December 06, 1996
It doesn't matter if you're a newborn calf, lamb, foal, pig, chick or human. Rotavirus can give you neonatal diarrhea, and today's vaccines aren't as effective against it as they need to be. Now, researchers from Ohio State are working to find a new way to treat this veteran virus.
Linda Saif, a researcher in the Food Animal Health Research Program at the Ohio Agricultural Research and Development Center, says current calf vaccination programs do not seem to curb the rotavirus problem. "Rotavirus is responsible for $500 million worth of economic losses in calves annually. And that's in addition to the treatment costs, poor growth rate and susceptibility to secondary infections producers face," Saif says.
Saif is working with Ohio State's Wonyong Kim and Kyeong-Ok Chang of the Food Animal Health Research Program, and John Finer and Harold Trick of the Department of Horticulture and Crop Sciences to find a new method for rotavirus control.
Initial research focuses on adding an edible oral rotavirus vaccine to corn and soybean feedstuffs. "An oral vaccine has advantages over current methods," Saif says. "It's cheaper to produce, can be manufactured in larger quantities, and because it needs no special purification, it is highly cost-effective."
Finer says researchers throughout the world are working on cloning rotavirus genes into potatoes or bananas with the idea of oral vaccines for humans, but no one has yet begun studying such a possibility for livestock.
"Few people are working on projects of this type, because it's so difficult to get the proper expertise together," Finer says. The work crosses plant and animal boundaries.
The project began in Saif's lab. The first stages involve cloning the bovine rotavirus genes. Then they'll be put into the corn and Kunitz cultivar of soybeans in Finer's lab.
Soybeans produce a trypsin inhibitor which requires heat processing before animal and human consumption can take place. Trypsin is the enzyme which allows the body to digest protein. The Kunitz cultivar does not have a trypsin inhibitor. "Our concern was that if regular soybeans were used and processed in the conventional manner, the processing might also destroy the rotavirus particle in the soybeans," Saif says.
After the genes are placed in the beans and corn, Saif says they'll use Western blot analysis and guinea pig inoculation to confirm their ability to induce antibodies.
"We'll grow up the plant tissue and plants, extract the DNA and protein, and perform some of the analysis of the tissue," Finer says. "Once the gene is in the plant and begins to express properly, we'll scale up somewhat to produce more of the vaccine for animal studies," he says. When they confirm that the plant-expressed proteins can induce antibodies to rotavirus in guinea pigs, they will begin testing the plants as oral vaccines for calves, Saif says.
Actual animal study is still in the distance, Finer says: "We are taking an animal gene and trying to put it into a plant. That's not an easy thing to do. There could be some incompatibility problems along the way."
"If all experimental trials look promising, then field trials in selected animal herds would be required to monitor vaccine efficacy under field conditions," Saif says. "I would estimate that these things would require at least 10 years or more before "test" pilot products could be available."
http://www.agriculture.purdue.edu/aganswers/story.asp?storyID=474