Epigenomic variability is associated with age-specific naïve CD4 T cell response to activation in infants and adolescents

Childhood is a critical period of immune development. During this time, naïve CD4 (nCD4) T cells undergo programmed cell differentiation, mediated by epigenetic changes, in response to external stimuli leading to a baseline homeostatic state that may determine lifelong disease risk. However, the ontogeny of epigenetic signatures associated with CD4 T cell activation during key developmental periods are yet to be described. We investigated genome-wide DNA methylation (DNAm) changes associated with nCD4 T activation following 72 h culture in media+anti-CD3/CD28 beads in healthy infants (aged 12 months, n = 18) and adolescents (aged 10-15 years, n = 15). We integrated these data with transcriptomic and cytokine profiling from the same samples. nCD4 T cells from both age groups show similar extensive epigenetic reprogramming following activation, with the majority of genes involved in the T cell receptor signaling pathway associated with differential methylation. Additionally, we identified differentially methylated probes showing age-specific responses, that is, responses in only infants or adolescents, including within a cluster of T cell receptor (TCR) genes. These encoded several TCR alpha joining (TRAJ), and TCR alpha variable (TRAV) genes. Cytokine data analysis following stimulation revealed enhanced release of IFN-γ, IL-2 and IL-10, in nCD4 T cells from adolescents compared with infants. Overlapping differential methylation and cytokine responses identified four probes potentially underpinning these age-specific responses. We show that DNAm in nCD4T cells in response to activation is dynamic in infancy and adolescence, with additional evidence for age-specific effects potentially driving variation in cytokine responses between these ages.

Out-of-hospital health care costs of childhood food allergy in Australia: A population-based longitudinal study

BACKGROUND

Australia has one of the highest prevalence of childhood food allergy in the world, but there are no data on its economic burden in Australia.

METHODS

We used data from the HealthNuts study, a population-based longitudinal study undertaken in Melbourne, Australia. Infants were recruited at age 12 months between Sept 2007 and Aug 2011 with food allergy diagnosed using oral food challenges. Health care costs of out-of-hospital services were collected through data linkage to Australia's universal health insurance scheme Medicare. Two-part model was used to compare costs after controlling for potential confounders.

RESULTS

2919 children were included, and 390 (13.4%) had challenge-confirmed food allergy at age 1 year. Compared with children without food allergy, children with food allergy had significantly higher costs for GP visits, specialist visits, tests, and prescriptions in the first four years of life. The total Medicare cost associated with food allergy from age 1 to 4 years was estimated to be AUD$889.7 (95% CI $566.1-$1188.3) or €411.0 (95% CI €261.5-€549.0) per child. This was projected into an annual Medicare cost of AUD$26.1 million (95% CI $20.1-$32.3 million) or €12.1 (95% CI €9.3-€14.9 million) based on population size in 2020.

CONCLUSIONS

Childhood food allergy causes considerable Medicare costs for out-of-hospital services in the first four years after birth in Australia. These findings can help anticipate the financial impact on the health care system associated with childhood food allergy, act as a useful costing resource for future evaluations, and inform management of childhood food allergy internationally.

Socioeconomic Determinants of Food Allergy Burden-A clinical introduction

OBJECTIVE

This review characterizes what is currently known about how prevalence, severity, distribution, and management of food allergy (FA) differs across socioeconomic strata and provides guidance for practicing clinicians about how to improve equity in research participation, healthcare delivery, and patient outcomes through a deeper understanding of the socioeconomic determinants of FA.

DATA SOURCES

Epidemiological and biomedical literature published prior to April 2022.

RESULTS

Socioeconomic status (SES) is a complex concept that not only encompasses economic resources (e.g., income, wealth) but also a person's social, economic and political power and standing, each of which can impact health. However, in many studies of individuals and families with FA, assessment of SES has been limited and often a respondent's membership within a racial and ethnic group is utilized as a proxy for low SES. As a whole, findings from US-population-based studies indicate a consistent trend: those who self-identify as non-Hispanic Black, and to a lesser extent other subpopulations who identify as being of non-White race and ethnicity, experience a greater burden of food-allergic sensitization and disease including higher rates of emergency health care utilization and food-induced anaphylactic fatality as compared to those identifying as White.

