title: Structural analysis of O-polysaccharide chains extracted from different Salmonella Typhimurium strains.
abstract: Salmonella Typhimurium is the major cause of invasive nontyphoidal Salmonella disease in Africa, with high mortality among children and HIV-infected individuals. Currently, no vaccine is available for use in humans. Antibodies directed against the O-polysaccharide of the lipopolysaccharide molecule of Salmonella mediate bacterial killing and are protective, and conjugation of the O-polysaccharide to a carrier protein represents a possible strategy for vaccine development. Here we have purified the O-polysaccharide from six different strains of S. Typhimurium and fully characterized them using analytical methods including HPLC-SEC, HPAEC-PAD, GC, GC-MS, 1D and 2D NMR spectroscopy. All the O-polysaccharide samples showed a similar bimodal molecular mass distribution, but differed with respect to the amount and position of O-acetylation and glucosylation. For some strains, O-acetyl groups were found not only on C-2 of abequose (factor 5 specificity), but also on C-2 and C-3 of rhamnose; glucose was found to be linked 1→4 or 1→6 to galactose in different amounts according to the strain of origin. This structural variability could have an impact on the immunogenicity of corresponding glycoconjugate vaccines and different strains need to be evaluated in order to identify the appropriate source of O-polysaccharide to use for the development of a candidate conjugate vaccine with broad coverage against S. Typhimurium.
authors.affiliation: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy. Electronic address: francesca.micoli@novartis.com.
authors.forename: Francesca
authors.initials: F
authors.lastname: Micoli
authors.affiliation: Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa.
authors.forename: Neil
authors.initials: N
authors.lastname: Ravenscroft
authors.affiliation: Dipartimento di Scienze della Vita, Ed. C11, Università di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Cescutti
authors.affiliation: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Stefanetti
authors.affiliation: Dipartimento di Scienze della Vita, Ed. C11, Università di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Londero
authors.affiliation: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Rondini
authors.affiliation: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy; Medical Research Council Centre for Immune Regulation, Institute of Biomedical Research, School of Immunity and Infection, College of Medicine and Dental Sciences, University of Birmingham, Birmingham B15 2TT, UK.
authors.forename: Calman A
authors.initials: CA
authors.lastname: Maclennan
mesh_terms: D000107:Acetylation; D002240:Carbohydrate Sequence; D008401:Gas Chromatography-Mass Spectrometry; D008968:Molecular Conformation; D019906:Nuclear Magnetic Resonance, Biomolecular; D019081:O Antigens / Q000737:chemistry*; D012486:Salmonella typhimurium / Q000276:immunology*
chemical_list: D019081:O Antigens
keywords: Bacterial polysaccharide structure; O-Polysaccharide; Salmonella Typhimurium