Monoclonal antibody with high affinity for 1,25-dihydroxycholecalciferol

We have developed a monoclonal antibody capable of detecting 1 pg/ml of 1,25-dihydroxycholecalciferol. At a dilution of 1:80,000 of ascitic fluid this antibody has an apparent KD of 3.3 X 10(-11) ML-1. The immunogen used was a vitamin D analogue, calcitroic acid [1 alpha, 3 beta-dihydroxy-9, 10 seco-24-nor 5, 7, 10 (19) cholatriene-23-oic acid], conjugated to bovine serum albumin. Although this antibody is extremely sensitive, it also recognizes other important vitamin D3 metabolites.