Large-scale candidate gene study of tuberculosis susceptibility in the Karonga district of northern Malawi.

Twenty-seven polymorphisms from 12 genes have been investigated for association with tuberculosis (TB) in up to 514 cases and 913 controls from Karonga district, northern Malawi. Homozygosity for the complement receptor 1 (CR1) Q1022H polymorphism was associated with susceptibility to TB in this population (odds ratio [OR] = 3.12, 95% Confidence interval [CI] = 1.13-8.60, P = 0.028). This association was not observed among human immunodeficiency virus (HIV)-positive TB cases, suggesting either chance association or that HIV status may influence genetic associations with TB susceptibility. Heterozygosity for a newly studied CAAA insertion/deletion polymorphism in the 3'-untranslated region of solute carrier family 11, member 1 (SLC11A1, formerly NRAMP1) was associated with protection against TB in both HIV-positive (OR = 0.70, 95% CI = 0.49-0.99, P = 0.046) and HIV-negative (OR = 0.65, 95% CI = 0.46-0.92, P = 0.014) TB cases, suggesting that the SLC11A1 protein may have a role in innate TB immune responses that influence susceptibility even in immunocompromised individuals. However, associations of other variants of SCLA11A with TB reported from other populations were not replicated in Malawi. Furthermore, associations with vitamin D receptor, interferon-gamma, and mannose-binding lectin observed elsewhere were not observed in this Karonga study. Genetic susceptibility to TB in Africans appears polygenic. The relevant genes and variants may vary significantly between populations, and may be affected by HIV infection status.

Large-scale candidate gene study of leprosy susceptibility in the Karonga district of northern Malawi.

We present a large case-control candidate gene study of leprosy susceptibility. Thirty-eight polymorphic sites from 13 genes were investigated for their role in susceptibility to leprosy by comparing 270 cases with 452 controls in Karonga district, northern Malawi. Homozygotes for a silent T-->C change in codon 352 of the vitamin D receptor gene appeared to be at high risk (odds ratio [OR] = 4.3, 95% confidence interval [CI] = 1.6-11.4, P = 0.004), while homozygotes for the McCoy b blood group defining variant K1590E in exon 29 of the complement receptor 1 (formerly CD35) gene appeared to be protected (OR = 0.3, 95% CI = 0.1-0.8, P = 0.02). Borderline evidence for association with leprosy susceptibility was found for seven polymorphic sites in an additional six genes. Some of these apparent associations may be false-positive results from multiple comparisons, and several associations suggested by studies in other populations were not replicated here. These data provide evidence of inter-population heterogeneity in leprosy susceptibility.