Increased expression of α2-6 linked sialic acids by nasal mucins in allergic rhinitis

Mucins have a polypeptide backbone, oligosaccharide side-chains and peripheral structures that include sialic acids. Several pathogens have specific receptors for sialic acids, including human strains of influenza A virus which preferentially recognise and bind α2-6 linked rather than α2-3 linked sialic acids.¹ 1 NElson J., COuceiro S.S., PAulson J.C. & BAum L. (1993) Influenza virus strains selectively recognise sialyloligosaccharides on human respiratory epithelium; the role of the host cell in selection of haemagglutinin receptor specificity. The aim of this study was to identify possible disease-related changes in the expression of sialic acids in nasal mucins. Nasal mucosal samples were placed in organ culture. Metabolically-labelled mucins were purified by gel filtration, blotted on to nitrocellulose membranes and probed with the sialic acid-binding lectins Sambucus nigra and Maackia amurensis. Ninety-five mucosal samples were collected (49 turbinates, 31 nasal polyps, 15 samples from FESS). Lectin binding, expressed as optical density, showed significantly increased binding of S. nigra to cellular (P = 0.02; Kruskal–Wallis) and secreted (P = 0.045) mucin from allergic mucosa compared to non-allergic mucosa. No significant differences were found in the binding patterns of M. amurensis. This study has demonstrated increased expression of α2-6 linked sialic acids in the mucins synthesised and secreted by allergic compared to non-allergic nasal mucosa. This may cause a change in the way mucins and pathogens interact in allergic rhinitis, leading to altered susceptibility to upper respiratory tract infection.