To what extent is allergen exposure a risk factor for the development of allergic disease?

Common pollen and related allergen components in patients with allergic diseases in the Beijing area

Background

Pollen is the most common outdoor allergen that causes allergic rhinitis and asthma, which seriously affects patient quality of life and extensive cross-reactivity occurs between pollen allergens.

Methods

The study enrolled 84 patients with respiratory allergies and at least one pollen allergy who visited the clinic. Specific-IgE was detected via immunoblotting in the sera of patients with positive respiratory allergies to pollen. IgE of the components and cross-reactive carbohydrate determinants (CCD) were evaluated using a fluorescence-encoded microsphere assay.

Results

Our results suggest that Artemisia absinthium, Artemisia vulgaris, Humulus scandens, Amaranthus, Parietaria micrantha allergies are most common in the northern region, and that weed pollen remains the major pollen allergen in the northern region. Among the different age groups, the positive rate of Platanus pollen allergens was significantly higher in patients ≤18 years of age than in those aged >18 years (55.56% vs. 9.17%, χ² = 0.55, p < 0.027). Patients with allergic rhinitis and asthma had an increased positive rate for Betula pollen allergen (20.00% vs. 37.93 χ² = 7.87, p = 0.005) and Platanus pollen allergen (27.27% vs. 51.72%, χ² = 11.05, p = 0.0008) than those with allergic rhinitis alone, although the allergen positivity rate did not significantly differ between sexes. In addition, the positivity of sIgE of allergen components did not reveal a correlation with clinical symptoms and anti-CCD IgE positivity was 1.19% (1/84) among all patients.

Conclusion

The study found the distribution characteristics of common pollen allergens in Beijing among patients of different ages and genders and with different allergic diseases, as well as the relationship between pollen allergen components and symptoms. The positivity rate of CCD for respiratory allergic diseases in Beijing was not high as well.

Clinical and molecular analysis of longitudinal rhinitis phenotypes in an urban birth cohort

BACKGROUND

Chronic rhinitis symptoms cause significant health burden among children and can have a heterogeneous presentation. Defining phenotypes of childhood chronic rhinitis and associated pathobiology may lead to prevention or improved treatments.

OBJECTIVES

We sought to identify longitudinal patterns of rhinitis symptoms in childhood and determine their associations with early life risk factors, allergic comorbidities, and nasal epithelial cell gene expression.

METHODS

Chronic rhinitis symptoms were evaluated from ages 1 through 11 years in 485 urban children at high risk for allergic disease in the URECA (Urban Environment and Childhood Asthma) birth cohort. We identified longitudinal rhinitis phenotypes and their relationships to early life exposures, atopic comorbidities, and patterns of nasal epithelial gene expression at age 11 years.

RESULTS

Chronic rhinitis symptoms started early in many children and were a risk factor for developing aeroallergen sensitization. We identified 4 longitudinal rhinitis phenotypes: low/minimal, persistent, persistent decreasing, and late increasing. Persistent rhinitis was most closely linked to allergic sensitization and asthma. Risk factors for persistent rhinitis included frequent colds (P < .001), antibiotic use (P < .001), and reduced exposure to common indoor aeroallergens (P = .003). Compared to low/minimal rhinitis phenotype, the other rhinitis phenotypes were associated with increased expression of canonical type 2 genes and decreased expression of immune response genes.

CONCLUSIONS

In urban children, rhinitis symptoms often precede aeroallergen sensitization. Rhinitis phenotypes based on symptoms had distinct risk factors and nasal transcriptome. These results suggest that focusing on early life risk factors and distinct immune mechanisms may be a target to preventing chronic rhinitis in childhood.

Investigating Forkhead Box O Transcription Factor 1 Gene's Relation to Immunoglobulin E in House Dust Mite-Allergic Asthma Patients

House dust mite (HDM)-allergic asthma is an abnormal immune response to extrinsic aeroallergens found in human vicinities. Studying the role of the associated immunity biomarkers and their interplay helps in discovering novel therapeutic strategies that can be used in adjunct with effective long-term immunotherapy. This study investigates the total serum IgE, FoxO1, and Sirtuin 1 (SIRT1) gene expressions in HDM-allergic asthma patients. We enrolled 40 patients for each of the following three groups: an HV group of healthy volunteers and HDM/AA and HDM/SCIT groups of HDM-allergic asthma patients who did not and who did receive immunotherapy before recruitment in this study, respectively. The results elucidated that total IgE was strikingly elevated in the HDM/AA group and showed little decline in the HDM/SCIT group. Both FoxO1 and SIRT1 gene expressions showed the highest levels in the HDM/SCIT group. There was a negative correlation between total IgE and both FoxO1 and SIRT1 in the HDM/AA group while there was a positive correlation with SIRT1 in the HDM/SCIT group. In conclusion, the interplay of the three immunity biomarkers related to HDM-allergic asthma after the course of immunotherapy treatment suggests further, broader studies on the feasibility of their role as immunity biomarkers in the control and remission of HDM-allergic asthma.

Blockade of MIF biological activity ameliorates house dust mite-induced allergic airway inflammation in humanized MIF mice

Macrophage migration inhibitory factor (MIF) expression is controlled by a functional promoter polymorphism, where the number of tetranucleotide repeats (CATT_n ) corresponds to the level of MIF expression. To examine the role of this polymorphism in a pre-clinical model of allergic asthma, novel humanized MIF mice with increasing CATT repeats (CATT₅ and CATT₇ ) were used to generate a physiologically relevant scale of airway inflammation following house dust mite (HDM) challenge. CATT₇ mice expressing high levels of human MIF developed an aggressive asthma phenotype following HDM challenge with significantly elevated levels of immune cell infiltration, production of inflammatory mediators, goblet cell hyperplasia, subepithelial collagen deposition, and airway resistance compared to wild-type controls. Importantly the potent MIF inhibitor SCD-19 significantly mitigated the pathophysiology observed in CATT₇ mice after HDM challenge, demonstrating the fundamental role of endogenous human MIF expression in the severity of airway inflammation in vivo. Up to now, there are limited reproducible in vivo models of asthma airway remodeling. Current asthma medications are focused on reducing the acute inflammatory response but have limited effects on airway remodeling. Here, we present a reproducible pre-clinical model that capitulates asthma airway remodeling and suggests that in addition to having pro-inflammatory effects MIF may play a role in driving airway remodeling.

Molecular Mapping of Allergen Exposome among Different Atopic Phenotypes

Climate change and exposure to environmental pollutants play a key role in the onset and aggravation of allergic diseases. As different climate-dependent patterns of molecular immunoglobulin E (IgE) reactivity have been regionally described, we sought to investigate the evolving allergen exposome in distinctive allergic phenotypes and subtropical weather conditions through a Precision Allergy Molecular Diagnosis (PAMD@) model. Concurrent sensitization to several house dust mites (HDM) and storage mite molecules were broadly dominant in the investigated cohort, followed by the major cat allergen Fel d 1, and regardless of the basal allergic disease. Although a complex repertoire of allergens was recognized, a steadily increasing number of IgE binding molecules was associated with the complexity of the underlying atopic disease. Besides the highly prevalent IgE responses to major HDM allergens, Der p 21, Der p 5, and Der p 7 also showed up as serodominant molecules, especially in subjects bothered by asthma and atopic dermatitis. The accurate characterization of the external exposome at the molecular level and their putative role as clinically relevant allergens is essential to elucidate the phenotypic diversity of atopic disease in terms of personalized diagnosis and therapy.

