The immunology of experimental Chagas' disease. IV. Production of lesions in rabbits similar to those of chronic Chagas' disease in man.

Eight rabbits that received a single inoculation of trypomastigotes of a virulent strain of Trypanosoma cruzi first developed a transient acute illness associated with parasitemia; later, 4 of these rabbits died with chronic myocarditis and/or with megacolon in the absence of demonstrable parasitemia or encysted parasites in tissues. Two of these rabbits with chronic myocarditis died unexpectedly. Three of the inoculated rabbits that survived the infection were sacrificed 18 months later and showed similar but less severe microscopic lesions. The remaining rabbit is alive and well at the time of writing (26 months) with negative blood cultures but high hemagglutinating antibody titers to T. cruzi antigens. The natural course of T. cruzi infection in rabbits and the lesions observed postmortem are similar to those recorded for humans with chronic Chagas' disease. Multiple injections of particulate subcellular antigens of T. cruzi in rabbits resulted in microscopic lesions similar to those observed in rabbits that survived protozoan infection. Sera of rabbits inoculated with T. cruzi have antibodies to striated and smooth muscle structures. However, evidence provided in this and in other experiments strongly suggest that the lesions of chronic Chagas' disease are produced by delayed hypersensitivity to T. cruzi antigens.