House dust mite sensitivity: a comparison of immune response with exposure to four species of Pyroglyphidae

Twenty-five atopic children under 11 years of age were studied, using skin and RAST tests, for their specific IgE response to four species of pyroglyphid house dust mites, Dermatophagoides pteronyssinus, D. farinae, D. microceras and Euroglyphus maynei. All of the children were sensitive to D. pteronyssinus, 20 (80%) of these children were also sensitive to D. farinae and D. microceras, and 16 of the latter (64%) were also sensitive to E. maynei. Dust samples from various sites in the homes of the children revealed D. pteronyssinus in all homes studied but no D. farinae or D. microceras. E. maynei, although identified, was not present in significant numbers in any site. A control group of 20 atopic children of similar age who were not sensitive to house dust mite allergens had a similar exposure to the four mite species. These results suggest that factors in addition to mite exposure are important in the development of specific IgE responses to house dust mites.     

Sensitization to Dermatophagoides siboney, Blomia tropicalis, and other domestic mites in asthmatic patients

Mite species adapted to warm, humid climates are commonly found in house dust in the tropics. In Cuba, Dermatophagoides pteronyssinus, D. siboney , and Blomia tropicalis are the most common and abundant mite species in house dust. To investigate the pattern of Sensitization of Cuban asthmatic patients to common mite species, we skin-prick-tested (SPT) 148 patients with a clinical history of asthma and possible mite allergy, and determined specific IgE antibodies against mite allergens ( D. pteronyssinus, D. farinae, D. siboney, B. tropicalis, Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae , and Glycyphagus domesticus ). The prevalence of positive SPT was high to D. siboney (88%), D. pteronyssinus (87%), A. siro (85%), B. tropicalis (85%), and D. farinae (83%). The largest skin reactions were obtained with D. siboney and B. tropicalis extracts. The skin test response to the D. siboney extract correlated to those of D. farinae, D. pteronyssinus, B. tropicalis , and A. siro. The highest IgE levels were found to Dermatophagoides species and B. tropicalis. IgE to D. siboney and B. tropicalis were found in 97% and 96% of the patients, respectively. The prevalence of specific IgE to the other mites studied varied from 46 to 65%. D. siboney and B. tropicalis are important sensitizers among asthmatic patients in Cuba.     

The effect of seasonal and domestic factors on the distribution of Euroglyphus maynei in the homes of Dermatophagoides pteronyssinus allergic patients

A survey of the house dust mite population was carried out in the homes of fifty asthmatic Liverpool individuals with strongly positive skin tests to Dermatophagoides pteronyssinus. As expected, D. pteronyssinus was the commonest species found. However, Euroglyphus maynei made up 37% of the total adult mite count and was the predominant species in 48% of beds examined. There was a good correlation between increasing numbers of E. maynei and decreasing social class, but only a weak one with percentage relative humidity. Ionic sodium levels in bed dust were found to correlate with decreasing social class and increasing E. maynei levels. In nineteen beds, mites were sampled at 4-monthly intervals for 1 year—this showed a relative decrease in the proportion of E. maynei compared with other mites in the autumn, when relative humidity was high. A further twenty beds underwent intensive house dust eradication (including the use of plastic covers) for 1 year—these beds showed a progressive fall in the proportion of E. maynei recovered, suggesting that this mite is more vulnerable to anti-house dust mite measures.
Euroglyphus maynei is a common house dust mite and further work needs to be done to assess its antigenic nature and clinical significance.     

Mite and mite allergen removal during machine washing of laundry

BACKGROUND: Few studies have investigated live house dust mite and mite allergen removal from clothing and bedding by washing machines. No studies have investigated the transfer of mites from infested to uninfested clothing and bedding during washing. OBJECTIVE: The purpose of this study was to wash different types of clothing and bedding in residential washing machines to determine the live Dermatophagoides farinae mite and allergen removal and the mite transfer from mite-infested items to mite-free items. METHODS: Clothing and bedding items were machine washed in 6- and 8-lb loads in warm (36 degrees C-38 degrees C) or cold (22 degrees C-27 degrees C) water with and without recommended concentrations of laundry detergent and sodium hypochlorite bleach. Live mites and allergen present in washed versus unwashed and washed mite-infested versus washed mite-free items were compared. RESULTS: Washing clothing and bedding in water alone, detergent, or detergent plus bleach removed 60% to 83% of the live mites. Washing removed more mites from some items than from others. When mite-infested items were washed with identical sets of mite-free items, many live mites were transferred to the previously mite-free items. Overall, 84% of Der f 1 was removed from items washed in water alone or in detergent and 98% from items washed in detergent plus bleach. CONCLUSIONS: Washing clothing and bedding in cold or warm water with detergent or detergent plus bleach removed most allergen and a significant (P <.05) portion of live mites. Repeated washing is required to further reduce mite levels. Live mites were transferred from mite-infested to mite-free items during washing.     

