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Gautam A, Lalande A, Ritter M, Freitas N, Lerolle S, Canus L, Amirache F, Lotteau V, Legros V, Cosset FL, Mathieu C, Boson B. The PACS-2 protein and trafficking motifs in CCHFV Gn and Gc cytoplasmic domains govern CCHFV assembly. Emerg Microbes Infect 2024; 13:2348508. [PMID: 38661085 PMCID: PMC11159592 DOI: 10.1080/22221751.2024.2348508] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2024] [Accepted: 04/23/2024] [Indexed: 04/26/2024]
Abstract
The Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne bunyavirus that causes high mortality in humans. This enveloped virus harbors two surface glycoproteins (GP), Gn and Gc, that are released by processing of a glycoprotein precursor complex whose maturation takes place in the ER and is completed through the secretion pathway. Here, we characterized the trafficking network exploited by CCHFV GPs during viral assembly, envelopment, and/or egress. We identified membrane trafficking motifs in the cytoplasmic domains (CD) of CCHFV GPs and addressed how they impact these late stages of the viral life cycle using infection and biochemical assays, and confocal microscopy in virus-producing cells. We found that several of the identified CD motifs modulate GP transport through the retrograde trafficking network, impacting envelopment and secretion of infectious particles. Finally, we identified PACS-2 as a crucial host factor contributing to CCHFV GPs trafficking required for assembly and release of viral particles.
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Affiliation(s)
- Anupriya Gautam
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Alexandre Lalande
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Maureen Ritter
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Natalia Freitas
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Solène Lerolle
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Lola Canus
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Fouzia Amirache
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | | | - Vincent Legros
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
- Campus vétérinaire de Lyon, VetAgro Sup, Université de Lyon, Marcy-l’Etoile, France
| | - François-Loïc Cosset
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Cyrille Mathieu
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
| | - Bertrand Boson
- CIRI – Centre International de Recherche en Infectiologie, Univ. Lyon, Université Claude Bernard Lyon 1, Lyon, France
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2
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Ferron F, Lescar J. The Phlebovirus Ribonucleoprotein: An Overview. Methods Mol Biol 2024; 2824:259-280. [PMID: 39039418 DOI: 10.1007/978-1-0716-3926-9_17] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/24/2024]
Abstract
In negative strand RNA viruses, ribonucleoproteins, not naked RNA, constitute the template used by the large protein endowed with polymerase activity for replicating and transcribing the viral genome. Here we give an overview of the structures and functions of the ribonucleoprotein from phleboviruses. The nucleocapsid monomer, which constitutes the basic structural unit, possesses a flexible arm allowing for a conformational switch between a closed monomeric state and the formation of a polymeric filamentous structure competent for viral RNA binding and encapsidation in the open state of N. The modes of N-N oligomerization as well as interactions with vRNA are described. Finally, recent advances in tomography open exciting perspectives for a more complete understanding of N-L interactions and the design of specific antiviral compounds.
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Affiliation(s)
- François Ferron
- Aix Marseille Univ, CNRS - Architecture et Fonction des Macromolécules Biologiques (AFMB) UMR7257, Marseille, France.
- European Virus Bioinformatics Center, Jena, Germany.
| | - Julien Lescar
- School of Biological Sciences, Nanyang Technological University, Singapore, Singapore.
- NTU Institute of Structural Biology, Nanyang Technological University, Experimental Medicine Building, Singapore, Singapore.
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3
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Hayashi M, Schultz EP, Lanchy JM, Lodmell JS. Time-Resolved Analysis of N-RNA Interactions during RVFV Infection Shows Qualitative and Quantitative Shifts in RNA Encapsidation and Packaging. Viruses 2021; 13:2417. [PMID: 34960686 PMCID: PMC8704896 DOI: 10.3390/v13122417] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2021] [Revised: 11/28/2021] [Accepted: 11/29/2021] [Indexed: 11/16/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a negative-sense, tripartite RNA virus that is endemic to Africa and the Arabian Peninsula. It can cause severe disease and mortality in humans and domestic livestock and is a concern for its potential to spread more globally. RVFV's nucleocapsid protein (N) is an RNA-binding protein that is necessary for viral transcription, replication, and the production of nascent viral particles. We have conducted crosslinking, immunoprecipitation, and sequencing (CLIP-seq) to characterize N interactions with host and viral RNAs during infection. In parallel, to precisely measure intracellular N levels, we employed multiple reaction monitoring mass spectrometry (MRM-MS). Our results show that N binds mostly to host RNAs at early stages of infection, yielding nascent virus particles of reduced infectivity. The expression of N plateaus 10 h post-infection, whereas the intracellular viral RNA concentration continues to increase. Moreover, the virions produced later in infection have higher infectivity. Taken together, the detailed examination of these N-RNA interactions provides insight into how the regulated expression of N and viral RNA produces both infectious and incomplete, noninfectious particles.
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Affiliation(s)
- Miyuki Hayashi
- Department of Chemistry and Biochemistry, University of Montana, Missoula, MT 59812, USA;
- Center for Biomolecular Structure and Dynamics, Missoula, MT 59812, USA;
| | - Eric P. Schultz
- Center for Biomolecular Structure and Dynamics, Missoula, MT 59812, USA;
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA;
| | - Jean-Marc Lanchy
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA;
| | - J. Stephen Lodmell
- Center for Biomolecular Structure and Dynamics, Missoula, MT 59812, USA;
- Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA;
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4
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Baseline mapping of severe fever with thrombocytopenia syndrome virology, epidemiology and vaccine research and development. NPJ Vaccines 2020; 5:111. [PMID: 33335100 PMCID: PMC7746727 DOI: 10.1038/s41541-020-00257-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2019] [Accepted: 10/13/2020] [Indexed: 12/13/2022] Open
Abstract
Severe fever with thrombocytopenia syndrome virus (SFTSV) is a newly emergent tick-borne bunyavirus first discovered in 2009 in China. SFTSV is a growing public health problem that may become more prominent owing to multiple competent tick-vectors and the expansion of human populations in areas where the vectors are found. Although tick-vectors of SFTSV are found in a wide geographic area, SFTS cases have only been reported from China, South Korea, Vietnam, and Japan. Patients with SFTS often present with high fever, leukopenia, and thrombocytopenia, and in some cases, symptoms can progress to severe outcomes, including hemorrhagic disease. Reported SFTSV case fatality rates range from ~5 to >30% depending on the region surveyed, with more severe disease reported in older individuals. Currently, treatment options for this viral infection remain mostly supportive as there are no licensed vaccines available and research is in the discovery stage. Animal models for SFTSV appear to recapitulate many facets of human disease, although none of the models mirror all clinical manifestations. There are insufficient data available on basic immunologic responses, the immune correlate(s) of protection, and the determinants of severe disease by SFTSV and related viruses. Many aspects of SFTSV virology and epidemiology are not fully understood, including a detailed understanding of the annual numbers of cases and the vertebrate host of the virus, so additional research on this disease is essential towards the development of vaccines and therapeutics.
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5
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Uckeley ZM, Moeller R, Kühn LI, Nilsson E, Robens C, Lasswitz L, Lindqvist R, Lenman A, Passos V, Voss Y, Sommerauer C, Kampmann M, Goffinet C, Meissner F, Överby AK, Lozach PY, Gerold G. Quantitative Proteomics of Uukuniemi Virus-host Cell Interactions Reveals GBF1 as Proviral Host Factor for Phleboviruses. Mol Cell Proteomics 2019; 18:2401-2417. [PMID: 31570497 PMCID: PMC6885706 DOI: 10.1074/mcp.ra119.001631] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2019] [Revised: 09/15/2019] [Indexed: 12/20/2022] Open
Abstract
Novel tick-borne phleboviruses in the Phenuiviridae family, which are highly pathogenic in humans and all closely related to Uukuniemi virus (UUKV), have recently emerged on different continents. How phleboviruses assemble, bud, and exit cells remains largely elusive. Here, we performed high-resolution, label-free mass spectrometry analysis of UUKV immunoprecipitated from cell lysates and identified 39 cellular partners interacting with the viral envelope glycoproteins. The importance of these host factors for UUKV infection was validated by silencing each host factor by RNA interference. This revealed Golgi-specific brefeldin A-resistance guanine nucleotide exchange factor 1 (GBF1), a guanine nucleotide exchange factor resident in the Golgi, as a critical host factor required for the UUKV life cycle. An inhibitor of GBF1, Golgicide A, confirmed the role of the cellular factor in UUKV infection. We could pinpoint the GBF1 requirement to UUKV replication and particle assembly. When the investigation was extended to viruses from various positive and negative RNA viral families, we found that not only phleboviruses rely on GBF1 for infection, but also Flavi-, Corona-, Rhabdo-, and Togaviridae In contrast, silencing or blocking GBF1 did not abrogate infection by the human adenovirus serotype 5 and immunodeficiency retrovirus type 1, the replication of both requires nuclear steps. Together our results indicate that UUKV relies on GBF1 for viral replication, assembly and egress. This study also highlights the proviral activity of GBF1 in the infection by a broad range of important zoonotic RNA viruses.
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Affiliation(s)
- Zina M Uckeley
- CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany; CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Rebecca Moeller
- Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany; CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Lars I Kühn
- Experimental Systems Immunology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Emma Nilsson
- Division of Virology, Department of Clinical Microbiology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Claudia Robens
- CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Lisa Lasswitz
- Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany
| | - Richard Lindqvist
- Division of Virology, Department of Clinical Microbiology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Annasara Lenman
- Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany
| | - Vania Passos
- Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany; Instituto De Ciências Biomédicas Abel Salazar, Universidade Do Porto, Porto, Portugal
| | - Yannik Voss
- CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Christian Sommerauer
- CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Martin Kampmann
- CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany
| | - Christine Goffinet
- Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany; Institute of Virology, Charité, Universitätsmedizin Berlin, Berlin, Germany and Berlin Institute of Health (BIH), Berlin, Germany
| | - Felix Meissner
- Experimental Systems Immunology, Max Planck Institute of Biochemistry, Martinsried, Germany
| | - Anna K Överby
- Division of Virology, Department of Clinical Microbiology, and Laboratory for Molecular Infection Medicine Sweden, Umeå University, Umeå, Sweden
| | - Pierre-Yves Lozach
- CellNetworks Cluster of Excellence and Department of Infectious Diseases, Virology, University Hospital Heidelberg, Heidelberg, Germany; IVPC UMR754, INRA, Univ. Lyon, EPHE, 50 Av. Tony Garnier, 69007 Lyon, France.
| | - Gisa Gerold
- Institute for Experimental Virology, TWINCORE, Centre for Experimental and Clinical Infection Research, a joint venture between the Medical School Hannover and the Helmholtz Centre for Infection Research, Hannover, Germany; Department of Clinical Microbiology, Virology & Wallenberg Centre for Molecular Medicine (WCMM), Umeå University, SE-90185 Umeå, Sweden.
