Structural analysis of the O-antigen of the lipopolysaccharide of Rhizobium tropici CIAT899

The structure of the O-antigen chain of the lipopolysaccharide isolated from Rhizobium tropici CIAT899, by the phenol-water procedure, and recovered from the phenol layer, has been investigated by hydrolysis, methylation analysis and 1D and 2D 1H and 13C NMR spectroscopy of the complete polysaccharide and of oligosaccharides obtained by partial hydrolysis. The O-antigen has the repeating unit [formula: see text]

Role of O-antigen variation in the immune response

The O antigen is an extremely variable surface polysaccharide of Gram-negative bacteria. This variation is thought to allow the various clones of a species each to present a surface that offers a selective advantage in the niche occupied by that clone. The interactions between O antigen and the immune system are central to determining the selective advantage of each clone.

Role of LPS length in clearance rate of bacteria from the bloodstream in mice

Strains of Pseudomonas aeruginosa isolated from patients with cystic fibrosis (CF) never spread systemically. This may be due to serum sensitivity since these strains are very sensitive to complement-mediated bactericidal activity. A serum-resistant mutant, P. aeruginosa TUM3 HSR, was obtained from serum-sensitive strain TUM3 from a CF patient in order to clarify the mechanism of failure of systemic spread. LPS profiles on silver-stained gels and immunological analysis revealed that a long O-polysaccharide side chain was overproduced on the LPS molecules of TUM3 HSR as compared with the LPS of TUM3. The clearance rate from the bloodstream in mice was compared in the two strains. The number of TUM3 bacteria in 1 ml of blood, 10 min after injection into the tail vein, significantly decreased from 1.7 x 10(8) to 3.7 x 10(5) c.f.u. ml-1. In contrast, TUM3 HSR was not eliminated during the same period (decrease from 1.9 x 10(8) to 3.4 x 10(7) c.f.u. ml-1). Interestingly, these isogenic strains were not killed by 40% murine serum, probably reflecting immaturity of the complement-mediated killing system in mice. These results pointed to a correlation between LPS structure and blood clearance rate in mice. This was confirmed by examining blood clearance kinetics using the smooth-LPS strain Salmonella typhimurium LT2 and LPS-deficient mutants derived from it. S. typhimurium LT2 resisted blood clearance while the LPS-deficient mutants were cleared rapidly. None of the S. typhimurium strains were killed by murine serum. The number of P. aeruginosa TUM3 and S. typhimurium LPS-deficient mutants trapped in the liver following injection into the peripheral circulation was greater than that of their counterparts.(ABSTRACT TRUNCATED AT 250 WORDS)

Synthesis and crystal structure of methyl 4-6-dideoxy-4-(3-deoxy-L- glycero-tetronamido)-2-O-methyl-alpha-D-mannopyranoside, the methyl alpha-glycoside of the terminal unit, and presumed antigenic determinant, of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Ogawa

Methyl 4-azido-4,6-dideoxy-3-O-benzyl-alpha-D-mannopyranoside and its analogous 3-O-(4-methoxybenzyl) derivative were methylated and the 2-O-methyl derivatives formed were converted into methyl 4-amino-4,6-dideoxy-2-O-methyl-alpha-D- mannopyranoside [sequence: see text]. Reaction of the latter with 3-deoxy-L-glycero-tetronolactone gave the methyl glycoside of 4,6-dideoxy-4-(3-deoxy-L-glycero- tetronamido)-2-methyl-alpha-D-mannopyranose [sequence: see text], the monosaccharide that is reported to be the terminal moiety of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Ogawa. The unit cell packing of the compound, which crystallized as a monohydrate, differs from that of the previously described crystalline compound lacking the 2-O-methyl group. The unmethylated sugar is the terminal moiety of the O-specific polysaccharide of Vibrio cholerae O:1, serotype Inaba. The crystal structure of methyl 4,6-dideoxy-2-O- methyl-4-trifluoroacetamido-alpha-D-mannopyranoside [sequence: see text] is also described.

Synthesis of specifically deoxygenated disaccharide derivatives of the Shigella dysenteriae type 1 O-antigen

The synthesis of methyl O-alpha-L-rhamnopyranosyl-(1-->2)-alpha-D-galactopyranosides specifically deoxygenated at position 2 (31), or 4 (21) of the rhamnopyranosyl residue was accomplished using methyl 3,4,6-tri-O-benzoyl-alpha-D-galactopyranoside (18) as the glycosyl acceptor. Phenyl thionocarbonate activation of the penta-O-benzoylated disaccharide precursor followed by Barton reduction and Zemplén transesterification gave 31, while 21 was obtained via condensation of the deoxygenated monosaccharide donor with 18, and subsequent debenzoylation of the product.

