Characterization of murine monoclonal and murine, rabbit, and human polyclonal antibodies against chlamydial lipopolysaccharide

Human genital antibody-mediated inhibition of Chlamydia trachomatis infection and evidence for ompA genotype-specific neutralization

The endocervix, the primary site of Chlamydia trachomatis (Ct) infection in women, has a unique repertoire of locally synthesized IgG and secretory IgA (SIgA) with contributions from serum IgG. Here, we assessed the ability of genital and serum-derived IgG and IgA from women with a recent positive Ct test to neutralize Ct elementary bodies (EBs) and inhibit inclusion formation in vitro in human endocervical epithelial cells. We also determined if neutralization was influenced by the major outer membrane protein (MOMP) of the infecting strain, as indicated by ompA gene sequencing and genotyping. At equivalent low concentrations of Ct EB (D/UW-3/Cx + E/UW-5/Cx)-specific antibody, genital-derived IgG and IgA and serum IgA, but not serum IgG, significantly inhibited inclusion formation, with genital IgA being most effective, followed by genital IgG, then serum IgA. The well-characterized Ct genotype D strain, D/UW-3/Cx, was neutralized by serum-derived IgG from patients infected with genotype D strains, genital IgG from patients infected with genotype D or E strains, and by genital IgA from patients infected with genotype D, E, or F strains. Additionally, inhibition of D/UW-3/Cx infection by whole serum, rather than purified immunoglobulin, was associated with levels of serum EB-specific IgG rather than the genotype of infecting strain. In contrast, a Ct genotype Ia clinical isolate, Ia/LSU-56/Cx, was neutralized by whole serum in a genotype and genogroup-specific manner, and inhibition also correlated with EB-specific IgG concentrations in serum. Taken together, these data suggest that (i) genital IgA most effectively inhibits Ct infection in vitro, (ii) human antibody-mediated inhibition of Ct infection is significantly influenced by the ompA genotype of the infecting strain, (iii) the genital antibody repertoire develops or matures differently compared to systemic antibody, and (iv) ompA genotype-specificity of inhibition of infection by whole serum can be overcome by high concentrations of Ct-specific IgG.

Subtle Changes in the Combining Site of the Chlamydiaceae-Specific mAb S25-23 Increase the Antibody-Carbohydrate Binding Affinity by an Order of Magnitude

Murine antibodies S25-23, S25-26, and S25-5 derive from a common germ-line origin, and all bind the Chlamydiaceae family-specific epitope αKdo(2→8)αKdo(2→4)αKdo (where Kdo is 3-deoxy-α-d- manno-oct-2-ulosonic acid) with high affinity and specificity. These antibodies recognize the entire trisaccharide antigen in a linkage-dependent manner via a groove composed largely of germ-line residues. Despite sharing identical heavy and light chain genes, S25-23 binds the family-specific epitope with nanomolar affinity, which is an order of magnitude higher than that of S25-26, while S25-5 displays an affinity between those of S25-23 and S25-26. We determined the high-resolution crystal structures of S25-23 and S25-5 antigen binding fragments in complex with a pentasaccharide derived from the LPS of Chlamydia and measured the affinity of S25-5 for chlamydial LPS antigens using isothermal titration microcalorimetry. The 1.75 Å resolution structure of S25-23 shows how subtle conservative mutations Arg(L)-27E to lysine and Ser(H)-56 to threonine lead to an order of magnitude increase in affinity. Importantly, comparison between previous S25-26 structures and the 1.99 and 2.05 Å resolution liganded and unliganded structures of S25-5, respectively, shows how a Ser(L)-27E mutation results in an intermediate affinity due to the reduced enthalpic penalty associated with complex formation that would otherwise be required for arginine in this position. This strategy allows for subtle adjustments in the combining site via affinity maturation that have dramatic consequences for the affinity of an antibody for its antigen.

A novel whole-bacterial enzyme linked-immunosorbant assay to quantify Chlamydia trachomatis specific antibodies reveals distinct differences between systemic and genital compartments

Chlamydia trachomatis (CT) is the leading sexually transmitted bacterial infection. The continued global burden of CT infection strongly predicates the need for a vaccine to supplement current chlamydial control programs. The correlates of protection against CT are currently unknown, but they must be carefully defined to guide vaccine design. The localized nature of chlamydial infection in columnar epithelial cells of the genital tract necessitates investigation of immunity at the site of infection. The purpose of this study was to develop a sensitive whole bacterial enzyme-linked immunosorbent assay (ELISA) to quantify and compare CT-specific IgG and IgA in sera and genital secretions from CT-infected women. To achieve this, elementary bodies (EBs) from two of the most common genital serovars (D and E) were attached to poly-L-lysine-coated microtiter plates with glutaraldehyde. EB attachment and integrity were verified by the presence of outer membrane antigens and the absence of bacterial cytoplasmic antigens. EB-specific IgG and IgA standards were developed by pooling sera with high titers of CT-specific antibodies from infected women. Serum, endocervical and vaginal secretions, and endocervical cytobrush specimens from CT-infected women were used to quantify CT-specific IgG and IgA which were then normalized to total IgG and IgA, respectively. Analyses of paired serum and genital samples revealed significantly higher proportions of EB-specific antibodies in genital secretions compared to sera. Cervical and vaginal secretions and cytobrush specimens had similar proportions of EB-specific antibodies, suggesting any one of these genital sampling techniques could be used to quantify CT-specific antibodies when appropriate normalization methodologies are implemented. Overall, these results illustrate the need to investigate genital tract CT antibody responses, and our assay provides a useful quantitative tool to assess natural immunity in defined clinical groups and CT vaccine trials.

Synthesis of Kdo-trisaccharide derivatives of chlamydial and enterobacterial LPS containing carboxyl-reduced or β-configurated Kdo-residues

Five allyl glycosides corresponding to the 3-deoxy-D- manno-2-octulosonic acid (Kdo) containing genus-specific LPS epitope of Chlamydia were synthesized. Compounds 5 and 22 contain one carboxyl-reduced Kdo moiety linked to O-4 of the proximal Kdo unit, whereas the analogues 28, 34 and 36 each contain one β-linked Kdo-residue within the trisaccharide sequence Kdo p-(2→8)-Kdo p-(2→4)-Kdo p. Elaboration of the carboxyl-reduced derivatives was achieved by BF3•Et2O-catalyzed coupling of Kdo-fluoride derivatives 1 or 14 with the 7,8- O-carbonyl-derivative 2. The β-linked oligosaccharides were obtained by Helferich-glycosidation of the respective Kdo-disaccharide bromide derivatives 26 and 31. The deprotected compounds - characterized by H and 13C NMR spectroscopy - are suitable haptens for the immunochemical study of monoclonal antibodies directed against the Kdo-region of chlamydial and enterobacterial LPS.

Identification of Chlamydia trachomatis outer membrane complex proteins by differential proteomics

The extracellular chlamydial infectious particle, or elementary body (EB), is enveloped by an intra- and intermolecular cysteine cross-linked protein shell called the chlamydial outer membrane complex (COMC). A few abundant proteins, including the major outer membrane protein and cysteine-rich proteins (OmcA and OmcB), constitute the overwhelming majority of COMC proteins. The identification of less-abundant COMC proteins has been complicated by limitations of proteomic methodologies and the contamination of COMC fractions with abundant EB proteins. Here, we used parallel liquid chromatography-mass spectrometry/mass spectrometry (LC-MS/MS) analyses of Chlamydia trachomatis serovar L2 434/Bu EB, COMC, and Sarkosyl-soluble EB fractions to identify proteins enriched or depleted from COMC. All well-described COMC proteins were specifically enriched in the COMC fraction. In contrast, multiple COMC-associated proteins found in previous studies were strongly enriched in the Sarkosyl-soluble fraction, suggesting that these proteins are not COMC components or are not stably associated with COMC. Importantly, we also identified novel proteins enriched in COMC. The list of COMC proteins identified in this study has provided reliable information for further understanding chlamydial protein secretion systems and modeling COMC and EB structures.

