IFITM1 and infection: Due to their differential subcellular localization, IFITM1 mainly restricts the viruses that enter the cells at the cell surface or in the early endosomes, such as parainfluenza viruses and hepatitis C virus (68, 69), whereas IFITM2 and 3 primarily restrict the infection of viruses that enter the cells at later endosomes and/or lysosomes (43, 70, 71).