Indoor allergen exposure in the development of allergy and asthma

The Efficacy of the Dyson Air Purifier in Improving Asthma Control: Protocol for a Single-Center, Investigator-Led, Randomized, Double-Blind, Placebo-Controlled Trial

BACKGROUND

Indoor air quality has been shown to influence asthma control and outcomes. Air purifiers and high-efficiency particulate air filtration devices can improve indoor air quality by reducing the indoor levels of air pollution and allergens. However, the influence of this improved indoor air quality on asthma control remains unclear; hence, randomized controlled trials are needed to further elucidate this phenomenon.

OBJECTIVE

This study aims to investigate the effect of reducing the levels of allergens and pollutants in the bedroom and living room through the use of Dyson air purifiers (Dyson Pure Cool) on asthma control.

METHODS

This is an 18-month long, investigator-led, randomized, double-blinded, placebo-controlled, single-center trial. Subjects will be randomized in a 1:1 ratio to active or placebo Dyson filters. The primary outcome is the change in the scores of Asthma Control Questionnaire 6 and Asthma-specific Quality of Life Questionnaire from baseline. Secondary outcomes include changes in lung function (forced expiratory volume in one second, forced expiratory volume in one second/forced vital capacity ratio, and midexpiratory flows), peak expiratory flow measurements, airway hyperresponsiveness (assessed by methacholine bronchial challenge), fractional exhaled nitric oxide, and indoor air pollutant levels. The sample size will be 50 subjects, and all subjects will have a confirmed diagnosis of mild persistent to moderate persistent asthma along with an Asthma Control Questionnaire 6 score of >1.5.

RESULTS

This study was approved by the West Midlands Research Ethics Committee (18/WM/0277). The study results will be published in peer-reviewed scientific journals; presented at relevant scientific conferences; and shared in plain English with participants in our newsletters, in our clinics, and via the David Hide Asthma and Allergy Research Centre website. Our trial began in September 2019 and is expected to end in August 2021.

CONCLUSIONS

This is a double-blinded, placebo-controlled, randomized, investigator-led study to investigate the efficacy of a novel air purifier in improving asthma control in adults. The trial period of 18 months will facilitate the collection of robust data and will therefore generate clear signals. However, this extended trial duration may lead to patient withdrawal. Furthermore, this trial is conducted at a single center and in a location with a homogenous cohort of people, which may affect translatability. Nonetheless, it is hoped that the findings of this trial may help further inform clinicians regarding the utility of this novel device as an adjunct in asthma care.

TRIAL REGISTRATION

ClinicalTrials.gov NCT04729530; https://clinicaltrials.gov/ct2/show/NCT04729530.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/28624.

The level of allergens in dust samples collected from selected schools in Shiraz, Iran and its asthma-risk implications

BACKGROUND

Both home and school are important places where children are exposed to various indoor allergens. This study aimed to identify the profile of indoor allergens in schools and its impact on asthma development.

METHODS

A total of 104 classrooms from 52 schools were selected for dust collection during the fall of 2017. The levels of indoor allergens including dust mite (Der f1, Der p1), cat (Fel d1), cockroach (Bla g1) and mouse (Mus m1) were measured by enzyme linked immunosorbent assay (ELISA). The diagnosis of asthma was made in all students of the selected classes by the allergist. The collected data were analyzed using SPSS version 21.0.

RESULTS

Out of 2816 students in the selected classes, 180 students were involved with asthma. Students were mostly exposed to Bla g1 (83.1%), followed by Der f1 (51.5%), Mus m 1 (45.5%), Der p1 (8.9%) and Fel d1 (7.9%) in the dust collected from 101 classrooms. Although levels of all studied allergens in the settled dust of the classrooms were low, there was a relationship between Fel d1 in the classroom dust and development of asthma.

CONCLUSION

This study showed considerable levels of cockroach allergens in schools. Exposure to cat allergen in our schools played an important role in asthma development; further school-based investigations require evaluating the role of classroom allergen on asthma development.

