IL-10 promoter SNPs and susceptibility to leprosy in ethnic groups from southwest China

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

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.

B. Durães S, C. Cardoso C, Nunes Sarno E, G. Pacheco A, C. F. Lana F, Ozório Moraes M. Association of IL10 Polymorphisms and Leprosy: A Meta-Analysis

Leprosy is a chronic infectious disease that depends on the interplay of several factors. Single nucleotide polymorphisms (SNPs) in host immune related genes have been consistently suggested as participants in susceptibility towards disease. Interleukin-10 (IL-10) is a crucial immunomodulatory cytokine in mycobacterial pathogenesis and especially the -819C>T SNP (rs1800871) has been tested in several case-control studies indicating association with leprosy risk, although a recent consensus estimate is still missing. In this study, we evaluated the association of the -819C>T SNP and leprosy in two new Brazilian family-based populations. Then, we performed meta-analysis for this polymorphism summarizing published studies including these Brazilian family-based groups. Finally, we also retrieved published studies for other distal and proximal IL10 polymorphisms: -3575 T>A (rs1800890), -2849 G>A (rs6703630), -2763 C>A (rs6693899), -1082 G>A (rs1800896) and -592 C>A (rs1800872). Results from meta-analysis supported a significant susceptibility association for the -819T allele, with pooled Odds Ratio of 1.22 (CI = 1.11–1.34) and P-value = 3x10^–5 confirming previous data. This result remained unaltered after inclusion of the Brazilian family-based groups (OR = 1.2, CI = 1.10–1.31, P-value = 2x10^–5). Also, meta-analysis confirmed association of -592 A allele and leprosy outcome (OR = 1.24, CI = 1.03–1.50, P-value = 0.02). In support of this, linkage disequilibrium analysis in 1000 genomes AFR, EUR, ASN and AMR populations pointed to r² = 1.0 between the -592C>A and -819C>T SNPs. We found no evidence of association for the other IL10 polymorphisms analyzed for leprosy outcome. Our results reinforce the role of the -819C>T as a tag SNP (rs1800871) and its association with leprosy susceptibility.