U.S. military researchers said on Wednesday they had produced a vaccine that protects mice from the deadly effects of inhaled ricin -- one of the most toxic substances known. They now plan to test the vaccine in other animals to see if it could be added to the armory of defenses against chemical and biological weapons. Ricin is made from the castor bean, and when made into a fine aerosol it kills within days. When eaten, it can cause severe gastrointestinal symptoms followed by vascular collapse and death. There is no cure. Because castor beans are so common, and because ricin is relatively easy to make, the poison is considered a leading candidate for a biological weapon.
