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Benedyk TH, Muenzner J, Connor V, Han Y, Brown K, Wijesinghe KJ, Zhuang Y, Colaco S, Stoll GA, Tutt OS, Svobodova S, Svergun DI, Bryant NA, Deane JE, Firth AE, Jeffries CM, Crump CM, Graham SC. pUL21 is a viral phosphatase adaptor that promotes herpes simplex virus replication and spread. PLoS Pathog 2021; 17:e1009824. [PMID: 34398933 PMCID: PMC8389370 DOI: 10.1371/journal.ppat.1009824] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2021] [Revised: 08/26/2021] [Accepted: 07/23/2021] [Indexed: 12/27/2022] Open
Abstract
The herpes simplex virus (HSV)-1 protein pUL21 is essential for efficient virus replication and dissemination. While pUL21 has been shown to promote multiple steps of virus assembly and spread, the molecular basis of its function remained unclear. Here we identify that pUL21 is a virus-encoded adaptor of protein phosphatase 1 (PP1). pUL21 directs the dephosphorylation of cellular and virus proteins, including components of the viral nuclear egress complex, and we define a conserved non-canonical linear motif in pUL21 that is essential for PP1 recruitment. In vitro evolution experiments reveal that pUL21 antagonises the activity of the virus-encoded kinase pUS3, with growth and spread of pUL21 PP1-binding mutant viruses being restored in adapted strains where pUS3 activity is disrupted. This study shows that virus-directed phosphatase activity is essential for efficient herpesvirus assembly and spread, highlighting the fine balance between kinase and phosphatase activity required for optimal virus replication. Herpes simplex virus (HSV)-1 is a highly prevalent human virus that causes life-long infections. While the most common symptom of HSV-1 infection is orofacial lesions (‘cold sores’), HSV-1 infection can also cause fatal encephalitis and it is a leading cause of infectious blindness. The HSV-1 genome encodes many proteins that dramatically remodel the environment of infected cells to promote virus replication and spread, including enzymes that add phosphate groups (kinases) to cellular and viral proteins in order to fine-tune their function. Here we identify that pUL21 is an HSV-1 protein that binds directly to protein phosphatase 1 (PP1), a highly abundant cellular enzyme that removes phosphate groups from proteins. We demonstrate that pUL21 stimulates the specific dephosphorylation of both cellular and viral proteins, including a component of the viral nuclear egress complex that is essential for efficient assembly of new HSV-1 particles. Furthermore, our in vitro evolution experiments demonstrate that pUL21 antagonises the activity of the HSV-1 kinase pUS3. Our work highlights the precise control that herpesviruses exert upon the protein environment within infected cells, and specifically the careful balance of kinase and phosphatase activity that HSV-1 requires for optimal replication and spread.
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Affiliation(s)
- Tomasz H. Benedyk
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Julia Muenzner
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Viv Connor
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Yue Han
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Katherine Brown
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | | | - Yunhui Zhuang
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Susanna Colaco
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Guido A. Stoll
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Owen S. Tutt
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | | | - Dmitri I. Svergun
- European Molecular Biology Laboratory (EMBL) Hamburg Site, Hamburg, Germany
| | - Neil A. Bryant
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Janet E. Deane
- Cambridge Institute for Medical Research, University of Cambridge, Cambridge Biomedical Campus, Cambridge, United Kingdom
| | - Andrew E. Firth
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Cy M. Jeffries
- European Molecular Biology Laboratory (EMBL) Hamburg Site, Hamburg, Germany
| | - Colin M. Crump
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (CMC); (SCG)
| | - Stephen C. Graham
- Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * E-mail: (CMC); (SCG)
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Glauser DL, Milho R, Lawler C, Stevenson PG. Antibody arrests γ-herpesvirus olfactory super-infection independently of neutralization. J Gen Virol 2018; 100:246-258. [PMID: 30526737 DOI: 10.1099/jgv.0.001183] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Protecting against persistent viruses is an unsolved challenge. The clearest example for a gamma-herpesvirus is resistance to super-infection by Murid herpesvirus-4 (MuHV-4). Most experimental infections have delivered MuHV-4 into the lungs. A more likely natural entry site is the olfactory epithelium. Its protection remains unexplored. Here, prior exposure to olfactory MuHV-4 gave good protection against super-infection. The protection was upstream of B cell infection, which occurs in lymph nodes, and showed redundancy between antibody and T cells. Adding antibody to virions that blocked heparan binding strongly reduced olfactory host entry - unlike in the lungs, opsonized virions did not reach IgG Fc receptor+ myeloid cells. However, the nasal antibody response to primary infection was too low to reduce host entry. Instead, the antibody acted downstream, reducing viral replication in the olfactory epithelium. This depended on IgG Fc receptor engagement rather than virion neutralization. Thus antibody can protect against natural γ-herpesvirus infection before it reaches B cells and independently of neutralization.
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Affiliation(s)
- Daniel L Glauser
- 1Division of Virology, University of Cambridge, UK
- ‡Present address: Suisselab AG, Bern, Switzerland
| | - Ricardo Milho
- 1Division of Virology, University of Cambridge, UK
- §Present address: Costello Medical, Cambridge, UK
| | - Clara Lawler
- 2School of Chemistry and Molecular Biosciences, University of Queensland, Australia
| | - Philip G Stevenson
- 3Royal Children's Hospital, Brisbane, Australia
- 1Division of Virology, University of Cambridge, UK
- 2School of Chemistry and Molecular Biosciences, University of Queensland, Australia
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3
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Möhl BS, Chen J, Park SJ, Jardetzky TS, Longnecker R. Epstein-Barr Virus Fusion with Epithelial Cells Triggered by gB Is Restricted by a gL Glycosylation Site. J Virol 2017; 91:e01255-17. [PMID: 28956769 PMCID: PMC5686762 DOI: 10.1128/jvi.01255-17] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Accepted: 09/21/2017] [Indexed: 12/17/2022] Open
Abstract
Epstein-Barr virus (EBV) entry into epithelial cells is mediated by the conserved core fusion machinery, composed of the fusogen gB and the receptor-binding complex gH/gL. The heterodimeric gH/gL complex binds to the EBV epithelial cell receptor or gp42, which binds to the B-cell receptor, triggering gB-mediated fusion of the virion envelope with cellular membranes. Our previous study found that the gL glycosylation mutant N69L/S71V had an epithelial cell-specific hyperfusogenic phenotype. To study the influence of this gL mutant on the initiation and kinetics of gB-driven epithelial cell fusion, we established a virus-free split-green fluorescent protein cell-cell fusion assay that enables real-time measurements of membrane fusion using live cells. The gL_N69L/S71V mutant had a large increase in epithelial cell fusion activity of up to 300% greater than that of wild-type gL starting at early time points. The hyperfusogenicity of the gL mutant was not a result of alterations in complex formation with gH or alterations in cellular localization. Moreover, the hyperfusogenic phenotype of the gL mutant correlated with the formation of enlarged syncytia. In summary, our present findings highlight an important role of gL in the kinetics of gB-mediated epithelial cell fusion, adding to previous findings indicating a direct interaction between gL and gB in EBV membrane fusion.IMPORTANCE EBV predominantly infects epithelial cells and B lymphocytes, which are the cells of origin for the EBV-associated malignancies Hodgkin and Burkitt lymphoma as well as nasopharyngeal carcinoma. Contrary to the other key players of the core fusion machinery, gL has the most elusive role during EBV-induced membrane fusion. We found that the glycosylation site N69/S71 of gL is involved in restricting epithelial cell fusion activity, strongly correlating with syncytium size. Interestingly, our data showed that the gL glycosylation mutant increases the fusion activity of the hyperfusogenic gB mutants, indicating that this gL mutant and the gB mutants target different steps during fusion. Our studies on how gL and gB work together to modulate epithelial cell fusion kinetics are essential to understand the highly tuned tropism of EBV for epithelial cells and B lymphocytes and may result in novel strategies for therapies preventing viral entry into target host cells. Finally, making our results of particular interest is the absence of gL syncytial mutants in other herpesviruses.
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Affiliation(s)
- Britta S Möhl
- Department of Microbiology and Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Jia Chen
- Department of Microbiology and Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Seo Jin Park
- Department of Microbiology and Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
| | - Theodore S Jardetzky
- Department of Structural Biology, Stanford University School of Medicine, Stanford, California, USA
| | - Richard Longnecker
- Department of Microbiology and Immunology, The Feinberg School of Medicine, Northwestern University, Chicago, Illinois, USA
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4
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The Major Envelope Glycoprotein of Murid Herpesvirus 4 Promotes Sexual Transmission. J Virol 2017; 91:JVI.00235-17. [PMID: 28424280 DOI: 10.1128/jvi.00235-17] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 04/10/2017] [Indexed: 12/25/2022] Open
Abstract
Gammaherpesviruses are important human and animal pathogens. Infection control has proven difficult because the key process of transmission is ill understood. Murid herpesvirus 4 (MuHV-4), a gammaherpesvirus of mice, is transmitted sexually. We show that this depends on the major virion envelope glycoprotein gp150. gp150 is redundant for host entry, and in vitro, it regulates rather than promotes cell binding. We show that gp150-deficient MuHV-4 reaches and replicates normally in the female genital tract after nasal infection but is poorly released from vaginal epithelial cells and fails to pass from the female to the male genital tract during sexual contact. Thus, we show that the regulation of virion binding is a key component of spontaneous gammaherpesvirus transmission.IMPORTANCE Gammaherpesviruses are responsible for many important diseases in both animals and humans. Some important aspects of their life cycle are still poorly understood. Key among these is viral transmission. Here we show that the major envelope glycoprotein of murid herpesvirus 4 functions not in entry or dissemination but in virion release to allow sexual transmission to new hosts.
