Influenza virus enters cells via receptor-mediated endocytosis and fuses in the acidic late endosomal compartment, depositing its genomic contents into the cytosol, thereby avoiding lysosomal hydrolases. In cells expressing IFITM3, viruses are localized in an enlarged acidic and degradative compartment staining positive for endosomal and lysosomal markers. Virus fusion is inhibited by alterations to the endolysosomal membrane imposed by IFITM3, and virions are subsequently degraded. IFITM3 is depicted as a dimer.
EE: Early endosome; EL: Endolysosome; L: Lysosome; LE: Late endosome.