Structure of the core oligosaccharide in the serotype O8 lipopolysaccharide from Klebsiella pneumoniae

Cloning, sequencing, and functional analysis of three glycosyltransferases involved in the biosynthesis of the inner core region of Klebsiella pneumoniae lipopolysaccharide

The genes encoding the 3-deoxy-D- manno-oct-2-ulosonic acid (Kdo) transferase ( waaA) and heptosyltransferases I ( waaC) and II ( waaF) in Klebsiella pneumoniae were cloned from a DNA library by functional complementation of corresponding Escherichia coli and Salmonella enterica mutants. Sequence analyses revealed extensive homologies of the deduced proteins to their counterparts in other Enterobacteriaceae. However, differences were evident with regard to the chromosomal organization of the genes. To perform in vitro studies, the waaA, waaC and waaF genes were subcloned and expressed in the Gram-positive host Corynebacterium glutamicum. WaaA was characterized as a bifunctional enzyme capable of transferring two Kdo residues to a synthetic bisphosphorylated tetraacyl-lipid A precursor of E. coli (compound 406). In contrast, waaC and waaF were shown to encode specific glycosyltransferases catalyzing the consecutive transfer of two L- glycero-D- manno-heptose residues to Kdo2-406.

A monoclonal antibody with specificity for the genus Klebsiella binds to a common epitope located in the core region of Klebsiella lipopolysaccharide

A mouse monoclonal antibody (mAb) which has been obtained after immunization of mice with heat-killed Klebsiella pneumoniae strain R20/O1— followed by standard plasmacytoma cell fusion protocols was investigated for its ability to identify various species of the genus Klebsiella. Based on the published observation that the antibody binds to an epitope located in the core region of lipopolysaccharide (LPS) of strain R20/O1—, we tested whether this epitope is shared and exposed by other species of the genus Klebsiella. The antibody was able to bind to LPS of clinical isolates of K. pneumoniae ( n = 77), K. oxytoca ( n = 50), K. terrigena ( n = 49) and K. planticola ( n = 50) in 93%, 98%, 96% and 100%, respectively, but did not bind to LPS of other Gram-negative genera ( n = 159) as tested by Western blots and dot blots using proteinase K-digested whole cell lysates as antigens. Western blot analyses indicated that the antibody bound only to those LPS molecules which did not carry an O-antigen and that the antibody is thus different from those already published.

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) as a characteristic component of bacterial endotoxin — a review of its biosynthesis, function, and placement in the lipopolysaccharide core

The sugar 3-deoxy-d-manno-oct-2-ulosonic acid (Kdo) is a characteristic component of bacterial lipopolysaccharide (LPS, endotoxin). It connects the carbohydrate part of LPS with C6 of glucosamine or 2,3-diaminoglucose of lipid A by acid-labile α-ketosidic linkage. The number of Kdo units present in LPS, the way they are connected, and the occurrence of other substituents (P, PEtn, PPEtn, Gal, or β-l-Ara4N) account for structural diversity of the inner core region of endotoxin. In a majority of cases, Kdo is crucial to the viability and growth of bacterial cells. In this paper, the biosynthesis of Kdo and the mechanism of its incorporation into the LPS structure, as well as the location of this unique component in the endotoxin core structures, have been described.

Structural characterization of bacterial lipopolysaccharides with mass spectrometry and on- and off-line separation techniques

The focus of this review is the application of mass spectrometry to the structural characterization of bacterial lipopolysaccharides (LPSs), also referred to as "endotoxins," because they elicit the strong immune response in infected organisms. Recently, a wide variety of MS-based applications have been implemented to the structure elucidation of LPS. Methodological improvements, as well as on- and off-line separation procedures, proved the versatility of mass spectrometry to study complex LPS mixtures. Special attention is given in the review to the tandem mass spectrometric methods and protocols for the analyses of lipid A, the endotoxic principle of LPS. We compare and evaluate the different ionization techniques (MALDI, ESI) in view of their use in intact R- and S-type LPS and lipid A studies. Methods for sample preparation of LPS prior to mass spectrometric analysis are also described. The direct identification of intrinsic heterogeneities of most intact LPS and lipid A preparations is a particular challenge, for which separation techniques (e.g., TLC, slab-PAGE, CE, GC, HPLC) combined with mass spectrometry are often necessary. A brief summary of these combined methodologies to profile LPS molecular species is provided.

