ERVW-1 and viral infectious disease: Chimpanzee SLC52A2-, human SLC52A2-, chimpanzee SLC52A1-, and human SLC52A1-expressing MDTF cells, designated MDTF-chSLC52A2, MDTF-huSLC52A2, MDTF-chSLC52A1, and MDTF-huSLC52A1, respectively, were characterized by permissiveness to CERV-1 Env-pseudotyped virus infection, whereas MDTF cells were not (Fig. 1A).