Mattress encasings and mite allergen levels in the Prevention and Incidence of Asthma and Mite Allergy study

BACKGROUND: Reduction of allergen exposure from birth may reduce sensitization and subsequent allergic disease. OBJECTIVE: To measure the influence of mite allergen-impermeable mattress encasings and cotton placebo encasings on the amount of dust and mite allergen in beds. METHODS: A total of 810 children with allergic mothers took part in the Prevention and Incidence of Asthma and Mite Allergy (PIAMA) study. Allergen-impermeable and placebo mattress encasings were applied to the childrens' and the parents' beds before birth. Dust samples were taken from the beds of children and their parents before birth and 3 and 12 months after birth. Extracts of dust samples were analysed for mite allergens (Der p 1 and Der f 1). RESULTS: Active mattress encasings were significantly more effective in reducing dust and mite allergen levels than placebo encasings. Mite allergen levels were low in general and the treatment effect was modest. Twelve months after birth, mattresses with active mattress encasings had about half the amount of Der 1 (Der p 1 + Der f 1)/m2, compared to mattresses with placebo encasings, for the child's and the parental mattress. CONCLUSION: This study shows that mite-impermeable mattress encasings have a significant but modest effect on dust and mite allergen levels of mattresses with low initial mite allergen levels, compared to placebo.     

Allergen-avoidance measures in homes of house-dust-mite-allergic asthmatic patients: effects of acaricides and mattress encasings

This double-blind, placebo-controlled study investigated whether the application of an acaricide (Acarosan®) on mattresses and on textile floor coverings in living rooms and bedrooms can contribute to improvement in lung function and airway hyperresponsiveness in 40 adult asthmatic patients sensitized to house-dust mite. In a second group of 19 patients who refused chemical intervention, the clinical effects of application of allergen-impermeable mattress encasings were studied. In all three treatment groups, Der p 1 levels in mattress dust were statistically significantly decreased after 12 months. However, this decrease was much greater in the group who received mattress encasings (final mean level 430 ng/g) than in groups with acaricide- or placebo-treated mattresses (final mean levels 1730 and 2100 ng/g, respectively). Treatment of textile floors with either Acarosan or placebo chemical caused a statistically significant decrease in the level of the house-dust-mite allergen Der p 1 in floor dust. In the group with mattress encasings, no significant changes of floor dust Der p 1 were found. Airway hyperresponsiveness (as measured by the PC²⁰ histamine) improved significantly in the mattress cover group after 6 months. The Acarosan group also showed a small but statistically significant improvement after 12 months.     

Effect of mattress encasings on atopic dermatitis outcome measures in a double-blind,placebo-controlled study: the Dutch mite avoidance study

BACKGROUND: House dust mite (HDM) allergen might induce and maintain atopic dermatitis (AD). Reduction of allergen load by applying encasings might improve the clinical symptoms of AD. OBJECTIVE: We sought to investigate, in a randomized, double-blind, placebo-controlled study, whether reducing HDM allergen levels by using mattress, duvet, and pillow encasings for 12 months will result in improvement in AD symptoms. METHODS: Patients with AD (8-50 years old and allergic to HDM), having a Leicester sign score (a dermatitis score) of at least 1% extent and a severity score of 6 points or greater, were randomly allocated to an active (n = 45) or a placebo allergen-avoidance group (n = 41). Avoidance measures consisted of applying HDM-impermeable encasings for mattresses, pillows, and duvets for the active treatment group and cotton encasings for the placebo group. Effect on allergen concentrations (Der p 1 and Der p 1 plus Der f 1), Leicester sign score extent and severity, visual analogue scale scores for itching and sleeplessness, intradermal test results, atopy patch test results, total serum IgE levels, anti-Der p 1-specific IgE levels, and total blood eosinophil counts were studied. RESULTS: The active encasings reduced the Der p 1 allergen concentration in the mattress after 12 months with a factor 2.1 (P =.007) and the Der p 1 plus Der f 1 allergen concentration with a factor of 2.5 (P =.005); no significant change in allergen concentrations in mattresses was seen in the placebo group. Although the decrease in allergen load was significant, no differences in treatment-induced changes were seen between the placebo and active groups. CONCLUSIONS: Use of HDM-impermeable encasings resulted in a significant decrease in Der p 1 and Der p 1 plus Der f 1 allergen concentrations. However, this reduction in allergen load did not result in significant changes in clinical parameters between the groups. Reduction of allergens in other environments (work, school, and outdoors) might be equally important in improving symptoms of AD.     

