Variants in the Toll-Like Receptor Signaling Pathway and Clinical Outcomes of Malaria

Background. Malaria is one of the most significant infectious diseases in the world and is responsible for a large proportion of infant deaths. Toll-like receptors (TLRs), key components of innate immunity, are central to countering infection. Variants in the TLR-signaling pathway are associated with susceptibility to infectious diseases. Methods. We genotyped single nucleotide polymorphisms (SNPs) of the genes associated with the TLR-signaling pathway in patients with mild malaria and individuals with asymptomatic Plasmodium infections by means of polymerase chain reaction. Results. Genotype distributions for the TLR -11602S differed significantly between patients with mild malaria and persons with asymptomatic infection. The TLR-1 602S allele was associated with an odds ratio (OR) of 2.2 (P = .003; P corrected = .015) for malaria among patients with mild malaria due to any Plasmodium species and 2.1 (P = .015; P corrected = .75) among patients with mild malaria due to Plasmodium falciparum only. The TLR-6 S249P SNP showed an excess of homozygotes for the TLR-6 249P allele in asymptomatic persons, compared with patients with mild malaria due to any Plasmodium species (OR 2.1; 95% confidence interval [CI], 1.1-4.2; P = .01; P corrected = .05), suggesting that the TLR-6 249S allele may be a risk factor for malaria (OR, 2.0; 95% CI, 1.1-3.7; P = 0.01; P corrected = .05). The TLR-9 -1486C allele showed a strong association with high parasitemia (P <.001). Conclusions. Our findings indicate that the TLR-1 and TLR-6 variants are significantly associated with mild malaria, whereas the TLR-9 -1486C/T variants are associated with high parasitemia. These discoveries may bring additional understanding to the pathogenesis of malaria.