Protease allergens as initiators-regulators of allergic inflammation

Tremendous progress in the last few years has been made to explain how seemingly harmless environmental proteins from different origins can induce potent Th2-biased inflammatory responses. Convergent findings have shown the key roles of allergens displaying proteolytic activity in the initiation and progression of the allergic response. Through their propensity to activate IgE-independent inflammatory pathways, certain allergenic proteases are now considered as initiators for sensitization to themselves and to non-protease allergens. The protease allergens degrade junctional proteins of keratinocytes or airway epithelium to facilitate allergen delivery across the epithelial barrier and their subsequent uptake by antigen-presenting cells. Epithelial injuries mediated by these proteases together with their sensing by protease-activated receptors (PARs) elicit potent inflammatory responses resulting in the release of pro-Th2 cytokines (IL-6, IL-25, IL-1β, TSLP) and danger-associated molecular patterns (DAMPs; IL-33, ATP, uric acid). Recently, protease allergens were shown to cleave the protease sensor domain of IL-33 to produce a super-active form of the alarmin. At the same time, proteolytic cleavage of fibrinogen can trigger TLR4 signaling, and cleavage of various cell surface receptors further shape the Th2 polarization. Remarkably, the sensing of protease allergens by nociceptive neurons can represent a primary step in the development of the allergic response. The goal of this review is to highlight the multiple innate immune mechanisms triggered by protease allergens that converge to initiate the allergic response.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Environmental influences on childhood asthma: Allergens

Allergen exposure is associated with the development of allergen-specific sensitization, but their relationship is influenced by other contemporaneous exposures (such as microbial exposure) and the genetic predisposition of the host. Clinical outcomes of the primary prevention studies that tested the effectiveness of allergen avoidance in pregnancy and early life on the subsequent development of sensitization and asthma published to date are inconsistent. Therefore, we cannot provide any evidence-based advice on the use of allergen avoidance for the primary prevention of these conditions. The evidence about the impact of allergen exposure among and among sensitized children with asthma is more consistent, and the combination of sensitization and high exposure to sensitizing allergen increases airway inflammation, triggers symptoms, adversely impacts upon disease control, and is associated with poorer lung function in preschool age. However, there are differing opinions about the role of inhalant allergen avoidance in asthma management, and recommendations differ in different guidelines. Evidence from more recent high-quality trials suggests that mite allergen-impermeable bed encasings reduce hospital attendance with asthma attacks and that multifaceted targeted environmental control improves asthma control in children. We therefore suggest a pragmatic approach to allergen avoidance in the management of childhood asthma for clinical practice, including the recommendations to: (1) tailor the intervention to the patient's sensitization and exposure status by using titer of allergen-specific IgE antibodies and/or the size of the skin test as indicators of potential response; (2) use a multifaceted allergen control regime to reduce exposure as much as possible; and (3) start intervention as early as possible upon diagnosis.

Evaluation of climate change adaptation measures for childhood asthma: A systematic review of epidemiological evidence

Global climate change (GCC) is widely accepted as the biggest threat to human health of the 21st century. Children are particularly vulnerable to GCC due to developing organ systems, psychological immaturity, nature of daily activities, and higher level of per-body-unit exposure. There is a rising trend in the disease burden of childhood asthma and allergies in many parts of the world. The associations of CC, air pollution and other environmental exposures with childhood asthma are attracting more research attention, but relatively few studies have focused on CC adaptation measures and childhood asthma. This study aimed to bridge this knowledge gap and conducted the first systematic review on CC adaptation measures and childhood asthma. We searched electronic databases including PubMed, Embase, and Web of Science using a set of MeSH terms and related synonyms, and identified 20 eligible studies included for review. We found that there were a number of adaptation measures proposed for childhood asthma in response to GCC, including vulnerability assessment, improving ventilation and heating, enhancing community education, and developing forecast models and early warning systems. Several randomized controlled trials show that improving ventilation and installing heating in the homes appear to be an effective way to relieve childhood asthma symptoms, especially in winter. However, the effectiveness of most adaptation measures, except for improving ventilation and heating, have not been explored and quantified. Given more extreme weather events (e.g., cold spells and heatwaves) may occur as climate change progresses, this finding may have important implications. Evidently, further research is urgently warranted to evaluate the impacts of CC adaptation measures on childhood asthma. These adaptation measures, if proven to be effective, should be integrated in childhood asthma control and prevention programs as GCC continues.

Allergic Asthma in the Era of Personalized Medicine

Allergic asthma is the most common asthma phenotype and is characterized by IgE sensitization to airborne allergens and subsequent typical asthmatic symptoms after exposure. A form of type 2 (T2) airway inflammation underlies allergic asthma. It usually arises in childhood and is accompanied by multimorbidity presenting with the occurrence of other atopic diseases, such as atopic dermatitis and allergic rhinitis. Diagnosis of the allergic endotype is based on in vivo (skin prick tests) and/or in vitro (allergen-specific IgE levels, component-resolved diagnosis (CRD)) documentation of allergic sensitization. Biomarkers identifying patients with allergic asthma include total immunoglobulin E (IgE) levels, fractional exhaled nitric oxide (FeNO) and serum eosinophil counts. The treatment of allergic asthma is a complex procedure and requires a patient-tailored approach. Besides environmental control involving allergen avoidance measurements and cornerstone pharmacological interventions based on inhaled drugs, allergen-specific immunotherapy (AIT) and biologics are now at the forefront when it comes to personalized management of asthma. The current review aims to shed light on the distinct phenotype of allergic asthma, ranging over its current definition, clinical characteristics, pathophysiology and biomarkers, as well as its treatment options in the era of precision medicine.

The links between allergen exposure and sensitization in children and adolescents: an overview for the clinician

INTRODUCTION

The links between allergen exposure and sensitization are complex and depend not only on the type of allergen but on various genetic and environmental factors.

AREAS COVERED

This review discusses the link between allergen exposure and atopic sensitization for different types of allergens and the factors that mediate or affect this link. For the purposes of this review search of PubMed was undertaken to identify English language articles using the terms 'sensitization' and 'allergen exposure' and 'children/or adolescents.'

EXPERT OPINION

Regarding food sensitization, the available data for peanuts and eggs suggest that there is a window period between 4 and 6 months of age when the introduction of these foods may limit sensitization and clinically overt allergy to the respective foods. As far as it concerns aeroallergens, it seems that there is a complex and variable relationship between mite exposure and specific sensitization especially if the exposure occurs early in life. Early exposure to dog allergens does not seem to be associated with specific sensitization; regarding cats, the results are still inconsistent. Several factors may mediate the relationship between early exposure to allergens and the development of sensitization or clinical allergy.

Preterm birth reduces the risk of IgE sensitization up to early adulthood: A population-based birth cohort study

BACKGROUND

Immunoglobulin E (IgE) sensitization is associated with asthma and allergic diseases. Gestational age influences early immune system development, thereby potentially affecting the process of tolerance induction to allergens.

