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Clinical and Vaccine Immunology, March 2009, p. 408-413, Vol. 16, No. 3
1071-412X/09/$08.00+0     doi:10.1128/CVI.00412-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Detection of Anthrax Toxin by an Ultrasensitive Immunoassay Using Europium Nanoparticles

Shixing Tang,^1* Mahtab Moayeri,² Zhaochun Chen,³ Harri Harma,⁴ Jiangqin Zhao,¹ Haijing Hu,² Robert H. Purcell,³ Stephen H. Leppla,² and Indira K. Hewlett^1*

Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Bethesda, Maryland 20892,¹ Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892,² Laboratory of Infectious Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892,³ Laboratory of Biophysics, University of Turku, Turku FIN-20520, Finland⁴

Received 10 November 2008/ Returned for modification 8 December 2008/ Accepted 17 December 2008

We developed a europium nanoparticle-based immunoassay (ENIA) for the sensitive detection of anthrax protective antigen (PA). The ENIA exhibited a linear dose-dependent pattern within the detection range of 0.01 to 100 ng/ml and was approximately 100-fold more sensitive than enzyme-linked immunosorbent assay (ELISA). False-positive results were not observed with serum samples from healthy adults, mouse plasma without PA, or plasma samples collected from mice injected with anthrax lethal factor or edema factor alone. For the detection of plasma samples spiked with PA, the detection sensitivities for ENIA and ELISA were 100% (11/11 samples) and 36.4% (4/11 samples), respectively. The assay exhibited a linear but qualitative correlation between the PA injected and the PA detected in murine blood (r = 0.97731; P < 0.0001). Anthrax PA was also detected in the circulation of mice infected with spores from a toxigenic Sterne-like strain of Bacillus anthracis, but only in the later stages of infection. These results indicate that the universal labeling technology based on europium nanoparticles and its application may provide a rapid and sensitive testing platform for clinical diagnosis and laboratory research.

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* Corresponding author. Mailing address: Laboratory of Molecular Virology, Center for Biologics Evaluation and Research, Food and Drug Administration, Building 29B, Room 4NN16, 8800 Rockville Pike, Bethesda, MD 20892. Phone: (301) 827-0795. Fax: (301) 480-7928. E-mail for Shixing Tang: Shixing.tang{at}fda.hhs.gov. E-mail for Indira K. Hewlett: Indira.hewlett{at}fda.hhs.gov

Published ahead of print on 7 January 2009.

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Clinical and Vaccine Immunology, March 2009, p. 408-413, Vol. 16, No. 3
1071-412X/09/$08.00+0     doi:10.1128/CVI.00412-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

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