[The role of the structural components of bacterial lipopolysaccharide in its inductive immunosuppressive activity]

The inductive immunosuppressive activity of lipopolysaccharides (LPS) and structural parts (O-chains,cor,lipid A) obtained from bacteria of the genus Shigella and Escherichia coli was studied. LPS preparations were extracted by phenol-water method. Its structural components were obtained by the acetic acid hydrolysis and gel filtration. It has been shown that all these preparations did not change the level of delayed type hypersensitivity (DTH) to test-antigen in mice in the case of intraperitoneal injection. They did not also induce immunosuppressive activity in avirulent bacterial strains. After the redox treatment all LPS preparations acquired the ability to induce immunosuppressive property in avirulent bacteria. As a result of redox treatment the immunosuppressive activity appeared in lipid A preparations. O-chains and cor preparations were not active. Immunosuppressive activity was lost after treatment with phenol. It is supposed that active chemical groups are located in lipid A.

Chlamydial lipopolysaccharide

Chlamydiae are obligatory intracellular parasites which are responsible for various acute and chronic diseases in animals and humans. The outer membrane of the chlamydial cell wall contains a truncated lipopolysaccharide (LPS) antigen, which harbors a group-specific epitope being composed of a trisaccharide of 3-deoxy-D-manno-oct-2-ulosonic (Kdo) residues of the sequence alpha-Kdo-(2-->8)-alpha-Kdo-(2-->4)-alpha-Kdo. The chemical structure was established using LPS of recombinant Escherichia coli and Salmonella enterica strains after transformation with a plasmid carrying the gene encoding the multifunctional chlamydial Kdo transferase. Oligosaccharides containing the Kdo region attached to the glucosamine backbone of the lipid A domain have been isolated or prepared by chemical synthesis, converted into neoglycoproteins and their antigenic properties with respect to the definition of cross-reactive and chlamydia-specific epitopes have been determined. The low endotoxic activity of chlamydial LPS is related to the unique structural features of the lipid A, which is highly hydrophobic due to the presence of unusual, long-chain fatty acids.

Monophosphoryl lipid A (MPL) formulations for the next generation of vaccines

Many of the latest trends in vaccine development are dependent on immunological adjuvants that mediate and promote a wide variety of immune responses. One promising adjuvant candidate, monophosphoryl lipid A (MPL) immunostimulant, is being investigated with many of these new vaccine approaches in either preclinical or clinical trials. This is possible because different vehicle formulations can significantly influence the type of immunological response MPL promotes. Procedures are provided for formulating MPL in an aqueous vehicle or an oil-in-water emulsion. These two MPL formulations can be beneficial for most vaccine approaches being investigated today.

[Characteristics of lipopolysaccharide from Pseudomonas fluorescens (biovar I)]

Lipopolysaccharide (LPS) of the Pseudomonas fluorescens strain IMV 7769 (biovar I) was isolated and investigated. Fractions of the structural parts of the LPS macromolecule, lipid A, the core oligosaccharide, and the O-specific polysaccharide (O-PS), were obtained in a homogeneous state. 2-Hydroxydecanoic, 3-hydroxydecanoic, dodecanoic, 2-hydroxydodecanoic, 3-hydroxydodecanoic, hexadecanoic, octadecanoic, hexadecenoic, and octadecenoic fatty acids were identified in lipid A. In the hydrophilic moiety of lipid A, after acid hydrolysis, several amino acids, phosphoethanolamine, glucosamine, and three unidentified peaks forming a separate cluster together with glucosamine were found. Lipid A was shown to be phosphorylated. Glucose, fucose, rhamnose, glucosamine, galactosamine, two unidentified amino sugars, 2-keto-3-deoxyoctulonic acid (KDO), heptose, ethanolamine, phosphoethanolamine, and alanine were identified in the core oligosaccharide. O-PS of the LPS consisted of repeating trisaccharide fragments that included residues of amino sugars: 4-acetamido-4,6-dideoxy-D-galactose, 2-acetamido-2,6-dideoxy-D-glucose, and 2-acetamido-2,6-dideoxy-L-glucose. During growth, the strain under study excreted exocellular LPS (ELPS) into the medium. The LPS studied was similar to the LPS of the earlier investigated strains P. fluorescens (biovar I) IMV 1152 and IMV 1433 in the structure of O-PS, but differed from them in the composition of both lipid A and the core oligosaccharide. The LPS of the strain studied differed from LPS of the type strain P. fluorescens IMV 4125 (ATCC 13525) in all characteristics determined.

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.

[Rapid method of isolation of lipid A from Yersinia pseudotuberculosis]

The possibility of preparing the lipid A (LA) from Yersinia pseudotuberculosis Serovar IB by the hydrolysis of whole cells instead of the preliminary isolation of lipopolysaccharide (LPS) was demonstrated. Direct extraction with an organic solvent of the bacterial mass preliminary treated with 10% acetic acid or 1 M HCl was shown to result in a di- (LAAcOH) or monophosphoryl derivative (LAHCl), respectively. These were completely extractable only after treatment with strong hydrolyzing agents. We concluded that two forms of LA (and LPS) exist in the pseudotuberculosis bacterium which differ in the stability of their bonding to the bacterial outer membrane.

Complement activation by bacterial surface glycolipids: a study with planar bilayer membranes

Planar asymmetric glycolipid/phospholipid bilayer membranes were used as a reconstitution model of the lipid matrix of the outer membrane of Gram-negative bacteria to study complement (C) activation by various bacterial surface glycolipids with the aim of defining the C activation pathway. As glycolipids the lipopolysaccharides of Salmonella enterica serovar Minnesota R mutant strains R595 (Re LPS) and R4 (Rd2 LPS), pentaacyl lipid A from the LPS of the Escherichia coli Re mutant F515, and glycosphingolipid GSL-1 of Sphingomonas paucimobilis IAM 12576 were used. Methylester and carboxyl-reduced derivatives of GSL-1 were used to elucidate the role of the carboxyl group as common functional group of LPS and GSL-1 for C activation. The formation of lytic pores was monitored via the measurement of changes in membrane current. For all glycolipids we observed a considerable increase in membrane current soon after addition of whole human serum due to the formation of lytic pores in the membranes. Pore formation was dependent on the presence of C9, indicating that the observed current changes were due to C activation. We found that in our reconstitution system of the outer membrane lipid A, Re LPS, and Rd2 LPS activated the classical pathway, the activation being independent of specific anti-LPS antibodies. In contrast, GSL-1 and the methylester derivative of GSL-1 activated the alternative pathway even at the low serum concentrations used in this study (about 0.2% v/v). Interestingly, the carboxyl reduced GSL-1 activated the classical pathway.

Chemical structure of lipid A isolated from Flavobacterium meningosepticum lipopolysaccharide

The chemical structure of the lipid A of the lipopolysaccharide component isolated from Flavobacterium meningosepticum IFO 12535 was elucidated. Methylation and nuclear magnetic resonance analyses showed that two kinds of hydrophilic backbone exist in the free lipid A: a beta (1-->6)-linked 2-amino-2-deoxy-D-glucose, which is usually present in enterobacterial lipid A's, and a 2-amino-6-O-(2, 3-diamino-2,3-dideoxy-beta-D-glucopyranosyl)-2-deoxy-D-glucose, in a molar ratio of 1.00:0.35. Both backbones were alpha-glycosidically phosphorylated in position 1, and the hydroxyl groups at positions 4, 4', and 6' were unsubstituted. Liquid secondary ion-mass spectrometry revealed a pseudomolecular ion at m/z 1673 [M-H]- as a major monophosphoryl lipid A component carrying five acyl groups. Fatty acid analysis showed that the lipid A contained 1 mol each of amide-linked (R)-3-OH iC17:0, ester-linked (R)-3-OH iC15:0, amide-linked (R)-3-O-(iC15:0)-iC17:0, and both amide- and ester-linked (R)-3-OH C16:0. Fatty acid distribution analyses using several mass spectrometry determinations demonstrated that the former two constituents were distributed on positions 2 and 3 of the reducing terminal unit of the backbones and that the latter two were attached to the 2' and 3' positions in the nonreducing terminal residue.

