Carbohydrate-Dependent Binding of Langerin to SodC, a Cell Wall Glycoprotein of Mycobacterium leprae

Abstract

M ycobacterium leprae infections lead to human leprosy, characterized by disfiguring skin lesions, nerve damage, and eventually permanent disability (1). As part of the disease process, M. leprae is phagocytized by numerous cell types, including dendritic cells (DCs) and epidermal DCs known as Langerhans cells (LCs) (2-4). The cell envelopes of pathogenic Mycobacterium spp., including M. leprae, are rich in mannosylated macromolecules such as mannose-capped lipoarabinomannan (ManLAM), lipomannan (LM), phosphatidylinositol mannosides (PIM) and presumably glycoproteins (5, 6). These glycoconjugates contribute to the interaction of pathogenic mycobacteria with host phagocytes, and the C-type lectin receptors (CLRs) that decorate the surface of phagocytes have been shown to directly bind specific mannosylated glycoconjugates of Mycobacterium spp (7). For DCs, the constitutive CLRs are the mannose receptor (CD206) and the dendritic cell-specific intracellular adhesion moleculegrabbing nonintegrin (DC-SIGN; CD209). However, langerin (CD207) is a CLR specific to LCs. DC-SIGN and langerin recognize the sugar residues of macromolecules produced by pathogens and altered self-antigens in a calcium-dependent manner. These CLRs are comprised of a short cytoplasmic domain, a transmembrane domain, and, on the outer surface of the cell, an extracellular domain (ECD) that encompasses the highly conserved carbohydrate recognition domains (CRDs) and the hydrophobic neck domain. The CRDs determine sugar-binding specificity, and DC-SIGN and langerin possess an EPN (Glu-Pro-Asn) motif that is generally specific to oligosaccharides containing mannose (Man), fucose, glucose, or N-acetylglucosamine residues (8). The ␣-helix coiled-coil formation in the neck domains is responsible for the trimeric and tetrameric structures of langerin and DC-SIGN, respectively, and these multimeric conformations promote carbohydrate spatial specificity (9, 10). Some of mycobacterial ligands of DC-SIGN have been defined. Specifically, DC-SIGN recognizes the ␣(1¡2) linkages of ManLAM and PIM 6 (11,12). The 45-kDa and 19-kDa glycoproteins of Mycobacterium tuberculosis are also DC-SIGN ligands based on their inhibition of bacterial cell uptake via DC-SIGNtransfected cell lines (13). However, it should be noted that studies to directly compare the binding affinity of protein and lipoglycan ligands for C-type lectins or to define the relative contribution of each ligand have not been performed.We previously demonstrated that langerin-positive LCs present cell wall antigens of M. leprae to CD1a-restricted T cells, resulting in T cell proliferation and gamma interferon (IFN-␥) production (2). This study demonstrated the biological significance for the interaction of M. leprae ligands with the langerin of LCs; however, the M. leprae binding partners of this CLR were not elucidated. Thus, in the present work we sought to characterize the biochemical and biophysical features of the M. leprae glycoconjugates recognized by langerin.

Langerhans cells mediate the skin‐induced tolerance to ovalbumin via Langerin in a murine model

“…As LCs express very few Toll‐like receptors, the interaction of LCs with foreign molecules may be mainly through other receptors, for example, C‐type lectin receptors. It has been shown that Langerin binds HIV as an endocytic receptor and Langerin can also bind other microbes, such as Mycobacterium leprae and measles virus . Here, we showed that Langerin could bind a foreign protein, OVA.…”

Biotechnological and Immunological Platforms Based on PGL-I Carbohydrate-Like Peptide of Mycobacterium leprae for Antibodies Detection Among Leprosy Clinical Forms

“…Interestingly, the binding affinity of PGLI-M3 to serum antibodies measured by SPR was almost 30-fold lower than that measured by a solution binding assay (ELISA), in which the SPR technology was able to detect antibodies with just as few as 0.03 µg of the peptide, while ELISA required 1 µg per reaction. It is important to note that the versatility of the SPR platform has allowed not only the evaluation of peptide ligands to mycobacteria (Ngubane et al, 2013), but also has been used as immunosensors for hepatitis (Villiers et al, 2015) or for detection of salivary proteins (Musso et al, 2015), and also for characterization of binding affinity of human proteins to M. leprae glycoproteins (Kim et al, 2015). Another advantage of this platform is the possibility to transform angular variations in absolute values, which present greater application in clinical practice.…”

“…So, it is possible to obtain small peptides that mimic specific antigen epitopes (Goulart et al, 2010), or develop biomarkers using Fab (fragment antigen-binding) or scFv (single-chain variable fragment) antibody fragments (Leow et al, 2014). One of the great advantages of peptides and antibodies obtained by PD is their flexibility to be used in different diagnostic platforms, from conventional enzyme-linked immunosorbent assay (ELISA) (Rojas et al, 2014) to biotechnological platforms, such as those involving immunosensors based on surface plasmon resonance (SPR) (Kim et al, 2015). SPR immunosensors explore the capacity of an antibody to recognize its antigen with different affinities and can be built using an optical signal transduction by a light bean that passes through a prism and reaches a metallic surface (Kretschmann, 1971).…”

Design and statistical modeling of mannose-decorated dapsone-containing nanoparticles as a strategy of targeting intestinal M-cells

“…In this context, M. leprae is the causative agent of leprosy, a chronic infectious disease. 8,22 M. leprae is phagocytized by numerous cell types; monocytederived macrophages are one of the most abundant host cells to come in contact with the mycobacteria. 23 The backbone of current treatment of leprosy is a multidrug therapy consisting of dapsone (DAP), clofazimine, and rifampicin as first-line drugs.…”