Recombinant proteins transgenic production

The first hurdle encountered during the development of alfalfa as a recombinant protein production system was the relative inefficiency of the available expression cassettes. A study in which a tomato proteinase inhibitor I transgene was expressed in tobacco and alfalfa under the control of the cauliflower mosaic virus (CaMV) 35S promoter showed that 3-4 times more protein accumulated in tobacco leaves compared to alfalfa leaves [5]. Despite the low efficiency of the CaMV 35S promoter in alfalfa, bio-pharmaceutical production using this system has been reported in the scientific literature. Such reports include expression of the foot and mouth disease virus antigen [6], an enzyme to improve phosphorus utilization [7] and the anti-human IgG C5-1 [8]. In this last work, the C5-1 antibody accumulated to 1% total soluble protein [8]. 

In order to reduce the time required to confirm the accumulation of a given recombinant protein, we have developed a cell culture system in which transgenic alfalfa callus material produced at the proliferation step of Agrobacterium-based transformation is used to initiate cell cultures. These cell suspensions can be subcultured to sustain batch production of modest protein amounts. The protein blot shown in Fig. 1.2 demonstrates our ability to detect a recombinant protein in total... 

There has been a large number of field trials of transgenic crops that accumulate recombinant proteins, but the results of only a few have been reported so far. Of particular interest for the future are reports of detailed trial protocols that address confinement concerns multi-location, multi-year performance and stability data environmental impact and non-target impact studies and GLP production. The impact of production conditions on extraction efficiency and product quality are also significant issues that should be addressed through field-testing. 

Recombinant proteins with unique properties can potentially generate new markets and penetrate into existing markets if they can be supplied on a large scale. An ideal system would produce the safest biologically active material at the lowest cost, and would be used in combination with an inexpensive and simple purification process. So far, there have been several examples of the high-yield production of recombinant proteins in transgenic crop plants, mainly in the area of molecular medicines such as antibodies, enzymes and vaccines [45, 48-50]. Modern agricultural practices offer... 

The development of a by-production system could further minimize the cost of such plant-derived products. For example, potatoes are the raw material for the production of technical grade starch. During this process, soluble proteins are separated by heat treatment and sold as animal fodder. Recombinant proteins could be produced in transgenic potato tubers as a by-product of starch extraction, and this would be useful for proteins produced in large amounts with a low commercial impact, like structural fiber proteins. 

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