INDUCTION OF HEAT-SHOCK PROTEIN CLOSELY CORRELATES WITH PROTECTION AGAINST TOXOPLASMA-GONDII INFECTION

Heat shock proteins (HSPs) are evolutionarily highly conserved polypep tides that appear to be produced by many cells to preserve cellular fu nctions under a variety of conditions of stress, including infections. We report that a 65-kDa HSP is present in mouse peritoneal cells that have been infected with a low-virulence (Beverley) strain of Toxoplas ma gondii, as determined by electroblot assay using a monoclonal antib ody specific for microbial HSP65. This HSP is, however, not expressed when infection occurs with the high-virulence RH strain of T. gondii. Furthermore, HSP was demonstrable in mice that acquired resistance aga inst infection with a lethal dose of bradyzoites of the Beverley strai n or even of an inoculum of a highly virulent strain of T. gondii (RH) . From these results, it can be suggested that HSPs play an important role in developing effective defenses that include effective immune re sponses against infection with Toxoplasma parasites in vivo.