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Scientists Reengineer "Harmless" Viruses to be Used as Vaccines

October 2, 1996. La Jolla, CA. Scientists have used techniques of genetic engineering to develop viruses that are "biologically dead" and can be used as vaccines against foot-and-mouth disease in cattle. They suggest that a similar approach may potentially be used to produce safer vaccines for people.

Generally, viruses are allowed access to cells by receptors, molecules on the cell surface that serve as docking points for infectious viruses. Work performed at the United States Department of Agriculture's Plum Island Animal Disease Center in New York, by Peter Mason, Elizabeth Rieder and Barry Baxt has demonstrated that the foot-and-mouth disease virus could be rendered harmless by removing that portion of the virus that permits it to dock to cells in livestock. When cattle were injected with viruses lacking the docking site, they did not show any signs of the disease. They did, however, develop immunity to the disease when exposed to the natural virus.

One drawback to the approach, however, was its inability to produce large amounts of the harmless virus. Infected cells release millions of copies of the original virus when they die and burst open. The "dead" virus could not infect cells because of its inability to bind to the cells.

To circumvent this problem, the research group, together with Angray Kang, Ph.D., of The Scripps Research Institute, developed the world's first artificial receptor for the virus, thereby creating an alternative route for the virus to gain entry into the cells. This receptor was produced by fusing the gene for an antibody fragment that recognized the virus to a gene for a molecule that can serve as the receptor for the virus that causes the common cold. Cells programmed to carry this new gene were able to produce large amounts of the virus that was completely harmless in cattle.

The results of this work are reported in a recent issue of Proceedings of the National Academy of Sciences, in an article entitled, "Propagation of an attenuated virus by design: Engineering a novel receptor for a non-infectious foot-and-mouth disease virus."

Now, the group is focusing its attention on developing similar vaccines for strains of foot-and-mouth disease that are prevalent in South America, and Dr. Kang is interested in applying the method to other pathogens, including those that cause disease in man.

For information from the USDA Agricultural Research Service, contact Sandy Miller Hays, (301) 344-2764.


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