Monoclonal Antibody Expression and Novel Purification in Nicotiana benthamiana
Fulton, Andrew Dale
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Over the past few decades researchers and industrial professionals alike have realized the vast potential of monoclonal antibodies to treat diseases ranging from arthritis, immune and infectious diseases to cancer. There are a number of antibodies on the market that constitute a large portion of the biopharmaceutical niche in the drug industry. Blockbuster drugs (selling greater than $1 billion/year), include antibodies such as Avastin (bevacizumab), Herceptin (trastuzumab), Rituxan (rituximab), Humira (adalimumab) and Remicade (infliximab), which are cornerstones in this type of sector. With the cost of development to market approval rising astronomically for a new drug, new ways to produce and process these molecules becomes a paramount objective to ultimately help both patients and drug developers. Plants, such as Nicotiana benthamiana, offer a unique production platform due to their recently found ability to produce large amounts of therapeutic proteins in a quick manner. While production would be simple and cheap, purification would not be due to the presence of toxic compounds in ground plant tissue. The current methods to purify these molecules from plant extract include expensive affinity column steps (Protein A/G) that are difficult to scale-up to bed volumes that would be necessary for this technology. In the following paper, a method to purify a monoclonal antibody by non-Protein A/G resins is accomplished and compared to purification by Protein A. The modified process involved an UF/DF step, a precipitation of native impurities step using a charged polymer, hydrophobic interaction chromatography and hydrophobic charge induction chromatography. The yield of this modified process was 19.0%. This process compared favorably with Protein A due to the fact that even with washing steps including NaCl and Tween-20, the Protein A elution fraction still contained a large portion of host cell impurities. A chromatography step would need to be included before Protein A to both protect the column resin and provide a more purified immunoglobulin.
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