Glycolipid Studies in Small Intestine and Pancreas of α1,3-Galactosyltransferase Knockout Miniature Swine: α1,3GALT-KO Animals Lack αGAL Antigens and Contain Novel Blood Group H Compounds

Background: To avoid hyperacute rejection of xeno-organs, α1,3-galactosyltransferase knock-out (GalT-KO) pigs have been produced. However, Galα1,3Gal (Gal) determinant elimination may expose cryptic carbohydrate antigens and/or generate new antigens that might interfere with the human immune response. Methods: Glycolipids isolated from small intestine and pancreas of two GalT-KO and one wild-type (WT) pig were tested for immune reactivity with antibodies on thin-layer chromatograms after separation by high-performance liquid chromatography, and selected fractions were analysed by proton NMR spectroscopy. Results: Immunostaining using purified human anti-Gal Abs revealed that tissues from WT animals express large amounts of Gal-antigens whereas GalT-KO tissues lacked these antigens. Proton NMR spectroscopy on small intestine fractions revealed both linear and branched nona- and decaglycosylceramides, respectively, with terminal Gal-epitopes. In corresponding GalT-KO fractions, Gal-epitopes seemed to be replaced by terminal α1,2fucoses. Two novel branched blood group H compounds was found in the GalT-KO intestine. Conclusions: The structural complexity of αGal-terminating antigens in the WT organs is very high. Knockout of α1,3GalT by gene-targeting results in elimination of Gal-determinants. In addition structurally novel α1,2fucose-terminated blood group H compounds were identified in the GalT-KO tissue. These compounds are not expected to be recognized by the human immune system.

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