Retroviral delivery of transforming growth factor-??1 to myeloid dendritic cells: inhibition of T-cell priming ability and influence on allograft survival12

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Abstract
Background. Transforming growth factor (TGF)-β inhibits the maturation and function of antigen-presenting cells. Our purpose was to evaluate the impact of retroviral delivery of human TGF-β1 to murine myeloid dendritic cell (DC) progenitors on (i) their in vitro properties, (ii) their in vivo function, and (iii) their influence on organ allograft survival. Methods. C57BL10 (B10; H2b) bone marrow cells were lineage depleted and stimulated with granulocyte-macrophage colony-stimulating factor for 6 days. Replicating DC progenitors were transduced on days 2, 3, and 4 of culture by ecotropic retrovirus encoding human TGF-β1 using centrifugal enhancement. Secretion of TGF-β1 and other cytokines was quantified by enzyme immunoassay. Allogeneic C3H/HeJ (C3H; H2k) T-cell proliferative responses and generation of cytotoxic T lymphocytes in mixed leukocyte reaction were determined by [3H]thymidine incorporation and 51Cr release assays, respectively. DC migration was analyzed by immunohistochemistry, and their impact on survival of intra-abdominal heart transplants was determined. Results. Maximal TGF-β1 transduction efficiency was 60%. The TGF-β–transduced DC showed pronounced impairment (>80%) of T-cell allostimulatory activity in vitro. After their IV injection, B10 TGF-β-transduced DC (IAb+) were detected in T-cell areas of spleens of allogeneic C3H recipients. Splenic T-cell responses to donor alloantigens of mice that received TGF-β–transduced DC were severely impaired. This was accompanied by marked inhibition of interleukin-2 and interferon-γ production in response to restimulation with donor alloantigen. Survival of B10 cardiac allografts in C3H mice given B10 TGF-β–transduced DC (2×106 IV, 7 days before transplantation), was extended modestly but significantly. Conclusion. Retroviral transduction of myeloid DC progenitors to overexpress TGF-β is associated with marked impairment of their T-cell allostimulatory activity but with only modest prolongation of organ allograft survival.