W189 - Intra-Bone Bone Marrow Transplant from Human CD47 Transgenic Swine as an Approach to Tolerance in Nonhuman Primates

M. Esad Gunes – Columbia University; Karina Bruestle – Columbia University; Sho Fujiwara – Columbia University; Susan Qudus – Columbia University; Benjamin Piegari – Columbia University; Alexander Cadelina – Columbia University; Emilie Nygaard – Columbia University; Dil Ekanayake-Alper – Columbia University; Dominik Hajosi – Columbia University; Robert Hawley – Columbia University; Adam Griesemer – Columbia University; David Sachs – Columbia University; Megan Sykes – Columbia University; Greg Nowak – Columbia University

Abstract Text:

Introduction: Tolerance will be essential to optimal clinical xenotransplantation. Mixed xenogeneic chimerism achieves T cell, B cell and NK cell tolerance in human immune system mice. We aim to achieve mixed xenogeneic chimerism and tolerance using non-myeloablative intra-bone bone marrow transplantation (IBBMT) in baboons. Since pig bone marrow cells are rapidly destroyed by baboon macrophages, donors were transgenic swine expressing human CD47 (hCD47), which binds to SIRP-alpha on macrophages, transmitting a “don’t eat me” signal.

Methods: Four baboons (papio hamadryas) received IBBMT from hCD47/hCD55 transgenic GalT-KO swine following low-dose total body irradiation and thymic irradiation and induction with anti-CD20mAb and thymoglobulin. Maintenance immunosuppression was MMF, FK506, and anti-CD40mAb. Two animals (#3 and 4) also received anti-CD2mAb (LoCD2b) and cobra venom factor (CVF). 1-2x10^9 BM cells/kg were administered intravenously and intra-bone. Chimerism was determined by flow cytometry on peripheral blood, and stained for baboon CD45, pCD45, pSLA1, pSWC3a, pCD3, pCD4, and pCD8. Non-Gal anti-swine antibody levels, mixed lymphocyte reactions (MLR) and ELISPOT responses were followed.

Results: Animals 1 and 2 demonstrated chimerism (>0.1% of pCD45+bCD45-) for < 48 hours. Animals 3 and 4 demonstrated multi-lineage chimerism for approximately 20-30 days. MLR and ELISPOT did not demonstrate donor hyporesponsiveness, but anti-swine antibody levels decreased in animal 3 from the pre-transplant levels. Studies in animal 4 are ongoing.

Conclusion: Enhancing addition cell depletion with anti-CD2mAb and inhibiting with CVF prolonged the duration of porcine chimerism in baboons.