Table 1.
Demographic data of leprosy patients and controls.
Fig 1.
CR1 gene and protein structure and localization of the investigated SNPs.
Each block in hexagon shape represents a SCR (short consensus repeat, numbered 1 to 30), encoded by the exons 2–35, shown just above. The other exons encode: the aminoterminal region (NH2, exon 1), transmembrane domain (TM, exons 36–37) and the intracytoplasmic carboxi-terminal domain (IC COOH, exons 38–39), which are all shown in blue. There are three binding sites for C4b opsonins (SCR 1–3, 8–10 and 15–1, in gray and lilac color), of which two are also C3b binding sites (SCR 8–10 and 15–17, both in lilac color). SCRs 22–28 bind C1q, MBL and ficolins (molecules that recognize either antibodies, sugar moieties or acetylated residues on the surface of the pathogen, respectively). SCRs 22, 24 and 25 (blue dashed blocks) carry York and McCoy blood group antigens frequent in Africans, but rare in Euro-descendants (downward pointing arrows indicate the responsible amino acid substitutions). The SNPs analysed in this study are indicated in the gene and the amino acid substitutions resulting from polymorphisms located in exons are indicated in the protein. The four long homologous repeats (LHR) of this protein are depicted: 1–7, 8–14, 15–21, 22–28. The functional sites of 8–10 and 15–17 are nearly identical. TM, transmembrane domain; IC, intracytoplasmic domain.
Table 2.
Sequence-specific primers* for selected CR1 polymorphisms.
Fig 2.
Maximum parsimony tree of CR1 haplotypes with nucleotide changes and phylogenetic nomenclature.
Table 3.
Frequencies of CR1 haplotypes.
Fig 3.
Association between CR1 mRNA and sCR1 levels and CR1 polymorphisms.
A Patients with the rs12034383*G allele presented higher mRNA expression, than A/A homozygotes. G+: G carriers. Excluded outliers: one (excluded for better visualization, inclusion did not change significance of the results). B: Paucibacillary patients have lower sCR1 concentration, if presenting the T allele of rs3849266 or Thr at rs3737002. T+: T carriers, Thr: threonine, Met: Methionine. Median, maximum and minimum values are in the Electronic Supplementary Material (S1 and S2 Tables). Scatter plots were constructed from the raw non-normalized, fold-change data. Comparisons were done with Mann-Whitney and Kruskal-Wallis tests, using GraphPad Software Prism v.6.
Fig 4.
Negative correlation between MBL and sCR1 levels.
MBL: mannose-binding lectin; sCR1: soluble complement receptor 1. Scatter plot was constructed from the raw non-normalized, fold-change data, using GraphPad Software Prism v.6.
Fig 5.
CR1 possible roles on leprosy susceptibility.
(1) Pathogen or damage-associated molecular sugar patterns (PAMPs/DAMPs) on Mycobacterium leprae are recognized by mannose-binding lectin (MBL) or ficolins (FCNs) and activate the lectin pathway of complement. Autoactivation of the serine protease MASP-1 is followed by transactivation of MASP-2, cleavage of C2 and C4 and formation of the C3 convertase C2aC4b. C3 convertase ultimately leads to the insertion of C3b opsonins on the surface of the pathogen. (2) Macrophages presenting rs3737002*T (p.1408Met) may produce CR1 molecules whose enzymatic cleavage site is hidden, producing less soluble CR1 molecules. Those with rs12034383*G present lower affinity for BAF155-containing SWI/SNF nucleosome remodelling complex, increasing CR1 gene expression. (3) Increased CR1 abundance is expected to enhance the uptake of C3b/C4b/ficolin/MBL-opsonized M. leprae, through the respective SCR (short consensus repeat) domains (shown in green and yellow).