Analysis of cross-reactive and specific anti-carbohydrate antibodies against lipopolysaccharide from Chlamydophila psittaci

Chlamydiae contain a rough-type lipopolysaccharide (LPS) of 3-deoxy-alpha-d-manno-oct-2-ulopyranosonic acid residues (Kdo). Two Kdo trisaccharides, 2.8/2.4- and 2.4/2.4-linked, and a branched 2.4[2.8]2.4-linked Kdo tetrasaccharide occur in Chlamydiaceae. While the 2.8/2.4-linked trisaccharide contains a family-specific epitope, the branched Kdo oligosaccharide occurs only in Chlamydophila psittaci and antibodies against it will be useful in human and veterinarian diagnostics. To overcome the generation of cross-reactive antibodies that bind with high affinity to a dominant epitope formed by 2.4/2.4-linked Kdo, we immunized mice with a synthetic 2.4[2.8]-linked branched Kdo trisaccharide and used phage display of scFv to isolate recombinant antibody fragments (NH2240-31 and SAG506-01) that recognize the branched Kdo oligosaccharide with a K(D) of less than 10 nM. Importantly, although these antibodies used germline genes coding for an inherited Kdo recognition site, they were able clearly to distinguish between 2.4[2.8]2.4- and 2.4/2.4-linked Kdo. Sequence determination, binding data, and X-ray structural analysis revealed the basis for the improved discrimination between similar Kdo ligands and indicated that the alteration of a stacking interaction from a phenylalanine residue in the center of the combining site to a tyrosine residue facing away from the center favors recognition of branched 2.4[2.8]2.4-linked Kdo residues. Immunofluorescence tests of infected cell monolayers using this antibody show specific staining of C. psittaci elementary bodies that allow it to be distinguished from other pathogenic chlamydiae.

Chlamydophila felis CF0218 is a novel TMH family protein with potential as a diagnostic antigen for diagnosis of C. felis infection

Chlamydophila felis is a causative agent of acute and chronic conjunctivitis and pneumonia in cats (feline chlamydiosis). Also, C. felis is a suspected zoonotic agent of such diseases as non-Chlamydia trachomatis conjunctivitis in humans, although this is controversial. At present, there is no serodiagnostic system that specifically detects C. felis infection conveniently. Current systems use antigens such as lipopolysaccharide that cross-react with all chlamydia species. In addition, it is difficult to distinguish between cats that are vaccinated with the commercial vaccine against C. felis and cats that are infected with C. felis. Here, we describe a new candidate diagnostic antigen for diagnosis of C. felis infection, CF0218, that was obtained by screening a genomic expression library of C. felis Fe/C-56 with C. felis-immunized serum. CF0218 was a putative transmembrane head (TMH) family protein with bilobed hydrophobic motifs at its N terminus, and orthologues of CF0218 were not found in the Chlamydophila pneumoniae or Chlamydia trachomatis genomes. The recombinant CF0218 was not recognized by antiserum against C. trachomatis, suggesting that CF0218 is C. felis specific. CF0218 transcription during the course of C. felis infection was confirmed by reverse transcription-PCR. By indirect immunofluorescence analysis, CF0218 was colocalized with the C. felis-formed inclusion bodies in the infected cells. The antibody response against CF0218 was elevated following C. felis infection but not by vaccination in experimentally vaccinated and infected cats. These results suggest that CF0218, a novel TMH family protein of C. felis, possesses potential as a C. felis infection-specific diagnostic antigen.

Production and characterization of monoclonal antibodies to Chlamydia trachomatis

In order to develop an indigenous and reliable immunodiagnostic assay for Chlamydia trachomatis in India, monoclonal antibodies (MAbs) were developed. Serovar D of C. trachomatis (which was previously isolated from the genital tract of infected women) was propagated, purified, and used for production of monoclonal antibody. A total of 12 murine hybrid clones producing immunoglobulin G (IgG) class monoclonal antibodies to C. trachomatis (species-specific, B serogroup-specific, and serovar-specific) were developed. Enzyme-linked immunosorbent assay (ELISA) was used to screen developed murine MAbs with C. trachomatis antigen. Dot-ELISA was used to check the specificity of clones and was used for selecting hybridomas that produced anti-C. trachomatis MAb. There was no cross-reactivity of species-specific, B serogroup-specific, and D serovar-specific anti-major outer membrane protein (MOMP) monoclonal antibodies with other species of Chlamydiae i.e., C. pneumoniae and C. psitacci. Immunoblotting was done for further characterization of six of these clones, i.e., B2.2 and D5.1 (B serogroup-specific), D10.4 and G1.5 (species-specific), and H5.6 and E4.2 (D serovar-specific). Three of these clones D10.4 (species-specific), B2.2 (B serogroup-specific), and H5.6 (D serovar-specific) which reacted with 40 kd MOMP protein in Immunoblotting were used for further screening to detect C. trachomatis in endocervical specimens. The percent positivity with these clones for detection of C. trachomatis antigen by enzyme immunoassay (EIA) was 45% with D10.4, 43% with H5.6, and 35% with B2.2, while 46% of the specimens were found positive by cell culture method. This indicates a high prevalence of C. trachomatis infection in the female genital tract. The sensitivity and specificity of developed anti- MOMP monoclonal antibody in EIA for chlamydial antigen detection was 91.3% and 94.4% for D10.4 clone (species-specific), 91.30% and 98.1% for H5.6 (D serovar-specific) and 75.00% and 99.07% for B2.2 (B serogroup-specific) compared to cell culture method.

Localization of TLR2 and MyD88 to Chlamydia trachomatis inclusions. Evidence for signaling by intracellular TLR2 during infection with an obligate intracellular pathogen

Chlamydia trachomatis is an obligate intracellular gram-negative pathogen and the etiologic agent of significant ocular and genital tract diseases. Chlamydiae primarily infect epithelial cells, and the inflammatory response of these cells to the infection directs both the innate and adaptive immune response. This study focused on determining the cellular immune receptors involved in the early events following infection with the L2 serovar of C. trachomatis. We found that dominant negative MyD88 inhibited interleukin-8 (IL-8) secretion during a productive infection with chlamydia. Furthermore, expression of Toll-like receptor (TLR)-2 was required for IL-8 secretion from infected cells, whereas the effect of TLR4/MD-2 expression was minimal. Cell activation was dependent on infection with live, replicating bacteria, because infection with UV-irradiated bacteria and treatment of infected cells with chloramphenicol, but not ampicillin, abrogated the induction of IL-8 secretion. Finally, we show that both TLR2 and MyD88 co-localize with the intracellular chlamydial inclusion, suggesting that TLR2 is actively engaged in signaling from this intracellular location. These data support the role of TLR2 in the host response to infection with C. trachomatis. Our data further demonstrate that TLR2 and the adaptor MyD88 are specifically recruited to the bacterial or inclusion membrane during a productive infection with chlamydia and provide the first evidence that intracellular TLR2 is responsible for signal transduction during infection with an intracellular bacterium.

Relationship between infectious burden, systemic inflammatory response, and risk of stable coronary artery disease: role of confounding and reference group

AIM

The purpose of the study was to assess the association between seropositivity to various infectious agents and stable coronary artery disease (CAD), controlling simultaneously for a variety of potential confounders. We also investigated whether the choice of a larger reference group might affect the results, and whether or not seropositivity to multiple agents was associated with a systemic inflammatory response.

