Penetration of light into carpet, and responses of the European house-dust mite (Dermatophagoides pteronyssinus) to varying light intensity and diurnal cycle

This study examined the question of what effect exposure to light might play in determining the vertical distribution of house-dust mites in carpet, and the degree to which light penetrates worn and unworn carpets of different pile conformation (loop- versus cut-pile), height and colour. The effect on population increase of a diurnal lighting cycle versus continual darkness was also investigated. It was found that the penetration of light into carpets was largely unaffected by pile colour or conformation. Pile height was an important factor, however, and for a given height within the pile, light intensity was higher in carpets subjected to a greater degree of wear. This corresponded to the reduction in effective pile height that occurs with carpet use. Whilst the differences observed were sometimes large (up to two-fold for a given height within the pile), Petri dish studies suggested no mite preference for habitation of areas of low light intensity compared to high intensity. Additionally, culturing mites under a diurnal light cycle was shown to be no more efficient than culturing in complete darkness. These results suggest that exposure to light is not an important determinant of house-dust mite behaviour, or their ability to colonise textile substrates.     

Acid-induced polymerization of the group 5 mite allergen from Dermatophagoides pteronyssinus.

House dust mites are the most important source of indoor allergens and cause allergic diseases. Our studies here suggest that the group 5 allergen from Dermatophagoides pteronyssinus (Der p 5) is monomeric at neutral pH, but forms filaments at low pH. Circular dichroism measurements show Der p 5 is a helical protein, and the protein sequence reveals Der p 5 contains coiled-coil helices. The acid-induced filament assembly could be explained in part by the high content of charged residues (40%) in the coiled-coil structure. Interestingly, some of the known Dermatophagoides allergens also contain a heptad repeat, which could potentially form coiled coils. Therefore, coiled-coil helices may be one of the common structural motifs of mite allergens that contribute to their allergenicity.     

Impact of Dermatophagoides pteronyssinus mite body raw material on house dust mite allergy diagnosis in a Serbian population

House dust mite (HDM) allergy has different clinical and immunological patterns in different geographic regions. The impact of raw material of commercial Dermatophadoides pteronyssinus (Acari: Pyroglyphidae) mite bodies on the quality of allergen extracts for allergy diagnosis in the Serbian population has not been previously evaluated. House dust mite bodies obtained from manufacturers in Europe, South America and Australia were used in the preparation of allergen extracts for in vivo diagnosis and serological analysis in a group of 14 HDM‐allergic adults. In the group of mite‐allergic patients, there was no statistically significant difference in skin test reactivity (Wilcoxon matched pairs test) among the three HDM body extract preparations. In a CAP inhibition assay, two extracts (A and C) achieved maximum inhibition of >90%, whereas extract B demonstrated a different inhibition slope and lower inhibition potential (80%). However, a remarkable difference in immunoglobulin E reactivity using Western blot analysis with individual patients' sera was observed in one of the preparations (extract B). These findings emphasize the need for the careful selection of starting material for the preparation of HDM diagnostic reagents intended for use in patients from geographically distinct regions as these preparations can have implications on the selection criteria for patient‐tailored immunotherapy of HDM allergy.     

Effects of five insect growth regulators on laboratory populations of the North American house-dust mite,Dermatophagoides farinae

The potential of insect growth regulators (methoprene, hydroprene, fenoxycarb, diflubenzuron and triflumuron) to control populations of the North American house-dust miteDermatophagoides farinae (Hughes) was assessed in laboratory bioassays. Methoprene was most effective at suppressing population growth, especially at concentrations of 1.0% (10 000 ppm) and 5.0% (5000 ppm) active ingredient. Hydroprene, structurally related to methoprene, also suppressed house-dust mite populations but not as consistently as methoprene. Fenoxycarb may be effective at controlling house-dust mites but at greater concentrations than were tested. Diflubenzuron and triflumuron, two chitin-synthesis inhibitors, failed to suppress mite numbers and may, in fact, stimulate reproduction in some cases. Almost all concentration of the insect growth regulators were shown to be ineffective when assayed 90 days after treatment.     

