Wipe test for the detection of indoor allergens

Repeated immunosensing by a dithiobis(succinimidyl propionate)-modified SAW device

The possibility of dithiobis(succinimidyl propionate) (DSP) for repeated immunoassay with a surface acoustic wave (SAW) immunosensor was explored. In the sensor, DSP was used to modify a gold-coated quartz sensing area of a SAW device by forming a self-assembled monolayer on the gold surface. In a model sandwich assay using mouse (mIgG) and anti-mouse (a-mIgG) antibodies, the primary antibody, mIgG, firstly reacted with N-hydroxysuccinimide ester groups of DSP and was immobilized on the SAW device to fabricate the SAW immunosensor. Optimization of adsorption time of mIgG revealed that both degrees of adsorption and immobilization of mIgG reached a saturation at 30 min although the immobilization was more dependent on the adsorption time. Through characterization of the DSP-modified SAW immunosensor, a high selectivity, with which no sensor output was observed from various kinds of secondary antibodies except for a-mIgG, along with 8-fold shorter measurement time (15 min) than that of enzyme-linked immunosorbent assay were obtained. Furthermore, 10 repeated measurement of a-mIgG demonstrated a high reproducibility of the sensor output (coefficient of variation of 7.0%). These validate the utility of DSP in the SAW immunosensor for rapid and repeated measurement of antigens.

Association between traffic-related air pollution and asthma in preschool children in a national Japanese nested case-control study

OBJECTIVES

There has been little study on the effect of traffic-related air pollution on the incidence and persistence of asthma in preschool children. We evaluated the association of exposure to traffic-related air pollution with the incidence/persistence of asthma during the first 3 years of life using a population-based study.

METHODS

A baseline survey was conducted in 1½-year-old children (n=63,266). A follow-up survey at 3 years of age (n=43,343) identified new-onset asthma cases (n=853) and persistence of asthma (n=214). In the prevalence/persistence study, the outdoor concentrations of nitrogen oxides (NOx) and elemental carbon (EC) at home during the first 1½ years of life were estimated by a dispersion model. In the nested case-control study, which regarded incidence of asthma as cases, the personal exposure levels were estimated by dispersion model including time-activity pattern.

RESULTS

There was no statistically significant association between the incidence of asthma between age 1½ and 3 years and personal exposure levels to NOx nor EC. However, the persistence of asthmatic symptoms (between 1½ and 3  ears) was significantly associated with outdoor concentrations of NOx. ORs for the persistence of asthmatic symptoms were 6.02 (95% CI 1.51 to 23.92) for the comparison between the upper 5th and lower 25th centiles of NOx.

CONCLUSIONS

While no statistically significant association was observed for the incidence of asthma, the persistence of asthmatic symptoms in preschool children was significantly associated with traffic-related air pollution. This supports its importance as a risk factor in childhood airway disease.

Indoor allergen assessment quantified by a thin-layer electrochemical cell and magnetic beads

We report the electrochemical determination of mite allergen in real house dust by using a thin layer electrochemical flow cell and magnetic beads. Der p1, which is an allergen from Dermatophagoides pteronyssinus, was immunochemically sandwiched between two dispersed monoclonal antibodies; one was modified on the surface of magnetic beads and the other was modified with alkaline phosphatase. After washing the beads, a small volume of p-aminophenol phosphate (p-APP) was added to produce p-aminophenol (p-AP). And then the p-AP concentration was measured electrochemically with a homemade electrochemical cell. The Der p1 assay was completed within 30 min and a low detection limit of 0.3 ng/mL was achieved. This is because the diffusion distance of Der p1 and the detection antibody was reduced to 22.3 μm by using dispersed magnetic beads. Only 10 min was required to complete the entire immunoreaction, and 54% of the Der p1 was confirmed to have immunoreacted in only 1 min of mixing. Furthermore, the p-APP volume could be reduced using the thin-layer electrochemical flow cell. This is advantageous in terms of concentrating p-AP, and provides a high signal-to-noise ratio measurement in a short time. We achieved a high correlation (r=0.967, p<0.001) between our assay and a conventional enzyme-linked immunosorbent assay (ELISA) for real house dust measurements.

