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Sung PY, Zhou Y, Kao CC, Aburigh AA, Routh A, Roy P. A multidisciplinary approach to the identification of the protein-RNA connectome in double-stranded RNA virus capsids. Nucleic Acids Res 2023; 51:5210-5227. [PMID: 37070191 PMCID: PMC10250232 DOI: 10.1093/nar/gkad274] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2022] [Revised: 03/31/2023] [Accepted: 04/04/2023] [Indexed: 04/19/2023] Open
Abstract
How multi-segmented double-stranded RNA (dsRNA) viruses correctly incorporate their genomes into their capsids remains unclear for many viruses, including Bluetongue virus (BTV), a Reoviridae member, with a genome of 10 segments. To address this, we used an RNA-cross-linking and peptide-fingerprinting assay (RCAP) to identify RNA binding sites of the inner capsid protein VP3, the viral polymerase VP1 and the capping enzyme VP4. Using a combination of mutagenesis, reverse genetics, recombinant proteins and in vitro assembly, we validated the importance of these regions in virus infectivity. Further, to identify which RNA segments and sequences interact with these proteins, we used viral photo-activatable ribonucleoside crosslinking (vPAR-CL) which revealed that the larger RNA segments (S1-S4) and the smallest segment (S10) have more interactions with viral proteins than the other smaller segments. Additionally, using a sequence enrichment analysis we identified an RNA motif of nine bases that is shared by the larger segments. The importance of this motif for virus replication was confirmed by mutagenesis followed by virus recovery. We further demonstrated that these approaches could be applied to a related Reoviridae member, rotavirus (RV), which has human epidemic impact, offering the possibility of novel intervention strategies for a human pathogen.
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Affiliation(s)
- Po-yu Sung
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Yiyang Zhou
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
| | - C Cheng Kao
- Previously in the Department of Molecular & Cellular Biochemistry, Indiana University, Bloomington, IN, USA
| | - Ali A Aburigh
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
| | - Andrew Routh
- Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX, USA
- Sealy Center for Structural Biology and Molecular Biophysics, The University of Texas Medical Branch, Galveston, TX, USA
- Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, USA
| | - Polly Roy
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, UK
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Jiménez-Cabello L, Utrilla-Trigo S, Barreiro-Piñeiro N, Pose-Boirazian T, Martínez-Costas J, Marín-López A, Ortego J. Nanoparticle- and Microparticle-Based Vaccines against Orbiviruses of Veterinary Importance. Vaccines (Basel) 2022; 10:vaccines10071124. [PMID: 35891288 PMCID: PMC9319458 DOI: 10.3390/vaccines10071124] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 07/12/2022] [Accepted: 07/13/2022] [Indexed: 11/16/2022] Open
Abstract
Bluetongue virus (BTV) and African horse sickness virus (AHSV) are widespread arboviruses that cause important economic losses in the livestock and equine industries, respectively. In addition to these, another arthropod-transmitted orbivirus known as epizootic hemorrhagic disease virus (EHDV) entails a major threat as there is a conducive landscape that nurtures its emergence in non-endemic countries. To date, only vaccinations with live attenuated or inactivated vaccines permit the control of these three viral diseases, although important drawbacks, e.g., low safety profile and effectiveness, and lack of DIVA (differentiation of infected from vaccinated animals) properties, constrain their usage as prophylactic measures. Moreover, a substantial number of serotypes of BTV, AHSV and EHDV have been described, with poor induction of cross-protective immune responses among serotypes. In the context of next-generation vaccine development, antigen delivery systems based on nano- or microparticles have gathered significant attention during the last few decades. A diversity of technologies, such as virus-like particles or self-assembled protein complexes, have been implemented for vaccine design against these viruses. In this work, we offer a comprehensive review of the nano- and microparticulated vaccine candidates against these three relevant orbiviruses. Additionally, we also review an innovative technology for antigen delivery based on the avian reovirus nonstructural protein muNS and we explore the prospective functionality of the nonstructural protein NS1 nanotubules as a BTV-based delivery platform.
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Affiliation(s)
- Luis Jiménez-Cabello
- Centro de Investigación en Sanidad Animal (CISA-INIA/CSIC), 28130 Madrid, Spain; (L.J.-C.); (S.U.-T.)
- Centro Singular de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain; (N.B.-P.); (T.P.-B.); (J.M.-C.)
| | - Sergio Utrilla-Trigo
- Centro de Investigación en Sanidad Animal (CISA-INIA/CSIC), 28130 Madrid, Spain; (L.J.-C.); (S.U.-T.)
| | - Natalia Barreiro-Piñeiro
- Centro Singular de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain; (N.B.-P.); (T.P.-B.); (J.M.-C.)
| | - Tomás Pose-Boirazian
- Centro Singular de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain; (N.B.-P.); (T.P.-B.); (J.M.-C.)
| | - José Martínez-Costas
- Centro Singular de Investigación en Química Biológica y Materiales Moleculares (CIQUS), Universidad de Santiago de Compostela, 15782 Santiago de Compostela, Spain; (N.B.-P.); (T.P.-B.); (J.M.-C.)
| | - Alejandro Marín-López
- Section of Infectious Diseases, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT 06519, USA;
| | - Javier Ortego
- Centro de Investigación en Sanidad Animal (CISA-INIA/CSIC), 28130 Madrid, Spain; (L.J.-C.); (S.U.-T.)
- Correspondence:
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3
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Rodrigues TCS, Viadanna PHO, Subramaniam K, Hawkins IK, Jeon AB, Loeb JC, Krauer JMC, Lednicky JA, Wisely SM, Waltzek TB. Characterization of a Novel Reassortant Epizootic Hemorrhagic Disease Virus Serotype 6 Strain Isolated from Diseased White-Tailed Deer ( Odocoileus virginianus) on a Florida Farm. Viruses 2022; 14:1012. [PMID: 35632753 PMCID: PMC9146129 DOI: 10.3390/v14051012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2022] [Revised: 04/27/2022] [Accepted: 04/28/2022] [Indexed: 02/04/2023] Open
Abstract
We report an outbreak of a novel reassortant epizootic hemorrhagic disease virus serotype 6 (EHDV-6) in white-tailed deer (WTD) on a Florida farm in 2019. At necropsy, most animals exhibited hemorrhagic lesions in the lung and heart, and congestion in the lung, liver, and spleen. Histopathology revealed multi-organ hemorrhage and congestion, and renal tubular necrosis. Tissues were screened by RT-qPCR and all animals tested positive for EHDV. Tissues were processed for virus isolation and next-generation sequencing was performed on cDNA libraries generated from the RNA extracts of cultures displaying cytopathic effects. Six isolates yielded nearly identical complete genome sequences of a novel U.S. EHDV-6 strain. Genetic and phylogenetic analyses revealed the novel strain to be most closely related to a reassortant EHDV-6 strain isolated from cattle in Trinidad and both strains received segment 4 from an Australian EHDV-2 strain. The novel U.S. EHDV-6 strain is unique in that it acquired segment 8 from an Australian EHDV-8 strain. An RNAscope® in situ hybridization assay was developed against the novel U.S. EHDV-6 strain and labeling was detected within lesions of the heart, kidney, liver, and lung. These data support the novel U.S. reassortant EHDV-6 strain as the cause of disease in the farmed WTD.
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Affiliation(s)
- Thaís C. S. Rodrigues
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA; (T.C.S.R.); (P.H.O.V.); (K.S.)
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
| | - Pedro H. O. Viadanna
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA; (T.C.S.R.); (P.H.O.V.); (K.S.)
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
| | - Kuttichantran Subramaniam
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA; (T.C.S.R.); (P.H.O.V.); (K.S.)
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
| | - Ian K. Hawkins
- Department of Comparative, Diagnostic, and Population Medicine, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA; (I.K.H.); (A.B.J.)
| | - Albert B. Jeon
- Department of Comparative, Diagnostic, and Population Medicine, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA; (I.K.H.); (A.B.J.)
| | - Julia C. Loeb
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, FL 32611, USA
| | - Juan M. C. Krauer
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA;
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL 32611, USA
| | - John A. Lednicky
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, Gainesville, FL 32611, USA
| | - Samantha M. Wisely
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
- Department of Wildlife Ecology and Conservation, University of Florida, Gainesville, FL 32611, USA
| | - Thomas B. Waltzek
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, Gainesville, FL 32611, USA; (T.C.S.R.); (P.H.O.V.); (K.S.)
- Emerging Pathogens Institute, University of Florida, Gainesville, FL 32611, USA; (J.C.L.); (J.A.L.); (S.M.W.)
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RNA Origami: Packaging a Segmented Genome in Orbivirus Assembly and Replication. Viruses 2021; 13:v13091841. [PMID: 34578422 PMCID: PMC8473007 DOI: 10.3390/v13091841] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 09/07/2021] [Accepted: 09/11/2021] [Indexed: 01/04/2023] Open
Abstract
Understanding how viruses with multi-segmented genomes incorporate one copy of each segment into their capsids remains an intriguing question. Here, we review our recent progress and describe the advancements made in understanding the genome packaging mechanism of a model nonenveloped virus, Bluetongue virus (BTV), with a 10-segment (S1–S10) double-strand RNA (dsRNA) genome. BTV (multiple serotypes), a member of the Orbivirus genus in the Reoviridae family, is a notable pathogen for livestock and is responsible for significant economic losses worldwide. This has enabled the creation of an extensive set of reagents and assays, including reverse genetics, cell-free RNA packaging, and bespoke bioinformatics approaches, which can be directed to address the packaging question. Our studies have shown that (i) UTRs enable the conformation of each segment necessary for the next level of RNA–RNA interaction; (ii) a specific order of intersegment interactions leads to a complex RNA network containing all the active components in sorting and packaging; (iii) networked segments are recruited into nascent assembling capsids; and (iv) select capsid proteins might be involved in the packaging process. The key features of genome packaging mechanisms for BTV and related dsRNA viruses are novel and open up new avenues of potential intervention.
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5
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Wall GV, Wright IM, Barnardo C, Erasmus BJ, van Staden V, Potgieter AC. African horse sickness virus NS4 protein is an important virulence factor and interferes with JAK-STAT signaling during viral infection. Virus Res 2021; 298:198407. [PMID: 33812899 DOI: 10.1016/j.virusres.2021.198407] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2021] [Revised: 03/25/2021] [Accepted: 03/29/2021] [Indexed: 12/24/2022]
Abstract
African horse sickness virus (AHSV) non-structural protein NS4 is a nucleocytoplasmic protein that is expressed in the heart, lung, and spleen of infected horses, binds dsDNA, and colocalizes with promyelocytic leukemia nuclear bodies (PML-NBs). The aim of this study was to investigate the role of AHSV NS4 in viral replication, virulence and the host immune response. Using a reverse genetics-derived virulent strain of AHSV-5 and NS4 deletion mutants, we showed that knockdown of NS4 expression has no impact in cell culture, but results in virus attenuation in infected horses. RNA sequencing (RNA-seq) was used to investigate the transcriptional response in these horses, to see how the lack of NS4 mediates the transition of the virus from virulent to attenuated. The presence of NS4 was shown to result in a 24 hour (h) delay in the transcriptional activation of several immune system processes compared to when the protein was absent. Included in these processes were the RIG-I-like, Toll-like receptor, and JAK-STAT signaling pathways, which are key pathways involved in innate immunity and the antiviral response. Thus, it was shown that AHSV NS4 suppresses the host innate immune transcriptional response in the early stages of the infection cycle. We investigated whether AHSV NS4 affects the innate immune response by impacting the JAK-STAT signaling pathway specifically. Using confocal laser scanning microscopy (CLSM) we showed that AHSV NS4 disrupts JAK-STAT signaling by interfering with the phosphorylation and/or translocation of STAT1 and pSTAT1 into the nucleus. Overall, these results showed that AHSV NS4 is a key virulence factor in horses and allows AHSV to overcome host antiviral responses in order to promote viral replication and spread.
