Influenza A virus hemagglutinin globular head domain (HA head)

The Influenza A virus hemagglutinin (HA) head domain is the globular, distal portion of the HA surface glycoprotein, primarily composed of the HA1 subunit [15, 17]. It contains the receptor-binding site (RBS) that recognizes sialic acid on host cell membranes, facilitating viral attachment and subsequent entry via endocytosis [2, 6, 12]. As the most exposed part of the virus, the head domain is the primary target for neutralizing antibodies elicited by infection or vaccination [3, 13, 19]. However, it is also highly plastic and subject to frequent mutations, a process known as antigenic drift, which allow the virus to evade the host immune system and necessitates the annual updating of seasonal influenza vaccines [4, 13, 17]. Therapeutic strategies targeting the head domain include the development of monoclonal antibodies that block receptor binding or disrupt the trimeric structure of the protein, as well as universal vaccine candidates designed to target more conserved epitopes within the head or at the trimer interface [1, 3, 10, 13]. These interventions aim to provide broader and more durable protection against diverse influenza strains by focusing on less variable regions of the head domain [3, 10, 14]. Understanding the structural dynamics of the head domain is critical for overcoming the challenges posed by viral evolution and ensuring the efficacy of future anti-influenza therapies [8, 13].

Other names

HA1 globular headHemagglutinin head domainGlobular head of HAHA1 domainReceptor-binding domain of hemagglutinin

Neutralization of viral infectivity by blocking the receptor-binding site (RBS) to prevent viral attachment to host cell sialic acid receptors, and in some cases, disrupting the integrity of the HA trimer.