Structural Studies of the Lipopolysaccharide Isolated from Plesiomonas shigelloides O22:H3 (CNCTC 90/89)

Plesiomonas shigelloides is a Gram-negative, rod-shaped bacterium which causes foodborne intestinal infections, including gastroenteritis. It is one of the most frequent causes of travellers’ diarrhoea. Lipopolysaccharide (LPS, endotoxin), an important virulence factor of the species, is in most cases characterised by a smooth character, demonstrated by the presence of all regions, such as lipid A, core oligosaccharide, and O-specific polysaccharide, where the latter part determines O-serotype. P. shigelloides LPS is still a poorly characterised virulence factor considering a “translation” of the particular O-serotype into chemical structure. To date, LPS structure has only been elucidated for 15 strains out of 102 O-serotypes. Structures of the new O-specific polysaccharide and core oligosaccharide of P. shigelloides from the Czechoslovak National Collection of Type Cultures CNCTC 90/89 LPS (O22), investigated by chemical analysis, mass spectrometry, and ¹H,¹³C nuclear magnetic resonance (NMR) spectroscopy, have now been reported. The pentasaccharide repeating unit of the O-specific polysaccharide is built of one d-QuipNAc and is rich in four d-GalpNAcAN residues. Moreover, the new core oligosaccharide shares common features of other P. shigelloides endotoxins, i.e., the lack of phosphate groups and the presence of uronic acids.

Interaction of Mannose-Binding Lectin With Lipopolysaccharide Outer Core Region and Its Biological Consequences

Lipopolysaccharide (LPS, endotoxin), the main surface antigen and virulence factor of Gram-negative bacteria, is composed of lipid A, core oligosaccharide, and O-specific polysaccharide (O-PS) regions. Each LPS region is capable of complement activation. We have demonstrated that LPS of Hafnia alvei, an opportunistic human pathogen, reacts strongly with human and murine mannose-binding lectins (MBLs). Moreover, MBL-LPS interactions were detected for the majority of other Gram-negative species investigated. H. alvei was used as a model pathogen to investigate the biological consequences of these interactions. The core oligosaccharide region of H. alvei LPS was identified as the main target for human and murine MBL, especially l-glycero-d-manno-heptose (Hep) and N-acetyl-d-glucosamine (GlcNAc) residues within the outer core region. MBL-binding motifs of LPS are accessible to MBL on the surface of bacterial cells and LPS aggregates. Generally, the accessibility of outer core structures for interaction with MBL is highest during the lag phase of bacterial growth. The LPS core oligosaccharide-MBL interactions led to complement activation and also induced an anaphylactoid shock in mice. Unlike Klebsiella pneumoniae O3 LPS, robust lectin pathway activation of H. alvei LPS in vivo was mainly the result of outer core recognition by MBL; involvement of the O-PS is not necessary for anaphylactoid shock induction. Our results contribute to a better understanding of MBL-LPS interaction and may support development of therapeutic strategies against sepsis based on complement inhibition.

Structure-Activity Relationship of Plesiomonas shigelloides Lipid A to the Production of TNF-α, IL-1β, and IL-6 by Human and Murine Macrophages

Plesiomonas shigelloides is a Gram-negative bacterium that is associated with diarrheal disease in humans. Lipopolysaccharide (LPS) is the main surface antigen and virulence factor of this bacterium. The lipid A (LA) moiety of LPS is the main region recognized by target cells of immune system. Here, we evaluated the biological activities of P. shigelloides LA for their abilities to induce the productions of proinflammatory cytokines (TNF-α, IL-1β, and IL-6) by human and murine macrophages [THP-1 macrophages and immortalized murine bone marrow-derived macrophages (iBMDM)]. Four native P. shigelloides LA preparations differing in their phosphoethanolamine (PEtn) substitution, length, number, and saturation of fatty acids were compared with Escherichia coli O55 LA. The bisphosphorylated, hexaacylated, and asymmetric forms of the P. shigelloides and E. coli LA molecules had similar activities in human and murine macrophages, indicating that shortening of the acyl chains in P. shigelloides LA had no effect on its in vitro activities. The PEtn decoration also had no impact on the interaction with the toll-like receptor 4/MD-2 receptor complex. The heptaacylated form of P. shigelloides LA decorated with 16:0 exhibited strong effect on proinflammatory activity, significantly decreasing the levels of all tested cytokines in both murine and human macrophages. Our results revealed that despite the presence of shorter acyl chains and an unsaturated acyl residue (16:1), the bisphosphorylated, hexaacylated, and asymmetric forms of P. shigelloides LA represent highly immunostimulatory structures.

The O-antigen of Plesiomonas shigelloides serotype O36 containing pseudaminic acid

The structure of the repeating unit of O-antigen of Plesiomonas shigelloides serotype O36 has been investigated by ¹H and ¹³C NMR spectroscopy, matrix-assisted laser-desorption/ionization time-of-flight mass spectrometry and chemical methods. The new structure of trisaccharide has been established: [Formula: see text] These trisaccharide O-antigen units substitute the core undecasaccharide at C-4 of the β-D-GlcpNAc residue. The core oligosaccharide and lipid A are identical with these of the serotype O17 (PCM 2231) (Maciejewska, A., Lukasiewicz, J., Kaszowska, M., Jachymek, W., Man-Kupisinska, A.; Lugowski, C. Mar. Drugs.2013, 11 (2), 440-454; Lukasiewicz, J., Dzieciatkowska, M., Niedziela, T., Jachymek, W., Augustyniuk, A., Kenne, L., Lugowski, C. Biochemistry, 2006, 45, 10434-10447).

