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PubMed2003

Immunology of bacterial polysaccharide antigens.

Carbohydrates in the form of capsular polysaccharides and/or lipopolysaccharides are the major components on the surface of bacteria. These molecules are important virulence factors in many bacteria isolated from infected persons. Immunity against these components confers protection against the disease. However, developing vaccines based on polysaccharides is difficult and several problems have to be solved. First of all, most of the bacterial polysaccharides are T-lymphocyte independent antigens. Anti-polysaccharide immune response is characterised by lack of T-lymphocyte memory, isotype restriction and delayed ontogeny. Children below 2 years of age and elderly respond poorly to polysaccharide antigens. Secondly, the wide structural heterogeneity among the polysaccharides within and between species is also a problem. Thirdly, some bacterial polysaccharides are poor immunogens in humans due to their structural similarities with glycolipids and glycoproteins present in man. The T-lymphocyte independent nature of a polysaccharide may be overcome by conjugating the native or depolymerised polysaccharide to a protein carrier. Such neoglycoconjugates have been proven to be efficient in inducing T-lymphocyte dependent immunity and to protect both infants as well as elderly from disease. Another approach to circumvent the T-lymphocyte independent property of polysaccharides is to select peptides mimicking the immunodominant structures. Several examples of such peptides have been described.

Adult↗

PubMed1995

NMR studies of acetan and the related bacterial polysaccharide, CR1/4, produced by a mutant strain of Acetobacter xylinum.

Acetan is a bacterial polysaccharide produced by Acetobacter xylinum NRRL B42. Chemical mutagenesis of A.xylinum allowed selection of a mutant strain which produced a new polysaccharide, CR1/4. 2D NMR methods have been used to assign the 1H and 13C spectra of the two polysaccharides and to determine that CR1/4 has the structure shown below. The total number of O-acetyl groups is slightly less than two per repeating unit. [formula: see text] The pentasaccharide side chain of acetan is truncated to a disaccharide unit in CR1/4, but the structures are otherwise identical. In particular, the degree of acetylation is about the same and the O-acetyl groups are located at the same position in both polysaccharides.

Carbohydrate Sequence↗

PubMed2004

Synergistic interactions between the genetically modified bacterial polysaccharide P2 and carob or konjac mannan.

Rheological studies have confirmed that the bacterial polysaccharide P2, a genetically modified variant of the Acetobacter xylinum polysaccharide acetan, undergoes synergistic gelation with either of the plant polysaccharides carob or konjac mannan. X-ray fibre diffraction data shows that P2 can form a 5-fold helical structure of pitch 4.7nm and an axial rise per disaccharide repeat of 0.92nm. Optical rotation data demonstrate that P2 undergoes a coil-helix transition in solution and that deacylation enhances the stability of the helical structure in solution. Studies made on mixtures prepared at different temperatures and ionic strengths suggest that denaturation of the P2 helix favours interaction and gelation. Deacetylation of P2 enhances gelation. X-ray diffraction data for oriented fibres prepared from deacetylated P2-konjac mannan mixed films reveal a 6-fold helical structure of pitch 5.54nm with an axial rise per disaccharide repeat also of 0.92nm. This mixed helix provides direct evidence for binding between the two polysaccharides. P2 contains two sites of acetylation: one on the backbone and one on the sidechain. The former site of acetylation inhibits helix formation for P2. It is suggested that this site of acetylation also inhibits formation of the mixed helix, explaining the enhanced gelation of mixtures on deacetylation.

Amorphophallus↗

PubMed1977

[Effect of bacterial polysaccharide on the quantity of rosette-forming cells in mice with decreased immunologic reactivity].

The influence of bacterial polysaccharide on the amount of the rosette-forming cells (RFC) in mice with decreased immunological reactivity (irradiation in a dose of 400 rad, gamma-rays, administration of cyclophosphamide in a dose of 200 mg/kg) was studied. Bacterial polysaccharide increased the amount of RFC in the intact, immunized and irradiated animals. However, polysaccharide produced no stimulating action on the RFC formation in mice treated with cyclophosphamide this confirming different nature of depression of the immunological reactivity under the effect of irradiation and cyclophosphamide.