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6
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Vesicular Stomatitis Virus-Based Vaccine Protects Mice against Crimean-Congo Hemorrhagic Fever. Sci Rep 2019; 9:7755. [PMID: 31123310 PMCID: PMC6533279 DOI: 10.1038/s41598-019-44210-6] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 05/01/2019] [Indexed: 01/17/2023] Open
Abstract
Crimean-Congo hemorrhagic fever virus (CCHFV), a tick-borne bunyavirus, can cause a life-threatening hemorrhagic syndrome in humans but not in its animal host. The virus is widely distributed throughout southeastern Europe, the Middle East, Africa, and Asia. Disease management has proven difficult and there are no broadly licensed vaccines or therapeutics. Recombinant vesicular stomatitis viruses (rVSV) expressing foreign glycoproteins (GP) have shown promise as experimental vaccines for several viral hemorrhagic fevers. Here, we developed and assessed a replication competent rVSV vector expressing the CCHFV glycoprotein precursor (GPC), which encodes CCHFV structural glycoproteins. This construct drives strong expression of CCHFV-GP, in vitro. Using these vectors, we vaccinated STAT-1 knock-out mice, an animal model for CCHFV. The vector was tolerated and 100% efficacious against challenge from a clinical strain of CCHFV. Anti-CCHFV-GP IgG and neutralizing antibody titers were observed in surviving animals. This study demonstrates that a rVSV expressing only the CCHFV-GP has the potential to serve as a replication competent vaccine platform against CCHF infections.
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7
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Sperber HS, Welke RW, Petazzi RA, Bergmann R, Schade M, Shai Y, Chiantia S, Herrmann A, Schwarzer R. Self-association and subcellular localization of Puumala hantavirus envelope proteins. Sci Rep 2019; 9:707. [PMID: 30679542 PMCID: PMC6345964 DOI: 10.1038/s41598-018-36879-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2017] [Accepted: 11/28/2018] [Indexed: 01/08/2023] Open
Abstract
Hantavirus assembly and budding are governed by the surface glycoproteins Gn and Gc. In this study, we investigated the glycoproteins of Puumala, the most abundant Hantavirus species in Europe, using fluorescently labeled wild-type constructs and cytoplasmic tail (CT) mutants. We analyzed their intracellular distribution, co-localization and oligomerization, applying comprehensive live, single-cell fluorescence techniques, including confocal microscopy, imaging flow cytometry, anisotropy imaging and Number&Brightness analysis. We demonstrate that Gc is significantly enriched in the Golgi apparatus in absence of other viral components, while Gn is mainly restricted to the endoplasmic reticulum (ER). Importantly, upon co-expression both glycoproteins were found in the Golgi apparatus. Furthermore, we show that an intact CT of Gc is necessary for efficient Golgi localization, while the CT of Gn influences protein stability. Finally, we found that Gn assembles into higher-order homo-oligomers, mainly dimers and tetramers, in the ER while Gc was present as mixture of monomers and dimers within the Golgi apparatus. Our findings suggest that PUUV Gc is the driving factor of the targeting of Gc and Gn to the Golgi region, while Gn possesses a significantly stronger self-association potential.
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Affiliation(s)
- Hannah Sabeth Sperber
- Institute for Biology, IRI Life Science, Humboldt-Universität zu Berlin, Invalidenstr. 42, 10115, Berlin, Germany.,Vitalant Research Institute, 270 Masonic Ave, San Francisco, CA, 94118, USA
| | - Robert-William Welke
- Institute for Biology, IRI Life Science, Humboldt-Universität zu Berlin, Invalidenstr. 42, 10115, Berlin, Germany
| | - Roberto Arturo Petazzi
- University of Potsdam, Institute of Biochemistry and Biology, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany
| | - Ronny Bergmann
- Institute for Biology, IRI Life Science, Humboldt-Universität zu Berlin, Invalidenstr. 42, 10115, Berlin, Germany
| | - Matthias Schade
- Institute for Biology, IRI Life Science, Humboldt-Universität zu Berlin, Invalidenstr. 42, 10115, Berlin, Germany
| | - Yechiel Shai
- Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel
| | - Salvatore Chiantia
- University of Potsdam, Institute of Biochemistry and Biology, Karl-Liebknecht-Str. 24-25, 14476, Potsdam, Germany
| | - Andreas Herrmann
- Institute for Biology, IRI Life Science, Humboldt-Universität zu Berlin, Invalidenstr. 42, 10115, Berlin, Germany.
| | - Roland Schwarzer
- Institute for Biology, IRI Life Science, Humboldt-Universität zu Berlin, Invalidenstr. 42, 10115, Berlin, Germany. .,Department of Biomolecular Sciences, Weizmann Institute of Science, Rehovot, Israel. .,Gladstone Institute of Virology and Immunology, 1650 Owens Street, San Francisco, CA, 95158, USA.
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8
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Two Point Mutations in Old World Hantavirus Glycoproteins Afford the Generation of Highly Infectious Recombinant Vesicular Stomatitis Virus Vectors. mBio 2019; 10:mBio.02372-18. [PMID: 30622188 PMCID: PMC6325249 DOI: 10.1128/mbio.02372-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Human hantavirus infections cause hantavirus pulmonary syndrome in the Americas and hemorrhagic fever with renal syndrome (HFRS) in Eurasia. No FDA-approved vaccines and therapeutics exist for these deadly viruses, and their development is limited by the requirement for high biocontainment. In this study, we identified and characterized key amino acid changes in the surface glycoproteins of HFRS-causing Hantaan virus that enhance their incorporation into recombinant vesicular stomatitis virus (rVSV) particles. The replication-competent rVSVs encoding Hantaan virus and Dobrava-Belgrade virus glycoproteins described in this work provide a powerful and facile system to study hantavirus entry under lower biocontainment and may have utility as hantavirus vaccines. Rodent-to-human transmission of hantaviruses is associated with severe disease. Currently, no FDA-approved, specific antivirals or vaccines are available, and the requirement for high biocontainment (biosafety level 3 [BSL-3]) laboratories limits hantavirus research. To study hantavirus entry in a BSL-2 laboratory, we set out to generate replication-competent, recombinant vesicular stomatitis viruses (rVSVs) bearing the Gn and Gc (Gn/Gc) entry glycoproteins. As previously reported, rVSVs bearing New World hantavirus Gn/Gc were readily rescued from cDNAs, but their counterparts bearing Gn/Gc from the Old World hantaviruses, Hantaan virus (HTNV) or Dobrava-Belgrade virus (DOBV), were refractory to rescue. However, serial passage of the rescued rVSV-HTNV Gn/Gc virus markedly increased its infectivity and capacity for cell-to-cell spread. This gain in viral fitness was associated with the acquisition of two point mutations: I532K in the cytoplasmic tail of Gn and S1094L in the membrane-proximal stem of Gc. Follow-up experiments with rVSVs and single-cycle VSV pseudotypes confirmed these results. Mechanistic studies revealed that both mutations were determinative and contributed to viral infectivity in a synergistic manner. Our findings indicate that the primary mode of action of these mutations is to relocalize HTNV Gn/Gc from the Golgi complex to the cell surface, thereby affording significantly enhanced Gn/Gc incorporation into budding VSV particles. Finally, I532K/S1094L mutations in DOBV Gn/Gc permitted the rescue of rVSV-DOBV Gn/Gc, demonstrating that incorporation of cognate mutations into other hantaviral Gn/Gc proteins could afford the generation of rVSVs that are otherwise challenging to rescue. The robust replication-competent rVSVs, bearing HTNV and DOBV Gn/Gc, reported herein may also have utility as vaccines.
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Dunlop JI, Szemiel AM, Navarro A, Wilkie GS, Tong L, Modha S, Mair D, Sreenu VB, Da Silva Filipe A, Li P, Huang YJS, Brennan B, Hughes J, Vanlandingham DL, Higgs S, Elliott RM, Kohl A. Development of reverse genetics systems and investigation of host response antagonism and reassortment potential for Cache Valley and Kairi viruses, two emerging orthobunyaviruses of the Americas. PLoS Negl Trop Dis 2018; 12:e0006884. [PMID: 30372452 PMCID: PMC6245839 DOI: 10.1371/journal.pntd.0006884] [Citation(s) in RCA: 8] [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: 04/13/2018] [Revised: 11/20/2018] [Accepted: 09/28/2018] [Indexed: 11/24/2022] Open
Abstract
Orthobunyaviruses such as Cache Valley virus (CVV) and Kairi virus (KRIV) are important animal pathogens. Periodic outbreaks of CVV have resulted in the significant loss of lambs on North American farms, whilst KRIV has mainly been detected in South and Central America with little overlap in geographical range. Vaccines or treatments for these viruses are unavailable. One approach to develop novel vaccine candidates is based on the use of reverse genetics to produce attenuated viruses that elicit immune responses but cannot revert to full virulence. The full genomes of both viruses were sequenced to obtain up to date genome sequence information. Following sequencing, minigenome systems and reverse genetics systems for both CVV and KRIV were developed. Both CVV and KRIV showed a wide in vitro cell host range, with BHK-21 cells a suitable host cell line for virus propagation and titration. To develop attenuated viruses, the open reading frames of the NSs proteins were disrupted. The recombinant viruses with no NSs protein expression induced the production of type I interferon (IFN), indicating that for both viruses NSs functions as an IFN antagonist and that such attenuated viruses could form the basis for attenuated viral vaccines. To assess the potential for reassortment between CVV and KRIV, which could be relevant during vaccination campaigns in areas of overlap, we attempted to produce M segment reassortants by reverse genetics. We were unable to obtain such viruses, suggesting that it is an unlikely event.
