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[摘要]：Escherichia coil O148 is a nonencapsulated enterotoxigenic (ETEC) Gram negative bacterium that can cause diarrhea, hemorrhagic colt:is, and hemolytic uremic syndrome in humans. The surface-exposed O-specific polysaccharide (O-SP) of the lipopolysaccharide of this bacterium is considered both;l virulence factor and a protective antigen. It is built up of the linear tetrasaccharide repeating unit [3)-alpha-L-Rhap-(1 -> 2)-alpha-D-Glcp-(1 -> 3)-alpha-D-GlcNAcp-(1 -> 3)-alpha-L-Rhap-(1 ->] differing from that of the O-SP of Shigella dysenteriae type 1 (SD) only in that the latter contains a D-Galp residue in place of the glucose moiety of the former. The close similarity of the O-SPs of these bacteria indicated a possible cross-reactivity, To answer this question we synthesized several oligosaccharide fragments of E. coil 0148 O-SP, up to a dodecasaccharide, as well as their bovine serum albumin or recombinant diphtheria toxin conjugates. Immunization of mice with these conjugates induced anti-O-SP-specific serum IgG antibody responses. The antisera reacted equally well with the LPSs of both bacteria, indicating cross-reactivity between the SD and E. coil 0148 O-SPs that was further supported by Western-blot and dot-blot analyses, as well as by inhibition of binding between the antisera and the O-SPs of both bacteria. |
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