A Synthetic Glycan Array Containing Cryptococcus Neoformans Glucuronoxylomannan Capsular Polysaccharide Fragments Allows the Mapping of Protective Epitopes

Abstract

A block synthetic strategy to Cryptococcus neoformans glucuronoxylomannan (GXM) capsular polysaccharide part structures has been developed based on di-, tri-, tetra-, penta- and hexasaccharide thioglycoside building blocks. The approach permitted the synthesis of a library of spacer-containing serotype A and D related GXM oligosaccharide structures, ranging from di- to octadecasaccharides. Ten deprotected GXM compounds (mono- to decasaccharide) were printed onto microarray plates and screened with seventeen mouse monoclonal antibodies (mAbs) to GXM. For the first time a GXM oligosaccharide structure (a serotype A decasaccharide), capable of being recognized by neutralizing forms of these GXMspecific mAbs, has been identified, offering insight into the binding epitopes of a range of protective monoclonal antibodies and furthering our efforts to develop semi-synthetic conjugate vaccine candidates against C. neoformans.<br>

Optimized Conditions for the Palladium‐Catalyzed Hydrogenolysis of Benzyl and Naphthylmethyl Ethers: Preventing Saturation of Aromatic Protecting Groups

“…Palladium is often preferred over ruthenium or platinum due to its lower propensity to cause the saturation of aromatics . Thus, the mild nature of palladium‐catalyzed hydrogenolysis has led to its popularity in global deprotections of, e.g., peptides and oligosaccharides, even allowing for the presence of biologically interesting functionalization of hydroxyl groups such as acetates ( Cryptococcus neoformans ) and cyclic phosphates ( Vibrio cholerae ) . Despite the widespread use of catalytic palladium hydrogenolysis, deprotections can sometimes be mired with poor yields, and are difficult to optimize, due to their late‐stage in total synthesis.…”

Antibodies to the Cryptococcus neoformans Capsule have Innate Glycosidase Activity

“…Building blocks were synthesized as described previously. 20,24,28,51 Growth Conditions C. neoformans Molecular modelling GLYCAM carbohydrate builder was used to construct ligands and auto-dock vina for antibody docking studies, both of which can be accessed at glycam.org. [32][33][34] PyMOL was used for visualisation and figure creation.…”

“…20 When screening this library with mAbs to C. neoformans GXM we found a decasaccharide that was recognized by a wide variety of antibodies. 20 Consequently, we selected it as a good structure for the development into a FRET probe to serve as a potential assay to identify catalytic antibodies. The synthesis of GXM related glycans are complicated by the presence of a 6-O-acetylation pattern.…”

“…Synthesis and assembly of the required building blocks for GXM assembly followed published protocols. 20,[23][24][25][26][27][28] Through a convert building block approach we achieved the synthesis of the bifunctionally armed decasaccharide (assembly of Compounds 1-13, Supplementary Figure 1).…”

Illuminating glycoscience: synthetic strategies for FRET-enabled carbohydrate active enzyme probes

“…67 This was undertaken as part of a strategy targeting glycoconjugate vaccine candidates against the opportunistic fungi Cryptococcus neoformans, where the capsule polysaccharide glucuronoxylomannan (GXM) dominates. Based on their prior work developing synthetic glycan arrays of GXM structures, 68 the group synthesised GXM decasaccharide targets 55 and 56, equipped with FRET capability, using a coumarin/DNP pairing (Fig. 13).…”