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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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Evidence of Intragenic Recombination in African Horse Sickness Virus. Viruses 2019; 11:v11070654. [PMID: 31323749 PMCID: PMC6669442 DOI: 10.3390/v11070654] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2019] [Revised: 05/06/2019] [Accepted: 05/07/2019] [Indexed: 12/24/2022] Open
Abstract
Intragenic recombination has been described in various RNA viruses as a mechanism to increase genetic diversity, resulting in increased virulence, expanded host range, or adaptability to a changing environment. Orbiviruses are no exception to this, with intragenic recombination previously detected in the type species, bluetongue virus (BTV). African horse sickness virus (AHSV) is a double-stranded RNA virus belonging to the Oribivirus genus in the family Reoviridae. Genetic recombination through reassortment has been described in AHSV, but not through homologous intragenic recombination. The influence of the latter on the evolution of AHSV was investigated by analyzing the complete genomes of more than 100 viruses to identify evidence of recombination. Segment-1, segment-6, segment-7, and segment-10 showed evidence of intragenic recombination, yet only one (Segment-10) of these events was manifested in subsequent lineages. The other three hybrid segments were as a result of recombination between field isolates and the vaccine derived live attenuated viruses (ALVs).
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Schade-Weskott ML, van Schalkwyk A, Koekemoer JJO. A correlation between capsid protein VP2 and the plaque morphology of African horse sickness virus in cell culture. Virus Genes 2018; 54:527-535. [PMID: 29730763 DOI: 10.1007/s11262-018-1567-y] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 04/30/2018] [Indexed: 12/29/2022]
Abstract
The attenuated live virus vaccine that is used in South Africa to protect against African horse sickness infection was developed more than 50 years ago. With the selection of the vaccine strains by cell culture passage, a correlation between the size of plaques formed in monolayer Vero cultures and attenuation of virus virulence in horses was found. The large plaque phenotype was used as an indication of cell culture adaptation and strongly correlated with attenuation of virulence in horses. There was never any investigation into the genetic causes of either the variation in plaque size, or the loss of virulence. An understanding of the underlying mechanisms of attenuation would benefit the production of a safer AHSV vaccine. To this end, the genomes of different strains of two African horse sickness isolates, producing varying plaque sizes, were compared and the differences between them identified. This comparison suggested that proteins VP2, VP3, VP5 and NS3 were most likely involved in the determination of the plaque phenotype. Comparison between genome sequences (obtained from GenBank) of low and high passage strains from two additional serotypes indicated that VP2 was the only protein with amino acid substitutions in all four serotypes. The amino acid substitutions all occurred within the same hydrophilic area, resulting in increased hydrophilicity of VP2 in the large plaque strains.
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Affiliation(s)
- Mathilde L Schade-Weskott
- Agricultural Research Council - Onderstepoort Veterinary Institute, 100 Old Soutpan Rd, Pretoria, South Africa.
- Department of Veterinary Tropical Diseases, Faculty of Veterinary Science, University of Pretoria, Pretoria, South Africa.
| | - Antoinette van Schalkwyk
- Agricultural Research Council - Onderstepoort Veterinary Institute, 100 Old Soutpan Rd, Pretoria, South Africa
| | - J J O Koekemoer
- Agricultural Research Council - Onderstepoort Veterinary Institute, 100 Old Soutpan Rd, Pretoria, South Africa
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4
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Faber F, van Kleef M, Tshilwane S, Pretorius A. African horse sickness virus serotype 4 antigens, VP1-1, VP2-2, VP4, VP7 and NS3, induce cytotoxic T cell responses in vitro. Virus Res 2016; 220:12-20. [DOI: 10.1016/j.virusres.2016.04.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2015] [Revised: 04/06/2016] [Accepted: 04/06/2016] [Indexed: 02/03/2023]
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Maree S, Maree FF, Putterill JF, de Beer TA, Huismans H, Theron J. Synthesis of empty african horse sickness virus particles. Virus Res 2016; 213:184-194. [DOI: 10.1016/j.virusres.2015.12.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2015] [Revised: 11/05/2015] [Accepted: 12/07/2015] [Indexed: 11/30/2022]
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de la Poza F, Marín-López A, Castillo-Olivares J, Calvo-Pinilla E, Ortego J. Identification of CD8 T cell epitopes in VP2 and NS1 proteins of African horse sickness virus in IFNAR(-/-) mice. Virus Res 2015; 210:149-53. [PMID: 26272673 DOI: 10.1016/j.virusres.2015.08.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2015] [Revised: 08/05/2015] [Accepted: 08/06/2015] [Indexed: 12/17/2022]
Abstract
African horse sickness virus (AHSV) is an Orbivirus of the family Reoviridae that causes severe pathology in equids. Previous work in our laboratory showed the presence of AHSV-specific CD8(+) T cells in mice immunized with recombinant Modified Vaccinia Ankara (rMVA) expressing VP2 and NS1 proteins. In the present work, we selected potential CD8 T cell epitopes (MHC-class I binding peptides) for the 129 mouse strain from the VP2 and NS1 proteins of AHSV-4, using a combination of four epitope prediction algorithms (SYFPEITHI, BYMAS, NetMHC I and NetMHCpan). ELISPOT and Intracellular Cytokine Staining (ICS) analysis showed that the VP2-720 (MSLLNFGAV), VP2-1044 (YTFGNKFLL), and NS1-83 (CVIKNADYV) peptides elicited IFN-γ production in splenocytes of MVA-VP2 and MVA-NS1 immunized mice and were identified as CD8(+) T cell epitopes. In addition, these three MHC-class I-binding peptides induced the expression of CD107a in CD8(+) T cells, an indirect marker of cytotoxic activity. Importantly, VP2-1044 and NS1-83 epitopes are conserved among all nine AHSV serotypes. These data demonstrate the activation of AHSV specific T-cell epitopes during vaccination with rMVAs expressing VP2 and NS1. Furthermore, the characterization of these CD8(+) T-cell epitopes provides information useful for the design of novel marker multiserotype vaccines against AHSV.
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Affiliation(s)
- Francisco de la Poza
- Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130 Madrid, Spain
| | - Alejandro Marín-López
- Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130 Madrid, Spain
| | | | | | - Javier Ortego
- Centro de Investigación en Sanidad Animal, INIA-CISA, Valdeolmos, 28130 Madrid, Spain.
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Weyer CT, Joone C, Lourens CW, Monyai MS, Koekemoer O, Grewar JD, van Schalkwyk A, Majiwa PO, MacLachlan NJ, Guthrie AJ. Development of three triplex real-time reverse transcription PCR assays for the qualitative molecular typing of the nine serotypes of African horse sickness virus. J Virol Methods 2015; 223:69-74. [DOI: 10.1016/j.jviromet.2015.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 07/14/2015] [Accepted: 07/27/2015] [Indexed: 11/25/2022]
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8
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Sánchez-Matamoros A, Beck C, Kukielka D, Lecollinet S, Blaise-Boisseau S, Garnier A, Rueda P, Zientara S, Sánchez-Vizcaíno JM. Development of a Microsphere-based Immunoassay for Serological Detection of African Horse Sickness Virus and Comparison with Other Diagnostic Techniques. Transbound Emerg Dis 2015; 63:e270-e277. [PMID: 25693720 DOI: 10.1111/tbed.12340] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2014] [Indexed: 11/29/2022]
Abstract
African horse sickness (AHS) is a viral disease that causes high morbidity and mortality rates in susceptible Equidae and therefore significant economic losses. More rapid, sensitive and specific assays are required by diagnostic laboratories to support effective surveillance programmes. A novel microsphere-based immunoassay (Luminex assay) in which beads are coated with recombinant AHS virus (AHSV) structural protein 7 (VP7) has been developed for serological detection of antibodies against VP7 of any AHSV serotype. The performance of this assay was compared with that of a commercial enzyme-linked immunosorbent assay (ELISA) and commercial lateral flow assay (LFA) on a large panel of serum samples from uninfected horses (n = 92), from a reference library of all AHSV serotypes (n = 9), on samples from horses experimentally infected with AHSV (n = 114), and on samples from West African horses suspected of having AHS (n = 85). The Luminex assay gave the same negative results as ELISA when used to test the samples from uninfected horses. Both assays detected antibodies to all nine AHSV serotypes. In contrast, the Luminex assay detected a higher rate of anti-VP7 positivity in the West African field samples than did ELISA or LFA. The Luminex assay detected anti-VP7 positivity in experimentally infected horses at 7 days post-infection, compared to 13 days for ELISA. This novel immunoassay provides a platform for developing multiplex assays, in which the presence of antibodies against multiple ASHV antigens can be detected simultaneously. This would be useful for serotyping or for differentiating infected from vaccinated animals.
