Meta-analysis identifies seven susceptibility loci involved in the atopic march

Atopic dermatitis

Atopic dermatitis is a common inflammatory skin disorder characterised by recurrent eczematous lesions and intense itch. The disorder affects people of all ages and ethnicities, has a substantial psychosocial impact on patients and relatives, and is the leading cause of the global burden from skin disease. Atopic dermatitis is associated with increased risk of multiple comorbidities, including food allergy, asthma, allergic rhinitis, and mental health disorders. The pathophysiology is complex and involves a strong genetic predisposition, epidermal dysfunction, and T-cell driven inflammation. Although type-2 mechanisms are dominant, there is increasing evidence that the disorder involves multiple immune pathways. Currently, there is no cure, but increasing numbers of innovative and targeted therapies hold promise for achieving disease control, including in patients with recalcitrant disease. We summarise and discuss advances in our understanding of the disease and their implications for prevention, management, and future research.

Epithelial cell dysfunction, a major driver of asthma development

Airway epithelial barrier dysfunction is frequently observed in asthma and may have important implications. The physical barrier function of the airway epithelium is tightly interwoven with its immunomodulatory actions, while abnormal epithelial repair responses may contribute to remodelling of the airway wall. We propose that abnormalities in the airway epithelial barrier play a crucial role in the sensitization to allergens and pathogenesis of asthma. Many of the identified susceptibility genes for asthma are expressed in the airway epithelium, supporting the notion that events at the airway epithelial surface are critical for the development of the disease. However, the exact mechanisms by which the expression of epithelial susceptibility genes translates into a functionally altered response to environmental risk factors of asthma are still unknown. Interactions between genetic factors and epigenetic regulatory mechanisms may be crucial for asthma susceptibility. Understanding these mechanisms may lead to identification of novel targets for asthma intervention by targeting the airway epithelium. Moreover, exciting new insights have come from recent studies using single‐cell RNA sequencing (scRNA‐Seq) to study the airway epithelium in asthma. This review focuses on the role of airway epithelial barrier function in the susceptibility to develop asthma and novel insights in the modulation of epithelial cell dysfunction in asthma.

Age-of-onset information helps identify 76 genetic variants associated with allergic disease

Risk factors that contribute to inter-individual differences in the age-of-onset of allergic diseases are poorly understood. The aim of this study was to identify genetic risk variants associated with the age at which symptoms of allergic disease first develop, considering information from asthma, hay fever and eczema. Self-reported age-of-onset information was available for 117,130 genotyped individuals of European ancestry from the UK Biobank study. For each individual, we identified the earliest age at which asthma, hay fever and/or eczema was first diagnosed and performed a genome-wide association study (GWAS) of this combined age-of-onset phenotype. We identified 50 variants with a significant independent association (P<3x10^-8) with age-of-onset. Forty-five variants had comparable effects on the onset of the three individual diseases and 38 were also associated with allergic disease case-control status in an independent study (n = 222,484). We observed a strong negative genetic correlation between age-of-onset and case-control status of allergic disease (r_g = -0.63, P = 4.5x10^-61), indicating that cases with early disease onset have a greater burden of allergy risk alleles than those with late disease onset. Subsequently, a multivariate GWAS of age-of-onset and case-control status identified a further 26 associations that were missed by the univariate analyses of age-of-onset or case-control status only. Collectively, of the 76 variants identified, 18 represent novel associations for allergic disease. We identified 81 likely target genes of the 76 associated variants based on information from expression quantitative trait loci (eQTL) and non-synonymous variants, of which we highlight ADAM15, FOSL2, TRIM8, BMPR2, CD200R1, PRKCQ, NOD2, SMAD4, ABCA7 and UBE2L3. Our results support the notion that early and late onset allergic disease have partly distinct genetic architectures, potentially explaining known differences in pathophysiology between individuals.

So far, genetic studies of allergic disease have investigated the presence of the disease rather than the age at which the first allergic symptoms develop. We aimed to identify genetic risk variants associated with the age at which symptoms of allergic disease first develop, considering information from asthma, hay fever and eczema by examining 117,130 genotyped individuals of European ancestry from the UK Biobank study. We identified 50 variants with a significant independent association (P<3x10^-8) with age-of-onset. Forty-five variants had comparable effects on the onset of the three individual diseases and 38 were also associated with allergic disease case-control status in an independent study (n = 222,484). We then performed a multivariate GWAS of age-of-onset and case-control status identified a further 26 associations that were missed by the univariate analyses of age-of-onset or case-control status only. 18 of 76 variants identified represent novel associations for allergic disease. We identified 81 likely target genes of the 76 genetic variants, including ADAM15, FOSL2, TRIM8, BMPR2, CD200R1, PRKCQ, NOD2, SMAD4, ABCA7 and UBE2L3. Our results support the notion that early and late onset allergic disease have partly distinct genetic architectures, potentially explaining known differences in pathophysiology between individuals.

Genome-wide association analysis of 350 000 Caucasians from the UK Biobank identifies novel loci for asthma, hay fever and eczema

Even though heritability estimates suggest that the risk of asthma, hay fever and eczema is largely due to genetic factors, previous studies have not explained a large part of the genetics behind these diseases. In this genome-wide association study, we include 346 545 Caucasians from the UK Biobank to identify novel loci for asthma, hay fever and eczema and replicate novel loci in three independent cohorts. We further investigate if associated lead single nucleotide polymorphisms (SNPs) have a significantly larger effect for one disease compared to the other diseases, to highlight possible disease-specific effects. We identified 141 loci, of which 41 are novel, to be associated (P ≤ 3 × 10⁻⁸) with asthma, hay fever or eczema, analyzed separately or as disease phenotypes that includes the presence of different combinations of these diseases. The largest number of loci was associated with the combined phenotype (asthma/hay fever/eczema). However, as many as 20 loci had a significantly larger effect on hay fever/eczema only compared to their effects on asthma, while 26 loci exhibited larger effects on asthma compared with their effects on hay fever/eczema. At four of the novel loci, TNFRSF8, MYRF, TSPAN8, and BHMG1, the lead SNPs were in Linkage Disequilibrium (LD) (>0.8) with potentially casual missense variants. Our study shows that a large amount of the genetic contribution is shared between the diseases. Nonetheless, a number of SNPs have a significantly larger effect on one of the phenotypes, suggesting that part of the genetic contribution is more phenotype specific.

Resolving Clinical Phenotypes into Endotypes in Allergy: Molecular and Omics Approaches

Allergic diseases are highly complex with respect to pathogenesis, inflammation, and response to treatment. Current efforts for allergic disease diagnosis have focused on clinical evidence as a binary outcome. Although outcome status based on clinical phenotypes (observable characteristics) is convenient and inexpensive to measure in large studies, it does not adequately provide insight into the complex molecular determinants of allergic disease. Individuals with similar clinical diagnoses do not necessarily have similar disease etiologies, natural histories, or responses to treatment. This heterogeneity contributes to the ineffective response to treatment leading to an annual estimated cost of $350 billion in the USA alone. There has been a recent focus to deconvolute the clinical heterogeneity of allergic diseases into specific endotypes using molecular and omics approaches. Endotypes are a means to classify patients based on the underlying pathophysiological mechanisms involving distinct functions or treatment response. The advent of high-throughput molecular omics, immunophenotyping, and bioinformatics methods including machine learning algorithms is facilitating the development of endotype-based diagnosis. As we move to the next decade, we should truly start treating clinical endotypes not clinical phenotype. This review highlights current efforts taking place to improve allergic disease endotyping via molecular omics profiling, immunophenotyping, and machine learning approaches in the context of precision diagnostics in allergic diseases. Graphical Abstract.