The structure and serological specificity of Proteus mirabilis O43 O antigen

On the basis of sugar analysis and NMR spectroscopy, including selective spin-decoupling, one-dimensional NOE, two-dimensional homonuclear and 13C,1H-heteronuclear correlation spectroscopy, the following structure of the acidic O-specific polysaccharide of Proteus mirabilis O43 was established: -->4)-alpha-D-GalpA-(1-->3)-alpha-D-GalpA-(1-->3)-alpha-D-Gl cpNAc-(1-->4)-alpha - D-Glcp-(1-->, where GalA is galacturonic acid and Galp is galactopyranose. No serological cross-reactivity was observed between lipopolysaccharides of P. mirabilis O43 and other studied Proteus strains, except for P. mirabilis O10. The O-specific polysaccharide of P. mirabilis O43 was serologically active in precipitation and inhibition tests but the activity was lost after periodate oxidation. These data suggest that the O43 specificity is determined by a wide epitope with the immunodominant role of 4-substituted D-Glc or/and D-GalA, which are destroyed by periodate oxidation.

Structures of the O-specific polysaccharide chains of Pectinatus cerevisiiphilus and Pectinatus frisingensis lipopolysaccharides

Mild acid hydrolysis of the smooth-type lipopolysaccharide (LPS) of Pectinatus frisingensis afforded no polysaccharide but monomeric 6-deoxy-L-altrose (L-6dAlt) which was identified by anion-exchange chromatography in borate buffer, GLC/MS, 1H-NMR spectroscopy, and optical rotation. LPS was degraded with alkali under reductive conditions to give a completely O-deacylated polysaccharide, which was studied by methylation analysis, 1H-NMR and 13C-NMR spectroscopy, including sequential, selective spin-decoupling, two-dimensional correlation spectroscopy (COSY), COSY with relayed coherence transfer, two-dimensional heteronuclear 13C, 1H-COSY, one-dimensional NOE and two-dimensional rotating-frame NOE spectroscopy. It was found that the O-specific polysaccharide chain of P. frisingensis LPS is a homopolymer of 6-deoxy-L-altrofuranose built up of tetrasaccharide-repeating units having the following structure: [sequence: see text] Similarly, mild acid degradation of smooth-type LPS of Pectinatus cerevisiiphilus resulted in depolymerisation of the polysaccharide chain to give a disaccharide consisting of D-glucose and D-fucose. Study of the disaccharide by methylation analysis and alkali-degraded LPS by one-dimensional and two-dimensional 1H-NMR and 13C-NMR spectroscopy showed that the O-specific polysaccharide of P. cerevisiiphilus has the following structure: -->2)-beta-D-Fucf-(1-->2)-alpha-D-Glcp-(1-->.

Structure of the O-specific polysaccharide of Hafnia alvei 1204 containing 3,6-dideoxy-3-formamido-D-glucose

The O-specific polysaccharide of Hafnia alvei strain 1204 has a hexasaccharide repeating unit containing D-mannose, D-glucuronic acid, 2-acetamido-2-deoxy-D-glucose, 2-acetamido-2-deoxy-D-galactose, and 3,6-dideoxy-3-formamido-D-glucose (Qui3NFo) in the ratios 2:1:1:1:1 as well as O-acetyl groups. On the basis of methylation analysis of the intact, carboxyl-reduced, and Smith-degraded polysaccharide as well as 1D and 2D NMR spectroscopy, including 1D total correlation spectroscopy, 1D NOE spectroscopy, 2D homonuclear shift-correlated spectroscopy (COSY), and 13C,1H heteronuclear COSY, the following structure of the O-deacetylated polysaccharide was established: -->3)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->3)-beta-D-GlcpN Ac-(1--> -->2)-beta-D-Quip3NFo-(1-->3)-alpha-D-GalpNAc-(1-->4)-alpha-D-G lcpA-(1--> Location of the N-formyl group, occurring as two stereoisomers in the ratio approximately 3:1, was determined by an NOE on H-3 Qui3N arising on pre-irradiation of HCO of the minor (E) isomer. The O-acetyl groups are attached in nonstoichiometric amounts at position 3 of GlcA and position 6 of a mannose residue or GlcNAc.

