Bacterial surface capsular polysaccharides from Streptococcus pneumoniae: A systematic review on structures, syntheses, and glycoconjugate vaccines

The polysaccharide capsule of Streptococcus pneumoniae constitutes the outermost surface structure of the organism and plays a critical role in virulence. The capsule is the target of current pneumococcal vaccines and glycoconjugates and has important medical and industrial applications. Widespread use of these vaccines is driving changes in serotype prevalence in disease. A massive array of sugars and glycosidic linkages experienced with complete diversity of potential polysaccharide structures. However, it is impossible to collect a sufficient quantity of glycan antigens for the preparation of CPS-based glycoconjugate vaccines from natural sources with high purity and for thorough biological evaluation. So nowadays, the development of a chemical synthetic strategy and their conjugation with a carrier protein to form synthetic glycoconjugate vaccines has been used to gain access on a large scale. This review provides a comprehensive summary of structures, synthesis as well as recent development of synthetic glycoconjugate vaccines, which will support research and may benefit the glycochemical and medical sciences.

Profiling pneumococcal type 3-derived oligosaccharides by high resolution liquid chromatography-tandem mass spectrometry

Pneumococcal type-3 polysaccharide (Pn3P) is considered a major target for the development of a human vaccine to protect against Streptococcus pneumoniae infection. Thus, it is critical to develop methods for the preparation and analysis of Pn3P-derived oligosaccharides to better understand its immunological properties. In this paper, we profile oligosaccharides, generated by the free radical depolymerization of Pn3P, using liquid chromatography (LC)-tandem mass spectrometry (MS/MS). Hydrophilic liquid interaction chromatography (HILIC)-mass spectrometry (MS) revealed a series of oligosaccharides with an even- and odd-number of saccharide residues, ranging from monosaccharide, degree of polymerization (dp1) to large oligosaccharides up to dp 20, generated by free radical depolymerization. Isomers of oligosaccharides with an even number of sugar residues were easily separated on a HILIC column, and their sequences could be distinguished by comparing MS/MS of these oligosaccharides and their reduced alditols. Fluorescent labeling with 2-aminoacridone (AMAC) followed by reversed phase (RP)-LC-MS/MS was applied to analyze and sequence poorly separated product mixtures, as RP-LC affords higher resolution of AMAC-labeled oligosaccharides than does HILIC-based separation. The present methodology can be potentially applied to profiling other capsular polysaccharides.

Capsular antigens of bacteria. Capsular antigens as the basis of vaccines against pathogenic bacteria

The role of bacterial capsular antigens represented in capsular polysaccharides and exoglycans in pathogenicity and virulence of bacteria is discussed in this review. Using capsular antigens for vaccines against severe diseases caused by capsular microorganisms is considered in detail. The use of conjugates of capsular polysaccharides and their fragments with proteins and peptides for vaccine as well as using liposomes as adjuvants for the capsular antigens are described. Data concerning structural elucidation of bacterial capsular antigens are given in the first part of this review.

An Expedient Synthesis of the Repeating Unit of the Acidic Polysaccharide of the Bacteriolytic Complex of Lysoamidase

The first synthesis of the trisaccharide repeating unit of the acidic polysaccharide of the bacteriolytic complex of lysoamidase is presented. The construction is based on a linear glycosylation strategy that starts from the reducing end and employs thio- and selenoglycosides in a highly stereoselective manner by a single set of activation conditions. The thus-formed trisaccharide is selectively deprotected and oxidised, after which a final deprotection step furnishes the desired repeating unit.

A facile preparation of uronates via selective oxidation with TEMPO/KBr/Ca(OCl)2 under aqueous conditions

Addition of solid Ca(OCl)(2) as the terminal oxidant in the TEMPO-mediated selective oxidation has the benefit of easier operation. A variety of partially protected saccharide derivatives (1a-l) have been successfully converted into the corresponding uronate derivatives, including disaccharide building blocks for GAG fragments and precursors to saponins. The beneficial effect of Aliquat 336 was also disclosed in the oxidation of certain substrates.

Isolation of oligosaccharides from a partial-acid hydrolysate of pneumococcal type 3 polysaccharide for use in conjugate vaccines

A series of well-defined oligosaccharide fragments of the capsular polysaccharide of Streptococcus pneumoniae type 3 has been generated. Partial-acid hydrolysis of the capsular polysaccharide, followed by fractionation of the oligosaccharide mixture by Sepharose Q ion-exchange chromatography yielded fragments containing one to seven [-->3)-beta-D-GlcpA-(1-->4)-beta-D-Glcp-(1-->] repeating units. The isolated fragments were analysed for purity by high-pH anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) using an IonPac AS11 column, and their structures were verified by 1H NMR spectroscopy and nano-electrospray mass spectrometry. The oligosaccharides can be used to produce neoglycoprotein vaccines with a defined carbohydrate part.