Tumor growth inhibition elicited by different vaccines and correlation with antigen specific cytotoxic T-cell frequencies determined by intracellular interferon-γ staining

Different vaccines based on naked DNA and the modified vaccinia virus Ankara (MVA) were compared for their efficiency to protect mice against tumors bearing the model antigen beta-galactosidase (β-Gal) and for their potential to induce an antigen specific cellular immune response. Mice were immunized with the LacZ gene applied as naked DNA. In accordance with the observed β-Gal-specific T-cell frequency, only 20% of mice boosted with LacZ naked DNA developed tumors whereas all mice boosted with MVA expressing LacZ developed a tumor. Mice vaccinated with mock DNA or mock virus developed tumors in 60 or 100%, respectively. MVA vaccination led to strong and long-lasting CD4- and CD8-T-cell responses against viral antigens but not against β-Gal.