Elder siblings enhance the effect of filaggrin mutations on childhood eczema: Results from the 2 birth cohort studies LISAplus and GINIplus

Adding Fuel to the Fire? The Skin Microbiome in Atopic Dermatitis

Atopic dermatitis (AD) is a multifactorial, heterogeneous disease characterized by epidermal barrier dysfunction, immune system dysregulation, and skin microbiome alterations. Skin microbiome studies in AD have demonstrated that disease flares are associated with microbial shifts, particularly Staphylococcus aureus predominance. AD-associated S. aureus strains differ from those in healthy individuals across various genomic loci, including virulence factors, adhesion proteins, and proinflammatory molecules-which may contribute to complex microbiome barrier-immune system interactions in AD. Different microbially based treatments for AD have been explored, and their future therapeutic successes will depend on a deeper understanding of the potential microbial contributions to the disease.

Genetic/Environmental Contributions and Immune Dysregulation in Children with Atopic Dermatitis

Atopic dermatitis (AD) is one of the most common skin conditions in humans. AD affects up to 20% of children worldwide and results in morbidity for both patients and their caregivers. The basis of AD is an interplay between genetics and the environment characterized by immune dysregulation. A myriad of mutations that compromise the skin barrier and/or immune function have been linked to AD. Of these, filaggrin gene (FLG) mutations are the most evidenced. Many other mutations have been implicated in isolated studies that are often unreplicated, creating an archive of genes with potential but unconfirmed relevance to AD. Harnessing big data, polygenic risk scores (PRSs) and genome-wide association studies (GWAS) may provide a more practical strategy for identifying the genetic signatures of AD. Epigenetics may also play a role. Staphylococcus aureus is the most evidenced microbial contributor to AD. Cutaneous dysbiosis may result in over-colonization by pathogenic strains and aberrant skin immunity and inflammation. Aeroallergens, air pollution, and climate are other key environmental contributors to AD. The right climate and/or commensals may improve AD for some patients.

Atopic dermatitis incidence and risk factors in young adults in Castellon (Spain): A prospective cohort study

INTRODUCTION

There are few atopic dermatitis (AD) incidence cohort studies in young adults, the etiology of this disease remains obscure, and AD risk factors in adults are not well understood. The objective of this study was to estimate AD ten-year incidence and prevalence in a cohort of adolescent aged 14-16 at inception in Castellon province in Valencia Region, Spain and describe related risk factors.

MATERIAL AND METHODS

From 2002 to 2012, a population-based prospective cohort study was carried out. Questionnaires from the International Study of Asthma and Allergies in Childhood (ISAAC) were used with an additional questionnaire for related factors completed by participants and their parents, respectively, in 2002. In 2012 the same questionnaires were completed by the participants' through a telephone interview, and incidence and prevalence of AD were estimated. Directed acyclic graphs, Poisson regression and inverse probability weighted regression adjustment were used.

RESULTS

The participation rate was 79.5% (1435/1805) with AD lifetime prevalence of 34.9% and AD incidence of 13.5 per 1000 person years. Females presented higher prevalence and incidence than males. After adjustment significant risk factors were being female, history of asthma or allergic rhinitis, family history of AD, history of respiratory infections, history of bronchitis, history of pneumonia, history of sinusitis, and birthplace outside Castellon province. The highest AD population attributable risks were female, 30.3%, and history of respiratory infections 15.3%. Differences with AD childhood risk factors were found.

CONCLUSIONS

AD incidence in our cohort was high and several risks factors were related to AD.

What is the evidence for interactions between filaggrin null mutations and environmental exposures in the aetiology of atopic dermatitis? A systematic review

BACKGROUND

Epidemiological studies indicate that gene-environment interactions play a role in atopic dermatitis (AD).

OBJECTIVES

To review the evidence for gene-environment interactions in AD aetiology, focusing on filaggrin (FLG) loss-of-function mutations.

METHODS

A systematic search from inception to September 2018 in Embase, MEDLINE and BIOSIS was performed. Search terms included all synonyms for AD and filaggrin/FLG; any genetic or epidemiological study design using any statistical methods were included. Quality assessment using criteria modified from guidance (ROBINS-I and Human Genome Epidemiology Network) for nonrandomized and genetic studies was completed, including consideration of power. Heterogeneity of study design and analyses precluded the use of meta-analysis.

