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Xia X, Sung PY, Martynowycz MW, Gonen T, Roy P, Zhou ZH. RNA genome packaging and capsid assembly of bluetongue virus visualized in host cells. Cell 2024; 187:2236-2249.e17. [PMID: 38614100 PMCID: PMC11182334 DOI: 10.1016/j.cell.2024.03.007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2023] [Revised: 10/18/2023] [Accepted: 03/07/2024] [Indexed: 04/15/2024]
Abstract
Unlike those of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and ssRNA viruses, the mechanism of genome packaging of dsRNA viruses is poorly understood. Here, we combined the techniques of high-resolution cryoelectron microscopy (cryo-EM), cellular cryoelectron tomography (cryo-ET), and structure-guided mutagenesis to investigate genome packaging and capsid assembly of bluetongue virus (BTV), a member of the Reoviridae family of dsRNA viruses. A total of eleven assembly states of BTV capsid were captured, with resolutions up to 2.8 Å, with most visualized in the host cytoplasm. ATPase VP6 was found underneath the vertices of capsid shell protein VP3 as an RNA-harboring pentamer, facilitating RNA packaging. RNA packaging expands the VP3 shell, which then engages middle- and outer-layer proteins to generate infectious virions. These revealed "duality" characteristics of the BTV assembly mechanism reconcile previous contradictory co-assembly and core-filling models and provide insights into the mysterious RNA packaging and capsid assembly of Reoviridae members and beyond.
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Affiliation(s)
- Xian Xia
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Po-Yu Sung
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Michael W Martynowycz
- Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Tamir Gonen
- Howard Hughes Medical Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA; Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095, USA
| | - Polly Roy
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK
| | - Z Hong Zhou
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, Los Angeles, CA 90095, USA; California NanoSystems Institute, University of California, Los Angeles, Los Angeles, CA 90095, USA.
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2
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Bissett SL, Roy P. Multi-Gene Recombinant Baculovirus Expression Systems: From Inception to Contemporary Applications. Viruses 2024; 16:492. [PMID: 38675835 PMCID: PMC11054102 DOI: 10.3390/v16040492] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2024] [Revised: 03/18/2024] [Accepted: 03/21/2024] [Indexed: 04/28/2024] Open
Abstract
Many protein expression systems are primarily utilised to produce a single, specific recombinant protein. In contrast, most biological processes such as virus assembly rely upon a complex of several interacting proteins rather than the activity of a sole protein. The high complexity of the baculovirus genome, coupled with a multiphase replication cycle incorporating distinct transcriptional steps, made it the ideal system to manipulate for high-level expression of a single, or co-expression of multiple, foreign proteins within a single cell. We have developed and utilised a series of recombinant baculovirus systems to unravel the sequential assembly process of a complex non-enveloped model virus, bluetongue virus (BTV). The high protein yields expressed by the baculovirus system not only facilitated structure-function analysis of each viral protein but were also advantageous to crystallography studies and supported the first atomic-level resolution of a recombinant viral protein, the major BTV capsid protein. Further, the formation of recombinant double-shelled virus-like particles (VLPs) provided insights into the structure-function relationships among the four major structural proteins of the BTV whilst also representing a potential candidate for a viral vaccine. The baculovirus multi-gene expression system facilitated the study of structurally complex viruses (both non-enveloped and enveloped viruses) and heralded a new generation of viral vaccines.
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Affiliation(s)
| | - Polly Roy
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, London, WC1E 7HT, UK
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3
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Viadanna PHO, Grace SG, Logan TD, DeRuyter E, Loeb JC, Wilson KN, White ZS, Krauer JMC, Lednicky JA, Waltzek TB, Wisely SM, Subramaniam K. Characterization of two novel reassortant bluetongue virus serotype 1 strains isolated from farmed white-tailed deer (Odocoileus virginianus) in Florida, USA. Virus Genes 2023; 59:732-740. [PMID: 37439882 DOI: 10.1007/s11262-023-02019-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Accepted: 06/27/2023] [Indexed: 07/14/2023]
Abstract
Hemorrhagic diseases caused by epizootic hemorrhagic disease virus or by bluetongue virus (BTV) are the most important orbivirus diseases affecting ruminants, including white-tailed deer (WTD). Bluetongue virus is of particular concern for farmed WTD in Florida, given its lethality and its wide distribution throughout the state. This study reports the clinical findings, ancillary diagnostics, and genomic characterization of two BTV serotype 1 strains isolated from two farmed WTD, from two different farms in Florida in 2019 and 2022. Phylogenetic and genetic analyses indicated that these two novel BTV-1 strains were reassortants. In addition, our analyses reveal that most genome segments of these strains were acquired from BTVs previously detected in ruminants in Florida, substantiating their endemism in the Southeastern U.S. Our findings underscore the need for additional research to determine the genetic diversity of BTV strains in Florida, their prevalence, and the potential risk of new BTV strains to WTD and other ruminants.
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Affiliation(s)
- Pedro H O Viadanna
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, 32611, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
| | - Savannah G Grace
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Wildlife Ecology and Conservation, University of Florida, 32611, Gainesville, FL, USA
| | - Tracey D Logan
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, 32611, Gainesville, FL, USA
| | - Emily DeRuyter
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, 32611, Gainesville, FL, USA
| | - Julia C Loeb
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, 32611, Gainesville, FL, USA
| | - Kristen N Wilson
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Wildlife Ecology and Conservation, University of Florida, 32611, Gainesville, FL, USA
| | - Zoe S White
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Wildlife Ecology and Conservation, University of Florida, 32611, Gainesville, FL, USA
| | - Juan M C Krauer
- Department of Large Animal Clinical Sciences, College of Veterinary Medicine, University of Florida, 32611, Gainesville, FL, USA
- Washington Animal Disease Diagnostic Laboratory, Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, 99164, Pullman, WA, USA
| | - John A Lednicky
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Environmental and Global Health, College of Public Health and Health Professions, University of Florida, 32611, Gainesville, FL, USA
| | - Thomas B Waltzek
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, 32611, Gainesville, FL, USA
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Washington Animal Disease Diagnostic Laboratory, Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, 99164, Pullman, WA, USA
| | - Samantha M Wisely
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA
- Department of Wildlife Ecology and Conservation, University of Florida, 32611, Gainesville, FL, USA
| | - Kuttichantran Subramaniam
- Department of Infectious Diseases and Immunology, College of Veterinary Medicine, University of Florida, 32611, Gainesville, FL, USA.
- Emerging Pathogens Institute, University of Florida, 32611, Gainesville, FL, USA.
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Zhang X, Wen F. Recent advances in Reovirales viruses reverse genetics research. Virus Res 2022; 321:198911. [PMID: 36113355 DOI: 10.1016/j.virusres.2022.198911] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2022] [Revised: 08/27/2022] [Accepted: 08/31/2022] [Indexed: 12/24/2022]
Abstract
Reovirales are segmented double-strand RNA viruses with a broad host range that pose a serious threat to human and animal health. However, there are numerous viral species within the Reovirales, some of which have lagged behind other RNA viruses in the study of their biology due to the lack of an effective reverse genetics (RG) system. The RG systems are the most powerful tools for studying viral protein function, viral gene expression regulation, viral pathogenesis, and the generation of engineered vaccines. Recently, several entirely plasmid-based RG systems have been developed for several members of the Reovirales. This review outlines the development and future direction of the RG system for the best studied Reovirales viruses.
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Affiliation(s)
- Xinyu Zhang
- College of Life Science and Engineering, Foshan University, No33 Guangyun Road, Shishan Town, Nanhai District, Foshan, Guangdong 528231, China
| | - Feng Wen
- College of Life Science and Engineering, Foshan University, No33 Guangyun Road, Shishan Town, Nanhai District, Foshan, Guangdong 528231, China.
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Investigating the Role of African Horse Sickness Virus VP7 Protein Crystalline Particles on Virus Replication and Release. Viruses 2022; 14:v14102193. [PMID: 36298748 PMCID: PMC9608501 DOI: 10.3390/v14102193] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2022] [Revised: 09/19/2022] [Accepted: 09/28/2022] [Indexed: 11/07/2022] Open
Abstract
African horse sickness is a deadly and highly infectious disease of equids, caused by African horse sickness virus (AHSV). AHSV is one of the most economically important members of the Orbivirus genus. AHSV is transmitted by the biting midge, Culicoides, and therefore replicates in both insect and mammalian cell types. Structural protein VP7 is a highly conserved major core protein of orbiviruses. Unlike any other orbivirus VP7, AHSV VP7 is highly insoluble and forms flat hexagonal crystalline particles of unknown function in AHSV-infected cells and when expressed in mammalian or insect cells. To examine the role of AHSV VP7 in virus replication, a plasmid-based reverse genetics system was used to generate a recombinant AHSV that does not form crystalline particles. We characterised the role of VP7 crystalline particle formation in AHSV replication in vitro and found that soluble VP7 interacted with viral proteins VP2 and NS2 similarly to wild-type VP7 during infection. Interestingly, soluble VP7 was found to form uncharacteristic tubule-like structures in infected cells which were confirmed to be as a result of unique VP7-NS1 colocalisation. Furthermore, it was found that VP7 crystalline particles play a role in AHSV release and yield. This work provides insight into the role of VP7 aggregation in AHSV cellular pathogenesis and contributes toward the understanding of the possible effects of viral protein aggregation in other human virus-borne diseases.
