Influenza virus hemagglutinin stem and trimer interface epitopes (HA stem/interface)

Influenza virus hemagglutinin (HA) is the major surface glycoprotein of the influenza virus, playing a critical role in viral attachment and entry into host cells (NIH, 2013). It is composed of two main regions: a highly variable globular head domain and a relatively conserved stem (or stalk) domain (Sci Rep, 2019). While seasonal vaccines primarily target the head domain, which frequently undergoes antigenic drift, the HA stem and the trimer interface have emerged as vital targets for universal influenza therapies (PNAS, 2022). These regions contain epitopes that are highly conserved across diverse influenza A and B strains, making them ideal for broadly neutralizing antibodies (bnAbs) (NIH, 2021). Therapeutics targeting the HA stem typically function by inhibiting the pH-triggered conformational changes required for the fusion of the viral envelope with the host cell membrane (NIH, 2013). Additionally, some antibodies targeting the trimer interface can disrupt the integrity of the HA trimer or block the proteolytic cleavage of the HA0 precursor (NIH, 2023). Clinical development of these targets includes monoclonal antibodies like MEDI8852 and VIS410, as well as novel vaccine platforms designed to redirect the immune response away from the immunodominant head (NIH, 2023). Successful targeting of these epitopes could provide long-lasting, cross-protective immunity against both seasonal and pandemic influenza viruses (Bioengineer.org, 2026).

Other names

HA stalkHA stemHA trimer interfaceHemagglutinin stalk domainHA head-stem interface

Inhibition of viral-host membrane fusion by stabilizing the prefusion conformation of hemagglutinin and preventing pH-induced conformational changes; additional mechanisms include blocking proteolytic cleavage of HA0 and mediating Fc-effector functions like ADCC.