Two novel formats of ELISA for the detection of
antibodies against
swine vesicular disease (SVD) virus were developed. One of the tests described is a
monoclonal antibody-based competitive ELISA (MAC-ELISA). In this test, specific
antibodies in serum are detected due to their ability to compete with a neutralizing
monoclonal antibody (MAb). The second is an indirect trapping ELISA which employs isotype-specific MAbs to detect swine
IgG or
IgM specific for SVD virus. The diagnostic sensitivity and specificity of the MAC-ELISA was studied on 5671 field sera of known origin, enabling the cut-off level to be defined. Using the MAC-ELISA, 100% of sera from infected pigs were found positive, whereas only 0.45% of negative sera gave a false-positive result. A positive correlation between MAC-ELISA and virus neutralizing titres was recorded for pig sera collected sequentially after experimental
infections. The results from the isotype-specific ELISA revealed the dynamics of the antibody response to SVD virus in pigs. The first
antibodies were detectable as early as 3 days after experimental
infection. Up to the 10th day, demonstrable
antibodies were exclusively of the
IgM class.
IgG developed later, between 11 and 14 days postinfection and remained at a plateaux level throughout the whole investigation period. The two tests satisfy different diagnostic requirements: the MAC-ELISA is useful as a screening test, the isotype-specific ELISA has potential application for the determination of stage of
infection. Both tests benefit from the use of MAbs in terms of specificity and standardization and have advantages over the virus neutralization test.