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Vaccination as a Strategy to Prevent Bluetongue Virus Vertical Transmission. Pathogens 2021; 10:pathogens10111528. [PMID: 34832683 PMCID: PMC8622840 DOI: 10.3390/pathogens10111528] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2021] [Revised: 11/13/2021] [Accepted: 11/19/2021] [Indexed: 11/17/2022] Open
Abstract
Bluetongue virus (BTV) produces an economically important disease in ruminants of compulsory notification to the OIE. BTV is typically transmitted by the bite of Culicoides spp., however, some BTV strains can be transmitted vertically, and this is associated with fetus malformations and abortions. The viral factors associated with the virus potency to cross the placental barrier are not well defined. The potency of vertical transmission is retained and sometimes even increased in live attenuated BTV vaccine strains. Because BTV possesses a segmented genome, the possibility of reassortment of vaccination strains with wild-type virus could even favor the transmission of this phenotype. In the present review, we will describe the non-vector-based BTV infection routes and discuss the experimental vaccination strategies that offer advantages over this drawback of some live attenuated BTV vaccines.
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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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Saminathan M, Singh KP, Khorajiya JH, Dinesh M, Vineetha S, Maity M, Rahman AF, Misri J, Malik YS, Gupta VK, Singh RK, Dhama K. An updated review on bluetongue virus: epidemiology, pathobiology, and advances in diagnosis and control with special reference to India. Vet Q 2021; 40:258-321. [PMID: 33003985 PMCID: PMC7655031 DOI: 10.1080/01652176.2020.1831708] [Citation(s) in RCA: 28] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Bluetongue (BT) is an economically important, non-contagious viral disease of domestic and wild ruminants. BT is caused by BT virus (BTV) and it belongs to the genus Orbivirus and family Reoviridae. BTV is transmitted by Culicoides midges and causes clinical disease in sheep, white-tailed deer, pronghorn antelope, bighorn sheep, and subclinical manifestation in cattle, goats and camelids. BT is a World Organization for Animal Health (OIE) listed multispecies disease and causes great socio-economic losses. To date, 28 serotypes of BTV have been reported worldwide and 23 serotypes have been reported from India. Transplacental transmission (TPT) and fetal abnormalities in ruminants had been reported with cell culture adopted live-attenuated vaccine strains of BTV. However, emergence of BTV-8 in Europe during 2006, confirmed TPT of wild-type/field strains of BTV. Diagnosis of BT is more important for control of disease and to ensure BTV-free trade of animals and their products. Reverse transcription polymerase chain reaction, agar gel immunodiffusion assay and competitive enzyme-linked immunosorbent assay are found to be sensitive and OIE recommended tests for diagnosis of BTV for international trade. Control measures include mass vaccination (most effective method), serological and entomological surveillance, forming restriction zones and sentinel programs. Major hindrances with control of BT in India are the presence of multiple BTV serotypes, high density of ruminant and vector populations. A pentavalent inactivated, adjuvanted vaccine is administered currently in India to control BT. Recombinant vaccines with DIVA strategies are urgently needed to combat this disease. This review is the first to summarise the seroprevalence of BTV in India for 40 years, economic impact and pathobiology.
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Affiliation(s)
- Mani Saminathan
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Karam Pal Singh
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | | | - Murali Dinesh
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Sobharani Vineetha
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Madhulina Maity
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - At Faslu Rahman
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Jyoti Misri
- Animal Science Division, Indian Council of Agricultural Research, New Delhi, India
| | - Yashpal Singh Malik
- Division of Biological Standardization, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Vivek Kumar Gupta
- Centre for Animal Disease Research and Diagnosis, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Raj Kumar Singh
- Director, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
| | - Kuldeep Dhama
- Division of Pathology, ICAR-Indian Veterinary Research Institute, Izatnagar, Bareilly, Uttar Pradesh, India
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Epidemiology and Genomic Analysis of Equine Encephalosis Virus Detected in Horses with Clinical Signs in South Africa, 2010-2017. Viruses 2021; 13:v13030398. [PMID: 33801457 PMCID: PMC8001977 DOI: 10.3390/v13030398] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2021] [Revised: 02/25/2021] [Accepted: 02/26/2021] [Indexed: 12/23/2022] Open
Abstract
Equine encephalosis virus (EEV) is a neglected virus endemic to South Africa and is considered to generally result in mild disease in equines. Specimens were analyzed from live horses that presented with undefined neurological, febrile, or respiratory signs, or sudden and unexpected death. Between 2010 and 2017, 111 of 1523 (7.3%) horse samples tested positive for EEV using a nested real-time reverse transcriptase polymerase chain reaction (rRT-PCR). Clinical signs were reported in 106 (7.2%) EEV positive and 1360 negative horses and included pyrexia (77/106, 72.6%), icterus (20/106, 18.9%) and dyspnea (12/106, 11.3%). Neurological signs were inversely associated with EEV infection (OR < 1, p < 0.05) relative to EEV negative cases despite a high percentage of animals presenting with neurological abnormalities (51/106, 48.1%). Seventeen of the EEV positive horses also had coinfections with either West Nile (5/106, 4.7%), Middelburg (4/106, 3.8%) or African Horse sickness virus (8/106, 7.6%). To investigate a possible genetic link between EEV strains causing the observed clinical signs in horses, the full genomes of six isolates were compared to the reference strains. Based on the outer capsid protein (VP2), serotype 1 and 4 were identified as the predominant serotypes with widespread reassortment between the seven different serotypes.
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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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Gale P. How virus size and attachment parameters affect the temperature sensitivity of virus binding to host cells: Predictions of a thermodynamic model for arboviruses and HIV. MICROBIAL RISK ANALYSIS 2020; 15:100104. [PMID: 32292808 PMCID: PMC7110232 DOI: 10.1016/j.mran.2020.100104] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2019] [Revised: 03/05/2020] [Accepted: 03/06/2020] [Indexed: 05/14/2023]
Abstract
Virus binding to host cells involves specific interactions between viral (glyco)proteins (GP) and host cell surface receptors (Cr) (protein or sialic acid (SA)). The magnitude of the enthalpy of association changes with temperature according to the change in heat capacity (ΔCp) on GP/Cr binding, being little affected for avian influenza virus (AIV) haemagglutinin (HA) binding to SA (ΔCp = 0 kJ/mol/K) but greatly affected for HIV gp120 binding to CD4 receptor (ΔCp = -5.0 kJ/mol/K). A thermodynamic model developed here predicts that values of ΔCp from 0 to ~-2.0 kJ/mol/K have relatively little impact on the temperature sensitivity of the number of mosquito midgut cells with bound arbovirus, while intermediate values of ΔCp of ~-3.0 kJ/mol/K give a peak binding at a temperature of ~20 °C as observed experimentally for Western equine encephalitis virus. More negative values of ΔCp greatly decrease arbovirus binding at temperatures below ~20 °C. Thus to promote transmission at low temperatures, arboviruses may benefit from ΔCp ~ 0 kJ/mol/K as for HA/SA and it is interesting that bluetongue virus binds to SA in midge midguts. Large negative values of ΔCp as for HIV gp120:CD4 diminish binding at 37 °C. Of greater importance, however, is the decrease in entropy of the whole virus (ΔSa_immob) on its immobilisation on the host cell surface. ΔSa_immob presents a repulsive force which the enthalpy-driven GP/Cr interactions weakened at higher temperatures struggle to overcome. ΔSa_immob is more negative (less favourable) for larger diameter viruses which therefore show diminished binding at higher temperatures than smaller viruses. It is proposed that small size phenotype through a less negative ΔSa_immob is selected for viruses infecting warmer hosts thus explaining the observation that virion volume decreases with increasing host temperature from 0 °C to 40 °C in the case of dsDNA viruses. Compared to arboviruses which also infect warm-blooded vertebrates, HIV is large at 134 nm diameter and thus would have a large negative ΔSa_immob which would diminish its binding at human body temperature. It is proposed that prior non-specific binding of HIV through attachment factors takes much of the entropy loss for ΔSa_immob so enhancing subsequent specific gp120:CD4 binding at 37 °C. This is consistent with the observation that HIV attachment factors are not essential but augment infection. Antiviral therapies should focus on increasing virion size, for example through binding of zinc oxide nanoparticles to herpes simplex virus, hence making ΔSa_immob more negative, and thus reducing binding affinity at 37 °C.