CONCLUSION

Reports of FA management and outcomes highlight inequities among specific low SES populations in the US. Clinicians can and should act to reduce inequities by engaging more diverse populations in clinical research, equitably implementing FA risk screening and prevention, thoughtfully utilizing emerging technologies to ameliorate disparities based on SES in healthcare delivery and outcomes, and advocating for social change.

Identification of vicilin, legumin and antimicrobial peptide 2a as macadamia nut allergens

Macadamia nut is an increasingly popular food item of a healthy diet. However, macadamia nut is also a potent allergenic food. To date, there is little information about the allergenic proteins involved. In this study, using sera from macadamia nut allergic individuals, four IgE-binding proteins were detected. Their identities were determined by tandem mass spectrometry with de novo sequencing. Three IgE-reactive proteins, the vicilin Mac i 1, the legumin Mac i 2 and the antimicrobial peptide 2a/Mac i 1 (28-76) were purified from the nut while the non-specific lipid transfer protein was produced as a recombinant in Pichia pastoris. IgE-binding assays using sera from well-characterized groups of tree nut and/or peanut allergic patients revealed that the allergens were mainly recognized by sera from macadamia nut allergic individuals. Hence, these newly discovered allergens will enable molecular diagnostics to identify patients at high risk of macadamia nut allergy.

Ana o 3 sIgE testing increases the accuracy of cashew allergy diagnosis using a two-step model

BACKGROUND

Measurement of cashew-specific IgE (sIgE) is often used to confirm sensitization but does not reliably diagnose clinical allergy. Ana o 3 is the dominant cashew allergen detected in 75-100% of patients with cashew allergy but not currently used in clinical practice.

OBJECTIVES

To determine if component-resolved diagnostics using specific IgE to the 2 S albumin from cashew, Ana o 3, improves the accuracy of diagnosing cashew allergy, thereby circumventing the need for an oral food challenge (OFC) in some patients.

METHODS

A population-based sample of 5276 children was recruited at age 1 year and followed up at age 6 years. Children with positive cashew skin prick test at age 6 underwent an OFC to clarify allergy status. Forty-seven children (mean age 5.02 ± 0.2) (33 cashew-allergic and 14 cashew-tolerant) had cashew sIgE and Ana o 3 sIgE quantified by ImmunoCAP System FEIA.

RESULTS

A cutoff of >0.32 kUA/L for Ana o 3 sIgE provided 95% specificity and 90% sensitivity and correctly identified 90% of clinical cashew allergy. At the same specificity, the sensitivity for cashew sIgE (>8.5 kUA/L) was only 26%. Sequential measurement of cashew sIgE followed by Ana o 3 sIgE diagnosed 90% of children with cashew allergy without the need for an OFC.

CONCLUSION

Ana o 3 sIgE testing provides higher diagnostic accuracy than cashew sIgE. Sequential measurement of cashew sIgE followed by Ana o 3 removed the need for a food challenge from 66% down to 12.8% (5-fold) of children compared with cashew sIgE testing alone.

The Exposome Approach in Allergies and Lung Diseases: Is It Time to Define a Preconception Exposome?

Emerging research suggests environmental exposures before conception may adversely affect allergies and lung diseases in future generations. Most studies are limited as they have focused on single exposures, not considering that these diseases have a multifactorial origin in which environmental and lifestyle factors are likely to interact. Traditional exposure assessment methods fail to capture the interactions among environmental exposures and their impact on fundamental biological processes, as well as individual and temporal factors. A valid estimation of exposure preconception is difficult since the human reproductive cycle spans decades and the access to germ cells is limited. The exposome is defined as the cumulative measure of external exposures on an organism (external exposome), and the associated biological responses (endogenous exposome) throughout the lifespan, from conception and onwards. An exposome approach implies a targeted or agnostic analysis of the concurrent and temporal multiple exposures, and may, together with recent technological advances, improve the assessment of the environmental contributors to health and disease. This review describes the current knowledge on preconception environmental exposures as related to respiratory health outcomes in offspring. We discuss the usefulness and feasibility of using an exposome approach in this research, advocating for the preconception exposure window to become included in the exposome concept.

552The lung function and airway inflammation markers associated with short-term pollen exposure- A systematic review

Background

Experimental challenge studies have shown that pollen can affect the lungs and airways. Here, we systematically reviewed community-based studies investigating outdoor pollen exposure, lung function and/or airway inflammation.