House dust acarofauna and Der p I equivalent in Australia: the relative importance of Dermatophagoides pteronyssinus and Euroglyphus maynei

The acarofauna and Der p I allergen concentrations in dust samples from mattresses and lounge room carpets obtained from 20 homes from two coastal cities. Perth and Bunbury, were determined. All samples were shown to contain mites and the geometric mean numbers of total mites/g of mattress and carpet dust for Perth and Bunbury were 480 and 263, and 585 and 992, respectively. Carpets from both centres had a significantly (P less than 0.02) greater mean number of mite species (Perth 9.1, Bunbury 9.0) than mattresses (Perth 5.2, Bunbury 5.7). The predominant mite species were D. pteronyssinus, E. maynei and Tarsonemus spp. D. farinae was found to be absent from all dust samples examined. E. maynei was present in the 10 Bunbury homes and in 50% of the Perth homes, ranging from 0 to 81% of mites identified. The arithmetic mean Der p I concentrations in the mattresses and carpets in Perth and Bunbury were 4.2 and 4.1, and 3.8 and 9.2 micrograms/per gram of fine dust, respectively, and Der p I concentration correlated with mite counts (r = 0.75; P less than 0.001). The concentration of Der p I equivalent per 100 mites was 1.5 micrograms. The data are consistent with the view that asthmatic patients in Western Australia have significant exposure to a variety of house dust mites and that E. maynei may be clinically significant.     

High-molecular-weight allergens of the house dust mite: an apolipophorin-like cDNA has sequence identity with the major M-177 allergen and the IgE-binding peptide fragments Mag1 and Mag3

BACKGROUND: A 349-residue recombinant polypeptide of Dermatophagoides farinae, Mag 3, has been shown to represent part of a larger 177-kD (M-177) allergen with very high IgE-binding activity. METHODS: Cloning and sequencing of cDNA from the house dust mites Dermatophagoides pteronyssinus and Euroglyphus maynei was used to characterise the polypeptide containing the Mag 3 sequence. RESULTS: cDNA clones containing the complete sequence of the E. maynei homologue of the M-177 allergen were isolated and analysed. The translation contained not only an amino acid sequence with 90% identity to the 349-residue Mag-3 fragment but also a further sequence with 90% identity to another IgE-binding recombinant D. farinae polypeptide designated Mag 1. The complete sequence encoded a mature polypeptide of 1,650 residues and a molecular mass of 189.5 kD. cDNA clones from D. pteronyssinus also encoded sequences equivalent to the Mag 1 and 3 polypeptides. The M-177 sequence showed strong similarity to the lipid transport apolipophorins found in insect lipophorins. CONCLUSIONS: cDNA sequence data show that the D. pteronyssinus and E. maynei homologues of the M-177 high-molecular-weight D. farinae allergen contain sequences equivalent to both the Mag 1 and Mag 3 recombinant IgE-binding fragments. The N-terminal sequence of the full-length 1,650 amino-acid allergen showed strong similarity to the insect apolipophorins which are poorly soluble in aqueous extracts and exist in the lipid transport particles in haemolymph. It is proposed that presentation in lipid particles could be a factor which enhances the immunogenicity of this group of allergens.     

Molecular characterisation of group I allergen Eur m I from house dust mite Euroglyphus maynei.

Using the polymerase chain reaction (PCR) we have amplified and cloned genomic DNA encoding the secreted group I allergen proteins from the house dust mite species Euroglyphus maynei, Dermatophagoides pteronyssinus and D. farinae. Affinity chromatography using a monoclonal antibody to the allergen Der p I was used to purify the group I protein from E. maynei. We present the deduced amino acid sequence of a new member of the group I house dust mite allergen family Eur m I. The three proteins show a high level of primary structure similarity: Eur m I and Der p I show 85% amino acid identity, and the three allergen amino acid sequences taken together show 78% identity. A potential N-glycosylation site and residues of the cysteine protease active site are also conserved between the three proteins.     

