(683g) A Chemically Inducible Cucumber Mosaic Virus Amplicon Expression System for Production of Recombinant Human Therapeutics in Transgenic Plant Cell Cultures

Plant cell cultures are entering a new phase of application and playing an increasingly important role in production of human therapeutics. However, efficient expression systems are currently lacking in transgenic plant cell cultures. In this study, we established a novel Cucumber mosaic virus (CMV) inducible viral amplicon (CMViva) expression system to inducibly and efficiently produce a human blood protein, alpha-1-antitrypsin (AAT), in transgenic plant cell cultures. We achieved higher levels of extracellular functional recombinant AAT and higher ratio of functional recombinant AAT to total recombinant AAT production in bioreactor using the CMViva system compared with either a Cauliflower mosaic virus (CaMV) 35S constitutive promoter expression system or a chemically inducible promoter expression system (an estrogen receptor-based, estradiol-inducible promoter system, XVE). We investigated the effects of timing of induction (TOI) and concentration of inducer (COI) on recombinant AAT production in inducible expression systems (XVE and CMViva), and medium exchange and pH on the recombinant AAT production using above three expression systems in transgenic Nicotiana benthamiana suspension cell cultures in bioreactors. A rational induction strategy is proposed for improving the functional recombinant AAT production yield.