title: Phase variation of the lpf operon is a mechanism to evade cross-immunity between Salmonella serotypes.
abstract: Conventional wisdom holds that phase variation is a mechanism for immune evasion. However, despite fimbrial phase variation, mice previously exposed to Salmonella typhimurium are protected against a subsequent challenge. We evaluated whether lpf phase variation instead may be a mechanism to evade cross-immunity between Salmonella serotypes. Mice were immunized orally with S. typhimurium aroA mutants either that expressed the lpf operon (phase-on variant) or in which the entire lpf operon had been removed by deletion. During a subsequent challenge with virulent Salmonella enteritidis a selection against lpf phase-on variants was observed in mice previously exposed to S. typhimurium long polar fimbriae. Vaccination with S. typhimurium did not confer protection against challenge with S. enteritidis, presumably because lpf phase-off variants were able to evade cross-immunity. We propose that lpf phase variation is a mechanism to evade cross-immunity between Salmonella serotypes, thereby allowing their coexistence in a host population.
authors.affiliation: Department of Medical Microbiology, Texas A&M University Health Science Center, 407 Reynolds Medical Building, College Station, TX 77843-1114, USA.
authors.forename: T L
authors.initials: TL
authors.lastname: Norris
authors.forename: A J
authors.initials: AJ
authors.lastname: Bäumler
mesh_terms: D000818:Animals; D001483:Base Sequence; D002432:Cecum / Q000382:microbiology; D003429:Cross Reactions; D017931:DNA Primers; D005243:Feces / Q000382:microbiology; D010861:Fimbriae, Bacterial; D051379:Mice; D008807:Mice, Inbred BALB C; D009876:Operon; D012477:Salmonella enteritidis / Q000235:genetics* / Q000276:immunology; D012486:Salmonella typhimurium / Q000235:genetics* / Q000276:immunology; D017384:Sequence Deletion; D013045:Species Specificity; D014158:Transcription, Genetic
chemical_list: D017931:DNA Primers