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Affiliation(s)
- A Sánchez-Matamoros
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid, Spain. .,Animal Health Department, Universidad Complutense de Madrid, Madrid, Spain. .,CEI Campus Moncloa, UCM-UPM, Madrid, Spain.
| | - C Beck
- French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Animal Health Laboratory, UPEC, UMR 1161 INRA, ANSES, ENVA, Maisons-Alfort, France
| | - D Kukielka
- Microbiology Area, Pharmacy Faculty, San Pablo CEU University, Madrid, Spain
| | - S Lecollinet
- French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Animal Health Laboratory, UPEC, UMR 1161 INRA, ANSES, ENVA, Maisons-Alfort, France
| | - S Blaise-Boisseau
- French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Animal Health Laboratory, UPEC, UMR 1161 INRA, ANSES, ENVA, Maisons-Alfort, France
| | - A Garnier
- French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Animal Health Laboratory, UPEC, UMR 1161 INRA, ANSES, ENVA, Maisons-Alfort, France
| | - P Rueda
- Inmunología y Genética Aplicada, S.A. (INGENASA), Madrid, Spain
| | - S Zientara
- French Agency for Food, Environmental and Occupational Health and Safety (ANSES), Animal Health Laboratory, UPEC, UMR 1161 INRA, ANSES, ENVA, Maisons-Alfort, France
| | - J M Sánchez-Vizcaíno
- VISAVET Health Surveillance Centre, Universidad Complutense de Madrid, Madrid, Spain.,Animal Health Department, Universidad Complutense de Madrid, Madrid, Spain
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9
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Factors that affect the intracellular localization and trafficking of African horse sickness virus core protein, VP7. Virology 2014; 456-457:279-91. [DOI: 10.1016/j.virol.2014.03.030] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2013] [Revised: 01/26/2014] [Accepted: 03/29/2014] [Indexed: 11/21/2022]
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Ayelet G, Derso S, Jenberie S, Tigre W, Aklilu N, Gelaye E, Asmare K. Outbreak investigation and molecular characterization of African horse sickness virus circulating in selected areas of Ethiopia. Acta Trop 2013; 127:91-6. [PMID: 23567554 DOI: 10.1016/j.actatropica.2013.03.018] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2013] [Revised: 03/25/2013] [Accepted: 03/31/2013] [Indexed: 12/01/2022]
Abstract
The study was conducted from June 2011 to May 2012 in central, northern and western parts of Ethiopia to investigate and identify circulating serotypes of African horse sickness virus (AHSV). The indigenous knowledge of equine owners about AHS in the study areas was assessed and also the retrospective data of AHS outbreaks for 2011 were analyzed. Whole blood samples were collected for virus isolation and serotyping from diseased horses and mules showing typical signs of the AHS. Virus isolation on Vero cell and detection of AHSV genomes using conventional RT-PCR were conducted. Further molecular characterization and serotyping were done on positive isolates. The questionnaire survey revealed that equine owners do recognize AHS clinically and have a local name that varies in different regions. From the 72 equine owners interviewed about their knowhow of AHS, 48 (66.7%) of respondents were not aware of AHS disease mode of transmission. The retrospective disease report data showed that a total of 208 outbreaks were reported and 3036 cases and 1167 deaths were recorded in 2011. AHS outbreaks were more frequently observed from September to December and the highest number of outbreaks was recorded in October. During the study period totally six outbreaks were investigated and a total of 62 horses and 10 mules were found sick and all the four forms of AHS were observed. Cardiac form accounted for 52.8%, followed by African horse sickness fever form 31.9%, pulmonary form 8.4% and mixed form 6.9%. AHSV-9 was the only serotype circulating in the outbreak areas.
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Affiliation(s)
- Gelagay Ayelet
- National Veterinary Institute, P.O. Box 19, Debre-zeit, Ethiopia.
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11
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Ns1 is a key protein in the vaccine composition to protect Ifnar(-/-) mice against infection with multiple serotypes of African horse sickness virus. PLoS One 2013; 8:e70197. [PMID: 23894615 PMCID: PMC3720900 DOI: 10.1371/journal.pone.0070197] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2013] [Accepted: 06/16/2013] [Indexed: 11/19/2022] Open
Abstract
African horse sickness virus (AHSV) belongs to the genus Orbivirus. We have now engineered naked DNAs and recombinant modified vaccinia virus Ankara (rMVA) expressing VP2 and NS1 proteins from AHSV-4. IFNAR((-/-)) mice inoculated with DNA/rMVA-VP2,-NS1 from AHSV-4 in an heterologous prime-boost vaccination strategy generated significant levels of neutralizing antibodies specific of AHSV-4. In addition, vaccination stimulated specific T cell responses against the virus. The vaccine elicited partial protection against an homologous AHSV-4 infection and induced cross-protection against the heterologous AHSV-9. Similarly, IFNAR((-/-)) mice vaccinated with an homologous prime-boost strategy with rMVA-VP2-NS1 from AHSV-4 developed neutralizing antibodies and protective immunity against AHSV-4. Furthermore, the levels of immunity were very high since none of vaccinated animals presented viraemia when they were challenged against the homologous AHSV-4 and very low levels when they were challenged against the heterologous virus AHSV-9. These data suggest that the immunization with rMVA/rMVA was more efficient in protection against a virulent challenge with AHSV-4 and both strategies, DNA/rMVA and rMVA/rMVA, protected against the infection with AHSV-9. The inclusion of the protein NS1 in the vaccine formulations targeting AHSV generates promising multiserotype vaccines.
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12
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Kaname Y, Celma CCP, Kanai Y, Roy P. Recovery of African horse sickness virus from synthetic RNA. J Gen Virol 2013; 94:2259-2265. [PMID: 23860489 DOI: 10.1099/vir.0.055905-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
African horse sickness virus (AHSV) is an insect-vectored emerging pathogen of equine species. AHSV (nine serotypes) is a member of the genus Orbivirus, with a morphology and coding strategy similar to that of the type member, bluetongue virus. However, these viruses are distinct at the genetic level, in the proteins they encode and in their pathobiology. AHSV infection of horses is highly virulent with a mortality rate of up to 90 %. AHSV is transmitted by Culicoides, a common European insect, and has the potential to emerge in Europe from endemic countries of Africa. As a result, a safe and effective vaccine is sought urgently. As part of a programme to generate a designed highly attenuated vaccine, we report here the recovery of AHSV from a complete set of RNA transcripts synthesized in vitro from cDNA clones. We have demonstrated the generation of mutant and reassortant AHSV genomes, their recovery, stable passage, and characterization. Our findings provide a new approach to investigate AHSV replication, to design AHSV vaccines and to aid diagnosis.
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Affiliation(s)
- Yuuki Kaname
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Cristina C P Celma
- Department of Pathogen Molecular Biology, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Yuta Kanai
- 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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13
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Guthrie AJ, MacLachlan NJ, Joone C, Lourens CW, Weyer CT, Quan M, Monyai MS, Gardner IA. Diagnostic accuracy of a duplex real-time reverse transcription quantitative PCR assay for detection of African horse sickness virus. J Virol Methods 2013; 189:30-5. [DOI: 10.1016/j.jviromet.2012.12.014] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2012] [Accepted: 12/10/2012] [Indexed: 10/27/2022]
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Thompson GM, Jess S, Murchie AK. A review of African horse sickness and its implications for Ireland. Ir Vet J 2012; 65:9. [PMID: 22553991 PMCID: PMC3390273 DOI: 10.1186/2046-0481-65-9] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2012] [Accepted: 05/03/2012] [Indexed: 11/12/2022] Open
Abstract
African horse sickness is an economically highly important non-contagious but infectious Orbivirus disease that is transmitted by various species of Culicoides midges. The equids most severely affected by the virus are horses, ponies, and European donkeys; mules are somewhat less susceptible, and African donkeys and zebra are refractory to the devastating consequences of infection. In recent years, Bluetongue virus, an Orbivirus similar to African horse sickness, which also utilises Culicoides spp. as its vector, has drastically increased its range into previously unaffected regions in northern Europe, utilising indigenous vector species, and causing widespread economic damage to the agricultural sector. Considering these events, the current review outlines the history of African horse sickness, including information concerning virus structure, transmission, viraemia, overwintering ability, and the potential implications that an outbreak would have for Ireland. While the current risk for the introduction of African horse sickness to Ireland is considered at worst ‘very low’, it is important to note that prior to the 2006 outbreak of Bluetongue in northern Europe, both diseases were considered to be of equal risk to the United Kingdom (‘medium-risk’). It is therefore likely that any outbreak of this disease would have serious socio-economic consequences for Ireland due to the high density of vulnerable equids and the prevalence of Culicoides species, potentially capable of vectoring the virus.