Effect of mattress and pillow encasings on children with asthma and house dust mite allergy

BACKGROUND: House dust mite (HDM) allergy is a frequent cause of allergic asthma in children. Reduction of exposure seems to be the most logical way to treat these patients. OBJECTIVE: Our aim was to investigate whether mattress and pillow encasings resulted in an effective long-term control of HDM allergen levels, thereby reducing the need for asthma medication in children with asthma and HDM allergy. METHODS: In a prospective, double-blind, placebo-controlled study 60 children (age range, 6-15 years) with asthma and HDM allergy were randomized to active (allergy control) or placebo mattress and pillow encasings. After a 2-week baseline period, follow-up was performed every 3 months for 1 year. During the entire study period, the dose of inhaled steroids was tapered off to the lowest effective dose according to well-defined criteria. RESULTS: Fifty-two patients completed the trial, and 5 were excluded, leaving data from 47 children (26 in the active treatment group and 21 in the placebo group) for analysis. A significant perennial reduction in HDM allergen concentrations was seen only for the active treatment group. Also, a significant decrease in the dose of inhaled steroids (mean, 408 to 227 microg/d; P <.001) was found for the active treatment group only, with significant differences between groups after 9 and 12 months. After 1 year, the dose of inhaled steroids was reduced by at least 50% in significantly more children in the active treatment group than in the placebo group (73% vs 24%, P <.01). CONCLUSION: Encasing of mattresses and pillows resulted in a significant long-term reduction in HDM allergen concentrations in mattresses and in the need for inhaled steroids in children with asthma and HDM allergy.     

Der p 1 and Der p 2 induce less severe late asthmatic responses than native Dermatophagoides pteronyssinus extract after a similar early asthmatic response

Background The models for exposure to house dust in research and clinical practice are selected with respect to their role in IgE‐mediated immediate hypersensitivity. The use of isolated major allergens instead of complex allergen extracts is becoming increasingly popular as it offers some important advantages for quantitative measures in diagnosis and research. Objective To compare house dust mite extract and isolated mite major allergens with respect to their ability to induce early and late asthmatic responses and bronchial hyperreactivity. Methods Bronchial responses to house dust mite (HDM, Dermatophagoides pteronyssinus) extract and isolated major allergens from HDM (Der p 1 and Der p 2) were compared in a double‐blind, randomized, cross‐over study in 20 patients with mild to moderate asthma who were allergic to HDM. Allergen was titrated to a standardized early asthmatic response. Bronchial hyper‐responsiveness to histamine (PC₂₀histamine) was determined before and after allergen inhalation to assess allergen‐induced bronchial hyper‐responsiveness and IL‐5 was measured in serum. In addition, the allergens were applied in intracutaneous skin tests and activation of basophil leucocytes and proliferation of peripheral blood mononuclear cells was tested in vitro. Results After a similar early asthmatic response (mean Δforced expiratory volume in 1 s (FEV₁)_,max?29.4 (SD 7.2) vs. ?33.1 (8.6) %; mean difference 3.6 (95% CI ?0.9 to 8.2) %), the late asthmatic response (mean ΔFEV_1,max?45.9 (21.9) vs. ?32.7 (22.3) %; mean difference 13.2 (3.8–22.3) %), the degree of allergen‐induced bronchial hyper‐responsiveness (mean ΔPC₂₀histamine, 1.8 (1.0) vs. 1.2 (0.9) doubling dose; mean difference 0.6 (0.2–1.1) doubling dose) and serum IL‐5 at 6 h were found to be significantly higher after bronchial challenge with HDM extract than after challenge with an isolated HDM major allergen. Likewise, there was an increased late skin reaction with HDM compared with isolated major allergen after a similar early skin reaction. Conclusion Constituents of HDM extract, other than Der p 1 or Der p 2, with no significant influence on the IgE‐mediated early asthmatic response contribute significantly to the allergen‐induced late asthmatic response and bronchial hyper‐reactivity.     

