Lipooligosaccharides (LOS) of some Haemophilus species mimic human glycosphingolipids, and some LOS are sialylated

Molecular mimicry of host structures by bacterial lipopolysaccharides and its contribution to disease

The core oligosaccharides of low-molecular-weight lipopolysaccharide (LPS), also termed lipooligosaccharide (LOS), of pathogenic Neisseria spp. mimic the carbohydrate moieties of glycosphingolipids present on human cells. Such mimicry may serve to camouflage the bacterial surface from the host. The LOS component is antigenically and/or chemically identical to lactoneoseries glycosphingolipids and can become sialylated in Neisseria gonorrhoeae when the bacterium is grown in the presence of cytidine 5'-monophospho-N-acetylneuraminic acid, the nucleotide sugar of sialic acid. Strains of Neisseria meningitidis and Haemophilus influenzae also express similarly sialylated LPS. Sialylation of the LOS influences susceptibility to bactericidal antibody, may decrease or prevent phagocytosis, cause down-regulation of complement activation, and decrease adherence to neutrophils and the subsequent oxidative burst response. The core oligosaccharides of LPS of Campylobacter jejuni serotypes which are associated with the development of the neurological disorder, Guillain-Barré syndrome (GBS), exhibit mimicry of gangliosides. Cross-reactive antibodies between C. jejuni LPS and gangliosides are considered to play an important role in GBS pathogenesis. In contrast, the O-chain of a number of Helicobacter pylori strains exhibit mimicry of Lewis(x) and Lewis(y) blood group antigens. The role of this mimicry remains to be investigated, but may play a role in bacterial camouflage, the induction of autoimmunity and immune suppression in H. pylori-associated disease.

Synthesis, characterization, and immunologic properties of detoxified lipooligosaccharide from nontypeable Haemophilus influenzae conjugated to proteins

Nontypeable Haemophilus influenzae (NTHi) is an important cause of otitis media in children and of pneumonitis in adults with depressed resistance. Lipooligosaccharide (LOS) is a major surface antigen of NTHi and elicits bactericidal and opsonic antibodies. We prepared detoxified LOS (dLOS) protein conjugates from NTHi for use as experimental vaccines. LOS from NTHi 9274 was treated with anhydrous hydrazine and had its toxicity reduced to clinically acceptable levels. dLOS was bound to tetanus toxoid (TT) or high- molecular-weight proteins (HMPs) from NTHi through a linker of adipic acid dihydrazide to form dLOS-TT or dLOS-HMP. The molar ratio of the dLOS to protein carriers ranged from 26:1 to 50:1. The antigenicity of the conjugates was similar to that of the LOS alone as determined by double immunodiffusion. Subcutaneous or intramuscular injection of the conjugates elicited a 28- to 486-fold rise in the level of immunoglobulin G antibodies in mice to the homologous LOS after two or three injections and a 169- to 243-fold rise in the level of immunoglobulin G antibodies in rabbits after two injections. The immunogenicity of the conjugates in mice and rabbits was enhanced by formulation with monophosphoryl lipid A plus trehalose dimycolate. In rabbits, conjugate-induced LOS antibodies induced complement-mediated bactericidal activity against the homologous strain 9274 and prototype strain 3189. These results indicate that a detoxified LOS-protein conjugate is a candidate vaccine for otitis media and pneumonitis caused by NTHi.

Purification, cloning, and expression of a cytidine 5'-monophosphate N-acetylneuraminic acid synthetase from Haemophilus ducreyi

An N-acetylneuraminic acid cytidylyltransferase (EC 2.7.7.43) (CMP-NeuAc synthetase) was isolated from a Haemophilus ducreyi strain 35000 cell lysate and partially characterized. The enzyme catalyzes the reaction of CTP and NeuAc to form CMP-NeuAc, which is the nucleotide sugar donor used by sialyltransferases. Previous studies have shown that the outer membrane lipooligosaccharides of H. ducreyi contain terminal sialic acid attached to N-acetyllactosamine and that this modification is likely important to its pathogenesis. Therefore, to investigate the role of sialic acid in H. ducreyi pathogenesis, the gene encoding the CMP-NeuAc synthetase was cloned using degenerate oligonucleotide probes derived from NH2-terminal sequence data, and the nucleotide sequence was determined. The derived amino acid sequence of the CMP-NeuAc synthetase gene has homology to other CMP-NeuAc synthetases and to a lesser extent to CMP-2-keto-3-deoxy-D-manno-octulosonic acid synthetases. The gene was cloned into a T7 expression vector, the protein expressed in Escherichia coli, and purified to apparent homogeneity by anion exchange, Green 19 dye, and hydrophobic interaction chromatography. The final step yielded 20 mg of pure protein/liter of culture. The protein has a predicted molecular mass of 25440.6 Da, which was confirmed by electrospray mass spectrometry (Mexpt = 25439.9 +/- 1.4 Da). The enzyme appears to exist as a dimer by size exclusion chromatography. In contrast to other bacterial CMP-NeuAc synthetases, the H. ducreyi enzyme exhibited a different substrate specificity, being capable of also using N-glycolylneuraminic acid as a substrate.

