Constitutive Upregulation of Transcription Factors Underlies Permissive Bradyzoite Differentiation in a Natural Isolate of

Importance: is a widespread protozoan that chronically infects ~30% of the world's population. can differentiate between the fast-growing life stage that causes acute infection and the slow-growing stage that persists in the host for extended periods of time. The slow-growing stage cannot be eliminated by the host immune response or currently known antiparasitic drugs. Studies on the slow-growing stage have been limited due to the limitations of experiments and the challenges of manipulation. Here, we characterize a natural isolate of , which constitutively expresses factors that drive development and that is permissive to convert to the slow-growing stage under stress conditions . The strain presents a novel model for studying the chronic phase of toxoplasmosis and identifying new therapeutic treatments for chronic infections.