Studies on lipopolysaccharides isolated from strains of Neisseria gonorrhoeae

Preparation of Lipooligosaccharide (LOS) from Neisseria gonorrhoeae

Neisseria gonorrhoeae is a gram-negative obligate human pathogen that contains lipooligosaccharide (LOS) as a major constituent within the outer membrane. LOS plays a major role in pathogenesis by inducing host inflammatory responses and also enabling evasion of host innate immunity through sialylation. Epitopes within LOS are also potential vaccine candidates. In this chapter, we describe a general method based on the Westphal hot phenol extraction process to purify whole LOS from N. gonorrhoeae for structural analyses and for use in in vivo and in vitro biological assays.

Strategies for mimicking Neisserial saccharide epitopes as vaccines

Monoclonal antibody (mAb) 2C7 recognizes a conserved and widely expressed oligosaccharide (OS) epitope on Neisseria gonorrhoeae. This OS epitope evokes a significant bactericidal and opsonic immune response after natural infection and vaccination. The OS epitope structure represents an excellent target for a potential protective gonococcal vaccine. Because carbohydrate antigens are T-cell independent, inducing weak antibody responses, OS molecules are not useful immunogens. We developed and examined two different strategies to mimic the 2C7 OS epitope: (i) an anti-idiotope (mAb CA1); and (ii) a peptide (PEP-1). These surrogate immunogens elicited antibody responses in mice (CA1 and PEP-1) and rabbits (CA1) that were bactericidal in vitro against gonococci. Both CA1 and PEP-1 are true immunologic mimics of OS and may form a basis for the development of vaccine candidates for human immunization against N. gonorrhoeae.

Shortened hydroxyacyl chains on lipid A of Escherichia coli cells expressing a foreign UDP-N-acetylglucosamine O-acyltransferase

The first reaction of lipid A biosynthesis in Gram-negative bacteria is catalyzed by UDP-N-acetylglucosamine (UDP-GlcNAc) O-acyltransferase, the product of the lpxA gene. The reaction involves the transfer of an acyl chain from hydroxyacyl-acyl carrier protein (ACP) to the glucosamine 3-OH position of UDP-GlcNAc. The lipid A isolated from Escherichia coli contains (R)-3-hydroxymyristate at the 3 and 3' positions. Accordingly, LpxA of E. coli is highly selective for (R)-3-hydroxymyristoyl-ACP over ACP thioesters of longer or shorter acyl chains. We now demonstrate that the lpxA gene from Neisseria meningitidis encodes a similar acyltransferase that selectively utilizes 3-hydroxylauroyl-ACP. Strains of E. coli harboring the temperature-sensitive lpxA2 mutation make very little lipid A and lose viability rapidly at 42 degrees C. We have created an E. coli strain in which the chromosomal lpxA2 mutation is complemented by the N. meningitidis lpxA gene introduced on a plasmid. This strain, RO138/pTO6, grows similarly to wild type cells at 42 degrees C and produces wild type levels of lipid A. However, the lipid A isolated from RO138/pTO6 contains mostly hydroxylaurate and hydroxydecanoate in the 3 and 3' positions. The strain RO138/pTO6 is more susceptible than wild type to certain antibiotics at 42 degrees C. This is the first report of an E. coli strain growing with shortened hydroxyacyl chains on its lipid A. The lpxA gene product appears to be a critical determinant of the length of the ester-linked hydroxyacyl chains found on lipid A in living cells.

Lipopolysaccharide and porin of Roseobacter denitrificans, confirming its phylogenetic relationship to the alpha-3 subgroup of Proteobacteria

Roseobacter denitrificans has rough (R)-type lipopolysaccharide, containing 2-keto-3-deoxyoctonate but no hepatoses. Its lipid A has a glucosamine-containing, phosphorylated backbone. It contains the rare 3-oxotetradecanoic (3-oxomyristic) acid as the only amide-bound fatty acid and ester-bound 3-hydroxydecanoic acid, this pattern being characteristic for the alpha-3 subgroup of Proteobacteria. Treatment of the major outer-membrane protein (porin, apparent molecular mass 88 kDa) of Roseobacter denitrificans with EDTA (2 mM, 30 degrees C, 20 min) resulted in the dissociation of the oligomers into monomers (apparent molecular mass 35 kDa). EDTA-sensitive dissociation has so far been observed only within the alpha-3 subgroup of Proteobacteria. The 12 N-terminal amino acids of the monomers exhibit sequence homology with the porins of Rhodobacter capsulatus, Rhodobacter sphaeroides and Rhodopseudomonas blastica. Renaming of Roseobacter denitrificans as Rhodobacter denitrificans is suggested.