METHODS

We assessed the simultaneous prevalence of antibodies against Helicobacter pylori, Chlamydia, cytomegalovirus, and herpes simplex virus in 312 patients with angiographically proven coronary artery disease (CAD) and in 479 age and sex matched controls. C-reactive protein, interleukin-6, fibrinogen, PAI-1-activity, D-dimer, von Willebrand Factor, plasma viscosity, and a complete blood cell count were determined in all subjects.

RESULTS

Seropositivity to all of the four agents was 21.8% in cases and 13.6% in controls (P=0.0003). We found a dose-response relationship between combined IgG-seropositivity to H. pylori, Chlamydia, cytomegalovirus, and herpes simplex virus and odds for the presence of angiographically confirmed stable CAD which, however, was strongly reduced after controlling for a variety of potential confounders. The dose-response pattern was no longer evident if a more stable reference group (subjects seropositive for two agents) was used instead of the relatively small reference group with zero or one seropositivity. We found no consistent pattern between IgG-seropositivity to several pathogens and inflammatory markers.

CONCLUSIONS

Based on serological evidence of various infectious agents, this study suggests that the aggregate number of persistent infections is not independently associated with an increased risk for CAD if control for confounding and use of a stable reference group are guaranteed.

Cross-reactive monoclonal antibodies raised against the lipopolysaccharide antigen of Salmonella minnesota Re chemotype: diagnostic relevance

Three cross-reactive monoclonal antibodies (MAbs) of IgM and IgG2b isotype were generated in two separate fusions after immunization of BALB/c mice with heat killed Salmonella minnesota R595 of Re chemotype and acid-treated bacteria, coated with Re lipopolysaccharide (LPS) antigen. The specificity of the MAbs was demonstrated as the Re LPS antigen. The activity and cross-reactivity against purified elementary bodies of Chlamydia trachomatis and various S- and R-LPS antigens of other Gram-negative bacteria were characterized in enzyme-linked immunosorbent assay, passive hemolysis assay, immunoblot and immunofluorescence with the available chlamydial strains. The results demonstrated cross-reaction between the Re LPS antigen, the genus-specific chlamydial LPS and the LPS antigens of Escherichia coli O119 and Acinetobacter baumannii, suggesting the presence of identical or similar epitopes in the lipopolysaccharide antigens. The findings are implying the necessity of novel approaches, improving the specificity of serologic assays in the laboratory diagnosis of chlamydial infections.

Chlamydial LPS antibodies, intima-media thickness and ischemic events in patients with established atherosclerosis

BACKGROUND

Chlamydia pneumoniae has been associated with cardiovascular disease. However, studies on the presence of chlamydial antibodies and intima-media thickness (IMT) or future ischemic events are inconclusive. We examined the relation between circulating antibodies to chlamydial lipopolysaccharide (cLPS Ab), IMT and the occurrence of ischemic events during follow-up in patients with manifest atherosclerotic disease.

METHODS

IgG and IgA antibodies against cLPS were determined in 273 out of 307 consecutive patients with a recent ischemic stroke (IS, n=90), a recent myocardial infarction (MI, n=87) or peripheral arterial disease (PAD, n=96). B-mode ultrasound IMT measurement of carotid and femoral arteries was performed and ischemic events, IS or MI, during follow-up were registered.

RESULTS

IgG and IgA were found in 66 and 46% of the patients, respectively. We did not detect any difference in IMT between patients with or without antibodies: IgA-0.97(0.28) mm versus IgA+0.95(0.26) mm, P=0.63, IgG-0.96(0.28) mm versus IgG+0.96(0.26) mm, P=0.98. During follow-up with a mean duration of 3.5 years the combined endpoint, MI or IS, was similar in patients with or without antibodies (IgA-24% vs. IgA+19%, IgG-23% vs. IgG+22%). However, a lower frequency of MI was observed in IgA positive patients (IgA-13% vs. IgA+8%). The number of ischemic events in the 12 patients who used anti-chlamydial antibiotics was similar compared with those who did not use antibiotics.

CONCLUSION

In patients with manifest atherosclerotic disease no association between the presence of cLPS Ab and IMT could be detected. In addition, no influence of cLPS Ab on the number of ischemic events was observed, the frequency of MI during follow-up in IgA positive patients was even lower.

A survey of infectious agents as risk factors for primary sclerosing cholangitis: are Chlamydia species involved?

OBJECTIVES

The aetiology of primary sclerosing cholangitis (PSC) is unknown, and the role of micro-organisms has been studied only to a limited extent. We tested the hypothesis that past or persisting infection with common viruses or atypical bacteria might play a role in genetically susceptible hosts.

DESIGN

Case-control study.

METHODS

Serological screening for antibodies against 22 viruses as well as Chlamydia spp. and Mycoplasma pneumoniae was carried out in 41 well-established PSC patients. All 5110 sera tested in 1997 for these micro-organisms at our laboratory served as a background reference group. Subsequently, Chlamydia anti-lipopolysaccharide (LPS) antibodies were determined by enzyme-linked immunosorbent assay (ELISA) in the PSC group and in three race-matched control groups (inflammatory bowel disease (IBD) group, n = 35; non-IBD patients group, n = 39; healthy blood donor group, n = 40). Subtyping in Chlamydia trachomatis and C. pneumoniae serotypes by specific anti-major outer membrane protein (MOMP) assays was carried out in the four groups. Immunohistochemical staining using specific markers for chlamydiae was carried out on liver biopsies of 14 PSC patients.

RESULTS

There was a markedly elevated seroprevalence of Chlamydia-LPS antibodies compared with the 1997 reference group. The odds ratios (ORs) for the presence of immunoglobulin G, immunoglobulin M and immunoglobulin A antibodies for the PSC patients versus the control group were 2.4 (95% confidence interval (CI) 1.1 to 5.4), 1.9 (95% CI 0.9 to 4.0) and 6.7 (95% CI 3.0 to 17.0), respectively. All other micro-organisms tested showed normal antibody profiles that did not differ from the 1997 reference group. The seroprevalence of Chlamydia-anti-LPS antibodies was elevated markedly in the PSC patients compared with the IBD, non-IBD and blood donor groups. The outcomes in the C. trachomatis and C. pneumoniae anti-MOMP assays did not correlate with the anti-LPS-positive PSC sera. The actual presence of Chlamydia bodies in liver tissue could not be demonstrated.

CONCLUSION

Our findings suggest an association between PSC and (previous) infection with Chlamydia.

Newly characterized species-specific immunogenic Chlamydophila pneumoniae peptide reactive with murine monoclonal and human serum antibodies

A monoclonal antibody (MAb) directed against an unknown Chlamydophila pneumoniae epitope has been characterized, and the respective peptide mimotope has been identified. A murine MAb specific for C. pneumoniae was used to select peptides from phage display libraries. The peptides identified from the phage display library clones reacted specifically with the respective target murine MAb and with human sera previously identified as having antibody titers to C. pneumoniae. The selected peptide mimotope sequences tended to be composed of charged residues surrounding a core of hydrophobic residues. The peptide with the best binding could inhibit >95% of binding to the MAb, suggesting that the selected peptide binds the paratope of the respective MAb. The peptide reacted with human sera previously determined by microimmunofluorescence to have anti-C. pneumoniae antibodies. The peptide was competitively competed with the MAb against Renografin-purified, sonicated C. pneumoniae in an enzyme-linked immunosorbent assay and with whole-cell C. pneumoniae in an indirect fluorescence assay format, demonstrating its potential utility in the development of diagnostics. The use of this novel peptide may allow investigators to establish standardized assays free from cross-reactive Chlamydia trachomatis and Chlamydophila psittaci epitopes and immunoreactivity.

