Releasing latent Toxoplasma gondii cysts from host cells to the extracellular environment induces excystation

In this study, we incubated T. gondii cysts from host cells in several solutions containing a variety of ionic compositions. Excystation occurred in a solution with an ionic composition which mimicked that of the extracellular environment. However, excystation did not occur in a solution that mimicked the intracellular environment. We also found that the specific Na+/K+ ratio and the presence of Ca2+, mimicking the extracellular environment, are required to trigger excystation. To examine whether the stage conversion of bradyzoite to tachyzoite occurs prior to egress, we constructed a gene-modified T. gondii strain expressing a green fluorescent protein specifically in the tachyzoite stage. During the process of cyst reactivation of this strain, green fluorescence was detected prior to excystation. This suggests that stage conversion from bradyzoite to tachyzoite occurs prior to cyst disruption. These results indicate that T. gondii bradyzoites monitor the ionic composition of their surroundings to recognize their expulsion from host cells, to effectively time their excystation and stage conversion.PMID:34081969 | DOI:10.1016/j.ijpara.2021.04.004
Source: International Journal for Parasitology - Category: Parasitology Authors: Source Type: research