Endogenous sialylation of the lipooligosaccharides of Neisseria meningitidis

Monoclonal antibodies (MAb) 3F11 and 06B4 recognize epitopes that are conserved on gonococcal lipooligosaccharides (LOS), present on some meningococcal LOS, and conserved on human erythrocytes. LOS of some group B and C prototype meningococcal LOS strains (LOS serotypes L1 to L8) treated with neuraminidase showed increased expression of the 3F11 and 06B4 MAb-defined epitopes. Neuraminidase-treated LOS separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and silver stained showed a shift in migration from a component with a mass of approximately 4.8 kDa to a component with a mass of between 4.5 and 4.6 kDa. The same strains grown in medium with excess CMP-N-acetylneuraminic acid had LOS that shifted in migration to a slightly higher component (mass, approximately 4.8 kDa). Chemical analysis of the neuraminidase-digested products from one LOS indicated it contained approximately 1.5% sialic acid. Covalent linkage between sialic acid and the LOS was confirmed by analysis of de-O-acylated and dephosphorylated LOS by liquid secondary ion mass spectrometry. Three studies show that some meningococci contain sialic acid in their LOS, that the sialic acid is cleaved and lost in conventional acetic acid hydrolysis, and that the sialic acid alters the expression of MAb-defined epitopes.

Interaction of chlamydiae and host cells in vitro

The obligately intracellular bacteria of the genus Chlamydia, which is only remotely related to other eubacterial genera, cause many diseases of humans, nonhuman mammals, and birds. Interaction of chlamydiae with host cells in vitro has been studied as a model of infection in natural hosts and as an example of the adaptation of an organism to an unusual environment, the inside of another living cell. Among the novel adaptations made by chlamydiae have been the substitution of disulfide-bond-cross-linked polypeptides for peptidoglycans and the use of host-generated nucleotide triphosphates as sources of metabolic energy. The effect of contact between chlamydiae and host cells in culture varies from no effect at all to rapid destruction of either chlamydiae or host cells. When successful infection occurs, it is usually followed by production of large numbers of progeny and destruction of host cells. However, host cells containing chlamydiae sometimes continue to divide, with or without overt signs of infection, and chlamydiae may persist indefinitely in cell cultures. Some of the many factors that influence the outcome of chlamydia-host cell interaction are kind of chlamydiae, kind of host cells, mode of chlamydial entry, nutritional adequacy of the culture medium, presence of antimicrobial agents, and presence of immune cells and soluble immune factors. General characteristics of chlamydial multiplication in cells of their natural hosts are reproduced in established cell lines, but reproduction in vitro of the subtle differences in chlamydial behavior responsible for the individuality of the different chlamydial diseases will require better in vitro models.

Amino and hydrazino alkyl benzoates as derivatizing agents for the separation and mass spectrometric analysis of oligosaccharides from bacterial lipooligosaccharides

In an attempt to develop more sensitive and versatile methods for the structure analysis of oligosaccharides derived from lipooligosaccharides (LOS) of gram-negative bacteria, amino and hydrazino alkyl benzoate derivatives were prepared. These oligosaccharide derivatives were separated by HPLC and then analyzed by liquid secondary ion mass spectrometry (LSIMS). Both the amino and hydrazino alkyl benzoates react with the free reducing termini of acid-treated LOS, increasing the hydrophobicity of the released oligosaccharides and allowing them to be separated by reverse-phase HPLC. In addition, these oligosaccharide derivatives now contain a sensitive uv chromophore for subsequent peak detection and improve the quality of the LSIMS spectra compared to underivatized oligosaccharides. However, the amino alkyl benzoates reacted poorly compared to the analogous hydrazino alkyl benzoates with 3-deoxy-manno-2-keto octulosonic acid (KDO), and oligosaccharides with KDO at the reducing terminus, especially when the oligosaccharide also contained phosphoethanolamine. Derivatization with the hydrazino compounds can be carried out quickly and under mild conditions using a minimal amount of reagent, and is therefore suitable for microscale analyses. The chromatographic and mass spectrometric characteristics of these derivatives make them excellent alternatives to permethylation and peracetylation techniques for the structural analysis of complex bacterial oligosaccharides derived from glycolipids.

In vitro and in vivo modification of Neisseria gonorrhoeae lipooligosaccharide epitope structure by sialylation

After growth of gonococci in the presence of cytidine monophospho-N-acetyl-neuraminic acid (CMP-NANA), their 4.5-kD lipooligosaccharide (LOS) component was increased by approximately 400 daltons, whereas the LOS of strains lacking the 4.5-kD component were unaffected. Expression of mAb-defined epitopes on the 4.5-kD component was decreased on LOS of strains grown in CMP-NANA, and treatment of the LOS with neuraminidase reversed this affect. Gonococci incubated with human PMNs also had decreased expression of the 4.5-kD+ epitopes. A detergent extract of gonococci incorporated radiolabeled NANA in the LOS, suggesting the presence of a sialyltransferase in gonococci. Exogenous sialyltransferases also could use LOS as an acceptor.

