Influenza A virus hemagglutinin (H5N1 subtype) (HA (commonly used); H5N1 hemagglutinin for subtype specificity)

Influenza A virus hemagglutinin (HA) is a homotrimeric glycoprotein embedded in the viral envelope, with each monomer consisting of a globular head (HA1) and a stalk domain (HA2)[1][3][5]. The HA protein is synthesized as an inactive precursor (HA0) that must be proteolytically cleaved into HA1 and HA2 to be functional for membrane fusion[4]. The globular head mediates binding to sialic acid receptors on host cell membranes, determining host range and cell tropism, while the stalk domain is crucial for mediating the fusion of viral and cellular membranes in the endosome after uptake[1][3].\nH5N1 hemagglutinin is the subtype-specific form found in avian influenza A (H5N1) viruses, notable for its role in zoonotic transmission and pandemic risk[1]. Its receptor-binding and antigenic properties make it the primary target for antibody therapeutics and vaccine design[5].\nHA’s high variability, especially in the receptor binding domain, leads to recurrent antigenic drift and presents challenges for lasting immunity[4]. The protein’s ability to agglutinate red blood cells gives it diagnostic utility in laboratory assays. In clinical development, anti-HA antibodies and fusion inhibitors focus on blocking HA’s key functions to prevent or treat influenza infection.

Other names

Influenza A H5N1 hemagglutininHA (H5 subtype)Avian influenza virus hemagglutinin (H5)

Block attachment (antibody-mediated neutralization); Inhibit membrane fusion (fusion inhibitors); Modify receptor binding specificity (mutation/adaptation)