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Capsular Polysaccharide (capsular + polysaccharide)

Distribution by Scientific Domains

Life Sciences	41%
Medical Sciences	38%
Chemistry	19%

Selected Abstracts

Synthesis of Structures Corresponding to the Capsular Polysaccharide of Neisseria meningitidis Group A.

CHEMINFORM, Issue 4 2006
Rikard Slaettegaard
No abstract is available for this article. [source]

Capsular polysaccharide from Actinobacillus actinomycetemcomitans inhibits IL-6 and IL-8 production in human gingival fibroblast

JOURNAL OF PERIODONTAL RESEARCH, Issue 2 2003
Yuko Ohguchi
We previously reported that a capsular polysaccharide (CP) from Actinobacillus actinomycetemcomitans Y4 induces bone resorption in a mouse organ culture system and osteoclast formation in mouse bone marrow cultures. However, the effects of A. actinomycetemcomitans Y4 CP on human gingival fibroblasts (HGF) are still unclear. The present study was undertaken to test the hypothesis that A. actinomycetemcomitans Y4 CP alters the production of inflammatory cytokines, such as interleukin-6 (IL-6) and IL-8 by HGF. When HGF were cultured with various concentrations of Y4 CP for 24 h, IL-6 and IL-8 production decreased in a concentration-dependent manner. Y4 CP (100 ,g/ml) suppressed the release of IL-6 from 9.09 ± 0.08 ng/ml to 0.34 ± 0.21 ng/ml (P < 0.01) and IL-8 production decreased from 3.76 ± 0.03 ng/ml to 0.09 ± 0.01 ng/ml (P < 0.01). Y4 CP suppressed 70,80% of the release of IL-6 and IL-8 from HGF stimulated with Y4 lipopolysaccharide (LPS), too. Interestingly, anti- A. actinomycetemcomitans Y4 CP completely inhibited the effect of A. actinomycetemcomitans Y4 CP on IL-6 and IL-8 production from HGF. These results indicate that Y4 CP inhibits the release of IL-6 and IL-8 from HGF, suggesting that A. actinomycetemcomitans Y4 modulates the inflammatory response in periodontitis. Remarkably, this inhibitory effect was reversed by specific anti- A. actinomycetemcomitans Y4 CP suggesting an important relationship between the organism and the humoral host response. [source]

Capsule enlargement in Cryptococcus neoformans confers resistance to oxidative stress suggesting a mechanism for intracellular survival

CELLULAR MICROBIOLOGY, Issue 10 2008
Oscar Zaragoza
Summary Cryptococcus neoformans is a facultative intracellular pathogen. The most distinctive feature of C. neoformans is a polysaccharide capsule that enlarges depending on environmental stimuli. The mechanism by which C. neoformans avoids killing during phagocytosis is unknown. We hypothesized that capsule growth conferred resistance to microbicidal molecules produced by the host during infection, particularly during phagocytosis. We observed that capsule enlargement conferred resistance to reactive oxygen species produced by H2O2 that was not associated with a higher catalase activity, suggesting a new function for the capsule as a scavenger of reactive oxidative intermediates. Soluble capsular polysaccharide protected C. neoformans and Saccharomyces cerevisiae from killing by H2O2. Acapsular mutants had higher susceptibility to free radicals. Capsular polysaccharide acted as an antioxidant in the nitroblue tetrazolium (NBT) reduction coupled to ,-nicotinamide adenine dinucleotide (NADH)/phenazine methosulfate (PMS) assay. Capsule enlargement conferred resistance to antimicrobial peptides and the antifungal drug Amphotericin B. Interestingly, the capsule had no effect on susceptibility to azoles and increased susceptibility to fluconazole. Capsule enlargement reduced phagocytosis by environmental predators, although we also noticed that in this system, starvation of C. neoformans cells produced resistance to phagocytosis. Our results suggest that capsular enlargement is a mechanism that enhances C. neoformans survival when ingested by phagocytic cells. [source]

Differential cytokine expression by human dendritic cells in response to different Porphyromonas gingivalis capsular serotypes

