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Science

Poop transplants could be used to treat peanut allergies — study

Fecal microbiota therapy shows early promise as a treatment for the potentially life-threatening allergy.

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Peanuts are some of the most unassuming dangers in the world. According to Food Allergy Research & Education, more than 6 million Americans have a peanut allergy. There’s no cure and currently very few available treatment options. But a novel remedy may be on the horizon, and it comes from an unlikely place.

A small, early-stage clinical trial looked at treating peanut allergies in people with fecal microbiota therapy (FMT). In a word: poop.

While the connection between poop and allergies might seem far off, it really isn’t: Our intestines are home to a multitude of microorganisms, many of which play a key role in our health.

Here’s the background — The legume we know and love can cause anaphylaxis, reactions ranging from difficulty breathing to death. In January 2020, the Food & Drug Administration approved the first treatment for peanut allergies in children.

It’s not so much that poop has curative properties as it is that the gut is a bacterial wonderland that has a hand in nearly every major bodily function. The gut microbiome flourishes with bacteria that keep the body healthy and break down food. Feces is the byproduct that comes from our gut, and takes some of the bacteria utopias with it. Currently, fecal microbial transplants have a high success rate in treating the intestinal infection C. diff.

Transplanting some bacteria from a non-peanut-allergic gut to an allergic one could help protect people from allergic reactions. The results of this trial were presented this month at the American Academy of Allergy, Asthma & Immunology Annual Meeting.

If you think of the gut microbiome as fertile ground for flourishing bacteria, then FMT adds new bacteria that previously weren’t there to flourish. These new bacteria can influence the immune system.

What’s new — “A single FMT led to a significant increase in the threshold of reactivity to peanut at both 1 month and 4 months after treatment, showing that the effect was prolonged. This study is offering hope that microbiome interventions may be effective in food allergy,” said Dr. Rima Rachid, the trial’s lead investigator, in a news release. “These results were very encouraging.” Rachid is also director of the Allergen Immunotherapy, Allergy, and Asthma Program at Boston Children’s Hospital.

Rachid says this may even be promising enough to help patients withstand trace amounts of peanut. Part of the reason peanut allergies can be so dangerous is that even foods processed in the same facility as peanuts can contain enough peanuts to trigger a life-threatening allergic reaction.

To the knowledge of Liping Zhao, a microbiology professor at Rutgers, this trial is the first to test peanut allergy treatment with FMT.

“I'm actually very pleased to see this success of this early trial,” he tells Inverse.

While feces might seem like a grotesque, bizarre starting point for allergy treatment, Zhao sees the reason behind it. The gut is a central player in holistic health, and it’s unsurprising that gut bacteria can influence the immune system and allergies.

“It’s lucky that we have such an important microbial organ be part of our immunity, our metabolism, our neuropsychology,” Zhao says. Gut microbiota, he says, play a role in nearly every major human function.

Why it matters — Many foods, like candy, contain trace amounts of peanuts. And because of the severity of some kids’ peanut allergies, there’s a question of whether schools should even allow peanuts. Right now, some people with severe peanut allergies undergo a form of exposure therapy by consuming gradually larger amounts of peanuts, training their system to build up a tolerance. However, this isn’t the most effective treatment in adults.

“The long-term effect of oral immunotherapy is not clear, and many patients stop therapy over time,” Rachid said in the news release. “Additionally, it requires daily administration and is not without risks of allergic reactions. Microbiome interventions are very promising alternatives for treating food allergy.”

What’s more, this oral capsule can be administered at home. Traditionally, doctors performed FMT via colonoscopy and enema, neither of which is fun or quick.

Digging into the details — This small trial tested FMT in 15 adults with a peanut allergy, and patients tolerated higher amounts of peanuts after their therapy. Everyone who participated had an allergic reaction to half a peanut or less. On the day the trial started, each participant took a total of 36 FMT capsules over three hours. This trial lasted one year.

This study had two groups. The first group of 10 people received FMT in the form of an oral capsule over two days. The second group of five people also received the capsule, but first took antibiotics in order to clear the gut of its existing bacteria metropolis so any difference from the FMT would be more distinct. After FMT, these two groups faced food challenges in which they consumed higher amounts of peanut protein.

The capsule is where poop comes in. The capsule’s contents are derived from stool donated by someone with no peanut allergy — but it’s not a pill full of poo. Inside the pill is a concentrated dose of the bacteria extracted from the donor’s stool. Rachid’s team sourced their donors from the stool bank OpenBiome. Furthermore, they sought donors with no nut allergies and instructed them to avoid even trace amounts of tree nuts so that the transplant had no chance of causing an allergic reaction in patients.

Years of groundwork precede this trial. Rachid and her colleagues began by comparing the intestinal bacteria in babies with and without food allergies. These studies, originally published in 2019 in the journal Nature Medicine, established that the stool bacteria in babies with food allergies were different from those in non-allergic babies.

The researchers then experimented with FMT in mice, transplanting fecal bacteria from the babies into allergy-prone mice. Mice given fecal bacteria from food-allergic babies went into anaphylaxis when challenged with an allergen; those given fecal bacteria from healthy babies did not.

What’s next — Rachid and her team will continue to refine the treatment in future clinical trials. She envisions the next phase will look at patients between 12 and 17 years old. For this round, they’d receive antibiotic pretreatment and an even more concentrated dose of human microbiota.

In this next trial, the fecal microbiota goes through at least two purification cycles. “We end up with highly concentrated bacteria and very little fecal material,” Rachid said during her presentation.

Zhao first points out that commercialization is a long way off, and says that in future trials he wants to see larger sample sizes in both patients and donors. He’s curious about which gut bacteria, in particular, might be associated with fortifying the body against allergic reactions. He also hopes Rachid and her team investigate how long the possible benefits of FMT persist.

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