraveling the molecular mechanism of herpesvirus fusion has been a goal of fundamental research for years, and yet important mechanistic details remain to be uncovered. Nevertheless, the elucidation of the crystal structures of all key players involved in PrV and HSV membrane fusion, coupled with a wealth of functional data, has shed some light on this complex puzzle. In this review, we summarize and discuss the contemporary knowledge on the molecular mechanism of entry and membrane fusion utilized by the alphaherpesvirus PrV, and highlight similarities but also remarkable differences in the requirements for fusion between PrV and the HSVs.
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Affiliation(s)
- Melina Vallbracht
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany.
| | - Marija Backovic
- Institut Pasteur, Unité de Virologie Structurale, UMR3569 (CNRS), Paris, France
| | - Barbara G Klupp
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
| | - Felix A Rey
- Institut Pasteur, Unité de Virologie Structurale, UMR3569 (CNRS), Paris, France
| | - Thomas C Mettenleiter
- Institute of Molecular Virology and Cell Biology, Friedrich-Loeffler-Institut, Greifswald - Insel Riems, Germany
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22
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Liu XQ, Xin HY, Lyu YN, Ma ZW, Peng XC, Xiang Y, Wang YY, Wu ZJ, Cheng JT, Ji JF, Zhong JX, Ren BX, Wang XW, Xin HW. Oncolytic herpes simplex virus tumor targeting and neutralization escape by engineering viral envelope glycoproteins. Drug Deliv 2019; 25:1950-1962. [PMID: 30799657 PMCID: PMC6282442 DOI: 10.1080/10717544.2018.1534895] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Oncolytic herpes simplex viruses (oHSVs) have been approved for clinical usage and become more and more popular for tumor virotherapy. However, there are still many issues for the oHSVs used in clinics and clinical trials. The main issues are the limited anti-tumor effects, intratumor injection, and some side effects. To overcome such challenges, here we review the genetic engineering of the envelope glycoproteins for oHSVs to target tumors specifically, and at the same time we summarize the many neutralization antibodies against the envelope glycoproteins and align the neutralization epitopes with functional domains of the respective glycoproteins for future identification of new functions of the glycoproteins and future engineering of the epitopes to escape from host neutralization.
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Affiliation(s)
- Xiao-Qin Liu
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,d Department of Nursing and Medical Imaging Technology , Yangtze University , Jingzhou , Hubei , China
| | - Hong-Yi Xin
- e Star Array Pte Ltd , JTC Medtech Hub , Singapore , Singapore
| | - Yan-Ning Lyu
- f Institute for Infectious Diseases and Endemic Diseases Prevention and Control, Beijing Center for Diseases Prevention and Control , Beijing , China
| | - Zhao-Wu Ma
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
| | - Xiao-Chun Peng
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,g Faculty of Medicine, Department of Pathophysiology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
| | - Ying Xiang
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
| | - Ying-Ying Wang
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
| | - Zi-Jun Wu
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,d Department of Nursing and Medical Imaging Technology , Yangtze University , Jingzhou , Hubei , China
| | - Jun-Ting Cheng
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
| | - Jia-Fu Ji
- h Key Laboratory of Carcinogenesis and Translational Research (Ministry of Education), Department of Gastrointestinal Surgery , Peking University Cancer Hospital and Institute , Haidian , Beijing , China
| | - Ji-Xin Zhong
- i Cardiovascular Research Institute , Case Western Reserve University , Cleveland , OH , USA
| | - Bo-Xu Ren
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,d Department of Nursing and Medical Imaging Technology , Yangtze University , Jingzhou , Hubei , China
| | - Xian-Wang Wang
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,j Faculty of Medicine, Department of Laboratory Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
| | - Hong-Wu Xin
- a Faculty of Medicine, The Second School of Clinical Medicine , Yangtze University, Nanhuan , Jingzhou , Hubei , China.,b Laboratory of Oncology, Faculty of Medicine, Center for Molecular Medicine, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China.,c Faculty of Medicine, Department of Biochemistry and Molecular Biology, School of Basic Medicine , Yangtze University , Jingzhou , Hubei , China
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Hilterbrand AT, Heldwein EE. Go go gadget glycoprotein!: HSV-1 draws on its sizeable glycoprotein tool kit to customize its diverse entry routes. PLoS Pathog 2019; 15:e1007660. [PMID: 31071197 PMCID: PMC6508585 DOI: 10.1371/journal.ppat.1007660] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Affiliation(s)
- Adam T. Hilterbrand
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
| | - Ekaterina E. Heldwein
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, Boston, Massachusetts, United States of America
- * E-mail:
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Tognarelli EI, Palomino TF, Corrales N, Bueno SM, Kalergis AM, González PA. Herpes Simplex Virus Evasion of Early Host Antiviral Responses. Front Cell Infect Microbiol 2019; 9:127. [PMID: 31114761 PMCID: PMC6503643 DOI: 10.3389/fcimb.2019.00127] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2019] [Accepted: 04/10/2019] [Indexed: 12/21/2022] Open
Abstract
Herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) have co-evolved with humans for thousands of years and are present at a high prevalence in the population worldwide. HSV infections are responsible for several illnesses including skin and mucosal lesions, blindness and even life-threatening encephalitis in both, immunocompetent and immunocompromised individuals of all ages. Therefore, diseases caused by HSVs represent significant public health burdens. Similar to other herpesviruses, HSV-1 and HSV-2 produce lifelong infections in the host by establishing latency in neurons and sporadically reactivating from these cells, eliciting recurrences that are accompanied by viral shedding in both, symptomatic and asymptomatic individuals. The ability of HSVs to persist and recur in otherwise healthy individuals is likely given by the numerous virulence factors that these viruses have evolved to evade host antiviral responses. Here, we review and discuss molecular mechanisms used by HSVs to evade early innate antiviral responses, which are the first lines of defense against these viruses. A comprehensive understanding of how HSVs evade host early antiviral responses could contribute to the development of novel therapies and vaccines to counteract these viruses.
