Vaccine works against deadly ricin - Discovery could protect people from bioterrorist attack

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Vaccine works against deadly ricin

Discovery could protect people from bioterrorist attack

By Maggie Fox


Sept. 4 — A vaccine against ricin, one of the deadliest toxins known, works in mice and may work to protect people in case of a bioterrorist attack, U.S. researchers said on Wednesday.


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Ricin, which comes from the castor bean, is considered a likely biowarfare or bioterrorist agent and is on the Center for Disease Control and Prevention’s “B” list of agents —considered a moderate threat.

THE RESEARCHERS, at the University of Texas Southwestern Medical Center at Dallas, came up with the vaccine as part of their work using the potent toxin to fight cancer. But they hope the government will fund further studies to develop the vaccine to protect troops or civilians against biowarfare.
Ricin, which comes from the castor bean, is considered a likely biowarfare or bioterrorist agent and is on the Center for Disease Control and Prevention’s “B” list of agents —considered a moderate threat.
It is most known as the poison used to assassinate Bulgarian exile Georgi Markov in London in 1978, delivered by a special needle-tipped umbrella.
“What is incredibly frightening about ricin is that it is so easy to make. It is so easy to stockpile,” said Dr. Ellen Vitetta, who led the study.
“You don’t have to be a brilliant chemist. You basically just grind up the castor beans. Castor beans grow everywhere in the world. There are stockpiles in many countries. It is extremely lethal to people and it been used in espionage for years.”
The toxin can be put into food, water or even made into an aerosol and sprayed. It is broken down quickly in the body and is almost impossible to trace.

“A very small dose of this is quite lethal for humans and the symptoms are very disconcerting,” Vitetta said in a telephone interview. “You feel flu-like for a few days and then you are dead. It’s terrible.”
Some vaccines have been tried but none has worked well. Vitetta said her team’s appears to be safe and potent in mice.
Vaccines against toxins are not unusual — the tetanus vaccine stimulates the body to produce antibodies against the toxin produced by the Clostridium tetani bacteria.
Antibodies are proteins that can hook onto a target such as a bacteria or virus, stopping it from doing any harm and holding it in place until immune system cells can come along and dispose of it.

Vitetta’s team took a similar approach to the ricin toxin, they report in the Sept. 10 issue of the journal Vaccine.
“The actual toxin that we are talking about has two proteins linked together,” she said. “The B chain — B stands for binding — binds it to all cells of higher organisms. Once it is bound, the A chain destroys all the ribosomes in cells.”
This stops all protein production and shuts the body down.
They made a genetically engineered version of the toxin that lacks the A chain and some other pieces, so it is harmless to cells.
The mice they tested it on were vaccinated with the genetically engineered ricin toxin, then injected with ricin. They did not become ill and suffered no apparent side effects, Vitetta reported. Next they will make a ricin aerosol and test the mice, she said.

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