A comparison between GalT-/-;hCD39;hCD55 and GalT-/-;hCD39;hCD46;hCD55;TBM pig kidney transplanted in non-human primates

Introduction: Due to a shortage of kidney donors, genetically modified kidney xenografts from pigs have been considered in renal failure. Over the recent years, research of xenotransplantation has advanced from producing multiple genetically-engineered pigs to overcoming hyperacute xenograft rejection. However, several immunological hurdles are still remained to apply living human patients. Therefore, non-clinical trials using genetically-engineered pig to monkey model was encouraged before transplanting porcine kidney into human body. Here, we reported two cases of non-clinical study by transplanting kidney of genetically engineered Yucatan minipigs into Cynomolgus monkeys. Method: Knockout of carbohydrate genes or knock-in of protective proteins has been applied to select the optimal gene modification for xenotransplantation. This study used two types of Yucatan minipig that has different genetic background. One is knocked out 1,3-Gal epitope, xeno-reactive antigens (GTKO) and knocked in human CD55 and CD39 (described as GalT-/-;hCD39;hCD55) and the other was additionally knocked in human CD46 and TBM (described as GalT-/-;hCD39;hCD46;hCD55;TBM). Surgical strategy was described in schematic diagram figure B. After surgery, health condition was monitored by performing daily clinical observation and blood sampling every week for hematology and serum chemistry analysis. Furthermore, immunohistochemistry and mRNA sequencing were performed to compare two case studies. Results: The NHPs survived for 4 weeks after kidney transplantation (4 WAT) from GalT-/-;hCD39;hCD55 pigs, and 6 WAT from GalT-/-;hCD39;hCD46;hCD55;TBM pigs. However, mRNA sequencing and immunohistochemistry analysis revealed that the kidneys of the NHPs that survived for 6 WAT showed severe apoptosis, inflammation, loss of renal function, and renal fibrosis compared to those of the NHPs that survived for 4 WAT. Conclusion: These results suggest that additional knock-in of anti-complement (hCD26) and anti-coagulation (TBM) proteins is insufficient to inhibit renal damage.