Already in the womb, the course is set for the future health of the child. This also applies to the risk of allergies: Studies suggest that the composition of the maternal intestinal flora plays an important role. Now researchers have identified a bacterium that is apparently crucial in this context. The presence of this type of microbe seems to protect the offspring from food allergies: the more microbial roommates there are, the lower the risk of allergies to peanuts etc.
Asthma, hay fever or food allergies: Allergic diseases often manifest themselves in childhood – and they are becoming more and more common. Doctors suspect that typical environmental factors such as air pollution or an unbalanced diet also contribute to this in modern societies. The lack of contact with certain bacteria could also play a role in the development of allergies. It is probably not only the microbe composition in the nursery that is important. Even the bacterial environment in the womb could influence the allergy risk, as studies suggest. It has long been known that the maternal intestinal flora also stimulates the development of the child’s immune system. But which germs are particularly important in this context?
Peter Vuillermin from Deakin University in Geelong, Australia, and his colleagues have now addressed this question. Specifically, they concentrated on the gram-negative bacterium Prevotella copri. “As a bacterial roommate, the genus Prevotella is much rarer in western populations than in traditional, non-industrialized societies,” the researchers explain. The interesting thing: These microbes ferment fiber in our intestine to acetates – short-chain fatty acids that have anti-inflammatory effects and can promote the development of certain immune cells. It has already been shown in pregnant mice that such substances produced by intestinal bacteria can cross the placenta and thus also influence the immune system of the offspring. But does this also apply to humans?
Targeting intestinal microbes from pregnant women
To find out, Vuillermin’s team evaluated data from an Australian test group with 1,064 mothers. The women and their offspring were accompanied during pregnancy and the first year after birth. For their study, the researchers now specifically selected 58 mothers whose children had developed a medically proven food allergy. In addition, they randomly selected 258 more mother-child pairs. Would there be a connection between the intestinal flora of women during pregnancy and the early childhood allergy risk?
The analyzes showed that Prevotella copri was not found in the stool samples examined in 80 percent of the pregnant women – the bacterium was missing in the body’s own microbial community. Exactly this apparently actually affected the later susceptibility of children to allergies. This was particularly true for food allergies, for example against egg, peanut, cashew nut or cow’s milk. “The presence and amount of P. copri was substantially higher in mothers of children without food allergies than in mothers of children with allergies,” the researchers report. This relationship was evident even when they considered other possible influencing factors. The team found that the protective effects of P. copri also seemed to depend on the mother’s diet. It was therefore particularly high for women who had a high fat and fiber diet.
The impact of antibiotics and household size
But what influences whether and how many Prevotella copri is present in the intestinal flora of pregnant women? The researchers also found evidence of this: on the one hand, the presence of this bacterial species depended on whether the expectant mothers had taken antibiotics during pregnancy. If this was not the case, the microbes were found more frequently and more frequently in the stool samples. The size of the household also seemed to play a role. The rule was: the bigger the better. As Vuillermin and his team explain, it has long been known that living in households with many people can protect against allergies. A possible explanation for this: People living together exchange their microbial roommates with each other and can thus also pass on useful germs.
“In view of the disease burden caused by allergies, our results are of great importance for public health,” the scientists state.
In the future, they want to take a closer look at the role of P. copri in immune function. They also want to investigate whether the effect of these microbes may differ from strain to strain and what influence the diet has. Whether P. copri can one day be used as a probiotic or as a biomarker for the allergy risk will only be possible to clarify such further studies. However, the researchers are already making clear recommendations based on their findings: In order to protect their offspring from food allergies, pregnant women should only take antibiotics if necessary and pay attention to their diet.
Source: Peter Vuillermin (Deakin University, Geelong, Australia) et al., Nature Communications, doi: 10.1038 / s41467-020-14552-1