The study has much relevance to those suffering from food allergies, which has negative effects on morbidity and quality of life.
The development of efficient approaches to reduce the risk of developing food allergies is therefore of considerable interest.
Food allergies have increased in prevalence in the last decades, especially in regions that follow a western diet.
The increase in allergic diseases over the past 20-30 years in industrialised countries suggests environmental changes are a factor for the development of allergies.
But studies have been quick to point to the intestinal bacteria as playing a crucial role in the intestinal immune system and maintenance of gut wall epithelial integrity.
Research has also reported intestinal imbalance in patients with allergic symptoms compared to healthy individuals.
Bacterial strain sampling
Lead researcher Anne-Judith Waligora-Dupriet from the Paris Descartes University and her colleagues began by looking at 31 bacterial strains, including 21 Lactobacillus spp., six Bifidobacterium spp., two Lactococcus spp. and two Streptococcus spp. strains.
Between day seven and day 48, mice received a dose of each bacterial strain four times per week. Each of the six candidate probiotic strains were studied in separate animal experiments. Animals from the control group received 200 μL of sterile saline solution.
These strains were then added to another in vitro cellular model that used human blood cells.
The researchers found six strains induced a high anti-inflammatory response on both cellular models. These strains were further evaluated in vivo in a mouse model to confirm their protective impact.
In addition, three bacterial strains showed a protective impact on sensitisation with a decrease in allergy-specific cell production as well as a decrease in cell response to inflammatory and allergic reactions.
Analysis of the impact of these three strains on the T-helper balance revealed different mechanisms of action. The L. salivarius strain proved to block two types of cell immune responses while the B. infantis strain induced a regulatory cell response. The L. rhamnosus strain induced both cell immune and regulatory responses.
The role of Treg and foxp3
The researchers pointed to the bacterial strain’s influence on foxp3, a main regulator for the development and the function of the Treg immune cells, which are essential for the induction and maintenance of immune tolerance.
“Indeed, Tregs are essential for the induction and maintenance of immune tolerance, by preventing Th2 induction and cytokine release,” the researchers noted.
“The average level of the foxp3 gene expression is significantly lower in allergic children compared with healthy children.”
Moreover, the researchers speculated that Foxp3 may have a suppressive role in the anaphylactic response, controlling the mast cell response.
“Our results therefore suggest a link between foxp3 gene expression in ileum and protection against food allergy.”
Source: Applied and Environmental Microbiology
Published online ahead of print, doi:10.1128/AEM.03440-15
“Identification of three novel candidate probiotic strains with prophylactic properties in a murine model of cow’s milk allergy.”
Authors: Anne-Judith Waligora-Dupriet et al.