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-D-Glutamic Acid, the Capsular Antigen from Bacillus anthracis
Department of Microbiology and Immunology,1 Cell and Molecular Biology Program,2 Department of Pathology, University of Nevada School of Medicine, Reno, Nevada 895573
Received 24 August 2007/ Returned for modification 1 October 2007/ Accepted 27 December 2007
Bacillus anthracis is surrounded by an antiphagocytic capsule composed of poly-
-D-glutamic acid (
DPGA). Bacterial and fungal capsular polysaccharides are shed into body fluids in large amounts during infection. The goal of our study was to examine the in vivo fate and distribution of the
DPGA capsular polypeptide. Mice were injected via the intravenous route with various amounts of purified
DPGA. Blood, urine, and various organs were harvested at different times after treatment. Sites of
DPGA accumulation were determined by immunoassay using monoclonal antibodies specific for
DPGA. The results showed that the liver and spleen were the primary sites for the accumulation of
DPGA. As found in previous studies of capsular polysaccharides, the Kupffer cells of the liver and splenic macrophages were sites for the cellular accumulation of
DPGA. Unlike capsular polysaccharides, the hepatic sinusoidal endothelial cells were also sites for
DPGA accumulation.
DPGA was rapidly cleared from serum and was excreted into the urine.
DPGA in the urine showed a reduced molecular size relative to native
DPGA. The results indicate that in vivo clearance of the polypeptide capsular antigen of B. anthracis shares several features with the clearance of capsular polysaccharides. Key differences between the in vivo behaviors of
DPGA and capsular polysaccharides include the accumulation of
DPGA in hepatic sinusoidal endothelial cells and a
DPGA clearance rate that was more rapid than the clearance reported for capsular polysaccharides.
Published ahead of print on 14 January 2008.
| J. Bacteriol. | J. Virol. | Eukaryot. Cell |
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| Microbiol. Mol. Biol. Rev. | Clin. Vaccine Immunol. | All ASM Journals |
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