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

The role of allergen exposure in the development of allergic disease has been a matter of considerable debate, and our understanding of the importance of allergens has evolved over the last 25 years. Several observational and primary prevention studies have investigated these relationships, and different studies reported inconsistent, and sometimes opposite findings. It has to be emphasized that a clear understanding of how aeroallergen exposure occurs, and accurate and reproducible measurement of exposure are essential prerequisites for understanding the role of exposure. However, our current understanding of how we get exposed to allergens is not based on solid evidence, but on a number of assumptions, and we urgently need to develop better proxy measures (or indices) of exposure. In addition, the relative importance of the timing of exposure (e.g. early compared to exposure in later life) is unknown. It is also unclear which route of exposure is the most relevant (e.g. inhaled vs. oral vs. transcutaneous). Available data suggest that the dose-response relationship between allergen exposure and allergic disease may differ between different allergens, dose ranges and exposure patterns, and these relationships may further differ between different populations and geographical areas. It is increasingly clear that childhood asthma and atopy are not single phenotypes, and it is likely that allergen exposure has different effect on distinct subgroups under the umbrella terms of 'sensitization' and 'asthma'. Susceptibility to allergen exposure, other environmental exposures and their interactions may also differ between individuals with different genetic predispositions. However, the precise nature of these complex relationships is unclear. We need a holistic approach offered by systems biology, with integration of information on the standardized and reliable measures of exposures (including allergens and other relevant exposures) with genetic and biological data to fully understand the role of allergens in the development of allergic disease.

Aggravation of atopic dermatitis-like symptoms by consecutive low concentration of formaldehyde exposure in NC/Nga mice

Formaldehyde (FA) has been known to be associated with development of asthma (AS) and atopic dermatitis (AD). In this study, we investigated whether FA inhalation would affect the provocation or exacerbation of AD-like symptoms. Atopic-prone NC/Nga mice were exposed to low (0.2 ppm) and high (1.0 ppm) concentration of FA by inhalation. Combined exposure to low concentration of FA inhalation and topical house dust mite (HDM) stimulation significantly upregulated HDM-induced total plasma IgE and IgG2a production, Th1-, Th2-, Th17-related cytokine as well as COX-2 mRNA expressions in the skin. Interestingly, independent FA inhalation, especially at low concentration (0.2 ppm), increased the skin mRNA expressions of IL-13, IL-17E/IL-25 and COX-2, even though it failed to induce AD-like skin inflammation. In conclusion, we suggest that increased skin mRNA expressions of IL-13, IL-25/IL-17E and COX-2 by independent low concentration of FA exposure might be a key factor to exacerbate HDM-mediated AD-like skin inflammation.

Analysis of T cell responses to the major allergens from German cockroach: epitope specificity and relationship to IgE production

Bla g allergens are major targets of IgE responses associated with cockroach allergies. However, little is known about corresponding T cell responses, despite their potential involvement in immunopathology and the clinical efficacy of specific immunotherapy. Bioinformatic predictions of the capacity of Bla g 1, 2, 4, 5, 6, and 7 peptides to bind HLA-DR, -DP, and -DQ molecules, and PBMC responses from 30 allergic donors, identified 25 T cell epitopes. Five immunodominant epitopes accounted for more than half of the response. Bla g 5, the most dominant allergen, accounted for 65% of the response, and Bla g 6 accounted for 20%. Bla g 5 induced both IL-5 and IFN-γ responses, whereas Bla g 6 induced mostly IL-5, and, conversely, Bla g 2 induced only IFN-γ. Thus, responses to allergens within a source are independently regulated, suggesting a critical role for the allergen itself, and not extraneous stimulation from other allergens or copresented immunomodulators. In comparing Ab with T cell responses for several donor/allergen combinations, we detected IgE titers in the absence of detectable T cell responses, suggesting that unlinked T cell-B cell help might support development of IgE responses. Finally, specific immunotherapy resulted in IL-5 down modulation, which was not associated with development of IFN-γ or IL-10 responses to any of the Bla g-derived peptides. In summary, the characteristics of T cell responses to Bla g allergens appear uncorrelated with IgE responses. Monitoring these responses may therefore yield important information relevant to understanding cockroach allergies and their treatment.

