Escherichia coli O148 is a nonencapsulated enterotoxigenic (ETEC) Gram negative bacterium that can cause diarrhea, hemorrhagic colitis, and hemolytic uremic syndrome in humans. The surface-exposed O-specific polysaccharide (O-SP) of the lipopolysaccharide of this bacterium is considered both a virulence factor and a protective antigen. It is built up of the linear tetrasaccharide repeating unit [3)-α-L-Rhap-(1→2)-α-D-Glcp-(1→3)-α-D-GlcNAcp-(1→3)-α-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. coli O148 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. coli O148 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.

Escherichia coli, polysaccharide antigen, synthetic oligosaccharides

13C NMR data:
Linkage	Residue	C1	C2	C3	C4	C5	C6
3,3,2	aLRhap	102.25	70.58	70.78	72.62	69.99	17.34
3,3	aDGlcp	98.49	77.15	73.14	69.81	72.95	60.88
3,2	Ac	174.81	22.89
3	aDGlcpN	94.94	52.65	75.98	71.69	72.49	60.71
	aLRhap	100.23	67.48	75.91	71.00	69.41	17.42


1H NMR data:
Linkage	Residue	H1	H2	H3	H4	H5	H6
3,3,2	aLRhap	5.106	4.069	3.788	3.471	3.840	1.293
3,3	aDGlcp	5.534	3.660	3.730	3.493	3.639	3.802-3.852
3,2	Ac	-	2.041
3	aDGlcpN	4.981	4.128	4.032	3.785	4.012	3.808-3.808
	aLRhap	4.806	4.067	3.810	3.525	3.722	1.312


1H/13C HSQC data:
Linkage	Residue	C1/H1	C2/H2	C3/H3	C4/H4	C5/H5	C6/H6
3,3,2	aLRhap	102.25/5.106	70.58/4.069	70.78/3.788	72.62/3.471	69.99/3.840	17.34/1.293
3,3	aDGlcp	98.49/5.534	77.15/3.660	73.14/3.730	69.81/3.493	72.95/3.639	60.88/3.802-3.852
3,2	Ac		22.89/2.041
3	aDGlcpN	94.94/4.981	52.65/4.128	75.98/4.032	71.69/3.785	72.49/4.012	60.71/3.808-3.808
	aLRhap	100.23/4.806	67.48/4.067	75.91/3.810	71.00/3.525	69.41/3.722	17.42/1.312

There is only one chemically distinct structure:

SVGMWSMILES3D molIonize

 

CC(=O)N[C@H]1[C@@H](O[C@@H]2[C@@H](O)[C@H](C)O[C@@H](O)[C@@H]2O)O[C@H](CO)[C@@H](O)[C@@H]1O[C@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@H]1O[C@@H]1O[C@@H](C)[C@H](O)[C@@H](O)[C@H]1O

675.634 g/mol (C₂₆H₄₅NO₁₉)