(228as) Transient Production of a Recombinant Anthrax Receptor Fusion Protein in Nicotiana Benthamiana Plant Cell Suspension Culture

Faster production of experimental protein therapeutics or vaccines at a large-scale is needed to respond to emerging infectious disease outbreaks or bioterrorist threats. We are investigating transient protein expression in plant cell suspension culture as a new platform that could be used to rapidly manufacture large quantities of novel protein therapeutics. Plant cells are being explored as an alternative to mammalian expression systems because they can also produce complex proteins, but enhance product safety and efficacy in some cases. Our system uses genetically engineered Agrobacterium tumefaciens to mediate transient protein expression in Nicotiana benthamiana plant cell suspension culture. A key advantage of our system is that these Agrobacterium constructs could be produced in a few weeks while stable transgenic plant or animal cell lines take months to develop and screen. By co-culturing recombinant Agrobacterium and N. benthamiana in suspension, we have produced an anthrax toxin receptor Fc fusion protein at levels up to 0.7 mg per kg of plant cell fresh weight after 9 days of co-culture. However, reduced intracellular protein levels and evidence of plant cell lysis have also been observed after co-culture with Agrobacterium. To increase recombinant protein expression levels in this system, we are testing various strategies to reduce effects on plant cell health associated with Agrobacterium infection.