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Affiliation(s)
- James I. Dunlop
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Agnieszka M. Szemiel
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Aitor Navarro
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Gavin S. Wilkie
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Lily Tong
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Sejal Modha
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Daniel Mair
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Vattipally B. Sreenu
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Ana Da Silva Filipe
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Ping Li
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Yan-Jang S. Huang
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
| | - Benjamin Brennan
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Joseph Hughes
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Dana L. Vanlandingham
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
- Biosecurity Research Institute, Kansas State University, Manhattan, Kansas, United States of America
| | - Stephen Higgs
- Department of Diagnostic Medicine/Pathobiology, College of Veterinary Medicine, Kansas State University, Manhattan, Kansas, United States of America
- Biosecurity Research Institute, Kansas State University, Manhattan, Kansas, United States of America
| | - Richard M. Elliott
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
| | - Alain Kohl
- MRC-University of Glasgow Centre for Virus Research, Glasgow, Scotland, United Kingdom
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10
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Robinson M, Schor S, Barouch-Bentov R, Einav S. Viral journeys on the intracellular highways. Cell Mol Life Sci 2018; 75:3693-3714. [PMID: 30043139 PMCID: PMC6151136 DOI: 10.1007/s00018-018-2882-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2018] [Revised: 07/01/2018] [Accepted: 07/19/2018] [Indexed: 12/24/2022]
Abstract
Viruses are obligate intracellular pathogens that are dependent on cellular machineries for their replication. Recent technological breakthroughs have facilitated reliable identification of host factors required for viral infections and better characterization of the virus-host interplay. While these studies have revealed cellular machineries that are uniquely required by individual viruses, accumulating data also indicate the presence of broadly required mechanisms. Among these overlapping cellular functions are components of intracellular membrane trafficking pathways. Here, we review recent discoveries focused on how viruses exploit intracellular membrane trafficking pathways to promote various stages of their life cycle, with an emphasis on cellular factors that are usurped by a broad range of viruses. We describe broadly required components of the endocytic and secretory pathways, the Endosomal Sorting Complexes Required for Transport pathway, and the autophagy pathway. Identification of such overlapping host functions offers new opportunities to develop broad-spectrum host-targeted antiviral strategies.
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Affiliation(s)
- Makeda Robinson
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA
| | - Stanford Schor
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA
| | - Rina Barouch-Bentov
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA
| | - Shirit Einav
- Division of Infectious Diseases and Geographic Medicine, Department of Medicine, Stanford University School of Medicine, 300 Pasteur Drive, Lane Building, Rm L127, Stanford, CA, 94305, USA.
- Department of Microbiology and Immunology, Stanford University School of Medicine, Stanford, CA, USA.
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11
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Lundu T, Tsuda Y, Ito R, Shimizu K, Kobayashi S, Yoshii K, Yoshimatsu K, Arikawa J, Kariwa H. Targeting of severe fever with thrombocytopenia syndrome virus structural proteins to the ERGIC (endoplasmic reticulum Golgi intermediate compartment) and Golgi complex. Biomed Res 2018; 39:27-38. [PMID: 29467349 DOI: 10.2220/biomedres.39.27] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Severe fever with thrombocytopenia syndrome phlebovirus (SFTSV) is a newly emerged phlebovirus identified in China, Japan, and South Korea. Phlebovirus glycoproteins (GP) play a key role in targeting viral structural components to the budding compartments in the ER-Golgi intermediate compartment (ERGIC) and Golgi complex. However, the role of SFTSV GP in targeting structural proteins to the ERGIC and Golgi complex remains unresolved. In this study, we show that SFTSV GP plays a significant role in targeting RNA-dependent RNA polymerase (L) and nucleocapsid protein (NP) to the budding sites. Confocal microscopy was used to investigate the subcellular localization of SFTSV structural proteins. In SFTSV-infected cells, GP and L localized to the ER, ERGIC and Golgi complex, whereas NP localized to the ERGIC and Golgi complex. In addition, GP colocalized with L and NP in infected cells. In cells singly transfected with GP, L or NP, GP localized to the same subcellular compartments as in infected cells. However, L or NP alone did not localize to the ER, ERGIC, or Golgi complex. Cotransfection experiments showed that GP altered the localization of L to the ERGIC and Golgi complex but not that of NP. Interestingly, plasmid-expressed NP fused with a hemagglutinin tag localized to the ERGIC and Golgi complex when expressed in SFTSV-infected cells and colocalised with GP, suggesting that GP plays a role in the subcellular localization of L and NP in infected cells. Thus, the SFTSV structural components start to assemble at the ERGIC to Golgi complex. GP is required for transporting L and NP to the ERGIC and Golgi complex. In addition, targeting of NP requires interaction with other factors besides GP.
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Affiliation(s)
- Tapiwa Lundu
- Laboratory of Public Health, Department of Preventive Veterinary Science, Division of Veterinary Medicine, Graduate School of Veterinary Medicine, Hokkaido University.,Department of Biomedical Sciences, School of Veterinary Medicine, University of Zambia
| | - Yoshimi Tsuda
- Laboratory of Microbiology and Infectious Diseases, Department of Microbiology and Immunology, Faculty of Medicine, Hokkaido University
| | - Ryo Ito
- Laboratory of Microbiology and Infectious Diseases, Department of Microbiology and Immunology, Faculty of Medicine, Hokkaido University
| | - Kenta Shimizu
- Laboratory of Microbiology and Infectious Diseases, Department of Microbiology and Immunology, Faculty of Medicine, Hokkaido University
| | - Shintaro Kobayashi
- Laboratory of Public Health, Department of Preventive Veterinary Science, Division of Veterinary Medicine, Faculty of Veterinary Medicine, Hokkaido University
| | - Kentaro Yoshii
- Laboratory of Public Health, Department of Preventive Veterinary Science, Division of Veterinary Medicine, Faculty of Veterinary Medicine, Hokkaido University
| | - Kumiko Yoshimatsu
- Laboratory of Microbiology and Infectious Diseases, Department of Microbiology and Immunology, Faculty of Medicine, Hokkaido University
| | - Jiro Arikawa
- Laboratory of Microbiology and Infectious Diseases, Department of Microbiology and Immunology, Faculty of Medicine, Hokkaido University
| | - Hiroaki Kariwa
- Laboratory of Public Health, Department of Preventive Veterinary Science, Division of Veterinary Medicine, Faculty of Veterinary Medicine, Hokkaido University
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12
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Ejiri H, Lim CK, Isawa H, Yamaguchi Y, Fujita R, Takayama-Ito M, Kuwata R, Kobayashi D, Horiya M, Posadas-Herrera G, Iizuka-Shiota I, Kakiuchi S, Katayama Y, Hayashi T, Sasaki T, Kobayashi M, Morikawa S, Maeda K, Mizutani T, Kaku K, Saijo M, Sawabe K. Isolation and characterization of Kabuto Mountain virus, a new tick-borne phlebovirus from Haemaphysalis flava ticks in Japan. Virus Res 2017; 244:252-261. [PMID: 29197549 DOI: 10.1016/j.virusres.2017.11.030] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 11/15/2017] [Accepted: 11/28/2017] [Indexed: 01/09/2023]
Abstract
In Japan, indigenous tick-borne phleboviruses (TBPVs) and their associated diseases first became evident in 2013 by reported human cases of severe fever with thrombocytopenia syndrome (SFTS). In this study, we report a novel member of the genus Phlebovirus designated as Kabuto Mountain virus (KAMV), which was isolated from the ixodid tick Haemaphysalis flava in Hyogo, Japan. A complete viral genome sequencing and phylogenetic analyses showed that KAMV is a novel member of TBPVs, which is closely related to the Uukuniemi and Kaisodi group viruses. However, unlike the Uukuniemi group viruses, the 165-nt intergenic region (IGR) in the KAMV S segment was highly C-rich in the genomic sense and not predicted to form a secondary structure, which are rather similar to those of the Kaisodi group viruses and most mosquito/sandfly-borne phleboviruses. Furthermore, the NSs protein of KAMV was highly divergent from those of other TBPVs. These results provided further insights into the genetic diversity and evolutionary relationships of TBPVs. KAMV could infect and replicate in some rodent and primate cell lines. We evaluated the infectivity and pathogenicity of KAMV in suckling mice, where we obtained a virulent strain after two passages via intracerebral inoculation. This is the first report showing the existence of a previously unrecognized TBPV in Japan, other than the SFTS virus.
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Affiliation(s)
- Hiroko Ejiri
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan; Division of infectious Diseases Epidemiology and Control, National Defense Medical Research Institute, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan
| | - Chang-Kweng Lim
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Haruhiko Isawa
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Yukie Yamaguchi
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Ryosuke Fujita
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Mutsuyo Takayama-Ito
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Ryusei Kuwata
- Laboratory of Veterinary Microbiology, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan
| | - Daisuke Kobayashi
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Madoka Horiya
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Guillermo Posadas-Herrera
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Itoe Iizuka-Shiota
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Satsuki Kakiuchi
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Yukie Katayama
- Research and Education Center for Prevention of Global Infectious Disease of Animal, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
| | - Toshihiko Hayashi
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Toshinori Sasaki
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Mutsuo Kobayashi
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Shigeru Morikawa
- Department of Veterinary Science, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Ken Maeda
- Laboratory of Veterinary Microbiology, Faculty of Agriculture, Yamaguchi University, 1677-1 Yoshida, Yamaguchi 753-8515, Japan
| | - Tetsuya Mizutani
- Research and Education Center for Prevention of Global Infectious Disease of Animal, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan
| | - Koki Kaku
- Division of infectious Diseases Epidemiology and Control, National Defense Medical Research Institute, National Defense Medical College, 3-2 Namiki, Tokorozawa, Saitama 359-8513, Japan
| | - Masayuki Saijo
- Department of Virology I, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan
| | - Kyoko Sawabe
- Department of Medical Entomology, National Institute of Infectious Diseases, 1-23-1 Toyama, Shinjuku-ku, Tokyo 162-8640, Japan; Department of Agricultural and Environmental Biology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo-ku, Tokyo 113-8657, Japan
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13
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Abstract
Orthobunyaviruses include several recently emerging viruses of significant medical and veterinary importance. There is currently very limited understanding on what determines the host species range of these pathogens. In this study we discovered that BST-2/tetherin restricts orthobunyavirus replication in a host-specific manner. We show that viruses with human tropism (Oropouche virus and La Crosse virus) are restricted by sheep BST-2 but not by the human orthologue, while viruses with ruminant tropism (Schmallenberg virus and others) are restricted by human BST-2 but not by the sheep orthologue. We also show that BST-2 blocks orthobunyaviruses replication by reducing the amount of envelope glycoprotein into viral particles egressing from infected cells. This is the first study identifying a restriction factor that correlates with species susceptibility to orthobunyavirus infection. This work provides insight to help us dissect the adaptive changes that bunyaviruses require to cross the species barrier and emerge into new species. BST-2 is a determinant of orthobuynyavirus host range. BST-2 restricts orthobunyavirus replication. BST-2 reduces the incorporation of envelope glycoprotein into virions.