Cross-reaction between the genus-specific lipopolysaccharide antigen of Chlamydia spp. and the lipopolysaccharides of Porphyromonas gingivalis, Escherichia coli O119 and Salmonella newington: implications for diagnosis

Seven hybridoma clones, secreting monoclonal antibodies (MAbs) against the genus-specific chlamydial lipopolysaccharide (LPS) antigen were obtained after immunization of BALB/c mice with formalin killed Chlamydia psittaci. The antigen-binding properties of the MAbs were characterized in different immunologic reactions with purified chlamydial elementary bodies and LPS antigens from S- and R-forms of Gram-negative bacteria. Four MAbs reacted with the heterologous LPS antigens of Salmonella R-mutants, Escherichia coli Re chemotype and Acinetobacter calcoaceticus. Two MAbs demonstrated in addition a significant reactivity with Porphyromonas gingivalis, E. coli O119 and Salmonella newington LPS in ELISA, dot-ELISA and passive hemolysis assay (for clone 204G9). One MAb cross-reacted only with Salmonella minnesota Re LPS in ELISA. In indirect immunofluorescent assay six MAbs produced bright green fluorescence with all tested chlamydial strains and five of them reacted with the Re and Rb2 chemotypes of S. minnesota. The results demonstrate a wide cross-reactivity of the produced MAbs with LPS antigens of various Gram-negative bacteria, posing the question for careful consideration and interpretation of serology results for Chlamydia spp.

Association of seropositivity for antibody to Chlamydia-specific lipopolysaccharide and coronary artery disease in Japanese men

Recent studies suggest an association between Chlamydia pneumoniae infection and coronary artery disease (CAD). To examine this relationship in Japanese men, serum IgA and IgG antibodies to Chlamydia-specific lipopolysaccharide were measured by enzyme-linked immunosorbent assay in 507 patients with CAD and 200 age-matched controls. CAD patients were divided into (1) 269 patients with myocardial infarction (MI) and (2) 238 patients with chronic coronary heart disease (CCHD). Compared with the control group, the CAD group did not differ in the prevalences of both antibodies (IgA: 23.7 vs 18.0%, p=0.10; IgG: 52.7 vs 51.0%, p=0.6). The index of IgG antibody was not significantly different between CAD and control groups (median 1.19 vs 1.18, p=0.3), whereas the index of IgA antibody was significantly higher in CAD than control group (median 0.60 vs 0.46, p<0.0001). Compared with the control group, the MI group had a significantly higher prevalence of IgA antibody (28.6 vs 18.0%, p=0.007); however, there was no difference in the prevalence of IgG antibody (58.0 vs 51.0%, p=0.13). The CCHD group did not differ in the prevalences of both antibodies (IgA: 18.1 vs 18.0%, p=0.9; IgG: 45.6 vs 51.0%, p=0.2). After the adjustment for coronary risk factors, odds ratios (ORs) of seropositive antibodies for CAD were 1.59 [95% confidence interval (CI): 0.88-2.87, p=0.12] for IgA seropositivity and 0.92 (95%CI: 0.58-1.47, p=0.7) for IgG seropositivity in all cases. In the MI and control groups, ORs of seropositive antibodies for MI were 2.67 (95%CI: 1.32-5.38, p=0.007) for IgA seropositivity, and 1.36 (95%CI: 0.79-2.36, p=0.2) for IgG seropositivity. This study discovered that IgA antibody to Chlamydia was significantly associated with CAD, especially with MI, in Japanese Men and the findings suggest that chronic infection of Chlamydia may be linked to the pathogenesis of MI.

Expression of gelatinase B in trachomatous conjunctivitis

BACKGROUND/AIMS

Gelatinase B is a matrix metalloproteinase involved in extracellular matrix (ECM) breakdown often associated with scarring and other pathological disorders. It was investigated whether gelatinase B is involved in the pathogenesis of ECM degradation associated with trachomatous conjunctivitis.

METHODS

Conjunctival biopsy specimens obtained from six patients with active trachoma, six patients with active vernal keratoconjunctivitis (VKC), and seven control subjects were studied. Immunohistochemical techniques and a specific monoclonal antibody against human gelatinase B were used, and a monoclonal antibody against macrophage CD68 to identify mononuclear cells with gelatinase B immunoreactivity. In addition, quantitative zymography was used to compare the activity of gelatinase B in conjunctival biopsy specimens from seven patients with active trachoma and seven control subjects.

RESULTS

Gelatinase B was detected by immunohistochemistry only in polymorphonuclear cells located in the vascular lumens in three normal conjunctival biopsy specimens. In all trachoma specimens and in five VKC specimens, gelatinase B was localised in monocyte/macrophage cells, positive for the CD68 marker, and in polymorphonuclear cells. The majority of the latter cell type was located in intravascular spaces. Compared with VKC specimens, trachoma specimens showed significantly more immunoreactive gelatinase B monocyte/macrophage cells (52.3 (21.9) v 8.2 (6.4); p <0.001) and polymorphonuclear cells (23.2 (14.2) v 6.3 (5.4); p = 0. 013). Activated macrophages with giant cell morphology clearly stained with the gelatinase B specific monoclonal antibody were observed in trachoma specimens. Zymography revealed that gelatinase B levels in trachoma specimens were significantly higher than the levels found in normal conjunctiva (1739.6 (1078.3) v 609.3 (395.9) scanning units; p = 0.0127).

CONCLUSIONS

The increased activity of gelatinase B and numbers of inflammatory cells containing gelatinase B in trachoma specimens suggest that this enzyme plays a part in the pathogenesis of conjunctival scarring in trachoma.

Seropositivity to chlamydial lipopolysaccharide and Chlamydia pneumoniae, systemic inflammation and stable coronary artery disease: negative results of a case-control study

OBJECTIVES

We investigated the association between seropositivity to chlamydial lipopolysaccharide (cLPS) or Chlamydia pneumoniae (CP) and angiographically documented coronary artery disease (CAD), and we examined the relationship between serostatus and markers of systemic inflammation.

BACKGROUND

The potential contribution of CP to atherogenesis is still a matter of debate, and inflammation has been suggested to represent the link between infection and atherosclerotic disease.

METHODS

Subjects age 40 to 68 years were recruited for this case-control study between October 1996 and November 1997: 312 patients with at least one coronary stenosis >50% and 479 age- and sex-matched blood donors without manifest CAD or history of angina. Antibodies against cLPS and CP, C-reactive protein (CRP), fibrinogen, plasma viscosity, leukocytes and neutrophils were determined. The study had a power of >80% to detect an odds ratio (OR) of 1.55 or above for the prevalence of immunoglobulin (IgG) antibodies against cLPS at a significance level of alpha = 0.05.

RESULTS

Prevalence of IgG antibodies against cLPS was not different between cases and controls (61% vs. 62%; p = 0.7). The adjusted OR for the presence of CAD given positive IgG serostatus against cLPS was 0.9 (95% CI; 0.6 to 1.3). Similarly, no difference in the prevalence of IgG antibodies against CP was seen (88% vs. 87%; p = 0.6); the adjusted OR was 1.0 (95% CI; 0.6 to 1.6). Markers of inflammation did not show any statistically significant difference between cLPS seropositives and seronegatives.

CONCLUSIONS

Our results indicate no strong association between CP and CAD, and increased systemic inflammation in patients with CAD does not seem to be due to seropositivity to cLPS or CP.

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.

Methods of detection of Chlamydia psittaci in domesticated and wild birds

OBJECTIVE

To study the occurrence of Chlamydia psittaci in domesticated and wild birds and compare the sensitivity of molecular detection with cell culture isolation.

DESIGN

Study of cell culture isolation and PCR detection of C psittaci in avian samples.

PROCEDURE

Samples were obtained from 485 birds. Domesticated birds were selected at random from pet shops, private aviaries and zoos, while wild birds were captured locally, sampled, and immediately released. Swabs were collected from choanal slit, conjunctiva and cloaca of each bird and pooled. Samples were divided into equal portions for use in PCR dot-blot and cell culture detection. PCR and dot-blot detection was based on the ompB gene.

