Allergy shots: A new twist
03-22-2006 09:09 AM
Allergy shots: A new twist
Nearly a century after two daring London doctors made medical history by injecting hay-fever patients with a watery extract of boiled pollen, Andy Saxon is trying to reinvent the allergy shot.
It's not that the "pollen vaccine" invented by Leonard Noon and John Freeman in 1911 doesn't work. It does. Until antihistamines came along in the 1950s, allergy shots were the only available allergy remedy. But their drawbacks, Saxon says, are nothing to sneeze at.
"The trouble with regular shots is that they're dangerous, take a long time to work and they're expensive," Saxon says. "You give too much and the person gets sick. And with peanuts, it's simply too dangerous. We want to be able to give (several) years' worth of allergy shots in a few months and safely retrain the immune system to have a healthy response."
Saxon and his team at the University of California-Los Angeles have developed a prototype for the allergy shot of the future. It marries a little bit of kitty with a snippet of the immune system in a configuration that's designed to shut the allergy response down.
The fused protein, which is being developed by Biogen Idec of Cambridge, Mass., is made of the cat allergen Fel d1, and part of the antibody IgG, which shuts down histamine-producing mast cells. It worked in laboratory mice, who no longer need to worry about being allergic to cats.
Saxon hopes to make similar proteins for other allergens, especially eggs and peanuts in which "allergy shots are not an option because of the risk."
Until then, Noon and Freeman's approach will hold sway.
"We make better extracts and we know better how to look for (dangerous) allergic reactions, but the whole process hasn't changed very much," says Philip Norman, one of several experts at Johns Hopkins University School of Medicine who have carried out studies that put allergy immunotherapy, or allergy shots, on a firm scientific foundation.
Controversial from the start
Studies by Norman and others show that allergy immunotherapy treatment reduces seasonal hay fever by 90% and year-round hay fever by up to 70%. And a study of children allergic to bee stings found that just 5% of those who got allergy shots had major allergic reactions to stings compared with 32% of those who did not. Protection lingered for three years after the shots were stopped, says David Golden of Johns Hopkins.
"There's nothing quite like allergy immunotherapy," says allergist Harold Nelson of National Jewish Medical and Research Center in Denver. "You're taking a disordered immune system and restoring it to health."
Yet allergy shots have been controversial from the start. Many doctors began offering it to patients, and collecting weekly fees for 40 injections a year, long before anyone had tested whether immunotherapy's benefits were real or imagined, says Sheldon Cohen of the National Institute of Allergy and Infectious Diseases.
The first controlled trial was carried out by Harvard researcher Francis Cabot Lowell in the 1930s, who marveled: "Isn't it amazing. We've been doing immunotherapy for 20 years and nobody knows if it really works," Cohen says.
Until antihistamines were developed in the 1950s, allergy shots were the mainstay of treatment. "We all gave shots to everybody," says Murray Dworetzky, emeritus professor of medicine at Weill Cornell Medical College in New York. "We had very little else."
In the past decade, major advances in medical technology and immune science have enabled researchers to examine how allergy shots reset the complex battery of immune defenses that in people with allergies goes off-kilter, attacking such hollow threats as cat dander and plant pollen.
Allergists today use hundreds of extracts, most commonly grass, house dust mites, ragweed and ****roach, and test patients to see which ones cause allergic reactions, says Robert Esch, scientific director of Greer Laboratories in Lenoir, N.C., one of the nation's largest extract suppliers.
Once testing is complete, he says, doctors blend a mix of extracts in their office labs for each patient. For safety's sake, they start with 1 in 1,000th to 1 in 10,000th of the dose needed to achieve tolerance and scale up. Wholesalers supply doctors with up to 50 million doses a year, Esch says.
The next big improvement in allergy immunotherapy might be to get away from shots entirely. Patients would simply place higher doses of the same extracts under their tongues for a minute or two. Widely used in Europe, sublingual immunotherapy is believed to be safer than injecting patients with allergy-causing extracts. It also could expand access to people in rural areas and children who are terrified of shots, says Esch, whose company is sponsoring the U.S. trials.
Just this month, researchers reported the first results of safety trials at a meeting of the American Academy of Allergy, Asthma and Immunology meeting in Miami. The tests involved 91 patients who, over eight weeks, took roughly 4,500 doses of cat dander, timothy grass, house dust mite or ragweed. "In a day we were able to achieve doses that it would take months to achieve by injection," Esch says, adding the approach was safe. If it works as well as shots do, he says, the sting will be a thing of the past.
Written by USA Today
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