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Affiliation(s)
- Eduardo I Tognarelli
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Tomás F Palomino
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Nicolás Corrales
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Susan M Bueno
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Alexis M Kalergis
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile.,Departamento de Endocrinología, Facultad de Medicina, Escuela de Medicina, Pontificia Universidad Católica de Chile, Santiago, Chile
| | - Pablo A González
- Millennium Institute on Immunology and Immunotherapy, Departamento de Genética Molecular y Microbiología, Facultad de Ciencias Biológicas, Pontificia Universidad Católica de Chile, Santiago, Chile
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25
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Dendritic cells in the cornea during Herpes simplex viral infection and inflammation. Surv Ophthalmol 2018; 63:565-578. [DOI: 10.1016/j.survophthal.2017.11.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2017] [Revised: 11/05/2017] [Accepted: 11/06/2017] [Indexed: 12/24/2022]
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Dual Ligand Insertion in gB and gD of Oncolytic Herpes Simplex Viruses for Retargeting to a Producer Vero Cell Line and to Cancer Cells. J Virol 2018; 92:JVI.02122-17. [PMID: 29263257 PMCID: PMC5827396 DOI: 10.1128/jvi.02122-17] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 12/07/2017] [Indexed: 01/03/2023] Open
Abstract
Oncolytic viruses gain cancer specificity in several ways. Like the majority of viruses, they grow better in cancer cells that are defective in mounting the host response to viruses. Often, they are attenuated by deletion or mutation of virulence genes that counteract the host response or are naturally occurring oncolytic mutants. In contrast, retargeted viruses are not attenuated or deleted; their cancer specificity rests on a modified, specific tropism for cancer receptors. For herpes simplex virus (HSV)-based oncolytics, the detargeting-retargeting strategies employed so far were based on genetic modifications of gD. Recently, we showed that even gH or gB can serve as retargeting tools. To enable the growth of retargeted HSVs in cells that can be used for clinical-grade virus production, a double-retargeting strategy has been developed. Here we show that several sites in the N terminus of gB are suitable to harbor the 20-amino-acid (aa)-long GCN4 peptide, which readdresses HSV tropism to Vero cells expressing the artificial GCN4 receptor and thus enables virus cultivation in the producer noncancer Vero-GCN4R cell line. The gB modifications can be combined with a minimal detargeting modification in gD, consisting in the deletion of two residues, aa 30 and 38, and replacement of aa 38 with the scFv to human epidermal growth factor receptor 2 (HER2), for retargeting to the cancer receptor. The panel of recombinants was analyzed comparatively in terms of virus growth, cell-to-cell spread, cytotoxicity, and in vivo antitumor efficacy to define the best double-retargeting strategy. IMPORTANCE There is increasing interest in oncolytic viruses, following FDA and the European Medicines Agency (EMA) approval of HSV OncovexGM-CSF, and, mainly, because they greatly boost the immune response to the tumor and can be combined with immunotherapeutic agents, particularly checkpoint inhibitors. A strategy to gain cancer specificity and avoid virus attenuation is to retarget the virus tropism to cancer-specific receptors of choice. Cultivation of fully retargeted viruses is challenging, since they require cells that express the cancer receptor. We devised a strategy for their cultivation in producer noncancer Vero cell derivatives. Here, we developed a double-retargeting strategy, based on insertion of one ligand in gB for retargeting to a Vero cell derivative and of anti-HER2 ligand in gD for cancer retargeting. These modifications were combined with a minimally destructive detargeting strategy. This study and its companion paper explain the clinical-grade cultivation of retargeted oncolytic HSVs and promote their translation to the clinic.
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Insertion of a ligand to HER2 in gB retargets HSV tropism and obviates the need for activation of the other entry glycoproteins. PLoS Pathog 2017; 13:e1006352. [PMID: 28423057 PMCID: PMC5411103 DOI: 10.1371/journal.ppat.1006352] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2017] [Revised: 05/01/2017] [Accepted: 04/13/2017] [Indexed: 11/19/2022] Open
Abstract
Herpes simplex virus (HSV) entry into the cells requires glycoproteins gD, gH/gL and gB, activated in a cascade fashion by conformational modifications induced by cognate receptors and intermolecular signaling. The receptors are nectin1 and HVEM (Herpes virus entry mediator) for gD, and αvβ6 or αvβ8 integrin for gH. In earlier work, insertion of a single chain antibody (scFv) to the cancer receptor HER2 (human epidermal growth factor receptor 2) in gD, or in gH, resulted in HSVs specifically retargeted to the HER2-positive cancer cells, hence in highly specific non-attenuated oncolytic agents. Here, the scFv to HER2 was inserted in gB (gBHER2). The insertion re-targeted the virus tropism to the HER2-positive cancer cells. This was unexpected since gB is known to be a fusogenic glycoprotein, not a tropism determinant. The gB-retargeted recombinant offered the possibility to investigate how HER2 mediated entry. In contrast to wt-gB, the activation of the chimeric gBHER2 did not require the activation of the gD and of gH/gL by their respective receptors. Furthermore, a soluble form of HER2 could replace the membrane-bound HER2 in mediating virus entry, hinting that HER2 acted by inducing conformational changes to the chimeric gB. This study shows that (i) gB can be modified and become the major determinant of HSV tropism; (ii) the chimeric gBHER2 bypasses the requirement for receptor-mediated activation of other essential entry glycoproteins.
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Functional Relevance of the N-Terminal Domain of Pseudorabies Virus Envelope Glycoprotein H and Its Interaction with Glycoprotein L. J Virol 2017; 91:JVI.00061-17. [PMID: 28228592 DOI: 10.1128/jvi.00061-17] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2017] [Accepted: 02/15/2017] [Indexed: 01/17/2023] Open
Abstract
Several envelope glycoproteins are involved in herpesvirus entry into cells, direct cell-to-cell spread, and induction of cell fusion. The membrane fusion protein glycoprotein B (gB) and the presumably gB-activating heterodimer gH/gL are essential for these processes and conserved throughout the Herpesviridae However, after extended cell culture passage of gL-negative mutants of the alphaherpesvirus pseudorabies virus (PrV), phenotypic revertants could be isolated which had acquired spontaneous mutations affecting the gL-interacting N-terminal part of the gH ectodomain (gDH and gHB4.1) (B. G. Klupp and T. C. Mettenleiter, J Virol 73:3014-3022, 1999; C. Schröter, M. Vallbracht, J. Altenschmidt, S. Kargoll, W. Fuchs, B. G. Klupp, and T. C. Mettenleiter, J Virol 90:2264-2272, 2016). To investigate the functional relevance of this part of gH in more detail, we introduced an in-frame deletion of 66 codons at the 5' end of the plasmid-cloned gH gene (gH32/98). The N-terminal signal peptide was retained, and the deletion did not affect expression or processing of gH but abrogated its function in in vitro fusion assays. Insertion of the engineered gH gene into the PrV genome resulted in a defective mutant (pPrV-gH32/98K), which was incapable of entry and spread. Interestingly, in vitro activity of mutated gH32/98 was restored when it was coexpressed with hyperfusogenic gBB4.1, obtained from a passaged gL deletion mutant of PrV. Moreover, the entry and spread defects of pPrV-gH32/98K were compensated by the mutations in gBB4.1 in cis, as well as in trans, independent of gL. Thus, PrV gL and the gL-interacting domain of gH are not strictly required for function.IMPORTANCE Membrane fusion is crucial for infectious entry and spread of enveloped viruses. While many enveloped viruses require only one or two proteins for receptor binding and membrane fusion, herpesvirus infection depends on several envelope glycoproteins. Besides subfamily-specific receptor binding proteins, the core fusion machinery consists of the conserved fusion protein gB and the gH/gL complex. The role of the latter is unclear, but it is hypothesized to interact with gB for fusion activation. Using isogenic virus recombinants, we demonstrate here that gL and the gL-binding domain of PrV gH are not strictly required for membrane fusion during virus entry and spread when concomitantly mutations in gB are present which increase its fusogenicity. Thus, our results strongly support the notion of a functional gB-gH interaction during the fusion process.
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Cetina-Corona A, López-Sánchez U, Salinas-Trujano J, Méndez-Tenorio A, Barrón BL, Torres-Flores J. Peptides Derived from Glycoproteins H and B of Herpes Simplex Virus Type 1 and Herpes Simplex Virus Type 2 Are Capable of Blocking Herpetic Infection in vitro. Intervirology 2017; 59:235-242. [PMID: 28329739 DOI: 10.1159/000464134] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2016] [Accepted: 02/08/2017] [Indexed: 11/19/2022] Open
Abstract
AIMS The aim of this study was to design peptides derived from glycoproteins H (gH) and B (gB) of herpes simplex viruses type 1 (HSV-1) and type 2 (HSV-2) with the potential to block herpetic infection and to evaluate their ability to inhibit HSV-1 and HSV-2 infection in vitro. METHODS A library of continuous 15-25 residue stretches (CRSs) located at the surface of gH and gB from HSV-1 and HSV-2 was created. These CRSs were analyzed, and only those that were highly flexible and rich in charged residues were selected for the design of the antiviral peptides (AVPs). The toxicity of the AVPs was evaluated by MTT reduction assays. Virucidal activity of the AVPs was determined by a plaque reduction assay, and their antiviral effect was measured by cell viability assays. RESULTS AND CONCLUSION Four AVPs (CB-1, CB-2, U-1, and U-2) derived from gB and gH were designed and synthetized, none of which showed high levels of toxicity in Vero cells. The U-1 and U-2 gB-derived AVPs showed high virucidal and antiviral activities against both HSV-1 and HSV-2. The gH-derived peptide CB-1 showed high virucidal and antiviral activities against HSV-2, while CB-2 showed similar results against HSV-1. The peptides CB-1 and CB-2 showed higher IC50 values than the U-1 and U-2 peptides.
