Organic Chemistry and Immunochemical Strategies in the Design of Potent Carbohydrate-based Vaccines

A brief overview of carbohydrate antigens processing and uptakes involved in the adaptive immune system is highlighted. To counter balance the poor immunogenicity and T-cell independent characteristics of carbohydrate antigens, chemists have developed original hybrid molecules aimed at targeting specific competent immune cell receptors. Amongst several potential vaccine candidates dedicated against diseases, this short report will focused on those most advance and state of the art organic chemistry involved therein. One case has led to the first example of a commercial vaccine entirely prepared from a synthetic carbohydrate antigen against infections caused by the Gram-negative bacteria Haemophilus influenza type b responsible for pneumonia and acute bacterial meningitis in infants. Other commendable examples will illustrate the immunochemical strategies engaged in the development of anticancer carbohydrate-based vaccines

Développement d'un vaccin synthétique contre Burkholderia Cepacia impliqué dans la fibrose kystique

La fibrose kystique (FK) est une maladie génétique causée par la mutation du gène codant pour la protéine CFTR (Cystic Fibrosis Transmembrane conductance Regulator). Celle-ci présente un défaut sur le canal à ions chlorures affectant ainsi entre autres la viscosité des muqueuses au niveau du système respiratoire. Cet environnement est alors propice aux colonisations bactériennes opportunistes sous la forme de biofilm. Burkholderia cepacia, bacille Gram-négatif mobile, multi-résistant aux antibiotiques et hautement transmissible, s'avère d'une extrême virulence pour les patients atteints de FK. Cette bactérie pathogène désigne en fait un ensemble de neuf souches rassemblées sous le nom de « complexe B. cepacia » (CBC). Au moins huit de ces neuf souches produisent un exopolysaccharide nommé Cepacian. Celui-ci est constitué d'un motif de répétition heptasaccharidique composé notamment de l'enchaînement α-D-Rhap-( 1→4 )-α-D-GlcpA. Le D-rhamnose (ou 6-deoxy-D-mannose) est un composant de glycoconjugués des parois de bactéries pathogènes mais ce sucre rare est absent chez l'homme. Ce dernier présente donc un fort potentiel antigénique dans le cadre de la préparation d'un vaccin entièrement synthétique et spécifique contre B. cepacia. L'élaboration de celui-ci consiste en un activateur universel immunogénique peptidique (Tc-épitope), PADRE ou P2TT préalablement synthétisés,\ud fonctionnalisé par une unité antigénique spécifique. Dans ce but, deux tri-O·saccharides constituants du LPS de B. cepacia et composés majoritairement de D-rhamnose, ainsi que des fragments du motif de répétition de l'exopolysaccharide (EPS) du CBC ont été synthétisés. Des méthodes de synthèses orthogonales ont été optimisées avec de très hauts rendements sur les cinq différents sucres constituant l'EPS ou les LPS du CBC, et plus spécifiquement sur le D-rhamnose. Une série de glycosylation suivie d'une conjugaison finale via une addition radicalaire ou une métathèse croisée a conduit à deux méthodes de conjugaison pour la synthèse de vaccins potentiels, ceci constituant le but final du projet. La synthèse linéaire en 21 étapes a conduit au trisaccharide, α-D-Rhap-(1→3)-α-D-Rhap-(1→2)-α-D-Rhap, avec 36% de rendement global (ou 19% en 18 étapes optimisables). Un rendement de 28% a été obtenu pour une synthèse séquentielle en 17 étapes pour le trisaccharide majeur du LPS, α-D-Rhap-(1→3)-α-D-Rhap-(1→4)-α-D-Galp. La conjugaison de ce dernier sur T-cell épitope constituera l'ultime étape afin d'obtenir un vaccin potentiel entièrement synthétique. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Vaccin synthétique, T-cell épitope, Burkholderia cepacia, Fibrose kystique, Oligosaccharide, D-rhamnose, Complexe B. cepacia

