Genetic variation among Trypanosoma cruzi populations

The analysis of enzyme electrophoretic patterns in 141 extracts of Trypanosoma cruzi isolated from humans and domesticated and wild animals from the endemic zone of Chagas' disease in Argentina allowed their characterization into 12 different "isozymic strains" or zymodemes (Z1 to Z12). In humans, the parasites most frequently found belong to Z1 and Z12. These zymodemes differ significantly in pathogenic activity, Z1 having fewer deleterious effects than Z12. Because of the good correlation existing between zymodemes and the groups of parasites characterized by the study of kinetoplast DNA (kDNA), it is possible to identify zymodemes by analyzing kDNA. A 270-base-pair probe of the highly variable region of minicircles (HVRm) of kDNA, purified from Z1 and Z12 reference stocks, hybridized specifically with PCR-amplified HVRm from T. cruzi isolates, allowing identification of the "major natural clones." It is suggested that this technique of zymodeme identification could be useful for the prognosis of the probable evolution of the disease.