Dual-acting vaccine offers mice protection in anthrax-related tests


Tuesday, September 2nd 2003, 12:00 am
By: News On 6


WASHINGTON (AP) _ A new vaccine that launches a two-pronged attack on anthrax _ battling both the bacteria itself and the toxin it produces _ is undergoing preliminary tests.

The dual-acting vaccine goes a step beyond the current product that only targets the deadly toxin, according to researchers at Harvard Medical School, who tested it in mice.

Their findings are being published this week in the online edition of Proceedings of the National Academy of Science.

Interest in anthrax was spurred two years ago when spores of the disease were mailed to news media and legislators. Five people died and the Postal Service had to shut down major facilities for decontamination. The agency continues to irradiate mail designated for federal offices to prevent another such attack.

In another sign of progress, researchers say they now know how to diagnose anthrax quickly and efficiently, an advance that could help doctors better deal with a large-scale attack.

In a new study, scientists report that fever and cough are common in both anthrax victims and flu sufferers. But people sickened by anthrax are also likely to suffer from mental confusion, dizziness, shortness of breath, nausea and vomiting. Runny noses and sore throats are much more common in people with the flu. The study appears in Tuesday's Annals of Internal Medicine.

Bacillus anthracis, the bacteria that causes the disease, protects itself in the human body with a coating of molecules that prevent the immune system from detecting it. It can then multiply and produce its deadly toxin.

Current vaccines sensitize the body to that toxin so the immune system can fight it. But the newly developed version also sensitizes the immune system to the coating that protects the bacteria, so it can attack and destroy the bacteria itself.

``Clearly, there is a need for a better anthrax vaccine,'' said Julia Y. Wang, an assistant professor of medicine who was part of the team. ``The bivalent vaccine we came up with is likely to be much more effective at protecting against systemic anthrax because it targets both virulence factors of Bacillus anthracis _ its toxin and its capsule.''

Theresa M. Koehler, a professor at the University of Texas Medical School at Houston, said the finding is ``exciting'' because the new vaccine causes two important responses in mice. Koehler, who studies anthrax, was not part of the research team.

In the Harvard test, mice immunized with the new vaccine and then injected with anthrax toxin survived, while non-immunized mice similarly injected died within hours.

The researchers didn't have access to anthrax bacteria, however, so they had to use a substitute to test the vaccine's effectiveness.

Blood from the immunized mice was tested with Bacillus licheniformis, which coats itself with a protective cover similar to that used by anthrax. They found that in lab tests blood from immunized mice coated and killed that bacteria.

Koehler said the results are promising because mice vaccinated with the new vaccine survive the challenge of purified anthrax toxin.

The next important step will be to determine if the vaccine protects against infection with the bacterium itself, said Koehler.

Wang said in a telephone interview that testing the ability of the vaccine to protect mice from the bacteria itself is being planned.