[The inductive immunosuppressive activity of the lipopolysaccharide from Shigella sonnei R forms]

Investigations have been carried out to find the position of lypopolysaccharide (LPS) structural part which can be activated by the redox system and to study peculiarities of its activation. Cell-free culture filtrate (CF) of Shigella sonnei strain R colonies on the nutrient agar medium was used. It was shown that CF contained three active fractions possessing inductive immunosuppressive properties. From all the phenol-water LPS fractions only lipid A possessed activity after redox treatment. O-chain and our fractions did not express such activity. The results of our investigations have shown that inductive immunosuppressive activity of the Shigella sonnei LPS was determined by lipid A.

Regulation of decidual cell and chorion cell production of interleukin-10 by purified bacterial products

PROBLEM

To determine whether cultured human decidual cells and chorion cells produce interleukin-10 (IL-10) after incubation with purified bacterial products.

METHOD OF STUDY

Decidual cell cultures and chorion cell cultures were established by standard techniques. With confluence, monolayers of each culture were incubated with purified bacterial products, including various concentrations of lipopolysaccharide (LPS), lipid A, and lipoteichoic acid (LTA) for 16 hr in quadruplicate. Culture supernatants were collected and assayed for immunodetectable IL-10 by enzyme-linked immunoadsorbent assay (ELISA).

RESULTS

Both decidual cell cultures and chorion cell cultures produced significant quantities of IL-10 after stimulation with LPS, lipid A, and LTA. Cultures of decidual cells produced more IL-10 than did chorion cell cultures.

CONCLUSIONS

Our data indicate that both maternal decidual cells and fetally derived chorion cells can produce IL-10 after incubation with bacterial virulence factors. This finding contrasts with our previous findings in which chorion cells did not produce IL-10 after stimulation with IL-1 beta, suggesting that chorion cell production after incubation with bacterial products is independent of IL-1 beta. We speculate that the contribution of anti-inflammatory IL-10 production by human gestational tissues to the inflammatory process in these tissues may be overcome or abrogated by the pro-inflammatory process.

Function of the Escherichia coli msbB gene, a multicopy suppressor of htrB knockouts, in the acylation of lipid A. Acylation by MsbB follows laurate incorporation by HtrB

Overexpression of the Escherichia coli msbB gene on high copy plasmids suppresses the temperature-sensitive growth associated with mutations in the htrB gene. htrB encodes the lauroyl transferase of lipid A biosynthesis that acylates the intermediate (Kdo)2-lipid IVA (Brozek, K. A., and Raetz, C. R. H. (1990) J. Biol. Chem. 265, 15410-15417). Since msbB displays 27.5% identity and 42.2% similarity to htrB, we explored the possibility that msbB encodes a related acyltransferase. In contrast to htrB, extracts of strains with insertion mutations in msbB are not defective in transferring laurate from lauroyl acyl carrier protein to (Kdo)2-lipid IVA. However, extracts of msbB mutants do not efficiently acylate the product formed by HtrB, designated (Kdo)2-(lauroyl)-lipid IVA. Extracts of strains harboring msbB+ bearing plasmids acylate (Kdo)2-(lauroyl)-lipid IVA very rapidly compared with wild type. We solubilized and partially purified MsbB from an overproducing strain, lacking HtrB. MsbB transfers myristate or laurate, activated on ACP, to (Kdo)2-(lauroyl)-lipid IVA. Decanoyl, palmitoyl, palmitoleoyl, and (R)-3-hydroxymyristoyl-ACP are poor acyl donors. MsbB acylates (Kdo)2-(lauroyl)-lipid IVA about 100 times faster than (Kdo)2-lipid IVA. The slow, but measurable, rate whereby MsbB acts on (Kdo)2-lipid IVA may explain why overexpression of MsbB suppresses the temperature-sensitive phenotype of htrB mutations. Presumably, the acyloxyacyl group generated by excess MsbB substitutes for the one normally formed by HtrB.

Structure of the monophosphoryl lipid A moiety obtained from the lipopolysaccharide of Chlamydia trachomatis

Monophosphoryl lipid A was prepared from the lipopolysaccharide of Chlamydia trachomatis, converted to the methyl ester, and fractionated by reverse-phase high-performance liquid chromatography. The peak fractions were collected and analyzed by mass spectrometry. Matrix-assisted laser desorption/ionization and liquid secondary ion mass spectrometry of the first of two major high-performance liquid chromatographic fractions showed multiple quasi-molecular ions of MNa+ at m/z 1780, 1794, 1808, 1822, and 1836. The positive-ion liquid secondary ion mass spectrometry spectrum also showed a minor series of peaks at m/z 1916, 1930, 1944, 1958, and 1971, consistent with the formation of matrix adducts with 3-nitrobenzyl alcohol. Oxonium ions representing the distal subunit were observed at m/z 1057, 1071, 1085, 1099, and 1113. The second fraction was similarly analyzed and found to contain structural homologs of the first fraction. Based on this study, the major lipid A component of chlamydial lipopolysaccharide is a glucosamine disaccharide that contains five fatty acids and a phosphate in the distal segment. Three fatty acyl groups are in the distal segment, and two are in the reducing end segment. The acyloxyacyl group is located in the distal segment in amide linkage. Two structural series, differing by 14 atomic mass units in the reducing subunit, were observed. Chlamydial lipid A is complex and consists of at least 20 homologous structural components. The relatively low potency of Chlamydia trachomatis lipopolysaccharide in activating lipopolysaccharide-responsive cells might be related to the unusual fatty acid composition of the lipid A moiety.

Analysis of a monophosphoryl lipid A immunostimulant preparation from Salmonella minnesota R595 by high-performance liquid chromatography

MPL immunostimulant, a 4'-monophosphoryl lipid A (MLA) preparation obtained from the lipopolysaccharide of Salmonella minnesota R595, is being developed for several clinical indications. MPL comprises a mixture of MLA congeners that contain 4, 5, and 6 fatty acids. In this paper, we report a new high-performance liquid chromatography (HPLC) method for analyzing the congener composition and purity of MPL. MPL is first derivatized with dinitrobenzyloxyamine (DNBA), resulting in incorporation of the dinitrobenzyl chromophore at the reducing end of all MLA congeners. DNBA-MPL is then analyzed by reversed-phase HPLC on a Waters NovaPak C18, 4 microns particle size, 300 mm x 3.9 mm column. Optimal separation of DNBA-MLA species is obtained using a linear gradient of 10% to 80% isopropanol-water (95:5, v/v), 5 mM tetrabutylammonium dihydrogenphosphate (TBAP), in acetonitrile-water (95:5, v/v), 5 mM.TBAP, over 45 min. A synthetic compound, corresponding to a hexaacyl MLA congener, is used for determination of the detector response factor, allowing the MLA content of MPL (i.e., purity) to be determined. Overall, this method provides better separation, higher sensitivity, and is faster and saler than previous methods used for the analysis of MPL.

Permeability and adsorption capacity of dialysis membranes to lipid A

Hemodialysis membranes were tested in vitro for possible penetration by low molecular weight endotoxins containing lipid A. Using lipid A from Escherichia coli as a model substance for this kind of pyrogen, different dialyzers (F4, E3. Acepal 1300, Altraflux, F 40, Polyflux 110, Filtral 12, F 60) were challenged by tangential filtration in aqueous medium. All membranes exhibited impermability to lipid A (as well as to LPS from Pseudomonas aeruginosa), which was proved by additional experiments using culture filtrates of Pseudomonas aeruginosa in bicarbonate dialysis fluid, as well as by employing miniaturized dialyzers with synthetic lipid A as a contaminant. Furthermore, the highest adsorption capacities were found for polysulfone and polyamide membranes.

Removal of lipid A and Pseudomonas aeruginosa endotoxin from dialysis fluids by high-flux polysulfone ultrafilter (dialyzer)

Ultrafilters (dialysis membranes) are generally considered to be impermeable to bacterial endotoxins (lipopolysaccharides) contaminating dialysates used for hemodialysis therapy, due to the self-aggregating properties of its molecules in aqueous media. The aim of the present investigation was to monitor the efficiency of high-flux polysulfone ultrafilters in removing lipid A and lipopolysaccharide (LPS) from dialysis fluids. To evaluate the safety of high-flux polysulfone membranes, an in-vitro circulation system (measuring lipopolysaccharide and lipid A penetrate from the ultrafilter to the other side and vice-versa), was utilized. Peritoneal dialysis solution was spiked with various concentration of Pseudomonas aeruginosa lipopolysaccharide (LPS) as well as lipid A diphosphoryl (E. coli F-583). Endotoxin and lipid A concentrations were detected by a chromogenic limulus amoebocyte lysate (LAL) assay. This investigation indicates that polysulfone ultrafiltration represents an efficient system to obtain an endotoxin and lipid A free dialysate when contaminated peritoneal solution was circulated through the dialysis membrane.