OBJECTIVE

To study IgE sensitization to common allergens by gestational age from childhood up to early adulthood.

METHODS

Population-based birth cohort, data from the Swedish BAMSE study were used. Allergen-specific IgE antibodies to a mix of common food (fx5) and inhalant (Phadiatop) allergens were analysed at 4, 8, 16 and 24 years. Sensitization was defined as allergen-specific IgE ≥0.35 kU_A /L to fx5 and/or Phadiatop at each time point. Using logistic regression and generalized estimated equations, adjusted odds ratios (aORs) for sensitization in relation to gestational age were calculated. Replication was sought within the Swedish twin study STOPPA.

RESULTS

In BAMSE, 3522 participants were screened for IgE antibodies during follow-up; of these, 197 (5.6%) were born preterm (<37 gestational weeks) and 330 (9.4%) post-term (≥42 weeks). Preterm birth reduced the risk of sensitization to common food and/or inhalant allergens up to early adulthood by 29% (overall aOR = 0.71; 95% CI: 0.52-0.98), and to food allergens specifically by 40% (overall aOR = 0.60; 95% CI: 0.38-0.93). No relation was found between post-term birth and IgE sensitization at any time point. Replication analyses in STOPPA (N = 675) showed similar risk estimates for sensitization to food and/or inhalant allergens (aOR = 0.72; 95% CI: 0.42-1.21), which resulted in a combined meta-analysis aOR = 0.71 (95% CI: 0.54-0.94).

CONCLUSIONS

Our study suggests an inverse association between preterm birth and long-term IgE sensitization.

Associations of early-life pet ownership with asthma and allergic sensitization: a meta-analysis of >77,000 children from the EU Child Cohort Network

BACKGROUND

Studies examining associations of early-life cat and dog ownership with childhood asthma have reported inconsistent results. Several factors could explain these inconsistencies, including type of pet, timing and degree of exposure.

OBJECTIVE

To study associations of early-life cat and dog ownership with school-age asthma, including the role of type (cat versus dog), timing (never, prenatal or early childhood) and degree (number) of ownership, and the role of allergic sensitisation.

METHODS

We used harmonised data from 77,434 mother-child dyads aged 5-11 years from nine birth cohorts in the EU Child Cohort Network. Associations were examined through the DataSHIELD platform using adjusted logistic regression models, fitted separately for each cohort and combined using random-effects meta-analysis.

RESULTS

Early-life cat and dog ownership ranged between 12-45% and 7-47% respectively, and prevalence of asthma between 2-20%. There was no overall association between either cat or dog ownership and asthma (OR: 0.97 (95% CI: 0.87-1.09) and 0.92 (0.85-1.01), respectively). Timing and degree of ownership did not strongly influence associations. Cat and dog ownership were also not associated with cat- and dog-specific allergic sensitisation (OR: 0.92 (0.75-1.13) and 0.93 (0.57-1.54), respectively). However, cat- and dog-specific allergic sensitisation were strongly associated with school-age asthma (OR: 6.69 (4.91-9.10) and 5.98 (3.14-11.36), respectively). There was also some indication of an interaction between ownership and sensitisation, suggesting that ownership may exacerbate the risks associated with pet-specific sensitisation, but offer some protection against asthma in the absence of sensitisation.

CONCLUSION

Our findings do not support early-life cat and dog ownership in themselves increasing the risk of school-age asthma, but suggest that ownership may potentially exacerbate the risks associated with cat- and dog-specific allergic sensitisation.

Abundance and Stability as Common Properties of Allergens

There have been many attempts to identify common biophysical properties which differentiate allergens from their non-immunogenic counterparts. This review will focus on recent studies which examine two such factors: abundance and stability. Anecdotal accounts have speculated that the elevated abundance of potential allergens would increase the likelihood of human exposure and thus the probability of sensitization. Similarly, the stability of potential allergens dictates its ability to remain a viable immunogen during the transfer from the source to humans. This stability could also increase the resilience of potential allergens to both gastric and endosomal degradation, further skewing the immune system toward allergy. Statistical analyses confirm both abundance and stability as common properties of allergens, while epidemiological surveys show a correlation between exposure levels (abundance) and allergic disease. Additional studies show that changes in protein stability can predictably alter gastric/endosomal processing and immunogenicity, providing a mechanistic link between stability and allergenicity. However, notable exceptions exist to both hypotheses which highlight the multifaceted nature of immunological sensitization, and further inform our understanding of some of these other factors and their contribution to allergic disease.

Climate Change and Global Issues in Allergy and Immunology

The steady increase in global temperatures, resulting from the combustion of fossil fuels and the accumulation of greenhouse gases (GHG), continues to destabilize all ecosystems worldwide. Although annual emissions must halve by 2030 and reach net-zero by 2050 to limit some of the most catastrophic impacts associated with a warming planet, the world's efforts to curb GHG emissions fall short of the commitments made in the 2015 Paris Agreement (1). To this effect, July 2021 was recently declared the hottest month ever recorded in 142 years (2). The ramifications of these changes on global temperatures are complex and further promote outdoor air pollution, pollen exposure, and extreme weather events. Besides worsening respiratory health, air pollution, promotes atopy and susceptibility to infections. The GHG effects on pollen affect the frequency and severity of asthma and allergic rhinitis. Changes in temperature, air pollution, and extreme weather events exert adverse multisystemic health effects and disproportionally affect disadvantaged and vulnerable populations. This article is an update for allergists and immunologists about the health impacts of climate change, already evident in our daily practices. It is also a call to action and advocacy, including integrating climate change-related mitigation, education, and adaptation measures to protect our patients and avert further injury to our planet.

Therapeutic Effects of an Anti-sialyl Lewis X Antibody in a Murine Model of Allergic Asthma

Asthma is an allergic disease that causes severe infiltration of leukocytes into the lungs. Leukocyte infiltration is mediated by the binding of sialyl Lewis X (sLex) glycans present on the leukocytes to E-and P-selectins present on the endothelial cells at the sites of inflammation. Here, we found that mouse eosinophils express sLex glycans, and their infiltration into the lungs and proliferation in the bone marrow were significantly suppressed by an anti-sLex monoclonal antibody (mAb) F2 in a murine model of ovalbumin-induced asthma. The percentage of eosinophils in the bronchoalveolar lavage fluid and bone marrow and serum IgE levels decreased significantly in the F2-administered mice. Levels of T helper type 2 (Th2) cytokines and chemokines, involved in IgE class switching and eosinophil proliferation and recruitment, were also decreased in the F2-administered mice. An ex vivo cell rolling assay revealed that sLex glycans mediate the rolling of mouse eosinophils on P-selectin-expressing cells. These results indicate that the mAb F2 exerts therapeutic effects in a murine model of allergen-induced asthma, suggesting that sLex carbohydrate antigen could serve as a novel therapeutic target for allergic asthma.

