Low serum zinc concentrations in Sudanese patients with visceral leishmaniosis does not impair the anti-Leishmania antibody response.

Abstract

Visceral leishmaniosis (VL) is a poverty-related disease, affecting poor peoples in the developing countries. For unknown reasons, the rK39 rapid test has poor diagnostic sensitivity in some endemic areas such as East Africa. Here, the hypothesis was tested whether micronutrient deficiency is associated with low Leishmania-specific antibody responses and consequently decreased diagnostic sensitivity. Serum zinc concentrations in 107 human sera of VL and controls that were HIV-negative were measured using atomic absorption spectroscopy. Anti-Leishmania donovani antibodies were detected quantitatively by rKLO8 ELISA. The influence of low serum zinc concentrations on the amount of anti-Leishmania antibody and outcome of the rK39 rapid test was tested. Serum zinc concentrations were significantly (p ˂ 0.0001) reduced in VL sera (mean 0.41 ± 0.15) as compared to healthy control groups (mean ˃ 0.75 ± 0.13). Interestingly, the majority (92.2%) of the VL patients had low serum zinc concentrations (˂ 0.6 mg/l) whereas all healthy controls showed normal levels. Unexpectedly, VL sera with normal (0.94-0.6 mg/l) or low (˂ 0.6 mg/l) zinc concentrations demonstrated no significant difference in amounts of Leishmania antibodies. In addition, VL sera with positive or negative rK39 rapid test results demonstrated similar serum zinc concentrations; mean values of 0.39 ± 0.14 mg/l and 0.38 ± 0.1 mg/l for VL sera of positive or negative rK39 results, respectively. Low serum zinc concentration seems not to play an important role in lowering anti-L. donovani antibody titers observed among Sudanese VL patients and doesn't affect rK39 rapid test results.