Cationic polyamines inhibit anthrax lethal factor protease.
BACKGROUND
Anthrax is a human disease that results from infection by the bacteria, Bacillus anthracis and has recently been used as a bioterrorist agent. Historically, this disease was associated with Bacillus spore exposure from wool or animal carcasses. While current vaccine approaches (targeted against the protective antigen) are effective for prophylaxis, multiple doses must be injected. Common antibiotics that block the germination process are effective but must be administered early in the infection cycle. In addition, new therapeutics are needed to specifically target the proteolytic activity of lethal factor (LF) associated with this bacterial infection.


RESULTS
Using a fluorescence-based assay to identify and characterize inhibitors of anthrax lethal factor protease activity, we identified several chemically-distinct classes of inhibitory molecules including polyamines, aminoglycosides and cationic peptides. In these studies, spermine was demonstrated for the first time to inhibit anthrax LF with a Ki value of 0.9 +/- 0.09 microM (mean +/- SEM; n = 3). Additional linear polyamines were also active as LF inhibitors with lower potencies.


CONCLUSIONS
Based upon the studies reported herein, we chose linear polyamines related to spermine as potential lead optimization candidates and additional testing in cell-based models where cell penetration could be studied. During our screening process, we reproducibly demonstrated that the potencies of certain compounds, including neomycin but not neamine or spermine, were different depending upon the presence or absence of nucleic acids. Differential sensitivity to the presence/absence of nucleic acids may be an additional point to consider when comparing various classes of active compounds for lead optimization.
Goldman
Mark Evan
ME
Hawaii Biotech, Inc,, 99-193 Aiea Heights Dr,, Aiea, HI 96701, USA. mgoldman@hawaii.edu
Cregar
Lynne
L
Nguyen
Dominique
D
Simo
Ondrej
O
O'Malley
Sean
S
Humphreys
Tom
T
D000617:Aminoglycosides / Q000494:pharmacology; D000818:Animals; D000942:Antigens, Bacterial; D001408:Bacillus anthracis / Q000201:enzymology*; D001427:Bacterial Toxins / Q000037:antagonists & inhibitors*; D002412:Cations; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D004247:DNA / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical; D045683:Furin / Q000037:antagonists & inhibitors; D007700:Kinetics; D008264:Macrophages / Q000382:microbiology / Q000473:pathology; D051379:Mice; D011073:Polyamines / Q000494:pharmacology*; D013379:Substrate Specificity
D000617:Aminoglycosides; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D002412:Cations; D011073:Polyamines; C030325:anthrax toxin; D004247:DNA; D045683:Furin