α2,3-linked sialic acid–containing glycoconjugates (α2,3-Sia)

α2,3-linked sialic acid–containing glycoconjugates are cell-surface molecules where a sialic acid residue is attached to the C-3 position of a galactose unit via an alpha-glycosidic bond. These structures are critical components of the glycocalyx and are involved in essential biological processes, including cell-cell recognition, immune signaling, and maintaining the integrity of the mucosal barrier (Varki et al., 2017). They are of significant clinical interest because they serve as the primary receptors for avian influenza viruses (e.g., H5N1, H7N9) and several bacterial pathogens, such as Streptococcus pneumoniae (Shinya et al., 2006). In humans, these α2,3-linkages are predominantly expressed in the lower respiratory tract, specifically on type II pneumocytes in the alveoli, which contributes to the deep lung infections associated with avian flu (Nicholls et al., 2007). Therapeutic strategies targeting these glycoconjugates include the use of inhaled sialidases like DAS181 to strip the receptors from the airway epithelium, effectively blocking viral entry. Furthermore, the interaction between these glycoconjugates and viral neuraminidase is the target of standard antiviral therapies that prevent viral egress and spread (Belser et al., 2007). Beyond infectious disease, these glycoconjugates, particularly in the form of sialyl-Lewis X, play roles in leukocyte trafficking and cancer metastasis.

Other names

Neu5Acα2-3GalAlpha-2,3-sialylglycansAvian influenza virus receptorsα2,3-sialyllactose-containing glycoconjugatesα2,3-Sia

The mechanism of action involves the enzymatic removal of terminal α2,3-linked sialic acids from host cell surfaces by recombinant sialidases (e.g., DAS181), which prevents the attachment of viruses that use these glycans as receptors (Belser et al., 2007). Alternatively, neuraminidase inhibitors (e.g., oseltamivir) block the viral enzyme from cleaving these same linkages, which is a necessary step for the release of new viral particles from the host cell surface (Nicholls et al., 2007).