ENZYME-IMMUNOASSAYS FOR POLYCHLORINATED-BIPHENYLS - STRUCTURAL ASPECTS OF HAPTEN-ANTIBODY BINDING

The syntheses of 4,4'-dichlorobiphenyl- and 3',4,4',5-tetrachlorobiphe nyl-2-azo-protein immunogens and the corresponding haptens conjugated to peroxidase through the amidoadipate spacer arm are described. Only one sheep of the 24 immunized animals yielded an antiserum with superi or antibody titres. The direct competitive enzyme-linked immunosorbent assay (ELISA) incorporating this antiserum showed IC50 values for com mercial polychlorinated biphenyl (PCB) mixtures Delor 103, 104, 105, a nd 106 (the corresponding formulations are Aroclor 1242, 1248, 1254 an d 1260) of about 200, 250, 600, and 900 mu g l(-1), respectively. No c ross-reactions with chlorinated phenols, phenoxyalkanoic acids, or chl orinated herbicides were observed and only a 5% cross-reactivity was f ound for DDE (Delor 103=100%). Molecular models of hapten determinants were constructed to examine potential conformational changes in the b iphenyl nucleus in relation to tracer immunoreactivity and assay selec tivity. The structural data were not consistent with the lack of immun oreactivity for peroxidase tracers in conjunction with almost all of t he tested antisera. Influence of the various molecular factors on the binding and competitive characteristics is discussed.