New Antidote to Botulism: Drug neutralizes toxin in mouse tests

An experimental drug disables deadly botulism toxin much better than current treatment does, researchers report. They also suggest that the drug could be mass-produced and stockpiled as a deterrent to the use of botulism toxin, or botulin, as a weapon.

Scientists in recent years have identified antibodies that people and animals make when exposed to botulin or a botulism vaccine. The researchers reporting the new finding fashioned their drug from three antibodies–two from mice and one from a person–that bind well to the toxin. None knocks it out alone, but two thwart it somewhat, and all three working in concert neutralize botulin, the researchers report in an upcoming Proceedings of the National Academy of Sciences.

When injected into mice, the triple antidote protects the animals even when they’re exposed to amounts of the toxin far beyond those that are normally lethal.

The precise mechanism by which the antibodies disable botulin isn’t known, says report coauthor Leonard A. Smith, a molecular biologist at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick in Frederick, Md.

Smith and his colleagues used one of seven known types of botulin in their study. With their strategy, the scientists will probably succeed in making antidotes against all six other types, predicts Bal Ram Singh, a biochemist at the University of Massachusetts in Dartmouth. “It’s a good approach,” he says.

The Centers for Disease Control and Prevention in Atlanta lists botulism as one of the six most dangerous bioterrorism threats. By one estimate, a single gram of botulin dispersed evenly in a form that could be inhaled would kill 1 million people. Having a powerful antidote–once it’s been tested in volunteers–will make a difference, Singh says. “This will be a deterrent,” he notes.

Mass vaccination against botulism appears unlikely since cases are rare and the current vaccine is scarce. Each year, only about 100 people in the United States get botulism poisoning, usually from contaminated food. With treatment and hospitalization, almost all of them recover.

Doctors now treat patients with antibodies purified from the blood of people or horses vaccinated against botulism toxin, but the new drug is up to 90 times as potent. Smith and his colleagues are considering growing it in yeast or rice as a way to mass-produce the new drug inexpensively.

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