Clinical effectiveness of a mite allergen-impermeable bed-covering system in asthmatic mite-sensitive patients

BACKGROUND: Exposure to allergens plays a role in the development of bronchial hyperresponsiveness and in the chronic inflammatory response seen in asthmatic patients. House dust mites (HDMs) are an important source of allergen. Reduction of these allergens might lead to better lung function and reduction of asthma symptoms. OBJECTIVE: The effect of HDM-impermeable covers on HDM allergen levels, peak flow values, and asthma symptoms were measured. Therefore a randomized clinical trial was carried out. METHODS: Fifty-two allergic asthmatic patients were randomly allocated to use the HDM-impermeable or placebo covers. During the study period, daily peak flow and asthma symptom scores were recorded. Dust samples were taken from the mattresses. RESULTS: We observed a significant reduction in HDM allergen levels on the mattresses after encasing them with HDM-impermeable covers (reduction of 87% of Der p 1 in micrograms per gram of dust; P <.001). Baseline symptoms were so low that no improvement could be established. Morning peak expiratory flow is significantly higher in the intervention group compared with that seen in the placebo group during the study period (beta=20.2; P <.01). CONCLUSIONS: HDM-impermeable covers significantly decreased the level of HDM allergens. Furthermore, morning peak flow was significantly increased during the intervention period. This study indicates that HDM allergen-avoidance measures might have beneficial effects on allergen reduction and asthma outcome.     

Frequency and intensity of late asthmatic reactions after bronchial allergen challenge in asthma and rhinitis

The occurrence of late asthmatic reactions after bronchial allergen challenge was studied in 50 house dust mite allergic patients subdivided in three groups: one group had asthma without nasal symptoms, another group had rhinitis without pulmonary symptoms and a third group had a combination of both asthma and rhinitis. Late asthmatic reactions were present in 80% of asthmatic patients and in 18.7% of rhinitis patients. The degree of non-specific bronchial reactivity to histamine (provocative dose 15 or PD15 histamine) and the degree of immediate reactivity to allergen (PD15 house dust mite) did not differ significantly between patients with and without late asthmatic reactions. These findings suggest that an important difference between asthma and rhinitis is the lack of late asthmatic reactions in rhinitis patients, whereas the degree of immediate bronchial reactivity to the allergen is similar in asthma and rhinitis.     

Validated safety predictions of airway responses to house dust mite in asthma

BACKGROUND: House dust mite (HDM) is the most common aeroallergen causing sensitization in many Western countries and is often used in allergen inhalation challenges. The concentration of inhaled allergen causing an early asthmatic reaction [provocative concentration of inhaled allergen causing a 20% fall of forced expiratory volume in 1 s (FEV(1))(PC(20) allergen)] needs to be predicted for safety reasons to estimate accurately the severity of allergen-induced airway responsiveness. This can be accomplished by using the degree of non-specific airway responsiveness and skin sensitivity to allergen. OBJECTIVE: We derived prediction equations for HDM challenges using PC(20) histamine or PC(20) methacholine and skin sensitivity data obtained from patients with mild to moderate persistent asthma and validated these equations in an independent asthma population. METHODS: PC(20) histamine or PC(20) methacholine, skin sensitivity, and PC(20) allergen were collected retrospectively from 159 asthmatic patients participating in allergen challenge trials. Both the histamine and methacholine groups (n=75 and n=84, respectively), were divided randomly into a reference group to derive new equations to predict PC(20) allergen, and a validation group to test the new equations. RESULTS: Multiple linear regression analysis revealed that PC(20) allergen could be predicted either from PC(20) methacholine only ((10)log PC(20) allergen=-0.902+0.741.(10)log PC(20) methacholine) or from PC(20) histamine and skin sensitivity (SS) ((10)log PC(20) allergen=-0.494+0.231.(10)log SS+0.546.(10)log PC(20) histamine). In the validation study, these new equations accurately predicted PC(20) allergen following inhalation of HDM allergen allowing a safe starting concentration of allergen of three doubling concentrations below predicted PC(20) allergen in all cases. CONCLUSION: The early asthmatic response to inhaled HDM extract is predominantly determined by non-specific airway responsiveness to methacholine or histamine, whereas the influence of the cutaneous sensitivity to HDM appears to be rather limited. Our new equations accurately predict PC(20) allergen and hence are suitable for implementation in HDM inhalation studies.     

