Background Filaggrin is an epidermal protein that has a role in skin barrier function. Filaggrin loss-of-function FLG-LOF) mutations are a significant risk factor for eczema and atopy, but their association with food allergy (FA) is less clear. Objective We explored the longitudinal relationship between three common FLG-LOF mutations and FA using the Isle of Wight birth cohort. Methods FA diagnosis was based on recognised allergic reactions within 4 hours following exposure to known food allergens. Food allergen sensitization (FAS) was identified by skin prick test conducted between 1–18 years to a range of food allergens. Three filaggrin mutations were genotyped in 1150/1456 children (79%). The temporal relationships between FA, FAS and eczema in children with filaggrin mutations were explored using path analysis with total, direct and indirect effect models. Results There was a significant total effect of FLG-LOF mutations on the risk of FA in later childhood at ages 10 (OR: 31.46, 95%CI 2.86, >100) and 18 years (OR: 4.25, 95%CI 1.55, 11.61). Path analysis showed that there was no direct effect of FLG-LOF mutations on FA at any age, however an indirect effect was found on FA at all ages via eczema and FAS in the earlier years Conclusion FLG-LOF mutations are associated with FA in older children via eczema and FAS in their early childhood. Our results highlight a biologically plausible pathway, which suggests that skin barrier function is important in the development and persistence of FA.

BackgroundThe occurrence of asthma is weakly explained by known genetic variants. Epigenetic marks, DNA methylation (DNA-M) in particular, are considered to add to the explanation of asthma. However, no etiological model has yet been developed that integrates genetic variants and DNA-M. To explore a new model, we focused on one asthma candidate gene, the IL-4 receptor (IL4R). We hypothesized that genetic variants of IL4R in interaction with DNA-M at cytosine-phosphate-guanine (CpG) sites jointly alter the risk of asthma during adolescence. Blood samples were collected at age 18 years from 245 female cohort participants randomly selected for methylation analysis from a birth cohort (n = 1,456, Isle of Wight, UK). Genome-wide DNA-M was assessed using the Illumina Infinium HumanMethylation450 BeadChip.ResultsThirteen single nucleotide polymorphisms (SNPs) and twelve CpG sites of IL4R gene were analyzed. Based on linkage disequilibrium and association with asthma, eight SNPs and one CpG site were selected for further analyses. Of the twelve CpG sites in the IL4R gene, only methylation levels of cg09791102 showed an association with asthma at age 18 years (Wilcoxon test: P = 0.01). Log-linear models were used to estimate risk ratios (RRs) for asthma adjusting for uncorrelated SNPs within the IL4R gene and covariates. Testing for interaction between the eight SNPs and the methylation levels of cg09791102 on the risk for asthma at age 18 years, we identified the statistically significant interaction term of SNP rs3024685 × methylation levels of cg09791102 (P = 0.002; after adjusting for false discovery rate). A total of 84 participants had methylation levels ≤0.88, 112 participants between 0.89 and 0.90, and 35 between 0.91 and 0.92. For the SNP rs3024685 (‘CC’ vs. ‘TT’) at methylation levels of ≤0.85, 0.86, 0.90, 0.91, and 0.92, the RRs were 0.01, 0.04, 4.65, 14.76, 14.90, respectively (interaction effect, P = 0.0003).ConclusionsAdjusting for multiple testing, our results suggest that DNA-M modulates the risk of asthma related to genetic variants in the IL4R gene. The strong interaction of one SNP and DNA-M is encouraging and provides a novel model of how a joint effect of genetic variants and DNA-M can explain occurrence of asthma.

BackgroundThe prevalence of allergic diseases are increasing worldwide, emphasizing the need to elucidate their pathogeneses. The aims of this study were to use a two-stage design to identify DNA methylation levels at cytosine–phosphate–guanine (CpG) sites across the genome associated with atopy and high serum immunoglobulin E (IgE), then to replicate our findings in an independent cohort.MethodsAtopy was assessed via skin prick tests and high serum IgE. Methylation levels were measured from whole blood using the Illumina Infinium HumanMethylation450 BeadChip from 18-year-old women (n = 245) and men (n = 122) in the Isle of Wight birth cohort. After data cleaning and processing, and removing probes with possible single nucleotide polymorphisms, DNA methylation levels from 254,460 CpG sites from the 245 women were subjected to recursive Random Forest feature selection for stage 1. The sites selected from stage 1 were tested in stage 2 for associations with atopy and high IgE levels (>200 kU/L) via logistic regression adjusted for predicted cell-type proportions and sex. Sites significantly associated with atopy in stage 2 underwent replication tests in the independent Swedish birth cohort BAMSE (n = 464).ResultsIn stage 1, 62 sites were selected, of which 22 were associated with atopy in stage 2 (P-value range 6.5E−9 to 1.4E−5) and 12 associated with high IgE levels (P-value range 1.1E−5 to 7.1E−4) at the Bonferroni adjusted alpha (0.05/62 = 0.0008). Of the 19 available sites, 13 were replicated.ConclusionsWe identified 13 novel epigenetic loci associated with atopy and high IgE that could serve as candidate loci for future studies; four were within genes with known roles in the immune response (cg04983687 in the body of ZFPM1, cg18219873 in the 5′UTR of PRG2, cg27469152 in the 3′UTR of EPX, and cg09332506 in the body of COPA).Electronic supplementary materialThe online version of this article (doi:10.1186/s13073-015-0213-8) contains supplementary material, which is available to authorized users.

