Polyclonal antibodies to EB1089 (seocalcitol), an analog of 1alpha,25-dihydroxyvitamin D(3)

A hapten derivative of EB1089 [1(R),3(S),25-trihydroxy-26,27-dimethyl-9,10-seco-24-homocholesta-5(Z),7(E),10(19),22(E),24(E)-pentaene], a side-chain analog of 1alpha,25-dihydroxyvitamin D(3), was synthesized for raising antibodies with a high specificity for EB1089. The A-ring moiety of EB1089 was replaced in the hapten by a linker for conjugation to a protein. Three polyclonal antibodies were obtained by immunizing rabbits with a BSA-conjugate of the hapten. The antibodies were characterized for titer, avidity and specificity using an enzyme immunoassay with covalently bound EB1089. The three antibodies had similar binding profiles and were highly selective for EB1089 and its metabolites over the naturally occurring vitamin D metabolites. Cross-reactivities with 25-hydroxyvitamin D(3), the most abundant vitamin D metabolite in serum, were in the range 0.01-0.2% relative to EB1089.