CHARACTERIZATION OF SUBPOPULATIONS (CLONES AND SUBCLONES) OF THE 21-SF STRAIN OF TRYPANOSOMA-CRUZI AFTER LONG-LASTING MAINTENANCE IN THE LABORATORY

Several studies have shown a clonal structure of Trypanosoma cruzi and its possible correlation with the behavioral heterogeneity of the par asite 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 characteris tics has been cloned, with the objective of establishing the character s of its clones and subclones. With the technique of isolation of a si ngle parasite from the blood of infected mice, 5 clones and 14 subclon es have been obtained. After four passages into mice, inoculum of 10(5 ) was obtained for each clone and subclone and inoculated into mice we ighing 10 to 12 g. These were used for the study of the biological beh avior of the clones: evolution of parasitemia, morphology of blood for ms and host mortality. For isoenzymic characterization the clones and subclones were analyzed for ALAT, ASAT, GPI and PGM enzymes. Results h ave shown that the 5 clones and the 14 subclones disclosed a biologica l behavior similar to the parental strain, with minor variability of t he parasitemic profiles and also the same isoenzymic patterns. These r esults confirm the stability of the 21 SF strain and indicate a clonal homogeneity of its populations. This is compatible with the hypothesi s that the T. cruzi strains represent an equilibrium of either homogen ous or heterogeneous populations.