Lectin typing of Pseudomonas aeruginosa strains of different serogroups, Habs and Fisher types

Sixteen Habs and three Fisher types of Pseudomonas aeruginosa were typed with lectins of know specificity resulting from their interaction with bacterial cell surface carbohydrates as evidenced by agglutination-inhibition assay with simple carbohydrates. Lipopolysaccharides of few strains of Pseudomonas are precipitated with different lectins and the results are corroborated by those of agglutination suggesting that Pseudomonas aeruginosa can be characterized intraspecifically by lectins.

Chemical composition of lipopolysaccharide from Moraxella bovis

Lipopolysaccharide from Moraxella bovis was isolated and its components characterized by paper and gas-liquid chromatography and mass spectrometry. The endotoxin showed a small amount of protein and contained 2-keto-3-deoxyoctonic acid glucose, mannose, glucosamine, heptose and phosphate. Six fatty acids (palmitic, palmitoleic, margaric, stearic, oleic and arachidic acids) were also identified. Margaric acid was the most prevalent fatty acid present in the lipid fraction.

Lipooligosaccharides (LOS) of Neisseria gonorrhoeae and Neisseria meningitidis have components that are immunochemically similar to precursors of human blood group antigens. Carbohydrate sequence specificity of the mouse monoclonal antibodies that recognize crossreacting antigens on LOS and human erythrocytes

We have used mouse mAbs, 3F11 and 06B4, that are specific for highly conserved epitopes of Neisseria gonorrhoeae lipooligosaccharides (LOS) to identify immunochemically similar structures on human erythrocytes. mAb 3F11 agglutinated erythrocytes from all randomly selected adult humans, while mAb 06B4 agglutinated only 80% of the same specimens. The antibodies had an activity with erythrocytes similar to human cold agglutinins in that agglutination occurred at 4 degrees C and decreased with increasing incubation temperature. Human infant erythrocytes were agglutinated less well, but enzymatic treatment of either infant or adult cells resulted in an increase in expression of the 3F11- and 06B4-defined epitopes. Both antibodies bound to a series of neutral glycosphingolipids from human erythrocytes and neutrophils that have a type 2 (Gal beta 1----4GlcNAc) or N-acetyllactosamine structure. Neither antibody bound to glycosphingolipids from human meconium, which have a type 1 (Gal beta 1----3GlcNAc) structure. The antibodies were unable to bind to N-acetyl-lactosamine glycosphingolipids with a nonreducing terminal sialic acid or a Gala1----3Gal disaccharide. Antibody binding also was blocked by the presence of fucose linked to the penultimate glucosamine residue of N-acetyllactosamine glycosphingolipids. Although both antibodies bound to linear and branched-chain N-acetyllactosamine glycosphingolipids, 3F11 had a higher affinity for branched structures than did 06B4. The activity of 3F11 with human adult and infant treated and untreated erythrocytes with N-acetyllactosamine glycosphingolipids, and with LOS was very similar, if not identical, in specificity to 1B2, an mAb prepared from mice inoculated with a linear N-acetyllactosamine glycosphingolipid.

Use of transformation to construct Neisseria gonorrhoeae strains with altered lipooligosaccharides

DNA isolated from a nalidixic acid- and rifampin-resistant derivative of Neisseria gonorrhoeae serum-resistant strain 302 (MUG116), a strain that reacts with monoclonal antibody (MAb) 2-1-L8, was used to transform N. gonorrhoeae DOV, a serum-sensitive strain, to antibiotic resistance and/or reactivity with the MAb. MAb 2-1-L8 binds to a 3.6-kilodalton lipooligosaccharide (LOS). Reactivity with MAb 2-1-L8 transformed as a single marker and was unlinked to either of the antibiotic resistance markers. Immunoblot analysis of LOSs separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis revealed that new LOSs were synthesized in the transformed cells and that these LOSs corresponded to those of the DNA donor. Although multiple LOS components were made by the transformants, the MAb recognized only one. All transformants that were selected for on the basis of strong reactivity with MAb 2-1-L8 were serum resistant; however, the level of resistance correlated with the apparent loss of recipient LOS components. MAb 2-1-L8-reactive transformants that still produced DOV LOS components remained serum sensitive.

Gonococcal variants selected by growth in vivo or in vitro have antigenically different LPS

Lipopolysaccharide (LPS) was extracted from two variants of strain gc40 of Neisseria gonorrhoeae obtained by repeated subculture in vitro or by growth in vivo in a subcutaneous chamber. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis followed by silver stain analysis revealed that both variants had three main LPS components, but the large size components were predominant in gonococci selected in vivo and the smallest size in those selected in vitro. Western blotting, ELISA and ELISA inhibition using monoclonal and polyclonal antibodies showed that the two variants had antigenically different LPS and that serum sensitivity may be due to the antigenic specificity of the large components. These results indicate that during infection clones of gonococci are selected with LPS of antigenic and physicochemical composition different from those seen after repeated subcultures.

