ITOC2 – 028. Transgenic antigen-specific, allogeneic HLA-A∗0201-restricted cytotoxic T cells recogniae tumour-associated target antigen STEAP1 with high specificity

Abstract

Background Ewing Sarcoma (ES) patients with disseminated disease into lung and bone have an approximate long-term survival rate of 10–30%, compelling the search for new therapeutic treatment modalities including engineered T cell therapy. Here, the specific recognition and lytic potential of transgenic allo-restricted CD8+ T cells directed against the ES-associated antigen STEAP1 was examined. Methods Following repetitive STEAP1130 peptide-driven stimulations with HLA-A∗0201+ dendritic cells, allo-restricted HLA-A∗0201- CD8+ T cells were sorted with HLA-A∗0201/peptide multimers and expanded by limiting dilution. After functional analysis of suitable T cell clones via ELISpot, flow cytometry and xCelligence assay, TCR α and β chains were identified, cloned into retroviral vectors, codon optimised, transfected into HLA-A∗0201– primary T cell populations and tested again for specificity and lytic capacity. Results Initially generated as well as transgenic T cells specifically recognised STEAP1130 pulsed or transfected cells in the context of HLA-A∗0201 with minimal cross-reactivity as determined by specificinterferon (IFN)-γ release, lysed cells and inhibited growth of HLA-A∗0201+ ES lines more effectively than HLA-A∗0201– ES lines. Conclusion Our results identify TCRs capable of recognising and inhibiting growth of STEAP1 expressing HLA-A∗0201+ ES cells in a highly restricted manner. Such STEAP1 specific TCRs are potentially useful for immunotherapy of other STEAP1 expressing tumours