• Majda Dzidic, Thomas R Abrahamsson, Alejandro Artacho, Bengt Björkstén, Maria Carmen Collado, Alex Mira, and Maria C Jenmalm.
• Department of Clinical and Experimental Medicine, Unit of Autoimmunity and Immune Regulation, Linköping University, Linköping, Sweden; Department of Health and Genomics, FISABIO Foundation, Center for Advanced Research in Public Health, Valencia, Spain; Institute of Agrochemistry and Food Technology, Spanish National Research Council (IATA-CSIC), Department of Biotechnology, Unit of Lactic Acid Bacteria and Probiotics, Valencia, Spain.
• J. Allergy Clin. Immunol. 2017 Mar 1; 139 (3): 1017-1025.e14.

BackgroundAlthough a reduced gut microbiota diversity and low mucosal total IgA levels in infancy have been associated with allergy development, IgA responses to the gut microbiota have not yet been studied.ObjectiveWe sought to determine the proportions of IgA coating together with the characterization of the dominant bacteria, bound to IgA or not, in infant stool samples in relation to allergy development.MethodsA combination of flow cytometric cell sorting and deep sequencing of the 16S rDNA gene was used to characterize the bacterial recognition patterns by IgA in stool samples collected at 1 and 12 months of age from children staying healthy or having allergic symptoms up to 7 years of age.ResultsThe children with allergic manifestations, particularly asthma, during childhood had a lower proportion of IgA bound to fecal bacteria at 12 months of age compared with healthy children. These alterations cannot be attributed to differences in IgA levels or bacterial load between the 2 groups. Moreover, the bacterial targets of early IgA responses (including coating of the Bacteroides genus), as well as IgA recognition patterns, differed between healthy children and children with allergic manifestations. Altered IgA recognition patterns in children with allergy were observed already at 1 month of age, when the IgA antibodies are predominantly maternally derived in breast-fed children.ConclusionAn aberrant IgA responsiveness to the gut microbiota during infancy precedes asthma and allergy development, possibly indicating an impaired mucosal barrier function in allergic children.Copyright © 2016 American Academy of Allergy, Asthma & Immunology. Published by Elsevier Inc. All rights reserved.

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