Population growth and allergen accumulation of Dermatophagoides pteronyssinus cultured at 20 and 25 °C

The house dust mites, Dermatophagoides pteronyssinus and D. farinae are cultured commercially and in research laboratories and material is harvested from these cultures to make extracts that are used for diagnosis, immunotherapy and research. Temperature and other climatic conditions can influence population growth rates, dynamics of allergen production, and the associated endotoxin, enzyme and protein levels of the mite material harvested from these cultures. Here we determined how temperature affected these parameters. Dermatophagoides pteronyssinus was cultured at 20 and 25 °C at 75% relative humidity, and at 2-week intervals the concentrations of mites, Der p 1 and Der p 2 allergens, endotoxin, and selected enzymes were determined. Mite density increased exponentially but growth rate and final population density were greater at 25 °C compared to 20 °C. The combined allergen (Der p 1 + Der p 2) concentrations accumulated in the cultures at about the same rate at both temperatures. However, individual Der p 1 and Der p 2 accumulation rates varied independently at the two temperatures. Der p 1 accumulated faster at 20 °C whereas Der p 2 accumulated faster at 25 °C. The amount of Der p 1 in whole cultures was greater than the amount of Der p 2. The concentration of allergen for washed mites harvested from the cultures was much less than for the whole cultures. Our study demonstrated that temperature is an important factor in population growth and the dynamics of allergen production in cultured mites.

Mucosal allergic sensitization to cockroach allergens is dependent on proteinase activity and proteinase-activated receptor-2 activation

We have shown that proteinase-activated receptor-2 (PAR(2)) activation in the airways leads to allergic sensitization to concomitantly inhaled Ags, thus implicating PAR(2) in the pathogenesis of asthma. Many aeroallergens with proteinase activity activate PAR(2). To study the role of PAR(2) in allergic sensitization to aeroallergens, we developed a murine model of mucosal sensitization to cockroach proteins. We hypothesized that PAR(2) activation in the airways by natural allergens with serine proteinase activity plays an important role in allergic sensitization. Cockroach extract (CE) was administered to BALB/c mice intranasally on five consecutive days (sensitization phase) and a week later for four more days (challenge phase). Airway hyperresponsiveness (AHR) and allergic airway inflammation were assessed after the last challenge. To study the role of PAR(2), mice were exposed intranasally to a receptor-blocking anti-PAR(2) Ab before each administration of CE during the sensitization phase. Mucosal exposure to CE induced eosinophilic airway inflammation, AHR, and cockroach-specific IgG1. Heat-inactivated or soybean trypsin inhibitor-treated CE failed to induce these effects, indicating that proteinase activity plays an important role. The use of an anti-PAR(2) blocking Ab during the sensitization phase completely inhibited airway inflammation and also decreased AHR and the production of cockroach-specific IgG1. PAR(2) activation by CE acts as an adjuvant for allergic sensitization even in the absence of functional TLR4. We conclude that CE induces PAR(2)-dependent allergic airway sensitization in a mouse model of allergic airway inflammation. PAR(2) activation may be a general mechanism used by aeroallergens to induce allergic sensitization.

Fms-like tyrosine kinase 3 ligand decreases T helper type 17 cells and suppressors of cytokine signaling proteins in the lung of house dust mite-sensitized and -challenged mice

We previously reported that Fms-like tyrosine kinase 3 ligand (Flt3-L) reversed airway hyperresponsiveness (AHR) and airway inflammation, and increased the number of regulatory CD11c(high)CD8α(high)CD11b(low) dendritic cells and CD4(+)CD25(+)ICOS(+)Foxp3(+)IL-10(+) T-regulatory cells in the lung of allergen-sensitized and -challenged mice. In this study, we evaluated the effect of Flt3-L on Th17 cells and expression of suppressors of cytokine signaling (SOCS) proteins in the lungs of house dust mite (HDM)-sensitized and -challenged mice. BALB/c mice were sensitized and challenged with HDM, and AHR to methacholine was established. Mice were treated with Flt3-L (5 μg, intraperitoneal) daily for 10 days. Levels of IL-4, -5, -6, -8, and -13, and transforming growth factor (TGF)-β in the bronchoalveolar lavage fluid (BALF) were examined by ELISA. Flt3-L treatment reversed existing AHR to methacholine and substantially decreased eosinophils, neutrophils, IL-5, -6, -8, and IL-13, and TGF-β levels in the BALF. HDM-sensitized and -challenged mice showed a significant increase in lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells with high expression of retinoic acid-related orphan receptor (ROR)-γt transcripts. However, administration of Flt3-L substantially decreased the number of lung CD4(+)IL-17(+)IL-23R(+)CD25⁻ T cells, with significantly decreased expression of ROR-γt mRNA in these cells. HDM sensitization caused a significant increase in the expression of SOCS-1, -3, and -5 in the lung. Flt3-L treatment abolished the increase in SOCS-1 and SOCS-3 proteins, whereas SOCS-5 expression was significantly reduced. These data suggest that the therapeutic effect of Flt3-L in reversing the hallmarks of allergic asthma in a mouse model is mediated by decreasing IL-6 and TGF-β levels in the BALF, which, in turn, decrease CD4(+)IL-17(+)IL-23R(+)ROR-γt(+)CD25⁻ T cells and the expression of SOCS-1 and SOCS-3 in the lung of HDM-sensitized and -challenged mice.