Chemical structure of lipid A isolated from Comamonas testosteroni lipopolysaccharide

The chemical structure of lipid A of lipopolysaccharide isolated from Comamonas testosteroni was determined by quantitative analysis, methylation analysis, mass spectrometry and NMR spectroscopy. The lipid A backbone was found to consist of 6-O-(2-deoxy-2-amino-beta-D-glucopyranosyl)-2-deoxy-2-amino-alpha-D-g luc ose which was phosphorylated in positions 1 and 4'. Hydroxyl groups at positions 4 and 6' were unsubstituted, and position 6' of the non-reducing terminal residue was identified as the attachment site of the polysaccharide part. Liquid secondary-ion/mass spectrometry revealed a pseudomolecular ion at m/z 1572 [M-H]- as a major diphosphoryl lipid component carrying six acyl groups. Fatty acid distribution analysis and electrospray ionization/mass spectrometry of the lipid A showed that positions 2,2',3, and 3' of the sugar backbone were N-acylated or O-acylated by (R)-3-hydroxydecanoic acid, and that the hydroxyl groups of the amide-linked residues attached to positions 2 and 2' were further O-acylated by tetradecanoic and dodecanoic acids, respectively.

Separation and characterization of O-deacylated lipooligosaccharides and glycans derived from Moraxella catarrhalis using capillary electrophoresis-electrospray mass spectrometry and tandem mass spectrometry

Electrophoretic methods have been developed for the analysis of complex carbohydrates derived from lipooligosaccharides (LOS) of Moraxella catarrhalis using capillary electrophoresis coupled to electrospray mass spectrometry (CE-ESMS). Separation of lipooligosaccharides (LOS) arising from mild hydrazinolysis of the intact lipopolysaccharides (LPS) was achieved using aqueous ammonium formate, and enabled identification of sites of heterogeneity (phosphates, phosphoethanolamine, and pendant acyl groups) on either the lipid A or the core oligosaccharide. More complex mixtures of carbohydrates obtained from the complete deacylation and dephosphorylation of LOS were amendable to electrophoretic conditions using both anionic and cationic separation. In particular, electrophoretic conditions were developed which permitted resolution of closely related oligosaccharides according to the number of carbohydrate residues appended to the core structure. Structural characterization of carbohydrates and LOS released from the hydrazinolysis and acid hydrolysis treatment of the intact LPS was achieved using tandem mass spectrometry (MS-MS) for samples introduced by direct flow injection. Taken together, the combination of CE-ESI-MS and MS-MS analyses provided valuable information on the heterogeneity of the LOS population in which a significant level of variability was found mostly in the lipid A portion.

Development of cationically modified cellulose adsorbents for the removal of endotoxins

The removal of endotoxins by extracorporeal adsorption processes seems the most promising therapeutic approach to Gram-negative sepsis and endotoxin shock. However, thus far adsorbents have failed to bind endotoxins efficiently or have shown adverse biocompatibility characteristics. To overcome these disadvantages, small particles of regenerated cellulose in the range of 1-8 microns in diameter were produced. Before use, the microspheres were cationically modified by substitution with polyethyleneimine (PEI) or diethylaminoethyl (DEAE) groups. A third kind of adsorbent was manufactured by (physically) coating the cellulose matrix with PEI. All three types of adsorbents exhibited a high adsorption capacity for endotoxins in human plasma, whereas activated charcoal and various anion exchange resins removed only small amounts of endotoxins under the same conditions. In addition, because the outer surface area is very large, adsorption takes place rapidly and diffusion becomes almost irrelevant. The adsorption process is primarily based on electrostatic interactions, which could be demonstrated by a significantly higher adsorption rate and binding capacity for lipid A-diphosphoryl, compared with lipid A-monophosphoryl. Use of these adsorbents in a newly developed plasma sorption system could be of great clinical interest because of the low production costs, the high adsorption efficiency, and the excellent biocompatibility data.

Detection of antigenic proteins in Porphyromonas gingivalis using two-dimensional electrophoresis and western blots

Using two-dimensional (2D) electrophoresis and western blot assay, we analyzed antigenic proteins in Porphyromonas gingivalis uniquely recognized by antibodies in sera of periodontitis subjects. Proteins in the total membrane fraction of P. gingivalis 381 were resolved into at least 70 protein spots by 2D electrophoresis. In the gel stained with silver, the substance around 47 kDa protein on the acidic side (at an isoelectric point of about 4.5) was stained as a smear. Antigenic substances were characterized using purified IgGs from sera of 16 adult periodontitis (AP), 19 rapidly progressive periodontitis (RPP) and 14 periodontally healthy volunteers. Western blots demonstrated that 75 kDa protein reacted with IgGs from 75% of AP patients (p < 0.001), the antigenic substance around acidic 47 kDa protein reacted with IgGs from 81.3% of AP (p < 0.01) and 68.4% of RPP patients (p < 0.01) and the acidic 47 kDa protein reacted with 87.5% of AP (p < 0.01) and 78.9% of RPP patients (p < 0.01). The reaction frequency was significantly different from that of the healthy volunteers. Also 51 kDa and 41 kDa proteins reacted with 47 and 43 of 49 IgG samples, respectively. The substance around acidic 47 kDa protein reacted with mouse antiserum to P. gingivalis-LPS. After treatment with pronase or heat, the antigenic reactions disappeared not only from the proteins, but also from the area around the acidic 47 kDa protein. When the fraction was digested with lipase, the antigenic reaction of the area decreased.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural study on the free lipid A isolated from lipopolysaccharide of Porphyromonas gingivalis

The chemical structure of lipid A isolated from Porphyromonas gingivalis lipopolysaccharide was elucidated by compositional analysis, mass spectrometry, and nuclear magnetic resonance spectroscopy. The hydrophilic backbone of free lipid A was found to consisted of beta(1,6)-linked D-glucosamine disaccharide 1-phosphate. (R)-3-Hydroxy-15-methylhexadecanoic acid and (R)-3-hydroxyhexadecanoic acid are attached at positions 2 and 3 of the reducing terminal residue, respectively, and positions 2' and 3' of the nonreducing terminal unit are acylated with (R)-3-O-(hexadecanoyl)-15-methylhexadecanoic acid and (R)-3-hydroxy-13-methyltetradecanoic acid, respectively. The hydroxyl group at position 4' is partially replaced by another phosphate group, and the hydroxyl groups at positions 4 and 6' are unsubstituted. Considerable heterogeneity in the fatty acid chain length and the degree of acylation and phosphorylation was detected by liquid secondary ion-mass spectrometry (LSI-MS). A significant pseudomolecular ion of lipid A at m/z 1,769.6 [M-H]- corresponding to a diphosphorylated GlcN backbone bearing five acyl groups described above was detected in the negative mode of LSI-MS. Predominant ions, however, were observed at m/z 1,434.9 [M-H]- and m/z 1,449.0 [M-H]-, each representing monophosphoryl lipid A lacking (R)-3-hydroxyhexadecanoic and (R)-3-hydroxy-13-methyltetradecanoic acids, respectively. The presence of mono- and diphosphorylated lipid A species was also confirmed by LSI-MS of de-O-acylated lipid A (m/z 955.3 and 1,035.2, respectively).

Lipid A-associated proteins from periodontopathogenic bacteria induce interleukin-6 production by human gingival fibroblasts and monocytes

The aim of this study was to determine whether lipid A-associated proteins (LAP) from two periodontopathogenic species of bacteria were able to stimulate interleukin-6 (IL-6) release from human gingival fibroblasts and myelomonocytic cells. LAP and lipopolysaccharide (LPS) were extracted from Porphyromonas gingivalis and Prevotella intermedia and added to cultures of human gingival fibroblasts and mono-mac-6 monocytic cells. Release of IL-6 into the culture supernatants was determined by ELISA. LAP and LPS from Por. gingivalis, but not from Prev. intermedia, stimulated IL-6 release from both cell types in a dose-dependent manner although LPS was less potent than LAP in inducing IL-6 release from the fibroblasts. IL-6 was detectable in cultures of both cell types following stimulation with LAP from Por. gingivalis at a concentration as low as 10 ng/ml. In response to LAP from Prev. intermedia, IL-6 was produced by mono-mac-6 cells but not by fibroblasts. Our results show that bacterial cell wall components other than LPS can induce IL-6 release from cells of the periodontium in vitro. The production of such potent immunomodulatory agents in vivo may contribute to the connective tissue breakdown characteristic of chronic periodontitis.

