Neuraminidase

Neuraminidase is a polymeric, viral enzyme that modifies the cellular receptor for virus binding/uptake by removing sialic acid residues from glycoproteins and glycolipids. This activity facilitates the release of newly-formed virus from infected cells and prevents the autoagglutination of free virus (which can occur when the viral hemagglutinin binds to receptor molecules in the host cell-derived viral envelope). Neuraminidase may also facilitate infection by preventing viral binding to receptor-like molecules in tracheal mucin, since binding to non-cellular receptors might impede access of the virus to host cells.

Antibodies to neuraminidase are produced after natural influenza infection or immunization. During subsequent infection, these antibodies function primarily to decrease the severity and duration of illness due to influenza. Very high titers of these antibody may also prevent infection. The two subtypes of neuraminidase, N1 and N2 are poorly cross-protective.