Hemagglutinin (Influenza B virus) (HA)

Influenza B hemagglutinin (HA) is a critical surface glycoprotein of the influenza B virus, serving as the primary mediator of viral entry into host cells. It functions as a class I fusion protein, facilitating the attachment of the virus to sialic acid-containing receptors on the respiratory epithelium and subsequently driving the fusion of the viral envelope with the endosomal membrane under acidic conditions [1, 4]. The influenza B virus is divided into two antigenically distinct lineages, B/Victoria and B/Yamagata, which are defined by variations in the HA protein [3, 6]. The B/Yamagata lineage HA has historically been a key component of quadrivalent influenza vaccines, which aim to elicit neutralizing antibodies that block the receptor-binding site on the HA globular head [14, 19]. However, recent epidemiological data suggests that the B/Yamagata lineage may have become extinct following the COVID-19 pandemic, leading to recommendations for its removal from future vaccine formulations [3]. Therapeutic strategies targeting this molecule include vaccines, broadly neutralizing monoclonal antibodies that target the conserved stem region, and small-molecule fusion inhibitors [16, 21]. The HA protein is also the primary target for diagnostic assays, such as the hemagglutination inhibition test, which measures the ability of antibodies to prevent viral attachment [2, 5].

Other names

HAHemagglutinin proteinInfluenza B HAB/Yamagata lineage hemagglutininSurface glycoprotein

Neutralization of viral entry by blocking the binding of the hemagglutinin protein to host cell sialic acid receptors or by inhibiting the pH-dependent membrane fusion process.