Effects of house dust mite avoidance measures on Der p 1 concentrations and clinical condition of mild adult house dust mite-allergic asthmatic patients, using no inhaled steroids.

BACKGROUND: Exposure to house dust mite (HDM) allergens often results in worsening of asthma. Therefore, avoidance of exposure to HDM allergens is often proposed. Unfortunately, the most effective and feasible avoidance strategy is still not completely assessed. Consequently, we investigated the effects of a combined HDM avoidance strategy on HDM allergen concentrations and clinical condition of allergic, mild asthmatic, patients using no inhaled steroids. METHODS: Asthmatic patients, allergic to HDM, using no inhaled corticosteroids, were randomly allocated to an active (n = 76) or a placebo allergen-avoidance group (n = 81). Avoidance measures consisted of applying Acarosan(R) (placebo: water) to the living room and bedroom floors, and the use of HDM-impermeable covers for mattresses and bedding (placebo: cotton covers for mattresses only). Effects on allergen concentrations (Der p 1), FEV1, bronchial hyperresponsiveness, peak flow parameters and asthma symptom scores were studied during 20 weeks and controlled for the allergic status of the patients. RESULTS: The active covers reduced Der p 1 concentrations to 9.4% (P = 0.0001), and were always significant lower than in the placebo group (P = 0.0002). Acarosan(R) resulted in slight but significant decreases (twofold, P = 0.0001), both on living room and bedroom floors, but concentrations were never significantly lower than the placebo group. Although the combined avoidance strategy resulted in a considerable reduction in allergen load in the active group, no differences were seen between the two groups in any of the clinical parameters during the follow-up period in this group of allergic asthmatics, using no inhaled corticosteroids. Corrections for the allergic status did not alter these results. CONCLUSIONS: The combined avoidance strategy was effective in reducing HDM allergen concentration. This was especially achieved by the allergen-impermeable covers, while the effects of Acarosan(R) were only marginal. However, this allergen reduction was not reflected in a convincing improvement in clinical condition in this group of mild allergic asthmatics, using no inhaled steroids. Perhaps, a longer follow-up period would have resulted in more pronounced effects.     

Relationship of house-dust mite allergen exposure in children's bedrooms in infancy to bronchial hyperresponsiveness and asthma diagnosis by age 6 to 7.

BACKGROUND: Several studies have suggested that exposure to house-dust mite (HDM) allergen in infancy increases the risk of developing asthma. OBJECTIVE: To determine whether exposure to higher levels of dust mite in infants increased the risk of developing bronchial hyperresponsiveness (BHR) or physician-diagnosed asthma by age 6 to 7 years. METHODS: A health maintenance organization-based cohort of 97 middle class suburban children born from 1987 to 1989 with a high cord blood immunoglobulin E, defined as > or = 0.56 IU/mL, was followed as a part of the Childhood Allergy Study. During the first 2 years of life, monthly bedroom dust samples were collected and analyzed for Der f 1 and Der p 1. Between 6 and 7 years of age, 64 of the original cohort answered a questionnaire used to determine the presence of physician-diagnosed asthma, underwent clinical examination, skin prick testing, and methacholine inhalation challenge. Mann-Whitney tests were used to compare Der f 1 and Der p 1 levels in homes of children with and without BHR, and those with and without physician-diagnosed asthma. RESULTS: In all, 1,421 dust samples were collected and assayed. No significant differences were seen in either the mean, maximum, or minimum dust mite allergen levels in homes of children with versus without BHR, or children with versus without asthma. However, sensitization to HDM was associated with physician-diagnosed asthma (P < 0.05). CONCLUSIONS: When compared with other studies, we were able to more accurately estimate the level of dust mite allergen exposure through repeated sampling over a relatively long period, incorporating seasonal variations. Although HDM sensitization and asthma were concurrently related, we were unable to find any relationship between level of HDM allergen exposure in children's bedrooms in early childhood and development of BHR or physician-diagnosed asthma by age 6 to 7 years.     