Clinical significance and allergenic cross-reactivity of Euroglyphus maynei and other nonpyroglyphid and pyroglyphid mites

The clinical significance and allergenic cross-reactivity of the storage mites Lepidoglyphus destructor and Acarus siro and the house dust mites Dermatophagoides pteronyssinus and Euroglyphus maynei were investigated with specific IgE antibodies by use of the RAST and the RAST-inhibition technique. RAST-positive sera were obtained from 64 Swedish farmers whose test results were positive to at least one of the four mite species. E. maynei was shown to be a common cause of sensitization among the whole farming population with a prevalence of 4.5% of positive RAST reactions. Farmers with astham alone or in combination with rhinitis were more often sensitized to storage mites and house dust mites than farmers with rhinitis only. No significant correlation was found between positive RAST resuts to L. destructor and E. maynei on the one hand and L. destructor and D. pteronyssinus on the other. Statistical significance was reached only between RAST results to E. maynei and D. pteryonssinus. However, by RAST-inhibition studies E. maynei was shown to possess its own unique allergen(s).     

Ecology of house dust mites in Oxfordshire

In a survey of the mite fauna in 30 homes in Oxfordshire, Dermatophagoides pteronyssinus and Euroglyphus maynei were found to be the most abundant species but D. farinae was absent. Of a total of 14 parameters investigated for their influence on mite numbers, relative humidity was apparently the most important factor. Bedrooms with humidities above 64% contained significantly more mites in mattresses than those with lower humidities. Bedroom humidity and thus mattress mite numbers were apparently related and were influenced by the bedroom minimum temperature, the age of the house and the use of central heating. These trends were not seen in the numbers of mites found in living-room carpets. Atopic and non-atopic participants involved in this study did not differ significantly in the numbers of mites found in their homes.     

Contact and fumigant toxicity of cinnamaldehyde and cinnamic acid and related compounds to Dermatophagoides farinae and Dermatophagoides pteronyssinus (Acari: Pyroglyphidae)

Toxicities of (E)-cinnamaldehyde and (E)-cinnamic acid and their 41 structurally related compounds to adult Dermatophagoides farinae Hughes and Dermatophagoides pteronyssinus Trouessart (Acari: Pyroglyphidae) were examined using fabric-circle contact plus fumigant and vapor-phase mortality bioassays. Results were compared with those of two acaricides, benzylbenzoate and dibutyl phthalate. In contact plus fumigant mortality bioassays, the most toxic compounds were (E)-cinnamaldehyde, methyl (E)-cinnamate, cinnamyl acetate, and hydrocinnamaldehyde against adult D.farinae (17.5-23.3 mg/m2) and D. pteronyssinus (19.0-24.0 mg/m2), based on 24-h 50% lethal concentration (LC50) values. These compounds were significantly more toxic than either benzyl benzoate (LC50, 64.9 and 60.5 mg/m2) or dibutyl phthalate (218.9 and 232.3 mg/m2). The toxicity of allyl cinnamate versus benzyl benzoate was not significantly different. Structure-activity relationship indicates that structural characteristics, such as types of functional groups, carbon skeleton, and saturation, appear to play a role in determining the compound toxicities. In vapor-phase mortality bioassays, these compounds were effective against adult D. farinae in closed, but not in open containers, indicating that their mode of delivery was largely a result of vapor action. The active compounds described merit further study as potential house dust mite control fumigants with contact action in light of global efforts to reduce the level of highly toxic synthetic acaricides in indoor environments.     

A comparative study of three serine proteases from Dermatophagoides pteronyssinus and D. farinae

Studies have shown that the dust mites Dermatophagoides pteronyssinus and D. farinae contain several serine proteases, two of which have been shown to be allergenic, and to include trypasin and chymotrypsin, corresponding to the groups III and VI mite allergens. However, mites also contain other serine proteases, and the data reported in this study show that an elastase-like enzyme is present in both species. This enzyme was differentiated from the other serine proteases, particularly chymotrypsin, on the basis of charge, substrate specificity, and inhibition by copper and mercury cations. Its apparent mol. mass, as judged by gel filtration, was similar to those previously described for trypsain and chymotrypsin, i.e., 30 kDa. Several isoforms were detected by isoelectric focusing, but the isoelectric points of the major forms in both D. pteronyssinus and D. farinae were 10.5 and 9.8, respectively, contrasting with the acidic mite chymotrypsins. All three serine proteases were detected in whole mite and faecally enriched extracts, but the activities of trypsin and the elastase-like enzyme were greater in the latter type of extract. These data were similar to those obtained by quantitative immunochemical analysis of the D. farinae group III allergen in appropriate extracts, suggesting that culture conditions may modulate protease production. A monoclonal antibody affinity matrix specific for the group III allergen from D. farinae was shown to bind mite trypsin. However, a small amount of mite chymotrypsin also bound, suggesting limited immunologic cross-reactivity, a finding consistent with known sequence data.     

