The Role of Zinc in Leishmaniasis and Tuberculosis

Abstract: The synergistic relation between nutritional deficiency and infection may have negative effects on the immune system, making individuals more vulnerable to infection. Zinc can affect the resistance to infections by modulating cytokine release, and by acting as a cofactor of thymulin, which induces the differentiation of immature T lymphocytes. To investigate the modulation of the immune response by zinc during infections, placebo-controlled intervention studies were conducted on individuals with leishmaniasis and tuberculosis through the oral administration of 45 mg zinc per day together with pharmacological therapy. The changes in biochemical markers in plasma were evaluated, and the immune response was assessed in plasma and blood lymphocytes. Changes in most of the biochemical and inflam¬matory markers were observed with time, independently of zinc supplementation. In tuberculosis, an increase of 22% was observed in the zinc plasma concentration in the zinc-supplemented group versus 6% in the placebo group. No differences were observed in the clinical signs in leishmaniasis at the time of healing. The function of the immune system did not appear to be affected by zinc supplementation in either of the diseases. Supplementation with 45 mg zinc during treatment for these two diseases failed to have additional effects on the clinical recovery or the immune response. The intralesional injection of antimony in leishmaniasis was also investigated in a separated study. This resulted in healing of lesions with a cure rate of 70%, indicating that this strategy could be useful.