Nonmyeloablative bone marrow transplant offers a safe, potentially curative treatment for non-malignant hematological diseases such as sickle cell anemia. Unfortunately, successful nonmyeloablative transplant to treat sickle cell anemia has been limited due to immune-mediated graft rejection. Our research has demonstrated that rapamycin can promote regulatory T cell (Treg) differentiation of naive T cells and anergy of Th1 cells following T cell activation. We used these observations to develop a novel preparative regimen to inhibit rejection and graft versus host disease (GVHD) by promoting T cell tolerance. Our strategy reduces the frequency of alloreactive T cells with alemtuzumab, creates "space" for engraftment with low dose total body irradiation, and allows lymphocyte recovery under extended rapamycin treatment. In the matched sibling setting this approach has had great success, resulting in stable mixed chimerism that corrects their hematological phenotype of sickle cell anemia and reverses pulmonary hypertension. Based on this success, a second clinical trial was developed to expand the potential donor pool to include haploidentical related donors, greatly increasing potential availability of this therapy to patients. The new trial employs the same fundamental principles in the choice of preparative regimen with the addition of dose escalation of post transplant cyclophosphamide to further reduce alloreactive T cells that could contribute to rejection or GVHD. Peripheral blood samples from patients and donors on this trial will provide a unique opportunity to systematically investigate the role of T cell tolerance in promoting stable chimerism. We propose to do this by examination of mixed lymphocyte reactions (MLRs) and intracellular cytokine staining (ICS) from samples obtained pretransplant, posttransplant on rapamycin, and posttransplant after completion of rapamycin therapy. We will determine whether the continued presence of rapamycin is necessary to suppress allogeneic responses in vitro and whether the tolerance measured in the MLR is dependent on the presence of Tregs. We will test whether addition of rapamycin or Tregs is able to suppress the MLR from a patient who develops graft rejection or GVHD while receiving rapamycin. We will determine if clinical resistance to rapamycin in the form of rejection or GVHD corresponds to biochemical resistance to rapamycin at the level of mTOR target phosphorylation and whether a novel mTOR kinase inhibitor can overcome such biochemical resistance in vitro.
A final aim i s to determine whether prolonged mTOR inhibition interferes with antigen specific T cell cytokine production or leads to generation of antigen specific Tregs to clinically relevant CMV or influenza A. We believe that a better understanding of the immunologic consequences of mTOR inhibition will result in safer and more successful bone marrow transplantation, allowing expansion of this potentially curative therapy to a wider number of patients with chronic hematologic illnesses.
(provided by applicant): Sickle cell anemia and other chronic anemias impose a huge burden of pain and suffering for patients and large health care costs related to hospitalizations and chronic transfusion/chelation therapy. In this proposal we seek to define the operative cellular and biochemical processes that promote T cell tolerance in a novel protocol to cure sickle cell disease with non-myeloablative bone marrow transplantation. It is hoped that the results of this study will allow safer application of this curative therapy to a greater number of patients and aid in improving tolerogenic therapy for autoimmunity and solid organ transplantation as well.
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|Delgoffe, Greg M; Powell, Jonathan D (2015) Feeding an army: The metabolism of T cells in activation, anergy, and exhaustion. Mol Immunol 68:492-6|
|Pollizzi, Kristen N; Powell, Jonathan D (2015) Regulation of T cells by mTOR: the known knowns and the known unknowns. Trends Immunol 36:13-20|
|Pollizzi, Kristen N; Patel, Chirag H; Sun, Im-Hong et al. (2015) mTORC1 and mTORC2 selectively regulate CD8âº T cell differentiation. J Clin Invest 125:2090-108|
|Lee, Chen-Fang; Lo, Ying-Chun; Cheng, Chih-Hsien et al. (2015) Preventing Allograft Rejection by Targeting Immune Metabolism. Cell Rep 13:760-70|
|Delgoffe, Greg M; Powell, Jonathan D (2015) Sugar, fat, and protein: new insights into what T cells crave. Curr Opin Immunol 33:49-54|
|Pollizzi, Kristen N; Waickman, Adam T; Patel, Chirag H et al. (2015) Cellular size as a means of tracking mTOR activity and cell fate of CD4+ T cells upon antigen recognition. PLoS One 10:e0121710|
|Heikamp, Emily B; Patel, Chirag H; Collins, Sam et al. (2014) The AGC kinase SGK1 regulates TH1 and TH2 differentiation downstream of the mTORC2 complex. Nat Immunol 15:457-64|
|Pollizzi, Kristen N; Powell, Jonathan D (2014) Integrating canonical and metabolic signalling programmes in the regulation of T cell responses. Nat Rev Immunol 14:435-46|
|Powell, Jonathan D; Heikamp, Emily B; Pollizzi, Kristen N et al. (2013) A modified model of T-cell differentiation based on mTOR activity and metabolism. Cold Spring Harb Symp Quant Biol 78:125-30|
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