Association of DOCK8, IL17RA, and KLK12 Polymorphisms with Atopic Dermatitis in Koreans

Background

Early-onset and severe atopic dermatitis (AD) in patients increase the probability of the development of allergic rhinitis or asthma. Treatment and prevention strategies in infants and young children with AD are targeted toward treating the symptoms, restoring skin barrier functions, and reducing the absorption of environmental allergens in an attempt to attenuate or block the onset of asthma and food allergy.

Objective

Given that the initiating events in AD remain poorly understood, identifying those at risk and implementing strategies to prevent AD is necessary.

Methods

Whole-exome sequencing (WES) was performed in a 43 control group and a disease group with 20 AD patients without atopic march (AM) and 20 with AM. Sanger sequencing was carried out to validate found variants in cohorts.

Results

DOCK8, IL17RA, and KLK12 single-nucleotide polymorphisms were identified by WES as missense mutations: c.1289C>A, p.P97T (rs529208); c.1685C>A, p.P562G (rs12484684); and c.457+27>C, rs3745540, respectively. A case-control study show that total immunoglobulin E (IgE) level was significantly increased in the AA genotype of DOCK8 compared to the CA genotype in allergic patients. The rs12484684 of IL17RA increased risk of adult-onset AD (odds ratio: 1.63) compared to the control for (A) allele frequency. AD and AM Patients with the IL17RA CA genotype also had elevated IgE levels. rs3745540 of KLK12 was associated with AD in dominant model (odds ratio: 2.86).

Conclusion

DOCK8 (rs529208), IL17RA (rs12484684), and KLK12 (rs3745540), were identified using a new WES filtering method. the result suggests that polymorphism of DOCK8 and IL17RA might be related to increase the total IgE level.

Genome-wide association study identifies 143 loci associated with 25 hydroxyvitamin D concentration

Vitamin D deficiency is a candidate risk factor for a range of adverse health outcomes. In a genome-wide association study of 25 hydroxyvitamin D (25OHD) concentration in 417,580 Europeans we identify 143 independent loci in 112 1-Mb regions, providing insights into the physiology of vitamin D and implicating genes involved in lipid and lipoprotein metabolism, dermal tissue properties, and the sulphonation and glucuronidation of 25OHD. Mendelian randomization models find no robust evidence that 25OHD concentration has causal effects on candidate phenotypes (e.g. BMI, psychiatric disorders), but many phenotypes have (direct or indirect) causal effects on 25OHD concentration, clarifying the epidemiological relationship between 25OHD status and the health outcomes examined in this study.

Aryl Hydrocarbon Receptor Activation Downregulates IL-33 Expression in Keratinocytes via Ovo-Like 1

Background: IL-33, one of the IL-1 superfamily cytokines, has been shown to be associated with pruritus and inflammation in atopic dermatitis (AD). Furthermore, IL-33 production derived from keratinocytes reportedly has a crucial role in the development of AD; however, the mechanism of IL-33 expression has not been fully understood. Methods: We analyzed IL-33 expression in normal human epidermal keratinocytes (NHEKs) treated with IL-4. Results: IL-4 induced the upregulation of IL-33 expression in NHEKs. Based on the findings 1) that ovo-like 1 (OVOL1), a susceptible gene of AD, upregulates filaggrin (FLG) and loricrin (LOR) expression in NHEKs and 2) that reduced expression of FLG and LOR leads to production of IL-1 superfamily cytokines, we examined the involvement of OVOL1 in IL-33 expression in NHEKs. Knockdown of OVOL1 induced upregulation of IL-33 expression. Moreover, because Glyteer, an activator of aryl hydrocarbon receptor (AHR), reportedly upregulates OVOL1 expression, we examined whether treatment with Glyteer inhibited IL-33 expression in NHEKs. Treatment with Glyteer inhibited IL-4-induced upregulation of IL-33 expression, which was canceled by knockdown of either AHR or OVOL1. Conclusions: Activation of the AHR-OVOL1 axis inhibits IL-4-induced IL-33 expression, which could be beneficial for the treatment of AD.

Prevalence of asthma in patients with atopic dermatitis: A systematic review and meta-analysis

BACKGROUND

It is well established that asthma is common in patients with atopic dermatitis (AD).

OBJECTIVES

We performed a systematic review and meta-analysis to determine the prevalence of asthma and respiratory symptoms in individuals with AD as well as the association between AD and asthma.

METHODS

At least 2 authors independently searched the medical databases PubMed, EMBASE, LILACS, and SCOPUS for all English-language studies with data on asthma prevalence among patients with AD or the association between AD and asthma. Pooled odds ratios with 95% confidence intervals (CIs) and pooled proportions were estimated with random-effects models. The Newcastle-Ottawa scale was used to assess study quality.

RESULTS

The search yielded 39,503 articles. Of these, 213 studies were included in a quantitative analysis. The overall pooled prevalence of asthma was 25.7% (95% CI, 23.7-27.7) in patients with AD and 8.1% (95% CI, 7.0-9.4) among reference individuals. There was a significant association between AD and asthma when compared with reference individuals (odds ratio, 3.03; 95% CI, 2.64-3.47).

LIMITATIONS

The definitions of AD and asthma differed across the included studies and varied from self-report to physician diagnosed.

CONCLUSIONS

Asthma is a common comorbidity of AD. Physicians should be cognizant of this relationship and address asthma symptoms in their patients.

How does parental history of atopic disease predict the risk of atopic dermatitis in a child? A systematic review and meta-analysis

BACKGROUND

Parental history of atopic disease is a well-established risk factor for the development of atopic dermatitis (AD), but several aspects of this association remain unclear.

OBJECTIVE

We sought to determine the association of parental history of atopic disease with AD in offspring.

METHODS

We searched PubMed and EMBASE through June 2018 for relevant records and adhered to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Pooled odds ratios (ORs) with 95% CI were calculated using random-effects models.

RESULTS

A total of 163 records covering 149 unique studies were included. Of these, 119 studies were included in the meta-analysis. Individuals with parental history of atopic disease had increased odds of AD (OR, 1.81; 95% CI, 1.65-1.99). Parental asthma (OR, 1.56; 95% CI, 1.18-2.05) and allergic rhinitis (OR, 1.68; 95% CI, 1.34-2.11) had a smaller effect than AD (OR, 3.30; 95% CI, 2.46-4.42). The effect of maternal and paternal history was comparable for all atopic diseases. An increase in odds was observed when comparing the effect of having 1 (OR, 1.30; 95% CI, 1.15-1.47) or 2 atopic parents (OR, 2.08; 95% CI, 1.83-2.36), as well as having a parent with 1 (OR, 1.49; 95% CI, 1.28-1.74) or more atopic diseases (OR, 2.32; 95% CI, 1.92-2.81).

CONCLUSIONS

This study provides evidence-based risk estimates that may guide physicians who counsel parents with a history of atopic disease about their children's risk of AD. This information is of particular importance for future efforts toward establishing prophylactic interventions for AD on a general population level.

Differential associations of allergic disease genetic variants with developmental profiles of eczema, wheeze and rhinitis

BACKGROUND

Allergic diseases (eczema, wheeze and rhinitis) in children often present as heterogeneous phenotypes. Understanding genetic associations of specific patterns of symptoms might facilitate understanding of the underlying biological mechanisms.

OBJECTIVE

To examine associations between allergic disease-related variants identified in a recent genome-wide association study and latent classes of allergic diseases (LCADs) in two population-based birth cohorts.

METHODS

Eight previously defined LCADs between birth and 11 years: "No disease," "Atopic march," "Persistent eczema and wheeze," "Persistent eczema with later-onset rhinitis," "Persistent wheeze with later-onset rhinitis," "Transient wheeze," "Eczema only" and "Rhinitis only" were used as the study outcome. Weighted multinomial logistic regression was used to estimate associations between 135 SNPs (and a polygenic risk score, PRS) and LCADs among 6345 individuals from The Avon Longitudinal Study of Parents and Children (ALSPAC). Heterogeneity across LCADs was assessed before and after Bonferroni correction. Results were replicated in Manchester Asthma and Allergy Study (MAAS) (n = 896) and pooled in a meta-analysis.

