Influenza A Virus Hemagglutinin H1 Subtype Antigenic Sites Sa, Sb, Ca, Cb (H1 HA Sa/Sb/Ca/Cb)

The hemagglutinin (HA) protein of the influenza A virus H1 subtype is a trimeric glycoprotein essential for viral entry into host cells. It mediates receptor binding via the globular head (primarily HA1) and membrane fusion via conformational changes (primarily HA2). The major antigenic sites Sa, Sb, Ca1/Ca2, and Cb are located on the HA1 subunit and are primary targets for neutralizing antibodies. Mutations within these sites (antigenic drift) allow the virus to evade pre-existing immunity. Sa and Sb are strain-specific while Ca/Cb may be more conserved.

Other names

H1 Hemagglutinin Antigenic SitesHA H1 Sa/Sb/Ca/Cb Epitopes

Neutralizing antibodies bind to antigenic sites (Sa, Sb, Ca, Cb), blocking virus attachment or membrane fusion. HA inhibitors block membrane fusion.