Influenza virus haemagglutinin and neuraminidase epitopes (HA and NA epitopes)

Influenza virus haemagglutinin (HA) and neuraminidase (NA) are the primary surface glycoproteins of the influenza virus and serve as the major targets for the host immune system (Gamblin & Skehel, 2010). HA facilitates viral entry by binding to sialic acid receptors on host cells and mediating the fusion of the viral envelope with the endosomal membrane (UniProt P03435). NA is an enzyme that cleaves sialic acid residues, allowing newly formed viral particles to be released from the infected cell and spread to neighboring cells (von Itzstein, 2007). Epitopes on these proteins are the focus of seasonal vaccines, which aim to induce neutralizing antibodies that block these critical steps in the viral life cycle (CDC, 2023). However, the high rate of mutation in these epitopes, known as antigenic drift, necessitates frequent updates to vaccine compositions and poses a challenge for long-term immunity. Therapeutic strategies include neuraminidase inhibitors that prevent viral shedding and monoclonal antibodies targeting conserved regions, such as the HA stalk, to provide broader protection against multiple strains (Krammer & Palese, 2013).

Other names

Influenza surface glycoproteinsHA and NA antigensFlu epitopesHemagglutinin and neuraminidase antigens

Neuraminidase inhibitors (e.g., Oseltamivir) competitively bind to the active site of the NA enzyme, preventing the cleavage of sialic acid and trapping virions on the host cell surface (von Itzstein, 2007). Hemagglutinin-targeted agents, including vaccines and monoclonal antibodies, bind to specific epitopes to neutralize the virus by blocking receptor binding or preventing the conformational change required for membrane fusion (Gamblin & Skehel, 2010).