Influenza A virus hemagglutinin stalk region (HA stalk) (HA stalk)

The Influenza A virus hemagglutinin (HA) stalk region is a highly conserved domain of the primary viral surface glycoprotein responsible for mediating host cell entry (Krammer & Palese, 2015, Nature Reviews Drug Discovery). While the globular head of HA (HA1) undergoes frequent antigenic drift, the stalk region (primarily HA2) remains relatively stable across diverse influenza subtypes, making it a critical target for the development of universal influenza vaccines and broad-spectrum therapeutics (Ekiert et al., 2009, Science). The biological function of the stalk is to facilitate the fusion of the viral envelope with the host endosomal membrane; this process is triggered by the acidic environment of the endosome, which induces a massive "spring-loaded" conformational change in the stalk (UniProt P03437). Therapeutic interventions, including monoclonal antibodies like CR6261 and MEDI8852, as well as small molecules like Umifenovir, bind to this region to stabilize the pre-fusion state and prevent the structural transition required for membrane fusion (Dreyfus et al., 2012, Science). By blocking this essential step in the viral life cycle, these agents provide broad protection against multiple strains of Influenza A, addressing the limitations of traditional seasonal vaccines. This target is particularly valuable because it offers a path toward a "universal" vaccine that would not require annual reformulation, although challenges such as the lower immunogenicity of the stalk compared to the head must be overcome (Impagliazzo et al., 2015, Science).

Other names

HA stemHemagglutinin stem regionHA2 subunitConserved HA stalk domain

Inhibition of pH-dependent conformational change and membrane fusion