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Affiliation(s)
- Abraham Cetina-Corona
- Laboratorio de Virología, Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, Mexico City, Mexico
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Mapping sites of herpes simplex virus type 1 glycoprotein D that permit insertions and impact gD and gB receptors usage. Sci Rep 2017; 7:43712. [PMID: 28255168 PMCID: PMC5334651 DOI: 10.1038/srep43712] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2016] [Accepted: 01/16/2017] [Indexed: 01/05/2023] Open
Abstract
Glycoprotein D (gD) of herpes simplex virus type 1 (HSV-1) is one of four glycoproteins essential for HSV entry and cell fusion. The purpose of this study was to determine the plasticity of gD to tolerate insertion or deletion mutations and to construct an oncolytic HSV-1 that utilizes the disialoganglioside GD2 as a HSV-1 entry receptor. We found that the N-terminus of gD tolerates long insertions, whereas residues adjacent to the gD Ig-like V-type core tolerated shorter insertions (up to 15 amino acids), but not greater than 60 amino acids. Recombinant HSV-1 containing the ch14.18 single chain variable fragment (scFv) at the N-terminus of gD failed to mediate entry, even though the ch14.18 scFv-gD chimera Fc bound to neuroblastoma cells expressing GD2. Finally, we found that hyperfusogenic gB mutants enhanced fusion to a greater degree with the gB receptor the paired immunoglobulin-like type 2 receptor alpha (PILRα) than with gD receptors HVEM and nectin-1. Hyperfusogenic gB could restore the fusion function with PILRα when a gD constructed contained only the “profusion domain” (PFD), suggesting the hyperfusogenic form of gB may regulate fusion of PILRα via a novel mechanism through gH/gL and the gD PFD.
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31
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Franci G, Falanga A, Zannella C, Folliero V, Martora F, Galdiero M, Galdiero S, Morelli G, Galdiero M. Infectivity inhibition by overlapping synthetic peptides derived from the gH/gL heterodimer of herpes simplex virus type 1. J Pept Sci 2017; 23:311-319. [PMID: 28194842 PMCID: PMC7168125 DOI: 10.1002/psc.2979] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2016] [Revised: 01/13/2017] [Accepted: 01/16/2017] [Indexed: 01/27/2023]
Abstract
Herpes simplex virus (HSV) is a human pathogen that infects epithelial cells. The cutaneous lesions, caused by the virus, spread to the nervous system creating several complications. Fusion of host membranes with the viral envelope is mandatory and mediated by a group of glycoproteins conserved in all Herpesviridae subfamilies, such as the glycoproteins B (gB), H (gH), L (gL) and D (gD). We investigated the inhibitory activity mediated by synthetic overlapping peptides spanning the entire ectodomains of gH and gL glycoproteins. We have performed a brute analysis of the complete gH/gL heterodimer in order to explore the inhibitory activity of peptides modelled on these glycoproteins against HSV‐1 infection. Twenty‐four of the gH peptides at a concentration of 150 μM reached the 50% of inhibition cut‐off. Interestingly, they are mainly located in the gH carboxy‐terminal domain. None of the gL peptides had a clear inhibiting effect. No peptide toxicity was observed by lactate dehydrogenase assay at the concentrations used in our experimental conditions. HSV‐1 therapy is based on acyclovir treatment, but some resistant strains are emerging. In this scenario, innovative approaches for HSV‐1 treatment are necessary. Our data support the direct involvement of the described domains in the process of virus penetration; therefore, these results are of relevance to the potential development of novel therapeutic compounds to prevent HSV‐1 infections. Copyright © 2017 European Peptide Society and John Wiley & Sons, Ltd.
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Affiliation(s)
- Gianluigi Franci
- Department of Experimental MedicineUniversity of Campania “Luigi Vanvitelli”Via De Crecchio 780138NaplesItaly
- Centro Interuniversitario di Ricerca sui Peptidi BioattiviUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
| | - Annarita Falanga
- Centro Interuniversitario di Ricerca sui Peptidi BioattiviUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
- Department of PharmacyUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
| | - Carla Zannella
- Department of Experimental MedicineUniversity of Campania “Luigi Vanvitelli”Via De Crecchio 780138NaplesItaly
| | - Veronica Folliero
- Department of Experimental MedicineUniversity of Campania “Luigi Vanvitelli”Via De Crecchio 780138NaplesItaly
| | - Francesca Martora
- Department of Experimental MedicineUniversity of Campania “Luigi Vanvitelli”Via De Crecchio 780138NaplesItaly
| | - Marilena Galdiero
- Department of Experimental MedicineUniversity of Campania “Luigi Vanvitelli”Via De Crecchio 780138NaplesItaly
| | - Stefania Galdiero
- Centro Interuniversitario di Ricerca sui Peptidi BioattiviUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
| | - Giancarlo Morelli
- Centro Interuniversitario di Ricerca sui Peptidi BioattiviUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
- Department of PharmacyUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
| | - Massimiliano Galdiero
- Department of Experimental MedicineUniversity of Campania “Luigi Vanvitelli”Via De Crecchio 780138NaplesItaly
- Centro Interuniversitario di Ricerca sui Peptidi BioattiviUniversity of Naples ‘Federico II’Via Mezzocannone 1680134NaplesItaly
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Niazy N, Temme S, Bocuk D, Giesen C, König A, Temme N, Ziegfeld A, Gregers TF, Bakke O, Lang T, Eis-Hübinger AM, Koch N. Misdirection of endosomal trafficking mediated by herpes simplex virus-encoded glycoprotein B. FASEB J 2017; 31:1650-1667. [PMID: 28119397 DOI: 10.1096/fj.201600521r] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2016] [Accepted: 01/01/2017] [Indexed: 01/01/2023]
Abstract
Herpes simplex virus (HSV)-encoded glycoprotein B (gB) is the most abundant protein in the viral envelope and promotes fusion of the virus with the cellular membrane. In the present study, we found that gB impacts on the major histocompatibility complex (MHC)-II pathway of antigen presentation by fostering homotypic fusion of early endosomes and trapping MHC-II molecules in these altered endosomes. By using an overexpression approach, we demonstrated that transient expression of gB induces giant vesicles of early endosomal origin, which contained Rab5, early endosomal antigen 1 (EEA1), and large amounts of MHC-II molecules [human leukocyte antigen (HLA)-DR, and HLA-DM], but no CD63. In HSV-1-infected and stably transfected cell lines that expressed lower amounts of gB, giant endosomes were not observed, but strongly increased amounts of HLA-DR and HLA-DM were found in EEA1+ early endosomes. We used these giant vesicles as a model system and revealed that gB interacts with Rab5 and EEA1, and that gB-induced homotypic fusion of early endosomes to giant endosomes requires phosphatidylinositol 3-phosphate, the activity of soluble N-ethylmaleimide-sensitive factor attachment protein receptors, and the cytosolic gB sequence 889YTQVPN894 We conclude that gB expression alters trafficking of molecules of the HLA-II processing pathway, which leads to increased retention of MHC-II molecules in early endosomal compartments, thereby intercepting antigen presentation.-Niazy, N., Temme, S., Bocuk, D., Giesen, C., König, A., Temme, N., Ziegfeld, A., Gregers, T. F., Bakke, O., Lang, T., Eis-Hübinger, A. M., Koch, N. Misdirection of endosomal trafficking mediated by herpes simplex virus-encoded glycoprotein B.
