Poster Session I: Gene therapy, cellular immunotherapy and vaccination - Biology & translational research
Melanoma-associated antigens (MAGE) are highly expressed in multiple myelomas as well as solid tumors, but silent in normal cells except for male germ line cells. This tumor-restricted expression makes it an excellent target for adoptive T cell therapy. However, due to thymic selection high-affinity T cells against self-antigens presented in the context of self-HLA are deleted from the T-cell repertoire of a patient. To overcome this problem, we identify T-cell receptors (TCRs) from the allogeneic-HLA repertoire instead of the autologous-HLA repertoire.
To identify high-affinity T-cell receptors from the allogeneic-HLA repertoire specific for melanoma-associated antigens.
In this study we selected MAGE peptides by peptide elution experiments from HLA class I and subsequent mass spectrometric analysis of tumor cells. Only peptides binding in the most frequently occurring HLA-alleles were selected. From the identified peptides, HLA-tetramers were formed to isolate peptide specific CD8+ T cells from healthy allogeneic donors. Avidity of the selected T-cell clones was determined by stimulation assays including a broad range of MAGE expressing tumor cell lines. To examine off-target recognition, T-cell clones were stimulated with MAGE negative cell lines and EBV-transformed B lymphoblastic cells expressing all prevalent HLA molecules.
MAGE peptides were eluted from multiple myelomas, EBV-transformed lymphoblastic cells, acute myeloid leukemia and ovarium carcinomas. For MAGE-A1, T-cell clones specific for four different epitopes presented in the context of HLA-A*01:01, HLA-A*03:01, HLA-B*07:02 and HLA-C*07:02 were selected. For MAGE-A3, T-cell clones specific for one epitope presented in the context of HLA-A*01:01 and HLA-B*35:01 were identified. The selected T-cell clones demonstrated efficient recognition of MAGE-A1 or MAGE-A3 positive multiple myeloma and solid tumor cell lines without detectable cross-reactivity.
MAGE-A1 and MAGE-A3 specific T-cell clones were isolated from the allogeneic-HLA repertoire of healthy individuals. The identified clones were activated upon exposure to MAGE-A1 or MAGE-A3 positive tumor cell lines and showed limited off-target recognition. These newly identified TCRs could potentially be used for TCR-gene therapy strategies targeting MAGE-A1 or MAGE-A3 positive tumors.