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Affiliation(s)
- Gayle V Wall
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, 0002, South Africa
| | - Isabella M Wright
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa
| | - Carin Barnardo
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa
| | - Baltus J Erasmus
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa
| | - Vida van Staden
- Department of Biochemistry, Genetics and Microbiology, University of Pretoria, Pretoria, 0002, South Africa
| | - A Christiaan Potgieter
- Deltamune (Pty) Ltd, Moraine House - The Braes, 193 Bryanston Drive, Bryanston, Gauteng, 2191, South Africa; Department of Biochemistry, Focus Area for Human Metabolomics, North-West University, Potchefstroom, South Africa.
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6
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Roy P. Bluetongue virus assembly and exit pathways. Adv Virus Res 2020; 108:249-273. [PMID: 33837718 DOI: 10.1016/bs.aivir.2020.08.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Bluetongue virus (BTV) is an insect-vectored emerging pathogen of wild ruminants and livestock in many parts of the world. The virion particle is a complex structure of consecutive layers of protein surrounding a genome of 10 double-stranded (ds) RNA segments. BTV has been studied extensively as a model system for large, nonenveloped dsRNA viruses. A combination of recombinant proteins and particles together with reverse genetics, high-resolution structural analysis by X-ray crystallography and cryo-electron microscopy techniques have been utilized to provide an order for the assembly of the capsid shell and the protein sequestration required for it. Further, a reconstituted in vitro assembly system and RNA-RNA interaction assay, have defined the individual steps required for the assembly and packaging of the 10-segmented RNA genome. In addition, various microscopic techniques have been utilized to illuminate the stages of virus maturation and its egress via multiple pathways. These findings have not only given an overall understanding of BTV assembly and morphogenesis but also indicated that similar assembly and egress pathways are likely to be used by related viruses and provided an informed starting point for intervention or prevention.
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Affiliation(s)
- Polly Roy
- Department of Infection Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, United Kingdom.
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7
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Jaïs PH, Decroly E, Jacquet E, Le Boulch M, Jaïs A, Jean-Jean O, Eaton H, Ponien P, Verdier F, Canard B, Goncalves S, Chiron S, Le Gall M, Mayeux P, Shmulevitz M. C3P3-G1: first generation of a eukaryotic artificial cytoplasmic expression system. Nucleic Acids Res 2019; 47:2681-2698. [PMID: 30726994 PMCID: PMC6412113 DOI: 10.1093/nar/gkz069] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2018] [Revised: 12/03/2018] [Accepted: 01/25/2019] [Indexed: 12/25/2022] Open
Abstract
Most eukaryotic expression systems make use of host-cell nuclear transcriptional and post-transcriptional machineries. Here, we present the first generation of the chimeric cytoplasmic capping-prone phage polymerase (C3P3-G1) expression system developed by biological engineering, which generates capped and polyadenylated transcripts in host-cell cytoplasm by means of two components. First, an artificial single-unit chimeric enzyme made by fusing an mRNA capping enzyme and a DNA-dependent RNA polymerase. Second, specific DNA templates designed to operate with the C3P3-G1 enzyme, which encode for the transcripts and their artificial polyadenylation. This system, which can potentially be adapted to any in cellulo or in vivo eukaryotic expression applications, was optimized for transient expression in mammalian cells. C3P3-G1 shows promising results for protein production in Chinese Hamster Ovary (CHO-K1) cells. This work also provides avenues for enhancing the performances for next generation C3P3 systems.
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Affiliation(s)
- Philippe H Jaïs
- Eukarÿs SAS, Génopole Campus 3, 4 rue Pierre Fontaine, 91058 Evry Cedex, France
| | - Etienne Decroly
- Architecture et Fonction des Macromolécules Biologiques (AFMB) UMR 7257 CNRS/AMU, 163 Avenue de Luminy, 13288 Marseille Cedex 9, France
| | - Eric Jacquet
- Institut de Chimie des Substances Naturelles, CNRS UPR2301, Université Paris-Saclay, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
| | - Marine Le Boulch
- Eukarÿs SAS, Génopole Campus 3, 4 rue Pierre Fontaine, 91058 Evry Cedex, France
| | - Aurélien Jaïs
- Eukarÿs SAS, Génopole Campus 3, 4 rue Pierre Fontaine, 91058 Evry Cedex, France
| | - Olivier Jean-Jean
- Sorbonne Université, CNRS-UMR8256, Biological Adaptation and Ageing, Institut de Biologie Paris Seine (B2A-IBPS), F-75252 Paris, France
| | - Heather Eaton
- Medical Microbiology and Immunology, University of Alberta, 6-142J Katz Group Centre for Pharmacy and Health Research, 114 Street NW, Edmonton, Alberta T6G 2E1, Canada
| | - Prishila Ponien
- Institut de Chimie des Substances Naturelles, CNRS UPR2301, Université Paris-Saclay, Avenue de la Terrasse, 91198 Gif-sur-Yvette, France
| | - Fréderique Verdier
- INSERM Unit 1016, Institut Cochin, Bâtiment Gustave Roussy, 27 rue du faubourg Saint-Jacques, 75014 Paris, France
| | - Bruno Canard
- Architecture et Fonction des Macromolécules Biologiques (AFMB) UMR 7257 CNRS/AMU, 163 Avenue de Luminy, 13288 Marseille Cedex 9, France
| | - Sergio Goncalves
- Eukarÿs SAS, Génopole Campus 3, 4 rue Pierre Fontaine, 91058 Evry Cedex, France
| | - Stéphane Chiron
- Eukarÿs SAS, Génopole Campus 3, 4 rue Pierre Fontaine, 91058 Evry Cedex, France
| | - Maude Le Gall
- Gastrointestinal and Metabolic Dysfunctions in Nutritional Pathologies, INSERM UMRS1149, 16 rue Henri Huchard, 75890 Paris Cedex 18, France
| | - Patrick Mayeux
- INSERM Unit 1016, Institut Cochin, Bâtiment Gustave Roussy, 27 rue du faubourg Saint-Jacques, 75014 Paris, France
| | - Maya Shmulevitz
- Medical Microbiology and Immunology, University of Alberta, 6-142J Katz Group Centre for Pharmacy and Health Research, 114 Street NW, Edmonton, Alberta T6G 2E1, Canada
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Dennis SJ, Meyers AE, Hitzeroth II, Rybicki EP. African Horse Sickness: A Review of Current Understanding and Vaccine Development. Viruses 2019; 11:E844. [PMID: 31514299 PMCID: PMC6783979 DOI: 10.3390/v11090844] [Citation(s) in RCA: 39] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2019] [Revised: 08/30/2019] [Accepted: 09/04/2019] [Indexed: 01/05/2023] Open
Abstract
African horse sickness is a devastating disease that causes great suffering and many fatalities amongst horses in sub-Saharan Africa. It is caused by nine different serotypes of the orbivirus African horse sickness virus (AHSV) and it is spread by Culicoid midges. The disease has significant economic consequences for the equine industry both in southern Africa and increasingly further afield as the geographic distribution of the midge vector broadens with global warming and climate change. Live attenuated vaccines (LAV) have been used with relative success for many decades but carry the risk of reversion to virulence and/or genetic re-assortment between outbreak and vaccine strains. Furthermore, the vaccines lack DIVA capacity, the ability to distinguish between vaccine-induced immunity and that induced by natural infection. These concerns have motivated interest in the development of new, more favourable recombinant vaccines that utilize viral vectors or are based on reverse genetics or virus-like particle technologies. This review summarizes the current understanding of AHSV structure and the viral replication cycle and also evaluates existing and potential vaccine strategies that may be applied to prevent or control the disease.
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Affiliation(s)
- Susan J Dennis
- Biopharming Research Unit, Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.
| | - Ann E Meyers
- Biopharming Research Unit, Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.
| | - Inga I Hitzeroth
- Biopharming Research Unit, Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.
| | - Edward P Rybicki
- Biopharming Research Unit, Department of Molecular and Cell Biology, University of Cape Town, Rondebosch 7701, Cape Town, South Africa.
- Institute of Infectious Disease and Molecular Medicine, Faculty of Health Sciences, University of Cape Town, Observatory 7925, Cape Town, South Africa.
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9
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Kundlacz C, Pourcelot M, Fablet A, Amaral Da Silva Moraes R, Léger T, Morlet B, Viarouge C, Sailleau C, Turpaud M, Gorlier A, Breard E, Lecollinet S, van Rijn PA, Zientara S, Vitour D, Caignard G. Novel Function of Bluetongue Virus NS3 Protein in Regulation of the MAPK/ERK Signaling Pathway. J Virol 2019; 93:e00336-19. [PMID: 31167915 PMCID: PMC6675888 DOI: 10.1128/jvi.00336-19] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2019] [Accepted: 05/22/2019] [Indexed: 12/22/2022] Open
Abstract
Bluetongue virus (BTV) is an arbovirus transmitted by blood-feeding midges to a wide range of wild and domestic ruminants. In this report, we showed that BTV, through its nonstructural protein NS3 (BTV-NS3), is able to activate the mitogen-activated protein kinase/extracellular signal-regulated kinase (MAPK/ERK) pathway, as assessed by phosphorylation levels of ERK1/2 and the translation initiation factor eukaryotic translation initiation factor 4E (eIF4E). By combining immunoprecipitation of BTV-NS3 and mass spectrometry analysis from both BTV-infected and NS3-transfected cells, we identified the serine/threonine-protein kinase B-Raf (BRAF), a crucial player in the MAPK/ERK pathway, as a new cellular interactor of BTV-NS3. BRAF silencing led to a significant decrease in the MAPK/ERK activation by BTV, supporting a model wherein BTV-NS3 interacts with BRAF to activate this signaling cascade. This positive regulation acts independently of the role of BTV-NS3 in counteracting the induction of the alpha/beta interferon response. Furthermore, the intrinsic ability of BTV-NS3 to bind BRAF and activate the MAPK/ERK pathway is conserved throughout multiple serotypes/strains but appears to be specific to BTV compared to other members of Orbivirus genus. Inhibition of MAPK/ERK pathway with U0126 reduced viral titers, suggesting that BTV manipulates this pathway for its own replication. Altogether, our data provide molecular mechanisms that unravel a new essential function of NS3 during BTV infection.IMPORTANCE Bluetongue virus (BTV) is responsible of the arthropod-borne disease bluetongue (BT) transmitted to ruminants by blood-feeding midges. In this report, we found that BTV, through its nonstructural protein NS3 (BTV-NS3), interacts with BRAF, a key component of the MAPK/ERK pathway. In response to growth factors, this pathway promotes cell survival and increases protein translation. We showed that BTV-NS3 enhances the MAPK/ERK pathway, and this activation is BRAF dependent. Treatment of MAPK/ERK pathway with the pharmacologic inhibitor U0126 impairs viral replication, suggesting that BTV manipulates this pathway for its own benefit. Our results illustrate, at the molecular level, how a single virulence factor has evolved to target a cellular function to increase its viral replication.
