Toxoplasma antigen isolated by affinity chromatography with monoclonal antibody protects mice against lethal infection with Toxoplasma gondii .

Abstract

A number of workers have reported success in conferring protection against the lethal effect of Toxoplasma gondii infection in mice with vaccines consisting of whole killed tachyzoites or live temperature-sensitive mutants of the organism. Current strategies for development of vaccines against T. gondii depend upon production of protective monoclonal antibodies and/or recombinant DNA technology. It has been recently demonstrated that passive transfer of monoclonal antibodies that react with cell surface antigens of Toxoplasma can confer resistance against a lethal challenge with this parasite. In addition the results of experiments performed in our laboratory indicate that partially purified antigens of Toxoplasma can protect mice against a lethal infection. The present studies were undertaken to examine whether monoclonal antibodies directed against cytoplasmic antigens of the parasite can induce protection, and if so, whether antigens isolated from such antibodies coupled to solid supports can be used as putative vaccines. Our results demonstrate that the monoclonal antibody F3G3 (IgG2 subclass), which reacts in an immunofluorescence test with formalin-fixed but not with live tachyzoites, does not fix complement (6), and reacts with cytoplasmic but not cell surface components of the organism, protects mice against a lethal challenge with T. gondii. Mice injected with the antigen recognized by the monoclonal antibody F3G3 were also protected against death due to challenge with live Toxoplasma.