Influenza A and Influenza B virus antigens (Flu A/B antigens)

Influenza A and Influenza B virus antigens, primarily the surface glycoproteins hemagglutinin (HA) and neuraminidase (NA), are the fundamental components recognized by the host immune system to provide protection against infection [CDC, 2023]. Hemagglutinin is responsible for binding the virus to sialic acid receptors on host cells, while neuraminidase facilitates the release of new viral particles from infected cells [WHO, 2023]. When these antigens are presented to the immune system—either through natural infection or vaccination—they stimulate B cells to produce neutralizing antibodies and activate T cells to provide cellular immunity [Krammer, 2019]. Most seasonal vaccines are designed to elicit antibodies against the HA protein to prevent the virus from entering cells [Nature, 2018]. However, the virus constantly evolves through antigenic drift, which involves small mutations in the HA and NA genes, necessitating annual updates to the vaccine composition [FDA, 2023]. Effective presentation of these antigens is the cornerstone of public health efforts to mitigate the impact of seasonal flu epidemics and potential pandemics [The Lancet, 2017].

Other names

Hemagglutinin and NeuraminidaseFlu antigensInfluenza surface glycoproteinsHA and NAInfluenza virus antigens

Vaccines present these viral antigens to the host immune system to induce an adaptive immune response. This involves the production of neutralizing antibodies that bind to the hemagglutinin protein, thereby blocking viral attachment and entry into host cells, as well as the activation of cytotoxic T lymphocytes that identify and destroy infected cells [Krammer, 2019; CDC, 2023].