Animals↗

PubMed2005

Flocculation of colloidal clay by bacterial polysaccharides: effect of macromolecule charge and structure.

The molecular mechanism of montmorillonite flocculation by bacterial polysaccharides was investigated, with special emphasis on the effect of carboxylic charges in the macromolecules on the mechanisms of interaction with the clay surface. An indirect way to quantify the energy of interaction was used, by comparing the flocculation ability of variously acidic polysaccharides. Data on tensile strength of aggregates in diluted suspension were collected by timed size measurements in the domain 0.1-600 microm, using laser diffraction. The flow behavior of settled aggregates was studied by rheology measurements. Flocculation of colloidal clay suspension by polysaccharides requires cancelling of the electrostatic repulsions by salts, which allows approach of clay surfaces close enough to be bridged by adsorbing macromolecules. The amount of acidic charges of the polysaccharides, and especially their location in the molecular structure, governs the bridging mechanism and the resulting tensile strength of the aggregates. The exposure of carboxylate groups located on side chains strongly promotes flocculation. In turn, charges located on the backbone of the polysaccharide are less accessible to interaction, and the flocculation ability of such polysaccharides is lowered. Measurements at different pH indicate that adsorption of acidic polysaccharides occurs via electrostatic interactions on the amphoteric edge surface of clay platelets, whereas neutral polysaccharides rather adsorb via weak interactions. Increased tensile strength in diluted aggregates due to strong surface interactions results in proportionally increased viscosity of the concentrated aggregates.

Aluminum Silicates↗

PubMed1987

The influence of sidechains on the calculated dimensions of three related bacterial polysaccharides.

The effect of van der Waals interactions between sidechain and backbone on the shape of three bacterial polysaccharides in solution has been investigated. The three polymers, namely, gellan, welan, and rhamsan, share the same four-sugar backbone repeating-unit. Gellan is unbranched, whereas welan and rhamsan display comblike branching. Consequently, the effect of chain branching on backbone conformation may be investigated. Van der Waals repulsive interactions of sidechain and backbone serve to limit, somewhat, the range of conformational freedom of the welan backbone in comparison to that of gellan. Attractive side-chain-backbone interactions, which may be as significant as 2-3 kcal/mol, predominate over much of the accessible conformational space of the welan backbone. Despite the strength of these interactions, the unperturbed shape of welan in solution is calculated to be very similar to that of the unbranched gellan. Attractive sidechain-backbone interactions in rhamsan have a modest influence on the conformational characteristics of the rhamsan backbone. The calculated, unperturbed conformation in solution is slightly more extended than that of gellan and welan, but the fundamental shape of the chain is changed only slightly. Significant differences in the physical properties of these polymers seem not to arise from differences in their random-coil conformations provoked by van der Waals interactions of sidechain and backbone. Other contributions to the sidechain-backbone interaction, e.g., hydrogen bonding, could be involved; interchain interactions are also likely to be important.

Carbohydrate Conformation↗

PubMedDate not supplied

Controlled sulfatation of natural anionic bacterial polysaccharides can yield agents with specific regenerating activity in vivo.

The regenerating activities of chemically modified anionic bacterial polysaccharides by O-sulfonation were investigated using a in vivo model of rat injured muscle regeneration. Glucuronan (GA), a linear homopolysaccharide of -->4)-beta-D-GlcpA-(1--> residues partially acetylated at the C-3 and/or the C-2 position, and glucoglucuronan (GGA), a linear heteropolysaccharide of -->3)-beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1--> residues were sulfated. SO3-DMF sulfatation complex provided polysaccharides with different sulfur contents, however, a depolymerization occurred because we did not use large excess of pyridine to obtain pure modified polysaccharides. A regenerating activity on injured extensor digitorum longus (EDL) muscles on rats was obtained with these two sulfated anionic polymers. The position of sulfate groups on glucoglucuronan (primary or secondary alcohol) seems to have no influence on the biological activity by opposition to the degree of sulfatation both for the glucuronans and the glucoglucuronans. The yield of acetate groups in the glucuronan polymer modulated the specific activity.