RESULTS

Of 1817 papers identified, 12 studies fulfilled the inclusion criteria required and performed formal interaction testing. There was some evidence for FLG-environment interactions in six of the studies (P-value for interaction ≤ 0·05), including early-life cat ownership, older siblings, water hardness, phthalate exposure, higher urinary phthalate metabolite levels (which all increased AD risk additional to FLG null genotype) and prolonged breastfeeding (which decreased AD risk in the context of FLG null genotype). Major limitations of published studies were the low numbers of individuals (ranging from five to 94) with AD and FLG loss-of-function mutations and exposure to specific environmental factors, and variation in exposure definitions.

CONCLUSIONS

Evidence on FLG-environment interactions in AD aetiology is limited. However, many of the studies lacked large enough sample sizes to assess these interactions fully. Further research is needed with larger sample sizes and clearly defined exposure assessment. Linked Comment: Park and Seo. Br J Dermatol 2020; 183:411.

Markers of microbial exposure lower the incidence of atopic dermatitis

BACKGROUND

The hygiene hypothesis proposes that reduced exposure to infectious agents in early life would explain the increase of allergic and autoimmune diseases observed over the past decades in high-income countries.

METHODS

We conducted a matched case-control study on incident atopic dermatitis (AD). Cases were 426 outpatient children with a first diagnosis of incident AD. Controls were 426 children attending a pediatric/dermatological visit for nonatopic disorders matched to cases (1:1). Particular attention was paid to the time elapsed between the markers of microbial exposure and disease onset, and we considered for controls the same time window of exposures from birth as his/her matched case. Odds ratios (ORs) were computed using multivariable conditional logistic regression models, according to center, sex, age, and period of enrollment, and including as potential confounders a family history of any allergy in parents, type of delivery, having siblings, keeping pets, age at weaning, and having had ≥4 infections.

RESULTS

The OR of AD first occurrence was 0.35 (P-value = .039) for children who had experienced ≥4 infections compared with those with no infections. A decreasing trend in risk was observed with increasing number of siblings (P-value = .023), the protective effect reaching about 40% for children with 2 or more siblings (OR = 0.62; P-value = .048). Pet keeping, in particular daily contact with dogs, was inversely associated with AD risk (OR = 0.40; P-value = .004).

CONCLUSIONS

These results support the hygiene hypothesis in its broad sense. Early-life environmental exposures, including pathogens and commensals, act as "microbes contact carriers" influencing immune system balance early in life.

Predicting Skin Barrier Dysfunction and Atopic Dermatitis in Early Infancy

BACKGROUND

Dry skin is associated with increased transepidermal water loss (TEWL), which has been found to precede atopic dermatitis (AD) in childhood.

OBJECTIVE

We aimed to identify parental, prenatal, and perinatal predictive factors of dry skin, high TEWL, and AD at 3 months of age, and to determine if dry skin or high TEWL at 3 months can predict AD at 6 months.

METHODS

From the Preventing Atopic Dermatitis and Allergies in children prospective birth cohort study, we included 1150 mother-child pairs. Dry skin, TEWL, and eczema were assessed at 3- and 6-month investigations. Eczema, used as a proxy for AD, was defined as the presence of eczematous lesions, excluding differential diagnoses to AD. High TEWL was defined as TEWL >90th percentile, equaling 11.3 g/m²/h. Potential predictive factors were recorded from electronic questionnaires at 18- and 34-week pregnancy and obstetric charts.

RESULTS

Significant predictive factors (P < .05) for dry skin at 3 months were delivery >38 gestational weeks and paternal age >37 years; for high TEWL, male sex, birth during winter season, and maternal allergic disease; and for eczema, elective caesarean section, multiparity, and maternal allergic diseases. Dry skin without eczema at 3 months was predictive for eczema at 6 months (adjusted odds ratio: 1.92, 95% confidence interval: 1.21-3.05; P = .005), whereas high TEWL at 3 months was not.

CONCLUSION

In early infancy, distinct parental- and pregnancy-related factors were predictive for dry skin, high TEWL, and AD. Dry skin at 3 months of age was predictive for AD 3 months later.

The Role of the Environmental Risk Factors in the Pathogenesis and Clinical Outcome of Atopic Dermatitis

Atopic dermatitis (AD) prevalence is rising worldwide. Literature data suggest the incidence of AD in developing countries is gradually getting close to that of developed ones, in which AD affects 20% of the paediatric population. Such an increment, associated with significant variations in prevalence among the various countries, underlines the importance of environmental factors in the disease onset. Among these, great importance is given to hygiene, intestinal microbiota, exposure to bacterial endotoxins, outdoor living with contact to animals, atmospheric pollution, weather, and diet. Genetic (alteration of the skin barrier function) as well as immunologic factors concur with the environmental ones. Only the systematical study of all these elements can best elucidate AD epidemiology.