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14
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Amroun A, Priet S, de Lamballerie X, Quérat G. Bunyaviridae RdRps: structure, motifs, and RNA synthesis machinery. Crit Rev Microbiol 2017; 43:753-778. [PMID: 28418734 DOI: 10.1080/1040841x.2017.1307805] [Citation(s) in RCA: 44] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Bunyaviridae family is the largest and most diverse family of RNA viruses. It has more than 350 members divided into five genera: Orthobunyavirus, Phlebovirus, Nairovirus, Hantavirus, and Tospovirus. They are present in the five continents, causing recurrent epidemics, epizootics, and considerable agricultural loss. The genome of bunyaviruses is divided into three segments of negative single-stranded RNA according to their relative size: L (Large), M (Medium) and S (Small) segment. Bunyaviridae RNA-dependent RNA polymerase (RdRp) is encoded by the L segment, and is in charge of the replication and transcription of the viral RNA in the cytoplasm of the infected cell. Viral RdRps share a characteristic right hand-like structure with three subdomains: finger, palm, and thumb subdomains that define the formation of the catalytic cavity. In addition to the N-terminal endonuclease domain, eight conserved motifs (A-H) have been identified in the RdRp of Bunyaviridae. In this review, we have summarized the recent insights from the structural and functional studies of RdRp to understand the roles of different motifs shared by RdRps, the mechanism of viral RNA replication, genome segment packaging by the nucleoprotein, cap-snatching, mRNA transcription, and other RNA mechanisms of bunyaviruses.
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Affiliation(s)
- Abdennour Amroun
- a Faculté de Médecine , UMR "Emergence des Pathologies Virales" (Aix-Marseille University - IRD 190 - Inserm 1207 - EHESP), Fondation IHU Méditerranée Infection, APHM Public Hospitals of Marseille , Marseille , France
| | - Stéphane Priet
- a Faculté de Médecine , UMR "Emergence des Pathologies Virales" (Aix-Marseille University - IRD 190 - Inserm 1207 - EHESP), Fondation IHU Méditerranée Infection, APHM Public Hospitals of Marseille , Marseille , France
| | - Xavier de Lamballerie
- a Faculté de Médecine , UMR "Emergence des Pathologies Virales" (Aix-Marseille University - IRD 190 - Inserm 1207 - EHESP), Fondation IHU Méditerranée Infection, APHM Public Hospitals of Marseille , Marseille , France
| | - Gilles Quérat
- a Faculté de Médecine , UMR "Emergence des Pathologies Virales" (Aix-Marseille University - IRD 190 - Inserm 1207 - EHESP), Fondation IHU Méditerranée Infection, APHM Public Hospitals of Marseille , Marseille , France
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15
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Evidence that Processing of the Severe Fever with Thrombocytopenia Syndrome Virus Gn/Gc Polyprotein Is Critical for Viral Infectivity and Requires an Internal Gc Signal Peptide. PLoS One 2016; 11:e0166013. [PMID: 27855227 PMCID: PMC5113920 DOI: 10.1371/journal.pone.0166013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2016] [Accepted: 10/21/2016] [Indexed: 12/20/2022] Open
Abstract
The severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging, highly pathogenic bunyavirus against which neither antivirals nor vaccines are available. The SFTSV glycoproteins, Gn and Gc, facilitate viral entry into host cells. Gn and Gc are generated from a precursor protein, Gn/Gc, but it is currently unknown how the precursor is converted into the single proteins and whether this process is required for viral infectivity. Employing a rhabdoviral pseudotyping system, we demonstrate that a predicted signal sequence at the N-terminus of Gc is required for Gn/Gc processing and viral infectivity while potential proprotein convertase cleavage sites in Gc are dispensable. Moreover, we show that expression of Gn or Gc alone is not sufficient for host cell entry while particles bearing both proteins are infectious, and we provide evidence that Gn facilitates Golgi transport and virion incorporation of Gc. Collectively, these results suggest that signal peptidase liberates mature Gc from the Gn/Gc precursor and that this process is essential for viral infectivity and thus constitutes a potential target for antiviral intervention.
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16
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The Role of Phlebovirus Glycoproteins in Viral Entry, Assembly and Release. Viruses 2016; 8:v8070202. [PMID: 27455305 PMCID: PMC4974537 DOI: 10.3390/v8070202] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2016] [Revised: 07/13/2016] [Accepted: 07/14/2016] [Indexed: 01/08/2023] Open
Abstract
Bunyaviruses are enveloped viruses with a tripartite RNA genome that can pose a serious threat to animal and human health. Members of the Phlebovirus genus of the family Bunyaviridae are transmitted by mosquitos and ticks to humans and include highly pathogenic agents like Rift Valley fever virus (RVFV) and severe fever with thrombocytopenia syndrome virus (SFTSV) as well as viruses that do not cause disease in humans, like Uukuniemi virus (UUKV). Phleboviruses and other bunyaviruses use their envelope proteins, Gn and Gc, for entry into target cells and for assembly of progeny particles in infected cells. Thus, binding of Gn and Gc to cell surface factors promotes viral attachment and uptake into cells and exposure to endosomal low pH induces Gc-driven fusion of the viral and the vesicle membranes. Moreover, Gn and Gc facilitate virion incorporation of the viral genome via their intracellular domains and Gn and Gc interactions allow the formation of a highly ordered glycoprotein lattice on the virion surface. Studies conducted in the last decade provided important insights into the configuration of phlebovirus Gn and Gc proteins in the viral membrane, the cellular factors used by phleboviruses for entry and the mechanisms employed by phlebovirus Gc proteins for membrane fusion. Here, we will review our knowledge on the glycoprotein biogenesis and the role of Gn and Gc proteins in the phlebovirus replication cycle.
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17
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Suda Y, Fukushi S, Tani H, Murakami S, Saijo M, Horimoto T, Shimojima M. Analysis of the entry mechanism of Crimean-Congo hemorrhagic fever virus, using a vesicular stomatitis virus pseudotyping system. Arch Virol 2016; 161:1447-54. [PMID: 26935918 PMCID: PMC7087235 DOI: 10.1007/s00705-016-2803-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2015] [Accepted: 02/21/2016] [Indexed: 11/24/2022]
Abstract
Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne disease causing severe hemorrhagic symptoms with a nearly 30 % case-fatality rate in humans. The experimental use of CCHF virus (CCHFV), which causes CCHF, requires high-biosafety-level (BSL) containment. In contrast, pseudotyping of various viral glycoproteins (GPs) onto vesicular stomatitis virus (VSV) can be used in facilities with lower BSL containment, and this has facilitated studies on the viral entry mechanism and the measurement of neutralizing activity, especially for highly pathogenic viruses. In the present study, we generated high titers of pseudotyped VSV bearing the CCHFV envelope GP and analyzed the mechanisms involved in CCHFV infection. A partial deletion of the CCHFV GP cytoplasmic domain increased the titer of the pseudotyped VSV, the entry mechanism of which was dependent on the CCHFV envelope GP. Using the pseudotype virus, DC-SIGN (a calcium-dependent [C-type] lectin cell-surface molecule) was revealed to enhance viral infection and act as an entry factor for CCHFV.
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Affiliation(s)
- Yuto Suda
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan.,Special Pathogens Laboratory, Department of Virology I, National Institute of Infectious Diseases, Gakuen 4-7-1, Musashimurayama, Tokyo, 208-0011, Japan
| | - Shuetsu Fukushi
- Special Pathogens Laboratory, Department of Virology I, National Institute of Infectious Diseases, Gakuen 4-7-1, Musashimurayama, Tokyo, 208-0011, Japan
| | - Hideki Tani
- Special Pathogens Laboratory, Department of Virology I, National Institute of Infectious Diseases, Gakuen 4-7-1, Musashimurayama, Tokyo, 208-0011, Japan
| | - Shin Murakami
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Masayuki Saijo
- Special Pathogens Laboratory, Department of Virology I, National Institute of Infectious Diseases, Gakuen 4-7-1, Musashimurayama, Tokyo, 208-0011, Japan
| | - Taisuke Horimoto
- Department of Veterinary Microbiology, Graduate School of Agricultural and Life Sciences, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo, 113-8657, Japan
| | - Masayuki Shimojima
- Special Pathogens Laboratory, Department of Virology I, National Institute of Infectious Diseases, Gakuen 4-7-1, Musashimurayama, Tokyo, 208-0011, Japan. shimoji-@nih.go.jp
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18
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Generation of mutant Uukuniemi viruses lacking the nonstructural protein NSs by reverse genetics indicates that NSs is a weak interferon antagonist. J Virol 2015; 89:4849-56. [PMID: 25673721 DOI: 10.1128/jvi.03511-14] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2014] [Accepted: 02/04/2015] [Indexed: 01/05/2023] Open
Abstract
UNLABELLED Uukuniemi virus (UUKV) is a tick-borne member of the Phlebovirus genus (family Bunyaviridae) and has been widely used as a safe laboratory model to study aspects of bunyavirus replication. Recently, a number of new tick-borne phleboviruses have been discovered, some of which, like severe fever with thrombocytopenia syndrome virus and Heartland virus, are highly pathogenic in humans. UUKV could now serve as a useful comparator to understand the molecular basis for the different pathogenicities of these related viruses. We established a reverse-genetics system to recover UUKV entirely from cDNA clones. We generated two recombinant viruses, one in which the nonstructural protein NSs open reading frame was deleted from the S segment and one in which the NSs gene was replaced with green fluorescent protein (GFP), allowing convenient visualization of viral infection. We show that the UUKV NSs protein acts as a weak interferon antagonist in human cells but that it is unable to completely counteract the interferon response, which could serve as an explanation for its inability to cause disease in humans. IMPORTANCE Uukuniemi virus (UUKV) is a tick-borne phlebovirus that is apathogenic for humans and has been used as a convenient model to investigate aspects of phlebovirus replication. Recently, new tick-borne phleboviruses have emerged, such as severe fever with thrombocytopenia syndrome virus in China and Heartland virus in the United States, that are highly pathogenic, and UUKV will now serve as a comparator to aid in the understanding of the molecular basis for the virulence of these new viruses. To help such investigations, we have developed a reverse-genetics system for UUKV that permits manipulation of the viral genome. We generated viruses lacking the nonstructural protein NSs and show that UUKV NSs is a weak interferon antagonist. In addition, we created a virus that expresses GFP and thus allows convenient monitoring of virus replication. These new tools represent a significant advance in the study of tick-borne phleboviruses.