RESULTS

Prevalence of infection varied markedly between flocks of captive birds. It was highest where there were frequent changes in the flock members or where there were many birds confined in small areas. C psittaci was not detected in wild birds or water birds. The sensitivity of cell culture compared to PCR dot-blot detection was 68%. All samples positive by cell culture were also positive by PCR.

CONCLUSIONS

PCR-dot blot detection of C psittaci in birds appears to be more sensitive than cell culture isolation in this study. C psittaci infection of birds may occur in clinically normal captive birds.

Evaluation of PCR, culture, and serology for diagnosis of Chlamydia pneumoniae respiratory infections

We prospectively studied 156 patients with a diagnosis of community-acquired pneumonia requiring admission. Several respiratory specimens were obtained for the detection of Chlamydia pneumoniae by cell culture and PCR. Three serum samples were obtained from each patient. Serological diagnosis of a C. pneumoniae infection was determined by the microimmunofluorescence (MIF) test, the complement fixation (CF) test, and recombinant lipopolysaccharide (LPS) enzyme-linked immunosorbent assay (ELISA; referred to as the rDNA LPS ELISA). Twenty-three patients (15%) had serological results compatible with acute C. pneumoniae infection; nine (39%) of these subjects were C. pneumoniae PCR positive. Twenty-two patients (14%) had positive PCR results without serological evidence of an acute C. pneumoniae infection. An attempt was made to calculate the sensitivities and specificities of the MIF test, rDNA LPS ELISA, and PCR for the diagnosis of chlamydial community-acquired pneumonia. Several "gold standards" were defined. Generally, the sensitivities of the rDNA LPS ELISA and MIF were comparable, while the sensitivity of the CF test was shown to be very low. Independent of the gold standard used, the best PCR results were obtained with nasopharyngeal specimens. However, the predictive value of a positive C. pneumoniae PCR result for patients with community-acquired pneumonia remains unknown and may be low. Although a widely accepted gold standard is still lacking, the rDNA LPS ELISA may currently be the preferred tool for diagnosing acute respiratory Chlamydia infections in routine clinical practice. However, the MIF test remains the method of choice for determining the prevalence of C. pneumoniae infections in a given community.

Chlamydia pneumoniae antibody response in patients with acute myocardial infarction and their follow-up

STUDY POPULATIONS

This study concerned the possible relations between seroreactivity to Chlamydia pneumoniae and myocardial infarction. A group of 29 patients with acute myocardial infarction (AMI), 74 members of a healthy control group, and a subgroup of 24 members of a healthy control group matched for age, sex, and coronary risk factors (HCM) were included in the study. In addition, we evaluated the AMI group in a 1-year patients' follow-up study. We used two different tests to detect anti-C. pneumoniae antibodies: recombinant enzyme immunoassay antilipopolysaccharide antibodies and a reference microimmunofluorescence test.

RESULTS

High titers of C. pneumoniae microimmunofluorescence antibodies were found in 89.65% of the AMI group and in 25% of the HCM group (p = 0.0000065). Immunoglobulin A-microimmunofluorescence was 51.72% in the AMI group and 20.83% in the HCM group (p = 0.0042). Immunoglobulin G and immunoglobulin A antilipopolysoccharide titers were 65.51% and 62.60% in the AMI group and 20.83% in the HCM group, respectively (p = 0.006). High concentrations of interleukin-6 were found in 86.20% of our AMI group (p value = 54.38 pg/ml) when compared with the control group. A good correlation between interleukin-6 levels and immunoglobulin A-lipopolysaccharide titers (r = 0.658) was found.

CONCLUSION

The presence of a high prevalence rate and high titers of immunoglobulin G and immunoglobulin A-specific anti-C. pneumoniae antibodies in AMI at admission demonstrated the presence of a specific anti-C. pneumoniae immunization in the AMI population.

Lipopolysaccharide biosynthesis genes in koala type I Chlamydia: cloning and characterization

We showed in 1988 that there are two strains of Chlamydia psittaci which infect the koala (Phascolarctos cinereus). In order to further investigate the role of these chlamydial strains in pathogenesis, we have attempted to identify genes of koala type I strain chlamydia which are involved in the immunogenic response. Transformation of Escherichia coli with a plasmid containing a 6.3-kb fragment (pKOC-10) of C. psittaci DNA caused the appearance of a specific chlamydial lipopolysaccharide (LPS) epitope on the host strain. The smallest DNA fragment capable of inducing the expression of chlamydial LPS was an XbaI fragment, 2.4 kb in size (pKOC-5). DNA sequence analysis of the complete fragment revealed regions of high identity, at the amino acid level, to the gseA genes of C. pneumoniae, C. psittaci 6BC and C. trachomatis, and the kdtA gene of E. coli which code for transferases catalysing the addition of 3-deoxy-D-manno-octulosonic acid (Kdo) residues to lipid A. Two open reading frames (ORFs) of 1,314 and 501 nucleotides in size, within the 2.4-kb fragment, were evident, and mRNA species corresponding to these ORFs were detected by Northern analysis. Both ORF1 and ORF2 are required for the appearance of chlamydia-specific LPS on the surface of recombinant E. coli.

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.

Chlamydial antibodies in semen: search for "silent" chlamydial infections in asymptomatic andrological patients

The importance of a serological diagnostic workup in male genitourinary infections with Chlamydia trachomatis and its relevance for male infertility is still under debate. In a prospective study, antichlamydial serum and seminal plasma antibodies of 131 consecutive patients (mean age 31: 20-57) without evidence of acute urethritis and with negative urethral chlamydial culture were investigated. The antibody determination was carried out with a genus specific rELISA. In patients with positive seminal plasma IgA, chlamydial genome was evaluated by polymerase chain reaction (PCR). The results were associated with standard semen parameters according to evaluated WHO guidelines. Specific serum IgG antibodies were found in 51 patients (38.9%), IgA in 39 (29.7%); both antibodies were present in 25 patients (19%). Seminal plasma IgG was demonstrable in seven patients (5.3%), IgA in 26 (19.9%), and five patients were positive for both antibody classes (3.8%). Of the 26 men positive for specific seminal plasma IgA antibodies 12 did not demonstrate a serum antibody reaction. Only two patients with positive IgA titers in their seminal plasma showed a positive chlamydial genome reaction in PCR (8%). Men with antichlamydial seminal plasma IgA and/or IgG did not differ significantly in any of the standard semen sperm parameters from men testing negative for antibodies, with the exception of peroxidase positive leukocytes (p < 0.01), nor was there an association between any of the ejaculate parameters and any of the antibody titers. The data of about 40% antichlamydial serum antibody findings without a significant association with seminal plasma antibodies and no clinical signs of infection seem to reflect a history of urogenital infection. The unique presence of seminal plasma IgA in 12 of 26 cases may be caused by a local antibody response due to a "silent" infection. Thus, seminal plasma IgA was associated with signs of inflammation, whereas, there was no association with genome or pathogen demonstration. Therefore, it appears to be necessary to reevaluate genus-specific seminal plasma IgA antibodies with a species-specific microimmunofluorescence test and to compare these results with a genome screening using PCR or in situ hybridization.

