Monoclonal antibody to human T-cell leukemia virus p19 defines polypeptide antigen in human choriocarcinoma cells and syncytiotrophoblasts of first-trimester placentas.

In previous studies we detected retrovirus RD114 p30-related antigen in human placental syncytiotrophoblasts and antibodies in cord blood sera. We now report that a monoclonal IgG antibody specific for the p19 protein of human T-cell leukemia virus (HTLV) reacts with human syncytiotrophoblastic antigen. When used in the immunoperoxidase tissue-staining procedure, the monoclonal antibody reacted with the syncytiotrophoblastic cells in sections of all early placentas (less than 15 weeks of gestation), blighted ova and benign (hydatidiform mole) or malignant placental tumors (destructive mole, choriocarcinoma). In all cases the reactivity was mainly confined to the cytoplasm of the cells with syncytiotrophoblastic morphology. Normal embryonal or adult tissues tested were negative. In immunoblotting of cultured choriocarcinoma cells, anti-HTLV p19 detected a single polypeptide at mol.wt 28,000 from proteins separated by electrophoresis.