Methods

Four online databases were searched. The search strategy included terms relating to both exposure and outcomes. Inclusion criteria were studies published in English that were representative of the community. We only considered cross-sectional or short-term longitudinal studies which investigated pollen exposure by levels or season. Study quality assessment was performed using the Newcastle-Ottawa scale. Meta-analysis was conducted using random-effects models.

Results

We included 27 of 6,551 studies identified from the search. Qualitative synthesis indicated associations between pollen exposure and predominantly type-2 inflammation in both the upper and lower airways, but little evidence for lung function changes. People with ever asthma and/or seasonal allergic rhinitis (SAR) were at higher risk of such airway inflammation. Meta-analysis confirmed a positive relationship between pollen season and eosinophilic airway inflammation in people with ever SAR but the results between studies were highly variable. Heterogeneity was reduced after further subgrouping by age and the forest plots indicated that eosinophilic airway inflammation to outdoor pollen exposure increased with age.

Conclusion

Among people with ever asthma and ever SAR, exposure to increased ambient pollen triggers type-2 airway inflammation rather than a non-specific or innate inflammation.

Key messages

This review indicates pollen exposure influences predominantly type-2 airway inflammation, but little evidence on lung function.

357Infant pacifier sanitization and risk of food allergy: the Barwon Infant Study

Background

Environmental microbial exposure and human gut microbiota play a role in development of the immune system and susceptibility to food allergy. Pacifier use has been inconsistently associated with allergy, but the association between sanitization and food allergy is unknown. We investigated the association between infant pacifier use, with a consideration of sanitization, and food allergy at age 1 in the Barwon Infant Study (BIS).

Methods

Questionnaire data were collected prospectively from pregnant mothers from the Barwon region of south-east Australia at baseline and at infant ages 1, 6, and 12 months. Pacifier sanitization was defined as the joint exposure of a pacifier and cleaning methods (antiseptic, mouth, tap water, boiling). Challenge-proven food allergy was determined at age 1.

Results

Any pacifier use at 6 months was associated with food allergy (aOR, 1.94; 95% CI, 1.04-3.61), but not at other ages. This overall association was driven by the joint exposure pacifier-antiseptic use (aOR, 5.90; 95% CI, 2.18-15.97) compared to no pacifier use. Among pacifier users, pacifier-antiseptic was still associated with food allergy (aOR, 3.88; 95% CI, 1.55-9.72) when compared to pacifier-no antiseptic use. Further, increased use of pacifier-antiseptic at 0, 1 or 2 interviews over the first 6 months was associated with higher food allergy risk (ptrend=0.005).

Conclusions

Joint exposure to antiseptics and pacifiers at 6 months increased the odds of food allergy, showing a trend with increased use over time.

Key messages

This is the first report of pacifiers used with antiseptic being positively associated with challenge-proven food allergy.

Epigenetic programming underpins B-cell dysfunction in peanut and multi-food allergy

OBJECTIVE

Rates of IgE-mediated food allergy (FA) have increased over the last few decades, and mounting evidence implicates disruption of epigenetic profiles in various immune cell types in FA development. Recent data implicate B-cell dysfunction in FA; however, few studies have examined epigenetic changes within these cells.

METHODS

We assessed epigenetic and transcriptomic profiles in purified B cells from adolescents with FA, comparing single-food-allergic (peanut only), multi-food-allergic (peanut and ≥1 other food) and non-allergic (control) individuals. Adolescents represent a phenotype of persistent and severe FA indicative of a common immune deviation.

RESULTS

We identified 144 differentially methylated probes (DMPs) and 116 differentially expressed genes (DEGs) that distinguish B cells of individuals with FA from controls, including differential methylation of the PM20D1 promoter previously associated with allergic disorders. Subgroup comparisons found 729 DMPs specific to either single-food- or multi-food-allergic individuals, suggesting epigenetic distinctions between allergy groups. This included two regions with increased methylation near three S100 genes in multi-food-allergic individuals. Ontology results of DEGs specific to multi-food-allergic individuals revealed enrichment of terms associated with myeloid cell activation. Motif enrichment analysis of promoters associated with DMPs and DEGs showed differential enrichment for motifs recognised by transcription factors regulating B- and T-cell development, B-cell lineage determination and TGF-β signalling pathway between the multi-food-allergic and single-food-allergic groups.

CONCLUSION

Our data highlight epigenetic changes in B cells associated with peanut allergy, distinguishing features of the epigenome between single-food- and multi-food-allergic individuals and revealing differential developmental pathways potentially underpinning these distinct phenotypes.

