February 1, 2014
DNA Verification Of Peanut Allergy Treatments
Brett Smith for redOrbit.com - Your Universe Online
Scientists with Stanford University are finding that healing a peanut allergy with oral immunotherapy alters the DNA of the patient's immune cells. The finding could serve as the basis for a simple blood test to monitor the long-term effectiveness of the allergy therapy.
Allergy scientists are currently performing clinical trials of doctor-supervised immunotherapy involving peanut-allergy sufferers taking escalating amounts of peanut powder in an attempt to desensitize them to the nuts. At the conclusion of the trial, patients are usually expected to eat some peanuts every day throughout 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 Dr. Kari Nadeau, an immunologist at Stanford Hospital & Clinics and Lucile Packard Children's Hospital Stanford.
Until now, doctors couldn't test if patients who had finished immunotherapy could safely give up 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 said.
In the study, which was published in the Journal of Allergy and Clinical Immunology, the scientists evaluated 20 peanut-allergic adults and children who had concluded two years of immunotherapy, which made it possible for them to eat one 4-gram serving of peanuts daily without experiencing a major allergic reaction.
The patients were asked to stop consuming peanuts for three months and were then given a bit of peanut powder to see if their allergy returned. Thirteen of the patients had a relapse of their allergy, while seven did not. The scientists evaluated the immune cells in the blood of patients from the two groups. Blood samples from peanut-allergic participants who had never acquired the immunotherapy were utilized as a control.
The scientists focused on the regulating T cells, which are white blood cells that help to reduce an allergic reaction. In these cells, the DNA at a gene called forkhead box protein 3 (FOXP3) was somewhat different in each of the three sets of patients. The FOXP3 gene has been previously found to play a role in allergies.
The scientists did not detect transformations in the genetic code. Instead, there were distinctive numbers of methyl groups connected to the DNA. These molecular attachments to the DNA control the pace at which the gene is expressed, turning the thermostat up or down on the gene's activity. Patients who preserved their tolerance to peanuts had lower levels of DNA methylation at FOXP3, while those who got back their allergy had more moderate levels. Peanut-allergic patients in the control group had a relatively high level of DNA methylation at the FOXP3 gene.
The DNA change may be used to monitor the efficiency of oral immunotherapy, Nadeau said, but needs further evaluating. The blood test vital to monitor the DNA is reasonably priced, requires only a bit of blood and uses common lab equipment. However, Food and Drug Administration validation would be needed before the test might be used clinically for this explicit purpose.
"It's interesting that the change we saw is at the epigenetic level," Nadeau said, referring to alterations in genetic activity. "This might help us tell people if they can safely go off of immunotherapy, or if they need to continue to eat the food every day."