Coexistence of heterogeneous populations of Toxoplasma gondii parasites within parasitophorous vacuoles of murine macrophages as revealed by a bradyzoite-specific monoclonal antibody.

The expression of bradyzoite-specific antigens (Bsa) of Toxoplasma gondii was studied in murine bone-marrow-derived macrophages that had previously been infected with tachyzoites. Growth conditions that allowed only restricted replication of Toxoplasma gondii resulted in heterogeneous populations; (1) Bsa-positive and Bsa-negative parasites could be observed within one parasitophorous vacuole (heterogeneous vacuole community), and (2) homogeneous Bsa-positive and homogeneous Bsa-negative vacuole communities coexisted within one macrophage host cell. These observations suggest that stage conversion does not seem to be a synchronous event for a vacuole community.