Toxoplasma gondii: Kinetics of Stage-Specific Protein Expression During Tachyzoite-Bradyzoite Conversion in Vitro

Abstract

Stage conversion by Toxoplasma gondii is a key step in the interaction of the parasite with its host. since it is responsible for the long-term maintenance of the infection in immunocompetent hosts.The ability of T. gondii to persist in the host explains the long-range success of the parasite. Stage conversion is also a major concern in human pathology, as it is the main cause of toxoplasmic reactivation, which is often fatal in AIDS patients. This last aspect has recently stimulated a strong interest in studying the mechanisms of stage conversion in T. gondii. Progress has been made possible by identification of stage-specific probes and development of in vitro procedures mimicking the in vivo conversion, facilitating study of the process in culture rather than in the organs of infected hosts. Most of the studies have been concerned with the tachyzoite to bradyzoite switch, and most of this review will deal with this conversion. The reverse phenomenon, i.e., reactivation by cyst rupture, is still very poorly understood, as no in vitro model is yet available for its analysis.