Do microbes cause milk allergy?

Over the past 30 years, food allergies have become increasingly common in the United States. Changes in human genetics can not explain this sudden rise. This is because it takes several generations for the changes to spread as widely within a population. The explanation may lie in the changes in our environment, including our internal environment. Lifestyle changes over the last fifty years – increased use of antibiotics and antimicrobials, surface sterilization, air filtration, and dietary modification – have altered our internal environment and eliminated important bacteria with beneficial effects on health.

My research group at the University of Chicago has for many years been exploring the role of intestinal bacteria in preventing allergic reactions to food. Bacteria, as well as viruses, fungi and other small organisms living in and on our body, collectively constitute the microbiome and play an essential supporting role for health.

Bacteria (red) reside in the epithelial cells (blue) and mucus (green) of a small intestine of mice. UChicago, [email protected], CC BY-SA

The microbiome is our internal environment. Humans and microbes have "grown" together: As humans evolved, so did their microbes. We tend to think that health practices are evolving slowly, but from the point of view of the bacteria in our gut, changes in their composition and function have occurred more quickly – and the results are dramatic.

Intestinal bacteria and allergies

Several years ago, my research group and a collaborator in Italy, Roberto Berni Canani, compared the bacteria found in infants with diagnosed cow's milk allergy to those who did not. We found remarkable differences between the two groups. This leads us to wonder if the different bacteria present in each of the two groups are sufficient to protect against allergies. And if so, could we understand why?

To test this idea, we transplanted the entire microbiome from two different groups – healthy infants and cow's milk allergy sufferers – into special laboratory mice, reared in a totally sterile environment, without any clean bacteria. The idea was simple: if we transplant the different groups of bacteria into mice, will the mice become allergic to cow's milk or not?

The results struck us: the bacteria of a healthy infant could prevent the mouse from developing an anaphylactic reaction to a cow's milk protein, unlike the bacteria of an infant allergic to cow's milk.

A new diagnosis?

When we cataloged bacteria present in mice colonized with healthy bacteria and those present in mice colonized with cow's milk allergic bacteria, we were able to calculate a ratio of protective / non-protective groups. This ratio could accurately predict whether or not the children had an allergy. We also learned that both groups of bacteria activate different genes in the mouse intestine.

These genes influence various processes in the intestine, such as metabolism and permeability. We identified one bacterial species in particular, Anaerostipes caccae, like the key. When we only introduced this species into a mouse without germs, the mouse was protected from food allergy.

These studies show that the microbiome plays a role in promoting health in food allergies. It is clear that the internal environment of the intestine is very different in infants with and without food allergy and that this internal environment changes the biochemistry of the intestine.

Our study also suggests a pathway to exploit these protective bacteria and the molecules they produce as treatments to prevent and treat food allergies. They could also work well as a diagnostic tool for predicting allergies and allergy risks. Therapies based on this idea remain in 5 to 10 years, but I am excited about their prospects. These therapies can provide relief to children, parents, caregivers and patients with food allergy.

Cathryn Nagler is a professor of food allergy at Bunning University of Chicago.
Disclosure Statement: Cathryn Nagler is the President and Co-Founder of ClostraBio, Inc.

Republished with the permission of our media partner The Conversation.