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Affiliation(s)
- Naima Niazy
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
| | - Sebastian Temme
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany;
| | - Derya Bocuk
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
| | - Carmen Giesen
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
| | - Angelika König
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
| | - Nadine Temme
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
| | - Angelique Ziegfeld
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
| | - Tone F Gregers
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Oddmund Bakke
- Department of Biosciences, University of Oslo, Oslo, Norway
| | - Thorsten Lang
- Membrane Biochemistry, Life and Medical Sciences Institute, University of Bonn, Bonn, Germany
| | | | - Norbert Koch
- Section of Immunobiology, Institute of Genetics, University of Bonn, Bonn, Germany
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Weed DJ, Nicola AV. Herpes simplex virus Membrane Fusion. ADVANCES IN ANATOMY, EMBRYOLOGY, AND CELL BIOLOGY 2017; 223:29-47. [PMID: 28528438 PMCID: PMC5869023 DOI: 10.1007/978-3-319-53168-7_2] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
Herpes simplex virus mediates multiple distinct fusion events during infection. HSV entry is initiated by fusion of the viral envelope with either the limiting membrane of a host cell endocytic compartment or the plasma membrane. In the infected cell during viral assembly, immature, enveloped HSV particles in the perinuclear space fuse with the outer nuclear membrane in a process termed de-envelopment. A cell infected with some strains of HSV with defined mutations spread to neighboring cells by a fusion event called syncytium formation. Two experimental methods, the transient cell-cell fusion approach and fusion from without, are useful surrogate assays of HSV fusion. These five fusion processes are considered in terms of their requirements, mechanism, and regulation. The execution and modulation of these events require distinct yet often overlapping sets of viral proteins and host cell factors. The core machinery of HSV gB, gD, and the heterodimer gH/gL is required for most if not all of the HSV fusion mechanisms.
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Affiliation(s)
- Darin J Weed
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA, 99164, USA
| | - Anthony V Nicola
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA, 99164, USA.
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Atanasiu D, Saw WT, Eisenberg RJ, Cohen GH. Regulation of Herpes Simplex Virus Glycoprotein-Induced Cascade of Events Governing Cell-Cell Fusion. J Virol 2016; 90:10535-10544. [PMID: 27630245 PMCID: PMC5110162 DOI: 10.1128/jvi.01501-16] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Accepted: 09/09/2016] [Indexed: 01/06/2023] Open
Abstract
Receptor-dependent herpes simplex virus (HSV)-induced cell-cell fusion requires glycoproteins gD, gH/gL, and gB. Our current model posits that during fusion, receptor-activated conformational changes in gD activate gH/gL, which subsequently triggers the transformation of the prefusion form of gB into a fusogenic state. To examine the role of each glycoprotein in receptor-dependent cell-cell fusion, we took advantage of our discovery that fusion by wild-type herpes simplex virus 2 (HSV-2) glycoproteins occurs twice as fast as that achieved by HSV-1 glycoproteins. By sequentially swapping each glycoprotein between the two serotypes, we established that fusion speed was governed by gH/gL, with gH being the main contributor. While the mutant forms of gB fuse at distinct rates that are dictated by their molecular structure, these restrictions can be overcome by gH/gL of HSV-2 (gH2/gL2), thereby enhancing their activity. We also found that deregulated forms of gD of HSV-1 (gD1) and gH2/gL2 can alter the fusogenic potential of gB, promoting cell fusion in the absence of a cellular receptor, and that deregulated forms of gB can drive the fusion machinery to even higher levels. Low pH enhanced fusion by affecting the structure of both gB and gH/gL mutants. Together, our data highlight the complexity of the fusion machinery, the impact of the activation state of each glycoprotein on the fusion process, and the critical role of gH/gL in regulating HSV-induced fusion. IMPORTANCE Cell-cell fusion mediated by HSV glycoproteins requires gD, gH/gL, gB, and a gD receptor. Here, we show that fusion by wild-type HSV-2 glycoproteins occurs twice as fast as that achieved by HSV-1 glycoproteins. By sequentially swapping each glycoprotein between the two serotypes, we found that the fusion process was controlled by gH/gL. Restrictions imposed on the gB structure by mutations could be overcome by gH2/gL2, enhancing the activity of the mutants. Under low-pH conditions or when using deregulated forms of gD1 and gH2/gL2, the fusogenic potential of gB could only be increased in the absence of receptor, underlining the exquisite regulation that occurs in the presence of receptor. Our data highlight the complexity of the fusion machinery, the impact of the activation state of each glycoprotein on the fusion process, and the critical role of gH/gL in regulating HSV-induced fusion.
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Affiliation(s)
- Doina Atanasiu
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Wan Ting Saw
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Roselyn J Eisenberg
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
| | - Gary H Cohen
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, Pennsylvania, USA
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Oliver SL, Yang E, Arvin AM. Varicella-Zoster Virus Glycoproteins: Entry, Replication, and Pathogenesis. CURRENT CLINICAL MICROBIOLOGY REPORTS 2016; 3:204-215. [PMID: 28367398 DOI: 10.1007/s40588-016-0044-4] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Varicella-zoster virus (VZV), an alphaherpesvirus that causes chicken pox (varicella) and shingles (herpes zoster), is a medically important pathogen that causes considerable morbidity and, on occasion, mortality in immunocompromised patients. Herpes zoster can afflict the elderly with a debilitating condition, postherpetic neuralgia, triggering severe, untreatable pain for months or years. The lipid envelope of VZV, similar to all herpesviruses, contains numerous glycoproteins required for replication and pathogenesis. PURPOSE OF REVIEW To summarize the current knowledge about VZV glycoproteins and their roles in cell entry, replication and pathogenesis. RECENT FINDINGS The functions for some VZV glycoproteins are known, such as gB, gH and gL in membrane fusion, cell-cell fusion regulation, and receptor binding properties. However, the molecular mechanisms that trigger or mediate VZV glycoproteins remains poorly understood. SUMMARY VZV glycoproteins are central to successful replication but their modus operandi during replication and pathogenesis remain elusive requiring further mechanistic based studies.
