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Before it was known how to manipulate living organisms, many materials that are used to benefit human health and industry were first isolated from natural resources. One example is the drug urokinase, which is used to break up blood clots following myocardial infarction. Twenty years ago, urokinase was purified from urine that was collected from public rest areas along highways. However, the development of recombinant DNA technology has made it possible to produce urokinase in large amounts at low cost by introducing the gene into microorganisms and growing them to produce the drug. In addition to urokinase, more than one hundred useful materials are now produced using recombinant DNA technology. Generally, microorganisms, such as E. coli and yeast, and animal cells, such as Chinese hamster ovary cells, are used to produce these materials in large amounts. For example, the vaccine used to prevent hepatitis B virus infection was first produced by collecting defective virus particles from the blood of hepatitis B virus carriers. However, this vaccine could potentially be contaminated with viral DNA, which can cause a hepatoma, or other infectious materials. Now, the vaccine is produced using recombinant yeast that has been modified to produce the antigen by introducing the virus antigen gene. Korea used to have to purchase the blood of hepatitis B virus carriers from China to produce vaccine, but using recombinant DNA technology we can now produce surplus hepatitis B vaccine and export it to other countries. Although microorganisms and animal cells are still the most popular hosts, these systems have possible pitfalls. For example, material produced using microorganisms might differ slightly from that produced in animal cells, making it less effective than the naturally available product, and perhaps causing unwanted immune responses in humans. For example, because the human growth hormone produced from microorganisms is slightly different from that of humans, an injection of human growth hormone from microorganisms sometimes induces an immune response against the hormone, rendering it ineffective. In addition, material produced using animal cells can contain contaminants, such as unwanted infectious materials, since serum from cows is added to animal cell cultures. Therefore, extreme caution must be taken to eliminate all possible contaminants from such products during the purification procedure, and this process increases production costs significantly. Until the early 1990s, plants were not considered useful for producing recombinant material owing to several technological shortfalls. For example, plants and plant cells grow too slowly in comparison with microorganisms and animal cells, and there was also no efficient vector system for delivering desirable genes into plant cells. With the recent accumulation of knowledge on plant molecular biology and the development of an efficient vector system that uses bacteria which infect plants and produce plant tumors, researchers are starting to consider plants for producing useful materials. Plant cells can be grown in very inexpensive media and require only sugars and salts for their growth, making plant-based expression systems very cost effective, with much lower production costs than other expression systems. In addition, plants do not require potentially harmful materials for their growth, such as the bovine serum that is essential for growing animal cells. Over the last seven years, our team has been concentrating on establishing a plant expression system for producing useful materials. Initially, we examined the production of cytokines, which are very expensive compounds that modulate biological responses in human and animals. One cytokine, granulocyte macrophage-colony stimulating factor (GM-CSF), is used to increase the number of blood cells in patients who have undergone bone marrow transplantation to treat leukemia, and we are successfully producing this and other valuable cytokines. We are very excited to have developed a way to produce human interleukin-12, a potent anti-tumor agent that cannot be produced from microorganisms. Based on our results with human interleukin-12, we have also succeeded in producing other therapeutic and diagnostic antibodies that also cannot be produced from microorganisms. Consequently, our laboratory has been designated a National Research Laboratory by the Ministry of Science and Technology in 2000, and is also supported by the Next Generation Technology Program of the Ministry of Commerce, Industry, and Energy. We are also studying the use of plants as an expression system to produce antigens to develop edible vaccines. Put simply, we want to produce transgenic plants that contain antigens in their tissue and that act as vaccines when eaten. We believe that this technology will prove very useful for producing vaccines against animal diseases and for vaccinating children. This method has several advantages, as it avoids the high cost of vaccinating animals by injection and it spares children the pain of conventional vaccine injections. In addition, many countries have neither sufficient refrigerated facilities to store conventional vaccines nor enough health care workers to administer them. In such countries, edible vaccines should prove a very useful delivery system. This technology was first suggested in 1990, and researchers now believe that commercial edible vaccines might be available within the next 3 to 5 years. We started research in this area in 1997. Our primary targets for developing plant-based edible vaccines are animal diseases, since clinical testing and application is much easier than when working with humans, although we are also targeting human diseases such as Dengue virus infection. These projects are currently supported by several grants, including a 21st Century Frontier Project from the Ministry of Science and Technology. The technologies that we are researching and developing might not prove commercially viable for a few years. Moreover, several points must be resolved before these technologies can be used successfully for practical purposes. However, research in new areas is always very interesting and challenging. Drs. Yong-Suk Jang and DaeHyuk Kim of the Division of Biological Sciences are collaborating in the research projects described above in the genetics/biotechnology, respectively. fields of immunology and molecular In addition, several researchers from other institutes and countries, such as the United States, Japan, Vietnam, Hungary, and France, are collaborating with us in this research.