RESULTS

We found strong evidence for differential genetic associations across the LCADs; pooled PRS heterogeneity P-value = 3.3 × 10-14 , excluding "no disease" class. The associations between the PRS and LCADs in MAAS were remarkably similar to ALSPAC. Two SNPs (a protein-truncating variant in FLG and a SNP within an intron of GSDMB) had evidence for differential association (pooled P-values ≤ 0.006). The FLG locus was differentially associated across LCADs that included eczema, with stronger associations for LCADs with comorbid wheeze and rhinitis. The GSDMB locus in contrast was equally associated across LCADs that included wheeze.

CONCLUSIONS AND CLINICAL RELEVANCE

We have shown complex, but distinct patterns of genetic associations with LCADs, suggesting that heterogeneous mechanisms underlie individual disease trajectories. Establishing the combination of allergic diseases with which each genetic variant is associated may inform therapeutic development and/or predictive modelling.

Analysis of associations of polymorphisms in the genes coding for L4, IL10, IL13 with the development of atopic bronchial asthma and its remission

Bronchial asthma is a multifactorial disease underpinned by chronic inflammation. The atopic phenotype of BA implies the presence of similar molecular mechanisms of pathogenesis between the patients. The aim of this study was to analyze the associations between the development of atopic BA/its remission and the following polymorphisms of interleukin genes: IL4 (rs2243250; C-589T), IL10 (rs1800896; G-1082A; rs1800872; C-592A), and IL13 (rs20541; Arg130Gln). Using allele-specific polymerase chain reaction (PCR), we studied the listed SNPs in the mixed urban sample of patients with BA (n = 53) and the controls (n = 30) residing in South Ural. The analysis revealed that genotype АА of IL10 (rs1800872) occurred more frequently in the control group (23.3%) than in the patients with atopic BA (5.7%) (OR = 0.197; 95% CI [0.047–0.832]; р = 0.031). No differences in genotype frequencies were observed between the patients with atopic BA and the controls for other studied polymorphisms. Our study failed to demonstrate the association of the listed polymorphisms and BA remission.

Genetic determinants of paediatric food allergy: A systematic review

BACKGROUND

The genetic determinants of food allergy have not been systematically reviewed. We therefore systematically reviewed the literature on the genetic basis of food allergy, identifying areas for further investigation.

METHODS

We searched three electronic databases (MEDLINE, EMBASE and PubMed) on 9 January 2018. Two authors screened retrieved articles for review according to inclusion criteria and extracted relevant information on study characteristics and measures of association. Eligible studies included those that reported an unaffected nonatopic control group, had genetic information and were carried out in children.

RESULTS

Of the 2088 studies retrieved, 32 met our inclusion criteria. Five were genome-wide association studies, and the remaining were candidate gene studies. Twenty-two of the studies were carried out in a predominantly Caucasian population with the remaining 10 from Asian-specific populations or unspecified ethnicity. We found FLG, HLA, IL10, IL13, as well as some evidence for other variants (SPINK5, SERPINB and C11orf30) that are associated with food allergy.

CONCLUSIONS

Little genetic research has been carried out in food allergy, with FLG, HLA and IL13 being the most reproducible genes for an association with food allergy. Despite promising results, existing genetic studies on food allergy are inundated with issues such as inadequate sample size and absence of multiple testing correction. Few included replication analyses or population stratification measures. Studies addressing these limitations along with functional studies are therefore needed to unravel the mechanisms of action of the identified genes.

Xenobiotic Receptors and Their Mates in Atopic Dermatitis

Atopic dermatitis (AD) is the most common inflammatory skin disease worldwide. It is a chronic, relapsing and pruritic skin disorder which results from epidermal barrier abnormalities and immune dysregulation, both modulated by environmental factors. AD is strongly associated with asthma and allergic rhinitis in the so-called 'atopic march.' Xenobiotic receptors and their mates are ligand-activated transcription factors expressed in the skin where they control cellular detoxification pathways. Moreover, they regulate the expression of genes in pathways involved in AD in epithelial cells and immune cells. Activation or overexpression of xenobiotic receptors in the skin can be deleterious or beneficial, depending on context, ligand and activation duration. Moreover, their impact on skin might be amplified by crosstalk among xenobiotic receptors and their mates. Because they are activated by a broad range of endogenous molecules, drugs and pollutants owing to their promiscuous ligand affinity, they have recently crystalized the attention of researchers, including in dermatology and especially in the AD field. This review examines the putative roles of these receptors in AD by critically evaluating the conditions under which the proteins and their ligands have been studied. This information should provide new insights into AD pathogenesis and ways to develop new therapeutic interventions.

The Genetics and Genomics of Asthma

Asthma is a common, clinically heterogeneous disease with strong evidence of heritability. Progress in defining the genetic underpinnings of asthma, however, has been slow and hampered by issues of inconsistency. Recent advances in the tools available for analysis-assaying transcription, sequence variation, and epigenetic marks on a genome-wide scale-have substantially altered this landscape. Applications of such approaches are consistent with heterogeneity at the level of causation and specify patterns of commonality with a wide range of alternative disease traits. Looking beyond the individual as the unit of study, advances in technology have also fostered comprehensive analysis of the human microbiome and its varied roles in health and disease. In this article, we consider the implications of these technological advances for our current understanding of the genetics and genomics of asthma.

3D-Organotypic Cultures to Unravel Molecular and Cellular Abnormalities in Atopic Dermatitis and Ichthyosis Vulgaris

Atopic dermatitis (AD) is characterized by dry and itchy skin evolving into disseminated skin lesions. AD is believed to result from a primary acquired or a genetically-induced epidermal barrier defect leading to immune hyper-responsiveness. Filaggrin (FLG) is a protein found in the cornified envelope of fully differentiated keratinocytes, referred to as corneocytes. Although FLG null mutations are strongly associated with AD, they are not sufficient to induce the disease. Moreover, most patients with ichthyosis vulgaris (IV), a monogenetic skin disease characterized by FLG homozygous, heterozygous, or compound heterozygous null mutations, display non-inflamed dry and scaly skin. Thus, all causes of epidermal barrier impairment in AD have not yet been identified, including those leading to the Th2-predominant inflammation observed in AD. Three dimensional organotypic cultures have emerged as valuable tools in skin research, replacing animal experimentation in many cases and precluding the need for repeated patient biopsies. Here, we review the results on IV and AD obtained with epidermal or skin equivalents and consider these findings in the context of human in vivo data. Further research utilizing complex models including immune cells and cutaneous innervation will enable finer dissection of the pathogenesis of AD and deepen our knowledge of epidermal biology.

Learning Causal Biological Networks With the Principle of Mendelian Randomization

Although large amounts of genomic data are available, it remains a challenge to reliably infer causal (i. e., regulatory) relationships among molecular phenotypes (such as gene expression), especially when multiple phenotypes are involved. We extend the interpretation of the Principle of Mendelian randomization (PMR) and present MRPC, a novel machine learning algorithm that incorporates the PMR in the PC algorithm, a classical algorithm for learning causal graphs in computer science. MRPC learns a causal biological network efficiently and robustly from integrating individual-level genotype and molecular phenotype data, in which directed edges indicate causal directions. We demonstrate through simulation that MRPC outperforms several popular general-purpose network inference methods and PMR-based methods. We apply MRPC to distinguish direct and indirect targets among multiple genes associated with expression quantitative trait loci. Our method is implemented in the R package MRPC, available on CRAN (https://cran.r-project.org/web/packages/MRPC/index.html).

