Influenza virus hemagglutinin head domain (HA head)

The influenza virus hemagglutinin (HA) head domain is the distal, globular portion of the HA protein, which serves as the primary surface glycoprotein of the influenza virus [6, 10]. It contains the receptor-binding site (RBS) responsible for attaching the virus to sialic acid residues on the surface of host respiratory epithelial cells, a critical first step in viral entry [7, 13]. As the most immunodominant region of the virus, the head domain is the primary target for neutralizing antibodies produced during infection or after vaccination [9, 11]. However, this domain is highly susceptible to antigenic drift, where frequent mutations allow the virus to escape existing host immunity, necessitating the annual reformulation of seasonal influenza vaccines [1, 17]. Beyond the RBS, recent research has identified conserved "sites of vulnerability" within the head domain, such as the trimer interface, which can be targeted by broadly neutralizing antibodies [15, 16]. Therapeutic strategies focusing on the head domain include the development of monoclonal antibodies that block receptor binding or disrupt the integrity of the HA trimer [15, 18]. Understanding the structural dynamics and evolutionary constraints of the HA head is essential for the design of next-generation "universal" influenza vaccines [1, 14].

Other names

HA1 globular headHemagglutinin receptor-binding domainGlobular head domainHA1 subunit

Inhibition of viral attachment to host cell sialic acid receptors, disruption of HA trimer integrity, and inhibition of viral egress.