EXPRESSION OF ALPHA-1,3-GALACTOSE AND OTHER TYPE-2 OLIGOSACCHARIDE STRUCTURES IN A PORCINE ENDOTHELIAL-CELL LINE TRANSFECTED WITH HUMAN ALPHA-1,2-FUCOSYL-TRANSFERASE CDNA

The binding of xenoreactive natural antibodies to the Gal alpha 1-3Gal beta 1-4GlcNAc (alpha-galactose) oligosaccharide epitope on pig cells activates the recipient's complement system in pig to primate xenotra nsplantation, Expression of human alpha-1,2-fucosyltransferase in pigs has been proposed as a strategy for reducing the expression level of the alpha-galactose epitope thereby rendering the pig organs more suit able for transplantation into humans. The aim of this study was to exa mine how the cell surface expression of alpha-galactose, H, and relate d fucosylated and sialylated structures on a pig liver endothelial cel l line is affected by transfection of human alpha-1,2-fucosyltransfera se cDNA. Nontransfected and mock-transfected cells expressed alpha-gal actose, alpha-2,3-sialylated, and alpha-2,6-sialylated epitopes strong ly, with low level expression of type 2 H and Lewis(X). By contrast, e xpression of the H epitope was increased 5-8-fold in transfected cells with a 40% reduction in the expression of alpha-galactose epitope and a 50% decrease in sialylation, as measured by binding of Maackia amur ensis and Sambuccus nigra agglutinins. Lewis(X) expression was reduced to background levels, while the Lewis(Y) neoepitope was induced in hu man alpha-1,2-fucosyltransferase-expressing pig cells. The activities of endogenous alpha-1,3-galactosyltransferase, alpha-1,3-fucosyltransf erases, and alpha-2,3- and alpha-2,6-sialyltransferases acting on lact osamine were unaffected, Our results show that a reduction in alpha-ga lactose epitope expression in porcine endothelial cells transfected wi th human alpha-1,2-fucosyltransferase cDNA may be achieved but at the expense of considerable distortion of the overall cell surface glycosy lation profile, including the appearance of carbohydrate epitopes that are absent from the parent cells.