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Diagnostic Procedure
Principle of Antigen
Detection ELISA
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An indirect sandwich enzyme-linked immunosorbent assay (ELISA)
(Principle of Antigen Detection ELISA), approved by the World Reference
Laboratory (WRL) for FMD, is used to determine the presence of FMDV, or
swine vesicular disease (SVD), antigen. (Roeder
and Le Blanc Smith, 1987; Ferris
and Dawson, 1988).
Rabbit antisera specific for the different serotypes of FMDV and SVDV are passively adsorbed to the wells of polystyrene microtitre plates. With the addition of the test sample, antigen (if present) is trapped by the immobilised antibodies. Specific guinea pig anti-FMDV and SVDV detecting antibodies are then added which react with the trapped antigen. The bound guinea pig antibodies are detected by means of rabbit anti-guinea pig immunoglobulin (IgG) conjugated with horseradish peroxidase. On the addition of a substrate/chromogen solution, a colour product develops the intensity of which may be measured to indicate the antigen content of the test sample.
The FAO/OIE WRL for FMD at Pirbright, UK, examines potential cases of vesicular disease for the presence of any of the seven serotypes of FMDV, or SVDV, and this test protocol, particularly with respect to microtitre plate layout, is described. Other laboratories, who wish to modify and design their own plate layouts, depending on the number of serotypes that concern them may develop alternatives based on the principles described.
The choice of vesicular viruses to be detected depends on the geographical area and species involved. For example, detection of SVD virus is only relevant in samples from pigs. Samples from animals showing vesicular lesions with direct or indirect epidemiological connection with the Americas should be examined for vesicular stomatitis.
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