Effect of the hapten linking arm on cross-reactivity of sulfonamide-specific antibodies in ELISA

Competitive enzyme-linked immunosorbent assay (ELISA) was used to explore the influence of the linking arm (azo or succinyl) of sulfonamide-protein immunogens on polyclonal antibody (pAb) cross-reactivity to sulfonamide N¹-analogues, N⁴-derivatives, or N⁴-protein conjugates. In addition to the sulfonamide's overall size and N¹-substituent structure, the dominant sulfonamide epitope of the immunogen was defined by the linking arm. Antibodies made from immunizations with azo and succinyl immunogens possessed 12- and 16-fold greater affinity for their N⁴-derivatives, respectively, compared to the underivatized sulfonamide form.