In vitro generation of cloned populations of Toxoplasma gondii.

Cloned populations were generated from Indian isolates of Toxoplasma gondii by transferring single tissue cysts from the brains of chronically infected mice to confluent murine macrophage (J774A.1) monolayers. The clones were then maintained continuously as tachyzoites in culture. Physical rupture of the tissue cysts and release of bradyzoites prior to seeding was found to be necessary for establishment of the parasite in culture. Although intact tissue cysts seeded over monolayers released bradyzoites spontaneously, they did not succeed in setting up an infection in the monolayers. Random amplified polymorphic DNA (RAPD)-PCR, which revealed distinct patterns for a clone and its progenitor, further confirmed the efficiency of the technique. The cloning technique was found to be simple and rapid compared to those involving limiting dilutions.