HOST-CELLS OF TOXOPLASMA-GONDII ENCYSTATION IN INFECTED PRIMARY CULTURE FROM MOUSE-BRAIN

In order to identify brain cell types that serve as host cells of Toxo plasma gondii encystation primary cultures from murine brain were infe cted and stained for neural and parasite stage-specific markers. In mi xed culture inoculated with T. gondii tachyzoites, MAP2(+) neurons, GF AP(+) astrocytes, F4/80(+) microglia, and O1(+) oligodendrocytes prove d to be infected as detected by parallel labeling of SAG1. At 4 days f ollowing infection with bradyzoites, cysts developed in neuronal, astr oglial, and microglial host cells as clarified using bradyzoite-specif ic antibody 4F8. Additional staining of SAG1 revealed that astrocytes in bradyzoite-infected brain cell culture can also harbor tachyzoite-c ontaining vacuoles. Stage conversion was observed shortly after inocul ation and was accompanied by an increase in parasite proliferation. Ho wever, tachyzoites became rare in prolonged culture. By contrast, the numbers of cysts and of the bradyzoites isolated multiplied during lon gterm culture. These findings demonstrate that both glial and neuronal host cells allow T. gondii encystation in the absence of T cell-deriv ed cytokines and imply that a brain-internal spreading of bradyzoites may sustain chronic infection.