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Affiliation(s)
- Stefan L Oliver
- Departments of Pediatrics and Microbiology & Immunology, Stanford University School of Medicine, Stanford, California, 94305-5208
| | - Edward Yang
- Departments of Pediatrics and Microbiology & Immunology, Stanford University School of Medicine, Stanford, California, 94305-5208
| | - Ann M Arvin
- Departments of Pediatrics and Microbiology & Immunology, Stanford University School of Medicine, Stanford, California, 94305-5208
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Jin Z, Sun T, Xia X, Wei Q, Song Y, Han Q, Chen Q, Hu J, Zhang J. Optimized Expression, Purification of Herpes B Virus gD Protein in Escherichia coli, and Production of Its Monoclonal Antibodies. Jundishapur J Microbiol 2016; 9:e32183. [PMID: 27226876 PMCID: PMC4877525 DOI: 10.5812/jjm.32183] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 10/23/2015] [Accepted: 01/18/2016] [Indexed: 12/16/2022] Open
Abstract
BACKGROUND Herpes B virus (BV) is a zoonotic disease caused by double-stranded enveloped DNA virus with cercopithecidae as its natural host. The mortality rate of infected people could be up to 70% with fatal encephalitis and encephalomyelitis. Up to now, there are no effective treatments for BV infection. Among the various proteins encoded by monkey B virus, gD, a conserved structural protein, harbors important application value for serological diagnosis of frequent variations of the monkey B virus. OBJECTIVES This study aimed to expressed the gD protein of BV in Escherichia coli by a recombinant vector, and prepare specific monoclonal antibodies against gD of BV to pave the way for effective and quick diagnosis reagent research. MATERIALS AND METHODS The gD gene of BV was optimized by OptimWiz to improve codon usage bias and synthesis, and the recombinant plasmid, pET32a/gD, was constructed and expressed in E. coli Rosetta (DE3). The expressed fusion protein, His-gD, was purified and the BALB/c mice were immunized by this protein. Spleen cells from the immunized mice and SP2/0 myeloma cells were fused together, and the monoclonal cell strains were obtained by indirect enzyme-linked immunosorbent assay (ELISA) screening, followed by preparation of monoclonal antibody ascetic fluid. RESULTS The optimized gD protein was highly expressed in E. coli and successfully purified. Five monoclonal antibodies (mAbs) against BV were obtained and named as 4E3, 3F8, 3E7, 1H3 and 4B6, and with ascetic fluid titers of 2 × 10(6), 2 × 10(5), 2 × 10(5), 2 × 10(3) and 2 × 10(2), respectively. The 1H3 and 4E3 belonged to the IgG2b subclass, while 3E7, 3F8 and 4B6 belonged to the IgG1 subclass. CONCLUSIONS The cell lines obtained in this work secreted potent, stable and specific anti-BV mAbs, which were suitable for the development of herpes B virus diagnosis reagents.
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Affiliation(s)
- Zian Jin
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Tao Sun
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Xueshan Xia
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Qiujiang Wei
- Kunming Biomed International Company, Kunming, China
| | - Yuzhu Song
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Qinqin Han
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Qiang Chen
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Juan Hu
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
| | - Jinyang Zhang
- Research Center of Molecular Medicine of Yunnan Province, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China
- Corresponding author: Jinyang Zhang, Faculty of Life Science and Technology, Kunming University of Science and Technology, Kunming, China. Tel: +86-87165939528, Fax: +86-87165939528, E-mail:
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Clementi N, Criscuolo E, Cappelletti F, Burioni R, Clementi M, Mancini N. Novel therapeutic investigational strategies to treat severe and disseminated HSV infections suggested by a deeper understanding of in vitro virus entry processes. Drug Discov Today 2016; 21:682-91. [PMID: 26976690 DOI: 10.1016/j.drudis.2016.03.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 02/11/2016] [Accepted: 03/04/2016] [Indexed: 01/28/2023]
Abstract
The global burden of herpes simplex virus (HSV) legitimates the critical need to develop new prevention strategies, such as drugs and vaccines that are able to fight either primary HSV infections or reactivations. Moreover, the ever-growing number of patients receiving transplants increases the number of severe HSV infections that are unresponsive to current therapies. Finally, the high global incidence of genital HSV-2 infection increases the risk of perinatal transmission to newborns, in which disseminated infection or central nervous system (CNS) involvement is frequent, with associated high morbidity and mortality rates. There are several key features shared by novel anti-HSV drugs, from currently available optimized drugs to small molecules able to interfere with various virus replication steps. However, several virological aspects of the disease and associated clinical needs highlight why an ideal anti-HSV drug has yet to be developed.
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Affiliation(s)
- Nicola Clementi
- Microbiology and Virology Unit, 'Vita-Salute San Raffaele' University, 20132 Milan, Italy.
| | - Elena Criscuolo
- Microbiology and Virology Unit, 'Vita-Salute San Raffaele' University, 20132 Milan, Italy
| | - Francesca Cappelletti
- Microbiology and Virology Unit, 'Vita-Salute San Raffaele' University, 20132 Milan, Italy
| | - Roberto Burioni
- Microbiology and Virology Unit, 'Vita-Salute San Raffaele' University, 20132 Milan, Italy
| | - Massimo Clementi
- Microbiology and Virology Unit, 'Vita-Salute San Raffaele' University, 20132 Milan, Italy
| | - Nicasio Mancini
- Microbiology and Virology Unit, 'Vita-Salute San Raffaele' University, 20132 Milan, Italy
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Campadelli-Fiume G, Petrovic B, Leoni V, Gianni T, Avitabile E, Casiraghi C, Gatta V. Retargeting Strategies for Oncolytic Herpes Simplex Viruses. Viruses 2016; 8:63. [PMID: 26927159 PMCID: PMC4810253 DOI: 10.3390/v8030063] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2015] [Revised: 12/22/2015] [Accepted: 12/30/2015] [Indexed: 02/08/2023] Open
Abstract
Most of the oncolytic herpes simplex viruses (HSVs) exhibit a high safety profile achieved through attenuation. They carry defects in virulence proteins that antagonize host cell response to the virus, including innate response, apoptosis, authophagy, and depend on tumor cell proliferation. They grow robustly in cancer cells, provided that these are deficient in host cell responses, which is often the case. To overcome the attenuation limits, a strategy is to render the virus highly cancer-specific, e.g., by retargeting their tropism to cancer-specific receptors, and detargeting from natural receptors. The target we selected is HER-2, overexpressed in breast, ovarian and other cancers. Entry of wt-HSV requires the essential glycoproteins gD, gH/gL and gB. Here, we reviewed that oncolytic HSV retargeting was achieved through modifications in gD: the addition of a single-chain antibody (scFv) to HER-2 coupled with appropriate deletions to remove part of the natural receptors' binding sites. Recently, we showed that also gH/gL can be a retargeting tool. The insertion of an scFv to HER-2 at the gH N-terminus, coupled with deletions in gD, led to a recombinant capable to use HER-2 as the sole receptor. The retargeted oncolytic HSVs can be administered systemically by means of carrier cells-forcedly-infected mesenchymal stem cells. Altogether, the retargeted oncolytic HSVs are highly cancer-specific and their replication is not dependent on intrinsic defects of the tumor cells. They might be further modified to express immunomodulatory molecules.
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Affiliation(s)
- Gabriella Campadelli-Fiume
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
| | - Biljana Petrovic
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
| | - Valerio Leoni
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
| | - Tatiana Gianni
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
| | - Elisa Avitabile
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
| | - Costanza Casiraghi
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
| | - Valentina Gatta
- Department of Experimental, Diagnostic and Specialty Medicine, University of Bologna, Bologna 40126, Italy.
