A MONOCLONAL-ANTIBODY AGAINST A SYNTHETIC PEPTIDE IS SPECIFIC FOR THE FREE NATIVE HUMAN CHORIONIC-GONADOTROPIN BETA-SUBUNIT

A totally synthetic molecule (109-145 peptide) analogous to the .beta.-subunit carboxyl terminus was used as an antigen in the development of antibodies by the hybridoma technique. A monoclonal antibody (702 D7) specifically recognized the free native .beta.-human chorionic gonadotropin (.beta.hCG). 702 D7 was of the IgG1 subclass and was directed against an antigenic site localized in a 10-amino acid sequence (109-118) or less. The recognition of an epitope located in the 109-118 region could explain the specific recognition of .beta.hCG observed with 702 D7, in contrast to monoclonal antibodies directed against a 118-145 region with a recognition of both .beta.hCG and whole hCG, as observed with a 2nd monoclonal antibody (1032) to synthetic peptide. Immunohistochemical results and preliminary data obtained from the immunoradiometric assay show that 702 D7 provides a clinical tool for the detection of free .beta.-subunit secretion even at low concentrations, and could allow the study of this subunit or its metabolites produced by normal and tumoral cells.