Cell Surface O-Glycans LimitStaphylococcus aureusAdherence to Corneal Epithelial Cells

Abstract

The mucin-rich environment of the intact corneal epithelium is thought to contribute to the prevention of Staphylococcus aureus infection. This study examined whether O-glycans, which constitute the majority of the mucin mass of epithelial cell glycocalyces, prevented bacterial adhesion and growth. Abrogation of mucin O glycosylation using the chemical primer benzyl-␣-GalNAc resulted in increased adherence of parental strain RN6390 to apical human corneal-limbal epithelial (HCLE) cells and to biotinylated cell surface protein in static and liquid phase adhesion assays, consistent with a role of mucin O-glycans in preventing bacterial adhesion. Comparable results were found with ALC135, an isogenic mutant strain defective in the accessory gene regulators agr and sar, indicating that the agr-and/or sar-regulated virulence factors did not play a major role in mediating adhesion to the corneal cell surface after mucin O-glycan truncation. In exoglycosidase digestion studies, treatment with sialidase from Arthrobacter ureafaciens-which hydrolyzed mucin-associated O-acetyl sialic acid-but not from Clostridium perfringens resulted in an increase in RN6390 and ALC135 adhesion. Abrogation of mucin O glycosylation in HCLE cell cultures did not affect bacterial growth. Overall, these data indicate that mucin O-glycans contribute to the prevention of bacterial adherence to the apical surface of corneal epithelial cells and suggest that alteration of cell surface glycosylation from disease or trauma, including that stemming from contact lens wear, could contribute to a higher risk of infection.

Tear film mucins: Front line defenders of the ocular surface; comparison with airway and gastrointestinal tract mucins

“…O -glycans are also known to prevent viruses from binding to cell surface. On the ocular surface, membrane-spanning mucins prevent binding of Staphylococcus aureus ( S. aureus ) and Streptococcus pneumonia to corneal and conjunctival epithelial cells, respectively (Argueso, 2013) as S.aureus was shown to bind to corneal epithelial cells which expressed truncated O -glycans (Ricciuto et al, 2008). This hypothesis is supported by an earlier study in which Kardon et al showed that MUC1 null mice are predisposed to developing eye inflammation compared to control mice (Kardon et al, 1999).…”

Development of a novel ex vivo model of corneal fungal adherence

“…The nonspecific interactions have been described including the pH, temperature, hydrophobicity, and charge [30][31][32]. The specific interactions have included the recognition of a receptor-ligand, such as laminin, fibronectin, collagen, or integrin [12,13,16,27,28]. As described previously, C. albicans can bind to immobilized extracellular matrix (ECM) components [15,16,29,33], which were rich in the basement membrane of the corneal epithelium, Bowman layer, and corneal stroma.…”

“…Comparisons of the inhibition of chondroitin sulfate on fungal adherence between the corneal organ culture model and the corneal epithelium monolayer model To compare the possible differences between the corneal epithelium monolayer and the corneal organ culture, we employed chondroitin sulfate to the confluent corneal epithelium monolayer for the evaluation of bacterial adherence as described previously [9,[26][27][28]. For the corneal organ culture model, the inoculation concentration of the fungal spores was 10 9 CFU/ml, and the incubation time was 60 min.…”

Host-pathogen interactions in the cornea

“…Loss of O-glycosylation resulted in increased adherence of S. aureus to differentiated HCLE cells, as well as to biotinylated cell surface proteins in static and liquid phase adhesion assays. 3 Thus, Muc16, in particular its O-glycosylation, poses a barrier to S. aureus adherence to the cornea. that S. aureus not only adheres to the surface of HCECs but is also internalized by them.…”