Hope in small doses for children suffering from peanut allergy
A small study shows immunotherapy can put peanut allergy into remission, but it is not a cure yet.
Peanut butter sandwiches at childcare are a thing of the past thanks to an alarming surge in peanut allergies over recent decades. But a new study has found that for some children the allergy can be coaxed into remission.
The prospect of a cure for peanut allergy is tantalising, not least because even small amounts can spark a potentially lethal reaction. Peanut allergy also has the pesky habit of sticking around – only 15% to 20% of kids grow out of it, compared with about 85% of kids with milk or egg allergies.
One approach being investigated to quell peanut allergies is oral immunotherapy. This involves feeding allergic kids a daily dose of peanuts, starting with tiny amounts and carefully increasing the dose over a period of months.
Oral immunotherapy has been shown to desensitise most children to peanuts, but usually only if taken religiously. Skip a day or two and the problem comes roaring back. Only a handful of kids ever manage to build a tolerance that persists after a couple of weeks of going without peanuts.
Mimi Tang and colleagues at the Murdoch Children’s Research Institute in Melbourne, Australia, wondered whether they could improve these odds by adding a probiotic into the mix.
“The intestinal microbiome is really important in programming healthy immune responses,” Tang says.
Lifestyle factors, such as diet and hygiene, that disrupt gut microbes in young children could be part of the reason for rising rates of food allergies. But probiotics might compensate.
“I though the immune system might benefit from a bit of a help to point it in the right direction. That’s what the probiotic is doing,” Tang adds.
The team used a strain of Lactobacillus rhamnosus shown to bump up production of immune cells that help to put a brake on overzealous immune reactions.
That original trial ended in 2011, and 82% of kids – 23 of 29 – treated with the peanut-probiotic combo had no reaction when fed peanuts following two weeks’ abstinence. This compared to just one of 28 given a mock immunotherapy.
The current study, published in the Lancet Child and Adolescent Health journal, is a follow-up to that trial, tracking how kids fare years after they stop daily treatment.
Two-thirds of the kids who were treated were still practising oral immunotherapy four years later.
The real test, though, was whether the tolerance held. Twelve participants who had been treated – 10 of whom had tested unresponsive immediately following treatment – underwent an oral food challenge after going cold turkey for eight weeks. Seven of these were unresponsive, compared to just one of 15 placebo kids.
“[In] no other study of oral immunotherapy have individuals been able to ingest the allergen with this infrequency and remain non-reactive,” writes Matthew Greenhawt of the University of Colorado School of Medicine in an accompanying commentary on the study.
But was the probiotic the crucial ingredient? From this research, it is not certain, says Robert Loblay, director of the Allergy Unit at Royal Prince Alfred Hospital in Sydney: “The trouble is it’s not clear what was responsible for the effect they observed.” To know if the probiotic boosted the immunotherapy’s effectiveness, he says, a head-tohead comparison with a peanut-only immunotherapy is needed.
Tang and her team are embarking on just such a study, enrolling 200 children across three hospitals. If the probiotic does turn out to have a genuine effect, additional studies will also be required to figure out exactly how and why it works.
As for a cure: “We’re quite a long way away, unfortunately, but we’re working towards it slowly,” Tang says.
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