Structural analysis of the core region of O-lipopolysaccharide of Porphyromonas gingivalis from mutants defective in O-antigen ligase and O-antigen polymerase

Porphyromonas gingivalis synthesizes two lipopolysaccharides (LPSs), O-LPS and A-LPS. Here, we elucidate the structure of the core oligosaccharide (OS) of O-LPS from two mutants of P. gingivalis W50, Delta PG1051 (WaaL, O-antigen ligase) and Delta PG1142 (O-antigen polymerase), which synthesize R-type LPS (core devoid of O antigen) and SR-type LPS (core plus one repeating unit of O antigen), respectively. Structural analyses were performed using one-dimensional and two-dimensional nuclear magnetic resonance spectroscopy in combination with composition and methylation analysis. The outer core OS of O-LPS occurs in two glycoforms: an "uncapped core," which is devoid of O polysaccharide (O-PS), and a "capped core," which contains the site of O-PS attachment. The inner core region lacks L(D)-glycero-D(l)-manno-heptosyl residues and is linked to the outer core via 3-deoxy-D-manno-octulosonic acid, which is attached to a glycerol residue in the outer core via a monophosphodiester bridge. The outer region of the "uncapped core" is attached to the glycerol and is composed of a linear alpha-(1-->3)-linked d-Man OS containing four or five mannopyranosyl residues, one-half of which are modified by phosphoethanolamine at position 6. An amino sugar, alpha-D-allosamine, is attached to the glycerol at position 3. In the "capped core," there is a three- to five-residue extension of alpha-(1-->3)-linked Man residues glycosylating the outer core at the nonreducing terminal residue. beta-D-GalNAc from the O-PS repeating unit is attached to the nonreducing terminal Man at position 3. The core OS of P. gingivalis O-LPS is therefore a highly unusual structure, and it is the basis for further investigation of the mechanism of assembly of the outer membrane of this important periodontal bacterium.

Expression cloning of three Rhizobium leguminosarum lipopolysaccharide core galacturonosyltransferases

The lipid A and core regions of the lipopolysaccharide in Rhizobium leguminosarum, a nitrogen-fixing plant endosymbiont, are strikingly different from those of Escherichia coli. In R. leguminosarum lipopolysaccharide, the inner core is modified with three galacturonic acid (GalA) moieties, two on the distal 3-deoxy-D-manno-octulosonic acid (Kdo) unit and one on the mannose residue. Here we describe the expression cloning of three novel GalA transferases from a 22-kb R. leguminosarum genomic DNA insert-containing cosmid (pSGAT). Two of these enzymes modify the substrate, Kdo2-[4'-(32)P]lipid IV(A) and its 1-dephosphorylated derivative on the distal Kdo residue, as indicated by mild acid hydrolysis. The third enzyme modifies the mannose unit of the substrate mannosyl-Kdo2-1-dephospho-[4'-(32)P]lipid IV(A). Sequencing of a 7-kb subclone derived from pSGAT revealed three putative membrane-bound glycosyltransferases, now designated RgtA, RgtB, and RgtC. Transfer by tri-parental mating of these genes into Sinorhizobium meliloti 1021, a strain that lacks these particular GalA residues, results in the heterologous expression of the GalA transferase activities seen in membranes of cells expressing pSGAT. Reconstitution experiments with the individual genes demonstrated that the activity of RgtA precedes and is necessary for the subsequent activity of RgtB, which is followed by the activity of RgtC. Electrospray ionization-tandem mass spectrometry and gas-liquid chromatography of the product generated in vitro by RgtA confirmed the presence of a GalA moiety. No in vitro activity was detected when RgtA was expressed in Escherichia coli unless Rhizobiaceae membranes were also included.

