Author
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Mecham, James |
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Submitted to: American Society for Virology Meeting
Publication Type: Abstract Only Publication Acceptance Date: 3/23/2005 Publication Date: 6/17/2005 Citation: Mecham, J.O. 2005. Epitope coding sequence used to predict sensitivity of bluetongue virus diagnostics. American Society for Virology. Paper No. P33-1. Interpretive Summary: Bluetongue virus (BTV) is an arthropod-borne virus that infects both domestic and wild ruminants. Bluetongue is classified as a list A disease by the Office of International Epizootics (OIE). Infections caused by this virus cause considerable economic loss due to both disease and livestock trade restrictions. Regulatory restrictions often require that animals be certified as BTV and/or antibody free before allowing import or export of these animals or their products. Competitive enzyme-linked immunosorbent assay (c-ELISA) procedures are the diagnostic assay of choice for the serologic diagnosis of infection caused by this virus. These assays measure competition between serum antibodies and a defined monoclonal antibody. The degree of competition reflects antibody titer in the host animal resulting from exposure to the virus. There are at least 24 serotypes of BTV worldwide, and numerous viral strains within each serotype. This offers tremendous opportunity for genetic and phenotypic variation within this group of viruses. Since monoclonal antibodies are specific for defined antigenic determinants (epitopes) on the proteins of the virus, variation within these epitopes between virus serotypes or strains can lead to false negative results with c-ELISA tests. Sequence data is available for a large repertoire of BTV serotypes and strains and can be used to determine the degree of variation between viruses. The purpose of this study was to define an epitope recognized by a monoclonal antibody used in a c-ELISA, and to determine the conservation of that epitope among serotypes and strains of BTV based on known genetic sequences. The results of the study indicated that the epitope studied is highly conserved; however, some variation between viruses could lead to misdiagnosis of BTV infections. This knowledge is useful in reconfiguring BTV diagnostics with improved sensitivity and specificity. Technical Abstract: Bluetongue virus is an arthropod-borne Orbivirus that infects domestic and wild ruminants. Enzyme-linked immunosorbent assays (ELISA) are routinely used in the diagnosis of infection caused by this virus. These assays are routinely configured around monoclonal antibodies that recognize specific epitopes on viral proteins. Depending on the monoclonal antibody, ELISA procedures can be configured to be highly specific for this virus. Our laboratory has developed ELISA tests for detection of either a highly conserved protein of bluetongue virus or antibody to that protein. These tests have been demonstrated to be useful for diagnosis of infection caused by different serotypes and strains of this virus. However, since these assays are based on reaction with a monoclonal antibody, strains or serotypes of virus lacking the appropriate epitope or having a mutation in the epitope may not be detected by the assay. To develop a way to rapidly evaluate the sensitivity of the ELISA tests, the genetic sequence of the epitope recognized by the monoclonal antibody in these tests was determined. The conservation of this epitope sequence was examined among serotypes and strains of bluetongue virus for which sequence data were available. Although highly conserved, there was some variability in the genetic coding sequence for the epitope, which was reflected in the sensitivity of ELISA tests. Information on epitope sequence and variability should be useful in validating ELISA based diagnostics for other viruses as well as bluetongue virus. |
