The -159 C-->T polymorphism of CD14 is associated with nonatopic asthma and food allergy

Multi-omics profiling approach in food allergy

The prevalence of food allergy (FA) among children is increasing, affecting nearly 8% of children, and FA is the most common cause of anaphylaxis and anaphylaxis-related emergency department visits in children. Importantly, FA is a complex, multi-system, multifactorial disease mediated by food-specific immunoglobulin E (IgE) and type 2 immune responses and involving environmental and genetic factors and gene-environment interactions. Early exposure to external and internal environmental factors largely influences the development of immune responses to allergens. Genetic factors and gene-environment interactions have established roles in the FA pathophysiology. To improve diagnosis and identification of FA therapeutic targets, high-throughput omics approaches have emerged and been applied over the past decades to screen for potential FA biomarkers, such as genes, transcripts, proteins, and metabolites. In this article, we provide an overview of the current status of FA omics studies, namely genomic, transcriptomic, epigenomic, proteomic, exposomic, and metabolomic. The current development of multi-omics integration of FA studies is also briefly discussed. As individual omics technologies only provide limited information on the multi-system biological processes of FA, integration of population-based multi-omics data and clinical data may lead to robust biomarker discovery that could translate into advances in disease management and clinical care and ultimately lead to precision medicine approaches.

Genetics of Food Allergy

The risk factors for food allergy (FA) include both genetic variants and environmental factors. Advances using both candidate-gene association studies and genome-wide approaches have led to the identification of FA-associated genes involved in immune responses and skin barrier functions. Epigenetic changes have also been associated with the risk of FA. In this chapter, we outline current understanding of the genetics, epigenetics and the interplay with environmental risk factors associated with FA. Future studies of gene-environment interactions, gene-gene interactions, and multi-omics integration may help shed light on the mechanisms of FA, and lead to improved diagnostic and treatment strategies.

Eosinophilic Esophagitis and Microbiota: State of the Art

Eosinophilic esophagitis (EoE) is a chronic, food-triggered, immune-mediated disease of the oesophagus, clinically characterized by symptoms referred to oesophagal dysfunction, and histologically defined by an eosinophil productive inflammation of the oesophagal mucosa, among other cell types. The involvement of an adaptive Th2-type response to food antigens in EoE was known since 2000; several cytokines and chemokines promote food-specific responses, during which local production of IgE, but also IgG4 derived from plasma cells in lamina propria of oesophagal mucosa might play an important role. Evidence pointing towards a possible role for the innate immunity in EoE has arisen recently. Together, this evidence gives rise to a potential role that the innate immune system in general, and also the microbial pattern recognition receptors (PRRs) might play in EoE pathogenesis. Among PRRs, Toll-like receptors (TLRs) are type-I transmembrane receptors expressed both on epithelial and lamina propria cells with the capacity to distinguish between pathogen and commensal microbes. As TLRs in the different intestinal epithelia represent the primary mechanism of epithelial recognition of bacteria, this evidence underlines that oesophagal TLR-dependent signaling pathways in EoE support the potential implication of microbiota and the innate immune system in the pathogenesis of this disease. The oesophagal mucosa hosts a resident microbiota, although in a smaller population as compared with other districts of the gastrointestinal tract. Few studies have focused on the composition of the microbiota of the normal oesophagus alone. Still, additional information has come from studies investigating the oesophagal microbiota in disease and including healthy patients as controls. Our review aims to describe all the evidence on the oesophagal and intestinal microbiota in patients with EoE to identify the specific features of dysbiosis in this condition.

Current insights into the genetics of food allergy

Food allergy (FA), a growing public health burden in the United States, and familial aggregation studies support strong roles for both genes and environment in FA risk. Deepening our understanding of the molecular and cellular mechanisms driving FAs is paramount to improving its prevention, diagnosis, and clinical management. In this review, we document lessons learned from the genetics of FA that have aided our understanding of these mechanisms. Although current genetic association studies suffer from low power, heterogeneity in definition of FA, and difficulty in our ability to truly disentangle FA from food sensitization (FS) and general atopy genetics, they reveal a set of genetic loci, genes, and variants that continue to implicate the importance of barrier and immune function genes across the atopic march, and FA in particular. The largest reported effects on FA are from MALT1 (odds ratio, 10.99), FLG (average odds ratio, ∼2.9), and HLA (average odds ratio, ∼2.03). The biggest challenge in the field of FA genetics is to elucidate the specific mechanism of action on FA risk and pathogenesis for these loci, and integrative approaches including genetics/genomics with transcriptomics, proteomics, and metabolomics will be critical next steps to translating these genetic insights into practice.

Children with nut allergies have impaired gene expression of Toll-like receptors pathway

BACKGROUND

Trends in food allergies prompted investigation into the underlying mechanisms. Genetic and epigenetic factors are of high interest, and, in particular, the interplay between genes relating to immune factors directly and indirectly involved in food allergy pathogenesis. We sought to determine potential links between gene expression and epigenetic factors relating to Toll-like receptor (TLR) pathways and childhood food allergies.

METHODS

In a cross-sectional study, samples from 80 children with and without food allergies were analysed for gene expression, DNA methylation and a range of immune factors relating to TLR pathways. TLR2, TLR4, CD14, IL5, IL13 and vitamin D were explored.

RESULTS

The importance of these immune factors appeared to vary between the different types of food allergies. Expression of TLR2 (P < .001), TLR4 (P = .014) and CD14 (P = .028) varied significantly between children with no food allergy, allergy to nuts and peanuts, and allergy to eggs. DNA methylation in the promoter regions of these genes had a significant association with gene expression. These trends persisted when subjects were stratified by nut allergy vs no nut allergy. Furthermore, TLR2 (P = .001) and CD14 (P = .007) expressions were significantly lower in children with food allergies when compared to those without.

CONCLUSION

Gene expression of TLR pathway genes was directly related to food allergy type, and DNA methylation had an indirect effect. TLR2 pathways are of significant interest in nut allergies.

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.

Maternal Perinatal Dietary Patterns Affect Food Allergy Development in Susceptible Infants

BACKGROUND

The increasing incidence of food allergy (FA) can be attributed to interactions between genes and the environment, but these interactions are not yet fully clear.

OBJECTIVE

We aimed to evaluate the interaction between infant genetic variations and maternal dietary patterns to identify risk factors in the development of FA.

METHODS

We used the Cohort for Childhood Origin of Asthma and allergic diseases birth cohort of 1628 infants, born between 2007 and 2015. Maternal dietary intakes were assessed at 26 weeks of pregnancy using a food frequency questionnaire and grouped according to 5 dietary patterns. Infant cord blood samples were genotyped at 12 loci.

RESULTS

Among 1628 infants, 147 (9.0%) were diagnosed with FA based on history. A maternal confectionery diet characterized by a higher intake of baked and sugary products during pregnancy was associated with a higher prevalence of FA (adjusted odds ratio [OR] = 1.517, P = .02); this dietary pattern tended to be higher in trans fat (r = 0.498, P < .001). Development of FA was associated with longer periods of breastfeeding (adjusted OR = 1.792, P = .03), and this dietary pattern was more significantly related to the development of FA in infants with the homozygous TT genotype of CD14 (rs2569190) and more than 1 copy of GSTM1 and GSTT1.

