The dendritic cell specific C-type lectin dendritic cell specific ICAM-3 grabbing non-integrin (DC-SIGN) binds to ''self'' glycan ligands found on human cells and to ''foreign'' glycans of bacterial or parasitic pathogens. Here, we investigated the binding properties of DC-SIGN to a large array of potential ligands in a glycan array format. Our data indicate that DC-SIGN binds with K d < 2 lM to a neoglycoconjugate in which Galb1-4(Fuca1-3)GlcNAc (Le x ) trisaccharides are expressed multivalently. A lower selective binding was observed to oligomannose-type N-glycans, diantennary N-glycans expressing Le x and GalNAcb1-4(Fuca1-3)GlcNAc (LacdiNAc-fucose), whereas no binding was observed to N-glycans expressing corefucose linked either a1-6 or a1-3 to the Asn-linked GlcNAc of N-glycans. These results demonstrate that DC-SIGN is selective in its recognition of specific types of fucosylated glycans and subsets of oligomannose-and complex-type N-glycans.

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Schistosoma mansoni soluble egg antigens (SEAs) are crucially involved in modulating the host immune response to infection by S. mansoni. We report that human dendritic cells bind SEAs through the C-type lectin dendritic cell-specific ICAM-3-grabbing nonintegrin (DC-SIGN). Monoclonal antibodies against the carbohydrate antigens Lewisx (Lex) and GalNAcbeta1-4(Fucalpha1-3)GlcNAc (LDNF) inhibit binding of DC-SIGN to SEAs, suggesting that these glycan antigens may be critically involved in binding. In a solid-phase adhesion assay, DC-SIGN-Fc binds polyvalent neoglycoconjugates that contain the Lex antigen, whereas no binding was observed to Galbeta1-4GlcNAc, and binding to neoglycoconjugates containing only alpha-fucose or oligosaccharides with a terminal alpha1-2-linked fucose is low. These data indicate that binding of DC-SIGN to Lex antigen is fucose-dependent and that adjacent monosaccharides and/or the anomeric linkage of the fucose are important for binding activity. Previous studies have shown that DC-SIGN binds HIV gp120 that contains high-mannose-type N-glycans. Site-directed mutagenesis within the carbohydrate recognition domain (CRD) of DC-SIGN demonstrates that amino acids E324 and E347 are involved in binding to HIV gp120, Lex, and SEAs. By contrast, mutation of amino acid Val351 abrogates binding to SEAs and Lex but not HIV gp120. These data suggest that DC-SIGN recognizes these ligands through different (but overlapping) regions within its CRD. Our data imply that DC-SIGN not only is a pathogen receptor for HIV gp120 but may also function in pathogen recognition by interaction with the carbohydrate antigens Lex and possibly LDNF, which are found on important human pathogens, such as schistosomes and the bacterium Helicobacter pylori.

The dendritic cell-specific C-type lectin DC-SIGN functions as a pathogen receptor that recognizes Schistosoma mansoni egg antigens through its major glycan epitope Gal␤1,4(Fuc␣1,3)GlcNAc (Le x ). Here we report that L-SIGN, a highly related homologue of DC-SIGN found on liver sinusoidal endothelial cells, binds to S. antigens. These data demonstrate for the first time that DC-SIGN and L-SIGN differ in their carbohydrate binding profiles and will contribute to our understanding of the functional roles of these C-type lectin receptors, both in recognition of pathogen and self-glycan antigens.

Helicobacter pylori is able to colonize gastric epithelia, causing chronic active gastritis, gastric and duodenal ulcers and presumably gastric malignancies. Attempts to identify the natural reservoir for this microorganism other than the stomach have been unsuccessful. It is suspected that H. pylori can be transmitted orally, since the microorganism has been detected at various sites of the oral cavity. The aim of the present study was to determine whether H. pylori can bind to salivary mucins, which in vivo coat the oral epithelia, and characterize further the interaction. Binding of salivary mucins and of synthetic oligosaccharides was studied in ELISA and immunoblotting, using specific mono- and polyclonal antibodies, and synthetic neoglycoconjugates. H. pylori bound most avidly to a highly sulfated subpopulation of high molecular weight salivary mucins, secreted from the palatine salivary glands, and with less avidity to mucin species secreted by the sublingual and submandibular salivary glands, which are less sulfated. Binding was strongly enhanced upon decreasing pH from 6.0 to 5.0. Using synthetic polyacrylamide coupled oligosaccharides it was found that SO3-3-Gal and the SO3-3-Lewis(a) blood group antigen bound to H. pylori. In contrast, binding of sialylated Lewis(a) and Lewis(b) antigens was much weaker. This study indicates that sulfated oligosaccharides on salivary mucins may provide receptor structures for adhesion of H. pylori to oral surfaces.