Hemagglutinin protein of Influenza A virus (HA)

Hemagglutinin protein of Influenza A virus is a homotrimeric, class I fusion glycoprotein found on the viral envelope. It mediates viral entry by binding to sialic acid-containing receptors on the surface of host cells, facilitating attachment and subsequent endocytosis[3][1]. Following acidification in the endosome, HA undergoes a dramatic conformational change that enables fusion of the viral and host membranes, allowing the viral genome to enter the host cytoplasm[4][7][1]. The HA protein is the major target for neutralizing antibodies and is therefore a critical antigen for vaccine design. Its sequence variability is the main factor behind influenza antigenic drift and the need for frequent updates of seasonal influenza vaccines. Subtypes of HA (e.g., H1, H3, H5, etc.) are used to classify influenza A virus strains and play a pivotal role in zoonotic potential and pathogenicity, especially when polybasic cleavage sites are present[1][7][4]. Hemagglutinin is not a human protein or receptor, but a viral target; as such, it is a validated therapeutic and vaccine target in the context of influenza infection.

Other names

Influenza hemagglutininHA proteinViral hemagglutininInfluenza virus hemagglutinin glycoprotein

Neutralizing antibodies inhibit HA interaction with host receptors (block attachment) Monoclonal antibodies target HA to prevent viral entry or fusion Small molecules and peptides (experimental) may stabilize pre-fusion HA conformation or block fusion