Adult and cord blood T cells can acquire HA-1 specificity through HA-1 T-cell receptor gene transfer

Background and Objectives. Minor histocompatibility antigen (mHag)-specific graft-versus-leukemia reactivities are observed following unselected donor lymphocyte infusion for the treatment of relapse after HLA-matched mHag-mismatched stem cell transplantation (SCT). Adoptive transfer of donor-derived ex vivo-generated HA-1-specific oligoclonal T cells or HA-1 peptide patient vaccination are currently being explored as curative tools for stem cell based immunotherapy of hematologic malignancies. Another treatment modality to eradicate residual leukemic cells after SCT is the transfer of the HA-1 hematopoietic-specific T-cell receptor (TCR) into cells from the stem cell donor. This strategy would be particularly useful in case of relapse after cord blood transplantation (CBT) and is explored in this study. Design and Methods. HLA-A2^neg adult peripheral blood and cord blood mononuclear cells were transduced with the genes encoding the HA-1α and β TCR chains derived from established HA-1 specific cytotoxic T lymphocyte clones. Results. The T cells transduced with HA-1 TCRαβ showed consistent marker gene expression, but low staining with HLA-A2/HA-1 tetrameric complexes. They did, however, show hematopoietic-restricted cytolytic activity against HLA-A2 ^pos/HA-1^pos target cells, including leukemic cells. Interpretation and Conclusions. The low level of HA-1-specific tetramer staining of HA-1 TCRαβ transduced T cells may be caused by hybrid TCR formation of the transferred TCRα and β chains with endogenous TCRα and β chains. This may cause unwanted alloreactivity and requires attention. The HA-1 TCRαβ transduced T cells show that the HA-1 TCR can be functionally transferred into donor mononuclear cells, which can be exploited in immunotherapeutic settings of SCT and CBT for hematologic malignancies.