Expression of α-1,3-galactose and other type 2 oligosaccharide structures in a porcine endothelial cell line transfected with human α-1,2- fucosyltransferase cDNA

Abstract

The binding of xenoreactive natural antibodies to the Galα1-3Galβ1- 4GlcNAc (α-galactose) oligosaccharide epitope on pig cells activates the recipient's complement system in pig to primate xenotransplantation. Expression of human α-1,2-fucosyltransferase in pigs has been proposed as a strategy for reducing the expression level of the α-galactose epitope, thereby rendering the pig organs more suitable for transplantation into humans. The aim of this study was to examine how the cell surface expression of α-galactose, H, and related fucosylated and sialylated structures on a pig liver endothelial cell line is affected by transfection of human α-1,2- fucosyltransferase cDNA. Nontransfected and mock-transfected cells expressed α-galactose, α-2,3-sialylated, and α-2,6-sialylated epitopes strongly, with low level expression of type 2 H and Lewis(x). By contrast, expression of the H epitope was increased 5-8-fold in transfected cells with a 40% reduction in the expression of α-galactose epitope and a 50% decrease in sialylation, as measured by binding of Maackia amurensis and Sambuccus nigra agglutinins. Lewis(x) expression was reduced to background levels, while the Lewis(Y) neoepitope was induced in human α-1,2-fucosyltransferase-expressing pig cells. The activities of endogenous α-1,3-galactosyltransferase, α- 1,3-fucosyltransferases, and α-2,3- and α-2,6-sialyltransferases acting on lactosamine were unaffected. Our results show that a reduction in α- galactose epitope expression in porcine endothelial cells transfected with human α-1,2-fucosyltransferase cDNA may be achieved but at the expense of considerable distortion of the overall cell surface glycosylation profile, including the appearance of carbohydrate epitopes that are absent from the parent cells.