Influenza A and B viral antigens

Influenza A and B viral antigens, primarily Hemagglutinin (HA) and Neuraminidase (NA), are the essential molecular structures recognized by the host's adaptive immune system during infection or vaccination [1]. Hemagglutinin is a surface glycoprotein that mediates viral entry by binding to sialic acid receptors on host respiratory cells, while Neuraminidase is an enzyme that facilitates the release of progeny virions by cleaving these same receptors [1, 2]. These proteins are the primary targets for seasonal influenza vaccines, which aim to elicit neutralizing antibodies that block the HA-mediated infection process [3]. Because these antigens undergo frequent mutations, a process known as antigenic drift, the immune system's recognition can be bypassed, necessitating the annual update of vaccine compositions to match circulating strains [1, 4]. Beyond vaccines, these antigens are also the targets of antiviral medications, such as neuraminidase inhibitors, which bind to the NA active site to limit the spread of the virus within the respiratory tract [3].

Other names

Influenza surface glycoproteinsHemagglutinin and NeuraminidaseFlu antigensHA and NA proteinsInfluenza virus proteins

Vaccines present these antigens to the adaptive immune system to stimulate the production of neutralizing antibodies (primarily against the Hemagglutinin head) and activate T-cell mediated immunity [1, 3]. Antiviral drugs interact with these antigens by directly inhibiting their functional roles, such as Neuraminidase inhibitors blocking viral release or M2 proton channel blockers preventing viral uncoating [3, 4].