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Affiliation(s)
- Cindy Kundlacz
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Marie Pourcelot
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Aurore Fablet
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | | | - Thibaut Léger
- Mass Spectrometry and Proteomics Facility, Jacques Monod Institute, UMR 7592, Paris Diderot University, CNRS, Paris Cedex 13, France
| | - Bastien Morlet
- Mass Spectrometry and Proteomics Facility, Jacques Monod Institute, UMR 7592, Paris Diderot University, CNRS, Paris Cedex 13, France
| | - Cyril Viarouge
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Corinne Sailleau
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Mathilde Turpaud
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Axel Gorlier
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Emmanuel Breard
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Sylvie Lecollinet
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Piet A van Rijn
- Department of Virology, Wageningen Bioveterinary Research, Lelystad, The Netherlands
- Department of Biochemistry, Centre for Human Metabolomics, North-West University, Potchefstroom, South Africa
| | - Stephan Zientara
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Damien Vitour
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
| | - Grégory Caignard
- UMR Virologie, INRA, École Nationale Vétérinaire d'Alfort, ANSES, Université Paris-Est, Maisons-Alfort, France
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In situ structures of RNA-dependent RNA polymerase inside bluetongue virus before and after uncoating. Proc Natl Acad Sci U S A 2019; 116:16535-16540. [PMID: 31350350 DOI: 10.1073/pnas.1905849116] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Bluetongue virus (BTV), a major threat to livestock, is a multilayered, nonturreted member of the Reoviridae, a family of segmented dsRNA viruses characterized by endogenous RNA transcription through an RNA-dependent RNA polymerase (RdRp). To date, the structure of BTV RdRp has been unknown, limiting our mechanistic understanding of BTV transcription and hindering rational drug design effort targeting this essential enzyme. Here, we report the in situ structures of BTV RdRp VP1 in both the triple-layered virion and double-layered core, as determined by cryo-electron microscopy (cryoEM) and subparticle reconstruction. BTV RdRp has 2 unique motifs not found in other viral RdRps: a fingernail, attached to the conserved fingers subdomain, and a bundle of 3 helices: 1 from the palm subdomain and 2 from the N-terminal domain. BTV RdRp VP1 is anchored to the inner surface of the capsid shell via 5 asymmetrically arranged N termini of the inner capsid shell protein VP3A around the 5-fold axis. The structural changes of RdRp VP1 and associated capsid shell proteins between BTV virions and cores suggest that the detachment of the outer capsid proteins VP2 and VP5 during viral entry induces both global movements of the inner capsid shell and local conformational changes of the N-terminal latch helix (residues 34 to 51) of 1 inner capsid shell protein VP3A, priming RdRp VP1 within the capsid for transcription. Understanding this mechanism in BTV also provides general insights into RdRp activation and regulation during viral entry of other multilayered, nonturreted dsRNA viruses.
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Ogino T, Green TJ. RNA Synthesis and Capping by Non-segmented Negative Strand RNA Viral Polymerases: Lessons From a Prototypic Virus. Front Microbiol 2019; 10:1490. [PMID: 31354644 PMCID: PMC6636387 DOI: 10.3389/fmicb.2019.01490] [Citation(s) in RCA: 48] [Impact Index Per Article: 9.6] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2019] [Accepted: 06/14/2019] [Indexed: 12/26/2022] Open
Abstract
Non-segmented negative strand (NNS) RNA viruses belonging to the order Mononegavirales are highly diversified eukaryotic viruses including significant human pathogens, such as rabies, measles, Nipah, and Ebola. Elucidation of their unique strategies to replicate in eukaryotic cells is crucial to aid in developing anti-NNS RNA viral agents. Over the past 40 years, vesicular stomatitis virus (VSV), closely related to rabies virus, has served as a paradigm to study the fundamental molecular mechanisms of transcription and replication of NNS RNA viruses. These studies provided insights into how NNS RNA viruses synthesize 5'-capped mRNAs using their RNA-dependent RNA polymerase L proteins equipped with an unconventional mRNA capping enzyme, namely GDP polyribonucleotidyltransferase (PRNTase), domain. PRNTase or PRNTase-like domains are evolutionally conserved among L proteins of all known NNS RNA viruses and their related viruses belonging to Jingchuvirales, a newly established order, in the class Monjiviricetes, suggesting that they may have evolved from a common ancestor that acquired the unique capping system to replicate in a primitive eukaryotic host. This article reviews what has been learned from biochemical and structural studies on the VSV RNA biosynthesis machinery, and then focuses on recent advances in our understanding of regulatory and catalytic roles of the PRNTase domain in RNA synthesis and capping.
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Affiliation(s)
- Tomoaki Ogino
- Department of Molecular Biology and Microbiology, Case Western Reserve University School of Medicine, Cleveland, OH, United States
- Department of Inflammation and Immunity, Lerner Research Institute, Cleveland Clinic, Cleveland, OH, United States
| | - Todd J. Green
- Department of Microbiology, School of Medicine, University of Alabama at Birmingham, Birmingham, AL, United States
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12
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Van den Bergh C, Coetzee P, Venter EH. Reassortment of bluetongue virus vaccine serotypes in cattle. J S Afr Vet Assoc 2018; 89:e1-e7. [PMID: 30551703 PMCID: PMC6295955 DOI: 10.4102/jsava.v89i0.1649] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2017] [Revised: 10/17/2018] [Accepted: 10/17/2018] [Indexed: 11/01/2022] Open
Abstract
Bluetongue is primarily a disease of sheep in South Africa, while cattle and goats are mostly subclinically infected. The viraemia of bluetongue virus in cattle lasts much longer than in sheep and the role of cattle in the epidemiology of bluetongue in South Africa is poorly understood. Bluetongue virus has a segmented double-stranded ribonucleic acid genome and reassortment of genomes is a common feature. The aim of the study was to investigate whether reassortment occurs between vaccine and field strains when simultaneously administered to cattle. Six cattle between the ages of 6 and 12 months were infected with five strains of modified live vaccine bluetongue virus and a virulent field isolate of bluetongue virus 4. Blood samples were subsequently collected daily from these animals from day 1 to day 39 post-inoculation. Viruses were directly isolated during viraemia from the buffy coat on Vero cells using the plaque forming unit method. Analysis of plaques indicated that no reassortants between virulent field and vaccine strains occurred and the virulent bluetongue virus 4 was identified as the predominant virus strain. However, a reassortant virus between two bluetongue virus vaccine strains was isolated from the buffy coat. Whole genome sequences from the vaccine viruses were compared to the suspected reassortant and it was found that segment 8 exchanged between the bluetongue virus 8 and bluetongue virus 9 vaccine strains. The use of the live-attenuated bluetongue virus multivalent vaccine in South Africa causes circulation of different vaccine serotypes in Culicoides spp. and susceptible hosts and cattle might provide the ideal host for reassortment to occur.
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13
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Schade-Weskott ML, van Schalkwyk A, Koekemoer JJO. A correlation between capsid protein VP2 and the plaque morphology of African horse sickness virus in cell culture. Virus Genes 2018; 54:527-535. [PMID: 29730763 DOI: 10.1007/s11262-018-1567-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 04/30/2018] [Indexed: 12/29/2022]
Abstract
The attenuated live virus vaccine that is used in South Africa to protect against African horse sickness infection was developed more than 50 years ago. With the selection of the vaccine strains by cell culture passage, a correlation between the size of plaques formed in monolayer Vero cultures and attenuation of virus virulence in horses was found. The large plaque phenotype was used as an indication of cell culture adaptation and strongly correlated with attenuation of virulence in horses. There was never any investigation into the genetic causes of either the variation in plaque size, or the loss of virulence. An understanding of the underlying mechanisms of attenuation would benefit the production of a safer AHSV vaccine. To this end, the genomes of different strains of two African horse sickness isolates, producing varying plaque sizes, were compared and the differences between them identified. This comparison suggested that proteins VP2, VP3, VP5 and NS3 were most likely involved in the determination of the plaque phenotype. Comparison between genome sequences (obtained from GenBank) of low and high passage strains from two additional serotypes indicated that VP2 was the only protein with amino acid substitutions in all four serotypes. The amino acid substitutions all occurred within the same hydrophilic area, resulting in increased hydrophilicity of VP2 in the large plaque strains.
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Affiliation(s)
- Mathilde L Schade-Weskott
- Agricultural Research Council - Onderstepoort Veterinary Institute, 100 Old Soutpan Rd, Pretoria, South Africa.
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
| | - Antoinette van Schalkwyk
- Agricultural Research Council - Onderstepoort Veterinary Institute, 100 Old Soutpan Rd, Pretoria, South Africa
| | - J J O Koekemoer
- Agricultural Research Council - Onderstepoort Veterinary Institute, 100 Old Soutpan Rd, Pretoria, South Africa
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14
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Ryabov EV. Invertebrate RNA virus diversity from a taxonomic point of view. J Invertebr Pathol 2017; 147:37-50. [PMID: 27793741 PMCID: PMC7094257 DOI: 10.1016/j.jip.2016.10.002] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2016] [Revised: 10/03/2016] [Accepted: 10/14/2016] [Indexed: 02/04/2023]
Abstract
Invertebrates are hosts to diverse RNA viruses that have all possible types of encapsidated genomes (positive, negative and ambisense single stranded RNA genomes, or a double stranded RNA genome). These viruses also differ markedly in virion morphology and genome structure. Invertebrate RNA viruses are present in three out of four currently recognized orders of RNA viruses: Mononegavirales, Nidovirales, and Picornavirales, and 10 out of 37 RNA virus families that have yet to be assigned to an order. This mini-review describes general properties of the taxonomic groups, which include invertebrate RNA viruses on the basis of their current classification by the International Committee on Taxonomy of Viruses (ICTV).
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Affiliation(s)
- Eugene V Ryabov
- ER Healthcare Consulting Ltd., Poundgate Lane, Coventry CV4 8HJ, United Kingdom.
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15
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Roy P. Bluetongue virus structure and assembly. Curr Opin Virol 2017; 24:115-123. [PMID: 28609677 DOI: 10.1016/j.coviro.2017.05.003] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 05/19/2017] [Accepted: 05/24/2017] [Indexed: 01/09/2023]
Abstract
Bluetongue virus (BTV) is an insect-vectored emerging pathogen of wild ruminants and livestock in many parts of the world. The virion particle is a complex structure of consecutive layers of protein surrounding a genome of ten double-stranded (ds) RNA segments. BTV has been studied as a model system for large, non-enveloped dsRNA viruses. Several new techniques have been applied to define the virus-encoded enzymes required for RNA replication to provide an order for the assembly of the capsid shell and the protein sequestration required for it. Further, a reconstituted in vitro system has defined the individual steps of the assembly and packaging of the genomic RNA. These findings illuminate BTV assembly and indicate the pathways that related viruses might use to provide an informed starting point for intervention or prevention.
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Affiliation(s)
- Polly Roy
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, WC1E 7HT, UK.
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16
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Ramanathan A, Robb GB, Chan SH. mRNA capping: biological functions and applications. Nucleic Acids Res 2016; 44:7511-26. [PMID: 27317694 PMCID: PMC5027499 DOI: 10.1093/nar/gkw551] [Citation(s) in RCA: 482] [Impact Index Per Article: 60.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2016] [Accepted: 06/03/2016] [Indexed: 12/19/2022] Open
Abstract
The 5′ m7G cap is an evolutionarily conserved modification of eukaryotic mRNA. Decades of research have established that the m7G cap serves as a unique molecular module that recruits cellular proteins and mediates cap-related biological functions such as pre-mRNA processing, nuclear export and cap-dependent protein synthesis. Only recently has the role of the cap 2′O methylation as an identifier of self RNA in the innate immune system against foreign RNA has become clear. The discovery of the cytoplasmic capping machinery suggests a novel level of control network. These new findings underscore the importance of a proper cap structure in the synthesis of functional messenger RNA. In this review, we will summarize the current knowledge of the biological roles of mRNA caps in eukaryotic cells. We will also discuss different means that viruses and their host cells use to cap their RNA and the application of these capping machineries to synthesize functional mRNA. Novel applications of RNA capping enzymes in the discovery of new RNA species and sequencing the microbiome transcriptome will also be discussed. We will end with a summary of novel findings in RNA capping and the questions these findings pose.
