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Departments of 1Cardiology, 2Microbiology, 3Nephrology, and 4Rheumatology and 5Transplantation Center, Centre Hospitalier Universitaire Vaudois and Université de Lausanne, Faculté de Biologie et Médicine, Lausanne, Switzerland; and 6Division of Immunogenetics, Department of Pediatrics, Children's Hospital of Pittsburgh, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania
Submitted 25 September 2007 ; accepted in final form 9 October 2007
Cells that express indoleamine 2,3-dioxygenase (IDO), the rate-limiting enzyme in the catabolism of tryptophan, suppress T cell responses and promote immunological tolerance. However, their role in solid organ transplantation is incompletely understood. We analyzed T cell responses to allogeneic dendritic cells (DCs) genetically modified to express the gene encoding IDO in vitro and IDO gene transfer into the donor heart in a cardiac transplant model in vivo. Bone marrow-derived DCs transduced with the gene encoding IDO produced active IDO protein. This was associated with decreased stimulation of allogeneic T cell proliferation in the mixed leukocyte reaction in vitro. In a cardiac transplant model, adenovirus-mediated IDO gene transfer into the donor heart resulted in transgene expression predominantly in cardiomyocytes. Fischer-344 rat donor hearts transduced with the gene encoding IDO survived for longer periods of time when placed in Lewis rat recipients compared with control vector or vehicle alone [median survival times of 17 (range: 12–22) days vs. 10 (range: 8–14) and 9 (range: 8–13) days, respectively, P < 0.0001]. IDO gene transfer combined with low-dose cyclosporin A (CsA) was more effective than CsA alone (P < 0.05). Numbers of monocytes/macrophages, CD4+ cells, and CD8
+ cells infiltrating the graft as well as intragraft cytokine transcript levels for IFN-
, IL-1, TNF-
, regulated upon secretion, normal T cell expressed, and secreted/chemokine (C-C motif) ligand 5 were decreased after IDO gene transfer (P < 0.05). In conclusion, DCs genetically engineered to overexpress IDO modulate T cell alloresponses in vitro. IDO gene transfer into the donor heart attenuates acute cardiac allograft rejection. Regulation of tryptophan catabolism by means of IDO overexpression may be a useful approach in heart transplantation.
dendritic cells; transforming growth factor-β; regulated on activation, normal T-cell expressed and secreted/C-C chemokine ligand 5
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