FRIDAY, Nov. 12, 2004 (HealthDayNews) -- Dogs with allergies to peanuts, milk and wheat experienced sharply fewer reactions after being vaccinated for those specific food allergens, researchers in California report.
Peanut-allergic dogs, after receiving the vaccine, were able to eat many more of the legumes without developing an allergic response. On average, they went from tolerating a single peanut to eating more than 37. Similar reductions in allergic responses were observed among milk- and wheat-allergic dogs after receiving the vaccine.
"Although we clearly have to do studies in humans, this study suggests [that] vaccine strategies can be developed to treat food allergies successfully," said study author Dr. Dale Umetsu, a professor of pediatrics at Stanford University and chief of the allergy and immunology division at Lucile Packard Children's Hospital in Palo Alto, Calif.
The study, said to be the first to reverse food allergies in an animal other than a mouse, appears in the Nov. 12 online issue of Allergy.
An estimated 11 million Americans suffer from food allergies, for which there are no cures, according to the Food Allergy & Anaphylaxis Network (FAAN), a Virginia-based advocacy group. A food allergy occurs when the body's immune system overreacts, treating a particular food as if it were a foreign invader. The body reacts by releasing chemicals that trigger a range of symptoms, including itching, swelling, hives and difficulty breathing.
Some food-induced reactions can be life-threatening, accounting for about 30,000 emergency-room visits and as many as 200 deaths each year, FAAN reports. Eight foods in particular -- milk, egg, peanut, tree nuts, fish, shellfish, soy and wheat -- account for 90 percent of all food-allergic reactions.
While there's a lot of research being done in the area of food allergy, particularly peanut allergy, it may be five to 10 years before effective treatments on available, said Anne Munoz-Furlong, FAAN's founder and CEO.
Umetsu's vaccine uses heat-killed Listeria, a food-borne contaminant, mixed with peanuts, milk or wheat, to stimulate a protective immune response.
While study results are based solely on animal testing, "the fact that this looks very promising means that we can look forward to it moving to human trials in the future," Munoz-Furlong said.
To test the vaccine, researchers used dogs that were both prone to allergies and treated to have very severe food allergies. Four of the dogs in the study had peanut allergy; they also were allergic to cow's milk and ragweed. Ten weeks after receiving a vaccine that combined heat-killed Listeria and peanut, the presence of allergic skin bumps was dramatically reduced. In addition, the dogs tolerated more peanut in their diet. Three of the four dogs, in fact, could eat a handful of peanuts -- about 57 of the legumes -- without developing symptoms.
Only their peanut allergy was treated, which shows that the vaccine is antigen-specific. "In those dogs, their peanut allergy got much better, but their milk allergy did not," Umetsu said.
Similarly, five dogs with milk, wheat, beef and ragweed allergies were tested for symptoms and skin reactions. Three were vaccinated for milk and wheat allergies; two served as controls. The vaccinated dogs had a 60 percent reduction in diarrhea and a 100 percent reduction in vomiting compared with reactions prior to vaccination. Likewise, skin tests showed marked reductions in allergic reactions.
"This study shows that by using a vaccination protocol, you can, in fact, get a protective type of response -- and we've showed this in an animal that is much closer to humans than, say, mice, on the evolutionary scale," Umetsu said.
More animal studies are needed that demonstrate, more specifically, the mechanism of this suppressive effect on the immune system, he added. Plus, researchers need to show what specific components of the heat-killed Listeria vaccine make it so effective.
Until there's an effective vaccine for treating symptoms, Munoz-Furlong urges food allergy sufferers to read food labels carefully and carry epinephrine, an injectable drug for treating severe allergic reactions.
More information
Check out the Food Allergy & Anaphylaxis Network for advice on preventing serious allergic reactions.