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Dual Function of the pUL7-pUL51 Tegument Protein Complex in Herpes Simplex Virus 1 Infection. J Virol 2017; 91:JVI.02196-16. [PMID: 27852850 PMCID: PMC5215335 DOI: 10.1128/jvi.02196-16] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2016] [Accepted: 11/04/2016] [Indexed: 12/14/2022] Open
Abstract
The tegument of herpesviruses is a highly complex structural layer between the nucleocapsid and the envelope of virions. Tegument proteins play both structural and regulatory functions during replication and spread, but the interactions and functions of many of these proteins are poorly understood. Here we focus on two tegument proteins from herpes simplex virus 1 (HSV-1), pUL7 and pUL51, which have homologues in all other herpesviruses. We have now identified that HSV-1 pUL7 and pUL51 form a stable and direct protein-protein interaction, their expression levels rely on the presence of each other, and they function as a complex in infected cells. We demonstrate that expression of the pUL7-pUL51 complex is important for efficient HSV-1 assembly and plaque formation. Furthermore, we also discovered that the pUL7-pUL51 complex localizes to focal adhesions at the plasma membrane in both infected cells and in the absence of other viral proteins. The expression of pUL7-pUL51 is important to stabilize focal adhesions and maintain cell morphology in infected cells and cells infected with viruses lacking pUL7 and/or pUL51 round up more rapidly than cells infected with wild-type HSV-1. Our data suggest that, in addition to the previously reported functions in virus assembly and spread for pUL51, the pUL7-pUL51 complex is important for maintaining the attachment of infected cells to their surroundings through modulating the activity of focal adhesion complexes. IMPORTANCEHerpesviridae is a large family of highly successful human and animal pathogens. Virions of these viruses are composed of many different proteins, most of which are contained within the tegument, a complex structural layer between the nucleocapsid and the envelope within virus particles. Tegument proteins have important roles in assembling virus particles as well as modifying host cells to promote virus replication and spread. However, little is known about the function of many tegument proteins during virus replication. Our study focuses on two tegument proteins from herpes simplex virus 1 that are conserved in all herpesviruses: pUL7 and pUL51. We demonstrate that these proteins directly interact and form a functional complex that is important for both virus assembly and modulation of host cell morphology. Further, we identify for the first time that these conserved herpesvirus tegument proteins localize to focal adhesions in addition to cytoplasmic juxtanuclear membranes within infected cells.
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6
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Structural analysis of herpes simplex virus by optical super-resolution imaging. Nat Commun 2015; 6:5980. [PMID: 25609143 PMCID: PMC4338551 DOI: 10.1038/ncomms6980] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 11/27/2014] [Indexed: 12/31/2022] Open
Abstract
Herpes simplex virus type-1 (HSV-1) is one of the most widespread pathogens among humans. Although the structure of HSV-1 has been extensively investigated, the precise organization of tegument and envelope proteins remains elusive. Here we use super-resolution imaging by direct stochastic optical reconstruction microscopy (dSTORM) in combination with a model-based analysis of single-molecule localization data, to determine the position of protein layers within virus particles. We resolve different protein layers within individual HSV-1 particles using multi-colour dSTORM imaging and discriminate envelope-anchored glycoproteins from tegument proteins, both in purified virions and in virions present in infected cells. Precise characterization of HSV-1 structure was achieved by particle averaging of purified viruses and model-based analysis of the radial distribution of the tegument proteins VP16, VP1/2 and pUL37, and envelope protein gD. From this data, we propose a model of the protein organization inside the tegument.
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7
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Cunha CW, Knowles DP, Taus NS, O'Toole D, Nicola AV, Aguilar HC, Li H. Antibodies to ovine herpesvirus 2 glycoproteins decrease virus infectivity and prevent malignant catarrhal fever in rabbits. Vet Microbiol 2014; 175:349-55. [PMID: 25542288 DOI: 10.1016/j.vetmic.2014.11.026] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2014] [Revised: 11/06/2014] [Accepted: 11/16/2014] [Indexed: 11/19/2022]
Abstract
Ovine herpesvirus-2 (OvHV-2) is the etiological agent of sheep-associated malignant catarrhal fever (SA-MCF), a fatal lymphoproliferative disease of many species in the order Artiodactyla. Development of a vaccine is critical to prevent mortality. Because OvHV-2 has not been cultured in vitro, SA-MCF research is hindered by the lack of in vitro tools to study viral constituents and specific host immune responses. As an alternative, in this study the neutralizing activity of antibodies against OvHV-2 glycoproteins gB and gH/gL was evaluated in vivo using rabbits. OvHV-2-specific antibodies were developed in rabbits by immunization using biolistic delivery of plasmids expressing the genes of interest. A lethal dose of OvHV-2 was incubated with the antisera and then nebulized into rabbits. Virus neutralization was assessed by measuring infection parameters associated with the virus infectious dose. Anti-gB or anti-gH/gL antibodies alone blocked infection in five out of six rabbits (83%), while a combination of anti-gB and anti-gH/gL antibodies protected all six rabbits (100%) from infection. These results indicate that antibodies to OvHV-2 gB and gH/gL are capable of neutralizing virions, and consequently, reduce virus infectivity and prevent SA-MCF in rabbits. Thus, OvHV-2 gB and gH/gL are suitable targets to be tested in a SA-MCF vaccine aimed at stimulating neutralizing antibody responses.
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Affiliation(s)
- Cristina W Cunha
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA.
| | - Donald P Knowles
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA; Animal Disease Research Unit, USDA-Agricultural Research Service, Washington State University, Pullman, WA 99164-6630, USA
| | - Naomi S Taus
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA; Animal Disease Research Unit, USDA-Agricultural Research Service, Washington State University, Pullman, WA 99164-6630, USA
| | - Donal O'Toole
- Wyoming State Veterinary Laboratory, University of Wyoming, Laramie, WY 82070-6752, USA
| | - Anthony V Nicola
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA
| | - Hector C Aguilar
- Paul G. Allen School for Global Animal Health, Washington State University, Pullman, WA 99164-7040, USA
| | - Hong Li
- Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, WA 99164-7040, USA; Animal Disease Research Unit, USDA-Agricultural Research Service, Washington State University, Pullman, WA 99164-6630, USA
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8
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Abstract
UNLABELLED Viruses commonly infect the respiratory tract. Analyses of host defense have focused on the lungs and the respiratory epithelium. Spontaneously inhaled murid herpesvirus 4 (MuHV-4) and herpes simplex virus 1 (HSV-1) instead infect the olfactory epithelium, where neuronal cilia are exposed to environmental antigens and provide a route across the epithelial mucus. We used MuHV-4 to define how B cells respond to virus replication in this less well-characterized site. Olfactory infection elicited generally weaker acute responses than lung infection, particularly in the spleen, reflecting slower viral replication and spread. Few virus-specific antibody-forming cells (AFCs) were found in the nasal-associated lymphoid tissue (NALT), a prominent response site for respiratory epithelial infection. Instead, they appeared first in the superficial cervical lymph nodes. The focus of the AFC response then moved to the spleen, matching the geography of virus dissemination. Little virus-specific IgA response was detected until later in the bone marrow. Neuroepithelial HSV-1 infection also elicited no significant AFC response in the NALT and a weak IgA response. Thus, olfactory herpesvirus infection differed immunologically from an infection of the adjacent respiratory epithelium. Poor IgA induction may help herpesviruses to transmit via long-term mucosal shedding. IMPORTANCE Herpesviruses are widespread, persistent pathogens against which vaccines have had limited success. We need to understand better how they interact with host immunity. MuHV-4 and HSV-1 inhaled by alert mice infect the olfactory neuroepithelium, suggesting that this is a natural entry route. Its immunology is almost completely unknown. The antibody response to neuroepithelial herpesvirus infection started in the cervical lymph nodes, and unlike respiratory influenza virus infection, did not significantly involve the nasal-associated lymphoid tissue. MuHV-4 and HSV-1 infections also elicited little virus-specific IgA. Therefore, vaccine-induced IgA might provide a defense that herpesviruses are ill-equipped to meet.
