title: Strain Selection for Generation of O-Antigen-Based Glycoconjugate Vaccines against Invasive Nontyphoidal Salmonella Disease.
abstract: Nontyphoidal Salmonellae, principally S. Typhimurium and S. Enteritidis, are a major cause of invasive bloodstream infections in sub-Saharan Africa with no vaccine currently available. Conjugation of lipopolysaccharide O-antigen to a carrier protein constitutes a promising vaccination strategy. Here we describe a rational process to select the most appropriate isolates of Salmonella as source of O-antigen for developing a bivalent glycoconjugate vaccine. We screened a library of 30 S. Typhimurium and 21 S. Enteritidis in order to identify the most suitable strains for large scale O-antigen production and generation of conjugate vaccines. Initial screening was based on growth characteristics, safety profile of the isolates, O-antigen production, and O-antigen characteristics in terms of molecular size, O-acetylation and glucosylation level and position, as determined by phenol sulfuric assay, NMR, HPLC-SEC and HPAEC-PAD. Three animal isolates for each serovar were identified and used to synthesize candidate glycoconjugate vaccines, using CRM197 as carrier protein. The immunogenicity of these conjugates and the functional activity of the induced antibodies was investigated by ELISA, serum bactericidal assay and flow cytometry. S. Typhimurium O-antigen showed high structural diversity, including O-acetylation of rhamnose in a Malawian invasive strain generating a specific immunodominant epitope. S. Typhimurium conjugates provoked an anti-O-antigen response primarily against the O:5 determinant. O-antigen from S. Enteritidis was structurally more homogeneous than from S. Typhimurium, and no idiosyncratic antibody responses were detected for the S. Enteritidis conjugates. Of the three initially selected isolates, two S. Typhimurium (1418 and 2189) and two S. Enteritidis (502 and 618) strains generated glycoconjugates able to induce high specific antibody levels with high breadth of serovar-specific strain coverage, and were selected for use in vaccine production. The strain selection approach described is potentially applicable to the development of glycoconjugate vaccines against other bacterial pathogens.
authors.affiliation: Sclavo Behring Vaccines Institute for Global Health S.r.l., a GSK company (formerly Novartis Vaccines Institute for Global Health S.r.l), Via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Luisa
authors.initials: L
authors.lastname: Lanzilao
authors.affiliation: Sclavo Behring Vaccines Institute for Global Health S.r.l., a GSK company (formerly Novartis Vaccines Institute for Global Health S.r.l), Via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Stefanetti
authors.affiliation: Sclavo Behring Vaccines Institute for Global Health S.r.l., a GSK company (formerly Novartis Vaccines Institute for Global Health S.r.l), Via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Allan
authors.initials: A
authors.lastname: Saul
authors.affiliation: Jenner Institute, Nuffield Department of Medicine, University of Oxford, Old Road Campus Research Building, Roosevelt Drive, Oxford, OX3 7DQ, United Kingdom; Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, United Kingdom.
authors.forename: Calman A
authors.initials: CA
authors.lastname: MacLennan
authors.affiliation: Sclavo Behring Vaccines Institute for Global Health S.r.l., a GSK company (formerly Novartis Vaccines Institute for Global Health S.r.l), Via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Micoli
authors.affiliation: Sclavo Behring Vaccines Institute for Global Health S.r.l., a GSK company (formerly Novartis Vaccines Institute for Global Health S.r.l), Via Fiorentina 1, 53100, Siena, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Rondini
mesh_terms: D000107:Acetylation; D000907:Antibodies, Bacterial / Q000032:analysis / Q000276:immunology; D001426:Bacterial Proteins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006001:Glycoconjugates / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D019081:O Antigens / Q000737:chemistry*; D012480:Salmonella Infections / Q000517:prevention & control*; D022562:Salmonella Vaccines / Q000276:immunology*; D012477:Salmonella enteritidis / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D012486:Salmonella typhimurium / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D018074:Vaccines, Conjugate / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D006001:Glycoconjugates; D019081:O Antigens; D022562:Salmonella Vaccines; D018074:Vaccines, Conjugate; C028581:CRM197 (non-toxic variant of diphtheria toxin)