Quadrivalent influenza virus haemagglutinin and neuraminidase antigens (QIV antigens)

Haemagglutinin (HA) and neuraminidase (NA) are the primary surface glycoproteins of the influenza virus, serving as the essential mediators of viral entry and exit, respectively. HA functions as a receptor-binding protein that attaches to sialic acid on host cells to initiate infection, while NA acts as an enzyme that cleaves these same sialic acids to facilitate the release of new viral particles [PubMed, 2002; PMC, 2011]. The quadrivalent target profile includes antigens from two influenza A subtypes (H1N1 and H3N2) and two influenza B lineages (Victoria and Yamagata), which are the predominant strains causing seasonal epidemics in humans [PMC, 2023; Wikipedia, 2024]. These antigens are the active components of seasonal vaccines, where they stimulate the production of antibodies that neutralize the virus and provide clinical protection [J Infect Dis, 2024; PMC, 2025]. Additionally, the neuraminidase protein is the specific target for the most common class of anti-influenza drugs, which inhibit the enzyme's catalytic activity to prevent the spread of the virus within the respiratory tract [PMC, 2021]. Because these proteins undergo continuous antigenic drift, the specific strains included in therapeutic products must be updated annually to match circulating viruses and maintain efficacy [Frontiers, 2020; News-Medical, 2024].

Other names

Influenza A (H1N1 and H3N2) and Influenza B (Victoria and Yamagata) antigensHA and NA antigensQuadrivalent influenza vaccine antigensH1N1, H3N2, B/Victoria, and B/Yamagata antigens

Vaccines containing these antigens induce neutralizing antibodies that bind to the haemagglutinin (HA) globular head to block viral attachment and entry, or to the neuraminidase (NA) active site to inhibit viral egress [PMC, 2011; Wikipedia, 2024]. Neuraminidase inhibitors (NAIs) competitively bind to the NA enzyme, preventing the cleavage of sialic acid residues and thereby trapping progeny virions on the surface of the infected host cell [PMC, 2021; PMC, 2014].