Recognition of bacterial capsular polysaccharides and lipopolysaccharides by the macrophage mannose receptor

The in vitro binding of the macrophage mannose receptor to a range of different bacterial polysaccharides was investigated. The receptor was shown to bind to purified capsular polysaccharides from Streptococcus pneumoniae and to the lipopolysaccharides, but not capsular polysaccharides, from Klebsiella pneumoniae. Binding was Ca(2+)-dependent and inhibitable with d-mannose. A fusion protein of the mannose receptor containing carbohydrate recognition domains 4-7 and a full-length soluble form of the mannose receptor containing all domains external to the transmembrane region both displayed very similar binding specificities toward bacterial polysaccharides, suggesting that domains 4-7 are sufficient for recognition of these structures. Surprisingly, no direct correlation could be made between polysaccharide structure and binding to the mannose receptor, suggesting that polysaccharide conformation may play an important role in recognition. The full-length soluble form of the mannose receptor was able to bind simultaneously both polysaccharide via the carbohydrate recognition domains and sulfated oligosaccharide via the cysteine-rich domain. The possible involvement of the mannose receptor, either cell surface or soluble, in the innate and adaptive immune responses to bacterial polysaccharides is discussed.

The core oligosaccharide component from Mannheimia (Pasteurella) haemolytica serotype Al lipopolysaccharide contains L-glycero-D-manno- and D-glycero-D-manno-heptoses: Analysis of the structure and conformation by high-resolution NMR spectroscopy

Previous studies from our laboratory have indicated that the lipopolysaccharide (LPS) from Mannheimia haemolytica serotype A1 contains both L-glycero-D-manno-heptose and D-glycero-D-manno-heptose residues. NMR methods making use of 1D 1H selective excitation and 2D (1H, 13C) and (1H, 31P) heteronuclear experiments were used for the structural determination of the major core oligosaccharide components of the deacylated low-molecular-mass LPS obtained following sequential treatment with anhydrous hydrazine and aq KOH. The core oligosaccharide region was found to be composed of a branched octasaccharide linked to the deacylated lipid A moiety via a 3-deoxy-4-phospho-D-manno-oct-2-ulosonate residue having the structure,[Formula: see text]Heterogeneity was found to be present at several linkages. NMR methods were devised to distinguish between the diastereomeric forms of the heptose residues. Synthesized monosaccharides of L-D- and D-D-heptose were used as model compounds for analysis of the 1H and 13C NMR chemical shifts and proton coupling constants. Molecular modeling using a Monte Carlo method for conformational analysis of saccharides was used to determine the conformation of the inner core of the oligosaccharide and to establish the stereochemical relationships between the heptoses.Key words: LPS, NMR, conformation, oligosaccharide, heptose.

Genetic characterization of the Klebsiella pneumoniae waa gene cluster, involved in core lipopolysaccharide biosynthesis

A recombinant cosmid containing genes involved in Klebsiella pneumoniae C3 core lipopolysaccharide biosynthesis was identified by its ability to confer bacteriocin 28b resistance to Escherichia coli K-12. The recombinant cosmid contains 12 genes, the whole waa gene cluster, flanked by kbl and coaD genes, as was found in E. coli K-12. PCR amplification analysis showed that this cluster is conserved in representative K. pneumoniae strains. Partial nucleotide sequence determination showed that the same genes and gene order are found in K. pneumoniae subsp. ozaenae, for which the core chemical structure is known. Complementation analysis of known waa mutants from E. coli K-12 and/or Salmonella enterica led to the identification of genes involved in biosynthesis of the inner core backbone that are shared by these three members of the Enterobacteriaceae. K. pneumoniae orf10 mutants showed a two-log-fold reduction in a mice virulence assay and a strong decrease in capsule amount. Analysis of a constructed K. pneumoniae waaE deletion mutant suggests that the WaaE protein is involved in the transfer of the branch beta-D-Glc to the O-4 position of L-glycero-D-manno-heptose I, a feature shared by K. pneumoniae, Proteus mirabilis, and Yersinia enterocolitica.

Structural and serological studies on Hafnia alvei O-specific polysaccharide of alpha-D-mannan type isolated from the lipopolysaccharide of strain PCM 1223

On the basis of chemical and methylation analyses, one- and two-dimensional (1)H- and (13)C-NMR spectroscopy, including COSY, TOCSY, NOESY and (1)H, (13)C HSQC experiments, a neutral O-specific polysaccharide isolated from Hafnia alvei strain PCM 1223 lipopolysaccharide (LPS) was found to be an alpha-mannan composed of pentasaccharide repeating units having the following structure:-->3)-alpha-D-Manp-(1-->3)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->2)-alpha-D-Manp-(1-->. Immunoblotting showed a strong cross-reactivity between anti-H. alvei PCM 1223 serum and LPSs of Escherichia coli O9 and Klebsiella pneumoniae O3. The serological relationship of the LPSs of these bacteria is due to the structural identity of their O-specific polysaccharides, though the LPSs differ in their core regions.