A New Ligand-Based Method for Purifying Active Human Plasma-Derived Ficolin-3 Complexes Supports the Phenomenon of Crosstalk between Pattern-Recognition Molecules and Immunoglobulins

Despite recombinant protein technology development, proteins isolated from natural sources remain important for structure and activity determination. Ficolins represent a class of proteins that are difficult to isolate. To date, three methods for purifying ficolin-3 from plasma/serum have been proposed, defined by most critical step: (i) hydroxyapatite absorption chromatography (ii) N-acetylated human serum albumin affinity chromatography and (iii) anti-ficolin-3 monoclonal antibody-based affinity chromatography. We present a new protocol for purifying ficolin-3 complexes from human plasma that is based on an exclusive ligand: the O-specific polysaccharide of Hafnia alvei PCM 1200 LPS (O-PS 1200). The protocol includes (i) poly(ethylene glycol) precipitation; (ii) yeast and l-fucose incubation, for depletion of mannose-binding lectin; (iii) affinity chromatography using O-PS 1200-Sepharose; (iv) size-exclusion chromatography. Application of this protocol yielded average 2.2 mg of ficolin-3 preparation free of mannose-binding lectin (MBL), ficolin-1 and -2 from 500 ml of plasma. The protein was complexed with MBL-associated serine proteases (MASPs) and was able to activate the complement in vitro. In-process monitoring of MBL, ficolins, and total protein content revealed the presence of difficult-to-remove immunoglobulin G, M and A, in some extent in agreement with recent findings suggesting crosstalk between IgG and ficolin-3. We demonstrated that recombinant ficolin-3 interacts with IgG and IgM in a concentration-dependent manner. Although this association does not appear to influence ficolin-3-ligand interactions in vitro, it may have numerous consequences in vivo. Thus our purification procedure provides Ig-ficolin-3/MASP complexes that might be useful for gaining further insight into the crosstalk and biological activity of ficolin-3.

Fractionation and analysis of lipopolysaccharide-derived oligosaccharides by zwitterionic-type hydrophilic interaction liquid chromatography coupled with electrospray ionisation mass spectrometry

Lipopolysaccharide (LPS, endotoxin) is a main surface antigen and virulence factor of Gram-negative bacteria. Regardless of the source of LPS, this molecule, isolated from the smooth forms of bacteria, is characterised by a general structural layout encompassing three regions: (i) an O-specific polysaccharide (O-PS) - a polymer of repeating oligosaccharide units, (ii) core oligosaccharide (OS), and (iii) the lipid A anchoring LPS in the outer membrane of the cell envelope of Gram-negative bacteria. Structural analysis usually requires degradation of LPS and further efficient separation of various poly- and oligosaccharide glycoforms. The hydrophilic interaction liquid chromatography (HILIC) was shown as an efficient technique for separation of labelled or native neutral and acidic glycans, glycopeptides, sialylated glycans, glycosylated and nonglycosylated peptides. Herein we adopted ZIC(®) (zwitterionic stationary phase covalently attached to porous silica)-HILIC technology in combination with electrospray ionisation mass spectrometry to separate different LPS-derived oligosaccharides. As a result three effective procedures have been developed: (i) to separate different core oligosaccharides of Escherichia coli R1 LOS, (ii) to separate RU-[Hep]-Kdo oligosaccharides from core OS glycoforms of Hafnia alvei PCM 1200 LPS, and (iii) to separate Hep and Kdo-containing mono, di-, tri- and tetrasaccharides of H. alvei PCM 1200 LPS. Moreover, some of developed analytical procedures were scaled to semi-preparative protocols and used to obtain highly-purified fractions of the interest in larger quantities required for future evaluation, analysis, and biological applications.

First evidence for a covalent linkage between enterobacterial common antigen and lipopolysaccharide in Shigella sonnei phase II ECALPS

Enterobacterial common antigen (ECA) is expressed by Gram-negative bacteria belonging to Enterobacteriaceae, including emerging drug-resistant pathogens such as Escherichia coli, Klebsiella pneumoniae, and Proteus spp. Recent studies have indicated the importance of ECA for cell envelope integrity, flagellum expression, and resistance of enteric bacteria to acetic acid and bile salts. ECA, a heteropolysaccharide built from the trisaccharide repeating unit, →3)-α-D-Fucp4NAc-(1→4)-β-D-ManpNAcA-(1→4)-α-D-GlcpNAc-(1→, occurs as a cyclic form (ECA(CYC)), a phosphatidylglycerol (PG)-linked form (ECA(PG)), and an endotoxin/lipopolysaccharide (LPS)-associated form (ECA(LPS)). Since the discovery of ECA in 1962, the structures of ECA(PG) and ECA(CYC) have been completely elucidated. However, no direct evidence has been presented to support a covalent linkage between ECA and LPS; only serological indications of co-association have been reported. This is paradoxical, given that ECA was first identified based on the capacity of immunogenic ECA(LPS) to elicit antibodies cross-reactive with enterobacteria. Using a simple isolation protocol supported by serological tracking of ECA epitopes and NMR spectroscopy and mass spectrometry, we have succeeded in the first detection, isolation, and complete structural analysis of poly- and oligosaccharides of Shigella sonnei phase II ECA(LPS). ECA(LPS) consists of the core oligosaccharide substituted with one to four repeating units of ECA at the position occupied by the O-antigen in the case of smooth S. sonnei phase I. These data represent the first structural evidence for the existence of ECA(LPS) in the half-century since it was first discovered and provide insights that could prove helpful in further structural analyses and screening of ECA(LPS) among Enterobacteriaceae species.

The novel structure of the core oligosaccharide backbone of the lipopolysaccharide from the Plesiomonas shigelloides strain CNCTC 80/89 (serotype O13)

The new structure of the core oligosaccharide of Plesiomonas shigelloides CNCTC 80/89 (serotype O13) lipopolysaccharide has been investigated by chemical methods, (1)H and (13)C NMR spectroscopy and matrix-assisted laser-desorption/ionization time of flight (MALDI-TOF). It was concluded that the core oligosaccharide of P. shigelloides CNCTC 80/89 is a nonasaccharide with the following structure: The position of glycine was determined by MALDI-TOF MS/MS analyses.

