An orally bioavailable formulation composed of eleven alive, distinct nonpathogenic, nontoxigenic, human commensal bacterial strains, isolated from healthy human donor feces, with potential immunostimulating and antineoplastic activities. Upon administration of the commensal bacterial strain formulation VE800, the bacterial strains induce an interferon-gamma (IFN-g)-producing CD8-positive T-cell-mediated immune response in the intestines. This may activate an IFN-g-expressing CD8+ T-cell -mediated anti-cancer immune response and may eradicate tumor cells.