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Key Words
- AIV, avian influenza virus
- Antivirals
- BBF, brush border fragments from midgut
- BTV, bluetongue virus
- C.VT, number of host cells with bound virus at temperature T
- CD4, host cell receptor for HIV
- Cp, heat capacity at constant pressure
- Cr, host cell receptor
- Ctotal, number of host cells which can bind virus in a given volume of host fluid (midgut or blood)
- DENV, Dengue virus
- EA, activation energy
- EBOV, Zaire ebolavirus
- EM, electron microscopy
- Entropy
- Env, HIV gp120 trimer envelope protein which binds to a single CD4 molecule
- FcT, fraction of arthropod midgut cells with bound virus at temperature T
- GP, viral (glyco)protein on virus surface that binds to Cr
- HA, haemagglutinin
- HIV, human immunodeficiency virus
- HSV-2, herpes simplex virus type 2
- Heat capacity
- Ka_virus_T, association constant for binding of virus to host cells at temperature T
- Kd_receptor_T, dissociation constant for GP from Cr at temperature T
- Kd_virus, dissociation constant for virus from host cell
- M, molar (moles dm-3)
- R, ideal gas constant
- SA, sialic acid
- SIV, simian immunodeficiency virus
- Temperature
- Vfree, virus not bound to cells
- Virus size
- Vtotal, virus challenge dose in volume of host fluid
- WEEV, Western equine encephalitis virus
- WNV, West Nile virus
- ZnOT, zinc oxide tetrapod
- n, number of GP/Cr contacts made on virus binding to cell
- pcompleteT, probability given a virion has bound to the surface of a midgut cell that that midgut cell becomes infected and that its progeny viruses go on to infect the salivary gland so completing the arthropod infection process within the life time of the arthropod at temperature T
- ptransmissionT, probability of successful infection of the arthropod salivary glands after oral exposure at temperature T
- ΔCp, change in heat capacity
- ΔGa_virus_T, change in Gibbs free energy on association of virus and host cell at temperature T
- ΔHa_receptor_T, change in enthalpy for binding of virus GP to host Cr receptor at a temperature T
- ΔHa_virus_T, change in enthalpy for binding of virus to host cell at temperature T
- ΔSa_immob, change in entropy on immobilization of whole virus to cell surface
- ΔSa_non_specific, change in entropy on immobilization of virus to cell surface through non-specific binding
- ΔSa_receptor_T, change in entropy for binding of virus GP to host Cr receptor
- ΔSa_specific, change in entropy on immobilization of virus to cell surface through specific GP/Cr-driven binding
- ΔSa_virus_T, change in entropy for binding of virus to host cell at temperature T
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Affiliation(s)
- Paul Gale
- Independent Scientist, 15 Weare Close, Portland, Dorset, DT5 1JP, United Kingdom
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Roy P. Highly efficient vaccines for Bluetongue virus and a related Orbivirus based on reverse genetics. Curr Opin Virol 2020; 44:35-41. [PMID: 32610251 DOI: 10.1016/j.coviro.2020.05.003] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Revised: 04/30/2020] [Accepted: 05/04/2020] [Indexed: 10/24/2022]
Abstract
Bluetongue virus (BTV) reverse genetics (RG), available since 2007, has allowed the dissection of the virus replication cycle, including discovery of a primary replication stage. This information has allowed the generation of Entry-Competent-Replication-Abortive (ECRA) vaccines, which enter cells and complete primary replication but fail to complete the later stage. A series of vaccine trials in sheep and cattle either with a single ECRA serotype or a cocktail of multiple ECRA serotypes have demonstrated that these vaccines provide complete protection against virulent virus challenge without cross-serotype interference. Similarly, an RG system developed for the related African Horse Sickness virus, which causes high mortality in equids has provided AHSV ECRA vaccines that are protective in horses. ECRA vaccines were incapable of productive replication in animals despite being competent for cell entry. This technology allows rapid generation of emerging Orbivirus vaccines and offers immunogenicity and safety levels that surpass attenuated or recombinant routes.
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Affiliation(s)
- Polly Roy
- Department of Infection Biology, London School of Hygiene and Tropical Medicine, United Kingdom.
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13
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Haegeman A, Vandaele L, De Leeuw I, Oliveira AP, Nauwynck H, Van Soom A, De Clercq K. Failure to Remove Bluetongue Serotype 8 Virus (BTV-8) From in vitro Produced and in vivo Derived Bovine Embryos and Subsequent Transmission of BTV-8 to Recipient Cows After Embryo Transfer. Front Vet Sci 2019; 6:432. [PMID: 31867345 PMCID: PMC6907088 DOI: 10.3389/fvets.2019.00432] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 11/15/2019] [Indexed: 11/13/2022] Open
Abstract
The behavior of BTV-8 in cattle is different from most other serotypes not only with regards to clinical signs but certainly with respect to virus transmission (transplacental, contact). Therefore, the possibility of virus transmission by means of embryo transfer was examined by in vitro exposure of in vitro produced and in vivo derived bovine blastocysts to BTV-8 followed by different washing protocols, including longer exposure times (up to 120 s) to 0.25% trypsin at room temperature or at 37°C. None of the washing protocols used was successful in removing the viral genome completely from the in vitro produced and in vivo derived embryos as was demonstrated by real-time PCR. Moreover, BTV-8 virus was transmitted to recipient cows after embryo transfer of in vivo derived BTV8-exposed embryos, which had been subjected to routine decontamination as recommended by IETS, consisting of 5 washes in PBS followed by a double treatment of 0.25% trypsin for 45s at 37°C, and an additional 5 washes in PBS with 2% FCS. This study clearly demonstrates the necessity of vigorous application of the directives for screening of potential donors and the collected embryos, especially in regions with BTV-8, to prevent transmission of the disease.
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Affiliation(s)
- Andy Haegeman
- Unit of Exotic and Particular Diseases, Sciensano, Brussels, Belgium
| | - Leen Vandaele
- Department of Reproduction, Obstetrics and Herd Health, Ghent University, Merelbeke, Belgium
| | - Ilse De Leeuw
- Unit of Exotic and Particular Diseases, Sciensano, Brussels, Belgium
| | - André P Oliveira
- Department of Reproduction, Obstetrics and Herd Health, Ghent University, Merelbeke, Belgium.,EPAMIG, Escola de Veterinaria da UFMG, Bolsista CAPES, Belo Horizonte, Brazil
| | - Hans Nauwynck
- Laboratory of Virology, Faculty of Veterinary Medicine, Ghent University, Merelbeke, Belgium
| | - Ann Van Soom
- Department of Reproduction, Obstetrics and Herd Health, Ghent University, Merelbeke, Belgium
| | - Kris De Clercq
- Unit of Exotic and Particular Diseases, Sciensano, Brussels, Belgium
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Mokoena NB, Moetlhoa B, Rutkowska DA, Mamputha S, Dibakwane VS, Tsekoa TL, O'Kennedy MM. Plant-produced Bluetongue chimaeric VLP vaccine candidates elicit serotype-specific immunity in sheep. Vaccine 2019; 37:6068-6075. [PMID: 31471154 DOI: 10.1016/j.vaccine.2019.08.042] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2019] [Revised: 08/01/2019] [Accepted: 08/19/2019] [Indexed: 01/28/2023]
Abstract
Bluetongue (BT) is a hemorrhagic non-contagious, biting midge-transmitted disease of wild and domestic ruminants that is caused by bluetongue virus (BTV). Annual vaccination plays a pivotal role in BT disease control in endemic regions. Due to safety concerns of the current BTV multivalent live attenuated vaccine (LAV), a safe efficacious new generation subunit vaccine such as a plant-produced BT virus-like particle (VLP) vaccine is imperative. Previously, homogenous BTV serotype 8 (BTV-8) VLPs were successfully produced in Nicotiana benthamiana plants and provided protective immunity in sheep. In this study, combinations of BTV capsid proteins from more than one serotype were expressed and assembled to form chimaeric BTV-3 and BTV-4 VLPs in N. benthamiana plants. The assembled homogenous BTV-8, as well as chimaeric BTV-3 and chimaeric BTV-4 VLP serotypes, were confirmed by SDS-PAGE, Transmission Electron microscopy (TEM) and protein confirmation using liquid chromatography-mass spectrometry (LC-MS/MS) based peptide sequencing. As VP2 is the major determinant eliciting protective immunity, the percentage coverage and number of unique VP2 peptides detected in assembled chimaeric BT VLPs were used as a guide to assemble the most appropriate chimaeric combinations. Both plant-produced chimaeric BTV-3 and BTV-4 VLPs were able to induce long-lasting serotype-specific neutralizing antibodies equivalent to the monovalent LAV controls. Antibody levels remained high to the end of the trial. Combinations of homogenous and chimaeric BT VLPs have great potential as a safe, effective multivalent vaccine with the ability to distinguish between vaccinated and infected individuals (DIVA) due to the absence of non-structural proteins.
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Affiliation(s)
| | | | - Daria A Rutkowska
- Council for Scientific and Industrial Research (CSIR) Biosciences, Pretoria, South Africa
| | - Sipho Mamputha
- Council for Scientific and Industrial Research (CSIR) Biosciences, Pretoria, South Africa
| | - Vusi S Dibakwane
- Onderstepoort Biological Products SOC Ltd, Onderstepoort, South Africa
| | - Tsepo L Tsekoa
- Council for Scientific and Industrial Research (CSIR) Biosciences, Pretoria, South Africa
| | - Martha M O'Kennedy
- Council for Scientific and Industrial Research (CSIR) Biosciences, Pretoria, South Africa.