The structure of the core part of Proteus penneri strain 16 lipopolysaccharide

The structure of the carbohydrate backbone of the lipid A-core region of the lipopolysaccharide (LPS) from Proteus penneri strain 16 was determined using NMR and chemical analysis of the core oligosaccharide, obtained by mild acid hydrolysis of the LPS, and of the products of alkaline deacylation of the LPS: formula [see text]. Incomplete substitution is indicated by bold italics. All sugars are in the pyranose form, alpha-Hep is the residue of L-glycero-alpha-D-manno-Hep, alpha-DD-Hep is the residue of D-glycero-alpha-D-manno-Hep, Bu is the (R)-3-hydroxybutyryl residue.

Mass spectrometric analysis of Klebsiella pneumoniae ssp. pneumoniae rough strain R20 (O1-: K20-) lipopolysaccharide preparations: identification of novel core oligosaccharide components and three 3-deoxy-D-manno-oct-2-ulopyranosonic artifacts

In an attempt to find the best approach for the mass spectrometric analysis of the whole range of lipopolysaccharide (LPS) structures from Klebsiella pneumoniae ssp. pneumoniae rough strain R20 (O1-:K20-), various methods of LPS preparation were applied and the products were analyzed using a range of mass spectrometric techniques. The most productive approach proved to be the removal of lipid A by mild acid hydrolysis and the study of the core oligosaccharide structures using nanoelectrospray time-of-flight mass spectrometry (TOF-MS) in combination with collision-induced dissociation tandem mass spectrometry. This procedure is very sensitive, but results in the generation of a reducing 3-deoxy-D-manno-oct-2-ulopyranosonic acid residue (Kdo) that is susceptible to the formation of artifacts, which give rise to pseudomolecular ions 18, 46, and 88 Da below the pseudomolecular ion for the unmodified species. Alternatively, matrix-assisted laser desorption/ionization TOF-MS combined with post-source decay can be used to study the de-O-acylated LPS preparation and especially to identify those residues bearing phosphate groups and the residues involved in the linkage between the core and lipid A. In addition to the five LPS core structures defined using NMR spectroscopy by Süsskind et al., several extra related LPS structure were identified. Larger LPS species were observed, which surprisingly do not represent species containing longer versions of the novel Klebsiella heptoglycan, but instead are species having the defined core and heptoglycan extended with up to three extra hexuronic acid and one or two extra hexose residues.

The structure of the carbohydrate backbone of the core-lipid A region of the lipopolysaccharide from a clinical isolate of Yersinia enterocolitica O:9

Yersinia enterocolitica O:9 strain Ruokola/71-c-PhiR1-37-R possesses mainly rough-type lipopolysaccaride (LPS) and smaller amounts of S-form LPS. Structural analysis of the former is reported here. After deacylation of the LPS, the phosphorylated carbohydrate backbone of the inner core-lipid A region could be isolated by using high-performance anion-exchange chromatography. Its structure was determined by means of compositional and methylation analyses and 1H-, 13C-, and 31P-NMR spectroscopy as: [see text] in which L-alpha-D-Hep is L-glycero-alpha-D-manno-heptopyranose, D-alpha-D-Hep is D-glycero-alpha-D-manno-heptopyranose, and Kdo is 3-deoxy-D-manno-oct-2-ulopyranosonic acid. All hexoses are pyranoses.

The structure of the lipopolysaccharide from Klebsiella oxytoca rough mutant R29 (O1-/K29-)

The lipopolysaccharide from Klebsiella oxytoca rough mutant R29 (O1-/K29-) has been isolated and its complete structure has been elucidated by compositional analyses, NMR spectroscopy, and laser-desorption mass spectrometry. The carbohydrate backbone has the structure [formula: see text] of which the GlcN residues (the lipid A backbone) are acylated by 14:(3-OH) (amide-linked) and 12:0, 14:0(3-OH)(ester-linked) fatty acids.