JOURNAL OF CLINICAL PERIODONTOLOGY, Issue 10 2009
Rolando Vernal
Abstract Aim: Capsular polysaccharides play an important role in the virulence of Gram-positive and Gram-negative bacteria. In Porphyromonas gingivalis, six serotypes have been described based on capsular antigenicity and its pathogenicity has been correlated both in vitro and in animal models. This study aimed to investigate the differential response of human dendritic cells (DCs) when stimulated with different P. gingivalis capsular serotypes. Materials and Methods: Using different multiplicity of infection (MOI) of the encapsulated strains K1,K6 and the non-encapsulated K, strain of P. gingivalis, the mRNA expression levels for interleukin (IL)-1,, IL-2, IL-5, IL-6, IL-10, IL-12, IL-13, interferon (IFN)- ,, tumour necrosis factor (TNF)- ,, and TNF- , in stimulated DCs were quantified by real-time reverse transcription-polymerase chain reaction. Results: All P. gingivalis capsular serotypes induced a T-helper type 1 (Th1) pattern of cytokine expression. K1- and K2-stimulated DCs expressed higher levels of IL-1,, IL-6, IL-12p35, IL-12p40, and IFN- , and at lower MOI than DCs stimulated with the other strains. Conclusions: These results demonstrate a differential potential of P. gingivalis capsular serotypes to induce DC responses and a higher capacity of strains K1 W83 and K2 HG184 than other K serotypes to trigger cytokine expression. [source]

Identification of structural and molecular determinants of the tyrosine-kinase Wzc and implications in capsular polysaccharide export

MOLECULAR MICROBIOLOGY, Issue 5 2010
Emmanuelle Bechet
Summary Capsular polysaccharides are well-established virulence factors of pathogenic bacteria. Their biosynthesis and export are regulated within the transmembrane polysaccharide assembly machinery by the autophosphorylation of atypical tyrosine-kinases, named BY-kinases. However, the accurate functioning of these tyrosine-kinases remains unknown. Here, we report the crystal structure of the non-phosphorylated cytoplasmic domain of the tyrosine-kinase Wzc from Escherichia coli in complex with ADP showing that it forms a ring-shaped octamer. Mutational analysis demonstrates that a conserved EX2RX2R motif involved in subunit interactions is essential for polysaccharide export. We also elucidate the role of a putative internal regulatory tyrosine and we show that BY-kinases from proteobacteria autophosphorylate on their C-terminal tyrosine cluster via a single-step intermolecular mechanism. This structure-function analysis also allows us to demonstrate that two different parts of a conserved basic region called the RK-cluster are essential for polysaccharide export and for kinase activity respectively. Based on these data, we revisit the dichotomy made between BY-kinases from proteobacteria and firmicutes and we propose a unique process of oligomerization and phosphorylation. We also reassess the function of BY-kinases in the capsular polysaccharide assembly machinery. [source]

1,,25-Dihydroxyvitamin D3 modulates the murine antibody response to pneumococcal capsular polysaccharide serotype 3 through IL-12

EUROPEAN JOURNAL OF IMMUNOLOGY, Issue 6 2005
Axel Jeurissen
Abstract 1,,25-Dihydroxyvitamin D3 [1,,25(OH)2D3] is a steroid hormone that regulates calcium metabolism. Besides, 1,,25(OH)2D3 also has pronounced immunomodulatory effects: it strongly inhibits dendritic cell (DC) maturation and impairs IL-12 production. We studied the effect of 1,,25(OH)2D3 on the antibody response to pneumococcal capsular polysaccharide (caps-PS) serotype 3. 1,,25(OH)2D3 inhibited the IgG2a antibody response to caps-PS serotype 3. Besides, 1,,25(OH)2D3 also inhibited IL-12 production and maturation of DC. Anti-IL-12 and exogenous IL-12, respectively, inhibited and stimulated the IgG2a antibody response to caps-PS serotype 3. Exogenous IL-12 abrogated the effect of 1,,25(OH)2D3 on the IgG2a antibody response to caps-PS serotype 3, indicating that the effect of 1,,25(OH)2D3 on the IgG2a antibody response to caps-PS serotype 3 was mediated through IL-12. In conclusion, we demonstrate that 1,,25(OH)2D3 has an inhibitory effect on the IgG2a antibody response to caps-PS serotype 3, and that this effect was mediated trough IL-12. [source]