Cross-reactivity of T-cell responses to Dermatophagoides pteronyssinus and D. farinae. Studies with group 1 and 7 allergens

BACKGROUND: Comparative information on T-cell responses to allergens from different Dermatophagoides species is limited even though differences in the epitypic recognition have been described. OBJECTIVE: To compare the level of T-cell proliferation and cytokine production to allergens from the mite species, D. pteronyssinus and D. farinae. METHODS: Freshly isolated peripheral blood mononuclear cells (PBMC) from house dust mite (HDM)-allergic and HDM-nonallergic donors were stimulated with the group 1 and group 7 allergens of D. pteronyssinus and D. farinae and the level of proliferation as well as IL-5 and IFNgamma production were measured. RESULTS: The proliferative response and the level of IL-5 produced after in vitro challenge with group 1 and group 7 allergens were equivalent for the allergens from both mite species even though D. farinae is not detected in the environment where the study population live. As expected the level of IL-5 production to the individual allergens was higher for the allergic donor group than for the nonallergic donors, however, there was no difference in the level of T-cell proliferation between the different donor groups. CONCLUSION: The proliferative and cytokine response to the group 1 and group 7 allergens for D. pteronyssinus and D. farinae indicates that there is a large degree of T-cell cross-reactivity between the whole purified allergens from each species. This is despite previous reports demonstrating different responses to synthetic peptides representing Der p 1 and Der f 1 in a similar study population.     

A New, Purified Dermatophagoides farinae Allergen Preparation

A purified, standardized and characterized allergen preparation of the house dust mite Dermatophagoides farinae (Df) was evaluated by skin prick test (SPT) and radioallergosorbent test (RAST) in 88 subjects. Skin reactions to the purified Df preparation and a corresponding crude Df preparation were compared. SPT was also performed with a crude Dermatophagoides pteronyssinus (Dpt) preparation to compare reactions obtained with the two mite preparations. By SPT the purified Df allergen preparation was representative of the crude Df preparation (r = 0.78) and the correlation between skin reactions to Df and Dpt was high (r = 0.78). The concordance between results obtained with RAST and SPT techniques with the purified Df preparation was high (84%). The purified D. farinae preparation was well tolerated and is well suited for SPT.     

Localization of antigens and allergens in thin sections of the house dust mite, Dermatophagoides pteronyssinus (Acari: Pyroglyphidae)

Cryostat sections of the house dust mite, Dermatophagoides pteronyssinus, were probed in fluorescent microscopy studies with rabbit polyclonal and mouse monoclonal antibodies specific for mite allergens including the major allergen, Der p I. Sections also were probed for allergens with sera from human mite-allergic subjects containing IgE antibodies to mite allergens and with lectins. Antibody binding was mainly to the gut lining and gut contents of the mite, although some specific labeling also was associated with the head region and cuticle. This is the first detailed localization of mite allergens in situ. The morphology of the mite was investigated using plastic embedded thin sections and was found to be similar to that previously described for D. farinae.     

Successful management of mite-allergic asthma with modified extracts of Dermatophagoides pteronyssinus and Dermatophagoides farinae in a double-blind, placebo-controlled study

