Production of a group-specific antibody to 1 alpha,25-dihydroxyvitamin D and its derivatives having the 1 alpha,3 beta-dihydroxylated A-ring structure

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.

Production and characterization of monoclonal antibodies against a novel 1alpha,25-dihydroxyvitamin D3-bovine serum albumin conjugate linked through the 11alpha-position

To obtain an antibody which is useful for developing a selective immunoaffinity chromatography (IAC) of 1alpha,25-dihydroxyvitamin D3 [1,25(OH)2D3], which is an effective pretreatment tool for determining this metabolite in biological fluids, a variety of monoclonal antibodies have been produced against a novel haptenic derivative, 11alpha-hemiglutaryloxy-1alpha,25-dihydroxyvitamin D3, linked to bovine serum albumin. BALB/c, A/J and C57BL/6 mice, as well as Wistar and SD rats, were immunized with the hapten-carrier conjugate and the titer of the anti-1,25(OH)2D3 antibody in serum was examined. Spleen cells from A/J mice or SD rats, which showed a high titer, were fused with P3/NS1/1-Ag4-1 myeloma cells. After serial screening by enzyme-linked immunosorbent assay and radioimmunoassay, sixteen kinds of hybridoma clones secreting different anti-1,25(OH)2D3 antibodies were established. Scatchard analysis revealed that 12 antibodies out of 16 have enough affinity to 1,25(OH)2D3 (Ka>10(9) M[-1]). By a cross-reaction study using various related compounds, two antibodies, M114 and M129, both derived from A/J mice, were found to have suitable specificity. Although they showed relatively high cross-reactivities with the 1,25(OH)2D3 derivatives having 24-hydroxylated (both 20%) or lactonized (30%, 8.9%) side chain, all the tested 1alpha-deoxy-type metabolites, some of which interfere with the 1,25(OH)2D3 assays, were successfully discriminated [25(OH)D3: 0.67%, 0.40%; 24,25(OH)2D3: 0.27%, 0.24%; 25(OH)D3 3-sulfate: 0.11%, 0.14%]. These monoclonal antibodies will be applicable for developing not only IAC but also various immunoassay procedures.

Tandem immunoaffinity chromatography for plasma 1 alpha,25-dihydroxyvitamin D3 utilizing two antibodies having different specificities: a novel and powerful pretreatment tool for 1 alpha,25-dihydroxyvitamin D3 radioreceptor assays

We report here a novel and powerful pretreatment method for radioreceptor assays (RRAs) for human plasma 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) based on "Tandem" immunoaffinity chromatography (Tandem IAC). Two antibodies having different specificities were each immobilized on agarose gel with cyanogen bromide to produce immunosorbents which were stable and repeatedly usable. An ethyl ether extract of plasma was applied to the first affinity column, from which 1,25(OH)2D3 could be preferentially eluted and separated from 1 alpha-deoxy type metabolites. The effluent was then submitted to the second column, and the 1,25(OH)2D3 retained was eluted after non- or weakly-absorbed interfering substances were washed out. This procedure allowed efficient purification without careful handling or strict time-management in the entire operation and enabled avoiding preparative high-performance liquid chromatography (HPLC) from RRA even with a conventional chick intestinal vitamin D receptor. Mean (+/- SD) plasma 1,25(OH)2D3 values of 56 normal subjects and 10 patients with chronic renal failure, obtained with this Tandem IAC/RRA system, were 36.4 (8.7) and 11.2 (4.0) pg/ml, respectively. The Tandem IAC will also be useful for developing immunoassays or gas chromatography-mass spectrometry of 1,25(OH)2D3.