Abstract B057: Optimizing the High Throughput in Vitro Priming of Tumor Specific T Cells

Peptide-based vaccines are a promising strategy for immunotherapy against cancer. Our group has characterized large numbers of HLA ligands from tumor cells; among them many that might be used for in vivo induction of tumor-specific immune responses. For the development of peptide-based immunotherapies such peptides should be able to induce in vivo tumor-directed immune responses, especially by CD8+ T cells that have a key role in inducing death of tumor cells. The aim of our work is to establish a fast and efficient workflow for immunogenicity testing of tumor-extracted HLA ligands. T cells usually depend on professional antigen presenting cells such as autologous dendritic cells (DCs) for specific induction and expansion. Since the generation of dendritic cells is expensive and time consuming with varying quality and amount of differentiated DCs, we established an artificial system to replace cell-based in vitro priming of T cells, streptavidin-coated artificial antigen presenting cells loaded with defined amounts of recombinant HLA molecules and costimulatory antibodies such as anti-CD28. Using the standard protocol, CD8+ T cells are stimulated three times with artificial antigen presenting cells in weekly intervals in the presence of IL-2 and IL-12. Peptide-specific CD8+ T cells are identified by tetramer staining. Our group started to vary different parameters of this protocol to increase the frequency and number of antigen specific T cells. Alternate costimulatory antibodies and cytokines proved successful to reach that goal. Employing artificial APCs for in vitro priming of tumor-reactive T cells will foster immunogenicity analysis of novel peptides for immunotherapy. Citation Format: Lea Prokop, Stefanie Souczek, Janet Peper, Hans-Georg Rammensee, Stefan Stevanovic. Optimizing the high throughput in vitro priming of tumor specific T cells. [abstract]. In: Proceedings of the CRI-CIMT-EATI-AACR Inaugural International Cancer Immunotherapy Conference: Translating Science into Survival; September 16-19, 2015; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2016;4(1 Suppl):Abstract nr B057.