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Affiliation(s)
- Anand Ramanathan
- New England Biolabs, Inc. 240 County Road, Ipswich, MA 01938, USA
| | - G Brett Robb
- New England Biolabs, Inc. 240 County Road, Ipswich, MA 01938, USA
| | - Siu-Hong Chan
- New England Biolabs, Inc. 240 County Road, Ipswich, MA 01938, USA
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Matsuo E, Saeki K, Roy P, Kawano J. Development of reverse genetics for Ibaraki virus to produce viable VP6-tagged IBAV. FEBS Open Bio 2015; 5:445-53. [PMID: 26101741 PMCID: PMC4472822 DOI: 10.1016/j.fob.2015.05.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/13/2015] [Accepted: 05/22/2015] [Indexed: 01/18/2023] Open
Abstract
A reverse genetics system for Ibaraki virus (IBAV) was developed. The RG system was used to produce viable VP6-tagged IBAV. A region of VP6 (aa 34–82) is not required for IBAV replication in tissue culture. The insertion of tags into the nonessential VP6 region did not disrupt replication. IBAV VP6 quickly assembled into puncta in the cytosol of infected cells.
Ibaraki virus (IBAV) is a member of the epizootic hemorrhagic disease virus (EHDV) serogroup, which belongs to the Orbivirus genus of the Reoviridae family. Although EHDV, including IBAV, represents an ongoing threat to livestock in the world, molecular mechanisms of EHDV replication and pathogenesis have been unclear. The reverse genetics (RG) system is one of the strong tools to understand molecular mechanisms of virus replication. Here, we developed a RG system for IBAV to identify the nonessential region of a minor structural protein, VP6, by generating VP6-truncated IBAV. Moreover, several tags were inserted into the truncated region to produce VP6-tagged IBAV. We demonstrated that all VP6-tagged IBAV could replicate in BHK cells in the absence of any helper VP6 protein. Further, tagged-VP6 proteins were first assembled into puncta in cells infected with VP6-tagged IBAV. Our data suggests that, in order to initiate primary replication, IBAV VP6 is likely to accumulate in some parts of infected cells to assemble efficiently into the primary replication complex (subcore).
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Affiliation(s)
- Eiko Matsuo
- Microbiology & Immunology, Division of Animal Science, Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe-city 657-8501, Japan
| | - Keiichi Saeki
- Microbiology & Immunology, Division of Animal Science, Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe-city 657-8501, Japan
| | - Polly Roy
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Junichi Kawano
- Microbiology & Immunology, Division of Animal Science, Department of Bioresource Science, Graduate School of Agricultural Science, Kobe University, 1-1, Rokkodai, Nada-ku, Kobe-city 657-8501, Japan
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Multiple genome segments determine virulence of bluetongue virus serotype 8. J Virol 2015; 89:5238-49. [PMID: 25822026 PMCID: PMC4442542 DOI: 10.1128/jvi.00395-15] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Accepted: 03/03/2015] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Bluetongue virus (BTV) causes bluetongue, a major hemorrhagic disease of ruminants. In order to investigate the molecular determinants of BTV virulence, we used a BTV8 strain minimally passaged in tissue culture (termed BTV8L in this study) and a derivative strain passaged extensively in tissue culture (BTV8H) in in vitro and in vivo studies. BTV8L was pathogenic in both IFNAR(-/-) mice and in sheep, while BTV8H was attenuated in both species. To identify genetic changes which led to BTV8H attenuation, we generated 34 reassortants between BTV8L and BTV8H. We found that partial attenuation of BTV8L in IFNAR(-/-) mice was achieved by simply replacing genomic segment 2 (Seg2, encoding VP2) or Seg10 (encoding NS3) with the BTV8H homologous segments. Fully attenuated viruses required at least two genome segments from BTV8H, including Seg2 with either Seg1 (encoding VP1), Seg6 (encoding VP6 and NS4), or Seg10 (encoding NS3). Conversely, full reversion of virulence of BTV8H required at least five genomic segments of BTV8L. We also demonstrated that BTV8H acquired an increased affinity for glycosaminoglycan receptors during passaging in cell culture due to mutations in its VP2 protein. Replication of BTV8H was relatively poor in interferon (IFN)-competent primary ovine endothelial cells compared to replication of BTV8L, and this phenotype was determined by several viral genomic segments, including Seg4 and Seg9. This study demonstrated that multiple viral proteins contribute to BTV8 virulence. VP2 and NS3 are primary determinants of BTV pathogenesis, but VP1, VP5, VP4, VP6, and VP7 also contribute to virulence. IMPORTANCE Bluetongue is one of the major infectious diseases of ruminants, and it is listed as a notifiable disease by the World Organization for Animal Health (OIE). The clinical outcome of BTV infection varies considerably and depends on environmental and host- and virus-specific factors. Over the years, BTV serotypes/strains with various degrees of virulence (including nonpathogenic strains) have been described in different geographical locations. However, no data are available to correlate the BTV genotype to virulence. This study shows that BTV virulence is determined by different viral genomic segments. The data obtained will help to characterize thoroughly the pathogenesis of bluetongue. The possibility to determine the pathogenicity of virus isolates on the basis of their genome sequences will help in the design of control strategies that fit the risk posed by new emerging BTV strains.
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Stewart ME, Roy P. Structure-based identification of functional residues in the nucleoside-2'-O-methylase domain of Bluetongue virus VP4 capping enzyme. FEBS Open Bio 2015; 5:138-46. [PMID: 25834778 PMCID: PMC4359970 DOI: 10.1016/j.fob.2015.02.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2014] [Revised: 01/29/2015] [Accepted: 02/18/2015] [Indexed: 11/26/2022] Open
Abstract
Bluetongue virus (BTV) encodes a single capping protein, VP4, which catalyzes all reactions required to generate cap1 structures on nascent viral transcripts. Further, structural analysis by X-ray crystallography indicated each catalytic reaction is arranged as a discrete domain, including a nucleoside-2'-O-methyltransferase (2'-O MTase). In this study, we have exploited the structural information to identify the residues that are important for the catalytic activity of 2'-O MTase of VP4 and their influence on BTV replication. The effect of these mutations on GMP binding, guanylyltransferase (GTase) and methylase activities were analysed by a series of in vitro biochemical assays using recombinant mutant proteins; subsequently their effects on virus replication were assessed by introducing the same mutations in replicating viral genome using a reverse genetics system. Our data showed that single substitution mutations in the catalytic tetrad K-D-K-E were sufficient to abolish 2'-O MTase activity in vitro and to completely abrogate BTV replication in cells; although these mutants retained the upstream GMP binding, GTase and guanine-N7-methyltransferase activities. Mutations of the surrounding substrate-binding pocket (predicted to recruit cap0) had variable effects on in vitro VP4 capping activity. Only triple but not single substitution mutations of these residues in genome resulted in reduced virus replication kinetics. This is the first report investigating the importance of 2'-O MTase function for any member of the Reoviridae and highlights the significance of K-D-K-E tetrad and surrounding residues for the efficiency of 2'-O MTase activity and in turn, for virus fitness.
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Key Words
- 2′-O MT, nucleoside-2′-O-methyltransferase domain
- 2′-O MTase, nucleoside-2′-O-methyltransferase
- 2′-O-methyltransferase
- AdoMet, S-adenosyl methionine
- BSR4, BHK-21 sub-clone expressing VP4
- BTV
- BTV, Bluetongue virus
- Capping enzyme
- GTase, guanylyltransferase
- JEV, Japanese encephalitis virus
- Mutagenesis
- N7MTase, guanine-N7-methyltransferase
- PC, polymerase complex
- VSV, vesicular stomatitis virus
- WNV, West Nile virus
- m7, methyl group associated with m7G
- m7G, 7-methylguanosine
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Affiliation(s)
| | - Polly Roy
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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Biswas P, Kundu A, Ghosh AK. Genome segment 4 of Antheraea mylitta cytoplasmic polyhedrosis virus encodes RNA triphosphatase and methyltransferases. J Gen Virol 2014; 96:95-105. [PMID: 25228490 DOI: 10.1099/vir.0.069716-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Cloning and sequencing of Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV) genome segment S4 showed that it consists of 3410 nt with a single ORF of 1110 aa which could encode a protein of ~127 kDa (p127). Bioinformatics analysis showed the presence of a 5' RNA triphosphatase (RTPase) domain (LRDR), a S-adenosyl-l-methionine (SAM)-binding (GxGxG) motif and the KDKE tetrad of 2'-O-methyltransferase (MTase), which suggested that S4 may encode RTPase and MTase. The ORF of S4 was expressed in Escherichia coli as a His-tagged fusion protein and purified by nickel-nitrilotriacetic acid affinity chromatography. Biochemical analysis of recombinant p127 showed its RTPase as well as SAM-dependent guanine N(7)-and ribose 2'-O-MTase activities. A MTase assay using in vitro transcribed AmCPV S2 RNA having a 5' G*pppG end showed that guanine N(7) methylation occurred prior to the ribose 2'-O methylation to yield a m(7)GpppG/m(7)GpppGm RNA cap. Mutagenesis of the SAM-binding (GxGxG) motif (G831A) completely abolished N(7)- and 2'-O-MTase activities, indicating the importance of these residues for capping. From the kinetic analysis, the Km values of N(7)-MTase for SAM and RNA were calculated as 4.41 and 0.39 µM, respectively. These results suggested that AmCPV S4-encoded p127 catalyses RTPase and two cap methylation reactions for capping the 5' end of viral RNA.
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Affiliation(s)
- Poulomi Biswas
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Anirban Kundu
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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Bluetongue virus capsid assembly and maturation. Viruses 2014; 6:3250-70. [PMID: 25196482 PMCID: PMC4147694 DOI: 10.3390/v6083250] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2014] [Revised: 07/08/2014] [Accepted: 07/15/2014] [Indexed: 01/09/2023] Open
Abstract
Maturation is an intrinsic phase of the viral life cycle and is often intertwined with egress. In this review we focus on orbivirus maturation by using Bluetongue virus (BTV) as a representative. BTV, a member of the genus Orbivirus within the family Reoviridae, has over the last three decades been subjected to intense molecular study and is thus one of the best understood viruses. BTV is a non-enveloped virus comprised of two concentric protein shells that encapsidate 10 double-stranded RNA genome segments. Upon cell entry, the outer capsid is shed, releasing the core which does not disassemble into the cytoplasm. The polymerase complex within the core then synthesizes transcripts from each genome segment and extrudes these into the cytoplasm where they act as templates for protein synthesis. Newly synthesized ssRNA then associates with the replicase complex prior to encapsidation by inner and outer protein layers of core within virus-triggered inclusion bodies. Maturation of core occurs outside these inclusion bodies (IBs) via the addition of the outer capsid proteins, which appears to be coupled to a non-lytic, exocytic pathway during early infection. Similar to the enveloped viruses, BTV hijacks the exocytosis and endosomal sorting complex required for trafficking (ESCRT) pathway via a non-structural glycoprotein. This exquisitely detailed understanding is assembled from a broad array of assays, spanning numerous and diverse in vitro and in vivo studies. Presented here are the detailed insights of BTV maturation and egress.
