Synthesis of neoglycoproteins containing Kdo epitopes specific for Chlamydophila psittaci lipopolysaccharide

Abstract

The oligosaccharides α-Kdop-(2→8)-α-Kdop-(2→6)-β-D-GlcpNAc-(1→OAll) 4, α-Kdop-(2→4)-α-Kdop-(2→4)-α-Kdop-(2→6)-β-D-GlcpNAc-(1→OAll) 10, and the branched Kdo tetrasaccharide α-Kdop-(2→4)-[α-Kdop-(2→8)]-α-Kdop-(2→4)-α-Kdop-(2→OAll) 21 have been prepared using en bloc transfer of Kdo oligosaccharide bromide donors to protected mono- or disaccharide accepters. Radical addition of cysteamine to the anomeric allyl glycosides afforded good yields of the corresponding 3-(2-aminoethylthio)propyl glycosides 5, 11 and 22. The spacer ligands were activated with thiophosgene and reacted with bovine serum albumin to give the neoglycoconjugates 6, 12 and 23 which were used to prepare solid-phase antigens in enzyme immune-assays for the characterization of monoclonal antibodies against chlamydial LPS. The data showed that the (2→8)-linked Kdo disaccharide and the (2→8)-(2→4)-linked Kdo trisaccharide portion of the neoglycoconjugate 23 were not available for binding of antibodies which recognize these structures as di- and trisaccharide, respectively.