Figure 3.

Virotherapy triggers cytotoxic neoepitope-specific CD8 T-cell responses and efficiently eradicates uninfected lung metastases. (a) C57BL/6 mice with subcutaneous CMT64 tumors were treated with or without oncolytic virotherapy. To determine cytotoxic activity of tumor-specific CD8 T-cells, an in vivo cytotoxic assay was performed by adoptive transfer of donor cells pulsed with a peptide pool consisting of all seven tumor-reactive epitopes triggered by oncolytic virotherapy. Cytotoxicity was calculated from ratios of the CFSE^hi-target peak pulsed with the tumor-specific peptide pool and the CFSE^lo-reference peak pulsed with irrelevant peptides. The virus-specific response to dbp served as positive control. Representative histograms are shown in the left panel. The right panel shows the calculated cytotoxicity of indicated groups. (b) Antitumoral efficacy of tumor-specific CD8 T-cells was investigated by clearance of pre-established CMT64 lung colonies. Mice received an i.v. injection of CMT64 cells to establish lung colonies and were treated with intratumoral injections of hTertAd. On day 18 after therapy, mice were sacrificed and lungs were prepared for histology. Untreated mice served as control. To assess the contribution of CD8 T-cells to the clearance of lung colonies, an additional group received virotherapy and CD8 depleting antibodies. The tumor-area of colonies was calculated by computer-based analysis from HE-stained lung sections. The ratio of tumor-area to total lung area is shown in the graph on the right side.