Shared and distinct genetic risk factors for childhood-onset and adult-onset asthma: genome-wide and transcriptome-wide studies

BACKGROUND

Childhood-onset and adult-onset asthma differ with respect to severity and comorbidities. Whether they also differ with respect to genetic risk factors has not been previously investigated in large samples. The goals of this study were to identify shared and distinct genetic risk loci for childhood-onset and adult-onset asthma, and to identify the genes that might mediate the effects of associated variation.

METHODS

We did genome-wide and transcriptome-wide studies, using data from the UK Biobank, in individuals with asthma, including adults with childhood-onset asthma (onset before 12 years of age), adults with adult-onset asthma (onset between 26 and 65 years of age), and adults without asthma (controls; aged older than 38 years). We did genome-wide association studies (GWAS) for childhood-onset asthma and adult-onset asthma each compared with shared controls, and for age of asthma onset in all asthma cases, with a genome-wide significance threshold of p<5 × 10^-8. Enrichment studies determined the tissues in which genes at GWAS loci were most highly expressed, and PrediXcan, a transcriptome-wide gene-based test, was used to identify candidate risk genes.

FINDINGS

Of 376 358 British white individuals from the UK Biobank, we included 37 846 with self-reports of doctor-diagnosed asthma: 9433 adults with childhood-onset asthma; 21 564 adults with adult-onset asthma; and an additional 6849 young adults with asthma with onset between 12 and 25 years of age. For the first and second GWAS analyses, 318 237 individuals older than 38 years without asthma were used as controls. We detected 61 independent asthma loci: 23 were childhood-onset specific, one was adult-onset specific, and 37 were shared. 19 loci were associated with age of asthma onset. The most significant asthma-associated locus was at 17q12 (odds ratio 1·406, 95% CI 1·365-1·448; p=1·45 × 10^-111) in the childhood-onset GWAS. Genes at the childhood onset-specific loci were most highly expressed in skin, blood, and small intestine; genes at the adult onset-specific loci were most highly expressed in lung, blood, small intestine, and spleen. PrediXcan identified 113 unique candidate genes at 22 of the 61 GWAS loci. Single-nucleotide polymorphism-based heritability estimates were more than three times larger for childhood-onset asthma (0·327) than for adult-onset disease (0·098). The onset of disease in childhood was associated with additional genes with relatively large effect sizes, with the largest odds ratio observed at the FLG locus at 1q21.3 (1·970, 95% CI 1·823-2·129).

INTERPRETATION

Genetic risk factors for adult-onset asthma are largely a subset of the genetic risk for childhood-onset asthma but with overall smaller effects, suggesting a greater role for non-genetic risk factors in adult-onset asthma. Combined with gene expression and tissue enrichment patterns, we suggest that the establishment of disease in children is driven more by dysregulated allergy and epithelial barrier function genes, whereas the cause of adult-onset asthma is more lung-centred and environmentally determined, but with immune-mediated mechanisms driving disease progression in both children and adults.

FUNDING

US National Institutes of Health.

Epigenome-wide association study reveals methylation pathways associated with childhood allergic sensitization

Epigenetic mechanisms integrate both genetic variability and environmental exposures. However, comprehensive epigenome-wide analysis has not been performed across major childhood allergic phenotypes. We examined the association of epigenome-wide DNA methylation in mid-childhood peripheral blood (Illumina HumanMethyl450K) with mid-childhood atopic sensitization, environmental/inhalant and food allergen sensitization in 739 children in two birth cohorts (Project Viva-Boston, and the Generation R Study-Rotterdam). We performed covariate-adjusted epigenome-wide association meta-analysis and employed pathway and regional analyses of results. Seven-hundred and five methylation sites (505 genes) were significantly cross-sectionally associated with mid-childhood atopic sensitization, 1411 (905 genes) for environmental and 45 (36 genes) for food allergen sensitization (FDR<0.05). We observed differential methylation across multiple genes for all three phenotypes, including genes implicated previously in innate immunity (DICER1), eosinophilic esophagitis and sinusitis (SIGLEC8), the atopic march (AP5B1) and asthma (EPX, IL4, IL5RA, PRG2, SIGLEC8, CLU). In addition, most of the associated methylation marks for all three phenotypes occur in putative transcription factor binding motifs. Pathway analysis identified multiple methylation sites associated with atopic sensitization and environmental allergen sensitization located in/near genes involved in asthma, mTOR signaling, and inositol phosphate metabolism. We identified multiple differentially methylated regions associated with atopic sensitization (8 regions) and environmental allergen sensitization (26 regions). A number of nominally significant methylation sites in the cord blood analysis were epigenome-wide significant in the mid-childhood analysis, and we observed significant methylation - time interactions among a subset of sites examined. Our findings provide insights into epigenetic regulatory pathways as markers of childhood allergic sensitization.

GWAS Follow-up Study Discovers a Novel Genetic Signal on 10q21.2 for Atopic Dermatitis in Chinese Han Population

Atopic dermatitis (AD) is a common inflammatory skin disease with high heritability. Two susceptibility loci have been confirmed in our previous AD genome-wide association study (GWAS). To look for additional genetic factors in Chinese Han ethnicity, we performed a large-scale GWAS follow-up study. Forty-nine top single nucleotide polymorphisms (SNPs) that had never been reported previously were genotyped using Sequenom Massarray system in an independent cohort, which consist of northern Chinese (1634 cases and 1263 controls) and southern Chinese (2985 cases and 9526 controls). Association analyses were performed using PLINK 2 software. Three SNPs in northern and ten SNPs in southern were found exhibiting association evidence with AD (P < 0.05). Finally, SNP rs224108 on 10q21.2 showed high significance for AD in joint analysis of GWAS and replication study (P_meta = 4.55 × 10⁻⁹, OR = 1.21), and was confirmed as an independent genetic marker by Linkage disequilibrium calculation and conditional logistic regression analysis. Bioinformatics analysis strongly suggested that rs224108 may have the potential to alter the target gene expression through non-coding epigenetic regulation effects. Meanwhile, SNP rs11150780 on 17q25.3 was also found suggestive association with AD (P_meta = 7.64 × 10⁻⁷, OR = 1.18). Our findings confirmed a novel susceptibility signal on 10q21.2 for AD in Chinese Han population and advanced the understanding of the genetic contribution to AD.

Identification of two early life eczema and non-eczema phenotypes with high risk for asthma development

BACKGROUND

The "atopic march" has been considered a linear progression starting with eczema and culminating with development of asthma. Not all asthma cases, however, are preceded by eczema, and not all children with eczema go on to develop asthma.

OBJECTIVE

The aim of this study was to explore the impact of allergic sensitization patterns on the association between early eczema and later childhood asthma. Given the numerous reported associations of the ciliary gene KIF3A with the atopic march, we also examined the impact of KIF3A risk allele rs12186803 on our analyses.

METHODS

We studied 505 participants in the Cincinnati Childhood Allergy and Air Pollution Study (CCAAPS), a prospective birth cohort, with longitudinal eczema and asthma outcomes as well as prospective data regarding timing of sensitization to foods and aeroallergens. KIF3A genotypes were available on all children.

RESULTS

Two high-risk groups were identified: one with and one without early eczema. The high-risk group with early eczema was more likely to be sensitized to food allergens, while the group without early eczema was more likely to be polysensitized to aeroallergens. The KIF3A rs12186803 risk allele interacted with food sensitization to increase asthma risk in children with eczema (P = 0.02). In children without eczema, asthma was associated with the interaction between rs12186803 and aeroallergen sensitization (P = 0.007).

CONCLUSIONS & CLINICAL RELEVANCE

KIF3A interacted differentially with sensitization pattern to increase the risk of asthma in two high-risk groups of children with and without early eczema. Given the reported role of KIF3A in epithelial cell functioning, the results add evidence to the hypothesis that an impaired epithelial barrier is a key aspect in the development of allergic disease.

