Publication Date


Degree Program

Department of Biology

Degree Type

Master of Science


Dietary supplementation with the antioxidants vitamin E and selenium (Se) has been shown to be beneficial against the intracellular parasite Trypanosoma cruzi during experimental Chagas' disease. Supplementation of mice with vitamin E and selenium at levels well above the recommended daily allowance for these two substances results in significantly decreased parasitemia levels and increased longevity. However, the mechanistic role of the antioxidants in this process is not well understood. It is known that vitamin E and selenium can reduce oxidative stress and improve host immune responses. In addition, the synthesis of many regulatory cytokines is known to be influenced by changes in the cellular oxidant/antioxidant balance. The present study was performed to determine the impact of the antioxidants vitamin E and selenium on the T helper (Th) 1/Th2 cytokine balance during experimental Chagas' disease. In the first phase of the study, two groups of female C3HeB/FeJ mice (24 mice each) were supplemented with vitamin E and selenium for 4-5 weeks and 8-9 weeks, respectively. In the second phase, 12 mice from each group were infected with a Brazil strain of Trypanosoma cruzi. In the final phase, levels of interferon gamma (IFN-y and interleukin 10 (IL-10) in serum were measured by antigen-capture enzyme linked immunosorbent assay (ELISA). Transcriptional levels of IFN-y and IL-10 message RNA (mRNA) in the heart and spleen were measured by a ribonuclease protection assay. The results of the study confirmed the previously observed beneficial effect of antioxidant supplementation during murine infection with T. cruzi. In addition, supplementation of mice with vitamin E and selenium was shown to affect IFN-y and IL-10 synthesis at both the serum level and transcriptional level. Furthermore, IFN-y and IL-10 levels differed in the heart and spleen of infected mice. The Thl/Th2 cytokine balance was shown to be predominantly Thl in mice receiving antioxidant supplementation. Vitamin E and selenium apparently exert a protective effect by enhancing IFN-y levels in mice infected with T. cruzi while decreasing the levels of IL-10 in non-infected, antioxidant-supplemented mice.


Medical Sciences