Aug. 1, 2000 CHAMPAIGN, Ill. -- A respiratory virus that strikes hardest at young children and the elderly in nursing homes has lost a preliminary bout with a two-fisted enemy -- genetically modified cherry tomatoes containing an edible vaccine. The match took place in lab tests at the University of Illinois.
The greenhouse-grown tomatoes carried genetic coding of a fruit-specific promoter that targets a major protein on the outside envelope of the respiratory syncytial virus. In a recent issue of the European journal Transgenic Research, UI scientists reported that 22 of 25 mice eating the
vaccine-containing tomatoes had increased antibody production in two of their immune systems.
Over 28 days, two sets of mice were fed five times with genetically modified or unaltered wild-type cherry tomatoes. Control mice fed unaltered tomatoes showed no protective response when subjected to the RSV antigen, a tamed form of the virus that still elicits immune responses.
"The results were very good," said Schuyler S. Korban, a professor of plant genetics. "They tell us that by feeding this tomato to mice, we can stimulate both the mucosal and serum immune systems."
Instead of injecting serum-based vaccines that stimulate an immune response in the bloodstream, edible vaccines could be used medicinally to build protection in the mucosal system -- immune cells along the nose, throat and mouth -- where the RSV virus first enters. The antibodies created by the immune response go after the F glycoprotein, which is responsible for the initial attachment of RSV to its target cells in the body.
"This paper establishes a vaccine approach to this virus, for which there currently is no effective vaccine," said corresponding author Dennis E. Buetow, a professor of molecular and integrative physiology. "For reasons that are not clear, injectable vaccines that have been attempted have not worked well in humans. Early attempts actually made the disease worse on subsequent infection."
The research offers hope -- albeit at least five years away depending on successes in additional testing -- for protecting babies and toddlers. They often get the virus from older school-age siblings. The younger children often suffer from high fever, wheezing, bronchiolitis, pneumonia and even respiratory failure. It is even more dangerous for children with asthma and other lung problems and heart disease.
The Illinois Council on Food and Agricultural Research and the State of Illinois Value-Added Program funded the study. With new USDA funding, researchers are seeking an optimum dosage in the tomatoes -- and eventually in apples -- and will test the product in rats.
Co-authors with Buetow and Korban were Jagdeep S. Sandhu, a postdoctoral researcher in crop sciences; Sergei F. Krasnyanski, a research associate in the department of natural resources and environmental sciences; molecular virologist Leslie L. Domier; and Mark D. Osadjan, who is now at the University of Colorado at Boulder.
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