Impact of Trypanosoma cruzi clonal evolution on its biological properties in mice

Twenty Trypanosoma cruzi stocks attributed to the 19, 20, 39, and 32 clonal genotypes were comparatively studied in BALB/c mice during the acute and chronic phases of the infection to test the working hypothesis that T. cruzi clonal structure has a major impact on its biological properties. Fourteen parameters were assayed: (1) infectivity; (2) prepatent period; (3) patent period; (4) maximum of parasitemia; (5) day of maximum of parasitemia; (6) parasitemia; (7) mortality, (8) percentage of positive hemoculture, (9) tissue parasitism; (10) inflammatory process during the acute phase of the infection; (11) mortality, (12) percentage of positive hemoculture; (13) tissue parasitism; and (14) inflammatory process during the chronic phase of the infection. Statistical comparison showed that the results are overall consistent with the working hypothesis that biological differences are proportional to the evolutionary divergence among the genotypes. Thus, closely related genotypes (19 vs 20 and 32 vs 39) show in general fewer differences than distantly related groups (19 or 20 vs 32 or 39) except for the comparison between 19 and 32. The working hypothesis is even more strongly supported by the result of the nonparametric Mantel test, which showed a highly significant correlation (P = 2.3 x 10(-3)) between biological differences and genetic distances among all pairs of stocks. These data taken together emphasize that it is crucial to take into account the phylogenetic diversity of T, cruzi natural clones in all applied studies dealing with diagnosis, drug and vaccine design, epidemiological surveys, and clinical diversity of Chagas' disease.