The receptor for hyaluronic acid-mediated motility induces specific CD8+ T cell response in healthy donors and patients with chronic myeloid leukemia after allogeneic stem cell transplantation

Recently, we described the receptor for hyaluronic acid-mediated motility (RHAMM) as a leukemia-associated antigen and characterized the RHAMM-derived peptide R3 (pos. 165-173: ILSLELMKL) as a CD8+ T cell epitope. Directing CD8+ T lymphocytes specifically to R3 might help to shape the graft-versus-leukemia effect observed after allogeneic stem cell transplantation (allo-SCT). To detect the potential induction of R3-specific cytotoxic T lymphocytes in chronic myeloid leukemia (CML) patients after allo-SCT and healthy donors, we used mixed lymphocyte peptide culture, enzyme-linked immunospot (ELISPOT) release assays for interferon (IFN)-γ and granzyme B, tetramer staining and 51Cr release cytotoxicity assays. The R3 peptide showed the capacity to elicit specific CD8+ T cell responses characterized by the release of IFN-γ and granzyme B upon stimulation with R3-pulsed T2 cells. Responses to R3 peptide were detected in 67% (6/9) of the CML patients after allo-SCT and 24% (8/34) of healthy donors in ELISPOT assays for IFN-γ and granzyme B. These R3-specific CD8+ T cells comprised predominantly effector cells (CCR7-CD45RA+ or CD27-CD45RA+) in patients with CML after allo-SCT or healthy donors respectively. Cytotoxicity assays demonstrated effective lysis of CML progenitor cells by R3-primed CD8+ T lymphocytes. Imatinib inhibited the functional activation of R3-specific CD8+ T lymphocytes. In summary, we demonstrated R3-specific CD8+ effector T lymphocytes after allo-SCT in CML patients which might have been augumented by R3 peptide vaccination and hampered at least partially by imatinib in this particular patient cohort.