Bioscavenging of organophosphate (OP) by human proteins is emerging as a promising medical intervention for prophylaxis and post-exposure treatment against chemical warfare nerve agents. The best-studied bioscavengers (BSCs) to date, meeting considerable success in pre-clinical research, are human cholinesterases (ChEs). However, ChEs, which are highly efficient in binding and sequestering OPs, are also inactivated by the toxins and therefore administration of large amounts of protein is necessary for full protection, raising the question of the practicality of this approach. However the development of a new generation of BSCs that can catalytically degrade OPs may address this concern. The proposed effort offers a novel means to biomanufacture recombinant catalytic BSCs based on the human proteins butyrylcholinesterase and paraoxonase 1. Through efforts of other projects participating in the Center, the capacity of these proteins to hydrolyze OPs will be improved by subjecting their genes to either random in vitro evolution or rational mutagenesis. Concomitantly to the protein engineering research, the ASU team in this Project 5 will utilize tobacco plants to first produce research-scale quantities of BSC enzyme, but also provide a sustainable large-scale production platform. At present, purification of BChE from outdated blood-banked human plasma enables research on how bioscavenger therapy can be used. But this stop-gap measure cannot be practically implemented to allow for a sustained supply of that enzyme, and is not applicable for the new recombinant catalytic BSCs that will be developed by the Center. If it will be decided that such scavengers should be a component of the medical arsenal of the Departments of Defense, Homeland Security and Health and Human Services, it is vital that a reliable, safe, non supply-limited and inexpensive source of such enzymes be identified and developed. The primary significance of the proposed work is that it translates basic studies on the first generation ChE-based BSCs into novel biomanufacturing technology leading to clinical product development of the second generation catalytic BSCs.
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