Background The timing and mechanisms of asthma inception remain imprecisely defined. Although epigenetic mechanisms likely contribute to asthma pathogenesis, little is known about their role in ...asthma inception. Objective We sought to assess whether the trajectory to asthma begins already at birth and whether epigenetic mechanisms, specifically DNA methylation, contribute to asthma inception. Methods We used the Methylated CpG Island Recovery Assay chip to survey DNA methylation in cord blood mononuclear cells from 36 children (18 nonasthmatic and 18 asthmatic subjects by age 9 years) from the Infant Immune Study (IIS), an unselected birth cohort closely monitored for asthma for a decade. SMAD3 methylation in IIS (n = 60) and in 2 replication cohorts (the Manchester Asthma and Allergy Study n = 30 and the Childhood Origins of Asthma Study n = 28) was analyzed by using bisulfite sequencing or Illumina 450K arrays. Cord blood mononuclear cell–derived IL-1β levels were measured by means of ELISA. Results Neonatal immune cells harbored 589 differentially methylated regions that distinguished IIS children who did and did not have asthma by age 9 years. In all 3 cohorts methylation in SMAD3 , the most connected node within the network of asthma-associated, differentially methylated regions, was selectively increased in asthmatic children of asthmatic mothers and was associated with childhood asthma risk. Moreover, SMAD3 methylation in IIS neonates with maternal asthma was strongly and positively associated with neonatal production of IL-1β, an innate inflammatory mediator. Conclusions The trajectory to childhood asthma begins at birth and involves epigenetic modifications in immunoregulatory and proinflammatory pathways. Maternal asthma influences epigenetic mechanisms that contribute to the inception of this trajectory.
Background Activated TH 2 cells and eosinophils are hallmarks of the allergic inflammation seen in patients with allergic rhinitis (AR). However, which cells activate and attract T cells and ...eosinophils to the inflammatory lesion has not been determined. Objective We wanted to assess the role of mucosal mononuclear phagocytes, consisting of monocytes, macrophages, and dendritic cells, in the local allergic inflammatory reaction. Methods Patients with AR and nonatopic control subjects were challenged with pollen extract, and nasal symptoms were recorded. Mucosal biopsy specimens obtained at different time points before and after challenge were used for immunostaining in situ and flow cytometric cell sorting. Sorted mononuclear phagocytes were subjected to RNA extraction and gene expression profiling. Results In an in vivo model of AR, we found that CD14+ monocytes were recruited to the nasal mucosa within hours after local allergen challenge, whereas conventional dendritic cells accumulated after several days of continued provocation. Transcriptomic profiling of mucosal mononuclear phagocytes sorted after 1 week of continued allergen challenge showed an activated phenotype at least partially driven by IL-4 signaling, IL-13 signaling, or both. Importantly, gene expression of several TH 2-related chemokines was significantly upregulated by the mononuclear phagocyte population concomitant with an increased recruitment of CD4+ T cells and eosinophils. Conclusion Our findings suggest that the mononuclear phagocyte population is directly involved in the production of proinflammatory chemokines that attract other immune cells. Rapid recruitment of CD14+ monocytes to the challenged site indicates that these proinflammatory mononuclear phagocytes have a central role in orchestrating local allergic inflammation.
Background Atopy and asthma are commonly initiated during early life, and there is increasing interest in the development of preventive treatments for at-risk children. However, effective methods for ...assessing the level of risk in individual children are lacking. Objective We sought to identify clinical and laboratory biomarkers in 2-year-olds that are predictive of the risk for persistent atopy and wheeze at age 5 years. Methods We prospectively studied 198 atopic family history–positive children to age 5 years. Clinical and laboratory assessments related to asthma history and atopy status were undertaken annually; episodes of acute respiratory illness were assessed and classified throughout and graded by severity. Results Aeroallergen-specific IgE titers cycled continuously within the low range in nonatopic subjects. Atopic subjects displayed similar cycling in infancy but eventually locked into a stable pattern of upwardly trending antibody production and TH 2-polarized cellular immunity. The latter was associated with stable expression of IL-4 receptor in allergen-specific TH 2 memory responses, which was absent from responses during infancy. Risk for persistent wheeze was strongly linked to early sensitization and in turn to early infection. Integration of these data by means of logistic regression revealed that attaining mite-specific IgE titers of greater than 0.20 kU/L by age 2 years was associated with a 12.7% risk of persistent wheeze, increasing progressively to an 87.2% risk with increasing numbers of severe lower respiratory tract illnesses experienced. Conclusion The risk for development of persistent wheeze in children can be quantified by means of integration of measures related to early sensitization and early infections. Follow-up studies along similar lines in larger unselected populations to refine this approach are warranted.
