Intramolecular Aglycon Delivery Enables the Synthesis of 6-Deoxy-β-<scp>d</scp>-manno-heptosides as Fragments of Burkholderia pseudomallei and Burkholderia mallei Capsular Polysaccharide

Kenfack, Marielle Tamigney; Blériot, Yves; Gauthier, Charles

doi:10.1021/jo500640n

Cited by 25 publications

(26 citation statements)

References 78 publications

(107 reference statements)

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“… 27 Indeed, this approach has recently been described for the synthesis of a protected β-(1,3)-linked manno -heptopyranose disaccharide. 24 The reservations with this strategy, however, were the uncertainty of the efficiency of this methodology for assembling larger oligosaccharides and the considerable manipulation that would be required on valuable advanced synthetic intermediates. Recent publications during the completion of this work have indeed demonstrated the successful implementation of intramolecular aglycon delivery for assembly of large oligosaccharides; 28 , 29 therefore, intramolecular aglycon delivery represents a potential alternative approach to oligosaccharides such as ( 1 ).…”

Section: Resultsmentioning

confidence: 99%

Protection against Experimental Melioidosis with a Synthetic manno-Heptopyranose Hexasaccharide Glycoconjugate

et al. 2016

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Melioidosis is an emerging infectious disease caused by Burkholderia pseudomallei and is associated with high morbidity and mortality rates in endemic areas. Antibiotic treatment is protracted and not always successful; even with appropriate therapy, up to 40% of individuals presenting with melioidosis in Thailand succumb to infection. In these circumstances, an effective vaccine has the potential to have a dramatic impact on both the scale and the severity of disease. Currently, no vaccines are licensed for human use. A leading vaccine candidate is the capsular polysaccharide consisting of a homopolymer of unbranched 1→3 linked 2-O-acetyl-6-deoxy-β-d-manno-heptopyranose. Here, we present the chemical synthesis of this challenging antigen using a novel modular disaccharide assembly approach. The resulting hexasaccharide was coupled to the nontoxic Hc domain of tetanus toxin as a carrier protein to promote recruitment of T-cell help and provide a scaffold for antigen display. Mice immunized with the glycoconjugate developed IgM and IgG responses capable of recognizing native capsule, and were protected against infection with over 120 × LD50 of B. pseudomallei strain K96243. This is the first report of the chemical synthesis of an immunologically relevant and protective hexasaccharide fragment of the capsular polysaccharide of B. pseudomallei and serves as the rational starting point for the development of an effective licensed vaccine for this emerging infectious disease.

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Section: Resultsmentioning

confidence: 99%

Protection against Experimental Melioidosis with a Synthetic manno-Heptopyranose Hexasaccharide Glycoconjugate

et al. 2016

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“…24 Ammonolysis of were injected over the sensor surface for 60 s, after which the mAb was allowed to passively dissociate for 120 s. Apparent kinetic k on and k off values were determined using a bivalent analyte kinetic algorithm. Both the experimental (colored lines) and fitted (black lines) data are shown.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Burkholderia pseudomallei Capsular Polysaccharide Recognition by a Monoclonal Antibody Reveals Key Details toward a Biodefense Vaccine and Diagnostics against Melioidosis

et al. 2015

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Burkholderia pseudomallei is the bacterium responsible for melioidosis, an infectious disease with high mortality rates. Since melioidosis is a significant public health concern in endemic regions and the organism is currently classified as a potential biothreat agent, the development of effective vaccines and rapid diagnostics is a priority. The capsular polysaccharide (CPS) expressed by B. pseudomallei is a highly conserved virulence factor and a protective antigen. Because of this, CPS is considered an attractive antigen for use in the development of both vaccines and diagnostics. In the present study, we describe the interactions of CPS with the murine monoclonal antibody (mAb) 4C4 using a multidisciplinary approach including organic synthesis, molecular biology techniques, surface plasmon resonance, and nuclear magnetic spectroscopy. Using these methods, we determined the mode of binding between mAb 4C4 and native CPS or ad hoc synthesized capsular polysaccharide fragments. Interestingly, we demonstrated that the O-acetyl moiety of CPS is essential for the interaction of the CPS epitope with mAb 4C4. Collectively, our results provide important insights into the structural features of B. pseudomallei CPS that enable antibody recognition that may help the rational design of CPS-based vaccine candidates. In addition, our findings confirm that the mAb 4C4 is suitable for use in an antibody-based detection assay for diagnosis of B. pseudomallei infections.

