Figure 1.

Schematic view of influenza virion. Hemagglutinin (HA), neuraminidase (NA) and matrix protein 2 (M2) are the proteins expressed on virus membrane. Trimeric HA protein consists of HA head and HA stalk. Viral ribonucleoprotein (vRNP) is composed of vRNA and nucleoprotein (NP, light purple). Viral polymerase complex includes polymerase basic proteins 1 (PB1, blue), 2 (PB2, tan) and acidic protein A (PA, light yellow). The matrix protein (M1) is a multi-functional protein involved in influenza virion assembly and infection.