Guanine content and Dermatophagoides pteronyssinus allergens in house dust samples

The study of the relationship between the guanine content and Dermatophagoides pteronyssinus (Dp) allergens in house dust samples is reported. Mattress and carpet dust of bedrooms from 22 different homes constituted the house dust samples. The guanine content was determined by quantitative measurements and the mite allergenicity by two immunochemical assays with a partially purified extract of Dp as internal reference: RAST inhibition and crossed and rocket line immunoelectrophoresis. A large scale range of guanine content was obtained among the 22 house dust samples studied (0.01 to 1.78 mg/0.1 gm of dust). Data of RAST inhibition, analyzed according to parallel line bioassay, demonstrated no significant difference between the slopes of the reference and the house dust sample lines, but a 100-fold variation in the relative Dp potencies was observed. By crossed and rocket line immunoelectrophoresis technique, the presence and the amounts of major Dp allergens (Der p I and Dp 4) were established in most house dust extracts. A significant correlation was found between the guanine content of the house dust samples and their relative Dp potencies (r = 0.86) on the one hand, and with their relative content of Der p I and Dp 4, two major Dp allergens (r = 0.75 and r = 0.74, respectively) on the other hand; in each case, a quantitative relationship was established. These results suggest that the guanine determination could assess mite allergens in house dust and may be a useful tool in large-scale investigations of house dust.     

Dermatophagoides farinae allergen levels from two different sources within the same home: evaluation of two different collection techniques

The allergens produced by the dust mites of the Dermatophagoides genus are now recognized as one of the major allergens in house dust. Quantification of those allergens helps to evaluate the effectiveness of avoidance measures and specific treatments aimed at the reduction of the mites and their allergens. The present study was undertaken to compare the level of D. farinae allergen collected by a standard vacuum cleaner with a disposable bag and the level of allergen collected by a hand-held vacuum equipped with a special filter. Samples were obtained from the main living area of 18 homes of patients allergic to D. farinae. Using a hand-held vacuum especially equipped with a removable micropore filter, a 2-m2 area of carpet was vacuumed for two minutes and an identical sample was collected from the major upholstered piece of furniture in the room. A third sample was obtained with an upright vacuum fitted with a clean disposable bag. The dust collected was extracted in phosphate buffered saline and resultant extracts were assayed for D. farinae allergen content by microtiter plate RAST inhibition assay. Results from these assays showed a large interhome variability regardless of sampling technique, but intrahome sampling showed remarkable consistency. A linear regression analysis demonstrated all of the comparisons correlated at a probability level of P less than .05. We conclude that dust mite allergen levels collected in a disposable bag vacuum cleaner are reliable indicators of the level of house dust mites present in the homes of patients.     

Wipe test for the detection of indoor allergens

BACKGROUND: The determination of house dust mite and cat allergens is a prerequisite for qualified assessment of exposure risk indoors. We describe the validation of integrated wipe tests comprising a porous sampling pin for the collection of settled house dust and an immunochemical test set-up for specific analysis of dust associated allergens. METHODS: Wipe tests comprised an immunochromatographic test system and a porous sampling pin for collecting dust by manually wiping a surface. Two different wipe tests were developed with specificity to cat allergen (Fel d 1) and to dust mite allergen (Der p 2/f 2). One-hundred and fifty on-site determinations for each of the allergens in 50 different households completed the field study to validate the analytical system. Reference analysis was based on collection of dust with a vacuum cleaner and analysis of dust associated allergens by ELISA. RESULTS: The wipe tests were found to produce semiquantitative results (class 0-3) on-site within 10 min of analysis time. For dust mite (cat) allergen the median of class 0-3 was 119 (263), 812 (844), 2708 (5670) and 8000 (56 800) ng/g dust, respectively. With respect to cut-off levels for dust mite (cat) allergens the clinical sensitivity was 62% (79%) and the clinical specificity was 94% (92%). CONCLUSIONS: The wipe tests proved to be a reliable tool for indoor allergen exposure screening, suitable for use even by untrained persons. This may have an impact on compliance with allergen avoidance measures.     

