Common bacteria could help prevent food allergies

"Bacteria which naturally live inside our digestive system can help prevent allergies and may become a source of treatment," BBC News reports after new research found evidence that Clostridia bacteria helps prevent peanut allergies in mice.

The study in question showed that mice lacking normal gut bacteria showed increased allergic responses when they were given peanut extracts.

The researchers then tested the effects of recolonising the mice's guts with specific groups of bacteria. They found that giving Clostridia bacteria (a group of bacteria that includes the "superbug" Clostridium difficile) reduced the allergic response.

The researchers hope the findings could one day support the development of new approaches to prevent or treat food allergies using probiotic treatments.

The hygiene hypothesis

One of the medical puzzles of recent decades is the sharp rise in allergic conditions. One theory that attempts to explain this trend is the hygiene hypothesis.

This is the idea that as people grow up in increasingly sterile, germ-free environments, their immune systems become oversensitive, mistaking harmless substances such as pollen or peanuts as a threat and triggering an allergic reaction.

This is not to say that being unhygienic is good for you.

What kind of research was this?

This was an animal study that aimed to see how alterations in gut bacteria are associated with food allergies.

As the researchers say, life-threatening anaphylactic reactions to food allergens (any substance that generates an allergic response) are an important concern, and the prevalence of food allergies appears to have been rising over a short space of time.

This has caused speculation about whether alterations in our environment could be driving allergic sensitivity to foods. One such theory is the "hygiene hypothesis" (discussed above).

This is the theory that reducing our exposure to infectious microbes during our early years – through overzealous sanitisation, for example – deprives people's immune systems of the "stimulation" of exposure, which could then lead to allergic disease. 

An extension of this theory is that environmental factors – including sanitation, but also increased use of antibiotics and vaccination – have altered the composition of natural gut bacteria, which play a role in regulating our sensitivity to allergens. It has been suggested that infants who have altered natural gut bacteria could be more sensitive to allergens.

This mouse study aimed to examine the role of gut bacteria in sensitivity to food allergens, with a focus on peanut allergy.

What were the basic results?

Faecal samples taken from the antibiotic mice were found to have a significantly reduced number and variety of gut bacteria. These mice also had increased sensitivity to peanut allergens, demonstrating an increased immune system response that produced antibodies specific to these allergens, as well as showing symptoms of allergy.  

When the germ-free mice were exposed to peanut allergens, they demonstrated a greater immune response than normal mice and also demonstrated features of an anaphylactic reaction.

The researchers found that adding Bacteroides to the gut of the germ-free mice had no effect on the allergic reaction. However, adding Clostridia bacteria reduced sensitivity to the peanut allergen, making their allergic response similar to normal mice.

This suggests that Clostridia plays a role in protecting against sensitisation to food allergens.

This was further confirmed when Clostridia was used to recolonise the guts of the antibiotics mice and was found to reduce their allergic response.

The researchers then carried out further laboratory experiments looking at the process by which Clostridia could be offering protection. They found the bacteria increases the immune defenses of the cells lining the gut.

One specific effect seen was how Clostridia increased the activity of a particular antibody, which reduced the amount of peanut allergen entering the bloodstream by making the gut lining less permeable (so substances are less likely to pass through it).


Conclusion

This research examined how normal populations of gut bacteria influence mouse susceptibility to peanut allergens. The findings suggest the Clostridia group of bacteria may have a particular role in altering the immune defenses of the gut lining and preventing some of the food allergen entering the bloodstream.

The findings inform the theory that our increasingly sterile environments and increased use of antibiotics could lead to a reduction in our normal gut bacteria, which could possibly lead to people developing a sensitivity to allergens.

http://www.nhs.uk/news/2014/08August/Pages/Common-bacteria-could-help-prevent-food-allergies.aspx