The capsular polysaccharide (CPS) of Streptococcus suis serotype 2 was isolated, purified, chemically modified, and characterized. Sugar and absolute configuration analyses of the CPS gave the following composition: D-Gal, 3; D-Glc, 1; D-GlcNAc, 1; D-Neu5Ac, 1; L-Rha, 1. Sialic acid was found to be terminal, and the CPS was quantitatively desialylated by mild acid hydrolysis. The CPS was also submitted to periodate oxidation followed by borohydride reduction and Smith degradation. Sugar and methylation analysis, 1H and 13C nuclear magnetic resonance, and mass spectrometry of the native CPS or of its specifically modified products allowed to determine the repeating unit sequence: [4)[Neu5Ac(alpha2-6)Gal(beta1-4)GlcNAc(beta1-3)]Gal(beta1-4)[Gal(alpha1-3)]Rha(beta1-4)Glc(beta1-]n. The backbone sequence was found to be identical to that of Streptococcus agalactiae or group B Streptococcus (GBS) type VIII and Streptococcus pneumoniae type 23F. The S. suis CPS shares the sequence Neu5Ac-Gal-GlcNAc-Gal in common with GBS types Ia, Ib, II, III, and IV CPSs but differs from them by the presence of rhamnose and the fact that sialic acid is 2,6- rather than 2,3-linked to the following Gal. A correlation between the S. suis CPS sequence and genes of the serotype 2 cps locus encoding putative enzymes responsible for the biosynthesis of the repeating unit was tentatively established.

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International audienceExopolysaccharides (EPS) from Lactobacillus rhamnosus RW- 9595M have been prepared from bacterial cultures, isolated, concentrated, fractionated and tested in vitro for their possible modulating properties on mouse splenocytes from the C57Bl/6 and BALB/c strains, on the murine RAW 264.7 macrophage-like cell line and on human Peripheral Blood Mononuclear Cells (PBMC) from a total of 14 healthy donors. A first step of EPS fractionation was attempted, using membranes with different molecular weight cut-off. Fractions were as follows: F1: $> $1000 kg$\cdot$mol$^{-1}$; F2: 1000-100 kg$\cdot$mol$^{-1}$; F3: 100-10 kg$\cdot$mol$^{-1}$; F4: $< $10 kg$\cdot$mol$^{-1}$. Total EPS, as well as F1, appeared slightly mitogenic in both mouse splenocytes and human PBMC in 2-3 d cultures, and F3 also exhibited such a property on human PBMC. Unfractionated concentrated ("total" ) EPS, as well as F1, elicited TNF, IL-6 and IL-12 p40 both in the mouse and human cells, in 6 h and 24 h cultures, with important variability depending on the cell source. In 24 h cultures, total EPS or F1 elicited bio-active IFN-$\gamma$ in both C57Bl/6 and BALB/c splenocytes, and this IFN-$\gamma$ secretion was sustained until at least 3 d of culture. In human PBMC, no IFN-$\gamma$ production was observed despite high IL-12p40 secretion. These results suggest the possibility of enhancing the immune system through EPS from lactic acid bacteria, in individuals responsive to such a stimulus.Productions de TNF, IL-6, IL-12 et IFN-g chez des cellules immunocompétentes traitées avec des exopolysaccharides du Lactobacillus rhamnosus RW-9595M. Différence entre les réponses de cellules de sang périphérique humain et de splénocytes de souris. Les exopolysaccharides (EPS) du Lactobacillus rhamnosus RW- 9595M ont été préparés à partir de cultures bactériennes, isolés, concentrés, fractionnés et testés in vitro quant à leur potentiel immunomodulateur sur des splénocytes de souris C57Bl/6 et BALB/c, sur la lignée macrophagique murine RAW.264.7 et sur des cellules mononuclées du sang humain provenant de 14 donneurs. Nous avons fractionné ces EPS en fonction des tailles moléculaires, avec des membranes filtrantes de différentes porosités. Les fractions correspondent aux tailles suivantes : F1 : $> $ 1000 kg$\cdot$mol$^{-1}$, F2 : 1000-100 kg$\cdot$mol$^{-1}$, F3 : 100-10 kg$\cdot$mol$^{-1}$ et F4 : $< $ 10 kg$\cdot$mol$^{-1}$. Les EPS concentrés, non fractionnés, ainsi que F1, se sont avérés légèrement mitogènes sur des splénocytes de la souris, ou des cellules sanguines humaines, cultivées 2-3 jours. Dans le dernier cas, F3 manifeste également cette propriété. Les EPS non fractionnés, ainsi que F1, sont capables de provoquer la production de TNF, IL-6, IL-12p40 après 6 ou 24 h de culture, l'origine des cellules étant importante pour l'intensité de la réponse. Après 24, 48 et 72 h de culture, les EPS non fractionnés, ainsi que F1, ont provoqué la production d'interféron gamma par des splénocytes de souris C57Bl/6 et BALB/c. Au contraire, dans le ca...