Inhibition Experiments with Solid Phase Mite or Epithelia in House Dust Hypersensitivity

The present study was undertaken to verify that mites are not the only allergens in house dust extracts and that other allergens such as cat epithelia can also be responsible for house dust hypersensitivities detected both by house dust skin tests and house dust RAST studies. In order to determine whether mite or epithelia fixed on a solid phase could remove not only the IgE antibodies reactive with the homologous allergens, but also the IgE antibodies reactive with house dust allergens, the authors have absorbed 10 sera of house dust allergic patients with solid phase mite or epithelia. The absorption procedure removed a large part of the IgE antibodies reactive with specific immunosorbent (Dermatophagoides pteronyssinus or cat epithelia) and in the same way the IgE antibodies reactive with house dust immunosorbent. The percentage of RAST inhibition varied from 65% to 92% for Dermatophagoides pteronyssinus and from 65% to 94% for house dust in patients allergic to house dust and mite; the percentage of RAST inhibition varied from 67% to 92% for cat epithelia and from 73% to 90% for house dust in patients allergic to house dust and cat epithelia. This is in accordance with the hypothesis that house dust is not an allergen per se, but rather a complex mosaic of several allergens including mite, animal epithelia, etc.     

Low-level exposure to house dust mites stimulates T-cell responses during early childhood independent of atopy

Background The imtnune responses which underlie the expression of allergic symptotns in childhood are believed lo be initiated in infancy and early childhood. The kinetics of this response have hardly been researched. Objective To analyse, in an environment with low house dust mite (HDM) exposure levels, the relationship between house dust mite (HDM)-specific T-cell reactivity as expressed by in vitro proliferation of blood mononuclear cells. Methods The study comprised a prospective analysis of patterns of allergen-specific T-cell reactivity in a cohort of 19 children, from whom blood samples were obtained in the spring during their second and third years of life. Blood mononuclear cell cultures were established in 200 μL AIM-V serum free medium. Crude house dust mite (HDM) and purified Der p 1 and Der p 2 extracts were used at optimal concentrations, i.e. 100μg/mL for HDM and 30μg/mL for the purified allergens. Tetanus toxoid (0.5 μglrnL) and ovalbumin (10 μg/mL) served as positive controls. A clinical diagnosis of allergy was verified with skin-prick tests. Dust samples were collected from a mattress and/or carpet or sofa in homes, day care centres and day care homes. Major mite allergen levels (Der p 1/Der f 1) in dust were analysed by an enzyme linked immunosorbent assay (ELISA). Results Specific T-cell responses were seen in the majority of the children against house dust mite (crude HDM extract. Der p 1 and Der p 2). The levels of the house dust mite allergens Der p 1 and Der f I were low, i.e. < 0.68 μg/g fine dust in the homes of the children and the day care centres that they were attending. This indicates that doses of mite antigen well below the suggested sensitization threshold level of 2 μg/g dust can induce mite-specific T-cell responses in young children. None of them showed clinical reactivity to house dust mites as indicated by negative skin-prick tests. Conclusions The findings suggest that active immunological recognition of environmental allergens and the ensuing initiation of allergen-specific T-cell responses, is a normal part of the ‘education’ of the immune system in early childhood and can occur even at very low exposure levels. Priming per se does not imply clinically significant sensitivity, however.     

Sensitization to house dust mites in Reykjavik, Iceland, in the absence of domestic exposure to mites

BACKGROUND: House dust mites are common sources of indoor allergens. In Reykjavik, Iceland, 9% of the young adult population had serum-specific IgE to Dermatophagoides pteronyssinus. Sensitization to mites is usually assumed to be due to exposure to house dust mites in the indoor environment. This investigation was carried out to measure the concentrations of house dust mite allergens and to investigate which species of mites were present in beds in Iceland. METHODS: A total of 197 randomly selected adults were visited at home using the European Community Respiratory Health Survey (ECRHS) II Indoor protocol. Dust samples were collected from mattresses for measurement of house dust mite allergen concentrations and to estimate the number and type of house dust mites. Additional samples from mattresses and floors were collected from the homes of 10 patients with positive skin prick tests (SPT) to D. pteronyssinus. House dust mite allergen concentrations were measured using ELISA and examination of mite species was carried out using microscopy. Climatic parameters were assessed using psychrometer readings in the bedrooms and outdoors. RESULTS: We found two single mite specimens, both D. pteronyssinus, in two dust samples. Mite allergen analyses indicated that two other dust samples had Der f 1 results close to the cut-off of 0.1 microg/g of dust. No samples were positive for Der p 1. In an additional collection of dust from the homes of 10 SPT-positive patients no Dermatophagoides spp. were found. CONCLUSIONS: Reykjavik citizens are exposed to extremely low amounts of house dust mite allergens in their homes. Possible alternative sources for sensitization are discussed, such as bird nests, exposure from travelling abroad, or other mites or invertebrates that cross-react with house dust mite allergens. Our findings suggest that exposures other than to house dust mites indoors are possible sources of mite allergen exposure.     

