A T-cell epitope determined with random peptide libraries and combinatorial peptide chemistry stimulates T cells specific for cutaneous T-cell lymphoma

Background: Mycosis fungoides is the most frequent T-cell lymphoma of the s kin. Despite numerous attempts, no tumour antigens have yet been identified . Only in one case has an idiotype-derived peptide been found to trigger CT L of the respective patient. The identification of natural antigens require s the cultivation of large amounts of tumour cells in vitro, which has been possible in two exceptional cases. The identification of synthetic epitope s for tumour-specific CTL with random peptide libraries can overcome this l imitation and is a powerful tool for application in the development of immu ne therapies for a wide range of patients. Materials and methods: The critical amino acids for the construction of epi topes for the CTCL-specific CTL clone My-La CTL were determined with synthe tic peptide libraries in positional scanning OX8 format in a standard (61)c hromium release assay. Sixteen different peptides could be synthesized from the combinatoric of these amino acids with the canonical anchor amino acid s for MHC binding. These peptides were tested for their capacity to stimula te My-La CTL and PBMC of an HLA-matched CTCL patient. Results: A synthetic epitope could be identified for My-La CTL, which was r ecognized in a HLA-restricted manner. The response towards this epitope was comparable to the response towards their natural target My-La. Using these synthetic spite pes, T cells of a HLA-matched patient could be induced in vitro and led to the establishment of different cell lines and clones. Some of these lints recognized the peptides as well as the allogenic but HLA-ma tched tumour cell line My-La, indicating that they are specific for a natur ally expressed tumour antigen. Conclusions: The identification of synthetic epitopes for tumour-specific C TL clones can be used for the development of vaccines for immune therapies of cancer: such peptides can be applied inter-individually. Synthetic epito pes must not correspond to the natural ones, but they can be even more pote nt as stimulation of specific T cells and can be fine-tuned to increase the success of the therapy.