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Affiliation(s)
- Geoffrey M Thompson
- School of Biological Sciences, Queen's University of Belfast, Belfast, BT7 1NN, Northern Ireland.
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15
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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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A new duplex real-time RT-PCR assay for sensitive and specific detection of African horse sickness virus. Mol Cell Probes 2011; 25:87-93. [PMID: 21315146 DOI: 10.1016/j.mcp.2011.01.006] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2010] [Revised: 01/18/2011] [Accepted: 01/21/2011] [Indexed: 11/23/2022]
Abstract
A new real-time reverse transcription-polymerase chain reaction (RT-PCR) assay for a simple and rapid diagnosis of African Horse Sickness (AHS) was developed. Primers and FAM-labeled TaqMan-MGB probes specific for African horse sickness virus (AHSV) were selected from the consensus sequence of the segment 8 of all 9 serotypes of AHSV reference strains. For the determination of the analytical sensitivity, an in vitro transcript (AHS_ns2T7) of the target region was constructed and tested. Furthermore, the AHS_ns2T7 transcript was used either as positive control or as a standard for quantifying target copies. A commercial heterologous Armored RNA was used as an internal positive control (IPC) for both RNA isolation and RT-PCR steps. The qRT-PCR AHS_ns2 was able to amplify the target sequence up to 0.71 copies/reaction. Its flexibility allowed to amplify a wide dynamic range of RNA copies from 1.5 to 0.001fg. Within this range, the Ct values varied from 18 to 38 cycles with SD values always lower than 0.5 confirming their strong and constant linear correlation with the RNA target. Furthermore the newly designed duplex real-time RT-PCR proved to be strictly AHSV-specific as it did not amplify close related viruses.
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Matsuo E, Celma CCP, Roy P. A reverse genetics system of African horse sickness virus reveals existence of primary replication. FEBS Lett 2010; 584:3386-91. [PMID: 20600010 DOI: 10.1016/j.febslet.2010.06.030] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Revised: 06/14/2010] [Accepted: 06/18/2010] [Indexed: 10/19/2022]
Abstract
African horse sickness virus (AHSV), a member of the orbivirus genus of the family Reoviridae, is an insect-vectored pathogen of horses of concern to the equine industry. Studies on AHSV replication and pathogenesis have been hampered by the lack of reverse genetics allowing targeted mutation of viral genomes. We demonstrate that AHSV single-stranded RNA synthesized in vitro (core transcripts) is infectious and that there are distinct primary and secondary stages of the replication cycle. Transfection with a mixture of core transcripts from two different serotypes or a mixture of core transcripts and a T7 derived transcript resulted in the recovery of reassortant viruses. Recovery of infectious ASHV from nucleic acid will benefit investigation of the virus and the generation of attenuated vaccines.
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Affiliation(s)
- Eiko Matsuo
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
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Boinas F, Calistrib P, Domingo M, Avilés MM, López BM, Sánchez BR, Sánchez‐Vizcaíno JM. Scientific review on African Horse Sickness. ACTA ACUST UNITED AC 2009. [DOI: 10.2903/sp.efsa.2009.en-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Fernando Boinas
- Faculdade de Medicina Veterinaria, Universidade Técnica de Lisboa, (FMV‐UTL)
| | - Paolo Calistrib
- Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise “G. Caporale” (IZSA&M)
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Guthrie AJ, Quan M, Lourens CW, Audonnet JC, Minke JM, Yao J, He L, Nordgren R, Gardner IA, Maclachlan NJ. Protective immunization of horses with a recombinant canarypox virus vectored vaccine co-expressing genes encoding the outer capsid proteins of African horse sickness virus. Vaccine 2009; 27:4434-8. [PMID: 19490959 DOI: 10.1016/j.vaccine.2009.05.044] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2009] [Revised: 04/27/2009] [Accepted: 05/11/2009] [Indexed: 11/25/2022]
Abstract
We describe the development and preliminary characterization of a recombinant canarypox virus vectored (ALVAC) vaccine for protective immunization of equids against African horse sickness virus (AHSV) infection. Horses (n=8) immunized with either of two concentrations of recombinant canarypox virus vector (ALVAC-AHSV) co-expressing synthetic genes encoding the outer capsid proteins (VP2 and VP5) of AHSV serotype 4 (AHSV-4) developed variable titres (<10-80) of virus-specific neutralizing antibodies and were completely resistant to challenge infection with a virulent strain of AHSV-4. In contrast, a horse immunized with a commercial recombinant canarypox virus vectored vaccine expressing the haemagglutinin genes of two equine influenza H3N8 viruses was seronegative to AHSV and following infection with virulent AHSV-4 developed pyrexia, thrombocytopenia and marked oedema of the supraorbital fossae typical of the "dikkop" or cardiac form of African horse sickness. AHSV was detected by virus isolation and quantitative reverse transcriptase polymerase chain reaction in the blood of the control horse from 8 days onwards after challenge infection whereas AHSV was not detected at any time in the blood of the ALVAC-AHSV vaccinated horses. The control horse seroconverted to AHSV by 2 weeks after challenge infection as determined by both virus neutralization and ELISA assays, whereas six of eight of the ALVAC-AHSV vaccinated horses did not seroconvert by either assay following challenge infection with virulent AHSV-4. These data confirm that the ALVAC-AHSV vaccine will be useful for the protective immunization of equids against African horse sickness, and avoids many of the problems inherent to live-attenuated AHSV vaccines.
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Affiliation(s)
- Alan J Guthrie
- Equine Research Centre, University of Pretoria, Private Bag X04, Onderstepoort 0110, South Africa.
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20
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Wilson A, Mellor PS, Szmaragd C, Mertens PPC. Adaptive strategies of African horse sickness virus to facilitate vector transmission. Vet Res 2008; 40:16. [PMID: 19094921 PMCID: PMC2695022 DOI: 10.1051/vetres:2008054] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2008] [Accepted: 12/16/2008] [Indexed: 11/14/2022] Open
Abstract
African horse sickness virus (AHSV) is an orbivirus that is usually transmitted between its equid hosts by adult Culicoides midges. In this article, we review the ways in which AHSV may have adapted to this mode of transmission. The AHSV particle can be modified by the pH or proteolytic enzymes of its immediate environment, altering its ability to infect different cell types. The degree of pathogenesis in the host and vector may also represent adaptations maximising the likelihood of successful vectorial transmission. However, speculation upon several adaptations for vectorial transmission is based upon research on related viruses such as bluetongue virus (BTV), and further direct studies of AHSV are required in order to improve our understanding of this important virus.
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Affiliation(s)
- Anthony Wilson
- Vector-Borne Disease Programme, Institute for Animal Health, Ash Road, Pirbright, Woking, Surrey, GU24 0NF, United Kingdom
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21
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Fernández-Pinero J, Fernández-Pacheco P, Rodríguez B, Sotelo E, Robles A, Arias M, Sánchez-Vizcaíno JM. Rapid and sensitive detection of African horse sickness virus by real-time PCR. Res Vet Sci 2008; 86:353-8. [PMID: 18782637 DOI: 10.1016/j.rvsc.2008.07.015] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2008] [Revised: 05/28/2008] [Accepted: 07/20/2008] [Indexed: 10/21/2022]
Abstract
A highly sensitive and specific TaqMan-MGB real-time RT-PCR assay has been developed and standardised for the detection of African horse sickness virus (AHSV). Primers and MGB probe specific for AHSV were selected within a highly conserved region of genome segment 7. The robustness and general application of the diagnostic method were verified by the detection of 12 AHSV isolates from all of the nine serotypes. The analytical sensitivity ranged from 0.001 to 0.15 TCID(50) per reaction, depending on the viral serotype. Real-time PCR performance was preliminarily assessed by analysing a panel of field equine samples. The same primer pair was used to standardise a conventional RT-PCR as an affordable, useful and simple alternative method in laboratories without access to real-time PCR instruments. The two techniques present novel tools to improve the molecular diagnosis of African horse sickness (AHS).
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Affiliation(s)
- J Fernández-Pinero
- Centro de Investigación en Sanidad Animal (CISA-INIA), Valdeolmos, 28130 Madrid, Spain.
