title: Synthesis and biological evaluation of phosphono analogues of capsular polysaccharide fragments from Neisseria meningitidis A.
abstract: Neisseria meningitidis type A (MenA) is a Gram-negative encapsulated bacterium that may cause explosive epidemics of meningitis, especially in the sub-Saharan region of Africa. The development and manufacture of an efficient glycoconjugate vaccine against Neisseria meningitidis A is greatly hampered by the poor hydrolytic stability of its capsular polysaccharide, which is made up of (1-->6)-linked 2-acetamido-2-deoxy-alpha-D-mannopyranosyl phosphate repeating units. Since this chemical lability is a product of the inherent instability of the phosphodiester bridges, here we report the synthesis of phosphonoester-linked oligomers of N-acetyl mannosamine as candidates for stabilised analogues of the corresponding phosphate-bridged saccharides. The installation of each interglycosidic phosphonoester linkage was achieved by Mitsunobu coupling of a glycosyl C-phosphonate building block with the 6-OH moiety of a mannosaminyl residue. Each of the synthesised compounds contains an O-linked aminopropyl spacer at its reducing end (alpha- or beta-oriented) to allow for protein conjugation. The relative affinities of the synthetic molecules were investigated by a competitive ELISA assay and showed that a human polyclonal anti-MenA serum can recognise both the phosphonoester-bridged fragments 1-3 and their monomeric subunits, glycosides 20 and 21. Moreover, the biological results suggest that the abilities of these compounds to inhibit the binding of a specific antibody to MenA polysaccharide are dependent on the chain lengths of the molecules, but independent on the orientations of the anomeric linkers.
authors.affiliation: Dipartimento di Chimica Organica e Industriale and Centro Interdisciplinare Studi Bio-molecolari e Applicazioni Industriali, Università degli Studi di Milano via Venezian 21, 20133 Milano, Italy.
authors.forename: Maria I
authors.initials: MI
authors.lastname: Torres-Sanchez
authors.forename: Cristina
authors.initials: C
authors.lastname: Zaccaria
authors.forename: Benedetta
authors.initials: B
authors.lastname: Buzzi
authors.forename: Gianluca
authors.initials: G
authors.lastname: Miglio
authors.forename: Grazia
authors.initials: G
authors.lastname: Lombardi
authors.forename: Laura
authors.initials: L
authors.lastname: Polito
authors.forename: Giovanni
authors.initials: G
authors.lastname: Russo
authors.forename: Luigi
authors.initials: L
authors.lastname: Lay
mesh_terms: D016667:Bacterial Capsules / Q000737:chemistry* / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D038381:Neisseria meningitidis, Serogroup A / Q000737:chemistry* / Q000276:immunology / Q000472:pathogenicity; D063065:Organophosphonates / Q000138:chemical synthesis*; D011135:Polysaccharides, Bacterial / Q000737:chemistry* / Q000276:immunology
chemical_list: D063065:Organophosphonates; D011135:Polysaccharides, Bacterial