Biological characterization of dhfr-ts-/+ mutant Trypanosoma cruzi parasites

PÉREZ BRANDÁN CM, XU D, PADILLA AM, TARLETON RL, BASOMBRÍO MA

Rosario, Santa Fe, Argentina

Congreso; VIII Congreso Argentino de Protozoologia y Enfermedades Parasitarias; 2008

We obtained mutant parasites of the attenuated TCC and virulent Tulahuen strains of Trypanosoma cruzi in which one allele of the dihydrofolate reductase thymidylate synthase gene (dhfr-ts) was disrupted. Several biological characteristics of the mutants were compared with those of their respective wild type ancestors in vitro and in vivo. TCC dhfr-ts-/+ epimastigotes showed a decrease in growth rate in culture when compared to wild type TCC parasites; however these differences were not observed in mutant parasites of the Tulahuen strain. In IFN-g -/- mice infected with Tulahuen mutant parasites the number of parasites circulating in peripheral blood was significantly lower as compared with Tulahuen wild type infected mice. This comparison could not be established in the TCC mutant, due to extremely low parasite loads. Infection of normal C57/B6 and IFN-g -/- mice with TCC dhfr-ts-/+ metacyclic trypomastigotes showed a reduced level of T. cruzi specific CD8+ T-cells when compared with mice infected with TCC wild type parasites. Such difference was not observed between Tulahuen wild type and Tulahuen dhfr-ts-/+ metacyclic trypomastigotes. Previous studies of our group have shown that vaccination of mice with TCC wild type parasites confers protection against a challenge with virulent parasites; the ability of TCC dhfr-ts-/+ to confer such protection was lower, as compared with the wild type. Currently we are completing experiments to asses the persistence of the mutant parasites in the chronically infected animals. We are also working in obtaining null, biallelic mutant parasites of both strains.