Influenza hemagglutinin receptor-binding domain (HA-RBD)

The **influenza hemagglutinin receptor-binding domain (HA-RBD)** is a region within the hemagglutinin (HA) glycoprotein located on the surface of the influenza virus[1][2][5][7]. HA is a trimeric envelope protein that mediates viral entry into host cells. Each HA monomer contains a globular head (mainly the HA1 subunit) that harbors the receptor-binding domain. The HA-RBD specifically binds to sialylated glycan receptors on the surface of host epithelial cells, initiating viral attachment and endocytosis. This interaction determines host specificity and tissue tropism. The HA protein must be cleaved into HA1 (globular head containing the RBD) and HA2 (stalk mediating membrane fusion) to be functional[5][6][7]. The RBD is highly immunogenic and is a primary target for neutralizing antibodies, including both strain-specific and broadly neutralizing antibodies. Its rapid antigenic evolution is a major reason for the ongoing need to reformulate influenza vaccines and for periodic influenza pandemics[5][6][9]. The region's high variability and essential role in infection make it both a therapeutic target and a key challenge for vaccine design.

Other names

Hemagglutinin receptor-binding domainHA receptor-binding domainHA RBDHA globular head domain

Neutralization of viral infectivity by blocking HA binding to sialylated host cell receptors (for antibodies) - Prevention of conformational changes needed for membrane fusion (antibodies that bind HA stem may prevent HA-mediated fusion)[5][7]