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Appl Environ Microbiol, March 1998, p. 982-991, Vol. 64, No. 3
Bacteriology Division, U.S. Army Medical
Research Institute of Infectious Diseases, Fort Detrick, Frederick,
Maryland 21702-5011
Received 22 October 1997/Accepted 23 December 1997
Bacillus anthracis, the etiologic agent for anthrax,
produces two bipartite, AB-type exotoxins, edema toxin and lethal
toxin. The B subunit of both exotoxins is an Mr
83,000 protein termed protective antigen (PA). The human anthrax
vaccine currently licensed for use in the United States consists
primarily of this protein adsorbed onto aluminum oxyhydroxide. This
report describes the production of PA from a recombinant, asporogenic,
nontoxigenic, and nonencapsulated host strain of B. anthracis and the subsequent purification and characterization of
the protein product. Fermentation in a high-tryptone,
high-yeast-extract medium under nonlimiting aeration produced 20 to 30 mg of secreted PA per liter. Secreted protease activity under these
fermentation conditions was low and was inhibited more than 95% by the
addition of EDTA. A purity of 88 to 93% was achieved for PA by
diafiltration and anion-exchange chromatography, while greater than
95% final purity was achieved with an additional hydrophobic
interaction chromatography step. The purity of the PA product was
characterized by reversed-phase high-pressure liquid chromatography,
sodium dodecyl sulfate (SDS)-capillary electrophoresis, capillary
isoelectric focusing, native gel electrophoresis, and
SDS-polyacrylamide gel electrophoresis. The biological activity of the
PA, when combined with excess lethal factor in the macrophage cell
lysis assay, was comparable to previously reported values.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Fermentation, Purification, and Characterization of
Protective Antigen from a Recombinant, Avirulent Strain of
Bacillus anthracis
*
Corresponding author. Mailing address: Bacteriology
Division, USAMRIID, 1425 Porter St., Fort Detrick, MD 21702-5011. Phone: (301) 619-4931. Fax: (301) 619-2152. E-mail:
dr._joseph_farchaus{at}ftdetrck-ccmail.army.mil.
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