Antigenic regions on the beta chain of human chorionic gonadotropin and development of hormone specific antibodies

Five peptides corresponding to four regions of the beta chain of human chorionic gonadotropin (hCG), were synthesized, purified and characterized. The four regions studied were selected on the basis of sequence differences between the beta chain of hCG (beta hCG) and the beta chains of related hormones. The peptides were found to bind rabbit and mouse anti-hCG antibodies as well as rabbit anti-beta chain antibodies, but did not bind antibodies against the alpha chain or against other hormones. All the peptides, even in their free form, were able to elicit high titer antisera in both rabbits and mice. In all cases, anti-peptide antisera bound to the immunizing peptide as well as to the native hCG and the isolated beta chain. These anti-peptide antisera did not bind to unrelated peptides, the alpha chain of hCG or to other hormones with very similar beta chains such as human luteotropic hormone (hLH), ovine luteotropic hormone (oLH) and equine chorionic gonadotropin (eCG). Since the areas represented by these peptides elicit antibodies that are specific for human beta hCG, they can formulate the basis for the development of discriminatory reagents for the beta chain of hCG.