A paper recently came out in Cell Host & Microbe about how the microbes in our saliva and gut – like Rothia and Staphylococcus species – can degrade peanut allergens and reduce the severity of anaphylaxis. The researchers confirmed this with in vitro tests and in mice. Mice treated with the bacteria had milder reactions when exposed to peanuts. In people with peanut allergies, those who can tolerate higher amounts of peanut before developing a reaction had higher levels of these bacteria. The researchers of this study hope that one day, microbes such as these could help manage food allergies therapeutically.
Moving beyond association
This isn’t the first study that shows the connection between the microbiome and peanut allergies (or food allergies in general). But, in contrast to most other studies that focus on associations between gut microbes and peanut allergies, this paper looks at the mechanisms: what are the microbes doing and how are they affecting the allergic response? This study identified the important microbes and showed that they metabolize the main allergens, which would otherwise bind an antibody called immunoglobulin E (IgE). During peanut allergies, once the allergen binds IgE, it causes a slew of inflammatory responses leading to anaphylaxis. When the bacteria degrade these allergens, the response lessens.
Before the paper: Gut bacteria and food allergies
Though there have been numerous papers on the connection between the gut microbiome and peanut allergies (a PubMed search of “peanut allergy microbiome” brought up 109 publications), here I’ll just highlight two papers that preceded the Cell Host & Microbe paper.
In 2023, a longitudinal study tracked the gut microbiome and metabolome in kids with allergy risk from infancy through mid childhood. The study found that a less diverse infant gut microbiome was associated with the development of a peanut allergy. They also noticed that kids who developed a peanut allergy had a different trajectories in the abundance of certain microbes or metabolites over time.
While the 2023 study shows that gut microbiome diversity can be linked to peanut allergy, a more recent study from the same researchers shows that it’s specific bacteria – and not just overall diversity – that have an impact. This study compared microbiomes from children without peanut allergy to those with a high-threshold peanut allergy (only reactions to higher amounts of peanut protein) and those with a low-threshold peanut allergy (reacts to much less peanut protein). From these studies, they identified “hub bacteria” such as Rothia aeria (same genus as the Cell Host & Microbe study mentioned above) and Bacteroides sp. that were associated with how much peanut triggers symptoms, though I couldn’t find any mention of whether they were negatively or positively correlated with this. However, the researchers did mention that these species were linked to lower levels of allergy-related gene expression.
Rise of food allergies in recent years
Beyond peanut allergies, studies have found an increase in food allergies incidence in recent decades. For example, researchers have found a 50% increase in food allergy prevalence between 1997 and 2011, which has also increased another 50% between 2007 and 2021 and self-reported peanut or tree nut allergies have tripled between 1997 and 2008 in children.
One theory behind these increases stems from the hygiene hypothesis, which states that early childhood exposure to harmless microbes protects children from developing allergies, asthma, and autoimmune conditions. Things like antibiotics, cesarean delivery, low-fiber diets, and processed foods can disrupt the microbiome or affect the gut barrier, making allergens easier to cross the gut barrier. However, there’s mixed evidence on whether the hygiene hypothesis supports these claims and has since become a misnomer (more on this in a later blog post…).
Many different therapeutic strategies exist to modulate the gut microbiome to help treat food allergies. Source: Chernikova et al. 2022. CC-BY 4.0.
How microbes can treat peanut allergies
Going back to the peanut allergy and microbiome studies, there is a lot of hope for applying microbes to help people with peanut allergies. A few of the ways microbes can help include:
- Degrading peanut allergens, as we’ve seen in the Cell Host & Microbe study
- Reinforcing the gut barrier, which prevents allergens to leak into the bloodstream
- Promoting immune tolerance, by boosting regulatory immune pathways
Currently, scientists have been studying whether fecal microbiota transplants, prebiotics, probiotics, synbiotics, and other types of therapies can help patients with peanut allergies and there have been many clinical trials that have been complete or are currently ongoing (see Table 1 and 2 here or ClinicalTrials.gov). The bottom line: microbes hold tremendous potential in treating or preventing peanut allergies, but we still need more human trials before real treatments can come to fruition.
Featured image source: Joel Camelot