Childhood vaccination and allergy: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

As the rise in prevalence of allergic diseases worldwide corresponds in time with increasing infant vaccination, it has been hypothesized that childhood vaccination may increase the risk of allergic disease. We aimed to synthesize the literature on the association between childhood vaccination and allergy.

DESIGN

We searched the electronic databases PubMed and EMBASE (January 1946-January 2018) using vaccination and allergy terms.

METHODS

Two authors selected papers according to the inclusion criteria. Pooled effects across studies were estimated using random-effects meta-analysis. Due to inadequate number of homogeneous publications on newer and underused vaccines, meta-analysis was limited to allergic outcomes following administration of (Bacillus Calmette-Guérin) BCG, measles or pertussis vaccination. The review was prospectively registered in the PROSPERO systematic review registry (NO: CRD42017071009).

RESULTS

A total of 35 publications based on cohort studies and 7 publications based on randomized controlled trials (RCTs) met the inclusion criteria. RCTs: From 2 studies, early vaccination with BCG vaccine was associated with a reduced risk of eczema (RR = 0.83; 95% CI = 0.73-0.93; I²  = 0%) but not food allergy or asthma. No association was found between pertussis vaccine and any allergic outcome based on a single RCT.

COHORT STUDIES

Childhood measles vaccination was associated with a reduced risk of eczema (RR = 0.65; 95% CI = 0.47-0.90, I²  = 0.0%), asthma (RR = 0.78; 95% CI = 0.62-0.98, I²  = 93.9%) and, with a similar, statistically non-significant reduction in sensitization (RR = 0.78; 95% CI = 0.61-1.01, I²  = 19.4%).

CONCLUSIONS

We found no evidence that childhood vaccination with commonly administered vaccines was associated with increased risk of later allergic disease. Our results from pooled analysis of both RCTs and cohort studies suggest that vaccination with BCG and measles vaccines were associated with a reduced risk of eczema.

Food Allergy Prevention: More Than Peanut

Given an apparent increase in food allergies worldwide, the focus on prevention strategies has intensified. Following the Learning Early About Peanut study, there is now a widespread acceptance that peanut should be introduced promptly into the diet of high-risk infants. However, most food allergies are caused by triggers other than peanut and additional prevention strategies are being evaluated. The appreciation of the role of an impaired skin barrier in the process of food sensitization and subsequent allergy has led to a spectrum of dermatologically orientated studies. Other prevention strategies address the role of the microbiome, dietary components, and other modifiable risk factors. With regard to early introduction of foods other than peanut, studies are heterogeneous in design and governmental and professional society response to the early introduction trials has varied, ranging from new guidelines confining advice specifically to peanut, to ones recommending prompt introduction of a broad spectrum of allergenic foods. Much remains to be determined with regard to the acceptability and uptake of the new guidelines and their impact on infant feeding behavior and food allergy outcomes. This review discusses the panoply of prevention approaches, their promise, and limitations.

Age at introduction to complementary solid food and food allergy and sensitization: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVE

An infant's age at introduction of complementary solids may contribute to food allergy. We aimed to synthesize the literature on the association between age at introduction of complementary solids, excluding milk products, and food allergy and sensitization.

DESIGN

We searched the electronic databases PubMed and EMBASE (January 1946-February 2017) using solid food, allergy and sensitization terms.

METHODS

Two authors selected papers according to inclusion criteria, identifying 16 cohort studies, 1 case-control study and 8 randomized controlled trials (RCTs). Pooled effects across studies were estimated using random-effects meta-analysis.

RESULTS

Cohort studies-Introducing complementary solids at age ≥ 4 months vs <4 months was not associated with food allergy (OR 1.22; 95% CI, 0.76-1.96) but was associated with food sensitization (OR 1.93; 95% CI 1.57-2.38). First exposure from age 4 to 6 months vs <4 months was not associated with food allergy (OR 1.01; 95% CI, 0.64-1.60) but was associated with food sensitization (OR 2.46; 95% CI 1.55-3.86). Randomized controlled trials-Egg exposure from age 4 months was associated with reduced egg allergy (OR 0.63, 95% CI, 0.44-0.90) and sensitization (OR 0.76, 95% CI, 0.51-0.95). Peanut exposure from age 4 months compared to delayed exposure was associated with reduced peanut allergy (OR 0.28, 95% CI 0.14-0.57).

