Hemagglutinin of Influenza A H1N1 virus (HA)

Hemagglutinin of Influenza A H1N1 virus is a trimeric, class I fusion glycoprotein displayed on the viral surface, essential for viral infectivity[1][3][4][5]. Each monomer consists of two subunits (HA1 and HA2) generated after proteolytic cleavage of a precursor (HA0); HA1 forms the globular head responsible for binding to sialic acid receptors on host cells, while HA2 forms the stalk region critical for fusion of viral and host cell membranes[1][2][5][6]. Hemagglutinin is the principal target of neutralizing antibodies and thus a central antigenic component of influenza vaccines[3][5]. The protein’s high variability, especially in its head domain, enables immune evasion and is the basis for seasonal influenza epidemics and occasional pandemics, such as the 2009 H1N1 outbreak[1][5]. Immunity to HA, as measured by hemagglutination inhibition assays, is considered the best correlate of protection for influenza vaccines[3][5].

Other names

Influenza virus hemagglutininInfluenza A virus hemagglutininHA proteinH1 hemagglutinin

Neutralizing antibodies prevent receptor binding by blocking HA head domain Neutralizing antibodies inhibit membrane fusion by binding HA stalk domain Vaccines induce immune response against HA to confer protective immunity