Nurse Sharks: Key to Anthrax Diagnosis, Treatment?

July 16, 2003

Nurse sharks may help detect—and treat—anthrax and other infectious diseases.

At the National Aquarium in Baltimore, a team of researchers is working with a pair of 4-foot-long nurse sharks to investigate how the creatures' immune system responds to the anthrax bacterium.

In nature, antibodies are the best defense against disease: these proteins, produced by immune cells, recognize invading bacteria and viruses and grab on, in effect, target them for destruction.

Nurse shark antibodies turn out to be not only sensitive but also hardy enough for quick transport to a battlefield or the site of a bio-terrorist attack.

"Most vaccines and diagnostics need refrigeration, and it just isn't that practical to carry around a fridge in the middle of Iraq," says Les Baillie, a microbiologist and head of bio-defense vaccines for the Navy at the Naval Medical Research Center in Silver Springs, Maryland.

Baillie was formerly the principal scientist for anthrax research at the Defense Science and Technologies Laboratory at Porton Down in Great Britain. He engineered anthrax proteins for a new anthrax vaccine that is now undergoing Phase one trials in the United States.

"There is a critical need for diagnostics for Class A agents, as we call them: things like anthrax, tularemia, plague and smallpox," says Brad Smith, a microbiologist and a fellow at the Center for Civilian Biodefense Strategies in Baltimore, Maryland. "In an attack, resources are limited and people on the front lines need to make quick decisions—who is sick, who isn't."

Shark Antibodies and Bio-defense

No rapid diagnostics for Class A agents have met FDA approval. A measure of the need is that the National Institutes of Health bio-defense research and development budget this year is $1.7 billion.

Baillie came upon the idea of shark antibodies as anthrax detectors when he met researchers nearby at the University of Maryland: immunologist Martin Flajnik, a specialist in shark and amphibian immune systems, and Helen Dooley, an antibody engineer who had developed antibodies to detect environmental pollutants.

Flajnik had discovered a new type of antibody—called IgNAR—in the nurse shark. IgNAR is simpler and tougher than mammalian antibodies, making it an attractive candidate for producing in the lab.

Sharks are the oldest living animals that have what scientists call an adaptive immune system.

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