Identification and characterization of epitopes of the receptor for hyaluronic acid-mediated motility (RHAMM/CD168) recognized by CD8+ T cells of HLA-A2-positive patients with acute myeloid leukemia

The receptor for hyaluronic acid-mediated motility (RHAMM/CD168) has been described as a leukemia-associated antigen. To define T-cell epitopes of RHAMM/ CD168 toward specific immunotherapies for acute myeloid leukemia (AMIL), 10 potential HLA-A2-binding RHAMM/CD168 pepticles (R1 to R10) were synthesized based on computer algorithms and screened by enzyme-linked immunospot (ELISPOT) analysis using CD8(+) T cells isolated from peripheral blood (PB) of patients with AMIL and healthy donors. We found that CD8(+) cells from 7 of 13 (54%) patients with AML presensitized with peptides R3 (ILSLELMKL) or R5 (SLEENIVIL) specifically recognized T2 cells pulsed with R3 (39%) or R5 (15%) peptide. In contrast, only 4 of 21 (19%) healthy volunteers had CD8(+) cells reactive with R3- or R5-pulsed T2 cells after presensitization. The presence of R3 peptide-specific effector T cells in the peripheral blood of patients with AMIL could be confirmed by staining as HLA-A2/R3 peptide tetramer(+) CCR7-CD45RA(+) cells. In chromium-51 release assays, peptide-primed CD8(+) T cells from patients with AMIL were able to lyse RHAMM/CD168 peptide-pulsed T2 cells, AMIL blasts, and dendritic cells generated thereof (AML DCs). Transfection of COS7 cells with RHAMM/CD168 cDNA revealed that peptides R3 and R5 are naturally processed epitopes of RHAMM/CD168 that are presented in an HLA-A2-restricted manner. In summary, RHAMM/CD168 is a promising target for immunotherapies in patients with AML, and we have therefore initiated a clinical vaccination trial with R3 peptide. Because RHAMM/CD168 is also expressed in various other hematologic malignancies and solid tumors, vaccines targeting this antigen may have even wider application.