CONCLUSIONS

A maternal confectionery diet during pregnancy that majorly consists of baked and sugary products, combined with a longer ensuing period of breastfeeding, may lead to the development of FA, suggesting a harmful effect of trans fats in the infant. Polymorphisms in CD14 and GST in the infant influence FA susceptibility.

Oral allergy syndrome

OBJECTIVES

To review oral allergy syndrome (OAS).

METHODS

We searched several medical literature data bases with the following key words: "oral allergy syndrome," "OAS," "pollen-food allergy syndrome," "PFAS," "allergy," "diagnosis," "treatment."

RESULTS

Oral allergy syndrome (OAS), also called "pollen-food allergy syndrome," is a type of food allergy brought about by flavors, nuts, raw fruit, and vegetables. The most well-known symptoms are mouth and throat itching, which starts rapidly after a food is placed in the mouth, and that, as a rule, continues for just a couple of minutes after the food has been swallowed. The frequency of OAS with pollen allergy has been reported as 5-8%; 1-2% of patients with OAS with pollen allergy show extreme responses, e.g., anaphylaxis. Birch tree pollen, ragweed pollen, and grass pollen hypersensitivity cause the symptoms. The diagnosis of OAS is confirmed by a positive history and positive skin-prick test result triggered by the food's fresh extract. Oral challenge result is normally positive with the raw food and negative with the similar cooked food.

CONCLUSION

Patients with grass allergy may have a response to peaches, oranges, celery, tomatoes, and melons. Patients with ragweed allergy may show OAS symptoms with melon, cucumber, banana, and zucchini. Physicians should be aware of OAS and know the appropriate treatment.

Microbial Insights into Asthmatic Immunopathology. A Forward-Looking Synthesis and Commentary

Asthma is an aberrant inflammatory condition of the airways affecting approximately 1 in 10 children in affluent countries. An increasing body of evidence suggests that microbial exposures during a "critical window" of development in early life play a central role in determining future asthma susceptibility. However, like the disease itself, considerable heterogeneity exists among studies in which researchers have investigated the associations between particular microbial taxa and asthma immunology. As our understanding of asthmatic pathology evolves to enable clearer definition of asthma endotypes, it will be important to consider the impact of various environmental factors on each endotype. Given the strong evidence in support of the hypothesis that early-life microbial exposures predict later disease states such as asthma, consideration of these endotypes when establishing experimental outcomes in epidemiological studies could allow for increased precision when determining exposure-outcome associations and engaging in more focused follow-up mechanistic investigations.

Inflammatory Markers and Genetic Polymorphisms in Workers Exposed to Flour Dust

OBJECTIVE

The aim of this study is to evaluate inflammatory markers and pro-inflammatory CD14 and Toll-like Receptor 4 (TLR4) polymorphisms in workers exposed to flour dust.

METHODS

Polymorphisms in TLR4 and CD14 were identified in our study population of 167 workers that included 63 healthy subjects (HS), 45 atopic subjects (A), and 59 subjects diagnosed clinically with occupational asthma/rhinitis (OAR). Endpoint measures in this study included fractional exhaled nitric oxide and serum concentrations of interleukin IL-6, IL-8, and tumor necrosis factor-alpha (TNF-α).

RESULTS

We identified a polymorphism in CD14 (rs2569190) that may be differentially expressed (P = 0.06). IL-6 concentrations in the serum were significantly higher in the A and OAR groups (P < 0.01) than in subjects in the HS group, while IL-8 concentrations were significantly elevated only in the OAR group (P < 0.01). Interestingly, TNF-α concentrations in the OAR group were significantly reduced when compared with subjects in the HS group (P < 0.01).

CONCLUSION

Cytokines are likely a defensive response in atopic and healthy workers. A protective genotype is hypothesized for occupational asthma.

Regulatory T cells in allergic diseases

The pathogenesis of allergic diseases entails an ineffective tolerogenic immune response to allergens. Regulatory T (Treg) cells play a key role in sustaining immune tolerance to allergens, yet mechanisms by which Treg cells fail to maintain tolerance in patients with allergic diseases are not well understood. We review current concepts and established mechanisms regarding how Treg cells regulate different components of allergen-triggered immune responses to promote and maintain tolerance. We will also discuss more recent advances that emphasize the "dual" functionality of Treg cells in patients with allergic diseases: how Treg cells are essential in promoting tolerance to allergens but also how a proallergic inflammatory environment can skew Treg cells toward a pathogenic phenotype that aggravates and perpetuates disease. These advances highlight opportunities for novel therapeutic strategies that aim to re-establish tolerance in patients with chronic allergic diseases by promoting Treg cell stability and function.

No Association Between -159C/T Polymorphism of the CD14 Gene and Asthma Risk: a Meta-Analysis of 36 Case-Control Studies

Numerous studies have evaluated the association between -159C/T polymorphism of the CD14 gene and asthma risk; however, these studies have yielded inconsistent results. We performed meta-analyses to investigate the association between CD14-159C/T polymorphism and asthma risk. Studies were identified from PubMed, Embase, and two Chinese databases. Odds ratios (ORs) with 95 % confidence interval (CI) were used to evaluate the strength of association. Thirty-six studies were collected for meta-analysis, which involved 6954 cases and 7525 controls. In the overall populations, no significant association between the CD14-159C/T polymorphism and asthma risk was found for the dominant (OR = 0.90, 95 % CI = 0.81-1.01, P = 0.08) or other models; stratified analyses indicated that the CD14-159C/T polymorphism was not associated with asthma risk in Caucasians or Asians or adults or children. Among the atopic asthma populations, no significant results were observed in the all-combined or subgroup analyses. This meta-analysis demonstrates that the CD14-159C/T polymorphism may not be a risk factor for asthma.

Microbiome and its impact on gastrointestinal atopy

The prevalence of allergic conditions has continuously increased in the last few decades in Westernized countries. A dysbiotic gut microbiome may play an important role in the development of allergic diseases. Genetic, environmental, and dietary factors may alter the commensal microbiota leading to inflammatory dysregulation of homeostasis. Murine and human studies have begun to elucidate the role of the microbiota in the pathogenesis of atopic diseases including asthma, atopic dermatitis, and food allergies. However, the role of the microbiome in most eosinophilic gastrointestinal diseases (EGIDs) is not yet known. This review provides an overview of what is currently known about the development of tolerance from both molecular and clinical standpoints. We also look at the gut-specific microbiome and its role in atopic conditions with the hope of applying this knowledge to the understanding, prevention, and treatment of EGIDs, particularly EoE.

Association of CD14 -159 (-260C/T) polymorphism and asthma risk: an updated genetic meta-analysis study

BACKGROUND

It has been reported that the cluster of differentiation 14 (CD14) gene -159C/T variant may be associated with asthma risk. However, some studies yielded conflicting results. Therefore, a comprehensive meta-analysis was designed to assess the precise association.

METHODS

A systematic search in PubMed, Embase (Ovid), China National Knowledge Internet (CNKI), and Wan fang databases was conducted up to August 15, 2015. Odds ratio (OR) and 95% confidence interval (CI) were used to pool the effect size. We used I to assess heterogeneity, and a funnel plot and Egger test to assess publication bias.

