Bacillus anthracis produces the deadly anthrax toxin. Credit: © SPL

Amid growing fear of biological warfare, two discoveries could aid the development of antidotes to the deadly disease anthrax.

William Dietrich and colleagues at Harvard Medical School in Boston, Massachusetts have pinpointed the gene that enables one strain of mice to resist the lethal anthrax toxin1. Released by the bacterium Bacillus anthracis, the toxin kills immune cells in the blood, causing severe shock and sometimes death.

The resistance gene produces a protein, Kif1C, that may transport the toxin around the cell, thinks Dietrich. Or it may transport molecules involved in the body's response to the poison. "It makes sure things go to the right place at the right time," he says," at a particularly stressful time."

Kif1C is unlikely to be a direct target for anthrax treatment - blocking it makes cells more, not less, susceptible to the toxin. But exploring how the cell reacts to the poison may provide "valuable leads" to targets, says anthrax researcher George Vande Woude of the Van Andel Research Institute in Grand Rapids, Michigan. People, too, have differing susceptibility to anthrax.

Meanwhile, a second Harvard team is trying to stop anthrax getting into the cell at all. Seven copies of one of the toxin's proteins assemble into a ring on a cell's membrane to puncture it; an enzyme then enters through this hole to wreak damage.

John Collier and colleagues screened small protein fragments called peptides and found one that prevents entry through the pore. Rats that normally die within 90 minutes of a toxin injection survived with no symptoms when given a dose of this peptide plug, the team reports2.

Spores and speed

"The events of the last three weeks have greatly increased interest in this area," says Collier, of the heightened awareness of bioweapons in the wake of September's US terrorist tragedies. A major anthrax attack would cause many deaths and a total re-evaluation of prevention measures, he predicts.

Currently, anthrax mainly occurs in cattle, sheep and other animals in the developing world, where livestock vaccination is poor. A few humans catch it each year from infected animals or animal products; 20 per cent die within weeks. More rare, but far more fatal, is the anthrax transmitted through spores - hardy, dormant forms of the bacteria.

The option to deliver the disease in the form of these spores, and the speed with which it can kill, make anthrax a potential bioweapon, explains Vande Woude.

Anthrax vaccinations are standard for US military personnel. Taken early enough, antibiotics targeted at the bacteria also work, but by the time symptoms appear, the toxin has accumulated to untreatable levels.

Neither vaccines nor antibiotics are produced on the large scale that might be needed after a bioweapon attack. "There'll be an increase in preparedness now," predicts Vande Woude.