Fungal Dysbiosis and Intestinal Inflammation in Children With Beta-Cell Autoimmunity.

Although gut bacterial dysbiosis is recognized as a regulator of beta-cell autoimmunity, no data is available on fungal dysbiosis in the children at the risk of type 1 diabetes (T1D). We hypothesized that the co-occurrence of fungal and bacterial dysbiosis contributes to the intestinal inflammation and autoimmune destruction of insulin-producing beta-cells in T1D. Fecal and blood samples were collected from 26 children tested positive for at least one diabetes-associated autoantibody (IAA, GADA, IA-2A or ICA) and matched autoantibody-negative children with HLA-conferred susceptibility to T1D (matched for HLA-DQB1 haplotype, age, gender and early childhood nutrition). Bacterial 16S and fungal ITS2 sequencing, and analyses of the markers of intestinal inflammation, namely fecal human beta-defensin-2 (HBD2), calprotectin and secretory total IgA, were performed. Anti-Saccharomyces cerevisiae antibodies (ASCA) and circulating cytokines, IFNG, IL-17 and IL-22, were studied. After these analyses, the children were followed for development of clinical T1D (median 8 years and 8 months). Nine autoantibody positive children were diagnosed with T1D, whereas none of the autoantibody negative children developed T1D during the follow-up. Fungal dysbiosis, characterized by high abundance of fecal Saccharomyces and Candida, was found in the progressors, i.e., children with beta-cell autoimmunity who during the follow-up progressed to clinical T1D. These children showed also bacterial dysbiosis, i.e., increased Bacteroidales and Clostridiales ratio, which was, however, found also in the non-progressors, and is thus a common nominator in the children with beta-cell autoimmunity. Furthermore, the progressors showed markers of intestinal inflammation detected as increased levels of fecal HBD2 and ASCA IgG to fungal antigens. We conclude that the fungal and bacterial dysbiosis, and intestinal inflammation are associated with the development of T1D in children with beta-cell autoimmunity.

Immunoglobulin A and immunoglobulin G antibodies against ß-lactoglobulin and gliadin at age 1 associate with immunoglobulin E sensitization at age 6.

BACKGROUND: Serum immunoglobulin A (IgA) and immunoglobulin G (IgG) antibodies against wheat gliadin and cow's milk ß-lactoglobulin (BLG) are considered markers of gut permeability and inflammation which modulate the development of mucosal tolerance. Living on a farm has been shown to decrease allergies in children. Our aim was to study whether farm environment affected mucosal tolerance, immunoglobulin E (IgE) sensitization, or allergic diseases. METHODS: The PASTURE birth cohort study was conducted in Finland, France, Germany, Austria, and Switzerland. At age 1, we measured serum IgA and IgG against wheat gliadin (N = 636) and cow's milk BLG (N = 639) using ELISA. Serum-specific IgE was measured at ages 1 and 6 (N = 459). Data on environmental factors and allergic diseases were collected by questionnaires. Discrete time hazard and multivariate logistic regression models were used for analyses. RESULTS: Increased IgA or IgG antibodies against BLG at age 1 increased the risk of sensitization to at least one of the measured allergens or food allergens at age 6. Increased IgG against gliadin at age 1 increased the risk of sensitization to any, at least one inhalant, or at least one food allergen at age 6. Early exposure to cow's milk formula associated with increased IgA or IgG against BLG. No association with farming or clinical allergy was found. CONCLUSIONS: Increased IgA or IgG against BLG or gliadin at age 1 was associated with IgE sensitization at age 6. We suggest that an enhanced antibody response to food antigens reflects mucosal tolerance aberrancies, e.g., altered microbiota and/or increased gut permeability, which is later seen as sensitization to allergens.

Inflammatory response and IgE sensitization at early age.

BACKGROUND: Microbial exposure may induce low-grade inflammation at an early age and decrease the risk of allergic diseases, as suggested by the hygiene hypothesis. We examined the associations between low-grade inflammation and the development of allergic sensitization, atopic dermatitis (AD), and asthma at the age of 4.5 yr. METHODS: We studied 636 children participating in the PASTURE study in Finland, Germany, Austria, France, and Switzerland. Data of environmental factors, doctor-diagnosed AD, and asthma were collected by questionnaire. The serum high-sensitivity C-reactive protein (CRP) values were measured at the age of 1 yr, and serum-specific IgE concentrations (sIgE) at the age of one and 4.5 yr. Analyses were made by logistic regression analysis. RESULTS: The risk of allergic sensitization at the age of 4.5 yr was decreased in children who had increased CRP levels at the age of 1 yr (level in the highest vs. lowest quartile: aOR 0.48, 95% CI 0.24-0.95; p = 0.014). The risk of AD and asthma was not significantly related to CRP. CONCLUSION: The findings confirm that elevated levels of CRP at early age showed association with decreased allergic sensitization later in life. Our results suggest that poor inflammatory response could predispose for IgE sensitization.

Fecal microbiota composition differs between children with ß-cell autoimmunity and those without.

The role of the intestinal microbiota as a regulator of autoimmune diabetes in animal models is well-established, but data on human type 1 diabetes are tentative and based on studies including only a few study subjects. To exclude secondary effects of diabetes and HLA risk genotype on gut microbiota, we compared the intestinal microbiota composition in children with at least two diabetes-associated autoantibodies (n = 18) with autoantibody-negative children matched for age, sex, early feeding history, and HLA risk genotype using pyrosequencing. Principal component analysis indicated that a low abundance of lactate-producing and butyrate-producing species was associated with ß-cell autoimmunity. In addition, a dearth of the two most dominant Bifidobacterium species, Bifidobacterium adolescentis and Bifidobacterium pseudocatenulatum, and an increased abundance of the Bacteroides genus were observed in the children with ß-cell autoimmunity. We did not find increased fecal calprotectin or IgA as marker of inflammation in children with ß-cell autoimmunity. Functional studies related to the observed alterations in the gut microbiome are warranted because the low abundance of bifidobacteria and butyrate-producing species could adversely affect the intestinal epithelial barrier function and inflammation, whereas the apparent importance of the Bacteroides genus in development of type 1 diabetes is insufficiently understood.