Vaccine against ricin to be tested

WASHINGTON (AP)-- Texas researchers will begin clinical trials of a candidate vaccine against the deadly toxin ricin, a biological agent that can be tested only in select labs.
University of Texas Southwestern Medical Center in Dallas received approval from the Food and Drug Administration to conduct the safety trial in humans.
According to the Centers for Disease Control and Prevention, as little as 500 micrograms of ricin -- about what fits on the head of a pin -- is enough to kill an adult. Lethal doses depend on how the poison is delivered -- by powder, mist, pellet or dissolved in water. The poison can be made from waste left over from processing castor beans.
Because castor beans are easy to obtain and the poison remains potent despite exposure to temperature extremes, government officials worry that it could become a tool of terrorists. Unless treated quickly, there is no antidote. Symptoms arrive late and can be confused with other illnesses.
In October 2003, someone left a threatening letter containing ricin at a South Carolina postal facility. A second letter, addressed to the White House, was discovered by the Secret Service at a Washington offsite mail processing facility the next month.
The FBI is offering a reward of up to $100,000 for information leading to the arrest and conviction of those responsible for the October 2003 mailings of letters containing ricin. No arrests have been made and no suspects identified.
British authorities, meanwhile, are scheduled to begin trials for five men charged with conspiring to produce a chemical weapon. During that investigation, British police said they found traces of ricin.