Specific IgE estimations by RAST in Japanese asthmatics compared with skin, passive transfer and bronchial provocation tests

198 asthmatics and twenty healthy persons were studied by RAST and in vivo tests with four common inhalant allergens, (a) Higher RAST classes were elicited with mite (Dermatophagoides farinae) extract and lower classes with other allergens. The agreement between positive RAST and skin or P-K tests was highest with the mite extract. RAST sensitivity was dependent on the kinds of allergens and was most sensitive to mite extract. Positive RAST was most closely related to the prick test reactions, (b) RASTs to house dust and mite extract were examined in terms of the threshold dosage of house dust and also the types of bronchial response (early, dual and late) induced by a certain amount of house dust; higher RAST classes were found in subjects with bronchial response of the dual or early type, elicited by a threshold dosage of diluted extract, while lower RAST classes were found in cases of the late-type response elicited by the threshold dosage of concentrated extract, (c) Changes in IgE antibodies to house dust and mite extract were estimated in patients with positive house dust provocation. A greater increase occurred in cases of dual or early response, a smaller increase in those with a late response. Despite discordances in skin tests and RAST between house dust and mite extracts, the increases in IgE antibodies to mite extracts as well as house dust were observed in all cases, presumably caused by an allergenic identity between the allergens.     

The study of house dust mites in Taiwan

By using a radioallergosorbent test (RAST) and intradermal skin testing, our previous studies strongly suggested that house dust mites are the most important allergen in Taiwan, especially in asthmatic children. This study was conducted to determine the distribution of house dust mites in houses of mite-sensitive asthmatic children and normals, the species of mites in various house dust samples, the seasonal prevalence, and the relation between the content of mite allergen and the mite density in dusts. Serial samples were collected every month between February 1986 and January 1987 from 61 houses of mite-allergic patients and nine normals. About 1 m2 surface area each of (A) family couch, (B) TV room floor carpet, (C) mattress, and (D) bed room floor carpet was vacuumed for one minute. The flotation method was used to collect mites in dusts and mites were counted under an inverted phase contrast microscope. Identification of house dust mite species was also performed. The RAST inhibition method was used for assay of mite allergen in dust extracts. The results showed the following six points. (1) Dermatophagoides pteronyssinus (DP) was the dominant species found in house dust in the Taipei area (78.8%). (2) The mean number of mites was greater in August through November and lowest in July. (3) The content of mite allergen did not correlate with the number of mites in dust sample. (4) The average number of mites in patients' houses was not different from that in normals' houses.(ABSTRACT TRUNCATED AT 250 WORDS)     

Nonlinear relations between house dust mite allergen levels and mite sensitization in farm and nonfarm children

BACKGROUND: Low sensitization rates to common allergens have been observed in farm children, which might be due to high exposure to microbial agents. It is not known how microbial agents modify the association between specific allergen exposure and sensitization. OBJECTIVE: To examine the relations between house dust mite allergen exposure and mite sensitization in farm and nonfarm children and to assess the effects of microbial agents levels on this association. METHODS: Major mite allergens of Dermatophagoides pteronyssinus (Der p 1) and Dermatophagoides farinae (Der f 1), endotoxin, beta(1,3)-glucans and fungal extracellular polysaccharides were measured in mattress dust of 402 children participating in a cross-sectional study in five European countries. Mite allergen (Der p 1 + Der f 1) levels were divided into tertiles with cut-offs 1.4 and 10.4 microg/g. Sensitization was assessed by measurement of allergen-specific immunoglobulin E against house dust mite. RESULTS: Prevalence ratios of mite sensitization for medium and high when compared with low mite allergen levels were 3.1 [1.7-5.7] and 1.4 [0.7-2.8] respectively. Highest mite sensitization rates at intermediate exposure levels were consistently observed across country (except for Sweden) and in both farm and nonfarm children. The shape of the dose-response curve was similar for above and below median mattress microbial agent levels, but the 'sensitization peak' appeared to be lower for above median levels. CONCLUSIONS: Our data suggest a bell-shaped dose-response relationship between mite allergen exposure and sensitization to mite allergens. In populations with high microbial agent levels and low sensitization rates, the curve is shifted down.     

Portable dehumidifiers in the control of house dust mites and mite allergens

Humidity is a decisive limiting factor for house dust mite (HDM) population growth and decreasing humidity may be the control method of choice. This study investigates the effects of portable dehumidifiers on the mite counts and concentration of the HDM allergen Der p I in the homes in northwest England. Mite counts and Der p I were measured in the paired dust samples collected by vacuuming a I m² area of bedroom carpet, living room carpet, mattress and sofa for 2 min in six houses supplied with the dehumidifier and six control houses, before and 1, 2 and 3 months after the instalment of dehumidifier. Temperature and relative humidity were recorded daily. There was no difference in mite counts in either of the groups throughout the study. Der p I decreased significantly in both groups and in all sampling sites, but no significant differences in the levels of reduction between the groups were found. Condensation was decreased in the dehumidifier group, but the level of indoor humidity capable of retarding mite population growth was not achieved. A single portable dehumidifier placed centrally in the house is unable to decrease indoor humidity to the level capable of retarding mite population growth and decreasing HDM allergens in the type of houses predominantly found in the northwest of England.     