Characterization of a lipopolysaccharide O antigen containing two different trisaccharide repeating units from Burkholderia cepacia serotype E (O2)

The O antigen of the lipopolysaccharide of Burkholderia cepacia serotype E (O2) was shown by a combination of methylation analysis, partial hydrolysis, NMR, and mass spectrometric methods to be a high molecular weight polysaccharide composed of two different trisaccharide repeating units in the ratio 2:1. The major trisaccharide component is composed of two alpha-D-mannopyranosyl and one beta-D-galactopyranosyl residues with the structure, [-->2)-alpha-D-Man p-(1-->2)-alpha-D-Man p-(1-->4)-beta-D-Gal p-(1-->]n The minor trisaccharide component is a D-mannan composed of two alpha- and one beta-D-mannopyranosyl residues with the structure, [-->2)-alpha-D-Man p-(1-->2)-alpha-D-Man p-(1-->3)-beta-D-Man p-(1-->]n

Structure of the O6 antigen of Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia

A polysaccharide containing D-xylose, L-rhamnose, and N-acetyl-D-glucosamine was released on mild acid hydrolysis of the lipopolysaccharide extracted from defatted cell walls of Stenotrophomonas (Xanthomonas or Pseudomonas) maltophilia strain 557, the reference strain for serotype O6. By means of NMR spectroscopy and chemical degradations, the repeating unit of the polymer was identified as a branched trisaccharide with the structure shown. [formula: see text]

Circular dichroism of the O-specific polysaccharide of Vibrio cholerae O1 and some related derivatives

The O-specific polysaccharide (O-SP) of Vibrio cholerae O1 is a homopolymer of alpha-(1 --> 2)-linked 4-amino-4, 6-dideoxy-D-mannopyranose whose amino group is acylated with 3-deoxy-L-glycero-tetronic acid [N-(3-deoxy-L-glycero- tetronyl)-alpha-D-perosamine]. The circular dichroism (CD) of the O-SP as well as of a number of N-acyl (formyl, acetyl, 4-hydroxybutyl, 3-deoxy-L-and D-glycero-tetronyl) derivatives of methyl alpha-glycosides of 4-amino-4,6-dideoxy-D-mannopyranose (methyl alpha-D-perosaminide) has been studied for solutions in water, acetonitrile and 1,1,1-trifluoroethanol. The strong solvent dependence of the sign and intensity of the CD observed for the monosaccharide amides bearing achiral acyl groups is explained by solvent-mediated change of the orientation of the amido group relative to the proximal hydroxyl group at C-3. A change in the population of the nonplanar conformers with a pyramidal arrangement of bonds at the amido nitrogen has also been considered. The effect of solvents upon the CD spectra of compounds bearing chiral N-acyl substituents is less pronounced than that of their counterparts bearing achiral N-acyl substituents. The sign of the CD for the O-SP was found negative in all solvents used. This result is in agreement with the negative sign of the CD of the n --> pi electron transition observed, independent of the solvent, for the monosaccharide derivative containing the L-glycero-3-deoxytetronamido group, and the positive sign found for its D-glycero-counterpart.

Appropriate coating methods and other conditions for enzyme-linked immunosorbent assay of smooth, rough, and neutral lipopolysaccharides of Pseudomonas aeruginosa

Smooth, rough, and neutral forms of lipopolysaccharide (LPS) from Pseudomonas aeruginosa were used to assess the appropriate conditions for effective enzyme-linked immunosorbent assay (ELISA) of LPS. Each of these forms of well-defined LPS was tested for the efficiency of antigen coating by various methods as well as to identify an appropriate type of microtiter plate to use. For smooth LPS, the standard carbonate-bicarbonate buffer method was as efficient as the other sensitivity-enhancing plate-coating methods compared. The rough LPS, which has an overall hydrophobic characteristic, was shown to adhere effectively, regardless of the coating method used, to only one type of microtiter plate, CovaLink. This type of plate has secondary amine groups attached on its polystyrene surface by carbon chain spacers, which likely favors hydrophobic interactions between the rough LPS and the well surfaces. Dehydration methods were effective for coating microtiter plates with the neutral LPS examined, which is composed predominantly of a D-rhamnan. For the two dehydration procedures, LPS suspended in water or the organic solvent chloroform-ethanol was added directly to the wells, and the solvent was allowed to dehydrate or evaporate overnight. Precoating of plates with either polymyxin or poly-L-lysine did not give any major improvement in coating with the various forms of LPS. The possibility of using proteinase K- and sodium dodecyl sulfate-treated LPS preparations for ELISAs was also investigated. Smooth LPS prepared by this method was as effective in ELISA as LPS prepared by the hot water-phenol method, while the rough and neutral LPSs prepared this way were not satisfactory for ELISA.