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22
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Firth AE. Bioinformatic analysis suggests that the Orbivirus VP6 cistron encodes an overlapping gene. Virol J 2008; 5:48. [PMID: 18489030 PMCID: PMC2373779 DOI: 10.1186/1743-422x-5-48] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2008] [Accepted: 04/14/2008] [Indexed: 11/25/2022] Open
Abstract
Background The genus Orbivirus includes several species that infect livestock – including Bluetongue virus (BTV) and African horse sickness virus (AHSV). These viruses have linear dsRNA genomes divided into ten segments, all of which have previously been assumed to be monocistronic. Results Bioinformatic evidence is presented for a short overlapping coding sequence (CDS) in the Orbivirus genome segment 9, overlapping the VP6 cistron in the +1 reading frame. In BTV, a 77–79 codon AUG-initiated open reading frame (hereafter ORFX) is present in all 48 segment 9 sequences analysed. The pattern of base variations across the 48-sequence alignment indicates that ORFX is subject to functional constraints at the amino acid level (even when the constraints due to coding in the overlapping VP6 reading frame are taken into account; MLOGD software). In fact the translated ORFX shows greater amino acid conservation than the overlapping region of VP6. The ORFX AUG codon has a strong Kozak context in all 48 sequences. Each has only one or two upstream AUG codons, always in the VP6 reading frame, and (with a single exception) always with weak or medium Kozak context. Thus, in BTV, ORFX may be translated via leaky scanning. A long (83–169 codon) ORF is present in a corresponding location and reading frame in all other Orbivirus species analysed except Saint Croix River virus (SCRV; the most divergent). Again, the pattern of base variations across sequence alignments indicates multiple coding in the VP6 and ORFX reading frames. Conclusion At ~9.5 kDa, the putative ORFX product in BTV is too small to appear on most published protein gels. Nonetheless, a review of past literature reveals a number of possible detections. We hope that presentation of this bioinformatic analysis will stimulate an attempt to experimentally verify the expression and functional role of ORFX, and hence lead to a greater understanding of the molecular biology of these important pathogens.
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Affiliation(s)
- Andrew E Firth
- Department of Biochemistry, BioSciences Institute, University College Cork, Cork, Ireland.
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23
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Koekemoer JJO, Dijk AAV. African horsesickness virus serotyping and identification of multiple co-infecting serotypes with a single genome segment 2 RT-PCR amplification and reverse line blot hybridization. J Virol Methods 2005; 122:49-56. [PMID: 15488620 DOI: 10.1016/j.jviromet.2004.08.002] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2004] [Revised: 07/30/2004] [Accepted: 08/09/2004] [Indexed: 11/28/2022]
Abstract
Since protection against African horsesickness (AHS) is serotype-specific, rapid serotyping of AHSV is crucial to identify the correct vaccine serotype for efficient control of the spread of AHS outbreaks, especially when they occur in non-endemic regions. This paper describes the first one-day serotyping procedure that requires only a single RT-PCR and hybridization and which can identify multiple serotypes in mixed infections in one assay. The same region of genome segment 2 of all nine AHSV serotypes is amplified in a single RT-PCR. A universal primer set, designed to amplify the 5'-terminal 521-553bp of genome segment 2 of all of the nine AHSV serotypes with one reaction, was used to generate serotype-specific probes from dsRNA prepared from infected tissue cultures or organ samples. These probes hybridized serotype-specifically with immobilized genome segment 2 cDNA of the nine AHSV reference serotypes in a checkerboard reverse line blot format. All nine AHSV reference and the seven vaccine strains and field viruses isolated up to 28 years apart could be serotyped accurately within a day. The sensitivity of the method is 1pg dsRNA which is sufficient to serotype AHSV directly from lung and spleen specimens of infected horses.
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Affiliation(s)
- J J O Koekemoer
- Biochemistry Division, Onderstepoort Veterinary Institute, Onderstepoort 0110, South Africa.
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24
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Sailleau C, Hamblin C, Paweska JT, Zientara S. Identification and differentiation of the nine African horse sickness virus serotypes by RT-PCR amplification of the serotype-specific genome segment 2. J Gen Virol 2000; 81:831-7. [PMID: 10675421 DOI: 10.1099/0022-1317-81-3-831] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This paper describes the first RT-PCR for discrimination of the nine African horse sickness virus (AHSV) serotypes. Nine pairs of primers were designed, each being specific for one AHSV serotype. The RT-PCR was sensitive and specific, providing serotyping within 24 h. Perfect agreement was recorded between the RT-PCR and virus neutralization for a coded panel of 56 AHSV reference strains and field isolates. Serotyping was achieved successfully with live and formalin-inactivated AHSVs, with isolates of virus after low and high passage through either tissue culture or suckling mouse brain, with viruses isolated from widely separated geographical areas and with viruses isolated up to 37 years apart. Overall, this RT-PCR provides a rapid and reliable method for the identification and differentiation of the nine AHSV serotypes, which is vital at the start of an outbreak to enable the early selection of a vaccine to control the spread of disease.
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Affiliation(s)
- C Sailleau
- Agence Française de Sécurité Sanitaire des Aliments - Alfort, Laboratoire Central de Recherches Vétérinaires, 22 rue Pierre Curie, 94703 Maisons-Alfort, France.
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25
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Lord CC, Barnard B, Day K, Hargrove JW, McNamara JJ, Paul RE, Trenholme K, Woolhouse ME. Aggregation and distribution of strains in microparasites. Philos Trans R Soc Lond B Biol Sci 1999; 354:799-807. [PMID: 10365405 PMCID: PMC1692560 DOI: 10.1098/rstb.1999.0432] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Recent research has shown that many parasite populations are made up of a number of epidemiologically distinct strains or genotypes. The implications of strain structure or genetic diversity for parasite population dynamics are still uncertain, partly because there is no coherent framework for the interpretation of field data. Here, we present an analysis of four published data sets for vector-borne microparasite infections where strains or genotypes have been distinguished: serotypes of African horse sickness (AHS) in zebra; types of Nannomonas trypanosomes in tsetse flies; parasite-induced erythrocyte surface antigen (PIESA) based isolates of Plasmodium falciparum malaria in humans, and the merozoite surface protein 2 gene (MSP-2) alleles of P. falciparum in humans and in anopheline mosquitoes. For each data set we consider the distribution of strains or types among hosts and any pairwise associations between strains or types. Where host age data are available we also compare age-prevalence relationships and estimates of the force of infection. Multiple infections of hosts are common and for most data sets infections have an aggregated distribution among hosts with a tendency towards positive associations between certain strains or types. These patterns could result from interactions (facilitation) between strains or types, or they could reflect patterns of contact between hosts and vectors. We use a mathematical model to illustrate the impact of host-vector contact patterns, finding that even if contact is random there may still be significant aggregation in parasite distributions. This effect is enhanced if there is non-random contact or other heterogeneities between hosts, vectors or parasites. In practice, different strains or types also have different forces of infection. We anticipate that aggregated distributions and positive associations between microparasite strains or types will be extremely common.
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Affiliation(s)
- C C Lord
- Wellcome Centre for the Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, UK
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26
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Bougrine SI, Fihri OF, Fehri MM. Western immunoblotting as a method for the detection of African horse sickness virus protein-specific antibodies: differentiation between infected and vaccinated horses. ARCHIVES OF VIROLOGY. SUPPLEMENTUM 1998; 14:329-36. [PMID: 9785518 DOI: 10.1007/978-3-7091-6823-3_29] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
A Western immunoblotting procedure has been developed for the detection of African horse sickness virus (AHSV) protein-specific antibody responses. This assay readily identifies antibodies specific for at least 4 distinct, AHSV proteins, including VP5, NS1, NS2 and NS3/NS3a. By using the AHSV non-structural proteins as 'markers', the Western blotting procedure could be employed to provide a reliable means of discriminating between animals vaccinated with a purified, inactivated AHSV vaccine and those either naturally infected or vaccinated with a live, attenuated AHSV vaccine.
