TRANSPLANT TOLERANCE IN NON-HUMAN PRIMATES

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Transplantation has emerged as the preferred method of treatment for many forms of end-stage organ failure. While short-term results have improved, long-term outcomes remain inadequate. To maintain their allografts, patients must rigidly adhere to life-long treatment regimens using costly immunosuppressive agents that dramatically increase the risks of cardiovascular disease, infections and malignancies. The development of strategies to promote the acceptance of allogeneic tissues without the need for chromic immunosupression could not only reduce the risk of these life-threatening complications, but also greatly expand the application of organ, tissue and cellular transplantation for diseases such as the hemoglobinopathies and genetic immunodeficiencies, Type I diabetes, and possibly other autoimmune diseases. In the past year, we have made significant progress towards the development of novel non-myeloablative protocols using CD28 and CD40/CD154 T cell costimulation-blockade-based therapeutics to permit the induction of high levels of hematopoietic chimerism in Rhesus macaques. However, in the setting of full MHC disparity, this chimerism was transient, did not confer immune tolerance to solid organ transplants, and resulted in significant immunodeficiency in transplant recipients. We therefore undertook a pedigree and MHC analysis of the Yerkes colony which has allowed us, in the past year, to perform the first bone marrow transplants between rhesus macaque donors and recipients with known familial relationships and MHC similarity. Our data suggests that in the setting of increased MHC matching between transplant donors and recipients, costimulation blockade-based induction of durable chimerism and resultant tolerance to solid organ transplants is achievable, with preservation of protective immunity.