Realtime observation of structural dynamic of influenza A hemagglutinin during viral entry

Unlike living organisms, to avoid extinction, viruses need to hijack living host machineries to generate new viruses. The devastating respiratory virus, influenza A virus, utilize its hemagglutinin (HA) proteins to search for suitable host cells. Generally, HA has two important functions: selection of host cell and viral entry. Upon attaching to host cells, Influenza A virus are brought into host cells via endocytosis. A lipid bilayer cargo, known as endosome, carries influenza A virus from cell membrane into cytoplasm of host cell. Although the environment inside endosome is acidic, influenza A virus remains alive. More strikingly, HA undergoes structural change to mediate viral membrane to fuse with host endosomal membrane to form a hole in order to release viral components.