INFLUENCE OF FEMALE GONADAL-HORMONES ON THE PARASITEMIA OF FEMALE CALOMYS CALLOSUS INFECTED WITH THE Y-STRAIN OF TRYPANOSOMA-CRUZI

Calomys callosus is a wild rodent found infected with Trypanosoma cruz i in nature. Groups of female C. callosus were subjected to ovariectom y or sham operation or served as intact controls. At 1 month after sur gery, animals were inoculated intraperitoneally with 4000 blood trypom astigotes of the ''Y'' strain of T. cruzi. Parasitemia during the cour se of infection was significantly higher in ovariectomized animals as compared with sham-operated rodents and controls. On steroid hormone r eplacement the parasitemia of ovariectomized animals dropped to levels close to those of controls. High or low doses of progesterone, estrog en, or a combination of both exerted similar effects. Splenocyte proli feration of ovariectomized animals was unresponsive to stimuli with co ncanavalin A and lipopolysaccharide as compared with that of control a nd sham-operated groups. The results show that gonadal hormones play a fundamental role in the defense against T. cruzi infection. The influ ence of these procedures on the immune defense in experimental Chagas' disease is being further investigated.