Home allergen monitoring and control--improving clinical practice and patient benefits

[Diagnosis of allergy in asthma]

Allergy is a hypersensitivity reaction induced by immunological mechanisms. In asthma, allergy has a complex role and is usually IgE mediated. Allergy must be evaluated during the work up but evidence of IgE sensitivity does not mean that allergens play a role in the pathophysiology of the disease. The clinical relevance of the sensitivity has to be considered. This paper describes current available tools to screen for IgE sensitivity, allergen exposure and their role in asthma.

How In Vitro Assays Contribute to Allergy Diagnosis

Diagnosis of allergic disorders is based upon the clinical history of the disease, the immunoglobulin E (IgE) antibody response, and the allergen exposure. During the last decade, many changes have occurred in the in vitro diagnostic tests used in daily practice. The most important one is the use of allergenic molecules, which helps to define severe profile of allergy and/or to better understand cross-reactivity. The correlation between IgE sensitization and bronchial or nasal response in provocation tests is not so clear, which implies that such tests are still helpful in allergy diagnosis. In order to strengthen the link between a real allergen exposure and allergic symptoms, environmental allergen load assessment can be performed. For clinicians, it appears obvious to know the pollen count to treat their patients; however, they rarely measure the allergen load in the indoor environment, while nowadays home-tests (semi-quantitative or quantitative) make the assessment very easy. In the future, assessment of the environmental exposure (preferably with an indoor technician) of an allergic patient should take into account not only the allergens but also the other indoor pollutants, which could enhance respiratory symptoms in allergic patients.

Ara h 6 complements Ara h 2 as an important marker for IgE reactivity to peanut

The similarities of two major peanut allergens, Ara h 2 and Ara h 6, in molecular size, amino acid sequence, and structure have made it difficult to obtain natural Ara h 6 free of Ara h 2. The objectives of this study were to purify natural Ara h 6 that is essentially free of Ara h 2 and to compare its IgE reactivity and potency in histamine release assays to Ara h 2. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the highly purified allergen (<0.01% Ara h 2) revealed a single 14.5 kD band, and the identity of Ara h 6 was confirmed by liquid chromatography-tandem mass spectrometry. Ara h 6 showed a higher seroprevalence in chimeric IgE enzyme-linked immunosorbent assay (n = 54) but a weaker biological activity in basophil histamine release assays than Ara h 2. Purified Ara h 6 will be useful for diagnostic IgE antibody assays as well as molecular and cellular studies to investigate the immunological mechanisms of peanut allergy.

A multi-allergen standard for the calibration of immunoassays: CREATE principles applied to eight purified allergens

BACKGROUND

Allergen measurements are widely used for environmental exposure assessments and for determining the potency of allergen vaccines, yet few purified allergen standards have been developed. The aim of the study was to develop a single standard containing multiple purified allergens that could be used in enzyme immunoassays and in multiplex arrays for the standardization of allergen measurements.

METHODS

Eight purified allergens were formulated into a single multi-allergen, or 'universal', standard based on amino acid analysis. Dose-response curves were compared with previous individual ELISA standards and allergen measurements of house dust extracts to obtain correction factors. Measured allergen concentrations were also modeled using linear regression, and the predictive accuracy was determined.

RESULTS

Parallel dose-response curves were obtained between the universal allergen standard and the individual ELISA standards, with close agreement between curves for 5/8 allergens. Quantitative differences of greater than twofold were observed for Fel d 1, Can f 1, and Der f 1, which were confirmed by the analysis of house dust extracts. Correction factors were developed that allowed ELISA data to be expressed in terms of the universal standard. Linear regression data confirmed the predictive accuracy of the universal standard.

CONCLUSION

This study shows that a single standard of eight purified allergens can be used to compare allergen measurements by immunoassay. This approach will improve the continuity of environmental exposure assessments and provide improved standardization of allergy diagnostics and vaccines used for immunotherapy.

Determination of Aspergillus fumigatus allergen 1 in poultry farms using the enzyme immunoassay

Poultry farms contain high levels of allergenic fungi, and Aspergillus spp. is the most common genus of moulds. Aspergillus fumigatus antigens are responsible for the development of several respiratory diseases including asthma. The aim of this study was to measure the mass fraction of Asp f 1, a major allergen of Asperillus fumigatus in 37 indoor dust samples collected from four poultry farms in a rural area of the Zagreb County (Croatia) using the enzyme-linked immunosorbent assay. More than 62 % of dust samples had detectable Asp f 1 levels (limit of detection 3.6 ng g(-1)). The overall mean Asp f 1 level was 17.9 ng g(-1) [range (3.8 to 72.4) ng g(-1)]. Satisfactory results were obtained for analytical within-run imprecision (6.7 %), between-run imprecision (10.5 %), and accuracy (91 % to 115 %). Microclimate parameters (air temperature, relative humidity, and velocity) were within the recommended ranges in all poultry farms. This study has shown that Asp f 1 settles on dust at poultry farms and that occupational exposure to this allergen deserves monitoring in livestock buildings.

