A novel synthesis of alpha-D-Galp-(1 -> 3)-beta-D-Galp-1-O-(CH2)(3)-NH2, its linkage to activated matrices and absorption of anti-alpha Gal xenoantibodies by affinity columns

Pig organs transplanted into primates are rapidly rejected because of the i nteraction between Ga1 alpha(1-->3)Ga1 epitopes carried by the graft and na tural antibodies (anti-alpha Ga1 antibodies) present in the blood of the re cipient. This report describes a simplified synthesis of the xenogeneic dis accharide and its linkage to activated gel matrices. The digalactosides alp ha-D-Ga1p-(1-->3)-alpha,beta-D-Ga1p-OAll were synthesized by the condensati on of the trichloroacetimidoyl 2,3,4,6-tetra-O-benzyl-beta-D-galactopyranos ide donor with the 3,4-unprotected allyl 2,6-di-O-benzyl-alpha- or beta-D-g alactopyranoside acceptor precursor. Deallylation and hydrogenolysis led to the free digalactoside, whereas hydrogenolysis alone resulted in the 1-O-p ropyl digalactoside. Both products were tested by inhibition ELISA of natur al anti-Ga1 alpha(1-->3)Ga1 antibodies. The alpha-D-Ga1p-(1-->3)-beta-D-Ga1 p-OPr was found to be the best inhibitor. Thus, the allyl group of the part ially benzylated alpha-D-Ga1p-(1-->3)-beta-D-Ga1p-OAll was engineered, via the hydroxy-, the tosyloxy- and the azidopropyl intermediates, into an amin opropyl group amenable to binding to N-hydroxysuccinimide-activated agarose gel matrices in order to obtain specific immunoabsorption columns. Columns made of gel substituted with 5 mu mol of disaccharide per milliliter were found efficient for the immunoabsorption of anti-alpha Ga1 antibodies from human plasma. (C) 2000 Elsevier Science Ltd. All rights reserved.