TOXOPLASMA-GONDII - APPEARANCE OF SPECIFIC MARKERS DURING THE DEVELOPMENT OF TISSUE CYSTS IN-VITRO

Cultures were initiated in Madin-Darby bovine kidney (MDBK) cells from ME49 strain bradyzoites. Specific antibody staining showed that two p opulations of parasites exist, one being a predominant population of t achyzoites that were positive for the tachyzoite-specific marker SAG1 and negative for the bradyzoite-specific marker P36. All of these para sites expressed the dense granule molecule GRAS, which in larger clust ers was seen faintly in the membrane of the parasitophorous vacuole. N o rosette formation or monolayer destruction was observed. Also seen w as a sub-population of bradyzoites that were positive for P36 and nega tive for SAG1. Approximately 90% of these parasites expressed the matr ix molecule P29. These parasites were also positive for the dense gran ule molecule GRAS, which was highly concentrated in the wall of the cy st. These bradyzoite clusters contained fewer parasites and were small er in diameter than those expressing tachyzoite markers.