Robust allograft tolerance in non-human primates

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Project Summery Mixed hematopoietic chimerism is a promising approach to inducing allograft and xenograft tolerance. Our preliminary studies have shown that the addition of expanded recipient regulatory T cells (Tregs) to allogeneic bone marrow transplantation results in more durable mixed chimerism in non-human primates. This is supported by in vivo data in mice. In humans, Treg also have potential for the prevention of graft-versus-host disease (GVHD), a major complication after allogeneic hematopoietic cell transplantation, and for preventing rejection or promoting tolerance of transplanted solid organs. Studies in mice indicate that durable mixed chimerism is associated with strong systemic tolerance that permits survival of challenging allografts. In our current study we focus on the addition of expanded recipient regulatory T cells (Tregs) to non-myeloablative allogeneic bone marrow transplantation to induce durable mixed chimerism and thereby robust allograft tolerance in the pre-clinical cynomolgus macaque model. However, with the current protocol we have found that we must euthanize the donor animal to obtain sufficient bone marrow cells to achieve high levels of chimerism, precluding delayed transplantation of donor kidneys as a robust test of tolerance. Equipment that would permit pheresis of mobilized hematopoietic stem cells from live donors would overcome this obstacle. Furthermore, a bioconfinement device for protective isolation that would reduce infectious complications in immunosuppressed recipient animals, infusion pumps that efficiently deliver immunosuppressive drugs and instruments that would enhanced the surgical efficiency (fluoroscopic table, retractor system) may substantially improve the results and outcome of the parent project. Since our establishment of the non-human primate transplant program at Columbia, there has been major growth of this and other NHP programs at Columbia University Medical Center (CUMC). Our research is advancing steadily in many areas of organ transplant including bone marrow, liver, kidney, lung, islet cells and skin and other areas of clinically relevant human diseases. Many investigators at CUMC are working closely together to bring xenotransplantation tolerance to clinical reality. In this exciting time of growth, the proposed state-of-the-art equipment proposed through this grant will not only help us to successfully progress with our primary goals but will also enhance research outcomes of other NIH-funded investigators at Columbia.