Hemagglutinin protein from Influenza A H1N1 (HA (sometimes H1 HA to specify subtype))

Hemagglutinin protein from Influenza A H1N1 is a **homotrimeric glycoprotein** present on the surface of **influenza A virus** particles, playing a **pivotal role in viral entry** into host cells. It mediates **attachment to sialic acid-containing receptors** on the host cell surface, followed by **fusion of viral and host membranes** in the acidic environment of the endosome. The HA protein consists of **two main domains**: the globular head (containing the receptor binding site) and a stem (responsible for membrane fusion). HA is the **major target of neutralizing antibodies** and underlies most immune pressure and antigenic drift in influenza evolution. The H1N1 subtype refers to specific antigenic forms (H1 for hemagglutinin and N1 for neuraminidase). HA's high variability and central role in infection make it both a major vaccine antigen and a focus for antiviral drug development[1][3][4][5].

Other names

HemagglutininHAInfluenza virus hemagglutininInfluenza A hemagglutininH1 hemagglutininH1 HA

Antibody-mediated neutralization (blocks receptor binding or fusion by binding HA head or stem); Small molecule or peptide inhibitors block HA-mediated membrane fusion or virus–host binding