Inhibition of pneumococcal choline-binding proteins and cell growth by esters of bicyclic amines

FEBS JOURNAL, Issue 2 2007
Beatriz Maestro
Streptococcus pneumoniae is one of the major pathogens worldwide. The use of currently available antibiotics to treat pneumococcal diseases is hampered by increasing resistance levels; also, capsular polysaccharide-based vaccination is of limited efficacy. Therefore, it is desirable to find targets for the development of new antimicrobial drugs specifically designed to fight pneumococcal infections. Choline-binding proteins are a family of polypeptides, found in all S. pneumoniae strains, that take part in important physiologic processes of this bacterium. Among them are several murein hydrolases whose enzymatic activity is usually inhibited by an excess of choline. Using a simple chromatographic procedure, we have identified several choline analogs able to strongly interact with the choline-binding module (C-LytA) of the major autolysin of S. pneumoniae. Two of these compounds (atropine and ipratropium) display a higher binding affinity to C-LytA than choline, and also increase the stability of the protein. CD and fluorescence spectroscopy analyses revealed that the conformational changes of C-LytA upon binding of these alkaloids are different to those induced by choline, suggesting a different mode of binding. In vitro inhibition assays of three pneumococcal, choline-dependent cell wall lytic enzymes also demonstrated a greater inhibitory efficiency of those molecules. Moreover, atropine and ipratropium strongly inhibited in vitro pneumococcal growth, altering cell morphology and reducing cell viability, a very different response than that observed upon addition of an excess of choline. These results may open up the possibility of the development of bicyclic amines as new antimicrobials for use against pneumococcal pathologies. [source]

Structural studies of the capsular polysaccharide and lipopolysaccharide O-antigen of Aeromonas salmonicida strain 80204-1 produced under in vitro and in vivo growth conditions

FEBS JOURNAL, Issue 22 2004
Zhan Wang
Aeromonas salmonicida is a pathogenic aquatic bacterium and the causal agent of furunculosis in salmon. In the course of this study, it was found that when grown in vitro on tryptic soy agar, A. salmonicida strain 80204-1 produced a capsular polysaccharide with the identical structure to that of the lipopolysaccharide O-chain polysaccharide. A combination of 1D and 2D NMR methods, including a series of 1D analogues of 3D experiments, together with capillary electrophoresis-electrospray MS (CE-ES-MS), compositional and methylation analyses and specific modifications was used to determine the structure of these polysaccharides. Both polymers were shown to be composed of linear trisaccharide repeating units consisting of 2-acetamido-2-deoxy- d -galacturonic acid (GalNAcA), 3-[(N -acetyl-L-alanyl)amido]-3,6-dideoxy- d -glucose{3-[(N -acetyl- l -alanyl)amido]-3-deoxy- d -quinovose, Qui3NAlaNAc} and 2-acetamido-2,6-dideoxy- d -glucose (2-acetamido-2-deoxy- d -quinovose, QuiNAc) and having the following structure: [,3)- , - d -GalpNAcA-(1,3)- , - d -QuipNAc-(1,4)- , - d -Quip3NAlaNAc-(1-]n, where GalNAcA is partly presented as an amide and AlaNAc represents N -acetyl- l -alanyl group. CE-ES-MS analysis of CPS and O-chain polysaccharide confirmed that 40% of GalNAcA was present in the amide form. Direct CE-ES-MS/MS analysis of in vivo cultured cells confirmed the formation of a novel polysaccharide, a structure also formed in vitro, which was previously undetectable in bacterial cells grown within implants in fish, and in which GalNAcA was fully amidated. [source]

Induction of a protective capsular polysaccharide antibody response to a multiepitope DNA vaccine encoding a peptide mimic of meningococcal serogroup C capsular polysaccharide