[Establishment of hybridoma lines and protective study of monoclonal antibodies against lipid A of endotoxins]

For developing monoclonal antibodies (MAb) that bound to lipid A of the LPS molecule, we established several hybridomas cell lines by fusion of SP2/0 and spleen cells from BALB/c mice immunized by J5 mutant strain of E. coli 0111:B4. Each MAb exhibited a high titer by ELISA assay. Six of MAb were of immunoglobulin G isotype and another one immunoglobulin M. All of these MAb demonstrated different capacity to cross-react with several gram-negative bacteria and their endotoxins. Among them, 9G6 MAb improved the survival rate of mice significantly when administered 2 hours before the challenge by pseudomonas A and E. coli. These findings suggest that MAb will probably be useful in the treatment of sepsis caused by a wide variety of gram-negative bacteria.

Affinity-purified Escherichia coli J5 lipopolysaccharide-specific IgG protects neutropenic rats against gram-negative bacterial sepsis

Antibodies were raised in rabbits by immunization with the heat-killed J5 mutant of Escherichia coli O111 (Rc chemotype). Serum antibodies were separated into purified IgG and IgM by sequential affinity chromatography on protein G-Sepharose and anti-rabbit IgG-Sepharose columns. J5 lipopolysaccharide (LPS)-specific IgG was prepared by affinity chromatography of purified IgG on a J5 LPS-EAH Sepharose 4B affinity column. Purified IgM, IgG, and J5 LPS-specific IgG protected neutropenic rats against lethal challenge with Pseudomonas aeruginosa 12:4:4 (Fisher Devlin immunotype 6). Nine of 16 rats treated with the IgM fraction were protected (P < .001). Thirteen of 20 rats treated with the purified IgG and 6 of 8 treated with J5 LPS-specific IgG were protected compared with none of 25 treated with IgG made from the preimmune serum of the same rabbit (P < .001). These results demonstrate that purified J5 LPS-specific IgG protects against the lethal consequences of gram-negative bacteremia.

Diphosphoryl lipid A derived from the lipopolysaccharide (LPS) of Rhodobacter sphaeroides ATCC 17023 is a potent competitive LPS inhibitor in murine macrophage-like J774.1 cells

Pentaacyl diphosphoryl lipid A derived from the nontoxic lipopolysaccharide (LPS) of Rhodobacter sphaeroides ATCC 17023 (RsDPLA) did not induce tumour necrosis factor-alpha nor interleukin-6 release in the murine macrophage-like cell line J774.1. However, it effectively inhibited the induction of these two cytokines by LPS of Salmonella minnesota Re mutant R595 (ReLPS) in a concentration-dependent manner. Maximal inhibition and half-maximal inhibition occurred when the ReLPS to RsDPLA mass ratio was 1:30 and 1:1, respectively. A binding study was performed in the presence of serum to determine whether RsDPLA is competing with ReLPS for LPS binding sites on J774.1 cells. This assay allows the determination of LPS binding to J774.1 cells via a mechanism involving CD14, a receptor for complexes of LPS with LPS binding protein (LBP), and its possible inhibition. The results show that RsDPLA strongly inhibits the binding of 125I-labelled ReLPS to J774.1 cells. Maximal and one-half maximal inhibition of binding occurred when the ReLPS to RsDPLA mass ratios were 1:2.5 and 1:0.5, respectively. It was found that the inhibition of binding by RsDPLA was much stronger than that by unlabelled ReLPS. These results suggest that RsDPLA is competing with ReLPS for CD14-dependent recognition of LPS on J774.1 cells.

Structure of lipid A component of Rhizobium leguminosarum bv. phaseoli lipopolysaccharide. Unique nonphosphorylated lipid A containing 2-amino-2-deoxygluconate, galacturonate, and glucosamine

The structure of lipid A from the lipopolysaccharide of Rhizobium leguminosarum bv. phaseoli (wild type strain CE3) was investigated by alkylation analysis, nuclear magnetic resonance spectroscopy, and electrospray and fast atom bombardment mass spectrometry of the de-O-acylated lipid A. The lipid A carbohydrate backbone was shown to be a trisaccharide containing galacturonic acid, glucosamine, and the unique sugar 2-amino-2-deoxygluconic acid, previously unreported in lipopolysaccharides. Nuclear magnetic resonance spectroscopy and ethylation analyses revealed that the galacturonic acid is alpha-1,4-linked to the glucosamine, while the amino aldonic acid residue, which may exist as the 1,5-lactone, is attached as an aglycone to the glucosamine and, thus, occupies the reducing end of the molecule. The resulting backbone is hydrophilic and analogous to the commonly observed bisphosphorylated glucosamine disaccharide from enteric bacterial lipopolysaccharides in that both the nonreducing and reducing ends carry negatively charged substituents. The fatty acids of the R. leguminosarum lipid A are attached both as O- and N-acyl substituents to glucosamine and 2-aminogluconate. All fatty acids are hydroxylated consisting of 3-hydroxymyristate (3-OH-C14.0), 3-hydroxypentadecanoate (3-OH-C15.0), 3-hydroxypalmitate (3-OH-C16.0), 3-hydroxystearate (3-OH-C18.0), and 27-hydroxyoctacosanoate (27-OH-C28.0) in the approximate mole ratio 3:0.2:1:0.6:1. Unlike lipid As from enteric bacteria, the R. leguminosarum lipid A lacks 3-acyloxyacyl substituents; however, the long chain 27-hydroxy fatty acid carries ester-linked beta-hydroxybutyrate at the 27-hydroxy position. Fast atom bombardment mass spectrometry of the de-O-acylated lipid A demonstrated the presence of 2 molecular species that differ by 28 mass units due to fatty acid heterogeneity at the two amide linkages. One species carries amide-linked 3-OH-C14.0 and 3-OH-C16.0; the second species carries 3-OH-C14.0 and 3-OH-C18.0. Each molecular species also exists as the aldonolactone, yielding molecular ions at ((M+H)+)-18. The heterogeneity in the amide-linked fatty acids further distinguishes the Rhizobium lipid A from enteric lipid As.

Anti-endotoxic activity of murine monoclonal antibody (E5) assessed by inhibition of priming of human phagocytes by endotoxin

The in vitro activity of a murine monoclonal antibody (E5) reactive with endotoxin was examined in human whole blood by measuring the luminol-chemiluminescence (CL) activity in response to phorbol myristate acetate (PMA) as an index of the priming effect of lipopolysaccharide (LPS) on the release of reactive oxygen species. Whole blood samples obtained from healthy adults showed a significantly enhanced CL response to PMA after incubation with LPS (100 ng/ml, Escherichia coli O111:B4) for 10 min at 37 degrees C, as compared with untreated blood samples, through no CL response was induced by LPS itself. This priming effect of LPS varied from person to person. Similarly, various degrees of the priming effect were observed with other LPS preparations derived from E. coli O55:B5, Klebsiella pneumoniae, Serratia marcescens and Salmonella typhimurium. However, the priming effects of these LPS or a synthetic lipid A (LA-15-PP) of E. coli were significantly prevented to various degrees when such endotoxins were treated with E5 for 30 min at 37 degrees C prior to being added to blood samples. The inhibitory effect E5 was dose-dependent and was most potent against the LPS of E. coli O111:B4. These results indicate that E5 suppresses the priming effect of LPS on oxygen radical release from human whole blood, and therefore suggest that E5 may be a useful drug for supportive therapy in patients with gram-negative septicemia or endotoxemia, especially in a case involving serious neutrophil-mediated organ injury caused by excessive release of oxygen free radicals.

