Recent clinical reports of allogeneic human islet transplantation provide proof of principle that cell-based diabetes therapy can reverse the course of diabetes mellitus. As demand for islet transplantation increases the human islet donor shortage precludes widespread application. Xenogeneic porcine islets could provide a limitless source of donor cells, if safe and effective protocols are crafted to promote long term islet xenograft survival. The rational design and development of such protocols requires greater understanding of the immunobiology of anti-pig islet immune responses in a preclinical nonhuman primate (NHP) model close to humans. The proposed research program brings together a group of collaborating investigators, combining diverse scientific interests and backgrounds in an endeavor to develop innovative therapeutic approaches for promoting long term pig-to-NHP islet xenograft (XPITx) acceptance without lifelong immunosuppressive therapy. Furthermore, the projects and supporting core facilities are unified in a multidisciplinary effort to elucidate underlying mechanisms related to long term XPITx acceptance and acquired tolerance in diabetic NHP. The program will be centered at the University of Alabama at Birmingham with 2 research projects and 1 administrative core, while the University of Minnesota is the consortium partner with 1 research project and 2 scientific cores. Project 1 will examine the efficacy of tolerance induction to XPITx in diabetic NHP without chronic therapy. The approach will apply a brief (2 wk) tolerance induction protocol that has induced long term allogeneic islet tolerance in NHP. Local and systemic immune adaptations and XPITx outcome will be examined in two anatomic sites, the liver and omental pouch (OP), wherein supplemental immunomodulatory molecules will be delivered. Project 2 will endeavor to engineer the NHP OP to enhance revascularization of the pig islets and to optimize local delivery of immunoregulatory proteins into the islet milieu, including gene transfer using transposon technology in collaboration with Core C. Project 3 will develop low-risk immunotherapeutic strategies to prevent XPITx rejection in liver and OP sites in diabetic NHP, by examining a novel protocol with triple costimulatory blockade. Project 3 will also compare the efficacy and safety of systemic vs. local immunosuppression in the OP XPITx site. Close interactions and data sharing among the projects will accelerate advances in basic understanding and success of NHP XPITx. ? ? PROJECT 1: A New Approach to Tolerance in Islet Xenografts (Thomas, J.) ? ? DESCRIPTION (provided by applicant) Diabetes mellitus (DM) is a leading public health concern, with over 1 million Type 1 DM patients in the USA. The Edmonton Study showed that intrahepatic pancreas islet transplantation can reverse DM, restoring euglycemia. At present, gradual loss of functional islet mass and a requirement for multiple transplants limit widespread application. With the critical shortage of human donors, there is a need for xenogeneic islets. Porcine islets are appealing, since pig insulin is well tolerated in humans, and pigs are adapted to large scale domestic farming. Unlike normal pig endothelial cells that express the galactose a(1,3) galactose (aGal), to which humans and old world nonhuman primates (NHP) have natural antibodies, adult pig islets express exceptionally low levels of aGal and are not subject to hyperacute rejection. Recent findings from Dr. Hering, showing long term survival of pig-to-NHP islet transplant (XPITx) under chronic immunosuppressive therapy, kindle optimism for clinical translation. The importance of tolerance induction to eliminate lifelong immunosuppressive therapy cannot be over-emphasized, since side effects of this therapy can generate problems as deleterious as the original disease. The goal of the proposed experiments is to develop new approaches that facilitate safe and effective immunosuppression to induce tolerance of pig-to-NHP XPITx, without need for chronic immunosuppressive therapy. The studies will build on our previous experience gained in NHP tolerance, using a strategy of brief anti-CD3 immunotoxin and 15-deoxyspegualin treatment that has yielded NHP islet allograft survivors, drug-free and euglycemic for >5 years post-transplant. This will involve intense immunological testing of the mechanisms involved in the; outcome of pig-to-NHP XPITx: The tolerance induction protocol will be modified to counter the rigorous immune response to discordant XPITx, and examined in both intrahepatic (IH) and omental pouch (OP) sites. Since there is no precedent for NHP xenotolerance, the data will guide the design and implementation of strategic refinements to achieve XPITx acceptance. Accordingly, the aims of the proposed experiments are to: (1) Compare the outcome of pig-to-NHP XPITx in IH vs. OP sites using brief systemic immunosuppression that targets T cells and DC, shown to promote stable tolerance to islet allografts in diabetic NHP; (2) Examine a hypothesis that long term acceptance of XPITx in the OP can be achieved following supplementation of the above tolerance protocol with local immunosuppression. We will examine supplemental local vs. systemic immunosuppression with IL- 10 and anti-LFA-1 to minimize macrophage infiltration; (3) Define the immune mechanisms governing XPITx acceptance or rejection in NHP recipients treated under the immunosuppressive conditions described in the previous aims. These studies are unique and will generate new data on pig-to-NHP XPITx immunobiology and the immune mechanisms influencing development of pig XPITx tolerance. ? ? ?
