Structural Study and Conformational Behavior of the Two Different Lipopolysaccharide O-Antigens Produced by the Cystic Fibrosis PathogenBurkholderia multivorans

Immunological studies of Burkholderia multivorans O-antigen oligosaccharide-rsScpA193 conjugates as potential candidates for vaccine development

The Burkholderia cepacia complex (Bcc) is a group of phenotypically similar but genotypically diverse Gram-negative bacteria that pose a significant threat to public health worldwide. Due to the absence of effective therapies, the development of an effective vaccine against Bcc infection is urgently needed. Lipopolysaccharide (LPS) O-antigens of B. multivorans (BM) are attractive immunogenic components and recognized as potential target antigens for vaccine development. In this study, we designed and prepared three BM oligosaccharide-based glycoconjugates rsScpA193-1-3 with rsScpA193 as a new carrier protein. We performed preliminarily immunological assessments to determine the immunogenicity of these glycoconjugates, alongside in vitro evaluations of their capacity to bind BM cells and trigger long-term immunological memory. Our findings revealed that the synthesized conjugate rsScpA193-1exhibited stronger immunogenicity and better recognition to trisaccharide 1 and nonasaccharide 3 than the other two glycoconjugates. Moreover, rsScpA193-1 could effectively bind to BM cells in vitro and successfully induce long-lasting immunological memory. Therefore, trisaccharide 1 was identified as an effective antigenic target, and the conjugate rsScpA193-1 may represent a promising candidate for BM vaccine development. Overall, our study presented the first exploitation of immunogenicity of BM oligosaccharide-protein conjugates and significantly paved the way for Bcc vaccine development.

Structure of the Cell-Wall-Associated Polysaccharides from the Deep-Sea Marine Bacterium Devosia submarina KMM 9415T

Two cell-wall-associated polysaccharides were isolated and purified from the deep-sea marine bacterium Devosia submarina KMM 9415^T, purified by ultracentrifugation and enzymatic treatment, separated by chromatographic techniques, and studied by sugar analyses and NMR spectroscopy. The first polysaccharide with a molecular weight of about 20.7 kDa was found to contain d-arabinose, and the following structure of its disaccharide repeating unit was established: →2)-α-d-Araf-(1→5)-α-d-Araf-(1→. The second polysaccharide was shown to consist of d-galactose and a rare component of bacterial glycans-d-xylulose: →3)-α-d-Galp-(1→3)-β-d-Xluf-(1→.

Chemical Synthesis Elucidates the Key Antigenic Epitope of the Autism-Related Bacterium Clostridium bolteae Capsular Octadecasaccharide

The gut pathogen Clostridium bolteae has been associated with the onset of autism spectrum disorder (ASD). To create vaccines against C. bolteae, it is important to identify exact protective epitopes of the immunologically active capsular polysaccharide (CPS). Here, a series of C. bolteae CPS glycans, up to an octadecasaccharide, was prepared. Key to achieving the total syntheses is a [2+2] coupling strategy based on a β-d-Rhap-(1→3)-α-d-Manp repeating unit that in turn was accessed by a stereoselective β-d-rhamnosylation. The 4,6-O-benzylidene-induced conformational locking is a powerful strategy for forming a β-d-mannose-type glycoside. An indirect strategy based on C2 epimerization of β-d-quinovoside was efficiently achieved by Swern oxidation and borohydride reduction. Sequential glycosylation, and regioselective and global deprotection produced the disaccharide and tetrasaccharide, up to the octadecasaccharide. Glycan microarray analysis of sera from rabbits immunized with inactivated C. bolteae bacteria revealed a humoral immune response to the di- and tetrasaccharide, but none of the longer sequences. The tetrasaccharide may be a key motif for designing glycoconjugate vaccines against C. bolteae.

