Publication Date

8-1-1995

Degree Program

Department of Biology

Degree Type

Master of Science

Abstract

Dietary supplementation with increased levels of vitamin E can enhance the immune system of C3HeB/FeJ mice to enable many of them to survive an otherwise lethal dose of Trypanosoma cruzi, the causative agent of Chagas' disease. To study the role of diet on the course of experimental Chagas' disease, C3HeB/FeJ mice were fed pelleted, synthetic food containing no vitamin E and selenium, 800 IU/kg vitamin E, 2 ppm selenium, or food containing 800 IU/kg vitamin E plus 2 ppm selenium. Mice on synthetic food were compared to control mice fed a commonly used Purina rodent chow # 5001. After diet supplementation for a minimum of 14 days, mice were infected with 103 bloodform trypomastigotes of T. cruzi. The mean peak parasitemia for all mice fed synthetic food was 2.56 x 10° parasites per ml of blood compared to 1.12 x 107 parasites per ml of blood for the infected control group fed Purina rodent chow # 5001. This difference in parasitemia levels represents a fourfold lower mean peak parasitemia for mice fed synthetic food as compared to the infected control mice. Parasitemias were not only lower for all the mice fed synthetic food but also the typical sharp rise in parasitemia during the acute phase was not observed. After the peak in parasitemia, on day 44, the surviving mice had a gradual decrease in parasite numbers until there were no blood-form trypomastigotes seen in the peripheral circulation. Statistical analysis showed that there was a close correlation between the replicate cages of mice fed diets deficient in vitamin E and selenium and the mice fed diets containing 2 ppm selenium. There also was a close correlation between the mice fed diets containing 800 IU/kg vitamin E plus 2 ppm selenium and the mice fed diets containing 800 IU/kg vitamin E only. By day 70, the percent survival for mice receiving diets deficient in vitamin E and selenium was 37.5% (n=8) while the percent survival for mice receiving diets containing 2 ppm selenium was 44.5% (n=9). In contrast, mice receiving diets containing 800 IU/kg vitamin E plus 2 ppm selenium had a percent survival of 77.8% (n=9) while the mice receiving diets containing 800 IU/kg vitamin E had a percent survival of 80.0% (n=10). The infected control mice that were fed Purina rodent chow # 5001 exhibited 0% survival by day 46. Parasite specific antibody levels were measured by ELISA to determine any existing pattern that could be correlated to parasitemia and mortality. In all treatment cages of mice, antibody levels increased by day 35 post-infection (acute phase) and remained elevated through day 53 post-infection (chronic phase). Mice receiving synthetic diets containing 800 IU/kg vitamin E not only maintained the lowest mean peak parasitemias but also maintained the highest percent survival. These results suggested that increased dietary intake of vitamin E can have a pronounced effect on the course of experimental Chagas' disease.

Disciplines

Medical Sciences

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