Immunoenzymatic detection of three kinds of 43,000-molecular-weight antigens by monoclonal antibodies in the insoluble fraction of Toxoplasma gondii.

Monoclonal antibodies (TpM 3, TpM 6, and TpM 19) against Toxoplasma gondii insoluble antigens were produced by the hybridization of NS-1, a mouse myeloma cell line, with spleen cells from mice immunized with T. gondii insoluble antigens. TpM 3, TpM 6, and TpM 19 were characterized by the dye test, the latex agglutination test, two types of enzyme-linked immunosorbent assays, using either T. gondii supernatant antigens or T. gondii insoluble antigens, and immunoperoxidase staining. TpM 3, TpM 6, and TpM 19 antigens were analyzed by the immunoblotting method, using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electrophoretic transfer of the antigens to nitrocellulose sheets. TpM 3, TpM 6, and TpM 19 were all negative by the dye test, the latex agglutination test, and the enzyme-linked immunosorbent assay, using T. gondii supernatant antigens but positive by the enzyme-linked immunosorbent assay, using T. gondii insoluble antigens. Each antibody gave unique spot patterns in the cytoplasm of tachyzoites, and each detected antigens of ca. 43,000 molecular weight with different electrophoretic patterns. Purified TpM 3 antigen bound only to TpM 3 but not to TpM 6 or TpM 19. Comparable results were obtained with TpM 6 and TpM 19 antigens. Rabbit anti-T. gondii sera reacted with both TpM 3 and TpM 19 antigens. However, human anti-T. gondii sera reacted only with TpM 3 antigen. These results indicate that T. gondii insoluble antigens contained at least three types of 43,000-molecular-weight antigens that have been revealed for the first time in this paper.