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Affiliation(s)
- S I Bougrine
- Département de Microbiologie Immunologie Maladies Contagieuses, Institut Agronomique et Vétérinaire Hassan II, Rabat, Morocco
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27
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Zientara S, Sailleau C, Moulay S, Crucière C, el-Harrak M, Laegreid WW, Hamblin C. Use of reverse transcriptase-polymerase chain reaction (RT-PCR) and dot-blot hybridisation for the detection and identification of African horse sickness virus nucleic acids. ARCHIVES OF VIROLOGY. SUPPLEMENTUM 1998; 14:317-27. [PMID: 9785517 DOI: 10.1007/978-3-7091-6823-3_28] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/09/2023]
Abstract
A coupled reverse transcriptase-polymerase chain reaction assay (RT-PCR) for the detection of African horse sickness virus (AHSV) dsRNA, has been developed using genome segment 7 as the target template for primers. RNA from isolates of all nine AHSV serotypes were readily detected. The potential inhibitory effects of either ethylene diamine tetra acetic acid (EDTA) or heparin on the RT-PCR were eliminated by washing blood samples before lysis of the red blood cells and storage. There was a close agreement in the sensitivity and the specificity of the RT-PCR and an indirect sandwich ELISA. Confirmation of the presence of AHSV using RT-PCR and dot-blot hybridization on blood samples collected from horses experimentally infected with AHSV serotype 4 (AHSV 4) and AHSV serotype 9 (AHSV 9), was achieved within 24 hours, compared to the period of several days required for virus isolation. The RT-PCR and virus isolation methods showed similar levels of sensitivity when used for the detection of AHSV in 3 horses infected with AHSV 4, and in 2 out of 3 horses infected with a less virulent isolate of AHSV 9. Although viraemia was detected in the third horse by virus isolation, from 6 to 14 days after infection, this animal remained consistently negative by RT-PCR. Conversely, AHSV viral RNA was detected by RT-PCR in the blood of 4 donkeys and 4 mules up to 55 days after their experimental infection despite the absence of any detectable infectious virus. RT-PCR is a sensitive and rapid method for detecting AHSV nucleic acids during either the incubation period at the start of an African horse sickness (AHS) epizootic, or for epidemiological investigations in species where clinical signs may be inapparent.
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Affiliation(s)
- S Zientara
- Centre National d'Etudes Veterinaires et Alimentaires, Laboratoire Central de Recherches Veterinaires, Maisons-Alfort, France
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28
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O'Hara RS, Meyer AJ, Burroughs JN, Pullen L, Martin LA, Mertens PP. Development of a mouse model system, coding assignments and identification of the genome segments controlling virulence of African horse sickness virus serotypes 3 and 8. ARCHIVES OF VIROLOGY. SUPPLEMENTUM 1998; 14:259-79. [PMID: 9785512 DOI: 10.1007/978-3-7091-6823-3_23] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Attenuated (att) and wild type (wt) strains of the nine AHSV serotypes were evaluated for virulence in adult Balb C mice. Although most were avirulent in this system, isolates of AHSV 1att, 3wt, 3att, 4wt, 5att, 7att and 8att caused some mortality when administered via an intranasal route. After plaque cloning, only the attenuated vaccine strain of AHSV 7att caused any mortality via an intravenous route. AHSV 3att and AHSV 8wt were virulent (V) and avirulent (AV) (respectively) in the mouse model and were selected as parental strains for production of genome segment reassortants. These progeny virus strains were plaque cloned, then characterised to identify the genome segments that influence virulence of AHSV in the mouse model. Three virulence phenotypes were observed: fully virulent (V); fully avirulent (A); and a novel intermediate virulence (N) not expressed by either parental strain. Genome segment 2 (encoding outer capsid protein VP2) from the avirulent parent appeared to have a controlling influence in production of the A phenotype. Reassortants with the V phenotype all contained segment 2 from the virulent parent, however in each case they also contained genome segments 5 and 10, also from AHSV 3 (V). Genome segments 5 and 10 encode the smaller outer capsid protein VP5 and the non structural proteins NS3/NS3a, respectively. A combination of genome segments 2, 5 and 6 from the avirulent parent and segment 10 from the virulent parent were found in each of the virus strains with the N phenotype. However, comparison of two reassortants (A79 and A790), which differ only in a single segment, showed that replacement of genome segment 10 from the avirulent parent with that from the virulent parent, conferred the N phenotype on A790.
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Affiliation(s)
- R S O'Hara
- Institute for Animal Health, Pirbright Laboratory, Woking, U.K
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29
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Stäuber N, Martinez-Costas J, Sutton G, Monastyrskaya K, Roy P. Bluetongue virus VP6 protein binds ATP and exhibits an RNA-dependent ATPase function and a helicase activity that catalyze the unwinding of double-stranded RNA substrates. J Virol 1997; 71:7220-6. [PMID: 9311795 PMCID: PMC192062 DOI: 10.1128/jvi.71.10.7220-7226.1997] [Citation(s) in RCA: 82] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
RNA-dependent ATPase and helicase activities have been identified associated with the purified VP6 protein of bluetongue virus, a member of the Orbivirus genus of double-stranded RNA (dsRNA; Reoviridae family) viruses. In addition, the protein has an ATP binding activity. RNA unwinding of duplexes occurred with both 3' and 5' overhang templates, as well as with blunt-ended dsRNA, an activity not previously identified in other viral helicases. Although little sequence similarity to other helicases was detected, certain similarities to motifs commonly attributed to such proteins were identified.
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Affiliation(s)
- N Stäuber
- Department of Biochemistry, Oxford University, United Kingdom
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30
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du Plessis M, Nel LH. Comparative sequence analysis and expression of the M6 gene, encoding the outer capsid protein VP5, of African horsesickness virus serotype nine. Virus Res 1997; 47:41-9. [PMID: 9037735 DOI: 10.1016/s0168-1702(96)01400-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
The entire nucleotide and deduced amino acid sequence of the M6 gene of African horsesickness virus (AHSV) serotype nine has been determined from four overlapping cDNA clones. The gene was found to be 1566 bp long, encoding a protein of 505 amino acids with a molecular weight of 56 737 Da and a nett charge of - 1 at neutral pH Comparative sequence analysis of the deduced amino acid sequence with the VP5 protein of AHSV-4, showed that only 81% of amino acids were conserved in type and position, although alternating regions of lower and higher conservation was identified by alignment of the primary sequences of different orbiviral VP5 proteins. Antigenically authentic AHSV-9 VP5 was also expressed in a baculovirus expression system and the expressed protein was shown to react specifically with anti-AHSV-9 as well as AHSV-3 serum in Western blot analysis.
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Affiliation(s)
- M du Plessis
- Department of Microbiology and Plant Pathology, University of Pretoria, South Africa
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31
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Zientara S, Sailleau C, Moulay S, Cruciere C. Differentiation of African horse sickness viruses by polymerase chain reaction and segments 10 restriction patterns. Vet Microbiol 1995; 47:365-75. [PMID: 8748551 DOI: 10.1016/0378-1135(95)00104-2] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
This paper describes a single tube reverse transcription-polymerase chain reaction (RT-PCR) method for detection of African horse sickness virus (AHSV). The genomic segments 10 of viruses of the 9 AHSV serotypes were amplified. The 758bp products were digested to completion by restriction enzymes. The restriction fragment length polymorphisms of segments 7 and 10 cDNA allowed the differentiation of the nine serotypes.
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Affiliation(s)
- S Zientara
- Centre National d'Etudes Vétérinaires et Alimentaires Laboratoire Central de Recherches Vétérinaires, Maisons-Alfort, France
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32
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Halabi G, McCullough KC. Influence of antigen presentation and exogenous cytokine activity during in vitro primary immunizations employed for the generation of monoclonal antibodies. J Immunol Methods 1995; 186:205-16. [PMID: 7594620 DOI: 10.1016/0022-1759(95)00144-y] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Hybridomas secreting monoclonal antibodies (MAbs) against African horse sickness virus (AHSV) were generated using different AHSV antigen preparations (inactivated AHSV, semi-purified virus, and a preparation of nonstructural viral proteins) in one of three different in vitro primary immunization systems: (i) the Cel-prime kit, a method using immunization of splenocytes aided by antigen-primed support cells; (ii) a system based on a cytokine soup derived from a mixed lymphocyte reaction plus stimulated EL4-IL-2 cells; (iii) a system based on a cytokine soup derived from splenocytes stimulated by pokeweed mitogen in order to obtain a mixture of cytokines enriched for Th2 lymphokines. The viability of immunized BALB/c mouse splenocytes, immunoglobulin production by the subsequently generated hybridomas, and the specificity of the MAbs were compared. The most efficient in vitro primary immunization system was the Cel-prime system employing semi-purified antigen. This efficiency was manifest in terms of a greater viability of the splenocytes in the immunization, as well as a higher number of specific antibody-secreting hybridomas. It seems probable that the support cells of the Cel-prime system have an accessory function such as that attributed to antigen-presenting cells. Such a function would result in impairment of apoptosis, and thus increase the viability of the splenocytes in the in vitro primary immunization system, as well as enhancing stimulation of the immune response against the antigen used. The presence of cytokines at the beginning of the in vitro primary immunization did have an influence, but this was secondary to what appeared to be the major event of cellular interaction associated with the accessory cell function of the support cells.