BackgroundThe role of breast milk on the risk of childhood asthma is in dispute. The aim of this prospective study is to determine the relationship of immune markers in maternal serum during gestation and breast milk to asthma-like symptoms (AS) in infancy.MethodsPregnant women were recruited in Columbia and Charleston, South Carolina. Blood (median: three weeks before delivery) and breast milk (three weeks after delivery) samples were collected. Concentrations of interferon (IFN)-γ, IFN gamma-induced protein 10 (IP-10 or CXCL10), CCL11, interleukin (IL) 1β, IL-4, IL-5, IL-6, CXCL8, IL-10, IL-12(p70), IL-13, transforming growth factor (TGF)-β1, and immunoglobulin (Ig) A in both maternal serum and milk whey were determined via immunoassays. Asthma-like symptoms (AS) of the infant were ascertained at 6 and 12 months, respectively. Generalized estimating equations assessed relative risks (RRs) of immune markers for repeated measurements of AS, considering intra-individual correlations and adjusting for confounders. To provide comparable risk estimates, quartiles of the immune markers were used, except for IL-5 in whey and IgA in serum, which were dichotomized.ResultsOf 178 women, 161 provided blood and 115 breast milk samples. IL-12(p70), IL-4, IL-10, IL-1β, and CCL11 in serum and in whey were not further considered for the statistical analyses since the proportion of non-detectable values was high. Most immune markers in serum and milk whey were moderately or highly correlated; however, IgA was negatively correlated. Infants in the highest quartile of IL-13 in both serum and whey were at a higher risk of AS (RR = 3.02 and 4.18; respectively) compared to infants in the first quartile. High levels of IL-5 in serum and whey was also identified as a risk. In addition, increased secretory IgA and TGF-β1 in breast milk reduced the risks of AS.ConclusionsMaternal serum and whey levels of IL-5 and IL-13 are risk markers for AS; whey IgA and TGF-β1 seem to be protective. Only focusing on breast milk portend that milk cytokines IL-5 and IL-13 have adverse effects. However, similar immune exposures during late gestation and via milk suggest that both may enhance AS among infants.

Background Breastfeeding is protective against many long-term diseases, yet the mechanisms involved are unknown. Leptin gene ( LEP ) is reported to be associated with body mass index (BMI). On the other hand, breastfeeding duration has been found to be associated with DNA methylation (DNAm) of the LEP gene. Therefore, epigenetic regulation of LEP may represent the mechanism underlying the protective effect of breastfeeding duration against obesity. Methods In the Isle of Wight Birth Cohort, peripheral blood DNAm at 23 cytosine-phosphate-guanine sites (CpGs) in the LEP locus in 10-year-old ( n = 297) samples and 16 CpGs in 18-year-old ( n = 305) samples, were generated using the Illumina Infinium MethylationEPIC and HumanMethylation450 Beadchips respectively and tested for association with breastfeeding duration (total and exclusive) using linear regression. To explore the association between breastfeeding durations and genome-wide DNAm, epigenome-wide association studies (EWASs) and differential methylation region (DMR) analyses were performed. BMI trajectories spanning the first 18 years of life were used as the outcome to test the association with breastfeeding duration (exposure) using multi-nominal logistic regression. Mediation analysis was performed for significant CpG sites. Results Both total and exclusive breastfeeding duration were associated with DNAm at four LEP CpG sites at 10 years ( P value < 0.05), and not at 18 years. Though no association was observed between breastfeeding duration and genome-wide DNAm, DMR analyses identified five significant differentially methylated regions (Sidak adjusted P value < 0.05). Breastfeeding duration was also associated with the early transient overweight trajectory. Furthermore, DNAm of LEP was associated with this trajectory at one CpG site and early persistent obesity at another, though mediation analysis was not significant. Conclusions Breastfeeding duration is associated with LEP methylation at age 10 years and BMI trajectory. LEP DNAm is also significantly associated with BMI trajectories throughout childhood, though sample sizes were small. However, mediation analysis did not demonstrate that DNAm of LEP explained the protective effect of breastfeeding against childhood obesity. Electronic supplementary material The online version of this article (10.1186/s13148-019-0727-9) contains supplementary material, which is available to authorized users.