521 Living donor islet allografts in haplotype identical macaques: effect of chimerism and anti-donor antibodies on islet allograft survival.
Tuesday November 17, 2015 from 15:30 to 17:00
Plenary Room 1

James V Harmon Jr., United States

Assistant Professor of Surgery


University of Minnesota


Living donor islet allografts in haplotype identical macaques: effect of chimerism and anti-donor antibodies on islet allograft survival.

James Harmon1, Tun Jie4, Martin Wijkstrom3, Melanie Graham1, Appakalai Balamurugan 2, Raja Kandaswamy1, David Sutherland1, Bernhard Hering1.

1Department of Surgery, University of Minnesota, Minneapolis, MN, United States; 2Department of Surgery, University of Louisville, Louisville, KY, United States; 3Department of Surgery, University of Pittsburgh, Pittsburgh, PA, United States; 4Department of Surgery, University of Arizona , Tucson, AZ, United States

Introduction:  The rhesus macaque is an established model for characterizing immune mechanisms related to hematopoietic chimerism and its effect on allograft survival.1,2  We evaluated the effect of donor specific HSC engraftment and the presence of anti-donor antibodies on living donor islet allograft survival.
Methods: Three donor and three recipient rhesus macaques that were mother/offspring pairs were confirmed to be ABO compatible and completed the hematopoietic stem cell (HSC) infusion and donor specific islet transplant protocol.  High numbers of donor hematopoietic stem cells (HSC) were mobilized and collected using leukopheresis. Antibody mediated T-cell costimulatory blockade was administered at the time of HCS infusions in the three rhesus macaque offspring/recipients following the administration of 200 cGy of total body irradiation and 200 mg/kg IV cyclophosphamide as low-intensity preconditioning. Administration of antibody mediated T-cell costimulation blockade and short-term immunosuppression using cyclosporine and rapamycin was limited to 42 days following the HSC infusions. The counts of CD34+ HSCs infused were greater than 2 x 107 HSC/kg in all of the donor/recipient pairs.  Donor HSCs were infused to recipient macaques on days 0, 8, and 28.  Informative PCR markers for each of the donor/recipient pairs were identified and used to measure the percentage of HSC engraftment in the recipients on days 28, 60, 90 and 150. Diabetes was induced in the three recipients using streptozotocin at day 90.  Donor macaques underwent a living donor distal hemi-pancreatectomy on day 118.  Islet isolation was performed following collagenase distention and the donor pancreatic tissue was processed using a Ricordi chamber.  The islets were purified using a COBE 2991 cell processor over a ficoll gradient. An average of 14,400 ± 4758, islet equivalents/kg were transplanted intraportally on day 120.  No immunosuppression was administered to any of the recipients at the time of islet allograft transplantation.
Results: Successful HSC engraftment was observed in two of three recipients, in these two animals multi-lineage donor HSC engraftment ranged from 39% to 68%.  HSC engraftment was transient; and no donor engraftment was detectible in any recipient at day 150. The recipient with the highest levels of HSC engraftment demonstrated islet allograft function for 92 days and donor antibodies were undetectable.  In contrast, the recipient with undetectable HSC engraftment lost islet allograft function after only14 days even in the absence of detectable donor antibodies.  One recipient developed donor specific alloantibodies that resulted in immediate allograft failure, despite high levels of donor HSC engraftment.  GVHD was not identified in any of the recipients.   
Conclusion: This preclinical NHP model can be used to study of HSC engraftment and islet allograft transplant immunology in the NHP.  Durable donor specific islet allograft tolerance was not achieved using this protocol.  Modifications of this pre-clinical NHP experimental protocol could lead to a better understanding of the immune mechanisms involved in donor specific islet allograft survival.


[1] Am J Transplant. 2012 Jan;12(1):115-25.
[2] Transplantation. 2007 Dec 27;84(12):1677-85.

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