title: Genetic modification of the O-polysaccharide of Francisella tularensis results in an avirulent live attenuated vaccine.
abstract: BACKGROUND
  Francisella tularensis, the causative agent of tularemia, is a highly virulent microbe. One significant virulence factor of F. tularensis is the O-polysaccharide (O-PS) portion of the organism's lipopolysaccharide.
  
  
  METHODS
  A wzy (O-antigen polymerase) deletion mutant of Ft. live attenuated vaccine strain (Ft.LVS), designated Ft.LVS::Δwzy, was created and evaluated as a live attenuated vaccine. Specifically, the mutant's virulence potential and its protective efficacy against type A and type B strains were investigated by challenge of immunized mice.
  
  
  RESULTS
  F. tularensis LVS::Δwzy expressed only 1 repeating unit of O-PS and yet, upon immunization, induced O-PS-specific antibodies. Compared with Ft.LVS, the mutant was highly sensitive to complement-mediated lysis, significantly attenuated in virulence, and was recovered in much lower numbers from the organs of infected mice. Intranasal immunization with Ft.LVS::Δwzy provided protection against subsequent intranasal infection with the highly virulent type A strain SchuS4 and with Ft.LVS. Immunization with Ft.LVS::Δwzy elicited both humoral and cell-mediated immunity.
  
  
  CONCLUSIONS
  Ft.LVS::Δwzy was avirulent in mice and, despite expressing only 1 repeating unit of the O-PS, induced antibodies to the full-length O-PS. Vaccination with Ft.LVS::Δwzy protected mice against intranasal challenge with both type A and type B strains of F. tularensis and induced functional immunity through both humoral and cellular mechanisms.
authors.affiliation: Department of Microbiology and Molecular Genetics, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02215, USA.
authors.forename: Tae-Hyun
authors.initials: TH
authors.lastname: Kim
authors.forename: Jessica T
authors.initials: JT
authors.lastname: Pinkham
authors.forename: Sara J
authors.initials: SJ
authors.lastname: Heninger
authors.forename: Sabina
authors.initials: S
authors.lastname: Chalabaev
authors.forename: Dennis L
authors.initials: DL
authors.lastname: Kasper
mesh_terms: D000825:Animal Structures / Q000382:microbiology; D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D058491:Bacterial Load; D001428:Bacterial Vaccines / Q000235:genetics / Q000276:immunology*; D004195:Disease Models, Animal; D005604:Francisella tularensis / Q000235:genetics* / Q000472:pathogenicity*; D007963:Leukocytes, Mononuclear / Q000276:immunology; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D019081:O Antigens / Q000235:genetics* / Q000378:metabolism*; D014406:Tularemia / Q000517:prevention & control; D014613:Vaccines, Attenuated / Q000235:genetics / Q000276:immunology; D037521:Virulence Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D000907:Antibodies, Bacterial; D001428:Bacterial Vaccines; D019081:O Antigens; D014613:Vaccines, Attenuated; D037521:Virulence Factors