A cure for peanut allergy?

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 revealed that for some kids, 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 reaction and those reactions can be lethal. Peanut allergy also has the pesky habit of sticking around – only 15–20% of kids ‘grow out’ of peanut allergies, compared with around 85% for kids with milk or egg allergies.

One approach that researchers are investigating to quell peanut allergies is oral immunotherapy. This involves feeding allergic kids a daily dose of peanuts, starting with tiny amounts and carefully ratcheting up 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 allergy roars back. Only a handful of kids ever manage to build tolerance that lasts after a couple of weeks of going without peanuts.

Mimi Tang and colleagues at the Murdoch Children’s Research Institute in Melbourne 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,” says Tang. Lifestyle factors that disrupt gut microbes in young kids, such as diet and hygiene, could be part of the explanation for the rising rates of food allergies, she adds. 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,” says Tang.

The team used a strain of Lactobacillus rhamnosus previously 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 2 weeks abstinence. (Compared to just 1 of 28 given a mock immunotherapy.)

The current study, published in the Lancet Child and Adolescent Health journal, is a follow-up of that trial, the first to track how kids fare years after they stop daily treatment.

Two-thirds of the kids who were treated were regularly eating peanuts four years later.  The real test, though, was whether the tolerance held after they stopped eating peanuts for a while.

Only 12 participants who had been treated – 10 of whom had tested unresponsive immediately following treatment – underwent an oral food challenge after going cold turkey for 8 weeks. Seven of these were unresponsive, compared to just 1 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 study, it’s not clear, says Robert Loblay, director of the Royal Prince Alfred Hospital Allergy Unit in Sydney. “The trouble is it’s not clear what was responsible for the effect they observed,” he says.

To test whether the probiotic boosted the immunotherapy’s effectiveness, a head-to-head comparison with a peanut-only immunotherapy is needed, he says. 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,” says Tang.

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