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9
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Abstract
Glycoprotein B (gB) is a conserved herpesvirus virion component implicated in membrane fusion. As with many—but not all—herpesviruses, the gB of murid herpesvirus 4 (MuHV-4) is cleaved into disulfide-linked subunits, apparently by furin. Preventing gB cleavage for some herpesviruses causes minor infection deficits in vitro, but what the cleavage contributes to host colonization has been unclear. To address this, we mutated the furin cleavage site (R-R-K-R) of the MuHV-4 gB. Abolishing gB cleavage did not affect its expression levels, glycosylation, or antigenic conformation. In vitro, mutant viruses entered fibroblasts and epithelial cells normally but had a significant entry deficit in myeloid cells such as macrophages and bone marrow-derived dendritic cells. The deficit in myeloid cells was not due to reduced virion binding or endocytosis, suggesting that gB cleavage promotes infection at a postendocytic entry step, presumably viral membrane fusion. In vivo, viruses lacking gB cleavage showed reduced lytic spread in the lungs. Alveolar epithelial cell infection was normal, but alveolar macrophage infection was significantly reduced. Normal long-term latency in lymphoid tissue was established nonetheless.
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10
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Milho R, Frederico B, Efstathiou S, Stevenson PG. A heparan-dependent herpesvirus targets the olfactory neuroepithelium for host entry. PLoS Pathog 2012; 8:e1002986. [PMID: 23133384 PMCID: PMC3486907 DOI: 10.1371/journal.ppat.1002986] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Accepted: 09/07/2012] [Indexed: 11/19/2022] Open
Abstract
Herpesviruses are ubiquitous pathogens that cause much disease. The difficulty of clearing their established infections makes host entry an important target for control. However, while herpesviruses have been studied extensively in vitro, how they cross differentiated mucus-covered epithelia in vivo is unclear. To establish general principles we tracked host entry by Murid Herpesvirus-4 (MuHV-4), a lymphotropic rhadinovirus related to the Kaposi's Sarcoma-associated Herpesvirus. Spontaneously acquired virions targeted the olfactory neuroepithelium. Like many herpesviruses, MuHV-4 binds to heparan sulfate (HS), and virions unable to bind HS showed poor host entry. While the respiratory epithelium expressed only basolateral HS and was bound poorly by incoming virions, the neuroepithelium also displayed HS on its apical neuronal cilia and was bound strongly. Incoming virions tracked down the neuronal cilia, and either infected neurons or reached the underlying microvilli of the adjacent glial (sustentacular) cells and infected them. Thus the olfactory neuroepithelium provides an important and complex site of HS-dependent herpesvirus uptake. Herpesviruses are supremely successful mammalian parasites. Yet their infections rarely present until well established, so how new hosts are first infected has been unclear. Understanding this is likely to be crucial for infection control. Using Murid Herpesvirus-4, a relative of the Kaposi's Sarcoma-associated Herpesvirus, we identified the olfactory neuroepithelium as a major portal of host entry. Heparan sulfate (HS) binding, which is common to many herpesviruses, played a key role. The HS of most epithelia is solely basolateral and therefore inaccessible to incoming, apical virions. The neuroepithelium, by contrast, also displayed HS on its apical surface. This comprises a dense meshwork of the neuronal cilia that mediate olfaction. Incoming virions bound to the cilia, as did a recombinant form of the virion glycoprotein H/L heterodimer. Some virions tracked down the cilia to infect neurons. Others were transferred to the microvilli of adjacent sustentacular cells. The central role of HS in this first detailed description of host entry by a mammalian herpesvirus, and the paucity of accessible HS on other epithelia, suggested that many HS-binding herpesviruses could follow a similar path.
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Affiliation(s)
| | | | | | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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11
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Glauser DL, Gillet L, Stevenson PG. Virion endocytosis is a major target for murid herpesvirus-4 neutralization. J Gen Virol 2012; 93:1316-1327. [PMID: 22377583 PMCID: PMC3755512 DOI: 10.1099/vir.0.040790-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Herpesviruses consistently transmit from immunocompetent carriers, implying that their neutralization is hard to achieve. Murid herpesvirus-4 (MuHV-4) exploits host IgG Fc receptors to bypass blocks to cell binding, and pH-dependent protein conformation changes to unveil its fusion machinery only after endocytosis. Nevertheless, neutralization remains possible by targeting the virion glycoprotein H (gH)–gL heterodimer, and the neutralizing antibody responses of MuHV-4 carriers are improved by boosting with recombinant gH–gL. We analysed here how gH–gL-directed neutralization works. The MuHV-4 gH–gL binds to heparan sulfate. However, most gH–gL-specific neutralizing antibodies did not block this interaction; neither did they act directly on fusion. Instead, they blocked virion endocytosis and transport to the late endosomes, where membrane fusion normally occurs. The poor endocytosis of gH–gL-neutralized virions was recapitulated precisely by virions genetically lacking gL. Therefore, driving virion uptake appears to be an important function of gH–gL that provides a major target for antibody-mediated neutralization.
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Affiliation(s)
- Daniel L. Glauser
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Laurent Gillet
- Immunology–Vaccinology, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
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12
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Glauser DL, Kratz AS, Stevenson PG. Herpesvirus glycoproteins undergo multiple antigenic changes before membrane fusion. PLoS One 2012; 7:e30152. [PMID: 22253913 PMCID: PMC3253813 DOI: 10.1371/journal.pone.0030152] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2011] [Accepted: 12/11/2011] [Indexed: 01/22/2023] Open
Abstract
Herpesvirus entry is a complicated process involving multiple virion glycoproteins and culminating in membrane fusion. Glycoprotein conformation changes are likely to play key roles. Studies of recombinant glycoproteins have revealed some structural features of the virion fusion machinery. However, how the virion glycoproteins change during infection remains unclear. Here using conformation-specific monoclonal antibodies we show in situ that each component of the Murid Herpesvirus-4 (MuHV-4) entry machinery—gB, gH/gL and gp150—changes in antigenicity before tegument protein release begins. Further changes then occurred upon actual membrane fusion. Thus virions revealed their final fusogenic form only in late endosomes. The substantial antigenic differences between this form and that of extracellular virions suggested that antibodies have only a limited opportunity to block virion membrane fusion.
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Affiliation(s)
- Daniel L Glauser
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
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13
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Svobodova S, Bell S, Crump CM. Analysis of the interaction between the essential herpes simplex virus 1 tegument proteins VP16 and VP1/2. J Virol 2012; 86:473-83. [PMID: 22013045 PMCID: PMC3255927 DOI: 10.1128/jvi.05981-11] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2011] [Accepted: 10/13/2011] [Indexed: 11/20/2022] Open
Abstract
The incorporation of tegument proteins into the herpes simplex virus 1 (HSV-1) virion during virion assembly is thought to be a complex, multistage process occurring via numerous interactions between the tegument and the capsid, within the tegument, and between the tegument and the envelope. Here, we set out to examine if the direct interaction between two essential tegument proteins VP1/2 and VP16 is required for connecting the inner tegument with the outer tegument. By using glutathione S-transferase (GST) pulldowns, we identified an essential role of lysine 343 in VP16, mutation of which to a neutral amino acid abrogated the interaction between VP1/2 and VP16. When the K343A substitution was inserted into the gene encoding VP16 (UL48) of the viral genome, HSV-1 replicated successfully although its growth was delayed, and final titers were reduced compared to titers of wild-type virus. Surprisingly, the mutated VP16 was incorporated into virions at levels similar to those of wild-type VP16. However, the analysis of VP16 on cytoplasmic capsids by fluorescence microscopy showed that VP16 associated with cytoplasmic capsids less efficiently when the VP16-VP1/2 interaction was inhibited. This implies that the direct interaction between VP1/2 and VP16 is important for the efficiency/timing of viral assembly but is not essential for HSV-1 replication in cell culture. These data also support the notion that the incorporation of tegument proteins into the herpesviruses is a very complex process with significant redundancy.
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Affiliation(s)
- Stanislava Svobodova
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
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14
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Bovine herpesvirus type 4 glycoprotein L is nonessential for infectivity but triggers virion endocytosis during entry. J Virol 2011; 86:2653-64. [PMID: 22205754 DOI: 10.1128/jvi.06238-11] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The core entry machinery of mammalian herpesviruses comprises glycoprotein B (gB), gH, and gL. gH and gL form a heterodimer with a central role in viral membrane fusion. When archetypal alpha- or betaherpesviruses lack gL, gH misfolds and progeny virions are noninfectious. However, the gL of the rhadinovirus murid herpesvirus 4 (MuHV-4) is nonessential for infection. In order to define more generally what role gL plays in rhadinovirus infections, we disrupted its coding sequence in bovine herpesvirus 4 (BoHV-4). BoHV-4 lacking gL showed altered gH glycosylation and incorporated somewhat less gH into virions but remained infectious. However, gL(-) virions showed poor growth associated with an entry deficit. Moreover, a major part of their entry defect appeared to reflect impaired endocytosis, which occurs upstream of membrane fusion itself. Thus, the rhadinovirus gL may be more important for driving virion endocytosis than for incorporating gH into virions, and it is nonessential for membrane fusion.
