Production of sequence specific polyclonal antibodies to human parathyroid hormone 1-37 by immunization with multiple antigenic peptides.

To generate site-specific antibodies to the N-terminal bioactive fragment of the parathyroid hormone hPTH 1-37, multiple antigenic peptide systems (MAP) for immunization were used. Two 10 residue fragments and a 14 residue fragment derived from knowledge of the secondary structure of hPTH 1-37 were selected to be synthesized as MAPs. Each peptide (hPTH 1-10, hPTH 9-18, and hPTH 24-37) was synthesized directly onto a branching heptalysine core matrix by automated solid phase synthesis. The hPTH 1-10 and the hPTH 24-37 MAP were highly immunogenic in rabbits. Ten polyclonal antisera obtained from rabbits were characterized by epitope mapping. Antigenic determinants were found as follows: 1) Sera K1-K3 raised to MAP 1-10 showed a predominant binding sequence at hPTH 1-5. 2) Sera K4-K6 raised to MAP 8-18 preferentially bound to residues 9-14. 3) Immunizing with hPTH 24-37 MAP led to antisera characterized as follows: serum K7 recognized residues 24-37, the sequence used for immunization, sera K8, K9 and K10 bound to residues 24-37 and 26-34. In summary, the favoured regions as deduced from the secondary structure of hPTH 1-37 were covered by the produced antibodies.