Intra‐bone bone marrow transplantation from hCD47 transgenic pigs to baboons prolongs chimerism to >60 days and promotes increased porcine lung transplant survival

Abstract

Background We have recently demonstrated that human‐CD47 (hCD47) expressed on endothelial cells of porcine lung xenografts extended median graft survival from 3.5 days to 8.7 days in baboons. Intra‐bone bone marrow transplantation (IBBMTx) in a pig‐to‐baboon model was previously shown to markedly prolong the duration of macrochimerism up to 21 days from 1 to 4 days by intravenous BMTx. We now examined whether the use of hCD47 transgenic (Tg) BM further prolonged the duration of chimerism following IBBMTx. We then tested if lung xenograft survival was prolonged following IBBMTx. Methods Baboons received GalTKO‐hCD47/hCD55Tg (n = 5) or ‐hCD55Tg (n = 1) or ‐hCD46/HLA‐E Tg (n = 1) pig IBBMTx. Macrochimerism, anti‐pig T cells and antibody responses were assessed. Animals received lung xenografts from either hCD47+ or hCD47‐ porcine lungs 1‐3 months later. Results All baboons that received hCD47Tg porcine IBBM maintained durable macrochimerism >30 days, and two maintained chimerism for >8 weeks. Notably, anti‐pig antibody levels decreased over time and anti‐pig cellular unresponsiveness developed following IBBMTx. Lungs from hCD47Tg IBBMTx matched pigs were transplanted at day 33 or day 49 after IBBMTx. These animals showed extended survival up to 13 and 14 days, while animals that received lungs from hCD47 negative pigs displayed no prolonged survival (1‐4 days). Conclusion This is the first report demonstrating durable macrochimerism beyond 8 weeks, as well as evidence for B cell tolerance in large animal xenotransplantation. Using hCD47Tg pigs as both IBBMTx and lung donors prolongs lung xenograft survival. However, additional strategies are required to control the acute loss of lung xenografts.

Application of Genetically Engineered Pigs in Biomedical Research

“…The longest survival time for orthotopic liver xenografts (29 days) was achieved using GGTA1 knock-out pigs, exogenous human coagulation factors, and immunosuppression, including co-stimulation blockade [104]. In turn, Watanabe et al demonstrated prolonged survival time of lung xenotransplants (14 days) from GGTA1 knock-out, hCD47/hCD55 donor pigs in immunosuppressed baboons [105]. The authors indicated the important role of hCD47 expression in reducing immunologic damages and extending lung graft survival in the pig-to-NHP model.…”

Xenotransplantation: Current Status in Preclinical Research

“…However, the xenografts were functional for only 3.5 h because of severe coagulation dysregulation (179). Recently, Watanabe et al reported that the survival time of NHP recipients of lungs from GTKO/CD47/CD55 transgenic pigs was extended by 14 days (163,180). These studies have demonstrated that the introduction of hCD47 can mitigate acute vascular rejection of lung xenografts and prolong porcine lung transplant survival time in NHP models.…”

Immunogenetics of xenotransplantation

“…Xenogeneic chimerism supported tolerance of recipient T and B cells towards lung xenograft. The porcine lung grafts used in this study carried three genetic modifications (GTKO/CD47/CD55) (Watanabe et al., 2019). Another study reported a prolonged lung xenograft survival of 31 days on a life‐supporting model.…”