New functional ligands for ficolin-3 among lipopolysaccharides of Hafnia alvei

Ficolin-1 (M), ficolin-2 (L), ficolin-3 (H) and mannan-binding lectin (MBL) activate the complement system and have opsonic activity. The specificity of ficolin-3 is poorly characterized and currently limited to a few ligands only. We present new specific targets for human ficolin-3, identified among lipopolysaccharides (LPSs, endotoxin) of Hafnia alvei. The interaction was restricted to LPSs of four strains: 23, Polish Collection of Microorganisms (PCM) 1200, PCM 1203 and PCM 1205 and limited to their O-specific polysaccharides (O-specific PSs) composed of different numbers of oligosaccharide (OS) repeating units (RUs). Moreover, these LPS/ficolin-3 complexes activated the lectin pathway of complement in a C4b-deposition assay in a calcium- and magnesium-dependent way. A neoglycoconjugate of the O-specific PS fraction of H. alvei 1200 LPS with bovine serum albumin (BSA) was prepared and used as a tool for the determination of ficolin-3 concentration and activity in serum. To confirm a structure of the O-specific PS 1200 selected for the conjugate preparation, structural analysis was performed on a series of O-specific PSs released by the mild acid hydrolysis of the LPS. The isolated O-specific PSs, showing the different length distributions, were devoid of a major part of the core OS region and had Hep-Kdo disaccharide at a reducing end. The neoglycoconjugate was a highly selective tool for the determination of ficolin-3 concentration and activity in serum (lectin pathway activation in the C4b deposition assay) and was not affected by MBL, ficolin-1 and ficolin-2 or natural antibodies.

H-ficolin (ficolin-3) concentrations and FCN3 gene polymorphism in neonates

Serum H-ficolin (ficolin-3) concentrations (n=613) and FCN3 genotypes (n=529) from a large group of neonates are presented. Both pre-term deliveries and low birthweight (independently of gestational age) were significantly associated with low H-ficolin concentrations but not with heterozygosity for the FCN3 1637delC frameshift mutation. The presence of the variant allele, however, apparently influenced the protein level. No association of FCN3 gene heterozygosity or relative functional H-ficolin insufficiency (determined as serum level ≤8.6 μg/ml) with perinatal infections was found. One premature newborn, with confirmed infection caused by Streptococcus agalactiae, was H-ficolin-deficient (FCN3 variant homozygote, no detectable protein). We present what is only the fourth case report of total H-ficolin deficiency in the world literature. This neonate was however previously found to be mannan-binding lectin (MBL) as well as MBL-associated serine protease-2 (MASP-2) deficient and also had low serum L-ficolin.

Structural analysis of the lipid A isolated from Hafnia alvei 32 and PCM 1192 lipopolysaccharides

Hafnia alvei, a Gram-negative bacterium, is an opportunistic pathogen associated with mixed hospital infections, bacteremia, septicemia, and respiratory diseases. The majority of clinical symptoms of diseases caused by this bacterium have a lipopolysaccharide (LPS, endotoxin)-related origin. The lipid A structure affects the biological activity of endotoxins predominantly. Thus, the structure of H. alvei lipid A was analyzed for the first time. The major form, asymmetrically hexa-acylated lipid A built of beta-D-GlcpN4P-(1-->6)-alpha-D-GlcpN1P substituted with (R)-14:0(3-OH) at N-2 and O-3, 14:0(3-(R)-O-12:0) at N-2', and 14:0(3-(R)-O-14:0) at O-3', was identified by ESI-MS(n) and MALDI-time-of-flight (TOF) MS. Comparative analysis performed by MS suggested that LPSs of H. alvei 32, PCM 1192, PCM 1206, and PCM 1207 share the identified structure of lipid A. LPSs of H. alvei are yet another example of enterobacterial endotoxins having the Escherichia coli-type structure of lipid A. The presence of hepta-acylated forms of H. alvei lipid A resulted from the addition of palmitate (16:0) substituting 14:0(3-OH) at N-2 of the alpha-GlcpN residue. All the studied strains of H. alvei have an ability to modify their lipid A structure by palmitoylation.

Structural analysis of the O-specific polysaccharide isolated from Plesiomonas shigelloides O51 lipopolysaccharide

Plesiomonasshigelloides strain CNCTC 110/92 (O51) was identified as a new example of plesiomonads synthesising lipopolysaccharides (LPSs) that show preference for a non-aqueous surrounding during phenol/water extraction. Chemical analyses combined with (1)H and (13)C NMR spectroscopy, MALDI-TOF and ESI mass spectrometry showed that the repeating units of the O-specific polysaccharides isolated from phenol and water phase LPSs of P. shigelloides O51 have the same structure: -->4)-beta-D-GlcpNAc3NRA-(1-->4)-alpha-L-FucpAm3OAc-(1-->3)-alpha-D-QuipNAc-(1-->, containing the rare sugar constituent 2,3-diamino-2,3-dideoxyglucuronic acid (GlcpNAc3NRA), and substituents such as D-3-hydroxybutyric acid (R) and acetamidino group (Am). The HR-MAS NMR spectra obtained for the isolated LPSs and directly on bacteria indicated that the O-acetylation pattern was consistent throughout the entire preparation. The (1)H chemical shift values of the structure reporter groups identified in the isolated O-antigens matched those present in bacteria. We have found that the O-antigens recovered from the phenol phase showed a higher degree of polymerisation than those isolated from the water phase.

Bacteriophage preparation inhibition of reactive oxygen species generation by endotoxin-stimulated polymorphonuclear leukocytes

It has been known that administration of antibiotics may lead to excessive release of bacterial endotoxins and complicate clinical course of patients with Gram-negative infections. This concern may also apply to phages. Endotoxin may in turn activate neutrophils to produce reactive oxygen species (ROS) that are believed to play an important role in the pathogenesis of multiple organ dysfunction in the course of sepsis. We showed that a purified T4 phage preparation with low-endotoxin content could significantly diminish the luminol-dependent chemiluminescence (CL) of peripheral blood polymorphonuclear leukocytes (PMNs) both stimulated by lipopolysaccharides (LPSs) isolated from different Escherichia coli strains. This effect was also observed for live bacteria used for PMNs stimulation and was independent of bacterial susceptibility for T4-mediated lysis. Our data suggest, that phage-mediated inhibition of LPS- or bacteria-stimulated ROS production by PMNs may be attributed not only to phage-PMNs interactions, but also to phage-LPS interactions and bacterial lysis (in case of homologous phage). Interestingly, the T4 preparation did not influence ROS formation by PMNs stimulated with PMA. This suggests that the observed phenomena are also dependent upon the nature of activator. Bacteriophage-mediated inhibition of ROS formation by cells exposed to endotoxin provides new evidence for possible interactions between phages and mammalian cells. It helps in understanding the role of phages in our environment and may also be of important clinical significance.

