Influenza A virus H3N2 hemagglutinin receptor-binding site (H3N2 HA RBS)

The influenza A virus H3N2 hemagglutinin receptor-binding site (RBS) is a critical shallow pocket located on the distal head of the hemagglutinin (HA) surface glycoprotein. Its primary biological function is to mediate the attachment of the virus to host cells by specifically recognizing and binding to terminal sialic acids linked to galactose on host cell surface glycoproteins and glycolipids. In H3N2 viruses, the RBS has a preference for alpha-2,6-linked sialic acids, which are prevalent in the human upper respiratory tract, facilitating efficient human-to-human transmission. As a primary target for the host immune system, the RBS is under constant evolutionary pressure, leading to frequent mutations known as antigenic drift that allow the virus to evade neutralizing antibodies. In drug development, the RBS is a major focus for the design of entry inhibitors, including monoclonal antibodies and small molecules, which aim to block the initial stage of the viral life cycle. Successfully targeting this site can prevent infection and reduce viral shedding, although the high rate of mutation in this region poses a significant challenge for maintaining long-term therapeutic efficacy.

Other names

H3N2 HA receptor-binding pocketHemagglutinin RBSSialic acid binding siteHA1 subunit receptor-binding domain

Drugs targeting the H3N2 hemagglutinin receptor-binding site typically act as entry inhibitors by sterically hindering the interaction between the viral hemagglutinin and the host cell's sialic acid receptors, thereby preventing viral attachment and subsequent endocytosis.