RESULTS

In total, 34 studies involving 15,641 subjects were included in this meta-analysis. There was a statistically significant association between CD14 -159C/T polymorphism and asthma risk observed in dominant model (TT+TC vs CC: OR = 0.86, 95% CI = 0.77-0.97, P = 0.012) and codominant model (TC vs CC: OR = 0.88, 95% CI = 0.78-0.99, P = 0.035) in adults. However, there may be no significant association between CD14 159C/T and atopic and nonatopic asthma risk.

CONCLUSION

In summary, the overall results suggested that the CD14 -159C/T variant may decrease the risk of asthma susceptibility in adults. However, no significant association between CD14 159C/T and atopic and nonatopic asthma susceptibility was identified. More studies with larger sample size are needed to validate the findings from this study.

Epigenetic modifications: mechanisms of disease and biomarkers of food allergy

The rise in IgE-mediated food allergy in recent times is the likely result of gene-environment interactions mediated via epigenetic pathways. As epigenetic modifications, including DNA methylation, are at the interface between the environment and the genome, they may be ideal biomarkers of modifiable disease pathways. High-throughput methylation profiling of immune cell subtypes or whole blood from patients allows the identification of disease specific epigenetic variants. If faithfully tracking with disease parameters, these 'signatures' may have clinical applications as biomarkers of disease or therapeutic response. Development of such tools will depend on a number of factors, including determining the most appropriate experimental approach, analysis methodology, patient groups, and informative target cells/tissues. Here we discuss these potential applications and their implications for food allergy practise.

Genome-wide genetic and transcriptomic investigation of variation in antibody response to dietary antigens

Increased immunoglobulin G (IgG) response to dietary antigens can be associated with gastrointestinal dysfunction and autoimmunity. The underlying processes contributing to these adverse reactions remain largely unknown, and it is likely that genetic factors play a role. Here, we estimate heritability and attempt to localize genetic factors influencing IgG antibody levels against food-derived antigens using an integrative genomics approach. IgG antibody levels were determined by ELISA in >1,300 Mexican Americans for the following food antigens: wheat gliadin; bovine casein; and two forms of bovine serum albumin (BSA-a and BSA-b). Pedigree-based variance components methods were used to estimate additive genetic heritability (h(2) ), perform genome-wide association analyses, and identify transcriptional signatures (based on 19,858 transcripts from peripheral blood lymphocytes). Heritability estimates were significant for all traits (0.15-0.53), and shared environment (based on shared residency among study participants) was significant for casein (0.09) and BSA-a (0.33). Genome-wide significant evidence of association was obtained only for antibody to gliadin (P = 8.57 × 10(-8) ), mapping to the human leukocyte antigen II region, with HLA-DRA and BTNL2 as the best candidate genes. Lack of association of known celiac disease risk alleles HLA-DQ2.5 and -DQ8 with antigliadin antibodies in the studied population suggests a separate genetic etiology. Significant transcriptional signatures were found for all IgG levels except BSA-b. These results demonstrate that individual genetic differences contribute to food antigen antibody measures in this population. Further investigations may elucidate the underlying immunological processes involved.

Beta2 adrenergic receptor (ADRβ2) haplotype pair (2/4) is associated with severe asthma

Background

β2 adrenergic receptor (ADRβ2) polymorphisms including ADRβ2+46G>A have been reported to cause adverse outcomes in mild asthmatics. The extent to which ADRβ2 polymorphisms and in particular their haplotypes contribute to severe asthma is unknown.

Objective

To determine the association of ADRβ2 polymorphisms and haplotypes with asthma severity.

Methods

Caucasians (n = 2979) were genotyped for 11 ADRβ2 polymorphisms. The cohort (mean age 39.6, 60% female) included 2296 non-asthmatics, 386 mild asthmatics, 172 moderate asthmatics and 125 severe asthmatics. Haplotype frequency and haplotype pair for each subject was determined using the PHASE algorithm.

Results

The three asthmatic cohorts were comparable in age and gender but were distinguishable from each other in terms of symptoms, spirometry, medication use and health care utilisation (p <0.001). None of the polymorphisms showed a genotypic or allelic association with asthma diagnosis or severity. Nine haplotypes were identified and no association was found with asthma diagnosis or severity per se. Haplotype pair 2/4 was associated with asthma severity (Trend Test, OR 1.42, p = 0.0008) but not with asthma per se. Prevalence of haplotype pair 2/2 appeared to decrease with asthma severity (Trend Test, OR 0.78, p = 0.067). Two new haplotypes were identified, occurring exclusively in asthmatics at a frequency of ≥ 1%. In addition, a positive association between carriage of ADRβ2 +523*C and increased risk of atopy was discovered.

Conclusions

ADRβ2 haplotype pair 2/4 is associated with severe asthma and is consistent with findings of poor bronchodilator response in mild asthmatics who are also haplotype 2/4.

Epistatic effects of multiple receptor genes on pathophysiology of asthma - its limits and potential for clinical application

To date, genome-wide association studies (GWAS) permit a comprehensive scan of the genome in an unbiased manner, with high sensitivity, and thereby have the potential to identify candidate genes for the prevalence or development of multifactorial diseases such as bronchial asthma. However, most studies have only managed to explain a small additional percentage of hereditability estimates, and often fail to show consistent results among studies despite large sample sizes. Epistasis is defined as the interaction between multiple different genes affecting phenotypes. By applying epistatic analysis to clinical genetic research, we can analyze interactions among more than 2 molecules (genes) considering the whole system of the human body, illuminating dynamic molecular mechanisms. An increasing number of genetic studies have investigated epistatic effects on the risk for development of asthma. The present review highlights a concept of epistasis to overcome traditional genetic studies in humans and provides an update of evidence on epistatic effects on asthma. Furthermore, we review concerns regarding recent trends in epistatic analyses from the perspective of clinical physicians. These concerns include biological plausibility of genes identified by computational statistics, and definition of the diagnostic label of 'physician-diagnosed asthma'. In terms of these issues, further application of epistatic analysis will prompt identification of susceptibility of diseases and lead to the development of a new generation of pharmacological strategies to treat asthma.

Genetic polymorphisms and associated susceptibility to asthma

As complex common diseases, asthma and allergic diseases are caused by the interaction of multiple genetic variants with a variety of environmental factors. Candidate-gene studies have examined the involvement of a very large list of genes in asthma and allergy, demonstrating a role for more than 100 loci. These studies have elucidated several themes in the biology and pathogenesis of these diseases. A small number of genes have been associated with asthma or allergy through traditional linkage analyses. The publication of the first asthma-focused genome-wide association (GWA) study in 2007 has been followed by nearly 30 reports of GWA studies targeting asthma, allergy, or associated phenotypes and quantitative traits. GWA studies have confirmed several candidate genes and have identified new, unsuspected, and occasionally uncharacterized genes as asthma susceptibility loci. Issues of results replication persist, complicating interpretation and making conclusions difficult to draw, and much of the heritability of these diseases remains undiscovered. In the coming years studies of complex diseases like asthma and allergy will probably involve the use of high-throughput next-generation sequencing, which will bring a tremendous influx of new information as well as new problems in dealing with vast datasets.

