A competitive ELISA for the detection of group-specific antibodies to African horse sickness virus.
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A competition enzyme-linked immunosorbent assay (ELISA) has been developed for the rapid identification and quantification of antibodies against African horse sickness (AHS) in sera from solipeds. The data showed the ELISA to be sensitive, specific and reliable. More than 1600 sera from 37 different countries were examined and results compared with those obtained by agar gel immuno-diffusion (AGID) tests. In no case did any of 775 sera from countries where AHS has never been reported and where AHS vaccines are not used, record an ELISA titre greater than 4. A titre equal to or greater than 8 was considered positive. Using this criterion, 96.3% of sera tested in both assays were in agreement. Doubtful results by AGID (1.7%) were clearly defined in terms of positivity and negativity by ELISA. This ELISA is suited for the rapid laboratory confirmation of AHS and should be considered as a replacement for the traditional AGID test. (+info)
Laboratory diagnosis of African horse sickness: comparison of serological techniques and evaluation of storage methods of samples for virus isolation.
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Five serological methods of diagnosing African horse sickness were evaluated, using a battery of serum samples from experimental horses vaccinated and challenged with each serotype of African horse sickness virus (AHSV1 through AHSV9): agar gel immunodiffusion (AGID), indirect fluorescent antibody (IFA), complement fixation (CF), virus neutralization (VN), and enzyme-linked immunosorbent assay (ELISA). The 5 tests were also compared using a panel of field samples, convalescent equine sera with antibodies to domestic equine viral diseases, and sera from horses awaiting export. The ELISA described in this paper was group specific. It did not require calibration with a standard positive serum but did yield elevated values with negative sera that were repeatedly frozen and thawed or heat inactivated. The IFA test was sensitive but could not be used on some field sera as the control cells exhibited fluorescence, possibly due to the animal being recently vaccinated with cell culture material. Sixty-two experimental sera were compared by VN, CF, AGID, and ELISA. Forty sera, 10 positive and 30 negative, were correctly classified by the 5 serologic assays. The 22 remaining sera gave mixed reactions. The AGID had no false positive results but had false negative results for up to 20% of the samples, depending upon the comparison. The VN, CF, and ELISA were similar in their variability. The length of time that virus could be recovered from a viremic blood sample was compared in an evaluation of storage methods for virus isolation samples. Washed erythrocytes were held at 4 C, washed erythrocytes plus stabilizer were held at -70 C, and blood that was drawn into a preservative (oxalate/phenol/glycerol) was held at 4 C.(ABSTRACT TRUNCATED AT 250 WORDS) (+info)
A modified vaccinia Ankara virus (MVA) vaccine expressing African horse sickness virus (AHSV) VP2 protects against AHSV challenge in an IFNAR -/- mouse model.
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Purification and characterization of the major group-specific core antigen VP7 of bluetongue virus synthesized by a recombinant baculovirus.
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The major core protein, VP7, of bluetongue virus serotype 10 (BTV-10) has been purified from insect cells infected with a genetically manipulated recombinant baculovirus. The high level expression of VP7 (in excess of 100 mg per litre of culture) and its presence in the soluble fraction of infected cells following lysis by detergent has allowed the purification of the protein virtually to homogeneity (95%) by a simple two-step procedure of ammonium sulphate fractionation and ion-exchange chromatography. The purified antigen is highly immunogenic and has been shown in an ELISA to be reactive with antisera of 24 BTV serotypes (1 to 24) as well as with an antiserum raised to African horsesickness virus type 4 (AHSV-4), a representative of another serogroup of orbiviruses. In confirmation of these data a monospecific antiserum raised with the expressed product has been shown by Western blot analyses to react with other BTV serotypes as well as with two serotypes of epizootic haemorrhagic disease virus (EHDV-1 and EHDV-2), a closely related orbivirus. The data indicated that VP7 is a highly conserved protein amongst BTV serotypes and at least partly conserved amongst three serogroups of orbiviruses. (+info)
Isolations of African horse sickness virus from vector insects made during the 1988 epizootic in Spain.
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This paper describes the first isolations of African horse sickness virus (AHSV) from insects in Spain. Seven isolations of AHSV serotype 4 were made; four from Culicoides imicola a known vector of the virus elsewhere, two from mixed pools of Culicoides species not including C. imicola and one from blood engorged mosquitoes. Three further isolations of AHSV serotype 4 were also made from horses kept adjacent to the insect collecting sites. This work presents the first definitive identification of the vectors of AHSV in Spain during the 1987, 88 and 89 epizootics. Suggestions are also made concerning the significance of these findings with regard to the epidemiology of African horse sickness in Spain. (+info)
Temperature dependence of the extrinsic incubation period of orbiviruses in Culicoides biting midges.
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