Influenza antigens

“Influenza antigens” most commonly refers to the two major surface glycoproteins, hemagglutinin (HA) and neuraminidase (NA), of the influenza virus. Hemagglutinin mediates viral binding to host cell sialic acid receptors and triggers membrane fusion necessary for viral entry. It is the principal target for neutralizing antibodies and vaccines, with multiple subtypes (eighteen in influenza A, two in influenza B). Neuraminidase is an enzyme that cleaves terminal sialic acids from cellular and viral glycoproteins, enabling efficient release of progeny virus and preventing aggregation. Both HA and NA undergo significant antigenic variation, driving seasonal influenza epidemics and complicating vaccine design. They are the primary focus of current influenza vaccines and antiviral drugs. Other, less prominent influenza antigens include matrix proteins (M2), nucleoprotein (NP), and nonstructural proteins (NS1), but HA and NA are overwhelmingly the most frequent and significant therapeutic and immune targets.

Other names

Influenza hemagglutininHAInfluenza virus hemagglutininH antigenInfluenza neuraminidaseNAN antigen

Vaccine-induced or therapeutic antibodies block viral entry by preventing receptor binding or membrane fusion; inhibitors block the enzymatic release of new virions from infected cells, limiting infection spread.