Differential Associations of IL-4 With Hippocampal Subfields in Mild Cognitive Impairment and Alzheimer's Disease

Background/Aims: We aimed to assess the association between in volumetric measures of hippocampal sub-regions - in healthy older controls (HC), subjects with mild cognitive impairment (MCI) and AD- with circulating levels of IL-4. Methods: From AddNeuroMed Project 113 HC, 101 stable MCI (sMCI), 22 converter MCI (cMCI) and 119 AD were included. Hippocampal subfield volumes were analyzed using Freesurfer 6.0.0 on high-resolution sagittal 3D-T1W MP-RAGE acquisitions. Plasmatic IL-4 was measured using ELISA assay. Results: IL-4 was found to be (a) positively associate with left subiculum volume (β = 0.226, p = 0.037) in sMCI and (b) negatively associate with left subiculum volume (β = -0.253, p = 0.011) and left presubiculum volume (β = -0.257, p = 0.011) in AD. Conclusion: Our results indicate a potential neuroprotective effect of IL-4 on the areas of the hippocampus more vulnerable to aging and neurodegeneration.

Report from the National Institute of Allergy and Infectious Diseases workshop on "Atopic dermatitis and the atopic march: Mechanisms and interventions"

Atopic dermatitis (AD) affects up to 20% of children worldwide and is an increasing public health problem, particularly in developed countries. Although AD in infants and young children can resolve, there is a well-recognized increased risk of sequential progression from AD to other atopic diseases, including food allergy (FA), allergic rhinitis, allergic asthma, and allergic rhinoconjunctivitis, a process referred to as the atopic march. The mechanisms underlying the development of AD and subsequent progression to other atopic comorbidities, particularly FA, are incompletely understood and the subject of intense investigation. Other major research objectives are the development of effective strategies to prevent AD and FA, as well as therapeutic interventions to inhibit the atopic march. In 2017, the Division of Allergy, Immunology, and Transplantation of the National Institute of Allergy and Infectious Diseases sponsored a workshop to discuss current understanding and important advances in these research areas and to identify gaps in knowledge and future research directions. International and national experts in the field were joined by representatives from several National Institutes of Health institutes. Summaries of workshop presentations, key conclusions, and recommendations are presented herein.

Mechanisms by Which Atopic Dermatitis Predisposes to Food Allergy and the Atopic March

The Atopic march denotes the progression from atopic dermatitis (AD) to the development of other allergic disorders such as immunoglobulin (Ig) E-mediated food allergy, allergic rhinitis and asthma in later childhood. There is increasing evidence from prospective birth cohort studies that early-onset AD is a risk factor for other allergic diseases or is found in strong association with them. Animal studies now provide mechanistic insights into the pathways that may be responsible for triggering the progression from the skin barrier dysfunction seen in AD to epicutaneous sensitization, food allergy and allergic airway disorders. Recent large randomized controlled trials have demonstrated the efficacy of early interventions targeted at AD and food allergy prevention. These show great promise for research into future strategies aimed at prevention of the atopic march.

Transcriptomic Analysis Links Eosinophilic Esophagitis and Atopic Dermatitis

Background: Eosinophilic esophagitis (EoE) is commonly associated with concomitant atopic diseases including atopic dermatitis (AD) and allergic airway (AA) diseases including asthma. Despite this link and the shared pathologic features across these three disorders, detailed analyses of the unifying molecular pathways are lacking. Objectives: We sought to investigate the mRNA expression profile overlap between EoE, AA, and AD and to identify the involvement of interleukin 13 (IL-13) in modulating gene expression. Methods: Whole-genome mRNA expression analyses were performed on tissue specimens (biopsies or nasal brushes) from patients with EoE, AD, and AA, and IL-13-stimulated primary human epithelial cells from the esophagus, the skin, and the airways. Results: By human disease expression profiles, EoE evidenced a significantly higher overlap (p = 0.0006) with AD (181 transcripts; 10%) than with AA (124 transcripts, 7%). Only 18 genes were found to be commonly dysregulated among the three diseases; these included filaggrin, histamine receptor H1, claudin 1, cathepsin C, plasminogen activator urokinase receptor, and suppressor of cytokine signaling 3. Ontogenetic analysis revealed a common immune/inflammatory response among the three diseases and a different epithelial response (epidermal cell differentiation) between EoE and AA. The overlap between the IL-13-stimulated epithelial cell transcriptome and the respective disease transcriptome was 22, 9, and 5% in EoE, AD, and AA, respectively, indicating a greater involvement of the IL-13 pathway in EoE than AA (p = 0.0007) or AD (p = 0.02). Conclusion: EoE, AD, and AA share a common set of disease-specific transcripts, highlighting common molecular etiology. Their comparative analysis indicates relatively closer relationships between EoE and AD, particularly centered around IL-13-driven pathways. Therefore, these findings provide an increased rationale for shared therapeutic strategies.

Zinc in Keratinocytes and Langerhans Cells: Relevance to the Epidermal Homeostasis

In the skin, the epidermis is continuously exposed to various kinds of external substances and stimuli. Therefore, epidermal barriers are crucial for providing protection, safeguarding health, and regulating water balance by maintaining skin homeostasis. Disruption of the epidermal barrier allows external substances and stimuli to invade or stimulate the epidermal cells, leading to the elicitation of skin inflammation. The major components of the epidermal barrier are the stratum corneum (SC) and tight junctions (TJs). The presence of zinc in the epidermis promotes epidermal homeostasis; hence, this study reviewed the role of zinc in the formation and function of the SC and TJs. Langerhans cells (LCs) are one of the antigen-presenting cells found in the epidermis. They form TJs with adjacent keratinocytes (KCs), capture external antigens, and induce antigen-specific immune reactions. Thus, the function of zinc in LCs was examined in this review. We also summarized the general knowledge of zinc and zinc transporters in the epidermis with updated findings.

Inflammation-Accelerated Senescence and the Cardiovascular System: Mechanisms and Perspectives

Low-grade chronic inflammation is a common denominator in atherogenesis and related diseases. Solid evidence supports the occurrence of an impairment in the innate and adaptive immune system with senescence, favoring the development of acute and chronic age-related diseases. Cardiovascular (CV) diseases (CVD), in particular, are a leading cause of death even at older ages. Inflammation-associated mechanisms that contribute to CVD development include dysregulated redox and metabolic pathways, genetic modifications, and infections/dysbiosis. In this review, we will recapitulate the determinants and consequences of the immune system dysfunction at older age, with particular focus on the CV system. We will examine the currently available and potential future strategies to counteract accelerated CV aging, i.e., nutraceuticals, probiotics, caloric restriction, physical activity, smoking and alcohol cessation, control of low-grade inflammation sources, senolytic and senescence-modulating drugs, and DNA-targeting drugs.

The atopic march and atopic multimorbidity: Many trajectories, many pathways

The atopic march recognizes the increased occurrence of asthma, allergic rhinitis, or both after atopic dermatitis (AD) onset. Mechanisms for developing atopic comorbidities after AD onset are poorly understood but can involve the impaired cutaneous barrier, which facilitates cutaneous sensitization. The association can also be driven or amplified in susceptible subjects by a systemic T_H2-dominant immune response to cutaneous inflammation. However, these associations might merely involve shared genetic loci and environmental triggers, including microbiome dysregulation, with the temporal sequence reflecting tissue-specific peak time of occurrence of each disease, suggesting more of a clustering of disorders than a march. Prospective longitudinal cohort studies provide an opportunity to explore the relationships between postdermatitis development of atopic disorders and potential predictive phenotypic, genotypic, and environmental factors. Recent investigations implicate disease severity and persistence, age of onset, parental atopic history, filaggrin (FLG) mutations, polysensitization, and the nonrural environment among risk factors for development of multiple atopic comorbidities in young children with AD. Early intervention studies to repair the epidermal barrier or alter exposure to the microbiome or allergens might elucidate the relative roles of barrier defects, genetic locus alterations, and environmental exposures in the risk and sequence of occurrence of T_H2 activation disorders.