Can we use indoor fungi as bioindicators of indoor air quality? Historical perspectives and open questions

Microbiological analysis of atmospheres witnessed substantial technical improvements in the 1940s to 1960s. May's cascade impactor and Hirst's spore trap allowed the counting of total cells but had limited capacity for identification of the spores. Bourdillon's sampler enabled the counting of cultivable fungi and their identification. A great step forward was given with the Andersen's six-stage impactor, which allowed discrimination of particles by size, counting of cultivable cells, and species identification. This period also witnessed the development of impingers, namely, the AGI-30 described by Malligo and Idoine, and the three-stage model designed by K. R. May. The 1990s to 2000s witnessed innovative discoveries on the biology of indoor fungi. Work carried out in several laboratories showed that indoor fungi can release groups of spores, individual spores and fungal fragments, and produce volatile organic compounds and mycotoxins. Integrating all findings a holistic interpretation emerged for the sick building syndrome. Healthy houses and buildings, with low indoor humidity, display no appreciable indoor fungal growth, and outdoor Cladosporium dominates. On the contrary, in sick houses and buildings, high indoor humidity allows fungal growth (mainly of Penicillium and Aspergillus), with concomitant release of conidia and fragments into the atmosphere. The intoxication probably results from a chronic exposure to volatile organic compounds and mycotoxins produced by Penicillium, Aspergillus, and Stachybotrys. Very clean atmospheres are difficult to study by conventional methods. However, some of these atmospheres, namely, those of hospital rooms, should be monitored. Sedimentary sampling, chemical methods applied to impinger's collection liquid, and selected molecular methods can be useful in this context. It was concluded that fungi can be useful indicators of indoor air quality and that it is important to deepen the studies of indoor atmospheres in order to promote air quality, the health and well-being of all, and a better understanding of the biology of indoor fungi.

An association between floor vacuuming and dust-mite and serum eosinophil cationic protein in young asthmatics

Although vacuum cleaning is recommended to reduce allergen levels and improve asthma and allergic rhinitis symptoms, some studies suggest it may increase allergen load in homes. We conducted a cross-sectional study to determine if home floor vacuuming was associated with sensitization to dust-mites and cockroaches, and serum eosinophil cationic protein (ECP), a biomarker for atopy, in 102 physician-diagnosed spirometry-confirmed asthmatics. We collected data on floor type, floor cleaning method and frequency, asthma severity, allergy medications used, serum ECP and skin prick tests (SPT) to three dust-mites [Dermatophagoides pteronyssisinus (Der p), Dermatophagoides farinae (Der f) and Blomia tropicalis (Blo t)] and two cockroaches [Periplanata americana (Per a) and Blatella germanica (Bla g)]. Those who vacuumed had increased sensitization to three dust-mites [adjusted ORs (95%CI) = Der p: 26.6 (1.8-405.2); Der f: 44.8 (3.2-620.9); Blo t: 14.1 (1.8-108.1)] but not to cockroaches, adjusted for cleaning frequency and other methods of floor cleaning. Subjects who vacuumed their floor had higher levels of serum ECP than those who did not [adjusted median difference (95%CI): 9.4 (1.1-17.7)], adjusted for use of nasal corticosteroids among those with allergic rhinitis. Vacuuming is associated with increased sensitization to dust-mite allergens and higher serum ECP.

PRACTICAL IMPLICATIONS

We found an association between floor vacuuming and increased sensitization to dust-mite allergens and higher levels of an atopy biomarker. Current recommendations to use vacuuming to control allergen exposure and allergic conditions may need to be reconsidered until further studies are performed.

