[Antigenic determinants of human chorionic gonadotropin (hCG): identification of epitopes and determination of their biological functions, for use in immunometric test systems and development of a fertility regulating vaccine].

Analysing immunologically relevant structures of human chorionic gonadotropin (hCG), a glycoprotein hormone, has bearing on a variety of clinical features. These structures are of importance for the establishment of immunometric assays for the diagnosis and monitoring of pregnancy and hCG producing tumours. Moreover, the development of fertility regulating vaccines by the use of one of the subunits of hCG (hCG beta) or a synthetic peptide corresponding to the carboxyl-terminal peptide thereof (hCG beta CTP, beta 109-145) requires detailed knowledge of the antigenic properties of hCG. It appeared that 16 different antigenic epitopes are localized on the protein backbone of hCG and that the carbohydrate moieties do not contribute significantly to the immunological properties of this hormone. Reduced and carboxylmethylated subunits of hCG, i.e., hCG alpha and hCG beta, express only 1 alpha- and 2 beta-epitopes, the majority of antigenic determinants being destroyed by this chemical procedure. Epitopes of hCG are thus predominantly dependent on the intact tertiary or quaternary structure of the protein. The urinary low molecular weight fragment of hCG beta (hcG beta cf), a predominant molecular fraction in the urine of pregnant women or patients with various tumours expresses 7 out of 9 epitopes of hCG beta (beta 1- beta 7), whereas two antigenic determinants, beta 8 and beta 9, are localized on the hCG beta CTP.(ABSTRACT TRUNCATED AT 250 WORDS)