Influenza virus hemagglutinin and neuraminidase (HA and NA)

Influenza virus hemagglutinin (HA) and neuraminidase (NA) are the two major surface glycoproteins of the influenza virus, playing essential and opposing roles in the viral life cycle [1, 13]. Hemagglutinin is a lectin responsible for viral attachment to host cells by binding to sialic acid receptors on the respiratory epithelium and subsequently mediating the fusion of the viral and endosomal membranes to release the viral genome [5, 16]. Neuraminidase acts as a sialidase enzyme that cleaves terminal sialic acid residues from glycoproteins and glycolipids, a process required for the release of progeny virions from infected cells and the prevention of viral aggregation [10, 13]. These proteins are the primary targets of the host's neutralizing antibody response and are the central components of seasonal influenza vaccines [20, 22]. Due to the high rate of mutation in the HA and NA genes, known as antigenic drift, the virus can evade pre-existing immunity, requiring the annual reformulation of vaccines to match circulating seasonal strains [16, 21]. Therapeutic interventions include neuraminidase inhibitors, such as oseltamivir and zanamivir, which block viral spread, and emerging HA inhibitors like umifenovir that prevent viral entry [2, 8].

Other names

HemagglutininNeuraminidaseHANASialidaseH and N antigensViral surface glycoproteinsInfluenza surface antigens

Inhibition of viral attachment to sialic acid receptors and/or inhibition of pH-dependent membrane fusion (HA); Inhibition of sialidase activity to prevent the cleavage of sialic acid and the release of progeny virions (NA)