Influenza A virus hemagglutinin H1 (HA) (HA (H1))

Influenza A hemagglutinin of the H1 subtype is a major surface glycoprotein and a primary target for the host immune response against H1N1 influenza viruses [1.2.3]. It functions as a homotrimeric class I fusion protein that mediates viral entry by binding to sialic acid receptors on host cells and facilitating the fusion of the viral and endosomal membranes [1.2.3, 1.2.4]. The protein consists of two subunits: HA1, which contains the highly variable globular head and receptor-binding site, and HA2, which forms the more conserved stem region responsible for the fusion machinery [1.2.2, 1.3.1]. HA is the central component of seasonal and pandemic influenza vaccines, which aim to elicit neutralizing antibodies that block viral infection [1.5.1]. Therapeutic interventions targeting HA include small-molecule fusion inhibitors like umifenovir and broadly neutralizing monoclonal antibodies such as CR6261 and MEDI8852 [1.1.2, 1.3.2]. These therapies often target the conserved stem to provide broader protection across different H1 strains [1.1.2]. However, the effectiveness of these interventions is constantly challenged by antigenic drift, where mutations in the HA head allow the virus to evade existing immunity [1.5.1, 1.5.3]. Additionally, antigenic shift through genetic reassortment can lead to the emergence of novel H1 subtypes with pandemic potential [1.2.2].

Other names

HemagglutininHAH1 HAH1N1 hemagglutininH1N1 HAHA0HA1HA2

Fusion inhibition, attachment inhibition, and viral neutralization [1.1.2, 1.3.2, 1.6.1]