Oral immunotherapy for peanut allergies — a treatment that exposes patients to escalating doses of allergen — carries a persistent risk that researchers and clinicians have struggled to quantify: why do some patients react mildly while others collapse into anaphylaxis? A new study points to the microbiome as a likely factor.
According to the report, published in Cell Host & Microbe, researchers examined three groups of mice, each with a different level of microbial diversity. All groups received a small amount of peanut delivered directly into the stomach. Forty minutes later, mice with no microbiome and those with minimal microbial diversity showed higher levels of two peanut allergy proteins — Ara h 1 and Ara h 2 — in their small intestines than mice with a typical, diverse microbiome.
The key difference appeared to be a group of bacteria called Rothia, particularly the strain Rothia R3. Mice with the most diverse microbiomes carried the highest concentrations of it. The bacterium appears to digest and degrade peanut proteins in the gut, potentially limiting how much allergen reaches the immune system.
What happened when Rothia R3 was implanted directly
To test causation rather than correlation, the team induced severe peanut allergies in mice with minimal microbiomes, then implanted Rothia R3 into a subset before exposing all animals to peanut paste. Every mouse developed anaphylaxis. But the mice that received the bacterium showed a body temperature drop of just 2 percent on average, compared to 3.5 percent for those without it. They also carried roughly half the blood levels of MMCP-1, an immune molecule that spikes during anaphylactic reactions.
“The findings are compelling,” said Mohamed Shamji of Imperial College London. “If a similar immunological change occurred in people, you would expect this to reduce the severity of anaphylaxis symptoms.”
The human data, while limited, points in the same direction. Among 19 people with peanut allergies, those with greater peanut tolerance had substantially higher levels of Rothia bacteria in their saliva than those with more severe reactions. This suggests the bacteria’s presence in the mouth — not only the gut — may influence anaphylaxis risk.
The question driving the research
“There’s a big question around why some patients are more susceptible to more severe reactions,” said Rodrigo Jiménez-Saiz of the Autonomous University of Madrid, who led the work. The microbiome, with its well-established influence on immune function, offered a plausible answer worth testing.
Shamji noted that a Rothia-based probiotic could reduce fear around accidental peanut exposure and lower the risk of adverse reactions during oral immunotherapy specifically. “The need for something like this is huge,” he said.
The next step, according to Jiménez-Saiz, is a clinical trial in which people with peanut allergies would receive either Rothia probiotics or a placebo before being exposed to low levels of peanuts.
This article is a curated summary based on third-party sources. Source: Read the original article