Seasonal differences in airway hyperresponsiveness in asthmatic patients: relationship with allergen exposure and sensitization to house dust mites

Background The degree of airway hyperresponsiveness in allergic asthmatic patients may be influenced by changes in environmental exposure to inhalant allergens. Objective This study investigates the relationship between seasonal changes in exposure to house dust mite (HDM) allergens and non-specific airway hyperresponsiveness in asthmatic patients with multiple sensitizations to inhaled allergens. Methods In 43 asthmatic patients sensitized to several inhalant allergens, lung function (FEV₁), airway hyperresponsiveness (PC₂₀ histamine), serum total IgE, house dust mite (HDM) specific IgE and number of peripheral blood eosinophils were measured during autumn 1990 (September-November) and spring 1991 (March—May). During each season. floor dust samples were collected twice from living- and bedrooms and the concentration of the HDM allergens Der p 1 and Der p 2 determined. Results More severe airway hyperresponsiveness (lower PC₂₀ histamine) during autumn was only found in patients sensitized to HDM(n= 32; autumn: 2.05mg/mL, spring: 4.51mg/mL (geometric means), P <0.0 1), whereas in patients not sensitized to HDM (n= 11) similar values were observed in both seasons (3.44 and 4.52 mg/mL. respectively, P= 0.56). More severe airway hyperresponsiveness of HDM sensitized patients in autumn was significantly associated with higher Der p 1 concentrations in floor dust. Aside from airway hyperresponsiveness, seasonal changes in serum total IgE and number of peripheral blood eosinophils were seen in patients sensitized to HDM, Conclusions In allergic asthmatic patients, airway hyperresponsiveness may increase during autumn, depending on sensitization to HDM and an increase of exposure to HDM allergen.     

Allergen-induced bronchial inflammation in house dust mite-allergic patients with or without asthma

BACKGROUND: It is presently unknown which factors determine the occurrence and persistence of asthma in house dust mite-allergic individuals. The level of allergen-specific IgE antibodies does not seem to be decisive for asthmatic symptoms. Moreover, levels of exposure to mite allergens do not seem to differ significantly between asthmatic and non-asthmatics individuals. AIM: It was hypothesized that the presence or absence of asthmatic symptoms in house dust mite-allergic patients is associated with quantitative or qualitative differences in the cellular bronchial inflammatory response during the late phase of the allergic reaction. This hypothesis was tested in the bronchial allergen challenge model. MATERIAL AND METHODS: Whole lung challenges with house dust mite extract were performed in 52 house dust mite-allergic subjects, of whom 26 had asthma and 26 had perennial rhinitis without asthmatic symptoms. Primary outcomes were parameters for bronchial inflammation in serial samples of induced sputum (cell differentials, eosinophil cationic protein (ECP), interleukin-8 (IL-8), myeloperoxydase (MPO)). In addition, lung function, non-specific bronchial hyper-responsiveness and serial blood samples (eosinophils and IL-5) were analysed. RESULTS: At baseline sputum eosinophils and ECP were similar in both groups but neutrophils and IL-8 were higher in asthmatics. The early bronchoconstriction after allergen challenge was similar in asthma and non-asthmatic rhinitis (median decrease in FEV1: asthma -31.7% vs. non-asthmatics -29.1%, P > 0.1). The late phase bronchoconstriction was significantly greater in asthma (median decrease in FEV1: asthma -27.6% vs. non-asthmatics -18.9%, P = 0.02). Induction of bronchial hyper-responsiveness was similar in both groups. Bronchial allergen challenge elicited significant increases in sputum eosinophils and ECP, which were indistinguishable for both groups (P > 0.1 and P = 0.07, respectively). In contrast, higher numbers of neutrophils persisted in asthma 24h after challenge and were accompanied by significant increases in IL-8 and MPO, which were absent in non-asthmatics (difference between groups P = 0.007 and P = 0.05, respectively). CONCLUSION: Allergen challenge inducedvery similar increases in eosinophils and ECP in induced sputum in allergic asthmatics and in allergic non-asthmatic patients. The difference in bronchial inflammation between asthma and non-asthmatic rhinitis appeared to be more closely related to indices for neutrophilic inflammation.     

