|
|
Nurse Sharks: Key to Anthrax Diagnosis, Treatment? |
|
Bijal P. Trivedi National Geographic Today |
| 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. "This is the earliest version of the human immune system," says Flajnik. Sharks and humans share immune-system components like B cells—which manufacture antibodies—and T-cells. Baillie wondered whether sharks exposed to anthrax would produce robust anthrax-fighting antibodies. He provided Flajnik and Dooley with anthrax proteins—which alone cannot cause disease—from his research in Great Britain. Flajnik and Dooley used the proteins to immunize two nurse sharks—a delicate procedure. Aquarium handlers in wet suits remove the sharks from their home tank and place them in a smaller one laced with anesthetic, which calms them. Then they are loaded onto a trolley for their injection—under their skin near the fin. Immunizing Sharks "It's the equivalent to giving a TB shot in the arm," Dooley says. The sharks received booster shots at one-month intervals for the next three months. Dooley and Flajnik took monthly blood samples from the sharks and found that with each successive booster the quantity of antibodies in the sharks' blood rose. Back in the lab, the serum collected from shark blood reacts with the anthrax proteins to produce a bright yellow color. "Ultimately, with this antibody you could see within a minute whether anthrax was present," Flajnik says. The researchers have isolated the antibody that binds tightest to the anthrax protein and thus has the greatest potential for both diagnosis and treatment. They are currently determining its genetic sequence, which will help reveal how to mass-produce the antibody. One day the antibody might even serve as a treatment for humans exposed to anthrax. "The shark does all the hard work," Flajnik says. "It makes all these very specific, sturdy antibodies and all we have to do is analyze and use them." National Geographic Today, 7 p.m. ET/PT in the United States, is a daily news journal available only on the National Geographic Channel. Click here to learn more about it. Have a high-speed connection? Watch National Geographic Today in streaming video. More Shark Resources on Nationalgeographic.com News Stories Underwater Photographer On Swimming With Sharks—includes photo gallery Shark Season: Hazard or Hype? Asian Shark-Fin Trade May Be Larger Than Expected North Atlantic Sharks on Sharp Decline, Experts Say Satellite Tags Keep Track of Great White Sharks Shark Gives "Virgin Birth" in Detroit Shark-Soup Boom Spurs Conservationist DNA Study Shark "Photo of the Year" is E-Mail Hoax Great Whites May Be Taking the Rap for Bull Shark Attacks Crittercams Provide Insights into Nurse Shark Behavior—includes photo gallery Researchers Tag Sharks to Study Breeding Habits—includes photo gallery Scientists Study Nurse Shark Mating Habits—includes photo gallery Jaws Author Peter Benchley Talks Sharks—hear him read from his new book Do Hammerheads Follow Magnetic Highways in Migration? Shark Nursery Yields Secrets of Breeding—includes photo gallery South Africa Rethinks Use of Shark Nets Sharks Falling Prey to Humans' Appetites Satellites Clear Up White Shark Mysteries Are People Eating Sharks Out of Existence? Featured Sites Field Tales: Filming Great White Sharks Oceans of Plenty: South Africa's Teaming Seas from National Geographic Magazine The Crittercam Chronicles: Sharks For Kids Creature Feature: Great White Sharks Ten Cool Things That You Didn't Know About Great White Sharks Print 'N' Go Coloring Book: Great White Sharks Shark Surfari: Online Quiz |
| © 1996-2008 National Geographic Society. All rights reserved. |