Researchers Find Inhibitor of Deadly Anthrax Toxin

BOSTON (Reuters) - A small group of molecules has been shown to inhibit a deadly toxin associated with inhalational anthrax, a discovery that could lead to new ways of treating the disease, researchers said on Monday.

Scientists at Harvard Medical School and Beth Israel Deaconess Medical Center in Boston said the finding may help in the development of a drug that, when combined with antibiotics, could treat inhalational anthrax at a point when antibiotics alone are no longer effective.

Inhalational anthrax is the most serious form of the disease and can develop when people breathe in tiny anthrax spores. Another form, cutaneous anthrax, is a skin infection that can be treated easily.

Unlike most types of bacteria, the anthrax germ can produce large amounts of a toxin that can kill a person even after antibiotics have destroyed the bacteria, said the study's senior author, Lewis Cantley.

Autopsies of patients who have died of inhalational anthrax reveal that high doses of antibiotics have killed the bacteria, indicating that the patients died from the toxins.

In October 2001, a series of anthrax-laced letters killed five people in the United States, including two Washington postal workers, and sickened 13. No one has been arrested in the attacks.

Anthrax spores spilled out of the envelopes and spread through a series of post offices, infecting several people who never touched the contaminated letters.

Writing in the January issue of the journal Nature Structural & Molecular Biology, the researchers said their discovery could enable scientists to develop drugs capable of fighting the anthrax toxin in a way similar to the protease inhibitors that tackle the AIDS (news - web sites) virus.

Protease inhibitors work by disabling native protease enzymes and -- like a key fitting perfectly into a lock -- they jam up the enzyme, rendering it ineffectual.

Cantley, chief of the Division of Signal Transduction at Beth Israel and professor of systems biology at Harvard Medical, said there could be a number of advantages to using protease inhibitors to attack anthrax.

"Unlike an anti-serum, which would require that whole populations be vaccinated -- regardless of whether or not an anthrax outbreak developed -- a therapeutic combination of antibiotics and protease inhibitor drugs wouldn't have to be used except in the incidence of actual disease," he said.

This could be more good news for military members that up until Dec 22nd were required to submit without informed consent to inoculation with the controversial 40-plus year old anthrax vaccine formulation. If this turns out to be a viable approach to treatment of anthrax illness, it may also help the Pentagon save face after this humiliating court defeat, which led to the current suspension of the anthrax immunization program.

It also hasn't been widely discussed just how the people who survived anthrax are doing. Both anthrax and heavy doses of antibiotics and other therapies can have long-lasting effects.

Antitoxin was always a more promising avenue than vaccines. The vaccine is of doubtful use for inhalation anthrax, and there has always been the possibility of the development of a new strain of anthrax that resists the vaccine. An antitoxin would work against all forms of anthrax.

It also hasn't been widely discussed just how the people who survived anthrax are doing.

There have been occasional articles in the Washington Post. Most of the survivors have severe health problems.

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