Acetylation↗

PubMed1979

[Effect of bacterial polysaccharide on the primary and secondary immunologic response following immunization with sheep erythrocytes].

The effect of typhoid bacterial polysaccharide on the primary and secondary immune response to SRBS was studied. The polysaccharide was shown to have both stimulating and depressive effect on the population of antibody-producing cells. This effect depended on the time and the number of polysaccharide injections. Thus, a single polysaccharide injection made on the day preceding immunization resulted in the maximum stimulation in the system of IgM- and IgG-producing cells, while the maximum depression of these cells could be observed after 2 polysaccharide injections: on the day preceding immunization and on the day of immunization. In the secondary immune response considerable stimulation of the populations of antibody-producing cells was observed after polysaccharide injections made on days 2 and 3 after reimmunization.

Animals↗

PubMed1990

A reverse approach to 1H-n.m.r. assignments of bacterial polysaccharides.

A new approach is reported for obtaining the assignment of the 1H-n.m.r. spectra of bacterial polysaccharides which are not amenable to analysis using conventional strategies. An unambiguous assignment of the 13C-n.m.r. spectrum is made by 13C-COSY of the polysaccharide labelled to a high level with 13C. Assignment of the 1H-n.m.r. spectrum is then made by proton-detected CH-correlation spectroscopy of material that is labelled at a low level. Using this approach, virtually complete assignments have been made for the Klebsiella K3 serotype polysaccharide under physiological conditions of temperature and pH.

Carbohydrate Conformation↗

PubMed1994

Reaction of germinal centers in the T-cell-independent response to the bacterial polysaccharide alpha(1-->6)dextran.

Primary immunization of BALB/c mice with alpha(1-->6)dextran (DEX), a native bacterial polysaccharide, induces an unexpected pattern of splenic B-cell responses. After a peak of antibody-secreting B-cell response at day 4, deposition of dextran-anti-dextran immune complexes, as revealed by staining with both dextran and antibodies to dextran, occurs and persists in splenic follicles until at least the fourth week after immunization. Antigen-specific B cells appear and proliferate in such follicles, leading by day 11 to development of DEX-specific germinal centers as characterized by the presence of distinct regions of DEX+ peanut agglutinin-positive (PNA+) cells. At this time, fluorescence-activated cell sorter analysis also reveals the appearance of a distinct population of DEX+ PNA+ splenic B cells. In contrast, DEX+ PNA- cells, characterized by intense cytoplasmic staining, are present outside of splenic follicles, peak at day 4 to day 5, and persist until at least day 28. The frequency of these cells correlates with DEX-specific antibody-secreting cells, as detected by the ELISA-spot assay. Thus, in addition to the expected plasma cellular response, the typical T-cell-independent type II antigen, DEX, surprisingly also elicits the formation of antigen-specific germinal centers. These observations raise fundamental questions about the roles of germinal centers in T-cell-independent immune responses.

Animals↗

PubMed1975

Effect of bacterial polysaccharide on the number of antibody-producing cells in the spleen of irradiated and unirradiated mice.

The effect of bacterial polysaccharide on the number of spleen cells producing antibodies against sheep's red cells was investigated in irradiated and unirradiated mice. The polysaccharide increased the number of antibody-producing cells both in lethally irradiated (psi rays) and in unirradiated mice, unimmunized with sheep's red cells. This increase was connected with the stimulation of proliferative processes in the recipient by the polysaccharide.

Animals↗

PubMed2005

Interaction of antimicrobial peptides with bacterial polysaccharides from lung pathogens.

