2 DIFFERENT APPROACHES FOR DEVELOPING IMMUNOMETRIC ASSAYS OF HAPTENS

To improve immunoassays of small haptens, we developed two different a pproaches for their measurement in a noncompetitive format. We first d evised two-site immunometric assays for small peptides (8-11 amino aci ds) by selecting two sets of antibodies specifically directed against C- and N-terminal moieties of the peptides. In each case, assay sensit ivity improved substantially over that of the corresponding competitiv e assays. More interestingly, all of these new immunometric assays wer e much more specific than the competitive assays. In a second approach , we developed a new procedure, solid-phase-immobilized epitope immuno assay (SPIE-IA(TM)(R)), in which a single monoclonal antibody uses the same epitope for capture and tracer binding and the hapten is covalen tly cross-linked to solid-phase proteins. To date, SPIE-IA have been s uccessfully applied to the determination of haptens bearing primary am ino groups, including substance P, thyroxine, leukotriene C4, endothel in, and angiotensin II. In each case, assay sensitivity was significan tly improved.