Glycans on secretory component participate in innate protection against mucosal pathogens.
In mucosal secretions, secretory component (SC) is found either free or bound to polymeric IgA within the secretory IgA complex. SC displays numerous and various glycans, which are potential ligands for bacterial compounds. We first established that human SC (hSC) purified from colostrum (hSCcol) or produced in Chinese hamster ovary cells (hSCrec) exhibits the same lectin reactivity. Both forms bind to Clostridium difficile toxin A and functionally protect polarized Caco-2 cell monolayers from the cytopathic effect of the toxin. The interaction is mediated by glycans present on hSC and involves galactose and sialic acid residues. hSCcol and hSCrec were also shown to bind enteropathogenic Escherichia coli adhesin intimin and to inhibit its infectivity on HEp-2 cells in a glycan-dependent manner as well. SC remained operative in the context of the whole secretory IgA molecule and can therefore enhance its Fab-mediated neutralizing properties. On the contrary, hSC did not interact with three different strains of rotavirus (RF, RRV, and SA11). Accordingly, infection of target MA104 cells with these rotavirus strains was not reduced in the presence of either form of hSC tested. Although not a universal mechanism, these findings identify hSC as a microbial scavenger contributing to the antipathogenic arsenal that protects the body epithelial surfaces.
R & D Laboratory of the Division of Immunology and Allergy, Centre Hospitalier Universitaire Vaudois, 1011 Lausanne, Switzerland.
Clémentine
C
Perrier
Norbert
N
Sprenger
Blaise
B
Corthésy
D000818:Animals; D001422:Bacterial Adhesion; D001427:Bacterial Toxins / Q000737:chemistry*; D016466:CHO Cells; D018938:Caco-2 Cells; D045744:Cell Line, Tumor; D006224:Cricetinae; D004768:Enterotoxins / Q000737:chemistry*; D004926:Escherichia coli / Q000378:metabolism; D006801:Humans; D009092:Mucous Membrane / Q000378:metabolism*; D011134:Polysaccharides / Q000737:chemistry*; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000737:chemistry; D012401:Rotavirus / Q000235:genetics / Q000378:metabolism
D001427:Bacterial Toxins; D004768:Enterotoxins; D011134:Polysaccharides; D011993:Recombinant Fusion Proteins; C041348:tcdA protein, Clostridium difficile