title: Salmonella Typhimurium LPS mutations for use in vaccines allowing differentiation of infected and vaccinated pigs.
abstract: Contaminated pork is a major source of human salmonellosis and the serovar most frequently isolated from pigs is Salmonella Typhimurium. Vaccination could contribute greatly to controlling Salmonella infections in pigs. However, pigs vaccinated with the current vaccines cannot be discriminated from infected pigs with the LPS-based serological tests used in European Salmonella serosurveillance programmes. We therefore examined which LPS encoding genes of Salmonella Typhimurium can be deleted to allow differentiation of infected and vaccinated pigs (DIVA), without affecting the vaccine strain's protective capacity. For this purpose, deletion mutants in Salmonella strain 112910a, used as vaccine strain, were constructed in the LPS encoding genes: ΔrfbA, ΔrfaL, ΔrfaJ, ΔrfaI, ΔrfaG and ΔrfaF. Primary inoculation of BALB/c mice with the parent strain, ΔrfaL, ΔrfbA or ΔrfaJ strain but not the ΔrfaG, ΔrfaF or ΔrfaI strain protected significantly against subsequent infection with the virulent Salmonella Typhimurium strain NCTC12023. Immunization of piglets with the ΔrfaJ or ΔrfaL mutants resulted in the induction of a serological response lacking detectable antibodies against LPS. This allowed a clear differentiation between sera from pigs immunized with the ΔrfaJ or ΔrfaL strains and sera from pigs infected with their isogenic wild type strain. In conclusion, applying deletions in the rfaJ or the rfaL gene in Salmonella Typhimurium strain 112910a allows differentiation of infected and vaccinated pigs in an LPS based ELISA without reducing the strain's protective capacities in mice.
authors.affiliation: Ghent University, Faculty of Veterinary Medicine, Department of Pathology, Bacteriology and Avian Diseases, Salisburylaan 133, 9820 Merelbeke, Belgium. Bregje.leyman@ugent.be
authors.forename: Bregje
authors.initials: B
authors.lastname: Leyman
authors.forename: Filip
authors.initials: F
authors.lastname: Boyen
authors.forename: Alexander
authors.initials: A
authors.lastname: Van Parys
authors.forename: Elin
authors.initials: E
authors.lastname: Verbrugghe
authors.forename: Freddy
authors.initials: F
authors.lastname: Haesebrouck
authors.forename: Frank
authors.initials: F
authors.lastname: Pasmans
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood / Q000276:immunology; D000914:Antibodies, Viral / Q000097:blood; D000917:Antibody Formation; D001428:Bacterial Vaccines / Q000008:administration & dosage* / Q000235:genetics / Q000276:immunology; D056738:Cross Protection; D004797:Enzyme-Linked Immunosorbent Assay / Q000662:veterinary; D008070:Lipopolysaccharides / Q000235:genetics* / Q000276:immunology; D051379:Mice; D008807:Mice, Inbred BALB C; D012481:Salmonella Infections, Animal / Q000175:diagnosis* / Q000276:immunology; D012486:Salmonella typhimurium / Q000235:genetics / Q000276:immunology; D017384:Sequence Deletion; D013552:Swine / Q000276:immunology / Q000382:microbiology*; D014611:Vaccination / Q000662:veterinary*
chemical_list: D000907:Antibodies, Bacterial; D000914:Antibodies, Viral; D001428:Bacterial Vaccines; D008070:Lipopolysaccharides