Complete Lipopolysaccharide of Plesiomonas shigelloides O74:H5 (Strain CNCTC 144/92). 1. Structural Analysis of the Highly Hydrophobic Lipopolysaccharide, Including the O-Antigen, Its Biological Repeating Unit, the Core Oligosaccharide, and the Linkage between Them,

The lipopolysaccharide of Plesiomonas shigelloides serotype O74:H5 (strain CNCTC 144/92) was obtained with the hot phenol/water method, but unlike most of the S-type enterobacterial lipopolysaccharides, the O-antigens were preferentially extracted into the phenol phase. The poly- and oligosaccharides released by mild acidic hydrolysis of the lipopolysaccharide from both phenol and water phases were separated and investigated by (1)H and (13)C NMR spectroscopy, MALDI-TOF mass spectrometry, and sugar and methylation analysis. The O-specific polysaccharide and oligosaccharides consisting of the core, the core with one repeating unit, and the core with two repeating units were isolated. It was concluded that the O-specific polysaccharide is composed of a trisaccharide repeating unit with the [-->2)-beta-d-Quip3NAcyl-(1-->3)-alpha-l-Rhap2OAc-(1-->3)-alpha-d-FucpNAc-(1-->] structure, in which d-Qui3NAcyl is 3-amino-3,6-dideoxy-d-glucose acylated with 3-hydroxy-2,3-dimethyl-5-oxopyrrolidine-2-carboxylic acid. The major oligosaccharide consisted of a single repeating unit and a core oligosaccharide. This undecasaccharide contains information about the biological repeating unit and the type and position of the linkage between the O-specific chain and core. The presence of a terminal beta-d-Quip3NAcyl-(1--> residue and the -->3)-beta-d-FucpNAc-(1-->4)-alpha-d-GalpA element showed the structure of the biological repeating unit of the O-antigen and the substitution position to the core. The -->3)-beta-d-FucpNAc-(1--> residue has the anomeric configuration inverted compared to the same residue in the repeating unit. The core oligosaccharide was composed of a nonphosphorylated octasaccharide, which represents a novel core type of P. shigelloides LPS characteristic of serotype O74. The similarity between the isolated O-specific polysaccharide and that found on intact bacterial cells and lipopolysaccharide was confirmed by HR-MAS NMR experiments.

Complete Lipopolysaccharide of Plesiomonas shigelloides O74:H5 (Strain CNCTC 144/92). 2. Lipid A, Its Structural Variability, the Linkage to the Core Oligosaccharide, and the Biological Activity of the Lipopolysaccharide,

Plesiomonas shigelloides is a Gram-negative bacterium associated with waterborne infections, which is common in tropical and subtropical habitats. Contrary to the unified antigenic classification of P. shigelloides, data concerning the structure and activity of their lipopolysaccharides (LPS and endotoxin) are limited. This study completes the structural investigation of phenol- and water-soluble fractions of P. shigelloides O74 (strain CNCTC 144/92) LPS with the emphasis on lipid A heterogeneity, describing the entire molecule and some of its biological in vitro activities. Structures of the lipid A and the affinity-purified decasaccharide obtained by de-N,O-acylation of P. shigelloides O74 LPS were elucidated by chemical analysis combined with electrospray ionization multiple-stage mass spectrometry (ESI-MS(n)), MALDI-TOF MS, and NMR spectroscopy. Lipid A of P. shigelloides O74 is heterogeneous, and three major forms have been identified. They all were asymmetric, phosphorylated, and hexaacylated, showing different acylation patterns. The beta-GlcpN4P-(1-->6)-alpha-GlcpN1P disaccharide was substituted with the primary fatty acids: (R)-3-hydroxytetradecanoic acid [14:0(3-OH)] at N-2 and N-2' and (R)-3-hydroxydodecanoic acid [12:0(3-OH)] at O-3 and O-3'. The heterogeneity among the three forms (I-III) of P. shigelloides O74 lipid A was attributed to the substitution of the acyl residues at N-2' and O-3' with the secondary acyls: (I) cis-9-hexadecenoic acid (9c-16:1) at N-2' and 12:0 at O-3', (II) 14:0 at N-2' and 12:0 at O-3', and (III) 12:0 at N-2' and 12:0 at O-3'. The pro-inflammatory cytokine-inducing activities of P. shigelloides O74 LPS were similar to those of Escherichia coli O55 LPS.

Structure of the lipid A-inner core region and biological activity of Plesiomonas shigelloides O54 (strain CNCTC 113/92) lipopolysaccharide

Plesiomonas shigelloides is a Gram-negative rod associated with episodes of intestinal infections and outbreaks of diarrhea in humans. The extraintestinal infections caused by this bacterium, for example, endopthalmitis, meningitidis, bacteremia, and septicemia, usually have gastrointestinal origin and serious course. The lipopolysaccharide (LPS, endotoxin) as virulence factor is important in enteropathogenicity of this bacterium. LPSs of P. shigelloides and especially their lipid A part, that is, the immunomodulatory center of LPS, have not been extensively investigated. The structure of P. shigelloides O54 lipid A was determined by chemical analysis combined with MALDI-TOF mass spectrometry, and the intact Kdo-containing core region was investigated by NMR spectroscopy on deacylated LPS. Products from alkaline deacylation of LPS, containing 4-substituted uronic acids, are usually very complex and difficult to separate. Since Kdo residues, like sialic acids, form complexes with serotonin, we used immobilized serotonin for one-step isolation of oligosaccharide containing the intact Kdo region from the reaction mixture by affinity chromatography. The major form of lipid A was built of beta-d-GlcpN4PPEtn-(1-->6)-alpha-d-GlcpN1P disaccharide substituted with 14:0(3-OH), 12:0(3-OH), 14:0(3-O-14:0), and 12:0(3-O-12:0) acyl groups at N-2, O-3, N-2', and O-3', respectively. This is a novel structure among known lipid A molecules. Analysis of intact Kdo-lipid A region, lipid A and its linkage with the core oligosaccharide completes the structural investigation of P. shigelloides O54 LPS, resolving the entire molecule. Biological activities and observed discrepancy between in vitro and in vivo activity of P. shigelloides and Escherichia coli LPS are discussed.

