title: A mutant of Francisella tularensis strain SCHU S4 lacking the ability to express a 58-kilodalton protein is attenuated for virulence and is an effective live vaccine.
abstract: Francisella tularensis subsp. tularensis (type A) strain SCHU S4 is a prototypic strain of the pathogen that is highly virulent for humans and other mammals. Its intradermal (i.d.) 50% lethal dose (LD50) for mice is <10 CFU. We discovered a spontaneous mutant, designated FSC043, of SCHU S4 with an i.d. LD50 of >10(8) CFU. FSC043 effectively vaccinated mice against challenge with a highly virulent type A strain, and the protective efficacy was at least as good as that of F. tularensis LVS, an empirically attenuated strain which has been used as an efficacious human vaccine. Comparative proteomics was used to identify two proteins of unknown function that were identified as defective in LVS and FSC043, and deletion mutants of SCHU S4 were created for each of the two encoding genes. One mutant, the DeltaFTT0918 strain, failed to express a 58-kDa protein, had an i.d. LD50 of approximately 10(5) CFU, and was found to be less capable than SCHU S4 of growing in peritoneal mouse macrophages. Mice that recovered from sublethal infection with the DeltaFTT0918 mutant survived when challenged 2 months later with >100 LD50s of the highly virulent type A strain FSC033. This is the first report of the generation of defined mutants of F. tularensis subsp. tularensis and their use as live vaccines.
authors.affiliation: Department of Clinical Microbiology, Clinical Bacteriology, Umeå University, SE-901 85 Umeå, Sweden.
authors.forename: Susan
authors.initials: S
authors.lastname: Twine
authors.forename: Mona
authors.initials: M
authors.lastname: Byström
authors.forename: Wangxue
authors.initials: W
authors.lastname: Chen
authors.forename: Mats
authors.initials: M
authors.lastname: Forsman
authors.forename: Igor
authors.initials: I
authors.lastname: Golovliov
authors.forename: Anders
authors.initials: A
authors.lastname: Johansson
authors.forename: John
authors.initials: J
authors.lastname: Kelly
authors.forename: Helena
authors.initials: H
authors.lastname: Lindgren
authors.forename: Kerstin
authors.initials: K
authors.lastname: Svensson
authors.forename: Carl
authors.initials: C
authors.lastname: Zingmark
authors.forename: Wayne
authors.initials: W
authors.lastname: Conlan
authors.forename: Anders
authors.initials: A
authors.lastname: Sjöstedt
mesh_terms: D000279:Administration, Cutaneous; D000595:Amino Acid Sequence; D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology; D001428:Bacterial Vaccines / Q000008:administration & dosage / Q000235:genetics* / Q000276:immunology; D005260:Female; D005604:Francisella tularensis / Q000235:genetics / Q000276:immunology* / Q000472:pathogenicity; D017737:Macrophages, Peritoneal / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009154:Mutation; D040901:Proteomics; D012867:Skin / Q000276:immunology; D014406:Tularemia / Q000517:prevention & control*; D014613:Vaccines, Attenuated / Q000008:administration & dosage / Q000235:genetics / Q000276:immunology; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D001428:Bacterial Vaccines; D014613:Vaccines, Attenuated