屋尘螨Ⅰ类变应原Der p1的体内定位

对过敏性疾病主要过敏原屋尘螨Dermatophagoides pteronyssinusⅠ类变应原（Der p1）进行了抗原定位研究。选用经表达和纯化的Der p1抗原蛋白,按常规方法免疫小鼠,分离血清获抗重组Der p1的抗体（Ⅰ抗）,用抗鼠IgG荧光抗体为Ⅱ抗,屋尘螨经石蜡切片,在荧光显微镜下对其特异性变应原的定位进行观察。HE染色显示屋尘螨消化系统占据大部分体腔。组织免疫荧光发现屋尘螨Ⅰ类变应原主要定位于螨的中肠组织及肠内容物,而螨的生殖系统、排泄系统等脏器以及几丁质甲壳均呈阴性反应。据此认为屋尘螨Ⅰ类变应原存在于螨的肠内容物和中肠组织中。     

Skin-associated Bacillus, staphylococcal and micrococcal species from the house dust mite, Dermatophagoides pteronyssinus and bacteriolytic enzymes

Dust mites produce bacteriolytic enzymes, one of which belongs to the NlpC/P60 superfamily comprising bacterial and fungal proteins. Whether this enzyme is derived from the mite or from mite-associated microbes is unclear. To this end, the bacteriology of mites per se, and carpet and mattress dust from a group of asthmatic children and their parents was investigated. Dust from parents’ and children’s mattresses yielded significantly more colony forming units compared with dust from their corresponding carpets. Zymography demonstrated some dusts contained bacteriolytic enzymes, and in nine of the twelve dust samples from three of five houses examined, a prominent bacteriolytic band was obtained that corresponded to the mite band, although in one home, other lytic bands were detected. Fifty bacterial isolates were obtained from surface-sterilised, commercially obtained Dermatophagoides pteronyssinus. 16S rRNA, tuf and rpoB gene sequencing of nine Gram-positive isolates identified them as Bacillus cereus, B. licheniformis, Staphylococcus aureus, S. epidermidis, S. capitis and Micrococcus luteus, known human skin commensals. 16S rRNA sequence homologies of four of the nine isolates identified as B. licheniformis formed a distinct phylogenetic cluster. All species secreted lytic enzymes during culture although the lytic profiles obtained differed between the rods and the cocci, and none of the bands detected corresponded to those observed in dust or mites. In conclusion, mites harbour a variety of bacterial species often associated with human skin and house dusts contain bacteriolytic enzymes that may be mite-derived. The identification of a novel cluster of B. licheniformis isolates suggests an ecological adaptation to laboratory-reared D. pteronyssinus. It remains to be determined whether the previously described mite-associated 14 K lytic enzyme is derived from a microbial source.     

The determination of allergen-specific IgE and IgG antibodies in patients sensitized to the house dust mite Dermatophagoides pteronyssinus

45 patients, hypersensitive to house-dust mites, were examined by the method of skin tests to D. pteronyssinus allergen. Besides, in their blood sera the levels of allergen-specific IgE antibodies were determined in the radioallergosorbent test and allergen-specific IgG antibodies, in the enzyme immunoassay. These tests revealed that in 91% of the patients the results of skin tests were positive, in 68% an elevated level of specific IgE antibodies and in 93% of the patients an elevated level of specific IgG antibodies were detected. All patients showed the positive result in one of the above-mentioned tests. The largest group of the patients (55%) included persons showing the positive result of the skin test and having elevated levels of allergen-specific IgG and IgE antibodies. Thus, in cases of hypersensitivity to house-dust mites the levels of allergen-specific IgG and IgE antibodies in the patients' blood sera should be determined.     

IgE antibodies to Dermatophagoides pteronyssinus (Housedust mite), Aspergillus fumigatus,and beta-lactoglobulin in sudden infant death syndrome.

The prevalence of serum IgE antibodies to Dermatophagoides pteronyssinus (house-dust mite), Aspergillus fumigatus, and bovine beta-lactoglobulin was significantly greater in cases of sudden infancy death (S.I.D.) than in a control group of infants of the same age range. This difference was most pronounced with D. pteronyssinus antibodies, which suggests that hypersensitivity to house-dust mite may be a factor in the aetiology of S.I.D. in Western Australia. Both the S.I.D. and control infants had similar serum concentrations of immunoglobulins G, M, and E but IgA levels were significantly higher in the control group.     

