SAN FRANCISCO – Research on desensitization looks promising, although it’s too early to offer it as a treatment for food allergies, according to Dr. Wesley Burks, chief of pediatric allergy and immunology at Duke University Medical Center, Durham, N.C.
In ongoing trials on patients with peanut allergies, researchers have administered gradually increasing doses of peanut flour and found that many patients can eventually consume peanuts without harm. What remains to be seen is how long this effect can last. "Can you develop tolerance from desensitization?" Dr. Burks asked at a plenary session at the meeting.
The question is important because food allergies have increased 18% from 1997 to 2007 and now affect 3.9% of all school-age children, according to the National Center for Health Statistics, Dr. Burks said.
The most common allergies are to milk, eggs, peanuts, tree nuts, shellfish, soy, and wheat, with peanuts allergy afflicting about one in a hundred kids. Peanut allergy is the most common cause of fatal food anaphylaxis.
Currently there is no way to cure patients of their allergies, although some children outgrow them. "The treatment is exclusion of only those foods that they are allergic to, not food groups," said Dr. Burks. Patients experiencing allergic reactions can be helped with self-injectable epinephrine and antihistamines.
One useful treatment undergoing research is anti-immunoglobulin. While it seems to help, it’s a long way from solving the problem. "Some people do not respond," said Dr. Burks. "It will be used as an adjunct." Also in the pipeline are some promising extracts of herbs used in traditional Chinese medicine. Finally, engineered recombinant proteins that might reduce immunoglobulin binding are also being researched.
For the desensitization studies, Dr. Burks and others are working on two routes of administering small amounts of the allergen: oral (swallowed with food) and sublingual (in which the allergen is placed under the tongue, where it dissolves and is absorbed). So far, the oral route has proved more effective in achieving desensitization.
In one blinded trial of the oral route, the patients started with 6 mg of peanut flour, then gradually worked up to 4,000 mg or more. (A whole peanut is 300 mg.)
The study enrolled 25 subjects, of which 16 were given peanut flour and 9 a placebo. The researchers found that the patients who had taken the flour were able to tolerate 5,000 mg at the end of the study, while the patients who had had only the placebo could tolerate less than 1,000 mg, a statistically significant difference (P = .008). "So the desensitization effect appears to be real," said Dr. Burks.
Of children who have been on the therapy for longer than 3 years, about 48% have been able to go off treatment and continue to meet a food challenge. By comparison, only about 10% or 15% of children would have outgrown the allergies during this time period. Another 32% had significantly lower peanut IgE levels and are still on treatment; they have not reached an IgE level low enough so they could they could be challenged. Around 20% of children, however, could not tolerate the treatment because of gastrointestinal effects.
The study revealed some interesting information about the etiology of food allergies. Immunoglobulin and regulatory T cells both increased until the 12th month of the study, then decreased. Proallergic peanut-specific cytokines decreased, while regulatory peanut-specific cytokines increased.
These trials continue, as Dr. Burks and his colleagues try to learn more about these biochemical reactions and conduct longer-term trials in search of an actual cure. Many families are clamoring for desensitization treatment because the allergies are such a burden, but they must be counseled that it’s still in the experimental stages.
"The right thing to do right now is appropriate diagnosis, and [then develop] a treatment and management plan," said Dr. Burks.
Dr. Burks disclosed he is on the advisory board of the Dannon Company Inc.; he is a consultant for McNeil Nutritionals LLC and Novartis; he has served on an expert panel for Nutricia; and he has received grants from the National Institutes of Health, the Food Allergy and Anaphylaxis Network, the Food Allergy Initiative, the Food Allergy Project, and the Wallace Research Foundation.