Influenza A virus hemagglutinin protein stem region (H1 subtype) (HA stem (H1))

The Influenza A virus hemagglutinin (HA) protein stem region is a highly conserved domain of the primary surface glycoprotein responsible for viral entry (UniProt P03452). While the HA globular head is subject to frequent antigenic drift, the stem region (primarily composed of the HA2 subunit and parts of HA1) is structurally stable across H1 subtype strains, making it a focal point for universal vaccine design (PubMed: 22675060). Its primary biological role is mediating the fusion of the viral envelope with the host cell endosomal membrane, a process triggered by acidic pH (PubMed: 19229033). Therapeutic strategies involve monoclonal antibodies, such as CR6261 and MEDI8852, which bind to the stem to prevent the conformational spring-loaded change required for fusion (PubMed: 26797771). By targeting this conserved site, these drugs can provide broad protection against multiple H1N1 strains, including those with pandemic potential (PubMed: 21835248).

Other names

Hemagglutinin stalkHA2 subunitConserved HA stem domainHA stalk region

Inhibition of the pH-dependent conformational change of the hemagglutinin protein, thereby blocking the fusion of the viral envelope with the host cell membrane (PubMed: 19229033, 26797771).