Trypanosoma cruzi is a heterogeneous group of parasites. The imposition of natural or artificial pressures can result in the selection of subsets of the population with concomitant changes in characteristics used to evaluate the group. In order to ascertain the extent of heterogeneity, stocks of single-cell clones were prepared from various sources. Selected cell
biological, biochemical, immunochemical, parasitological, and histopathological parameters of these clones have been studied. A ten-fold difference in the rate of growth of the epimastigote stage of T cruzi clones has been observed. The extracellular growth rates of the clones correlate with the rate of growth of the obligate intracellular amastigote stage and consequently, the length of intracellular cycle of the parasite. A 40% difference in the amount of total
DNA/parasite has been found between clones. Although the amount of
DNA/kinetoplast and nucleus varies between clones, the major contribution to the differences in total
DNA/parasite appears to be the nucleus. From 16 to 35
antigens have been demonstrated in the T cruzi clones assayed to date. Five to seven of these
antigens are common to all of the stocks assayed. However, both isolate- and clone-specific
antigens have also been demonstrated. The susceptibility of inbred strains of mice to T cruzi clones varies with the clone of the parasite. These data imply that the genetics of the parasite as well as the host modulate both the course and outcome of a T cruzi
infection. The influence of
monosaccharides on the receptor-mediated
infection of vertebrate cells by trypomastigotes of T cruzi also varies between clones. The implications of these findings upon our concept and understanding of present and future problems in
Chagas disease are discussed.