Involvement of waaY, waaQ, and waaP in the modification of Escherichia coli lipopolysaccharide and their role in the formation of a stable outer membrane

The waaY, waaQ, and waaP genes are located in the central operon of the waa (formerly rfa) locus on the chromosome of Escherichia coli. This locus contains genes whose products are involved in the assembly of the core region of the lipopolysaccharide molecule. In the R1 core prototype strain, E. coli F470, there are nine genes in this operon, and all but waaY, waaQ, and waaP have been assigned function. In this study, the waaY, waaQ, and waaP genes were independently mutated by insertion of a non-polar antibiotic resistance cassette, and the structures of the resulting mutant core oligosaccharides were determined by chemical analyses and phosphorus-nuclear magnetic resonance spectroscopy. All three of these mutations were shown to affect the modification of the heptose region of the core, a region whose structure is critical to outer membrane stability. Mutation of waaY resulted in a core oligosaccharide devoid of phosphate on HepII. Mutation of waaQ resulted in loss of the branch HepIII residue on HepII and impeded the activity of WaaY. Mutation of waaP resulted in loss of phosphoryl substituents on HepI and obviated WaaQ and WaaY activity. Only mutation of waaP resulted in hypersensitivity to novobiocin and sodium dodecyl sulfate, a characteristic of deep-rough mutations.

Molecular basis for structural diversity in the core regions of the lipopolysaccharides of Escherichia coli and Salmonella enterica

Bacterial lipopolysaccharides (LPS) are unique and complex glycolipids that provide characteristic components of the outer membranes of Gram-negative bacteria. In LPS of the Enterobacteriaceae, the core oligosaccharide links a highly conserved lipid A to the antigenic O-polysaccharide. Structural diversity in the core oligosaccharide is limited by the constraints imposed by its essential role in outer membrane stability and provides a contrast to the hypervariable O-antigen. The genetics of core oligosaccharide biosynthesis in Salmonella and Escherichia coli K-12 have served as prototypes for studies on the LPS and lipo-oligosaccharides from a growing range of bacteria. However, despite the wealth of knowledge, there remains a number of unanswered questions, and direct experimental data are not yet available to define the precise mechanism of action of many gene products. Here we present a comparative analysis of the recently completed sequences of the major core oligosaccharide biosynthesis gene clusters from the five known core types in E. coli and the Ra core type of Salmonella enterica serovar Typhimurium and discuss advances in the understanding of the related biosynthetic pathways. Differences in these clusters reflect important structural variations in the outer core oligosaccharides and provide a basis for ascribing functions to the genes in these model clusters, whereas highly conserved regions within these clusters suggest a critical and unalterable function for the inner region of the core.

Identification of a novel heptoglycan of alpha1-->2-linked D-glycero-D-manno-heptopyranose. Chemical and antigenic structure of lipopolysaccharides from Klebsiella pneumoniae ssp. pneumoniae rough strain R20 (O1-:K20-)

In a preliminary investigation (Süsskind, M., Müller-Loennies, S., Nimmich, W., Brade, H., and Holst, O. (1995) Carbohydr. Res. 269, C1-C7), we identified after deacylation of lipopolysaccharides (LPS) from Klebsiella pneumoniae ssp. pneumoniae rough strain R20 (O1(-):K20(-)) as a major fraction the oligosaccharide,-structure; see text- where Kdo was 3-deoxy-D-manno-oct-2-ulopyranosonic acid and Hepp was manno-heptopyranose. The presence of the threo-hex-4-enuronopyranosyl residue indicated a substituent at O-4 of the second GalA residue linked to O-3 of the second L,D-Hep residue, which had been eliminated by treatment with hot alkali. We now report the complete structure of lipopolysaccharide, which was elucidated by additional characterization of isolated core oligosaccharides and analysis of the lipid A. The substituent at O-4 of the second GalpA is D-GlcpN, which in a fraction of the LPS is substituted at O-6 by three or four residues of D-glycero-D-manno-heptopyranose (D,D-Hepp). The complete carbohydrate backbone of the LPS is as follows, -structure; see text- (L-glycero-D-manno-heptopyranose; L,D-Hepp), where all hexoses possess the D-configuration. Sugars marked with an asterisk are present in nonstoichiometric amounts. The structure is unique with regard to the presence of an alpha1-->2-linked D-glycero-D-manno-heptoglycan (oligosaccharide), which has not been described to date, and does not contain phosphate substituents in the core region. Fatty acid analysis of lipid A identified (R)-3-hydroxytetradecanoic acid as sole amide-linked fatty acid and (R)-3-hydroxytetradecanoic acid, tetradecanoic acid, small amounts of 2-hydroxytetradecanoic acid, hexadecanoic acid, and traces of dodecanoic acid as ester-linked fatty acids, substituting the carbohydrate backbone D-GlcpN4Pbeta1-->6D-GlcpNalpha1P. The nonreducing GlcN carries four fatty acids, present as two 3-O-tetradecanoyltetradecanoic acid residues, one of which is amide-linked and the other ester-linked to O-3'. The reducing GlcN is substituted in a nature fraction of lipid A by two residues of (R)-3-hydroxytetradecanoic acid, one in amide and the other in ester linkage at O-3. Two minor fractions of lipid A were identified; in one, the amide-linked (R)-3-hydroxytetradecanoic acid at the reducing GlcN is esterified with hexadecanoic acid, resulting in 3-O-hexadecanoyltetradecanoic acid, and in the second, one of the 3-O-tetradecanoyltetradecanoic acid residues at the nonreducing GlcN is replaced by 3-O-dodecanoyltetradecanoic acid. Thus, the complete structure of LPS is as shown in Fig. 1. After immunization of BALB/c mice, two monoclonal antibodies were obtained that were shown to be specific for the core of LPS from K. pneumoniae ssp. pneumoniae, since they did not react with LPS or whole-cell lysates of a variety of other Gram-negative species. Both monoclonal antibodies could be inhibited by LPS but not by isolated oligosaccharides and are thus considered to recognize a conformational epitope in the core region.

