Terminal sialic acid residues (SIA) (SIA)

Terminal sialic acid residues are nine-carbon acidic monosaccharides located at the distal ends of glycan chains on the surface of respiratory epithelial cells (Varki, 2008). These residues play a pivotal role in the respiratory system by mediating cell-cell interactions and contributing to the physicochemical properties of airway mucus (Varki, 2008). Crucially, they serve as the primary receptors for the attachment of various respiratory viruses, including influenza A and B, as well as human parainfluenza viruses (Shinya et al., 2006). The specific linkage of the sialic acid to the underlying galactose—typically alpha-2,3 or alpha-2,6—determines the host range and tissue tropism of these viruses (Shinya et al., 2006; Nicholls et al., 2007). In the context of pharmacology, these residues are the target of host-directed antiviral therapies like DAS181 (Fludase), a recombinant sialidase that enzymatically removes them to prevent viral entry (Malakhov et al., 2006). By stripping these receptors from the cell surface, the drug creates a temporary barrier that is effective against a broad spectrum of viral strains, including those resistant to traditional neuraminidase inhibitors (Malakhov et al., 2006). Beyond viral infection, alterations in sialic acid expression are associated with inflammatory lung diseases and certain malignancies (Varki, 2008). Therapeutic manipulation of these residues requires precision to avoid disrupting essential physiological processes such as immune signaling and mucosal clearance (Varki, 2008).

Other names

N-acetylneuraminic acidNeu5AcSialic acid receptorHost cell glycan receptorInfluenza virus receptor

Enzymatic removal of terminal sialic acid residues from the host cell surface to prevent viral attachment and entry.