MYELOID DENDRITIC CELLS RETROVIRALLY TRANSDUCED TO EXPRESS VIRAL IL-10 PROMOTE TUMOR GROWTH INHIBIT IFN-γ PRODUCTION AND CTL GENERATION IN VIVO

Abstract

968 Dendritic cells (DCs) are important antigen-presenting cells (APC) that play critical roles in the initiation and modulation of immune responses, and may determine the balance between tolerance and immunity. DC genetically engineered to express immunosuppressive molecule(s) may offer potential for therapy of T cell-mediated immune responses, such as allograft rejection. Viral IL-10 (vIL-10), encoded by the Epstein Barr virus, is highly homologous to the immunosuppressive cytokine, mammalian IL-10 (mIL-10). It impairs APC function, but lacks certain immunostimulatory properties of mIL-10. Retroviral delivery of vIL-10 to DC impairs their T cell stimulatory activity, and induces antigenspecific hyporesponsiveness in vitro. The Aim here was to determine the influence of vIL-10 gene-modified DC on growth of transplanted tumors, IFN-γ production, and cytotoxic T lymphocyte (CTL) generation in vivoMethods: DC progenitors propagated from bone marrow cells of C57BL6 (H2b) mice in granulocyte-macrophage colony-stimulating factor (GM-CSF) + IL-4 were transduced by the centrifugal enhancement method, using retroviral supernatant obtained from the Cre ecotropic packaging cell line. MCA205 (H2b) sarcoma cells mixed with either vIL-10-transduced DC or enhanced green fluorescence protein (EGFP; marker gene)-transduced DC were inoculated intradermally into C57BL6 mice. The influence of the DC on host resistance to the MCA205 tumor cells was assessed by measurement of tumor growth, tumor-specific CTL activity (Effector:Target ratio; 50:1) both in draining lymph node or spleen, and IFN-γ production by ex vivo tumor cell-stimulated lymphocytes obtained from the draining lymph node and spleen of tumor-bearing animals. Results: Compared to control gene-modified DC, vIL-10-transduced DC promoted tumor growth (155%; on day 7 after inoculation of cells), inhibited CTL activity both in draining lymph node (11% reduction) and spleen (40% reduction), and suppressed IFN-γ production by host lymphocytes (lymph node; 50% reduction, spleen; 38% reduction). Conclusion: vIL-10 genetically-engineered DC have potential for the in vivo inhibition of T cell-mediated immune responses. (Supported by NIH-AI-41011)