Several studies have shown a clonal structure of
Trypanosoma cruzi and its possible correlation with the
behavioral heterogeneity of the parasite strains. In the
present study, the 21 SF strain, that have been maintained in
laboratory by successive passages in mice, for more than 15
years, showing a stability of biological and isoenzymic
characteristics has been cloned, with the objective of
establishing the characters of its clones and subclones. With
the technique of isolation of a single parasite from the blood
of infected mice, 5 clones and 14 subclones have been
obtained. After four passages into mice, inoculum of 105 was
obtained for each clone and subclone and inoculated into mice
weighing 10 to 12 g. These were used for the study of the
biological behavior of the clones: evolution of parasitemia,
morphology of blood forms and host mortality. For isoenzymic
characterization, the clones and subclones were analyzed for
ALAT, ASAT, GPI and PGM enzymes. Results have shown that the 5
clones and the 14 subclones disclosed a biological behavior
similar to the parental strain, with minor variability of the
parasitemic profiles and also the same isoenzymic patterns.
These results confirm the stability of the 21 SF strain and
indicate a clonal homogeneity of its populations. This is
compatible with the hypothesis that the T. cruzi
strains represent an equilibrium of either homogenous or
heterogeneous populations.