The lipooligosaccharides of pathogenic gram-negative bacteria

Lipooligosaccharides (LOSs) are the major glycolipids expressed on mucosal Gram-negative bacteria, including members of the genera Neisseria, Haemophilus, Bordetella, and Branhamella. They can also be expressed on some enteric bacteria such as Campylobacter jejuni and Campylobacter coli strains. LOS is analogous to the lipopolysaccharide (LPS) found in other Gram-negative families. LOSs share similar lipid A structures with an identical array of functional activities as LPSs. LOSs lack O-antigen units with the LOS oligosaccharide structures limited to 10 saccharide units. The LOS species of pathogenic Neisseria can play a major role in pathogenesis through enhancing the resistance of the organism to killing by normal human serum. Other distinguishing characteristics of LOS are the structural and antigenic similarity of some LOS species to human glycolipids and the potential for certain LOSs to be modified in vivo by host substances or secretions. These modifications of LOS in different environments of the host result in synthesis of new LOS structures that probably benefit the survival of the pathogen. The LOS of N. gonorrhoeae can act as a ligand of human receptors, promoting invasion of host cells. It is becoming clearer that LOSs are crucial factors in the pathogenesis of bacteria that express them.

The lipooligosaccharides of Haemophilus ducreyi are highly sialylated

The major lipooligosaccharides of the sexually transmitted pathogen Haemophilus ducreyi 35000 have been previously found to terminate in N-acetyllactosamine and sialyl-N-acetyllactosamine, Neu5Ac alpha 2-->3Gal beta 1-->4GlcNAc (W. Melaugh, N. J. Phillips, A. A. Campagnari, M. V. Tullius, and B. W. Gibson, Biochemistry 33: 13070-13078, 1994). In this study, mass spectrometry and composition analyses have shown that the lipooligosaccharides from three other H. ducreyi strains also contain N-acetyllactosamine and are highly sialylated (approximately 30 to 50%), although one African strain was found to contain neither of these structural features.

Variation of gonococcal lipooligosaccharide structure is due to alterations in poly-G tracts in lgt genes encoding glycosyl transferases

The lipooligosaccharide (LOS) expressed by gonococci spontaneously varies its structure at high frequency, but the underlying genetic mechanism has not been described. We have previously reported that the genes encoding the glycosyl transferases responsible for the biosynthesis of the variable alpha chain of the LOS of Neisseria gonorrhoeae are located in a locus containing five genes, lgtA, lgtB, lgtC, lgtD, and lgtE. Sequence analysis showed that lgtA, lgtC, and lgtD contained poly-G tracts within the coding frames, leading to the hypothesis that shifts in the number of guanosine residues in the poly-G tracts might be responsible for the high frequency variation in structure of gonococcal LOS. We now provide experimental evidence confirming this hypothesis.

Role of O-antigen variation in the immune response

The O antigen is an extremely variable surface polysaccharide of Gram-negative bacteria. This variation is thought to allow the various clones of a species each to present a surface that offers a selective advantage in the niche occupied by that clone. The interactions between O antigen and the immune system are central to determining the selective advantage of each clone.