Expression of a cloned lipopolysaccharide antigen from Neisseria gonorrhoeae on the surface of Escherichia coli K-12

A gonococcal gene bank maintained in Escherichia coli K-12 was screened by colony immunoblotting, and a transformant expressing a surface antigen reactive to anti-gonococcal outer membrane antiserum was isolated. The isolate carried a recombinant plasmid, pTME6, consisting of approximately 9 kilobases of Neisseria gonorrhoeae DNA inserted into the BamHI site of pBR322. Surface labeling of E. coli HB101(pTME6) confirmed that the antigen was expressed on the E. coli cell surface. The antigenic material was resistant to proteinase K digestion and sensitive to periodate oxidation, indicating that the material was carbohydrate. Purified lipopolysaccharide (LPS) from HB101(pTME6) produced a unique band on silver-stained polyacrylamide gels that contained immunoreactive material as seen on Western blots of LPS samples. Only two of three E. coli LPS mutant strains carrying pTME6 reacted with the antigonococcal antiserum, suggesting that a certain E. coli core structure is necessary for antigen expression. We conclude that pTME6 contains one or more gonococcal genes encoding an LPS core biosynthetic enzyme(s) which can modify E. coli core LPS to produce a gonococcuslike epitope(s).

The immunochemistry of neisserial LOS

The outer membrane glycolipids of Neisseria lack long polysaccharides and are properly termed lipooligosaccharides (LOS). A Neisseria strain makes from two to six LOS of Mr 3150-7100. Different species commonly make LOS of identical Mr and epitope content. Oligosaccharide (OS) differences account for physical heterogeneity. OS consist of a conserved triantenary basal oligosaccharide, two linear segments of (n) hexose residues that determine OS mass, and terminal sequences similar to those of glycosphyngolipids. Epitope expression is linked to physical heterogeneity and conditioned by the molecular environment of the outer membrane. Serotype epitopes are expressed on Mr-restricted LOS. LOS regulate complement activation onto the bacterial surface and, hence, immune lysis.

Stability of expression of Neisseria gonorrhoeae lipooligosaccharides

We compared multiple lipooligosaccharide (LOS) extracts from individual strains of Neisseria gonorrhoeae. Each of the extracts was prepared from single mass cultures grown on solid media under similar conditions but separated by time. We found only subtle variations in the number, electrophoretic mobility, and concentration of components of the LOSs from individual strains. We found no variation in the expression of a 3.6-kilodalton LOS component that carries the L8 LOS epitope. A significant variation in the 3-deoxy-D-manno-octulosonic acid content was found among different extracts from the same strain, but this variation appeared to be unrelated to the other LOS characteristics studied.

Analyses of gonococcal lipopolysaccharide in whole-cell lysates by sodium dodecyl sulfate-polyacrylamide gel electrophoresis: stable association of lipopolysaccharide with the major outer membrane protein (protein I) of Neisseria gonorrhoeae

The lipopolysaccharide (LPS) of Neisseria gonorrhoeae whole-cell lysates and proteinase K-digested lysates was examined and compared with purified homologous LPS by a method which preferentially stains LPS in polyacrylamide gels. The silver-stained profile of gonococcal LPS in the proteinase K-digested lysate was similar to that of homologous purified LPS; however, the LPS profile in whole-cell lysates was much smaller than that of digested lysates or purified LPS. Conditions of solubilization did not affect these differences. Since it is known that LPS migrates in a unique fashion in second-dimension electrophoresis, the location of LPS in the whole-cell lysates was probed by second-dimension sodium dodecyl sulfate-polyacrylamide gel electrophoresis with a variety of stains and radiolabels. Results from these experiments indicated a stable and reproducible association of LPS with proteins ranging between 23,000 to 36,000 in Mr, in particular major outer membrane protein I. In addition to staining with the silver method, which preferentially stains LPS, the putative LPS was resistant to digestion by proteinase K, did not stain with Coomassie brilliant blue, and was not labeled extrinsically with 125I (Iodogen method) or intrinsically with [35S]methionine. Analysis of two-dimensional gels by immunoblotting with rabbit antisera prepared from protein I bands removed from a polyacrylamide gel revealed the presence of antigens in the same area of the gel (below proteins that were 23,000 to 36,000 in Mr). Antibodies to constituents which migrated below the diagonal were essentially removed by adsorption of antisera with purified LPS, as were antibodies to homologous LPS and LPS in proteinase K-digested whole-cell lysates. Immunoblotting with a monoclonal antibody specific for LPS demonstrated reactivity of the antibody with LPS and with the protein I band. On the basis of these data, we conclude that protein I and perhaps other proteins in the whole-cell lysate are stably associated with LPS; this complex is resistant to dissociation in sodium dodecyl sulfate at high temperature (approximately 100 degrees C) but does, for unknown reasons, dissociate with electrophoresis in the second dimension. The association of LPS with protein antigens in sodium dodecyl sulfate-polyacrylamide gels adds another dimension of complexity to analysis of these antigens by immunoelectroblotting. Furthermore, the tight association of LPS with the major outer membrane protein I may alter the nature of the immune response generated by "purified" protein I vaccine antigens. The possible role of protein-LPS complexes in the pathogenesis of gonorrhea is discussed.