Relationship between the clinical course of bronchial asthma from childhood to adulthood (deterioration/improvement), bronchial hyperreactivity and incidence of house dust mite allergens in households of persons treated for atopic bronchial asthma as children

The aim of the study was to determine the impact of the exposition to house dust mite allergens or its lack on clinical state of asthma in young adults treated in their childhood for atopic bronchial asthma. The concentration of house mite allergen was studied with the method of Acarex test (detection of guanine--excretory product of house dust mites) in the flats of 55 persons treated for atopic asthma before adolescence. There was significant difference (p < 0.006) between the clinical course of asthma (improvement) in persons living in flats free of house dust mite allergens and those living in flats infested with mites. House dust mite allergens were present significantly more frequently in flats of persons with a low histamine threshold (19 of 20 examined flats) than in flats of persons with a high histamine threshold or without hyperreactivity to histamine (6 of 20 examined flats).     

Activation of human serum complement with allergens. I. Generation of C3a, C4a, and C5a and induction of human neutrophil aggregation

To understand the relevance of allergens in generation of C3a, C4a, and C5a in normal human serum, we studied extracts of several allergens (house dust, house dust mite, Aspergillus fumigatus, and perennial ryegrass). Known complement activators zymosan and endotoxin were used as controls. Generation of C3a, C4a, and C5a (determined by radioimmunoassays) occurred with extracts of house dust and Aspergillus more than with house dust mite and ryegrass. Anaphylatoxins were produced both in dose and time-dependent fashions. Serum activated with house dust and Aspergillus extracts induced neutrophil aggregation when this serum was added to neutrophil suspensions. Less aggregation occurred when house dust mite and perennial ryegrass extract-activated sera were added to human neutrophils. We propose that some allergens may induce biologic responses by activation of sera and generation of anaphylatoxins as well as by IgE-mediated responses.     

Effect of an air cleaner with electrostatic filter on the removal of airborne house dust mite allergens

Purpose

The effects of air cleaners on the removal of airborne indoor allergens, especially house dust mites (HDM), are still controversial. The objective of this study is to evaluate the effect of an air cleaner with an electrostatic filter on the removal of airborne mite allergens.

Materials and Methods

A dried HDM culture medium that contained mite body particles and excretions was dispersed in a chamber equipped with an electrostatic air cleaner. The number of airborne particles was recorded continuously by a dust spectrometer for 60 minutes. Airborne particles in the chamber were collected on a sampling filter at a flow rate of 10 L/min and the Der f 1 concentration in the filter extracts was measured by two-site ELISA.

Results

The air cleaner efficiently removed airborne HDM particles. The air cleaner removed airborne HDM particles (size 2-12.5 µm) 11.4 ± 2.9 fold (cleaner operating for 15 minutes), 5.4 ± 0.7 fold (cleaner operating for 30 minutes), and 2.4 ± 0.2 fold (cleaner operating for 60 minutes) more than the removal of HDM particles by natural settle down. Removal kinetics differed according to the particle size of the airborne particles. The air cleaner decreased the concentration of Der f 1 in the extraction of airborne particles collected on the air sampling filter by 60.3%.

Conclusion

The electrostatic air cleaner can remove airborne HDM allergens and may be useful as a supplementary environmental control tool for HDM sensitized respiratory allergic patients.     

Identification of allergens from the mite Blomia tropicalis

In some tropical areas the mite Blomia tropicalis is a clinically important allergenic component of house dust, inducing specific IgE immune response in patients with allergic respiratory diseases such as asthma and rhinitis. The identification of allergens of this mite is necessary to obtain appropriate reagents for diagnostic and treatment procedures. We carried out this study using immunoblotting to detect the allergens of B. tropicalis. Our results demonstrate that this mite has one major allergen (11–13kDa) and three other important allergens with about 50% binding (64, 36 and 33 kDa). Therefore, B. tropicalis should be regarded as an important source of allergens in the house dust in tropical areas, besides those derived from other mites.     

