ClpX contributes to innate defense peptide resistance and virulence phenotypes of Bacillus anthracis.
Bacillus anthracis is a National Institute of Allergy and Infectious Diseases Category A priority pathogen and the causative agent of the deadly disease anthrax. We applied a transposon mutagenesis system to screen for novel chromosomally encoded B. anthracis virulence factors. This approach identified ClpX, the regulatory ATPase subunit of the ClpXP protease, as essential for both the hemolytic and proteolytic phenotypes surrounding colonies of B. anthracis grown on blood or casein agar media, respectively. Deletion of clpX attenuated lethality of B. anthracis Sterne in murine subcutaneous and inhalation infection models, and markedly reduced in vivo survival of the fully virulent B. anthracis Ames upon intraperitoneal challenge in guinea pigs. The extracellular proteolytic activity dependent upon ClpX function was linked to degradation of cathelicidin antimicrobial peptides, a front-line effector of innate host defense. B. anthracis lacking ClpX were rapidly killed by cathelicidin and alpha-defensin antimicrobial peptides and lysozyme in vitro. In turn, mice lacking cathelicidin proved hyper-susceptible to lethal infection with wild-type B. anthracis Sterne, confirming cathelicidin to be a critical element of innate defense against the pathogen. We conclude that ClpX is an important factor allowing B. anthracis to subvert host immune clearance mechanisms, and thus represents a novel therapeutic target for prevention or therapy of anthrax, a foremost biodefense concern.
McGillivray
Shauna M
SM
Department of Pediatrics, University of California San Diego, La Jolla, CA 92093-0687, USA.
Ebrahimi
Celia M
CM
Fisher
Nathan
N
Sabet
Mojgan
M
Zhang
Dawn X
DX
Chen
Yahua
Y
Haste
Nina M
NM
Aroian
Raffi V
RV
Gallo
Richard L
RL
Guiney
Donald G
DG
Friedlander
Arthur M
AM
Koehler
Theresa M
TM
Nizet
Victor
V
D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D000881:Anthrax / Q000382:microbiology; D023181:Antimicrobial Cationic Peptides / Q000494:pharmacology*; D001408:Bacillus anthracis / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics / Q000472:pathogenicity*; D004251:DNA Transposable Elements; D024881:Drug Resistance, Bacterial; D049071:Endopeptidase Clp / Q000235:genetics / Q000378:metabolism*; D006168:Guinea Pigs; D006461:Hemolysis; D006801:Humans; D007113:Immunity, Innate; D051379:Mice; D016296:Mutagenesis; D010641:Phenotype; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
D023181:Antimicrobial Cationic Peptides; D004251:DNA Transposable Elements; D037521:Virulence Factors; D049071:Endopeptidase Clp; D000251:Adenosine Triphosphatases