Epitope of the vaccine-type Bordetella pertussis strain 186 lipooligosaccharide and antiendotoxin activity of antibodies directed against the terminal pentasaccharide-tetanus toxoid conjugate

Lipooligosaccharides (LOS) isolated from Bordetella pertussis strains 186 and 606 were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and high-resolution magic angle spinning nuclear magnetic resonance (NMR). These analyses distinguished between the LOS of strains 186 and 606, suggesting that the structure of LOS in B. pertussis is heterogeneous. The pentasaccharide was selectively cleaved from LOS of B. pertussis strain 186, purified, and covalently linked to a monomer fraction of tetanus toxoid. Injection of rabbits with the neoglycoconjugate emulsified in complete Freund's adjuvant yielded immunoglobulin G antibodies that were reactive with the LOS. These antibodies reacted strongly with B. pertussis LOS possessing the complete dodecasaccharide, as determined by an enzyme-linked immunosorbent assay, immunoblotting, and flow cytometry with intact, live bacterial cells. The binding epitope within the pentasaccharide was investigated by saturation transfer difference (STD) NMR spectroscopy. Protons H-1 and H-4 of the terminal alpha-D-GlcpNAc and proton H-6 and protons of an N-methyl group at H-4 of 3-substituted beta-L-FucpNAc4NMe exhibited the largest saturation transfers. STD NMR experiments confirmed that the immunodominant epitope recognized by the antineoglycoconjugate antibodies is located predominantly in the distal trisaccharide of B. pertussis 186 LOS. The antipentasaccharide antibodies induced by the conjugate inhibited the secretion of tumor necrosis factor alpha, interleukin-6, and NO by LOS-stimulated J774A.1 cells.

The O-acetylation patterns in the O-antigens of Hafnia alvei strains PCM 1200 and 1203, serologically closely related to PCM 1205

Serological tests revealed immunochemical similarities between the lipopolysaccharides of Hafnia alvei strains PCM 1200, 1203 and 1205. Immunoblotting and ELISA showed cross-reactions between the strains. NMR spectroscopy showed that the O-deacetylated O-specific polysaccharides isolated from lipopolysaccharides of H. alvei strains PCM 1200 and 1203 possessed the same composition and sequence as the O-deacetylated O-specific polysaccharide of H. alvei strain PCM 1205, that is a glycerol teichoic-acid-like polymer with a repeating unit of the following structure: [carbohydrate structure: see text] NMR spectroscopic studies of the polysaccharides concluded that O-3 of the side chain beta-D-GlcpNAc is partially O-acetylated (50-80%) in both investigated strains. In strain PCM 1203 an additional O-acetyl group (50-80%) is linked to O-6 of the chain -->3)-alpha-D-GlcpNAc-(1--> residue. The structural features of the isolated O-specific polysaccharides were also the same as those of the O-specific polysaccharides on the bacterial cells directly observed by the HR-MAS NMR technique.

Serological characterization of anti-endotoxin serum directed against the conjugate of oligosaccharide core of Escherichia coli type R4 with tetanus toxoid

The covalent conjugate of oligosaccharide core of Escherichia coli type R4 with tetanus toxoid was prepared using reaction of reductive amination. The neoglycoconjugate was a good immunogen in rabbits yielding a high level of anti-lipopolysaccharide (LPS) antibodies of the IgG class. It was found that antiserum was able to react with the smooth LPS molecules of identical (R4) or related (R1) core type. The reactions were shown in the enzyme-linked immunosorbent assay and the immunoblotting test. Flow cytometry showed that anti-core antibodies reacted with LPS present on intact, live, smooth bacteria labelling more than 90% of cells. The anti-OS R4-TT serum used for in vitro studies showed high endotoxin neutralization activity. The serum inhibited endotoxin-induced tumor necrosis factor alpha and nitric oxide synthesis by the J-774A.1 cell line and attenuated pulmonary retention of YAC-1 cells.

Comparison of serological specificity of anti-endotoxin sera directed against whole bacterial cells and core oligosaccharide of Escherichia coli J5-tetanus toxoid conjugate

The rough mutants of Gram-negative bacteria are widely used to induce protective antisera but the nature of the target epitope for such antibodies is not precisely defined. Endotoxin is one of several antigens present on the surface of bacterial cells, which are able to elicit specific antibodies. We studied the specificity of antibodies produced against a conjugate of E. coli J5 endotoxin core oligosaccharide with tetanus toxoid. The use of chemically defined antigen for immunisation excludes the possibility of production of antibodies against other cell surface antigens. A comparison of this monospecific anti-endotoxin serum with antiserum against E. coli J5 whole cells was performed in order to distinguish the role that endotoxin core oligosaccharide plays in the interaction with humoral host defences from that of other potentially important Gram-negative bacterial surface antigens. The reactivity of both sera with smooth and rough lipopolysaccharides was determined in ELISA, immunoblotting and by flow cytometry. Both antisera reacted with similar specificity with most lipopolysaccharides of identical or related core type. Less distinct reactions with endotoxins of the antibacterial serum in comparison with the anti-conjugate serum were found in all serological tests. LPS of E. coli O100 that showed the strongest reactions with both sera was used to stimulate IL-6, TNFalpha and nitric oxide production by the J-774A.1 cell line. Both sera were used to inhibit that stimulation and no inhibitory effects of the examined sera in comparison with non-immune serum were observed.

