Tobacco Plants as Biofactories: Rapid and Cost-Effective Production of an Anthrax Therapy

The 2001 anthrax mailings raised awareness of the devastating effect a massive bioterrorist attack could have. In case of a large-scale outbreak, responsive, scalable, and cost-effective manufacturing technologies are needed to rapidly deliver effective therapeutics into the clinical setting. Non-transgenic tobacco plants can be used as cost-effective biofactories of therapeutic proteins. Agrobacterium, a bacteria that naturally transfers genetic material into plants, can be engineered to rapidly enable production of a protein of interest in tobacco. The infiltration of Agrobacterium into tobacco comprises the innovative manufacturing platform we are developing. Our research focuses on developing this technology for producing CMG2-Fc, an experimental antibody for anthrax. Of particular interest is using suppression of plant gene silencing as a strategy to increase the yield of CMG2-Fc in tobacco. We tested the co-production of CMG2-Fc with nine different gene silencing suppressors: p1, p10, p19, p21, p24, p25, p38, 2b, and HCPro. The ELISA assay was performed to quantitatively measure the amount of CMG2-Fc protein produced in tobacco. We observed that using gene silencing suppressor p1 resulted in a maximum production of 0.56 g CMG2-Fc per kg of tobacco leaf after only 3.5 days post-infiltration, a ten-fold increase in the production level when compared to absence of suppression. This result is significant because 1 g/kg is considered the production threshold that will make this technology commercially viable. This innovative manufacturing platform has great promise, because it is easy to customize for quick and large-scale production of virtually any therapeutic protein, including vaccines and antibodies.