Structural studies of lipooligosaccharides from Haemophilus ducreyi ITM 5535, ITM 3147, and a fresh clinical isolate, ACY1: evidence for intrastrain heterogeneity with the production of mutually exclusive sialylated or elongated glycoforms

The structures of the lipooligosaccharides (LOSs) from Haemophilus ducreyi ITM 5535 and ITM 3147 and a fresh clinical isolate, ACY1, have been investigated. Oligosaccharides were obtained from phenol-water-extracted LOS by mild acid hydrolysis and were studied by methylation analysis, fast atom bombardment and electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy. The major oligosaccharide obtained from all strains was a nonasaccharide with the structure beta-D-Galp-(1-->4)-beta-D-GlcNAcp-(1-->3)-beta-D-Galp-(1-->4)-D-a lpha-D-Hepp- (1-->6)-beta-D-Glcp-(1-->[L-alpha-D-Hepp-(1-->2)-L-alpha-D-Hepp - (1-->3)]4)-L-alpha-D-Hepp-Kdo (Kdo stands for 3-deoxy-D-manno-octulosonic acid) and is thus identical to that identified as the major oligosaccharide in H. ducreyi ITM 2665 (E. K. H. Schweda, A. C. Sundström, L. M. Eriksson, J.A. Jonasson, and A. A. Lindberg, J. Biol. Chem. 269:12040-12048, 1994). Electrospray ionization mass spectrometry on O-deacylated LOS from H. ducreyi ITM 5535 obtained after treatment with anhydrous hydrazine gave evidence for the presence of a sialylated major compound, Neu5Ac alpha(2-->3)-beta-D-Galp-(1-->4)-beta-D-GlcNAcp-(1-->3)-beta-D-Gal p- (1-->4)-D-alpha-D-Hepp-(1-->6)-beta-D-Glcp-(1-->[L-alpha-D-Hepp -(1-->2)-L- alpha-D-Hepp-(1-->3)]4)-L-alpha-D-Hepp-Kdo(P)-O-deacylated lipid A (Neu5Ac stands for N-acetylneuraminic acid). However, an even larger oligosaccharide could be isolated from all strains as a minor component, viz., the undecasaccharide beta-D-Galp-(1-->4)-beta-D-GlcNAcp-(1-->3)-beta-d-Galp-(1-->4)-beta-D-glcNAcp-(1-->3)-beta-D-Galp-(1-->4)-D-alpha-D-Hepp-(1-->6)-beta-D-Glcp-(1-->[L-alpha-D-Hepp-(1-->2)-L-alpha-D-Hepp-(1-->3)]4-L-alpha-D-Hepp-Kdo, which represents an N-acetyl lactosamine disaccharide unit elongation of the LOS outer core. No Sialylation of this latter minor component undecasaccharide was detected.

Phenotypic variation of carbohydrate surface antigens and the pathogenesis of Haemophilus influenzae infections

Phenotypic variation of two major carbohydrate surface antigens of Haemophilus influenzae, the capsule and lipopolysaccharide, exemplifies some of the genetic mechanisms used by pathogenic bacteria in interacting with host microenvironments. The ability to generate phenotypic variety at high frequency within clonal populations of microorganisms provides an adaptive mechanism to combat the polymorphisms and immune repertoires of the host.

Monoclonal antibodies against Haemophilus lipopolysaccharides: clone DP8 specific for Haemophilus ducreyi and clone DH24 binding to lacto-N-neotetraose

Mouse monoclonal antibodies (MAbs) DP8 [immunoglobulin G1(kappa)] and DH24 [immunoglobulin M(kappa)], which are specific for Haemophilus ducreyi lipopolysaccharide (LPS), were generated by fusing mouse myeloma NS0 cells with spleen cells of BALB/c mice immunized with a total membrane preparation of H. ducreyi. MAb DP8 reacted in whole-cell enzyme immunoassay (EIA) and colony dot immunoblotting with all 50 strains of H. ducreyi but not with any other bacteria tested, which suggests an exposed and species-specific epitope on the H. ducreyi cell surface. This conclusion was supported by the finding that DP8 bound to all six H. ducreyi LPSs tested but not to any of the Haemophilus influenzae or enterobacterial LPSs or synthetic glycoconjugates. The MAb DH24 bound to 43 of 50 strains of H. ducreyi and to few strains of H. influenzae, Neisseria gonorrhoeae, and Neisseria meningitidis, as evaluated by whole-cell EIA and colony dot immunoblotting. The MAb DH24 reacted with five of the six H. ducreyi LPSs tested and with the lacto-N-neotetraose (Gal beta 1-->4GlcNAc beta 1-->3Gal beta 1-->4Glc) series of synthetic glycoconjugates, as determined by EIA. By using polysaccharides obtained after both mild acidic hydrolysis and strong alkali treatment and dephosphorylated samples as inhibitors of the MAbs binding to H. ducreyi LPS antigens, it could be shown that phosphate groups were essential for the binding of DP8 to LPS but that they did not affect antigenic recognition by DH24. None of the MAbs bound to isolated lipid A, but aggregation caused by the fatty acids of lipid A was essential for epitope recognition.