Polysaccharides from Burkholderia species as targets for vaccine development, immunomodulation and chemical synthesis

Covering: up to 2018 Burkholderia species are a vast group of human pathogenic, phytopathogenic, and plant- or environment-associated bacteria. B. pseudomallei, B. mallei, and B. cepacia complex are the causative agents of melioidosis, glanders, and cystic fibrosis-related infections, respectively, which are fatal diseases in humans and animals. Due to their high resistance to antibiotics, high mortality rates, and increased infectivity via the respiratory tract, B. pseudomallei and B. mallei have been listed as potential bioterrorism agents by the Centers for Disease Control and Prevention. Burkholderia species are able to produce a large network of surface-exposed polysaccharides, i.e., lipopolysaccharides, capsular polysaccharides, and exopolysaccharides, which are virulence factors, immunomodulators, major biofilm components, and protective antigens, and have crucial implications in the pathogenicity of Burkholderia-associated diseases. This review provides a comprehensive and up-to-date account regarding the structural elucidation and biological activities of surface polysaccharides produced by Burkholderia species. The chemical synthesis of oligosaccharides mimicking Burkholderia polysaccharides is described in detail. Emphasis is placed on the recent research efforts toward the development of glycoconjugate vaccines against melioidosis and glanders based on synthetic or native Burkholderia oligo/polysaccharides.

Structure of polysaccharide moiety of Pseudomonas xanthomarina KMM 1447T lipopolysaccharide

The structural analysis of a polysaccharide moiety of Pseudomonas xanthomarina KMM 1447^T lipopolysaccharide (LPS) was carried out. Mild acid degradation of LPS resulted in identification of two polysaccharides. The major one was built of β-D-GlcpNAcA residues amidated with L-Ala and Gly residues randomly. The minor polysaccharide was composed of branched tetrasaccharide repeating units constituted by two D-Galр, D-GalpNAc and ether of D-Glc with (2R,4R)-2,4-dihydroxypentanoic acid lactone (2R,4R-Dhpl): →3)-α-D-Galр-(1 → 3)-β-D-Galр-(1 → 3)-[β-D-Glcp4(2R,4R-Dhpl)-(1 → 4)]-β-D-GalpNAc-(1 → .

A novel rhamno-mannan exopolysaccharide isolated from biofilms of Burkholderia multivorans C1576

Burkholderia multivorans C1576 is a Gram negative opportunistic pathogen causing serious lung infection in cystic fibrosis patients. Considering that bacteria naturally form biofilms, and exopolysaccharides are recognized as important factors for biofilm architecture set-up, B. multivorans was grown both in biofilm and in non-biofilm mode on two different media in order to compare the exopolysaccharides biosynthesized in these different experimental conditions. The exopolysaccharides produced were purified and their structure was determined resorting mainly to NMR spectroscopy, ESI mass spectrometry and gas chromatography coupled to mass spectrometry. The experimental data showed that both in biofilm and non-biofilm mode B. multivorans C1576 produced a novel exopolysaccharide having the following structure: [Formula: see text]. About 50% of the 2-linked rhamnose residues are substituted on C-3 with a methyl ether group. The high percentage of deoxysugar Rha units, coupled with OMe substitutions, suggest a possible role for polymer domains with marked hydrophobic characteristics able to create exopolysaccharide junction zones favouring the stability of the biofilm matrix.

Structure of the lipopolysaccharide isolated from the novel species Uruburuella suis

Uruburuella suis is a novel species isolated from lungs and heart of pigs with pneumonia and pericarditis. Phenotypic and phylogenetic evidences showed that it represented a hitherto unknown subline within the family Neisseriaceae. In the present work we defined the whole structure of the LPS isolated from Uruburuella suis. The structural determination, which was achieved by chemical, spectroscopic and spectrometric approaches, indicates a novel rough type lipopolysaccharide rich in negatively charged groups in the lipid A-inner core region. The elucidation of the structural features of the LPS from Uruburuella suis is a first step toward the comprehension of the characteristics of the cell envelope in such new and interesting microorganisms.

A unique bicyclic monosaccharide from the Bradyrhizobium lipopolysaccharide and its role in the molecular interaction with plants

Sugar coat: The nitrogen-fixing soil bacterium Bradyrhizobium sp. BTAi1 is coated with a unique lipopolysaccharide that does not induce innate immune responses in its host plant Aeschynomene indica or in different plant families. The chemical nature of the monosaccharide forming the polymer (see picture) is unprecedented in nature, which helps to avoid "harmful" recognition by its symbiotic host.

Structural characterization of two lipopolysaccharide O-antigens produced by the endofungal bacterium Burkholderia sp. HKI-402 (B4)

Two different polysaccharides were isolated and identified from the lipopolysaccharide fraction of endofungal bacterium Burkholderia sp. HKI-402 (B4). The complete structure was elucidated by chemical analysis and 2D NMR spectroscopy as the following: