Background: Humoral responses to food antigens may reflect the propensity of a child's immune system to develop tolerance to innocuous antigens. Early nutrition as well as probiotics may influence these immunological responses.
Objective: To study the association of humoral responses to early food antigens with the administration of prebiotics and probiotics, with the occurrence of allergy, and with the length of exclusive breastfeeding.
Methods: In a randomized double-blind allergy prevention trial in high-risk children, 1018 mothers took probiotics or placebo from the 36th week of gestation, and their newborn infants received probiotics and prebiotics or placebo during 6 months. At 2 and 5 years, we evaluated the cumulative incidence of allergic diseases (food allergy, eczema, asthma, rhinitis) and sensitization (skin prick test ≥3 mm or serum antigen-specific IgE>0.7 kU/L). In 688 infants at age 2, we measured in sera-specific IgA, IgG, IgG1, and IgG4 antibody levels to cow's milk (CM), α-casein (CAS), β-lactoglobulin (BLG), and ovalbumin (OVA) with ELISA, and specific IgE levels to CM and hen's egg with UniCap.
Results: Probiotic treatment (n=342) compared with placebo (n=346) showed no effect on serum food-specific IgA, IgG, IgG1, or IgG4 concentrations at age 2. Atopic children had higher OVA-IgA (P<0.001), OVA-IgG (P=0.001), OVA-IgG1 (P<0.001), and egg-IgE but lower OVA-IgG4/egg-IgE ratio (P<0.001) than non-atopic children. Longer duration of exclusive breastfeeding (≥4 vs. <4 months) was associated with reduced CM- and CAS-specific serum IgA (P<0.001) and IgG levels (P<0.001; P=0.003).
Conclusion and clinical relevance: Allergy was associated with more intense IgA and IgG responses to OVA. Breastfeeding depressed humoral responses, whereas prebiotics and probiotics supplementation showed no immunomodulatory effect. The effect of probiotics on allergies is not mediated through food-specific antibody responses. Furthermore, OVA-specific IgA and IgG antibodies may help in assessing the risk for atopy.
Trial registration: ClinicalTrials.gov NCT00298337.
© 2011 Blackwell Publishing Ltd.