The prevalence and risk factors of atopic dermatitis in 6-8 year-old first graders in Taipei

BACKGROUND

Despite the advance in the understanding of etiology, pathophysiology and diagnosis of atopic dermatitis (AD), its prevalence has increased annually in Taiwan.

PURPOSES

The purpose of this study is to explore the prevalence, and personal and environmental risk factors of AD.

METHODS

A cross-sectional survey was conducted via health centers of elementary schools in Taipei city. We used the Chinese version of ISAAC questionnaire to examine possible personal and environmental risk factors of AD. Questionnaires were completed by parents or guardians of first graders (6-8 year-old) who agreed to participate in this study. Logistic regression was conducted to examine possible personal and environmental factors related to AD (in early life and currently).

RESULTS

The 12-month prevalence of AD (in the past 12 months) was 10.7% (2683/24,999) among 6- to 8-year-old first graders in Taipei. Forty-five percent of first graders with AD had their first episode of AD symptoms before the age of two. Children with asthma history were 1.65 times (95% CI: 1.51-1.79, p < 0.001) and children with rhinitis were 2.57 times (95% CI: 2.34-2.84, p < 0.001) more likely to have AD than those without the conditions. Compare to their counterarts, children who used antibiotics during their first year of life (OR = 1.37, 95% CI: 1.22-1.53, p < 0.001) and who had bronchiolitis before the age of two (OR = 1.47, 95% CI: 1.33-1.63, p < 0.001) had a higher chance to have AD during the last 12 months of the study. However, receiving breastfeeding for less than 4 months (OR = 0.75, 95% CI: 0.67-0.83, p < 0.001) and having older siblings (OR = 0.83, 95% CI: 0.76-0.92, p < 0.001) had 25% and 17% reduced risks for AD in the 12 months before this study, respectively.

CONCLUSION

Our study verified personal and environmental risk factors of AD in children in Taiwan. Based on the results, we propose that avoiding bronchiolitis before the age of two, using antibiotics properly in babies, and providing diet counseling for breastfeeding mothers may be good prevention strategies of AD.

GINIplus and LISAplus - Design and selected results of two German birth cohorts about natural course of atopic diseases and their determinants

The increasing prevalence of asthma, hay fever, and allergic sensitization in Western Germany after east-west division in 1949 and their rapid increase in East German children after re-unification in 1990 are strong indications for the role of life-style and/or environmental factors in the development of atopic diseases. Obviously, the perinatal period is crucial for priming the immune system. Therefore, explorations of determinants of atopic diseases need pregnancy or birth cohorts as the most appropriate epidemiological study designs. This review presents the design and selected results of the two German birth cohorts GINIplus and LISAplus. GINIplus and LISAplus recruited 5.991 and 3.097 healthy, term newborns, respectively, from Munich, Wesel, Leipzig, and Bad Honnef. Approximately 55% could be followed for the first 10 years. We analyzed the natural course of atopic diseases and the role of life-style, environmental, and genetic factors for disease onset, intermediate phenotypes, and genes involved in detoxification and oxidative stress. The results of these two large birth cohorts contributed substantially to the understanding of atopic diseases and their determinants.

Topographical and physiological differences of the skin mycobiome in health and disease

Skin constantly encounters external elements, including microbes. Culture-based studies have identified fungi present on human skin and have linked some species with certain skin diseases. Moreover, modern medical treatments, especially immunosuppressants, have increased the population at risk for cutaneous and invasive fungal infections, emphasizing the need to understand skin fungal communities in health and disease. A major hurdle for studying fungal flora at a community level has been the heterogeneous culture conditions required by skin fungi. Recent advances in DNA sequencing technologies have dramatically expanded our knowledge of the skin microbiome through culture-free methods. This review discusses historical and recent research on skin fungal communities - the mycobiome - in health and disease, and challenges associated with sequencing-based mycobiome research.

The Skin Microbiome in Atopic Dermatitis and Its Relationship to Emollients

BACKGROUND

Human-associated bacterial communities on the skin, skin microbiome, likely play a central role in development of immunity and protection from pathogens. In atopic patients, the skin bacterial diversity is smaller than in healthy subjects.

