Mus dunni tail fibroblast (MDTF) cells that were resistant to enFeLV infection (Fig. 2D), MDTF cells expressing fePit1 (MDTF-fePit1), and MDTF cells expressing fePit2 (MDTF-fePit2) were tested for infection with enFeLV Env-pseudotyped viruses prior to analysis 2 days later. Here, ERVW-1 is linked to infection.