Monoclonal Antibodies to Human Chorionic Gonadotropin (HCG) and Their Use in Two-Site Binding Enzyme Immunoassays

A panel of mouse monoclonal antibodies (MABs) was produced against human chorionic gonadotropin (HCG) and its isolated β-subunit (β-HCG). According to their binding specificities the antibodies could be divided into HCG-specific and cross0reactive MABs. The HCG-specific antibodies reacted with antigenic sites on holo-HCG or holo-HCG and β-HCG, or exclusively with the non-associated β-HCG chain. The cross-reactive antibodies reacted with either HCG and luteinizing hormone (LH) or with HCG, LH, follicle-stimulating hormone (FSH) and thyreoidea-stimulating hormone (TSH). According to the binding specificities of the MABs and their reciprocal inhibition detected in two-site binding enzyme immunoassays (EIA), altogether 13 epitopes (including the 3 hidden epitopes detectable only on free non-associated β-HCG) were distinguished by the antibodies described here. Antibody combinations resulting in most effective and specific HCG- or β-HCG-determination were used as clinical assays and proved their reliability and correctness for monitoring patients with HCG- and/or β-HCG-producing tumors before and after therapy.