Figure 4. Viral neuraminidase inhibition.

a | The neuraminidase cleaves off sialic acid (SA, also known as N-acetylneuraminic acid or NANA) from the cell receptor for influenza virus (b), so that the newly formed virus particles can be released from the cells. Neuraminidase inhibitors, such as zanamivir and oseltamivir (Fig. 5), interfere with the release of progeny influenza virions from the surface of infected host cells. In doing so, the neuraminidase inhibitors prevent virus infection of new host cells and thereby halt the spread of infection in the respiratory tract. b | SA linked to galactose (Gal) by an α2–3 linkage (SAα2–3Gal) or α2–6 linkage (SAα2–6Gal). Galactose is linked to N-acetylglucosamine (GlcNAc) through a β1–4 linkage. Panel a adapted with permission from Ref. 25 © (2005) Massachusetts Medical Society.