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15
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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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16
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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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17
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White JR, Williams DT, Wang J, Chen H, Melville LF, Davis SS, Weir RP, Certoma A, Di Rubbo A, Harvey G, Lunt RA, Eagles D. Identification and genomic characterization of the first isolate of bluetongue virus serotype 5 detected in Australia. Vet Med Sci 2019; 5:129-145. [PMID: 30747479 PMCID: PMC6556758 DOI: 10.1002/vms3.156] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Bluetongue virus (BTV), transmitted by midges (Culicoides sp), is distributed worldwide and causes disease in ruminants. In particular, BT can be a debilitating disease in sheep causing serious trade and socio-economic consequences at both local and global levels. Across Australia, a sentinel cattle herd surveillance program monitors the BTV activity. Prior to 2014, BTV-1, -2, -3, -7, -9, -15, -16, -20, -21 and -23 had been isolated in Australia, but no bluetongue disease has occurred in a commercial Australian flock. We routinely use a combination of serology, virus isolation, RT-PCR and next generation and conventional nucleotide sequencing technologies to detect and phylogenetically characterize incursions of novel BTV strains into Australia. Screening of Northern Territory virus isolates in 2015 revealed BTV-5, a serotype new to Australia. We derived the complete genome of this isolate and determined its phylogenetic relationship with exotic BTV-5 isolates. Gene segments 2, 6, 7 and 10 exhibited a close relationship with the South African prototype isolate RSArrrr/5. This was the first Australian isolation of a Western topotype of segment 10. Serological surveillance data highlighted the antigenic cross-reactivity between BTV-5 and BTV-9. Phylogenetic investigation of segments 2 and 6 of these serotypes confirmed their unconventional relationships within the BTV serogroup. Our results further highlighted a need for a revision of the current serologically based system for BTV strain differentiation and importantly, implied a potential for genome segments of pathogenic Western BTV strains to rapidly enter Southeast Asia. This emphasized a need for continued high-level surveillance of vectors and viruses at strategic locations in the north of Australia The expansion of routine characterization and classification of BTV to a whole genome approach is recommended, to better monitor the presence and level of establishment of novel Western topotype segments within the Australian episystem.
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Affiliation(s)
- John R. White
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | | | - Jianning Wang
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | - Honglei Chen
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | - Lorna F. Melville
- Department of Primary Industry and ResourcesBerrimah Veterinary LaboratoriesNorthern Territory GovernmentBerrimahNorthern TerritoryAustralia
| | - Steven S. Davis
- Department of Primary Industry and ResourcesBerrimah Veterinary LaboratoriesNorthern Territory GovernmentBerrimahNorthern TerritoryAustralia
| | - Richard P. Weir
- Department of Primary Industry and ResourcesBerrimah Veterinary LaboratoriesNorthern Territory GovernmentBerrimahNorthern TerritoryAustralia
| | - Andrea Certoma
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | - Antonio Di Rubbo
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | - Gemma Harvey
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | - Ross A. Lunt
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
| | - Debbie Eagles
- CSIRO Australian Animal Health LaboratoryGeelongVictoriaAustralia
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18
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The Interaction of Bluetongue Virus VP6 and Genomic RNA Is Essential for Genome Packaging. J Virol 2019; 93:JVI.02023-18. [PMID: 30541863 PMCID: PMC6384066 DOI: 10.1128/jvi.02023-18] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2018] [Accepted: 12/10/2018] [Indexed: 02/06/2023] Open
Abstract
The genomes of the Reoviridae, including the animal pathogen bluetongue virus (BTV), are multisegmented double-stranded RNA (dsRNA). During replication, single-stranded (ss) positive-sense RNA segments are packaged into the assembling virus capsid, triggering genomic dsRNA synthesis. However, exactly how this packaging event occurs is not clear. A minor capsid protein, VP6, unique for the orbiviruses, has been proposed to be involved in the RNA-packaging process. In this study, we sought to characterize the RNA binding activity of VP6 and its functional relevance. A novel proteomic approach was utilized to map the ssRNA/dsRNA binding sites of a purified recombinant protein and the genomic dsRNA binding sites of the capsid-associated VP6. The data revealed that each VP6 protein has multiple distinct RNA-binding regions and that only one region is shared between recombinant and capsid-associated VP6. A combination of targeted mutagenesis and reverse genetics identified the RNA-binding region that is essential for virus replication. Using an in vitro RNA-binding competition assay, a unique cell-free assembly assay, and an in vivo single-cycle replication assay, it was possible to identify a motif within the shared binding region that binds BTV ssRNA preferentially in a manner consistent with specific RNA recruitment during capsid assembly. These data highlight the critical roles that this unique protein plays in orbivirus genome packaging and replication.IMPORTANCE Genome packaging is a critical stage during virus replication. For viruses with segmented genomes, the genome segments need to be correctly packaged into a newly formed capsid. However, the detailed mechanism of this packaging is unclear. Here we focus on VP6, a minor viral protein of bluetongue virus, which is critical for genome packaging. We used multiple approaches, including a robust RNA-protein fingerprinting assay, to map the ssRNA binding sites of recombinant VP6 and the genomic dsRNA binding sites of capsid-associated VP6. By these means, together with virological and biochemical methods, we identify the viral RNA-packaging motif of a segmented dsRNA virus for the first time.
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19
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Ramesh R, Lim XX, Raghuvamsi PV, Wu C, Wong SM, Anand GS. Uncovering metastability and disassembly hotspots in whole viral particles. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2018; 143:5-12. [PMID: 30553754 DOI: 10.1016/j.pbiomolbio.2018.12.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/07/2018] [Revised: 10/26/2018] [Accepted: 12/12/2018] [Indexed: 01/18/2023]
Abstract
Viruses are metastable macromolecular assemblies that toggle between multiple conformational states through molecular rearrangements that are critical for mediating viral host entry. Viruses respond to different host specific environmental cues to form disassembly intermediates for the eventual release of genomic material required for replication. Although static snapshots of these intermediates have been captured through structural techniques such as X-ray crystallography and cryo-EM, the mechanistic details of these conformational rearrangements underpinning viral metastability have been poorly understood. Amide hydrogen deuterium exchange mass spectrometry (HDXMS) is a powerful tool that measures hydrogen bonding propensities to probe changes in the dynamics of different macromolecular interactions. Chaotropic agents such as urea can be used to disrupt hydrogen bonds between different subunits, thereby ranking regions of the virus that are critical in maintaining viral stability. By controlled urea denaturation with HDXMS, we have identified specific loci in a Turnip Crinkle Virus (TCV) model showing increased deuterium exchange with even minimally disruptive concentrations of urea. These loci represent dynamic disassembly hotspots. These hotspots are predominantly present at the quaternary contacts at the 3-fold and 5-fold axes. This approach can be applied to detect vulnerabilities in virus icosahedral structures to uncover the molecular mechanism of viral disassembly.
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Affiliation(s)
- Ranita Ramesh
- Department of Biological Sciences, National University of Singapore, 117543, Singapore
| | - Xin Xiang Lim
- Department of Biological Sciences, National University of Singapore, 117543, Singapore
| | | | - Chao Wu
- Department of Biological Sciences, National University of Singapore, 117543, Singapore
| | - Sek Man Wong
- Department of Biological Sciences, National University of Singapore, 117543, Singapore; Temasek Life Sciences Laboratory, Singapore, 117604, Singapore
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20
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In Situ Structures of the Polymerase Complex and RNA Genome Show How Aquareovirus Transcription Machineries Respond to Uncoating. J Virol 2018; 92:JVI.00774-18. [PMID: 30068643 DOI: 10.1128/jvi.00774-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2018] [Accepted: 07/19/2018] [Indexed: 12/28/2022] Open
Abstract
Reoviruses carry out genomic RNA transcription within intact viruses to synthesize plus-sense RNA strands, which are capped prior to their release as mRNA. The in situ structures of the transcriptional enzyme complex (TEC) containing the RNA-dependent RNA polymerase (RdRp) and NTPase are known for the single-layered reovirus cytoplasmic polyhedrosis virus (CPV), but not for multilayered reoviruses, such as aquareoviruses (ARV), which possess a primed stage that CPV lacks. Consequently, how the RNA genome and TEC respond to priming in reoviruses is unknown. Here, we determined the near-atomic-resolution asymmetric structure of ARV in the primed state by cryo-electron microscopy (cryo-EM), revealing the in situ structures of 11 TECs inside each capsid and their interactions with the 11 surrounding double-stranded RNA (dsRNA) genome segments and with the 120 enclosing capsid shell protein (CSP) VP3 subunits. The RdRp VP2 and the NTPase VP4 associate with each other and with capsid vertices; both bind RNA in multiple locations, including a novel C-terminal domain of VP4. Structural comparison between the primed and quiescent states showed translocation of the dsRNA end from the NTPase to the RdRp during priming. The RNA template channel was open in both states, suggesting that channel blocking is not a regulating mechanism between these states in ARV. Instead, the NTPase C-terminal domain appears to regulate RNA translocation between the quiescent and primed states. Taking the data together, dsRNA viruses appear to have adapted divergent mechanisms to regulate genome transcription while retaining similar mechanisms to coassemble their genome segments, TEC, and capsid proteins into infectious virions.IMPORTANCE Viruses in the family Reoviridae are characterized by the ability to endogenously synthesize nascent RNA within the virus. However, the mechanisms for assembling their RNA genomes with transcriptional enzymes into a multilayered virion and for priming such a virion for transcription are poorly understood. By cryo-EM and novel asymmetric reconstruction, we determined the atomic structure of the transcription complex inside aquareoviruses (ARV) that are primed for infection. The transcription complex is anchored by the N-terminal segments of enclosing capsid proteins and contains an NTPase and a polymerase. The NTPase has a newly discovered domain that translocates the 5' end of plus-sense RNA in segmented dsRNA genomes from the NTPase to polymerase VP2 when the virus changes from the inactive (quiescent) to the primed state. Conformation changes in capsid proteins and transcriptional complexes suggest a mechanism for relaying information from the outside to the inside of the virus during priming.
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Abstract
Ticks are important vectors for the transmission of pathogens including viruses. The viruses carried by ticks also known as tick-borne viruses (TBVs), contain a large group of viruses with diverse genetic properties and are concluded in two orders, nine families, and at least 12 genera. Some members of the TBVs are notorious agents causing severe diseases with high mortality rates in humans and livestock, while some others may pose risks to public health that are still unclear to us. Herein, we review the current knowledge of TBVs with emphases on the history of virus isolation and identification, tick vectors, and potential pathogenicity to humans and animals, including assigned species as well as the recently discovered and unassigned species. All these will promote our understanding of the diversity of TBVs, and will facilitate the further investigation of TBVs in association with both ticks and vertebrate hosts.
