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Toxins 2011, 3(11), 1405-1419;

Llama-Derived Single Domain Antibodies Specific for Abrus Agglutinin

Naval Research Laboratory, Center for Bio/Molecular Science and Engineering, 4555 Overlook Ave SW, Washington, DC 20375, USA
National Research Council Postdoctoral Fellow resident at the Naval Research Laboratory, Center for Bio/Molecular Science and Engineering, 4555 Overlook Ave SW, Washington, DC 20375, USA
Nova Research Inc., 1900 Elkin Street, Suite 230, Alexandria, VA 22308, USA
US Army-Edgewood Chemical Biological Center RDCB-DRB-C, 5183 Blackhawk Aberdeen Proving Ground, MD 21010, USA
Tetracore Inc., 9901 Belward Campus Drive Suite 300, Rockville, MD 20850, USA
Food and Drug Administration, Center for Food Safety and Applied Nutrition, Office of Regulatory Science, Division of Bioanalytical Chemistry, 5100 Paint Branch Parkway, College Park, MD 20740, USA
Author to whom correspondence should be addressed.
Received: 2 September 2011 / Revised: 23 October 2011 / Accepted: 1 November 2011 / Published: 11 November 2011
(This article belongs to the Special Issue Ricin Toxin)
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Llama derived single domain antibodies (sdAb), the recombinantly expressed variable heavy domains from the unique heavy-chain only antibodies of camelids, were isolated from a library derived from llamas immunized with a commercial abrin toxoid preparation. Abrin is a potent toxin similar to ricin in structure, sequence and mechanism of action. The selected sdAb were evaluated for their ability to bind to commercial abrin as well as abrax (a recombinant abrin A-chain), purified abrin fractions, Abrus agglutinin (a protein related to abrin but with lower toxicity), ricin, and unrelated proteins. Isolated sdAb were also evaluated for their ability to refold after heat denaturation and ability to be used in sandwich assays as both capture and reporter elements. The best binders were specific for the Abrus agglutinin, showing minimal binding to purified abrin fractions or unrelated proteins. These binders had sub nM affinities and regained most of their secondary structure after heating to 95 °C. They functioned well in sandwich assays. Through gel analysis and the behavior of anti-abrin monoclonal antibodies, we determined that the commercial toxoid preparation used for the original immunizations contained a high percentage of Abrus agglutinin, explaining the selection of Abrus agglutinin binders. Used in conjunction with anti-abrin monoclonal and polyclonal antibodies, these reagents can fill a role to discriminate between the highly toxic abrin and the related, but much less toxic, Abrus agglutinin and distinguish between different crude preparations. View Full-Text
Keywords: abrin; single domain antibody; reversible refolding abrin; single domain antibody; reversible refolding

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Goldman, E.R.; Anderson, G.P.; Zabetakis, D.; Walper, S.; Liu, J.L.; Bernstein, R.; Calm, A.; Carney, J.P.; O’Brien, T.W.; Walker, J.L.; Garber, E.A.E. Llama-Derived Single Domain Antibodies Specific for Abrus Agglutinin. Toxins 2011, 3, 1405-1419.

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