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Blocking anthrax at the PA channel

Abstract number: C1-031P

Karginov¹ V. A., Nestorovich² E. M., Moayeri³ M., Leppla³ S. H., Fahmi⁴ N. E., Vaisman⁵ I. I., Hecht⁴ S. M., Bezrukov² S. M.

¹Innovative Biologics, Inc., Manassas, Virginia, United States of America ²Laboratory of Physical and Structural Biology, NICHD, National Institutes of Health, Bethesda, Maryland, United States of America ³Bacterial Toxins and Therapeutics Section, NIAID, National Institutes of Health, Bethesda, Maryland, United States of America ⁴Pinnacle Pharmaceuticals, Inc., Charlottesville, Virginia, United States of America ⁵School of Computational Sciences, George Mason University, Manassas, Virginia, United States of America. E-mail: vak@innovbio.com

The two toxins playing a key role in anthrax pathogenesis are formed by three polypeptides secreted by Bacillus anthracis: protective antigen (PA) which either combines with lethal factor (LF) to form lethal toxin (LeTx), or with edema factor (EF) to form edema toxin (EdTx). LF and EF are enzymes that target substrates within the cytosol; PA provides a heptameric trans-membrane pore to facilitate LF and EF transport into cytosol. Here we demonstrate a novel approach to disable the toxin: high-affinity blockage of the PA pore by unique low-molecular weight compounds that prevent LF and EF entry into the cells. Guided by the sevenfold symmetry and predominantly negative charge of the PA pore, we designed cyclic molecules of sevenfold symmetry using b-cyclodextrin chemically modified to add seven positive charges. Several derivatives of b-cyclodextrin were evaluated for their ability to protect RAW 264.7 macrophages from anthrax lethal toxin cytotoxicity. Per-6-aminoalkyl-b-cyclodextrins displayed inhibitory activity, and they were protective against anthrax lethal toxin action at low micromolar concentrations. By channel reconstitution into planar lipid bilayers and high-resolution conductance recording, we show that they interact strongly with the PA pore lumen, blocking PA-induced transport at nanomolar concentrations. One of the aminoalkyl derivatives completely protected the highly susceptible Fischer F344 rats from anthrax lethal toxin. We anticipate that this approach will serve as the basis for a structure-directed drug discovery program to find new and effective treatments for anthrax.

To cite this abstract use the following format:

[author] (2005) [title] FEBS Journal 272 (s1), [abstract number]

Session Details

Subject:	C1–Membrane ATPases and channels
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