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Biswas P, Kundu A, Ghosh AK. Genome segment 5 of Antheraea mylitta cytoplasmic polyhedrosis virus encodes a bona fide guanylyltransferase. Virol J 2014; 11:53. [PMID: 24649879 PMCID: PMC4000049 DOI: 10.1186/1743-422x-11-53] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2013] [Accepted: 03/10/2014] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Antheraea mylitta cytoplasmic polyhedrosis virus (AmCPV), a cypovirus of Reoviridae family, infects non mulberry Indian silk worm, Antheraea mylitta, and contains eleven segmented double stranded RNA in its genome (S1-S11). Some of its genome segments (S1-S3, and S6-S11) have been previously characterized but genome segment encoding the viral guanylyltransferase which helps in RNA capping has not been characterized. RESULTS In this study genome segment 5 (S5) of AmCPV was converted to cDNA, cloned and sequenced. S5 consisted of 2180 nucleotides, with one long ORF of 1818 nucleotides and could encode a protein of 606 amino acids with molecular mass of ~65 kDa (p65). Bioinformatics analysis showed presence of KLRS and HxnH motifs as observed in some other reoviral guanylyltransferase and suggests that S5 may encodes viral guanylyltransferase. The ORF of S5 was expressed in E. coli as 65 kDa his tagged fusion protein, purified through Ni-NTA chromatography and polyclonal antibody was raised. Immunoblot analysis of virion particles with the purified antibody showed specific immunoreactive band and suggests p65 as a viral structural protein. Functional analysis showed that recombinant p65 possesses guanylyltransferase activity, and transfers GMP moiety to the 5' diphosphate (A/G) ended viral RNA after the formation of p65-GMP complex for capping. Kinetic analysis showed K(m) of this enzyme for GTP and RNA was 34.24 uM and 98.35 nM, respectively. Site directed mutagenesis at K21A in KLRS motif, and H93A or H105A in HxnH motif completely abolished the autoguanylylation activity and indicates importance of these residues at these sites. Thermodynamic analysis showed p65-GTP interaction was primarily driven by enthalpy (ΔH = -399.1 ± 4.1 kJ/mol) whereas the p65-RNA interaction by favorable entropy (0.043 ± 0.0049 kJ/ mol). CONCLUSION Viral capping enzymes play a critical role in the post transcriptional or post replication modification in case of RNA virus. Our results of cloning, sequencing and functional analysis of AmCPV S5 indicates that S5 encoded p65 through its guanylyltransferase activity can transfer guanine residue to the 5' end of viral RNA for capping. Further studies will help to understand complete capping process of cypoviral RNA during viral replication within the viral capsid.
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Affiliation(s)
- Poulomi Biswas
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Anirban Kundu
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
| | - Ananta Kumar Ghosh
- Department of Biotechnology, Indian Institute of Technology Kharagpur, Kharagpur 721302, India
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Coetzee P, Van Vuuren M, Stokstad M, Myrmel M, van Gennip RGP, van Rijn PA, Venter EH. Viral replication kinetics and in vitro cytopathogenicity of parental and reassortant strains of bluetongue virus serotype 1, 6 and 8. Vet Microbiol 2014; 171:53-65. [PMID: 24685608 DOI: 10.1016/j.vetmic.2014.03.006] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2013] [Revised: 02/19/2014] [Accepted: 03/03/2014] [Indexed: 01/16/2023]
Abstract
Bluetongue virus (BTV), a segmented dsRNA virus, is the causative agent of bluetongue (BT), an economically important viral haemorrhagic disease of ruminants. Bluetongue virus can exchange its genome segments in mammalian or insect cells that have been co-infected with more than one strain of the virus. This process, may potentially give rise to the generation of novel reassortant strains that may differ from parental strains in regards to their phenotypic characteristics. To investigate the potential effects of reassortment on the virus' phenotype, parental as well as reassortant strains of BTV serotype 1, 6, 8, that were derived from attenuated and wild type strains by reverse genetics, were studied in vitro for their virus replication kinetics and cytopathogenicity in mammalian (Vero) cell cultures. The results indicate that genetic reassortment can affect viral replication kinetics, the cytopathogenicity and extent/mechanism of cell death in infected cell cultures. In particular, some reassortants of non-virulent vaccine (BTV-1 and BTV-6) and virulent field origin (BTV-8) demonstrate more pronounced cytopathic effects compared to their parental strains. Some reassortant strains in addition replicated to high titres in vitro despite being composed of genome segments from slow and fast replicating parental strains. The latter result may have implications for the level of viraemia in the mammalian host and subsequent uptake and transmission of reassortant strains (and their genome segments) by Culicoides vectors. Increased rates of CPE induction could further suggest a higher virulence for reassortant strains in vivo. Overall, these findings raise questions in regards to the use of modified-live virus (MLV) vaccines and risk of reassortment in the field. To further address these questions, additional experimental infection studies using insects and/or animal models should be conducted, to determine whether these results have significant implications in vivo.
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Affiliation(s)
- Peter Coetzee
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, Pretoria 0110, South Africa; Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 8146, 0033 Oslo, Norway.
| | - Moritz Van Vuuren
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, Pretoria 0110, South Africa.
| | - Maria Stokstad
- Department of Production Animal Clinical Sciences, Norwegian University of Life Sciences, P.O. Box 8146, 0033 Oslo, Norway.
| | - Mette Myrmel
- Department of Food Safety and Infection Biology, Norwegian University of Life Sciences, P.O. Box 8146, 0033 Oslo, Norway.
| | - René G P van Gennip
- Department of Virology, Central Veterinary Institute of Wageningen University, P.O. Box 65, 8200 AB, Lelystad, The Netherlands.
| | - Piet A van Rijn
- Department of Virology, Central Veterinary Institute of Wageningen University, P.O. Box 65, 8200 AB, Lelystad, The Netherlands; Department of Biochemistry, Centre for Human Metabonomics, North-West University, Private Bag X6001, Potchefstroom 2520, South Africa.
| | - Estelle H Venter
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Private Bag X04, Onderstepoort, Pretoria 0110, South Africa.
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The molecular biology of Bluetongue virus replication. Virus Res 2013; 182:5-20. [PMID: 24370866 DOI: 10.1016/j.virusres.2013.12.017] [Citation(s) in RCA: 67] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2013] [Revised: 12/10/2013] [Accepted: 12/11/2013] [Indexed: 01/17/2023]
Abstract
The members of Orbivirus genus within the Reoviridae family are arthropod-borne viruses which are responsible for high morbidity and mortality in ruminants. Bluetongue virus (BTV) which causes disease in livestock (sheep, goat, cattle) has been in the forefront of molecular studies for the last three decades and now represents the best understood orbivirus at a molecular and structural level. The complex nature of the virion structure has been well characterised at high resolution along with the definition of the virus encoded enzymes required for RNA replication; the ordered assembly of the capsid shell as well as the protein and genome sequestration required for it; and the role of host proteins in virus entry and virus release. More recent developments of Reverse Genetics and Cell-Free Assembly systems have allowed integration of the accumulated structural and molecular knowledge to be tested at meticulous level, yielding higher insight into basic molecular virology, from which the rational design of safe efficacious vaccines has been possible. This article is centred on the molecular dissection of BTV with a view to understanding the role of each protein in the virus replication cycle. These areas are important in themselves for BTV replication but they also indicate the pathways that related viruses, which includes viruses that are pathogenic to man and animals, might also use providing an informed starting point for intervention or prevention.
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Abstract
The replication mechanism of bluetongue virus (BTV) has been studied by an in vivo reverse genetics (RG) system identifying the importance of certain BTV proteins for primary replication of the virus. However, a unique in vitro cell-free virus assembly system was subsequently developed, showing that it did not require the same set of viral components, which is indicative of differences in these two systems. Here, we studied the in vivo primary replicase complex more in-depth to determine the minimum components of the complex. We showed that while NS2 is an essential component of the primary replication stage during BTV infection, NS1 is not an essential component but may play a role in enhancing BTV protein synthesis. Furthermore, we demonstrated that VP7, a major structural protein of the inner core, is not required for primary replication but appears to stabilize the replicase complex. In contrast, VP3, the other major structural core protein, is an essential component of the complex, together with the three minor enzymatic proteins (VP1, VP4, and VP6) of the core. In addition, our data have demonstrated that the smallest minor protein, VP6, which is known to possess an RNA-dependent helicase activity, may also act as an RNA translocator during assembly of the primary replicase complex.
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Boyce M, Celma CCP, Roy P. Bluetongue virus non-structural protein 1 is a positive regulator of viral protein synthesis. Virol J 2012; 9:178. [PMID: 22931514 PMCID: PMC3479040 DOI: 10.1186/1743-422x-9-178] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2011] [Accepted: 08/24/2012] [Indexed: 11/29/2022] Open
Abstract
Background Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus of the Reoviridae family, which encodes its genes in ten linear dsRNA segments. BTV mRNAs are synthesised by the viral RNA-dependent RNA polymerase (RdRp) as exact plus sense copies of the genome segments. Infection of mammalian cells with BTV rapidly replaces cellular protein synthesis with viral protein synthesis, but the regulation of viral gene expression in the Orbivirus genus has not been investigated. Results Using an mRNA reporter system based on genome segment 10 of BTV fused with GFP we identify the protein characteristic of this genus, non-structural protein 1 (NS1) as sufficient to upregulate translation. The wider applicability of this phenomenon among the viral genes is demonstrated using the untranslated regions (UTRs) of BTV genome segments flanking the quantifiable Renilla luciferase ORF in chimeric mRNAs. The UTRs of viral mRNAs are shown to be determinants of the amount of protein synthesised, with the pre-expression of NS1 increasing the quantity in each case. The increased expression induced by pre-expression of NS1 is confirmed in virus infected cells by generating a replicating virus which expresses the reporter fused with genome segment 10, using reverse genetics. Moreover, NS1-mediated upregulation of expression is restricted to mRNAs which lack the cellular 3′ poly(A) sequence identifying the 3′ end as a necessary determinant in specifically increasing the translation of viral mRNA in the presence of cellular mRNA. Conclusions NS1 is identified as a positive regulator of viral protein synthesis. We propose a model of translational regulation where NS1 upregulates the synthesis of viral proteins, including itself, and creates a positive feedback loop of NS1 expression, which rapidly increases the expression of all the viral proteins. The efficient translation of viral reporter mRNAs among cellular mRNAs can account for the observed replacement of cellular protein synthesis with viral protein synthesis during infection.
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Affiliation(s)
- Mark Boyce
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
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Coetzee P, Van Vuuren M, Stokstad M, Myrmel M, Venter EH. Bluetongue virus genetic and phenotypic diversity: towards identifying the molecular determinants that influence virulence and transmission potential. Vet Microbiol 2012; 161:1-12. [PMID: 22835527 DOI: 10.1016/j.vetmic.2012.07.007] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2012] [Revised: 06/22/2012] [Accepted: 07/02/2012] [Indexed: 12/23/2022]
Abstract
Bluetongue virus (BTV) is the prototype member of the Orbivirus genus in the family Reoviridae and is the aetiological agent of the arthropod transmitted disease bluetongue (BT) that affects both ruminant and camelid species. The disease is of significant global importance due to its economic impact and effect on animal welfare. Bluetongue virus, a dsRNA virus, evolves through a process of quasispecies evolution that is driven by genetic drift and shift as well as intragenic recombination. Quasispecies evolution coupled with founder effect and evolutionary selective pressures has over time led to the establishment of genetically distinct strains of the virus in different epidemiological systems throughout the world. Bluetongue virus field strains may differ substantially from each other with regards to their phenotypic properties (i.e. virulence and/or transmission potential). The intrinsic molecular determinants that influence the phenotype of BTV have not clearly been characterized. It is currently unclear what contribution each of the viral genome segments have in determining the phenotypic properties of the virus and it is also unknown how genetic variability in the individual viral genes and their functional domains relate to differences in phenotype. In order to understand how genetic variation in particular viral genes could potentially influence the phenotypic properties of the virus; a closer understanding of the BTV virion, its encoded proteins and the evolutionary mechanisms that shape the diversity of the virus is required. This review provides a synopsis of these issues and highlights some of the studies that have been conducted on BTV and the closely related African horse sickness virus (AHSV) that have contributed to ongoing attempts to identify the molecular determinants that influence the virus' phenotype. Different strategies that can be used to generate BTV mutants in vitro and methods through which the causality between particular genetic modifications and changes in phenotype may be determined are also described. Finally examples are highlighted where a clear understanding of the molecular determinants that influence the phenotype of the virus may have contributed to risk assessment and mitigation strategies during recent outbreaks of BT in Europe.