Structural and antigenic heterogeneity of lipopolysaccharides of Campylobacter jejuni and Campylobacter coli

The techniques of sodium dodecyl sulfate-polyacrylamide gel electrophoresis, silver staining, and immunoblotting were used to analyze the lipopolysaccharide (LPS) structure of 20 strains of Campylobacter jejuni and 4 strains of Campylobacter coli belonging to more than 22 thermostable serotypes. The LPSs of all strains examined were shown to be of a low-molecular-weight type, and these low-molecular-weight LPSs conferred heat-stable serospecificity. High-molecular-weight banding observed with both in vivo LPS in proteinase K digests of whole cell lysates and purified LPS was shown to be due to the ready ability of Campylobacter lipopolysaccharide to form aggregates rather than to the presence of O polysaccharide chains. Purified LPSs from two strains of C. jejuni were also subjected to gross chemical analysis. The high-lipid A to low-neutral sugar ratio of both LPSs was typical of LPSs lacking O polysaccharide chains.

Lipopolysaccharide banding patterns of Neisseria meningitidis and Neisseria gonorrhoeae

The lipopolysaccharides of Neisseria meningitidis and Neisseria gonorrhoeae were examined by electrophoresis after whole-cell lysis and proteinase K digestion. The banding patterns observed from clinical isolates and laboratory strains demonstrated lipopolysaccharide which included a small number of smooth high-molecular-weight molecules as well as the previously reported lower-molecular-weight rough lipopolysaccharide.

Gonococcal pilus subunit size heterogeneity correlates with transitions in colony piliation phenotype, not with changes in colony opacity

The apparent subunit sizes for pili of gonococci (Gc) have been visualized by using either Iodogen 125I-labeled whole Gc or immunoblotting with antipilus antiserum. These methods permitted definition of pilus subunit sizes for Gc of a given strain that had undergone changes either in piliation phenotype or in colonial opacity/protein II phenotype. The results indicate that pilus subunit size does not change coincident with changes in colony opacity/protein II phenotypes; but change in pilus subunit size is seen after a change in piliation phenotype (P+ leads to P++, and vice versa). Marked diversity in pilus subunit sizes is found for Gc of individual strains when P+ derivatives of P- colonies are compared. This diversity extends to pilus subunits of Gc found in single colonies; two distinct pilus forms were demonstrated for Gc residing in several single colonies. These findings show that Gc of a given strain are able to express any of a number of different pilus subunit size forms.

Chemical and immunochemical studies on lipopolysaccharides from pyocin 103-sensitive and -resistant Neisseria gonorrhoeae

The chemical and immunochemical properties of lipopolysaccharides (LPS) isolated from pyocin 103-sensitive and -resistant Neisseria gonorrheae were investigated. Marked differences were found in immunochemical behavior of LPS from pyocin-sensitive gonococcal strain JW31 and its isogenic pyocin-resistant variant JW31R. JW31 LPS readily precipitated wheat-germ agglutinin, soybean lectin, and rabbit anti-Streptococcus faecalis or horse anti-type 14 pneumococcal antibody. In contrast, JW31R LPS precipitated only soybean lectin. The combining-site specificity of anti-S. faecalis cross-precipitated by JW31 LPS, or type 14 pneumococcal capsular polysaccharide, was examined by hapten inhibition, and lactose found to be the most potent inhibitor. Horse anti-pneumococcal type 14 antibodies, cross-precipitated by JW31 LPS and streptococcal lactose polymer, exhibited heterogeneity with respect to combining site specificity. Gel filtration of LPS-derived core oligosaccharide showed both strain JW31 and JW31 R to possess R-type lipopolysaccharide with cores having a Mr approximately 1800. JW31R LPS contains more galactose but less hexosamine than JW31 LPS. Both JW31 and JW31R core oligosaccharides possess D-glucosamine and D-galactosamine, probably N-acetylated, as the only nonreducing end-groups, and (1 leads to 4)-linked D-glucose residues. Chemical data support immunochemical findings which indicate that lactose units occur as a structural feature of JW31 gonococcal LPS.

The meningococcus and mechanisms of pathogenicity

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Synthesis of immunogenic oligosaccharide-protein conjugates from the lipopolysaccharide of Neisseria gonorrhoeae P9

Oligosaccharide was isolated from the lipopolysaccharide of Neisseria gonorrhoeae P9 following partial acid hydrolysis. The exposed terminal keto-deoxyoctonic acid group of the oligosaccharide was convert into the reactive phenylisothiocyanato derivative by reaction with 2-(4-aminophenyl)-ethylamine followed by reduction with sodium cyanoborohydride and treatment with thiophosgene. This intermediate was used to prepare an oligosaccharide-protein conjugate with either bovine serum albumin or purified gonococcal pili. Immunisation of rabbits with protein conjugates produced antibodies reactive with both pure protein and intact lipopolysaccharide.