Predicting the population dynamics of the house dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) in response to a constant hygrothermal environment using a model of the mite life cycle

A generalised model of the life cycle of a house dust mite, which can be tailored to any particular species of domestic mite, is presented. The model takes into account the effects of hygrothermal conditions on each life cycle phase. It is used in a computer simulation program, called POPMITE, which, by incorporating a population age structure, is able to predict population dynamics. The POPMITE simulation is adapted to the Dermatophagoides pteronyssinus (Acari: Pyroglyphidae) (DP) mite using published data on the egg development period, total development period, adult longevity, mortality during egg development, mortality during juvenile development, and fecundity of individual DP mites held at a range of constant hygrothermal conditions. An example is given which illustrates how the model functions under constant hygrothermal conditions. A preliminary validation of POPMITE is made by a comparison of the POPMITE predictions with published measurements of population growth of DP mites held at a range constant hygrothermal conditions for 21 days. The POPMITE simulation is used to provide predictions of population growth or decline for a wide range of constant relative humidity and temperature combinations for 30 and 60 days. The adaptation of the model to correctly take account of fluctuating hygrothermal conditions is discussed.     

Evaluation of the immunospecific activity of allergens prepared from house dust and the mite Dermatophagoides pteronyssinus in the bacteriosorption reaction on a flat surface

The content of protein A-reactive IgG to allergens prepared from house dust and D. pteronyssinus was determined in the sera of 4 immunized rabbits, 10 sensitized and hyposensitized guinea pigs and 37 treated and untreated allergic patients by means of the previously developed bacteriosorption test (BST). The sensitivity of the test for the determination of allergen-specific antibodies was 50-100 ng/ml. This test was shown to permit the detection of IgG in the sera of immunized, sensitized and hyposensitized animals, as well as in the sera of some treated and untreated patients. The antigenic similarity of both allergens was confirmed. Three batches of D. pteronyssinus allergen, standardized as to the content of protein nitrogen, differed in their immunospecific activity in BST with one of the rabbit sera and with the set of the patients' sera. The covalent immobilization of house-dust allergen on polystyrene by means of water-soluble carbodiimide gave no advantages in BST in comparison with adsorption immobilization in alkaline carbonate-bicarbonate buffer.     

Biological characterization of a formulated allergoid from Dermatophagoides pteronyssinus.

A comparative study between the biological properties of the allergen Dermatophagoides pteronyssinus (Dp) and its formulated allergoid (DpHCHO) was performed. After immunizing rats with Dp or DpHCHO the serum level time course of IgE and IgG was determined by passive cutaneous anaphylaxis (PCA) and indirect-ELISA, respectively. The avidity for IgE (PCA and PCA-inhibition) or IgG (indirect ELISA and ELISA inhibition) and the ability to induce anaphylactic shock were also determined. Serum IgE pattern differs between Dp and DpHCHO while IgG levels were greater after DpHCHO. The allergoid has lost the ability to bind IgE while its avidity for IgG falls 5-6 times. The allergoid, but not the allergen, fails to induce anaphylactic shock. A schedule for assaying the biological characteristics of allergoids is presented.     

A simple model for predicting the effect of hygrothermal conditions on populations of house dust mite Dermatophagoides pteronyssinus (Acari: Pyroglyphidae)

A simple mite population index (MPI) model is presented which predicts the effect on house dust mite populations of any combination of temperature and relative humidity (RH). For each combination, the output is an index, or multiplication factor, such that 1.1 indicates 10% population growth and 0.9 indicates 10% population decline. To provide data for the model, laboratory experiments have been carried out using lab cultures of Dermatophagoides pteronyssinus. The population change was observed for mites held in steady-state conditions at different combinations of temperature and RH over 21 days. From the results, a best-fit equation has been derived which forms the basis of the MPI model. The results also enable a new term to be defined: the Population Equilibrium Humidity, PEH, the RH for a given temperature at which house dust mite populations neither grow nor decline. It is similar to Critical Equilibrium Humidity, the RH below which house dust mites are unable to maintain water balance, but relates to a population of mites (rather than a physiological phenomenon) and is more able to take account of the observed effects of extremes of temperature and RH. Compared with previous population models, the MPI model is potentially more accurate and comprehensive. It can be combined with other simple models (described in previous papers), such as BED, which simulates the average hygrothermal conditions in a bed, given room␣conditions, and Condensation Targeter II, which simulates room conditions given a range of easily obtainable inputs for climate, house type and occupant characteristics. In this way it is now possible, for any individual dwelling, to assess the most effective means of controlling mite populations by environmental means, such as by improving standards of ventilation and insulation, or by modifying the occupant behaviour that affects the hygrothermal environment within a dwelling. Although the MPI model requires further development and validation, it has already proved useful for understanding more clearly how the different hygrothermal conditions found in beds and bedrooms can affect mite populations. It has also demonstrated that there is considerable scope for controlling mites by environmental means in cold winter climates such as the UK.     