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15
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Machiels B, Lété C, Guillaume A, Mast J, Stevenson PG, Vanderplasschen A, Gillet L. Antibody evasion by a gammaherpesvirus O-glycan shield. PLoS Pathog 2011; 7:e1002387. [PMID: 22114560 PMCID: PMC3219721 DOI: 10.1371/journal.ppat.1002387] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2011] [Accepted: 10/04/2011] [Indexed: 12/02/2022] Open
Abstract
All gammaherpesviruses encode a major glycoprotein homologous to the Epstein-Barr virus gp350. These glycoproteins are often involved in cell binding, and some provide neutralization targets. However, the capacity of gammaherpesviruses for long-term transmission from immune hosts implies that in vivo neutralization is incomplete. In this study, we used Bovine Herpesvirus 4 (BoHV-4) to determine how its gp350 homolog--gp180--contributes to virus replication and neutralization. A lack of gp180 had no impact on the establishment and maintenance of BoHV-4 latency, but markedly sensitized virions to neutralization by immune sera. Antibody had greater access to gB, gH and gL on gp180-deficient virions, including neutralization epitopes. Gp180 appears to be highly O-glycosylated, and removing O-linked glycans from virions also sensitized them to neutralization. It therefore appeared that gp180 provides part of a glycan shield for otherwise vulnerable viral epitopes. Interestingly, this O-glycan shield could be exploited for neutralization by lectins and carbohydrate-specific antibody. The conservation of O-glycosylation sites in all gp350 homologs suggests that this is a general evasion mechanism that may also provide a therapeutic target.
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Affiliation(s)
- Bénédicte Machiels
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases (B43b), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Céline Lété
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases (B43b), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Antoine Guillaume
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases (B43b), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Jan Mast
- Department Biocontrole, Research Unit Electron Microscopy, Veterinary and Agrochemical Research Centre, CODA-CERVA, Groeselenberg, Ukkel, Belgium
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Alain Vanderplasschen
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases (B43b), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Laurent Gillet
- Immunology-Vaccinology (B43b), Department of Infectious and Parasitic Diseases (B43b), Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
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16
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Analysis of Rab GTPase-activating proteins indicates that Rab1a/b and Rab43 are important for herpes simplex virus 1 secondary envelopment. J Virol 2011; 85:8012-21. [PMID: 21680502 DOI: 10.1128/jvi.00500-11] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Assembly of herpes simplex virus 1 (HSV-1) occurs in the cytoplasm, where the capsid and tegument bud into host cell membranes. It is at this point that the viral glycoproteins are incorporated into the virion, as they are located at the assembly site. We investigated the role of the Rab GTPases in coordinating the assembly process by overexpressing 37 human Rab GTPase-activating proteins (GAPs) and assessing infectious titers. Rab GTPases are key cellular regulators of membrane trafficking events that, by their membrane association and binding of effector proteins, ensure the appropriate fusion of membranes. We identified that TBC1D20 and RN-tre and their partner Rabs, Rab1a/b and Rab43, respectively, are important for virion assembly. In the absence of Rab1a/b, the viral glycoproteins are unable to traffic from the endoplasmic reticulum to the assembly compartment, and thus unenveloped particles build up in the cytoplasm. The defect resulting from Rab43 depletion is somewhat more complex, but it appears that the fragmentation and dispersal of the trans-Golgi network and associated membranes render these compartments unable to support secondary envelopment.
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17
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Glauser DL, Kratz AS, Gillet L, Stevenson PG. A mechanistic basis for potent, glycoprotein B-directed gammaherpesvirus neutralization. J Gen Virol 2011; 92:2020-2033. [PMID: 21593277 PMCID: PMC3353389 DOI: 10.1099/vir.0.032177-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Glycoprotein B (gB) is a conserved, essential component of gammaherpes virions and so potentially vulnerable to neutralization. However, few good gB-specific neutralizing antibodies have been identified. Here, we show that murid herpesvirus 4 is strongly neutralized by mAbs that recognize an epitope close to one of the gB fusion loops. Antibody binding did not stop gB interacting with its cellular ligands or initiating its fusion-associated conformation change, but did stop gB resolving stably to its post-fusion form, and so blocked membrane fusion to leave virions stranded in late endosomes. The conservation of gB makes this mechanism a possible general route to gammaherpesvirus neutralization.
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Affiliation(s)
- Daniel L Glauser
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Anne-Sophie Kratz
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Laurent Gillet
- Immunology-Vaccinology, Faculty of Veterinary Medicine, University of Liège, Liège, Belgium
| | - Philip G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
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18
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May JS, Stevenson PG. Vaccination with murid herpesvirus-4 glycoprotein B reduces viral lytic replication but does not induce detectable virion neutralization. J Gen Virol 2010; 91:2542-52. [PMID: 20519454 PMCID: PMC3052599 DOI: 10.1099/vir.0.023085-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2010] [Accepted: 05/31/2010] [Indexed: 01/17/2023] Open
Abstract
Herpesviruses characteristically disseminate from immune hosts. Therefore in the context of natural infection, antibody neutralizes them poorly. Murid herpesvirus-4 (MuHV-4) provides a tractable model with which to understand gammaherpesvirus neutralization. MuHV-4 virions blocked for cell binding by immune sera remain infectious for IgG-Fc receptor(+) myeloid cells, so broadly neutralizing antibodies must target the virion fusion complex - glycoprotein B (gB) or gH/gL. While gB-specific neutralizing antibodies are rare, its domains I+II (gB-N) contain at least one potent neutralization epitope. Here, we tested whether immunization with recombinant gB presenting this epitope could induce neutralizing antibodies in naive mice and protect them against MuHV-4 challenge. Immunizing with the full-length gB extracellular domain induced a strong gB-specific antibody response and reduced MuHV-4 lytic replication but did not induce detectable neutralization. gB-N alone, which more selectively displayed pre-fusion epitopes including neutralization epitopes, also failed to induce neutralizing responses, and while viral lytic replication was again reduced this depended completely on IgG Fc receptors. gB and gB-N also boosted neutralizing responses in only a minority of carrier mice. Therefore, it appears that neutralizing epitopes on gB are intrinsically difficult for the immune response to target.
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Affiliation(s)
- Janet S May
- Division of Virology, Department of Pathology, University of Cambridge, UK
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19
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Steer B, Adler B, Jonjic S, Stewart JP, Adler H. A gammaherpesvirus complement regulatory protein promotes initiation of infection by activation of protein kinase Akt/PKB. PLoS One 2010; 5:e11672. [PMID: 20657771 PMCID: PMC2908122 DOI: 10.1371/journal.pone.0011672] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Accepted: 06/27/2010] [Indexed: 12/22/2022] Open
Abstract
Background Viruses have evolved to evade the host's complement system. The open reading frames 4 (ORF4) of gammaherpesviruses encode homologs of regulators of complement activation (RCA) proteins, which inhibit complement activation at the level of C3 and C4 deposition. Besides complement regulation, these proteins are involved in heparan sulfate and glycosaminoglycan binding, and in case of MHV-68, also in viral DNA synthesis in macrophages. Methodology/Principal Findings Here, we made use of MHV-68 to study the role of ORF4 during infection of fibroblasts. While attachment and penetration of virions lacking the RCA protein were not affected, we observed a delayed delivery of the viral genome to the nucleus of infected cells. Analysis of the phosphorylation status of a variety of kinases revealed a significant reduction in phosphorylation of the protein kinase Akt in cells infected with ORF4 mutant virus, when compared to cells infected with wt virus. Consistent with a role of Akt activation in initial stages of infection, inhibition of Akt signaling in wt virus infected cells resulted in a phenotype resembling the phenotype of the ORF4 mutant virus, and activation of Akt by addition of insulin partially reversed the phenotype of the ORF4 mutant virus. Importantly, the homologous ORF4 of KSHV was able to rescue the phenotype of the MHV-68 ORF4 mutant, indicating that ORF4 is functionally conserved and that ORF4 of KSHV might have a similar function in infection initiation. Conclusions/Significance In summary, our studies demonstrate that ORF4 contributes to efficient infection by activation of the protein kinase Akt and thus reveal a novel function of a gammaherpesvirus RCA protein.
