"Ricin is not only dangerous, but it is also cheap and easy to make," said Dr. Ellen Vitetta, director of the Cancer Immunobiology Center at UT Southwestern and senior author of the study to be published in the Sept. 10 issue of the journal Vaccine.

Large stockpiles of ricin have been found in several countries in the Middle East, Vitetta said. It is a protein produced by castor beans. A single ricin molecule inside a cell shuts down protein synthesis, killing the cell. Ricin can be administered in foods and water or sprayed as an aerosol. A small dose can produce flulike symptoms and result in death in a few days.

Because of its ease of production and high toxicity, ricin has found its way into the arsenals of extremist individuals, groups and governments. Iraq is known to have ricin as part of its biological weapons program, and it is believed that at least one group linked to the terrorist organization al-Qaeda also has experimented with the poison as a weapon. Domestically, several individuals have been arrested and convicted of ricin possession in recent years under the 1989 Biological Weapons Antiterrorism Act.

In creating the new vaccine, UT Southwestern researchers, led by Vitetta, mutated the DNA encoding the active A chain of the toxin. They took out the site that inhibits protein synthesis, as well as the site responsible for inducing vascular leak. The latter was identified by Vitetta's group several years ago in its ongoing efforts to produce safer immunotoxins containing the A chain. Immunotoxins are anti-cancer drugs that have been used by Vitetta and her colleagues in more than 200 cancer patients. The new recombinant A chain induces a protective immune response in mice and protects them against very high dose
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Contact: Wayne Carter
wayne.carter@utsouthwestern.edu
214-648-3404
UT Southwestern Medical Center
4-Sep-2002