The interaction of two cathelicidin antimicrobial peptides, LL-37 and SMAP-29, with three bacterial polysaccharides, respectively, produced by Pseudomonas aeruginosa, Burkholderia cepacia and Klebsiella pneumoniae, was investigated to identify possible mechanisms adopted by lung pathogens to escape the action of innate immunity effectors. In vitro assays indicated that the antibacterial activity of both peptides was inhibited to a variable extent by the three polysaccharides. Circular dichroism experiments showed that these induced an alpha-helical conformation in the two peptides, with the polysaccharides from K. pneumoniae and B. cepacia showing, respectively, the highest and the lowest effect. Fluorescence measurements also indicated the presence of peptide-polysaccharide interactions. A model is proposed in which the binding of peptides to the polysaccharide molecules induces, at low polysaccharide to peptide ratios, a higher order of aggregation, due to peptide-peptide interactions. Overall, these results suggest that binding of the peptides by the polysaccharides produced by lung pathogens can contribute to the impairment of peptide-based innate defenses of airway surface.

Antigens, Bacterial↗

PubMedDate not supplied

Selective antibody deficiency to bacterial polysaccharide antigens in patients with Netherton syndrome.

Three patients with Netherton syndrome, recurrent sinopulmonary infections, and humoral immune deficiency are described. Although quantitative serum immunoglobulin levels were generally normal, two patients had selective antibody deficiency to bacterial polysaccharide antigens, one associated with IgA-IgG-2 deficiency. A third patient had an antibody deficiency to protein antigens. This is the first report, to our knowledge, that describes antibody deficiency in patients with Netherton syndrome. This finding demonstrates the importance of evaluating functional antibody responses to both protein and bacterial polysaccharide antigens and not relying on IgG subclass determination.

Antigens, Bacterial↗

PubMed1989

Naturally-evolved changes in bacterial polysaccharides.

Major roles suggested for extracellular polysaccharides are as antigens, 'phage receptor sites or for protecting cells against dehydration. The evolution of bacterial species has led to a large number of bacterial polysaccharides with complex chemical repeat units. There is growing evidence that such structures may be grouped into families of polymers differing in only small changes in chemical structure. Physico-chemical studies of such families are starting to reveal which variations are important in changing the functional properties of the polymers.

Biological Evolution↗

PubMed1993

Bacterial polysaccharide immune globulin for prophylaxis of acute otitis media in high-risk children.

We evaluated the prevention of recurrences of acute otitis media (AOM) by bacterial polysaccharide immune globulin (BPIG), a hyperimmune human immune globulin prepared by immunizing donors with bacterial polysaccharide vaccines. We used a randomized, stratified, double-blind, placebo-controlled design. Children < or = 24 months of age with 1 to 3 prior episodes of AOM received BPIG, 0.5 ml/kg, or saline placebo intramuscularly at entry and 30 days later. During the 120-day follow-up period, AOM was diagnosed by using clinical criteria and was confirmed with tympanocentesis and culture of the middle ear exudates. Eighty-eight episodes of AOM were observed in 76 patients who completed the study. The incidence of AOM during the entire 120-day study period was similar in BPIG and placebo recipients. Pneumococcal AOM was significantly less frequent in BPIG recipients (0.21 episode per patient) than in placebo recipients (0.45 episode per patient; p = 0.05). Time spent free of AOM was significantly prolonged in recipients of BPIG, in comparison with placebo recipients (51 vs 35 days; p = 0.034). This study demonstrated that circulating antibody, even without stimulation of specific local immunity, may prevent infection of the middle ear. The use of immune globulin preparations for longer periods or at a higher dosage might decrease the incidence of recurrent AOM in otitis-prone children, and deserves further evaluation.

Acute Disease↗

PubMed2006

Understanding the bacterial polysaccharide antigenicity of Streptococcus agalactiae versus Streptococcus pneumoniae.

