LAUSR

CCL22 is a macrophage-derived chemokine that exerts immunosuppressive functions by the recruitment of regulatory T cells (Tregs) through the CCL22/CCR4 axis. It is expressed by cells in the tumor microenvironment (TME) in many different cancer tissues including breast, lung, and pancreatic cancer and is thought to promote the suppression of anti-cancer immunity. Recently, we described that CCL22-specific T-cells from cancer patients can kill CCL22-expressing tumor cells, and activation of CCL22-specific T cells may directly influence the CCL22 concentration in the TME, suggesting that CCL22 may be an interesting target for an immune modulatory vaccine. Thus, in the present study we have targeted CCL22-expressing cells by activation of CCL22-specific effector T cells by peptide vaccination in tumor models. We present here that CCL22-targeting peptide vaccination leads to expansion of predominantly CD8+, IFNγ-secreting CCL22-specific T cells in both BALB/c and C57BL/6 mice. Furthermore, CCL22 vaccination results in delayed tumor growth and enhanced survival in tumor harboring hosts in CT26 and Pan02 models. Preliminary assessment of gene expression in the tumors reveals that CCL22 vaccination leads to a reduction of CCL22 expression, alongside other immune suppressive molecules, such as IDO1 in the TME. Characterization of vaccine-mediated changes of cellular composition of the TME is currently ongoing. In conclusion, our findings provide a rationale for a novel cancer immunotherapy to target the immune suppressive TME. Citation Format: Ines Lecoq, Katharina L. Kopp, Rikke Christensen, Ayako W. Pedersen, Evelina Martinenaite, Mai-Britt Zocca, Mads H. Andersen. Therapeutic potential of an immune modulatory CCL22-based vaccine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 5020.