Immunogenicity of a soluble partially purified oncofetal antigen from murine fibrosarcoma in syngeneic mice.

Abstract

A tumor/fetal associated antigen, termed oncofetal antigen (OFA), conserved in the tumor and fetal tissue of rodents and humans, was extracted from murine fibrosarcoma cells and tumors and was fractionated on an Ultrogel AcA34 gel filtration column. A monoclonal antibody 115 specific for the OFA identified three peaks of antigenic activity in the eluted fractions, designated fractions (Fr.) I, II, and III, in the molecular weight range of greater than 160, 90, and 44 kDa, respectively. Most of the activity resided in the high molecular weight fraction, Fr. I. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis and gel scanning of Fr. I showed multiple bands, one of which, constituting about 5.6% of the total protein bands in Fr. I, was the 44 kDa oncofetal antigen, apparently present in this fraction in a soluble complex form. Lectin binding studies and isoelectric focusing showed that the 44 kDa OFA is a glycoprotein, whose pI is 6.8. Spleen and peritoneal exudate cells of BALB/c mice immunized with Fr. I protected naive syngeneic mice, in adoptive transfer experiments, from developing tumors when challenged with syngeneic fibrosarcoma tumor cells, MCA-1315. Also, immune spleen cells were cytotoxic to the tumor target cells, MCA-1315, in a 51Cr release assay at several different effector to target cell ratios. This is the first description of a conserved, true, oncofetal antigen capable of inducing tumor transplantation resistance in syngeneic rodents in a semipurified form.