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Affiliation(s)
- G Halabi
- Institut für Viruskrankheiten und Immunprophylaxe, Mittelhäusern, Switzerland
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33
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Zientara S, Sailleau C, Moulay S, Wade-Evans A, Cruciere C. Application of the polymerase chain reaction to the detection of African horse sickness viruses. J Virol Methods 1995; 53:47-54. [PMID: 7543488 DOI: 10.1016/0166-0934(94)00175-g] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
The development of a coupled reverse transcriptase-polymerase chain reaction assay (RT-PCR) is described for the detection of African horse sickness virus (AHSV) double-stranded RNA. Genome segments 7 and 10 were chosen as target templates for primers selected for use in the RT-PCR. Using these AHSV-specific primers all 9 serotypes were detectable. The sensitivity and specificity of the RT-PCR results were compared to those obtained by competition ELISA.
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Affiliation(s)
- S Zientara
- CNEVA-Laboratoire Central de Recherches Vétérinaires, Maisons-Alfort, France
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34
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van Staden V, Stoltz MA, Huismans H. Expression of nonstructural protein NS3 of African horsesickness virus (AHSV): evidence for a cytotoxic effect of NS3 in insect cells, and characterization of the gene products in AHSV infected Vero cells. Arch Virol 1995; 140:289-306. [PMID: 7710356 DOI: 10.1007/bf01309863] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The smallest genome segment of African horsesickness virus (AHSV), segment 10 (S10), encodes two minor nonstructural proteins, NS3 and NS3A. While the cognate bluetongue virus (BTV) proteins have been suggested to play a role in the release of virus particles from infected cells, no function has yet been ascribed to AHSV NS3/NS3A. When the AHSV-3 S10 gene was expressed in a baculovirus system only a single NS3 protein (24 K) was synthesized, at lower levels than expected. It was shown that this could be due to a membrane association of NS3, leading to an alteration in host cell membrane permeability and eventual cell death. Based on computer predictions a general model for the membrane-associated topology of NS3 of five different orbiviruses was proposed. Studies on AHSV-3 infected Vero cells showed that equimolar amounts of NS3 and NS3A were synthesized. No evidence was found for the glycosylation of NS3. The S10 genes and NS3/3A proteins of AHSV-3 and AHSV-7 were shown to be closely related, and clearly distinct from the cognate proteins of the other 7 AHSV serotypes. This distinguishes the AHSV S10 gene product from that of BTV NS3, which appears to be much more conserved.
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Affiliation(s)
- V van Staden
- Department of Genetics, University of Pretoria, South Africa
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35
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Brown CC, Meyer RF, Grubman MJ. Presence of African horse sickness virus in equine tissues, as determined by in situ hybridization. Vet Pathol 1994; 31:689-94. [PMID: 7863585 DOI: 10.1177/030098589403100609] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
In a retrospective study, a negative-sense digoxigenin-labeled RNA probe, corresponding to the gene encoding nonstructural protein-1 of African horse sickness virus (AHSV) serotype 4, was applied to formalin-fixed, paraffin-embedded tissue taken from horses in the terminal stages of infection with AHSV. Fifteen infected ponies and one noninfected control were studied. Ponies exhibited a range of clinical signs and lesions. Thirteen ponies were infected with serotype 4, one with serotype 1, and one with serotype 2. Ponies were monitored clinically and euthanatized when severely clinically ill. The following tissues were available for study by in situ hybridization and histopathology: lung, heart, spleen, neck muscle, and supraorbital fat. Histologically, the most striking changes were pulmonary edema and, in some, acute myocardial necrosis. In situ hybridization revealed virus distributed widely in sections of lung and heart examined, with relatively less in spleen, neck muscle, or supraorbital fat. Virus was localized to target cells with morphologic features compatible with endothelium in all organs except spleen, where it was found in both endotheliumlike cells and large mononuclear cells.
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Affiliation(s)
- C C Brown
- Foreign Animal Disease Diagnostic Laboratory, US Department of Agriculture, Greenport, NY
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36
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Abstract
African horse sickness virus (AHSV), of which there are nine serotypes (AHSV-1, -2, etc.), is a member of Orbivirus genus within the Reoviridae family. Both in morphology and molecular constituents AHSV particles are comparable to those of bluetongue virus (BTV), the prototype virus of the genus. The two viruses have seven structural proteins (VP1-7) organized in two layered capsid. The outer capsid is composed of VP2 and VP5. The inner capsid, or core, is composed of two major proteins, VP3 and VP7, and three minor proteins, VP1, VP4 and VP6. Within the core is the virus genome. This genome consists of 10 double-stranded (ds)RNA segments of different sizes, three large, designated L1-L3, three medium, M4-M6, and four small, S7-S10. In addition to the seven structural proteins that are coded by seven of the RNA species, four non-structural proteins, NS1, NS2, NS3 and NS3A, are coded by three RNA segments, M5, S8 and S10. The two smallest proteins (NS3 and NS3A) are synthesized by the S10 RNA segment, probably from different in-frame translation initiation codons. Nucleotide sequences of eight RNA segments (L2, L3, M4, M5, M6, S7, S8 and S10) and the predicted amino acid sequences of the encoded gene products are also available, mainly representing one serotype, AHSV-4. In this review the properties of the AHSV genes and gene products are discussed. The sequence and hybridization analyses of the different AHSV dsRNA segments indicate that the segments that code for the core proteins, as well as those that code for NS1 and NS2 proteins, are highly conserved between the different virus serotypes. However, the RNA encoding NS3 and NS3A, and the two segments encoding the outer capsid proteins, are more variable between the AHSV serotypes. A close phylogenetic relationship between AHSV, BTV and epizootic haemorrhagic disease virus (EHDV), three Culicoides-transmitted orbiviruses, has been revealed when the equivalent sequences of genes and gene products are compared. Recently, the four major AHSV capsid proteins have been expressed using recombinant baculoviruses. Biochemically and antigenically these proteins are similar to the authentic proteins. Since the AHSV VP7 protein is highly conserved among the different serotypes, it has been utilized as a diagnostic reagent. The expressed VP7 protein has also been purified to homogeneity and crystallized for three-dimensional X-ray analysis.(ABSTRACT TRUNCATED AT 400 WORDS)
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Affiliation(s)
- P Roy
- School of Public Health, University of Alabama at Birmingham 35294-0008
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37
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de Sá RO, Zellner M, Grubman MJ. Phylogenetic analysis of segment 10 from African horsesickness virus and cognate genes from other orbiviruses. Virus Res 1994; 33:157-65. [PMID: 7975880 DOI: 10.1016/0168-1702(94)90052-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Utilizing the reverse transcriptase-polymerase chain reaction (RT-PCR) procedure, we have synthesized full-length copies of segment 10 from African horsesickness virus (AHSV) serotypes 1, 4 and 8. The genes were cloned, sequenced and compared with the sequence of the cognate gene from AHSV serotypes 3 and 9. Sequences were analyzed to assess evolutionary relationships among serotypes using cladistics. Based on this analysis the data support a close relationship between serotypes 4 and 9 and between serotypes 1 and 8 and a closer relationship of serotype 3 to the 4 and 9 group.
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Affiliation(s)
- R O de Sá
- Department of Biology, University of Richmond, VA 23173
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38
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Abstract
African horsesickness (AHS) is a very serious, non-contagious disease of horses and other solipeds caused by an arthropod-borne orbivirus of the family Reoviridae. The epizootic nature of the disease makes rapid, accurate diagnosis of AHS absolutely essential. Currently, diagnosis of AHS is based on typical clinical signs and lesions, a history consistent with vector transmission and confirmation by laboratory detection of virus and/or anti-AHS virus antibodies. The clinicopathologic presentation of AHS, current and next generation laboratory diagnostic methods are discussed.