Lipopolysaccharide (LPS) binding to 73-kDa and 38-kDa surface proteins on lymphoreticular cells: preferential inhibition of LPS binding to the former by Rhodopseudomonas sphaeroides lipid A

Using a photoactivable, radioiodinated lipopolysaccharide probe, [125I]ASD-LPS (derivatized from purified E. coli 0111:B4 S-LPS), we earlier reported the presence of a 73-kDa (p73) predominant LPS-binding protein on mouse lymphocytes and macrophages with specificity for the lipid A region of LPS. Both Re-LPS from Salmonella minnesota and purified lipid A will inhibit the binding of LPS to the p73 LPS receptor. In the studies reported here, we have found that non-toxic diphosphoryl lipid A purified from Rhodo-pseudomonas sphaeroides has the capability to inhibit the binding of [125I]ASD-LPS to the p73 protein. However, using the same LPS probe and photoaffinity cross-linking techniques, our data suggest that a less dominant 38-kDa (p38) LPS-specific binding protein identified on mouse splenocytes, J774.1 macrophage-like cell line, and 70Z/3 pre B-cell line by SDS-PAGE is not inhibited by purified lipid A, even at a concentration in 50-fold excess of that of [125]ASD-LPS. The binding of the LPS probe to the 38 protein could be inhibited in a dose-dependent manner by underivatized native S. minnesota Re-LPS (composed only of Kdo and lipid A). We speculate that this p38 LPS-binding protein may manifest a specificity for inner core oligosaccharide determinants on LPS.

Lipopolysaccharide interaction with S2 subunit of pertussis toxin

Using radioiodinated, photoactivable, reducible cross-linker conjugated bacterial endotoxic lipopolysaccharide (125I-ASD-LPS), we have demonstrated that LPS selectively binds to the S2 subunit of pertussis toxin (PT). Since LPS also interacts with the S2 subunit of the B-oligomer of the toxin, the binding of LPS to PT is not A-protomer (S1 subunit) dependent. The binding can be inhibited with native underivatized LPS and with purified lipid A, suggesting that the binding is mediated through the lipid A moiety of the LPS molecule. The binding of PT to LPS can be inhibited by bovine fetuin glycoprotein. Since PT has been demonstrated to interact specifically with N-linked oligosaccharide side chains of fetuin, the interaction of LPS with the S2 subunit of PT may involve carbohydrate-dependent interactions of the disaccharide backbone of lipid A with S2. Additional studies have documented that LPS binding to PT may be competitively inhibited by lysozyme but not by polymyxin B. Sequence analysis has allowed identification of a high degree of amino acid sequence similarity between the S2 subunit of PT and hen egg white lysozyme at the N-terminal 80-residue regions. Shared N-terminal sequence similarity between lysozyme, PT-S2, and a third LPS-binding protein alpha-lactalbumin allows tentative identification of a second family of LPS binding proteins.

A comparison of the immunomodulating properties of two forms of monophosphoryl lipid A analogues

This investigation compared the immunomodulating activities of two forms monophosphoryl lipid A, which are analogues of bacterial lipopolysaccharides with little or no toxicity. Tested were a synthetic compound designated 504 and a purified compound, isolated from bacterial cell walls designated MPL. Both of these clinical adjuvant candidates were effective in mice in exerting strong immunomodulating activity in the following areas: (a) enhancing antibody production in young and aging mice; (b) suppressing antibody formation under different experimental conditions; (c) activating macrophages to secrete interleukin 1, hydrogen peroxide, and superoxide anion; and (d) stimulating proliferation of spleen cells from C3H/HeN mice. Both exhibited considerably reduced toxicity in LD50 assays when compared to native lipopolysaccharides (LPS). The LD50 for MPL was 225 times and that of compound 504, 40 times that of native LPS in the exquisitely sensitive, galactosamine-loaded C57BL/6 murine strain.

[The protective properties of the endotoxin protein]

The isolation and properties of endotoxin protein, or lipid A-associated protein (LAP), from Shigella sonnei were described earlier (Zh. mikrobiol. epidemiol. immunobiol., 1991, No. 4, pp. 11-17, and No. 7). In this report the data on its protective activity are presented. In experiments on mice one nanogram of LAP injected i. v. protected 50% of the animals against i. p. challenge with 40 LD50 of virulent S. sonnei. Guinea pigs injected s. c. with 10 micrograms of LAP were protected against local (keratoconjunctival) challenge with S. sonnei, the efficiency of immunization being 58%. LAP preparations containing no detectable amounts of O-antigen (less than 0.003%) were found to have a protective effect. Hyperimmune anti-LAP rabbit serum prevented local infection when incubated with S. sonnei challenge inoculum before injection into guinea pigs. Both active and passive protection induced by LAP was specific since no effect was observed in animals challenged with Shigella flexneri. In the homologous system the protective effect of anti-LAP serum was abolished by the addition of protein-free LPS. These results are compatible with the hypothesis that the protective activity of LAP depends on the presence of minute amounts of O-antigen whose immunogenic effect is greatly amplified by the protein component of the natural endotoxin complex.

[The immunogenic properties of the endotoxin protein: serum antibodies in animals and man]

Endotoxin protein or lipid A-associated protein (LAP) from Shigella sonnei was isolated and characterized earlier (Zh. mikrobiol. epidemiol. immunobiol., 1991, No. 4, pp. 47-50). In this investigation serum antibodies against LAP were studied in ELISA Anti-LAP antibodies were detected in high titers in the sera of nonimmunized mice, guinea pigs, rabbits, monkeys and healthy adults. We suppose that normal anti-LAP antibodies resulted from interaction between the immune system and environmental endotoxin. Parenteral injections of LAP to different animals induced intensive antibody response with a 100- to 1000-fold increase in the serum anti-LAP antibody level and a significant rise in the serum O-antibody level. The latter is seemingly due to the contamination of LAP with minute amounts of O-antigen (0.12% or less) and to the amplification of its immunogenicity by LAP. Both antigenic and amplifying activity of LAP was destroyed by proteinase K. The biological function of LAP and its possible use as a component of bacterial vaccines are briefly discussed.

Structural characterization of the lipid A component of Pseudomonas aeruginosa wild-type and rough mutant lipopolysaccharides

The structure of the lipid A component of lipopolysaccharides isolated from two wild-type strains (Fisher 2 and 7) and one rough mutant (PAC 605) of Pseudomonas aeruginosa was investigated using chemical analysis, methylation analysis, combined gas-liquid chromatography/mass spectrometry, laser-desorption mass spectrometry and NMR spectroscopy. The lipid A backbone was found to consist of a pyranosidic beta 1,6-linked D-glucosamine disaccharide [beta-D-GlcpN-(1----6)-D-GlcpN], phosphorylated in positions 4' and 1. Position 6' of the beta-D-GlcpN-(1----6)-D-GlcpN disaccharide was identified as the attachment site of the core oligosaccharide and the hydroxyl group at C-4 was not substituted. Lipid A of the three P. aeruginosa strains expressed heterogeneity with regard to the degree of acylation: a hexaacyl as well as a pentaacyl component were structurally characterized. The hexaacyl lipid A contains two amide-bound 3-O-acylated (R)-3-hydroxydodecanoic acid groups [12:0(3-OH)] at positions 2 and 2' of the GlcN dissacharide and two ester-bound (R)-3-hydroxydecanoic acid groups [10:0(3-OH)] at positions 3 and 3'. The pentaacyl species, which represents the major lipid A component, lacks one 10:0(3-OH) residue, the hydroxyl group in position 3 of the reducing GlcN residue being free. In both hexa- and pentaacyl lipid A the 3-hydroxyl group of the two amide-linked 12:0(3-OH) residues are acylated by either dodecanoic (12:0) or (S)-2-hydroxydodecanoic acid [12:0(2-OH)], the lipid A species with two 12:0(2-OH) residues, however, being absent. The presence of only five acyl residues in the major lipid A fraction may account for the low endotoxic activity observed with P. aeruginosa lipopolysaccharide.

