Influenza A virus H7N9 hemagglutinin globular head domain (H7N9 HA head) (H7N9 HA head)

The Influenza A H7N9 hemagglutinin (HA) head domain is the distal, globular portion of the HA protein, which serves as the primary surface antigen of the influenza virus (Shi et al., 2013). This domain contains the receptor-binding site (RBS) that specifically recognizes and binds to sialic acid receptors on the surface of host respiratory cells, facilitating viral attachment and subsequent entry (UniProt Consortium, 2024). As the most immunodominant region of the virus, the head domain is the primary target for neutralizing antibodies elicited by vaccines, such as the adjuvanted H7N9 monovalent vaccine Audenz (FDA, 2020). However, the head domain is characterized by high genetic plasticity, frequently undergoing mutations known as antigenic drift to evade host immune pressure (Throsby et al., 2008). These mutations can render existing vaccines and monoclonal antibodies ineffective, necessitating constant surveillance and updated therapeutic strategies. Despite its variability, the head domain remains a critical focus for developing subtype-specific interventions against zoonotic H7N9 outbreaks. Therapeutic approaches targeting this domain primarily aim to sterically hinder the RBS, effectively neutralizing the virus before it can infect host cells (Whittle et al., 2014).

Other names

HA1 domainH7N9 HA1Hemagglutinin subunit 1Globular head domain

Neutralization of viral infectivity by blocking the receptor-binding site, thereby preventing the interaction with host cell sialic acid receptors.