PRELIMINARY REPORT ON THE PUTATIVE ASSOCIATION OF IL10 -3575 T/A GENETIC POLYMORPHISM WITH MALARIA SYMPTOMS

Abstract

Only a small percentage of individuals living in endemic areas develop severe malaria suggesting that host genetic factors may play a key role. This study has determined the frequency of single nucleotide polymorphisms (SNPs) in some pro and anti-inflammatory cytokine gene sequences: IL6 (-174; rs1800795), IL12p40 (+1188; rs3212227), IL4 (+33; rs2070874), IL10 (-3575; rs1800890) and TGFb1 (+869; rs1800470), by means of PCR-RFLP. Blood samples were collected from 104 symptomatic and 37 asymptomatic subjects. Laboratory diagnosis was assessed by the thick blood smear test and nested-PCR. No association was found between IL6 (-174), IL12p40 (+1188), IL4 (+33), IL10 (- 3575), TGFb1 (+869) SNPs and malaria symptoms. However, regarding the IL10 -3575 T/A SNP, there were significantly more AA and AT subjects, carrying the polymorphic allele A, in the symptomatic group (c2 = 4.54, p = 0.01, OR = 0.40 [95% CI - 0.17- 0.94]). When the analysis was performed by allele, the frequency of the polymorphic allele A was also significantly higher in the symptomatic group (c2 = 4.50, p = 0.01, OR = 0.45 [95% CI - 0.21-0.95]). In conclusion, this study has suggested the possibility that the IL10 - 3575 T/A SNP might be associated with the presence and maintenance of malaria symptoms in individuals living in endemic areas. Taking into account that this polymorphism is related to decreased IL10 production, a possible role of this SNP in the pathophysiology of malaria is also suggested, but replication studies with a higher number of patients and evaluation of IL10 levels are needed for confirmation.

Fig. 1. - IL10 -3575 SNP (rs1800890) after RFLP. The heterozygous genotype (TA) generates fragments of 227, 124, 107 bp. The first image on the left displays the capillary electrophoresis analysis of the IL10 -3575 (T/A) SNP after RFLP performed with the ApoI enzyme. The image shows in the X axis, a sample carrying a heterozygous genotype (TA) generating, after RFLP, three fragments of 227, 124, 107 bp (in red); the alignment markers (20 to 1000 bp, in pink) and their corresponding migration times (in minutes). The electropherogram also shows the relative fluorescent unit (RFU) of each fragment (semi-quantitation results) in the Y axis. The second image (below) shows the three DNA fragments located within the region delineated by the alignment markers, as they would appear in an agarose gel.