EXPRESSION OF TOXOPLASMA-GONDII-SPECIFIC HEAT-SHOCK-PROTEIN-70 DURINGIN-VIVO CONVERSION OF BRADYZOITES TO TACHYZOITES

Stage conversion between bradyzoites and tachyzoites was investigated in C57BL/6 mice chronically infected with the ME-49 strain of Toxoplas ma gondii. In order to promote bradyzoite-tachyzoite conversion, mice were treated in vivo with neutralizing doses of anti-gamma interferon (IFN-gamma) or anti-tumor necrosis factor alpha (TNF-alpha) antibodies . Expression of parasite-specific antigens SAG-I, SAG-2, and heat shoc k protein 70 (Hsp-70) was visualized in the central nervous system by immunocytochemistry and measured by photometric assay. The immunosuppr essive effect of anti-IFN-gamma or anti-TNF-alpha treatment was immedi ate, leading to parasite stage conversion as indicated by the increase d expression of tachyzoite-specific antigens (SAG-1 and SAG-2) and by rapid parasite replication. We also observed expression of high levels of Hsp-70 during a short period of conversion of bradyzoites to tachy zoites. Our data suggest that Hsp-70 may have an important role in the process of bradyzoite-tachyzoite conversion during the reactivation o f chronic toxoplasmosis.