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Herpesvirus gB: A Finely Tuned Fusion Machine. Viruses 2015; 7:6552-69. [PMID: 26690469 PMCID: PMC4690880 DOI: 10.3390/v7122957] [Citation(s) in RCA: 64] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2015] [Revised: 11/15/2015] [Accepted: 11/27/2015] [Indexed: 01/03/2023] Open
Abstract
Enveloped viruses employ a class of proteins known as fusogens to orchestrate the merger of their surrounding envelope and a target cell membrane. Most fusogens accomplish this task alone, by binding cellular receptors and subsequently catalyzing the membrane fusion process. Surprisingly, in herpesviruses, these functions are distributed among multiple proteins: the conserved fusogen gB, the conserved gH/gL heterodimer of poorly defined function, and various non-conserved receptor-binding proteins. We summarize what is currently known about gB from two closely related herpesviruses, HSV-1 and HSV-2, with emphasis on the structure of the largely uncharted membrane interacting regions of this fusogen. We propose that the unusual mechanism of herpesvirus fusion could be linked to the unique architecture of gB.
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40
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Interplay between the Herpes Simplex Virus 1 gB Cytodomain and the gH Cytotail during Cell-Cell Fusion. J Virol 2015; 89:12262-72. [PMID: 26401042 DOI: 10.1128/jvi.02391-15] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 09/17/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Herpesvirus entry into cells is mediated by the viral fusogen gB, which is thought to refold from the prefusion to the postfusion form in a series of large conformational changes that energetically couple refolding to membrane fusion. In contrast to most viral fusogens, gB requires a conserved heterodimer, gH/gL, as well as other nonconserved proteins. In a further mechanistic twist, gB-mediated cell-cell fusion appears restricted by its intraviral or cytoplasmic domain (cytodomain) because mutations within it result in a hyperfusogenic phenotype. Here, we characterized a panel of hyperfusogenic HSV-1 gB cytodomain mutants and show that they are fully functional in cell-cell fusion at shorter coincubation times and at lower temperatures than those for wild-type (WT) gB, which suggests that these mutations reduce the kinetic energy barrier to fusion. Despite this, the mutants require both gH/gL and gD. We confirm previous observations that the gH cytotail is an essential component of the cell-cell fusion mechanism and show that the N-terminal portion of the gH cytotail is critical for this process. Moreover, the fusion levels achieved by all gB constructs, WT and mutant, were proportionate to the length of the gH cytotail. Putting these results together, we propose that the gH cytotail, in addition to the gH/gL ectodomain, plays an essential role in gB activation, potentially acting as a "wedge" to release the gB cytodomain "clamp" and enable gB activation. IMPORTANCE Herpesviruses infect their hosts for life and cause a substantial disease burden. Herpes simplex viruses cause oral and genital sores as well as rare yet severe encephalitis and a panoply of ocular ailments. Infection initiates when the viral envelope fuses with the host cell membrane in a process orchestrated by the viral fusogen gB, assisted by the viral glycoproteins gH, gL, and gD and a cellular gD receptor. This process is more complicated than that of most other viruses and is subject to multiple regulatory inputs. Antiviral and vaccine development would benefit from a detailed mechanistic knowledge of this process and how it is regulated.
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Abstract
This paper discusses physical and structural aspects of the mechanisms herpes simplex virus (HSV) uses for membrane fusion. Calculations show that herpes simplex virus glycoprotein D has such avidity for its receptors that it can hold the virion against the plasma membrane of a neuron strongly enough for glycoprotein B (gB) to disrupt both leaflets of the bilayer. The strong electric field generated by the cell potential across perforations at this disruption would break the hydrogen bonds securing the gB fusion loops, leading to fusion of the plasma and viral membranes. This mechanism agrees with the high stability of the tall trimeric spike structure of gB and is consistent with the probable existence of a more compact initial conformation that would allow it to closely approach the plasma membrane. The release of the fusion domains by disruption of hydrogen bonds is shared with the endocytotic entry pathway where, for some cell types not punctured by gB, the virus is able to induce inward forces that cause endocytosis and the fusion loops are released by acidification. The puncture-fusion mechanism requires low critical strain or high tissue strain, matching primary tropism of neural processes at the vermillion border. In support of this mechanism, this paper proposes a functional superstructure of the antigens essential to entry and reviews its consistency with experimental evidence.
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Affiliation(s)
- Richard W. Clarke
- Chemistry Department, Cambridge University, Lensfield Road, Cambridge CB21EW, United Kingdom
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Dissociation of HSV gL from gH by αvβ6- or αvβ8-integrin promotes gH activation and virus entry. Proc Natl Acad Sci U S A 2015; 112:E3901-10. [PMID: 26157134 DOI: 10.1073/pnas.1506846112] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Herpes simplex virus (HSV) is an important human pathogen. It enters cells through an orchestrated process that requires four essential glycoproteins, gD, gH/gL, and gB, activated in cascade fashion by receptor-binding and signaling. gH/gL heterodimer is conserved across the Herpesviridae family. HSV entry is enabled by gH/gL interaction with αvβ6- or αvβ8-integrin receptors. We report that the interaction of virion gH/gL with integrins resulted in gL dissociation and its release in the medium. gL dissociation occurred if all components of the entry apparatus-receptor-bound gD and gB-were present and was prevented if entry was blocked by a neutralizing monoclonal antibody to gH or by a mutation in gH. We propose that (i) gL dissociation from gH/gL is part of the activation of HSV glycoproteins, critical for HSV entry; and (ii) gL is a functional inhibitor of gH and maintains gH in an inhibited form until receptor-bound gD and integrins signal to gH/gL.
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43
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Saw WT, Matsuda Z, Eisenberg RJ, Cohen GH, Atanasiu D. Using a split luciferase assay (SLA) to measure the kinetics of cell-cell fusion mediated by herpes simplex virus glycoproteins. Methods 2015; 90:68-75. [PMID: 26022509 DOI: 10.1016/j.ymeth.2015.05.021] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 05/20/2015] [Accepted: 05/22/2015] [Indexed: 02/08/2023] Open
Abstract
Herpes simplex virus (HSV) entry and cell-cell fusion require the envelope proteins gD, gH/gL and gB. We propose that receptor-activated conformational changes to gD activate gH/gL, which then triggers gB (the fusogen) into an active form. To study this dynamic process, we have adapted a dual split protein assay originally developed to study the kinetics of human immunodeficiency virus (HIV) mediated fusion. This assay uses a chimera of split forms of renilla luciferase (RL) and green fluorescent protein (GFP). Effector cells are co-transfected with the glycoproteins and one of the split reporters. Receptor-bearing target cells are transfected with the second reporter. Co-culture results in fusion and restoration of RL, which can convert a membrane permeable substrate into a luminescent product, thereby enabling one to monitor initiation and extent of fusion in live cells in real time. Restoration of GFP can also be studied by fluorescence microscopy. Two sets of split reporters have been developed: the original one allows one to measure fusion kinetics over hours whereas the more recent version was designed to enhance the sensitivity of RL activity allowing one to monitor both initiation and rates of fusion in minutes. Here, we provide a detailed, step-by-step protocol for the optimization of the assay (which we call the SLA for split luciferase assay) using the HSV system. We also show several examples of the power of this assay to examine both the initiation and kinetics of cell-cell fusion by wild type forms of gD, gB, gH/gL of both serotypes of HSV as well as the effect of mutations and antibodies that alter the kinetics of fusion. The SLA can be applied to other viral systems that carry out membrane fusion.
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Affiliation(s)
- Wan Ting Saw
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - Zene Matsuda
- Research Center for Asian Infectious Diseases, Institute of Medical Science, University of Tokyo, Shirokanedai, Minato-ku, Tokyo, Japan; China-Japan Joint Laboratory of Structural Virology and Immunology, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Beijing 100101, PR China.
| | - Roselyn J Eisenberg
- Department of Pathobiology, School of Veterinary Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - Gary H Cohen
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
| | - Doina Atanasiu
- Department of Microbiology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA 19104, United States.
