Structural and immunological studies of the Haemophilus influenzae type d capsular polysaccharide

Conformational comparisons of Pasteurella multocida types B and E and structurally related capsular polysaccharides

Pasteurella multocida, an encapsulated gram-negative bacterium, is a significant veterinary pathogen. The P. multocida is classified into 5 serogroups (A, B, D, E, and F) based on the bacterial capsular polysaccharide (CPS), which is important for virulence. Serogroups B and E are the primary causative agents of bovine hemorrhagic septicemia that is associated with significant yearly losses of livestock worldwide, primarily in low- and middle-income countries. The P. multocida disease is currently managed by whole-cell vaccination, albeit with limited efficacy. CPS is an attractive antigen target for an improved vaccine: CPS-based vaccines have proven highly effective against human bacterial diseases and could provide longer-term protection against P. multocida. The recently elucidated CPS repeat units of serogroups B and E both comprise a N-acetyl-β-D-mannosaminuronic acid/N-acetyl-β-D-glucosamine disaccharide backbone with β-D-fructofuranose (Fruf) side chain, but differ in their glycosidic linkages, and a glycine (Gly) side chain in serogroup B. Interestingly, the Haemophilus influenzae types e and d CPS have the same backbone residues. Here, comparative modeling of P. multocida serogroups B and E and H. influenzae types e and d CPS identifies a significant impact of small structural differences on both the chain conformation and the exposed potential antibody-binding epitopes (Ep). Further, Fruf and/or Gly side chains shield the immunogenic amino-sugar CPS backbone-a possible common strategy for immune evasion in both P. multocida and H. influenzae. As the lack of common epitopes suggests limited potential for cross-reactivity, a bivalent CPS-based vaccine may be necessary to provide adequate protection against P. multocida types B and E.

Cognition of polysaccharides from confusion to clarity: when the next "omic" will come?

With the accelerated pace of modern life, people are facing more and more health pressure. The study of polysaccharides seemed a good choice as a potential treasure trove. Polysaccharides, one of the four basic substances (proteins, nucleic acids, lipids and carbohydrates) that constitute life activities, are obviously an underrated macromolecular substance with great potential. Compared with protein and nucleic acid, the research of polysaccharides is still in the primary stage. The relationship between structure and function of polysaccharides is not clear. In this review, we highlighted the main methods of extraction, purification and structure identification of polysaccharides; summarized their biological activities including immunoregulation, hypoglycemic, anti-tumor, anti-virus, anti-coagulation, and so on. Particularly, the relationship between their structures and activities was described. In addition, the applications of polysaccharides in health food, medicine and cosmetics were also reviewed. This review can help polysaccharide researchers quickly understand the whole process of polysaccharides research, and also provide a reference for the comprehensive utilization of polysaccharides. We need to standardize the research of polysaccharides to make the experimental data more universal, and take it as important references in the review process. Glycomic may appear as the next "omic" after genomic and proteomic in the future. This review provides support for the advancement of glycomics.

The capsular polysaccharides of Pasteurella multocida serotypes B and E: Structural, genetic and serological comparisons

We describe the structural characterization of the capsular polysaccharides (CPSs) of Pasteurella multocida serotypes B and E. CPS was isolated following organic solvent precipitation of the supernatant from flask grown cells. Structural analysis utilizing nuclear magnetic resonance spectroscopy enabled the determination of the CPS structures and revealed significant structural similarities between the two serotypes, but also provided an explanation for the serological distinction. This observation was extended by the development of polyclonal sera to the glycoconjugate of serotype B CPS that corroborated the structural likenesses and differences. Finally, identification of these structures enabled a more comprehensive interrogation of the genetic loci and prediction of roles for some of the encoded proteins in repeat unit biosynthesis.

Sequence analysis of serotype-specific synthesis regions II of Haemophilus influenzae serotypes c and d: evidence for common ancestry of capsule synthesis in Pasteurellaceae and Neisseria meningitidis

Sequencing of yet unknown Haemophilus influenzae serotype c (Hic) and d (Hid) capsule synthesis regions II revealed four (ccs1-4) and five (dcs1-5) open reading frames, respectively. The inferred gene functions were in line with capsular polysaccharide structures. One or more proteins encoded by the Hic capsule synthesis region II showed similarity to Actinobacillus pleuropneumoniae serotype 1 and Actinobacillus suis K1 enzymes. Orthologues to the complete operon were observed in Actinobacillus minor strain 202, where even the gene order was conserved. Furthermore, Ccs4 was related to the capsule O-acetyltransferase of Neisseria meningitidis serogroup W-135. For the Hid locus, similarities to Hie, Mannheimia haemolytica A1 and N. meningitidis serogroup A were identified and the succession of genes was similar in the different species. The resemblance of genes and gene organization found for Hic and Hid with other species suggested horizontal gene transfer during capsule evolution across the bacterial classes.