The axis of the receptor for advanced glycation endproducts in asthma and allergic airway disease

Asthma is a generalized term that describes a scope of distinct pathologic phenotypes of variable severity, which share a common complication of reversible airflow obstruction. Asthma is estimated to affect almost 400 million people worldwide, and nearly ten percent of asthmatics have what is considered "severe" disease. The majority of moderate to severe asthmatics present with a "type 2-high" (T2-hi) phenotypic signature, which pathologically is driven by the type 2 cytokines Interleukin-(IL)-4, IL-5, and IL-13. However, "type 2-low" (T2-lo) phenotypic signatures are often associated with more severe, steroid-refractory neutrophilic asthma. A wide range of clinical and experimental studies have found that the receptor for advanced glycation endproducts (RAGE) plays a significant role in the pathogenesis of asthma and allergic airway disease (AAD). Current experimental data indicates that RAGE is a critical mediator of the type 2 inflammatory reactions which drive the development of T2-hi AAD. However, clinical studies demonstrate that increased RAGE ligands and signaling strongly correlate with asthma severity, especially in severe neutrophilic asthma. This review presents an overview of the current understandings of RAGE in asthma pathogenesis, its role as a biomarker of disease, and future implications for mechanistic studies, and potential therapeutic intervention strategies.

Association of frequent moisturizer use in early infancy with the development of food allergy

Background

Objectives

Methods

Results

Conclusions

The neighbourhood natural environment is associated with asthma in children: A birth cohort study

BACKGROUND

A lower exposure to the natural environment has been hypothesized to adversely affect the human microbiome and its immunomodulatory capacity. However, the underlying effects of this hypothesis are still not understood. We aimed to evaluate the effect of early-life exposure to greenness and species richness on the development of allergic diseases and asthma in children.

METHODS

A longitudinal study was conducted comprising 1050 children from a population-based birth cohort recruited in Portugal. Residential normalized difference vegetation index (NDVI) and species richness index (SRI) were assessed at baseline to estimate their association with allergic diseases and asthma at the ages of 4 and 7.

RESULTS

Significant predisposing associations were observed between the exposure to species richness at baseline and the onset of asthma and wheezing at the age of 7. Children living in neighbourhoods surrounded by high levels of SRI were at a significantly higher risk developing allergic sensitization(OR [95% CI] = 2.00 [1.04:3.86] at age 4; 2.35 [1.20:4.63] at age 7). Living surrounded by greener environments was significantly associated with a lower prevalence of asthma and rhinitis at the age of 7(0.41 [0.18:0.97] and 0.37 [0.15:0.93], respectively).

CONCLUSIONS

Living in close proximity to a greener environment at birth has a protective effect on the development of allergic diseases and asthma at the age of 7. Conversely, living in neighbourhoods with a high number of fauna species appears to be associated with a higher risk for allergy, asthma and wheezing.

Update on House Dust Mite Allergen Avoidance Measures for Asthma

PURPOSE OF REVIEW

To critically review the evidence in favor or against the use of house dust mite (HDM) allergen avoidance measures in patients with asthma.

RECENT FINDINGS

Systematic reviews and meta-analyses suggested no positive effect of mite allergen avoidance strategies on asthma outcomes, resulting in a lack of consensus regarding the utility of these measures. However, such analyses have a number limitations and might not be the most adequate tool to evaluate current evidence and to derive clinical recommendations regarding mite allergen avoidance in asthmatic patients. We should not disproportionately rely on the results of meta-analyses and systematic reviews to inform clinical practice and asthma guidelines in this area. Recent high-quality evidence from randomized controlled trial in children confirmed that mite allergen-impermeable bed encasings reduce emergency hospital attendance with acute severe asthma exacerbations. Until better evidence is available, we suggest that physicians should adopt a pragmatic approach to mite allergen avoidance and advise sensitized patients to implement a multifaceted set of measures to achieve as great a reduction in exposure as possible. Potential predictors of positive response (e.g., patient's sensitization and exposure status) can pragmatically be evaluated using the size of skin test wheal or the titer of allergen-specific IgE. Finally, the intervention should be started as early as possible.

A prenatally disrupted airway epithelium orchestrates the fetal origin of asthma in mice

BACKGROUND

Prenatal challenges such as maternal stress perception increase the risk and severity of asthma during childhood. However, insights into the trajectories and targets underlying the pathogenesis of prenatally triggered asthma are largely unknown. The developing lung and immune system may constitute such targets.

OBJECTIVE

Here we have aimed to identify the differential sex-specific effects of prenatal challenges on lung function, immune response, and asthma severity in mice.

METHODS

We generated bone marrow chimeric (BMC) mice harboring either prenatally stress-exposed lungs or a prenatally stress-exposed immune (hematopoietic) system and induced allergic asthma via ovalbumin. Next-generation sequencing (RNA sequencing) of lungs and assessment of airway epithelial barrier function in ovalbumin-sensitized control and prenatally stressed offspring was also performed.

RESULTS

Profoundly enhanced airway hyperresponsiveness, inflammation, and fibrosis were exclusively present in female BMC mice with prenatally stress-exposed lungs. These effects were significantly perpetuated if both the lungs and the immune system had been exposed to prenatal stress. A prenatally stress-exposed immune system alone did not suffice to increase the severity of these asthma features. RNA sequencing analysis of lungs from prenatally stressed, non-BMC, ovalbumin-sensitized females unveiled a deregulated expression of genes involved in asthma pathogenesis, tissue remodeling, and tight junction formation. It was also possible to independently confirm a tight junction disruption. In line with this, we identified an altered perinatal and/or postnatal expression of genes involved in lung development along with an impaired alveolarization in female prenatally stressed mice.

CONCLUSION

Here we have shown that the fetal origin of asthma is orchestrated by a disrupted airway epithelium and further perpetuated by a predisposed immune system.

Novel Biological Therapies in Severe Asthma: Targeting the Right Trait

Asthma is a heterogeneous disease characterized by chronic airway inflammation that results in a wide spectrum of clinical manifestations. Patients with severe asthma represent a substantial share of consumption of healthcare resources and hospitalization. Moreover, these patients are at risk of increased morbidity and mortality. Recently, several phenotypes and endotypes of asthma have been identified. The identification of specific subtypes of asthma is fundamental for optimizing the clinical benefit of novel treatments. Although in most patients the disease can be controlled by some combination of pharmacologic agents, in some 5-10% of patients the disease remains uncontrolled. Several monoclonal antibodies (mAbs) targeting pathogenetic molecules (e.g., IgE, IL-5, IL- 5Rα, IL-4, IL-13, TSLP) are currently available or under development for the treatment of different forms of severe type 2 asthma. The identification of diagnostic and predictive biomarkers (e.g., IgE, blood eosinophil count, FeNO, periostin, etc.) has revolutioned the field of targeted therapy in severe asthma. Monoclonal antibodies targeting Th2-driven inflammation are generally safe in adult patients with moderate-to-severe asthma. The long-term safety of these biologics is a relevant issue that should be addressed. Unfortunately, little is known about non-type 2 asthma. Further studies are needed to identify biomarkers to guide targeted therapies of different forms of non-type 2 asthma.

Early-life inhalant allergen exposure, filaggrin genotype, and the development of sensitization from infancy to adolescence

Background

We hypothesized that filaggrin (FLG) loss-of-function mutations modify the effect of allergen exposure on the development of allergic sensitization.

Objective

We sought to determine whether early-life exposure to inhalant allergens increases the risk of specific sensitization and whether FLG mutations modulate these odds.

Methods

In a population-based birth cohort we measured mite, cat, and dog allergen levels in dust samples collected from homes within the first year of life. Sensitization was assessed at 6 time points between infancy and age 16 years. Genotyping was performed for 6 FLG mutations.