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19
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Abstract
Uukuniemi virus (UUKV) is a model system for investigating the genus Phlebovirus of the Bunyaviridae. We report the UUKV glycome, revealing differential processing of the Gn and Gc virion glycoproteins. Both glycoproteins display poly-N-acetyllactosamines, consistent with virion assembly in the medial Golgi apparatus, whereas oligomannose-type glycans required for DC-SIGN-dependent cellular attachment are predominant on Gc. Local virion structure and the route of viral egress from the cell leave a functional imprint on the phleboviral glycome.
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20
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Murakami S, Terasaki K, Ramirez SI, Morrill JC, Makino S. Development of a novel, single-cycle replicable rift valley Fever vaccine. PLoS Negl Trop Dis 2014; 8:e2746. [PMID: 24651859 PMCID: PMC3961198 DOI: 10.1371/journal.pntd.0002746] [Citation(s) in RCA: 15] [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: 11/01/2013] [Accepted: 01/30/2014] [Indexed: 12/25/2022] Open
Abstract
Rift Valley fever virus (RVFV) (genus Phlebovirus, family Bunyaviridae) is an arbovirus that causes severe disease in humans and livestock in sub-Saharan African countries. Although the MP-12 strain of RVFV is a live attenuated vaccine candidate, neuroinvasiveness and neurovirulence of MP-12 in mice may be a concern when vaccinating certain individuals, especially those that are immunocompromised. We have developed a novel, single-cycle replicable MP-12 (scMP-12), which carries an L RNA, M RNA mutant encoding a mutant envelope protein lacking an endoplasmic reticulum retrieval signal and defective for membrane fusion function, and S RNA encoding N protein and green fluorescent protein. The scMP-12 underwent efficient amplification, then formed plaques and retained the introduced mutation after serial passages in a cell line stably expressing viral envelope proteins. However, inoculation of the scMP-12 into naïve cells resulted in a single round of viral replication, and production of low levels of noninfectious virus-like particles. Intracranial inoculation of scMP-12 into suckling mice did not cause clinical signs or death, a finding which demonstrated that the scMP-12 lacked neurovirulence. Mice immunized with a single dose of scMP-12 produced neutralizing antibodies, whose titers were higher than in mice immunized with replicon particles carrying L RNA and S RNA encoding N protein and green fluorescent protein. Moreover, 90% of the scMP-12-immunized mice were protected from wild-type RVFV challenge by efficiently suppressing viremia and replication of the challenge virus in the liver and the spleen. These data demonstrated that scMP-12 is a safe and immunogenic RVFV vaccine candidate.
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MESH Headings
- Animals
- Antibodies, Neutralizing/blood
- Antibodies, Viral/blood
- Disease Models, Animal
- Female
- Mice
- Mutant Proteins/genetics
- Mutant Proteins/metabolism
- Rift Valley Fever/prevention & control
- Rift Valley fever virus/genetics
- Rift Valley fever virus/immunology
- Rift Valley fever virus/physiology
- Survival Analysis
- Vaccines, Attenuated/administration & dosage
- Vaccines, Attenuated/adverse effects
- Vaccines, Attenuated/genetics
- Vaccines, Attenuated/immunology
- Vaccines, Synthetic/administration & dosage
- Vaccines, Synthetic/adverse effects
- Vaccines, Synthetic/genetics
- Vaccines, Synthetic/immunology
- Viral Proteins/genetics
- Viral Proteins/immunology
- Viral Vaccines/administration & dosage
- Viral Vaccines/adverse effects
- Viral Vaccines/genetics
- Viral Vaccines/immunology
- Virus Internalization
- Virus Replication
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Affiliation(s)
- Shin Murakami
- Department of Microbiology and Immunology, the University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Kaori Terasaki
- Department of Microbiology and Immunology, the University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Sydney I. Ramirez
- Department of Pathology, the University of Texas Medical Branch, Galveston, Texas, United States of America
| | - John C. Morrill
- Department of Microbiology and Immunology, the University of Texas Medical Branch, Galveston, Texas, United States of America
| | - Shinji Makino
- Department of Microbiology and Immunology, the University of Texas Medical Branch, Galveston, Texas, United States of America
- Center for Biodefense and Emerging Infectious Diseases, the University of Texas Medical Branch, Galveston, Texas, United States of America
- UTMB Center for Tropical Diseases, the University of Texas Medical Branch, Galveston, Texas, United States of America
- Sealy Center for Vaccine Development, the University of Texas Medical Branch, Galveston, Texas, United States of America
- * E-mail:
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21
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Yao M, Liu X, Li S, Xu Y, Zhou Y, Zhou X, Tao X. Rice stripe tenuivirus NSvc2 glycoproteins targeted to the golgi body by the N-terminal transmembrane domain and adjacent cytosolic 24 amino acids via the COP I- and COP II-dependent secretion pathway. J Virol 2014; 88:3223-34. [PMID: 24390331 PMCID: PMC3957912 DOI: 10.1128/jvi.03006-13] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2013] [Accepted: 12/24/2013] [Indexed: 01/28/2023] Open
Abstract
UNLABELLED The NSvc2 glycoproteins encoded by Rice stripe tenuivirus (RSV) share many characteristics common to the glycoproteins found among Bunyaviridae. Within this viral family, glycoproteins targeting to the Golgi apparatus play a pivotal role in the maturation of the enveloped spherical particles. RSV particles, however, adopt a long filamentous morphology. Recently, RSV NSvc2 glycoproteins were shown to localize exclusively to the ER in Sf9 insect cells. Here, we demonstrate that the amino-terminal NSvc2 (NSvc2-N) targets to the Golgi apparatus in Nicotiana benthamiana cells, whereas the carboxyl-terminal NSvc2 (NSvc2-C) accumulates in the endoplasmic reticulum (ER). Upon coexpression, NSvc2-N redirects NSvc2-C from the ER to the Golgi bodies. The NSvc2 glycoproteins move together with the Golgi stacks along the ER/actin network. The targeting of the NSvc2 glycoproteins to the Golgi bodies was strictly dependent on functional anterograde traffic out of the ER to the Golgi bodies or on a retrograde transport route from the Golgi apparatus. The analysis of truncated and chimeric NSvc2 proteins demonstrates that the Golgi targeting signal comprises amino acids 269 to 315 of NSvc2-N, encompassing the transmembrane domain and 24 adjacent amino acids in the cytosolic tail. Our findings demonstrate for the first time that the glycoproteins from an unenveloped Tenuivirus could target Golgi bodies in plant cells. IMPORTANCE NSvc2 glycoprotein encoded by unenveloped Rice stripe tenuivirus (RSV) share many characteristics in common with glycoprotein found among Bunyaviridae in which all members have membrane-enveloped sphere particle. Recently, RSV NSvc2 glycoproteins were shown to localize exclusively to the ER in Sf9 insect cells. In this study, we demonstrated that the RSV glycoproteins could target Golgi bodies in plant cells. The targeting of NSvc2 glycoproteins to the Golgi bodies was dependent on active COP II or COP I. The Golgi targeting signal was mapped to the 23-amino-acid transmembrane domain and the adjacent 24 amino acids of the cytosolic tail of the NSvc2-N. In light of the evidence from viruses in Bunyaviridae that targeting Golgi bodies is important for the viral particle assembly and vector transmission, we propose that targeting of RSV glycoproteins into Golgi bodies in plant cells represents a physiologically relevant mechanism in the maturation of RSV particle complex for insect vector transmission.
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Affiliation(s)
- Min Yao
- Key Laboratory for the Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing, People's Republic of China
| | - Xiaofan Liu
- Key Laboratory for the Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing, People's Republic of China
| | - Shuo Li
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, People's Republic of China
| | - Yi Xu
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, People's Republic of China
| | - Yijun Zhou
- Institute of Plant Protection, Jiangsu Academy of Agricultural Sciences, Nanjing, People's Republic of China
| | - Xueping Zhou
- State Key Laboratory of Rice Biology, Institute of Biotechnology, Zhejiang University, Hangzhou, People's Republic of China
- State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of Agricultural Sciences, Beijing, People's Republic of China
| | - Xiaorong Tao
- Key Laboratory for the Integrated Management of Crop Diseases and Pests, Ministry of Education, Department of Plant Pathology, Nanjing Agricultural University, Nanjing, People's Republic of China
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Hoenen A, Gillespie L, Morgan G, van der Heide P, Khromykh A, Mackenzie J. The West Nile virus assembly process evades the conserved antiviral mechanism of the interferon-induced MxA protein. Virology 2014; 448:104-16. [DOI: 10.1016/j.virol.2013.10.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2013] [Revised: 06/28/2013] [Accepted: 10/03/2013] [Indexed: 02/04/2023]
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Carnec X, Ermonval M, Kreher F, Flamand M, Bouloy M. Role of the cytosolic tails of Rift Valley fever virus envelope glycoproteins in viral morphogenesis. Virology 2013; 448:1-14. [PMID: 24314631 DOI: 10.1016/j.virol.2013.09.023] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2013] [Revised: 08/05/2013] [Accepted: 09/25/2013] [Indexed: 11/30/2022]
Abstract
The correct folding, heterodimerization and trafficking of Gn/Gc envelope glycoproteins of Rift Valley fever virus, RVFV (Bunyaviridae and Phlebovirus genus) are essential for Golgi assembly and budding of viral particles. The Gn and Gc carboxy-terminus contain a Golgi targeting and an ER-retrieval signal, respectively. We generated RVFV-like particles with mutations in the cytosolic tails of Gn or Gc and identified regions important for release of infectious particles. The role of specific amino-acids in these regions was further investigated by creating recombinant mutant viruses by reverse-genetics. Residues outside the suspected Golgi targeting motif, i.e. the di-lysine K29-K30 motif and the N43, R44 and I46 residues of the Gn cytosolic domain, appeared important for Golgi localization and RNP packaging. Concerning the Gc tail, replacement of K2 or K3 in the di-lysine motif, had a drastic impact on Gn trafficking and induced an important organelle redistribution and cell remodeling, greatly affecting particle formation and release.