IMMUNOLOGY, Issue 2 2003
Deborah M. Prinz
Summary Systemic infection by encapsulated organisms, such as Neisseria meningitidis, is a major cause of morbidity and mortality worldwide, especially in individuals less than 2 years of age. Antibodies directed at the capsular polysaccharide are shown to be protective against disease by inducing complement-dependent bactericidal activity. The current polysaccharide vaccine has been shown to be poorly immunogenic in high-risk groups and this is probably related to its T-independent properties. An alternative approach to eliciting a T-dependent serum immunoglobulin G (IgG) antibody response to encapsulated pathogens is DNA vaccination. We assessed the immunogenicity of a multiepitope DNA vaccine encoding a T-cell helper epitope and a peptide mimic of N. meningitidis serogroup C. The DNA construct induced a significant anti-polysaccharide antibody response that was bactericidal. Mice immunized with the DNA construct were subsequently protected against challenge with a lethal dose of N. meningitidis serogroup C. [source]

Studies on bioemulsifier production by Acinetobacter strains isolated from healthy human skin

JOURNAL OF APPLIED MICROBIOLOGY, Issue 2 2001
J.R. Patil
Aims: In recent years, interest has been growing in the search for novel bioemulsifiers. Many bacterial genera including Acinetobacter have been reported to produce bioemulsifiers. The present study aims to screen Acinetobacter isolates from healthy human skin for bioemulsifier production. Methods and Results: Acinetobacter junii SC14 produced maximum bioemulsifier in the presence of almond oil during stationary growth phase at 37°C and pH 7·2. Partially purified, nondialysable bioemulsifier from SC14 was a proteoglycan. The protein and polysaccharide fractions resulted in 95·2% reconstitution of the emulsification activity. The role of esterase in the release of cell-bound emulsifier and the contribution of capsular polysaccharide to the emulsification activity were observed. Conclusion:Acinetobacter strains from human skin exhibited better emulsification activity than that by burn wound or soil isolates, owing to the inherent differences in chemical microenvironment of their habitats. Significance and Impact of the Study: Investigation of skin commensals, especially acinetobacters, would lead to the discovery of novel bioemulsifiers with interesting properties. Attempts of screening and strain improvement directed towards skin commensals will open up new avenues for strains producing bioemulsifier on a commercial scale. [source]

Analysis of the capsular polysaccharide biosynthesis locus of Porphyromonas gingivalis and development of a K1-specific polymerase chain reaction-based serotyping assay

JOURNAL OF PERIODONTAL RESEARCH, Issue 6 2008
J. Brunner
Background and Objective:,Porphyromonas gingivalis is a gram-negative obligate anaerobe that is strongly associated with severe periodontitis. Previous reports showed an association of P. gingivalis capsular polysaccharide with virulence. The K1 capsular polysaccharide was found to be more immunostimulatory than the other serotypes. Our objective was to explore the genetic background of the capsule biosynthesis (K-antigen) locus in a representative group of K1 serotype strains. Material and Methods:, We used restriction fragment length polymorphism, polymerase chain reaction (PCR) and DNA sequencing to study the capsular polysaccharide locus in P. gingivalis K1 strains. For serotyping by double immunodiffusion and PCR we used 32 strains of P. gingivalis, including strains of all six known K serotypes. Results:, All tested K1 strains showed high conservation of the capsular polysaccharide locus, although a DNA re-arrangement was found in two strains. Based on this information a K1-specific PCR-based serotyping assay was designed. The specificity and sensitivity of this test were confirmed using non-K1 P. gingivalis serotypes. Conclusion:, The capsular polysaccharide locus of P. gingivalis is conserved but may vary slightly among K1 strains. The new K1 serotyping assay presented here is much faster than double immunodiffusion and can detect K1 strains in a very selective and sensitive way. This method may therefore be clinically relevant in the detection of the virulent P. gingivalis K1 serotype. [source]

Capsular polysaccharide from Actinobacillus actinomycetemcomitans inhibits IL-6 and IL-8 production in human gingival fibroblast

Analysis of Campylobacter jejuni capsular loci reveals multiple mechanisms for the generation of structural diversity and the ability to form complex heptoses