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Affiliation(s)
- Beatrix Steer
- The Institute of Molecular Immunology, Clinical Cooperation Group Hematopoietic Cell Transplantation, Helmholtz Zentrum München - German Research Center for Environmental Health, Munich, Germany
| | - Barbara Adler
- Max von Pettenkofer-Institute, Ludwig-Maximilians-University Munich, Munich, Germany
| | - Stipan Jonjic
- Department of Histology and Embryology, Faculty of Medicine, University of Rijeka, Rijeka, Croatia
| | - James P. Stewart
- Centre for Comparative Infectious Diseases, Department of Medical Microbiology, University of Liverpool, Liverpool, United Kingdom
| | - Heiko Adler
- The Institute of Molecular Immunology, Clinical Cooperation Group Hematopoietic Cell Transplantation, Helmholtz Zentrum München - German Research Center for Environmental Health, Munich, Germany
- * E-mail:
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20
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May JS, Bennett NJ, Stevenson PG. An in vitro system for studying murid herpesvirus-4 latency and reactivation. PLoS One 2010; 5:e11080. [PMID: 20552028 PMCID: PMC2884032 DOI: 10.1371/journal.pone.0011080] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2010] [Accepted: 05/24/2010] [Indexed: 12/21/2022] Open
Abstract
The narrow species tropisms of Epstein-Barr Virus (EBV) and the Kaposi's Sarcoma -associated Herpesvirus (KSHV) have made Murid Herpesvirus-4 (MuHV-4) an important tool for understanding how gammaherpesviruses colonize their hosts. However, while MuHV-4 pathogenesis studies can assign a quantitative importance to individual genes, the complexity of in vivo infection can make the underlying mechanisms hard to discern. Furthermore, the lack of good in vitro MuHV-4 latency/reactivation systems with which to dissect mechanisms at the cellular level has made some parallels with EBV and KSHV hard to draw. Here we achieved control of the MuHV-4 lytic/latent switch in vitro by modifying the 5′ untranslated region of its major lytic transactivator gene, ORF50. We terminated normal ORF50 transcripts by inserting a polyadenylation signal and transcribed ORF50 instead from a down-stream, doxycycline-inducible promoter. In this way we could establish fibroblast clones that maintained latent MuHV-4 episomes without detectable lytic replication. Productive virus reactivation was then induced with doxycycline. We used this system to show that the MuHV-4 K3 gene plays a significant role in protecting reactivating cells against CD8+ T cell recognition.
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Affiliation(s)
- Janet S. May
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Neil J. Bennett
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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21
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Peng L, Ryazantsev S, Sun R, Zhou ZH. Three-dimensional visualization of gammaherpesvirus life cycle in host cells by electron tomography. Structure 2010; 18:47-58. [PMID: 20152152 DOI: 10.1016/j.str.2009.10.017] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2009] [Revised: 09/03/2009] [Accepted: 10/30/2009] [Indexed: 12/27/2022]
Abstract
Gammaherpesviruses are etiologically associated with human tumors. A three-dimensional (3D) examination of their life cycle in the host is lacking, significantly limiting our understanding of the structural and molecular basis of virus-host interactions. Here, we report the first 3D visualization of key stages of the murine gammaherpesvirus 68 life cycle in NIH 3T3 cells, including viral attachment, entry, assembly, and egress, by dual-axis electron tomography. In particular, we revealed the transient processes of incoming capsids injecting viral DNA through nuclear pore complexes and nascent DNA being packaged into progeny capsids in vivo as a spool coaxial with the putative portal vertex. We discovered that intranuclear invagination of both nuclear membranes is involved in nuclear egress of herpesvirus capsids. Taken together, our results provide the structural basis for a detailed mechanistic description of gammaherpesvirus life cycle and also demonstrate the advantage of electron tomography in dissecting complex cellular processes of viral infection.
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Affiliation(s)
- Li Peng
- Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA
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22
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Wright DE, Colaco S, Colaco C, Stevenson PG. Antibody limits in vivo murid herpesvirus-4 replication by IgG Fc receptor-dependent functions. J Gen Virol 2009; 90:2592-2603. [PMID: 19625459 PMCID: PMC2885036 DOI: 10.1099/vir.0.014266-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2009] [Accepted: 07/17/2009] [Indexed: 12/11/2022] Open
Abstract
Antibody is an important antiviral defence. However, it is considered to do little against human gamma-herpesviruses, which establish predominantly latent infections regulated by T cells. One limitation on analysing these infections has been that latency is already well-established at clinical presentation; early infection may still be accessible to antibody. Here, using murid herpesvirus-4 (MuHV-4), we tested the impact of adoptively transferred antibody on early gamma-herpesvirus infection. Immune sera and neutralizing and non-neutralizing monoclonal antibodies (mAbs) all reduced acute lytic MuHV-4 replication. The reductions, even by neutralizing mAbs, were largely or completely dependent on host IgG Fc receptors. Therefore, passive antibody can blunt acute gamma-herpesvirus lytic infection, and does this principally by IgG Fc-dependent functions rather than by neutralization.
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Affiliation(s)
- Debbie E. Wright
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Susanna Colaco
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Camilo Colaco
- Immunobiology Ltd, Babraham Research Campus, Cambridge, UK
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23
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Stevenson PG, Simas JP, Efstathiou S. Immune control of mammalian gamma-herpesviruses: lessons from murid herpesvirus-4. J Gen Virol 2009; 90:2317-2330. [PMID: 19605591 DOI: 10.1099/vir.0.013300-0] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Many acute viral infections can be controlled by vaccination; however, vaccinating against persistent infections remains problematic. Herpesviruses are a classic example. Here, we discuss their immune control, particularly that of gamma-herpesviruses, relating the animal model provided by murid herpesvirus-4 (MuHV-4) to human infections. The following points emerge: (i) CD8(+) T-cell evasion by herpesviruses confers a prominent role in host defence on CD4(+) T cells. CD4(+) T cells inhibit MuHV-4 lytic gene expression via gamma-interferon (IFN-gamma). By reducing the lytic secretion of immune evasion proteins, they may also help CD8(+) T cells to control virus-driven lymphoproliferation in mixed lytic/latent lesions. Similarly, CD4(+) T cells specific for Epstein-Barr virus lytic antigens could improve the impact of adoptively transferred, latent antigen-specific CD8(+) T cells. (ii) In general, viral immune evasion necessitates multiple host effectors for optimal control. Thus, subunit vaccines, which tend to prime single effectors, have proved less successful than attenuated virus mutants, which prime multiple effectors. Latency-deficient mutants could make safe and effective gamma-herpesvirus vaccines. (iii) The antibody response to MuHV-4 infection helps to prevent disease but is suboptimal for neutralization. Vaccinating virus carriers with virion fusion complex components improves their neutralization titres. Reducing the infectivity of herpesvirus carriers in this way could be a useful adjunct to vaccinating naive individuals with attenuated mutants.
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Affiliation(s)
- P G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - J P Simas
- Instituto de Microbiologia e Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Portugal
| | - S Efstathiou
- Division of Virology, Department of Pathology, University of Cambridge, UK
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Functional analysis of glycoprotein L (gL) from rhesus lymphocryptovirus in Epstein-Barr virus-mediated cell fusion indicates a direct role of gL in gB-induced membrane fusion. J Virol 2009; 83:7678-89. [PMID: 19457993 DOI: 10.1128/jvi.00457-09] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Glycoprotein L (gL), which complexes with gH, is a conserved herpesvirus protein that is essential for Epstein-Barr virus (EBV) entry into host cells. The gH/gL complex has a conserved role in entry among herpesviruses, yet the mechanism is not clear. To gain a better understanding of the role of gL in EBV-mediated fusion, chimeric proteins were made using rhesus lymphocryptovirus (Rh-LCV) gL (Rh gL), which shares a high sequence homology with EBV gL but does not complement EBV gL in mediating fusion with B cells. A reduction in fusion activity was observed with chimeric gL proteins that contained the amino terminus of Rh gL, although they retained their ability to process and transport gH/gL to the cell surface. Amino acids not conserved within this region in EBV gL when compared to Rh gL were further analyzed, with the results mapping residues 54 and 94 as being functionally important for EBV-mediated fusion. All chimeras and mutants displayed levels of cell surface expression similar to that of wild-type gL and interacted with gH and gp42. Our data also suggest that the role of gL involves the activation or recruitment of gB with the gH/gL complex, as we found that reduced fusion of Rh gL, EBV/Rh-LCV chimeras, and gL point mutants could be restored by replacing EBV gB with Rh gB. These observations demonstrate a distinction between the role of gL in the processing and trafficking of gH to the cell surface and a posttrafficking role in cell-cell fusion.