Serological diagnosis of ovine enzootic abortion by comparative inclusion immunofluorescence assay, recombinant lipopolysaccharide enzyme-linked immunosorbent assay, and complement fixation test

Since the 1950s, serological diagnosis of ovine enzootic abortion (OEA), caused by strains of Chlamydia psittaci, has been based mainly on the complement fixation test (CFT), which is neither particularly sensitive nor specific since antibodies to other chlamydial and enterobacterial pathogens may be detected. In this study. a recombinant enzyme-linked immunosorbent assay (rELISA) (medac, Hamburg, Germany), based on a unique chlamydial genus-specific epitope of Chlamydia trachomatis L2 lipopolysaccharide, was evaluated for sensitivity and specificity as a primary screening assay for OEA by comparison with the CFT. A comparative inclusion immunofluorescence assay (IFA), in which antibody titers to C. psittaci and Chlamydia pecorum were examined, was used as the reference test for 573 serum samples from four flocks. Reactivity to C. pecorum was measured since inapparent intestinal infections by C. pecorum are believed to be common in British flocks. In detecting positive sera from an abortion-affected flock, in which a C. pecorum infection was also suggested by IFA, the rELISA outperformed the CFT with significant evidence for increased sensitivity (P = 0.003). In two flocks in which C. pecorum infections alone were suggested by IFA, the rELISA and CFT were prone to detect low levels of false-positive results, but the values were not significant. The rELISA provided results in one flock in which sera that were anticomplementary could not be resolved by the CFT. In another flock in which abortion had not occurred but infection by both chlamydial species was suspected, no significant difference was found between the sensitivities of the rELISA and CFT. The rELISA could not differentiate ovine C. psittaci and C. pecorum infections but was shown to be a more sensitive primary screening test for OEA than was the CFT, particularly where abortion had occurred and even when antibodies due to additional inapparent infection(s) by C. pecorum were present.

Antibodies to lipopolysaccharide

Lipopolysaccharides (LPS) are indispensable structural components of the Gram-negative bacterial outer membrane and are major determinants of virulence in pathogenic species. In the infected host LPS is better known as endotoxin where it acts as a potent stimulator of the inflammatory response. This article reviews the methods for the production and measurement of anti-LPS antibodies, and then describes the uses to which these methods have been employed. Antibodies to LPS (either monoclonal or polyclonal) may be used directly as immunotherapeutic agents for the treatment of Gram-negative sepsis or endotoxaemia, or as probes for the diagnosis and epidemiological investigation of Gram-negative bacterial infections. Antibodies are useful tools for investigation of the chemical structure of LPS, its expression on bacteria and to study the role of LPS in pathogenic mechanisms. The detection and quantitation of anti-LPS antibodies has formed the basis of classical and more recent serological studies of major bacterial infections.

The inflammatory cytokine response to Chlamydia trachomatis infection is endotoxin mediated

Chlamydia trachomatis is a major etiologic agent of sexually transmitted diseases. Although C. trachomatis is a gram-negative pathogen, chlamydial infections are not generally thought of as endotoxin-mediated diseases. A molecular characterization of the acute immune response to chlamydia, especially with regard to the role of its lipopolysaccharide (LPS), remains to be undertaken. We extracted 15 mg of LPS from 5 x 10(12) C. trachomatis elementary bodies (EB) for analysis of structure and biological activity. When methylated lipid A was subjected to high-pressure liquid chromatography followed by mass spectrometry, the majority of the lipid A was found to be pentaacyl. The endotoxin activities of whole C. trachomatis EB and purified LPS were characterized in comparison with whole Salmonella minnesota R595 and with S. minnesota R595 LPS and lipooligosaccharide from Neisseria gonorrhoeae. Both C. trachomatis LPS and whole EB induced the release of tumor necrosis factor alpha from whole blood ex vivo, and C. trachomatis LPS was capable of inducing the translocation of nuclear factor kappa B in a Chinese hamster ovary fibroblast cell line transfected with the LPS receptor CD14. In both assays, however, C. trachomatis was approximately 100-fold less potent than S. minnesota and N. gonorrhoeae. The observation that C. trachomatis is a weak inducer of the inflammatory cytokine response correlates with the clinical observation that, unlike N. gonorrhoeae infection, genital tract infection with C. trachomatis is often asymptomatic. The ability of specific LPS antagonists to completely inhibit the tumor necrosis factor alpha-inducing activity of whole C. trachomatis EB suggests that the inflammatory cytokine response to chlamydia infection may be mediated primarily through LPS. This implies that the role of other surface protein antigens, at least in terms of eliciting the proinflammatory cytokine response, is likely to be minor.

Detection of Chlamydia trachomatis in semen by antibody-enzyme immunoassay compared with polymerase chain reaction, antigen-enzyme immunoassay, and urethral cell culture

OBJECTIVE

To compare the results obtained by four different techniques for the detection of Chlamydia trachomatis in the male genital tract.

DESIGN

Prospective study.

SETTING

Andrology unit of a university hospital.

PATIENTS

Male infertility patients.

INTERVENTIONS

Analysis of semen samples and urethral swabs for the presence of C. trachomatis by recombinant antibody-enzyme-linked immunosorbent assay (rELISA), polymerase chain reaction (PCR), antigen-enzyme immunoassay (EIA) and McCoy cell culture.

MAIN OUTCOME MEASURE

Detection of C. trachomatis.

RESULTS

In 57 of 205 semen samples (27.8%) immunoglobulin A-antibodies against C. trachomatis were found. In contrast, only 1 of 56 semen samples (1.8%) was positive for C. trachomatis-DNA by PCR, only 1 of 139 semen samples (0.7%) was positive by antigen-EIA, and only 4 of 173 urethral swabs (2.3%) grew C. trachomatis in cell culture.

CONCLUSIONS

The discrepancy of positive results found by the antibody-rELISA and direct methods for the detection of C. trachomatis indicates successful eradication of the microorganism in > 90% of antibody-positive men. Therefore, detection of antibodies against C. trachomatis in seminal plasma appears to be of limited diagnostic value.

Synthesis of carboxyl-reduced analogues related to the Chlamydia-specific Kdo trisaccharide epitope

The disaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-3-deoxy-a lph a-D- manno-2-octulopyranoside (8), allyl O-(3-deoxy-alpha-D-manno-2-octulopyranosyl)-(2-->8)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosidonate) (24), and allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)-3-deoxy-a lph a-D- manno-2-octulopyranoside (35), and the trisaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-3-deoxy-a lph a-D-manno-2-octulopyranoside (13) and allyl O-(3-deoxy-alpha-D-manno-2-octulopyranosyl)-(2-->8)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosidonate) (30) were prepared. The ketosidic linkages were formed in good yields and high stereoselectivity by BF3 . Et2O-catalyzed reaction of the per-O-acetylated 3-deoxy-alpha-D-manno-2-octulopyranosyl fluoride derivative (16) with 8-O-SiButMe2 derivatives 19 and 21. Coupling reactions using the Kdo monosaccharide bromide derivative 4 or the alpha-(2-->8)-linked Kdo disaccharide bromide derivatives 9 and 26 were performed under Helferich conditions in MeCN or MeNO2, respectively. The disaccharide halides were prepared in good overall yields starting from the readily available allyl beta-glycoside of Kdo. The deprotected oligosaccharides correspond to the genus-specific lipopolysaccharide epitope of Chlamydia and part structures thereof, containing the carboxyl-reduced Kdo-residues at the distal and proximal position of the Kdo trisaccharide epitope, respectively.

