Modulation Of Immune Responses Induced By Gene-Transduced Dendritic Cells.

115 Recent clinical and animal studies suggest that dendritic (DC) pulsed with specific peptide antigens and injected back into the host can provide strong immune regulatory responses. The critical role of DCs in organ transplantation has been clearly recognized. Therefore, this study intended to explore the ability of DCs to modulate immune stimulatory responses. Results from these studies may provide alternate means of modulation of immune responses against solid organ transplants. Human DCs were infected with an adenoviral vector (AdLacZ) expressing the LacZ gene. Our results show that 30-40% of peripheral blood and umbilical cord blood derived dendritic cells express high levels of β-Gal after infection with the AdLacZ virus. These results also demonstrated that transduction with adenoviral vectors did not inhibit the function of the DCs as measured by their mixed lymphocyte reaction (MLR) stimulatory capacity. We next wanted to examine whether the function of DCs could be modulated by transduction of the B7 adhesion molecule and CTLA-4Ig. For these experiments, adenoviral vectors were designed to express both the B7 and the AdCTLA-4Ig gene products. Adenoviral transduction of human DCs with the mouse B7 gene demonstrated efficient expression of the mouse B7 gene product. Thus, 25-30% of the B7 transduced human DCs expressed the mouse B7 antigen on the surface. Mixed Leukocyte Reaction (MLR) cultures were then established between allogenic T cells and DCs transduced with a control adenoviral vector and adenoviral vectors expressing the B7 and the CTLA-4Ig genes. The results show that adenoviral expression of the mouse B7 significantly enhance the MLR stimulatory capacity of the transduced DCs. In contrast, expression of CTLA-4Ig reduced the MLR stimulatory capacity of the transduced cells. These results are consistent with the expected inhibitory effect of soluble CTLA-4Ig on B7 and CD28 interaction. In summary, these studies demonstrate the potential effect of immune modulation of DCs. In vivo studies are currently examining of the potential use of gene transduction of DCs in prevention of graft rejection.