Molecular Weight Analysis of Soluble Antigens from Toxoplasma gondii

Abstract

Ultrasonicated T. gondii (RH strain) tachyzoites were fractionated into a water-solubic and a deoxycholate-soluble fraction. Polyclonal immune mouse serum was prepared by challenging chronically-infected mice with viable RH strain tachyzoites. The parasite fractions were labeled with 125I, and the radiolabeled antigens were precipitated by the immune mouse serum or a monoclonal anti-Toxoplasma antibody (FMC20), that reacts only in the indirect hemagglutination antibody test. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and autoradiography of the immunoprecipitates showed that the water-soluble fraction contained 10 antigenic polypeptides, and the deoxycholate-soluble fraction contained 7 antigenic peptides. The FMC20 reacted against a 98,000-dalton antigen that was present in the water-soluble fraction only.