Studies on glycolipid antigens in small intestine and pancreas from α1,3-galactosyltransferase knockout miniature swine

BACKGROUND. To avoid hyperacute rejection of xeno-organs, α1,3-galactosyltransferase knockout (GalT-KO) pigs have been produced. Galα1,3Gal determinant elimination may expose cryptic carbohydrate antigens and/or generate new antigens. This is the first biochemical study of carbohydrate antigens in GalT-KO pig organs. METHODS. Neutral and acidic glycolipids were isolated from small intestine and pancreas of two GalT-KO and one wild-type (WT) pig. Glycolipid immune reactivity was tested on thin-layer chromatograms. Small intestine neutral glycolipids were separated by high-performance liquid chromatography and selected fractions were analyzed by proton nuclear magnetic resonance spectroscopy. Total gangliosides were quantified on thin-layer chromatograms and in microtiter wells. RESULTS. Using Galα1,3nLc4 glycolipid reference, total Galα1,3Gal glycolipid antigens in the WT animal was estimated at about 30 μg (small intestine) and 3 μg (pancreas) per gram of dry tissue. Galα1,3Gal determinants were not detected in GalT-KO tissues at a detection limit of less than 0.25% (small intestine) and 0.5% (pancreas) of the WT tissues. Isoglobotriaosylceramide (iGb3) was absent but trace amounts of Fuc-iGb3 was found in both GalT-KO and WT pig small intestine. Blood group H type 2 core saccharide compounds were increased in GalT-KO pancreas. Total amount of gangliosides was decreased in GalT-KO tissues. The α1,3-galactosyltransferase acceptor, N-acetyllactosamine determinant, was not increased in GalT-KO tissues. Human serum antibodies reacted with WT organ Galα1,3Gal antigens and gangliosides, of which the ganglioside reactivity remained in GalT-KO tissues. CONCLUSIONS. Knockout of porcine α1,3-galactosyltransferase gene results in elimination of Galα1,3Gal-terminated glycolipid compounds. GalT-KO genetic modification did not produce new compensatory glycolipid compounds reactive with human serum antibodies.

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