Structural analysis of the lipid A component of Campylobacter jejuni CCUG 10936 (serotype O:2) lipopolysaccharide. Description of a lipid A containing a hybrid backbone of 2-amino-2-deoxy-D-glucose and 2,3-diamino-2,3-dideoxy-D-glucose

The chemical structure of Campylobacter jejuni CCUG 10936 lipid A was elucidated. The hydrophilic backbone of the lipid A was shown to consist of three (1----6)-linked bisphosphorylated hexosamine disaccharides. Neglecting the phosphorylation pattern, a D-glucosamine (2-amino-2-deoxy-D-glucose) disaccharide [beta-D-glucosaminyl-(1----6)-D-glucosamine], a hybrid disaccharide of 2,3-diamino-2,3-dideoxy-D-glucose and D-glucosamine [2,3-diamino-2,3-dideoxy-beta-D-glucopyranosyl-(1----6)-D-glucosamine], and a 2,3-diamino-2,3-dideoxy-D-glucose disaccharide were present in a molar ratio of 1:6:1.2. Although the backbones are bisphosphorylated, heterogeneity exists in the substitution of the polar head groups. Phosphorylethanolamine is alpha-glycosidically bound to the reducing sugar residue of the backbone, though C-1 is also non-stoichiometrically substituted by diphosphorylethanolamine. Position 4' of the non-reducing sugar residue carries an ester-bound phosphate group or is non-stoichiometrically substituted by diphosphorylethanolamine. By methylation analysis it was shown that position 6' is the attachment site for the polysaccharide moiety in lipopolysaccharide. These backbone species carry up to six molecules of ester- and amide-bound fatty acids. Four molecules of (R)-3-hydroxytetradecanoic acid are linked directly to the lipid A backbone (at positions 2, 3, 2', and 3'). Laser desorption mass spectrometry showed that both (R)-3-hydroxytetradecanoic acids linked to the non-reducing sugar unit carry, at their 3-hydroxyl group, either two molecules of hexadecanoic acid or one molecule of tetradecanoic and one of hexadecanoic acid. It also suggested that the (R)-3-(tetradecanoyloxy)-tetradecanoic acid was attached at position 2', whereas (R)-3-(hexadecanoyloxy)-tetradecanoic acid was attached at position 3', or at positions 2' and 3'. Therefore, the occurrence of three backbone disaccharides differing in amino sugar composition and presence of a hybrid disaccharide differentiate the lipid A of this C. jejuni strain from enterobacterial and other lipids A described previously.

[Shigella endotoxin protein--its isolation and physicochemical characteristics]

The scheme of the isolation of endotoxic protein from S. sonnei 9090 is presented. The isolation procedure includes the 10-minute hot (at 68 degrees C) extraction of protein from endotoxin with 45% aqueous phenol, the precipitation of protein from phenolic extract with 9.5 volumes of 95% ethanol, the purification of protein from lipid material and pigments by multiple extraction with the mixture of chloroform and ethanol in the proportion 2:1 by volume. The yield of protein obtained with the use of this isolation scheme is about 3% of the initial endotoxin preparation. Protein preparations obtained in accordance with this scheme contain 92-95% of protein (determined by Lowry's method), 2.3-3.0% of saccharides (determined by the phenol-sulfate method) and 0.02% of hexose amine, its presence indicating that the preparations contain lipid A (or its fragments) which is firmly bound with endotoxic protein and cannot be extracted with chloroform. As shown in the passive hemagglutination inhibition test, the content of endotoxin in the preparations is less than 0.003%. Out of 7-11 bands revealed by electrophoresis in 15% polyacrylamide gel in the presence of sodium dodecyl sulfate, 3 main bands have molecular weights of 43, 38 and 18 KD. Three antigens differing in their electrophoretic mobility and diffusion rate in 1% agarose gel can be detected in the preparations by the method of immunoelectrophoresis with the use of antisera to both endotoxin and endotoxic protein.

[Shigella endotoxin protein--its electrophoretic and serological properties]

The electrophoretic analysis of lipid A-associated protein (LAP), obtained from S. sonnei, in polyacrylamide gel in the presence of sodium dodecyl sulfate and urea has revealed the heterogeneity of the preparation; it has found to contain three main components with molecular weights of 43, 38 and 18 KD and some minor components with molecular weights of 49, 45 35, 30, 29, 27, 5, 21 and 14 KD. The electrophoretic mobility of the main protein components in the isolated preparation of LAP coincides with that of endotoxin components. The dissociation of proteins and lipopolysaccharide in the process of boiling the endotoxin in 2% sodium dodecyl sulfate is indicative of the noncovalent binding of these components. LAP contained in the endotoxin, in contrast to isolated LAP, is resistant to trypsin and proteinase K. The enzyme immunoassay (EIA) system with the use of LAP as a component of its solid phase has been developed, which makes it possible to carry out the quantitative determination of antibodies to this protein. The EIA system shows high sensitivity in the determination of anti-LAP IgG antibodies: in hyperimmune rabbit sera their titer is 1:250,000-1:800,000. As shown by the method of competitive EIA, the antigenic affinity of LAP of different origin corresponds to the degree of taxonomic propinquity of microorganisms: the maximal degree of cross reactions is observed between LAP obtained from S. sonnei, S. flexneri and Escherichia coli, while their affinity to Salmonella typhi is considerably less; remote microbial species (Bacterium bifidum and Sarcina marcescens) give practically no cross reactions.

Phase diagram of lipid A from Salmonella minnesota and Escherichia coli rough mutant lipopolysaccharide

We have reported here on the structural polymorphism of lipid A, the "endotoxic principle" of bacterial lipopolysaccharide. For lipid A of rough mutant lipopolysaccharide from Salmonella minnesota and Escherichia coli, the three-dimensional supramolecular structures were determined with x-ray diffraction utilizing synchrotron radiation. The investigations were performed in the water concentration range 10 to 95% by weight, at [lipid A]:[Mg2+] molar ratios from 1:0 to 0.1:1, and in the temperature range from 20 to 70 degrees C. These data were correlated with measurements of the beta----alpha phase behaviour which was monitored with differential scanning calorimetry and Fourier-transform infrared spectroscopy. We found that the transition temperature of the acyl chains ranges--in the absence of Mg2(+)-from 45 degrees C at high to 56 degrees C at low water content, and-at an equimolar content of Mg2(+)-from 52 degrees C at high to 59 degrees C at low water concentrations. In the gel phase-in which the lipid A acyl chains are more disordered than those from saturated phospholipids-cubic phases are adopted at high water content (greater than 60%) and at high [lipid A]:[Mg2+] molar ratios. At low water contents, lamellar states are assumed exclusively. In the liquid crystalline state of lipid A, the hexagonal HII state is adopted under all conditions. The structural variability of lipid A is highest at high water concentrations, and structural changes may be induced by only slight changes in temperature, water content, and Mg2+ concentration. Under physiological conditions, however, the lipid A assemblies exhibit a strong preference to cubic structures.

Biosynthesis of lipid A in Escherichia coli. Acyl carrier protein-dependent incorporation of laurate and myristate

In previous studies we described enzyme(s) from Escherichia coli that transfer two 3-deoxy-D-manno-octulosonate (KDO) residues from two CMP-KDO molecules to a tetraacyldisaccharide-1,4'-bis-phosphate precursor of lipid A, termed lipid IVA (Brozek, K. A., Hosaka, K., Robertson, A. D., and Raetz, C. R. H. (1989) J. Biol. Chem. 264, 6956-6966). The product, designated (KDO)2-IVA, can be prepared in milligram quantities and/or radiolabeled with 32P at position 4' of the IVA moiety. We now demonstrate the presence of enzymes in E. coli extracts that transfer laurate and/or myristate residues from lauroyl or myristoyl-acyl carrier protein (ACP) to (KDO)2-IVA. Thioesters of coenzyme A are not substrates. The cytosolic fraction catalyzes rapid acylation with lauroyl-ACP, but not with myristoyl, R-3-hydroxymyristoyl, palmitoyl, or palmitoleoyl-ACP. The membrane fraction transfers both laurate and myristate to (KDO)2-IVA. Evidence for the enzymatic acylation of (KDO)2-IVA is provided by (a) conversion of [4'-32P](KDO)2-IVA to more rapidly migrating products in the presence of the appropriate acyl-ACP, (b) incorporation of [1-14C]laurate or [1-14C]myristate into these metabolites in the presence of (KDO)2-IVA, (c) fast atom bombardment-mass spectrometry, and (d) 1H NMR spectroscopy. At protein concentrations less than 0.5 mg/ml, the acylation of (KDO)2-IVA by the cytoplasmic fraction is absolutely dependent upon the addition of exogenous acyl-ACP. These acyltransferases cannot utilize lipid IVA as a substrate, demonstrating that they possess novel KDO recognition domains. The unusual substrate specificity of these enzymes provides compelling evidence for their involvement in lipid A biosynthesis. Depending on the conditions it is possible to acylate (KDO)2-IVA with 1 or 2 lauroyl residues, with 1 or 2 myristoyl residues, or with 1 of each.