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“…In spite of the huge progresses achieved in the chemical synthesis of CPS fragments [24] , [25] , the CPS molecule still represents a challenge for carbohydrate chemistry, given the ambiguity surrounding whether the α-1,3-mannan and 6-deoxy- d - manno -heptose-based glycans are part of the same chain or are closely associated chains that are difficult to separate; in addition, the β- manno configuration also presents a challenge, particularly given the presence of the 2- O -acetyl group. As recently reported by Marchetti et al., [26] the acetyl group is required for 3C5 monoclonal antibody recognition of the molecule, although this study did not determine whether the acetyl group was important for achieving immune protection.…”

Section: Discussionmentioning

confidence: 99%

“…The use of short chain, oligosaccharide fragments of CPS would assist development of a defined glycoconjugate and provide more vaccine doses per mg of CPS extracted. While cutting-edge chemical synthesis, including of a hexasaccharide fragment of CPS has recently been reported [24] , [25] , such approaches remain challenging at this time. Plausible acid- or base-mediated conditions for partial depolymerisation of native CPS give rise to de-O-acetylation (unpublished observations).…”

Section: Introductionmentioning

confidence: 99%

Structural characterisation of the capsular polysaccharide expressed by Burkholderia thailandensis strain E555:: wbiI (pKnock-KmR) and assessment of the significance of the 2-O-acetyl group in immune protection

Bayliss

Donaldson

Nepogodiev

et al. 2017

Carbohydrate Research

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Burkholderia pseudomallei and its close relative B. mallei are human pathogens that are classified as Tier 1 bio-threat agents. Both organisms have previously been shown to constitutively produce a capsular polysaccharide (CPS) that is both a virulence determinant and protective antigen. Extraction and purification of CPS for use as a potential vaccine candidate requires containment level 3 laboratories which is expensive and time-consuming. B. thailandensis strain E555 is closely related to B. pseudomallei and B. mallei, but is non-pathogenic to humans and based on immunological cross-reactivity has previously been shown to express a B. pseudomallei-like CPS. In this study, capsular polysaccharide isolated from an O-antigen deficient strain of B. thailandensis E555 was identified by 1H and 13C NMR spectroscopy as -3-)-2-O-acetyl-6-deoxy-β-d-manno-heptopyranose-(-1, and identical to that produced by B. pseudomallei. This was further substantiated by anti-CPS monoclonal antibody binding. In connection with the production of CPS fragments for use in glycoconjugate vaccines, we set out to assess the importance or otherwise of the CPS 2-OAc groups in immune protection. To this end conjugates of the native and de-O-acetylated CPS with the Hc fragment of tetanus toxin (TetHc) were used as vaccines in a mouse model of melioidosis. The level of protection provided by deacetylated CPS was significantly lower than that from native, acetylated CPS. In addition, sera from mice vaccinated with the deacetylated CPS conjugate did not recognise native CPS. This suggests that CPS extracted from B. thailandensis can be used as antigen and that the acetyl group is essential for protection.

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Intramolecular Aglycon Delivery Enables the Synthesis of 6-Deoxy-β-d-manno-heptosides as Fragments of Burkholderia pseudomallei and Burkholderia mallei Capsular Polysaccharide

Cited by 25 publications

References 78 publications

Protection against Experimental Melioidosis with a Synthetic manno-Heptopyranose Hexasaccharide Glycoconjugate

Protection against Experimental Melioidosis with a Synthetic manno-Heptopyranose Hexasaccharide Glycoconjugate

Burkholderia pseudomallei Capsular Polysaccharide Recognition by a Monoclonal Antibody Reveals Key Details toward a Biodefense Vaccine and Diagnostics against Melioidosis

Structural characterisation of the capsular polysaccharide expressed by Burkholderia thailandensis strain E555:: wbiI (pKnock-KmR) and assessment of the significance of the 2-O-acetyl group in immune protection

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