While protein synthesis using transgenic plants like maize, tobacco, oilseed rape and soya is at an advanced stage of development, conventional methods require the creation and maintenance of crop strains that contain genetic material that encodes the desired protein. Bayer's process, which was developed Icon Genetics prior to its acquisition by Bayer in December 2005, utilises a virus-based mechanism to transfer the desired DNA sequences to the tobacco plants in order to expedite the protein production process, and remove the need to develop transgenic plant strains. Speaking at the new facility's inauguration, a Bayer spokesman said that: "Under normal circumstances, new production processes tend to be of minor significance in the manufacture of medicines. But the importance of this project to produce therapeutic proteins in tobacco plants goes well beyond the idea of producing a single drug. It is intended to mark the start of a whole range of innovative new active substances which can offer customized solutions for a number of diseases." "We are now able to use plants to produce active pharmaceutical ingredients in a quality that we need for clinical trials with new drugs. This has brought us a big step closer to our vision of being able to 'harvest' medicines from plants in the future," he added. Virus-based DNA transfer Bayer's technique uses high-yield tobacco plants produced in a rich growth media containing a modified version of the bacteria Agrobacterium tumefaciens that has been implanted with a tobacco mosaic virus (TMV) containing DNA encoding the desired protein. The virus infects the tobacco plants, injecting its genetic material into the nucleus of the plant's cells where it is expressed when they are subsequently retuned to the Halle facility's greenhouses. The advantage of Bayer's technique is that because the DNA sequences can be rapidly transferred to wild-type tobacco plants, no potentially time consuming crop development steps are necessary. While the tobacco plants eventually lose the recombinant DNA as the TMV infection runs its course, a batch production process can be implemented to ensure that there are always plants available. In addition, because genetic manipulation of TMV is a relatively straightforward and established technique, Bayer's approach could be readily adapted to produce a wide range of proteins in a relatively short period of time.
Germany's Bayer hopes that its pilot-scale production facility in Halle, Saxony-Anhalt will help establish its tobacco plant-based expression system as leader of the lucrative protein manufacturing sector.