Bacterial surface capsular polysaccharides (CPS) that are similar in carbohydrate sequence may differ markedly in immunogenicity and antigenicity. The structural origin of these phenomena is poorly understood. Such a case is presented by the Gram-positive bacteria Streptococcus agalactiae (Group B Streptococcus; GBS) type III (GBSIII) and Streptococcus pneumoniae (Pn) type 14 (Pn14), which share closely related CPS sequences. Nevertheless, antibodies (Abs) against GBSIII rarely cross-react with the CPS from Pn14. To establish the origin for the variation in CPS antigenicity, models for the immune complexes of CPS fragments from GBSIII and Pn14, with the variable fragment (Fv) of a GBS-specific mAb (mAb 1B1), are presented. The complexes are generated through a combination of comparative Ab modeling and automated ligand docking, followed by explicitly solvated 10-ns molecular dynamics simulations. The relationship between carbohydrate sequence and antigenicity is further quantified through the computation of interaction energies using the Molecular Mechanics-Generalized Born Surface Area (MM-GBSA) method, augmented by conformational entropy estimates. Despite the electrostatic differences between Pn14 and GBSIII CPS, analysis indicates that entropic penalties are primarily responsible for the loss of affinity of the highly flexible Pn14 CPS for mAb 1B1. The similarity of the solution conformation of the relatively rigid GBSIII CPS with that in the immune complex characterizes the previously undescribed 3D structure of the conformational epitope. The analysis provides a comprehensive interpretation for a large body of biochemical and immunological data related to Ab recognition of bacterial polysaccharides and should be applicable to other Ab-carbohydrate interactions.

Amino Acid Sequence↗

PubMed1992

Intranasal immunization with liposomes containing IL-2 enhances bacterial polysaccharide antigen-specific pulmonary secretory antibody response.

Secretory IgA (sIgA) present at mucosal surfaces such as the lungs and intestine plays an important role in resistance to infection occurring at these anatomic sites. Because IL-2 and IL-4 can augment B cell proliferation and Ig production, we investigated possible adjuvant effects of these cytokines on bacterial polysaccharide-specific pulmonary sIgA generation. As shown in previous studies, intranasal immunization with liposomes containing bacterial polysaccharide from Aerobacter levanicum and Pseudomonas aeruginosa resulted in increased numbers of bacterial polysaccharide-specific pulmonary plasma cells and sIgA titers, compared with those found in unimmunized mice. Inclusion of IL-2, but not IL-4, into the intranasally administered liposomes further increased titers of bacterial polysaccharide specific sIgA and pulmonary plasma cells. Intranasal vaccination with liposomes containing bacterial polysaccharide and 10 micrograms/kg IL-2 increased bacterial polysaccharide-specific pulmonary plasma cell numbers by more than 80-fold compared with the response in mice immunized with liposomes containing bacterial polysaccharide, but without IL-2. The percentage of pulmonary plasma cells producing antibody to polysaccharide from A. levanicum rose from 0.14% in mice intranasally immunized with liposomes containing only polysaccharide to 4.1% in animals vaccinated with liposomes containing polysaccharide and IL-2. Intranasal immunization with liposomes containing P. aeruginosa polysaccharide and IL-2 significantly reduced mortality from P. aeruginosa pneumonia. These results demonstrate that IL-2 has potent adjuvant effects on bacterial Ag-specific sIgA production in the lungs when included in intranasally administered liposomes.

Adjuvants, Immunologic↗

PubMed1979

Effect of bacterial polysaccharides on the growth of Gaeumannomyces graminis var. tritici and wheat roots.

Agrobacterium sp. and related species which in the soil and in the rhizosphere of wheat accompany the fungus Gaemannomyces graminis var. tritici and cause take-all of the wheat roots produced polysaccharides in pure cultures (glucans, mannoglucans and galactomannoglucans). These polysaccharides were utilized better by the mycelium of G. graminis than glucose and polysaccharides of plant origin that occurred on the surface of wheat roots (the so-called mucigel). At lower concentrations these bacterial polysaccharides stimulated growth of wheat roots, higher concentrations (more than 0.1%) were inhibitory. Bacteria inoculated on the surface of wheat first inhibited and then stimulated the development of the plants and their growth. Changes in the growth rate of wheat, the rhizosphere of which was colonized by bacteria simultaneously with the fungus G. graminis and also some changes in the course of the disease of wheat roots caused by the fungus can be explained by the inhibitory or stimulatory effect of polysaccharides of accompanying bacteria.

Ascomycota↗