Reduction in Gal‐α1,3‐Gal epitope expression in transgenic mice expressing human H‐transferase

Abstract

There is now considerable evidence implicating anti‐Gal xenoantibodies as a key instigator in the hyperacute rejection of discordant xenografts. As a consequence it is generally held that elimination or reduction of the Gal/anti‐Gal component is critical to overcoming hyperacute rejection. We have recently shown that in mice inactivation of the GalT gene by homologous recombination completely eliminates the expression of the Gal‐epitope and that hearts from these mice demonstrate prolonged survival when perfused ex vivo with human plasma. Unfortunately this strategy is currently not feasible in pigs because the technology to isolate porcine embryonic stem cells, which are critical for homologous recombination, is not yet available. This study investigates an alternative competition‐based transgenic strategy to suppress the level of the Gal epitope by expression of H‐transferase (α1,2‐fucosyltransferase) an enzyme which has the same substrate specificity (lactobiose) as α1,3‐galactosyltransferase. In vitro transfection of murine cells with H‐transferase reduced Gal‐epitope expression by 80–90%. A similar reduction in Gal expression was observed on PBL and thymocytes from H‐transferase transgenic mice. This reduction in Gal epitope expression resulted in a marked reduction in the reactivity of these cells with human serum. In tissues from these mice the reduction in Gal expression was inversely proportional to the endogenous level of Gal. The results of this study support pursuing this strategy as a means to reduce the xenoantigenicity of porcine tissues.

Thromboregulatory manifestations in human CD39 transgenic mice and the implications for thrombotic disease and transplantation

“…Similar numbers of the dense granules that contain adenine nucleotides were present in both (data not shown). Consistent with our previous results using the H-2K b promoter (24,25), transgene expression was widespread in all tissues examined, including heart, lung, and pancreas, and was particularly strong on endothelium ( Figure 1B). Correct processing of hCD39 in the tissues of transgenic mice was confirmed by Western blot analysis ( Figure 1C).…”

Potential Application of Neonatal Porcine Islets as Treatment for Type 1 Diabetes: A Review

“…51–54 A third strategy is to generate transgenic pigs that over express a fucosyltransferase that competes with the substrate for αGal attachment so that a fucose group, representing a natural human blood group antigen, is substituted for αGal. 50,55–57 A fourth approach is to knock out the pig gene that encodes α 1–3 galactosyltransferase. 58,59 This would presumably eliminate the main cause of hyperacute rejection, but the technology for porcine knockouts is not yet available.…”

Altered Glycosylation in Donor Mice Causes Rejection of Strain-Matched Skin and Heart Grafts

“…As part of our xenotransplantation program, we generated hFUT1 transgenic mice expressing human α1,2‐fucosyltransferase , also known as H‐transferase (HTF) because it is responsible for the synthesis of H substance (blood group O). The rationale for this strategy was that HTF reduces the expression of the major porcine xenoantigen galactose‐α1,3‐galactose (αGal) by competing for the substrate of α1,3‐galactosyltransferase .…”