Oxygen consumption in active and quiescent protonymphs of the American house-dust mite

Oxygen consumption in protonymphs of the American house-dust mite was measured by the Cartesian diver technique. Active protonymphs consumed 1.14 × 10^?2 μl/hr/mite under close to optimum temperature and humidity conditions for the species. This consumption is higher than that reported for fasting non-reproducing females. The protonymphs were active when confined in the diver and exhausted their energy reserves in less than 20 hr. Quiescent protonymphs consumed 4 × 10^?4 μl/hr/mite of oxygen, which is 28 times less than the consumption of active mites. The quiescence was not a static state, disturbed quiescent protonymphs had a six times higher oxygen consumption. This additional energy is thought to be spent in repair of injuries caused by collecting, e.g. secretion of wax on places where the layer has been removed.     

Antigen Der f I from the dust mite Dermatophagoides farinae: structural comparison with Der p I from Dermatophagoides pteronyssinus and epitope specificity of murine IgG and human IgE antibodies

The physicochemical and antigenic properties of an allergen purified from Dermatophagoides farinae, Der f I, were compared with Der p I from Dermatophagoides pteronyssinus. On SDS-PAGE, Der f I migrated as a single polypeptide chain with the same m.w. as Der p I (24,000). Two isoallergenic peaks of Der f I were identified on preparative isoelectric focusing (pI 5.7 to 6.3 and pI 6.6 to 6.95). Fractions from each peak were shown to have an identical amino acid composition (which was similar but not identical to Der p I) and the same N-terminal amino acid sequence. There was a good correlation between quantitative intradermal skin tests to both purified allergens and to D. farinae extract in mite-allergic patients, with positive results when using as little as 10(-5) micrograms/ml of Der f I. The majority of sera with detectable IgE antibody to D. farinae also had IgE antibody to Der f I both among children (29/42 = 69%) and adults (55/63 = 87%). By RAST, there was an excellent correlation between IgE antibody to Der f I and Der p I in sera from 42 mite-allergic children (n = 0.94, p less than 0.001). Polyclonal IgG antibodies from six mice immunized with Der f I showed preferential binding to that allergen, and most monoclonal antibodies (16 of 18) raised against Der f I did not bind Der p I. However, two monoclonal antibodies from this fusion showed cross-reactive binding to both allergens. Immunoabsorption experiments, using D. pteronyssinus and D. farinae extracts coupled to Sepharose, showed that a large proportion of murine antibodies (74% to Der p I and 60 to 93% to Der f I) could not be absorbed by the heterologous extract on the immunosorbent. In contrast, in sera from seven mite-allergic patients, most of the specific IgE and IgG antibody (i.e., greater than or equal to 82%) was removed by either immunosorbent. Thus, Der f I and Der p I represent a homologous pair of major allergens which possess both cross-reacting and species-specific epitopes. The antibody response in mice immunized with either allergen in complete Freund's adjuvant was largely directed against species-specific epitopes, whereas in allergic humans, IgE- and IgG-specific antibodies bound predominately to cross-reacting epitopes.     

Kinetics of active and passive components of water exchange between the air and a mite, Dermatophagoides farinae

Female North American house dust mites were found to exchange water with the ambient air from two compartments. At humidities above the critical equilibrium activity (CEA), transpiration out of a single large compartment was observed using HTO as a tracer for water. Total sorption into this compartment was also observed by following changes in the specific radioactivity. The sorption data required that an active process or pump be present. The water in this pump is the second compartment above the CEA. Below the CEA the large compartment could be identified as a compartment characterized by a small transpiration rate constant. The pump below the CEA becomes a rapidly transpiring fast compartment. By separating the water pool into two compartments, it was possible to relate a_v to k and $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$. The major effect of a_v on k was related to its effect on the permeability of the cuticle. The influence of a_v on $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$ was different for active and passive sorption. Above the CEA the pump operated at full capacity and active $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$ was directly proportional to a_v. Passive sorption was influenced by a_v in two ways. The driving force for $\text{m}\text{?}{}_{\mathrm{<mtext>S</mtext>}}$ was further reduced below saturation by the effect of a_v on the permeability of the exchange surface.