Childhood asthma is associated with COPD and known asthma variants in COPDGene: a genome-wide association study

BACKGROUND

Childhood asthma is strongly influenced by genetics and is a risk factor for reduced lung function and chronic obstructive pulmonary disease (COPD) in adults. This study investigates self-reported childhood asthma in adult smokers from the COPDGene Study. We hypothesize that childhood asthma is associated with decreased lung function, increased risk for COPD, and that a genome-wide association study (GWAS) will show association with established asthma variants.

METHODS

We evaluated current and former smokers ages 45-80 of non-Hispanic white (NHW) or African American (AA) race. Childhood asthma was defined by self-report of asthma, diagnosed by a medical professional, with onset at < 16 years or during childhood. Subjects with a history of childhood asthma were compared to those who never had asthma based on lung function, development of COPD, and genetic variation. GWAS was performed in NHW and AA populations, and combined in meta-analysis. Two sets of established asthma SNPs from published literature were examined for association with childhood asthma.

RESULTS

Among 10,199 adult smokers, 730 (7%) reported childhood asthma and 7493 (73%) reported no history of asthma. Childhood asthmatics had reduced lung function and increased risk for COPD (OR 3.42, 95% CI 2.81-4.18). Genotype data was assessed for 8031 subjects. Among NHWs, 391(7%) had childhood asthma, and GWAS identified one genome-wide significant association in KIAA1958 (rs59289606, p = 4.82 × 10- 8). Among AAs, 339 (12%) had childhood asthma. No SNPs reached genome-wide significance in the AAs or in the meta-analysis combining NHW and AA subjects; however, potential regions of interest were identified. Established asthma SNPs were examined, seven from the NHGRI-EBI database and five with genome-wide significance in the largest pediatric asthma GWAS. Associations were found in the current childhood asthma GWAS with known asthma loci in IL1RL1, IL13, LINC01149, near GSDMB, and in the C11orf30-LRRC32 region (Bonferroni adjusted p < 0.05 for all comparisons).

CONCLUSIONS

Childhood asthmatics are at increased risk for COPD. Defining asthma by self-report is valid in populations at risk for COPD, identifying subjects with clinical and genetic characteristics known to associate with childhood asthma. This has potential to improve clinical understanding of asthma-COPD overlap (ACO) and enhance future research into ACO-specific treatment regimens.

TRIAL REGISTRATION

ClinicalTrials.gov, NCT00608764 (Active since January 28, 2008).

Higher Polygenetic Predisposition for Asthma in Cow's Milk Allergic Children

Cow’s milk allergy (CMA) is an early-onset allergy of which the underlying genetic factors remain largely undiscovered. CMA has been found to co-occur with other allergies and immunological hypersensitivity disorders, suggesting a shared genetic etiology. We aimed to (1) investigate and (2) validate whether CMA children carry a higher genetic susceptibility for other immunological hypersensitivity disorders using polygenic risk score analysis (PRS) and prospective phenotypic data. Twenty-two CMA patients of the Dutch EuroPrevall birth cohort study and 307 reference subjects were genotyped using single nucleotide polymorphism (SNP) array. Differentially genetic susceptibility was estimated using PRS, based on multiple P-value thresholds for SNP inclusion of previously reported genome-wide association studies (GWAS) on asthma, autism spectrum disorder, atopic dermatitis, inflammatory bowel disease and rheumatoid arthritis. These associations were validated with prospective data outcomes during a six-year follow-up in 19 patients. We observed robust and significantly higher PRSs of asthma in CMA children compared to the reference set. Association analyses using the prospective data indicated significant higher PRSs in former CMA patients suffering from asthma and related traits. Our results suggest a shared genetic etiology between CMA and asthma and a considerable predictive sensitivity potential for subsequent onset of asthma which indicates a potential use for early clinical asthma intervention programs.

Eosinophilic Esophagitis Is a Late Manifestation of the Allergic March

BACKGROUND

The allergic march describes the natural history of allergic conditions as they develop during childhood. Eosinophilic esophagitis (EoE) is a chronic allergic inflammatory disease that can be triggered by specific foods. Despite its allergic pathophysiology, the epidemiologic relationship between EoE and established members of the allergic march is unknown.

OBJECTIVE

We sought to determine whether EoE meets epidemiologic criteria for being considered a member of the allergic march.

METHODS

Using a primary care birth cohort of 130,435 children, we determined the natural histories of atopic dermatitis (AD), IgE-mediated food allergy (IgE-FA), asthma, EoE, and allergic rhinitis (AR) in individual patients. We then performed case-control analyses to establish the extent that existing allergic conditions influence the rate of subsequent EoE diagnosis.

RESULTS

A total of 139 children developed EoE during the observation period (prevalence of 0.11%). The peak age of EoE diagnosis was 2.6 years, as compared with 0.3 years, 1 year, 1.1 years, and 2.1 years for AD, IgE-FA, asthma, and AR, respectively. The presence of AD (hazard ratio [HR] 3.2, 95% confidence interval [CI] 2.2-4.6), IgE-FA (HR 9.1, 95% CI 6.5-12.6), and asthma (HR 1.9, 95% CI 1.3-2.7) was independently and cumulatively associated with subsequent EoE diagnosis. The presence of AR was associated with subsequent EoE diagnosis (HR 2.8, 95% CI 2.0-3.9), and the presence of EoE was associated with subsequent AR diagnosis (HR 2.5, 95% CI 1.7-3.5).

CONCLUSIONS

Allergic comorbidities are positively associated with EoE diagnosis. Together, our findings suggest that EoE is a late manifestation of the allergic march.

Genetic variants at the 16p13 locus confer risk for eosinophilic esophagitis

Eosinophilic esophagitis (EoE) is a chronic inflammatory disease of the esophagus triggered by immune hypersensitivity to food. Herein, we tested whether genetic risk factors for known, non-allergic, immune-mediated diseases, particularly those involving autoimmunity, were associated with EoE risk. We used the high-density Immunochip platform, encoding 200,000 genetic variants for major auto-immune disease. Accordingly, 1214 subjects with EoE of European ancestry and 3734 population controls were genotyped and assessed using data directly generated or imputed from the previously published GWAS. We found lack of association of EoE with the genetic variants in the major histocompatibility complex (MHC) class I, II, and III genes and nearly all other loci using a highly powered study design with dense genotyping throughout the locus. Importantly, we identified an EoE risk locus at 16p13 with genome-wide significance (P_combined=2.05 × 10⁻⁹, odds ratio = 0.76−0.81). This region is known to encode for the genes CLEC16A, DEXI, and CIITI, which are expressed in immune cells and esophageal epithelial cells. Suggestive EoE risk were also seen 5q23 (intergenic) and 7p15 (JAZF1). Overall, we have identified an additional EoE risk locus at 16p13 and highlight a shared and unique genetic etiology of EoE with a spectrum of immune-associated diseases.

Asthma in children and adolescents with type 1 diabetes in Germany and Austria: Frequency and metabolic control

OBJECTIVE

To investigate the prevalence of asthma in young patients with type 1 diabetes mellitus (T1D) from Austria and Germany and its influence on their metabolic control.

METHODS

This prospective, multicenter observational cohort study was based on the DPV-registry (German/Austrian DPV initiative) including 51 926 patients with T1D (<20 years). All clinical data were documented prospectively. To identify patients with additional asthma, the entry of the diagnosis asthma as well as asthma medication was used for classification.