Food allergy: temporal trends and determinants

This review summarizes studies discussing temporal trends in the prevalence of food allergy as well as potential factors associated with the development of food allergy. In addition, we will address the potential hypotheses accounting for the apparent increase in food allergy prevalence. Studies suggest increased prevalence of food allergy. However, relatively little is known about its pathogenesis. This review aims to assess temporal trends in the prevalence of food allergy and discuss potential genetic, environmental, and demographic determinants. The search strategy examined the medical literature database MEDLINE (using PubMed) for the time period of January 1, 2002 to January 31, 2012. In recent decades, the prevalence of food allergy in general has increased by 0.60 % [95 % confidence interval (CI), 0.59 %-0.61 %] and the prevalence of peanut allergy by 0.027 % (95 % CI, 0.026 %-0.028 %), but it has now likely stabilized in developed countries. Genes, the environment, and demographic characteristics play a role in the pathogenesis of food allergy. Numerous environmental and demographic factors as well as gene-environment interactions may account for this increase in prevalence, but further studies are required to tease out their relative contribution.

Factors that predict the clinical reactivity and tolerance in children with cow's milk allergy

BACKGROUND

Specific IgE (sIgE) may be used for the diagnosis of cow's milk allergy (CMA) and as a guide to perform food challenge tests in patients with CMA. The effect of genetic variants on the prognosis of food allergy is largely unknown.

OBJECTIVE

To examine the performance of sIgE analysis and the utility of the genetic variants of CD14, STAT6, IL13, IL10, SPINK5, and TSLP in predicting the clinical course in children with CMA.

METHODS

Serum sIgE levels of 94 children who underwent open food challenges and 54 children with anaphylaxis due to cow's milk (CM) were retrospectively analyzed between January 2002 and May 2009. The genetic polymorphisms were determined in 72 children.

RESULTS

A total of 148 children were followed up for a median of 3.5 years, and 42 of the 94 challenge results were positive. The probability curves with 95% decision points were 2.8 kU/L for younger than 1 year, 11.1 for younger than 2 years, 11.7 for younger than 4 years, and 13.7 for younger than 6 years. Sixty-six children outgrew CMA during follow-up. Children with initial an CM sIgE level less than 6 kU/L outgrew CMA earlier than children with an initial CM sIgE level of 6 kU/L or higher (P < .001). The age of tolerance development for CM was significantly higher in children with the GG genotype at rs324015 of the STAT6 gene compared with those with the AA+AG genotype (2 years [range, 1.5-3.9 years] vs 1.2 years [range, 1.0-2.2 years]) (P = .02).

CONCLUSION

The decision points of sIgE obtained in different age groups may help to determine the likelihood of clinical reactivity more precisely. The results suggest that sIgE levels and STAT6 gene variants may be important determinants to predict longer persistence of CMA.

A microbiota signature associated with experimental food allergy promotes allergic sensitization and anaphylaxis

BACKGROUND

Commensal microbiota play a critical role in maintaining oral tolerance. The effect of food allergy on the gut microbial ecology remains unknown.

OBJECTIVE

We sought to establish the composition of the gut microbiota in experimental food allergy and its role in disease pathogenesis.

METHODS

Food allergy-prone mice with a gain-of-function mutation in the IL-4 receptor α chain (Il4raF709) and wild-type (WT) control animals were subjected to oral sensitization with chicken egg ovalbumin (OVA). Enforced tolerance was achieved by using allergen-specific regulatory T (Treg) cells. Community structure analysis of gut microbiota was performed by using a high-density 16S rDNA oligonucleotide microarrays (PhyloChip) and massively parallel pyrosequencing of 16S rDNA amplicons.

RESULTS

OVA-sensitized Il4raF709 mice exhibited a specific microbiota signature characterized by coordinate changes in the abundance of taxa of several bacterial families, including the Lachnospiraceae, Lactobacillaceae, Rikenellaceae, and Porphyromonadaceae. This signature was not shared by similarly sensitized WT mice, which did not exhibit an OVA-induced allergic response. Treatment of OVA-sensitized Il4raF709 mice with OVA-specific Treg cells led to a distinct tolerance-associated signature coincident with the suppression of the allergic response. The microbiota of allergen-sensitized Il4raF709 mice differentially promoted OVA-specific IgE responses and anaphylaxis when reconstituted in WT germ-free mice.

CONCLUSION

Mice with food allergy exhibit a specific gut microbiota signature capable of transmitting disease susceptibility and subject to reprogramming by enforced tolerance. Disease-associated microbiota may thus play a pathogenic role in food allergy.

Single nucleotide polymorphisms (SNPs) in key cytokines may modulate food allergy phenotypes

Single nucleotide polymorphisms (SNPs) can play a direct or indirect role in phenotypic expression in food allergy pathogenesis. Our goal was to quantitate the expression of SNPs in relevant cytokines that were expressed in food allergic patients. SNPs in cytokine genes IL-4 and IL-10 are known to be important in IgE generation and regulation. We examined IL-4 (C-590T), IL-4Rα (1652A/G) and IL-10 (C-627A) SNPs using real-time PCR followed by restriction fragment length polymorphism (RFLP) analysis. Our results show that the AA, AG and GG genotypes for IL-4Rα (1652A/G) polymorphisms were statistically different in radioallergosorbent test (RAST) positive versus negative patients, and although no statistically significant differences were observed between genotypes in the IL-4 (C-590T) and IL-10 (C-627A) SNPs, we observed a significant decrease in IL-4 (C-590T) gene expression and increase in IL-4Rα (1652A/G) and IL-10 (C-627A) gene expression between RAST(+) versus RAST(-) patients, respectively. We also observed significant modulation in the protein expression of IL-4 and IL-10 in the serum samples of the RAST(+) patients as compared to the RAST(-) patients indicating that changes in SNP expression resulted in altered phenotypic response in these patients.

Early life precursors, epigenetics, and the development of food allergy

Food allergy (FA), a major clinical and public health concern worldwide, is caused by a complex interplay of environmental exposures, genetic variants, gene-environment interactions, and epigenetic alterations. This review summarizes recent advances surrounding these key factors, with a particular focus on the potential role of epigenetics in the development of FA. Epidemiologic studies have reported a number of nongenetic factors that may influence the risk of FA, such as timing of food introduction and feeding pattern, diet/nutrition, exposure to environmental tobacco smoking, prematurity and low birth weight, microbial exposure, and race/ethnicity. Current studies on the genetics of FA are mainly conducted using candidate gene approaches, which have linked more than 10 genes to the genetic susceptibility of FA. Studies on gene-environment interactions of FA are very limited. Epigenetic alteration has been proposed as one of the mechanisms to mediate the influence of early life environmental exposures and gene-environment interactions on the development of diseases later in life. The role of epigenetics in the regulation of the immune system and the epigenetic effects of some FA-associated environmental exposures are discussed in this review. There is a particular lack of large-scale prospective birth cohort studies that simultaneously assess the interrelationships of early life exposures, genetic susceptibility, epigenomic alterations, and the development of FA. The identification of these key factors and their independent and joint contributions to FA will allow us to gain important insight into the biological mechanisms by which environmental exposures and genetic susceptibility affect the risk of FA and will provide essential information to develop more effective new paradigms in the diagnosis, prevention, and management of FA.