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Affiliation(s)
- Junming Shi
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Zhihong Hu
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China
| | - Fei Deng
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
| | - Shu Shen
- State Key Laboratory of Virology, Wuhan Institute of Virology, Chinese Academy of Sciences, Wuhan, 430071, China.
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22
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Interaction between a Unique Minor Protein and a Major Capsid Protein of Bluetongue Virus Controls Virus Infectivity. J Virol 2018; 92:JVI.01784-17. [PMID: 29142128 PMCID: PMC5774872 DOI: 10.1128/jvi.01784-17] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2017] [Accepted: 11/03/2017] [Indexed: 11/30/2022] Open
Abstract
Among the Reoviridae family of double-stranded RNA viruses, only members of the Orbivirus genus possess a unique structural protein, termed VP6, within their particles. Bluetongue virus (BTV), an important livestock pathogen, is the prototype Orbivirus. BTV VP6 is an ATP-dependent RNA helicase, and it is indispensable for virus replication. In the study described in this report, we investigated how VP6 might be recruited to the virus capsid and whether the BTV structural protein VP3, which forms the internal layer of the virus capsid core, is involved in VP6 recruitment. We first demonstrated that VP6 interacts with VP3 and colocalizes with VP3 during capsid assembly. A series of VP6 mutants was then generated, and in combination with immunoprecipitation and size exclusion chromatographic analyses, we demonstrated that VP6 directly interacts with VP3 via a specific region of the C-terminal portion of VP6. Finally, using our reverse genetics system, mutant VP6 proteins were introduced into the BTV genome and interactions between VP6 and VP3 were shown in a live cell system. We demonstrate that BTV strains possessing a mutant VP6 are replication deficient in wild-type BSR cells and fail to recruit the viral replicase complex into the virus particle core. Taken together, these data suggest that the interaction between VP3 and VP6 could be important in the packaging of the viral genome and early stages of particle formation. IMPORTANCE The orbivirus bluetongue virus (BTV) is the causative agent of bluetongue disease of livestock, often causing significant economic and agricultural impacts in the livestock industry. In the study described in this report, we identified the essential region and residues of the unique orbivirus capsid protein VP6 which are responsible for its interaction with other BTV proteins and its subsequent recruitment into the virus particle. The nature and mechanism of these interactions suggest that VP6 has a key role in packaging of the BTV genome into the virus particle. As such, this is a highly significant finding, as this new understanding of BTV assembly could be exploited to design novel vaccines and antivirals against bluetongue disease.
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23
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Mohl BP, Roy P. Elucidating virus entry using a tetracysteine-tagged virus. Methods 2017; 127:23-29. [PMID: 28802715 DOI: 10.1016/j.ymeth.2017.08.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Revised: 07/20/2017] [Accepted: 08/05/2017] [Indexed: 01/30/2023] Open
Abstract
Fluorescent tags constitute an invaluable tool in facilitating a deeper understanding of the mechanistic processes governing virus-host interactions. However, when selecting a fluorescent tag for in vivo imaging of cells, a number of parameters and aspects must be considered. These include whether the tag may affect and interfere with protein conformation or localization, cell toxicity, spectral overlap, photo-stability and background. Cumulatively, these constitute challenges to be overcome. Bluetongue virus (BTV), a member of the Orbivirus genus in the Reoviridae family, is a non-enveloped virus that is comprised of two architecturally complex capsids. The outer capsid, composed of two proteins, VP2 and VP5, together facilitate BTV attachment, entry and the delivery of the transcriptionally active core in the cell cytoplasm. Previously, the significance of the endocytic pathway for BTV entry was reported, although a detailed analysis of the role of each protein during virus trafficking remained elusive due to the unavailability of a tagged virus. Described here is the successful modification, and validation, of a segmented genome belonging to a complex and large capsid virus to introduce tags for fluorescence visualization. The data generated from this approach highlighted the sequential dissociation of VP2 and VP5, driven by decreasing pH during the transition from early to late endosomes, and their retention therein as the virus particles progress along the endocytic pathway. Furthermore, the described tagging technology and methodology may prove transferable and allow for the labeling of other non-enveloped complex viruses.
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Affiliation(s)
- Bjorn-Patrick Mohl
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - 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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24
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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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25
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Abstract
Bluetongue virus (BTV) is the type species of genus Orbivirus within family Reoviridae. Bluetongue virus is transmitted between its ruminant hosts by the bite of Culicoides spp. midges. Severe BT cases are characterized by symptoms including hemorrhagic fever, particularly in sheep, loss of productivity, and death. To date, 27 BTV serotypes have been documented. These include novel isolates of atypical BTV, which have been almost fully characterized using deep sequencing technologies and do not rely on Culicoides vectors for their transmission among hosts. Due to its high economic impact, BT is an Office International des Epizooties (OIE) listed disease that is strictly controlled in international commercial exchanges. During the 20th century, BTV has been endemic in subtropical regions. In the last 15 years, novel strains of nine "typical" BTV serotypes (1, 2, 4, 6, 8, 9, 11, 14, and 16) invaded Europe, some of which caused disease in naive sheep and unexpectedly in bovine herds (particularly serotype 8). Over the past few years, three novel "atypical" serotypes (25-27) were characterized during sequencing studies of animal samples from Switzerland, Kuwait, and France, respectively. Classical serotype-specific inactivated vaccines, although expensive, were very successful in controlling outbreaks as shown with the northern European BTV-8 outbreak which started in the summer of 2006. Technological jumps in deep sequencing methodologies made rapid full characterizations of BTV genome from isolates/tissues feasible. Next-generation sequencing (NGS) approaches are powerful tools to study the variability of BTV genomes on a fine scale. This paper provides information on how NGS impacted our knowledge of the BTV genome.
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Patel A, Mohl BP, Roy P. Entry of Bluetongue Virus Capsid Requires the Late Endosome-specific Lipid Lysobisphosphatidic Acid. J Biol Chem 2016; 291:12408-19. [PMID: 27036941 PMCID: PMC4933286 DOI: 10.1074/jbc.m115.700856] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Indexed: 12/03/2022] Open
Abstract
The entry of viruses into host cells is one of the key processes of infection. The mechanisms of cellular entry for enveloped virus have been well studied. The fusion proteins as well as the facilitating cellular lipid factors involved in the viral fusion entry process have been well characterized. The process of non-enveloped virus cell entry, in comparison, remains poorly defined, particularly for large complex capsid viruses of the family Reoviridae, which comprises a range of mammalian pathogens. These viruses enter cells without the aid of a limiting membrane and thus cannot fuse with host cell membranes to enter cells. Instead, these viruses are believed to penetrate membranes of the host cell during endocytosis. However, the molecular mechanism of this process is largely undefined. Here we show, utilizing an in vitro liposome penetration assay and cell biology, that bluetongue virus (BTV), an archetypal member of the Reoviridae, utilizes the late endosome-specific lipid lysobisphosphatidic acid for productive membrane penetration and viral entry. Further, we provide preliminary evidence that lipid lysobisphosphatidic acid facilitates pore expansion during membrane penetration, suggesting a mechanism for lipid factor requirement of BTV. This finding indicates that despite the lack of a membrane envelope, the entry process of BTV is similar in specific lipid requirements to enveloped viruses that enter cells through the late endosome. These results are the first, to our knowledge, to demonstrate that a large non-enveloped virus of the Reoviridae has specific lipid requirements for membrane penetration and host cell entry.
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Affiliation(s)
- Avnish Patel
- From the Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom
| | - Bjorn-Patrick Mohl
- From the Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom
| | - Polly Roy
- From the Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, United Kingdom
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27
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Alshaikhahmed K, Roy P. Generation of virus-like particles for emerging epizootic haemorrhagic disease virus: Towards the development of safe vaccine candidates. Vaccine 2016; 34:1103-8. [PMID: 26805595 DOI: 10.1016/j.vaccine.2015.12.069] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 12/17/2015] [Accepted: 12/19/2015] [Indexed: 11/25/2022]
Abstract
Epizootic haemorrhagic disease virus (EHDV) is an insect-transmitted pathogen which causes high mortality in deer populations and may also cause high morbidity in cattle. EHDV belongs to the Orbivirus genus and is closely related to the prototype Bluetongue virus (BTV). To date seven distinct serotypes have been recognized. However, a live-attenuated vaccine is commercially available against only one serotype namely EHDV-2, which has been responsible for multiple outbreaks in North America, Canada, Asia and Australia. Here we expressed four major capsid proteins (VP2, VP3, VP5 and VP7) of EHDV-1 using baculovirus multiple gene expression systems and demonstrated that three-layered VLPs were assembled mimicking the authentic EHDV particles but lacking the viral genomic RNA segments and the transcriptase complex (TC). Antibodies generated with VLPs not only neutralized EHDV-1 infection in cell culture but also showed cross neutralizing reactivity against two other serotypes, EHDV-2 and EHDV-6. For proof of concept, we demonstrated that EHDV-2 VLPs could be generated rapidly by expressing the EHDV-2 variable outer capsid proteins (VP2, VP5) together with EHDV-1 VP3 and VP7, the two inner capsid proteins, which are highly conserved among the 7 serotypes. Data presented in this study validate the VLPs as a potential vaccine and demonstrate that a vaccine could be developed rapidly in the event of an outbreak of a new serotype.