Distribution of pyroglyphid mites in Birmingham with particular reference to Euroglyphus maynei

The Dermatophagoides mites are well recognized as allergens in bronchial asthma. A survey of mattress dust in Birmingham showed large numbers of Euroglyphus maynei to be present in addition. A variation was found in mite populations in dust collected by vacuum cleaner when compared to brushed samples, which may explain previous findings of only small numbers of E. maynei. A mean density of 296 pyroglyphid mites; 100 μg dust was found in mattress dust. Glycyphagus species formed only 1%, of all mites seen.     

Reduction of house dust mites and mite allergens: effects of spraying carpets and blankets with Allersearch DMS, an acaricide combined with an allergen reducing agent

Two studies were made to determine the acaricidal and allergen reducing properties of Allersearch DMS solution. In Study 1, samples of dust and carpet containing living mites were treated, in vitro, with DMS solution. No living mites were found in dust after 3-4 min or in carpets 50 min after treatment. In Study 2, mite counts and allergen estimation made on bed blankets before and after spraying with DMS solution showed a marked reduction in mite numbers (95%) and allergenicity (100-fold). Mite numbers and allergenicity stayed at this low level for 6 weeks. At 16 weeks both mites and allergens showed a slight increase, but were still significantly (P less than 0.001) below pretreatment levels.     

Newly generated IgE antibodies to Dermatophagoides pteronyssinus in children are directed against components distinct from Der p I and Der p II

The specificity of newly generated IgE antibodies (Abs) to the house dust mite, Dermatophagoides pteronyssinus, in longitudinal serum samples from 18 young children with an increased risk for IgE-mediated allergy was studied. The first IgE Ab response to house dust mite was detected early in life (mean age, 32 months; range, 11 to 60 months). For 83% of the children, more than half of the newly generated IgE Ab response to house dust mite was directed against components distinct from the major allergens, Der p I (Pl) and Der p II (DpX). These results suggest that the early IgE Ab response to house dust mite is induced by components distinct from the major allergens, Der p I and Der p II.     

Allergy to storage mites

Summary. There is now much evidence of sensitization to storage mites in urban populations as well as in the well-documented rural populations. Sensitization is therefore not restricted only to those with occupational exposure.
There appears to be a limited allergenic crossreactivity between storage mites and house dust mites, although both species also possess their own unique allergens.
More research on identification and characterization of storage mite allergens and their crossreactivity is needed to understand their complexity. Such studies are necessary to obtain high quality extracts for diagnosis and possible immunotherapy.
Development of immunoassays employing MoAbs will allow measurement of storage mite concentrations in workplaces and houses and the study of exposure-response relationships.     

Environmental and Social Influences on Skin Test Results in Children

Skin tests with 13 inhalant allergens were performed in 788 children with respiratory allergy. Positive reactions were common to animal danders (65%), to grass pollens (55%) and to tree pollens (44%) but rare to moulds (13%) and to house dust mite (12%). Children exposed to cows, dogs or horses at home more often had skin test reactions to these allergens than the children not exposed, but reactions to cat dander occurred as frequently in children exposed to cats at home as to those not exposed. Reactions to three pollens occurred most often in children from upper social classes and from urban areas and reactions to house dust mite occurred most often in children from lower social classes and from rural areas. Children with positive reactions to house dust mite came from larger families than children with negative test results.     

Dust from carpeted and smooth floors. V. Cat (Fel d I) and mite (Der p I and Der f I) allergen levels in school dust. Demonstration of the basophil histamine release induced by dust from classrooms

Sixty dust samples from schools in Norway were analysed for major allergens from cat and mite after sampling with the regularly used vacuum cleaners for 5 days and with a new model vacuum cleaner for 10 days, respectively. The major feline allergen Felis domesticus allergen I (Fel d I) was detected in all the classrooms, with ranges from 12 to 16,840 ng/m2 floor area. The mean Fel d I concentration was about 11 times higher per unit area carpeted floors as compared with smooth floors after the 10 days sampling period. Mite allergens Dermatophagoides pteronyssinus allergen I (Der p I) and Dermatophagoides farinae allergen I (Der f I) were detected in very low concentrations, with ranges from < 1 ng to 104 ng/m2 floor area. These findings suggest that the school is a protective environment against mite infestation, while the prevalence of cat allergens in classrooms seems higher than previously assumed. Basophil histamine release was measured after provocation with 20 dust extracts from 10 different schools. In nine of the 10 schools examined, the basophil histamine release caused by challenge with carpet dust was higher than the corresponding release with smooth floor dust. The calculated floor areas in each school in which dust led to 15% histamine release were from 2 to 55 times larger for smooth floors compared with carpeted floors. These results emphasize previous findings regarding higher allergen concentrations in classrooms with carpeted floors.