MOLECULAR MICROBIOLOGY, Issue 1 2005
Andrey V. Karlyshev
Summary We recently demonstrated that Campylobacter jejuni produces a capsular polysaccharide (CPS) that is the major antigenic component of the classical Penner serotyping system distinguishing Campylobacter into >60 groups. Although the wide variety of C. jejuni serotypes are suggestive of structural differences in CPS, the genetic mechanisms of such differences are unknown. In this study we sequenced biosynthetic cps regions, ranging in size from 15 to 34 kb, from selected C. jejuni strains of HS:1, HS:19, HS:23, HS:36, HS:23/36 and HS:41 serotypes. Comparison of the determined cps sequences of the HS:1, HS:19 and HS:41 strains with the sequenced strain, NCTC11168 (HS:2), provides evidence for multiple mechanisms of structural variation including exchange of capsular genes and entire clusters by horizontal transfer, gene duplication, deletion, fusion and contingency gene variation. In contrast, the HS:23, HS:36 and HS:23/36 cps sequences were highly conserved. We report the first detailed structural analysis of 81-176 (HS:23/36) and G1 (HS:1) and refine the previous structural interpretations of the HS:19, HS:23, HS:36 and HS:41 serostrains. For the first time, we demonstrate the commonality and function of a second heptose biosynthetic pathway for Campylobacter CPS independent of the pathway for lipooligosaccharide (LOS) biosynthesis and identify a novel heptosyltransferase utilized by this alternate pathway. Furthermore, we show the retention of two functional heptose isomerases in Campylobacter and the sharing of a phosphatase for both LOS and CPS heptose biosynthesis. [source]

Scavenger receptor A is expressed by macrophages in response to Porphyromonas gingivalis, and participates in TNF-, expression

MOLECULAR ORAL MICROBIOLOGY, Issue 6 2009
M. T. Baer
Introduction:,Porphyromonas gingivalis is a periodontopathic bacterium closely associated with generalized aggressive periodontal disease. Pattern recognition receptors (PRRs) participate in host response to this organism. It is likely that PRRs not previously recognized as part of the host response to P. gingivalis also participate in host response to this organism. Methods and Results:, Employing qRT-PCR, we observed increased msr1 gene expression at 2, 6, and 24 h of culture with P. gingivalis strain 381. Flow cytometry revealed increased surface expression of SR-A protein by the 24 h time point. Macrophages cultured with an attachment impaired P. gingivalis fimA - mutant (DPG3) expressed intermediate levels of SR-A expression. Heat-killed P. gingivalis stimulated SR-A expression similar to live bacteria, and purified P. gingivalis capsular polysaccharide stimulated macrophage SR-A expression, indicating that live whole organisms are not necessary for SR-A protein expression in macrophage response. As SR-A is known to play a role in lipid uptake by macrophages, we tested the ability of low-density lipoprotein (LDL) to influence the SR-A response of macrophages to P. gingivalis, and observed no effect of LDL on P. gingivalis -elicited SR-A expression. Lastly, we observed that SR-A knockout (SR-A,/,) mouse macrophages produced significantly more tumor necrosis factor (TNF)-, than wild type mouse macrophages cultured with P. gingivalis. Conclusion:, These data identify that SR-A is expressed by macrophages in response to P. gingivalis, and support that this molecule plays a role in TNF-, production by macrophages to this organism. [source]

Isolation and characterization of the cell-surface polysaccharides of Porphyromonas gingivalis ATCC 53978

MOLECULAR ORAL MICROBIOLOGY, Issue 3 2000
S. I. Farquharson
The cell-surface carbohydrates of Porphyromonas gingivalis strain ATCC 53978 were isolated and partially characterized. Three separate polysaccharides were found to be present: an extracellular polysaccharide, capsular polysaccharide and lipopolysaccharide. The capsular polysaccharide, which had peculiar, gel-like viscoelastic properties, was found to be comprised of mannuronic acid, glucuronic acid, galacturonic acid, galactose, and 2-acetamido-2-deoxy- d -glucose in relative molar ratios of 0.6:0.9:0.5:0.5:1.0, respectively. The extracellular polysaccharide was found to contain mannose, rhamnose, glucose, galactose, and 2-acetamido-2-deoxy- d -glucose in relative molar ratios of 13.5:1.4:1.0:2.0:1.0, respectively. The lipopolysaccharide was found to contain an O -antigen with a regular tetrasaccharide repeat unit comprised of 4-linked ,- l -rhamnopyranosyl, 6-linked ,- d -glucopyranosyl, 3-linked ,- d -galactopyranosyl, and 4-linked 2-acetamido-2-deoxy-,- d -glucopyranosyl residues in equimolar proportions. [source]