Glycodendrimers: versatile tools for nanotechnology

A combinação de nanotecnologia com glicobiologia tem desencadeado o crescimento exponencial de atividades de pesquisa em desenvolvimento de novos biomateriais funcionais (gliconanotecnologia). Mais especificamente, recentes avanços sintéticos para o planejamento sob medida e versátil de nanopartículas glicosiladas, ou seja, gliconanopartículas, consideradas como miméticos sintéticos de glicoconjugados naturais, prepararam o caminho para diversas aplicações biomédicas. A acessibilidade da grande variedade destes nanossistemas estruturados, em termos de forma, tamanho e organização, tem prontamente contribuído para seu desenvolvimento e aplicações em nanomedicina. Neste contexto, nanopartículas de ouro glicosiladas (do inglês, GNPs), pontos quânticos glicosilados (do inglês, QDs), fulerenos, nanotubos de parede simples (do inglês, SWNTs) e gliconanopartículas autoconstruídas usando glicopolímeros anfifílicos ou glicodendrímeros têm recebido considerável atenção para originar poderosos instrumentos de imagem, terapêutico e de biodiagnóstico. Esta revisão fornecerá a visão global das mais recentes sínteses e aplicações de glicodendrímeros em glicociência que têm permitindo aprofundar nosso conhecimento das interações multivalentes proteína-carboidrato. Estes novos biomateriais estão sendo considerados de grande relevância, junto com vacinas sintéticas de câncer de mama, inibidores de adesão bacteriana em tecidos hospedeiros incluindo instrumentos de detecção sensível.Combining nanotechnology with glycobiology has triggered an exponential growth of research activities in the design of novel functional bionanomaterials (glyconanotechnology). More specifically, recent synthetic advances towards the tailored and versatile design of glycosylated nanoparticles namely glyconanoparticles, considered as synthetic mimetics of natural glycoconjugates, paved the way toward diverse biomedical applications. The accessibility of a wide variety of these structured nanosystems, in terms of shapes, sizes, and organized around stable nanoparticles have readily contributed to their development and applications in nanomedicine. In this context, glycosylated gold-nanoparticles (GNPs), glycosylated quantum dots (QDs), fullerenes, single-wall natotubes (SWNTs), and self-assembled glycononanoparticles using amphiphilic glycopolymers or glycodendrimers have received considerable attention to afford powerful imaging, therapeutic, and biodiagnostic devices. This review will provide an overview of the most recent syntheses and applications of glycodendrimers in glycoscience that have permitted to deepen our understanding of multivalent carbohydrate-protein interactions. Together with synthetic breast cancer vaccines, inhibitors of bacterial adhesions to host tissues including sensitive detection devices, these novel bionanomaterials are finding extensive relevance

SinicView: A visualization environment for comparisons of multiple nucleotide sequence alignment tools

BACKGROUND: Deluged by the rate and complexity of completed genomic sequences, the need to align longer sequences becomes more urgent, and many more tools have thus been developed. In the initial stage of genomic sequence analysis, a biologist is usually faced with the questions of how to choose the best tool to align sequences of interest and how to analyze and visualize the alignment results, and then with the question of whether poorly aligned regions produced by the tool are indeed not homologous or are just results due to inappropriate alignment tools or scoring systems used. Although several systematic evaluations of multiple sequence alignment (MSA) programs have been proposed, they may not provide a standard-bearer for most biologists because those poorly aligned regions in these evaluations are never discussed. Thus, a tool that allows cross comparison of the alignment results obtained by different tools simultaneously could help a biologist evaluate their correctness and accuracy. RESULTS: In this paper, we present a versatile alignment visualization system, called SinicView, (for Sequence-aligning INnovative and Interactive Comparison VIEWer), which allows the user to efficiently compare and evaluate assorted nucleotide alignment results obtained by different tools. SinicView calculates similarity of the alignment outputs under a fixed window using the sum-of-pairs method and provides scoring profiles of each set of aligned sequences. The user can visually compare alignment results either in graphic scoring profiles or in plain text format of the aligned nucleotides along with the annotations information. We illustrate the capabilities of our visualization system by comparing alignment results obtained by MLAGAN, MAVID, and MULTIZ, respectively. CONCLUSION: With SinicView, users can use their own data sequences to compare various alignment tools or scoring systems and select the most suitable one to perform alignment in the initial stage of sequence analysis

Acute-on-chronic kidney injury at hospital discharge is associated with long-term dialysis and mortality