Structural and functional analyses of the secondary cell wall polymer of Bacillus sphaericus CCM 2177 that serves as an S-layer-specific anchor

Sacculi of Bacillus sphaericus CCM 2177 contain a secondary cell wall polymer which was completely extracted with 48% hydrofluoric acid. Nuclear magnetic resonance analysis showed that the polymer is composed of repeating units, as follows: -->3)-[4, 6-O-(1-carboxyethylidene)]( approximately 0. 5)-beta-D-ManpNAc-(1-->4)-beta-D-GlcpNAc-(1-->. The N-terminal part of the S-layer protein carrying S-layer homologous motifs recognizes this polymer as a binding site.

Assembly of the K40 antigen in Escherichia coli: identification of a novel enzyme responsible for addition of L-serine residues to the glycan backbone and its requirement for K40 polymerization

Escherichia coli O8:K40 coexpresses two distinct lipopolysaccharide (LPS) structures on its surface. The O8 polysaccharide is a mannose homopolymer with a trisaccharide repeat unit and is synthesized by an ABC-2 transport-dependent pathway. The K40LPS backbone structure is composed of a trisaccharide repeating unit of N-acetylglucosamine (GlcNAc) and glucuronic acid (GlcA) and has an uncommon substitution, an L-serine moiety attached to glucuronic acid. The gene cluster responsible for synthesis of the K40 polysaccharide has previously been cloned and sequenced and was found to contain six open reading frames (ORFs) (P. A. Amor and C. Whitfield, Mol. Microbiol. 26:145-161, 1997). Here, we demonstrate that insertional inactivation of orf1 results in the accumulation of a semirough (SR)-K40LPS form which retains reactivity with specific polyclonal serum in Western immunoblots. Structural and compositional analysis of the SR-K40LPS reveals that it comprises a single K40 repeat unit attached to lipid A core. The lack of polymerization of the K40 polysaccharide indicates that orf1 encodes the K40 polymerase (Wzy) and that assembly of the K40 polysaccharide occurs via a Wzy-dependent pathway (in contrast to that of the O8 polysaccharide). Inactivation of orf3 also results in the accumulation of an SR-LPS form which fails to react with specific polyclonal K40 serum in Western immunoblots. Methylation linkage analysis and fast atom bombardment-mass spectrometry of this SR-LPS reveals that the biological repeat unit of the K40 polysaccharide is GlcNAc-GlcA-GlcNAc. Additionally, this structure lacks the L-serine substitution of GlcA. These results show that (i) orf3 encodes the enzyme responsible for the addition of the L-serine residue to the K40 backbone and (ii) substitution of individual K40 repeats with L-serine is essential for their recognition and polymerization into the K40 polysaccharide by Wzy.

Occurrence of 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid as an N-acyl substituent in the O-polysaccharide chain of the lipopolysaccharide of Vibrio anguillarum V-123

A new and highly branched amino acid was found as an N-acyl substituent of the O-polysaccharide chain obtained from the lipopolysaccharide of Vibrio anguillarum V-123 (serogroup JO-2) and evidence is presented to support the structure as 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid. Acid hydrolysis of the O-polysaccharide gave the lactone of 2,4-dihydroxy-3,3,4-trimethylglutamic acid, together with 2-amino-2-deoxy-D-galacturonic acid, 2-amino-2,6-dideoxy-D-glucose (D-quinovosamine), and 4-amino-4,6-dideoxy-D-glucose (D-viosamine). Degradation of the O-polysaccharide with hydrogen fluoride yielded a fragment (H1) that was indicated by the 1H-NMR data to be 4-amino-4,6-dideoxy-D-glucose N-acetylated with 2,4-dihydroxy-3,3,4-trimethylpyroglutamic acid. The configuration of the amino acid was not determined.

Synthesis of carbohydrate-amino acid conjugates related to the capsular antigen K54 from Escherichia coli O6:K54:H10 and artificial antigens therefrom

The disaccharides alpha-L-Rhap-(1----3)-beta-D-GlcpA and beta-D-GlcpA-(1----3)-alpha-L-Rhap bearing amide-linked L-serine or L-threonine, which represent the repeating unit(s) of the capsular polysaccharide from E. coli O6:K54:H10, have been synthesised. O-tert-Butyl-protected amino acid tert-butyl esters were condensed with the corresponding biouronic acid as the 2-acrylamidoethyl or 2-azidoethyl glycosides. The azido function was replaced by the acrylamido group by catalytic hydrogenation followed by N-acryloylation. The tert-butyl groups were removed by treatment with trifluoroacetic acid to give the target monomers which were copolymerised with acrylamide to give neoglycoconjugates that are potentially useful for immunochemical studies.

