Botulinum Toxin Plantibodies

Our overall goal in this project is to make available inexpensive neutralizing antibodies against Botulinum neurotoxin (BoNT) in large quantity, using transgenic plants. Dr. James Marks (UC San Francisco School of Medicine) has identified murine and humansingle chain Fv (scFv) that bind non-overlapping epitopes on BoNT/A and neutralize toxin in vitro and in vivo. At present, plants offer the best system for the large scale, inexpensive production of these antibodies. Genes encoding the three bestantibodies, codon-optimized for plant expression, will be cloned into vectors designed for the expression of human IgG1 in leaves of transgenic tobacco and seed of Tepary bean (Phaseolus acutifolius). Plants will be transformed with these constructs,regenerated and screened for expression of antibody. Plants expressing high levels of the antibodies will be identified and used to purify enough of each antibody to characterize structure and binding affinity. We estimate that plants will facilitate theproduction of metric ton quantities of antibodies at 1-5% of the cost of steel tank bioreactors. Plantibody technology will greatly reduce the costs to stockpile antibodies for protection of the population from this serious threat. The successfulcompletion of the aims of this project will result in the availability of lage quantities of neutralizing anti-botulinum toxin antibodies at low cost. These antibodies would be used for passive immunization of people exposed to, or at risk of exposure tobotulinum toxin.