A comparison of challenge with Trypanosoma cruzi blood-stream trypomastigotes and metacyclic trypomastigotes from Rhodnius prolixus in mice immunized with killed antigens.

Groups of CD-1 mice were immunized with vaccines prepared from freeze-thawed or ultra-sonicated epimastigotes, blood trypomastigotes, or "plasma antigen", of Trypanosoma cruzi strains Y, M1 and Tulahuen. The mice were challenged by the injection of blood stream trypomastigotes obtained from mice, or of metacyclic trypomastigotes harvested from the rectum of Rhodnius prolixus. Both challenges induced virulent infections in control mice. Blood-stream trypomastigotes killed mice more rapidly than the same number of bug-derived trypomastigotes. Vaccinated mice resisted infection with bug-derived trypomastigotes as well as with blood trypomastigotes, and in some instances better. It is concluded that results obtained with the more convenient, but artificial blood trypomastigote challenge are comparable with the more natural, bug-derived, challenge.