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 May 12, 2005
Science Closing in on Allergy Prevention
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By Amanda Gardner, HealthDay Reporter

TUESDAY, March 22 (HealthDay News) -- Physicians today can spot and treat most allergies once they've appeared, but prevention remains an elusive goal.

"We have the expertise to diagnose, and we have a broad spectrum of tools to treat patients with allergic disease, but wouldn't it be better if we could actually prevent allergic disease?" said Dr. Paul Williams, an allergy specialist from Seattle.

Williams moderated a news conference Tuesday that highlighted research efforts to do just that. All the research is being presented at the annual meeting of the American Academy of Allergy, Asthma and Immunology in San Antonio.

UCLA scientists, for instance, have found early evidence that exposure to high doses of an allergen may actually prevent the development of allergies.

Conventional wisdom has long held that the more allergen a person is exposed to, the more likely he or she will become allergic. Recently, however, challenges to that idea have emerged.

British researchers found that reducing exposure to dust mites actually increased allergies. Another study found that children who grew up in an environment with two or more cats had a significantly lower rate of cat allergy than children who grew up in households bereft of felines.

For this study, the UCLA researchers recruited 51 individuals and gave them a nasal wash with diesel exhaust particles (about the equivalent of two days' exposure in downtown Los Angeles) as well as an allergen from a mollusk on the sea floor off the coast of California.

The diesel exhaust was supposed to boost any allergic response. The choice of the mollusk allergen -- a protein called keyhole limpet hemocyanin (KLH) -- was "an ethical issue," explained Dr. Marc Riedl, of the David Geffen School of Medicine at UCLA. "If we're going to make people allergic, we don't want it to be something that will affect health," he explained. "Also, KLH has been used safely in many human studies."

All of the patients exposed to a low dose of the protein became allergic, and 57 percent of those exposed to a medium dose. However, only 11 percent of those exposed to a high dose developed an allergy.

"For the first time that we know of, high doses of nasal antigen exposure actually generated a nonallergic immune response," Riedl said.

Riedl and his colleagues do not yet know how long the response will last or if other allergens will prompt the same reaction.

"Whether this applies to real-world therapeutics remains to be seen," Riedl said.

On a similar note, investigators in Finland conducted a study to see if administering probiotics, or bacteria from the intestines of healthy individuals, might reduce the risk of skin allergies in infants.

The so-called hygiene hypothesis maintains that contact with microbes in the first few months of life might induce an appropriate immune response, so the person does not become allergic later on. Although the hypothesis has not yet panned out with infectious agents, scientists are turning their attention to environmental and intestinal microbes.

Specifically, the authors of this study wanted to see if probiotics would have an effect on CD14, an immune molecule that enables a host or person to recognize microbes and pathogens and interact with them.

Reduced levels of CD14 in amniotic fluid, breast milk and blood have been associated with skin, or atopic, allergies.

The researchers looked at 19 infants who had developed eczema during the first year of life, and compared them with healthy controls. The infants with the skin condition had significantly lower blood levels of CD14.

"This we interpret to imply that there is a misinterpretation in host-microbe cross talk in infancy leading to the development of atopic disease," said study co-author Dr. Samuli Rautava, a researcher at the University of Turku, in Finland.

"Healthy host-microbe reaction is the key to disease-free state," he concluded.

The researchers then administered probiotics to 18 infants and compared allergy outcomes with 20 infants who received a placebo.

"At 12 months, infants receiving probiotics had higher amounts of CD14 in their blood," Rautava said. "We take this to imply that probiotics exert an effect on the innate immune system."

CD14 may one day be a target for drugs to prevent allergic disease, he said.

More information

For more information on allergies and asthma, visit the National Institute for Allergies and Infectious Diseases (www.niaid.nih.gov ).

SOURCES: March 22, 2005, news conference with Paul Williams, M.D., Seattle; Samuli Rautava, M.D., researcher, University of Turku, Finland; Marc A. Riedl, M.D., David Geffen School of Medicine, University of California-Los Angeles; scientific presentations, annual meeting, American Academy of Allergy, Asthma and Immunology, San Antonio

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