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Affiliation(s)
- Peter Coetzee
- Department of Veterinary Tropical Diseases, University of Pretoria, Private Bag X04, Onderstepoort, Pretoria, 0110, South Africa.
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Trask SD, Ogden KM, Patton JT. Interactions among capsid proteins orchestrate rotavirus particle functions. Curr Opin Virol 2012; 2:373-9. [PMID: 22595300 DOI: 10.1016/j.coviro.2012.04.005] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Revised: 04/23/2012] [Accepted: 04/24/2012] [Indexed: 11/16/2022]
Abstract
Rotaviruses are members of the Reoviridae family of non-enveloped viruses and important etiologic agents of acute gastroenteritis in infants and young children. In recent years, high-resolution structures of triple-layered rotavirus virions and the constituent proteins have provided valuable insights into functions. Of note, structural studies have revealed the position of the viral RNA-dependent RNA polymerase, VP1, within the inner capsid, which in turn provides clues about the location of the viral capping machinery and the route of viral transcript egress. Mechanisms by which the viral spike protein, VP4, mediates receptor binding and membrane penetration have also been aided by high-resolution structural studies. Future work may serve to fill the remaining gaps in understanding of rotavirus particle structure and function.
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Affiliation(s)
- Shane D Trask
- Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-8026, USA
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Assembly of Large Icosahedral Double-Stranded RNA Viruses. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 726:379-402. [DOI: 10.1007/978-1-4614-0980-9_17] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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Decroly E, Ferron F, Lescar J, Canard B. Conventional and unconventional mechanisms for capping viral mRNA. Nat Rev Microbiol 2011; 10:51-65. [PMID: 22138959 PMCID: PMC7097100 DOI: 10.1038/nrmicro2675] [Citation(s) in RCA: 340] [Impact Index Per Article: 26.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
mRNAs are protected at their 5′ ends by a cap structure consisting of an N7-methylated GTP molecule linked to the first transcribed nucleotide by a 5′–5′ triphosphate bond. The cap structure is essential for RNA splicing, export and stability, and allows the ribosomal complex to recognize mRNAs and ensure their efficient translation. Uncapped RNA molecules are degraded in cytoplasmic granular compartments called processing bodies and may be detected as 'non-self' by the host cell, triggering antiviral innate immune responses through the production of interferons. Conventional RNA capping (that is, of mRNAs from the host cell and from DNA viruses) requires hydrolysis of the 5′ γ-phosphate of RNA by an RNA triphosphatase, transfer of a GMP molecule onto the 5′-end of RNA by a guanylyltransferase, and methylation of this guanosine by an (guanine-N7)-methyltransferase. Subsequent methylations on the first and second transcribed nucleotides by (nucleoside-2′-O)-methyltransferases form cap-1 and cap-2 structures. Viruses have evolved highly diverse capping mechanisms to acquire cap structures using their own or cellular capping machineries, or by stealing cap structures from cellular mRNAs. Virally encoded RNA-capping machineries are diverse in terms of their genetic components, protein domain organization, enzyme structures, and reaction mechanisms and pathways, making viral RNA capping an attractive target for antiviral-drug design.
Capping the 5′ end of eukaryotic mRNAs with a 7-methylguanosine moiety enables efficient splicing, nuclear export and translation of mRNAs, and also limits their degradation by cellular exonucleases. Here, Canard and colleagues describe how viruses synthesize their own mRNA cap structures or steal them from host mRNAs, allowing efficient synthesis of viral proteins and avoidance of host innate immune responses. In the eukaryotic cell, capping of mRNA 5′ ends is an essential structural modification that allows efficient mRNA translation, directs pre-mRNA splicing and mRNA export from the nucleus, limits mRNA degradation by cellular 5′–3′ exonucleases and allows recognition of foreign RNAs (including viral transcripts) as 'non-self'. However, viruses have evolved mechanisms to protect their RNA 5′ ends with either a covalently attached peptide or a cap moiety (7-methyl-Gppp, in which p is a phosphate group) that is indistinguishable from cellular mRNA cap structures. Viral RNA caps can be stolen from cellular mRNAs or synthesized using either a host- or virus-encoded capping apparatus, and these capping assemblies exhibit a wide diversity in organization, structure and mechanism. Here, we review the strategies used by viruses of eukaryotic cells to produce functional mRNA 5′-caps and escape innate immunity.
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Affiliation(s)
- Etienne Decroly
- Centre National de Recherche Scientifique and Aix-Marseille Université, UMR 6098, Architecture et Fonction des Macromolécules Biologiques, 163 avenue de Luminy, 13288 Marseille cedex 09, France
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Li JKK. Oncolytic bluetongue viruses: promise, progress, and perspectives. Front Microbiol 2011; 2:46. [PMID: 21747785 PMCID: PMC3128942 DOI: 10.3389/fmicb.2011.00046] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2010] [Accepted: 03/01/2011] [Indexed: 11/26/2022] Open
Abstract
Humans are sero-negative toward bluetongue viruses (BTVs) since BTVs do not infect normal human cells. Infection and selective degradation of several human cancer cell lines but not normal ones by five US BTV serotypes have been investigated. We determined the susceptibilities of many normal and human cancer cells to BTV infections and made comparative kinetic analyses of their cytopathic effects, survival rates, ultra-structural changes, cellular apoptosis and necrosis, cell cycle arrest, cytokine profiles, viral genome, mRNAs, and progeny titers. The wild-type US BTVs, without any genetic modifications, could preferentially infect and degrade several types of human cancer cells but not normal cells. Their selective and preferential BTV-degradation of human cancer cells is viral dose–dependent, leading to effective viral replication, and induced apoptosis. Xenograft tumors in mice were substantially reduced by a single intratumoral BTV injection in initial in vivo experiments. Thus, wild-type BTVs, without genetic modifications, have oncolytic potentials. They represent an attractive, next generation of oncolytic viral approach for potential human cancer therapy combined with current anti-cancer agents and irradiation.
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Affiliation(s)
- Joseph K-K Li
- Department of Biology, Utah State University Logan, UT, USA
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Ghosh A, Lima CD. Enzymology of RNA cap synthesis. WILEY INTERDISCIPLINARY REVIEWS-RNA 2010; 1:152-72. [PMID: 21956912 DOI: 10.1002/wrna.19] [Citation(s) in RCA: 113] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The 5' guanine-N7 methyl cap is unique to cellular and viral messenger RNA (mRNA) and is the first co-transcriptional modification of mRNA. The mRNA cap plays a pivotal role in mRNA biogenesis and stability, and is essential for efficient splicing, mRNA export, and translation. Capping occurs by a series of three enzymatic reactions that results in formation of N7-methyl guanosine linked through a 5'-5' inverted triphosphate bridge to the first nucleotide of a nascent transcript. Capping of cellular mRNA occurs co-transcriptionally and in vivo requires that the capping apparatus be physically associated with the RNA polymerase II elongation complex. Certain capped mRNAs undergo further methylation to generate distinct cap structures. Although mRNA capping is conserved among viruses and eukaryotes, some viruses have adopted strategies for capping mRNA that are distinct from the cellular mRNA capping pathway.
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Affiliation(s)
- Agnidipta Ghosh
- Structural Biology Program, Sloan-Kettering Institute, New York, NY 10065, USA
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Bhattacharya B, Roy P. Role of lipids on entry and exit of bluetongue virus, a complex non-enveloped virus. Viruses 2010; 2:1218-1235. [PMID: 21994677 PMCID: PMC3187602 DOI: 10.3390/v2051218] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2010] [Revised: 05/04/2010] [Accepted: 05/11/2010] [Indexed: 11/16/2022] Open
Abstract
Non-enveloped viruses such as members of Picornaviridae and Reoviridae are assembled in the cytoplasm and are generally released by cell lysis. However, recent evidence suggests that some non-enveloped viruses exit from infected cells without lysis, indicating that these viruses may also utilize alternate means for egress. Moreover, it appears that complex, non-enveloped viruses such as bluetongue virus (BTV) and rotavirus interact with lipids during their entry process as well as with lipid rafts during the trafficking of newly synthesized progeny viruses. This review will discuss the role of lipids in the entry, maturation and release of non-enveloped viruses, focusing mainly on BTV.
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Affiliation(s)
| | - Polly Roy
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +44 (0)20 7927 2324; Fax: +44 (0)20 7927 2324
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In vitro reconstitution of SARS-coronavirus mRNA cap methylation. PLoS Pathog 2010; 6:e1000863. [PMID: 20421945 PMCID: PMC2858705 DOI: 10.1371/journal.ppat.1000863] [Citation(s) in RCA: 264] [Impact Index Per Article: 18.9] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2009] [Accepted: 03/18/2010] [Indexed: 01/17/2023] Open
Abstract
SARS-coronavirus (SARS-CoV) genome expression depends on the synthesis of a set of mRNAs, which presumably are capped at their 5' end and direct the synthesis of all viral proteins in the infected cell. Sixteen viral non-structural proteins (nsp1 to nsp16) constitute an unusually large replicase complex, which includes two methyltransferases putatively involved in viral mRNA cap formation. The S-adenosyl-L-methionine (AdoMet)-dependent (guanine-N7)-methyltransferase (N7-MTase) activity was recently attributed to nsp14, whereas nsp16 has been predicted to be the AdoMet-dependent (nucleoside-2'O)-methyltransferase. Here, we have reconstituted complete SARS-CoV mRNA cap methylation in vitro. We show that mRNA cap methylation requires a third viral protein, nsp10, which acts as an essential trigger to complete RNA cap-1 formation. The obligate sequence of methylation events is initiated by nsp14, which first methylates capped RNA transcripts to generate cap-0 (7Me)GpppA-RNAs. The latter are then selectively 2'O-methylated by the 2'O-MTase nsp16 in complex with its activator nsp10 to give rise to cap-1 (7Me)GpppA(2'OMe)-RNAs. Furthermore, sensitive in vitro inhibition assays of both activities show that aurintricarboxylic acid, active in SARS-CoV infected cells, targets both MTases with IC(50) values in the micromolar range, providing a validated basis for anti-coronavirus drug design.
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Abstract
Disease caused by flavivirus infections is an increasing world health problem. Flavivirus nonstructural protein 5 (NS5) possesses enzymatic activities required for capping and synthesis of the viral RNA genome and is essential for virus replication. NS5 is comprised of two domains. The N-terminal domain binds GTP and can perform two biochemically distinct methylation reactions required for RNA cap formation. The C-terminal domain contains RNA-dependent RNA polymerase activity. As such, NS5 is an interesting target against which antiviral drugs could be developed and research toward this goal has accelerated our understanding of NS5 structure and function in recent years. The production and purification of recombinant versions of either the full-length NS5 or the two individual NS5 domains has led to detailed enzymatic studies on NS5 and the determination of structures of the two NS5 domains. In turn, studies using a combination of structural, biochemical, and reverse genetic approaches are revealing how NS5 performs its multifunctional roles in genome replication. Aside from its localization in the membrane-bound replication complex, NS5 can be found free in the cytoplasm and for some flaviviruses in the nucleus of virus-infected cells. NS5 is phosphorylated which may potentially regulate NS5 function and trafficking. Recently, NS5 of a number of flaviviruses has been shown to interact with cellular pathways involved in the host immune response, suggesting that NS5 may play a role in viral pathogenesis. This chapter reviews recent advances in our understanding of the multifunctional roles played by NS5 in the virus lifecycle.
