Abstract: Objective: In order to develop a toxin-free detection method for okadaic acid (OA) from the shellfish, an anti-idiotypic antibody against anti-OA toxin monoclonal antibody (McAb) was prepared and identified. Methods: F(ab’)2 fragment from anti-OA McAb that was massively produced by the mouse ascites method and purified by caprylic acid and saturated ammonium sulfate was prepared by pepsin cleavage. Japanese big-ear white rabbits were immunized with the F(ab’)2 fragment and then their sera were taken for determination of reactivity between serum antibodies and anti-OA McA by agar gel diffusion test, indirect ELISA and indirect competitive ELISA. Results: The anti-idiotypic antibody had positive reaction with anti-OA McAb and competitively inhibited the binding of anti-OA McAb with detection antigen (OA-OVA). Conclusion: The prepared anti-idiotypic antibody against anti-OA monoclonal antibody has inner image of OA antigen and can be used to replace OA toxin standard in ELISA.

Key words: okadaic acid (OA), F(ab’)2 fragment, anti-idiotype antibody, inner image