Background Exacerbations are responsible for a substantial burden of morbidity and health care use in children with asthma. Most asthma exacerbations are triggered by viral infections; however, the ...underlying mechanisms have not been systematically investigated. Objective The objective of this study was to elucidate the molecular networks that underpin virus-induced exacerbations in asthmatic children in vivo. Methods We followed exacerbation-prone asthmatic children prospectively and profiled global patterns of gene expression in nasal lavage samples obtained during an acute, moderate, picornavirus-induced exacerbation and 7 to 14 days later. Coexpression network analysis and prior knowledge was used to reconstruct the underlying gene networks. Results The data showed that an intricate modular program consisting of more than 1000 genes was upregulated during acute exacerbations in comparison with 7 to 14 days later. The modules were enriched for coherent cellular processes, including interferon-induced antiviral responses, innate pathogen sensing, response to wounding, small nucleolar RNAs, and the ubiquitin-proteosome and lysosome degradation pathways. Reconstruction of the wiring diagram of the modules revealed the presence of hyperconnected hub nodes, most notably interferon regulatory factor 7, which was identified as a major hub linking interferon-mediated antiviral responses. Conclusions This study provides an integrated view of the inflammatory networks that are upregulated during virus-induced asthma exacerbations in vivo . A series of innate signaling hubs were identified that could be novel therapeutic targets for asthma attacks.
Although evidence suggests that the immune system plays a key role in the pathophysiology of nut allergy, the precise immunological mechanisms of nut allergy have not been systematically ...investigated. The aim of the present study was to identify gene network patterns and associated cellular immune responses in children with or without nut allergy.
Transcriptome profiling of whole blood cells was compared between children with and without nut allergy. Three genes were selected to be validated on a larger cohort of samples (n = 86) by reverse transcription-polymerase chain reactions (RT-qPCR). The composition of immune cells was inferred from the transcriptomic data using the CIBERSORTx algorithm. A co-expression network was constructed employing weighted gene co-expression network analysis (WGCNA) on the top 5000 most variable transcripts. The modules were interrogated with pathway analysis tools (InnateDB) and correlated with clinical phenotypes and cellular immune responses.
Proportions of neutrophils were positively correlated and CD4+ T-cells and regulatory T-cells (Tregs) were negatively correlated with modules of nut allergy. We also identified 2 upregulated genes, namely Interferon Induced With Helicase C Domain 1 (IFIH1), DNA damage-regulated autophagy modulator 1 (DRAM1) and a downregulated gene Zinc Finger Protein 512B (ZNF512B) as hub genes for nut allergy. Further pathway analysis showed enrichment of type 1 interferon signalling in nut allergy.
Our findings suggest that upregulation of type 1 interferon signalling and neutrophil responses and downregulation of CD4+ T-cells and Tregs are features of the pathogenesis of nut allergy.
Background Although most children with asthma and rhinitis are sensitized to aeroallergens, only a minority of sensitized children are symptomatic, implying the underlying operation of efficient ...anti-inflammatory control mechanisms. Objective We sought to identify endogenous control mechanisms that attenuate expression of IgE-associated responsiveness to aeroallergens in sensitized children. Methods In 3 independent population samples we analyzed relationships between aeroallergen-specific IgE and corresponding allergen-specific IgG (sIgG) and associated immunophenotypes in atopic children and susceptibility to asthma and rhinitis, focusing on responses to house dust mite and grass. Results Among mite-sensitized children across all populations and at different ages, house dust mite–specific IgG/IgE ratios (but not IgG4 /IgE ratios) were significantly lower in children with asthma compared with ratios in those without asthma and lowest among the most severely symptomatic. This finding was mirrored by relationships between rhinitis and antibody responses to grass. Depending on age/allergen specificity, 20% to 40% of children with allergen-specific IgE (sIgE) of 0.35 kU/L or greater had negative skin test responses, and these children also expressed the high sIgG/sIgE immunophenotype. sIgG1 from these children inhibited allergen-induced IgE-dependent basophil activation in a dose-dependent fashion. Profiling of aeroallergen-specific CD4+ TH memory responses revealed positive associations between sIgG/sIgE ratios and IL-10–dependent gene signatures and significantly higher IL-10/TH 2 cytokine (protein) ratios among nonsymptomatic children. Conclusion In addition to its role in blocking TH 2 effector activation in the late-phase allergic response, IL-10 is a known IgG1 switch factor. We posit that its production during allergen-induced memory responses contributes significantly to attenuation of inflammation through promoting IgG1 -mediated damping of the FcεRI-dependent acute-phase reaction. sIgG1 /sIgE balance might represent a readily accessible therapeutic target for asthma/rhinitis control.
Background Dendritic cells (DCs) are important in allergic diseases such as asthma, although little is known regarding the mechanisms by which DCs induce TH 2-polarized responses in atopic ...individuals. It has been suggested that intrinsic properties of allergens can directly stimulate TH 2 polarizing functions of DCs, but little is known of the underlying mechanisms. Objective To identify novel genes expressed by house dust mite (HDM) allergen–exposed DCs. Methods We screened for allergen-induced gene expression by microarray, and validated differentially expressed genes at the mRNA and protein levels. Results Thrombomodulin (CD141, blood dendritic cell antigen 3) expression by microarray was higher on HDM-stimulated DCs from atopic (relative to nonatopic) individuals. These findings were confirmed at both the mRNA and protein levels in an independent group. Purified thrombomodulin+ DCs induced a strongly TH 2-polarized cytokine response by allergen-specific T cells compared with DCs lacking thrombomodulin. In vivo , thrombomodulin+ circulating DCs were significantly more frequent in subjects with HDM allergy and asthma, compared with control subjects. Furthermore, thrombomodulin expression in blood leukocytes was higher in children with acute asthma than at convalescence 6 weeks later. Conclusion Thrombomodulin expression on DCs may be involved in the pathogenesis of atopy and asthma.
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