The dendritic cell-specific C-type lectin DC-SIGN is a receptor for Schistosoma mansoni egg antigens and recognizes the glycan antigen Lewis x

Abstract

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 Lewis^x (Le^x) and GalNAcβ1-4(Fucα1-3)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 Le^x antigen, whereas no binding was observed to Galβ1-4GlcNAc, and binding to neoglycoconjugates containing only α-fucose or oligosaccharides with a terminal α1-2-linked fucose is low. These data indicate that binding of DC-SIGN to Le^x 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, Le^x, and SEAs. By contrast, mutation of amino acid Val³⁵¹ abrogates binding to SEAs and Le^x 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 Le^x and possibly LDNF, which are found on important human pathogens, such as schistosomes and the bacterium Helicobacter pylori.