An improved ELISA for the detection of serum antibodies directed against classical swine fever virus.

The complex-trapping-blocking (CTB) ELISA for detection of antibodies against classical swine fever virus (CSFV) using two monoclonal antibodies (mAbs) directed against envelope glycoprotein E2, has been improved using recombinant CSFV E2-antigen. The newly developed Ceditest ELISA for CSFV-Ab is a modification of the CTB-ELISA as described by Wensvoort et al. (1988) and Bloemraad et al. (1993). The old CTB-ELISA format comprised of a two-step, single-dilution test which had to be performed by hand at 37 degrees C. The Ceditest ELISA is a one-step, single-dilution test which can be performed by hand, or automated at room temperature. A set of 505 pig sera was tested for CSFV antibodies in the CTB-ELISA, in the Ceditest ELISA and in the neutralizing peroxidase-linked assay (NPLA). Concordance between the two ELISAs was 96.7%. Sensitivity and specificity of the Ceditest ELISA were 99% and 99% compared to the CTB-ELISA. The Ceditest ELISA discriminates between antibodies directed against bovine viral diarrhea virus (BVDV) and CSFV. The discrimination between antibodies directed against some Border disease virus (BDV) strains and CSFV is as inconsistent as with the NPLA. We conclude that the Ceditest ELISA for CSFV-Ab is a promising tool for the fast and simple screening of large numbers of pig sera for detection of antibodies directed against CSFV.