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- New York Thompson Institute for Plant 26 - "WEEKEND STAR" FRIDAY, NOVEMBER 24, 2000 Take two potatoes and call me in the morning Foods may replace needles for the delivery of vaccines By Jenny Dobbin Edible vaccines produced in plants could provide a low cost and needle-free "alternative for protection against disease, espe- cially in developing countries. Clinical human trials using edible vaccines in raw potatoes to immu- nize against viral and bacterial diarrhea have been conducted by state's Boyce Research at Comell University, at the University of Maryland School of Medicine, Center for Vaccine Development in Baltimore, Maryland. Preliminary results are encouraging - . Dr. Charles Amtzen, President and CEO of the institute, is confident a proto- type product of edible vaccines could be ready in the next three years. An estimated 10 million children die each year from infectious dis- eases, and diarrhea caused by bacteria or viruses accounts for one-quarter of them. Amtzen says the plant-produced vaccines will meet the need for more effective and less.expensive oral vaccines that can be produced worldwide. "Although vaccines to prevent these diseases are theoretically possible, the cost of production and the limited income of potential recipients prevents their use in parts of the world where the dis- eases have the most profound impact," he says. Vaccines being used today are generally of two types - killed (dead) or attenuated (live) - that induce immunity to specific dis- eases in recipients. Because they don't replicate in the host, the killed vaccines are not as effective as the attenuated vaccines. They require relatively large doses, and because there is no way to ensure the killed micro-organisms are indeed all dead, infection can still occur. On the other hand, live vaccines use attenuated - or weakened - strains of living microorganisms that have lost their virulence or toxicity. Because the weakened viruses are still alive, they contin- ue to replicate in the body and improve immune response. Although rare, infection can also occur with the use of this type of vaccine, as the attenuated micro- organisms may revert back to their virulent form. These vaccines require refrigeration and are quite costly to produce, limiting their accessability. The new edible vaccines being produced in plants are recombi- nant vaccines, developed through genetic engineering technology. Central to this process are anti- gens, protein components of the "DURHAM COUNSELLING SERVICES | COUNSELLING FOR Families &E Individuals Specializing In: e Step Families ® Relationships e Abuse Counselling ® Children & Teens ® Depression call Suzanne Doupe pathogen that induce an immune response when administered to humans or animals. Selected genes of the pathogen that code for the antigens are introduced into the genetic make- up of the host plant. To do this, a common soil bacterium called Agrobacterium is used. The gene that codes for a particular antigen is introduced into the DNA of the Agrobacterium. When it infects the host plant it inserts its DNA, including the gene for the antigen, into the chromosomes of the plant. Following the transfer of the anti- gen gene to the plant, the gene is expressed and the antigenic pro- tein is produced. The antigen accumulates and assembles with- in each plant cell, existing as a pre-packaged and stable vaccine. The strategy of oral vaccines is to induce an immune response in the human/animal following ingestion of plant material containing the antigen. With this method, there is no risk of infection because the whole pathogen is not present in the plant, just the antigens. Ideally, the antigens stimulate an immune response in the intestine through the secretion of antibodies which bind to the pathogen and inhibit uptake therefore preventing infec- tion. These types of vaccines are also being studied for animal health and welfare. Prof. Larry Erickson of the University of Guelph's Plant Agriculture Department, who is working with researchers at the Ontario Veterinary College to develop edible plant proteins for enhancing immunity in livestock, says the technology has a lot of potential. However, he notes that more research is needed to deter- mine its impact. "The use of edible vaccines may not be as simple as it sounds," says Erickson. "It probably would- n't come to the point where a doc- tor recommends buying 12 cobs of DION TdT Mg Ele [e [TO MD B OPTOMETRIST * Primary Eye Care * Full Ocular Assessments « Laser Co-management & Consul NEW PATIENTS WELCOME! 28B Water Street, Port Perry * Computerized Field Analysis * Customized Contact Lenses The Ontario Association of Optometrists recommends that every child have their eyes examined first (905) 085-9385 by age three and then regularly as advised by their optometrist. Katy Morgan, sa. PSYCHOTHERAPIST Clinical Member of Ontario Society of Psychotherapists Certified Member of Ontario Association of Consultants, Counsellors, Psychometrists & Psychotherapists, Certified Imago Relationship Therapist e Individual And Couple Counselling ¢ Grief Counselling ¢ Counselling For Incest and Sexual Abuse Survivors 870 REGIONAL RD. #21, Port PERRY OFFIicE 985-4161 | fl; 219 ST. CLAIR AVE. W. SUITE 203, TORONTO, OFFICE 416-967-6262 corn for vaccination purposes. They would have to control dosage and account for the differ- ences in how the body absorbs food and immune response." Though the risks for this technolo- gy seem to be few, there are still a number of questions that need to be answered regarding the effects of overuse and its impact on pro- tection. Erickson says regulatory organizations will have to look at potential environmental and food chain impacts that growing these modified plants could have, although none can be foreseen as yet. 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