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Affiliation(s)
- Kinda Alshaikhahmed
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, United Kingdom
| | - Polly Roy
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, United Kingdom.
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van Zyl AR, Meyers AE, Rybicki EP. Transient Bluetongue virus serotype 8 capsid protein expression in Nicotiana benthamiana. ACTA ACUST UNITED AC 2015; 9:15-24. [PMID: 28352588 PMCID: PMC5360979 DOI: 10.1016/j.btre.2015.12.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Revised: 11/27/2015] [Accepted: 12/01/2015] [Indexed: 12/11/2022]
Abstract
Expression of BTV-8 capsid genes results in CLPs and VLPs in Nicotiana benthamiana. Density of infiltrated Agrobacterium cells influences protein expression levels. CLPs/VLPs can be purified from leaf extracts using density gradient centrifugation. CLPs/VLPs are present in paracrystalline arrays within the plant cell cytoplasm.
Bluetongue virus (BTV) causes severe disease in domestic and wild ruminants, and has recently caused several outbreaks in Europe. Current vaccines include live-attenuated and inactivated viruses; while these are effective, there is risk of reversion to virulence by mutation or reassortment with wild type viruses. Subunit or virus-like particle (VLP) vaccines are safer options: VLP vaccines produced in insect cells by expression of the four BTV capsid proteins are protective against challenge; however, this is a costly production method. We investigated production of BTV VLPs in plants via Agrobacterium-mediated transient expression, an inexpensive production system very well suited to developing country use. Leaves infiltrated with recombinant pEAQ-HT vectors separately encoding the four BTV-8 capsid proteins produced more proteins than recombinant pTRA vectors. Plant expression using the pEAQ-HT vector resulted in both BTV-8 core-like particles (CLPs) and VLPs; differentially controlling the concentration of infiltrated bacteria significantly influenced yield of the VLPs. In situ localisation of assembled particles was investigated by using transmission electron microscopy (TEM) and it was shown that a mixed population of core-like particles (CLPs, consisting of VP3 and VP7) and VLPs were present as paracrystalline arrays in the cytoplasm of plant cells co-expressing all four capsid proteins.
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Affiliation(s)
- Albertha R van Zyl
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch 7700, South Africa
| | - Ann E Meyers
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch 7700, South Africa
| | - Edward P Rybicki
- Department of Molecular and Cell Biology, University of Cape Town, Private Bag X3, Rondebosch 7700, South Africa
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29
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Zhang X, Ding K, Yu X, Chang W, Sun J, Zhou ZH. In situ structures of the segmented genome and RNA polymerase complex inside a dsRNA virus. Nature 2015; 527:531-534. [PMID: 26503045 PMCID: PMC5086257 DOI: 10.1038/nature15767] [Citation(s) in RCA: 78] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2015] [Accepted: 10/07/2015] [Indexed: 01/15/2023]
Abstract
Viruses in the Reoviridae, like the triple-shelled human rotavirus and the single-shelled insect cytoplasmic polyhedrosis virus (CPV), all package a genome of segmented double-stranded RNAs (dsRNAs) inside the viral capsid and carry out endogenous messenger RNA synthesis through a transcriptional enzyme complex (TEC). By direct electron-counting cryoelectron microscopy and asymmetric reconstruction, we have determined the organization of the dsRNA genome inside quiescent CPV (q-CPV) and the in situ atomic structures of TEC within CPV in both quiescent and transcribing (t-CPV) states. We show that the ten segmented dsRNAs in CPV are organized with ten TECs in a specific, non-symmetric manner, with each dsRNA segment attached directly to a TEC. The TEC consists of two extensively interacting subunits: an RNA-dependent RNA polymerase (RdRP) and an NTPase VP4. We find that the bracelet domain of RdRP undergoes marked conformational change when q-CPV is converted to t-CPV, leading to formation of the RNA template entry channel and access to the polymerase active site. An amino-terminal helix from each of two subunits of the capsid shell protein (CSP) interacts with VP4 and RdRP. These findings establish the link between sensing of environmental cues by the external proteins and activation of endogenous RNA transcription by the TEC inside the virus.
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MESH Headings
- Capsid Proteins/chemistry
- Capsid Proteins/metabolism
- Capsid Proteins/ultrastructure
- Catalytic Domain
- Cryoelectron Microscopy
- Genome, Viral/genetics
- Models, Molecular
- Multienzyme Complexes/chemistry
- Multienzyme Complexes/metabolism
- Multienzyme Complexes/ultrastructure
- Nucleoside-Triphosphatase/metabolism
- Nucleoside-Triphosphatase/ultrastructure
- Protein Subunits/chemistry
- Protein Subunits/metabolism
- RNA, Double-Stranded/genetics
- RNA, Double-Stranded/ultrastructure
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- RNA, Messenger/ultrastructure
- RNA, Viral/biosynthesis
- RNA, Viral/genetics
- RNA, Viral/ultrastructure
- RNA-Dependent RNA Polymerase/chemistry
- RNA-Dependent RNA Polymerase/metabolism
- RNA-Dependent RNA Polymerase/ultrastructure
- Reoviridae/enzymology
- Reoviridae/genetics
- Reoviridae/ultrastructure
- Templates, Genetic
- Transcription, Genetic
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Affiliation(s)
- Xing Zhang
- California Nanosystems Institute, Los Angeles, CA 90095, USA
| | - Ke Ding
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Bioengineering, University of California, Los Angeles, CA 90095, USA
| | - Xuekui Yu
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
| | - Winston Chang
- California Nanosystems Institute, Los Angeles, CA 90095, USA
| | - Jingchen Sun
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Subtropical Sericulture and Mulberry Resources Protection and Safety Engineering Research Center, Guangdong Provincial Key Laboratory of Agro-animal Genomics and Molecular Breeding, College of Animal Science, South China Agricultural University, Guangzhou, Guangdong 510642, China
| | - Z. Hong Zhou
- California Nanosystems Institute, Los Angeles, CA 90095, USA
- Department of Microbiology, Immunology and Molecular Genetics, University of California, Los Angeles, CA 90095, USA
- Bioengineering, University of California, Los Angeles, CA 90095, USA
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30
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Miyazaki N, Higashiura A, Higashiura T, Akita F, Hibino H, Omura T, Nakagawa A, Iwasaki K. Electron microscopic imaging revealed the flexible filamentous structure of the cell attachment protein P2 of Rice dwarf virus located around the icosahedral 5-fold axes. J Biochem 2015; 159:181-90. [PMID: 26374901 DOI: 10.1093/jb/mvv092] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2015] [Accepted: 07/30/2015] [Indexed: 02/02/2023] Open
Abstract
The minor outer capsid protein P2 of Rice dwarf virus (RDV), a member of the genus Phytoreovirus in the family Reoviridae, is essential for viral cell entry. Here, we clarified the structure of P2 and the interactions to host insect cells. Negative stain electron microscopy (EM) showed that P2 proteins are monomeric and flexible L-shaped filamentous structures of ∼20 nm in length. Cryo-EM structure revealed the spatial arrangement of P2 in the capsid, which was prescribed by the characteristic virion structure. The P2 proteins were visualized as partial rod-shaped structures of ∼10 nm in length in the cryo-EM map and accommodated in crevasses on the viral surface around icosahedral 5-fold axes with hydrophobic interactions. The remaining disordered region of P2 assumed to be extended to the radial direction towards exterior. Electron tomography clearly showed that RDV particles were away from the cellular membrane at a uniform distance and several spike-like densities, probably corresponding to P2, connecting a viral particle to the host cellular membrane during cell entry. By combining the in vitro and in vivo structural information, we could gain new insights into the detailed mechanism of the cell entry of RDV.
