SYMPOSIA S1 S1.1 Genetically modified plants S1.1-1 Novel plant systems for the production of pharmaceutical recombinant proteins

The rapidly growing number of therapeutic proteins in clinical development has created a major manufacturing shortage. Animal, bacterial, fungal and plant systems have been recruited to alleviate the production bottleneck. However, plants may provide a particularly efficient manufacturing system for this rapidly growing market. Transient or stable expression has already been used to produce many recombinant proteins in various plant species. While most plant systems require plant harvesting and extraction, we have engineered tobacco roots to produce and continuously secrete heterologous recombinant proteins, such as antibodies. The yield of a recombinant protein produced via this, so-called rhizosecretion technology exceeded 20 mg/g root dry weight. In order to further decrease gene-to-protein time while increasing the yield of a target recombinant protein produced by rhizosecretion, we have developed a new strategy based on the ability of Agrobacterium rhizogenes rol genes to induce massive proliferation of recombinant roots. When a heterologous gene was cloned next to the rol cluster, more than 90% of the proliferating roots express the transgene cassette, and the expressed protein could be assayed as early as 3 weeks after inoculation. When combined with a root-specific promoter and a strong plant secretion peptide, this strategy resulted in the continuous secretion of the target protein from the transgenic root system into the hydroponics medium. Gene amplification strategies that employed parts of nontranscribed spacer region of tobacco rDNA genes further increased the yield of the recombinant protein.