RELATIONSHIPS BETWEEN HISTOPATHOLOGICAL FINDINGS AND PHYLOGENETIC DIVERGENCE IN TRYPANOSOMA-CRUZI

Problems have been raised by natural genetic diversity of Trypanosoma cruzi, the causal agent of Chagas' disease, and other protozoa in term s of both basic and applied science. T. cruzi manifests a great divers ity of medical and biological properties which could be the origin of clinical variability in the disease. Me propose possible correlations between genetic distances, or phylogenetic divergence, and histopathol ogical data. To ascertain this aspect, 15 cloned stocks pertaining to three major clones or genotypes (19, 20 and 39) were compared. Sets of 24 mice infected with each stock were studied for histopathological l esions. Brain, heart, lung, liver, spleen, urinary bladder, bone marro w colon, kidney and skeletal muscle were extracted from each mouse. Qu alitative and quantitative differences showed at histopathological exa mination. An important encephalic softening was found in brains of mos t mice infected by genotype 20, corresponding to areas of inflammation and liquified necrosis. Other inflammatory tissue lesions in the hist ological sections of the three genotypes were similar. Skeletal muscle tropism was higher than cardiac tropism in all the studied genotypes. All three genotypes shared parasite presence in skeletal muscle. Diff erences related to cardiac tropism were important: in genotype 19, 50% of studied stocks presented pseudocysts; 20% in genotype 20 and 83% i n genotype 39. Parasite presence in other tissues was scanty: in brain only in genotype 20 and in spleen and liver only in genotype 39. We f ound important histopathogenicity differences among the three studied genotypes, but they do not support the hypothesis of zymodeme pathogen ic specificity due to the great diversity among stocks within each gen otype.