Interaction with lectins and differential wheat germ agglutinin binding of pyocin 103-sensitive and -resistant Neisseria gonorrhoeae

Strains of Neisseria gonorrhoeae were treated with pyocin 611 131 (pyocin 103) from Pseudomonas aeruginosa PA103, and isogenic resistant variants were isolated. The interaction of pyocin-sensitive and isogenic pyocin-resistant strains with wheat germ agglutinin (WGA) agglutinated all pyocin-sensitive, but not pyocin-resistant, strains. Binding of WGA to three pyocin-sensitive strains and their isogenic pyocin-resistant variants was examined quantitatively by using fluorescein-conjugated lectin. Pyocin-resistant strains maximally bound one-third to one-eighth the quantity of WGA bound by isogenic-sensitive strains. Linear Scatchard plots revealed homogeneous WGA-binding sites on three pyocin-sensitive and one pyocin-resistant strains. Biphasic Scatchard plots, obtained with two pyocin-resistant strains, show that WGA-binding sites in these strains are heterogeneous. The number of WGA-binding sites for pyocin-sensitive organisms ranged from 8 x 10(5) to 1 x 10(6) sites per coccus and from 1 x 10(5) to 3 x 10(5) sites per coccus for pyocin-resistant strains. The apparent association constant for WGA binding to pyocin-sensitive strains ranged from 3 x 10(6) to 6 x 10(6) liters/mol and from 6 x 10(6) to 1 x 10(7) liters/mol for pyocin-resistant strains. Gonococcal lipopolysaccharide was shown to serve as the pyocin 103 receptor by inhibition of pyocin activity. Lipopolysaccharide from a pyocin 103-resistant strain was not able to inhibit pyocin 103 activity. Pyocin 103 resistance was correlated with a structural alteration involving N-acetylglucosamine residues in gonococcal lipopolysaccharide. Based on interactions with wheat germ, soybean, and ricin lectins, a model of lipopolysaccharide structure in N. gonorrhoeae is presented.

Enhancement of coagglutination reactions of the Phadebact gonococcus test by ethylenediaminetetraacetate and ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetate

Incubation of gonococci under conditions optimal for autolysis resulted in increased sensitivity and enhancement of the coagglutination reaction of the Phadebact gonococcus test. These conditions included an alkaline pH (pH 8.3) and the presence of divalent cation chelators such as ethylenediaminetetraacetic acid or ethylene glycol-bis(beta-aminoethyl ether)-N,N-tetraacetic acid. Heating cell suspensions at 90 degrees C for 15 min before assay by coagglutination produced a further increase in sensitivity and enhancement of the reaction. Gonococcal lipopolysaccharide was found to be an important antigen in these coagglutination reactions. The detection of lipopolysaccharide was markedly enhanced by the addition of chelating agents.

The use of specific antiserum induced by lectin-antigen complexes to investigate the outer membrane antigens of Neisseria gonorrhoeae

Extracts of gonococcal surface antigens, examined by crossed affinity electrophoresis (CAE) with wheat germ agglutinin (WGA), yielded a single antigen-lectin precipitate in agarose gels. This precipitate induced in rabbits a potent antiserum specific for the gonococcal antigen which reacted with WGA. Immune electron microscopy on whole gonococci showed that this antiserum reacted with outer membrane vesicles. Lipopolysaccharide (LPS) purified by phenol-water extraction of whole gonococci reacted with WGA and also with the antiserum to the WGA-antigen complex. This indicated that the antiserum was specific for antigen(s) of the outer membrane complex.

Rapid presumptive diagnosis of gonococcal cervicitis by the limulus lysate assay

In an evaluation of the limulus lysate assay (LLA) as a method for detecting gonococcal endotoxin in cervical exudates diluted 1:800, positive LLA results were obtained from 17 of 18 patients (94%) with culture-proved gonococcal cervicitis, and negative results were obtained from 22 of 22 patients (100%) with culture-negative specimens. In vitro tests comparing the sensitivity of the LLA for Neisseria gonorrhoeae and other gram-negative organisms showed the LLA to be more sensitive in detecting N. gonorrhoeae (minimum sensitivity, 10(4) organisms per milliliter) than other commonly encountered urogenital gram-negative bacteria (minimum sensitivity, greater than 10(5) organisms per milliliter). Thus, in preliminary studies involving otherwise healthy women, the LLA appeared to correlate with bacteriologic methods for diagnosing gonococcal cervicitis and may aid in identifying nongonococcal cervicitis. In addition, the LLA was easy to perform, with test results available within an hour after the patient's initial examination.