Gonococcal opacity: lectin-like interactions between Opa proteins and lipooligosaccharide

Previous evidence from our laboratory suggested that the tight intercellular adhesions between the outer membranes of gonococci displaying the opacity colony phenotype occurred because Opa proteins expressed on one gonococcus adhered to the lipooligosaccharide (LOS) of the opposing bacterium (M.S. Blake, p. 51-66, in G. G. Jackson and H. Thomas, ed., The Pathogenesis of Bacterial Infections, 1985, and M. S. Blake and E. C. Gotschlich, p. 377-400, in M. Inouye, ed., Bacterial Outer Membranes as Model Systems, 1986). A noncompetitive inhibition assay used previously to determine the carbohydrate structures recognized by the major hepatic asialoglycoprotein receptor was modified to determine the gonococcal LOS structures that bind Opa proteins (R. T. Lee, Targeted Diagn. Ther. Ser. 4:65-84, 1991). The LOS carbohydrates used in these assays were LOS structures purified from pyocin LOS mutants of Neisseria gonorrhoeae 1291 described by K. C. Dudas and M. A. Apicella (Infect. Immun. 56:499-504, 1988) and further characterized by C. M. John et al. (J. Biol. Chem. 266:19303-19311, 1991). Purified gonococcal Opa proteins were incubated with each of the parent and mutant LOS, and the amount of binding of Opa proteins was measured by a direct enzyme-linked immunosorbent assay using the Opa-specific monoclonal antibody 4B12. The affinities of the Opa proteins for each of the LOS were determined indirectly by measuring the concentrations of Opa proteins that noncompetitively inhibited 50% of the binding of LOS-specific monoclonal antibodies. This concentration is inversely proportional to the affinity of the inhibitor (R. T. Lee, Targeted Diagn. Ther. Ser. 4:65-84, 1991). Our data suggest that the gonococcal Opa proteins tested had the highest affinity for the Gal beta 1-4GlcNAc residue present on the gonococcal lactoneoseries LOS. This affinity was comparable to that reported for the binding of the major hepatic asialoglycoprotein receptor to glycoconjugates containing terminal galactose and N-acetylgalactosamine (R. T. Lee, Targeted Diagn. Ther. Ser. 4:65-84, 1991). After sialylation of the lactoneoseries LOS, presumably on the terminal galactose residue, the interaction with the Opa proteins was ablated. Therefore, the gonococcal Opa-LOS and mammalian epithelial cell asialoglycoprotein receptor-carbohydrate interactions have quite similar specificities.

Use of pyocin to select a Haemophilus ducreyi variant defective in lipooligosaccharide biosynthesis

Haemophilus ducreyi, a cause of genital ulcer disease in developing countries, appears to facilitate the heterosexual transmission of the human immunodeficiency virus in Africa. Despite an increase in studies of this gram-negative human pathogen, little is known about the pathogenesis of chancroid. Our studies have shown that the lipooligosaccharides (LOS) of H. ducreyi may play an important role in ulcer formation. Monoclonal antibody and mass spectrometric analyses identified a terminal trisaccharide present on H. ducreyi LOS that is immunochemically similar to human paragloboside. This epitope is present on the LOS of Neisseria gonorrhoeae, and it may be the site of attachment for pyocin lysis. We have used pyocin, produced by Pseudomonas aeruginosa, to select LOS variants with sequential saccharide deletions from N. gonorrhoeae. On the basis of the similarities between N. gonorrhoeae and H. ducreyi LOS, we employed the same technique to determine if H. ducreyi strains were susceptible to pyocin lysis. In this study, we report the generation of a pyocin N-resistant H. ducreyi strain which synthesizes a truncated version of the parental LOS. Further studies have shown that this H. ducreyi variant has lost the terminal LOS epitope defined by monoclonal antibody 3F11. This report demonstrates that H. ducreyi is sensitive to pyocins and that this technique can be used to generate H. ducreyi LOS variants. Such variants could be used in comparative studies to relate LOS structure to biologic function in the pathogenesis of chancroid.