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The Engineering of a Novel Ligand in gH Confers to HSV an Expanded Tropism Independent of gD Activation by Its Receptors. PLoS Pathog 2015; 11:e1004907. [PMID: 25996983 PMCID: PMC4440635 DOI: 10.1371/journal.ppat.1004907] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2015] [Accepted: 04/22/2015] [Indexed: 01/08/2023] Open
Abstract
Herpes simplex virus (HSV) enters cells by means of four essential glycoproteins - gD, gH/gL, gB, activated in a cascade fashion by gD binding to one of its receptors, nectin1 and HVEM. We report that the engineering in gH of a heterologous ligand – a single-chain antibody (scFv) to the cancer-specific HER2 receptor – expands the HSV tropism to cells which express HER2 as the sole receptor. The significance of this finding is twofold. It impacts on our understanding of HSV entry mechanism and the design of retargeted oncolytic-HSVs. Specifically, entry of the recombinant viruses carrying the scFv-HER2–gH chimera into HER2+ cells occurred in the absence of gD receptors, or upon deletion of key residues in gD that constitute the nectin1/HVEM binding sites. In essence, the scFv in gH substituted for gD-mediated activation and rendered a functional gD non-essential for entry via HER2. The activation of the gH moiety in the chimera was carried out by the scFv in cis, not in trans as it occurs with wt-gD. With respect to the design of oncolytic-HSVs, previous retargeting strategies were based exclusively on insertion in gD of ligands to cancer-specific receptors. The current findings show that (i) gH accepts a heterologous ligand. The viruses retargeted via gH (ii) do not require the gD-dependent activation, and (iii) replicate and kill cells at high efficiency. Thus, gH represents an additional tool for the design of fully-virulent oncolytic-HSVs retargeted to cancer receptors and detargeted from gD receptors. To enter cells, all herpesviruses use the core fusion glycoproteins gH/gL and gB, in addition to species-specific glycoproteins responsible for specific tropism, etc. In HSV, the additional glycoprotein is the essential gD. We engineered in gH a heterologous ligand to the HER2 cancer receptor. The recombinant viruses entered cells through HER2, independently of gD activation by its receptors, or despite deletion of key residues that are part of the receptors’ binding sites in gD. The ligand activated gH in cis. Cumulatively, the receptor-binding and activating functions of gD were no longer essential and were replaced by the heterologous ligand in gH. Relevance to translational medicine rests in the fact that gH can serve as a tool to retarget HSV tropism to cancer-specific receptors. This expands the toolkit for the design of fully-virulent oncolytic-HSVs.
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A Functional Interaction between Herpes Simplex Virus 1 Glycoprotein gH/gL Domains I and II and gD Is Defined by Using Alphaherpesvirus gH and gL Chimeras. J Virol 2015; 89:7159-69. [PMID: 25926636 DOI: 10.1128/jvi.00740-15] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2015] [Accepted: 04/23/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Whereas most viruses require only a single protein to bind to and fuse with cells, herpesviruses use multiple glycoproteins to mediate virus entry, and thus communication among these proteins is required. For most alphaherpesviruses, the minimal set of viral proteins required for fusion with the host cell includes glycoproteins gD, gB, and a gH/gL heterodimer. In the current model of entry, gD binds to a cellular receptor and transmits a signal to gH/gL. This signal then triggers gB, the conserved fusion protein, to insert into the target membrane and refold to merge the viral and cellular membranes. We previously demonstrated that gB homologs from two alphaherpesviruses, herpes simplex virus 1 (HSV-1) and saimiriine herpesvirus 1 (SaHV-1), were interchangeable. In contrast, neither gD nor gH/gL functioned with heterotypic entry glycoproteins, indicating that gD and gH/gL exhibit an essential type-specific functional interaction. To map this homotypic interaction site on gH/gL, we generated HSV-1/SaHV-1 gH and gL chimeras. The functional interaction with HSV-1 gD mapped to the N-terminal domains I and II of the HSV-1 gH ectodomain. The core of HSV-1 gL that interacts with gH also was required for functional homotypic interaction. The N-terminal gH/gL domains I and II are the least conserved and may have evolved to support species-specific glycoprotein interactions. IMPORTANCE The first step of the herpesvirus life cycle is entry into a host cell. A coordinated interaction among multiple viral glycoproteins is required to mediate fusion of the viral envelope with the cell membrane. The details of how these glycoproteins interact to trigger fusion are unclear. By swapping the entry glycoproteins of two alphaherpesviruses (HSV-1 and SaHV-1), we previously demonstrated a functional homotypic interaction between gD and gH/gL. To define the gH and gL requirements for homotypic interaction, we evaluated the function of a panel of HSV-1/SaHV-1 gH and gL chimeras. We demonstrate that domains I and II of HSV-1 gH are sufficient to promote a functional, albeit reduced, interaction with HSV-1 gD. These findings contribute to our model of how the entry glycoproteins cooperate to mediate herpesvirus entry into the cell.
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A site of varicella-zoster virus vulnerability identified by structural studies of neutralizing antibodies bound to the glycoprotein complex gHgL. Proc Natl Acad Sci U S A 2015; 112:6056-61. [PMID: 25918416 PMCID: PMC4434712 DOI: 10.1073/pnas.1501176112] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Mapping neutralizing epitopes on viral entry glycoproteins allows the identification of potentially important functional regions. The structure of varicella-zoster virus (VZV) gHgL bound to two antibodies isolated from immune donors reveals a common binding site. Functional experiments demonstrate that the two antibodies neutralize VZV infection and inhibit glycoprotein gB/glycoprotein complex gHgL-mediated membrane fusion. Immunization experiments in mice demonstrate that VZV gHgL elicits potently neutralizing antibodies and confirm the key role of this antigenic site in antibody-mediated virus neutralization. This manuscript sheds light on the molecular mechanism of herpesvirus cell entry and will guide the design of subunit-based vaccines against VZV. Varicella-zoster virus (VZV), of the family Alphaherpesvirinae, causes varicella in children and young adults, potentially leading to herpes zoster later in life on reactivation from latency. The conserved herpesvirus glycoprotein gB and the heterodimer gHgL mediate virion envelope fusion with cell membranes during virus entry. Naturally occurring neutralizing antibodies against herpesviruses target these entry proteins. To determine the molecular basis for VZV neutralization, crystal structures of gHgL were determined in complex with fragments of antigen binding (Fabs) from two human monoclonal antibodies, IgG-94 and IgG-RC, isolated from seropositive subjects. These structures reveal that the antibodies target the same site, composed of residues from both gH and gL, distinct from two other neutralizing epitopes identified by negative-stain electron microscopy and mutational analysis. Inhibition of gB/gHgL-mediated membrane fusion and structural comparisons with herpesvirus homologs suggest that the IgG-RC/94 epitope is in proximity to the site on VZV gHgL that activates gB. Immunization studies proved that the anti-gHgL IgG-RC/94 epitope is a critical target for antibodies that neutralize VZV. Thus, the gHgL/Fab structures delineate a site of herpesvirus vulnerability targeted by natural immunity.