Synthesis of an artificial antigen that corresponds to a disaccharide repeating unit of the capsular polysaccharide of Haemophilus influenzae type d. A facile synthesis of methyl 2-acetamido-2-deoxy-beta-D-mannopyranoside

The synthesis is described of p-nitrophenyl 2-acetamido-3-O-(2-acetamido-2-deoxy-beta-D-glucopyranosyl)-2-deoxy-beta -D- mannopyranosiduronic acid, corresponding to the disaccharide repeating unit of the capsular polysaccharide of Haemophilus influenzae type d, which, after conversion of the p-nitro- into a p-amino-phenyl residue, may be attached to a protein to make an artificial antigen for immunological studies. The synthesis incorporates a facile route to the 2-acetamido-2-deoxy-beta-D-mannopyranosyl unit.

Synthesis of glycuronamides of amino acids, constituents of microbial polysaccharides and their conversion into neoglycoconjugates of copolymer type

Glycopyranosiduronic acids, amidically linked to amino acids (alanine, serine, threonine, and lysine) were prepared. O-tert-Butyl and N epsilon-tert-butyloxycarbonyl protected amino acid tert-butyl esters were used in ethyl 2-ethoxy-1,2-dihydroquinoline-1-carboxylate promoted condensation with 2-azidoethyl glycosides of glucuronic and galacturonic acid. Reduction of the azido-function followed by N-acryloylation and removal of blocking groups with trifluoroacetic acid gave the target monomers. These were converted into neoglycoconjugates of copolymer type, potentially useful for immunochemical studies.

Structure of the amino acid-containing capsular polysaccharide from Escherichia coli O8:K49:H21

The structure of the capsular antigen of E. coli K49 and the oligosaccharides derived from it by partial acid hydrolysis were studied by 1D- and 2D-n.m.r. spectroscopy, g.l.c.-c.i.-mass spectrometry, and methylation analysis. The K49 polysaccharide consists of the repeating unit----4)-beta-D-GlcpA-(1----6)-beta-D-Galp-(1----6)-beta-D-Glcp- (1----3)-beta - D-GalpNAc-(1----. The glucuronic acid residues are substituted, in the apparent molar ratio of 4:1, with L-threonine and L-serine linked amidically to the carboxyl group.

Structural studies of acidic polymers produced by the O23 reference strain of Serratia marcescens: presence of amide-linked glutamic acid

The major fraction of an acidic galactoglucomannan present in lipopolysaccharide extracts from cell walls of the O23 reference strain of Serratia marcescens has the tetrasaccharide repeating-unit shown. In a minor fraction, L-glutamic acid was amide-linked to about half of the D-glucuronic acid residues. The possible contributions of the acidic polymers and a neutral polymer produced by the organism to cross-reactions with other serogroups are discussed.

Structural studies on the neutral polysaccharide of Bacillus subtilis AHU 1219 cell walls

A neutral and an acidic polysaccharide with molecular masses of about 22 kDa and 45 kDa, respectively, were isolated from the N-acetylated cell walls of Bacillus subtilis AHU 1219 by heating at pH 2.5, followed by separation of the water-soluble product by ion-exchange chromatography and gel chromatography. The neutral polysaccharide, accounting for 40% of the mass of the cell walls, contained glucose, N-acetylglucosamine, N-acetylgalactosamine and N-acetylmannosamine in a molar ratio of 1:2:1:1. The minor, acidic polysaccharide contained glucuronic acid, glucose, galactose, L-serine and L-threonine in an approximate molar ratio of 1:1:1:0.5:0.5. Lysozyme digestion of the N-acetylated cell walls gave a polymer containing the neutral polysaccharide and glycopeptide components and another polymer which contained the acidic polysaccharide components together with small proportions of the neutral polysaccharide and glycopeptide components. Thus, the neutral and acidic polysaccharide chains seem to be attached to peptidoglycan through acid-labile linkages in the cell walls of this strain. Structural analysis of the neutral-polysaccharide preparation, involving 1H-NMR and 13C-NMR measurement, methylation and Smith degradation, led to the most likely structure, ----6)[Glc(beta 1----3)]GalNAc(alpha 1----4)-[GlcNAc(beta 1----3)]ManNAc(beta 1----4)GlcNAc(beta 1----, for the repeating units of this polysaccharide.

