Treating a peanut allergy with oral immunotherapy changes the DNA of the patient's immune cells, according to a new study from the Stanford University School of Medicine and Lucile Packard Children's Hospital Stanford. The DNA change could serve as the basis for a simple blood test to monitor the long-term effectiveness of the allergy therapy.
Peanut allergy, like other food allergies, currently has no cure. Scientists are conducting clinical trials of doctor-supervised immunotherapy, in which peanut-allergic patients take increasing amounts of peanut powder to try to desensitize them to the peanut allergen. At the end of the trial, patients are usually asked to eat some peanuts every day for the rest of their lives.
"At first, eating two peanut butter cups a day might seem fun, but it gets a little boring and a lot of people might stop," said Kari Nadeau, MD, PhD, associate professor of pediatrics at Stanford and an immunologist at Stanford Hospital & Clinics and Lucile Packard Children's Hospital Stanford. Until now, doctors could not test whether patients who had completed immunotherapy could safely stop eating daily doses of peanuts, she said. "Our new finding can help us try to determine whether, for the long term, someone's allergy has truly been shut off so people can eat ad lib."
Nadeau is the senior author of a paper describing the new findings, which will be published online Jan. 31 in the Journal of Allergy and Clinical Immunology.
In the new study, Nadeau's team examined 20 peanut-allergic children and adults who had completed two years of immunotherapy, which enabled them to eat one 4-gram serving of peanuts daily without experiencing a major allergic reaction.
The patients were asked to stop eating peanuts for three months and then were given a small amount of peanut powder to see if their allergy returned. Thirteen of the patients regained their allergy, while seven did not. The researchers compared the immune cells in the blood of patients from the two groups. Blood samples from peanut-allergic patients who had never received oral immunotherapy were used as a control.
The researchers focused on the regulatory T cells, which are white blood cells that help to suppress an allergy response. In these cells, the DNA at a gene called forkhead box protein 3, or FOXP3, was slightly different in each of the three groups of patients. The FOXP3 gene has previously been shown to play a role in allergies.