How a poo transplant partially cured peanut allergies in adults

A faecal transplant enabled patients with severe peanut allergy to safely eat small amounts of peanuts.

A faecal transplant enabled patients with severe peanut allergy to safely eat small amounts of peanuts. Photo: Getty

A group of young adults, all of them severely allergic to peanuts, were able to safely consume a small amount of nuts four months after undergoing a faecal microbiota transplant (FMT).

The clinical trial, apparently a world first, suggests that a ‘poo transplant’ stimulates a partial cure for some allergic people – by increasing their tolerance and freeing them from fretting about trace amounts of peanuts in packaged, restaurant and take-away foods.

According to a statement from Boston Children’s Hospital, the transplant enabled some study participants – who initially had allergic reactions to less than half a peanut – to consume more than two peanuts before reacting.

“That amount may be enough to eliminate concern about traces of peanut in foods,” said Dr Rima Rachid, MD, of Boston’s Division of Allergy and Immunology.

The trouble with peanut allergies

Peanut allergies are difficult to treat.

A common strategy in small children is ‘oral immunotherapy’, where patients receive an incrementally increased dosing of peanuts.

This, when it works, eventually provokes a more tolerant response.

These treatments, which must be given daily, occur under medical supervision, and sometimes the patient is given medications to suppress their immune response.

“But this method is not curative and is not effective in adults,” Dr Rachid said.

The alternative that Dr Rachid is exploring is called a microbiome intervention.

What’s a microbiome intervention?

It’s a simple idea: The bacteria living in our intestines help shape our immune systems.

So, when we have an allergy, it begins in our gut.

A poo transplant takes a sample of bacteria from a healthy person and uses it to replace the unhealthy intestinal bacteria of a peanut-allergic patient.

Hence the name ‘faecal microbiota transplant’, or FMT.

Where’s the evidence?

Evidence has been accumulating for some time that FMTs can repair an unhealthy gut. It’s not all about peanuts or allergies. See here.

The Boston trial was a consequence of earlier research in which Dr Rachid and her colleagues compared the intestinal bacteria in babies with and without food allergies.

These studies, published in 2019, “established that the stool bacteria in babies with food allergies were different from those in non-allergic babies”.

From there, the researchers experimented with FMT in mice, transplanting faecal bacteria from the babies into allergy-prone mice: “Mice given faecal bacteria from food-allergic babies went into anaphylaxis when challenged with an allergen; those given faecal bacteria from healthy babies did not.”

The new trial

This was a Phase 1 open-label trial that enrolled 15 participants, aged 18 to 33, who had allergic reactions to 100 milligrams of peanut (half a peanut) or less.

All received FMT, which required them to swallow 36 capsules over three hours.

The capsules contained stool samples from rigorously screened healthy donors.

In one arm of the study, 10 participants received a single dose of FMT alone.

Three participants (30 per cent) were able to tolerate larger amounts of peanut – one as much as four peanuts – when challenged both one and four months after FMT.

In the second arm, five participants were pretreated with antibiotics to kill off their own microbiome, clearing the way for the donor bacteria.

This led to a doubled success rate. Three of the five (60 per cent) became more peanut-tolerant after FMT.

There were no serious adverse reactions to FMT.

Dr Rachid said that while the number of participants was small, laboratory tests were consistent with the clinical results.

Participants who responded to FMT “had increases in the regulatory T cells associated with immune tolerance and reductions in the T helper cells associated with allergy”.

The next step

“These results were very encouraging,” Dr Rachid said.

“A single FMT led to a significant increase in the threshold of reactivity to peanut at both one month and four months after treatment, showing that the effect was prolonged. This study is offering hope that microbiome interventions may be effective in food allergy.”

Dr Rachid now hopes to conduct a Phase II clinical trial in 12- to 17-year-olds, providing antibiotic pre-treatment and a purified Microbial Transplantation Therapy preparation.

The preparation can be stored in a home refrigerator, avoiding the need for patients to come to the clinic to be treated.

“Home administration makes microbiome interventions very attractive,” Dr Rachid said.

The results of the trial were presented last week at the American Academy of Allergy, Asthma and Immunology annual meeting.

They are yet to be published in a peer-review journal.

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