Toxoplasma gondii: a rapid method for the isolation of pure tachyzoites. Preliminary characterization of its genome.

A rapid and simple technique for the purification of Toxoplasma gondii tachyzoites was developed. Highly purified parasites were obtained from the peritoneal exudates of infected mice by means of two consecutive discontinuous sucrose gradients run at low speed (10,000xg, 30 min). Parasites obtained by this method conserved its biological activity. Hybridization studies with DNA from healthy mice and from purified tachyzoites preparations demonstrated that Toxoplasma gondii tachyzoites DNA could be obtained with better than 90% purity. Preliminary studies with DNA endonucleases showed the presence in the tachyzoites genome of highly repetitive sequences.