Effect of mite-impermeable mattress encasings and an educational package on the development of allergies in a multinational randomized, controlled birth-cohort study – 24 months results of the Study of Prevention of Allergy in Children in Europe

BACKGROUND: Sensitization to house dust mite (HDM) is an important risk factor for the development of asthma and allergic disease in childhood. Higher levels of HDM allergen are linked to increased sensitization to HDM. OBJECTIVE: To study the effect of mite-impermeable mattress encasings and an educational package on the development of allergies in a newborn cohort. METHODS: Six hundred and ninety-six newborns at high risk of developing allergies were enrolled in three European countries (Germany, Austria, UK) in a prospective, randomized, controlled birth-cohort study. Children were randomly assigned to an intervention and control group. Intervention measures included the use of mite-impermeable mattress encasings for the child's bed and a simple educational package on allergen avoidance. The control group received basic information about allergies. Children were followed up at age 6, 12, 18 and 24 months. RESULTS: 80.9% of the children were followed up to the age of 24 months. No difference in the prevalence of sensitization to HDM (control vs. intervention group: 8.4% vs. 6.1%, P=0.33) or the development of symptoms (recurrent wheezing 10.3% vs. 10.7%, nocturnal cough 12.5% vs. 12.5%) or allergic diseases (asthma 3.5% vs. 5.1%, eczema 20.0% vs. 19.6%, rhinitis 28.9% vs. 25.8%) could be found between the control and intervention group. CONCLUSION: In this study, HDM avoidance did not show a protective effect on the development of sensitization to HDM or symptomatic allergy in children at age 24 months.     

A combined approach to reduce mite allergen in the bedroom

Background Asthma is a common chronic disease of childhood. House dust mite (HDM) are known to be a major source of allergen affecting atopic asthmatics. No single control method has been demonstrated to consistently reduce asthma. Objective We investigated the effect of a combination of two methods of HDM allergen control on HDM allergen content in the bedding and carpets of asthmatic children. Methods This was a double-blind placebo-controlled trial treating the bedrooms of 56 mite-sensitive asthmatic children. The carpel and the mattress, duvet and pillows (bedding) in the bedroom of children of the active group were treated with the acaricide Acarosan (benzyl benzoate). The bedding was then encased in vapour permeable waterproof fabric (Intervent cotton coated with polyurethane) for 24 weeks. The carpet and bedding of the control group were treated with placebo and the bedding encased in cotton covers for 24 weeks. Dust samples were collected from all these items in a standard manner at regular intervals and Der p I content analysed. Results The group with active treatment had a median reduction of 480 ng (100%) in mite allergen from the mattress vs 215 ng (53%) reduction in placebo-treated group by 6 weeks. The Der p I content of the active group's bedding was always less than the placebo group after treatment (P < 0.01). The acaricide applied to the carpets or inside the mattress covers was ineffective in reducing allergen content. Conclusion This study confirms the effectiveness of encasing covers in reducing the mile allergen exposure but indicates there is no further advantage in applying acaricide simultaneously.     

The respiratory effects of reduction of mite allergen in the bedrooms of asthmatic children — a double-blind controlled trial

Background Inhalation of house dust mite (HDM) allergen may provoke attacks of asthma. Objective We investigated whether a double-blind placebo-controlled community-based study aimed at reducing the HDM allergens in the bedrooms of HDM sensitive asthmatic children using the best methods available would prove beneficial to the children's health. Methods The children (mean age 9.9 years, 34 boys) were recruited by a questionnaire submitted to 7386 families in a geographically-defined area of the UK. Subjects were chosen to take part in the double-blind placebo-controlled trial if they were asthmatic, skin sensitive to mites, and had mite allergen in their mattresses. Seventy children were randomly allocated to groups. In the active group, the children's bedrooms were treated with an acaricide (Acarosan) and the mattresses, pillows and duvets were encased in exclusion covers. The control group received placebo treatments. Results Forty-nine complete data sets were obtained. Applying bedding covers and Acarosan led to a median reduction of 480 ng (100%) in mite allergen on the mattress vs 215 ng (53%) reduction in placebo-treated group by 6 weeks. No evidence was found that the acaricide reduced mite allergen level. A change in bronchial reactivity to histamine was observed in the children after 6 weeks. This was not associated with any change in thrice-daily records of peak expiratory flow rate. By 24 weeks, the actively-treated children had improved forced expiratory volume in 1s (FEV₁) and fewer required bronchodilator therapy or reported asthmatic symptoms than did the controls. Conclusions The results suggest that mite removal procedures may modestly improve mite-sensitive asthmatics and could perhaps be of value in exceptionally mite-sensitive and/or highly mite-exposed individuals whose response to the attempted removal should be measured.     