Preparation and structural analysis of oligosaccharide monophosphates obtained from the lipopolysaccharide of recombinant strains of Salmonella minnesota and Escherichia coli expressing the genus-specific epitope of Chlamydia lipopolysaccharide

The lipopolysaccharide of the recombinant strain Salmonella minnesota r595-207 expressing the genus-specific epitope of Chlamydia lipopolysaccharide [Holst, O., Brade, L., Kosma, P. and Brade, H. (1991) J. Bacteriol, 173, 1862-1866] was sequentially de-O- and de-N-acylated by mild hydrazinolysis and treatment with 4 M KOH, respectively. The resulting mixture of compounds was separated by high-performance anion-exchange chromatography and gel-permeation chromatography, yielding four oligosaccharide phosphates two of which were readily identified by their 1H-NMR- and 13C-NMR spectra as alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcpN-(1-6)-alpha-D-Glcp N 1,4'-bisphosphate (tetrasaccharide bisphosphate; Kdo = 3-deoxy-D-manno-octulopyranosonic acid) and alpha-Kdo-(2-8)-alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcpN-(1-6) -alpha-D- GlcpN 1,4'-bisphosphate (pentasaccharide bisphosphate) [Holst, O., Broer, W., Thomas-Oates, J.E., Mamat, U. and Brade, H. (1993) Eur. J. Biochem. 214, 703-710]. The structures of the other two compounds were established by chemical analysis, NMR spectroscopy, and fast-atom-bombardment mass spectrometry as alpha-Kdo- (2-4)-alpha-Kdo-(2-6)-beta-D-GlcpN-(1-6)-alpha-D-GlcpN 1-phosphate (tetrasaccharide 1-phosphate) and alpha-Kdo-(2-8)-alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcpN-(1-6) -alpha-D- GlcpN 1-phosphate (pentasaccharide 1-phosphate). alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcpN-(1-6)-alpha/beta- D-GlcpN 4'-phosphate (tetrasaccharide 4'-phosphate) and alpha-Kdo-(2-8)-alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcpN-(1-6) -alpha/beta-D-GlcpN 4'-phosphate (pentasaccharide 4'-phosphate) were prepared from the 1,4'-bisphosphates isolated from the recombinant strain Escherichia coli F515-207 by treatment with alkaline phosphatase and purification by high-performance anion-exchange chromatography and gel-permeation chromatography. Their structures were characterised by chemical analysis, NMR spectroscopy, and fast-bombardment mass spectrometry.

Synthesis of pentasaccharide core structures corresponding to the genus-specific lipopolysaccharide epitope of Chlamydia

The trisaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->6)-O-2-aceta mid o-2-deoxy- beta-D-glucopyranosyl-(1-->6)-2-acetamido-2-deoxy-alpha- and -beta-D-glucopyranoside (16a and 16b), the tetrasaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->6)-O-2-aceta mid o-2-deoxy- beta-D-glucopyranosyl-(1-->6)-2-acetamido-2-deoxy-alpha- and -beta-D-glucopyranoside (19a and 19b), and the pentasaccharides allyl O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->8)-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->4)-O-(sodium 3-deoxy-alpha-D-manno-2-octulopyranosylonate)-(2-->6)-O-2-aceta mid o-2-deoxy-bet a -D-glucopyranosyl-(1-->6)-2-acetamido-2-deoxy-alpha- and -beta-D-glucopyranoside (23a and 23b) were prepared. The glycosidic linkages were formed using 1,3,4,6-tetra-O-acetyl-2-chloroacetamido-2-deoxy-beta-D-glucopy ran ose (6) and FeCl3 as promoter as well as per-O-acetylated Kdo mono- and di-saccharide bromide derivatives (12 and 20) under Helferich conditions. The oligosaccharides, which correspond to dephosphorylated part-structures of enterobacterial and chlamydial lipopolysaccharides, were characterized by NMR spectroscopy as well as plasma desorption and matrix-assisted laser desorption mass spectrometry.

Occurrence of antibodies against chlamydial lipopolysaccharide in human sera as measured by ELISA using an artificial glycoconjugate antigen

An artificial glycoconjugate containing, as a ligand, the deacylated carbohydrate backbone of a recombinant Chlamydia-specific lipopolysaccharide was used as a solid-phase antigen in ELISA to measure antibodies against chlamydial LPS. The specificity and reproducibility of the assay was shown by using a panel of prototype monoclonal antibodies representing the spectrum of antibodies also occurring in patient sera. These mAbs recognized Chlamydia-specific epitopes [alpha 2-->8-linked disaccharide of 3-deoxy-D-manno-octulosonic acid (Kdo) or the trisaccharide alpha Kdo-(2-->8)-alpha Kdo-(2-->4)-alpha Kdo] or those shared between chlamydial and Re-type LPS (alpha Kdo, alpha 2-->4-linked Kdo disaccharide). The assay was used to measure IgG, IgA and IgM antibodies against chlamydial LPS in patients with genital or respiratory tract infections. In comparison to the results obtained with sera from blood donors, it became evident that both types of infection result in significant changes in the profile of LPS antibodies.

Specificity of rabbit antisera against the rough lipopolysaccharide of Salmonella minnesota strain R7 (chemotype Rd1P-)

Rabbit polyclonal antibodies against the lipopolysaccharide (LPS) of the Rd1P- mutant strain R7 of Salmonella minnesota were serologically characterized using R7 LPS, dephosphorylated LPS, deacylated LPS, deacylated, dephosphorylated and reduced LPS, and synthetic partial structures. The latter comprised partial structures of the core region of Rd1P- LPS bound to the beta 1-->6-linked glucosamine dissacharide with two amide-linked 3-hydroxytetradecanoic acid residues or artificial glycoconjugates comprised of the synthetic oligosaccharides coupled to bovine serum albumin. Using a passive hemolysis and an enzyme immunoassay, absorption and inhibition experiments, the antibody specificites present could be determined. One group of antibodies required components of the core region and the phosphorylated glucosamine disaccharide of the lipid A moiety for binding. The majority of phosphate-independent antibodies was directed against the trisaccharide L-glycero-alpha-D-manno-heptopyranose(1-->3)- L-glycero-alpha-D-manno-heptopyranose(1-->5)3-deoxy-D-manno-oct ulo sonic acid. Antibodies against the 1-->3- and 1-->7-linked heptose disaccharides and against a single heptose were also detected, however, with low titers. No antibodies were found which required the presence of fatty acids.

A broadly cross-protective monoclonal antibody binding to Escherichia coli and Salmonella lipopolysaccharides

During the last decade, episodes of sepsis have increased and Escherichia coli has remained the most frequent clinical isolate. Lipopolysaccharides (LPS; endotoxin) are the major toxic and antigenic components of gram-negative bacteria and qualify as targets for therapeutic interventions. Molecules that neutralize the toxic effects of LPS are actively investigated. In this paper, we describe a murine monoclonal antibody (MAb; WN1 222-5), broadly cross-reactive and cross-protective for smooth (S)-form and rough (R)-form LPS. As shown in enzyme-linked immunosorbent assay and the passive hemolysis assay, WN1 222-5 binds to the five known E. coli core chemotypes, to Salmonella core, and to S-form LPS having these core structures. In immunoblots, it is shown to react with both the nonsubstituted core LPS and with LPS carrying O-side chains, indicating the exposure of the epitope in both S-form and R-form LPS. This MAb of the immunoglobulin G2a class is not lipid A reactive but binds to E. coli J5, an RcP+ mutant which carries an inner core structure common to many members of the family Enterobacteriaceae. Phosphate groups present in the inner core contribute to the epitope but are not essential for the binding of WN1 222-5 to complete core LPS. Cross-reactivity for clinical bacterial isolates is broad. WN1 222-5 binds to all E. coli clinical isolates tested so far (79 blood isolates, 80 urinary isolates, and 21 fecal isolates) and to some Citrobacter, Enterobacter, and Klebsiella isolates. This pattern of reactivity indicates that its binding epitope is widespread among members of the Enterobacteriaceae. WN1 222-5 exhibits biologically relevant activities. In vitro, it inhibits the Limulus amoebocyte lysate assay activity of S-form and R-form LPS in a dose-dependent manner and it neutralizes the LPS-induced release of clinically relevant monokines (interleukin 6 and tumor necrosis factor). In vivo, WN1 222-5 blocks endotoxin-induced pyrogenicity in rabbits and lethality in galactosamine-sensitized mice. The discovery of WN1 222-5 settles the long-lasting controversy over the existence of anti-core LPS MAbs with both cross-reactive and cross-protective activity, opening new possibilities for the immunotherapy of sepsis caused by gram-negative bacteria.