Effects of feeding probiotics during weaning on infections and antibody responses to diphtheria, tetanus and Hib vaccines

PEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 1 2008
Christina E. West
Microbial exposure is necessary for the development of normal immune function, which has driven the idea of using probiotics for treatment and prevention of immune-mediated diseases in infancy and childhood. Mounting evidence indicates that probiotics have immunomodulatory effects. However, the mechanisms are still poorly understood. Specific antibody response is a valuable proxy for immune system maturation status in infancy. We aimed at determining the impact of Lactobacillus F19 (LF19) during weaning on infections and IgG antibody responses to routine vaccines. In a double-blind, placebo-controlled randomized intervention trial, infants were fed cereals with (n = 89) or without LF19 (n = 90) from 4 to 13 months of age. Infants were immunized with DTaP (diphtheria and tetanus toxoid and acellular pertussis), polio and Hib-conjugate vaccines at (3), 5 and 12 months of age. We assessed the number of days with infections, antibiotic prescriptions and antibody concentrations to Hib capsular polysaccharide (HibPS), diphtheria toxin (D) and tetanus toxoid (T) before and after the second and third doses. Days with infectious symptoms did not differ between the groups. Days with antibiotic prescriptions were fewer in the LF19 group (p = 0.044). LF19 enhanced anti-D concentrations when adjusting for breastfeeding duration and colonization with LF19 (p = 0.024). There was an interaction of the intervention and colonization with LF19 on anti-T concentrations during the course of vaccination (p = 0.035). The anti-HibPS concentrations were higher after the first and second dose of Hib vaccine in infants breastfed <6 months compared with those breastfed ,6 months (p < 0.05), with no effect by LF19. In conclusion, feeding LF19 did not prevent infections, but increased the capacity to raise immune responses to protein antigens, with more pronounced effects in infants breastfed <6 months. [source]

Exploring the proteome of meningococcal outer membrane vesicle vaccines

PROTEOMICS - CLINICAL APPLICATIONS, Issue 9 2007
Jun X. Wheeler Dr.
Abstract Neisseria meningitidis, one of the principal causes of bacterial meningitis and septicemia, continues to present a challenge for vaccine developers. While significant progress has been made in the development and implementation of conjugate vaccines, which are based on the capsular polysaccharide of the organism, this approach has failed to produce a vaccine against organisms expressing a serogroup B capsule. The completion of the first meningococcal genome sequences in 2000 provided new ways of meeting this challenge. One approach has been to learn more about meningococcal biology and pathogenesis through exploring its proteome. This article reviews the results of ten recent studies of the meningococcal proteome and compares the different methodologies employed. Not surprisingly, given the renewed impetus to develop a comprehensive vaccine and the continuing clinical development of outer membrane vesicle vaccines, many of these studies focus on the proteome of the outer membrane fraction. As in other areas of proteome research, the direct comparison of data from different studies is hampered by the lack of standardization of separation technologies and data formats. Nevertheless, proteomic analysis, especially when combined with detailed knowledge of meningococcal population structures, represents a powerful tool in the development of vaccines against this important pathogen. [source]

Capsule enlargement in Cryptococcus neoformans confers resistance to oxidative stress suggesting a mechanism for intracellular survival

Neisseria meningitidis type C capsular polysaccharide inhibits lipooligosaccharide-induced cell activation by binding to CD14