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Affiliation(s)
- W W Laegreid
- Molecular Pathology Unit, Plum Island Animal Disease Center, USDA/ARS, Greenport, NY 11944-0848
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39
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Martyn JC, Gould AR, Yu M. Expression of the outer capsid proteins VP2 and VP5 of bluetongue virus in Saccharomyces cerevisiae. Virus Res 1994; 33:11-25. [PMID: 7941697 DOI: 10.1016/0168-1702(94)90014-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
cDNAs transcribed from bluetongue virus serotype 1 (Australia) ds RNA 2 and ds RNA 6 coding for the major neutralising antigen VP2 and the outer capsid protein VP5, respectively, were amplified in polymerase chain reactions and ligated downstream of the copper-inducible metallothionein promoter in the yeast expression plasmid pYELC5. Saccharomyces cerevisiae transformed with the recombinant plasmid pYELC5-VP2 expressed full-length VP2 only following induction with 1 mM CuSO4 and reached the maximum level after 6 h. In contrast, S. cerevisiae transformants harboring the recombinant plasmid pYELC5-VP5 expressed VP5 constitutively, although induction increased the level to a maximum after 4 h. A sheep trial was done testing the recombinant proteins, however it was shown that none of these were effective immunogens for eliciting a protective response against a subsequent challenge with bluetongue virus. An analysis of the yeast expression products for the VP2 outer coat protein using a panel of monoclonal antibodies showed that the yeast expressed VP2 was in a conformation different from native VP2 and hence probably unable to elicite an appropriate protective immune response.
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Affiliation(s)
- J C Martyn
- CSIRO, Australian Animal Health Laboratory, Geelong, Victoria
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40
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Bremer CW, du Plessis DH, van Dijk AA. Baculovirus expression of non-structural protein NS2 and core protein VP7 of African horsesickness virus serotype 3 and their use as antigens in an indirect ELISA. J Virol Methods 1994; 48:245-56. [PMID: 7989441 DOI: 10.1016/0166-0934(94)90123-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Non-structural protein NS2 and core protein VP7 of African horsesickness virus serotype 3 (AHSV3) were expressed in Spodoptera frugiperda cells by recombinant baculoviruses containing the relevant genes. These proteins were purified and analysed by polyacrylamide gel electrophoresis and Western blot. NS2 and VP7 were used separately as antigens in an indirect ELISA for the detection of AHSV antibodies. Both antigens cross-reacted with hyperimmune guinea-pig antisera to infected cell lysates of all nine known AHSV serotypes and to antisera obtained from horses immunized with attenuated virus of seven AHSV serotypes.
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Affiliation(s)
- C W Bremer
- Biochemistry Division, Onderstepoort Veterinary Institute, Republic of South Africa
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41
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Jensen MJ, Cheney IW, Thompson LH, Mecham JO, Wilson WC, Yamakawa M, Roy P, Gorman BM. The smallest gene of the orbivirus, epizootic hemorrhagic disease, is expressed in virus-infected cells as two proteins and the expression differs from that of the cognate gene of bluetongue virus. Virus Res 1994; 32:353-64. [PMID: 8079516 DOI: 10.1016/0168-1702(94)90083-3] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The smallest gene (S10) of the virus of epizootic hemorrhagic disease of deer (EHD, serotype 2) is expressed as two proteins in virus-infected cells. By contrast, the non-structural proteins (NS3 and NS3A) encoded in the smallest gene of bluetongue (BT) viruses are difficult to detect in virus-infected cells. The nucleotide sequence of S10 of EHDV-2 contains two in-frame initiation codons which allow for translation of proteins of mol. wt. 25503 and 23921 analogous to NS3 and NS3A of BT viruses. The S10 genes of BT viruses are highly conserved (82%-99%); the nucleotide sequence similarity of S10 of EHDV-2 and BT viruses is about 64%. Some structural features of NS3 and NS3A are conserved in the two viruses, despite the divergence in the amino acid sequences of the proteins. The hydrophobic domains of the proteins and the putative transmembrane sequences are conserved, as are potential glycosylation sites in the proteins. A cluster of proline residues, which is conserved at residues 36-50 in all of the published sequences of NS3 of BT viruses, is conserved exactly in the alignment of the sequence of NS3 of EHDV-2 with that of the BT viruses. An explanation for the differences in expression of NS3/NS3A in EHD and BT viruses was not evident in comparing the nucleotide sequences of S10 of the viruses.
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Affiliation(s)
- M J Jensen
- USDA, Agricultural Research Service, Arthropod-borne Animal Diseases Research Laboratory, Laramie, WY 82071
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42
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Brown CC, Meyer RF, Grubman MJ. Identification of African horse sickness virus in cell culture using a digoxigenin-labeled RNA probe. J Vet Diagn Invest 1994; 6:153-5. [PMID: 8068745 DOI: 10.1177/104063879400600204] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
A digoxigenin-labeled RNA probe was synthesized from a plasmid containing a portion of the African horse sickness virus (AHSV) serotype 4 genome segment coding for nonstructural protein 1. In an in situ hybridization procedure, this probe hybridized successfully to Vero cells infected with each of the 9 serotypes of AHSV. There was no hybridization with noninfected cell cultures or cell cultures infected with bluetongue virus.
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Affiliation(s)
- C C Brown
- Foreign Animal Disease Diagnostic Laboratory, USDA, Greenport, NY 11944
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43
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Stone-Marschat M, Carville A, Skowronek A, Laegreid WW. Detection of African horse sickness virus by reverse transcription-PCR. J Clin Microbiol 1994; 32:697-700. [PMID: 8195381 PMCID: PMC263109 DOI: 10.1128/jcm.32.3.697-700.1994] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Reverse transcription-PCR (RT-PCR) was used to detect African horse sickness virus (AHSV). A single primer pair which amplified a 423-bp fragment of the S8 gene which encodes the NS2 protein of AHSV was identified. Amplification of this fragment from all nine serotypes of AHSV was achieved with these primers. Between 10(1) and 10(2) copies of AHSV genomic double-stranded RNA could be detected by RT-PCR followed by agarose gel electrophoresis and ethidium bromide staining. Application of RT-PCR to blood samples from AHSV-infected horses resulted in earlier detection of viremia than virus isolation did. Furthermore, viremia was detected by RT-PCR in blood samples from horses infected with an avirulent isolate of AHSV which were negative by virus isolation. AHSV was also detected by RT-PCR in spleen and lung samples from horses which died of AHSV infection. These results indicate that RT-PCR is a rapid and sensitive method for the identification of horses infected with AHSV.
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Affiliation(s)
- M Stone-Marschat
- Molecular Pathology Unit, Plum Island Animal Disease Center, USDA Agricultural Research Service, Greenport, New York 11944-0848
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44
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Sakamoto K, Punyahotra R, Mizukoshi N, Ueda S, Imagawa H, Sugiura T, Kamada M, Fukusho A. Rapid detection of African horsesickness virus by the reverse transcriptase polymerase chain reaction (RT-PCR) using the amplimer for segment 3 (VP3 gene). Arch Virol 1994; 136:87-97. [PMID: 8002793 DOI: 10.1007/bf01538819] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The complete sequence of the major core protein (VP3) gene of African horsesickness virus serotype 4 (AHSV-4; vaccine strain) was determined by analysis of a complete cDNA clone representing segment 3. The RNA was 2,789 bp long and a comparison of its sequence with that of bluetongue virus serotype 10 (BTV-10) revealed 58% nucleotide similarity. Based on these data, the reverse transcriptase-polymerase chain reaction (RT-PCR) technique was applied to the specific detection of AHSV using a pair of primers designed for AHSV-4 VP3 gene. Approximately 230 bp of PCR products were amplified by RT-PCR from the total RNA extracts (mRNA and dsRNA) of Vero cells infected with eight serotypes of AHSV. No product was observed analogous to other orbiviruses. The supernatant of the infected cell culture fluid without any RNA purification was also suitable as a template for RT-PCR after being denatured at 94 degrees C for 5 min. The sensitivity of this method was between 10(0) and 10(1) TCID50 when viral RNA from the supernatant of infected cell culture was subjected to RT-PCR. The whole procedure for detecting the virus RNA by RT-PCR could be carried out within 5 h. The RT-PCR with AHSV VP3 gene as a target was found to be a simple, highly specific and sensitive assay for AHSV.
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Affiliation(s)
- K Sakamoto
- Exotic Diseases Research Division, National Institute of Animal Health, Tokyo, Japan
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45
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Wilson WC. Development of a nested-PCR test based on sequence analysis of epizootic hemorrhagic disease viruses non-structural protein 1 (NS1). Virus Res 1994; 31:357-65. [PMID: 8191788 DOI: 10.1016/0168-1702(94)90028-0] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Two orbiviruses, epizootic hemorrhagic disease (EHD) and bluetongue (BTV) viruses, cause disease in domestic and wild ruminant species. The gene that encodes non-structural protein 1 (NS1) of EHD virus, serotype 1, was sequenced and compared to EHD and BTV NS1 sequences. The NS1 gene was found to be more conserved than the VP3 gene, and was selected as a target for polymerase chain reaction (PCR) amplification. The NS1 genes of several BTV viruses and another orbivirus, African horse sickness (AHS), were compared to the EHD NS1 genes. This information was used to develop a capture nested-PCR for detection and differentiation of EHD from BTV viral RNA.