OBJECTIVE

To review treatment strategies for atopic dermatitis in Canada, taking the skin microbiome concept into account.

METHODS

An expert panel of 8 Canadian dermatologists explored the role of skin microbiome in clinical dermatology, specifically looking at atopic dermatitis.

RESULTS

The panel reached consensus on the following: (1) In atopic patients, the skin microbiome of lesional atopic skin is different from nonlesional skin in adjacent areas. (2) Worsening atopic dermatitis and smaller bacterial diversity are strongly associated. (3) Application of emollients containing antioxidant and antibacterial components may increase microbiome diversity in atopic skin.

CONCLUSION

The skin microbiome may be the next frontier in preventive health and may impact the approach to atopic dermatitis treatment.

8th Georg Rajka International Symposium on Atopic Dermatitis: meeting report

The 8th Georg Rajka International Symposium on Atopic Dermatitis was held in Nottingham in May 2014. The 3-day meeting featured a number of lectures by experts in the field of atopic dermatitis from around the world, as well as several original research presentations and a question and answer session. This paper aims to summarize the main oral presentations from the meeting, but is not meant to be a substitute for reading the conference proceedings and related references.

Recent advances in epidemiology and prevention of atopic eczema

Atopic dermatitis (AD), named also atopic eczema, is a chronic relapsing inflammatory skin disease with a considerable social and economic burden. The primum movens of AD is in most cases a genetic and/or immune-supported defect of the skin barrier, facilitating penetration and sensitization to food or airborne allergens, as well as infections by Staphylococcus aureus, herpes simplex virus, or other microbes. New pathogenetic concepts have generated new approaches to prevention and therapy of AD. In particular, the daily use of emollients in newborns at high risk of AD has shown interesting results, with a reduction in the cumulative incidence of AD ranging from 32% to 50% of the treated infants. On the other hand, the AD preventive efficacy of food and/or inhalant allergen avoidance has been questioned, and supplementation strategies (vitamin D, probiotics, or other compounds) need to be further investigated.

The role of filaggrin in the skin barrier and disease development

Filaggrin is a structural protein that is fundamental in the development and maintenance of the skin barrier. The function of filaggrin and its involvement in various cutaneous and extracutaneous disorders has been the subject of considerable research in recent years. Mutations in FLG, the gene that encodes filaggrin, have been shown to cause ichthyosis vulgaris, increase the risk of atopic dermatitis and other atopic diseases, and exacerbate certain conditions. The present article reviews the current knowledge on the role of filaggrin in the skin barrier, FLG mutations, and the consequences of filaggrin deficiency.

New insights into the epidemiology of childhood atopic dermatitis

There is a growing desire to explain the worldwide rise in the prevalence of atopic dermatitis (AD). Trend data on the burden of AD suggest that the picture in the developing world may soon resemble that of wealthier nations, where AD affects over 20% of children. This, combined with significant variations in prevalence within countries, emphasizes the importance of environmental factors. Many hypotheses have been explored, from the modulation of immune priming by hygiene, gut microbiota diversity, and exposure to endotoxins through farm animals to the effects of pollution, climate, and diet. The discovery of the filaggrin skin barrier gene and its importance in AD development and severity has brought the focus on gene-environment interactions and the identification of environmental factors that impact on skin barrier function. This article reviews our current understanding of the epidemiology of AD, with an emphasis on the findings reported in the international literature over the last 5 years.

The multifunctional role of filaggrin in allergic skin disease

Filaggrin is a major structural protein in the stratum corneum of the epidermis. Mutations in the filaggrin gene are the most significant known genetic risk factor for the development of atopic dermatitis. Mutations in the human filaggrin gene (FLG) also confer risk for the associated allergic diseases of food allergy, asthma, and allergic rhinitis. These discoveries have highlighted the importance of skin barrier function in the pathogenesis of atopic diseases and have motivated a surge in research characterizing the filaggrin-deficient skin barrier and its consequences. In this review we discuss the mechanisms through which mutations in this protein contribute to the pathogenesis of atopic dermatitis and associated atopic conditions. We focus on recent human and murine discoveries characterizing the filaggrin-deficient epidermis with respect to biophysical, immunologic, and microbiome abnormalities.

