Lack of T-Cell-mediated Recognition of the Fusion Region of the pmLIRAR-a Hybrid Protein by Lymphocytes of Acute Promyelocytic Leukemia Patients’

In previous studies, it was shown that the fusion region of the pmIIRAR-a protein, expressed by acute promyelocytic leukemia (APL) cells, can be specifically recognized in vitro by donor (D. E.) CD4 T cells in a HLA class II DR11restricted fashion. We present here the results on the recognition of several pm1IRAR-a peptides by APL patients expressing HLA DR1 1. The in vitro immunization of penipheral blood lymphocytes from four patients in remission (S. R., F. R., M. M., P. G.) with BCR1/25, a 25-men pml/ RAR-a, did not elicit either a polyclonal or a clonal immune response specific to the peptide. We then generated new donor anti-pmlIRAR-a CD4 1-cell clones. These clones were tested for their recognition of BCR1/25. One clone (C3/5, CD3 , CD4 , CD8) was selected for further analysis. Clone C3/5 showed specific proliferation, cytotoxicity, and cytokine (tumor necrosis factor a, granulocyte-macrophage colony-stimulating factor) production when challenged with autologous lymphoblastic cell lines pulsed with peptide BCR1/25. C3/5 cells developed specific proliferation and cytotoxicity when challenged with peptide-pulsed lymphoblastic cell lines and peripheral blood lymphocytes from the four DR1 1 APL patients. APL blasts, available only from patients F. R. and P. G., were not lysed by C3/5 and were unable to present peptide BCR1/25. Incubation of APL cells with IFNj failed to induce HLA class II molecules and recognition by the C3/5 clone. Since APL cells do not express HLA class II molecules, we tested in two donors (D. E. and C. H. R.) and in patients S. R. and P. G. whether the use of 9-mer peptides (BCR1/9) would generate a CD8IHLA class I-restricted response. No peptide-specific 1-cell line or clone Received 6/15/95; revised 10/18/95: accepted 1 1/28/95. I This work was supported in part by the Italian Association tir Cancer Research. the Italy-United States Program on Therapy ofTumors (Grant 531 23.12.87). and a donation from CEVA SpA, Monza. 2 To whom requests for reprints should be addressed. Phone: 39.2.2390207: Fax: 39.2.236-2692. could be generated from both donors and patients. These findings are discussed in relation to possible therapeutic approaches to the immunotherapy of APL.