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Affiliation(s)
- Xavier Carnec
- Institut Pasteur, Unité de Génétique Moléculaire des Bunyavirus, 25 rue du Docteur Roux, 75015 Paris, France
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Shimizu K, Yoshimatsu K, Koma T, Yasuda SP, Arikawa J. Role of nucleocapsid protein of hantaviruses in intracellular traffic of viral glycoproteins. Virus Res 2013; 178:349-56. [PMID: 24070985 DOI: 10.1016/j.virusres.2013.09.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2013] [Revised: 09/11/2013] [Accepted: 09/12/2013] [Indexed: 01/03/2023]
Abstract
To understand the role of nucleocapsid protein (NP) of hantaviruses in viral assembly, the effect of NP on intracellular traffic of viral glycoproteins Gn and Gc was investigated. Double staining of viral and host proteins in Hantaan virus (HTNV)-infected Vero E6 cells showed that Gn and Gc were localized to cis-Golgi, in which virus particles are thought to be formed. When HTNV Gn and Gc were expressed by a plasmid encoding glycoprotein precursor (GPC), which is posttranslationally cleaved into Gn and Gc, Gn was localized to cis-Golgi, whereas Gc showed diffuse distribution in the cytoplasm in 32.9% of Gc-positive cells. The ratio of the diffused Gc-positive cells was significantly decreased to 15.0% by co-expression of HTNV NP. Co-expression of HTNV GPC with NPs of other hantaviruses, such as Seoul virus, Puumala virus and Sin Nombre virus, also reduced the ratios of diffused Gc-positive cells to 13.5%, 25.2%, and 11.6%, respectively. Among amino- and carboxyl-terminally truncated HTNV NPs, NP75-429, NP116-429, NP1-333, NP1-233, and NP1-155 possessed activity to reduce the ratio of diffused Gc-positive cells, while NP155-429 and NP1-116 did not. NP30-429 has partial activity. These results indicate that amino acid region 116-155 of NP is important for the activity, although amino acid region 1-30 is partially related. Truncation of the HTNV Gc cytoplasmic tail caused an increase in diffused Gc-positive cells. In addition, the effect of coexpression of HTNV NP was weakened. These results suggest that HTNV NP has a role to promote Golgi localization of Gc through a mechanism possibly mediated by the Gc cytoplasmic tail.
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Affiliation(s)
- Kenta Shimizu
- Department of Microbiology, Hokkaido University Graduate School of Medicine, Kita-15, Nishi-7, Kita-ku, Sapporo 060-8638, Japan
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Briese T, Calisher CH, Higgs S. Viruses of the family Bunyaviridae: are all available isolates reassortants? Virology 2013; 446:207-16. [PMID: 24074583 DOI: 10.1016/j.virol.2013.07.030] [Citation(s) in RCA: 123] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2013] [Revised: 06/11/2013] [Accepted: 07/24/2013] [Indexed: 01/27/2023]
Abstract
Viruses of the family Bunyaviridae (the bunyaviruses) possess three distinct linear, single-stranded, negative sense or ambisense RNA segments (large, medium, and small). Dual infections of arthropod and perhaps vertebrate and plant hosts provide substantial opportunity for segment reassortment and an increasingly recognized number of the nearly 300 viruses in this family have been shown to be reassortants. Reassortment of RNA segments (genetic shift) complements genetic drift (accumulation of point mutations) as a powerful mechanism underlying bunyavirus evolution. Here we consider the possibility, if not likelihood, that most if not all bunyaviruses currently recognized may represent reassortants, some of which may be reassortants of existing viruses, and some of which may be reassortants of extinct viruses. If this hypothesis is correct, then the roots of the family and genus trees of bunyaviruses as currently described (or ignored) are incomplete or incorrect.
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Affiliation(s)
- Thomas Briese
- Center for Infection and Immunity and Department of Epidemiology, Mailman School of Public Health, Columbia University, 722 West 168th Street, New York, NY 10032, USA.
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26
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Systems to establish bunyavirus genome replication in the absence of transcription. J Virol 2013; 87:8205-12. [PMID: 23698297 DOI: 10.1128/jvi.00371-13] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The L polymerase of bunyaviruses replicates and transcribes the viral genome. While replication products are faithful copies of the uncapped genomic RNA, transcription products contain capped 5' extensions which had been cleaved from host cell mRNAs. For La Crosse virus (LACV; genus Orthobunyavirus), the nuclease responsible for host cell mRNA cleavage is located at the N terminus of the L protein, with an active site of five conserved amino acids (H34, D52, D79, D92, and K94) surrounding two Mn(2+) ions (J. Reguera, F. Weber, and S. Cusack, PLoS Pathog. 6:e1001101, 2010). Here, we present reverse genetics systems and L mutants enabling us to study bunyaviral genome replication in the absence of transcription. Transcription was evaluated with an enhanced minigenome system consisting of the viral polymerase L, nucleocapsid protein N, a negative-sense minigenome, and--to alleviate antiviral host responses--a dominant-negative mutant (PKRΔE7) of the antiviral kinase protein kinase R (PKR). The transcriptional activity was strongly reduced by mutation of any of the five key amino acids, and the H34K, D79A, D92A, and K94A LACV L mutants were almost entirely silent in transcription. The replication activity of the L mutants was measured by packaging of progeny minigenomes into virus-like particles (VLPs). All mutant L proteins except K94A retained full replication activity. To test the broader applicability of our results, we introduced the homolog of mutation D79A (D111A) into the L sequence of Rift Valley fever virus (RVFV; genus Phlebovirus). As for LACV D79A, the RVFV D111A was incapable of transcription but fully active in replication. Thus, we generated mutants of LACV and RVFV L polymerases that are specifically deficient in transcription. Genome replication by bunyavirus polymerases can now be studied in the absence of transcription using convenient reverse genetics systems.
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Epidemiology, molecular virology and diagnostics of Schmallenberg virus, an emerging orthobunyavirus in Europe. Vet Res 2013; 44:31. [PMID: 23675914 PMCID: PMC3663787 DOI: 10.1186/1297-9716-44-31] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2012] [Accepted: 04/22/2013] [Indexed: 12/26/2022] Open
Abstract
After the unexpected emergence of Bluetongue virus serotype 8 (BTV-8) in northern Europe in 2006, another arbovirus, Schmallenberg virus (SBV), emerged in Europe in 2011 causing a new economically important disease in ruminants. The virus, belonging to the Orthobunyavirus genus in the Bunyaviridae family, was first detected in Germany, in The Netherlands and in Belgium in 2011 and soon after in the United Kingdom, France, Italy, Luxembourg, Spain, Denmark and Switzerland. This review describes the current knowledge on the emergence, epidemiology, clinical signs, molecular virology and diagnosis of SBV infection.
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Strandin T, Hepojoki J, Vaheri A. Cytoplasmic tails of bunyavirus Gn glycoproteins-Could they act as matrix protein surrogates? Virology 2013; 437:73-80. [PMID: 23357734 DOI: 10.1016/j.virol.2013.01.001] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2012] [Revised: 11/21/2012] [Accepted: 01/02/2013] [Indexed: 12/31/2022]
Abstract
Viruses of the family Bunyaviridae are negative-sense RNA viruses (NRVs). Unlike other NRVs bunyaviruses do not possess a matrix protein, which typically facilitates virus release from host cells and acts as an anchor between the viral membrane and its genetic core. Therefore the functions of matrix protein in bunyaviruses need to be executed by other viral proteins. In fact, the cytoplasmic tail of glycoprotein Gn (Gn-CT) of various bunyaviruses interacts with the genetic core (nucleocapsid protein and/or genomic RNA). In addition the Gn-CT of phleboviruses (a genus in the family Bunyaviridae) has been demonstrated to be essential for budding. This review brings together what is known on the role of various bunyavirus Gn-CTs in budding and assembly, and hypothesizes on their yet unrevealed functions in viral life cycle by comparing to the matrix proteins of NRVs.
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Affiliation(s)
- Tomas Strandin
- Department of Virology, Haartman Institute, P.O. Box 21, FI-00014, University of Helsinki, Finland.
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29
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Characterization of the Bhanja serogroup viruses (Bunyaviridae): a novel species of the genus Phlebovirus and its relationship with other emerging tick-borne phleboviruses. J Virol 2013; 87:3719-28. [PMID: 23325688 DOI: 10.1128/jvi.02845-12] [Citation(s) in RCA: 79] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Bhanja virus (BHAV) and its antigenically close relatives Forecariah virus (FORV), Kismayo virus (KISV), and Palma virus (PALV) are thought to be members of the family Bunyaviridae, but they have not been assigned to a genus or species. Despite their broad geographical distribution and reports that BHAV causes sporadic cases of febrile illness and encephalitis in humans, the public health importance of the Bhanja serogroup viruses remains unclear, due in part to the lack of sequence and biochemical information for the virus proteins. In order to better define the molecular characteristics of this group, we determined the full-length sequences of the L, M, and S genome segments of multiple isolates of BHAV as well as FORV and PALV. The genome structures of these Bhanja viruses are similar to those of viruses belonging to the genus Phlebovirus. Functional domains and amino acid motifs in the viral proteins that are conserved among other known phleboviruses were also identified in proteins of the BHAV group. Phylogenetic and serological analyses revealed that the BHAVs are most closely related to the novel emerging tick-borne phleboviruses severe fever with thrombocytopenia syndrome virus and Heartland virus, which have recently been implicated as causing severe acute febrile illnesses associated with thrombocytopenia in humans in China and the United States. Our results indicate that the Bhanja serogroup viruses constitute a single novel species in the genus Phlebovirus. The results of this study should facilitate epidemiological surveillance for other, similar tick-borne phleboviruses that may represent unrecognized causes of febrile illness in humans.
