Influenza B virus hemagglutinin globular head (HA1)

The Influenza B virus hemagglutinin globular head, also known as the HA1 domain, is the membrane-distal globular region of the hemagglutinin (HA) glycoprotein on the influenza B virus surface. It primarily functions in receptor binding by engaging sialic acid-containing receptors on host cells, such as those in the upper respiratory tract, enabling viral attachment and initiating infection.[1][2][5][8] Composed mainly of antiparallel beta-sheets with alpha/beta structures, this domain surrounds the receptor-binding site (RBS) and includes key antigenic epitopes like the 120 loop, 150 loop, 160 loop, and 190 helix, which are targets for neutralizing antibodies.[1][2] The globular head is highly variable due to antigenic drift, allowing the virus to evade host immunity, unlike the more conserved HA2 stalk.[1][5] In disease, it plays a central role in influenza B infections, contributing to seasonal epidemics and significant human morbidity.[2][5][7] As a therapeutic target, antibodies binding the head block sialic acid interactions, preventing viral entry, though broad protection is challenged by rapid mutation; efforts include stabilized head constructs for vaccines.[1][3][5]

Other names

HA headglobular domain of hemagglutininreceptor-binding domain

Antibody-mediated inhibition of receptor binding, Antibody-mediated inhibition of membrane fusion