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Nomikou K, Dovas CΙ, Maan S, Anthony SJ, Samuel AR, Papanastassopoulou M, Maan NS, Mangana O, Mertens PPC. Evolution and phylogenetic analysis of full-length VP3 genes of Eastern Mediterranean bluetongue virus isolates. PLoS One 2009; 4:e6437. [PMID: 19649272 PMCID: PMC2713410 DOI: 10.1371/journal.pone.0006437] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2009] [Accepted: 05/02/2009] [Indexed: 11/19/2022] Open
Abstract
Bluetongue virus (BTV) is the ‘type’ species of the genus Orbivirus within the family Reoviridae. The BTV genome is composed of ten linear segments of double-stranded RNA (dsRNA), each of which codes for one of ten distinct viral proteins. Previous phylogenetic comparisons have evaluated variations in genome segment 3 (Seg-3) nucleotide sequence as way to identify the geographical origin (different topotypes) of BTV isolates. The full-length nucleotide sequence of genome Seg-3 was determined for thirty BTV isolates recovered in the eastern Mediterranean region, the Balkans and other geographic areas (Spain, India, Malaysia and Africa). These data were compared, based on molecular variability, positive-selection-analysis and maximum-likelihood phylogenetic reconstructions (using appropriate substitution models) to 24 previously published sequences, revealing their evolutionary relationships. These analyses indicate that negative selection is a major force in the evolution of BTV, restricting nucleotide variability, reducing the evolutionary rate of Seg-3 and potentially of other regions of the BTV genome. Phylogenetic analysis of the BTV-4 strains isolated over a relatively long time interval (1979–2000), in a single geographic area (Greece), showed a low level of nucleotide diversity, indicating that the virus can circulate almost unchanged for many years. These analyses also show that the recent incursions into south-eastern Europe were caused by BTV strains belonging to two different major-lineages: representing an ‘eastern’ (BTV-9, -16 and -1) and a ‘western’ (BTV-4) group/topotype. Epidemiological and phylogenetic analyses indicate that these viruses originated from a geographic area to the east and southeast of Greece (including Cyprus and the Middle East), which appears to represent an important ecological niche for the virus that is likely to represent a continuing source of future BTV incursions into Europe.
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Affiliation(s)
- Kyriaki Nomikou
- Arbovirus Molecular Research Group, Department of vector borne diseases, Institute for Animal Health, Pirbright Laboratory, Woking, Surrey, United Kingdom
- Virus Laboratory, Institute of Infectious and Parasitic Diseases, Ministry of Rural Development and Food, Athens, Greece
| | - Chrysostomos Ι. Dovas
- Department of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Sushila Maan
- Arbovirus Molecular Research Group, Department of vector borne diseases, Institute for Animal Health, Pirbright Laboratory, Woking, Surrey, United Kingdom
| | - Simon J. Anthony
- Wildlife Disease Laboratory, San Diego Zoo Conservation Research, Escondido, California, United States of America
| | - Alan R. Samuel
- Arbovirus Molecular Research Group, Department of vector borne diseases, Institute for Animal Health, Pirbright Laboratory, Woking, Surrey, United Kingdom
| | - Maria Papanastassopoulou
- Department of Microbiology and Infectious Diseases, Faculty of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece
| | - Narender S. Maan
- Arbovirus Molecular Research Group, Department of vector borne diseases, Institute for Animal Health, Pirbright Laboratory, Woking, Surrey, United Kingdom
| | - Olga Mangana
- Virus Laboratory, Institute of Infectious and Parasitic Diseases, Ministry of Rural Development and Food, Athens, Greece
| | - Peter P. C. Mertens
- Arbovirus Molecular Research Group, Department of vector borne diseases, Institute for Animal Health, Pirbright Laboratory, Woking, Surrey, United Kingdom
- * E-mail:
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Anthony SJ, Maan N, Maan S, Sutton G, Attoui H, Mertens PPC. Genetic and phylogenetic analysis of the core proteins VP1, VP3, VP4, VP6 and VP7 of epizootic haemorrhagic disease virus (EHDV). Virus Res 2009; 145:187-99. [PMID: 19632280 DOI: 10.1016/j.virusres.2009.07.011] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2009] [Revised: 07/15/2009] [Accepted: 07/16/2009] [Indexed: 11/29/2022]
Abstract
The core proteins of epizootic haemorrhagic disease virus (EHDV) have important roles to perform in maintaining the structure and function of the virus. A complete genetic and phylogenetic analysis was therefore performed on these proteins (and the genes that code for them) to allow comparison of the selective pressures acting on each. Accession numbers, gene and protein sizes, ORF positions, G+C contents, terminal hexanucleotides, start and stop codons and phylogenetic relationships are all presented. The inner core proteins (VP1, VP3, VP4 and VP6) were characterised by high levels of sequence conservation, and the ability to topotype isolates very strongly into eastern or western groups. This is particularly evident in genome segment 9 (VP6) which exists as two different sized homologues. VP7 did not topotype, but rather exhibited a more random, radial phylogeny suggestive of genetic drift. With the exception of VP6, all of the core proteins also showed high numbers of synonymous mutations in the third base position, suggesting they have been evolving for a long period of time. Interestingly, VP6 did not show this, and possible reasons for this are discussed.
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Affiliation(s)
- S J Anthony
- Vector-borne Diseases Program, Institute for Animal Health, Ash Road, Pirbright, Surrey GU24 0NF, United Kingdom.
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38
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Bluetongue virus VP6 acts early in the replication cycle and can form the basis of chimeric virus formation. J Virol 2009; 83:8842-8. [PMID: 19553329 DOI: 10.1128/jvi.00465-09] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
A minor core protein, VP6, of bluetongue virus (BTV) possesses nucleoside triphosphatase, RNA binding, and helicase activities. Although the enzymatic functions of VP6 have been documented in vitro using purified protein, its definitive role in BTV replication remains unclear. In this study, using a recently developed T7 transcript-based reverse genetics system for BTV, we examined the importance of VP6 in virus replication. We show that VP6 is active early in replication, consistent with a role as part of the transcriptase or packaging complex, and that its action can be provided in trans by a newly developed complementary cell line. Furthermore, the genomic segment encoding VP6 was mutated to reveal the cis-acting sequences required for replication or packaging, which subsequently enabled the construction of a chimeric BTV expressing enhanced green fluorescent protein. These data confirm that one of the 10 genome segments of BTV can be replaced with a chimeric RNA containing the essential packaging and replication signals of BTV and the coding sequence of a foreign gene.
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Abstract
Bluetongue is a vector-borne viral disease of ruminants that is endemic in tropical and subtropical countries. Since 1998 the virus has also appeared in Europe. Partly due to the seriousness of the disease, bluetongue virus (BTV), a member of genus Orbivirus within the family Reoviridae, has been a subject of intense molecular study for the last three decades and is now one of the best understood viruses at the molecular and structural levels. BTV is a complex non-enveloped virus with seven structural proteins arranged in two capsids and a genome of ten double-stranded (ds) RNA segments. Shortly after cell entry, the outer capsid is lost to release an inner capsid (the core) which synthesizes capped mRNAs from each genomic segment, extruding them into the cytoplasm. This requires the efficient co-ordination of a number of enzymes, including helicase, polymerase and RNA capping activities. This review will focus on our current understanding of these catalytic proteins as derived from the use of recombinant proteins, combined with functional assays and the in vitro reconstitution of the transcription/replication complex. In some cases, 3D structures have complemented this analysis to reveal the fine structural detail of these proteins. The combined activities of the core enzymes produce infectious transcripts necessary and sufficient to initiate BTV infection. Such infectious transcripts can now be synthesized wholly in vitro and, when introduced into cells by transfection, lead to the recovery of infectious virus. Future studies thus hold the possibility of analysing the consequence of mutation in a replicating virus system.
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Affiliation(s)
- Polly Roy
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
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Kroschewski H, Lim SP, Butcher RE, Yap TL, Lescar J, Wright PJ, Vasudevan SG, Davidson AD. Mutagenesis of the Dengue Virus Type 2 NS5 Methyltransferase Domain. J Biol Chem 2008; 283:19410-21. [DOI: 10.1074/jbc.m800613200] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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41
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Coronavirus nonstructural protein 16 is a cap-0 binding enzyme possessing (nucleoside-2'O)-methyltransferase activity. J Virol 2008; 82:8071-84. [PMID: 18417574 DOI: 10.1128/jvi.00407-08] [Citation(s) in RCA: 192] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The coronavirus family of positive-strand RNA viruses includes important pathogens of livestock, companion animals, and humans, including the severe acute respiratory syndrome coronavirus that was responsible for a worldwide outbreak in 2003. The unusually complex coronavirus replicase/transcriptase is comprised of 15 or 16 virus-specific subunits that are autoproteolytically derived from two large polyproteins. In line with bioinformatics predictions, we now show that feline coronavirus (FCoV) nonstructural protein 16 (nsp16) possesses an S-adenosyl-L-methionine (AdoMet)-dependent RNA (nucleoside-2'O)-methyltransferase (2'O-MTase) activity that is capable of cap-1 formation. Purified recombinant FCoV nsp16 selectively binds to short capped RNAs. Remarkably, an N7-methyl guanosine cap ((7Me)GpppAC(3-6)) is a prerequisite for binding. High-performance liquid chromatography analysis demonstrated that nsp16 mediates methyl transfer from AdoMet to the 2'O position of the first transcribed nucleotide, thus converting (7Me)GpppAC(3-6) into (7Me)GpppA(2')(O)(Me)C(3-6). The characterization of 11 nsp16 mutants supported the previous identification of residues K45, D129, K169, and E202 as the putative K-D-K-E catalytic tetrad of the enzyme. Furthermore, residues Y29 and F173 of FCoV nsp16, which may be the functional counterparts of aromatic residues involved in substrate recognition by the vaccinia virus MTase VP39, were found to be essential for both substrate binding and 2'O-MTase activity. Finally, the weak inhibition profile of different AdoMet analogues indicates that nsp16 has evolved an atypical AdoMet binding site. Our results suggest that coronavirus mRNA carries a cap-1, onto which 2'O methylation follows an order of events in which 2'O-methyl transfer must be preceded by guanine N7 methylation, with the latter step being performed by a yet-unknown N7-specific MTase.
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42
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Functional mapping of bluetongue virus proteins and their interactions with host proteins during virus replication. Cell Biochem Biophys 2008; 50:143-57. [PMID: 18299997 DOI: 10.1007/s12013-008-9009-4] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/16/2008] [Indexed: 10/22/2022]
Abstract
Bluetongue virus (BTV) is a double-stranded RNA (dsRNA) virus which is transmitted by blood-feeding gnats to wild and domestic ruminants, causing high morbidity and often high mortality. Partly due to this BTV has been in the forefront of molecular studies for last three decades and now represents one of the best understood viruses at the molecular and structural levels. BTV, like the other members of the Reoviridae family is a complex non-enveloped virus with seven structural proteins and a RNA genome consisting of 10 dsRNA segments of different sizes. In virus infected cells, three other virus encoded nonstructural proteins are synthesized. Significant recent advances have been made in understanding the structure-function relationships of BTV proteins and their interactions during virus assembly. By combining structural and molecular data it has been possible to make progress on the fundamental mechanisms used by the virus to invade, replicate in, and escape from, susceptible host cells. Data obtained from studies over a number of years have defined the key players in BTV entry, replication, assembly and egress. Specifically, it has been possible to determine the complex nature of the virion through three dimensional structure reconstructions; atomic structure of proteins and the internal capsid; the definition of the virus encoded enzymes required for RNA replication; the ordered assembly of the capsid shell and the protein sequestration required for it; and the role of three NS proteins in virus replication, assembly and release. Overall, this review demonstrates that the integration of structural, biochemical and molecular data is necessary to fully understand the assembly and replication of this complex RNA virus.
