Researchers at the Biotechnology Foundation at Jefferson Medical College have genetically engineered tobacco plants to produce human proteins – antibodies – against rabies. Scientists, led by Hilary Koprowski, M.D., professor of microbiology and immunology and director of the Biotechnology Foundation Laboratories and the Center for Neurovirology at Jefferson Medical College of Thomas Jefferson University in Philadelphia and Kisung Ko, Ph.D., research associate at the Biotechnology Foundation at Jefferson Medical College, have inserted DNA coding for an antibody against the rabies virus into tobacco plants. The plants, in turn, become factories churning out antibody.
The report appears online this week in the Proceedings of the National Academy of Sciences.
According to Dr. Koprowski, who created the currently used vaccine against rabies, there is a worldwide shortage of antibodies against rabies. They are expensive to get from humans and antibodies derived from horse blood carry unwanted side effects.
The researchers first showed that antibody could neutralize rabies virus and prevent infection in mice. Using plant antibody, Chuck Rupprecht, D.V.M., chief of rabies at the Centers for Disease Control and Prevention in Atlanta, prevented rabies in hamsters inoculated with a lethal dose of "street" virus.
"The antibody produced in tobacco is as good as the antibody produced in animal cells," says Dr. Koprowski, noting that tobacco-derived human rabies antibody should be safer and less expensive to produce.
Rabies, which is fatal and incurable, is usually acquired through the bite of an infected animal. If treatment with antibody and vaccine is given as soon as possible after exposure to the virus, it may prevent rabies.
Dr. Koprowski points out that an antibody would be used in cases of severe animal bites. "A vaccine might be too late to develop antibodies," he says. "The recommendation is to first inject the antibody serum, then give the vaccine," which in turn elicits the production of antibodies for long-term protection.
Dr. Koprowski stresses the need for a commercially available antibody against rabies. He says that up to about 50,000 cases of human rabies occur annually in Asia (40 percent in children) and 7.5 million people receive the treatment after exposure.
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