CONCLUSIONS

We found no evidence from observational studies that introducing solids before 4 months protected against food allergy, but there was evidence for protection against food sensitization. From RCTs, introducing egg from 4 to 6 months and peanut from 4 to 11 months reduced the risk of egg allergy, peanut allergy and egg sensitization. PROSPERO systematic review registry (CRD42016033473).

Severity and threshold of peanut reactivity during hospital-based open oral food challenges: An international multicenter survey

BACKGROUND

Peanut allergy is classically managed by food avoidance. Immunotherapy programs are available at some academic centers for selected patients reacting to small amounts of peanut during food challenge. We aimed to determine and compare reaction thresholds and prevalence of anaphylaxis during peanut oral challenges at multiple specialist allergy centers.

METHODS

A retrospective, international survey of anonymized case records from seven specialist pediatric allergy centers from the UK and Ireland, as well as the Australian HealthNuts study. Demographic information, allergy test results, reaction severity and threshold during open oral peanut challenges were collated and analyzed.

RESULTS

Of the 1634 children aged 1-18 years old included, 525 (32%) failed their peanut challenge. Twenty-eight percent reacted to 25 mg, while 38% only reacted after consuming 1 g or more of whole peanut. Anaphylaxis (55 [11%]) was 3 times more common in teenagers than younger children and the likelihood increased at all ages as children consuming more peanut at the challenge. Children who developed anaphylaxis to 25-200 mg of whole peanut were significantly older. Previous history of reaction did not predict reaction threshold or severity.

CONCLUSIONS

More than a third of the children in this large international cohort tolerated the equivalent of one peanut in an oral challenge. Anaphylaxis, particularly to small amounts of peanut, was more common in older children. Tailored immunotherapy programs might be considered not only for children with low, but also higher reaction thresholds. Whether these programs could prevent heightened sensitivity and anaphylaxis to peanut with age also deserves further study.

Maternal age at delivery, lung function and asthma in offspring: a population-based survey

There is limited information about potential impact of maternal age on the respiratory health of offspring. We investigated the association of maternal age at delivery with adult offspring's lung function, respiratory symptoms and asthma, and potential differences according to offspring sex.10 692 adults from 13 countries participating in the European Community Respiratory Health Survey (ECRHS) II responded to standardised interviews and provided lung function measurements and serum for IgE measurements at age 25-55 years. In logistic and linear multilevel mixed models we adjusted for participants' characteristics (age, education, centre, number of older siblings) and maternal characteristics (smoking in pregnancy, education) while investigating for differential effects by sex. Maternal age was validated in a subsample using data from the Norwegian birth registry.Increasing maternal age was associated with increasing forced expiratory volume in 1 s (2.33 mL per year, 95% CI 0.34-4.32 mL per year), more consistent in females (p_trend 0.025) than in males (p_trend 0.14). Asthma (OR 0.85, 95% CI 0.79-0.92) and respiratory symptoms (OR 0.87, 95% CI 0.82-0.92) decreased with increasing maternal age (per 5 years) in females, but not in males (p_interaction 0.05 and 0.001, respectively). The results were consistent across centres and not explained by confounding factors.Maternal ageing was related to higher adult lung function and less asthma/symptoms in females. Biological characteristics in offspring related to maternal ageing are plausible and need further investigation.

Father's environment before conception and asthma risk in his children: a multi-generation analysis of the Respiratory Health In Northern Europe study

Background

Whereas it is generally accepted that maternal environment plays a key role in child health, emerging evidence suggests that paternal environment before conception also impacts child health. We aimed to investigate the association between children's asthma risk and parental smoking and welding exposures prior to conception.

Methods

In a longitudinal, multi-country study, parents of 24 168 offspring aged 2-51 years provided information on their life-course smoking habits, occupational exposure to welding and metal fumes, and offspring's asthma before/after age 10 years and hay fever. Logistic regressions investigated the relevant associations controlled for age, study centre, parental characteristics (age, asthma, education) and clustering by family.

Results

Non-allergic early-onset asthma (asthma without hay fever, present in 5.8%) was more common in the offspring with fathers who smoked before conception {odds ratio [OR] = 1.68 [95% confidence interval (CI) = 1.18-2.41]}, whereas mothers' smoking before conception did not predict offspring asthma. The risk was highest if father started smoking before age 15 years [3.24 (1.67-6.27)], even if he stopped more than 5 years before conception [2.68 (1.17-6.13)]. Fathers' pre-conception welding was independently associated with non-allergic asthma in his offspring [1.80 (1.29-2.50)]. There was no effect if the father started welding or smoking after birth. The associations were consistent across countries.

