Extended Data Fig. 3: Schematic structure model of the influenza A virion.
From: Generation of a live attenuated influenza A vaccine by proteolysis targeting
Influenza A virions are enveloped spherical structures with diameters of 80–120 nm54. The genome of each influenza A virion contains eight single-stranded negative-sense RNA segments, encoding 10 main viral proteins: hemagglutinin (HA), neuraminidase (NA), matrix protein 1 (M1), M2, polymerase basic protein 1 (PB1), polymerase basic protein 2 (PB2), polymerase acidic protein (PA), nucleoprotein (NP), nonstructural protein 1 (NS1), and nuclear export protein (NEP, also known as NS2). HA and NA are two main antigenic determinants of influenza virus, which are on the surface of the viral envelope and mediate viral entry into host cells and release of progeny virions from host cells, respectively. M2 is the third integral membrane protein, which forms ion channels in virion particles and has roles in viral entry, assembly, and budding. M1, the most abundant protein in the virion, lines the internal surface of the viral lipid bilayer and mediates the interactions between the viral membrane and ribonucleoprotein (RNP). The RNP is a complex structure composed of multiple copies of the viral NP, which wraps eight viral RNA genome segments, and a single RNA polymerase, which binds to the termini of each RNA genome segment. The RNA polymerase has three subunits: PB1, PB2, and PA, which are responsible for viral replication and transcription17,54. NS1 plays an important role in evasion of the host innate immune system and facilitates viral replication. NEP mediates the export of the newly synthesized viral RNP from the nucleus into the cytoplasm.
