Influenza A virus group 1 hemagglutinin stalk domain (HA stalk (Group 1))

The Influenza A virus group 1 hemagglutinin (HA) stalk domain is a highly conserved region of the HA surface glycoprotein, which is essential for viral entry into host cells [1, 2]. While the globular head domain of HA mediates initial attachment to sialic acid receptors, the stalk domain (primarily composed of the HA2 subunit and parts of HA1) undergoes a dramatic pH-triggered conformational change in the endosome to facilitate fusion between the viral and host membranes [4, 6]. Because the stalk domain is much more conserved across different influenza subtypes than the rapidly mutating head domain, it has become a primary target for the development of universal influenza vaccines and broadly neutralizing monoclonal antibodies [3, 5]. Therapeutic agents targeting this domain typically work by preventing the structural rearrangements necessary for membrane fusion or by recruiting immune effector cells through Fc-mediated pathways like antibody-dependent cellular cytotoxicity (ADCC) [7, 10]. Group 1 hemagglutinins include subtypes H1, H2, H5, H6, H8, H9, H11, H12, H13, H16, H17, and H18, making this domain a critical focus for broad-spectrum antiviral strategies against both seasonal and pandemic strains [2, 10, 13].

Other names

HA2 subunitHemagglutinin stem domainHA stalk regionConserved HA stalk

Inhibition of pH-induced conformational change to prevent membrane fusion, blocking of HA0 precursor cleavage, and induction of Fc-mediated effector functions such as antibody-dependent cellular cytotoxicity (ADCC) [1, 5, 7, 10].