O-antigen seroepidemiology of Klebsiella clinical isolates and implications for immunoprophylaxis of Klebsiella infections

To provide a database for the development of an O-antigen-polysaccharide-containing vaccine against Klebsiella spp., we examined the O-antigen seroepidemiology of 378 Klebsiella clinical isolates collected prospectively in two university centers. Strains were typed by competitive enzyme-linked immunosorbent assay with rabbit antisera specific for serogroups O1 to O12 and monoclonal antibodies (MAbs) specific for serogroups O1, O2ab, O2ac, and the genus-specific core antigen. The numbers of isolates (percentages) of individual O serogroups were as follows: 148 (39.2) for serogroup O1, 40 (10.6) for serogroup O2ab, 4 (1.1) for serogroup O2ac, 89 (23.6) for serogroup O3, 2 (0.5) for serogroup O4, 32 (8.5) for serogroup O5, none for serogroups O7, O9, and O12, and 21 (5.6) for serogroup O11. Forty-two (11.1) of the strains were non-O-typeable. O-serogroup distributions were virtually identical between isolates from invasive infections and those from noninvasive infections or colonizations. A vaccine containing the O-specific polysaccharides of serogroups O1, O2ab, O3, and O5 would cover 82% of clinically occurring O-antigen specificities. Three hundred thirty-eight of 378 isolates (89.4%) reacted with the genus-specific MAb V/9-5, which recognizes an epitope of the outer core region of Klebsiella lipopolysaccharide. Antibodies directed against this epitope may represent a further alternative for O-antigen-targeted immunoprophylaxis of Klebsiella infections. These data support further experimental investigations on the protective potential of O-antigen-based vaccines and/or hyperimmune globulins in Klebsiella infection.

Phosphate groups in lipopolysaccharides of Salmonella typhimurium rfaP mutants

Lipopolysaccharides (LPS) of Salmonella typhimurium rfaP mutants and of a galE strain as a control were subjected to analysis by 31P-NMR in order to assess the location of phosphate groups. This was done to obtain direct proof for our earlier finding by chemical analysis that phosphate was lacking in the core oligosaccharide part of the mutant LPS, whereas the core oligosaccharide normally contains several phosphate groups. Such phosphate deficiency has been associated with the increased susceptibility of the rfaP mutants to hydrophobic antibiotics and detergents. Analysis of the de-O-acylated LPS derivatives of S. typhimurium rfaP strains SH7770, SH8551, and SH8572 by 31P-NMR revealed an almost total lack of phosphate groups in the core oligosaccharide part, the LPS phosphates being largely accounted for by the two monophosphate monoesters of lipid A, linked to positions C-1 and C-4' of the lipid A backbone. Core oligosaccharide-linked phosphates were detected in minor proportions only, indicating the presence of some normally phosphorylated core oligosaccharide, due to the inherently leaky nature of the mutation.

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.