Getting A Boost From Edible Vaccines

A team of researchers from the University of Guelph, in collaboration with Agriculture and Agri-Food Canada (AAFC), is joining forces to produce edible animal vaccines in crops plants. Using genetic enhancement techniques, the researchers are introducing special genes into the plants to generate novel proteins which they believe will ward off specific diseases. The proteins can be isolated from plants, incorporated into livestock feed and used to vaccinate animals in a more humane -- and economical -- way than by the traditional "injection" method.

The first edible product, designed to promote improved gut development and function in pigs, is expected to be available to the swine industry within five years. A vaccine for transmissible gastroenteritis virus (TGEV), a disease that causes severe diarrhea in swine and high mortality in piglets, could save the Canadian swine industry more than $10 million per year. "We're starting with pigs, but there's no reason this technology couldn't be applied to other species," says research team member Larry Erickson, from the University of Guelph's Department of Plant Agriculture. "The potential to enhance the health and productivity of Canada's farm animals is considerable." Edible technologies are part of a new science known as molecular farming. In a nutshell, molecular farming is a form of biotechnology used to produce medicinal or industrially significant compounds in plants traditionally used in agriculture. These "super plants" include corn, soybeans, alfalfa, potatoes and tobacco that grow, look and yield like their conventional cousins, but are outfitted with certain traits that give them therapeutic properties. Farmers across the country could grow these high-value, single harvest, medicinal plants alongside traditional crops, giving rural economies a healthy boost through diversification. Crop plants are ideal "bioreactors" to produce the prized proteins -- they're able to produce large amounts of the proteins in seeds and leaves, and lend themselves to easy harvesting.

The potential of technologies like molecular farming are far-reaching for livestock and humans. Production of oral vaccines against Porcine Reproductive and Respiratory Syndrome (PRRS) is being investigated by Erickson and AAFC scientist Jim Brandle. Oral vaccines for other diseases like parvovirus are also under development.

Erickson predicts the same technology could be used to tackle bacterial infections by producing plants with antibiotic properties. As well, growth factor proteins could be grown in plants and fed to livestock to bolster production and combat stress caused by weaning or disease recovery. On the human front, edible medicines designed to prevent juvenile diabetes and to treat Crohn's disease are being investigated in a joint project being conducted by AAFC and the London Health Sciences Centre. Clinical trials for an edible vaccine that protects against "traveler's diarrhea" are already underway in the United States. Dr. Jim Brandle is a plant geneticist from AAFC's Southern Crop Protection and Food Research Centre in London, Ontario. He's optimistic that producing low-cost, therapeutic proteins free of pathogens and toxins — as a very renewable agricultural resource — will become more widespread as the technology becomes more accepted. "Plants have always been a source of medicines," says Brandle. "Now, we can createspecific medicinal properties in plants using genetic enhancement techniques." Many of these research projects were presented at the 1999 International Molecular Farming Conference, held August 29 to September 1 in London, Ontario.

The PRRS research is supported in part by the Ontario Research Enhancement Program, a $4-million federally funded research initiative administered by the Research Branch of AAFC with input from the agriculture and agri-food sector, universities and the province. OREP supports 25 research projects in universities and research centres across the province, with the University of Guelph as a major participant. Projects focus on two key areas identified by the agriculture and agri-food community: consumer demand for higher quality safe products and ensuring crop production management systems that are environmentally sustainable.