Polymorphisms in Genes Involved in Innate Immunity Predispose Toward Mycetoma Susceptibility

Madurella mycetomatis is the main causative agent of mycetoma, a tumorous fungal infection characterized by the infiltration of large numbers of neutrophils at the site of infection. In endemic areas the majority of inhabitants have Abs to M. mycetomatis, although only a small proportion of individuals actually develop mycetomal disease. It therefore appears that neutrophils are unable to clear the infection in some individuals. To test this hypothesis, 11 single nucleotide polymorphisms involved in neutrophil function were studied in a population of Sudanese mycetoma patients vs geographically and ethnically matched controls. Significant differences in allele distribution for IL-8 (CXCL8), its receptor CXCR2, thrombospondin-4 (TSP-4), NO synthase 2 (NOS2), and complement receptor 1 (CR1) were found. Further, the NOS2(Lambaréné) polymorphism was clearly associated with lesion size. The genotypes obtained for CXCL8, its receptor CXCR2, and TSP-4 all predisposed to a higher CXCL8 expression in patients, which was supported by the detection of significantly elevated levels of CXCL8 in patient serum. The NOS2 genotype observed in healthy controls was correlated with an increase in NOS2 expression and higher concentrations of nitrate and nitrite in control serum. We present the first evidence of human genetic predisposition toward susceptibility to mycetoma, a neglected infection of the poor.