title: Structural analysis of the O-acetylated O-polysaccharide isolated from Salmonella paratyphi A and used for vaccine preparation.
abstract: Salmonella paratyphi A is increasingly recognized as a common cause of enteric fever cases and there are no licensed vaccines against this infection. Antibodies directed against the O-polysaccharide of the lipopolysaccharide of Salmonella are protective and conjugation of the O-polysaccharide to a carrier protein represents a promising strategy for vaccine development. O-Acetylation of S. paratyphi A O-polysaccharide is considered important for the immunogenicity of S. paratyphi A conjugate vaccines. Here, as part of a programme to produce a bivalent conjugate vaccine against both S. typhi and S. paratyphi A diseases, we have fully elucidated the O-polysaccharide structure of S. paratyphi A by use of HPLC-SEC, HPAEC-PAD/CD, GLC, GLC-MS, 1D and 2D-NMR spectroscopy. In particular, chemical and NMR studies identified the presence of O-acetyl groups on C-2 and C-3 of rhamnose in the lipopolysaccharide repeating unit, at variance with previous reports of O-acetylation at a single position. Moreover HR-MAS NMR analysis performed directly on bacterial pellets from several strains of S. paratyphi A also showed O-acetylation on C-2 and C-3 of rhamnose, thus this pattern is common and not an artefact from O-polysaccharide purification. Conjugation of the O-polysaccharide to the carrier protein had little impact on O-acetylation and therefore should not adversely affect the immunogenicity of the vaccine.
authors: Department of Chemistry, University of Cape Town, Rondebosch 7701, South Africa.
authors: N
authors: N
authors: Ravenscroft
authors: Department of Life Sciences, Blg. C11, Università di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
authors: P
authors: P
authors: Cescutti
authors: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy.
authors: M
authors: M
authors: Gavini
authors: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy.
authors: G
authors: G
authors: Stefanetti
authors: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy.
authors: C A
authors: CA
authors: MacLennan
authors: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy.
authors: L B
authors: LB
authors: Martin
authors: Novartis Vaccines Institute for Global Health, Via Fiorentina 1, I-53100 Siena, Italy. Electronic address: francesca.micoli@novartis.com.
authors: F
authors: F
authors: Micoli
mesh_terms: D000107:Acetylation; D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D009682:Magnetic Resonance Spectroscopy; D019081:O Antigens / Q000737:chemistry*; D011135:Polysaccharides, Bacterial / Q000737:chemistry*; D012210:Rhamnose / Q000737:chemistry*; D022562:Salmonella Vaccines / Q000737:chemistry; D012482:Salmonella paratyphi A / Q000276:immunology*; D018074:Vaccines, Conjugate / Q000737:chemistry
chemical_list: D019081:O Antigens; D011135:Polysaccharides, Bacterial; D022562:Salmonella Vaccines; D018074:Vaccines, Conjugate; D012210:Rhamnose
keywords: Bacterial polysaccharide structure; O-Acetylation; O-Polysaccharide; Salmonella paratyphi A