CELLULAR MICROBIOLOGY, Issue 5 2007
Can Kocabas
Summary Encapsulated Neisseria meningitidis can invade mucosal barriers and cause systemic diseases. Activation of the innate immune system by conserved meningococcal molecules such as lipooligosaccharides (LOS) is essential for the generation of an effective host immune response. Here we show that the type C capsular polysaccharide of N. meningitidis (MCPS) inhibited LOS-induced interleukin-6 and TNF-, secretion from monocytes, and blocked the maturation of dendritic cells induced by LOS, while the capsular polysaccharide from group B streptococcus type III and t(4-hydroxy-3-nitrophenyl) acetyl (NP)-Ficoll had no such effect. MCPS also inhibited the LOS-induced NF-,B activation and phosphorylation of signalling molecules such as ERK1/2, p38 and Jun N-terminal kinase. In a direct binding assay, MCPS manifested a concentration-dependent binding to recombinant lipoprotein binding protein and CD14, the two members of the LOS receptor complex. In addition, the binding of LOS to CD14 and lipopolysaccharide binding protein was inhibited by MCPS. We established that MCPS binding to CD14 is responsible for the inhibition of LOS-mediated cell activation because MCPS inhibition of LOS was reversed when access amounts of CD14 were added to culture media of HEK293 cells expressing TLR4 and MD-2, and the magnitude of recovery in LOS stimulation correlated with the increase in CD14 concentration. These results suggest a new virulence property of meningococcal capsular polysaccharides. [source]

Microreview: Zwitterionic capsular polysaccharides: the new MHCII-dependent antigens

CELLULAR MICROBIOLOGY, Issue 10 2005
Brian A. Cobb
Summary The immune system has evolved the ability for T cells to recognize nearly any biological polymer, including peptides, protein superantigens, and glycolipids through presentation by the major histocompatibility complex (MHC) proteins such as MHC class I (MHCI), MHC class II (MHCII), and CD1. A recent and unexpected addition to this list is the zwitterionic capsular polysaccharide (ZPS). These bacterial molecules utilize MHCII presentation to activate T cells via recognition by ,, T cell receptor (,,TCR) proteins. In this review, we explore what is currently known about ZPS processing and presentation within antigen-presenting cells (APCs) and the immune response that follows. [source]

Structural Determination of the O-Chain Polysaccharide from the Lipopolysaccharide of the Haloalkaliphilic Halomonas pantelleriensis Bacterium,

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 7 2006
M. Michela Corsaro
Abstract The structural determination of the O-chain repeating unit of the lipopolysaccharide from the haloalkaliphilic Halomonas pantelleriensis bacterium is described. The structure of the repeating unit was suggested on the basis of chemical analysis and NMR and MS data. The 4- O -[(S)-1-carboxyethyl]- D -GlcA residue has been found for the first time in a lipopolysaccharide, being previously only found in capsular polysaccharides. A comparison of the O-chain structures of Halomonas magadiensis and H. pantelleriensis is also reported. The results show that both bacteria present lipopolysaccharides containing a high number of carboxylate groups whose salification might determine a protective buffer effect on bacterium against extreme life conditions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006) [source]

The surface-associated elongation factor Tu is concealed for antibody binding on viable pneumococci and meningococci

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 2 2008
Jan Kolberg
Abstract Proteome analyses revealed that elongation factor-Tu (EF-Tu) is associated with cytoplasmic membranes of Gram-positive bacteria and outer membranes of Gram-negative bacteria. It is still debatable whether EF-Tu is located on the external side or the internal side of the membranes. Here, we have generated two new monoclonal antibodies (mAbs) and polyclonal rabbit antibodies against pneumococcal EF-Tu. These antibodies were used to investigate the amount of surface-exposed EF-Tu on viable bacteria using a flow cytometric analysis. The control antibodies recognizing the pneumococcal surface protein A and phosphorylcholine showed a significant binding to viable pneumococci. In contrast, anti-EF-Tu antibodies did not recognize pneumococcal EF-Tu. However, heat killing of pneumococci lacking capsular polysaccharides resulted in specific antibody binding to EF-Tu and, moreover, increased the exposure of recognized phosphorylcholine epitopes. Similarly, our EF-Tu-specific antibodies did not recognize EF-Tu of viable Neisseria meningitidis. However, pretreatment of meningococci with ethanol resulted in specific antibody binding to EF-Tu on outer membranes. Importantly, these treatments did not destroy the membrane integrity as analysed with control mAbs directed against cytoplasmic proteins. In conclusion, our flow cytrometric assays emphasize the importance of using viable bacteria and not heat-killed or ethanol-treated bacteria for surface-localization experiments of proteins, because these treatments modulate the cytoplasmic and outer membranes of bacteria and the binding results may not reflect the situation under physiological conditions. [source]

