Variable sensitivity to complement-mediated lysis among Trypanosoma rangeli reference strains.

Six reference strains of Trypanosoma rangeli from different days of growth in axenic cultures were assayed for susceptibility to complement-mediated lysis by non-immune guinea-pig serum. Their authenticity was also confirmed by isoenzyme analyses. Parasites were incubated with 25% active or 68°C-inactivated serum (37°C, 30 min) for all tests; thereafter the lysis rates were determined. Highly variable lysis percentages were observed among T. rangeli strains and in the same stock at different growing days. In a few assays, three strains (Macias, R-1625 and Choachi) presented total or very high resistance. The others (H-14, San Agustín and SC-58) were generally most susceptible, and could reach lysis rates as high as Trypanosoma cruzi. After incubation with active sera, the epimastigotes were usually the predominant stages, being followed by spheromastigotes and/or transitional forms. Those stages and trypomastigotes could also be partially susceptible. In four strains, the short epimastigotes were more resistant to lysis than the long ones. Experiments with C3-deficient serum displayed total or partial participation of the alternative-complement pathway in T. rangeli lysis. This study confirmed the variable complement sensitivity of T. rangeli, which can be related to its intraspecific heterogeneity, to the remarkable complexity of its life-cycle stages, and to the methodology employed.

Trypanosoma rangeli Tejera, 1920, in chronic Chagas' disease patients under ambulatory care at the Evandro Chagas Clinical Research Institute (IPEC-Fiocruz, Brazil).

We report the finding, the isolation by hemoculture, and the characterization of Trypanosoma rangeli stocks from two chronic Chagas' disease patients who received ambulatory care at the Evandro Chagas Clinical Research Institute (IPEC, FIOCRUZ). Both patients proceeded from Bahia State (Brazil). One of them presented the cardiac form of the disease and the other indeterminate symptomalogy. Giemsa-stained smears of the hemocultures from these patients evidenced that they were coinfected with T. rangeli and Trypanosoma cruzi, with predominance of the former species. These isolates could only be successfully grown in Novy-MacNeal-Nicolle + liver infusion-tryptose supplemented with 20-30% fetal calf serum. After 6 months of serial maintenance, rich and apparently pure cultures of T. rangeli were obtained. Both stocks were analyzed with different approaches and compared with two T. cruzi isolates also from chagasic patients under care at IPEC, besides T. rangeli and T. cruzi reference strains. All stocks were characterized by morphology, biometry, electrophoresis of isoenzymes, and products of kDNA minicircle amplified by polymerase chain reaction. The identification of T. rangeli was largely confirmed by all techniques. Taken together, these data represent the third report on T. rangeli in human hosts in Brazil.