Conclusions

Environmental exposures in young men appear to influence the respiratory health of their offspring born many years later. Influences during susceptible stages of spermatocyte development might be important and needs further investigation in humans. We hypothesize that protecting young men from harmful exposures may lead to improved respiratory health in future generations.

The skin barrier function gene SPINK5 is associated with challenge-proven IgE-mediated food allergy in infants

BACKGROUND

A defective skin barrier is hypothesized to be an important route of sensitization to dietary antigens and may lead to food allergy in some children. Missense mutations in the serine peptidase inhibitor Kazal type 5 (SPINK5) skin barrier gene have previously been associated with allergic conditions.

OBJECTIVE

To determine whether genetic variants in and around SPINK5 are associated with IgE-mediated food allergy.

METHOD

We genotyped 71 "tag" single nucleotide polymorphisms (tag-SNPs) within a region spanning ~263 kb including SPINK5 (~61 kb) in n=722 (n=367 food-allergic, n=199 food-sensitized-tolerant and n=156 non-food-allergic controls) 12-month-old infants (discovery sample) phenotyped for food allergy with the gold standard oral food challenge. Transepidermal water loss (TEWL) measures were collected at 12 months from a subset (n=150) of these individuals. SNPs were tested for association with food allergy using the Cochran-Mantel-Haenszel test adjusting for ancestry strata. Association analyses were replicated in an independent sample group derived from four paediatric cohorts, total n=533 (n=203 food-allergic, n=330 non-food-allergic), mean age 2.5 years, with food allergy defined by either clinical history of reactivity, 95% positive predictive value (PPV) or challenge, corrected for ancestry by principal components.

RESULTS

SPINK5 variant rs9325071 (A⟶G) was associated with challenge-proven food allergy in the discovery sample (P=.001, OR=2.95, CI=1.49-5.83). This association was further supported by replication (P=.007, OR=1.58, CI=1.13-2.20) and by meta-analysis (P=.0004, OR=1.65). Variant rs9325071 is associated with decreased SPINK5 gene expression in the skin in publicly available genotype-tissue expression data, and we generated preliminary evidence for association of this SNP with elevated TEWL also.

CONCLUSIONS

We report, for the first time, association between SPINK5 variant rs9325071 and challenge-proven IgE-mediated food allergy.

Genetic variation at the Th2 immune gene IL13 is associated with IgE-mediated paediatric food allergy

BACKGROUND

Food allergies pose a considerable world-wide public health burden with incidence as high as one in ten in 12-month-old infants. Few food allergy genetic risk variants have yet been identified. The Th2 immune gene IL13 is a highly plausible genetic candidate as it is central to the initiation of IgE class switching in B cells.

OBJECTIVE

Here, we sought to investigate whether genetic polymorphisms at IL13 are associated with the development of challenge-proven IgE-mediated food allergy.

METHOD

We genotyped nine IL13 "tag" single nucleotide polymorphisms (tag SNPs) in 367 challenge-proven food allergic cases, 199 food-sensitized tolerant cases and 156 non-food allergic controls from the HealthNuts study. 12-month-old infants were phenotyped using open oral food challenges. SNPs were tested using Cochran-Mantel-Haenszel test adjusted for ancestry strata. A replication study was conducted in an independent, co-located sample of four paediatric cohorts consisting of 203 food allergic cases and 330 non-food allergic controls. Replication sample phenotypes were defined by clinical history of reactivity, 95% PPV or challenge, and IL13 genotyping was performed.

RESULTS

IL13 rs1295686 was associated with challenge-proven food allergy in the discovery sample (P=.003; OR=1.75; CI=1.20-2.53). This association was also detected in the replication sample (P=.03, OR=1.37, CI=1.03-1.82) and further supported by a meta-analysis (P=.0006, OR=1.50). However, we cannot rule out an association with food sensitization. Carriage of the rs1295686 variant A allele was also associated with elevated total plasma IgE.

CONCLUSIONS AND CLINICAL RELAVANCE

We show for the first time, in two independent cohorts, that IL13 polymorphism rs1295686 (in complete linkage disequilibrium with functional variant rs20541) is associated with challenge-proven food allergy.