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Affiliation(s)
- Naoyuki Miyazaki
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan; Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Aichi, Japan;
| | | | - Tomoko Higashiura
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan
| | - Fusamichi Akita
- Laboratory of Virology, National Agricultural Research Center, Tsukuba, Ibaraki, Japan; and Photosynthesis Research Center, Graduate School of Natural Science and Technology, Okayama University, Okayama, Okayama, Japan
| | - Hiroyuki Hibino
- Laboratory of Virology, National Agricultural Research Center, Tsukuba, Ibaraki, Japan; and
| | - Toshihiro Omura
- Laboratory of Virology, National Agricultural Research Center, Tsukuba, Ibaraki, Japan; and
| | - Atsushi Nakagawa
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan
| | - Kenji Iwasaki
- Institute for Protein Research, Osaka University, Suita, Osaka, Japan;
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31
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Nomikou K, Hughes J, Wash R, Kellam P, Breard E, Zientara S, Palmarini M, Biek R, Mertens P. Widespread Reassortment Shapes the Evolution and Epidemiology of Bluetongue Virus following European Invasion. PLoS Pathog 2015; 11:e1005056. [PMID: 26252219 PMCID: PMC4529188 DOI: 10.1371/journal.ppat.1005056] [Citation(s) in RCA: 95] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Accepted: 06/30/2015] [Indexed: 11/24/2022] Open
Abstract
Genetic exchange by a process of genome-segment ‘reassortment’ represents an important mechanism for evolutionary change in all viruses with segmented genomes, yet in many cases a detailed understanding of its frequency and biological consequences is lacking. We provide a comprehensive assessment of reassortment in bluetongue virus (BTV), a globally important insect-borne pathogen of livestock, during recent outbreaks in Europe. Full-genome sequences were generated and analysed for over 150 isolates belonging to the different BTV serotypes that have emerged in the region over the last 5 decades. Based on this novel dataset we confirm that reassortment is a frequent process that plays an important and on-going role in evolution of the virus. We found evidence for reassortment in all ten segments without a significant bias towards any particular segment. However, we observed biases in the relative frequency at which particular segments were associated with each other during reassortment. This points to selective constraints possibly caused by functional relationships between individual proteins or genome segments and genome-wide epistatic interactions. Sites under positive selection were more likely to undergo amino acid changes in newly reassorted viruses, providing additional evidence for adaptive dynamics as a consequence of reassortment. We show that the live attenuated vaccines recently used in Europe have repeatedly reassorted with field strains, contributing to their genotypic, and potentially phenotypic, variability. The high degree of plasticity seen in the BTV genome in terms of segment origin suggests that current classification schemes that are based primarily on serotype, which is determined by only a single genome segment, are inadequate. Our work highlights the need for a better understanding of the mechanisms and epidemiological consequences of reassortment in BTV, as well as other segmented RNA viruses. Segmented viruses have genomes that are separated into multiple segments, comparable to chromosomes in higher organisms. When two segmented viruses of the same species infect the same cell, their progeny may incorporate segments picked up from the “parental” viruses. This process is called “reassortment” and represents an important way for segmented viruses to evolve. Whereas reassortment has received a lot of attention in certain segmented viruses, especially influenza A, its frequency and biological consequences remain poorly understood for most of the others. Here, we present a comprehensive analysis of the reassortment patterns in bluetongue virus, an important pathogen of livestock, during its repeated emergence in Europe in recent decades. We confirm earlier reports that reassortment is common and can involve segments derived from live vaccines used to control outbreaks. However, the mixing of viral genomes is not strictly random and reassortment is commonly followed by novel adaptive changes in the progeny virus. This points to important functional links (paired associations) between certain segments. Our findings have important implications for the classification and control of segmented viruses and generate new insights and hypotheses about the biological interactions among different parts of the bluetongue virus genome.
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Affiliation(s)
- Kyriaki Nomikou
- Vector-Borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Woking, United Kingdom
| | - Joseph Hughes
- MRC–University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Rachael Wash
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
| | - Paul Kellam
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, United Kingdom
- Division of Infection and Immunity, Research Department of Infection, University College London, London, United Kingdom
| | - Emmanuel Breard
- French Agency for Food, Environment and Occupational Health and Safety (ANSES), Maisons-Alfort, France
| | - Stéphan Zientara
- French Agency for Food, Environment and Occupational Health and Safety (ANSES), Maisons-Alfort, France
| | - Massimo Palmarini
- MRC–University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
| | - Roman Biek
- MRC–University of Glasgow Centre for Virus Research, Glasgow, United Kingdom
- Institute of Biodiversity, Animal Health and Comparative Medicine, Boyd Orr Centre for Population and Ecosystem Health, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
- * E-mail: (RB); (PM)
| | - Peter Mertens
- Vector-Borne Viral Diseases Programme, The Pirbright Institute, Pirbright, Woking, United Kingdom
- * E-mail: (RB); (PM)
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32
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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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33
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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: 36] [Impact Index Per Article: 4.0] [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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34
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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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35
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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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Trafficking of bluetongue virus visualized by recovery of tetracysteine-tagged virion particles. J Virol 2014; 88:12656-68. [PMID: 25142589 DOI: 10.1128/jvi.01815-14] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Bluetongue virus (BTV), a member of the Orbivirus genus in the Reoviridae family, is a double-capsid insect-borne virus enclosing a genome of 10 double-stranded RNA segments. Like those of other members of the family, BTV virions are nonenveloped particles containing two architecturally complex capsids. The two proteins of the outer capsid, VP2 and VP5, are involved in BTV entry and in the delivery of the transcriptionally active core to the cell cytoplasm. Although the importance of the endocytic pathway in BTV entry has been reported, detailed analyses of entry and the role of each protein in virus trafficking have not been possible due to the lack of availability of a tagged virus. Here, for the first time, we report on the successful manipulation of a segmented genome of a nonenveloped capsid virus by the introduction of tags that were subsequently fluorescently visualized in infected cells. The genetically engineered fluorescent BTV particles were observed to enter live cells immediately after virus adsorption. Further, we showed the separation of VP2 from VP5 during virus entry and confirmed that while VP2 is shed from virions in early endosomes, virus particles still consisting of VP5 were trafficked sequentially from early to late endosomes. Since BTV infects both mammalian and insect cells, the generation of tagged viruses will allow visualization of the trafficking of BTV farther downstream in different host cells. In addition, the tagging technology has potential for transferable application to other nonenveloped complex viruses. IMPORTANCE Live-virus trafficking in host cells has been highly informative on the interactions between virus and host cells. Although the insertion of fluorescent markers into viral genomes has made it possible to study the trafficking of enveloped viruses, the physical constraints of architecturally complex capsid viruses have imposed practical limitations. In this study, we have successfully genetically engineered the segmented RNA genome of bluetongue virus (BTV), a complex nonenveloped virus belonging to the Reoviridae family. The resulting fluorescent virus particles could be visualized in virus entry studies of both live and fixed cells. This is the first time a structurally complex capsid virus has been successfully genetically manipulated to generate virus particles that could be visualized in infected cells.
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Matsuo E, Leon E, Matthews SJ, Roy P. Structure based modification of Bluetongue virus helicase protein VP6 to produce a viable VP6-truncated BTV. Biochem Biophys Res Commun 2014; 451:603-8. [PMID: 25128829 PMCID: PMC4169673 DOI: 10.1016/j.bbrc.2014.08.028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 08/06/2014] [Indexed: 12/05/2022]
Abstract
NMR analysis on BTV VP6 reveals two large loop regions. The loss of a loop (aa 34–130) does not affect the overall fold of the protein. A region of VP6 (aa 34–92) is not required for BTV replication. A region of VP6 (aa 93–130) plays an essential role in the virus replication.
Bluetongue virus core protein VP6 is an ATP hydrolysis dependent RNA helicase. However, despite much study, the precise role of VP6 within the viral capsid and its structure remain unclear. To investigate the requirement of VP6 in BTV replication, we initiated a structural and biological study. Multinuclear nuclear magnetic resonance spectra were assigned on his-tagged full-length VP6 (329 amino acid residues) as well as several truncated VP6 variants. The analysis revealed a large structured domain with two large loop regions that exhibit significant conformational exchange. One of the loops (amino acid position 34–130) could be removed without affecting the overall fold of the protein. Moreover, using a BTV reverse genetics system, it was possible to demonstrate that the VP6-truncated BTV was viable in BHK cells in the absence of any helper VP6 protein, suggesting that a large portion of this loop region is not absolutely required for BTV replication.
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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; Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Esther Leon
- Division of Molecular Biosciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Steve J Matthews
- Division of Molecular Biosciences, Centre for Structural Biology, Imperial College London, South Kensington, London SW7 2AZ, UK
| | - Polly Roy
- Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK.
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Purification, stability, and immunogenicity analyses of five bluetongue virus proteins for use in development of a subunit vaccine that allows differentiation of infected from vaccinated animals. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2014; 21:443-52. [PMID: 24451327 DOI: 10.1128/cvi.00776-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Bluetongue virus (BTV) causes bluetongue disease, a vector-borne disease of ruminants. The recent northerly spread of BTV serotype 8 in Europe resulted in outbreaks characterized by clinical signs in cattle, including unusual teratogenic effects. Vaccination has been shown to be crucial for controlling the spread of vector-borne diseases such as BTV. With the aim of developing a novel subunit vaccine targeting BTV-8 that allows differentiation of infected from vaccinated animals, five His-tagged recombinant proteins, VP2 and VP5 of BTV-8 and NS1, NS2, and NS3 of BTV-2, were expressed in baculovirus or Escherichia coli expression systems for further study. Optimized purification protocols were determined for VP2, NS1, NS2, and NS3, which remained stable for detection for at least 560 to 610 days of storage at +4°C or -80°C, and Western blotting using sera from vaccinated or experimentally infected cattle indicated that VP2 and NS2 were recognized by BTV-specific antibodies. To characterize murine immune responses to the four proteins, mice were subcutaneously immunized twice at a 4-week interval with one of three protein combinations plus immunostimulating complex ISCOM-Matrix adjuvant or with ISCOM-Matrix alone (n = 6 per group). Significantly higher serum IgG antibody titers specific for VP2 and NS2 were detected in immunized mice than were detected in controls. VP2, NS1, and NS2 but not NS3 induced specific lymphocyte proliferative responses upon restimulation of spleen cells from immunized mice. The data suggest that these recombinant purified proteins, VP2, NS1, and NS2, could be an important part of a novel vaccine design against BTV-8.
