Immunomodulatory effects of probiotic supplementation during pregnancy and infancy in allergy prevention studies

Abstract: The incidence of allergic diseases is increasing, possibly due to a reduced intensity and diversity of microbial stimulation. More knowledge is needed on the immunological mechanisms underlying the eczema preventive effect of pre- and postnatal probiotic supplementation. The pregnancy period seems to be of essential importance, since both epidemiological and experimental animal studies show the importance of microbial exposure during gestation on allergy prevention.We have performed a study where the probiotic lactic acid producing bacteria Lactobacillus reuteri was supplemented to pregnant women, at risk of having an allergic infant. The pregnant mothers received the study product from gestational week 36 until delivery, and the infants then continued with the same product until one year of age. The probiotic, as compared with placebo, supplemented infants had less IgE-associated eczema at two years of age.In order to investigate how the supplementation affected the immune system peripheral blood was collected and immune cells were stimulated with common allergens and TLR ligands. The probiotic treated group responded with a more regulated response to allergens and TLR2 ligands in comparison to the placebo supplemented group. We also investigated how the probiotic supplementation affected the epigenetic methylation pattern in circulating T helper cells during infancy, observing the most pronounced effects at birth.In a follow up study, supplementation was started earlier to possibly gain a stronger allergy preventive effect via changes in maternal immune regulation. Supplementation with Lactobacillus reuteri and ω-3 fatty acids started at gestational week 20 and throughout pregnancy. After 20 weeks of supplementation, some immunomodulatory effects among circulating activated regulatory T cells and a subpopulation of monocytes were noted. Several systemic immune modifying effects of pregnancy were observed.In summary, probiotics show several immunomodulatory effects in infants and pregnant women. However, more research is needed to better understand the effects of the probiotic supplementation to aid future identification of more efficacious allergy preventive strategies.