For centuries, aboriginal peoples have known the aspirin-like compound found in the bark of willow tree would ease pain. More recently, a random deposit of a fungus spore on a bacterial culture started Sir Alexander Fleming on the road to discovering penicillin. Although plants have always been a source of medicines, modern biotechnology has created a twist on what will be considered a medicinal plant.
It can be argued the first medical product of biotechnology was recombinant human insulin. By inserting the human insulin gene into a bacterium, scientists created "Humulin." It became a commercial product to treat people with diabetes in 1982. Recombinant human insulin has made life much better for diabetics, who no longer suffer the complications of using insulin isolated from pigs.
Today, scientists are using recombinant DNA technologies and common agricultural plants to produce a wide range of pharmaceutical compounds. These medicine-producing engineered plants are often called pharma-crops. Scientists have successfully inserted genes into barley, maize, carrots, tomatoes, alfalfa, bananas, rice and tobacco. The engineered genes range from those that code for proteins found in milk and tears, to potential vaccines.
There has been a large outcry about a biotech pharma-crop that was recently planned to be grown in California and then later in Missouri. The biotech crop is rice and the engineered proteins are lactoferrin and lysozyme. These two human proteins can be found in breast milk, saliva and tears. They hardly represent a dire threat to our food supply, as many media stories have stated. Recently, such stories convinced a major beer producer to not buy any rice grown in the vicinity of these engineered crops. Why? Because critics have spread fear that these engineered rice crops could contaminate other rice fields by cross-pollination.
The problem with that story is that rice self-pollinates and therefore does not spread its pollen to the wind. There are also very conservative, mandatory geographic isolation and harvesting procedures to reduce the chances of cross-pollination to near zero for all pharma-crops. Those who demand zero risk do not seem to understand there is no such thing as risk-free anything.
The production of these two proteins in large quantities may help reduce infant mortality in many parts of the world. Bacterial infections cause severe diarrhoea that kill millions of children in the developing world each year. Lactoferrin and lysozyme have been proven to help reduce these bacterial infections.
Unfortunately, it is all too common to read or watch a story that greatly exaggerates a scary aspect of biotechnology. Somehow the positive side of the story never seems to be given equal exposure. It is important that we look at the whole risk/benefit evaluation for this biotech crop and stop publishing only the hypothetical risks. There are millions of children who could benefit from this engineered rice.
It may be that the demands of critics will slow the use of food crops for pharmaceutical production in the near future, but that does not mean that these technologies will stop. Non-food crops like tobacco are becoming a favourite of biotechnology researchers. There is something deliciously ironic about tobacco becoming a major medicine-generating crop.
Research has shown promising results in the production of Insulin-like Growth Factor (IGF-1) in both rice and tobacco. Injection of this human protein is one of the few treatments that slow the progress of Lou Gehrig's disease. Similar successes have been demonstrated with plant derived genetically engineered monoclonal antibodies that protect against rabies and colorectal cancer.
It has been estimated that vaccines save three million lives each year. For the past 30 years chicken eggs have been used to make vaccines. Unfortunately not all vaccines can be made this way. A good example involves the Human Papilloma Virus (HPV). This virus can be grown only in human cells and, therefore, we cannot produce a Papilloma vaccine in chicken eggs.
There are over 140 different types of this virus, most do not cause any harm but a few are associated with cancer. According to the World Health Organization there are 600 million people infected with HPV worldwide, over 20 million in North America alone. The pathogenic strains cause a half million cases of cervical cancer each year, mostly in the developing world. Poor access to PAP smears in developing countries means that nearly half of those cases are fatal.
Researchers have engineered a tobacco plant to produce the VP16-L1 protein from the HP virus. Tests have shown the recombinant protein to be very effective at generating an immune response against the virus. With this breakthrough, it will soon be possible to make large amounts of this protein vaccine. There are significant logistical problems with production and storage of purified vaccines in the developing world; therefore researchers are working to produce an oral version of the HPV vaccine in tomatoes. It is hoped that soon young women in less developed countries will only have to eat a few specially engineered tomatoes to gain immunity to this killer virus. Other researchers are developing vaccines in bananas or other local crops. If a vaccine could be grown locally, many of the huge logistical problems associated with vaccination programs would be eliminated.
The cost of developing a single pharmaceutical product is often close to a billion dollars. A significant portion of the expense is for special cell culture laboratories. Often tens of millions of dollars worth of cell culture will produce less than a gram of medicine. Plant-made pharmaceuticals can greatly reduce these costs and increase the yields.
The potential of pharma-crops is best illustrated with the anthrax story. At present, there is only one form of vaccine that protects against anthrax. Along with being expensive to produce and store, it has generated significant side effects in some people. Researchers have engineered the protective antigen (PA) from anthrax into tobacco. This time, instead of inserting the gene into the nucleus, of which there is one per cell, they inserted it into the chloroplast. With up to hundreds of chloroplasts per cell, this greatly increases the yield of the engineered protein. The fact that chloroplasts are not present in pollen also means the potential cross-pollination problem is eliminated. With 40 tonnes of leaf tissue per acre and 2-3 harvests per year, the ability to produce large amounts of the anthrax vaccine in tobacco is soon to be a reality. Only one acre of genetically engineered tobacco will produce 400 million doses of stable anthrax vaccine.
Today pharma-crops produce $19-billion of pharmaceuticals. It is estimated that by 2010 genetically engineered crops will generate $100-billion of medicinal products. Golden Rice, with its engineered beta-carotene, will soon be available to help prevent 500,000 children from going blind from lack of vitamin A each year.
Salt and drought tolerant crops will allow present lands to remain productive and even increase yields in marginal soils. Insect resistant crops will continue to generate large yields with reduced pesticide use. Herbicide tolerant crops will continue to allow farmers to preserve precious topsoil. Bio-fuels will help reduce our needs for foreign oil.
The future will see pharma-crops adding to the benefits agricultural biotechnology brings to the world.
Thursday, December 1, 2005 Posted at 9:56 AM EST
Special to Globe and Mail Update