Chagas' disease. Immunotoxin inhibition of Trypanosoma cruzi release from infected host cells in vitro

Virulent tissue culture-derived Trypanosoma cruzi trypomastigotes were readily killed by immune IgG-ricin A chain conjugates (ITR) in vitro. Forty micrograms of ITR immobilized 10(6) trypomastigotes after 48 hours of incubation at 37 degrees C. ITR showed antibody specificity and 125I-labeled anti-T. cruzi IgG bound to parasitized host cells 9-fold more than to nonparasitized host cells. The degree of specificity was evaluated further in experiments in which 10 micrograms of ITR showed 78% inhibition of [3H]thymidine incorporation by T. cruzi. In contrast, nonimmune IgG-ricin A chain conjugate neither immobilized nor inhibited [3H]thymidine incorporation by the parasite. Furthermore, 20 micrograms of ITR significantly inhibited T. cruzi trypomastigote release from infected host cells and thus prevented reinfection of other cells in vitro.