Drug neutralises anthrax toxin in rats

Researchers at Harvard Medical School have just published the first results of a drug designed to neutralise the toxin that makes anthrax infection lethal.

When Collier, Harvard Medical School, and his co-scientists simultaneously injected rats with 10 times the lethal dose of anthrax toxin and a toxin inhibitor developed in Collier's lab, the animals' symptoms were delayed or did not appear after one week, depending on how much of the drug they were given.

They were also protected by an antitoxin injected three to four minutes later. Such rats normally die within a few hours of exposure to anthrax. The drug still has to be tested against whole bacteria, but this initial result suggests the drug or something like it "could be a useful therapeutic ally against clinical anthrax," Collier said.

Antibiotics can kill the anthrax bacterium, but the toxin it secretes, which actually causes symptoms and kills host cells, may already be present in lethal amounts by the time the drugs are administered. Anthrax toxin is composed of a protein-digesting enzyme, or protease, and seven small pieces that attach to the host cell, forming a pore.

After the cell unwittingly swallows the toxin, the protease enzyme slides through the pore and into the cell to chew up its innards. The antitoxin consists of more than 20 linked copies of a small protein that latch onto the pore, preventing the protease from getting inside the cell.