Immunotherapy to treat Hematological Malignancies

Leukemia, lymphoma and myeloma together account for about 500.000 deaths per year worldwide. Often, the only curative treatment for patients suffering from these hematological malignancies is allogeneic stem cell transplantation (allo-SCT) from an MHC-matched donor. The transplant not only consists of stem cells, but also of T cells. These T cells mediate severe Graft versus Host Disease (GvHD) as well as the beneficial Graft versus Tumor (GvT) effect. The epitopes recognized by T cells after MHC-matched allo-SCT are called minor Histocompatibility antigens (mHags). mHags are peptides derived from polymorphic intracellular proteins. Because the stem cell patient has another polymorphism in this protein than the donor, T cells against this peptide were not depleted during T cell development in the donor.

Since some mHags are derived from hematopoietic system-specific proteins, targeting donor T cells to these mHags can induce a GvT effect without GvHD. The recent identification of a first series of hematopoietic mHags made it indeed possible to develop mHag-specific immunotherapy for recurrent leukemia patients after allo-SCT. Yet, the applicability of the therapy is limited to a small fraction of patients, because many of the identified hematopoietic mHags are presented by infrequent MHC molecules or display unfavorable allele frequencies. The key priority for extending the applicability of mHag-specific therapy to a broad spectrum of recipients is the identification of a large array of clinically useful mHags.
The accomplishment of this important task requires a systematic and highly focused approach. Therefore we developed two different strategies, which we believe are two excellent student projects.

Project 1

For identification of novel mHags we can use a "mHag-specific" reverse immunology strategy, which is the only systematical approach offering the possibility to specifically search for mHags derived from known hematopoietic-specific proteins with balanced allele frequencies and are presented by desired HLA molecules. Unique in our strategy is that we apply a mHag-specific algorithm, which searches for single aminoacid polymorphisms that alter surface expression of the allelic peptides. The approach enables us to focus on the most probable mHag candidates. We have already performed the predictions and are at the time point of proving the accuracy of this method. The generation of cytotoxic T cells against the mHags using dendritic cells out of healthy donor peripheral blood cells is the next step. Here after the T cells will be tested for their reactivity against malignant and non-malignant hematopoietic cells. We already have performed promising pilot experiments for this project and want to offer a student the unique opportunity to expand these and identify a true and novel mHag.

Project 2

The other strategy can be classified as a forward immunology strategy. For this project mHag specific cytotoxic T cell clones will be generated from patients who had a strong anti-tumor response after MHC-matched allo-SCT. In order to attack the exciting puzzle of what the exact mHag peptide sequence is (recognized by a mHag specific T cell), we very recently developed a revolutionary technique (unpublished results). The genetic approach used for this will reveal a narrow genomic area where the mHag encoding gene is located. Analysis of this region and than identification of the polymorphism encoding for the mHag are also part of the project. Furthermore the student gets the opportunity to show the immunotherapeutic potential of these newly identified mHags in various functional and patient based assays.

Project 1: Peptide binding assays; FACS analysis; culture of dendritic cells, T cells, malignant hematopoietic cells; handling peripheral blood;IFN-gamma capture assay; ELISA; cytotoxic experiments.
Project 2: Culture of different cell lines and T cells; FACS analysis; ELISA; genetic approaches using families; biochemical techniques including PCR, gene cloning and sequencing; transfections; retroviral gene transductions; cytotoxic experiments; tetramer stainings.

Duration: 6-9 months

Dr. T. Mutis, t.mutis@umcutrecht.nl, tel 088-7556504
Drs. R. Spaapen, r.spaapen@umcutrecht.nl, tel 088-7559771
Dr. K. Denzer, k.denzer@umcutrecht.nl, tel 088-7557673
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