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Gillet L, Alenquer M, Glauser DL, Colaco S, May JS, Stevenson PG. Glycoprotein L sets the neutralization profile of murid herpesvirus 4. J Gen Virol 2009; 90:1202-1214. [PMID: 19264603 PMCID: PMC2885041 DOI: 10.1099/vir.0.008755-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Antibodies readily neutralize acute, epidemic viruses, but are less effective against more indolent pathogens such as herpesviruses. Murid herpesvirus 4 (MuHV-4) provides an accessible model for tracking the fate of antibody-exposed gammaherpesvirus virions. Glycoprotein L (gL) plays a central role in MuHV-4 entry: it allows gH to bind heparan sulfate and regulates fusion-associated conformation changes in gH and gB. However, gL is non-essential: heparan sulfate binding can also occur via gp70, and the gB–gH complex alone seems to be sufficient for membrane fusion. Here, we investigated how gL affects the susceptibility of MuHV-4 to neutralization. Immune sera neutralized gL− virions more readily than gL+ virions, chiefly because heparan sulfate binding now depended on gp70 and was therefore easier to block. However, there were also post-binding effects. First, the downstream, gL-independent conformation of gH became a neutralization target; gL normally prevents this by holding gH in an antigenically distinct heterodimer until after endocytosis. Second, gL− virions were more vulnerable to gB-directed neutralization. This covered multiple epitopes and thus seemed to reflect a general opening up of the gH–gB entry complex, which gL again normally restricts to late endosomes. gL therefore limits MuHV-4 neutralization by providing redundancy in cell binding and by keeping key elements of the virion fusion machinery hidden until after endocytosis.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Marta Alenquer
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Daniel L Glauser
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Susanna Colaco
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Janet S May
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
| | - Philip G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
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26
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Gillet L, May JS, Stevenson PG. In vivo importance of heparan sulfate-binding glycoproteins for murid herpesvirus-4 infection. J Gen Virol 2009; 90:602-613. [PMID: 19218205 PMCID: PMC2885066 DOI: 10.1099/vir.0.005785-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2008] [Accepted: 11/27/2008] [Indexed: 11/18/2022] Open
Abstract
Many herpesviruses bind to heparan sulfate (HS). Murid herpesvirus-4 (MuHV-4) does so via its envelope glycoproteins gp70 and gH/gL. MuHV-4 gp150 further regulates an HS-independent interaction to make that HS-dependent too. Cell binding by MuHV-4 virions is consequently strongly HS-dependent. Gp70 and gH/gL show some in vitro redundancy: an antibody-mediated blockade of HS binding by one is well tolerated, whereas a blockade of both severely impairs infection. In order to understand the importance of HS binding for MuHV-4 in vivo, we generated mutants lacking both gL and gp70. As expected, gL(-)gp70(-) MuHV-4 showed very poor cell binding. It infected mice at high dose but not at low dose, indicating defective host entry. But once entry occurred, host colonization, which for MuHV-4 is relatively independent of the infection dose, was remarkably normal. The gL(-)gp70(-) entry deficit was much greater than that of gL(-) or gp70(-) single knockouts. And gp150 disruption, which allows HS-independent cell binding, largely rescued the gL(-)gp70(-) cell binding and host entry deficits. Thus, it appeared that MuHV-4 HS binding is important in vivo, principally for efficient host entry.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Janet S May
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Philip G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, UK
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27
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Persistent gammaherpesvirus replication and dynamic interaction with the host in vivo. J Virol 2008; 82:12498-509. [PMID: 18842717 DOI: 10.1128/jvi.01152-08] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Gammaherpesviruses establish life-long persistency inside the host and cause various diseases during their persistent infection. However, the systemic interaction between the virus and host in vivo has not been studied in individual hosts continuously, although such information can be crucial to control the persistent infection of the gammaherpesviruses. For the noninvasive and continuous monitoring of the interaction between gammaherpesvirus and the host, a recombinant murine gammaherpesvirus 68 (MHV-68, a gammaherpesvirus 68) was constructed to express a firefly luciferase gene driven by the viral M3 promoter (M3FL). Real-time monitoring of M3FL infection revealed novel sites of viral replication, such as salivary glands, as well as acute replication in the nose and the lung and progression to the spleen. Continuous monitoring of M3FL infection in individual mice demonstrated the various kinetics of transition to different organs and local clearance, rather than systemically synchronized clearance. Moreover, in vivo spontaneous reactivation of M3FL from latency was detected after the initial clearance of acute infection and can be induced upon treatment with either a proteasome inhibitor Velcade or an immunosuppressant cyclosporine A. Taken together, our results demonstrate that the in vivo replication and reactivation of gammaherpesvirus are dynamically controlled by the locally defined interaction between the virus and the host immune system and that bioluminescence imaging can be successfully used for the real-time monitoring of this dynamic interaction of MHV-68 with its host in vivo.
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28
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Gillet L, Colaco S, Stevenson PG. The Murid Herpesvirus-4 gL regulates an entry-associated conformation change in gH. PLoS One 2008; 3:e2811. [PMID: 18665235 PMCID: PMC2481400 DOI: 10.1371/journal.pone.0002811] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2008] [Accepted: 07/02/2008] [Indexed: 11/18/2022] Open
Abstract
The glycoprotein H (gH)/gL heterodimer is crucial for herpesvirus membrane fusion. Yet how it functions is not well understood. The Murid Herpesvirus-4 gH, like that of other herpesviruses, adopts its normal virion conformation by associating with gL. However, gH switched back to a gL-independent conformation after virion endocytosis. This switch coincided with a conformation switch in gB and with capsid release. Virions lacking gL constitutively expressed the down-stream form of gH, prematurely switched gB to its down-stream form, and showed premature capsid release with poor infectivity. These data argue that gL plays a key role in regulating a gH and gB functional switch from cell binding to membrane fusion.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Susanna Colaco
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * E-mail:
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Multiple functions for ORF75c in murid herpesvirus-4 infection. PLoS One 2008; 3:e2781. [PMID: 18648660 PMCID: PMC2464709 DOI: 10.1371/journal.pone.0002781] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2008] [Accepted: 07/01/2008] [Indexed: 11/23/2022] Open
Abstract
All gamma-herpesviruses encode at least one homolog of the cellular enzyme formyl-glycineamide-phosphoribosyl-amidotransferase. Murid herpesvirus-4 (MuHV-4) encodes 3 (ORFs 75a, 75b and 75c), suggesting that at least some copies have acquired new functions. Here we show that the corresponding proteins are all present in virions and localize to infected cell nuclei. Despite these common features, ORFs 75a and 75b did not substitute functionally for a lack of ORF75c, as ORF75c virus knockouts were severely impaired for lytic replication in vitro and for host colonization in vivo. They showed 2 defects: incoming capsids failed to migrate to the nuclear margin following membrane fusion, and genomes that did reach the nucleus failed to initiate normal gene expression. The latter defect was associated with a failure of in-coming virions to disassemble PML bodies. The capsid transport deficit seemed to be functionally more important, since ORF75c− MuHV-4 infected both PML+ and PML− cells poorly. The original host enzyme has therefore evolved into a set of distinct and multi-functional viral tegument proteins. One important function is moving incoming capsids to the nuclear margin for viral genome delivery.
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Gillet L, Colaco S, Stevenson PG. Glycoprotein B switches conformation during murid herpesvirus 4 entry. J Gen Virol 2008; 89:1352-1363. [PMID: 18474550 PMCID: PMC2886948 DOI: 10.1099/vir.0.83519-0] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2007] [Accepted: 02/07/2008] [Indexed: 11/18/2022] Open
Abstract
Herpesviruses are ancient pathogens that infect all vertebrates. The most conserved component of their entry machinery is glycoprotein B (gB), yet how gB functions is unclear. A striking feature of the murid herpesvirus 4 (MuHV-4) gB is its resistance to neutralization. Here, we show by direct visualization of infected cells that the MuHV-4 gB changes its conformation between extracellular virions and those in late endosomes, where capsids are released. Specifically, epitopes on its N-terminal cell-binding domain become inaccessible, whilst non-N-terminal epitopes are revealed, consistent with structural changes reported for the vesicular stomatitis virus glycoprotein G. Inhibitors of endosomal acidification blocked the gB conformation switch. They also blocked capsid release and the establishment of infection, implying that the gB switch is a key step in entry. Neutralizing antibodies could only partially inhibit the switch. Their need to engage a less vulnerable, upstream form of gB, because its fusion form is revealed only in endosomes, helps to explain why gB-directed MuHV-4 neutralization is so difficult.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Susanna Colaco
- Division of Virology, Department of Pathology, University of Cambridge, UK
| | - Philip G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, UK
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Kayhan B, Yager EJ, Lanzer K, Cookenham T, Jia Q, Wu TT, Woodland DL, Sun R, Blackman MA. A replication-deficient murine gamma-herpesvirus blocked in late viral gene expression can establish latency and elicit protective cellular immunity. THE JOURNAL OF IMMUNOLOGY 2008; 179:8392-402. [PMID: 18056385 DOI: 10.4049/jimmunol.179.12.8392] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
The human gamma-herpesviruses, EBV and Kaposi's sarcoma-associated herpesvirus, are widely disseminated and are associated with the onset of a variety of malignancies. Thus, the development of prophylactic and therapeutic vaccination strategies is an important goal. The experimental mouse gamma-herpesvirus, gammaHV68 (or MHV-68), has provided an in vivo model for studying immune control of these persistent viruses. In the current studies, we have examined infectivity, immunogenicity, and protective efficacy following infection with a replication-deficient gammaHV68 blocked in late viral gene expression, ORF31STOP. The data show that ORF31STOP was able to latently infect B cells. However, the anatomical site and persistence of the infection depended on the route of inoculation, implicating a role for viral replication in viral spread but not the infectivity per se. Furthermore, i.p. infection with ORF31STOP elicited strong cellular immunity but a non-neutralizing Ab response. In contrast, intranasal infection was poorly immunogenic. Consistent with this, mice infected i.p. had enhanced control of both the lytic and latent viral loads following challenge with wild-type gammaHV68, whereas intranasal infected mice were not protected. These data provide important insight into mechanisms of infection and protective immunity for the gamma-herpesviruses and demonstrate the utility of replication-deficient mutant viruses in direct testing of "proof of principal" vaccination strategies.