Immunogenicity of ribosomal preparations from Neisseria gonorrhoeae

Protection against gonococcal infection was obtained by immunization with ribosomal preparations from Neisseria gonorrhoeae. Ribosomes were isolated from disrupted cells by differential ultracentrifugation and treatment of the microsomal fraction with 0.25% sodium dodecyl sulfate. The isolated ribosomal preparations contained 55% ribonucleic acid, 39% protein, and 0.35% carbohydrate. The ribosomal preparations contained small amounts of endotoxin as determined by thiobarbituric acid- and lead acetate-sensitized mice assays. Guinea pigs immunized subcutaneously with ribosomal preparations were challenged intrachamberially with 10(7) colony-forming units of N. gonorrhoeae, and protection was assessed by clearance of the organism from subcutaneous chambers. The ribosomal preparations elicited significant protection, which was enhanced by incoporation of the immunogen into adjuvant. This protection was comparable to that obtained with whole cells. Treatment with proteolytic enzymes destroyed the protective effect of the ribosomal preparations, but ribonuclease had no measurable effect. Passive hemagglutination and immunodiffusion tests with sera from immunized animals demonstrated the presence of antibody to the ribosomal antigens. Results of adsorption of antiribosomal sera with enzyme-treated ribosomal preparations also indicated the protein nature of the immunogen. These results indicate that protein associated with the gonococcal ribosomal preparation is the major protective immunogen. The role of endotoxin contamination in the immunogenicity of gonococcal ribosomal preparations warrants further investigation.

Capnocytophaga: new genus of gram-negative gliding bacteria. II. Morphology and ultrastructure

Gram-negative, anaerobic gliding bacteria were isolated from normal supragingival plaque and from periodontal lesions. Isolates could be divided into two size classes: small 2.4-4.2 micrograms x 0.38-0.5 microgram and large 4.8-5.8 micrograms x 0.42-0.6 microgram cells. The outer membrane was either loose-fitting and wavy, or taut, and of variable thickness. An electron-dense fuzz was discernible on several of the isolates. The periplasmic region was of variable electron-density. The genus Capnocytophaga has been proposed for these organisms based on morphological and cultural characteristics.

The biology of the gonococcus

Gonorrhea has been known since antiquity. Today, this disease is the most commonly reported infectious disease in the U.S. The natural environment of the etiological agent, Neisseria gonorrhoeae, is man. In this host, the organism usually parasitizes mucosal surfaces populated by columnar epithelial cells. Under certain conditions, the gonococcus may disseminate or spread to adjacent organs. The gonococcus is well adapted to its environment and is a successful parasite. Until recently, gonococci were uniformly sensitive to penicilin. However, a plasmid encoding beta-lactamase has been identified in some isolates. Most strains exhibit specific requirements for various amino acids, vitamins, purines, and pyrimidines. Only glucose, pyruvate, and lactate are utilized as sources of energy. Glucose is dissimilated by a combination of the Entner-Doudoroff and pentose phosphate pathways. A tricarboxylic acid cycle is also present and active under certain conditions. Structurally, the cell envelope of the gonococcus resembles that of a typical Gram-negative bacterium. Gonococci are highly autolytic, especially in older cultures or after depletion of the energy source. Autolysis is not due solely to peptidoglycan hydrolysis, but appears to involve a destabilization of the outer membrane as well. Cell surface components such as pili, lipopolysaccharide, outer membrane proteins, and a capsule are associated with the virulence and pathogenicity of this organism.

Identification of amino sugars from bacterial lipopolysaccharides by gas chromatography electron impact and chemical ionization mass spectrometry

Amino sugars isolated from lipopolysaccharides of Brucella suis, Brucella abortus and Neisseria gonorrhoeae colony types 1 and 4 were identified using gas chromatography electron impact and chemical ionization mass spectrometry. Lipopolysaccharides were obtained by aqueous ether or aqueous phenol extraction. Isolated lipopolysaccharides were hydrolyzed in 1% acetic acid followed by hydrolysis of the polysaccharide moiety in 2 NHCl for 6 h at 100 degrees C. Amino sugars were first isolated by elution from Dowex 50 H+ and then N-acetylated, followed by trimethylsilylation. Trimethylsilyl ethers of 2-acetamido-2-deoxysugars; N-acetylglucosamine, N-acetylmannosamine, N-acetylgalactosamine, and a 2-acetamido-2.6-dideoxysugar, N-acetylquinovosamine, were identified by their fragmentation patterns. In the electron impact mode, N-acetylglucosamine and N-acetyl-galactosamine were distinguished from one another by comparing peak intensities at m/e 233 and 305. However, N-acetylglucosamine and N-acetylmannosamine could not be differentiated by electron impact mass spectrometry. In the chemical ionization mode, N-acetylglucosamine and N-acetylmannosamine both with base peaks at m/e 494, could be distinguished from N-acetylgalactosamine and N-acetylquinovosamine by their base peaks at m/e 420 and 332, respectively. N-Acetylglucosamine and N-acetylmannosamine were differentiated from one another by comparing peak intensities at m/e 330, 404, 420, and 510 [MH]+. This is the first report of chemical ionization mass spectrometry applied to the identification of amino sugars in bacterial lipopolysaccharides and shows that some 2-amino-2-deoxysugars can be differentiated by both electron impact and chemical ionization mass spectrometry.

