Use of monoclonal antibodies against horse immunoglobulin in an enzyme immunoassay of bacterial toxins and toxoids

Immunization of BALB/c mice by horse antiserum against diphtheria made it possible to obtain IgG₁ monoclonal antibodies (MoAbs) 2B7E4 specific for light chains of horse immunoglobulin (Ig). Unlike commercial preparations of anti-horse immunoglobulin antibodies, which are specific for the whole Ig molecule or its Fc-fragment, the peroxidase (HRP) conjugate of the MoAb, 2B7E4-HRP did not interact with human, mouse, rabbit, and sheep Igs, or horse albumin. The conjugate obtained was used with MoAbs against bacterial toxins and commercial horse antitoxins, as a universal reagent in sandwich enzyme immunoassay (ELISA) for bacterial toxins and toxoids. The detection sensitivity of diphtheria toxin/toxoid equaled 0.0005 Lf/ml; tetanus toxin and toxoid were detected with sensitivities of 20 LD₅₀/ml and 0.005 UI/ml, respectively. A similar sandwich ELISA for botulinum toxoids (group measurement) allowed types A, B, and E to be detected at 0.02, 0.002, and 0.001 UI/ml, respectively; selective measurement was only possible in the case of type E toxoid (0.001 UI/ml).