Division 2

The discriminatory test is a liquid phase blocking enzyme-linked immunoassay. The samples to be tested are incubated onto microtitre plates precoated with monoclonal anti-Erns antibodies together with a defined amount of Erns antigen. Any antibody specific for Erns binds to the defined amount of Erns antigen in the solution and an antigen/antibody complex is formed, which does not react with the anti-Erns antibodies on the microtitre plate. After washing of the plates to remove unbound material a peroxidase labelled anti-Erns conjugate is added which binds to the Erns antigen complexed with the antibody coated on the surface of the microtitre plate. Unbound conjugate is removed by washing and chromogen-containing substrate is added. The degree of colour, which develops, is reversely proportional to the amount of antibody specific for Erns present in the sample. If the sample does not contain antibodies (negative sample) much of the defined amount of Erns antigen that was added can bind to the anti-Erns antibodies on the plate surface and a strong colour reaction is observed.

A result is obtained by comparing the optical density (OD) in wells containing test samples with those of wells containing the negative and positive controls.