Ichthyosis vulgaris: the filaggrin mutation disease

Ichthyosis vulgaris is caused by loss-of-function mutations in the filaggrin gene (FLG) and is characterized clinically by xerosis, scaling, keratosis pilaris, palmar and plantar hyperlinearity, and a strong association with atopic disorders. According to the published studies presented in this review article, FLG mutations are observed in approximately 7·7% of Europeans and 3·0% of Asians, but appear to be infrequent in darker-skinned populations. This clinical review article provides an overview of ichthyosis vulgaris epidemiology, related disorders and pathomechanisms. Not only does ichthyosis vulgaris possess a wide clinical spectrum, recent studies suggest that carriers of FLG mutations may have a generally altered risk of developing common diseases, even beyond atopic disorders. Mechanistic studies have shown increased penetration of allergens and chemicals in filaggrin-deficient skin, and epidemiological studies have found higher levels of hand eczema, irritant contact dermatitis, nickel sensitization and serum vitamin D levels. When relevant, individuals should be informed about an increased risk of developing dermatitis when repeatedly or continuously exposed to nickel or irritants. Moreover, with our current knowledge, individuals with ichthyosis vulgaris should be protected against neonatal exposure to cats to prevent atopic dermatitis and should abstain from smoking to prevent asthma. Finally, they should be advised against excessive exposure to factors that decrease skin barrier functions and increase the risk of atopic dermatitis.

The skin microbiome: current perspectives and future challenges

Complex communities of bacteria, fungi, and viruses thrive on our skin. The composition of these communities depends on skin characteristics, such as sebaceous gland concentration, moisture content, and temperature, as well as on host genetics and exogenous environmental factors. Recent metagenomic studies have uncovered a surprising diversity within these ecosystems and have fostered a new view of commensal organisms as playing a much larger role in immune modulation and epithelial health than previously expected. Understanding microbe-host interactions and discovering the factors that drive microbial colonization will help us understand the pathogenesis of skin diseases and develop new promicrobial and antimicrobial therapeutics.

Genetic association between obstructive bronchitis and enzymes of oxidative stress

OBJECTIVE

Obstructive respiratory diseases, mainly the chronic obstructive pulmonary disease (COPD) and asthma, are associated with functional polymorphisms of xenobiotic-metabolizing enzymes (XMEs). To date, association for obstructive bronchitis has not been described.

MATERIAL/METHODS

In this study, we investigated the genotypes from 26 functional polymorphisms of 20 XMEs in children (n, 1028) at the age of 6 years from the German prospective birth cohort study (LISAplus) and analyzed the associations between genotypes and obstructive bronchitis.

RESULTS

For the first time, we found noteworthy gene-disease associations for the functional PON1 M55L and EPHX1 H139R polymorphisms and gene-environment associations for the functional COMT V158M and NQO1 P187S polymorphisms after stratification for maternal active smoking behaviour during pregnancy. The noteworthy associations were substantiated by the biological findings that all the risk genotypes belong to genes involved in oxidative stress and code for proteins with a fast enzymatic activity or concomitantly appear in common estrogene-metabolizing pathway (COMT, NQO1).

CONCLUSION

The oxidative stress has to be taken into account in mechanism of the obstructive bronchitis in early childhood. The risk genotypes may serve as risk factors for respiratory obstruction rather than for signs of COPD or asthma.

Microbiota and dietary interactions: an update to the hygiene hypothesis?

The dramatic increase in the incidence and severity of allergy and asthma has been proposed to be linked with an altered exposure to, and colonization by, micro-organisms, particularly early in life. However, other lifestyle factors such as diet and physical activity are also thought to be important, and it is likely that multiple environmental factors with currently unrecognized interactions contribute to the atopic state. This review will focus on the potential role of microbial metabolites in immunoregulatory functions and highlights the known molecular mechanisms, which may mediate the interactions between diet, microbiota, and protection from allergy and asthma.

One remarkable molecule: filaggrin

The discovery, in 2006, that loss-of-function mutations in the filaggrin (FLG) gene are the cause of ichthyosis vulgaris-the most common disorder of keratinization-and also a strong genetic risk factor for atopic eczema, marked a significant breakthrough in the understanding of eczema pathogenesis. Subsequent investigations of the role of FLG-null mutations have identified a series of significant associations with atopic disease phenotypes, including atopic asthma, allergic rhinitis, and peanut allergy. However, many questions remain to be answered in relation to the precise mechanisms by which deficiency of an intracellular protein expressed primarily in the differentiating epidermis may contribute to the development of cutaneous and systemic pathology. This review aims to highlight the key milestones in filaggrin research over the past 25 years, to discuss the mechanistic, clinical, and therapeutic implications, and to consider possible future directions for ongoing investigation.