Brucella abortus 16S rRNA and lipid A reveal a phylogenetic relationship with members of the alpha-2 subdivision of the class Proteobacteria

On the basis of ribosomal 16S sequence comparison, Brucella abortus has been found to be a member of the alpha-2 subdivision of the class Proteobacteria (formerly named purple photosynthetic bacteria and their nonphototrophic relatives). Within the alpha-2 subgroup, brucellae are specifically related to rickettsiae, agrobacteria, and rhizobiae, organisms that also have the faculty or the obligation of living in close association to eucaryotic cells. The composition of Brucella lipid A suggests a close phylogenetical relationship with members of the alpha-2 group. The chemical analysis of the lipid A fraction revealed that Brucella species contain both glucosamine and diaminoglucose, thus suggesting the presence of a so-called mixed lipid A type. The serological analysis with polyclonal and monoclonal antibodies is in agreement with the existence of mixed lipid A type in B. abortus. The amide-linked fatty acid present as acyl-oxyacyl residues were 3-O-C(16:0)12:0, 3-O-C(16:0)13:0, 3-O-C(16:0)14:0, and 3-O-C(18:0)14:0. The only amide-linked unsubstituted fatty acid detected was 3-OH-C16:0. The ester-linked fatty acids are 3-OH-C16:0, 3-OH-C18:0, C16:0, C17:0, and C18:0. Significant amounts of the large-chain 27-OH-C28:0 were detected together with traces of 25-OH-C26:0 and 29-OH-C30:0. Comparison of the Brucella lipid composition with that of the other Proteobacteria also suggests a close phylogenetical relationship with members of the alpha-2 subdivision. The genealogical grouping of Brucella species with pericellular and intracellular plant and animal pathogens as well as with intracellular plant symbionts suggests a possible evolution of Brucella species from plant-arthropod-associated bacteria.

Structural characterization of monophosphoryl lipid A homologs obtained from Salmonella minnesota Re595 lipopolysaccharide

Sixteen monophosphoryl Lipid A (MLA) homologs obtained from the lipopolysaccharides of Salmonella minnesota Re595 were separated by preparative thin layer chromatography into eight fractions. The components of these fractions were analyzed directly (or as structural analogs) and characterized by mass spectrometry. Molecular weights were determined by negative and positive ion fast atom bombardment mass spectrometry and component structures were assigned following a study of fragmentation and metastable ion kinetic energy spectrometry. One fraction (TLC-8) contained a single heptaacyl MLA of Mr = 1,954, a structure previously elucidated (Qureshi, N., Mascagni, P., Ribi, E., and Takayama, K. (1985) J. Biol. Chem. 260, 5271-5278). The remaining seven fractions contained 15 additional MLAs with decreasing acylation. Two of these components have been previously reported in S. minnesota and Salmonella typhimurium. Three of the eight TLC fractions (TLC-8, -7, -6) were found to be biologically active toward human platelets inducing their aggregation and secretion of serotonin. All tested fractions induced varying degrees of phosphorylation of a platelet protein of Mr = 47,000 (P47) reflecting protein kinase C activation (Grabarek, J., Her, G. R., Reinhold, V. N., and Hawiger, J. J. (1990) J. Biol. Chem. 265, 8117-8121).

Endotoxic lipid A interaction with human platelets. Structure-function analysis of lipid A homologs obtained from Salmonella minnesota Re595 lipopolysaccharide

We previously reported that human blood platelets are directly stimulated by endotoxic Lipid A via the protein kinase C pathway (Grabarek, J., Timmons, S., and Hawiger, J. (1988) J. Clin. Invest. 82, 964-971). To study the relationship between the molecular structure of Lipid A and its ability to activate human platelets, we used Lipid A homologs derived from Salmonella minnesota Re595 lipopolysaccharide. Preparations of Lipid A are heterogeneous in regard to the degree of substitution of fatty acids which result in multiple homologs. These were separated by thin-layer chromatography and characterized by fast atom bombardment spectroscopy and related techniques (Johnson R. S., Her, G.-R., Grabarek, J., Hawiger, J., and Reinhold, V. N. (1990) J. Biol. Chem. 265, 8108-8116). The homologs of monophosphoryl Lipid A (MLA) present in fractions TLC-8 (heptaacyl MLA ion, m/z 1953), TLC-7 (three hexaacyl species with predominant MLA ion m/z 1715), and TLC-6 (four pentaacyl homologs with predominant MLA ion, m/z 1505) induced secretion of [14C]serotonin and aggregation of platelets. Lipid A homologs in fractions TLC-5 (three tetraacyl MLA ions, m/z 1323, 1307, and 1279), TLC-4 (one major triacyl MLA ion, m/z 1097), TLC-3 (tetraacyl MLA ion, m/z 1278), TLC-2 (a diphosphoryl hexaacyl Lipid A ion, m/z 1795, and several ions of low abundance), and TLC-1 (two ions, m/z 1097 and 666) were not active in regard to human platelet aggregation and [14C]serotonin secretion. The most active homolog was heptaacyl MLA ion, m/z 1953, present in TLC-8, while homologs present in TLC-7 and TLC-6 were 5 and 10 times less active, respectively. Rapid phosphorylation of a human platelet protein of Mr 40,000-47,000 (P47), a substrate for protein kinase C activation, preceded secretion of serotonin when platelets were triggered by the most active heptaacyl MLA ion, m/z 1953. These events were time-dependent, with half-maximal response of phosphorylation of P47 at 30 s and [14C]serotonin secretion at 45 s. A marked difference in the degree of phosphorylation of P47 was observed with heptaacyl MLA homolog present in TLC-8 inducing complete phosphorylation (97%), whereas less acylated Lipid A homologs present in TLC-1 caused marginal phosphorylation (20%). These results indicate that the degree of acylation of monophosphoryl Lipid A determines its functional properties toward human platelets in regard to secretion of [14C]serotonin, aggregation, and activation of protein kinase C.(ABSTRACT TRUNCATED AT 400 WORDS)

A mutant of Escherichia coli defective in the first step of endotoxin biosynthesis

Using localized mutagenesis of whole cells, we have isolated a temperature-sensitive UDP-N-acetylglucosamine acyltransferase mutant of Escherichia coli that loses all detectable acyltransferase activity and quickly dies after a shift from 30 to 42 degrees C. Acyltransferase activity and temperature resistance are restored by transforming the mutant with a hybrid plasmid containing the E. coli gene for UDP-GlcNAc acyltransferase (lpxA). In addition, a new assay has been developed for quantitating the amount of lipid A (the active component of endotoxin) in E. coli and related Gram-negative strains. Cells are labeled with 32Pi and extracted with chloroform/methanol/water (1:2:0.8, v/v) to remove glycerophospholipids. The residue is then hydrolyzed with 0.2 M HCl to liberate the "monophosphoryl" lipid A degradation products (Qureshi, N., Cotter, R. J. and Takayama, K. (1986) J. Microbiol. Methods 5, 65-77), each of which bears a single phosphate residue at position 4'. The amount of lipid A is normalized to the total amount of labeled glycerophospholipid present in the cells. The steady state ratio of lipid A to glycerophospholipid in wild-type cells is approximately 0.12. The lipid A content of the acyltransferase mutant is reduced 2-3-fold, and the rate of lipid A synthesis is reduced 10-fold when compared to wild-type after 60 min at 42 degrees C. These results provide physiological evidence that UDP-N-acetylglucosamine acyltransferase is the major committed step for lipid A biosynthesis in E. coli and that lipid A is an essential molecule.

Acute respiratory response of guinea pigs to lipopolysaccharide, lipid A, and monophosphoryl lipid A from Salmonella minnesota

Exposure to endotoxin has been associated with systemic toxicity, including pulmonary disorders such as byssinosis, as well as with beneficial biologic activities such as adjuvanticity and mitogenicity. The purified lipopolysaccharide (LPS) from endotoxin has been employed to investigate structure-activity relationships for various biologic effects. The current study was undertaken to examine the relationship between LPS structure and its ability to cause respiratory toxicity in guinea pigs after inhalation exposure. Animals were exposed to atmospheres containing 0.076 to 2.1 micrograms/m3 Salmonella minnesota LPS (S. minn. LPS), LPS from the mutant S. minn. Re595, S. minn. Re595 lipid A, and monophosphoryl S. minn. Re595 lipid A (S. minn. Re595 MPL). Each of the LPS aerosols caused increased breathing frequency (f), decreased tidal volume (VT), and airflow disturbance when measured 18 h after the 6-h inhalation exposure. The LPS preparations had equivalent toxicity, whereas the lipid A aerosol had slightly reduced toxicity. The MPL preparation did not produce this respiratory toxicity response. The results indicated that absence of the terminal phosphate group from the reducing end of the lipid A disaccharide destroyed its ability to cause the respiratory effect. These results initiate structure-activity studies of defined LPS in the lung and indicate the possibility of chemically treating endotoxins to remove adverse pulmonary effects.

