Wound healing genes and susceptibility to cutaneous leishmaniasis in Brazil

Abstract

Leishmania braziliensis causes cutaneous (CL) and mucosal (ML) leishmaniasis. In the mouse, Fli1 was identified as a gene influencing enhanced wound healing and resistance to CL caused by Leishmania major. Polymorphism at FLI1 is associated with CL caused by L. braziliensis in humans, with an inverse association observed for ML disease. Here we extend the analysis to look at other wound healing genes, including CTGF, TGFB1, TGFBR1/2, SMADS 2/3/4/7 and FLII, all functionally linked along with FLI1 in the TGF beta pathway. Haplotype tagging single nucleotide polymorphisms (tag-SNPs) were genotyped using Taqman technology in 325 nuclear families (652 CL cases; 126 ML cases) from Brazil. Robust case-pseudocontrol (CPC) conditional logistic regression analysis showed associations between CL and SNPs at CTGF (SNP rs6918698; CC genotype; OR 1.67; 95%CI 1.10-2.54; P=0.016), TGFBR2 (rs1962859; OR 1.50; 95%CI 1.12-1.99; P=0.005), SMAD2 (rs1792658; OR 1.57; 95%CI 1.04-2.38; P=0.03), SMAD7 (rs4464148; AA genotype; OR 2.80; 95%CI 1.00-7.87; P=0.05) and FLII (rs2071242; OR 1.60; 95%CI 1.14-2.24; P=0.005), and between ML and SNPs at SMAD3 (rs1465841; OR 2.15; 95%CI 1.13-4.07; P=0.018) and SMAD7 (rs2337107; TT genotype; OR 3.70; 95%CI 1.27-10.7; P=0.016). Stepwise logistic regression analysis showed that all SNPs associated with CL at FLI1, CTGF, TGFBR2, and FLII showed independent effects from each other, but SNPs at SMAD2 and SMAD7 did not add independent effects to SNPs from other genes. These results suggest that TGFβ signalling via SMAD2 is important in directing events that contribute to CL, whereas signalling via SMAD3 is important in ML. Both are modulated by the inhibitory SMAD7 that acts upstream of SMAD2 and SMAD3 in this signalling pathway. Along with the published FLI1 association, these data further contribute to the hypothesis that wound healing processes are important determinants of pathology associated with cutaneous forms of leishmaniasis.

Figure 1

Mean size of largest cutaneous lesion in ML compared to CL cases for (A) the primary collection period, and (B) the secondary collection period. Graphs (C) and (D) compare ML cases and CL cases across primary and secondary collection periods, respectively. Bars indicate results of between group T tests.

Figure 2

Diagram of genes that have been implicated in susceptibility to CL and ML disease caused by L. braziliensis in the area of Corte de Pedra, Bahia, Brazil, showing involvement of, and interaction with, the TGFβ pathway. Polymorphisms in genes annotated in red lettering have been associated with CL or ML disease.