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30
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Rusu M, Bonneau R, Holbrook MR, Watowich SJ, Birmanns S, Wriggers W, Freiberg AN. An assembly model of rift valley Fever virus. Front Microbiol 2012; 3:254. [PMID: 22837754 PMCID: PMC3400131 DOI: 10.3389/fmicb.2012.00254] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2012] [Accepted: 06/29/2012] [Indexed: 11/13/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a bunyavirus endemic to Africa and the Arabian Peninsula that infects humans and livestock. The virus encodes two glycoproteins, Gn and Gc, which represent the major structural antigens and are responsible for host cell receptor binding and fusion. Both glycoproteins are organized on the virus surface as cylindrical hollow spikes that cluster into distinct capsomers with the overall assembly exhibiting an icosahedral symmetry. Currently, no experimental three-dimensional structure for any entire bunyavirus glycoprotein is available. Using fold recognition, we generated molecular models for both RVFV glycoproteins and found significant structural matches between the RVFV Gn protein and the influenza virus hemagglutinin protein and a separate match between RVFV Gc protein and Sindbis virus envelope protein E1. Using these models, the potential interaction and arrangement of both glycoproteins in the RVFV particle was analyzed, by modeling their placement within the cryo-electron microscopy density map of RVFV. We identified four possible arrangements of the glycoproteins in the virion envelope. Each assembly model proposes that the ectodomain of Gn forms the majority of the protruding capsomer and that Gc is involved in formation of the capsomer base. Furthermore, Gc is suggested to facilitate intercapsomer connections. The proposed arrangement of the two glycoproteins on the RVFV surface is similar to that described for the alphavirus E1-E2 proteins. Our models will provide guidance to better understand the assembly process of phleboviruses and such structural studies can also contribute to the design of targeted antivirals.
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Affiliation(s)
- Mirabela Rusu
- School of Biomedical Informatics, University of Texas Health Science Center at Houston Houston, TX, USA
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31
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Zhao S, Zhang G, Dai X, Hou Y, Li M, Liang J, Liang C. Processing and intracellular localization of rice stripe virus Pc2 protein in insect cells. Virology 2012; 429:148-54. [PMID: 22575054 DOI: 10.1016/j.virol.2012.04.018] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2011] [Revised: 03/02/2012] [Accepted: 04/26/2012] [Indexed: 10/28/2022]
Abstract
Rice stripe virus (RSV) belongs to the genus Tenuivirus and its genome consists of four single-stranded RNAs encoding seven proteins. Here, we have analyzed the processing and membrane association of Pc2 encoded by vcRNA2 in insect cells. The enhanced green fluorescent protein (eGFP) was fused to the Pc2 and used for the detection of Pc2 fusion proteins. The results showed that Pc2 was cleaved to produce two proteins named Pc2-N and Pc2-C. When expressed alone, either Pc2-N or Pc2-C could transport to the Endoplasmic reticulum (ER) membranes independently. Further mutagenesis studies revealed that Pc2 contained three ER-targeting domains. The results led us to propose a model for the topology of the Pc2 in which an internal signal peptide immediately followed a cleavage site, and two transmembrane regions are contained.
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Affiliation(s)
- Shuling Zhao
- College of Bioscience and Biotechnology, Yangzhou University, Yangzhou 225009, People's Republic of China
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32
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Abstract
Rift Valley fever virus (RVFV; family Bunyaviridae) is a clinically important, mosquito-borne pathogen of both livestock and humans, which is found mainly in sub-Saharan Africa and the Arabian Peninsula. RVFV has a trisegmented single-stranded RNA (ssRNA) genome. The L and M segments are negative sense and encode the L protein (viral polymerase) on the L segment and the virion glycoproteins Gn and Gc as well as two other proteins, NSm and 78K, on the M segment. The S segment uses an ambisense coding strategy to express the nucleocapsid protein, N, and the nonstructural protein, NSs. Both the NSs and NSm proteins are dispensable for virus growth in tissue culture. Using reverse genetics, we generated a recombinant virus, designated r2segMP12, containing a two-segmented genome in which the NSs coding sequence was replaced with that for the Gn and Gc precursor. Thus, r2segMP12 lacks an M segment, and although it was attenuated in comparison to the three-segmented parental virus in both mammalian and insect cell cultures, it was genetically stable over multiple passages. We further show that the virus can stably maintain an M-like RNA segment encoding the enhanced green fluorescent protein gene. The implications of these findings for RVFV genome packaging and the potential to develop multivalent live-attenuated vaccines are discussed.
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Hoenen T, Groseth A, de Kok-Mercado F, Kuhn JH, Wahl-Jensen V. Minigenomes, transcription and replication competent virus-like particles and beyond: reverse genetics systems for filoviruses and other negative stranded hemorrhagic fever viruses. Antiviral Res 2011; 91:195-208. [PMID: 21699921 DOI: 10.1016/j.antiviral.2011.06.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Revised: 06/02/2011] [Accepted: 06/08/2011] [Indexed: 12/27/2022]
Abstract
Reverse-genetics systems are powerful tools enabling researchers to study the replication cycle of RNA viruses, including filoviruses and other hemorrhagic fever viruses, as well as to discover new antivirals. They include full-length clone systems as well as a number of life cycle modeling systems. Full-length clone systems allow for the generation of infectious, recombinant viruses, and thus are an important tool for studying the virus replication cycle in its entirety. In contrast, life cycle modeling systems such as minigenome and transcription and replication competent virus-like particle systems can be used to simulate and dissect parts of the virus life cycle outside of containment facilities. Minigenome systems are used to model viral genome replication and transcription, whereas transcription and replication competent virus-like particle systems also model morphogenesis and budding as well as infection of target cells. As such, these modeling systems have tremendous potential to further the discovery and screening of new antivirals targeting hemorrhagic fever viruses. This review provides an overview of currently established reverse genetics systems for hemorrhagic fever-causing negative-sense RNA viruses, with a particular emphasis on filoviruses, and the potential application of these systems for antiviral research.
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Affiliation(s)
- Thomas Hoenen
- Laboratory of Virology, Rocky Mountain Laboratories, Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, MT, USA; Department of Virology, Philipps University Marburg, Marburg, Germany
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Structure of the Rift Valley fever virus nucleocapsid protein reveals another architecture for RNA encapsidation. Proc Natl Acad Sci U S A 2010; 107:11769-74. [PMID: 20547879 DOI: 10.1073/pnas.1001760107] [Citation(s) in RCA: 107] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a negative-sense RNA virus (genus Phlebovirus, family Bunyaviridae) that infects livestock and humans and is endemic to sub-Saharan Africa. Like all negative-sense viruses, the segmented RNA genome of RVFV is encapsidated by a nucleocapsid protein (N). The 1.93-A crystal structure of RVFV N and electron micrographs of ribonucleoprotein (RNP) reveal an encapsidated genome of substantially different organization than in other negative-sense RNA virus families. The RNP polymer, viewed in electron micrographs of both virus RNP and RNP reconstituted from purified N with a defined RNA, has an extended structure without helical symmetry. N-RNA species of approximately 100-kDa apparent molecular weight and heterogeneous composition were obtained by exhaustive ribonuclease treatment of virus RNP, by recombinant expression of N, and by reconstitution from purified N and an RNA oligomer. RNA-free N, obtained by denaturation and refolding, has a novel all-helical fold that is compact and well ordered at both the N and C termini. Unlike N of other negative-sense RNA viruses, RVFV N has no positively charged surface cleft for RNA binding and no protruding termini or loops to stabilize a defined N-RNA oligomer or RNP helix. A potential protein interaction site was identified in a conserved hydrophobic pocket. The nonhelical appearance of phlebovirus RNP, the heterogeneous approximately 100-kDa N-RNA multimer, and the N fold differ substantially from the RNP and N of other negative-sense RNA virus families and provide valuable insights into the structure of the encapsidated phlebovirus genome.
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35
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Wang H, Alminaite A, Vaheri A, Plyusnin A. Interaction between hantaviral nucleocapsid protein and the cytoplasmic tail of surface glycoprotein Gn. Virus Res 2010; 151:205-12. [PMID: 20566401 DOI: 10.1016/j.virusres.2010.05.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Revised: 05/12/2010] [Accepted: 05/17/2010] [Indexed: 01/07/2023]
Abstract
Hantaviral N and Gn proteins were shown to interact, thus providing the long-awaited evidence for one of the crucial steps in the virus replication at which RNPs are directed to the site of the virus assembly. Using pull-down assay and point mutagenesis it was demonstrated that intact, properly folded zinc fingers in the Gn protein cytoplasmic tail as well as the middle domain of the N protein (that includes aa residues 80-248) are essential for the interaction.
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Affiliation(s)
- Hao Wang
- Department of Virology, Infection Biology Research Program, Haartman Institute, University of Helsinki, Finland.
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36
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Hepojoki J, Strandin T, Wang H, Vapalahti O, Vaheri A, Lankinen H. Cytoplasmic tails of hantavirus glycoproteins interact with the nucleocapsid protein. J Gen Virol 2010; 91:2341-50. [PMID: 20444994 DOI: 10.1099/vir.0.021006-0] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Here we characterize the interaction between the glycoproteins (Gn and Gc) and the ribonucleoprotein (RNP) of Puumala virus (PUUV; genus Hantavirus, family Bunyaviridae). The interaction was initially established with native proteins by co-immunoprecipitating PUUV nucleocapsid (N) protein with the glycoprotein complex. Mapping of the interaction sites revealed that the N protein has multiple binding sites in the cytoplasmic tail (CT) of Gn and is also able to bind to the predicted CT of Gc. The importance of Gn- and Gc-CTs to the recognition of RNP was further verified in pull-down assays using soluble peptides with binding capacity to both recombinant N protein and the RNPs of PUUV and Tula virus. Additionally, the N protein of PUUV was demonstrated to interact with peptides of Gn and Gc from a variety of hantavirus species, suggesting a conserved RNP-recognition mechanism within the genus. Based on these and our previous results, we suggest that the complete hetero-oligomeric (Gn-Gc)(4) spike complex of hantaviruses mediates the packaging of RNP into virions.
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Affiliation(s)
- J Hepojoki
- Department of Virology, Haartman Institute, University of Helsinki, Finland.