Associations between cat keeping, allergen exposure, allergic sensitization and atopic diseases: results from the Children of Lübeck Allergy and Environment Study (KLAUS)

The role of cat keeping on the promotion of allergies is discussed controversially. We investigated the associations between cat keeping, allergen exposure, allergic sensitization and atopic diseases in pre-school children. A total of 606 children (5- to 6-yr old) were studied in the course of the mandatory school entrance examination. Information on doctor diagnosed asthma and allergic rhinitis, pet keeping and confounders was obtained by questionnaire. The prevalence of atopic eczema was determined by dermatological examination, allergic sensitization was assessed by skin prick test, and the allergen exposure to cat allergen Fel d 1 was measured by a commercial wipe test. Cats were present in 16% of the households and results of the exposure categories (0-III) on cat allergen were 47.2%, 25.5%, 24.3% and 3.0% respectively. The prevalence of cat keeping increased significantly with exposure categories from 0.5% to 61.5% (p(trend) < 0.001). Children (6.3%) were sensitized to cat allergen and sensitization rates increased also significantly with exposure categories from 3.0% to 15.4% (p(trend) < 0.001). Children (9.3%) were diagnosed with atopic eczema and a positive history of asthma/rhinitis was given in 3.6% and 3.9% respectively. Sensitization to cat was associated with atopic eczema (23.3% vs. 7.4%; OR(adj.)= 3.8, CI: 1.4-10.8), asthma (12.5% vs. 3.7%; OR(adj.)= 4.9, CI: 1.1-21.2), allergic rhinitis (6.9% vs. 2.7%; OR(adj.)= 3.1, CI: 0.7-15.2) and any atopic disease (43.5% vs. 16.3%; OR(adj.)= 3.8, CI: 1.5-9.5). The data suggest a promoting effect of cat keeping for atopic diseases.

Use of an electrostatic dust cloth for self-administered home allergen collection

Most epidemiologic studies employ a vacuum cleaner used by a trained technician to collect household allergens. This approach is labor intensive, equipment dependent, and impractical if study subjects reside over a wide geographic area. We examined the feasibility of a self-administered dust collection method, using an electrostatic cloth sent by conventional mail, to obtain allergen measurements. Thirty-two nonasthmatic twins from the California Twin Program wiped areas in the family room, kitchen, and bedroom, according to standardized instructions, and returned the cloths by mail. Allergen concentrations for Der-p-1, Der-f-1, Fel-d-1, and Bla-g-2 were determined using ELISA, and intrahouse and room-to-room concentrations were compared. Der-p-1 and Fel-d-1 were found in most homes, with highest concentrations in bedrooms and kitchens, respectively. Der-f-1 and Bla-g-2 were rarely found. Intrahouse Der-p-1 and Fel-d-1 concentrations were highly correlated and statistically significant (for Der-p-1, bedroom vs. kitchen, p=.0003, bedroom vs. family room, p=.0001, and family room vs. kitchen, p=.002; for Fel-d-1, bedroom vs. kitchen, p=.0004, bedroom vs. family room, p<.0001, and family room vs. kitchen, p=.0001). Reported cat ownership was strongly correlated with household Fel-d-1 concentrations (p<.005). In another comparison from different homes of children enrolled in the La Casa atopy prevention study, allergen concentrations measured from dust collected by a single operator from the left and right half of the same room in 21 homes were compared. Levels of Bla-g-2, Der-p-1, and Fel-d-1 concentrations collected from right and left halves of the same room were highly correlated, with r2 ranging from .7 to .9, and were highly statistically significant (all p values<.01). We conclude that nonintrusive and self-administered dust collection, using commercially available electrostatic dust cloths, sent by conventional mail services, is a promising alternative to technician-collected vacuumed dust for measuring indoor allergens in population-based studies, although further validation of the method is necessary.

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.

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.