The capsular polysaccharide (CPS) is a major virulence factor in many encapsulated pathogens, as it is the case for Streptococcus suis, an important swine pathogen and emerging zoonotic agent. Moreover, the CPS is the antigen at the origin of S. suis classification into serotypes. Hence, analyses of the CPS structure are an essential step to dissect its role in virulence and the serological relations between important serotypes. Here, the CPSs of serotypes 1 and 1/2 were purified and characterized for the first time. Chemical and spectroscopic data gave the following repeating unit sequences: [6)[Neu5Ac(␣2-6)GalNAc (␤1-4)GlcNAc(␤1-3)]Gal(␤1-3)Gal(␤1-4)Glc(␤1-] n (serotype 1) and [4)[Neu5Ac(␣2-6)GalNAc(␤1-4)GlcNAc(␤1-3)]Gal (␤1-4)[Gal(␣1-3)]Rha(␤1-4)Glc(␤1-] n (serotype 1/2). The Sambucus nigra lectin, which recognizes the Neu5Ac(␣2-6)Gal/GalNAc sequence, showed binding to both CPSs. Compared with previously characterized serotype 14 and 2 CPSs, N-acetylgalactosamine replaces galactose as the sugar bearing the sialic acid residue in the side chain. Serological analyses of the cross-reaction of serotype 1/2 with serotypes 1 and 2 and that between serotypes 1 and 14 suggested that the side chain, and more particularly the terminal sialic acid, constitutes one important epitope for serotypes 1/2 and 2. The side chain is also an important serological determinant for serotype 1, yet sialic acid seems to play a limited role. In contrast, the side chain does not seem to be part of a major epitope for serotype 14. These results contribute to the understanding of the relationship between S. suis serotypes and provide the basis for improving diagnostic tools.

bStreptococcus agalactiae (also known as group B Streptococcus [GBS]) and Streptococcus suis are encapsulated streptococci causing severe septicemia and meningitis. Bacterial capsular polysaccharides (CPSs) are poorly immunogenic, but anti-CPS antibodies are essential to the host defense against encapsulated bacteria. The mechanisms underlying anti-CPS antibody responses are not fully elucidated, but the biochemistry of CPSs, particularly the presence of sialic acid, may have an immunosuppressive effect. We investigated the ability of highly purified S. suis and GBS native (sialylated) CPSs to activate dendritic cells (DCs), which are crucial actors in the initiation of humoral immunity. The influence of CPS biochemistry was studied using CPSs extracted from different serotypes within these two streptococcal species, as well as desialylated CPSs. No interleukin-1␤ (IL-1␤), IL-6, IL-12p70, tumor necrosis factor alpha (TNF-␣), or IL-10 production was observed in S. suis or GBS CPS-stimulated DCs. Moreover, these CPSs exerted immunosuppressive effects on DC activation, as a diminution of gamma interferon (IFN-␥)-induced B cell-activating factor of the tumor necrosis factor family (BAFF) expression was observed in CPS-pretreated cells. However, S. suis and GBS CPSs induced significant production of CCL3, via partially Toll-like receptor 2 (TLR2)-and myeloid differentiation factor 88 (MyD88)-dependent pathways, and CCL2, via TLR-independent mechanisms. No major influence of CPS biochemistry was observed on the capacity to induce chemokine production by DCs, indicating that DCs respond to these CPSs in a patterned way rather than a structure-dedicated manner.

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In this study, we report that Lactococcus lactis strains producing exopolysaccharides (EPSstrains were insensitive to these phages. The monosaccharide composition of the polymer produced by the seven Eps ؉ strains was determined. The EPS produced by strains MLT3, SMQ-419, and SMQ-575 contained glucose, galactose, and rhamnose. The EPS fabricated by H414 contained only galactose. The EPS made by MLT2, SMQ-420, and SMQ-461 contained glucose and galactose. These findings indicate that the sugar composition of the EPS has no effect on phage sensitivity. The plasmid encoding the eps operon was cured from the two phage-sensitive strains. The cured derivatives were still phage sensitive, which indicates that EPS are not necessary for phage infection. Phage adsorption assays showed that the production of EPS does not confer a significant phage resistance phenotype.

Abstract. Phytochemical characterization of the major phenolic compounds and their ultrastructural localization were carried out on onion roots (Allium cepa L.) colonized by two vesicular-arbuscular mycorrhizal (VAM) fungi: Glomus intraradix Schenck & Smith and G. versiforme (Karst.) Berch. Free and wall-bound forms of phenolic components were quantified in relation to the duration of symbiosis. Both ferulic and pcoumaric acids, as well as N-feruloyltyramine were identified as the major phenolic metabolites bound to the cell walls of VAM onion roots. Results from mycorrhized and control Plants suggest the presence of a mechanism leading to the oxidative condensation of phenols, the latter process depending on the presence or absence of symbiosis. Bioassays reveal that N-feruloyltyramine induces the branching of hyphae and reduces total fungal development. The overall results lead us to suggest that the progressive binding of phenolic compounds in VAM roots is directly involved in the control of VAM endophytic establishment and development, as it gradually reduces the plasticity and elasticity of the symbiotic matrix. Phenolic compounds bound to cell walls could also be indirectly responsible for the resistance of VAM roots to pathogenic fungi, since they result in increased resistance by the cell wall to the action of digestive enzymes.