Structural studies on the amino-acid-linked teichuronic acid of Bacillus subtilis AHU 1219 cell walls

Structural studies were carried out on a teichuronic acid isolated from a mild acid extract of Bacillus subtilis AHU 1219 cell walls. The teichuronic acid contained D-glucuronic acid, D-glucose, D-galactose, L-serine and L-threonine in a molar ratio of 1:1:1:0.5:0.5. Results of analyses of the polysaccharide by Smith degradation, methylation and 1H-NMR and 13C-NMR spectroscopy, in combination with data on analyses of oligosaccharides obtained by partial acid hydrolysis and alkaline hydrolysis of the polymer, led to the most likely structure for the repeating unit, ----4)(L-Ser/L-Thr)-D-GlcA(beta 1----3)-D-Glc(beta 1----4)-D-Gal(alpha 1----. In each unit, either amino acid is linked to the glucuronic acid residue through an amide bond.

Pyruvic-acid-containing polysaccharide in the cell wall of Bacillus polymyxa AHU 1385

Three acidic polymer fractions with molecular masses of about 16 kDa, 35 kDa and 70 kDa were isolated from lysozyme digests of N-acetylated cell walls of Bacillus polymyxa AHU 1385 by ion-exchange chromatography and gel chromatography. These fractions, containing mannosamine, glucosamine and pyruvic acid in a molar ratio of about 1:1:1 together with glycopeptide components, were characterized as polysaccharide-linked glycopeptides with one, two and more polysaccharide chains. On the other hand, treatment of the cell walls with glycine/HC1 buffer, pH 2.5, at 100 degrees C for 10 min followed by separation of water-soluble products on ion-exchange chromatography gave three polysaccharide fractions, PS-I-III, which contained different amounts of pyruvic acid (0,0.6 and 0.9 residue/mannosamine residue) along with equimolar amounts of mannosamine and glucosamine. Pyruvate-free polysaccharides similar to PS-I were also obtained from PS-II, PS-III and polysaccharide-linked glycopeptides by treatment with 10 mM HC1 at 100 degrees C for 1 h. Results of analyses of these polysaccharide preparations by 1H-NMR and 13C-NMR measurement and methylation, together with data from characterization of fragments obtained by hydrogen fluoride hydrolysis, lead to the most likely structure, ----3)[4,6-O-(1-carboxyethylidene)]ManNAc(beta 1----4)GlcNac(beta 1----, for the acidic polysaccharide of this strain.

[Synthesis of trisaccharide determinants of enterobacterial common antigens]

In the presence of silver silicate, the reaction of 3,4,6-tri-O-acetyl-2-azido-2-deoxy-alpha-D-mannopyranosyl bromide with 1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-beta-D-glucopyranose gave beta-glycosidically linked 1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-4-O-(3,4,6- tri-O-acetyl-2-azido-2-deoxy-beta-D-mannopyranosyl)-beta-D- glucopyranose. After deacetylation and catalytic oxidation with oxygen and platinum, 1,6-anhydro-2-azido-4-O-[(2-azido-2-deoxy-beta-D-mannopyranosyl) uronic acid]-3-O-benzyl-2-deoxy-beta-D-glucopyranose was obtained. A series of intermediate steps led to the glycosyl donor 6-O-acetyl-2-azido-3-O-benzyl-4-O-[benzyl (3,4-di-O-acetyl-2-azido-2-deoxy-beta-D-mannopyranosyl)uronate]-2-deoxy- alpha, beta-glucopyranosyl chloride which was coupled with 8-methoxycarbonyloctyl 4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-galactopyranoside to give 8-methoxycarbonyloctyl O-[benzyl (3,4-di-O-acetyl-2-azido-2-deoxy-beta-D-mannopyranosyl)uronate]- (1----4)-O-(6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-alpha-D-glucopyranosyl )-(1----3)-4-azido-2-O-benzyl-4,6-dideoxy-alpha-D-galactopyranoside. Deblocking gave the spacer-linked repeating unit of the enterobacterial common antigen, beta-D-ManpNAcA-(1----4)-alpha-D-GlcpNAc-(1----3)-alpha- D-Fucp4NACO(CH2)8CO2CH3.

Structure of the capsular antigen of Neisseria meningitidis serogroup K

The capsular antigen isolated from the culture liquid of a Neisseria meningitidis serogroup K(1811) fermentation consists of the 2-acetamido-2-deoxymannuronic acid disaccharide repeating unit as follows: ----3)-beta-D-ManpNAcA-(1----4)-beta-D-ManpNAcA-(1---- The polysaccharide is O-acetylated at the non-glycosylated C-4. Structural evidence has been obtained from sugar analysis, methylation analysis, as well as 1H and 13C NMR spectroscopy.

