Reduktion der Immunogenität von Vorläuferzellen durch Regulation der MHC-Expression
Final Report Abstract
Despite recent improvements in the immunosuppressive regimens, the occurrence of graft rejection based on HLA mismatch remains a relevant problem after allogeneic transplantation. In addition, long-term immunosuppressive therapies have undesirable side effects which also may compromise the patient's life such as the development of hematological malignancies. Therefore, we investigated whether the genetic modification of the graft by knocking down the expression of HLA class I and/or class II expression would be effective in the prevention of an antibody or cell-based immune response against the allogeneic tissue, but maintaining the capacity to mount effective immune responses against pathogens or cancer cells. Previously, we have shown the feasibility of silencing HLA class I expression on adult cell types. During this project, we have silenced the expression of HLA class I in CD34+ hematopoietic progenitor cells. Furthermore, we have shown the possibility of differentiating HLA deficient cells from those genetically modified progenitor cells. HLA-free platelets differentiated from HLA-silenced CD34+progenitor cells presented morphological and phenotypic characteristics similar to blood derived platelets. Moreover, HLA-free platelets showed to be functional as demonstrated in aggregation assays or by the upregulation of activation markers in response to extracellular stimulus. HLA class II mismatches may also cause acute or chronic rejection. In this work, we have silenced the expression of HLA class II molecules (HLA-DM and HLA-DR). We have demonstrated that the knockdown of HLA-DR molecules expression efficiently prevents the activation of CD4+ T-cell responses. CD4+ T-cells demonstrated a decreased proliferative capacity when exposed to HLA-DR silenced allogeneic cells in comparison to non-modified cells. In addition, levels of granzyme B mRNA or Interferon-gamma secretion by CD4+ T-cells were significantly reduced in presence of HLA-DR silenced cells. One of the major findings of this work were achieved by the transplantation of MHC class I silenced cells in a rat transplantation model. We have shown that MHC class I silenced cells transplanted in an allogeneic setting were able to surviye and did not induce the activation of effector cells. In contrast, non-modified cells were rejected when transplanted in the allogeneic cells. The results generated by this project demonstrated that silencing of MHC proteins does not affect cell function or survival but efficiently prevents the allogeneic immune response in vitro and in vivo. These data strongly supports further studies for the translation of HLA silencing into the clinic and represents an alternative method to induce tolerance in transplantation.
Publications
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Gene therapy in the transplantation of allogeneic organs and stem cells. Curr Gene Ther 2007; 7: 458-68
Horn PA, Figueiredo C, Kiem HP
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Embryonic Stem Cells: MHC Expression and Immunogenicity of Stem Cell-Derived Cellular Therapeutics. 2010; 165-198. In: Advances in Medicina and Biology - Vol. 1, Nova Science Publishers, Inc. Editor: Leori V. Berhardt
Fleischmann G, Figueiredo C, Seltsam A, Blasczyk R, Horn PA
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Generation of HLA-deficient platelets from hematopoietic progenitor cells. Transfusion, 2010; 50(8):1690-701
Figueiredo C, Goudeva L, Eiz-Vesper B, Horn PA, Blasczyk R, Seltsam A
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HLA-G expression in human embryonic stem cells and preimplantation embryos. J Immunol., 2011; 186(4):2663-2671
Verloes A, Van de Velde H, LeMaoult J, Mateizel I, Cauffman G. Horn PA, Carosella ED, Devroey P, De Waele M, Rebmann V, Vercammen M
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Regulation of HLA class II expression prevents allogeneic T-cell responses. Tissue Antigens. 2011 ;77(1 ):36-44
Jaimes Y, Seltsam A, Eiz-Vesper B, Blasczyk R, Figueiredo C
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The importance of HLA-G expression in embryos, trophoblast cells, and embryonic stem cells. Cell Mol Life Sci. 2011;68(3):341-52
Rizzo R, Vercammen M, van de Velde H, Horn PA, Rebmann V