Population-wide preventive interventions for reducing the burden of chronic respiratory disease

Chronic obstructive pulmonary disease and asthma impose a substantial burden of disease. This narrative review focuses on potential population-wide interventions that are likely to have an impact on these diseases. The developmental origins of adult disease commence in utero, with maternal nutrition being of particular interest. However, to date, trials of maternal allergen avoidance, dietary supplementation or probiotics have not shown consistent protective effects against asthma. Poor indoor air quality, especially from biomass fuels as well as second-hand tobacco smoke, is a well-recognised risk factor for chronic respiratory diseases. This can be modified by cleaner fuels, cooking stoves or heaters, and improved ventilation. Although allergens are a risk factor for childhood asthma, the results of interventions to reduce exposures have been disappointing. Traffic-related air pollution is associated with an increased incidence of asthma in children. Primary prevention of the adverse effects of air pollution has focused on the development of ambient air quality guidelines, but enforcement remains a challenge in many countries. Occupational asthma may be induced by sensitisers or irritants in the workplace. Prevention involves eliminating the agent or reducing exposure as far as possible, which is more effective than respiratory protective equipment. Smoking cessation remains a key proven preventive strategy for chronic respiratory diseases. There is now an international framework for tobacco control, and recent innovations include plain packaging of tobacco. Chronic respiratory diseases can be substantially prevented by the above population-wide interventions.

Blood DNA methylation biomarkers predict clinical reactivity in food-sensitized infants

BACKGROUND

The diagnosis of food allergy (FA) can be challenging because approximately half of food-sensitized patients are asymptomatic. Current diagnostic tests are excellent makers of sensitization but poor predictors of clinical reactivity. Thus oral food challenges (OFCs) are required to determine a patient's risk of reactivity.

OBJECTIVE

We sought to discover genomic biomarkers of clinical FA with utility for predicting food challenge outcomes.

METHODS

Genome-wide DNA methylation (DNAm) profiling was performed on blood mononuclear cells from volunteers who had undergone objective OFCs, concurrent skin prick tests, and specific IgE tests. Fifty-eight food-sensitized patients (aged 11-15 months) were assessed, half of whom were clinically reactive. Thirteen nonallergic control subjects were also assessed. Reproducibility was assessed in an additional 48 samples by using methylation data from an independent population of patients with clinical FA.

RESULTS

Using a supervised learning approach, we discovered a DNAm signature of 96 CpG sites that predict clinical outcomes. Diagnostic scores were derived from these 96 methylation sites, and cutoffs were determined in a sensitivity analysis. Methylation biomarkers outperformed allergen-specific IgE and skin prick tests for predicting OFC outcomes. FA status was correctly predicted in the replication cohort with an accuracy of 79.2%.

CONCLUSION

DNAm biomarkers with clinical utility for predicting food challenge outcomes are readily detectable in blood. The development of this technology in detailed follow-up studies will yield highly innovative diagnostic assays.

Is caesarean delivery associated with sensitization to food allergens and IgE-mediated food allergy: a systematic review

Several studies have shown differences in the composition of the gastrointestinal flora of children who develop sensitization to food allergens compared with non-allergic children. It has been hypothesized that changes in the gut microbiota resulting from caesarean section delivery could increase a child's risk of developing food allergy; however, studies examining the relationship between mode of delivery and food allergy have produced conflicting results. The objective of this review was to determine whether there is sufficient evidence to support an association between delivery by caesarean section and the development of sensitization to food allergens and immunoglobulin E (IgE) mediated food allergy. Using predefined inclusion and exclusion criteria, MEDLINE and PubMed were searched for studies investigating the relationship between caesarean section delivery and food allergy. The information on the quality of the studies and results were extracted and analysed systematically. The search identified four relevant studies as per our protocol. Symptomatic food allergy was used as the outcome in two studies and was found to occur more frequently in children born by caesarean section in one study while the second study found no association between food allergy diagnoses and mode of delivery. The other two studies measured levels of food antigen-specific IgE, with both studies showing an increase in sensitization to food allergens among children born by caesarean section. Overall, there is evidence that the risk of developing IgE-mediated sensitization to food allergens is increased among children delivered by caesarean section, however further studies using objectively diagnosed food allergy as the outcome are needed to verify whether this equates to an increase in confirmed food allergy. Future birth cohort studies should control for the effects of mode of delivery when investigating environmental modifiers of food allergy.