ERVW-1 and neoplasm: AH1 represents one of the best characterized tumor rejection antigens in mice and is derived from the gp70 envelope protein of murine leukemia virus (MuLV), which is endogenous in the genome of most laboratory mouse strains, including the BALB/c strain used in these studies.24 Starting at 11 days post tumor engraftment, mice were treated intratumorally with BCG, anti-PD-1 alone, PeptiBAC-AH1, BCG in combination with anti-PD-1, PeptiBAC-AH1 in combination with anti-PD-1 or saline as a mock-treated group.