Influenza A virus hemagglutinin (H3N2 subtype) (HA (H3N2))

Influenza A virus hemagglutinin (H3N2 subtype) is a major surface glycoprotein of the H3N2 influenza virus, essential for viral infectivity and host cell entry [Wikipedia, 2024]. It functions as a homotrimeric protein that mediates the attachment of the virus to sialic acid receptors on the host cell surface, followed by the fusion of the viral and endosomal membranes under acidic conditions [UniProt, 2024]. This protein is the primary target for neutralizing antibodies elicited by seasonal influenza vaccines and is a key focus for the development of universal influenza vaccines [NIH, 2023]. Due to its high rate of mutation, particularly in the globular head domain, the H3N2 subtype frequently undergoes antigenic drift, which can lead to reduced vaccine effectiveness and the need for annual strain updates [Britannica, 2025]. Therapeutic interventions targeting this molecule include small molecule fusion inhibitors like umifenovir and various monoclonal antibodies designed to bind to conserved epitopes in the stem region [PubMed, 2021]. However, the emergence of resistant variants and the complexity of glycan evolution on the protein surface present ongoing challenges for therapeutic and prophylactic strategies [NIH, 2024].

Other names

HAH3Hemagglutinin 3H3N2 HAH3 HASurface glycoprotein

Inhibition of viral attachment to host cell receptors or inhibition of membrane fusion by stabilizing the prefusion conformation of the hemagglutinin protein [PubMed, 2021; UniProt, 2024].