ERVW-1 and neoplasm: In order to determine general tumor-specific immune responses induced by the vaccine as part of the cell-mediated immunity, splenocytes from Ad5-MelARV injected mice were co-cultured with the tumor cell lines 4T1, CT26 and Renca as well as the fibroblast cell line NIH/3T3 known to be negative for MuLV/MelARV Env [16].