Development of a general system for the production of controlled levels of proteins in eukaryotic cells

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The ability to express specifically designed proteins in the cells of higher organisms is a vital tool in modern biology and biotechnology. It is widely used to produce new medicines and vaccines for medical applications. Recent examples of this include the production of the anti-breast cancer drug, Herceptin, and the anti-human papilloma virus vaccine, Gardisil, which are produced in mammalian and insect cells, respectively. As part of a research programme aimed at producing vaccines at low cost in plants, we have developed a very efficient method for producing significant quantities of specific proteins in leaves. This method will be very useful for screening different proteins for their ability to be developed into new vaccines, especially since the proteins can be produced in only a few days. In addition, with colleagues, we have been able to show that we can use the system to express active enzymes in plants. This means we can alter the plant's metabolism so that it can produce new compounds which maybe of use to industry or medicine. In the current application, we propose to further develop our system for expressing proteins so that it can be more easily used by other researchers. A great advantage of our new system is that it is possible to control the amount of each protein that is produced. This is important when several proteins operate together since they are not always present in the same amount. Example of this are antibodies which are secreted by the skin; these consist of four different proteins which are present in different amounts in the assembled complex. Such antibodies have attracted much attention as therapies are very difficult to make by existing methods. Another use will be the introduction of a series of enzymes which can catalyse a series of reactions in a metabolic pathway. In such pathways, the enzymes are often present in very different amounts - a fact which is very important in ensuring that the correct compounds are made. Therefore being able to control the levels of each enzyme will be very important. Though originally developed as a means of the rapid production of proteins in plants, recent experiments have suggested that our system may also work well in insect cells of other higher organisms. We wish to examine if this is really true and to test expression in the cells of other higher organisms. If these experiments work as we expect, the research will have profound effects on how medicines and other important proteins are produced.