Asthma and allergy: short texts and recommendations of the expert conference of the French Speaking Pneumology Society (SPLF), in partnership with the French Society of Allergology and Clinical Immunology (SFAIC), the French Society of Occupational Medicine (SFMT) and the "Asthma-Allergy" association

The Asthma Plan published by the French Health Ministry in 2002, the experts conferences edited by ANAES on therapeutic education and follow-up of asthma, the inclusion of this disease in the Public Health Law have been remarkable steps in France during the last few years. The medical community, more particularly the pneumological community, has shown its commitment in the treatment of this public health problem. But allergy was not sufficiently taken into account, although it is responsible for nearly 50 to 60% cases of asthma. In most so-called developed countries the prevalence of asthma and of allergies has increased in the last twenty years. Its progress varies according to country and age group: the increased prevalence of allergy, more specifically of rhinitis and eczema, is most marked in children aged 6-7 year. The prevalence of asthma seems to have reached a plateau in certain northern countries or seems to have decreased in 13-14 year olds (Anglo-Saxon countries). There were multiple reasons, generally attributed to changes in life-style. Asthma is the result of an interaction between a genetic predisposition and the environment, where allergens are present, but also smoking. The relationships between allergy and asthma are complex. This conference discussed the various essential issues that face doctors who treat patients with asthma in their daily practice. The risk factors, the methods of exploration in children and adults and the specific treatments are, indeed, essential issues to be evaluated in a frequent pathology that interests a large number of physicians. The variety of experts is wide, representing pneumology (French Speaking Pneumology Society), the occupational medicine world (French Society of Occupational Medicine), the allergic pathology (French Society of Allergology and Clinical Immunology), and patients with the patient association "Asthma & Allergy", physicians belonging to the general medicine community, general hospitals, private hospitals and academic hospitals in France. The proposed guidelines are aimed at helping practitioners in distinguishing what is established from what remains to be demonstrated and/or assessed with respect to the different modalities for the exploration or treatment of allergic asthma.

Determination of mite allergens in house dust using the enzyme immunoassay

The aim of this study was to determine the level of two major mite allergens Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1) in 30 urban homes in Zagreb, Croatia, using the enzyme immunoassay with two monoclonal antibodies which has been established as the reference method for indoor allergen analysis. Dust samples were taken by vacuuming a carpeted area and collected on cellulose filters. The ranges of Der p 1 and Der f 1 were (0.1-12.5) microg g-1 (median 0.32 microg g-1) and (0.1-31.2) microg g-1 (median 0.35 microg g-1), respectively. Der p 1 and Der f 1 (>2 microg g-1) associated with increased risk of sensitization to mite allergens were found in approximately 16% homes for each allergen. The sum of allergen (Der p 1 + Der f 1) exceeded the lower threshold in 27% of homes. Analytical evaluation of the ELISA assay showed satisfactory results for precision (intra-assay CV <6.9%, inter-assay CV<13.3%), accuracy (91% to 93%), and sensitivity (2 ng mL-1). The ELISA assay for the measurement of dust mite allergens demonstrated very good analytical characteristics for routine laboratory use, and will provide the essential basis for our future studies of various indoor allergens.

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.

Environmental detection of mouse allergen by means of immunoassay for recombinant Mus m 1

BACKGROUND

Mouse urinary allergens are an important cause of occupational asthma in animal facilities. Domestic exposure to mouse allergens is a risk factor for asthma among inner-city residents.

OBJECTIVE

We sought to develop a sensitive and specific assay for assessing environmental mouse allergen exposure.

METHODS

An ELISA for recombinant (r)Mus m 1 was developed by using rabbit polyclonal antibodies to rMus m 1 that were affinity purified against the natural allergen. Assay specificity was established by means of immunoblotting and ELISA. Mus m 1 levels in mouse, other mammalian allergenic products, and house dust samples from inner-city homes were compared.

RESULTS

Polyclonal antibodies to Mus m 1 showed a single 20-kd band on immunoblots against rMus m 1 and male mouse urine. Parallel dose-response curves were obtained by using mouse urine extract and natural Mus m 1 or rMus m 1. Mus m 1 was detected in mouse allergenic products (0.10-10.0 microg/mL) and in gerbil allergenic products (0.1 microg/mL) but was less than the limit of detection in epithelial extracts from 10 other animal species. Environmental measurements showed an excellent correlation between Mus m 1 levels in house dust extracts from inner-city asthma studies by using 2 different Mus m 1 standards (n=22; r=0.99; P <.001).

CONCLUSIONS

A highly sensitive ELISA has been developed with rMus m 1. This assay is suitable for monitoring domestic and environmental exposure to mouse urinary allergens.

