Nuclease-Resistant Aptamers for Anthrax Opsonization

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DESCRIPTION (provided by investigator): The anti-phagocytic poly-D-glutamic acid (PDGA) capsule of Bacillus anthracis is a major virulence factor of inhalation anthrax. Although generation of antibodies to PDGA might be of value in opsonizing vegetative anthrax, such antibodies would require "humanization". A simpler and less expensive approach would be the development of nuclease-resistant ('shielded') DNA aptamers against PDGA with an Fc-TR or C3bR binding domain at the other end of a 'hybrid' aptamer. In Phase I, Operational Technologies (OpTech) in conjunction with the Biochemistry Department of the University of Texas at San Antonio (UTSA), proposes to develop 2'- amino pyrimidine modified shielded DNA aptamers against PDGA, murine Fc-yR, and C3bR by the SELEX process. OpTech will link the aptamers and compare phagocytosis of PDGA-conjugated microbeads by the RAW 264.7 macrophage-like cell line in the presence and absence of shielded aptamers and versus serum opsonized PDGA-conjugated microbeads. Since polyanionic PDGA appears to inhibit phagolysosome formation and killing of ingested bacteria, targeting PDGA with 2'-amino-modified aptamers may serve to partially neutralize the polyanionic charge and enable bacterial killing by the respiratory burst. In Phase II, OpTech will clone and sequence all aptamers, then assess aptamer-opsonization and bacterial killing in RAW 264.7 cells with virulent anthrax at the Southwest Research Foundation. Since anthrax and some other infectious bacteria utilize capsules to evade phagocytosis, any inexpensive reagent that acts as an effective opsonin would be of tremendous value in the medical, veterinary or agricultural communities. If successful, OpTech will possess a pharmaceutical substance of great commercial value in the post-exposure treatment of anthrax. Further development of the concept for shielded aptamers against hyaluronic acid or other capsule materials, for example, would also lead to better treatments for many Streptococcus-related infections. Such shielded aptamers could even be used in inhalers to enhance alveolar macrophage phagocytosis.