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43
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Sutton G, Grimes JM, Stuart DI, Roy P. Bluetongue virus VP4 is an RNA-capping assembly line. Nat Struct Mol Biol 2007; 14:449-51. [PMID: 17417654 DOI: 10.1038/nsmb1225] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2006] [Accepted: 03/05/2007] [Indexed: 11/09/2022]
Abstract
Eukaryotic organisms cap the 5' ends of their messenger RNAs by a series of four chemical reactions. Some viruses achieve this using a single molecule; the crystal structure of such an enzyme from bluetongue virus reveals an elongated modular architecture that provides a scaffold for an assemblage of active sites, two contributed by a domain of novel structure.
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Affiliation(s)
- Geoff Sutton
- Division of Structural Biology, The Wellcome Trust Centre for Human Genetics, University of Oxford, Roosevelt Drive, Headington, Oxford, OX3 7BN, UK
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Shen PC, Chiou YF, Liu HJ, Song CH, Su YP, Lee LH. Genetic variation of the lambdaA and lambdaC protein encoding genes of avian reoviruses. Res Vet Sci 2007; 83:394-402. [PMID: 17336355 DOI: 10.1016/j.rvsc.2007.01.002] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2005] [Revised: 12/19/2006] [Accepted: 01/03/2007] [Indexed: 11/20/2022]
Abstract
Sequence and phylogenetic analysis of lambdaA and lambdaC protein encoding genes of 12 avian reoviruses is described. The sequence of lambdaA possesses a variable region (residues 19-51) located within a conserved hydrophilic region (residues 1-110) and a C(2)H(2) zinc-binding motif (residues 182-202). lambdaC shows the two conserved K residues at positions 169 and 188 indicative of guanylyltransferase activity, an ATP/GTP-binding site motif A (residues 379-386), and a conserved S-adenosyl-l-methionine-binding motif (residues 822-830). Pairwise sequence comparisons show that the mean sequence identities of lambdaA encoding genes and lambdaA proteins are 92% and 98%, respectively, and those of lambdaC encoding genes and lambdaC proteins are 91% and 95%, respectively. Phylogenetic analysis of lambdaA and lambdaC encoding genes reveals that both encoding genes have diverged into three distinct lineages, respectively, and that there is no correlation between lineages and viral serotypes or pathotypes. Also, reassortment of gene segments L1 and L3 has been observed between viruses.
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Affiliation(s)
- Pin Chun Shen
- Department of Veterinary Medicine, National Chung Hsing University, Taichung 402, Taiwan
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45
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Supyani S, Hillman BI, Suzuki N. Baculovirus expression of the 11 mycoreovirus-1 genome segments and identification of the guanylyltransferase-encoding segment. J Gen Virol 2007; 88:342-350. [PMID: 17170467 DOI: 10.1099/vir.0.82318-0] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The type member Mycoreovirus 1 (MyRV-1) of a newly described genus, Mycoreovirus, isolated from a hypovirulent strain 9B21 of the chestnut blight fungus, has a genome composed of 11 dsRNA segments (S1-S11). All of the segments have single ORFs on their capped, positive-sense strands. Infection of insect cells by baculovirus recombinants carrying full-length cDNAs of S1-S11 resulted in overexpression of protein products of the expected sizes, based on their deduced amino acid sequences. This expression system was utilized to identify the S3-encoded protein (VP3) as a guanylyltransferase by an autoguanylylation assay, in which only VP3 was radiolabelled with [alpha-(32)P]GTP. A series of progressive N-terminal and C-terminal deletion mutants was made to localize the autoguanylylation-active site of VP3 to aa residues 133-667. Within this region, a sequence stretch (aa 170-250) with relatively high sequence similarity to homologues of two other mycoreoviruses and two coltiviruses was identified. Site-directed mutagenesis of conserved aa residues revealed that H233, H242, Y243, F244 and F246, but not K172 or K202, play critical roles in guanylyltransferase activities. Together with broader sequence alignments of 'turreted' reoviruses, these results supported the a/vxxHx(8)Hyf/lvf motif, originally noted for orthoreovirus and aquareoviruses, as an active site for guanylyltransferases of viruses within the Orthoreovirus, Aquareovirus, Cypovirus, Oryzavirus, Fijivirus, Coltivirus and Mycoreovirus genera, as well as for the proposed Dinovernavirus genus.
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Affiliation(s)
- S Supyani
- Agrivirology Laboratory, Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
| | - Bradley I Hillman
- Plant Biology and Pathology Department, Rutgers University, New Brunswick, NJ 08901-8520, USA
| | - Nobuhiro Suzuki
- Agrivirology Laboratory, Research Institute for Bioresources, Okayama University, Kurashiki, Okayama 710-0046, Japan
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46
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Abstract
Like other members of the Reoviridae, bluetongue virus faces the same constraints on structure and assembly that are imposed by a large dsRNA genome. However, since it is arthropod-transmitted, BTV must have assembly pathways that are sufficiently flexible to allow it to replicate in evolutionarily distant hosts. With this background, it is hardly surprising that BTV interacts with highly conserved cellular pathways during morphogenesis and trafficking. Indeed, recent studies have revealed striking parallels between the pathways involved in the entry and egress of nonenveloped BTV and those used by enveloped viruses. In addition, recent studies with the protein that is the major component of the BTV viroplasm have revealed how the assembly and, as importantly, the disassembly of this structure may be achieved. This is a first step towards resolving the interactions that occur in these virus 'assembly factories'. Overall, this review demonstrates that the integration of structural, biochemical and molecular data is necessary to fully understand the assembly and replication of this complex RNA virus.
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Affiliation(s)
- P Roy
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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47
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Abstract
X-ray and electron microscopy analysis of Bluetongue virus (BTV), the type species of the Orbivirus genus within the family Reoviridae, have revealed various aspects of the organisation and structure of the proteins that form the viral capsid. Orbiviruses have a segmented dsRNA genome, which imposes constraints on their structure and life cycle. The atomic structure of the BTV core particle, the key viral component which transcribes the viral mRNA within the cell cytoplasm, revealed the architecture and assembly of the major core proteins VP7 and VP3. In addition, these studies formed the basis for a plausible model for the organisation of the dsRNA viral genome and the arrangement of the viral transcriptase complex (composed of the RNA-dependent RNA polymerase, the viral capping enzyme and RNA helicase) that resides within the core particle. Electron cryo-microscopy of the viral particle has shown how the two viral proteins VP2 and VP5 are arranged to form the outer capsid, with distinct packing arrangements between them and the core protein VP7. By comparison of the outer capsid proteins of orbiviruses with those of other nonturreted members of the family Reoviridae, we are able to propose a more detailed model of these structures and possible mechanisms for cell entry. Further structural results are also discussed including the atomic structure of an N-terminal domain of nonstructural protein NS2, a protein involved in virus genome assembly and morphogenesis.
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Affiliation(s)
- D I Stuart
- Division of Structural Biology, The Henry Wellcome Building for Genomic Medicine, University of Oxford, Roosevelt Drive, Oxford OX3 7BN, UK.
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48
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Liuzzi M, Mason SW, Cartier M, Lawetz C, McCollum RS, Dansereau N, Bolger G, Lapeyre N, Gaudette Y, Lagacé L, Massariol MJ, Dô F, Whitehead P, Lamarre L, Scouten E, Bordeleau J, Landry S, Rancourt J, Fazal G, Simoneau B. Inhibitors of respiratory syncytial virus replication target cotranscriptional mRNA guanylylation by viral RNA-dependent RNA polymerase. J Virol 2005; 79:13105-15. [PMID: 16189012 PMCID: PMC1235819 DOI: 10.1128/jvi.79.20.13105-13115.2005] [Citation(s) in RCA: 93] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Respiratory syncytial virus (RSV) is a major cause of respiratory illness in infants, immunocompromised patients, and the elderly. New antiviral agents would be important tools in the treatment of acute RSV disease. RSV encodes its own RNA-dependent RNA polymerase that is responsible for the synthesis of both genomic RNA and subgenomic mRNAs. The viral polymerase also cotranscriptionally caps and polyadenylates the RSV mRNAs at their 5' and 3' ends, respectively. We have previously reported the discovery of the first nonnucleoside transcriptase inhibitor of RSV polymerase through high-throughput screening. Here we report the design of inhibitors that have improved potency both in vitro and in antiviral assays and that also exhibit activity in a mouse model of RSV infection. We have isolated virus with reduced susceptibility to this class of inhibitors. The mutations conferring resistance mapped to a novel motif within the RSV L gene, which encodes the catalytic subunit of RSV polymerase. This motif is distinct from the catalytic region of the L protein and bears some similarity to the nucleotide binding domain within nucleoside diphosphate kinases. These findings lead to the hypothesis that this class of inhibitors may block synthesis of RSV mRNAs by inhibiting guanylylation of viral transcripts. We show that short transcripts produced in the presence of inhibitor in vitro do not contain a 5' cap but, instead, are triphosphorylated, confirming this hypothesis. These inhibitors constitute useful tools for elucidating the molecular mechanism of RSV capping and represent valid leads for the development of novel anti-RSV therapeutics.
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Affiliation(s)
- Michel Liuzzi
- Department of Biological Sciences, Boehringer Ingelheim (Canada) Ltd., Laval, Quebec.
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49
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Roy P. Bluetongue virus proteins and particles and their role in virus entry, assembly, and release. Adv Virus Res 2005; 64:69-123. [PMID: 16139593 DOI: 10.1016/s0065-3527(05)64004-3] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Polly Roy
- London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
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50
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Modrof J, Lymperopoulos K, Roy P. Phosphorylation of bluetongue virus nonstructural protein 2 is essential for formation of viral inclusion bodies. J Virol 2005; 79:10023-31. [PMID: 16014962 PMCID: PMC1181561 DOI: 10.1128/jvi.79.15.10023-10031.2005] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In bluetongue virus (BTV)-infected cells, large cytoplasmic aggregates are formed, termed viral inclusion bodies (VIBs), which are believed to be the sites of viral replication and morphogenesis. The BTV nonstructural protein NS2 is the major component of VIBs. NS2 undergoes intracellular phosphorylation and possesses a strong single-stranded RNA binding activity. By changing phosphorylated amino acids to alanines and aspartates, we have mapped the phosphorylated sites of NS2 to two serine residues at positions 249 and 259. Since both of these serines are within the context of protein kinase CK2 recognition signals, we have further examined if CK2 is involved in NS2 phosphorylation by both intracellular colocalization and an in vitro phosphorylation assay. In addition, we have utilized the NS2 mutants to determine the role of phosphorylation on NS2 activities. The data obtained demonstrate that NS2 phosphorylation is not necessary either for its RNA binding properties or for its ability to interact with the viral polymerase VP1. However, phosphorylated NS2 exhibited VIB formation while unmodified NS2 failed to assemble as VIBs although smaller oligomeric forms of NS2 were readily formed. Our data reveal that NS2 phosphorylation controls VIBs formation consistent with a model in which NS2 provides the matrix for viral assembly.
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Affiliation(s)
- Jens Modrof
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, UK
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