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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: 64] [Impact Index Per Article: 5.8] [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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Qin YL, Sun EC, Liu NH, Yang T, Xu QY, Zhao J, Wang WS, Wei P, Feng YF, Li JP, Wu DL. Identification of a linear B-cell epitope within the Bluetongue virus serotype 8 NS2 protein using a phage-displayed random peptide library. Vet Immunol Immunopathol 2013; 154:93-101. [PMID: 23747319 DOI: 10.1016/j.vetimm.2013.05.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2013] [Revised: 04/25/2013] [Accepted: 05/05/2013] [Indexed: 01/04/2023]
Abstract
The NS2 protein of Bluetongue virus (BTV) is an important non-structural protein and plays important roles in viral replication and assembly. In this study, one monoclonal antibody (mAb), 4D4, was raised against BTV8 NS2. Phage display technology was used and identified the consensus binding motif SNYD recognized by mAb 4D4. To define the minimal region required for antibody binding, a panel of synthetic peptides encompassing SNYD derived from the BTV8 NS2 was then used to more specifically define the 4D4 epitope as (149)RSNYDV(154). Furthermore, amino acid sequence alignments of different BTV serotypes and other orbiviruses suggested that this epitope is highly conserved among the BTV serotypes. The mAb reagent generated in this study may be applied to the development of BTV diagnosis and surveillance programs and the epitope defined here can lead to important insights into how BTV might interact with the sheep's immune system.
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Affiliation(s)
- Yong-Li Qin
- The Key Laboratory of Veterinary Public Health, Ministry of Agriculture, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin 150001, PR China.
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Wang WS, Sun EC, Liu NH, Yang T, Xu QY, Qin YL, Zhao J, Feng YF, Li JP, Wei P, Zhang CY, Wu DL. Identification of three novel linear B-cell epitopes on the VP5 protein of BTV16. Vet Microbiol 2013; 162:631-642. [DOI: 10.1016/j.vetmic.2012.11.042] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2012] [Revised: 11/28/2012] [Accepted: 11/30/2012] [Indexed: 11/30/2022]
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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: 56] [Impact Index Per Article: 4.7] [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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Abstract
African horsesickness (AHS) is a devastating disease of horses. The disease is caused by the double-stranded RNA-containing African horsesickness virus (AHSV). Using electron cryomicroscopy and three-dimensional image reconstruction, we determined the architecture of an AHSV serotype 4 (AHSV-4) reference strain. The structure revealed triple-layered AHS virions enclosing the segmented genome and transcriptase complex. The innermost protein layer contains 120 copies of VP3, with the viral polymerase, capping enzyme, and helicase attached to the inner surface of the VP3 layer on the 5-fold axis, surrounded by double-stranded RNA. VP7 trimers form a second, T=13 layer on top of VP3. Comparative analyses of the structures of bluetongue virus and AHSV-4 confirmed that VP5 trimers form globular domains and VP2 trimers form triskelions, on the virion surface. We also identified an AHSV-7 strain with a truncated VP2 protein (AHSV-7 tVP2) which outgrows AHSV-4 in culture. Comparison of AHSV-7 tVP2 to bluetongue virus and AHSV-4 allowed mapping of two domains in AHSV-4 VP2, and one in bluetongue virus VP2, that are important in infection. We also revealed a protein plugging the 5-fold vertices in AHSV-4. These results shed light on virus-host interactions in an economically important orbivirus to help the informed design of new vaccines.
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Allison AB, Holmes EC, Potgieter AC, Wright IM, Sailleau C, Breard E, Ruder MG, Stallknecht DE. Segmental configuration and putative origin of the reassortant orbivirus, epizootic hemorrhagic disease virus serotype 6, strain Indiana. Virology 2012; 424:67-75. [PMID: 22230700 DOI: 10.1016/j.virol.2011.12.004] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2011] [Revised: 12/02/2011] [Accepted: 12/06/2011] [Indexed: 11/17/2022]
Abstract
In 2006, an exotic reassortant orbivirus, epizootic hemorrhagic disease virus serotype 6 (EHDV-6) [strain (Indiana)], was first detected in the United States. To characterize the reassortment configuration of this virus and to conclusively determine the parental virus of each RNA segment, the complete genome of EHDV-6 (Indiana) was sequenced, in addition to the genomes of representative EHDV-6 and EHDV-2 isolates. Based on genomic comparisons to all other EHDV serotypes, we determined that EHDV-6 (Indiana) originated from a reassortment event between the Australian prototype strain of EHDV-6 (CSIRO 753) and the North American topotype of EHDV-2 (Alberta). Additionally, phylogenetic analysis of all EHDV-6 (Indiana) isolates detected in the United States from 2006 to 2010 suggests that the virus may be undergoing continual reassortment with EHDV-2 (Alberta). In 2010, EHDV-6 (CSIRO 753) was detected in Guadeloupe, demonstrating that the parental virus of the reassortment event is circulating in the Caribbean.
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Affiliation(s)
- A B Allison
- Southeastern Cooperative Wildlife Disease Study, College of Veterinary Medicine, University of Georgia, Athens, GA 30602, 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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Ratinier M, Caporale M, Golder M, Franzoni G, Allan K, Nunes SF, Armezzani A, Bayoumy A, Rixon F, Shaw A, Palmarini M. Identification and characterization of a novel non-structural protein of bluetongue virus. PLoS Pathog 2011; 7:e1002477. [PMID: 22241985 PMCID: PMC3248566 DOI: 10.1371/journal.ppat.1002477] [Citation(s) in RCA: 201] [Impact Index Per Article: 15.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2011] [Accepted: 11/26/2011] [Indexed: 12/19/2022] Open
Abstract
Bluetongue virus (BTV) is the causative agent of a major disease of livestock (bluetongue). For over two decades, it has been widely accepted that the 10 segments of the dsRNA genome of BTV encode for 7 structural and 3 non-structural proteins. The non-structural proteins (NS1, NS2, NS3/NS3a) play different key roles during the viral replication cycle. In this study we show that BTV expresses a fourth non-structural protein (that we designated NS4) encoded by an open reading frame in segment 9 overlapping the open reading frame encoding VP6. NS4 is 77–79 amino acid residues in length and highly conserved among several BTV serotypes/strains. NS4 was expressed early post-infection and localized in the nucleoli of BTV infected cells. By reverse genetics, we showed that NS4 is dispensable for BTV replication in vitro, both in mammalian and insect cells, and does not affect viral virulence in murine models of bluetongue infection. Interestingly, NS4 conferred a replication advantage to BTV-8, but not to BTV-1, in cells in an interferon (IFN)-induced antiviral state. However, the BTV-1 NS4 conferred a replication advantage both to a BTV-8 reassortant containing the entire segment 9 of BTV-1 and to a BTV-8 mutant with the NS4 identical to the homologous BTV-1 protein. Collectively, this study suggests that NS4 plays an important role in virus-host interaction and is one of the mechanisms played, at least by BTV-8, to counteract the antiviral response of the host. In addition, the distinct nucleolar localization of NS4, being expressed by a virus that replicates exclusively in the cytoplasm, offers new avenues to investigate the multiple roles played by the nucleolus in the biology of the cell. Bluetongue is a major infectious disease of ruminants caused by bluetongue virus (BTV), an “arbovirus” transmitted from infected to susceptible hosts by biting midges. Historically, bluetongue has been endemic almost exclusively in temperate and tropical areas of the world. However, in the last decade BTV has spread extensively in several geographical areas causing a serious burden to both animal health and the economy. BTV possesses a double-stranded RNA segmented genome. For over two decades, it has been widely accepted that the 10 segments of BTV genome encode for 7 structural and 3 non-structural proteins. In this study we discovered that BTV expresses a previously uncharacterized non-structural protein that we designated NS4. Although BTV replicates exclusively in the cytoplasm, we found NS4 to localize in the nucleoli of the infected cells. Our study shows that NS4 is not needed for viral replication both in mammalian and insect cells, and in mice. However, NS4 confers a replication advantage to BTV in cells in an antiviral state induced by interferon. In conclusion, we have elucidated a possible route by which BTV can counteract the defences of the host.
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Affiliation(s)
- Maxime Ratinier
- MRC-University of Glasgow Centre for Virus Research, Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, United Kingdom
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Rossmann MG, Rao VB. Principles of virus structural organization. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 726:17-47. [PMID: 22297509 PMCID: PMC3767311 DOI: 10.1007/978-1-4614-0980-9_3] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Viruses, the molecular nanomachines infecting hosts ranging from prokaryotes to eukaryotes, come in different sizes, shapes, and symmetries. Questions such as what principles govern their structural organization, what factors guide their assembly, how these viruses integrate multifarious functions into one unique structure have enamored researchers for years. In the last five decades, following Caspar and Klug's elegant conceptualization of how viruses are constructed, high-resolution structural studies using X-ray crystallography and more recently cryo-EM techniques have provided a wealth of information on structures of a variety of viruses. These studies have significantly -furthered our understanding of the principles that underlie structural organization in viruses. Such an understanding has practical impact in providing a rational basis for the design and development of antiviral strategies. In this chapter, we review principles underlying capsid formation in a variety of viruses, emphasizing the recent developments along with some historical perspective.
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Affiliation(s)
- Michael G. Rossmann
- grid.169077.e0000000419372197Dept. Biological Sciences, Purdue University, W. State St. 915, West Lafayette, 47907-2054 Indiana USA
| | - Venigalla B. Rao
- grid.39936.360000000121746686Dept. Biology, Catholic University of America, Washington, 20064 District of Columbia USA
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Rojas JM, Rodríguez-Calvo T, Peña L, Sevilla N. T cell responses to bluetongue virus are directed against multiple and identical CD4+ and CD8+ T cell epitopes from the VP7 core protein in mouse and sheep. Vaccine 2011; 29:6848-57. [DOI: 10.1016/j.vaccine.2011.07.061] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2011] [Revised: 07/15/2011] [Accepted: 07/16/2011] [Indexed: 01/30/2023]
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