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Protection against anthrax toxin by recombinant antibody fragments correlates with antigen affinity

Nature Biotechnology volume 20, pages 597601 (2002) | Download Citation

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Abstract

The tripartite toxin produced by Bacillus anthracis is the key determinant in the etiology of anthrax. We have engineered a panel of toxin-neutralizing antibodies, including single-chain variable fragments (scFvs) and scFvs fused to a human constant κ domain (scAbs), that bind to the protective antigen subunit of the toxin with equilibrium dissociation constants (Kd) between 63 nM and 0.25 nM. The entire antibody panel showed high serum, thermal, and denaturant stability. In vitro, post-challenge protection of macrophages from the action of the holotoxin correlated with the Kd of the scFv variants. Strong correlations among antibody construct affinity, serum half-life, and protection were also observed in a rat model of toxin challenge. High-affinity toxin-neutralizing antibodies may be of therapeutic value for alleviating the symptoms of anthrax toxin in infected individuals and for medium-term prophylaxis to infection.

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Acknowledgements

We are grateful for the expert technical assistance of Robert Geiger. We particularly thank Mark Sharp and Robert Shade (Southwest Foundation for Biological Research) for help with the statistical analysis of the animal data. We also thank Andrew Hayhurst and Barrett Harvey (University of Texas at Austin) for many helpful discussions and Dr. Hayhurst for providing pMoPac16. This work was supported by grants from the Department of Defense through Measurement and Signature Intelligence, the US Army ARO/MURI program, and in connection with contract number DAAD17-01-D-0001 with the US Army Research Laboratory. The views and conclusions contained in this document/presentation are those of the authors and should not be interpreted as presenting the official policies or position, either expressed or implied, of the US Army Research Laboratory or the US Government unless so designated by other authorized documents. Citation of manufacturer or trade names does not constitute an official endorsement or approval of the use thereof.

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Affiliations

  1. Department of Chemical Engineering, University of Texas, Austin, TX 78712.

    • Jennifer A. Maynard
    •  & George Georgiou
  2. Institute for Cellular and Molecular Biology, University of Texas, Austin, TX 78712.

    • Jennifer A. Maynard
    • , Catharina B.M. Maassen
    • , Brent L. Iverson
    •  & George Georgiou
  3. National Institute of Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892.

    • Stephen H. Leppla
  4. Southwest Foundation for Biological Research, San Antonio, TX 78227.

    • Kathleen Brasky
    •  & Jean L. Patterson
  5. Department of Chemistry and Biochemistry, University of Texas, Austin, TX 78712.

    • Brent L. Iverson
  6. Department of Biomedical Engineering, University of Texas, Austin, TX 78712.

    • Jennifer A. Maynard
    •  & George Georgiou

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The authors declare no competing financial interests.

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Correspondence to George Georgiou.

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DOI

https://doi.org/10.1038/nbt0602-597

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