Temporal shifts in the skin microbiome associated with disease flares and treatment in children with atopic dermatitis

Atopic dermatitis (AD) has long been associated with Staphylococcus aureus skin colonization or infection and is typically managed with regimens that include antimicrobial therapies. However, the role of microbial communities in the pathogenesis of AD is incompletely characterized. To assess the relationship between skin microbiota and disease progression, 16S ribosomal RNA bacterial gene sequencing was performed on DNA obtained directly from serial skin sampling of children with AD. The composition of bacterial communities was analyzed during AD disease states to identify characteristics associated with AD flares and improvement post-treatment. We found that microbial community structures at sites of disease predilection were dramatically different in AD patients compared with controls. Microbial diversity during AD flares was dependent on the presence or absence of recent AD treatments, with even intermittent treatment linked to greater bacterial diversity than no recent treatment. Treatment-associated changes in skin bacterial diversity suggest that AD treatments diversify skin bacteria preceding improvements in disease activity. In AD, the proportion of Staphylococcus sequences, particularly S. aureus, was greater during disease flares than at baseline or post-treatment, and correlated with worsened disease severity. Representation of the skin commensal S. epidermidis also significantly increased during flares. Increases in Streptococcus, Propionibacterium, and Corynebacterium species were observed following therapy. These findings reveal linkages between microbial communities and inflammatory diseases such as AD, and demonstrate that as compared with culture-based studies, higher resolution examination of microbiota associated with human disease provides novel insights into global shifts of bacteria relevant to disease progression and treatment.

A genome-wide meta-analysis of genetic variants associated with allergic rhinitis and grass sensitization and their interaction with birth order

BACKGROUND

Hay fever or seasonal allergic rhinitis (AR) is a chronic disorder associated with IgE sensitization to grass. The underlying genetic variants have not been studied comprehensively. There is overwhelming evidence that those who have older siblings have less AR, although the mechanism for this remains unclear.

OBJECTIVE

We sought to identify common genetic variant associations with prevalent AR and grass sensitization using existing genome-wide association study (GWAS) data and to determine whether genetic variants modify the protective effect of older siblings.

METHOD

Approximately 2.2 million genotyped or imputed single nucleotide polymorphisms were investigated in 4 large European adult cohorts for AR (3,933 self-reported cases vs 8,965 control subjects) and grass sensitization (2,315 cases vs 10,032 control subjects).

RESULTS

Three loci reached genome-wide significance for either phenotype. The HLA variant rs7775228, which cis-regulates HLA-DRB4, was strongly associated with grass sensitization and weakly with AR (P(grass) = 1.6 × 10(-9); P(AR) = 8.0 × 10(-3)). Variants in a locus near chromosome 11 open reading frame 30 (C11orf30) and leucine-rich repeat containing 32 (LRRC32), which was previously associated with atopic dermatitis and eczema, were also strongly associated with both phenotypes (rs2155219; P(grass) = 9.4 × 10(-9); P(AR) = 3.8 × 10(-8)). The third genome-wide significant variant was rs17513503 (P(grass) = 1.2 × 10(-8); PAR = 7.4 × 10(-7)) which was located near transmembrane protein 232 (TMEM232) and solute carrier family 25, member 46 (SLC25A46). Twelve further loci with suggestive associations were also identified. Using a candidate gene approach, where we considered variants within 164 genes previously thought to be important, we found variants in 3 further genes that may be of interest: thymic stromal lymphopoietin (TSLP), Toll-like receptor 6 (TLR6) and nucleotide-binding oligomerization domain containing 1 (NOD1/CARD4). We found no evidence for variants that modified the effect of birth order on either phenotype.

CONCLUSIONS

This relatively large meta-analysis of GWASs identified few loci associated with AR and grass sensitization. No birth order interaction was identified in the current analyses.

Predictive value of food sensitization and filaggrin mutations in children with eczema

BACKGROUND

It was reported that in infants with eczema and food sensitization, the presence of a filaggrin (FLG) null mutation predicts future asthma with a specificity and positive predictive value of 100%.

OBJECTIVES

We sought to evaluate the predictive value of food sensitization and food allergy, FLG haploinsufficiency, and their combination in infants with early-onset eczema for persistent eczema and childhood asthma.