Core oligosaccharides of Plesiomonas shigelloides O54:H2 (strain CNCTC 113/92): structural and serological analysis of the lipopolysaccharide core region, the O-antigen biological repeating unit, and the linkage between them

The structure of the core oligosaccharide moiety of the lipopolysaccharide (LPS) of Plesiomonas shigelloides O54 (strain CNCTC 113/92) has been investigated by (1)H and (13)C NMR, fast atom bombardment mass spectrometry (MS)/MS, matrix-assisted laser-desorption/ionization time-of-flight MS, monosaccharide and methylation analysis, and immunological methods. It was concluded that the main core oligosaccharide of this strain is composed of a decasaccharide with the following structure: (see text) in which l-alpha-D-Hepp is l-glycero-alpha-D-manno-heptopyranose. The nonasaccharide variant of the core oligosaccharide ( approximately 10%), devoid of beta-D-Glcp substituting the alpha-D-GlcpN at C-6, was also identified. The core oligosaccharide substituted at C-4 of the outer core beta-D-Glcp residue with the single O-polysaccharide repeating unit was also isolated yielding a hexadecasaccharide structure. The determination of the monosaccharides involved in the linkage between the O-specific polysaccharide part and the core, as well as the presence of -->3)-D-beta-D-Hepp-(1--> instead of -->3,4)-D-beta-D-Hepp-(1--> in the repeating unit, revealed the structure of the biological repeating unit of the O-antigen. The core oligosaccharides are not substituted by phosphate residues and represent novel core type of bacterial LPS that is characteristic for the Plesiomonas shigelloides serotype O54. Serological screening of 69 different O-serotypes of P. shigelloides suggests that epitopes similar to the core oligosaccharide of serotype O54 (strain CNCTC 113/92) might also be present in the core region of the serotypes O24 (strain CNCTC 92/89), O37 (strain CNCTC 39/89) and O96 (strain CNCTC 5133) LPS.

Comparison of serological specificity of anti-endotoxin sera directed against whole bacterial cells and core oligosaccharide of Escherichia coli J5-tetanus toxoid conjugate

The rough mutants of Gram-negative bacteria are widely used to induce protective antisera but the nature of the target epitope for such antibodies is not precisely defined. Endotoxin is one of several antigens present on the surface of bacterial cells, which are able to elicit specific antibodies. We studied the specificity of antibodies produced against a conjugate of E. coli J5 endotoxin core oligosaccharide with tetanus toxoid. The use of chemically defined antigen for immunisation excludes the possibility of production of antibodies against other cell surface antigens. A comparison of this monospecific anti-endotoxin serum with antiserum against E. coli J5 whole cells was performed in order to distinguish the role that endotoxin core oligosaccharide plays in the interaction with humoral host defences from that of other potentially important Gram-negative bacterial surface antigens. The reactivity of both sera with smooth and rough lipopolysaccharides was determined in ELISA, immunoblotting and by flow cytometry. Both antisera reacted with similar specificity with most lipopolysaccharides of identical or related core type. Less distinct reactions with endotoxins of the antibacterial serum in comparison with the anti-conjugate serum were found in all serological tests. LPS of E. coli O100 that showed the strongest reactions with both sera was used to stimulate IL-6, TNFalpha and nitric oxide production by the J-774A.1 cell line. Both sera were used to inhibit that stimulation and no inhibitory effects of the examined sera in comparison with non-immune serum were observed.

Structural studies of the O-specific polysaccharide from Plesiomonas shigelloides strain CNCTC 113/92

The structure of the O-specific side chain of the lipopolysaccharide (LPS) of Plesiomonas shigelloides, strain CNCTC 113/92 has been investigated by NMR spectroscopy, matrix-assisted laser desorption/ionization time of flight mass spectrometry and sugar and methylation analysis. It was concluded that the polysaccharide is composed of a hexasaccharide repeating unit with the following structure: in which D-beta-D-Hepp is Dglycero-beta-Dmanno-heptopyranose and 6d-beta-D-Hep is 6-deoxy-beta-Dmanno-heptopyranose. This structure represents a novel hexasaccharide repeating unit of bacterial O-antigen that is characteristic and unique to the Plesiomonas shigelloides strain. Using the high-resolution magic angle spinning technique, 1H-NMR spectra were also obtained for the O-polysaccharide components of isolated LPS and in their original form directly on the surface of bacterial cells.

Structural studies of the O-specific polysaccharide of Hafnia alvei strain PCM 1207 lipopolysaccharide

The structure of the O-specific side-chain of the Hafnia alvei strain PCM 1207 lipopolysaccharide (LPS) has been investigated. Methylation analysis, partial acid hydrolysis, matrix-assisted laser-desorption ionization time-of-flight (MALDI-TOF) MS, fast atom bombardment (FAB)-MS/MS and 1H- and 13C-NMR spectroscopy were the principal methods used. Glycerol phosphate was identified as a constituent in the polysaccharide and the following structure of a pentasaccharide repeating unit was established: The polysaccharide is partially (approximately 10%) substituted with O-acetyl groups. The lipopolysaccharide was also subjected to high resolution magic angle spinning (HR-MAS) NMR analysis, which showed both the signals of the O-specific polysaccharide as well as several signals from unsubstituted core oligosaccharides. This confirmed the presence of the described structure in the native LPS.

Structures of the O-specific polysaccharides from Yokenella regensburgei (Koserella trabulsii) strains PCM 2476, 2477, 2478, and 2494: high-resolution magic-angle spinning NMR investigation of the O-specific polysaccharides in native lipopolysaccharides and directly on the surface of living bacteria

The structures of the carbohydrate O-specific side-chain moiety of the lipopolysaccharides (LPS) of Yokenella regensburgei, strains PCM 2476, 2477, 2478, and 2494, have been investigated by (1)H and (13)C NMR, fast atom bombardment tandem mass spectrometry (FAB-MSMS), matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, methylation analysis, partial acid hydrolysis, and immunological methods. It was concluded that the O-specific polysaccharides of strains 2476, 2477, 2478, and 2494 are composed of the same basic trisaccharide repeating unit having the structure -->3)-alpha-D-FucpNAc-(1-->2)-L-alpha-D-Hepp-(1-->3)-6-deoxy -alpha-L- Talp-(1-->, in which L-alpha-D-Hepp is L-glycero-alpha-D-manno-heptopyranose. The detailed analysis revealed, however, differences in O-acetylation patterns of the 6-deoxy-L-talose residue, with 2- and 4-O-acetyl disubstituted -->3)-6-deoxy-alpha-L-Talp-(1--> in strain PCM 2476 and a 2-O-acetylated residue in strains 2477, 2478, and 2494. These structures represent novel, trisaccharide repeating units of bacterial O-antigens that are characteristic and unique to the Y. regensburgeispecies. By use of the high-resolution magic-angle spinning (HR-MAS) technique, (1)H NMR spectra of the O-polysaccharides directly in isolated LPS were obtained. This allowed for almost full assignment and structural determination of the polysaccharide. By this technique the O-polysaccharide components were also observed in their original form directly on the surface of living bacterial cells.