Results

In the longitudinal multivariable model (age 1-16 years), we observed a significant interaction between FLG and Fel d 1 exposure on cat sensitization, with the effect of exposure being significantly greater among children with FLG mutations compared with those without (odds ratio, 1.36; 95% CI, 1.02-1.80; P = .035). The increase in risk of mite sensitization with increasing Der p 1 exposure was consistently greater among children with FLG mutations, but the interaction did not reach statistical significance. Different associations were observed for dogs: there was a significant interaction between FLG and dog ownership, but the risk of sensitization to any allergen was significantly lower among children with FLG mutations who were exposed to a dog in infancy (odds ratio, 0.16; 95% CI, 0.03-0.86; P = .03).

Conclusions

FLG loss-of-function mutations modify the relationship between allergen exposure and sensitization, but effects differ at different ages and between different allergens.

Asymptomatic toddlers with house dust mite sensitization at risk of asthma and abnormal lung functions at age 7 years

Objective

To evaluate the predictive value of asymptomatic early house dust mite sensitization on allergic outcomes and pulmonary functions in 7-year olds.

Study design

The Prediction of Allergies in Taiwanese Children (PATCH) birth cohort study recruited healthy newborns at birth. At age 1.5–2 years, a Dermatophagoides pteronyssinus-specific immunoglobulin E level ≥ 0.35 kU/L was defined as early sensitization. At age 7 years, allergic outcomes were evaluated by pediatric allergists and pulmonologists, and fractional exhaled nitric oxide and pulmonary functions were measured.

Results

At age 1.5–2 years, 28.0% of toddlers were sensitized to D. pteronyssinus. Among them, 68.2% had no allergic symptoms at that time. At age 7 years, the children with early sensitization had higher risks of asthma (OR = 13.4, 95% CI, 1.2 to 153.0; P = 0.037), allergic rhinitis (OR = 10.2, 95% CI, 2.1 to 49.6; P = 0.004), and atopic dermatitis (OR = 38.5, 95% CI, 2.1 to 696.4; P = 0.014). Notably, even the asymptomatic toddlers with early D. pteronyssinus sensitization had higher probabilities of asthma (12.5% vs. 1.7%, P = 0.040), allergic rhinitis (83.3% vs. 43.1%, P = 0.009), and atopic dermatitis (20.8% vs. 0.0%, P < 0.001) at age 7 years. The asymptomatic toddlers with early sensitization also had higher exhaled nitric oxide levels and higher prevalence of airway hyperresponsiveness at age 7 years.

Conclusion

Asymptomatic toddlers with early house dust mite sensitization have higher risks of developing asthma, allergic rhinitis, atopic dermatitis, and abnormal lung functions at age 7 years.

Cross-reactivity of sIgE to mite and shrimp induced allergies in different age groups and clinical profiles of shrimp sIgE in vegetarians

The sensitization to house dust mites (HDMs) and shrimps affects the development of hypersensitivity with an increase in age. Due to the cross-reactivity between shellfish and HDMs, HDMs were considered as the primary sensitizer for shellfish allergy. Thus, vegetarians might be sensitized to shrimp through the inadvertent inhalation of HDMs. Therefore, we assessed the prevalence of shrimp or mite allergy among different age groups and vegetarians. The serum specific-IgE (sIgE) level of HDMs and shrimp in 60 children/adolescence (un-adults), 30 adults, 30 elderly, and four vegetarian adults patients were measured. The sera with sIgE levels greater than 3.5 kUA/L were cross-reactivity examined. We found that HDMs induced higher sIgE than shrimp in un-adults. In contrast, shrimp-induced sIgE was higher in the adults and elderly patients. Moreover, adults were more frequently sensitized to shrimp and mite at the same time compared with the un-adult or elderly groups. The mite-Der p 10 not only displayed high cross-reactivity to the shrimp-Pen a 1 in all age groups and vegetarians but functioned as the major allergen to sensitize un-adults. Overall, the level of mite or shrimp sIgE is influenced by alterations in age, and vegetarians are at risk of shrimp sensitization via cross-reactivity between shrimp and mite.

Dust-mite inducing asthma: what advice can be given to patients?

Introduction: Amongst allergic asthmatics, high allergen exposure increases asthma severity. However, there is no consensus on the role of mite allergen avoidance in the management of asthma, and various guidelines differ in their recommendations. Areas covered: Several systematic reviews/meta-analyses on mite avoidance in the management of asthma have been published, and their findings have been used for a call to provide a recommendation in British guidelines that dust-mite control measures should not be recommended. However, there are several problems with such analysis (such as combining studies in adults and children), and we question whether these are appropriate tools to evaluate available evidence about mite allergen avoidance, and whether it is correct to rely disproportionately on the results of meta-analyses/systematic reviews to inform clinical practice in this area. Recent evidence in children suggests that mite-impermeable bed encasings reduce emergency hospital attendance with severe asthma exacerbations. Expert opinion: The practical questions include how to achieve a sufficient real-life reduction allergen exposure, and how to identify patients who will benefit from effective intervention. The intervention should start early in the natural history of asthma, and consideration for choosing patients should include using the titre of allergen-specific IgE antibodies or the size of skin test wheal as an indicator.

Allergy Development in Adulthood: An Occupational Cohort Study of the Manufacturing of Industrial Enzymes

BACKGROUND

Occupational allergy may serve as a model of allergy development in adults.

OBJECTIVE

We aimed at describing respiratory allergy and IgE sensitization across different exposure strata defined by time, technology, and exposure control.

METHODS

In a retrospective (1970-2017) cohort of industrial enzyme production employees, monitored by an occupational medical center, 5024 individuals were surveyed. Five exposure groups and risk levels for sensitization and allergic disease were analyzed on the basis of demographic characteristics, hiring decade, and smoking status.

RESULTS

Of all persons entering the company 47 years from 1970, 149 developed occupational allergy (incidence rate, 2.72/1000 person-years). In a multivariate cause-specific Cox proportional hazards model, the hazard of allergy was significantly related to decade of recruitment. Compared with the 1970s, the hazard ratio (HR) uniformly decreased from 0.85 (95% CI, 0.57-1.27) in the 1980s to 0.16 (95% CI, 0.05-0.52) in the 2010s. Compared with expected highest exposed group, the HRs were 0.48 (95% CI, 0.31-76) and 0.13 (95% CI, 0.06-0.30) in less exposed production areas and 0.92 (95% CI, 0.48-1.73) and 0.23 (95% CI, 0.10-0.53) in different laboratory areas. The HR of smoking was 2.03 (95% CI, 1.41-2.93). The pattern of sensitizations also showed clear associations to recruitment decade, exposure, and smoking. Among individuals sensitized but not yet allergic, a high IgE level was the only risk factor (HR, 3.03; 95% CI, 1.82-5.04) for subsequent allergy development.

CONCLUSIONS

The impact of exposure is dose-related and linked to the sensitization step, which may subsequently lead to allergy development. For primary prevention of enzyme allergy, exposure control is mandatory and achievable despite increasing production volumes.

Sensitization to Cat: When Is Nasal Challenge Needed?

