Modulation induced by estradiol in the acute phase of Trypanosoma cruzi infection in mice

We investigated the effect of 17 beta -estradiol on mice resistant to infec tion by Trypanosoma cruzi. Infected Balb/C, C3H and C57BL/6 female mice had a longer survival time than males, C57BL/6 showing the highest difference (50% cumulative mortality in females versus 100% in males). This lineage wa s treated with estradiol (from 0.05 mug to 500 mug/mouse) 1 day before infe ction. Treatment with 50 mug or 500 mug estradiol/mouse increased mortality and parasitaemia. Low doses had no effect or tended to reduce both paramet ers. Given that estradiol presented no in vitro effect on trypomastigotes o r epimastigotes, the involvement of a direct hormonal effect on the parasit e is improbable. Alterations in the humoral T. cruzi-specific response were also discarded, since the kinetics and concentration of anti-T. cruzi IgG were not affected by the treatment. Females infected during an estradiol-de scending phase (meta-oestrus) survived longer than those infected during ot her phases of the oestrous cycle. We confirmed that estradiol interferes wi th T. cruzi infection.