AbstractBACKGROUND AND OBJECTIVES: Cytotoxic T-lymphocytes (CTL) have been generated in vitro against chronic myeloid leukemia (CML)-associated BCR/ABL-specific peptides. We analyzed the existence of high-avidity T cells recognizing endogenously processed BCR/ABL-specific proteins. DESIGN AND METHODS: We performed binding studies of BCR/ABL-specific peptides, proteosomal digestion of BCR/ABL breakpoint overlapping protein, mass spectrometry of eluates from HLA-*0301-transduced K562 cells, and tried to isolate peptide-specific T-cells using tetramers. RESULTS: We confirmed the binding of the BCR/ABL-specific peptides KQSSKALQR to HLA-A*0301 and GFKQSSKAL to HLA-B*0801. Proteasomal digestion showed cleavage sites leading to KQSSKALQR but not to GFKQSSKAL. Using mass spectrometry KQSSKALQR could not be detected in the eluates from HLA-A*0301-transduced K562 cells. We attempted to induce BCR/ABL-specific CTL lines from 4 healthy donors using dendritic cells pulsed with KQSSKALQR and performed single cell sorting to isolate tetramer-positive T cells. None of 31 generated clones showed BCR/ABL-specific cytotoxicity. Isolation of tetramer-positive cells from peripheral blood of relapsed CML patients after allogeneic transplantation treated with donor lymphocyte infusion resulted in 38 T-cell clones which did not show peptide-specific cytotoxicity. INTERPRETATION AND CONCLUSIONS: We provide evidence that BCR/ABL protein processing can lead to KQSSKALQR peptide binding to HLA-A*0301. However, KQSSKALQR could not be detected in HLA-A*0301-transduced K562 cells, and KQSSKALQR could not be demonstrated to induce high-avidity BCR/ABL-specific CTL.
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Vol. 89 No. 9 (2004): September, 2004 : Comparative Studies
Ferrata Storti Foundation, Pavia, Italy
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