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32
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Abstract
The first contact a virus makes with cells is an important determinant of its tropism. Murid Herpesvirus-4 (MuHV-4) is highly dependent on glycosaminoglycans (GAGs) for cell binding. Its first contact is therefore likely to involve a GAG-binding virion glycoprotein. We have previously identified two such proteins, gp70 and gp150. Gp70 binds strongly to GAGs. However, deleting it makes little difference to MuHV-4 cell binding or GAG-dependence. Deleting gp150, by contrast, frees MuHV-4 from GAG dependence. This implies that GAGs normally displace gp150 to allow GAG-independent cell binding. But the gp150 GAG interaction is weak, and so would seem unlikely to make an effective first contact. Since neither gp70 nor gp150 matches the expected profile of a first contact glycoprotein, our understanding of MuHV-4 GAG interactions must be incomplete. Here we relate the seemingly disconnected gp70 and gp150 GAG interactions by showing that the MuHV-4 gH/gL also binds to GAGs. gH/gL-blocking and gp70-blocking antibodies individually had little effect on cell binding, but together were strongly inhibitory. Thus, there was redundancy in GAG binding between gp70 and gH/gL. Gp150-deficient MuHV-4 largely resisted blocks to gp70 and gH/gL binding, consistent with its GAG independence. The failure of wild-type MuHV-4 to do the same argues that gp150 is normally engaged only down-stream of gp70 or gH/gL. MuHV-4 GAG dependence is consequently two-fold: gp70 or gH/gL binding provides virions with a vital first foothold, and gp150 is then engaged to reveal GAG-independent binding.
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33
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Selection of mutant CHO clones resistant to murine gammaherpesvirus 68 infection. Virology 2008; 373:376-86. [PMID: 18191980 DOI: 10.1016/j.virol.2007.12.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2007] [Revised: 11/14/2007] [Accepted: 12/03/2007] [Indexed: 11/20/2022]
Abstract
Murine gammaherpesvirus 68 (MHV68) is used as a model to study gammaherpesvirus pathogenesis both in tissue culture systems and in vivo. We used a gene-trapping approach to get insight into cellular factors involved in MHV68 infection. By generating a library of gene-trapped CHO cells, we were able to isolate several clones that exhibited various degrees of resistance to MHV68-induced cytopathic effect. Clones that showed the highest degree of resistance were affected at the early stage of the viral cycle, with the vast majority of these clones being deficient for heparan sulfate (HS) expression at the cell surface. Heparan sulfate expression could be restored in all the HS-deficient clones by expression of EXT1, an enzyme that is essential for the biosynthesis of HS. Consistent with the role of HS in viral entry, HS-deficient CHO cells did not support viral internalization. Cell surface heparan sulfate proteoglycans (HSPG) are mostly composed of HS chains attached to two families of core proteins, the transmembrane syndecans and the GPI-anchored glypicans. Treatment of CHO cells with phosphatidylinositol-specific phospholipase C (PI-PLC) did not significantly affect the level of HS expression, indicating that the glypicans are not a major source of HSPG in CHO cells. By contrast, treatment of CHO cells with PMA, a drug known to accelerate syndecan shedding, resulted in a decrease in both HS expression and susceptibility to MHV68; these effects were abolished by TIMP-3, a specific inhibitor of syndecan shedding. All together, our results confirm the essential role of HS in MHV68 infection and identify the syndecans as a major source of HSPG used by the virus as coreceptors to infect CHO cells.
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34
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Gillet L, Stevenson PG. Antibody evasion by the N terminus of murid herpesvirus-4 glycoprotein B. EMBO J 2007; 26:5131-42. [PMID: 18034158 PMCID: PMC2094095 DOI: 10.1038/sj.emboj.7601925] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 10/19/2007] [Indexed: 01/30/2023] Open
Abstract
Herpesviruses characteristically transmit infection from immune hosts. Although their success in escaping neutralization by pre-formed antibody is indisputable, the underlying molecular mechanisms remain largely unknown. Glycoprotein B (gB) is the most conserved component of the herpesvirus entry machinery and its N terminus (gB-NT) is a common neutralization target. We used murid herpesvirus-4 to determine how gB-NT contributes to the virus–antibody interaction. Deleting gB-NT had no obvious impact on virus replication, but paradoxically increased virion neutralization by immune sera. This reflected greater antibody access to neutralization epitopes on gH/gL, with which gB was associated. gB-NT itself was variably protected against antibody by O-linked glycans; on virions from epithelial cells it was protected almost completely. gB-NT therefore provides a protective and largely protected cover for a vulnerable part of gH/gL. The conservation of predicted glycosylation sites in other mammalian herpesvirus gB-NTs suggests that this evasion mechanism is widespread. Interestingly, the gB-NT glycans that blocked antibody binding could be targeted for neutralization instead by a lectin, suggesting a means of therapeutic counterattack.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, UK
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35
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Smith CM, Gill MB, May JS, Stevenson PG. Murine gammaherpesvirus-68 inhibits antigen presentation by dendritic cells. PLoS One 2007; 2:e1048. [PMID: 17940612 PMCID: PMC2002512 DOI: 10.1371/journal.pone.0001048] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 10/01/2007] [Indexed: 01/18/2023] Open
Abstract
Dendritic cells (DCs) play a central role in initiating adaptive immunity. Murine gammaherpesvirus-68 (MHV-68), like many persistent viruses, infects DCs during normal host colonization. It therefore provides a means to understanding what host and viral genes contribute to this aspect of pathogenesis. The infected DC phenotype is likely to depend on whether viral gene expression is lytic or latent and whether antigen presentation is maintained. For MHV-68, neither parameter has been well defined. Here we show that MHV-68 infects immature but not mature bone marrow-derived DCs. Infection was predominantly latent and these DCs showed no obvious defect in antigen presentation. Lytically infected DCs were very different. These down-regulated CD86 and MHC class I expression and presented a viral epitope poorly to CD8+ T cells. Antigen presentation improved markedly when the MHV-68 K3 gene was disrupted, indicating that K3 fulfils an important function in infected DCs. MHV-68 infects only a small fraction of the DCs present in lymphoid tissue, so K3 expression is unlikely to compromise significantly global CD8+ T cell priming. Instead it probably helps to maintain lytic gene expression in DCs once CD8+ T cell priming has occurred.