RESULTS

1755 patients (3.4%) of the cohort had the diagnosis asthma or received asthma-specific drugs. Patients with asthma needed higher insulin doses (0.88 ± 0.3 vs 0.84 ± 0.3 U/kg, P < .01) and had decreased height-standard deviation score (SDS) (-0.002 ± 1.04 vs 0.085 ± 1.02, P < .01); they were more often males (61% vs 52%, P < .01), had an increased body mass index (BMI)-SDS (0.31 ± 0.89 vs 0.28 ± 0.89, P = .04) and experienced more severe hypoglycemia (4.5 [4.2; 4.8] vs 3.2 [3.2; 3.3] events/100 pts. years, P < .01). Glycated hemoglobin A1c (HbA1c) did not differ between patients with and without asthma overall, only sub groups (corticosteroids vs leukotriene antagonist and corticosteroids vs sympatomimetics) revealed differences. No influence of asthma medication on metabolic control or BMI-SDS could be found.

CONCLUSION

In our DPV-database, frequency of asthma and T1D seems similar to the prevalence of asthma in the healthy German background population. The concomitant diagnosis of asthma and T1D had minor influence on metabolic control and diabetes complication rate, although there was no difference in HbA1c overall. Patients with both diseases seem to be slightly growth restricted and require slightly higher insulin doses.

New insights into the phenotypes of atopic dermatitis linked with allergies and asthma in children: An overview

Atopic dermatitis (AD) is a complex disease with multiple causes and complex mechanistic pathways according to age of onset, severity of the illness, ethnic modifiers, response to therapy and triggers. A group of difficult-to-manage patients characterized by early-onset AD and severe lifelong disease associated with allergic asthma and/or food allergy (FA) has been identified. In this study, we focus on these severe phenotypes, analysing their links with other atopic comorbidities, and taking into account the results from recent cohort studies and meta-analyses. The main hypothesis that is currently proposed to explain the onset of allergic diseases is an epithelial barrier defect. Thus, the atopic march could correspond to an epithelial dysfunction, self-sustained by a secondary allergenic sensitization, explaining the transition from AD to allergic asthma. Furthermore, AD severity seems to be a risk factor for associated FA. Results from population-based, birth and patient cohorts show that early-onset and severe AD, male gender, parental history of asthma, and early and multiple sensitizations are risk factors leading to the atopic march and the development of asthma. The importance of environmental factors should be recognized in these high-risk children and prevention programs adapted accordingly. Effective targeted therapies to restore both barrier function and to control inflammation are necessary; early emollient therapy is an important approach to prevent AD in high-risk children. Clinicians should also keep in mind the specific risk of atopic comorbidities in case of filaggrin loss-of-function mutations and the rare phenotypes of orphan syndromes due to heritable mutations in skin barrier components.

Mechanism for initiation of food allergy: Dependence on skin barrier mutations and environmental allergen costimulation

BACKGROUND

Mechanisms for the development of food allergy in neonates are unknown but clearly linked in patient populations to a genetic predisposition to skin barrier defects. Whether skin barrier defects contribute functionally to development of food allergy is unknown.

OBJECTIVE

The purpose of the study was to determine whether skin barrier mutations, which are primarily heterozygous in patient populations, contribute to the development of food allergy.

METHODS

Mice heterozygous for the filaggrin (Flg)ft and Tmem79ma mutations were skin sensitized with environmental and food allergens. After sensitization, mice received oral challenge with food allergen, and then inflammation, inflammatory mediators, and anaphylaxis were measured.

RESULTS

We define development of inflammation, inflammatory mediators, and food allergen-induced anaphylaxis in neonatal mice with skin barrier mutations after brief concurrent cutaneous exposure to food and environmental allergens. Moreover, neonates of allergic mothers have increased responses to suboptimal sensitization with food allergens. Importantly, responses to food allergens by these neonatal mice were dependent on genetic defects in skin barrier function and on exposure to environmental allergens. ST2 blockade during skin sensitization inhibited the development of anaphylaxis, antigen-specific IgE, and inflammatory mediators. Neonatal anaphylactic responses and antigen-specific IgE were also inhibited by oral pre-exposure to food allergen, but interestingly, this was blunted by concurrent pre-exposure of the skin to environmental allergen.

CONCLUSION

These studies uncover mechanisms for food allergy sensitization and anaphylaxis in neonatal mice that are consistent with features of human early-life exposures and genetics in patients with clinical food allergy and demonstrate that changes in barrier function drive development of anaphylaxis to food allergen.

The atopic march: current insights into skin barrier dysfunction and epithelial cell-derived cytokines

Atopic dermatitis often precedes the development of other atopic diseases. The atopic march describes this temporal relationship in the natural history of atopic diseases. Although the pathophysiological mechanisms that underlie this relationship are poorly understood, epidemiological and genetic data have suggested that the skin might be an important route of sensitization to allergens. Animal models have begun to elucidate how skin barrier defects can lead to systemic allergen sensitization. Emerging data now suggest that epithelial cell-derived cytokines such as thymic stromal lymphopoietin (TSLP), IL-33, and IL-25 may drive the progression from atopic dermatitis to asthma and food allergy. This review focuses on current concepts of the role of skin barrier defects and epithelial cell-derived cytokines in the initiation and maintenance of allergic inflammation and the atopic march.

Whole exome sequencing in three families segregating a pediatric case of sarcoidosis

BACKGROUND

Sarcoidosis (OMIM 181000) is a multi-systemic granulomatous disorder of unknown origin. Despite multiple genome-wide association (GWAS) studies, no major pathogenic pathways have been identified to date. To find out relevant sarcoidosis predisposing genes, we searched for de novo and recessive mutations in 3 young probands with sarcoidosis and their healthy parents using a whole-exome sequencing (WES) methodology.

METHODS

From the SARCFAM project based on a national network collecting familial cases of sarcoidosis, we selected three families (trios) in which a child, despite healthy parents, develop the disease before age 15 yr. Each trio was genotyped by WES (Illumina HiSEQ 2500) and we selected the gene variants segregating as 1) new mutations only occurring in affected children and 2) as recessive traits transmitted from each parents. The identified coding variants were compared between the three families. Allelic frequencies and in silico functional results were analyzed using ExAC, SIFT and Polyphenv2 databases. The clinical and genetic studies were registered by the ClinicalTrials.gov - Protocol Registration and Results System (PRS) ( https://clinicaltrials.gov ) receipt under the reference NCT02829853 and has been approved by the ethical committee (CPP LYON SUD EST - 2 - REF IRB 00009118 - September 21, 2016).

RESULTS

We identified 37 genes sharing coding variants occurring either as recessive mutations in at least 2 trios or de novo mutations in one of the three affected children. The genes were classified according to their potential roles in immunity related pathways: 9 to autophagy and intracellular trafficking, 6 to G-proteins regulation, 4 to T-cell activation, 4 to cell cycle and immune synapse, 2 to innate immunity. Ten of the 37 genes were studied in a bibliographic way to evaluate the functional link with sarcoidosis.

CONCLUSIONS

Whole exome analysis of case-parent trios is useful for the identification of genes predisposing to complex genetic diseases as sarcoidosis. Our data identified 37 genes that could be putatively linked to a pediatric form of sarcoidosis in three trios. Our in-depth focus on 10 of these 37 genes may suggest that the formation of the characteristic lesion in sarcoidosis, granuloma, results from combined deficits in autophagy and intracellular trafficking (ex: Sec16A, AP5B1 and RREB1), G-proteins regulation (ex: OBSCN, CTTND2 and DNAH11), T-cell activation (ex: IDO2, IGSF3), mitosis and/or immune synapse (ex: SPICE1 and KNL1). The significance of these findings needs to be confirmed by functional tests on selected gene variants.

International Consensus Statement on Allergy and Rhinology: Allergic Rhinitis

BACKGROUND

Critical examination of the quality and validity of available allergic rhinitis (AR) literature is necessary to improve understanding and to appropriately translate this knowledge to clinical care of the AR patient. To evaluate the existing AR literature, international multidisciplinary experts with an interest in AR have produced the International Consensus statement on Allergy and Rhinology: Allergic Rhinitis (ICAR:AR).