Chlamydia pneumoniae infections in asthma: clinical implications

Chlamydia pneumoniae is an intracellular pathogen that has been suggested to play a role in the pathology of asthma. However, so far none of the studies have provided clear evidence for a causative role of C. pneumoniae infections in asthma, although there is little doubt that chronic C. pneumoniae infection does aggravate asthma and should be treated. The diagnosis of C. pneumoniae infection is still a matter of concern for it is dependent on trained skilled personnel and can vary significantly between different diagnostic laboratories. This fact is also one of the major problems encountered when comparing epidemiological studies investigating the possible role of C. pneumoniae infections and their impact on the pathogenesis of other diseases. With regard to therapy, long-term treatment with macrolides is the best available method to eradicate C. pneumoniae. Successful therapy for C. pneumoniae, however, can also be complicated by the high possibility of de novo infection as epidemiological studies have shown that the prevalence of antibodies to C. pneumoniae increases with age in all populations studied. In the northern hemisphere the prevalence of C. pneumoniae is also affected by seasonal conditions. It is too early to draw any conclusions from the equatorial belt countries. The available data on C. pneumoniae in tropical countries indicate a much faster infection rate during early adulthood with 100% serological prevalence at an age greater than 25 years. This data, if confirmed, would argue against C. pneumoniae causing asthma since the asthma prevalence in those countries does not increase in a parallel pattern. An alternative interpretation of most studies could be that the increased rate of C. pneumoniae infections in patients with asthma results from a modified susceptibility towards the microorganism, due to yet unknown changes of the host cell's physiology. It should be kept in mind that increased prevalence of C. pneumoniae infection is not restricted to asthma. Further studies are needed to understand the role of C. pneumoniae, especially of chronic infection, in the pathogenesis of inflammatory diseases with a specific focus on the effect that the microorganism triggers in the infected host cell. Only when we understand what C. pneumoniae does to its host cell will we be able to judge its impact on the overall status of an affected patient, and this knowledge will help us to develop a successful therapy.

Cockroach allergy

The ubiquitous existence of cockroaches and the large-scale domestic infestation seen in inner cities make cockroach proteins a significant indoor allergen and a risk factor for asthma among inner-city residents. Studies have shown that early exposure to high levels of allergen may lead to the development of asthma in individuals with a genetic predisposition to asthma. Although field trials at cockroach abatement do not yield promising results, integrated pest management still remains the best control strategy. In highly susceptible or symptomatic patients, allergen-specific immunotherapy may be beneficial, although data are limited. As molecular techniques improve and recombinant allergens are developed, a more novel form of T-cell-specific immunotherapy may prove to be efficacious without the anaphylactic side effects seen with traditional allergy vaccines.

Measurement of Dermatophagoides mite allergens on bedding and human skin surfaces

BACKGROUND

The level of the Dermatophagoides mite group 1 (Der 1) allergens in reservoir dust has been used as an index of exposure in most studies. However, the mite allergen level in reservoir dust cannot directly reflect the personal exposure level.

OBJECTIVE

We sought to develop a new method for quantifying the Der 1 allergens on bedding and human skin surfaces as an index of exposure to mite allergens.

METHODS

Samples were obtained with a small adhesive tape from the forearm skin of 30 healthy volunteers and from their regularly used mattresses. The level of Der 1 allergens collected onto the adhesive tape was measured by a newly developed sensitive fluorometric ELISA for Der p 1 and Der f 1.

RESULTS

The Der 1 allergens could be detected in all the samples from bedding surfaces and in 28 of the 30 samples from skin surfaces. The Der 1 levels by adhesive tape sampling from the mattresses correlated with those by reservoir dust sampling. The sampling of the skin and bedding surface with adhesive tape correlated, but skin sampling did not correlate with reservoir sampling.

CONCLUSION

The Der 1 allergens on bedding surfaces and on human skin surfaces could be quantified with a very simple sampling technique. The system developed in this study will provide a new tool for the assessment of mite allergen exposure in daily life.

Differences in mite fauna between the continental and Mediterranean climates of Croatia: microscopy and Dustscreen test findings

BACKGROUND

The aim of this study was to evaluate the difference between the mite fauna in the inland and coastal Croatia.

METHODS

Ninety-nine floor house dust samples were collected: 28 from the coastal area, 31 from the inland rural and 40 from the inland urban area. Data on basic household characteristics were collected for 81 of 99 households. The mites were separated from the dust using the floatation method and then microscopically identified. The levels of Dermatophagoides pteronyssinus (Der p) 1, Dermatophagoides farinae (Der f) 1 and Der 2 were measured using the Dustscreen test. Ordinal descriptive statistics and nonparametric tests were used for data analysis, assuming statistical significance at P < 0.05.