INTRODUCTION

Although the skin prick test (SPT) is a reliable diagnostic tool in perennial allergic rhinitis (PER) for patients allergic to cats, the minimum necessary SPT wheal size required to distinguish cat sensitization from true allergy remains controversial. The cat nasal challenge test (cNCT) could be considered the gold standard for detecting true cat allergy.

AIMS

To assess the difference in the frequency of cNCT positivity between cat owners and non-owners and to determine an appropriate cut-off level for SPT wheal size in detecting positive cNCT in PER patients who are candidates for allergen immunotherapy (AIT) with cat allergen extracts.

SUBJECTS AND METHODS

cNCT in the form of a nasal spray was administered to 60 adult patients with PER, i.e., cat owners (n = 19) and cat non-owners (n = 41) with positive SPT to cat fur allergen (Diater, Spain). Subjective (total nasal symptom score [TNSS]) and objective measurements (peak nasal inspiratory flow [PNIF]) for assessment of nasal patency and nasal eosinophil count [NEo]) were used to assess the nasal response. Peak expiratory flow (PEF) was used as a safety parameter during cNCT.

RESULTS

No differences were obtained in SPT wheal size and cNCT positivity between cat owners and non-owners. Positive cNCT detecting true cat allergy could be predicted by a cat SPT wheal size > 6.5 mm with 71.11% sensitivity and 100% specificity.

CONCLUSIONS

In adult patients with PER, the frequency of cat allergy was similar among cat owners and non-owners. A cat SPT wheal size ≥6.5 mm could be helpful in detecting true cat allergy by avoiding the demanding, time-consuming, and often unavailable cNCT when cat AIT is needed.

Allergic Diseases and Atopy Among Schoolchildren in Eastern Croatia

SUMMARY – A cross-sectional study was carried out in Brod-Posavina County, Croatia, to assess the prevalence of allergic diseases and atopy, as well as to investigate the possible etiologic factors for asthma, allergic rhinitis and eczema in childhood. The study included 1687 schoolchildren aged 10-11 years. Data were collected using standardized International Study of Asthma and Allergies in Childhood (ISAAC) Phase II written questionnaire. Skin prick tests were performed to provide an objective measure of atopy, defined as skin reactivity to one or more allergens. Lifetime prevalence of wheezing was 22.7%, rhinitis symptoms 22.5%, and eczema symptoms 17.9%. Period prevalence in the past 12 months was 7.9% for attacks of wheezing, 9.9% for rhinoconjunctivitis symptoms, and 10.1% for eczema symptoms. Of the children in which skin prick test was performed, 20.2% were positive for at least one of the allergens used, with house dust mite sensitization being the most frequent one. Risk factors for allergic disease include allergic disease in family, atopy, sensitization to indoor and outdoor allergens, and environmental tobacco smoke exposure at home. International comparison with the results of other ISAAC Phase II studies showed the Brod-Posavina County to be an area with moderate prevalence of atopy and current asthma symptoms.

Boiling and roasting treatment affecting the peanut allergenicity

Background

Peanut allergy appears to be less prevalent in other parts of the world than North America and several European countries, and it has been proposed difference in cooking practices may be responsible. In this study, the boiling and roasting processes were investigated to find a potential method to enhanced or reduce the allergenicity.

Methods

The allergenicity of different peanut products, as reflected by changes in ethology (diarrhea and weight loss) and pathology (splenomegaly and jejunum breakage) were observed, and relevant serological indexes were determined after feeding different peanut products. Different peanut proteins were used to analyze the ability to resistance digestion in simulated gastric fluid (SGF). Ultraviolet spectrum and CD spectra were used to analyze structure changes of Ara h 2 in roasting and boiling treatment.

Results

In the detection of the corresponding serological indicators, boiled peanuts show a lower sensitization than roasted and raw peanuts. SGF experiments demonstrated an increased resistance of roasted peanut protein to digestion. The results of ultraviolet spectrum and CD spectra showed that the roasting and boiling causes altered structures of the Ara h 2 peanut allergens.

Conclusions

The summary show that different thermal processing may affect the structure and immunoreactivity, and the sensitization of roasted or boiled peanuts will be enhanced or reduced.

Bedroom Allergen Exposure Beyond House Dust Mites

PURPOSE OF REVIEW

The review provides insight into recent findings on bedroom allergen exposures, primarily focusing on pet, pest, and fungal exposures.

RECENT FINDINGS

Large-scale studies and improved exposure assessment technologies, including measurement of airborne allergens and of multiple allergens simultaneously, have extended our understanding of indoor allergen exposures and their impact on allergic disease. Practical, streamlined methods for exposure reduction have shown promise in some settings, and potential protective effects of early-life exposures have been further elucidated through the investigation of specific bacterial taxa. Advances in molecular allergology have yielded novel data on sensitization profiles and cross-reactivity. The role of indoor allergen exposures in allergic disease is complex and remains incompletely understood. Advancing our knowledge of various co-exposures, including the environmental and host microbiome, that interact with allergens in early life will be crucial for the development of efficacious interventions to reduce the substantial economic and social burden of allergic diseases including asthma.

Contribution of repeated infections in asthma persistence from preschool to school age: Design and characteristics of the PreDicta cohort

BACKGROUND

The PreDicta cohort was designed to prospectively evaluate wheeze/asthma persistence in preschoolers in association with viral/microbial exposures and immunological responses. We present the cohort design and demographic/disease characteristics and evaluate unsupervised and predefined phenotypic subgroups at inclusion.

METHODS

PreDicta is a 2-year prospective study conducted in five European regions, including children 4-6 years with a diagnosis of asthma as cases and healthy age-matched controls. At baseline, detailed information on demographics, asthma and allergy-related disease activity, exposures, and lifestyle were recorded. Lung function, airway inflammation, and immune responses were also assessed. Power analysis confirmed that the cohort is adequate to answer the initial hypothesis.

RESULTS

A total of 167 asthmatic children (102 males) and 66 healthy controls (30 males) were included. Groups were homogeneous in respect to most baseline characteristics, with the exception of male gender in cases (61%) and exposure to tobacco smoke. Comorbidities and number and duration of infections were significantly higher in asthmatics than controls. 55.7% of asthmatic children had at least one positive skin prick test to aeroallergens (controls: 33.3%, P = .002). Spirometric and exhaled nitric oxide values were within normal limits; only baseline FEV_0.5 and FEV₁ reversibility values were significantly different between groups. Viral infections were the most common triggers (89.2%) independent of severity, control, or atopy; however, overlapping phenotypes were also common. Severity and control clustered together in an unsupervised analysis, separating moderate from mild disease.

CONCLUSIONS

The PreDicta cohort presented no differences in non-asthma related measures; however, it is well balanced regarding key phenotypic characteristics representative of "preschool asthma".

Bedroom exposure to airborne allergens in the Chicago area using a patient-operated sampling device

BACKGROUND

In current practice, allergens in vacuum-collected dust are used as surrogates for inhalable allergens. We developed an air-sampling device that can be used by patients for direct measurement of airborne allergen concentrations in their own homes.

OBJECTIVE

To demonstrate the use of this device to establish allergen concentration reference ranges in a target population and to evaluate associations between patient-reported information and measured allergen concentrations.