Basophil histamine release and airway response to mite allergen in atopic dermatitis.

Twelve patients with atopic dermatitis (AD) were subjected to in vitro histamine release from peripheral blood leukocytes (basophils) and in vivo bronchial inhalation challenge using house dust mite (Dermatophagoides farinae) allergen. Not only seven patients with asthmatic history but also five patients without asthma responded to both the in vitro and the in vivo challenges. A significant correlation was observed between HR30 (a mite concentration producing a 30% release of total cellular histamine) and PC20 allergen (a mite concentration producing a 20% fall in FEV1). There was also a significant correlation between MHR (maximal histamine release) and the maximal fall in FEV1. The relationship held for both AD patients with asthma and without asthma. These results suggest that histamine release induced by the house dust mite allergen is a good in vitro test for predicting the bronchial response to this allergen. They also suggest that these tests are not disease specific, but are valuable in evaluating the degree of atopic state in a subject.     

House dust mite allergen levels in Chiang Mai homes

The quantitative assays for house dust mite (HDM) allergens provide a valid index of exposure and can be used for risk evaluation. We assessed group I HDM allergen levels in mattress and living room floor dust from 35 Chiang Mai homes and identified factors associated with high allergen levels. One-third of mattress and living room floor dust had group I HDM allergen levels of between 2-10 microg/g. Two-thirds of mattress dust and a small amount of living room floor dust had group I HDM allergen levels of over 10 microg/g. The geometric means of Der p I, Der f I and total group I allergens in mattress and living room floor dust were 8.61, 2.88, and 15.81 microg/g and 1.61, 0.27 and 2.43 microg/g, respectively. Mattresses made of kapok and rugs kept in the living room were associated with high group I allergen levels.     

Effectiveness of an intervention to reduce house dust mite allergen levels in children's beds

BACKGROUND: In temperate climates, exposure to house dust mite (HDM) allergens is the strongest environmental risk factor for childhood asthma. Environmental modifications to limit exposure have the potential to reduce the prevalence of asthma. The aim of this study was to reduce allergen exposure for children at high risk of developing asthma. METHODS: A total of 616 pregnant women were randomized to HDM intervention and control groups. The control group had no special recommendations whereas the intervention group was given allergen impermeable mattress covers and an acaricidal washing detergent for bedding. Children were visited regularly until 18 months of age to have dust collected from their bed. RESULTS: Der p 1 concentrations in the control group increased from 5.20 microg/g at 1 month to 22.18 microg/g at 18 months but remained low in the intervention group, ranging from 3.27 microg/g at 1 month to 6.12 microg/g at 18 months. CONCLUSIONS: In a high HDM allergen environment, a combined approach using physical barriers and an acaricidal wash, is effective in reducing HDM allergen concentrations in bedding. However, even with these control measures in place, HDM allergen levels remained high by international standards.     

Effect of a bronchial provocation test with house-dust mite on blood eosinophilia, eosinophil cationic protein, soluble interleukin-2 receptor, and interleukin-6 in asthmatic children

