DNA-Based Anthrax Vaccine in the Works

Study found it successfully protects mice, but human trials still long way off

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By
HealthDay Reporter

FRIDAY, Oct. 19, 2001 (HealthDayNews) -- A new anthrax vaccine that uses pieces of the bacteria's DNA seems to work -- at least in mice, say researchers at Ohio State University.

The vaccine has successfully protected mice against anthrax, according to a recently published study in Infection and Immunity. And the study's lead author, Darrell Galloway, an associate professor of microbiology at Ohio State, says the researchers have had success with other animals as well.

But despite all that, Galloway adds, don't look for the vaccine any time soon. The earliest human trials are still at least 18 months away.

Galloway's research comes amid heightened concern. Officials are scurrying to find more ways to counter the disease as increasing incidents of anthrax exposure are reported. The only approved vaccine, made by only one factory, is earmarked for the military and must be taken over many months.

Anxiety over anthrax has swept across the United States since a Florida photo editor died from it two weeks ago. A number of his co-workers were found to have spores on them; 31 people on Capitol Hill in Washington, D.C., have tested positive for exposure; two aides to network news anchors Tom Brokaw and Dan Rather and a U.S. postal worker have tested positive for skin anthrax,; and spores were found in the New York governor's Manhattan office complex. The finely powdered form of anthrax most have confronted appears to have been delivered through the mail.

Anthrax is caused by the bacteria Bacillus anthracis. Once the bacteria enter the bloodstream, it produces three toxins. When these toxins combine with each other, they can then enter human cells and cause the cells to die. Untreated, anthrax can be fatal.

Traditional vaccines use the actual pathogens or proteins produced by the disease and can be made in several ways: by crippling the disease organism so it can't cause the full-blown disease but it can trigger the body's immune system; by using only the part of the organism that causes an immune response; or by using a weakened or aged disease organism.

Unlike those vaccines, Galloway's research used fragments of DNA from anthrax toxins. This approach is also known as genetic immunization. The researchers focused on two of the toxins -- protective antigen (PA) and lethal factor (LF).

They injected some mice with PA fragments, others with LF fragments, and still more with both. A control group received none. Each animal received three vaccines over a two-week period and then was exposed to five times the lethal dose of anthrax.

The mice in the control group died within hours of exposure, but all the vaccinated animals survived. Those who were co-immunized with both PA and LF showed the strongest immunity against the disease.

"If we co-immunized, we got a better response than if we immunized with either alone," Galloway says.

Galloway adds that a DNA-based vaccine offers definite advantages over traditional vaccines. DNA-based vaccines produce a stronger immune response. They are easier and less costly to produce. They require no cold storage, and they are very stable compounds with a long shelf life. And because DNA-based vaccines are so specifically targeted, there is less chance of side effects, he says.

Like the current anthrax vaccine, Galloway says the DNA-based vaccine would also probably require a series of shots. "I would envision that it will probably be a two- to three-dose situation," he says.

Dr. Stephen Johnson, director of the Center for Biomedical Inventions at the University of Texas Southwestern Medical Center in Dallas, worked on the original development of genetic vaccines and says this was a good test of the anthrax vaccine. The mice were, in fact, protected against the disease, he adds.

"Genetic vaccines are attractive to use against bio-threats because they are very easy to produce and rapidly scale up," he says.

Galloway thinks it could eventually be possible to immunize against three or four bio-threat agents in one vaccine. No DNA-based vaccines have yet been approved for use in humans, however.

What To Do

For more information on anthrax and the current vaccine, read this information from the Centers for Disease Control and Prevention or the Utah Department of Health.

Learn more about bioterrorism from the CDC.

Curious about how vaccines are made? Check out this BBC article.

For more on the various bioterror weapons, try the American Medical Association.

For more on anthrax and the mail, try the U.S. Postal Service.

SOURCES: Interviews with Darrell Galloway, Ph.D., associate professor of microbiology, Ohio State University, Columbus; Stephen Johnston, M.D., Ph.D., director, Center for Biomedical Inventions, University of Texas Southwestern Medical Center, Dallas; July 2001 Infection and Immunity

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