METHODS

Patients from 5 allergist's practices in the Chicagoland region were provided with instructions, questionnaires, informed consent forms, and samplers to run for 5 days in their bedrooms. Samples were collected from cartridges and assayed by multiplex immunoassays for 12 common household allergens and enzyme-linked immunosorbent assay for ragweed.

RESULTS

Unique allergen profiles were obtained for 102 patient homes. Samples with allergen concentrations above the limit of detection were as follows: total dust mite, 28%; cat, 61%; dog, 64%; mouse, 12%; rat, 0%; cockroach, 4%; Alternaria, 6%; Aspergillus, 21%; birch pollen 1%; grass, 8%; and ragweed, 5%. Of those, 75 completed questionnaires, providing meta-data for further analysis. Pet allergens correlated significantly with number of pets owned. Humidity correlated with dust mite allergens, open windows with Alternaria and mouse allergens, and high-efficiency particulate air filter use with reduced levels of several allergens. Many other variables showed no significant correlations.

CONCLUSION

The combination of ease of use, high air-sampling rate, and sensitive immunoassays permitted the measurement of airborne allergen concentrations in homes and establishment of reference ranges. Patient-reported information permitted identification of factors that could relate to allergen concentrations and suggested remedial measures.

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

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

Consideration of methods for identifying mite allergens

House dust mites are small arthropods that produce proteins—found in their feces, body parts, and eggs—that are major triggers of human allergies worldwide. The goal of this review is to describe the current methods used to identify these allergens. A literature search for allergen identification methods employed between 1995 and 2016 revealed multiple techniques that can be broadly grouped into discovery and confirmation phases. The discovery phase employs screening for mite proteins that can bind IgEs in sera from animals or patients allergic to dust mites. The confirmation phase employs biochemical methods to isolate either native or recombinant mite proteins, confirms the IgE binding of the purified allergens, and uses either in vitro or in vivo assays to demonstrate that the purified antigen can stimulate an immune response. The methods used in the two phases are defined and their strengths and weaknesses are discussed. The majority of HDM-allergic patients may respond to just a small subset of proteins, but new protein discovery methods are still warranted in order to develop a complete panel of HDM allergens for component resolved diagnosis and patient-tailored therapies.

Airborne protein concentration: a key metric for type 1 allergy risk assessment-in home measurement challenges and considerations

Background

Exposure to airborne proteins can be associated with the development of immediate, IgE-mediated respiratory allergies, with genetic, epigenetic and environmental factors also playing a role in determining the likelihood that sensitisation will be induced. The main objective of this study was to determine whether airborne concentrations of selected common aeroallergens could be quantified in the air of homes using easily deployable, commercially available equipment and analytical methods, at low levels relevant to risk assessment of the potential to develop respiratory allergies. Additionally, air and dust sampling were compared and the influence of factors such as different filter types on allergen quantification explored.

Methods

Low volume air sampling pumps and DUSTREAM^® dust samplers were used to sample 20 homes and allergen levels were quantified using a MARIA^® immunoassay.

Results

It proved possible to detect a range of common aeroallergens in the home with sufficient sensitivity to quantify airborne concentrations in ranges relevant to risk assessment (Limits of Detection of 0.005–0.03 ng/m³). The methodology discriminates between homes related to pet ownership and there were clear advantages to sampling air over dust which are described in this paper. Furthermore, in an adsorption–extraction study, PTFE (polytetrafluoroethylene) filters gave higher and more consistent recovery values than glass fibre (grade A) filters for the range of aeroallergens studied.

Conclusions

Very low airborne concentrations of allergenic proteins in home settings can be successfully quantified using commercially available pumps and immunoassays. Considering the greater relevance of air sampling to human exposure of the respiratory tract and its other advantages, wider use of standardised, sensitive techniques to measure low airborne protein concentrations and how they influence development of allergic sensitisation and symptoms could accelerate our understanding of human dose–response relationships and refine our knowledge of thresholds of allergic sensitisation and elicitation via the respiratory tract.

The potential impact of paternal age on risk of asthma in childhood: a study within the Danish National Birth Cohort

BACKGROUND

Advanced paternal age has been associated with offspring morbidity and mortality, possibly due to de novo mutations and epigenetic changes in male germ cells. Epigenetic changes in the cord blood cells have been linked to asthma symptoms in offspring, but the role of paternal age has been less studied.

METHODS

From the Danish National Birth Cohort, 48,785 children who completed the 7-year follow-up were included. Parental reports of physician-diagnosed asthma had been obtained by a posted or web-based questionnaire. Paternal age at delivery was obtained through linkage with maternal civil registration number in the Danish Civil Registration System and classified into four groups: ≤24, 25-34 (reference), 35-39, and >40 years. We calculated the prevalence proportion of asthma and prevalence ratios (PRs) with 95% confidence intervals (CIs) using log-binomial regression, adjusting for paternal smoking, paternal asthma, and paternal socioeconomic status.

RESULTS

At the 7-year follow-up, 5875 children (12%) had physician-diagnosed asthma. The prevalence of asthma in 7-year old children was higher with paternal age of ≤24 (adjusted PR 1.40; 95% CI: 1.26; 1.55) and lower with the paternal age of ≥35 years (adjusted PR 0.84; 95% CI: 0.78; 0.89) compared to the reference group.

CONCLUSIONS

Paternal age of ≥35 years was associated with a lower prevalence of asthma in childhood, and paternal age of ≤24 years with higher prevalence compared with paternal age of 25-34 years. The potential causes of higher asthma prevalence among offspring of young fathers warrant further investigation.

Better understanding of childhood asthma, towards primary prevention - are we there yet? Consideration of pertinent literature

Asthma is a chronic disease, characterized by reversible airway obstruction, airway inflammation and hyper-reactivity. The prevalence of asthma has risen dramatically over the past decade, affecting around 300,000,000 people. The etiology is multifactorial, with genetic, epigenetic, developmental and environmental factors playing a role. A complex interaction between the intrauterine environment, the developing immune system, the infant's microbiome and infectious organisms may lead to the development of allergic sensitization and asthma. Thus, a large number of studies have investigated the risk factors for childhood asthma, with a meticulous search of modifiable factors that could aid in primary prevention.

We present a current literature review from 2014-2017, as well as older classic publications, on the pathogenesis and the potential modifiable factors for primary prevention of asthma. No ideal preventive measure has yet been found. Rather, creating favorable prenatal and postnatal environments, minimal exposure to hostile environmental factors, prevention of infections in early life, allergic desensitization and nutritional modifications could possibly reduce asthma inception. In the era of personalized medicine, identifying individual risk factors and tailoring specific preventive measures is warranted.

Approaches to assess IgE mediated allergy risks (sensitization and cross-reactivity) from new or modified dietary proteins

The development and introduction of new dietary protein sources has the potential to improve food supply sustainability. Understanding the potential allergenicity of these new or modified proteins is crucial to ensure protection of public health. Exposure to new proteins may result in de novo sensitization, with or without clinical allergy, or clinical reactions through cross-reactivity. In this paper we review the potential of current methodologies (in silico, in vitro degradation, in vitro IgE binding, animal models and clinical studies) to address these outcomes for risk assessment purposes for new proteins, and especially to identify and characterise the risk of sensitization for IgE mediated allergy from oral exposure. Existing tools and tests are capable of assessing potential crossreactivity. However, there are few possibilities to assess the hazard due to de novo sensitization. The only methods available are in vivo models, but many limitations exist to use them for assessing risk. We conclude that there is a need to understand which criteria adequately define allergenicity for risk assessment purposes, and from these criteria develop a more suitable battery of tests to distinguish between proteins of high and low allergenicity, which can then be applied to assess new proteins with unknown risks.