The HLA-DRB1 Polymorphism is Associated With Atopic Dermatitis, but not Egg Allergy in Korean Children

Purpose

We investigated whether particular HLA-DRB1 polymorphisms contribute to egg allergy development in Korean children with atopic dermatitis (AD).

Methods

HLA-DRB1 alleles were determined by PCR-sequence-specific oligonucleotide (SSO) and PCR-single-strand conformation polymorphism (SSCP) methods in 185 patients with AD and 109 normal control (NC) subjects. AD patients were divided into two groups: 1) AD with egg allergy, consisting of 96 patients with egg allergies as determined by egg-specific immunoglobulin E (IgE) reactivity; and 2) AD without egg allergy, consisting of 89 patients without egg allergies. HLA-DRB1 alleles were classified into functional groups (A, De, Dr, E, Q, R, a). HLA-DRB1 phenotype and functional group frequencies in the AD, AD with egg allergy, and AD without egg allergy groups were compared with those in the NC group.

Results

The frequency of DRB1^*08:02 was decreased in the AD with egg allergy group compared with the AD without egg allergy group (2.1% vs. 10.1%, P=0.021), and DRB1^*15:01 was increased in the AD with egg allergy group compared with the AD without egg allergy group (22.9% vs. 11.2%, P=0.036). However, significance was lost after Bonferroni correction. HLA-DRB1^*11:01 had a significantly higher frequency in AD patients compared with NCs (12.4% vs. 1.8%, corrected P=0.048) and was regarded as a susceptibility factor associated with AD. DRB1^*08:03 was decreased in AD patients compared with NCs (10.8% vs. 19.3%, P=0.043). HLA-DRB1 functional group 'a', which includes DRB1^*15:01, seemed to be associated with the development of egg allergy in AD (P=0.033), but this result was not significant after Bonferroni correction.

Conclusions

HLA-DRB1 polymorphism is not associated with egg allergy, but HLA-DRB1^*11:01 is associated with AD in Korean children.

Intestinal epithelial barrier dysfunction in food hypersensitivity

Intestinal epithelial barrier plays a critical role in the maintenance of gut homeostasis by limiting the penetration of luminal bacteria and dietary allergens, yet allowing antigen sampling for the generation of tolerance. Undigested proteins normally do not gain access to the lamina propria due to physical exclusion by tight junctions at the cell-cell contact sites and intracellular degradation by lysosomal enzymes in enterocytes. An intriguing question then arises: how do macromolecular food antigens cross the epithelial barrier? This review discusses the epithelial barrier dysfunction in sensitized intestine with special emphasis on the molecular mechanism of the enhanced transcytotic rates of allergens. The sensitization phase of allergy is characterized by antigen-induced cross-linking of IgE bound to high affinity FcεRI on mast cell surface, leading to anaphylactic responses. Recent studies have demonstrated that prior to mast cell activation, food allergens are transported in large quantity across the epithelium and are protected from lysosomal degradation by binding to cell surface IgE and low-affinity receptor CD23/FcεRII. Improved immunotherapies are currently under study including anti-IgE and anti-CD23 antibodies for the management of atopic disorders.

Pathways activated during human asthma exacerbation as revealed by gene expression patterns in blood

BACKGROUND

Asthma exacerbations remain a major unmet clinical need. The difficulty in obtaining airway tissue and bronchoalveolar lavage samples during exacerbations has greatly hampered study of naturally occurring exacerbations. This study was conducted to determine if mRNA profiling of peripheral blood mononuclear cells (PBMCs) could provide information on the systemic molecular pathways involved during asthma exacerbations.

METHODOLOGY/PRINCIPAL FINDINGS

Over the course of one year, gene expression levels during stable asthma, exacerbation, and two weeks after an exacerbation were compared using oligonucleotide arrays. For each of 118 subjects who experienced at least one asthma exacerbation, the gene expression patterns in a sample of peripheral blood mononuclear cells collected during an exacerbation episode were compared to patterns observed in multiple samples from the same subject collected during quiescent asthma. Analysis of covariance identified genes whose levels of expression changed during exacerbations and returned to quiescent levels by two weeks. Heterogeneity among visits in expression profiles was examined using K-means clustering. Three distinct exacerbation-associated gene expression signatures were identified. One signature indicated that, even among patients without symptoms of respiratory infection, genes of innate immunity were activated. Antigen-independent T cell activation mediated by IL15 was also indicated by this signature. A second signature revealed strong evidence of lymphocyte activation through antigen receptors and subsequent downstream events of adaptive immunity. The number of genes identified in the third signature was too few to draw conclusions on the mechanisms driving those exacerbations.

CONCLUSIONS/SIGNIFICANCE

This study has shown that analysis of PBMCs reveals systemic changes accompanying asthma exacerbation and has laid the foundation for future comparative studies using PBMCs.

Association of CD14 -260 (-159) C>T and asthma: a systematic review and meta-analysis

Background

Asthma is a phenotypically diverse disease with genetic susceptibility. A single nucleotide polymorphism (SNP) in the CD14 gene at position -260 (also known as -159) C>T has been inconsistently associated with asthma. The aim of this study was to estimate the combined likelihood of developing asthma given the CD14 -260C>T genotype.

Methods

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, a systematic search and meta-analysis of the literature was conducted to estimate the association between this SNP and asthma. Planned subgroup analyses were performed to detect potential sources of heterogeneity from selected study characteristics. Post-hoc sensitivity analysis was performed to identify studies exerting excessive influence on among-study heterogeneity and combined effects.

Results

Meta-analysis of 23 studies yielded a non-significant overall association with high heterogeneity across studies. After restricting analysis to studies using atopic asthma and non-atopic non-asthma case-control phenotypes and excluding studies influencing heterogeneity, the genotype-specific odds ratios (ORs) suggested a codominant model. Carriers of the TT and CT genotypes were about 33% less likely (OR = 0.67, 95% CI: 0.54-0.84) and about 20% less likely (OR = 0.80, 95% CI: 0.66-0.95), respectively, to have atopic asthma compared to carriers of the CC genotype. Among-study heterogeneity may be explained by overly broad asthma phenotype definitions, gene-environment interactions, and gene-gene interactions.

Conclusions

A protective dose-response relationship between the CD14 -260T allele and atopic asthma susceptibility was observed. These results demonstrate the importance of precisely specified case-control groups as well as the need to assess interactions in the investigation of complex diseases such as asthma.

Heredity of food allergies in an unselected child population: an epidemiological survey from Finland

The heredity of food allergies (FA) has not previously been addressed in a large unselected child population. Our target population comprised all children born from April 2001 to March 2006 resident in one province of South-East Finland (n c. 6000), as identified from the national population register. In a questionnaire survey conducted in 2005-2006, data were obtained on allergic manifestations (FA symptoms, atopic rash, allergic asthma, hay fever/pollen allergy, or animal allergy) in the biologic parents of 3800 children (64% of the total). Concurrently with the survey but independently of it, results of specific immunoglobulin E antibodies (sIgE), skin prick tests (SPT), and open food challenges (OFC) in the offspring were collected from patient records throughout the province. Up to the age of 4 yr, the incidences of any positive FA test, a positive SPT or sIgE for food items, and a positive OFC in these children were threefold higher if both parents reported having an allergic manifestation and twofold higher if either mother or father had such a manifestation when compared with children whose parents did not report any of these conditions. The estimated risk of any positive FA test increased by a factor of 1.3 (95% CI 1.2-1.4) for each additional allergic manifestation in the parents. Positive FA tests in the offspring were relatively strongly associated with the reports of allergic phenotypes and the number of these phenotypes in their biologic parents.