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Affiliation(s)
- W C Wilson
- United States Department of Agriculture, Arthropod-borne Animal Diseases Research Laboratory, Laramie, WY 82071-3965
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46
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Zientara S, Sailleau C, Moulay S, Cruciere C. Diagnosis of the African horse sickness virus serotype 4 by a one-tube, one manipulation RT-PCR reaction from infected organs. J Virol Methods 1994; 46:179-88. [PMID: 8188813 DOI: 10.1016/0166-0934(94)90102-3] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
A single tube reverse transcription-polymerase chain reaction (RT-PCR) method for detection of African horse sickness virus (AHSV) in splenic tissues from infected horses is described. Double stranded RNA was extracted from infected organs of horses and used to produce complementary DNA (cDNA) with the two primers selected for the PCR. The 1179 bp amplified product (the segment 7 which encodes for VP 7), detected by electrophoresis on agarose gel and ethidium bromide staining, was hydrolysed with eight restriction endonucleases for characterization of the AHSV. The sensitivity of this method is discussed. Application of the RT-PCR method should improve detection and shorten the time required to confirm a clinical diagnosis of AHSV infection.
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Affiliation(s)
- S Zientara
- CNEVA-Laboratoire Central de Recherches Véérinaires, Maisons Alfort, France
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47
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Wade-Evans AM, Woolhouse T, O'Hara R, Hamblin C. The use of African horse sickness virus VP7 antigen, synthesised in bacteria, and anti-VP7 monoclonal antibodies in a competitive ELISA. J Virol Methods 1993; 45:179-88. [PMID: 8113344 DOI: 10.1016/0166-0934(93)90102-w] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A full-length cDNA clone of genome segment 7 of African Horse Sickness Virus, serotype 9 (AHSV9) was obtained using the PCR technique. The clone was sequenced and found to be 98.27% homologous to the previously published sequence of the equivalent cDNA clone from AHSV4 at the nucleotide level and to exhibit 99.7% identity at the amino acid level. The cDNA clone was transferred to pGEX-2T (Pharmacia), a bacterial expression vector, such that the reading frame of AHSV9 VP7 was continuous with that of the bacterial glutathione-S-transferase (GST) protein, under the control of the bacterial tac promoter. On induction with IPTG a fusion protein consisting of GST and VP7 was synthesised, which was readily purified on a GST-sepharose column (Pharmacia). The fusion protein reacted equally well in an indirect ELISA using monoclonal antibodies specific for AHSV9 VP7 or polyclonal guinea pig antisera raised against AHSV9 infectious sub-viral particles. This protein was also shown to be a suitable substitute for virus antigen, prepared from infected BHK cell extracts, in a competitive ELISA. Antibodies titres recorded for AHSV9 positive and negative horse sera were similar in the competitive ELISA using either bacterial AHSV VP7 or BHK extracted virus as the source of antigen, in combination with monoclonal or polyclonal antibodies, respectively, as the detectors.
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Affiliation(s)
- A M Wade-Evans
- AFRC, Institute for Animal Health, Pirbright Laboratory, Woking, Surrey, UK
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48
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Mizukoshi N, Sakamoto K, Iwata A, Tsuchiya T, Ueda S, Apiwatnakorn B, Kamada M, Fukusho A. The complete nucleotide sequence of African horsesickness virus serotype 4 (vaccine strain) segment 4, which encodes the minor core protein VP4. Virus Res 1993; 28:299-306. [PMID: 8346671 DOI: 10.1016/0168-1702(93)90029-m] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
The complete sequence of RNA segment 4 of African horsesickness virus serotype 4 (AHSV-4) vaccine strain was determined from the full-length cDNA clone inserted into pBR322. The RNA is 1978 bp long (M(r) 1.27 x 10(6)) and contains an open reading frame encoding a protein of 642 amino acids (M(r) 75826) with a net charge of +10 at neutral pH. The 5' and 3' termini of AHSV-4 segment 4,5'GTTTAT... and ...CCTTAC3', were different from orbivirus characteristic terminal sequences, being 5'GTTAAA... and ...ACTTAC3'. A comparison of the sequence of AHSV-4 segment 4 with that of bluetongue virus (BTV) serotype 10 revealed 55.4% nucleotide similarity and 48.5% amino acid similarity. In addition, Northern blot hybridization showed that the full-length AHSV-4 segment 4 cDNA cross-hybridized well with the corresponding genes of serotype 1, 2, 3, 4 and 7 but slightly with serotype 5, 6 and 8 of attenuated AHSV.
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Affiliation(s)
- N Mizukoshi
- Exotic Diseases Research Division, National Institute of Animal Health, Kodaira, Tokyo, Japan
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49
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Stäuber N, Kihm U, McCullough KC. Rapid generation of monoclonal antibody-secreting hybridomas against African horse sickness virus by in vitro immunization and the fusion/cloning technique. J Immunol Methods 1993; 161:157-68. [PMID: 8505546 DOI: 10.1016/0022-1759(93)90291-e] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Splenocytes from non-immune mice were stimulated in vitro using an equimolar mixture of factors from mixed lymphocyte reaction (MLR) and from phorbol-12-myristate 13-acetate (PMA) stimulated EL-4 cells, and concomitantly immunized with inactivated African horse sickness virus (AHSV) antigen serotype 4 or viral proteins 2 and 5 from AHSV serotype 9. Fusion with NSO myeloma cells was performed five days after primary or secondary stimulation/immunization. The record of hybridoma growth after a standard method of fusion, expansion of cells and subsequent cloning was compared with a fusion/cloning method in which cells were cloned within 2 to 3 days of the fusion event. Detection of antigen specific antibodies in the hybridoma culture supernatants was successful only with cells derived from primary stimulation/immunizations. Antibodies were detected using an indirect ELISA with the immunizing antigen coated on to the surface of the plates. Monoclonal hybridomas were isolated within 2 to 3 weeks using the fusion/cloning method, compared with the standard method, where it took 4 to 5 weeks. Although the total number of clones isolated from the fusion/cloning method was less than that obtained through the standard method, the yield of specific antibody-producing hybridomas as a percentage of the total picked was often more efficient with the fusion/cloning method. With respect to the immunoglobulin isotype produced, not all of the antibodies could be classified by the ELISA system used; 14% of anti-AHSV positive clones were identified as IgG-secreting cells, 25% as IgM-secreting, 18% were cross-reacting with IgG and IgM, and 43% could not be classified. Similar results in all aspects of the work were obtained whether a crude infected cell extract or purified outer capsid polypeptides VP2/5, from serotype 4 and serotype 9 respectively, were used.
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Affiliation(s)
- N Stäuber
- Institut für Viruskrankheiten und Immunprophylaxe (IVI), Mittelhäusern, Switzerland
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50
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Iwata H, Yamagawa M, Roy P. Evolutionary relationships among the gnat-transmitted orbiviruses that cause African horse sickness, bluetongue, and epizootic hemorrhagic disease as evidenced by their capsid protein sequences. Virology 1992; 191:251-61. [PMID: 1329319 DOI: 10.1016/0042-6822(92)90187-t] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The amino acid sequences of four major capsid proteins of African horse sickness virus (serotype 4, AHSV-4) have been compared with those of Bluetongue virus of sheep. Epizootic hemorrhagic disease virus of deer, and the phylogenetic relationships established. Complete nucleotide sequence analysis of three RNA segments (L2, L3, and M6) of AHSV-4 and their encoded products, VP2, VP3, and VP5, together with previously published data for VP7 (Roy et al., 1991), have revealed that of the four capsid proteins the innermost protein, VP3, is the most conserved, and the outermost protein, VP2, is the most variable. Some 57-58% of the aligned BTV-10 and EHDV-1 VP3 amino acids are identical with those of AHSV-4. This compares to an identity of 79% between the BTV and EHDV VP3 sequences. For the VP7 proteins 64% of the aligned amino acids are identical between BTV-10 and EHDV-1, while they share 44-46% amino acid residues with the aligned VP7 protein of AHSV-4. By contrast, the VP2 proteins of the three viruses share only 19-24% identical amino acids. Various other comparative analyses of the proteins indicate that the VP2 species of the three orbiviruses are similar. Unlike VP2, the other outer capsid protein, VP5 is more conserved among the three viruses. On alignment, the VP5 of AHSV-4 has some 43-45% identical amino acids with that of BTV-10 and EHDV-1. Between BTV and EHDV, 62% of the aligned sequences are identical.
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Affiliation(s)
- H Iwata
- University of Alabama, Birmingham 35294
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