Bedroom allergen exposures in US households

BACKGROUND

Bedroom allergen exposures contribute to allergic disease morbidity because people spend considerable time in bedrooms, where they come into close contact with allergen reservoirs.

OBJECTIVE

We investigated participant and housing characteristics, including sociodemographic, regional, and climatic factors, associated with bedroom allergen exposures in a nationally representative sample of the US population.

METHODS

Data were obtained from National Health and Nutrition Examination Survey 2005-2006. Information on participant and housing characteristics was collected by using questionnaires and environmental assessments. Concentrations of 8 indoor allergens (Alt a 1, Bla g 1, Can f 1, Fel d 1, Der f 1, Der p 1, Mus m 1, and Rat n 1) in dust vacuumed from nearly 7000 bedrooms were measured by using immunoassays. Exposure levels were classified as increased based on percentile (75th/90th) cutoffs. We estimated the burden of exposure to multiple allergens and used multivariable logistic regression to identify independent predictors for each allergen and household allergen burden.

RESULTS

Almost all participants (>99%) had at least 1 and 74.2% had 3 to 6 allergens detected. More than two thirds of participants (72.9%) had at least 1 allergen and 18.2% had 3 or more allergens exceeding increased levels. Although exposure variability showed significant racial/ethnic and regional differences, high exposure burden to multiple allergens was most consistently associated with the presence of pets and pests, living in mobile homes/trailers and older and rental homes, and living in nonmetropolitan areas.

CONCLUSIONS

Exposure to multiple allergens is common. Despite highly variable exposures, bedroom allergen burden is strongly associated with the presence of pets and pests.

Asthma phenotypes and IgE responses

The discovery of IgE represented a major breakthrough in allergy and asthma research, whereas the clinical interest given to IgE in asthma has been blurred until the arrival of anti-IgE biotherapy. Novel facets of the complex link between IgE and asthma have been highlighted by the effect of this treatment and by basic research. In parallel, asthma phenotyping recently evolved to the concept of endotypes, relying on identified/suspected pathobiological mechanisms to phenotype patients, but has not yet clearly positioned IgE among biomarkers of asthma.In this review, we first summarise recent knowledge about the regulation of IgE production and its main receptor, FcεRI. In addition to allergens acting as classical IgE inducers, viral infections as well as air pollution may trigger the IgE pathway, notably resetting the threshold of IgE sensitivity by regulating FcεRI expression. We then analyse the place of IgE in different asthma endo/phenotypes and discuss the potential interest of IgE among biomarkers in asthma.

Proposed Iraq/Afghanistan War-Lung Injury (IAW-LI) Clinical Practice Recommendations: National Academy of Sciences' Institute of Medicine Burn Pits Workshop

High rates of respiratory symptoms (14%) and new-onset asthma in previously healthy soldiers (6.6%) have been reported among military personnel post-deployment to Iraq and Afghanistan. The term Iraq/Afghanistan War-Lung Injury (IAW-LI) is used to describe the constellation of respiratory diseases related to hazards of war, such as exposure to burning trash in burn pits, improvised explosive devices, and sandstorms. Burnpits360.org is a nonprofit civilian website which voluntarily tracks medical symptoms among soldiers post-deployment to the Middle East. Subsequent to initiation of the Burnpits360.org website, the Department of Veterans Affairs started the Airborne Hazards and Open Burn Pit registry. This paper: (a) analyzes the latest 38 patients in the Burnpits360.org registry, validated by DD214 Forms; (b) compares strengths and weaknesses of both registries as outlined at the National Academy of Sciences Institute of Medicine Burn Pits Workshop;

Ever dispense of prescribed allergy medication in children growing up close to traffic: a registry-based birth cohort

Background

Epidemiologic studies have shown conflicting results regarding the role of traffic pollution in the development of allergic disease. This study investigated the relationship between living close to traffic and ever dispense of prescribed oral antihistamines or nasal anti-allergic medication, among young children. The underlying aim was to investigate if children growing up close to traffic pollution are at higher risk of developing allergy in early childhood.

Methods

We investigated a birth cohort in southern Sweden, consisting of N = 26 128 children (0–6 years) with health outcome and exposure data. Of these children, N = 7898, had additional covariate information. Traffic intensity and yearly averages of dispersion-modeled concentrations of NO_X (100 × 100 m grid) at residential addresses, were linked with registry data on dispensed allergy medication (the Swedish Prescribed Drug Register). Individual level covariate information was obtained from questionnaires distributed to parents at Child Health Care-center visits, eight months after birth. Cox proportional hazards regression was used for the statistical analyses.

Results

Living in close proximity to a road with equal to or greater than 8640 cars/day (compared to 0–8639 cars/day), was not associated with higher incidence of ever dispensed oral antihistamine or nasal anti-allergic medication, with or without adjustment for confounders (sex, breastfeeding, parental allergy, parental origin, season, and year of birth). Similar results were found in relation to NO_X.

Conclusions

Traffic-related exposure was not associated with higher incidence of ever dispensed medication against allergy, in children 0–6 years in southern Sweden. These results indicates that traffic-related exposure may not be a risk factor for early onset allergy in children in southern Sweden. However, children with dispense of prescribed allergy medication may be a selected subgroup, and the results for this group may not be generalizable to all children with allergy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12889-015-2356-3) contains supplementary material, which is available to authorized users.

Early Exposure to Respiratory Allergens by Placental Transfer and Breastfeeding

The relationship between allergen exposure and the onset of or protection from allergic diseases remains unclear. Many factors could be related to immunological responses, such as the age when the exposure occurs, type of allergen, timing, dose, and allergen route. In this study, we investigated whether exposure to respiratory allergens could occur in pregnancy or early life. In particular, we assessed whether Der p 1 and Blo t 5, as well as specific antibodies against these allergens, could be detected in 90 paired cord blood and colostrum samples. Der p 1 was detected in 58.6% of colostrum and 29% of cord blood samples, whereas Blot 5 was positive in 41.3% and 9.6% of the samples, respectively. Similar to specific IgA, which could be detected in all samples for both mites, specific IgG was found in a high number of colostrum samples, 93.5% and 94.8% for Dp and Bt, respectively. Although allergens were not detected in all cord blood samples, a high percentage of them (≥95%) were positive for specific IgM to both mites in cord blood samples, suggesting that neonates can be exposed and sensitized to airborne allergens during pregnancy. Many studies have attempted to correlate allergen exposure or its prevention in early infancy with the onset of or protection from allergic diseases. However, conflicting and inconsistent data do not show a clear correlation with or suggest a way to prevent allergen sensitization. Nevertheless, these unconvincing results could be better understood if the relationship with many aspects of allergen exposure after pregnancy could be clarified. Thus, it is necessary to address basic issues related to allergen exposure, including the development of reproducible, standardized and reliable methods, and to determine how and where the exposure occurs.