Hemagglutinin of Influenza B virus (HA (Hemagglutinin))

Hemagglutinin of Influenza B virus is a trimeric, glycosylated surface protein essential for viral infectivity. Each monomer consists of the HA1 (globular head domain, responsible for receptor binding) and HA2 (stem domain, mediates membrane fusion) subunits, linked by disulfide bridges after host protease cleavage. HA binds to sialic acid-containing receptors on host epithelial cells, triggers endocytosis, and, in low-pH endosomes, undergoes conformational rearrangements that enable fusion of the viral envelope with the host membrane. As the primary antigenic determinant, HA is subject to antigenic drift (gradual mutations enabling immune escape) and occasionally antigenic shift (major changes leading to pandemics in Influenza A, less dramatic in B). Structural studies highlight four major epitopes: the 120 loop, 150 loop, 160 loop, and 190 helix, concentrated in the globular head. HA is a critical target for vaccines and the focus of most neutralizing antibody responses to Influenza B; modern vaccine and therapeutic designs frequently address its antigenic variability. Therapeutic challenges include antigenic diversity, potential for immune escape, and need for ongoing antigenic surveillance.

Other names

Influenza B HemagglutininHABHAHemagglutinin (Influenza B)Influenza B virus surface glycoprotein

Neutralizing antibodies block receptor binding or fusion domain, preventing viral entry. Vaccines prime host immune system to recognize antigenic epitopes on HA for immunity. Inhibitors disrupt conformational changes needed for membrane fusion.