title: Design and immunological properties of Helicobacter pylori glycoconjugates based on a truncated lipopolysaccharide lacking Lewis antigen and comprising an α-1,6-glucan chain.
abstract: To investigate the vaccine potential of H. pylori lipopolysaccharide (LPS), truncated LPS of H. pylori strain 26695 HP0826::Kan lacking O-chain polysaccharide and comprising an extended α-1,6-linked glucan chain was conjugated to tetanus toxoid (TT) or bovine serum albumin (BSA). Two approaches were used for delipidation or partial delipidation of H. pylori LPS: (1) mild hydrolysis resulting in delipidated LPS (dLPS) and (2) treatment with anhydrous hydrazine resulting in removal of O-linked fatty acids (LPS-OH). Both LPS-OH and dLPS were covalently linked through a 2-keto-3-deoxy-octulosonic acid (Kdo) residue to a diamino group-containing spacer, followed by conjugation to thiolated TT or BSA to give conjugates LPS-OH-TT, dLPS-BSA and dLPS-TT, respectively. The LPS-OH-TT, dLPS-BSA and dLPS-TT conjugates were immunogenic in both rabbits and mice, inducing strong and specific IgG responses against homologous and heterologous strains of H. pylori. Moreover, the rabbit post-immune sera showed cross-reactivity against clinical isolates of H. pylori in a whole-cell indirect ELISA, which was further confirmed by indirect immunofluorescent microscopy. A tenfold stronger IgG immune response to the immunizing antigen was generated in mice and rabbits that received dLPS-containing conjugate. The post-immune sera of rabbits immunized with LPS-OH-TT, dLPS-BSA or dLPS-TT displayed significant bactericidal activity against mutant and wild-type α-1,6-glucan-expressing strains and selected clinical isolates of H. pylori. Finally, partial protection against H. pylori challenge was demonstrated in mice vaccinated with dLPS-TT conjugate adjuvanted with cholera toxin. In summary, this study shows that glycoconjugates based on delipidated or partially delipidated LPS from H. pylori 26695 HP0826::Kan mutant induce broadly cross-reactive functional antibodies in immunized animals and should be considered for further vaccine development and testing.
authors.affiliation: Institute for Biological Sciences, National Research Council of Canada, Ottawa, Ontario K1A 0R6, Canada. Eleonora.altman@nrc-cnrc.gc.ca
authors.forename: Eleonora
authors.initials: E
authors.lastname: Altman
authors.forename: Vandana
authors.initials: V
authors.lastname: Chandan
authors.forename: Blair A
authors.initials: BA
authors.lastname: Harrison
authors.forename: Roberto
authors.initials: R
authors.lastname: Veloso-Pita
authors.forename: Jianjun
authors.initials: J
authors.lastname: Li
authors.forename: Rhonda
authors.initials: R
authors.lastname: KuoLee
authors.forename: Wangxue
authors.initials: W
authors.lastname: Chen
authors.forename: Vicente
authors.initials: V
authors.lastname: Vérez-Bencomo
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D000942:Antigens, Bacterial / Q000737:chemistry / Q000276:immunology*; D001428:Bacterial Vaccines / Q000737:chemistry / Q000276:immunology*; D005260:Female; D005936:Glucans / Q000737:chemistry / Q000276:immunology*; D006001:Glycoconjugates / Q000737:chemistry / Q000276:immunology*; D016480:Helicobacter pylori / Q000737:chemistry / Q000276:immunology*; D007074:Immunoglobulin G / Q000097:blood; D008070:Lipopolysaccharides / Q000737:chemistry / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D011817:Rabbits; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000276:immunology; D013745:Tetanus Toxoid / Q000737:chemistry / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D000942:Antigens, Bacterial; D001428:Bacterial Vaccines; D005936:Glucans; D006001:Glycoconjugates; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D013745:Tetanus Toxoid; D012710:Serum Albumin, Bovine