title: Prior Inoculation with Type B Strains of Francisella tularensis Provides Partial Protection against Virulent Type A Strains in Cottontail Rabbits.
abstract: Francisella tularensis is a highly virulent bacterium that is capable of causing severe disease (tularemia) in a wide range of species. This organism is characterized into two distinct subspecies: tularensis (type A) and holarctica (type B) which vary in several crucial ways, with some type A strains having been found to be considerably more virulent in humans and laboratory animals. Cottontail rabbits have been widely implicated as a reservoir species for this subspecies; however, experimental inoculation in our laboratory revealed type A organisms to be highly virulent, resulting in 100% mortality following challenge with 50-100 organisms. Inoculation of cottontail rabbits with the same number of organisms from type B strains of bacteria was found to be rarely lethal and to result in a robust humoral immune response. The objective of this study was to characterize the protection afforded by a prior challenge with type B strains against a later inoculation with a type A strain in North American cottontail rabbits (Sylvilagus spp). Previous infection with a type B strain of organism was found to lengthen survival time and in some cases prevent death following inoculation with a type A2 strain of F. tularensis. In contrast, inoculation of a type A1b strain was uniformly lethal in cottontail rabbits irrespective of a prior type B inoculation. These findings provide important insight about the role cottontail rabbits may play in environmental maintenance and transmission of this organism.
authors.affiliation: Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, 80523, United States of America.
authors.forename: Vienna R
authors.initials: VR
authors.lastname: Brown
authors.affiliation: Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, 80523, United States of America.
authors.forename: Danielle R
authors.initials: DR
authors.lastname: Adney
authors.affiliation: Department of Clinical Sciences, Colorado State University, Fort Collins, Colorado, 80523, United States of America.
authors.forename: Francisco
authors.initials: F
authors.lastname: Olea-Popelka
authors.affiliation: Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, 80523, United States of America.
authors.forename: Richard A
authors.initials: RA
authors.lastname: Bowen
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000276:immunology; D056738:Cross Protection; D005260:Female; D005604:Francisella tularensis / Q000276:immunology* / Q000502:physiology*; D008297:Male; D011817:Rabbits; D013045:Species Specificity; D016019:Survival Analysis
chemical_list: D000907:Antibodies, Bacterial