title: Effective antiprotease-antibiotic treatment of experimental anthrax.
abstract: BACKGROUND
  Inhalation anthrax is characterized by a systemic spread of the challenge agent, Bacillus anthracis. It causes severe damage, including multiple hemorrhagic lesions, to host tissues and organs. It is widely believed that anthrax lethal toxin secreted by proliferating bacteria is a major cause of death, however, the pathology of intoxication in experimental animals is drastically different from that found during the infectious process. In order to close a gap between our understanding of anthrax molecular pathology and the most prominent clinical features of the infectious process we undertook bioinformatic and experimental analyses of potential proteolytic virulence factors of B. anthracis distinct from lethal toxin.
  
  
  METHODS
  Secreted proteins (other than lethal and edema toxins) produced by B. anthracis were tested for tissue-damaging activity and toxicity in mice. Chemical protease inhibitors and rabbit immune sera raised against B. anthracis proteases were used to treat mice challenged with B. anthracis (Sterne) spores.
  
  
  RESULTS
  B. anthracis strain delta Ames (pXO1-, pXO2-) producing no lethal and edema toxins secrets a number of metalloprotease virulence factors upon cultivation under aerobic conditions, including those with hemorrhagic, caseinolytic and collagenolytic activities, belonging to M4 and M9 thermolysin and bacterial collagenase families, respectively. These factors are directly toxic to DBA/2 mice upon intratracheal administration at 0.5 mg/kg and higher doses. Chemical protease inhibitors (phosphoramidon and 1, 10-phenanthroline), as well as immune sera against M4 and M9 proteases of B. anthracis, were used to treat mice challenged with B. anthracis (Sterne) spores. These substances demonstrate a substantial protective efficacy in combination with ciprofloxacin therapy initiated as late as 48 h post spore challenge, compared to the antibiotic alone.
  
  
  CONCLUSIONS
  Secreted proteolytic enzymes are important pathogenic factors of B. anthrasis, which can be considered as effective therapeutic targets in the development of anthrax treatment and prophylactic approaches complementing anti-lethal toxin therapy.
authors.affiliation: Advanced Biosystems, Inc., Manassas, VA, USA. spopov@gmu.edu
authors.forename: Serguei G
authors.initials: SG
authors.lastname: Popov
authors.forename: Taissia G
authors.initials: TG
authors.lastname: Popova
authors.forename: Svetlana
authors.initials: S
authors.lastname: Hopkins
authors.forename: Raymond S
authors.initials: RS
authors.lastname: Weinstein
authors.forename: Rebecca
authors.initials: R
authors.lastname: MacAfee
authors.forename: Karl J
authors.initials: KJ
authors.lastname: Fryxell
authors.forename: Vikas
authors.initials: V
authors.lastname: Chandhoke
authors.forename: Charles
authors.initials: C
authors.lastname: Bailey
authors.forename: Ken
authors.initials: K
authors.lastname: Alibek
mesh_terms: D000818:Animals; D000881:Anthrax / Q000188:drug therapy*; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D001408:Bacillus anthracis / Q000187:drug effects / Q000201:enzymology*; D001426:Bacterial Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D002939:Ciprofloxacin / Q000627:therapeutic use; D004359:Drug Therapy, Combination; D005260:Female; D006020:Glycopeptides / Q000627:therapeutic use; D007116:Immunization, Passive; D051379:Mice; D008811:Mice, Inbred DBA; D010447:Peptide Hydrolases / Q000378:metabolism*; D010618:Phenanthrolines / Q000627:therapeutic use; D011480:Protease Inhibitors / Q000494:pharmacology / Q000627:therapeutic use*; D037521:Virulence Factors / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001426:Bacterial Proteins; D006020:Glycopeptides; D010618:Phenanthrolines; D011480:Protease Inhibitors; D037521:Virulence Factors; D002939:Ciprofloxacin; D010447:Peptide Hydrolases; C008890:phosphoramidon