Brain cysts from three strains of Toxoplasma gondii were purified and analysed by SDS-PAGE and immunoblotting. Western blot analysis revealed the presence of major cyst/bradyzoite antigens at Mr 25000, 36000 and 67000 common to all strains and recognized by many individual sera. There was also evidence of strain variation in cyst antigens with, for example, antigens at Mr 88000, 28000 and 26000 unique to the 17025 strain. There was some overlap in the molecular weight of cyst and tachyzoite antigens, but the major tachyzoite surface antigen (P30) could not be detected in brain cysts.
