Burst and xenograft assays. A. Burst assays showing that the E1A-HD2 viruses vCF212 (derived from vCF22: Tcf-E1A, E1B, E2, E4) and vCF192 (derived from vKH1: Tcf-E1A, E1B, E4) have similar burst size to the parental viruses in SW480, Hct116 and Co115 colon cancer cells and HeLa cells. Error bars: SEM, n = 3. B. Growth curves of subcutaneous SW620 xenografts in NMRI nu/nu mice. Mice received 1011 particles of vKH1, vCF192 or buffer control i.v. on day 0. Error bars: SEM, n = 6.