METHODS

The German Infant Nutritional Intervention (GINI) and Influence of Lifestyle-related Factors on the Immune System and the Development of Allergies in Childhood (LISA) birth cohorts, as well as a collection of 65 cases of early-onset eczema with and without food allergy were investigated.

RESULTS

The risk for asthma was significantly increased by food sensitization (positive diagnostic likelihood ratios [PLRs] of 1.9 [95% CI, 1.1-3.4] in the GINI cohort and 5.5 [95% CI, 2.8-10.8] in the LISA cohort) and the presence of an FLG mutation (PLRs of 2.9 [95% CI, 1.2-6.6] in the GINI cohort and 2.8 [95% CI, 1.0-7.9] in the LISA cohort) with a rather high specificity (79.1% and 92.9% in the GINI cohort and 89.0% and 91.7% in the LISA cohort, respectively) but low sensitivity (40.0% and 39.3% in the GINI cohort and 31.6% and 23.5% in the LISA cohort, respectively). Likewise, the risk for persistent eczema was increased. In the clinical cases neither food allergy nor FLG mutations had a significant effect. The combination of both parameters did not improve prediction and reached positive predictive values of 52.3% (GINI cohort), 66.9% (LISA cohort), and 30.6% (clinical cases), assuming an asthma prevalence in children with early eczema of 30%.

CONCLUSION

Early food sensitization and the presence of an FLG mutation in infants with early eczema increase the risk for later asthma, but the combination of the 2 factors does not represent a clinically useful approach to reliably identify children at risk.

Genetics of atopic dermatitis

Atopic dermatitis (AD) is a multifactorial disease, with a strong genetic predisposition. Genome-wide studies as well as candidate gene studies revealed several susceptibility loci. Since the observation of a strong association of "loss of function" mutations in the filaggrin gene with AD, the epidermal barrier was rediscovered as important pathophysiological co-factor of this disease.

Role of dendritic cells: a step forward for the hygiene hypothesis

The hygiene hypothesis was proposed more than two decades ago, but its mechanism remains unclear. This review focuses on recent advances in the field, especially on the role played by dendritic cells (DCs) and their modulating effects on various infections and allergic diseases, including allergic asthma. DCs isolated from mice long after the resolution of an infection were reported to have a significant modulating effect on allergen-specific Th2 responses in both in vitro and in vivo systems. These DCs showed DC1-like and/or tolerogenic DC capacity, which allowed for the inhibition of allergic responses by immune deviation (enhancing Th1 response) and immune regulation (through regulatory T-cell and Th2 hyporesponsiveness) mechanisms. These findings represented a significant advance in the elucidation of the mechanisms underlying the hygiene hypothesis. Further investigation on the mechanisms by which DCs are 'educated' by infectious agents and the influence of the type, time, and extent of infections on this 'education' process will help us understand immune regulation in disease settings and in the rational design of preventive/therapeutic approaches to allergy/asthma and infections.

Association between attendance of day care centres and increased prevalence of eczema in the German birth cohort study LISAplus

BACKGROUND

Day care centre attendance is much more common in East than in West Germany. Although there is evidence that early day care might be protective against atopic diseases, several studies have shown a higher prevalence of childhood eczema in East Germany compared to West Germany.

OBJECTIVES

To compare prevalence and cumulative incidence of eczema in a birth cohort study in East and West Germany and to identify risk factors that are associated with eczema, which might explain regional differences.

METHODS

We used data from the ongoing population-based birth cohort study Influence of Life-style factors on the development of the Immune System and Allergies in East and West Germany Plus the influence of traffic emissions and genetics. In 1997, 3097 children from study areas in East and West Germany were recruited. Cumulative incidence and 1-year prevalences of eczema up to the age of 6 years were determined from yearly questionnaires. Cox regression and generalized estimating equations/logistic regression were used to quantify regional differences and to identify risk factors that might explain them.

RESULTS

Prevalence and incidence of eczema were higher in children living in East Germany than those living in West Germany. We identified 11 risk factors that showed significant regional differences. From these factors, only 'day care attendance during the first 2 years of life' was significantly associated with eczema (odds ratio 1.56, 95% confidence interval CI 1.31-1.86). The regional differences in eczema could be explained by differences in early day care utilization.

CONCLUSION

Day care centre attendance is associated with an increased prevalence and incidence of eczema. Regional differences in eczema prevalence could be explained by regional differences in utilization of early day care.