Existing chronic kidney disease (CKD) is among the most potent predictors of postoperative acute kidney injury (AKI). Here we quantified this risk in a multicenter, observational study of 9425 patients who survived to hospital discharge after major surgery. CKD was defined as a baseline estimated glomerular filtration rate <45ml/min per 1.73m2. AKI was stratified according to the maximum simplified RIFLE classification at hospitalization and unresolved AKI defined as a persistent increase in serum creatinine of more than half above the baseline or the need for dialysis at discharge. A Cox proportional hazard model showed that patients with AKI-on-CKD during hospitalization had significantly worse long-term survival over a median follow-up of 4.8 years (hazard ratio, 3.3) than patients with AKI but without CKD. The incidence of long-term dialysis was 22.4 and 0.17 per 100 person-years among patients with and without existing CKD, respectively. The adjusted hazard ratio for long-term dialysis in patients with AKI-on-CKD was 19.8 compared to patients who developed AKI without existing CKD. Furthermore, AKI-on-CKD but without kidney recovery at discharge had a worse outcome (hazard ratios of 4.6 and 213, respectively) for mortality and long-term dialysis as compared to patients without CKD or AKI. Thus, in a large cohort of postoperative patients who developed AKI, those with existing CKD were at higher risk for long-term mortality and dialysis after hospital discharge than those without. These outcomes were significantly worse in those with unresolved AKI at discharge

Glycodendrimers: versatile tools for nanotechnology

Combining nanotechnology with glycobiology has triggered an exponential growth of research activities in the design of novel functional bionanomaterials (glyconanotechnology). More specifically, recent synthetic advances towards the tailored and versatile design of glycosylated nanoparticles namely glyconanoparticles, considered as synthetic mimetics of natural glycoconjugates, paved the way toward diverse biomedical applications. The accessibility of a wide variety of these structured nanosystems, in terms of shapes, sizes, and organized around stable nanoparticles have readily contributed to their development and applications in nanomedicine. In this context, glycosylated gold-nanoparticles (GNPs), glycosylated quantum dots (QDs), fullerenes, single-wall natotubes (SWNTs), and self-assembled glycononanoparticles using amphiphilic glycopolymers or glycodendrimers have received considerable attention to afford powerful imaging, therapeutic, and biodiagnostic devices. This review will provide an overview of the most recent syntheses and applications of glycodendrimers in glycoscience that have permitted to deepen our understanding of multivalent carbohydrate-protein interactions. Together with synthetic breast cancer vaccines, inhibitors of bacterial adhesions to host tissues including sensitive detection devices, these novel bionanomaterials are finding extensive relevance

Practical synthesis of valuable d-rhamnoside building blocks for oligosaccharide synthesis

International audienceThe efficient synthesis of d-rhamnoside and the corresponding methods for its regioselective protections and deprotections have been developed in order to provide key building blocks for complex oligosaccharide syntheses toward vaccines against bacterial infections

En route to a carbohydrate-based vaccine against Burkholderia cepacia

International audienceWe report a very high yielding first total synthesis of trisaccharide 5, α-D-Rhap-(1→3)-α-D-Rhap-(1→4)-α-D-Galp, corresponding to the repeating unit 1 of an O-polysaccharide present in the lipopolysaccharide of clinical isolate of Burkholderia cepacia. The approach included two successive glycosylations, based on D-rhamnosyl trichloroacetimidate donors 12 and 14. The oligosaccharide5 has been further functionalized by photochemical coupling or cross-metathesis with non-natural amino acid derivatives. Trisaccharidylamino acids 16 and 17 are now available, with the aim of preparing a novel synthetic carbohydrate-based vacci

Synthesis of Dense and Chiral Dendritic Polyols Using Glyconanosynthon Scaffolds

Most classical dendrimers are frequently built-up from identical repeating units of low valency (usually AB2 monomers). This strategy necessitates several generations to achieve a large number of surface functionalities. In addition, these typical monomers are achiral. We propose herein the use of sugar derivatives consisting of several and varied functionalities with their own individual intrinsic chirality as both scaffolds/core as well as repeating units. This approach allows the construction of chiral, dense dendrimers with a large number of surface groups at low dendrimer generations. Perpropargylated β-D-glucopyranoside, serving as an A5 core, together with various derivatives, such as 2-azidoethyl tetra-O-allyl-β-D-glucopyranoside, serving as an AB4 repeating moiety, were utilized to construct chiral dendrimers using “click chemistry” (CuAAC reaction). These were further modified by thiol-ene and thiol-yne click reactions with alcohols to provide dendritic polyols. Molecular dynamic simulation supported the assumption that the resulting polyols have a dense structure