Specificity of rabbit antisera against the rough lipopolysaccharide of Salmonella minnesota R4 (chemotype Rd2P-)

Rabbit polyclonal antibodies against the rough mutant lipopolysaccharide (LPS) of Salmonella minnesota R4 (chemotype Rd2P-) were serologically characterized by using R4 LPS, deacylated LPS, dephosphorylated LPS, and synthetic partial structures, including compounds comprising the core region of Rd2P- LPS bound to the beta 1-->6-linked glucosamine disaccharide with two amide-linked 3-hydroxytetradecanoic acid residues or coupled to bovine serum albumin. By using a passive hemolysis assay and an enzyme immunoassay and absorption and inhibition experiments, the antibody specificities present could be determined. One group of antibodies required components of the core oligosaccharide (with or without the side chain 3-deoxy-D-manno-octulosonic acid [Kdo]) and the phosphorylated glucosamine disaccharide of the lipid A moiety for binding. The phosphate-independent antibodies were directed against the core oligosaccharide, recognizing an epitope consisting of one terminal heptose linked to Kdo or to the reducing moiety of the alpha 2-->4-linked Kdo disaccharide. Antibodies requiring the presence of acyl residues and those reacting with a single heptose or Kdo residue were not detected.

Structural analysis of two oligosaccharide bisphosphates isolated from the lipopolysaccharide of a recombinant strain of Escherichia coli F515 (Re chemotype) expressing the genus-specific epitope of Chlamydia lipopolysaccharide

The lipopolysaccharide of the recombinant strain Escherichia coli F515-207, expressing the genus-specific epitope of Chlamydia lipopolysaccharide, was sequentially de-O- and de-N-acylated by mild hydrazinolysis and treatment with 4 M KOH, respectively, yielding two oligosaccharide bisphosphates which were isolated by high-performance anion-exchange chromatography and gel-permeation chromatography. Their structures were determined by chemical analysis, NMR spectroscopy, and mass spectrometry as alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcN-(1-6)-alpha-D-GlcN 1,4'-P2 (tetrasaccharide bisphosphate) and alpha-Kdo-(2-8)-alpha-Kdo-(2-4)-alpha-Kdo-(2-6)-beta-D-GlcN-(1-6)-alpha- D-GlcN 1,4'-P2 (pentasaccharide bisphosphate).

Staining of surface antigens of Chlamydia trachomatis L2 in tissue culture

Surface labeling of chlamydial elementary and reticulate bodies in L929 cells infected with Chlamydia trachomatis serotype L2 was monitored by using monoclonal antibodies (MAb) against the major outer membrane protein and lipopolysaccharide (LPS). Different staining and fixation procedures were used to detect these surface antigens during the developmental cycle. Anti-major outer membrane protein MAb yielded a clear staining pattern of exclusively chlamydial inclusions independent of the fixation or staining technique used. Anti-LPS MAb gave a faint staining pattern of reticulate bodies when methanol fixation was used and showed that LPS was released from chlamydiae into the host cell cytoplasm and into the surroundings of the infected host cell. However, when paraformaldehyde-glutardialdehyde fixation was used, extracellular LPS staining was not observed. The data show that chlamydial LPS is loosely bound in the bacterial outer membrane but suggest that shedding of LPS is a fixation artifact.

A nuclear magnetic resonance spectroscopic investigation of Kdo-containing oligosaccharides related to the genus-specific epitope of Chlamydia lipopolysaccharides

The 1H- and 13C-NMR parameters, chemical shifts and coupling constants, for the pentasaccharide of the genus-specific epitope of Chlamydia lipopolysaccharide and related di-, tri-, and tetra-saccharides have been measured and assigned completely using 1D and 2D techniques, and their structures have been confirmed. NOE experiments indicated the preferred conformation of the pentasaccharide and the component oligosaccharides. The 3JH,H demonstrate a change in conformation by rotation of the C-6-C-7 bond of the side chain of the (2----8)-linked Kdo (unit b) in alpha-Kdo-(2----8)-alpha-Kdo-(2----4)-alpha-Kdo-(2----6)-beta-GlcN-(1--- -6)- GlcNol, alpha-Kdo-(2----8)-alpha-Kdo-(2----4)-alpha-Kdo-(2----6)-beta-GlcNAc-(1- ---O)- allyl, and alpha-Kdo-(2----8)-alpha-Kdo-(2----4)-alpha-Kdo-(2----O)-allyl relative to that preferred in alpha-Kdo-(2----4)-alpha-Kdo-(2----6)-beta-GlcNAc-(1----O)-allyl, alpha-Kdo-(2----8)-alpha-Kdo-(2----O)-allyl, alpha-Kdo-(2----4)-alpha-Kdo-(2----O)-allyl, and alpha-Kdo-(2----6)-beta-GlcNAc-(1----O)-allyl, irrespective of the size of the aglycon, e.g., allyl or beta-D-GlcN residues. The conformational results have been substantiated by computer calculations using the HSEA approach.

A synthetic glycoconjugate representing the genus-specific epitope of chlamydial lipopolysaccharide exhibits the same specificity as its natural counterpart

The tetrasaccharide 3-deoxy-alpha-D-manno-2-octulosonic acid (alpha-KDO) (2----8)-alpha-KDO(2----4)-alpha-KDO(2----6)-beta GlcNAc, a partial structure of chlamydial lipopolysaccharide (LPS) representing a genus-specific epitope, was synthesized and covalently linked to bovine serum albumin, resulting in an artificial glycoconjugate antigen. Mice were immunized with the glycoconjugate to prepare chlamydia-specific monoclonal antibodies. They were selected with chlamydia-specific LPS antigens and the structurally and antigenically related Re-type LPS of a Salmonella minnesota rough mutant. Characterization of the selected antibodies was by (i) hemagglutination of sheep erythrocytes coated with recombinant chlamydia-specific LPS, (ii) inhibition by synthetic polyacrylamide derivatives containing the genus-specific epitope or partial structures thereof, (iii) enzyme immunoassay with recombinant LPS and synthetic bovine serum albumin glycoconjugates as solid-phase antigens, (iv) immunofluorescence of L929 monolayers infected with Chlamydia psittaci or C. trachomatis, and (v) Western immunoblots with glycoconjugates and LPS as the antigen. Two groups of monoclonal antibodies were obtained; the monoclonal antibodies in one group cross-reacted with chlamydial and Re-type LPS, but those of the other group were chlamydia specific. Among the latter, KDO trisaccharide-specific antibodies that had the same epitope specificity as antibodies obtained after immunization with chlamydial elementary bodies were identified; however, they exhibited a more than 100-fold higher affinity. In addition, antibodies that bound preferentially to the 2.8-linked KDO disaccharide were detected, although with lower affinity. The data show that the artificial glycoconjugate antigen is similar to its natural counterpart.

Structure, serological specificity, and synthesis of artificial glycoconjugates representing the genus-specific lipopolysaccharide epitope of Chlamydia spp

The human bacterial pathogens Chlamydia spp. possess a genus-specific lipopolysaccharide as a major surface antigen, the structure of which has been determined by analytical chemistry as Kdop alpha 2-8-Kdop alpha 2-4-Kdop alpha 2-6GlcNp beta 1-6-GlcNol (Kdo, 3-deoxy-D-manno-2-octulosonic acid). Immunochemical studies on this pentasaccharide and the chemically synthesized partial structures Kdop alpha 2-8-Kdop alpha 2-4-Kdop alpha 2-6GlcNp beta, Kdop alpha 2-8-Kdop alpha 2-4-Kdop alpha, Kdop alpha 2-4-Kdop alpha, Kdop alpha 2-8-Kdop alpha, and Kdop alpha using artificial glycoconjugate antigens and monoclonal antibodies showed that fatty acids and phosphoryl groups (as present in native lipopolysaccharide) are dispensable for constitution of the genus-specific epitope and that the minimal structure to exhibit chlamydia specificity is the Kdo trisaccharide moiety.