Chief, Transplantation Section
Cardiothoracic Surgery Research Program
NHLBI / NIH
Critical need of continuous co-stimulation blockade with anti CD40 antibody (2C10.R4) for long-term maintenance of GTKO.hCD46.hTBM pig cardiac xenograft survival in baboons
Muhammad Mohiuddin1, Avneesh Singh1, Philip Corcoran1, Marvin Thomas4, Billeta Lewis4, Tannia Clark4, Michael Eckhaus4, Aaron Belli3, Keith Reimann3, Nikolai Klymuik2, Eckhard Wolf2, David Ayares5, Keith Horvath1.
1Cardiothoracic Surgery Research Program, NHLBI /NIH, Bethesda, MD, United States; 2LMU, Munich, Germany; 3University of Massachusetts, Boston, MA, United States; 4DVR / ORS, NIH, Bethesda, MD, United States; 5Revivicor, Inc, Blacksburg, VA, United States
Introduction: The process of xenograft rejection in a pig to baboon large animal cardiac xenotransplantation model is very complex and therefore an equally multifaceted treatment is required to overcome this hurdle. Here we describe a successful strategy to subdue the strong xenogeneic immune response and achieve prolong graft survival.
Material and methods: Five 6-8 week old piglets which were genetically engineered to remove alpha 1-3 galactosyltransferase gene and expressed human CD46 and thrombomodulin transgenes, served as heterotopic heart donors. Size matched specific pathogen free baboons were used as the recipients (n=5). Immunomodulation consisted of B cell depletion with four doses of anti CD20 (19mg/kg) (days -7,0,7,14) in the induction phase, immune suppression with mycophenolate mofitel (20mg/kg) daily and steroids (2mg/kg) (tapered off in 2 months), and co-stimulation blockade with high dose anti CD40 antibody (Clone 2C10R4) (50mg/kg) on days -1, 0, 5,9,14 then weekly. The dose of anti CD40 antibody was first reduced in two baboons on day 100, in two baboons on day 365 (in these baboons, anti CD40 antibody treatment was tapered off and was completely stopped on day 560 in one and day 861 in another) and in one baboon the dose was not reduced.
Results: Significant graft survival was achieved in all 5 baboons. In two baboons in which antibody was reduced (25mg/Kg) on day 100, grafts were rejected within 290 days while the baboons in which antibody was tapered after 1 year, grafts survived for the longest period of time (616 and 945 days). One baboon where dose reduction did not occur developed an antibiotic resistant infection and rejected the graft on day 146. The most interesting finding was that the two long-term (>600 days) surviving hearts rejected within 12 weeks of discontinuing anti CD40 antibody therapy indicating the dependence of graft survival on the anti CD40 antibody treatment. The period taken for these hearts to reject after cessation of anti CD40 antibody treatment also coincided with the time for complete washout of this antibody from the recipient’s blood circulation.
Conclusion: Our results clearly indicate that, for long-term xenograft survival, genetically engineered donor pig hearts and high dose of anti CD40 antibody are required to avoid; antibody mediated rejection, complement activation and thrombotic coagulopathies. However, it is also clear that dose and duration of anti CD40 antibody treatment had a critical impact on maintenance of graft survival.
NHLBI Animal Surgery and Resources. DVR/ ORS/ NIH.
08:00 - 09:00
|Progress in Solid Organ Xenotransplantation||Heart||Room 109|
15:30 - 17:00
|Solid Organ Xenotransplantation (1)||Critical need of continuous co-stimulation blockade with anti CD40 antibody (2C10.R4) for long-term maintenance of GTKO.hCD46.hTBM pig cardiac xenograft survival in baboons.||Room 109|
15:30 - 17:00
|Solid Organ Xenotransplantation (1)||Histological evidence of acute rejection after terminating anti CD40 antibody (2C10R4) treatment in GTKO.hCD46.hTBM pig to baboon cardiac xenografts surviving for over one year||Room 109|