Toxoplasma gondii: identification and characterization of a cyst molecule.

Monoclonal antibodies were raised against the RRA strain of Toxoplasma gondii, and those with specific reactivity against tissue cysts were selected by differential FAST-ELISA screen. One clone, E7B2, reacted with a novel cyst-specific molecule of approximate molecular weight 29,000. The molecule is predominantly found in soluble fractions from intact cysts and bradyzoites, and immunofluorescence studies suggest that it accumulates in the matrix of the cyst. Western blotting experiments show the molecule to be a minor antigen recognized by polyclonal antisera from infected mice.