[Minor antigens - major impact. The role of minor histocompatibility antigens in allogeneic hematopoietic stem cell transplantation]. / Kleine Antigene - grosse Wirkung. Die Rolle von Minor-Histokompatibilitätsantigenen bei der allogenen Blutstammzelltransplantation.

Allogeneic hematopoietic cell transplantation (HCT) is often the only curative treatment option for patients with malignant and non-malignant hematological diseases. There is striking evidence that immunological Graft-versus-Leukemia (GvL)-reactions efficiently eradicate malignant cells after transplant. After HLA-matched HCT both the beneficial GvL-effect and the detrimental Graft-versus-Host Disease (GvHD) are mediated by donor derived T-cells specific for minor histocompatibility antigens (mHag) that differ between patient and stem cell donor. In addition, tumor-specific antigens can also be targeted and contribute to GvL-reactivity. This review summarizes the state-of-the-art knowledge on mHag and presents the potential therapeutical options on example of the mHag HA-1. HA-1 is currently the best characterized mHag and particularly attractive for immunotherapy due to the restricted expression on hematopoietic cells and on some solid tumors but not on cells involved during GvHD. This would allow amplifying the endogenous GvL-effect and selectively targeting malignant HA-1-positive cells without causing GvHD. HA-1-specific immunotherapy in eligible patient and donor pairs may range from vaccination with the immunogenic HA-1 peptide to the infusion of HA-1-specific cytotoxic T-cells (adoptive immunotherapy).

Identification of NM23-H2 as a tumour-associated antigen in chronic myeloid leukaemia.

Therapeutic effects of haematopoietic stem cell transplantation are not limited to maximal chemoradiotherapy and subsequent bone marrow regeneration, but include specific as well as unspecific immune reactions known as graft-versus-leukaemia (GvL) effects. Specific immune reactions are likely to be particularly relevant to the long-term treatment of diseases, such as chronic myeloid leukaemia (CML), in which residual cells may remain quiescent and unresponsive to cytotoxic and molecular therapies for long periods of time. Specific GvL effects result from the expression on leukaemic cells of specific tumour-associated antigens (TAAs) in the context of HLA proteins. As human leukocyte antigen (HLA) types vary widely, the development of broadly applicable tumour vaccines will require the identification of multiple TAAs active in different HLA backgrounds. Here, we describe the identification of NM23-H2 as a novel HLA-A32-restricted TAA of CML cells and demonstrate the presence of specifically reactive T cells in a patient 5 years after transplantation. As the NM23 proteins are aberrantly expressed in a range of different tumours, our findings suggest potential applications beyond CML and provide a new avenue of investigation into the molecular mechanisms underlying CML.