Comparative study of different methods used to isolate Trypanosoma cruzi from defibrinated blood of irradiated mice

Different methods are being used for the isolation and purification of Trypanosoma cruzi blood forms from infected vertebrate hosts. In this study we compare four of these methods (differential centrifugation, Ficoll-Hypaque, Histopaque 1077 and metrizamide) in terms of parasite recovery rates, contamination with cells, duration of the process and role of host irradiation. Male albino Swiss mice irradiated in a Gamma Cell 220 (500 rads) were inoculated with CL and VL-10 T. cruzi strains and bled at the peak of parasitemia. Infected defibrinated blood was then used for the isolation. Although all methods permitted the recovery of viable trypomastigotes, the best results were obtained with Ficoll-Hypaque and Histopaque 1077. Recovery rates ranged between 71% to 88% and parasite-enriched preparations were obtained in approximately 75 min. Irradiation and blood defibrination drastically reduced platelet and leukocyte contamination of the preparations.