IFITM2 and infection: In accordance with the role played by endosomal IFITM2/-3 in protecting cells against SARS-CoV-2 infection (47), pseudovirus infection mediated by Omicron (BA.1) spike protein (which favors the endosomal route for entry) (48) was as sensitive to temsirolimus-mediated enhancement as infection mediated by ancestral (WA1) spike (Figure 5D).