Cultivation of Trypanosoma cruzi in irradiated muscle cells: improved synchronization and enhanced trypomastigote production.

Since the in vitro production of trypomastigote stages of Trypanosoma cruzi in cell culture is frequently limited by (1) host cell overgrowth and (2) by the unequal redistribution of parasites after cell division resulting in asynchronous release of trypomastigotes, a culture system was devised in which host cell mitosis was inhibited by irradiation prior to parasite infection. L-6 rat myoblast cells when exposed to 3000 rad. of gamma radiation lost their ability to divide but remained susceptible to infection with, and capable of supporting the intracellular growth of, T. cruzi. Using this approach it proved possible to have virtually 100% of cells infected and achieve much better synchronization of trypomastigote release than with conventional culture systems. Additionally, the total number of parasites provided approached 1 x 10(9) trypomastigotes/150 cm2 flask, a significant increase over other culture systems. Preliminary studies with Plasmodium fallax an Eimeria tenella indicate that irradiated host cells may be utilized to advantage for the cultivation of other intracellular protozoa.