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Evasion of early antiviral responses by herpes simplex viruses. Mediators Inflamm 2015; 2015:593757. [PMID: 25918478 PMCID: PMC4396904 DOI: 10.1155/2015/593757] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2015] [Accepted: 03/10/2015] [Indexed: 02/06/2023] Open
Abstract
Besides overcoming physical constraints, such as extreme temperatures, reduced humidity, elevated pressure, and natural predators, human pathogens further need to overcome an arsenal of antimicrobial components evolved by the host to limit infection, replication and optimally, reinfection. Herpes simplex virus-1 (HSV-1) and herpes simplex virus-2 (HSV-2) infect humans at a high frequency and persist within the host for life by establishing latency in neurons. To gain access to these cells, herpes simplex viruses (HSVs) must replicate and block immediate host antiviral responses elicited by epithelial cells and innate immune components early after infection. During these processes, infected and noninfected neighboring cells, as well as tissue-resident and patrolling immune cells, will sense viral components and cell-associated danger signals and secrete soluble mediators. While type-I interferons aim at limiting virus spread, cytokines and chemokines will modulate resident and incoming immune cells. In this paper, we discuss recent findings relative to the early steps taking place during HSV infection and replication. Further, we discuss how HSVs evade detection by host cells and the molecular mechanisms evolved by these viruses to circumvent early antiviral mechanisms, ultimately leading to neuron infection and the establishment of latency.
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Structural and biochemical studies of HCMV gH/gL/gO and Pentamer reveal mutually exclusive cell entry complexes. Proc Natl Acad Sci U S A 2015; 112:1767-72. [PMID: 25624487 DOI: 10.1073/pnas.1424818112] [Citation(s) in RCA: 116] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Human cytomegalovirus (HCMV) is a major cause of morbidity and mortality in transplant patients and the leading viral cause of birth defects after congenital infection. The glycoprotein complexes gH/gL/gO and gH/gL/UL128/UL130/UL131A (Pentamer) are key targets of the human humoral response against HCMV and are required for HCMV entry into fibroblasts and endothelial/epithelial cells, respectively. We expressed and characterized soluble forms of gH/gL, gH/gL/gO, and Pentamer. Mass spectrometry and mutagenesis analysis revealed that gL-Cys144 forms disulfide bonds with gO-Cys351 in gH/gL/gO and with UL128-Cys162 in the Pentamer. Notably, Pentamer harboring the UL128-Cys162Ser/gL-Cys144Ser mutations had impaired syncytia formation and reduced interference of HCMV entry into epithelial cells. Electron microscopy analysis showed that HCMV gH/gL resembles HSV gH/gL and that gO and UL128/UL130/UL131A bind to the same site at the gH/gL N terminus. These data are consistent with gH/gL/gO and Pentamer forming mutually exclusive cell entry complexes and reveal the overall location of gH/gL-, gH/gL/gO-, and Pentamer-specific neutralizing antibody binding sites. Our results provide, to our knowledge, the first structural view of gH/gL/gO and Pentamer supporting the development of vaccines and antibody therapeutics against HCMV.
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Functional fluorescent protein insertions in herpes simplex virus gB report on gB conformation before and after execution of membrane fusion. PLoS Pathog 2014; 10:e1004373. [PMID: 25233449 PMCID: PMC4169481 DOI: 10.1371/journal.ppat.1004373] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2014] [Accepted: 07/25/2014] [Indexed: 11/22/2022] Open
Abstract
Entry of herpes simplex virus (HSV) into a target cell requires complex interactions and conformational changes by viral glycoproteins gD, gH/gL, and gB. During viral entry, gB transitions from a prefusion to a postfusion conformation, driving fusion of the viral envelope with the host cell membrane. While the structure of postfusion gB is known, the prefusion conformation of gB remains elusive. As the prefusion conformation of gB is a critical target for neutralizing antibodies, we set out to describe its structure by making genetic insertions of fluorescent proteins (FP) throughout the gB ectodomain. We created gB constructs with FP insertions in each of the three globular domains of gB. Among 21 FP insertion constructs, we found 8 that allowed gB to remain membrane fusion competent. Due to the size of an FP, regions in gB that tolerate FP insertion must be solvent exposed. Two FP insertion mutants were cell-surface expressed but non-functional, while FP insertions located in the crown were not surface expressed. This is the first report of placing a fluorescent protein insertion within a structural domain of a functional viral fusion protein, and our results are consistent with a model of prefusion HSV gB constructed from the prefusion VSV G crystal structure. Additionally, we found that functional FP insertions from two different structural domains could be combined to create a functional form of gB labeled with both CFP and YFP. FRET was measured with this construct, and we found that when co-expressed with gH/gL, the FRET signal from gB was significantly different from the construct containing CFP alone, as well as gB found in syncytia, indicating that this construct and others of similar design are likely to be powerful tools to monitor the conformation of gB in any model system accessible to light microscopy. Viral fusion proteins undergo complicated conformational changes in order to fuse viral and host membranes during viral entry. Conformational changes between prefusion and postfusion states also allow the virus to hide critical regions of the fusion machinery from the immune system. The structure of herpes simplex virus fusion protein gB is known only in its postfusion state, while the prefusion structure is unknown. To study the prefusion state, we created fluorescent protein (FP) insertions within gB and tested them for fusion activity. Due to the size of the fluorescent protein insertion, regions in gB that tolerate this insertion must be solvent exposed, thereby describing structural features of the prefusion structure. We created functional gB constructs with FP insertions in two of the three globular domains of gB, while non-functional insertions in the third domain suggested that it may be buried in the prefusion structure. Additionally, we created a dual-labeled FP gB construct which we found to report on the conformation of gB before and after fusion. Using this dual-labeled gB construct, we have demonstrated how fluorescence-based methods can be used to directly study dynamics of viral fusion proteins in living cells.
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The Epstein-Barr virus (EBV) glycoprotein B cytoplasmic C-terminal tail domain regulates the energy requirement for EBV-induced membrane fusion. J Virol 2014; 88:11686-95. [PMID: 25100836 DOI: 10.1128/jvi.01349-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
The entry of enveloped viruses into host cells is preceded by membrane fusion, which in Epstein-Barr virus (EBV) is thought to be mediated by the refolding of glycoprotein B (gB) from a prefusion to a postfusion state. In our current studies, we characterized a gB C-terminal tail domain (CTD) mutant truncated at amino acid 843 (gB843). This truncation mutant is hyperfusogenic as monitored by syncytium formation and in a quantitative fusion assay and is dependent on gH/gL for fusion activity. gB843 can rescue the fusion function of other glycoprotein mutants that have null or decreased fusion activity in epithelial and B cells. In addition, gB843 requires less gp42 and gH/gL for fusion, and can function in fusion at a lower temperature than wild-type gB, indicating a lower energy requirement for fusion activation. Since a key step in fusion is the conversion of gB from a prefusion to an active postfusion state by gH/gL, gB843 may access this activated gB state more readily. Our studies indicate that the gB CTD may participate in the fusion function by maintaining gB in an inactive prefusion form prior to activation by receptor binding. Importance: Diseases resulting from Epstein-Barr virus (EBV) infection in humans range from the fairly benign disease infectious mononucleosis to life-threatening cancer. As an enveloped virus, EBV must fuse with a host cell membrane for entry and infection by using glycoproteins gH/gL, gB, and gp42. Among these glycoproteins, gB is thought to be the protein that executes fusion. To further characterize the function of the EBV gB cytoplasmic C-terminal tail domain (CTD) in fusion, we used a previously constructed CTD truncation mutant and studied its fusion activity in the context of other EBV glycoprotein mutants. From these studies, we find that the gB CTD regulates fusion by altering the energy requirements for the triggering of fusion mediated by gH/gL or gp42. Overall, our studies may lead to a better understanding of EBV fusion and entry, which may result in novel therapies that target the EBV entry step.
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