Dosing, Duration of Therapy Examined In Peanut Allergy Studies
Researchers seeking to reduce the dangers of peanut allergies have seen encouraging results in recent years from oral immunotherapy. But many questions remain: How large of a dose? For how long? And, once treatment ends, does its effectiveness last, or does it eventually wear off?
Two studies that examined some of these questions were presented Sunday, both in a press conference and in sessions at the 2014 Annual Meeting of the American Academy of Allergy, Asthma & Immunology in San Diego, California.
Incidence of peanut allergies in the United States has soared over the past 20 years: A study sponsored by the nonprofit organization Food Allergy Research and Education (FARE) found that the number of children allergic to peanuts tripled from 1997 to 2008.1 The allergy presents special challenges because it has turned a lunchroom classic—the peanut butter and jelly sandwich—into a potentially deadly substance that can cause allergic children to suffer anaphylaxis.
Parents and school districts around the country have grappled with peanut allergies in different ways; a separate lunch table for children with peanut allergies is not uncommon in US schools. Scientists, too, have shifted course in their response, with the movement toward oral immunotherapy gaining steam in recent years.
Through oral immunotherapy, persons with the allergy consume tiny amounts of peanut protein to desensitize them to reactions. The expectation is not that these patients will someday eat large amounts of peanut butter, but rather that consuming small amounts inadvertently will no longer cause severe reactions.
One study, presented at the press conference by Scott Commins, MD, PhD, started with a simple reality among children: If something makes them sick, they tend not to want to eat it. This, of course, posed a problem for researchers at the University of Virginia who had asked parents to serve ever-increasing doses of peanut flour to the test subjects. So here was the question: Would a low-dose therapy, such as eating an actual peanut or two, do the trick?2
“Encouraging continued peanut consumption after reaching the point of desensitization is one of the challenges of oral immunotherapy. In light of that, our goal was to find out if consuming just a small amount of peanut would be enough to allow for sustained unresponsiveness,” Dr Commins said in a statement.
Based on the results, it appears that a peanut a day can work. In the study, 20 children ages 4 to 19 were given oral immunotherapy with peanut flour, gradually building up to 300 mg/day over the course of 1 year. Then, the children ate 1 or 2 peanuts a day. After their serum peanut-specific immunoglobulin E (IgE) was less than 15 IU/mL, they took part in a second test, known as a food challenge. This measured whether the children had developed sustained unresponsiveness to peanuts.
Of the group, 17 of the 20 children (85%) achieved desensitization; they had abstained from all peanut products for 4 weeks, then consumed 5000 mg of peanut protein. Three subjects withdrew early in the study because of side effects. The initial median peanut IgE was 285.4 IU/mL (range, 22.1-795.0 IU/mL). After desensitization had occurred, 10 children kept eating 1 to 2 peanuts daily at home for a median of 8.7 months until peanut IgE was <15 IU/mL. These 10 children passed another test, consuming 5000 mg of peanut after not eating any for 4 weeks. The remaining 7 are eating 1 to 2 peanuts daily, awaiting word on whether or not they have qualified for another food challenge.
A different study examined whether the effect of immunotherapy lasts once it ends, and whether there is a such a thing as staying off peanut therapy for too long. It appears there is, according to A. Wesley Burks, MD, who presented results at Sunday’s press conference that were later examined at a discussion session.3 The issue of how long the effects of therapy last, Burks said, “is a significant issue in the use of oral immunotherapy.”
Burks and other investigators at University of North Carolina at Chapel Hill studied 20 patients who were on daily oral immunotherapy but then took part in double-blind placebo-controlled food challenges with peanut, while oral immunotherapy continued, to assess desensitization. All 20 passed.
Then, the subjects avoided peanut in their diets for either 1 or 3 months, at which time they participated in a second double-blind placebo-controlled food challenge. All 16 patients who had avoided peanut for just 1 month passed the follow-up food challenge, while only 1 of the 4 who had avoided peanut for 3 months passed. Researchers additionally examined responses of basophil cells, which store histamine that is released in response to an allergen. A slide presented Sunday afternoon compared basophil levels between the 2 groups at the 1-month and 3-month marks, with more differentiation between the groups at the 3-month mark.
1. Peanut Allergy. Food Allergy Research and Education. http://www.foodallergy.org/allergens/peanut-allergy. Accessed March 3, 2014.