Hemagglutinin glycoprotein of Influenza virus (HA)

Hemagglutinin glycoprotein of Influenza virus (HA) is a trimeric surface glycoprotein present on Influenza A and B viruses, essential for virus infectivity[1][3][4][6]. Each monomer consists of a globular head (with the receptor binding site) and a stem region (responsible for membrane fusion)[1][6]. HA mediates two essential steps in viral entry: 1) binding to sialic acid residues on host cell surface receptors, which determines host specificity, and 2) facilitating fusion between the viral envelope and host endosomal membranes following endocytosis and acidification[1][2][3][6]. The protein is the principal target of neutralizing antibodies and thus a focus of both vaccine and monoclonal antibody development efforts[1][3][6]. Antigenic variation in HA is the main driver of seasonal influenza epidemics and periodic pandemics[6]. The hemagglutinin gene encodes several subtypes, especially for Influenza A (e.g., H1, H3, H5), which pair with different neuraminidase subtypes to define viral strains[1][4]. No direct, approved small-molecule HA inhibitors exist, but HA is a critical target for experimental therapeutics and all current influenza vaccines[1][6].

Other names

Influenza hemagglutininHAInfluenza virus hemagglutininHemagglutinin protein

Inhibition of HA-mediated viral attachment (by antibodies or experimental inhibitors)\n- Inhibition of membrane fusion (by antibodies or research agents)