Influenza hemagglutinin (HA)

Influenza hemagglutinin (HA) is a homotrimeric surface glycoprotein found on the envelope of influenza viruses, serving as a critical mediator of viral entry into host cells [1.1.1, 1.3.1]. It possesses two primary functions: binding to sialic acid-containing receptors on the host cell surface to initiate attachment and facilitating the fusion of the viral envelope with the endosomal membrane following endocytosis [1.1.4, 1.3.2]. This fusion process is triggered by the low pH environment of the endosome, which induces a massive conformational change in the HA molecule [1.1.1, 1.2.3]. As the major antigen on the virus surface, HA is the primary target for neutralizing antibodies and the central component of most influenza vaccines [1.2.1, 1.4.3]. Therapeutic interventions targeting HA include small-molecule fusion inhibitors, such as umifenovir, and broadly neutralizing monoclonal antibodies that aim to provide protection against multiple viral subtypes [1.2.1, 1.2.3, 1.5.4]. However, the rapid evolution of HA through antigenic drift and shift necessitates frequent vaccine updates and presents a constant challenge for long-term immunity and pandemic control [1.4.3, 1.5.2].

Other names

HAHaemagglutininHemagglutinin glycoproteinHemagglutinin-esterase-fusion proteinHEFH1-H18 subtypes

Inhibition of viral attachment by blocking the receptor-binding site or inhibition of membrane fusion by preventing pH-induced conformational changes [1.2.1, 3.3.1, 3.3.2].