Remodeling of glycoantigen in xenotransplantation

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The knockout (KO) of the α1,3 galactosyl transferase (α1,3GT) has been of considerable interest. However, the KO of this gene might well have other harmful effects on swine. Two lines of mice earring theα1,3GT targeting vector with three IoxP sites were produced. Two kinds of the transgenic mice with Cre recombinase gene, pCX-Cre and pLIV-Cre, were also obtained. The established conditional homologous recombination system was then tested. However, the efficiency of the recombination, via the Cre-/loxP system leaved considerable room for improvement.On the other hand, we synthesized "mammalian Cre recombinase gene" and examined its expression in Chinese hamster ovarian tumor (CHO) cells. This gene recombined the loxP sites much more efficiently than the wild-type Cre recombinase gene.Next, the effect of the various glycosyltransferases on glycosphingolipids was examined, using transfecte swine endothelial cell (SEC) lines. The overexpression of all two different types of glycosyltransferase, N-acetylglucosarninyl transferase III (GnT-III), as well as α2,6-sialyltransferase, α2,3-sialyltransferase andα1,2-fucosyltransferase, suppress the total antigenicity of SEC significantly. The levels of theα-galactosyl opitope in glycosphingolipids were not decreased in the GnT-III transfectants but were in the ST6Gal I, ST3Gal III, andα1,2FT transfectants.Finally, we have been successful in generating several lines of transgenic mice and pigs that contain the human GnT-III gene. The overexpression of the GnT-III gene in mice and pigs reduced their antigenicity to human natural antibodies, especially the α-galactosyl epitope