Allo-specific T-cells encoding for viral IL-10 exert strong immunomodulatory effects in vitro but fail to prevent graft rejection

Recently, we demonstrated the capacity of allo-specific gene-engineered T lymphocytes as transport vehicle for therapeutic transgenes into allografts. In this study, the influence of viral IL-10 as therapeutic transgene was addressed. Lewis rat T-cell lines specific for DA rat alloantigens were engineered to express vIL-10 by using a retroviral gene expression system. Like T regulatory 1 cells, vIL-10 transgenic T lymphocytes express the phenotype CD4 ⁺25⁺ and secrete, in addition to vIL-10, rat IL-10 and IFN-7 but no IL-4. First, the capacity of vIL-10 transgenic T-cell lines to modulate alloantigen-specific immune responses was evaluated in vitro. In comparison to control MLR with no transgenic cells of equal numbers of control T_EGFP-lymphocytes, the proliferation as well as production of IFN-γ by naive responder cells were significantly diminished. Despite this regulatory capacity in vitro, T_vIL-10-lmphocytes were not able, either alone or in combination with suboptimal doses of Cyclosporine A, to prolong the survival of either DA rat cardiac or renal allografts in Lewis rat recipients. These data demonstrate that intra-graft IL-10 over-expression is not sufficient to prolong allograft survival in a high-responder strain combination and that the regulatory capacity of T cells in vitro does not predict their in vivo efficiency.