Novel vaccine strategies with protein antigens of Streptococcus pneumoniae

FEMS IMMUNOLOGY & MEDICAL MICROBIOLOGY, Issue 1 2003
Edwin Swiatlo
Abstract Infections caused by Streptococcus pneumoniae (pneumococcus) are a major cause of mortality throughout the world. This organism is primarily a commensal in the upper respiratory tract of humans, but can cause pneumonia in high-risk persons and disseminate from the lungs by invasion of the bloodstream. Currently, prevention of pneumococcal infections is by immunization with vaccines which contain capsular polysaccharides from the most common serotypes causing invasive disease. However, there are more than 90 antigenically distinct serotypes and there is concern that serotypes not included in the vaccines may become more prevalent in the face of continued use of polysaccharide vaccines. Also, certain high-risk groups have poor immunological responses to some of the polysaccharides in the vaccine formulations. Protein antigens that are conserved across all capsular serotypes would induce more effective and durable humoral immune responses and could potentially protect against all clinically relevant pneumococcal capsular types. This review provides a summary of work on pneumococcal proteins that are being investigated as components for future generations of improved pneumococcal vaccines. [source]

Cryptococcus neoformans capsule biosynthesis and regulation

FEMS YEAST RESEARCH, Issue 8 2004
Guilhem Janbon
Abstract The capsule is certainly the most prominent virulence factor in Cryptococcus neoformans: acapsular strains are avirulent, and capsular polysaccharides have a deleterious effect on the immune system. Until very recently, very few genes involved in capsule biosynthesis had been identified , and this despite the existence of a detailed body of work concerning the capsule's composition, structure and their regulation by environmental factors. The tremendous development of experimental tools and techniques suited to the study of C. neoformans biology together with the sequencing of three complete genomes have, over the last three years, enabled the identification of a number of proteins which participate directly in biosynthesis of the capsule or which regulate its size. Even though this knowledge is still preliminary, it gives us a clearer picture of the various events needed for biosynthesis of this fascinating structure. [source]

Crystallization and preliminary X-ray diffraction studies of the carbohydrate-recognition domain of SIGN-R1, a receptor for microbial polysaccharides and sialylated antibody on splenic marginal zone macrophages

ACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 12 2009
Noella Silva-Martin
SIGN-R1, or CD209b, is a mouse C-type lectin receptor that is expressed at high levels on macrophages in lymphoid tissues, especially within the marginal zone of the spleen. SIGN-R1 can bind and mediate the uptake of various microbial polysaccharides, including dextrans, lipopolysaccharides and pneumococcal capsular polysaccharides. It has been shown that SIGN-R1 mediates the clearance of encapsulated pneumococcus, complement fixation via binding C1q independent of antibody and innate resistance to pneumococcal infection. Recently, SIGN-R1 has also been demonstrated to bind sialylated antibody and mediate its activity to suppress autoimmunity. The carbohydrate-recognition domain (CRD) of SIGN-R1 has been cloned and overexpressed in a soluble secretory form in mammalian Chinese hamster ovary (CHO) cells. The CRD protein of SIGN-R1 was purified from CHO cell-culture supernatant and concentrated for crystallization using the hanging-drop vapour-diffusion method at 291,K. Crystals grew from a mixture of 2,M ammonium sulfate in 0.1,M bis-tris pH 5.5. Single crystals, which belonged to the monoclinic space group C2 with unit-cell parameters a = 146.72, b = 92.77, c = 77.06,Å, , = 121.66°, allowed the collection of a full X-ray data set to a maximum resolution of 1.87,Å. [source]