Genetic knockout of porcine GGTA1 or CMAH/GGTA1 is associated with the emergence of neo-glycans

BackgroundPig-derived tissues could overcome the shortage of human donor organs in transplantation. However, the glycans with terminal alpha-Gal and Neu5Gc, which are synthesized by enzymes, encoded by the genes GGTA1 and CMAH, are known to play a major role in immunogenicity of porcine tissue, ultimately leading to xenograft rejection. MethodsThe N-glycome and glycosphingolipidome of native and decellularized porcine pericardia from wildtype (WT), GGTA1-KO and GGTA1/CMAH-KO pigs were analyzed by multiplexed capillary gel electrophoresis coupled to laser-induced fluorescence detection. ResultsWe identified biantennary and core-fucosylated N-glycans terminating with immunogenic alpha-Gal- and alpha-Gal-/Neu5Gc-epitopes on pericardium of WT pigs that were absent in GGTA1 and GGTA1/CMAH-KO pigs, respectively. Levels of N-glycans terminating with galactose bound in beta(1-4)-linkage to N-acetylglucosamine and their derivatives elongated by Neu5Ac were increased in both KO groups. N-glycans capped with Neu5Gc were increased in GGTA1-KO pigs compared to WT, but were not detected in GGTA1/CMAH-KO pigs. Similarly, the ganglioside Neu5Gc-GM3 was found in WT and GGTA1-KO but not in GGTA1/CMAH-KO pigs. The applied detergent based decellularization efficiently removed GSL glycans. ConclusionGenetic deletion of GGTA1 or GGTA1/CMAH removes specific epitopes providing a more human-like glycosylation pattern, but at the same time changes distribution and levels of other porcine glycans that are potentially immunogenic.

Automated summary

The study investigates the immunogenicity of porcine tissue in xenotransplantation by analyzing the glycome and glycosphingolipidome of porcine pericardia with different genetic deletions. The results show that the removal of specific epitopes changes the distribution and levels of other potentially immunogenic porcine glycans.