Histopathological and parasitological evidence of immunization of mice against challenge with 17 wild isolates of Trypanosoma cruzi

The possibility of preventing chronic infection by a battery of 17 wild isolates of Trypanosoma cruzi was studied in Swiss mice preimmunized with culture forms of an attenuated strain (TCC). Mice were challenged intradermally with low numbers of wild trypomastigotes obtained from naturally infected insect vectors captured within a 57,000 km 2 subtropical area in northern Argentina and which had not undergone any laboratory propagation. A significant degree of protection was observed in all cases, according to one or more parameters. Immunization reduced the level of parasitemia ( P < 0.05) in infections caused by 4 out of 13 isolates, as evaluated by microscope counts performed on fresh blood mounts and in 10 out of 15 isolates as evaluated by xenodiagnosis. A lesser degree of histopathology ( P < 0.05) was detected in the heart (7 out of 17 isolates), urinary bladder (10 out of 17 isolates) and skeletal muscle (10 out of 17 isolates). None of these parameters reflected infection or pathology in TCC-immunized, non-challenged mice. While antigenic variation frustrates vaccination against African trypanosomes, the effective protection shown here against 17 T. cruzi primary isolates indicates lack of antigenic variation and thus the possibility of effective vaccination in Chagas' disease.