Non-typical lipopolysaccharide core regions of some Hafnia alvei strains: structural and serological studies

The lipopolysaccharides of Hafnia alvei strains 23, 1222 and 39 were found to have non-typical core region. On the basis of sugar and methylation analyses, 1H-nuclear magnetic resonance spectra and matrix-assisted laser-desorption ionization-time of flight mass spectrometry, it was concluded that the core oligosaccharide of strains 23 and 1222 has the same structure as Escherichia coli R4 core region, and the core oligosaccharide of strain 39 has the structure of Salmonella Ra core. Using the serological methods (passive hemagglutination, enzyme-linked immunosorbent assay and immunoblotting) and the anti-conjugate sera directed against E. coli R4 and Salmonella Ra core oligosaccharides we have confirmed the structural results presented above.

[An antigenic analysis and the protective properties of the R-form lipopolysaccharides of gram-negative bacteria]

The antigenic and immunogenic properties of the R-form lipopolysaccharides (R-LPS) of Pseudomonas aeruginosa, Salmonella minnesota, Escherichia coli and Shigella were studied. The results of the study revealed the existence of antigenic relationship between P.aeruginosa R-LPS and R-LPS Escherichia and Shigella. In serological tests no antigenic relationship between P. aeruginosa R-LPS and Salmonella R-LPS was revealed, but as shown in earlier experiments of the protection of mice, Re-glycolipid stimulated protective immunity against Pseudomonas infection in the animals. On the basis of R-LPS obtained from selected P. aeruginosa and Salmonella strains a vaccine was prepared which proved to be effective against infection caused by P. aeruginosa S-strain in experiments on mice. The vaccine induced protection in 40-100% of immunized mice, depending on the scheme of immunization. The vaccine may probably be effective against infections caused by other gram-negative bacteria.

R-form lipopolysaccharides (LPS) of Gram-negative bacteria as possible vaccine antigens

The antigenic and immunogenic properties of R-form lipopolysaccharides (LPS) of Pseudomonas aeruginosa, Salmonella spp., Escherichia coli and Shigella spp. were studied. The results showed the presence of antigenic relationships among P. aeruginosa R mutants with different structures of the LPS core lipid A region and also among E. coli, Shigella and P. aeruginosa R-LPS, but not with S. minnesota Re-LPS. Vaccines prepared with R-LPS proved to be effective preparations for the active immunization of mice against P. aeruginosa infection. The vaccine stimulated 40-100% protection in mice depending upon the scheme of immunization.

Structural studies of the O-specific chains of Hafnia alvei strains 744, PCM 1194 and PCM 1210 lipopolysaccharides

The structures of the O-specific chains of the Hafnia alvei strain 744 and PCM strains 1194 and 1210 lipopolysaccharides have been investigated. Methylation analysis, dephosphorylation, NMR spectroscopy, matrix-assisted laser-desorption ionisation time-of-flight mass spectrometry and fast-atom-bombardment mass spectrometry were the principal methods used. It was concluded that the polysaccharides of strains 744 and PCM 1194 are composed of the same pentasaccharide repeating unit having the following structure: [structure in text] and that the polysaccharide of strain PCM 1210 is composed of a pentasaccharide repeating unit having the following structure: [structure in text].

Structural studies of the O-specific chain of Hafnia alvei strain PCM 1190 lipopolysaccharide

The structure of the O-specific side-chain of the lipopolysaccharide of Hafnia alvei strain PCM 1190 has been investigated. Methylation analysis, partial acid hydrolysis, Smith degradation, NMR spectroscopy, MALDI-TOF, and FAB mass spectrometry in combination with collision-induced-decomposition MS/MS were the principal methods used. It was concluded that the polysaccharide is composed of heptasaccharide repeating units having the following structure: [formula: see text] Only 80% of the repeating units are complete, whereas 20% of them are lacking the alpha-D-glucopyranosyl group.

Structural studies of the O-specific polysaccharide of Hafnia alvei strain PCM 1206 lipopolysaccharide containing D-allothreonine

The structure of the O-specific side-chain of the Hafnia alvei strain PCM 1206 lipopolysaccharide has been investigated. Methylation analysis, partial acid hydrolysis, FAB-MS/MS and 1H-NMR and 13C-NMR spectroscopy were the principal methods used. D-Allothreonine (D-aThr), amide-linked to the D-galacturonic acid, was identified as a constituent in the polysaccharide and the following structure of a pentasaccharide repeating unit was established: [structure: see text].

Serological characterisation of anti-endotoxin sera directed against the conjugates of oligosaccharide core of Escherichia coli type R1, R2, R3, J5 and Salmonella Ra with tetanus toxoid

The covalent conjugates of oligosaccharide core: Escherichia coli type R1, R2, R3, J5 and Salmonella Ra with tetanus toxoid have been prepared using reaction of reductive amination. The neoglycoconjugates were good immunogens in rabbits yielding a high level of anti-lipopolysaccharide antibodies of IgG class. The antibodies were used to examine the possibility of their reactions with smooth lipopolysaccharides. We have found that all antisera were able to react with the lipopolysaccharide molecules of identical or related core type, possessing core oligosaccharides substituted with O-specific chains. These reactions were shown in both the ELISA assay and the immunoblotting test.

Anti-endotoxin antibodies directed against Escherichia coli R-1 oligosaccharide core-tetanus toxoid conjugate bind to smooth, live bacteria and smooth lipopolysaccharides and attenuate their tumor necrosis factor stimulating activity

The reactivity of anti-OS R1-tetanus toxoid serum with various smooth and rough lipopolysaccharides have been determined in enzyme-linked immunosorbent assay (ELISA) and with intact, live smooth bacterial cells in flow cytometry. All tested smooth lipopolysaccharides of R1 core type belonging to nine different O-serotypes reacted strongly with anti-conjugate antibodies. Flow cytometry showed that anti-core antibodies labelled more than 95% of bacterial cells with high intensity of fluorescence. The anti-conjugate serum was able to react with free form of smooth lipopolysaccharides and to inhibit their TNF stimulation activity in in vitro and in vivo models.

