ERVW-1 and infection: As expected, all three IFITM proteins did not inhibit the entry of lentiviral particles pseudotyped with the envelope protein of Lassa fever virus (LASVpp), which served as a negative control, and significantly reduced the infection of lentiviral particles pseudotyped with the envelope proteins of influenza A virus (IAV) (IAVpp), which served as a positive control (Figure 4(B)).