The -159C/T polymorphism in the CD14 gene and the risk of asthma: a meta-analysis

The -159C/T polymorphism in the CD14 gene has been implicated in susceptibility to asthma, but a large number of studies have reported inconclusive results. The aim of this study is to investigate the association between the -159C/T polymorphism in the CD14 gene and the risk of asthma by meta-analysis. We searched Pubmed, Embase, CNKI database, Wanfang database, Weipu database, and Chinese Biomedical database, covering all publications (last search been performed on April 20, 2010). Statistical analysis was performed by using the softwares Revman 4.2 and STATA 10.0. A total of 17 case-control studies in 17 articles (4,246 cases and 3,631 controls) were included in this meta-analysis. There was no association between this polymorphism and asthma risk in combined analyses (odds ratio (OR) = 0.86 and 95% confidence interval (95% CI) = 0.72-1.02, P = 0.09 for TC + TT vs. CC). In the subgroup analysis by age, ethnicity, and atopic status, no significant associations of asthma risks were obtained from age groups, ethnic groups, and atopic groups for TC + TT vs. CC comparison. For atopic population, significant decreased atopic asthma risks were found among Asian population (OR = 0.69, 95% CI 0.52-0.92, P = 0.01) and children population (OR = 0.69, 95% CI 0.54-0.89, P = 0.0004) for TC + TT vs. CC comparison. This meta-analysis suggests that CD14 is a candidate gene for atopic asthma susceptibility. The -159C/T polymorphism may be a protective factor for atopic asthma in Asian and children. More studies are needed to validate these associations.

Modulation of asthma by endotoxin

Asthma is a common inflammatory disease triggered by both allergic and non-allergic stimuli. The most common risk factor in the development of asthma is induction of IgE against indoor allergens and imbalance in the T-helper type 1 (Th1) and Th2 with skewing towards Th2 response. Interplay of genetic and environmental factors is involved in induction and propagation of asthma. Endotoxin is a common environmental pollutant and elicits a Th1 response. The amount of endotoxin varies with several factors but of significant interest has been the role of pets. Endotoxin not only protects against the development of asthma but also enhances an already established inflammation. The difference of outcomes is likely not only due to the time and dose of exposure but also as we discuss the variable interaction of genes with environment. We focus on studies since 2001 that have explored the role of endotoxin in asthma and the gene-environment interactions of the endotoxin effect.

Genetic polymorphism of manganese superoxide dismutase is associated with childhood asthma

OBJECTIVE

Cellular defenses against allergens and reactive oxygen species (ROS) exposure are critical in the pathogenesis of asthma. CD14 is a receptor for various bacterial products, such as lipopolysaccharides (LPS), and is also a mediator of inflammatory processes. Manganese superoxide dismutase (MnSOD) is an ROS scavenger, and myeloperoxidase (MPO) can convert hydrogen peroxide into hypochlorous acid; thus, they are considered to be involved in inflammatory defense. The authors conducted a case-control study to evaluate the susceptibility to childhood asthma based on CD14, MnSOD, and MPO genes.

METHODS

The CD14 -260, MnSOD -9, and MPO -463 genotypes were identified by polymerase chain reactions for 116 asthmatic children and 232 healthy controls. Questionnaires were administered to obtain demographic characteristics. Allergen testing used common Taiwanese aeroallergens.

RESULTS

A higher level of parental education, family history of asthma, incense burning at home, allergen-test positive, and the MnSOD Val-Ala/Ala-Ala genotypes (matched relative risk = 2.0; 95% confidence interval = 1.0-4.2) were significantly associated with childhood asthma. Interactions between CD14, MnSOD, MPO genotypes and allergy status were significantly associated with asthma risk in these children (all p <.001). Furthermore, atopic cases with MnSOD Val-Ala/Ala-Ala (log eosinophil 2.66/mm(3), log total serum immunoglobulin E [IgE] 2.48 IU/ml) or Val-Val (log eosinophil 2.61/mm(3), log total serum IgE 2.63 IU/ml) genotypes had elevated eosinophil counts and total serum IgE levels as compared to nonatopic cases with MnSOD Val-Val genotype (log eosinophil 2.27/mm(3), log total serum IgE 1.83 IU/ml).

CONCLUSIONS

Susceptible MnSOD genotypes might modulate the development of asthma in Taiwanese children.

CD14, a key candidate gene associated with a specific immune response to cockroach

BACKGROUND

Sensitization to cockroach allergen is one of the strongest predictors of asthma morbidity, especially among African Americans.

OBJECTIVE

Our aims were to determine the genomic basis of cockroach sensitization and the specific response to cockroach antigen.

METHODS

We investigated the Th1/Th2 cytokine profile of co-cultured plasmacytoid dendritic cells (pDCs) and CD4+ T cells and the 'transcript signature' of the immune response to cockroach antigen using high-throughput expression profiling of co-cultured cells.

RESULTS

We observed significantly elevated levels of IL-13, IL-10, and TNF-alpha, but undetectable levels of IL-12p70 and IFN-alpha, when cultures were exposed to crude cockroach antigen. A significant difference was observed for IL-13 between cockroach-allergic and non-allergic individuals (P=0.039). Microarray analyses demonstrated a greater response at 48 h compared with 4 h, with 50 genes being uniquely expressed in cockroach antigen-treated cells, including CD14, S100A8, CCL8, and IFI44L. The increased CD14 expression was further observed in purified pDCs, human monocytic THP-1 cells, and the supernatant of co-cultured pDCs and CD4+ T cells on exposure to cockroach extract. Furthermore, the most differential expression of CD14 between cockroach allergy and non-cockroach allergy was only observed among individuals with the CC 'high-risk' genotype of the CD14-260C/T. Ingenuity Pathways Analysis analyses suggested the IFN signalling as the most significant canonical pathway.

CONCLUSION

Our results suggest that these differentially expressed genes, particularly CD14, and genes in the IFN signalling pathway may be important candidates for further investigation of their role in the immune response to cockroach allergen.

Genetics of food allergy

PURPOSE OF REVIEW

Food allergy, a growing clinical and public health problem in the United States and worldwide, is likely determined by multiple environmental and genetic factors. The purpose of this review is to summarize recent advances in food allergy genetic research.

RECENT FINDINGS

There is compelling evidence that genetic factors may play a role in food allergy. However, the specific genetic loci that may modulate individual risk of food allergy remain to be identified. To date, only a limited number of candidate gene association studies of food allergy have been reported. Polymorphism(s) in nine genes have been associated with the incidence of food allergy or food allergy severity in at least one study. But most of these findings remain to be replicated in independent populations. In contrast, there are considerable advances in genetics of other allergic diseases such as asthma and atopic dermatitis. Although asthma and atopic dermatitis often coexist with food allergy, the relevance of their candidate genes to food allergy remains to be evaluated.

