Epithelial cells, sialic acid

Nasal mucus. The nasal mucus protects the body against airborne substances. Nasal mucus consists of mucopolysaccharides complexed with sialic acid, sloughed epithelial cells, bacteria, water (95 percent), glycoproteins and lipids (0.5 to 5 percent), mineral salts (0.5 to 1 percent), and free proteins (albumin, immunoglobulins, lysozyme, interferon, lactoferin, etc., 1 percent).13 45 111 112 The surface pH of the nasal mucosa is 5.5 to 6.5.113... 

Sialic acid specific E. coli CFA/I Human epithelial cells 26 kDa gp [62]... 

Thereafter the ookinete encounters the microvillar network and binds to the mid-gut epithelium. Although there are an array of possible receptors on the mid-gut epithelial cells little is known about their significance other than that sialic acid-like moieties are involved in the binding of the ookinete to the isolated mid-gut epithelium and that these interactions are blocked by the expression of the peptide SMI (PCQRAIFQSCIN) (Ito et ah, 2002) or pre-treatment of the epithelium with snake or bee venom phospholipase 2 (Moreira et ah, 2002 Zieler et ah, 2001). 

Binding of influenza viruses to the human cell surface is mediated by the hemagglutinin (HA) proteins. The attachment initiates the uptake of the virus particle into the host cell. Influenza HAs bind to carbohydrates bearing sialic acids (A-acetylneuraminic acid). The human influenza virus HA proteins preferentially bind to a2-6-linked sialic acids (Fig. 8A) that are found in the upper respiratory tract of humans. In contrast, avian HA proteins preferentially bind to a2-3-hnked sialic acid (Fig. 8B) (61-63). Glycans of this type occur in the respiratory tract and intestine of birds. This way, species specificity of the influenza strains is generated and a barrier exists for avian strains infecting humans, as the sialic acid with an a2-3 linkage is rare on the cell surface of human epithelial cells in the readily accessible upper respiratory tract (61,64). 

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