Influenza hemagglutinin protein (H1N1 subtype) (HA (Hemagglutinin))

The influenza hemagglutinin protein (HA), specifically of the H1N1 subtype such as A/Victoria/4897/2022 or similar annual strains, is a viral surface glycoprotein essential for influenza virus infectivity[1][3][6]. It is a homotrimeric class I fusion protein, with each monomer consisting of a globular head domain that binds sialic acid receptors on host cells and a stem domain that mediates membrane fusion upon endosomal acidification[1][2][5]. HA is the major antigen targeted by neutralizing antibodies and the principal target of seasonal and pandemic influenza vaccines[4][5]. The protein’s ability to change structure by antigenic drift (mutation) and antigenic shift (reassortment) enables frequent immune escape and necessitates annual vaccine reformulation[4][5]. HA’s role as the receptor-binding and fusion protein makes it a key therapeutic target for antibody drugs and universal vaccine research. It also serves as an important diagnostic biomarker and poses challenges for vaccine design due to its high variability, affecting safety and efficacy especially in high-risk populations[1][4][5].

Other names

Hemagglutinin (influenza)HA proteinH1 hemagglutininInfluenza A hemagglutininH1N1 hemagglutinin

Drug-mediated neutralization: antibodies and vaccines target HA and prevent receptor binding or membrane fusion, blocking viral entry[4][5] - Inhibition of viral attachment to host cells - Immune recognition and neutralization (antibody recruitment)