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Affiliation(s)
- Christopher M. Smith
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Michael B. Gill
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Janet S. May
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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36
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Abstract
Herpesviruses use multiple virion glycoproteins to enter cells. How these work together is not well understood: some may act separately or they may form a single complex. Murine gammaherpesvirus 68 (MHV-68) gB, gH, gL, and gp150 all participate in entry. gB and gL are involved in binding, gB and gH are conserved fusion proteins, and gp150 inhibits cell binding until glycosaminoglycans are engaged. Here we show that a gH-specific antibody coprecipitates gB and thus that gH and gB are associated in the virion membrane. A gH/gL-specific antibody also coprecipitated gB, implying a tripartite complex of gL/gH/gB, although the gH/gB association did not require gL. The association was also independent of gp150, and gp150 was not demonstrably bound to gB or gH. However, gp150 incorporation into virions was partly gL dependent, suggesting that it too contributes to a single entry complex. gp150- and gL- gp150- mutants bound better than the wild type to B cells and readily colonized B cells in vivo. Thus, gp150 and gL appear to be epithelial cell-adapted accessories of a core gB/gH entry complex. The cell binding revealed by gp150 disruption did not require gL and therefore seemed most likely to involve gB.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
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37
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Gillet L, May JS, Stevenson PG. Post-exposure vaccination improves gammaherpesvirus neutralization. PLoS One 2007; 2:e899. [PMID: 17878934 PMCID: PMC1964807 DOI: 10.1371/journal.pone.0000899] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2007] [Accepted: 08/27/2007] [Indexed: 02/07/2023] Open
Abstract
Herpesvirus carriers transmit infection despite making virus-specific antibodies. Thus, their antibody responses are not necessarily optimal. An important question for infection control is whether vaccinating carriers might improve virus neutralization. The antibody response to murine gamma-herpesvirus-68 (MHV-68) blocks cell binding, but fails to block and even enhances an IgG Fc receptor-dependent infection of myeloid cells. Viral membrane fusion therefore remains intact. Although gH/gL-specific monoclonal antibodies can block infection at a post-binding step close to membrane fusion, gH/gL is a relatively minor antibody target in virus carriers. We show here that gH/gL-specific antibodies can block both Fc receptor-independent and Fc receptor-dependent infections, and that vaccinating virus carriers with a gH/gL fusion protein improves their capacity for virus neutralization both in vitro and in vivo. This approach has the potential to reduce herpesvirus transmission.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Cambridge, United Kingdom
| | - Janet S. May
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Cambridge, United Kingdom
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Addenbrookes Hospital, Cambridge, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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38
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Gillet L, May JS, Colaco S, Stevenson PG. The murine gammaherpesvirus-68 gp150 acts as an immunogenic decoy to limit virion neutralization. PLoS One 2007; 2:e705. [PMID: 17684552 PMCID: PMC1931612 DOI: 10.1371/journal.pone.0000705] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2007] [Accepted: 07/05/2007] [Indexed: 11/19/2022] Open
Abstract
Herpesviruses maintain long-term infectivity without marked antigenic variation. They must therefore evade neutralization by other means. Immune sera block murine gammaherpesvirus-68 (MHV-68) infection of fibroblasts, but fail to block and even enhance its infection of IgG Fc receptor-bearing cells, suggesting that the antibody response to infection is actually poor at ablating virion infectivity completely. Here we analyzed this effect further by quantitating the glycoprotein-specific antibody response of MHV-68 carrier mice. Gp150 was much the commonest glycoprotein target and played a predominant role in driving Fc receptor-dependent infection: when gp150-specific antibodies were boosted, Fc receptor-dependent infection increased; and when gp150-specific antibodies were removed, Fc receptor-dependent infection was largely lost. Neither gp150-specific monoclonal antibodies nor gp150-specific polyclonal sera gave significant virion neutralization. Gp150 therefore acts as an immunogenic decoy, distorting the MHV-68-specific antibody response to promote Fc receptor-dependent infection and so compromise virion neutralization. This immune evasion mechanism may be common to many non-essential herpesvirus glycoproteins.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Janet S. May
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Susanna Colaco
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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39
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Rosa GT, Gillet L, Smith CM, de Lima BD, Stevenson PG. IgG fc receptors provide an alternative infection route for murine gamma-herpesvirus-68. PLoS One 2007; 2:e560. [PMID: 17593961 PMCID: PMC1891442 DOI: 10.1371/journal.pone.0000560] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2007] [Accepted: 05/30/2007] [Indexed: 01/22/2023] Open
Abstract
Background Herpesviruses can be neutralized in vitro but remain infectious in immune hosts. One difference between these settings is the availability of immunoglobulin Fc receptors. The question therefore arises whether a herpesvirus exposed to apparently neutralizing antibody can still infect Fc receptor+ cells. Principal Findings Immune sera blocked murine gamma-herpesvirus-68 (MHV-68) infection of fibroblasts, but failed to block and even enhanced its infection of macrophages and dendritic cells. Viral glycoprotein-specific monoclonal antibodies also enhanced infection. MHV-68 appeared to be predominantly latent in macrophages regardless of whether Fc receptors were engaged, but the infection was not abortive and new virus production soon overwhelmed infected cultures. Lytically infected macrophages down-regulated MHC class I-restricted antigen presentation, endocytosis and their response to LPS. Conclusions IgG Fc receptors limit the neutralization of gamma-herpesviruses such as MHV-68.
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MESH Headings
- Animals
- Antibodies, Monoclonal/immunology
- Antibodies, Neutralizing/immunology
- Antigen Presentation
- Cells, Cultured
- Cytomegalovirus/genetics
- DNA, Viral/genetics
- Fibroblasts/immunology
- Fibroblasts/metabolism
- Fibroblasts/pathology
- Flow Cytometry
- Fluorescent Antibody Technique
- Glycoproteins/immunology
- Green Fluorescent Proteins/metabolism
- Herpesviridae Infections/immunology
- Herpesviridae Infections/metabolism
- Herpesviridae Infections/pathology
- Immediate-Early Proteins/genetics
- Macrophages, Peritoneal/immunology
- Macrophages, Peritoneal/metabolism
- Macrophages, Peritoneal/pathology
- Mice
- Mice, Inbred BALB C
- Mice, Inbred C57BL
- Neutralization Tests
- Promoter Regions, Genetic/genetics
- Receptors, Fc/immunology
- Receptors, IgG/immunology
- Rhadinovirus/immunology
- Tumor Virus Infections/immunology
- Tumor Virus Infections/metabolism
- Tumor Virus Infections/pathology
- Virion/immunology
- Virus Replication
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Affiliation(s)
- Gustavo T. Rosa
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Christopher M. Smith
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Brigitte D. de Lima
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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40
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Gillet L, Adler H, Stevenson PG. Glycosaminoglycan interactions in murine gammaherpesvirus-68 infection. PLoS One 2007; 2:e347. [PMID: 17406671 PMCID: PMC1829177 DOI: 10.1371/journal.pone.0000347] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2007] [Accepted: 03/14/2007] [Indexed: 11/19/2022] Open
Abstract
Glycosaminoglycans (GAGs) commonly participate in herpesvirus entry. They are thought to provide a reversible attachment to cells that promotes subsequent receptor binding. Murine gamma-herpesvirus-68 (MHV-68) infection of fibroblasts and epithelial cells is highly GAG-dependent. This is a function of the viral gp150, in that gp150-deficient mutants are much less GAG-dependent than wild-type. Here we show that the major MHV-68 GAG-binding protein is not gp150 but gp70, a product of ORF4. Surprisingly, ORF4-deficient MHV-68 showed normal cell binding and was more sensitive than wild-type to inhibition by soluble heparin rather than less. Thus, the most obvious viral GAG interaction made little direct contribution to infection. Indeed, a large fraction of the virion gp70 had its GAG-binding domain removed by post-translational cleavage. ORF4 may therefore act mainly to absorb soluble GAGs and prevent them from engaging gp150 prematurely. In contrast to gp70, gp150 bound poorly to GAGs, implying that it provides little in the way of adhesion. We hypothesize that it acts instead as a GAG-sensitive switch that selectively activates MHV-68 entry at cell surfaces.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
| | - Heiko Adler
- GSF-Research Center for Environment and Health, Institute of Molecular Immunology, Clinical Cooperation Group Hematopoietic Cell Transplantation, Munich, Germany
| | - Philip G. Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Cambridge, United Kingdom
- * To whom correspondence should be addressed. E-mail:
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41
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Gillet L, Gill MB, Colaco S, Smith CM, Stevenson PG. Murine gammaherpesvirus-68 glycoprotein B presents a difficult neutralization target to monoclonal antibodies derived from infected mice. J Gen Virol 2006; 87:3515-3527. [PMID: 17098966 PMCID: PMC2884974 DOI: 10.1099/vir.0.82313-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Persistent viruses disseminate from immune hosts. They must therefore resist neutralization by antibody. Murine gammaherpesvirus-68 (MHV-68) represents an accessible model with which to address how resistance to neutralization is achieved and how overcoming it might improve infection control. The MHV-68 glycoprotein B (gB), like that of other herpesviruses, is a virion protein that is essential for infectivity. As such, it presents a potential neutralization target. In order to test whether virus-induced antibodies reduce virion infectivity by binding to gB, monoclonal antibodies (mAbs) were derived from MHV-68-infected mice. gB-specific mAbs were common, but only an IgM specific for the gB N terminus reduced virion infectivity significantly. It inhibited MHV-68 entry into BHK-21 cells at a post-binding step that was linked closely to membrane fusion. Reducing the mAb to IgM monomers compromised neutralization severely, suggesting that a pentameric structure was crucial to its function. Antibody treatment never blocked BHK-21 cell infection completely and blocked the infection of NMuMG epithelial cells hardly at all. Virions saturated with antibody also remained infectious to mice. Thus, the MHV-68 gB presents at best a very difficult target for antibody-mediated neutralization.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Michael B Gill
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Susanna Colaco
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Christopher M Smith
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
| | - Philip G Stevenson
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, UK
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42
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Gillet L, May JS, Colaco S, Stevenson PG. Glycoprotein L disruption reveals two functional forms of the murine gammaherpesvirus 68 glycoprotein H. J Virol 2006; 81:280-91. [PMID: 17050601 PMCID: PMC1797276 DOI: 10.1128/jvi.01616-06] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
The herpesvirus glycoprotein H (gH) and gL associate to form a heterodimer that plays a central role in virus-driven membrane fusion. When archetypal alpha- or betaherpesviruses lack gL, gH misfolds and progeny virions are noninfectious. In order to define the role that gL plays in gamma-2 herpesvirus infections, we disrupted its coding sequence in murine gammaherpesvirus-68 (MHV-68). MHV-68 lacking gL folded gH into a conformation antigenically distinct from the form that normally predominates on infected cells. gL-deficient virions bound less well than the wild type to epithelial cells and fibroblasts. However, they still incorporated gH and remained infectious. The cell-to-cell spread of gL-deficient viruses was remarkably normal, as was infection, dissemination, and latency establishment in vivo. Viral membrane fusion was therefore gL independent. The major function of gL appeared to be allowing gH to participate in cell binding prior to membrane fusion. This function was most important for the entry of MHV-68 virions into fibroblasts and epithelial cells.
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Affiliation(s)
- Laurent Gillet
- Division of Virology, Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge CB2 1QP, United Kingdom
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