Life cycle of influenza A virus: a brief introduction
Influenza A virus life cycle is divided into several sequential steps (see
Fig. 1). The virus first attaches to host cell surface sialic acid (SA)
receptor via the viral surface glycoprotein hemagglutinin. The influenza
virus then enters into the cell via receptor-mediated endocytosis,
followed by low-pH-induced membrane fusion of the viral envelope
with the endosomal membrane of the cell. In this step, the viral M2
protein transports protons from the late endosome into interior of the
virus. The resulting acidification induces the conformation change of
viral hemagglutinin, which leads to hemagglutinin-mediated membrane
fusion followed by the dissociation of viral M1 matrix protein from the
viral ribonucleoprotein complexes (vRNPs), resulting in the release of
vRNPs into cytoplasm