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Bouloy M, Weber F. Molecular biology of rift valley Fever virus. Open Virol J 2010; 4:8-14. [PMID: 20517489 PMCID: PMC2878978 DOI: 10.2174/1874357901004020008] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2009] [Revised: 11/25/2009] [Accepted: 11/25/2009] [Indexed: 12/25/2022] Open
Abstract
Rift Valley fever virus (RVFV) causes large outbreaks of acute febrile and often fatal illness among humans and domesticated animals in sub-saharan Africa and the Arabian peninsula. RVFV is a member of the family Bunyaviridae, genus Phlebovirus. Like all members of this large virus family, it contains a three-segmented genome of negative/ambisense strand RNA, packaged into viral nucleocapsid protein, and enveloped by a lipid bilayer containing two viral glycoproteins. During the past years, there was an increased interest in RVFV epidemiology, molecular biology, and virulence mechanisms. Here, we will try to provide an overview over the basic features of this significant pathogen, and review the latest developments in this highly active research field.
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Affiliation(s)
- Michele Bouloy
- Unite de Genetique Moleculaire des Bunyavirus, Institut Pasteur, Paris, France
| | - Friedemann Weber
- Department of Virology, University of Freiburg, D-79008 Freiburg, Germany
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Electron cryotomography of Tula hantavirus suggests a unique assembly paradigm for enveloped viruses. J Virol 2010; 84:4889-97. [PMID: 20219926 DOI: 10.1128/jvi.00057-10] [Citation(s) in RCA: 103] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Hantaviruses (family Bunyaviridae) are rodent-borne emerging viruses that cause a serious, worldwide threat to human health. Hantavirus diseases include hemorrhagic fever with renal syndrome and hantavirus cardiopulmonary syndrome. Virions are enveloped and contain a tripartite single-stranded negative-sense RNA genome. Two types of glycoproteins, G(N) and G(C), are embedded in the viral membrane and form protrusions, or "spikes." The membrane encloses a ribonucleoprotein core, which consists of the RNA segments, the nucleocapsid protein, and the RNA-dependent RNA polymerase. Detailed information on hantavirus virion structure and glycoprotein spike composition is scarce. Here, we have studied the structures of Tula hantavirus virions using electron cryomicroscopy and tomography. Three-dimensional density maps show how the hantavirus surface glycoproteins, membrane, and ribonucleoprotein are organized. The structure of the G(N)-G(C) spike complex was solved to 3.6-nm resolution by averaging tomographic subvolumes. Each spike complex is a square-shaped assembly with 4-fold symmetry. Spike complexes formed ordered patches on the viral membrane by means of specific lateral interactions. These interactions may be sufficient for creating membrane curvature during virus budding. In conclusion, the structure and assembly principles of Tula hantavirus exemplify a unique assembly paradigm for enveloped viruses.
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Mandell RB, Koukuntla R, Mogler LJ, Carzoli AK, Freiberg AN, Holbrook MR, Martin BK, Staplin WR, Vahanian NN, Link CJ, Flick R. A replication-incompetent Rift Valley fever vaccine: chimeric virus-like particles protect mice and rats against lethal challenge. Virology 2010; 397:187-98. [PMID: 19932911 PMCID: PMC2813982 DOI: 10.1016/j.virol.2009.11.001] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2009] [Revised: 10/27/2009] [Accepted: 11/02/2009] [Indexed: 11/09/2022]
Abstract
Virus-like particles (VLPs) present viral antigens in a native conformation and are effectively recognized by the immune system and therefore are considered as suitable and safe vaccine candidates against many viral diseases. Here we demonstrate that chimeric VLPs containing Rift Valley fever virus (RVFV) glycoproteins G(N) and G(C), nucleoprotein N and the gag protein of Moloney murine leukemia virus represent an effective vaccine candidate against Rift Valley fever, a deadly disease in humans and livestock. Long-lasting humoral and cellular immune responses are demonstrated in a mouse model by the analysis of neutralizing antibody titers and cytokine secretion profiles. Vaccine efficacy studies were performed in mouse and rat lethal challenge models resulting in high protection rates. Taken together, these results demonstrate that replication-incompetent chimeric RVF VLPs are an efficient RVFV vaccine candidate.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Nicholas N. Vahanian
- BioProtection Systems Corporation, Ames, IA, USA,NewLink Genetics Corporation, Ames, IA, USA
| | - Charles J. Link
- BioProtection Systems Corporation, Ames, IA, USA,NewLink Genetics Corporation, Ames, IA, USA
| | - Ramon Flick
- BioProtection Systems Corporation, Ames, IA, USA,Corresponding author. Fax: +1 515 296 3820
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40
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Bouloy M, Flick R. Reverse genetics technology for Rift Valley fever virus: current and future applications for the development of therapeutics and vaccines. Antiviral Res 2009; 84:101-18. [PMID: 19682499 PMCID: PMC2801414 DOI: 10.1016/j.antiviral.2009.08.002] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2009] [Revised: 07/22/2009] [Accepted: 08/06/2009] [Indexed: 11/30/2022]
Abstract
The advent of reverse genetics technology has revolutionized the study of RNA viruses, making it possible to manipulate their genomes and evaluate the effects of these changes on their biology and pathogenesis. The fundamental insights gleaned from reverse genetics-based studies over the last several years provide a new momentum for the development of designed therapies for the control and prevention of these viral pathogens. This review summarizes the successes and stumbling blocks in the development of reverse genetics technologies for Rift Valley fever virus and their application to the further dissection of its pathogenesis and the design of new therapeutics and safe and effective vaccines.
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Affiliation(s)
- Michele Bouloy
- Institut Pasteur, Unité de Génétique Moléculaire des Bunyavirus, 25 rue du Dr Roux, 75724 Paris Cedex, France
| | - Ramon Flick
- BioProtection Systems Corporation, 2901 South Loop Drive, Suite 3360, Ames, IA 50010-8646, USA
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41
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Electron cryo-microscopy and single-particle averaging of Rift Valley fever virus: evidence for GN-GC glycoprotein heterodimers. J Virol 2009; 83:3762-9. [PMID: 19193794 DOI: 10.1128/jvi.02483-08] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rift Valley fever virus (RVFV) is a member of the genus Phlebovirus within the family Bunyaviridae. It is a mosquito-borne zoonotic agent that can cause hemorrhagic fever in humans. The enveloped RVFV virions are known to be covered by capsomers of the glycoproteins G(N) and G(C), organized on a T=12 icosahedral lattice. However, the structural units forming the RVFV capsomers have not been determined. Conflicting biochemical results for another phlebovirus (Uukuniemi virus) have indicated the existence of either G(N) and G(C) homodimers or G(N)-G(C) heterodimers in virions. Here, we have studied the structure of RVFV using electron cryo-microscopy combined with three-dimensional reconstruction and single-particle averaging. The reconstruction at 2.2-nm resolution revealed the organization of the glycoprotein shell, the lipid bilayer, and a layer of ribonucleoprotein (RNP). Five- and six-coordinated capsomers are formed by the same basic structural unit. Molecular-mass measurements suggest a G(N)-G(C) heterodimer as the most likely candidate for this structural unit. Both leaflets of the lipid bilayer were discernible, and the glycoprotein transmembrane densities were seen to modulate the curvature of the lipid bilayer. RNP densities were situated directly underneath the transmembrane densities, suggesting an interaction between the glycoprotein cytoplasmic tails and the RNPs. The success of the single-particle averaging approach taken in this study suggests that it is applicable in the study of other phleboviruses, as well, enabling higher-resolution description of these medically important pathogens.
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Habjan M, Penski N, Wagner V, Spiegel M, Overby AK, Kochs G, Huiskonen JT, Weber F. Efficient production of Rift Valley fever virus-like particles: The antiviral protein MxA can inhibit primary transcription of bunyaviruses. Virology 2009; 385:400-8. [PMID: 19155037 DOI: 10.1016/j.virol.2008.12.011] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2008] [Revised: 10/30/2008] [Accepted: 12/08/2008] [Indexed: 11/15/2022]
Abstract
Rift Valley fever virus (RVFV) is a highly pathogenic member of the family Bunyaviridae that needs to be handled under biosafety level (BSL) 3 conditions. Here, we describe reverse genetics systems to measure RVFV polymerase activity in mammalian cells and to generate virus-like particles (VLPs). Recombinant polymerase (L) and nucleocapsid protein (N), expressed together with a minireplicon RNA, formed transcriptionally active nucleocapsids. These could be packaged into VLPs by additional expression of viral glycoproteins. The VLPs resembled authentic virus particles and were able to infect new cells. After infection, VLP-associated nucleocapsids autonomously performed primary transcription, and co-expression of L and N in VLP-infected cells allowed subsequent replication and secondary transcription. Bunyaviruses are potently inhibited by a human interferon-induced protein, MxA. However, the affected step in the infection cycle is not entirely characterized. Using the VLP system, we demonstrate that MxA inhibits both primary and secondary transcriptions of RVFV. A set of infection assays distinguishing between virus attachment, entry, and subsequent RNA synthesis confirmed that MxA is able to target immediate early RNA synthesis of incoming RVFV particles. Thus, our reverse genetics systems are useful for dissecting individual steps of RVFV infection under non-BSL3 conditions.
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Affiliation(s)
- Matthias Habjan
- Department of Virology, University of Freiburg, D-79008 Freiburg, Germany
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Insights into bunyavirus architecture from electron cryotomography of Uukuniemi virus. Proc Natl Acad Sci U S A 2008; 105:2375-9. [PMID: 18272496 DOI: 10.1073/pnas.0708738105] [Citation(s) in RCA: 83] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Bunyaviridae is a large family of viruses that have gained attention as "emerging viruses" because many members cause serious disease in humans, with an increasing number of outbreaks. These negative-strand RNA viruses possess a membrane envelope covered by glycoproteins. The virions are pleiomorphic and thus have not been amenable to structural characterization using common techniques that involve averaging of electron microscopic images. Here, we determined the three-dimensional structure of a member of the Bunyaviridae family by using electron cryotomography. The genome, incorporated as a complex with the nucleoprotein inside the virions, was seen as a thread-like structure partially interacting with the viral membrane. Although no ordered nucleocapsid was observed, lateral interactions between the two membrane glycoproteins determine the structure of the viral particles. In the most regular particles, the glycoprotein protrusions, or "spikes," were seen to be arranged on an icosahedral lattice, with T = 12 triangulation. This arrangement has not yet been proven for a virus. Two distinctly different spike conformations were observed, which were shown to depend on pH. This finding is reminiscent of the fusion proteins of alpha-, flavi-, and influenza viruses, in which conformational changes occur in the low pH of the endosome to facilitate fusion of the viral and host membrane during viral entry.
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