Eighteen children with perennial asthma and allergy to house-dust mite (HDM) underwent a bronchial challenge with HDM. Before and 24 h after the test, a venous blood sample was taken to determine levels of eosinophils, eosinophil cationic protein (ECP), soluble interleukin-2 receptor (IL-2R), and interleukin-6 (IL-6). A histamine challenge was performed before and 24 h after the HDM challenge. All subjects showed an immediate asthmatic reaction (IAR). A definite late asthmatic reaction (LAR) was observed in 15 children, a probable LAR in two, and no LAR in one. Because of persistent bronchial obstruction (FEV₁>70%), eight children were unable to perform a histamine challenge 24 h after the allergen challenge. These were the children with the lowest prechallenge provocation dose (PD₂₀) of histamine. In the other 10 children, the mean PD₂₀ histamine decreased after the HDM challenge (mean PD₂₀ before was 0.56 mg/ml; after challenge it was 0.14 mg/ml; P= 0.007). After the HDM challenge, an increase was detected in the mean values of blood eosinophils (mean before was 446/mm³; mean after was 733/mm³; P= 0.002), ECP (mean before was 26.3 μg/1; mean after was 34.3 μg/1; P<0.040), and IL-2R (mean before was 116.35 U/ml; mean after was 128.52 U/ml; P<0.040). On the other hand, IL-6 remained unchanged after the HDM challenge (mean before was 9.47 pg/1; mean after was 9.70 pg/1; P= 0.360). Furthermore, as compared with a group of normal, age-matched children (n =18), asthmatic children were found to have higher prechallenge levels of ECP (mean: 10.3 μg/1 compared with 26.3 μg/1) (P>0.001) and IL-2R (mean: 80.30 U/ml compared with 116.35 U/ml) (P =0.009), but not of IL-6 (mean: 11.34 pg/1 compared with 9.47 pg/1) (P = 0.436). A correlation was found between the duration of asthma and the severity of the LAR expressed as area under the curve (AUCLAR) (r = 0.50; P<0.040). Furthermore, a correlation was detected between the level of total IgE and the level of ECP (r = 0.51; P<0.030). The decrease in FEV₁ during the LAR tended to correlate with the increase of IL-2R (r = 0.48; P = 0.050). This tendency was not found with the increase of eosinophils, nor with the increase of ECP. We conclude that both lymphocytes and eosinophils are activated by an allergen challenge, but that only the activation of lymphocytes tends to correlate with the LAR, suggesting that lymphocytes are also closely involved in the pathogenesis of the allergen-induced LAR.     

Liposome-entrapped D. pteronyssinus vaccination in mild asthma patients: effect of 1-year double-blind, placebo-controlled trial on inflammation, bronchial hyper-responsiveness and immediate and late bronchial responses to the allergen

BACKGROUND: Allergen vaccination is effective in mite-allergic asthma. Liposomes are immunological adjuvants that can act as allergen carriers. OBJECTIVE: To evaluate the immunological and functional effects of a liposome-entrapped D. pteronyssinus vaccine on mite monosensitive, mild asthma patients. METHODS: A double-blind, placebo-controlled trial was conducted on 26 asthma patients who randomly received vaccination or placebo for 1 year. The levels of exposure to Der p 1 allergen were constant during the study. Allergen bronchial challenge was made at the beginning (T0) and after 1 year of treatment (T12). The day before and 24 h after the allergen provocation, patients were challenged with methacholine (Mth) (until FEV1 fell by 40%) and blood and sputum samples were obtained. Dose-response curves to Mth were evaluated in terms of Mth-PD20 (dose of Mth that induced 20% drop in FEV1), slope (Mth-DRS) and level of plateau. Blood and sputum eosinophils and serum levels of eosinophil cationic protein (ECP) and intercellular adhesion molecule-1 (ICAM-1) were measured. RESULTS: Groups were comparable at the start of the trial. At TI2, previous to the allergen challenge, the active group showed higher values of both FEV1 and Mth-PD20 and lower values of Mth-DRS. The number of patients presenting a level of plateau increased in the active group (from two to four) and decreased in the placebo group (from two to one). At T12, before the allergen challenge, serum ECP levels increased in the placebo group and blood eosinophils showed a trend towards lower numbers in the active one. The immediate response and the changes in Mth-DRS values, sputum eosinophils and serum ECP levels following the allergen challenge were attenuated in the active group. CONCLUSION: Liposome-entrapped D. Pteronyssinus vaccination: (i) protects mild asthma patients from the worsening of asthma due to sustained mite exposure; and (ii) reduces the functional and inflammatory changes induced by allergen bronchial provocation.