We propose to use a novel gene repair technology (chimeraplasty) to generate serum carboxylesterase (CaE) deficient mice. Serum CaE acts as an endogenous anti-organophosphate (OPs) bioscavenger that provides mice with inherent protection against OPs. Unlike mice, humans and non-human primates lack serum CaE and are much more susceptible to OP toxicity. The inherent resistance of rodents limits their use as a model system for development of prophylactics that detoxify organophosphate based agents. A transgenic mouse that lacks serum CaE would provide an inexpensive alternative to non-human primates. Creation of serum CaE deficient mice is proposed by treating embryonic stem cells with chimeric RNA/DNA oligonucleotides (Chimeraplasts) directed at disrupting the Es-1 gene that encodes CaE in mice. RNA/DNA oligonucleotides have been used (Chimeraplasty) both in vitro and in vivo to correct, mutate, and disrupt genes in systems as diverse as bacterial cells and rodents. Chimeraplasty uses endogenous DNA repair mechanisms and does not introduce foreign DNA or potentially deleterious reporter genes. Once the animals are established they will function as models for the testing of antidotes and establishing the in vivo safety and efficacy of a number of bioscavenger molecules and to develop prophylactics to eliminate OP toxicity. The availability of a small rodent model will increase the rate of development of antidotes designed to eliminate the toxicity of organophosphate nerve agent exposure. This model will provide a high throughput system for establishing the safety and efficacy of a number of different prophylactics. At the present time only expensive primates serve as a reasonable animal model for human toxicity and development of prophylactics against OP based nerve agents. This inexpensive rodent model will dramatically decrease the costs associated with this much needed development. This model will also be of commercial interest to the pesticide business community to help identify means for detoxification of organophosphorus based pesticide exposure. Of the 25,000 brands of pesticides available in the U.S., most are either organophosphate or carbamate compounds. These compounds are responsible for 80% of the pesticide poisoning in the U.S. The pesticide industry is a $30 billion dollar industry that has been stagnant due to several issues, which include the contemporary awareness to environmental issues. This model system will help to develop less toxic compounds, which will spurn market growth, especially appealing to the residential consumer.