A solid phase radiommunoassay on hydrophobic membrane filters: detection of antibodies to gonococcal surface antigens

A solid phase radioimmunoassay (SPRIA) has been developed for detection of IgG antibodies to gonococcal outer membrane components. Gonococcal antigens were immobilized on a solid support by covalent coupling to CNBr-activated Sepharose in the presence of the detergent Triton X-100. Binding of specific antibody to the Sepharose-antigen complex was detected using radiolabelled Protein A as the antiglobulin. Protein A was labelled by radioacetylation with tritiated acetic anhydride, yielding a product of high specific activity and high stability. No detectable loss of activity was observed over a ten month period. The entire assay was performed on Mitex teflon hydrophobic membrane filters which held the Sepharose beads and aqueous supernatant as a discrete drop of liquid. The supernatants and incubation media were easily and rapidly removed from the beads by suction on a specially designed manifold system. This procedure removed the need for repeated and time-consuming centrifugations. Titres were obtained graphically from double log plots of cpm bound versus antiserum dilution by extrapolation of the straight line to a point corresponding to twice the control level of radioactivity binding. The assay proved to be a very reliable and simple procedure for the detection of IgG antibodies to gonococcal surface antigens.

Serological diagnosis of gonorrhoea by an enzyme-linked immunosorbent assay (Elisa)

IgG antibody to an outer membrane protein extracted from Neisseria gonorrhoeae was measured in patients with gonorrhoea. The level in such patients was significantly higher than in normal controls or in patients with other conditions who were attending the clinic for sexually transmitted diseases. Significantly higher antibody levels were detectable in half the patients within a few days of infection and in a similar proportion of carriers--both male and female. Men with rectal gonorrhoea had particularly high antibody levels. Sixteen per cent of presumptively normal men and 11% of normal women gave positive results but the actual false positive rate could be lower.

Inhibition of Neisseria gonorrhoeae by a bacteriocin from Pseudomonas aeruginosa

Supernatants from broth-grown cultures of Pseudomonas aeruginosa PA 103 exhibited bactericidal activity against Neisseria gonorrhoeae. The concentration of the bactericidal substance increased significantly after induction by mitomycin C. Purification was effected by salt fractionation, chromatography on diethylaminoethyl-cellulose, and sedimentation by centrifugation at 100,000 x g for 90 min. Electron microscopy of this purified preparation revealed structures resembling R-type pyocins in both the contracted and uncontracted state. Pyocins in the contracted state were observed in association with the gonococcal cell surface. No loss of bactericidal activity was observed after treatment with proteolytic enzymes. Standard pyocin typing procedures identified the pyocin pattern as 611 131. The bactericidal activity of this pyocin was examined on various species of Neisseria. Out of 56 strains of N. gonorrhoeae from disseminated and nondisseminated infections, all were susceptible to pyocin 611 131. However, only 3 of 20 strains of N. meningitidis and 5 of 16 strains of N. lactamica were susceptible. The bactericidal activity that pyocin 611 131 has for N. gonorrhoeae and other species of Neisseria is significant because it departs from the expected specificity that heretofore has distinguished bacteriocins from most "classical" antibiotics.

Cell envelope of Neisseria gonorrhoeae. A comparative study with Escherichia coli

The cell envelope of Neisseria gonorrhoeae was studied and compared to that of Escherichia coli. Outer membranes (OM) from both species were isolated by an identical method, and subjected to biochemical analysis. Differences in OM structure were sought that might explain the dissimilarity in OM permeability of these two species. The most pronounced difference appeared to reside in the OM proteins as judged by gel electrophoresis. Moreover, gonococcal OM proteins appeared to be more hydrophilic than those of E. coli.

Comparison of lipopolysaccharides from Agmenellum quadruplicatum to Escherichia coli and Salmonella typhimurium by using thin-layer chromatography

Lipopolysaccharide (LPS) was isolated from the unicellular blue-green bacterium Agmenellum quadruplicatum using the procedure of Westphal and Jann (1965). It was composed of a lipid A and polysaccharide region suggesting a similarity to other gram-negative LPSs. Chemical analyses demonstrated the presence of glucose, rhamnose, mannose, and xylose in the polysaccharide region, as well as 2-keto-3-deoxyoctonate, glucosamine, and phosphorous in the lipid A. Studies on the lipid composition revealed the presence of palmitic, behenic, and three beta-hydroxy fatty acids. A new procedure for thin-layer chromatography of bacterial LPSs was used to compare LPS from A. quadruplicatum to other gram-negative organisms. The method is capable of distinguishing between LPSs of different bacteria as well as between the wild-type organism and mutated forms unable to synthesize complete LPS. A comparison of LPS from A. quadruplicatum to Escherichia coli and Salmonella typhimurium demonstrated that, although the blue-green LPS was rather similar to that of the Enterobacteriaceae, distinct differences also existed. However, when several cell division mutants of A. quadruplicatum were compared chromatographically to the parent strain BG-1, no differences were observed. This suggests that cell division mutations in A. quadruplicatum are not associated with changes in the LPS.