METHODS

Using previously described methodology, specific topics were developed relating to AR. Each topic was assigned a literature review, evidence-based review (EBR), or evidence-based review with recommendations (EBRR) format as dictated by available evidence and purpose within the ICAR:AR document. Following iterative reviews of each topic, the ICAR:AR document was synthesized and reviewed by all authors for consensus.

RESULTS

The ICAR:AR document addresses over 100 individual topics related to AR, including diagnosis, pathophysiology, epidemiology, disease burden, risk factors for the development of AR, allergy testing modalities, treatment, and other conditions/comorbidities associated with AR.

CONCLUSION

This critical review of the AR literature has identified several strengths; providers can be confident that treatment decisions are supported by rigorous studies. However, there are also substantial gaps in the AR literature. These knowledge gaps should be viewed as opportunities for improvement, as often the things that we teach and the medicine that we practice are not based on the best quality evidence. This document aims to highlight the strengths and weaknesses of the AR literature to identify areas for future AR research and improved understanding.

Eosinophilic esophagitis (EoE) genetic susceptibility is mediated by synergistic interactions between EoE-specific and general atopic disease loci

BACKGROUND

Eosinophilic esophagitis (EoE) is an esophageal inflammatory disease associated with atopic diseases. Thymic stromal lymphopoietin (TSLP) and calpain 14 (CAPN14) genetic variations contribute to EoE, but how this relates to atopy is unclear.

OBJECTIVE

The purpose of this study was to explore the relationship between EoE, atopy, and genetic risk.

METHODS

EoE-atopy enrichment was tested by using 700 patients with EoE and 801 community control subjects. Probing 372 single nucleotide polymorphisms (SNPs) in 63 atopy genes, we evaluated EoE associations using 412 nonatopic and 868 atopic disease control subjects. Interaction and stratified analyses of EoE-specific and atopy-related SNPs were performed.

RESULTS

Atopic disease was enriched in patients with EoE (P < .0001). Comparing patients with EoE and nonatopic control subjects, EoE associated strongly with IL-4/kinesin family member 3A (IL4/KIF3A) (P = 2.8 × 10^-6; odds ratio [OR], 1.87), moderately with TSLP (P = 1.5 × 10^-4; OR, 1.43), and nominally with CAPN14 (P = .029; OR, 1.35). Comparing patients with EoE with atopic disease control subjects, EoE associated strongly with ST2 (P = 3.5 × 10^-6; OR, 1.77) and nominally with IL4/KIF3A (P = .019; OR, 1.25); TSLP's association persisted (P = 4.7 × 10^-5; OR, 1.37), and CAPN14's association strengthened (P = .0001; OR, 1.71). Notably, there was gene-gene interaction between TSLP and IL4 SNPs (P = .0074). Children with risk alleles for both genes were at higher risk for EoE (P = 2.0 × 10^-10; OR, 3.67).

CONCLUSIONS

EoE genetic susceptibility is mediated by EoE-specific and general atopic disease loci, which can have synergistic effects. These results might aid in identifying potential therapeutics and predicting EoE susceptibility.

Genome-wide association study identifies the SERPINB gene cluster as a susceptibility locus for food allergy

Genetic factors and mechanisms underlying food allergy are largely unknown. Due to heterogeneity of symptoms a reliable diagnosis is often difficult to make. Here, we report a genome-wide association study on food allergy diagnosed by oral food challenge in 497 cases and 2387 controls. We identify five loci at genome-wide significance, the clade B serpin (SERPINB) gene cluster at 18q21.3, the cytokine gene cluster at 5q31.1, the filaggrin gene, the C11orf30/LRRC32 locus, and the human leukocyte antigen (HLA) region. Stratifying the results for the causative food demonstrates that association of the HLA locus is peanut allergy-specific whereas the other four loci increase the risk for any food allergy. Variants in the SERPINB gene cluster are associated with SERPINB10 expression in leukocytes. Moreover, SERPINB genes are highly expressed in the esophagus. All identified loci are involved in immunological regulation or epithelial barrier function, emphasizing the role of both mechanisms in food allergy.

Association between Allergies and Hypercholesterolemia: A Systematic Review

BACKGROUND

There is controversy in the literature regarding the potential relationship between atopic predisposition (AP) and serum cholesterol levels. To this purpose, we reviewed human studies that investigated this possible link.

METHODS

Following PRISMA guidelines, a literature search of PubMed and Science Direct for peer-reviewed journal articles in English from January 2003, with updates through to August 2016, was conducted. Relevant publications were reviewed that included pediatric and adult populations. Information on the study design, sample, intervention, comparators, outcome, time frame, and risk of bias were abstracted for each article.

RESULTS

Of 601 reviewed reports, 18 were included in this systematic review. Fifteen studies assessed the relationship between AP and serum cholesterol levels. Due to the lack both of observational and cross-sectional studies from the literature search at this time (only 8 studies also analyzed confounding factors) there is a high possibility of confounding variables (familial and genetic predisposition, age, gender, BMI, comorbidity, and medication status) that could not be ruled out.

CONCLUSION

Existing studies are heterogeneous, making it difficult to draw broad conclusions. Future studies and more detailed analyses, considering confounding variables and including a larger and homogeneous population, are needed to strengthen the argument for a link between lipid metabolism and atopy.

Genome-wide association study and meta-analysis in multiple populations identifies new loci for peanut allergy and establishes C11orf30/EMSY as a genetic risk factor for food allergy

BACKGROUND

Peanut allergy (PA) is a complex disease with both environmental and genetic risk factors. Previously, PA loci were identified in filaggrin (FLG) and HLA in candidate gene studies, and loci in HLA were identified in a genome-wide association study and meta-analysis.

OBJECTIVE

We sought to investigate genetic susceptibility to PA.

METHODS

Eight hundred fifty cases and 926 hyper-control subjects and more than 7.8 million genotyped and imputed single nucleotide polymorphisms (SNPs) were analyzed in a genome-wide association study to identify susceptibility variants for PA in the Canadian population. A meta-analysis of 2 phenotypes (PA and food allergy) was conducted by using 7 studies from the Canadian, American (n = 2), Australian, German, and Dutch (n = 2) populations.

RESULTS

An SNP near integrin α6 (ITGA6) reached genome-wide significance with PA (P = 1.80 × 10^-8), whereas SNPs associated with Src kinase-associated phosphoprotein 1 (SKAP1), matrix metallopeptidase 12 (MMP12)/MMP13, catenin α3 (CTNNA3), rho GTPase-activating protein 24 (ARHGAP24), angiopoietin 4 (ANGPT4), chromosome 11 open reading frame (C11orf30/EMSY), and exocyst complex component 4 (EXOC4) reached a threshold suggestive of association (P ≤ 1.49 × 10^-6). In the meta-analysis of PA, loci in or near ITGA6, ANGPT4, MMP12/MMP13, C11orf30, and EXOC4 were significant (P ≤ 1.49 × 10^-6). When a phenotype of any food allergy was used for meta-analysis, the C11orf30 locus reached genome-wide significance (P = 7.50 × 10^-11), whereas SNPs associated with ITGA6, ANGPT4, MMP12/MMP13, and EXOC4 and additional C11orf30 SNPs were suggestive (P ≤ 1.49 × 10^-6). Functional annotation indicated that SKAP1 regulates expression of CBX1, which colocalizes with the EMSY protein coded by C11orf30.

CONCLUSION

This study identifies multiple novel loci as risk factors for PA and food allergy and establishes C11orf30 as a risk locus for both PA and food allergy. Multiple genes (C11orf30/EMSY, SKAP1, and CTNNA3) identified by this study are involved in epigenetic regulation of gene expression.