Hemagglutinin (H1 subtype) (H1 HA)

Hemagglutinin (HA) is the primary surface glycoprotein of the Influenza A virus and serves as the essential mediator of viral infectivity. The H1 subtype is a major component of seasonal and pandemic influenza strains, including the 1918 and 2009 H1N1 viruses [UniProt P03452]. HA functions by binding to sialic acid receptors on host respiratory epithelial cells, triggering receptor-mediated endocytosis, followed by a pH-induced conformational change that facilitates the fusion of the viral and endosomal membranes [Skehel & Wiley, 2000]. In the context of the immune system, H1 HA is the immunodominant antigen targeted by the host's neutralizing antibody response. Most current influenza vaccines work by presenting H1 HA antigens to stimulate the production of antibodies that primarily target the highly variable 'head' region of the protein to prevent viral attachment [WHO, 2024]. Due to frequent antigenic drift, therapeutic development also focuses on the more conserved 'stem' region of H1 HA to create universal vaccines or broadly neutralizing monoclonal antibodies [NIH, 2023].

Other names

HAH1Influenza A virus hemagglutininSurface glycoprotein hemagglutininH1N1 hemagglutinin

Active immunization via presentation of HA antigens to B and T cells to elicit neutralizing antibodies [CDC, 2023]; Passive immunization via monoclonal antibodies that bind the HA head or stem to block viral entry or fusion [Nature Communications, 2016].