RESULTS

More than 70% of mites identified in all areas were pyroglyphids. Nonpyroglyphid mites accounted for 20-25% of all identified mites in the coastal areas (Blomia, Lepidoglyphus and Glycyphagus) and with 15% in the inland areas (Lepidoglyphus and Acarus). The highest Der p 1 median levels were found in the coastal area, with significantly lower levels in the inland rural and inland urban areas (4.5; 2; 0.85 microg/g of dust; P = 0.0001). The highest Der f 1 median levels were found in the inland urban area, with significantly lower levels in the inland rural and coastal areas (0.88; 0.75; 0 microg/g of dust; P = 0.0013). The levels of Der f 1 were significantly higher in samples taken from households with central heating than from those with traditional heating (1; 0.25 microg/g of dust; P < 0.01).

CONCLUSIONS

Separate diagnostic dust mite lists for the coastal and inland areas because of climatic and dwelling differences required to be implemented. Compared with traditional heating, central heating significantly increases the risk of exposure to Der f 1 levels >2 microg/g of dust (odds ratio, 7.35; 95% confidence interval, 1.43-37.87; P = 0.01).

Use of an amplified ELISA technique for detection of a house dust mite allergen (Der f 1) in skin and coat dust samples from dogs

OBJECTIVE

To use an amplified ELISA technique to document the presence and quantify the concentration of the house dust mite allergen, Der f 1, in skin and coat dust samples collected from dogs.

ANIMALS

29 pet dogs of various breeds.

PROCEDURE

Dogs were weighed, and body surface area in square meters was determined. Skin and coat dust samples were obtained by vacuuming dogs. Collected dust was analyzed by use of standard and amplified ELISA techniques.

RESULTS

By use of the standard ELISA technique, Der f 1 was detected in skin and coat dust samples from 6 of 29 (21%) dogs. Mean concentration of Der f 1 in the 6 samples with positive assay results was 16.16 ng/mL (range, 5.61 to 31.24 ng/mL). Samples with negative assay results were retested for dust mite allergen by use of an amplified ELISA technique; an additional 14 dogs had positive assay results. Mean concentration of allergen was 0.36 ng/mL (range, 0.19 to 2.20 ng/mL). Combining both techniques, 20 of 29 (69%) dogs had positive assay results for Der f 1.

CONCLUSIONS AND CLINICAL RELEVANCE

Results of our study indicate that house dust mite allergens are present on the skin and in the coat of dogs, and this source of allergen may act as a reservoir for allergen exposure in hypersensitive dogs. Use of an amplified ELISA technique to determine environmental concentrations of house dust mite allergens in homes and on dogs will help to identify the relationship between immunologic findings and environmental exposures in dogs with atopic dermatitis.

A rapid test for detection of mite allergens in homes

BACKGROUND

International guidelines recommend allergen avoidance for asthma management, but do not include making assessments of allergen exposure. Mite allergen exposure cannot be assumed, especially in geographical regions where climatic conditions vary.

OBJECTIVE

To develop a rapid test that would enable consumers to detect mite allergen in the home.

METHODS

A lateral flow test using gold labelled antibody for mite group 2 allergen was developed as part of a detection kit incorporating the MITEST dust sampling device. Dust samples were assayed by ELISA for group 1 and group 2 allergens and by using the rapid test. The tests were compared as indices of mite allergen exposure.

RESULTS

There was a good correlation between group 1 and group 2 levels by ELISA (n = 349, r = 0.60, P < 0.001). In a multi-centre study of 65 homes (263 dust samples) in five countries, there was a strong correlation between ELISA and the rapid test. Most samples with high scores in the test (43/48, 90%) contained > 1 microg/m2 group 2 allergen, whereas most low samples contained < 1 microg/m2 (50/64, 78%). Differences between mean group 2 levels of samples that scored low (0.28 microg/m2), medium (1.68 microg/m2) or high (3.18 microg/m2) on the test were highly significant (P 0.007 to < 0.001).

CONCLUSIONS

A simple rapid test has been developed that detects mite allergen in the home within 10 min. The mite screening test should educate consumers about allergen exposure and encourage compliance with allergen-avoidance procedures. This technology has applications for the detection of other common environmental allergens.

Environmental controls in the management of allergic asthma

Environmental allergen control is one of the four primary goals of good asthma management. The American Academy of Allergy, Asthma, and Immunology has published a position statement [78] that endorses the National Asthma Education and Prevention Program management guidelines [23] and recommends that every patient with persistent asthma be evaluated for environmental allergen sensitivity. Patients who have sensitivities should receive practical advice on allergen avoidance. An accumulating body of knowledge indicates that such measures, when strictly applied for a sufficient period of time, can indeed reduce asthma symptoms, need for medication, and airway hyperresponsiveness. Ongoing prospective trials in large numbers of patients are being conducted and should enhance the ability to make proper recommendations to patients.