Chemical structure of the lipopolysaccharide of Haemophilus influenzae strain I-69 Rd-/b+. Description of a novel deep-rough chemotype

The chemical structure of the lipopolysaccharide of a deep-rough mutant (strain I-69 Rd-/b+) of Haemophilus influenzae was investigated. The hydrophilic backbone of lipid A was shown to consist of a beta-(1',6)-linked D-glucosamine disaccharide with phosphate groups at C-1 of the reducing D-glucosamine and at C-4' of the non-reducing one. Four molecules of (R)-3-hydroxytetradecanoic acid were found directly linked to the lipid A backbone, two by amide and two by ester linkage (positions 2,2' and 3,3', respectively). Laser-desorption mass spectrometry showed that both 3-hydroxytetradecanoic acids linked to the non-reducing glucosamine carry tetradecanoic acid at their 3-hydroxyl group, so that altogether six molecules of fatty acid are present in lipid A. The lipopolysaccharide was the first described to contain only one sugar unit linked to lipid A. This, sugar in accordance with a previous report [Zamze et al. (1987) Biochem. J. 245, 583-587], was shown to be a dOclA phosphate. The phosphate group was found at position 4, but the analytical procedures employed (permethylation and methanolysis followed by gas-liquid chromatography/mass spectrometry) also revealed dOclA 5-phosphate. Since a cyclic 4,5-phosphate could be ruled out by 31P-NMR, we conclude that, in this lipopolysaccharide, a mixture of dOclA 4- and 5-phosphate is present. By methylation analysis of the dephosphorylated, deacylated and reduced lipopolysaccharide the attachment site of the dOclA was assigned to position C-6' of the non-reducing glucosamine of lipid A. The anomeric linkages present in the lipopolysaccharide were assessed by 1H-NMR and 13C-NMR of deacylated lipopolysaccharide. The saccharide backbone of this Haemophilus influenzae lipopolysaccharide possesses the following structure: (Formula; see text)

Lipid A binding sites in membranes of macrophage tumor cells

Lipopolysaccharide affects a variety of eukaryotic cells and mammalian organisms. These actions are involved in the pathogenesis of Gram-negative septicemia. Many of the actions of lipopolysaccharide are believed to be caused by its active moiety, lipid A. Our laboratory has previously identified a bioactive lipid A precursor, termed lipid IVA (Raetz, C. R. H., Purcell, S., Meyer, M. V., Qureshi, N., and Takayama, K. (1985) J. Biol. Chem. 260, 16080-16888), which can be labeled with 32P of high specific activity and purified. In this work we have used the labeled probe, 4'-32P-lipid IVA, to develop a novel assay for the specific binding of lipid IVA to whole cells. We have also demonstrated its use in a ligand blotting assay of immobilized cellular proteins. Using the whole cell assay, we show that 4'-32P-lipid IVA specifically binds to RAW 264.7 macrophage-like cultured cells. The binding is saturable, is inhibited with excess unlabeled lipid IVA, and is proteinase K-sensitive. It displays cellular and pharmacological specificity. Using the ligand blotting assay, we show that several RAW 264.7 cell proteins can bind 4'-32P-lipid IVA. The two principal binding proteins have Mr values of 31 and 95 kDa, as judged by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Fractionation studies indicate that the 31-kDa protein is enriched in the nuclear fraction and may be a histone, whereas the 95-kDa protein is enriched in the membrane fraction. The binding assays that we have developed should lead to a clearer understanding of lipid A/animal cell interactions.

Structural heterogeneity regarding local Shwartzman activity of lipid A

The relation of chemical structure to local Shwartzman activity of lipid A preparations purified by thin-layer chromatography from five bacterial strains was examined. Two lipid A fractions from E. coli F515--Ec-A2 and Ec-A3--exhibited strong activity, similar to that of previous synthetic E. coli-type lipid A (compound 506 or LA-15-PP). The Ec-A3 fraction contained a component that appeared to be structurally identical to compound 506, and the main component of Ec-A2 fraction was structurally similar to compound 506 except that it carried a 3-hydroxytetradecanoyl group at the C-3' position of the backbone in place of a 3-tetradecanoyloxytetradecanoyl group. Free lipid A (12 C) and purified lipid A fractions, Ec-A2 (12 C) and Ec-A3 (12 C), respectively, obtained from bacteria grown at 12 C, exhibited activity comparable to Ec-A2 or Ec-A3. In these preparations, a large part of the 3-dodecanoyloxytetradecanoyl group might be replaced by 3-hexadecenoyloxytetradecanoyl group. Salmonella minnesota R595 free lipid A also contained at least two active lipid A components as seen in E. coli lipid A, but the third component corresponding to the synthetic Salmonella-type lipid A (compound 516 or LA-16-PP) exhibited low activity. A lipid A fraction, Cv-A4 from Chromobacterium violaceum IFO 12614, which was proposed to have two acyloxyacyl groups at the C-2 and C-2' positions with other acyl groups, exhibited weaker activity than the free lipid A or LPS. The purified lipid A fractions from Pseudomonas diminuta JCM 2788 and Pseudomonas vesicularis JCM 1477 contained an unusual backbone with 2,3-diamino-2,3-dideoxy-D-glucose disaccharide phosphomonoester, and these lipid A (Pd-A3 and Pv-A3) exhibited strong activity comparable to the E. coli lipid A. Thus, the present results show that the local Shwartzman reaction can be expressed by partly different lipid A structures in both hydrophilic backbone and fatty acyl residues; when they have the same backbone the potency varies markedly depending on the structure of the acyl residues.

Lipid A precursor from Pseudomonas aeruginosa is completely acylated prior to addition of 3-deoxy-D-manno-octulosonate

Inhibition of lipopolysaccharide (LPS) synthesis in Pseudomonas aeruginosa at the stage of incorporation of 3-deoxy-D-manno-octulosonate (KDO) caused accumulation of a lipid A precursor which contained all of the fatty acids present on the lipid A of mature LPS. The enzyme CTP:CMP-3-deoxy-D-manno-octulosonate cytidylyltransferase (CMP-KDO synthetase) from P. aeruginosa is inhibited by the KDO analog alpha-C-[1,5-anhydro-8-amino-2,7,8-trideoxy-D-manno-octopyranosyl] carboxylate (I), and I is effectively delivered to P. aeruginosa following attachment by amide linkage to the carboxyl terminus of alanylalanine. Intracellular hydrolysis releases the free inhibitor (I) which then inhibits activation of KDO by CMP-KDO synthetase causing accumulation of lipid A precursor and subsequent growth stasis. The major lipid A precursor species accumulated was purified and found to contain glucosamine, phosphate, C12:O, 2OH-C12:O and 3OH-C10:0 (in ester linkage), and 3OH-C12:0 (in amide linkage) in molar ratios of 1:1:0.5:0.5:1:1. Analysis of precursor by fast atom bombardment mass spectroscopy yielded a major ion (M - H)- of mass 1616 and fragments which were consistent with the structure of lipid A from P. aeruginosa. In contrast, Salmonella typhimurium, Escherichia coli, Citrobacter sp., Serratia marcescens, Enterobacter aerogenes, and Enterobacter cloacae all accumulated underacylated lipid A precursors which only contained 3-OH-C14:0, glucosamine, and phosphate. This difference and species-specific patterns of major and minor precursor species show that early steps in the assembly of lipid A are similar, but not identical in enteric and nonenteric Gram-negative bacteria.

Biological activities of lipid A from Vibrio parahaemolyticus: stimulation of murine peritoneal macrophages

The toxicity and macrophage stimulating property of Vibrio parahaemolyticus lipid A was studied. The LD50 dose of lipid A in galactosamine-sensitized mice was found to be 0.6 micrograms when injected intraperitoneally. Administration of lipid A resulted in stimulation of peritoneal macrophages as evident by increase in their cellular RNA contents and lysosomal enzyme activities. The treatment also caused enhancement in the phagocytic activity of macrophages.