The search for novel treatments to cure gravely ill victims of inhaled anthrax has taken on new urgency, but experts caution they are still probably years away from useful new medicines.
The research targets the most insidious aspect of this frightening disease: By the time symptoms start, it is often too late to do anything.
By then, anthrax bacteria have flooded the bloodstream with deadly poison. Killing the germs with antibiotics may not help much, because the damage is already done.
Scientists are working on ways to block this toxin so it does not enter blood cells after being released by the bacteria. Several teams are working on competing approaches, and researchers say they have made significant headway in recent months.
If the treatments work in people as well as they seem to in lab animals, they will probably be given along with antibiotics in the future as a one-two punch.
The search for new anthrax treatments ``has always been of great interest, but it obviously will get ratcheted up,'' Dr. Anthony Fauci, head of the National Institute of Allergy and Infectious Diseases, said Tuesday.
His agency and the Defense Department have financed most of the research. He said they hope to back more research, as well as speed up testing of any new drugs that are discovered.
``The fact that somebody has died from inhalation of anthrax spores for the first time in 25 years has certainly galvanized a lot of people into action,'' said Dr. Robert Liddington, who studies the poison's atom-by-atom structure at the Burnham Institute in San Diego.
If anthrax enters the body through a break in the skin, it causes a sore that is easily cured with antibiotics. Bacteria inhaled deep into the lungs are far more serious. They can lead to a bloodstream infection that begins with vague, flu-like symptoms and quickly progresses to shock and death.
``You feel a little sick one day, and the next they put you on a ventilator,'' said Dr. Philip Hanna of the University of Michigan.
By the time the first symptoms appear, the bacteria have already spewed out their toxin. This poison seeps into blood cells called macrophages. There it prompts the cells to manufacture normally useful disease-fighting substances, then kills them, releasing the substances in dangerously high quantities.
To block this process, scientists at the U.S. Army Medical Research Institute of Infectious Diseases at Fort Detrick, Md., have screened dozens of antibodies against the poison. Two that seem to work are being investigated at the University of Texas at Austin.
The bacteria actually make three different proteins to poison cells. One is called protective antigen. (It got that deceptively innocent name because it is also part of the anthrax vaccine reserved for military use.) The other two are edema factor and lethal factor.
Protective antigen starts the process. It hooks onto blood cells and opens a hole that lets edema factor and the even more deadly lethal factor ooze inside. The antibodies block this by covering up the spot the protective antigen uses to anchor itself on the cells.
Dr. John Collier of Harvard Medical School developed another approach. He makes slightly altered forms of protective antigen. It takes seven good copies of the antigen to make the hole for poison to enter cells. He found that even one bogus copy of the antigen keeps the hole from forming.
Both the antibodies and the fake antigen have been found to protect lab animals from the effects of anthrax toxin, and experts say the next step will be against the actual bacteria, which can only be done at high-security labs. Nevertheless, Collier says human testing could start within a year.