Investigation of the structural heterogeneity of lipooligosaccharides from pathogenic Haemophilus and Neisseria species and of R-type lipopolysaccharides from Salmonella typhimurium by electrospray mass spectrometry

Heterogeneity in the lipooligosaccharides (LOS) of pathogenic Haemophilus and Neisseria species is evident from the multiplicity of components observed with electrophoretic analyses. Knowledge of the precise structures that make up these diverse LOS molecules is clearly the key to reaching an understanding of pathogenic processes such as phase variation and molecular mimicry. Except for a few cases, little is known about the specific structural features of LOS that underlie phase variation and molecular mimicry, partly because of the inherent difficulties in the structural elucidation of these complex glycolipids. In the lipopolysaccharides (LPS) from Salmonella typhimurium and Escherichia coli, rough, or R-type, mutants have been isolated that have provided insight into the biosynthetic pathways and associated genetics that control LPS expression. Nonetheless, recent work has shown that these R-type LPS are more complex than originally thought, and significant heterogeneity is still observed, primarily in their phosphorylation states. In order to investigate the structures of LPS and LOS in a more rapid fashion, we have determined the precise molecular weights of LOS (and LPS) preparations from various Haemophilus, Neisseria, and Salmonella species by electrospray ionization-mass spectrometry. The LOS (or LPS) were first O-deacylated under mild hydrazine conditions to remove O-linked esters primarily from the lipid A portion. Under negative-ion conditions, the O-deacylated LOS yield abundant multiply deprotonated molecular ions, (M-nH)n-, where n refers to the number of protons removed and therefore determines the absolute charge state, n = z. Mass spectra from different LOS and LPS preparations have provided detailed information concerning the structural basis for LOS (and LPS) heterogeneity and corresponding saccharide compositions. The identification of sialic acid in the LOS of Haemophilus and Neisseria species and the variable phosphorylation of the core of S. typhimurium LPS have afforded insights into the biosynthetic pathways used by these organisms. Information of this type is important for understanding the underlying genetic and environmental factors controlling LOS and LPS expression.

Lipo-oligosaccharides (LOS) of mucosal pathogens: molecular mimicry and host-modification of LOS

Immunochemical studies of the lipo-oligosaccharides (LOS) of the Gram-negative bacteria Neisseria gonorrhoeae and Neisseria meningitidis have revealed some interesting structural characteristics of these LOS that might relate to their roles during pathogenesis. The carbohydrate moieties of the LOS of pathogenic Neisseria mimic carbohydrates present in glycosphingolipids of human cells. Firstly, an LOS component present among a number of Neisseria species is antigenically and/or chemically identical to lactoneoseries glycosphingolipids present in human cells. The lactoneoseries LOS becomes sialylated on Neisseria gonorrhoeae when they are grown in the presence of cytidine 5'-monophospho-N-acetyl-neuraminic acid (CMP-NANA), the nucleotide sugar for sialic acid. Examination of gonococci present in exudates from males with natural infection indicates that sialylation also occurs in vivo. The mechanism for this process apparently involves a bacterial sialyltransferase scavenging available host CMP-NANA ("host-modification" of LOS) and transferring the sialic acid to the lactoneoserieslike LOS. Strains of N. meningitidis and Haemophilus influenzae also express similarly sialylated LOS suggesting that this is a common mechanism of pathogenesis among these bacteria. Additional examples of LOS that mimic other glycosphingolipid series have been identified also and the fact that multiple series can be expressed in a single population of gonococci suggests that a diverse set of LOS can be presented to the host during infection. It is possible that this diverse set of LOS serve different functions for the bacteria in various hosts and/or environments during infection.

Structural studies of the lipooligosaccharides from Haemophilus influenzae type b strain A2

The outer membrane lipooligosaccharides (LOS) from Haemophilus influenzae type b strain A2 are a heterogeneous mixture of glycolipids containing a conserved Lipid A structure and a variable oligosaccharide moiety. After O-deacylation by treatment with anhydrous hydrazine, the O-deacylated LOS mixture was analyzed by electrospray mass spectrometry and shown to contain 11 components, ranging in M(r) from 2277.8 to 3416.4. The majority of these structures contained a variable number of hexoses, three L-glycero-D-manno-heptoses, and one 3-deoxy-D-manno-octulosonic acid (KDO) residue attached to a diphosphorylated O-deacylated Lipid A moiety. Additional phosphate and phosphoethanolamine (PEA) groups were also present on the oligosaccharide structures. Two minor high molecular weight components were also observed that contained N-acetylhexosamine and sialic acid. Neuraminidase treatment of the O-deacylated LOS mixture resulted in the loss of sialic acid from these latter two species. After mild acid hydrolysis and separation by size-exclusion chromatography, liquid secondary ion mass spectrometry identified six major and four minor oligosaccharides, ranging in M(r) from 1243.4 to 2215.8. These released oligosaccharides contained a common heptose trisaccharide core structure with anhydro-KDO at the reducing terminus, which arises as an artifact of the hydrolysis procedure by beta-elimination of a phosphate group from the 4-position of KDO. Selected oligosaccharide fractions were subjected to composition and methylation analyses and sequenced by tandem mass spectrometry. Taken together, these data defined the major O-deacylated LOS as follows: [formula: see text] Higher molecular weight structures in the mixture contained galactose, N-acetylglucosamine, and sialic acid as additional branch sugars, suggesting that H. influenzae A2 is capable of forming a sialylated lactosamine structure.

