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Germ Fighters Are Right Under Your Nose

Natural 'antibiotics' combat infection in mucous membranes, skin, says study

MONDAY, Nov. 26, 2001 (HealthDayNews) -- As you read this, streptococcal bacteria may be trying to invade your body. They're the nasty germs that can cause everything from severe sore throats and skin infections to flesh-eating disease and toxic shock syndrome. But you probably won't get sick, and new research suggests you can thank an army of tiny soldiers that guard your skin, lungs and nasal passages.

This infantry, made up of ingredients of protein known as peptides, acts as the front lines of the immune system. Scientists in California have confirmed that the peptides behave just like antibiotics, and in some ways are even better. They attack bacteria and kill them, apparently without inspiring the germs to regroup for attacks in a different form, a resistance that man-made drugs create.

"What we have done is proven the existence of a layer of the immune system that hasn't really been recognized before in mammals and humans," says Dr. Richard Gallo, a professor of medicine at the University of California at San Diego and co-author of a study into peptides that are known as cathelicidins.

Gallo said the findings could be used to develop new antibiotics and figure out why some people are more prone to illness.

The peptides live in parts of the body that come in contact with the air, like mucous membranes, and in white blood cells. Scientists have long thought the peptides were an important part of the "innate" immune system, which targets incoming germs with a powerful but primitive line of defenses. If germs get past the innate immune system, they then encounter the "adaptive" system, which is more sophisticated and can remember how to fight invaders it has encountered before.

Researchers decided to study the peptides by removing them from mice through genetic engineering. When infected with streptococcal bacteria, also known as strep, the mice became more ill than their counterparts that still had their peptides.

In another experiment, researchers created a strain of strep that was strong enough to resist attacks from the peptides. Mice infected with that strain became sicker than those infected with normal strep.

The results of the research appear in a recent issue of the journal Nature.

The proteins, a kind of natural antibiotic, "are probably not as powerful as the antibiotics you get from the drugstore," Gallo says. "They don't completely wipe out bacteria. What they do is slow them down and weaken them, so they're around long enough for other parts of the immune system to recognize them and battle them."

The proteins appear to be effective enemies of a variety of bacteria, including the germs that cause fungal and yeast infections, diphtheria, meningitis, ear infections and cholera, says study co-author Dr. Victor Nizet, a professor of pediatrics at UC, San Diego. It's also possible that the peptides could attack the germs that cause anthrax, he says.

The peptides apparently attack the cell walls of bacteria, making them collapse so the germs fall apart, he says.

The innate immune system is a "hot new area of research," Nizet says. "People are beginning to recognize this first layer of defense, especially in infections such as strep, which can cause very rapid infection before you have a chance to produce an adaptive immune response."

Germs seem unable to develop resistance to the peptides, even though they've found ways around antibiotics like penicillin in just a matter of decades. Scientists may be able to make the peptides artificially and create new medicines, Nizet says.

That may take a while, cautions Tomas Ganz, a professor of medicine and pathology at the University of California at Los Angeles. "There's a lot of work going on in that area [of drug development], but there's no specific product yet that you could look at."

He adds that while the peptide research is a "nice development," it should not be seen as a huge breakthrough.

What To Do

Learn about the immune system, and what happens when it begins to attack the body itself, in this primer from the National Institutes of Health.

Doctors fear that more germs are becoming resistant to antibiotics. Read about the threat in this fact sheet from the Food and Drug Administration.

SOURCES: Interviews with Richard Gallo, M.D., Ph.D., associate professor of medicine and pediatrics, University of California at San Diego, and chief of dermatology section, VA Medical Center, San Diego; Victor Nizet, M.D., infectious disease specialist and assistant professor of pediatrics, UC San Diego; and Tomas Ganz, M.D., Ph.D., professor of medicine and pathology, UCLA; Nov. 22, 2001 Nature
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