Remodeling of glycoantigen in xenotransplantation

α1,3半乳糖转移酶（α 1,3gt）的敲除（KO）引起了相当大的兴趣。然而，这种基因的KO很可能对猪有其他有害影响。制备了具有3个IoxP位点的α 1,3gt靶向载体的2株小鼠。同时获得了两种Cre重组酶基因转基因小鼠pCX-Cre和pLIV-Cre。对所建立的条件同源重组体系进行了测试。然而，通过Cre-/loxP系统重组的效率仍有很大的改进空间。另一方面，我们合成了“哺乳动物Cre重组酶基因”，并检测了其在中国仓鼠卵巢肿瘤（CHO）细胞中的表达。该基因比野生型Cre重组酶基因更有效地重组了loxP位点。接下来，利用转染猪内皮细胞（SEC）系，研究了各种糖基转移酶对鞘糖脂的影响。过表达两种不同类型的糖基转移酶n -乙酰葡萄糖氨基转移酶III （GnT-III）以及α2,6-唾液基转移酶、α2,3-唾液基转移酶和α1,2- focusyltransferase均可显著抑制SEC的总抗原性。在鞘糖脂的水平α半乳糖opitope并不减少GnT-III转染子但ST6Gal我,ST3Gal三世和α1、2英尺转染子。最后，我们已经成功地培育了几种含有人类GnT-III基因的转基因小鼠和猪。小鼠和猪的GnT-III基因过表达降低了它们对人类天然抗体的抗原性，尤其是α-半乳糖表位

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