title: Toxin-independent virulence of Bacillus anthracis in rabbits.
abstract: The accepted paradigm states that anthrax is both an invasive and toxinogenic disease and that the toxins play a major role in pathogenicity. In the guinea pig (GP) model we have previously shown that deletion of all three toxin components results in a relatively moderate attenuation in virulence, indicating that B. anthracis possesses an additional toxin-independent virulence mechanism. To characterize this toxin-independent mechanism in anthrax disease, we developed a new rabbit model by intravenous injection (IV) of B. anthracis encapsulated vegetative cells, artificially creating bacteremia. Using this model we were able to demonstrate that also in rabbits, B. anthracis mutants lacking the toxins are capable of killing the host within 24 hours. This virulent trait depends on the activity of AtxA in the presence of pXO2, as, in the absence of the toxin genes, deletion of either component abolishes virulence. Furthermore, this IV virulence depends mainly on AtxA rather than the whole pXO1. A similar pattern was shown in the GP model using subcutaneous (SC) administration of spores of the mutant strains, demonstrating the generality of the phenomenon. The virulent strains showed higher bacteremia levels and more efficient tissue dissemination; however our interpretation is that tissue dissemination per se is not the main determinant of virulence whose exact nature requires further elucidation.
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Haim
authors.initials: H
authors.lastname: Levy
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Itai
authors.initials: I
authors.lastname: Glinert
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Shay
authors.initials: S
authors.lastname: Weiss
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Assa
authors.initials: A
authors.lastname: Sittner
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Josef
authors.initials: J
authors.lastname: Schlomovitz
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: Zeev
authors.initials: Z
authors.lastname: Altboum
authors.affiliation: Department of Infectious Diseases, Israel Institute for Biological Research, Ness Ziona, Israel.
authors.forename: David
authors.initials: D
authors.lastname: Kobiler
mesh_terms: D000818:Animals; D001408:Bacillus anthracis / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity*; D016667:Bacterial Capsules / Q000378:metabolism; D005260:Female; D009154:Mutation; D011817:Rabbits; D013171:Spores, Bacterial / Q000235:genetics / Q000378:metabolism / Q000472:pathogenicity; D014118:Toxins, Biological / Q000235:genetics / Q000378:metabolism; D014774:Virulence
chemical_list: D014118:Toxins, Biological