Structural studies of the O-specific chain of Hafnia alvei strain 32 lipopolysaccharide

The structure of the O-specific side chain of the Hafnia alvei strain 32 lipopolysaccharide has been investigated. Methylation analysis, partial acid hydrolysis, Smith degradations, NMR spectroscopy, MALDI-TOF and FAB mass spectrometry in combination with collision-induced decomposition MS/MS were the principal methods used. It is concluded that the polysaccharide is composed of pentasaccharide repeating units having the following structure which is partially O-acetylated in the 2- (20%) and 3- (50%) position of the-->4)-alpha-D-GalpA-(1-->residue. [sequence :see text] A MALDI-TOF mass spectrum of the O-specific chains indicated that they consisted of up to 16 repeating units.

Structural studies of the O-specific polysaccharide of Hafnia alvei strain 1209 lipopolysaccharide

The structure of the O-specific side chains of the Hafnia alvei strain 1209 lipopolysaccharide has been investigated. Methylation analysis and 1H-NMR and 13C-NMR spectroscopy were the principal methods used. It is concluded that the polysaccharide is composed of pentasaccharide repeating units that have the following structure: -->3)-beta-D-Galp-(1-->4)-alpha-D-Glcp-(1-->4)-beta-D-GlepA-(1--> 3)-beta-D-GalpNAc-(1 --> 4 increases 1 alpha-L-Rhap The relative intensity of the signals from the terminal repeating unit in the 1H-NMR spectrum, the amount of 2,3,6-tri-O-methylgalactose in the methylation analysis, and the matrix-assisted laser-desorption ionisation time-of-flight (MALDI-TOF) mass spectrum of the O-polysaccharide indicated that the structure is also the biological repeating unit and that the O-chains mainly consisted of 8-11 repeating units and, on average, ten repeating units.

[Bacterial endotoxins--methods of structural analysis]

The modern structural methods used in the determination of lipopolysaccharides chemical structures were described. The combination of nuclear magnetic resonance (NMR) spectroscopy and mass spectrometry (MALDI-TOF, FAB and EI) applied to structural analysis of lipopolysaccharides, with a few chosen examples of characteristic original spectra were presented.

Structural and serological studies of lipopolysaccharides of Citrobacter O35 and O38 antigenically related to Salmonella

Structural analysis using 13C NMR spectroscopy and methylation showed that lipopolysaccharides (LPSs) of Citrobacter freundii O35 and Salmonella arizonae O59 have structurally identical O-specific polysaccharide chains, and those of C. freundii O38 and Salmonella kentucky differ only in the presence of O-acetyl groups in the former. Serological relationships between the structurally similar LPSs were demonstrated using inhibition of ELISA, rocket immunoelectrophoresis, double gel diffusion, and immunoblotting. The O-acetyl groups present in C. freundii O38 LPS are of little importance for its serological specificity. A cross-reaction was observed in immunoblotting between O-antisera to C. freundii O35 and S. arizonae O59 and a structurally related LPS of Pseudomonas aeruginosa O11a, 11b (Lányi-Bergan classification).

Structural studies of the O-specific chain and a core hexasaccharide of Hafnia alvei strain 1192 lipopolysaccharide

The structure of the O-specific side-chain and a core hexasaccharide of the Hafnia alvei strain 1192 lipopolysaccharide has been investigated. Methylation analysis, NMR spectroscopy, MALDI-TOF spectrometry, and various specific chemical degradations were the principal methods used. It is concluded that the polysaccharide is composed of hexasaccharide repeating-units having the following structure which is partially O-acetylated in the 2-position of the --> 4)-alpha-D-Glc pA-(1-->(70%) and on different positions of the L-Rha residues (50%). [Formula: see text] The core hexasaccharide was found to have the following structure: [Formula: see text]

Immunotherapy in gram-negative bacterial infections

Endotoxins are responsible for initiation of septic shock which increases the number of fatalities in Gram-negative bacteremia among hospital patients. The mortality from septic shock is still high despite recent developments in antibiotic therapy because antibiotics are unable to decrease the level of free lipopolysaccharide in the blood stream. Another approach to the treatment and prevention of septicaemia involves stimulation of an immune response against LPS. It was found that immunization with the core structures of endotoxin conjugated with proteins protected animals against infections and endotoxic shock. Anticonjugate sera are of great interest because they are directed against conserved parts of LPS and therefore could have cross-reactive and cross-protective properties with respect to many Gram-negative rods.

Structural and serological characterization of Hafnia alvei lipopolysaccharide core region

The structures and serological activities of core oligosaccharide of Hafnia alvei strains have been investigated. Methylation analysis, NMR spectroscopy and various specific degradation procedures were the principal methods used. It is concluded that, core hexasaccharides are identical in the lipopolysaccharides tested and are built of two glucose, three heptose and one 2-keto-3-deoxyoctulosonic acid residues. The antiserum raised against the ATCC13337 oligosaccharide core-tetanus toxoid conjugate cross-reacted strongly with all lipopolysaccharides used as antigens in ELISA test, suggesting that this core region is the common structure in the Hafnia genus.

Lipopolysaccharide core region of Hafnia alvei: serological characterization

Covalent glycoconjugates containing, as a ligand lipopolysaccharide core, oligosaccharides of Hafnia alvei standard strain ATCC 13337 and R mutant 1 M were used to produce anti-H. alvei core antibodies. The sera obtained were tested in rocket immunoelectrophoresis, immunoblotting and ELISA using H. alvei lipopolysaccharides of various strains. The experiments were carried out to study the antigenic relationships between lipopolysaccharide core regions in the H. alvei genus.

Immunochemical characterization of Citrobacter strain PCM 1487 O-specific polysaccharide- and core oligosaccharide-protein conjugates

O-specific-polysaccharide and core oligosaccharide were isolated from Citrobacter strain PCM 1487 lipopolysaccharide and purified. The polysaccharide was selectively devoid of 4-deoxy-D-arabinohexose residues. Covalent conjugates of the modified O-specific polysaccharide and of the core oligosaccharide with tetanus toxoid were prepared. Immunochemical characterization of these conjugates proved that they are strong immunogens. Using monospecific rabbit antisera raised against the conjugates, the antigenic relationships between lipopolysaccharides of various strains of Citrobacter, Shigella sonnei, and Shigella flexneri were studied by quantitative microprecipitin and quantitative microprecipitin inhibition and immunoblotting tests.