Structure of the amino acid-containing capsular polysaccharide (K54 antigen) from Escherichia coli O6:K54:H10

The structure of the K54-antigenic polysaccharide (K54 antigen) of Escherichia coli O6:K54:H10 was elucidated by determination of the composition, 1H- and 13C-n.m.r. spectroscopy, periodate oxidation, and a study of the oligosaccharides obtained by partial hydrolysis with acid. The K54 polysaccharide consists of----3)-beta-D-glucosyluronic acid-(1----3)-alpha-L-rhamnosyl-(1----repeating-units. Of the glucuronic acid residues, approximately 85% are substituted in the ratio 9:1 with L-threonine and L-serine amidically linked to the carboxyl group. The K54 polysaccharide has a molecular weight of approximately 160,000, corresponding to approximately 380 repeating-units.

The structure of the polysaccharide moiety of Rhodopseudomonas sphaeroides ATCC 17023 lipopolysaccharide

The chemical structure of the polysaccharide moiety of the lipopolysaccharide Rhodopseudomonas sphaeroides ATCC 17023 was established. Mild acetic acid hydrolysis of isolated lipopolysaccharide, followed by preparative high-voltage paper electrophoresis afforded three oligosaccharides. They were characterized by chemical and physicochemical studies to be: GlcA(alpha 1----4)dOclA8P, Thr(6') GlcA(alpha 1----4)GlcA and GlcA(alpha 1----4)dOclA, where GlcA is D-glucuronic acid and dOc1A is 3-deoxy-D-manno-octulosonic acid. Carboxyl-reduction of the lipopolysaccharide followed by acid hydrolysis gave a trisaccharide: GlcA(alpha 1----4)Glc(alpha 1----4)Glc, showing the presence of three residues of glucuronic acids in the O-specific chain and indicating that only two of them are reducible by NaBH4. The linkage between the polysaccharide and lipid A was shown to be through a single 1,4-linked residue of dOc1A attached by a 2,6'-linkage to the lipid A moiety.

Cell-wall lipopolysaccharide of Escherichia coli 0114:H2. Structure of the polysaccharide chain

The O-specific polysaccharide of the 0114 antigen (lipopolysaccharide) of Escherichia coli 0114 and oligosaccharides obtained from it by Smith degradation and hydrogen fluoride solvolysis were analyzed, using proton and 13C nuclear magnetic resonance spectroscopy and methylation. The results indicated that the 0114 polysaccharide has the tetrasaccharide repeating unit alpha-N-acetylglucosamine(1 leads to 4) beta-3,6-dideoxy-3-(N-acetyl-L-seryl)aminoglucose(1 leads to 3) beta-ribofuranose(1 leads to 4)galactose. In the polysaccharide the repeating units are joined through beta 1 leads to 3-galactosyl linkages. This structure is compared with that of the serologically cross-reacting Shigella boydii 08 antigen and the serological similarity is discussed.

Structural and immunological studies of the Escherichia coli K7 (K56) capsular polysaccharide

The structure of the Escherichia coli K7 capsular polysaccharide has been investigated by a combination of chemical and spectroscopic methods. The Structure of the repeating unit of the polymer was found to be goes to 3)-beta-D-ManNAcA-(1 leads to 4)-beta-D-Glc-(1 goes to ; the O-6 atom of the D-glucosyl residue in the repeating unit is acetylated. The K7 polysaccharide is cross-reactive with the Streptococcus pneumoniae type 3 polysaccharide, the structure of which had previously been determined; our n.m.r. studies of the S. pneumoniae type 3 polysaccharide are in accord with this structure. The E. coli K7 and K56 capsular antigens have been shown by serology and 13C-n.m.r. spectroscopy to be identical.

Structural studies of the capsular polysaccharide elaborated by Haemophilus influenza type d

The structure of the capsular polysaccharide elaborated by Haemophilus influenzae type d has been investigated, methylation analysis and n.m.r. spectrometry being the principal methods used. It is concluded that the polysaccharide is composed of repeating units having the structure: leads to 4)-beta-D-GlcpNAc-(1 leads to 3)-beta-D-ManpNAcA-(1 leads to. In addition, single residues of L-alanine, L-serine, or L-threonine, in the proportions 2:2:1, are linked, through their amino groups, to C-6 of the 2-acetamido-2-deoxy-beta-D-mannopyranosyluronic acid residues. The degree of substitution (75-85%) varies for different preparations.