Sialic acid residue on respiratory epithelial cell

Sialic acid residues are a family of acidic sugars with a nine-carbon backbone that are typically found at the terminal positions on glycan chains attached to proteins and lipids on the surface of nearly all vertebrate cells. On respiratory epithelial cells, these residues are highly expressed—especially as part of secreted mucins—and play critical roles in maintaining mucus hydration and viscoelasticity for effective mucociliary clearance. Functionally, they provide a major source of negative charge at the airway surface. Sialic acids serve as key receptors for many respiratory pathogens. For example: • Human influenza viruses preferentially bind to α(2,6)-linked sialic acids present on human airway epithelial cells. • Avian influenza viruses bind α(2,3)-linked sialic acids found in lower abundance in human airways but more common in avian species. • Respiratory syncytial virus (RSV) also attaches via interactions with these residues. Bacterial pathogens such as Streptococcus pneumoniae express neuraminidases that cleave host cell surface sialic acids to facilitate colonization or invasion. The presence or removal/modification of these residues can modulate immune responses by altering recognition by immune factors. Because their presence is essential for pathogen binding and entry into host cells—and because drugs like neuraminidase inhibitors act by preventing their cleavage—sialic acid residues on respiratory epithelial cells represent an important functional “receptor” classically targeted during infection prevention strategies.

Other names

Sialic acidSASialylated glycanTerminal sialic acid (on mucins/glycoproteins)Cell-surface sialic acid receptor

Blockade or inhibition of neuraminidases prevents the removal/cleavage of sialic acids from host cell surfaces, thereby inhibiting viral release and spread.