The percentage of killing in VSVΔG-GL-, VSVΔG-NP-, VSVΔG-GLN-, and VSVΔG-GLNS-superinfected, Env-expressing cell lines (HUT-102, SLB-1, MT-2, and ATL-056i cells) was significantly higher (P < 0.01 by Student's t test) than that in the same cell lines following VSVΔG infection (control). Here, ERVW-1 is linked to infection.