Intranasal ciclesonide coadministration with inhaled fluticasone propionate-salmeterol does not suppress cortisol in allergic rhinitis patients

Intranasal and inhaled corticosteroid administration concurrently in comorbid allergic rhinitis (AR) and asthma may potentially enhance cortisol suppression. This study determined whether intranasal ciclesonide 200 micro g once daily has an additional effect on cortisol suppression when coadministered with inhaled fluticasone propionate-salmeterol (FP-SAL) 500 to 50 micro g twice daily. Adults (N = 150) with perennial AR received FP-SAL and placebo nasal spray during the run-in period. Patients were randomized to ciclesonide or placebo and FP-SAL (43 days). A single 2-mg dose of dexamethasone was administered on the last treatment day. Plasma cortisol decreased during run-in period (p < 0.001), indicating cortisol suppression by FP-SAL. After ciclesonide was added to FP-SAL, plasma cortisol was similar in both groups. Dexamethasone decreased mean plasma cortisol (p < 0.001), demonstrating that further suppression was possible. Ciclesonide coadministered with FP-SAL did not have an additive effect on cortisol suppression compared with FP-SAL.

Assessment of indoor allergen exposure

Of the four modes of treating human allergic disease, avoidance or separation of the allergic patient from the allergen source is most effective and least expensive. The clinical immunology laboratory has established efficient and inexpensive "reservoir" dust sampling and processing procedures to obtain a surface dust specimen that reflects the allergen burden of the environment. Following extraction, allergens are quantified by reproducible, validated immunoenzymetric assays for the quantification of "indicator" aeroallergen levels in home, school, and work environments. In this paper, the strategies and methods for collecting and processing dust samples are discussed, and assays are reviewed for quantifying indoor aeroallergen exposure from dust mites (Der p 1 and 2, Der f 1 and 2), animals (cat: Fel d 1; dog: Can f 1; mouse: Mus m 1; rat: Rat n 1), and insects (cockroach: Bla g 1 and 2). Accurate quantification of the levels of allergen in indoor environments facilitates avoidance therapy by identifying environmental risk factors for asthma and allergy exacerbation and allowing the allergic patient to monitor the effectiveness of environmental remediation actions.

Evaluation of home allergen sampling devices

BACKGROUND

Simple, inexpensive methods of sampling from allergen reservoirs are necessary for large-scale studies or low-cost householder-operated allergen measurement.

METHODS

We tested two commercial devices: the Indoor Biotechnologies Mitest Dust Collector and the Drager Bio-Check Allergen Control; two devices of our own design: the Electrostatic Cloth Sampler (ECS) and the Press Tape Sampler (PTS); and a Vacuum Sampler as used in many allergen studies (our Reference Method). Devices were used to collect dust mite allergen samples from 16 domestic carpets. Results were examined for correlations between the sampling methods.

RESULTS

With mite allergen concentration expressed as microg/g, the Mitest, the ECS and the PTS correlated with the Reference Method but not with each other. When mite allergen concentration was expressed as microg/m2 the Mitest and the ECS correlated with the Reference Method but the PTS did not. In the high allergen conditions of this study, the Drager Bio-Check did not relate to any methods.

CONCLUSIONS

The Mitest Dust Collector, the ECS and the PTS show performance consistent with the Reference Method. Many techniques can be used to collect dust mite allergen samples. More investigation is needed to prove any method as superior for estimating allergen exposure.