Can Lactobacillus Reuteri PreventAllergic Disease in Early Childhood?
Background: An altered microbial exposure may be partly responsible for the increase of allergic diseases in populations with a western lifestyle. Activation of the immune system by microbes early in life is probably required for an accurate maturation of the immune system. Probiotics, live bacteria which are considered to confer health when ingested, have been suggested to prevent eczema and sensitisation infants.Aim: The general aim of this thesis was to assess the effect of oral supplementation with the probiotic bacterium Lactobacillus reuteri (L. reuteri) in infancy on the development of allergic disease and sensitisation during the first 2 years of life and to examine mechanisms possibly underlying eventual effects on allergic manifestations.Subjects: The thesis is based on results obtained from a prospective double-blind placebo-controlled multicenter trial, comprising 232 families with allergic disease, of whom 188 completed the study.Methods: The families were recruited at the antenatal clinic, and the mothers received L. reuteri ATCC 55730 (1 x 108 colony forming units) or placebo daily from gestational week 36 until delivery. Their babies then continued with the same study product from birth until 12 months of age and were followed up for another year. The primary outcomes were allergic disease, with or without positive skin prick test or circulating IgE to food allergens. Bacterial counts and prevalence were assessed in maternal breast milk and faeces and infant faeces, employing conventional cultivation methods. Cytokines and IgA antibodies were analysed in colostrum and mature milk from the mothers with ELISA, and Na/K- ratio in breast milk with ion selective electrodes. Circulating Th1/Th2-associated chemokines were analysed in cord and peripheral blood in the infants with Luminex or ELISA technique.Results: The incidence of eczema was similar, 36% in the treated versus 34% in the placebo group. The L. reuteri group had a lower cumulative incidence of IgE-associated allergic disease, 20% versus 35% (p=0.04), and less IgE-associated eczema during the second year, 8% versus 20% (p=0.02). The prevalence of L. reuteri was higher during the first year of life in stool samples from infants, as well as in colostrum, in the active as compared to the placebo treated group. Colostrum from L. reuteri supplemented mothers had lower levels of TGF-?2, and low levels of this cytokine were associated with less sensitisation. Low Th1- and high Th2-associated chemokine levels preceded allergic disease. The presence of L. reuteri in stool was associated with lower levels of the Th2-associated chemokines CCL17 and CCL22 and higher levels of the Th1-associated CXCL11.Conclusion: Although a preventive effect of probiotics on infant eczema was not confirmed, the L. reuteri treated infants had lower incidence of IgE-associated allergic disease at two years of age, and therefore possibly run a reduced risk to develop later respiratory allergic disease. The mechanisms underlying this effect require further elucidation.
Source Type:Doctoral Dissertation
Date of Publication:01/01/2009