Role of lipooligosaccharide in virulence of the Brazilian purpuric fever clone of Haemophilus influenzae biogroup aegyptius for infant rats

Clonally related strains of Haemophilus influenzae biogroup aegyptius have recently been associated with Brazilian purpuric fever (BPF), a fulminant, systemic disease in children. Using an infant rat bacteremia model for BPF, we found that a rat blood-passaged BPF isolate of H. influenzae biogroup aegyptius was more virulent than the original strain was. When compared with the original strain, the animal-passaged variant was found to display an altered lipooligosaccharide (LOS) phenotype and to lack pili. To examine the role of LOS phenotype and pili in virulence, we isolated isogenic variants differing in LOS phenotype or expression of pili. The virulence of variants was compared by examining the results of blood cultures obtained 24 h after intraperitoneal inoculation with 10(5) CFU. Our results indicate that the LOS phenotype is a critical determinant of BPF clone virulence for infant rats. To a lesser extent, the absence of piliation and an undefined additional factor(s) contribute to virulence.

Neisserial surface variation: how and why?

Neisseria gonorrhoeae exhibits striking variability in several of its surface components (pili, Opa proteins and lipooligosaccharide) in vivo and in vitro. Such flagrant variation of this mucosal pathogen's surface components contrasts sharply with changes in single surface components of blood-borne trypanosomes and borreliae. Despite these differences, similar molecular events are sometimes involved.

Generation of lipooligosaccharide mutants of Haemophilus influenzae type b

We previously reported the analysis of recombinant plasmids from Haemophilus influenzae type b (Hib) that lead to modifications of Escherichia coli lipopolysaccharide (LPS) (Y. Abu Kwaik, R. E. McLaughlin, M. A. Apicella, and S. M. Spinola, Mol. Microbiol. 5:2475-2480, 1991). The modified LPS species are recognized by monoclonal antibodies (MAbs) 6E4 and 3F11. MAb 6E4 binds to a stable 2-keto-3-deoxyoctulosonic acid epitope, while MAb 3F11 binds to a Gal beta 1-4GlcNac epitope that phase varies in Hib at a frequency of 2 to 5%. The internal EcoRI fragment containing most of the DNA required for LPS modification in E. coli was used as the target for transposon mutagenesis. Plasmids containing minitransposon m-Tn3(Cm) randomly inserted into the target fragment were transformed into the isogenic Hib strain, and transposon integration into the Hib chromosome was verified by colony hybridization. The lipooligosaccharides of 36 transformants were phenotypically and antigenically characterized by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reactivity with a variety of MAbs that recognize both stable and phase-varying lipooligosaccharide epitopes. The majority of the mutants had altered reactivity with MAb 6E4. With one exception, these mutants retained the ability to express phase-varying epitopes. Analysis of the transformants suggested that the 6E4 epitope was contained on an oligosaccharide chain separate from that of phase-varying epitopes and appeared to be assembled in at least three separate steps.

Further antigenic similarities of Neisseria gonorrhoeae lipooligosaccharides and human glycosphingolipids

Anticarbohydrate monoclonal antibodies were tested for their ability to bind to various strains of Neisseria. A monoclonal antibody that binds to the ganglio-series glycosphingolipid, ganglio-N-triaosylceramide, also bound to strains of Neisseria gonorrhoeae but not to other species of Neisseria. An antibody specific for the globo-series glycosphingolipid, globotriaosylceramide, also bound to strains of N. gonorrhoeae, Neisseria meningitidis, Neisseria lactamica, and Branhamella catarrhalis but not to any other strains of nonpathogenic Neisseria.