title: Characterization of O-antigen delivered by Generalized Modules for Membrane Antigens (GMMA) vaccine candidates against nontyphoidal Salmonella.
abstract: Invasive nontyphoidal Salmonella disease (iNTS) is a leading cause of death and morbidity in Africa. The most common pathogens are Salmonella enterica serovars Typhimurium and Enteritidis. The O-antigen portion of their lipopolysaccharide is a target of protective immunity and vaccines targeting O-antigen are currently in development. Here we investigate the use of Generalized Modules for Membrane Antigens (GMMA) as delivery system for S. Typhimurium and S. Enteritidis O-antigen. Gram-negative bacteria naturally shed outer membrane in a blebbing process. By deletion of the tolR gene, the level of shedding was greatly enhanced. Further genetic modifications were introduced into the GMMA-producing strains in order to reduce reactogenicity, by detoxifying the lipid A moiety of lipopolysaccharide. We found that genetic mutations can impact on expression of O-antigen chains. All S. Enteritidis GMMA characterized had an O-antigen to protein w/w ratio higher than 0.6, while the ratio was 0.7 for S. Typhimurium ΔtolR GMMA, but decreased to less than 0.1 when further mutations for lipid A detoxification were introduced. Changes were also observed in O-antigen chain length and level and/or position of O-acetylation. When tested in mice, the GMMA induced high levels of anti-O-antigen-specific IgG functional antibodies, despite variation in density and O-antigen structural modifications. In conclusion, simplicity of manufacturing process and low costs of production, coupled with encouraging immunogenicity data, make GMMA an attractive strategy to further investigate for the development of a vaccine against iNTS.
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy; Dipartimento di Scienze della Vita, Ed. C11, Università degli Studi di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
authors.forename: G
authors.initials: G
authors.lastname: De Benedetto
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: R
authors.initials: R
authors.lastname: Alfini
authors.affiliation: Dipartimento di Scienze della Vita, Ed. C11, Università degli Studi di Trieste, via L. Giorgieri 1, 34127 Trieste, Italy.
authors.forename: P
authors.initials: P
authors.lastname: Cescutti
authors.affiliation: Antimicrobial Discovery Center, Department of Biology, 360 Huntington Ave., Boston, MA 02115, United States.
authors.forename: M
authors.initials: M
authors.lastname: Caboni
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Lanzilao
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: F
authors.initials: F
authors.lastname: Necchi
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: A
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, UK.
authors.forename: C A
authors.initials: CA
authors.lastname: MacLennan
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy.
authors.forename: S
authors.initials: S
authors.lastname: Rondini
authors.affiliation: GSK Vaccines Institute for Global Health (GVGH) S.r.l. (former Novartis Vaccines Institute for Global Health, NVGH), Via Fiorentina 1, 53100 Siena, Italy. Electronic address: francesca.x.micoli@gsk.com.
authors.forename: F
authors.initials: F
authors.lastname: Micoli
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D016503:Drug Delivery Systems; D005260:Female; D007074:Immunoglobulin G / Q000097:blood; D051379:Mice; D009154:Mutation; D019081:O Antigens / Q000276:immunology*; D022562:Salmonella Vaccines / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology*; D012477:Salmonella enteritidis / Q000235:genetics / Q000276:immunology*; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology*
chemical_list: D000907:Antibodies, Bacterial; D007074:Immunoglobulin G; D019081:O Antigens; D022562:Salmonella Vaccines
keywords: GMMA; O-antigen; Outer membrane vesicles; Salmonella Enteritidis; Salmonella Typhimurium; Vaccine