877. Differential Expression of Indoleamine 2,3-dioxygenase (IDO) by Endothelial Cells and Its Overexpression by Gene Transfer: Implications for Cardiovascular Biology

Abstract

Background: Indoleamine 2,3-dioxygenase (IDO) is an important enzyme in the regulation of immune responses. The cells that express IDO can suppress T cell responses and promote tolerance. We have investigated the role of IDO expression by vascular endothelial cells and its overexpression by gene transfer and its consequence on immunoregulation. Many studies have now indicated that in atherosclerosis, there is a defect in the immunoregulation1. Thus far, very few investigations have been conducted to modify this defective component of immune system. We have therefore explored the role of IDO following gene transfer on immune system with a long-term goal to modulate alloresponse or atherosclerotic process. Methods ? Results: We compared the expression of IDO by primary human umbilical vein endothelial cells (HUVECs) (fetal tissues) and human saphenous vein endothelial cells (HSVECs) (adult tissues) using reverse transcriptase PCR, Western blotting and assays for enzymatic activity. IDO is constitutively expressed by HUVECs, and can be upregulated by incubation with cytokines. On the other hand, HSVEC express little IDO, which is poorly upregulated upon activation (except by mycoplasma). Inhibition of IDO activity improved the ability of HUVEC to stimulate allogeneic T cell responses. If either HUVEC or HSVEC are transfected with the gene encoding IDO then they are incapable of stimulating allogeneic T cell responses, and induce anergy in allospecific T cells, which can also act as regulatory cells. Using our immunolipoplexes targeting specifically against vascular EC 2,3, IDO construct was successfully transfected into HUVEC and HSVEC. This resulted in a functional effect on T cell tolerance induction. These data indicate that IDO is a good therapeutic gene to modulate rejection process or to modulate that the immune components seen in the chronic atherosclerosis. Conclusion: The variable expression of IDO in different endothelial cells is important not only in understanding the role of endothelial cells in the regulation of immune responses, but also as a potential therapeutic strategy through a gene-based treatment to modulate the alloresponse or the immune component of the atherosclerosis.Reference:1. Mallat, Z. et al. Induction of a regulatory T cell type 1 response reduces the development of atherosclerosis in apolipoprotein E-knockout mice. Circulation108, 1232–7 (2003).2. Tan, P. H. et al. Antibody targeted gene transfer to endothelium. J Gene Med5, 311–323 (2003).3. Tan, P. H. et al. Immunolipoplexes: an efficient, nonviral alternative for transfection of human dendritic cells with potential for clinical vaccination. Mol Ther11, 790–800 (2005). Background: Indoleamine 2,3-dioxygenase (IDO) is an important enzyme in the regulation of immune responses. The cells that express IDO can suppress T cell responses and promote tolerance. We have investigated the role of IDO expression by vascular endothelial cells and its overexpression by gene transfer and its consequence on immunoregulation. Many studies have now indicated that in atherosclerosis, there is a defect in the immunoregulation1. Thus far, very few investigations have been conducted to modify this defective component of immune system. We have therefore explored the role of IDO following gene transfer on immune system with a long-term goal to modulate alloresponse or atherosclerotic process. Methods ? Results: We compared the expression of IDO by primary human umbilical vein endothelial cells (HUVECs) (fetal tissues) and human saphenous vein endothelial cells (HSVECs) (adult tissues) using reverse transcriptase PCR, Western blotting and assays for enzymatic activity. IDO is constitutively expressed by HUVECs, and can be upregulated by incubation with cytokines. On the other hand, HSVEC express little IDO, which is poorly upregulated upon activation (except by mycoplasma). Inhibition of IDO activity improved the ability of HUVEC to stimulate allogeneic T cell responses. If either HUVEC or HSVEC are transfected with the gene encoding IDO then they are incapable of stimulating allogeneic T cell responses, and induce anergy in allospecific T cells, which can also act as regulatory cells. Using our immunolipoplexes targeting specifically against vascular EC 2,3, IDO construct was successfully transfected into HUVEC and HSVEC. This resulted in a functional effect on T cell tolerance induction. These data indicate that IDO is a good therapeutic gene to modulate rejection process or to modulate that the immune components seen in the chronic atherosclerosis. Conclusion: The variable expression of IDO in different endothelial cells is important not only in understanding the role of endothelial cells in the regulation of immune responses, but also as a potential therapeutic strategy through a gene-based treatment to modulate the alloresponse or the immune component of the atherosclerosis. Reference: 1. Mallat, Z. et al. Induction of a regulatory T cell type 1 response reduces the development of atherosclerosis in apolipoprotein E-knockout mice. Circulation108, 1232–7 (2003). 2. Tan, P. H. et al. Antibody targeted gene transfer to endothelium. J Gene Med5, 311–323 (2003). 3. Tan, P. H. et al. Immunolipoplexes: an efficient, nonviral alternative for transfection of human dendritic cells with potential for clinical vaccination. Mol Ther11, 790–800 (2005).