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Antibiotic use during pregnancy may increase the risk for asthma in children. We performed a meta-analysis assessing prenatal antibiotic exposure and the risk for childhood wheeze or asthma, as well as for diseases associated with the atopic march.A systematic literature search protocol (PROSPERO-ID: CRD42020191940) was registered and searches were completed using Medline, Proquest, Embase, and the Cochrane central register of controlled trials. Screening for inclusion criteria: published in English, German, French, Dutch, or Arabic, intervention (use of any antibiotic at any time point during pregnancy), and disease (reporting atopic disease incidence in children with a primary outcome of asthma or wheeze), and exclusion criteria: reviews, preclinical data, and descriptive studies, yielded 27 studies. Study quality was assessed using the Newcastle-Ottawa Assessment Scale. Quality of the evidence was assessed using the Grading of Recommendations Assessment, Development, 42

Background Maternal asthma during pregnancy is considered an environmental risk factor for asthma development in children. Immunoglobulin G (IgG) antibodies that are transferred from the mother to the fetus are known to act in a pro‐ or anti‐inflammatory manner depending on their glycosylation status. Objective Using a mouse model, we examined how maternal allergic airway inflammation during pregnancy influenced offspring experimental asthma severity, as well as maternal and offspring serum IgG antibody glycosylation patterns. Additionally, the effects of maternal and offspring exposure to the same or different allergens were investigated. Methods Female mice were either sham sensitized or sensitized to casein (CAS) or ovalbumin (OVA) before mating. Subsequently, allergic lung inflammation was induced in pregnant dams via aerosol allergen challenge (sham, CAS or OVA). After weaning, pups were subjected to an experimental asthma protocol using OVA. Asn‐297 IgG glycosylation was analysed in maternal and offspring serum. Results When mothers and offspring were sensitized to the same allergen (OVA‐OVA), offspring had more severe experimental asthma. This was evidenced by altered antibody concentrations, increased bronchoalveolar lavage inflammatory cell influx and decreased lung tissue and lung draining lymph node regulatory T cell percentages. When mothers and offspring were sensitized to different allergens (CAS‐OVA), this phenotype was no longer observed. Additionally, maternal serum from allergic mothers had significantly higher levels of pro‐inflammatory IgG1, shown by decreased galactosylation and sialylation at the Asn‐297 glycosylation site. Similar glycosylation patterns were observed in the serum of adult allergic offspring from allergic mothers. Conclusions and Clinical Relevance We observed a strong association between maternal experimental asthma during pregnancy, increased offspring airway inflammation and pro‐inflammatory IgG glycosylation patterns in mothers and offspring. IgG glycosylation is not a standard measurement in the clinical setting, and we argue that it may be an important parameter to include in future clinical studies.

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Antibiotic use during pregnancy is associated with increased asthma risk in children. Since approximately 25% of women use antibiotics during pregnancy, it is important to identify the pathways involved in this phenomenon. We investigate how mother‐to‐offspring transfer of antibiotic‐induced gut microbial dysbiosis influences immune system development along the gut–lung axis. Using a mouse model of maternal antibiotic exposure during pregnancy, we immunophenotyped offspring in early life and after asthma induction. In early life, prenatal‐antibiotic exposed offspring exhibited gut microbial dysbiosis, intestinal inflammation (increased fecal lipocalin‐2 and IgA), and dysregulated intestinal ILC3 subtypes. Intestinal barrier dysfunction in the offspring was indicated by a FITC‐dextran intestinal permeability assay and circulating lipopolysaccharide. This was accompanied by increased T‐helper (Th)17 cell percentages in the offspring's blood and lungs in both early life and after allergy induction. Lung tissue additionally showed increased percentages of RORγt T‐regulatory (Treg) cells at both time points. Our investigation of the gut–lung axis identifies early‐life gut dysbiosis, intestinal inflammation, and barrier dysfunction as a possible developmental programming event promoting increased expression of RORγt in blood and lung CD4+ T cells that may contribute to increased asthma risk.

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