Influenza virus hemagglutinin stem region (HA stem)

The influenza virus hemagglutinin stem region is a highly conserved part of the hemagglutinin (HA) glycoprotein present on the surface of influenza viruses, particularly within the subunit known as HA2. The stem serves as the membrane fusion machinery, enabling the virus to enter host cells after attachment to sialic acid receptors by the HA head domain. Unlike the highly variable head region, the stem region is conserved among diverse influenza strains, making it an attractive target for the development of broadly neutralizing antibodies and universal vaccines. Therapeutic antibodies and experimental immunogens targeting the stem can prevent the conformational changes required for viral fusion, thus blocking infection and transmission of multiple influenza subtypes. This target is a focal point in efforts to develop universal influenza vaccines and broadly acting antiviral therapies.

Other names

Hemagglutinin stemHA stemStalk region of hemagglutininHA2 subunitInfluenza hemagglutinin stalk

Drugs and antibodies targeting the HA stem primarily block membrane fusion, preventing viral envelope and host membrane mixing. They affect conformational changes required for viral entry. Some antibodies can also act via antibody-dependent cell-mediated cytotoxicity and complement activation.