SUMMARY

Genetics in food allergy is a promising research area but is still in its infancy. More studies are needed to dissect susceptible genes of food allergy. A genome-wide association approach may serve as a powerful tool to identify novel genes related to food allergy. Furthermore, the role of gene-environment interaction, gene-gene interaction, and epigenetics in food allergy remains largely unexplored. Given the complex nature of food allergy, future studies need to integrate environment, genomics, and epigenomics in order to better understand the multifaceted etiology and biological mechanisms of food allergy.

The role of lipopolysaccharide in the development of atopy in humans

Atopy is a highly prevalent condition and remains the single biggest risk factor for asthma. Although atopy has a heritable component, the time frame of the increase in the prevalence indicates that it is not due to genetic factors alone. The relationship between allergen exposure and sensitization is complex. Lipopolysaccharide (LPS) and its bioactive moiety endotoxin are common to all gram-negative bacteria, and have been used as a surrogate of microbial load. Endotoxin can be readily measured in dust collected from homes. Some studies have demonstrated a clear inverse dose-response relationship between exposure to endotoxin and the risk of atopy but this finding has not been reproduced in all studies. Our innate immune system recognizes LPS readily via the LPS signal transduction pathway, which has the trimolecular complex of CD14/TLR4/MD2 at the core. A common single-nucleotide polymorphism in the promoter region of CD14 rs2569190 C to T (CD14/-260 or CD14/-159) has been associated with elevated sCD14. Although early studies suggested that this variant was associated with more severe atopy, this finding was not uniformly replicated. It has now been demonstrated in four independent populations that high exposure to endotoxin in the domestic environment is protective against the development of atopy, but only among carriers of the C allele, that is, the environmental exposure is only relevant when taken in the context of the genotype. Furthermore, this interaction is biologically plausible. We propose that neither the environmental exposure nor the genotype in isolation is sufficient to cause complex diseases like asthma and atopy, but disease results from the one acting in the context of the other, of which CD14 and endotoxin is one example contributing to the risk for atopy.

Genetic variants in the mannose receptor gene (MRC1) are associated with asthma in two independent populations

Mannose receptor is a member of the C-type lectin receptor family involved in pathogen molecular pattern recognition and thought to be critical in shaping host immune responses and maintaining homeostasis. The aim of this study was to investigate potential associations of genetic variants in the MRC1 gene with asthma in two independent populations. Seven single-nucleotide polymorphisms (SNPs; rs2477637, rs2253120, rs2477631, rs2477664, rs692527, rs1926736, and rs691005) in the MRC1 gene locus were genotyped and evaluated regarding association with asthma in 870 unrelated Japanese subjects (446 asthmatics, 424 controls). The same markers were validated in 176 unrelated African-American subjects (86 asthmatics, 90 controls). Suggestive evidence of association between five SNPs (rs2477637, rs2253120, rs2477664, rs692527, and rs1926736) and asthma was observed in the analysis of the Japanese population independent of sex, age, smoking status, and atopic status. SNPs rs692527 and rs691005 showed significant association with asthma in the African-American population. Haplotypes containing two linked SNPs (rs692527 and rs1926736) were significantly associated with asthma in both Japanese and African-American populations. Our results suggest that sequence variations in the MRC1 gene are associated with the development of asthma in two independent and ethnically diverse populations.

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) in inflammatory disorders

Toll-like receptors (TLRs) and Nod-like receptors (NLRs) are two major forms of innate immune sensors, which provide immediate responses against pathogenic invasion or tissue injury. Activation of these sensors induces the recruitment of innate immune cells such as macrophages and neutrophils, initiates tissue repair processes, and results in adaptive immune activation. Abnormalities in any of these innate sensor-mediated processes may cause excessive inflammation due to either hyper responsive innate immune signaling or sustained compensatory adaptive immune activation. Recent gene association studies appear to reveal strong associations of NLR gene mutations and development of several idiopathic inflammatory disorders. In contrast, TLR polymorphisms are less often associated with inflammatory disorders. Nevertheless, TLRs are up-regulated in the affected tissue of most inflammatory disorders, suggesting TLR signaling is involved in the pathogenesis of chronic and/or idiopathic inflammatory disorders. NLR signaling results in the formation of a molecular scaffold complex (termed an inflammasome) and orchestrates with TLRs to induce IL-1beta and IL-18, both of which are important mediators in the majority of inflammatory disorders. Therefore, understanding the roles of TLRs and NLRs in the pathogenesis of chronic and idiopathic inflammatory disorders may provide novel targets for the prevention and/or treatment of many common and uncommon diseases involving inflammation.

Associations of functional NLRP3 polymorphisms with susceptibility to food-induced anaphylaxis and aspirin-induced asthma

BACKGROUND

NLR family, pyrin domain containing 3 (NLRP3), controls the activity of inflammatory caspase-1 by forming inflammasomes, which leads to cleavage of the procytokines IL-1beta and IL-18. Recent studies have shown associations of human NLRP3 polymorphisms with susceptibility to various inflammatory diseases; however, the association with allergic diseases remains unclear.

OBJECTIVE

We sought to examine whether NLRP3 polymorphisms are associated with susceptibility to food allergy, food-induced anaphylaxis, and aspirin-induced asthma (AIA).

METHODS

We selected 15 tag single nucleotide polymorphisms (SNPs) of NLRP3 and conducted association analyses of NLRP3 using 574 and 1279 samples for food allergy and AIA, respectively. We further performed functional analyses of the susceptible SNPs.

RESULTS

Two NLRP3 SNPs (rs4612666 and rs10754558) were significantly associated with susceptibility to food-induced anaphylaxis (P = .00086 and P = .00068, respectively). The NLRP3 haplotype of the 2 SNPs also showed a significant association (P = .000098). We could confirm the association with susceptibility to another hypersensitivity phenotype, AIA (rs4612666, P = .0096). Functional analysis revealed that the risk alleles of rs4612666 and rs10754558 increased the enhancer activity of NLRP3 expression and NLRP3 mRNA stability, respectively.

CONCLUSION

Our results indicate that the NLRP3 SNPs might play an important role in the development of food-induced anaphylaxis and AIA in a gain-of-function manner. Further research on the NLRP3 inflammasome will contribute to the development of novel diagnostic and therapeutic methods for food-induced anaphylaxis and AIA.

Factors influencing the incidence and prevalence of food allergy

Food allergy is an increasing problem in Europe and elsewhere and severe reactions to food are also becoming more common. As food allergy is usually associated with other forms of allergic sensitisation it is likely that many risk factors are common to all forms of allergy. However the potential severity of the disease and the specific public heath measures required for food allergy make it important to identify the specific risk factors for this condition. Food allergy is unusual in that it often manifests itself very early in life and commonly remits with the development of tolerance. Hypotheses that explain the distribution of food allergy include specific genetic polymorphisms, the nature of the allergens involved and the unique exposure to large quantities of allergen through the gut. Progress has been made in developing more specific and testable hypotheses but the evidence for any of these is still only preliminary. Further collaborative research is required to develop an appropriate public health response to this growing problem.

