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Single-Domain Antibodies: Rugged Recognition Element

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The ability to quickly and accurately detect potential bio-threat agents is a priority for the Department of Defense and for homeland security. Most rapid diagnostic and detection immunoassays rely on monoclonal or polyclonal antibodies IgG as the recognition elements. Although sensitive and specific, these conventional antibodies are time-consuming to develop and have limited stability. To form the antigen binding site, conventional IgG require the pairing of variable V heavy and light domains. Cloned derivatives of conventional IgG that comprise just these V domains form a minimal antigen binding site. These derivatives have long been used to develop recognition elements for biosensor applications. However, these single-chain antibodies scFv are often less stable than the parental full-length antibodies and aggregate irreversibly at elevated temperatures due to their two-domain structure. Ideally, development of a one- or single-domain structure capable of antigen binding may avoid aggregation upon heating and would facilitate the application of biosensors at elevated environmental temperatures or for continuous use over long periods of time. In the mid 1990s, it was discovered that certain animals, such as camels, llamas, and sharks, possess a class of unconventional immunoglobulins consisting of heavy-chain homodimers where antigen binding is mediated through a single V domain. These V domains, when cloned as single-domain antibodies sdAb, comprise the smallest known antigen binding fragments 13-15 KDa. SdAb can refold to bind antigen after chemical or heat denaturation, enabling them to retain the ability to bind antigen after exposure to elevated temperatures. Our goal was to develop recombinant libraries of sdAb to permit the selection and evaluation of these unique biomaterials for the benefit of future biodefense requirements.

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  • Medicine and Medical Research
  • Microbiology
  • Chemical, Biological and Radiological Warfare
  • Thermodynamics

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