Evaluation of a gp 55 (E2) recombinant-based ELISA for the detection of antibodies induced by classical swine fever virus.

An enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against classical swine fever virus (CSFV) based on the competition of the serum antibodies with a CSFV-specific monoclonal antibody directed against the viral glycoprotein gp 55 (E2), has been evaluated. A total of 553 sera obtained from pigs experimentally infected in groups with different pestiviruses were included in this study. The ELISA was applied to a group of sera collected from pigs prior to pestivirus inoculation and therefore expected to have no detectable CSFV neutralizing antibodies. The specificity of the ELISA was calculated to range between 93% and 98%. The sensitivity of the ELISA was determined by testing predominantly sera of pigs exposed to CSFV and exhibiting CSFV neutralizing antibodies. When the cut-off level was reduced by 10%, the average sensitivity increased from 60% to 70% for the groups of sera tested. The ELISA was able to discriminate between CSFV and bovine viral diarrhoea virus (BVDV) induced antibodies.