IL-10 gene polymorphism, but not TGF-beta1 gene polymorphisms, is associated with food allergy in a Japanese population

The regulatory IL-10 and TGF-beta1 cytokine gene polymorphisms have been associated with allergic diseases in different populations, like Caucasian, Chinese and Indians. We investigated the association between the polymorphisms IL-10 A-1082G, C-819T, C-627A and TGF-beta1 T+869C, G+915C, C-509T and food allergy in Japanese children. One hundred and eleven children with food allergy and 115 atopic control children without food allergy were recruited. DNA samples from these subjects were genotyped by using PCR. The odds ratio of IL-10 -1082 AA genotype was 2.5 (95% CI, 1.0-6.4) for food allergy risk when compared with atopic control subjects (p = 0.03). There were no significative differences in the frequency of TGF-beta1 gene polymorphisms between both groups. Our results indicate that IL-10 A-1082G gene polymorphism is associated with food allergy susceptibility in atopic Japanese children.

Does the relationship between IgE and the CD14 gene depend on ethnicity?

This review considers the data from studies analysing associations between the CD14C-159T single nucleotide polymorphism (SNP) and asthmatic phenotypes and discusses the variability of the conclusions. By searching PubMed and EMBASE for articles on CD14C-159T -related population or family-based association studies, 47 were identified up till September 2007. Collectively, the studies reviewed herein consistently showed population differences in frequencies of the alleles of the SNP, with African descent having the highest C allele frequencies, followed by Caucasians and Asians. The T allele of the SNP was associated with increased sCD14 in some studies but not in others. Inconsistently, the C allele, or even occasionally the T allele, was associated with atopic phenotypes in a population subgroup. There are several explanations for these inconsistencies, including lack of power, linkage disequilibrium, gene-gene interactions, population admixture and gene-environment interactions. If the SNP was associated with functional changes to the coded protein and thus modulating susceptibility to allergic disease, its effect may be modest and dependent on other co-existent, ethnicity-specific, genetic or environmental risk factors.

Familial aggregation of food allergy and sensitization to food allergens: a family-based study

BACKGROUND

The increasing prevalence of food allergy (FA) is a growing clinical and public health problem. The contribution of genetic factors to FA remains largely unknown.

OBJECTIVE

This study examined the pattern of familial aggregation and the degree to which genetic factors contribute to FA and sensitization to food allergens.

METHODS

This study included 581 nuclear families (2,004 subjects) as part of an ongoing FA study in Chicago, IL, USA. FA was defined by a set of criteria including timing, clinical symptoms obtained via standardized questionnaire interview and corroborative specific IgE cut-offs for > or =95% positive predictive value (PPV) for food allergens measured by Phadia ImmunoCAP. Familial aggregation of FA as well as sensitization to food allergens was examined using generalized estimating equation (GEE) models, with adjustment for important covariates including age, gender, ethnicity and birth order. Heritability was estimated for food-specific IgE measurements.

RESULTS

FA in the index child was a significant and independent predictor of FA in other siblings (OR=2.6, 95% CI: 1.2-5.6, P=0.01). There were significant and positive associations among family members (father-offspring, mother-offspring, index-other siblings) for total IgE and specific IgE to all the nine major food allergens tested in this sample (sesame, peanut, wheat, milk, egg white, soy, walnut, shrimp and cod fish). The estimated heritability of food-specific IgE ranged from 0.15 to 0.35 and was statistically significant for all the nine tested food allergens.

CONCLUSION

This family-based study demonstrates strong familial aggregation of FA and sensitization to food allergens, especially, among siblings. The heritability estimates indicate that food-specific IgE is likely influenced by both genetic and environmental factors. Together, this study provides strong evidence that both host genetic susceptibility and environmental factors determine the complex trait of IgE-mediated FA.

Gut eosinophilia in food allergy and systemic and autoimmune diseases

Eosinophilic gastroenteritis is a rare disease characterized by striking tissue eosinophilia in any layer of the gut wall; however, many diseases can cause increased gut eosinophilia. Allergic reactions to food are an important cause of gut eosinophilia. Not all adverse reactions to food are IgE mediated, and most cases of IgE-mediated food allergy do not have eosinophilic gastroenteritis. Parasitic, bacterial, and viral pathogens as well as certain systemic diseases such as vasculitis can cause gut eosinophilia. These heterogeneous conditions are reviewed in this article.

Discovering susceptibility genes for asthma and allergy

Asthma and asthma-related traits are complex diseases with strong genetic and environmental components. Rapid progress in asthma genetics has led to the identification of several candidate genes that are associated with asthma-related traits. Typically the phenotypic impact of each of these genes, including the ones most often replicated in association studies, is mild, but larger effects may occur when multiple variants synergize within a permissive environmental context. Despite the achievements made in asthma genetics formidable challenges remain. The development of novel, powerful tools for gene discovery, and a closer integration of genetics and biology, should help to overcome these challenges.

Host defense genes in asthma and sepsis and the role of the environment

PURPOSE OF REVIEW

There is growing evidence that innate immunity genes contribute to asthma pathogenesis. At the core of the innate immune response are ubiquitous, soluble fragments of bacterial lipopolysaccharide or endotoxin, and chronic exposure to domestic endotoxin has been shown to influence asthma severity. Asthmatic and atopic individuals are more sensitive to endotoxin than nonallergic individuals, suggesting a role for genetics in the innate immunity response, and the potential for gene-environment interactions. Variants in genes associated with classic innate immunity-related disorders, such as sepsis, may be unique candidates for asthma susceptibility.

RECENT FINDINGS

Candidate genes for asthma and allergic diseases co-associated with sepsis including innate immunity receptors and related molecules (CD14, TLR4 and AOAH) and novel genes such as MYLK provide good examples of pleitropic effects of innate immunity genes, where variants conferring risk to specific traits (i.e. sepsis) under one set of genetic and environmental circumstances confer a reduced risk in a different (but possibly related) clinical outcome (i.e. allergic asthma), and support the 'common variant/multiple disease' hypothesis.

SUMMARY

Collectively, these observations suggest a greater role for the innate immunity response in allergic asthma than previously assumed, and implicate host defense genes in disease pathology.

Toll-like receptors and airway inflammation

The respiratory tract opens to the external environment at the oral side edge, and the other edge of the respiratory tract connects to the closed space (alveoli), and so to preserve the sterility in the terminal respiratory tract is critical for protection against pathogens. The recognition machinery for the invasion of microbes is indispensable for the preservation of the sterility in the lungs. Our general understanding of how microbes are recognized by the innate immune system has increased considerably over the past several years, and the contribution of Toll-Like Receptors (TLRs) to innate immunity is now well documented. In the meantime, it has come to understand that many inflammatory processes may depend on TLR signaling, it has been considered to be involved in the pathogenesis of airway inflammatory diseases such as airway infections, bronchial asthma, and occupational airway diseases. In this review, we focus on physiological roles of TLRs in defense mechanisms of the airways, and pathophysiological roles on airway diseases.

Risk factors for the development of food allergy

Both genetic and environmental factors seem to predispose to the development of food allergy. A most notable factor is diet, particularly during infancy. Possible other factors include maternal diet during pregnancy and lactation, birth by cesarean section, exposure to tobacco smoke, multivitamin supplementation, and intake of antacids. It is important to identify and control such risk factors to reduce the development of food allergy.