title: Immunochemical studies of Shigella flexneri 2a and 6, and Shigella dysenteriae type 1 O-specific polysaccharide-core fragments and their protein conjugates as vaccine candidates.
abstract: There is no licensed vaccine for the prevention of shigellosis. Our approach to the development of a Shigella vaccines is based on inducing serum IgG antibodies to the O-specific polysaccharide (O-SP) domain of their lipopolysaccharides (LPS). We have shown that low molecular mass O-SP-core (O-SPC) fragments isolated from Shigella sonnei LPS conjugated to proteins induced significantly higher antibody levels in mice than the full length O-SP conjugates. This finding is now extended to the O-SPC of Shigella flexneri 2a and 6, and Shigella dysenteriae type 1. The structures of O-SPC, containing core plus 1-4 O-SP repeat units (RUs), were analyzed by NMR and mass spectroscopy. The first RUs attached to the cores of S. flexneri 2a and 6 LPS were different from the following RUs in their O-acetylation and/or glucosylation. Conjugates of core plus more than 1 RU were necessary to induce LPS antibodies in mice. The resulting antibody levels were comparable to those induced by the full length O-SP conjugates. In S. dysenteriae type 1, the first RU was identical to the following RUs, with the exception that the GlcNAc was bound to the core in the beta-configuration, while in all other RUs the GlcNAc was present in the alpha-configuration. In spite of this difference, conjugates of S. dysenteriae type 1 core with 1, 2, or 3 RUs induced LPS antibodies in mice with levels statistically higher than those of the full size O-SP conjugates. O-SPC conjugates are easy to prepare, characterize, and standardize, and their clinical evaluation is planned.
authors.affiliation: The Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA. kielbj@mail.nih.gov
authors.forename: Joanna
authors.initials: J
authors.lastname: Kubler-Kielb
authors.forename: Evgeny
authors.initials: E
authors.lastname: Vinogradov
authors.forename: Christopher
authors.initials: C
authors.lastname: Mocca
authors.forename: Vince
authors.initials: V
authors.lastname: Pozsgay
authors.forename: Bruce
authors.initials: B
authors.lastname: Coxon
authors.forename: John B
authors.initials: JB
authors.lastname: Robbins
authors.forename: Rachel
authors.initials: R
authors.lastname: Schneerson
mesh_terms: D000818:Animals; D001428:Bacterial Vaccines / Q000737:chemistry / Q000276:immunology*; D002240:Carbohydrate Sequence; D002417:Cattle; D006023:Glycoproteins / Q000737:chemistry / Q000276:immunology*; D007120:Immunochemistry; D051379:Mice; D008969:Molecular Sequence Data; D019081:O Antigens / Q000737:chemistry* / Q000276:immunology*; D012762:Shigella dysenteriae / Q000737:chemistry* / Q000276:immunology; D012763:Shigella flexneri / Q000737:chemistry* / Q000276:immunology
chemical_list: D001428:Bacterial Vaccines; D006023:Glycoproteins; D019081:O Antigens