California researchers report that dogs I who were allergic to peanuts, milk and wheat experienced sharply fewer reactions after being vaccinated for those specific food allergens.
The vaccine used heat-killed Listeria, a food borne contaminant, mixed with peanuts, milk or wheat, to stimulate a protective immune response.
To test the vaccine, researchers looked at nine dogs-four had peanut allergies and were also allergic to cow's milk and ragweed; five had both milk and wheat allergies.
Ten weeks after the dogs were vaccinated, they could tolerate larger quantities of the food before having an allergic reaction.
All four peanut-allergic dogs tolerated eating many more peanuts after vaccination.
As a whole, the group of peanut-allergic dogs went from tolerating an average of one peanut to more than 37. Three of the four dogs could even eat a handful of peanuts, approximately 57, without developing any symptoms. One dog had more than a 100-fold improvement-from a half a peanut to 57.
Only the peanut allergy was treated, not the cow's milk allergy, which indicates that the vaccine is antigen-specific, according to 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, California.
Similarly, five dogs that had 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% reduction in diarrhea and a 100% reduction in vomiting compared with reactions prior to vaccination. Likewise, skin tests showed marked reductions in allergic reactions.
More animal studies are needed that demonstrate, more specifically, the mechanism of this suppressive effect on the immune system, Umetsu adds. Plus, researchers need to show what specific components of the heat-killed Listeria vaccine make it so effective.
"Although we clearly have to do studies in humans, this study suggests [that] vaccine strategies can be developed to treat food allergies successfully," says Umetsu.
"This study shows that by using a vaccination protocol, you can, in fact, get a protective type of response-and we've shown this in an animal that is much closer to humans than, say, mice, on the evolutionary scale," Umetsu says. The study is the first to reverse food allergies in an animal other than a mouse.
While study results are based solely on animal testing, Anne Munoz-Furlong, founder and chief executive officer of the Food Allergy & Anaphylaxis Network (FAAN), a Virginia-based advocacy group, says the vaccine looks very promising and "we can look forward to it moving to human trials in the future."
Until there is an effective vaccine for treating symptoms, Munoz-Furlong urges people who have food allergies to read food labels carefully and carry epinephrine, an injectable drug for treating severe allergic reactions.