Paris: Researchers in France said on Thursday they had found two possible compounds that could protect against ricin, a naturally-occurring poison used in murder and political assassinations and eyed as a bioterror weapon.The two molecules allowed lab-dish cells to survive the assaults of ricin, as well as so-called Shiga-like toxins that are made by the bacterium Escherichia coli.
They worked not by acting on the poisons themselves but on the pathways taken by the poisons to cross the cell, the scientists reported.
Dubbed Retro-1 and Retro-2, the compounds were found by a team led by Daniel Gillet of France`s Atomic Energy Commission (CEA) during a screen of 16,500 chemical candidates.
"We gave one of the compounds to lab mice and then gave the mice ricin, and found they were protected," Gillet told. "There is no protection if you give the poison first followed by the compound."
Ricin is one of the world`s most notorious poisons, killing the victim within three to five days. As little as one milligram could suffice to kill an adult. No antidote currently exists.
It works by travelling into a part of the cell called the cytosol, where it knocks out the ribosome, a tiny "factory" that produces all the proteins needed to keep the cell functioning.
The toxin was used to kill Bulgarian dissident Georgi Markov in London in 1978. He was jabbed with a ricin-filled pellet, just 0.6 millimeters (0.024 of an inch) in diameter, fired from a KGB agent`s umbrella.
Ricin is a byproduct of the seeds of the castor oil plant, which is used to manufacture brake fluid, soap, varnish, ink and other products.
As a result, the plant is widely grown, which makes ricin more easily accessible to bioterrorists. It could be delivered in food, water, in a mist or, as in the Markov case, injected.
"There is a real need for countermeasures against ricin. There are many plants growing and there is about one milligram of toxin per seed," said Gillet.
The work is published online in a US journal, Cell.
First Published: Friday, April 16, 2010, 14:24