Michael A. Plesha1, Ting-Kuo Huang1, Mysore R. Sudarshana2, Sandra L. Uratsu3, Bryce W. Falk4, Abhaya M. Dandekar3, Alan P. Jackman1, and Karen A. McDonald1. (1) Department of Chemical Engineering and Materials Science, University of California at Davis, One Shields Avenue, Davis, CA 95616, (2) Western Institute for Food Safety and Security, University of California at Davis, One Shields Avenue, Davis, CA 95616, (3) Department of Plant Sciences, University of California at Davis, One Shields Avenue, Davis, CA 95616, (4) Department of Plant Pathology, University of California at Davis, One Shields Avenue, Davis, CA 95616
Transient recombinant protein expression has been evaluated as a production route capable of enabling rapid, large-scale production of functional human therapeutic proteins that could be needed for widespread treatment and/or vaccination in the event of a crisis. In this study, transient expression of a model human blood protein, alpha-1-antitrypsin (AAT), was demonstrated by agroinfiltration of Nicotiana benthamiana leaves and suspension cultures. Production of functional recombinant human AAT was evaluated in planta after coinfiltration with Agrobacterium tumefaciens carrying one of three different expression cassettes (constitutive, chemically inducible, or a chemically-inducible viral amplicon) and Agrobacterium tumefaciens carrying the potent gene silencing suppressor p19. Functional recombinant AAT reached levels of up to 17 mg per 100 g leaf tissue and was stable in plant biomass for up to four days. Production in planta was compared to recombinant AAT produced constitutively in suspension cultures. By utilizing this transient expression system, functional human protein was produced in just 4 days from a frozen stock of recombinant Agrobacterium tumefaciens.