BACKGROUND: Mite sensitivity is highly prevalent in tropical and subtropical regions, such as the Canary Islands. OBJECTIVES: To evaluate the clinical efficacy and safety of a depigmented polymerized allergen vaccine containing a 50% mixture of Dermatophagoides pteronyssinus and Dermatophagoides farinae. METHODS: Sixty-four patients participated in the study. It was prospective, double-blind, and placebo-controlled, with random allocation of patients to receive active treatment or placebo. The active group received a mixture of modified allergen extracts containing 50% D pteronyssinus and 50% D farinae; the control group received placebo. All individuals were diagnosed with mild/moderate asthma and rhinoconjunctivitis caused by sensitization to D pteronyssinus and D farinae. Bronchial provocation test (BPT) was considered the main outcome to document clinical efficacy. RESULTS: Fifty-four patients completed the study. The active group experienced a significant improvement in BPT (P < .001), whereas the placebo group did not (P = .648). At the end of the study, 20 patients in the active versus 9 in the placebo group (P = .013; odds ratio, 5.71 [1.76, 18.51]) needed more than twice the amount of allergen to obtain a positive BPT. The median improvement in the active group over placebo was 53.76% in total symptom and 58.09% in medication scores. CONCLUSION: Immunotherapy with a mixture of modified allergen extracts of D pteronyssinus and D farinae is safe and efficacious to treat mite-allergic asthma. CLINICAL IMPLICATIONS: This immunotherapy modifies the natural course of the illness because it improves all clinical outcomes measured and prevents the worsening of specific bronchial hyperreactivity.     

The group III allergen from the house dust mite Dermatophagoides pteronyssinus is a trypsin-like enzyme.

Faecally enriched extracts of Dermatophagoides pteronyssinus were shown to contain a trypsin-like enzyme which was allergenic. Chromatofocusing studies revealed the presence of nine major isoforms in D. pteronyssinus, with pI in the range 4 to greater than 8, but only two (range 4-5) in D. farinae. Trypsin isolated from D. pteronyssinus by benzamidine-Sepharose 6B affinity chromatography and gelfiltration was found to be a 31-kDa protein which was enzymatically similar to both invertebrate and vertebrate trypsins. The N-terminal sequence obtained (IVGGEXALAGEXPYQISL) was identical to that reported for the mite allergen Der p III and showed homology with crayfish trypsin and Der f III from D. farinae. Mite trypsin underwent autolysis and the N-terminal sequences of two fragments were found to be ALAGEXPYQI and NNQVXGI respectively. Both showed homology with crayfish trypsin, and the former sequence was identical to residues 7-18 of the native enzyme and Der p III. All isoforms of mite trypsin were showed to be allergenic by radioallergosorbent assay and further studies indicated that the trypsin degradation products were also allergenic. The enzyme was compared with other mite allergens and the rank order of allergenic potency was shown to be: whole mite extract greater than Der p I greater than trypsin. However, all sera from a panel of mite allergic individuals showed IgE reactivity to trypsin, comparable to that seen using whole mite extract and Der p I. These data indicate that mite trypsin is a major allergen corresponding to the previously described allergen, Der p III.     

Skin test and crossreactivity studies with Euroglyphus maynei and Dermatophagoides pteronyssinus

Background The prevalence of sensitization to Euroglyphus maynei (E. maynei) in the United States has not been reported previously. Objectives To determine: (l) the prevalence of skin-test reactivity in allergic subjects to E. maynei compared to D. pteronyssinus, D. farinae, and B. tropicalis and (2) the allergenic crossreactivity between D. pteronyssinus and E. maynei. Methods Skin testing with extracts of B. tropicalis and E. maynei (1:50 w/v) and standardized D. pteronyssinus and D. farinae extracts (1:50 w/v; 10000 AU/mL) provided data on 250 subjects (87 males and 163 females) aged 9–77 years (mean age, 39.8 years) with possible allergic respiratory diseases. RAST inhibition assays were used to study crossreactivity between D. pteronyssinus and E. maynei. Results One hundred (40%) of 250 subjects had insignificant or no allergic diseases. Of the 150 allergic subjects (53 males, 97 females), 101 (67.3%) had a positive test (a percutaneous test with a weal diameter ≥ 3 mm larger than the saline control) to at least one mite species; 60.7%, 60.0%, 28.7%, and 52.0% reacted to D. farinae, D. pteronyssinus, B. tropicalis, and E. maynei, respectively; 40(26.7%) reacted to the four mite species. Positive tests to D. farinae, D. pteronyssinus, B. tropicalis, or E. maynei alone occurred in six (4.0%), four (2.7%), two (1.3%), and 0%, respectively. D. pteronyssinus and E. maynei showed moderately high crossreactivity in RAST inhibition assays. Conclusion There is a high rate of skin-test reactivity to E. maynei in Florida. Moderately high crossreactivity exists between E. maynei and D. pteronyssinus.     

Identification of neryl formate as the airborne aggregation pheromone for the American house dust mite and the European house dust mite (Acari: Epidermoptidae)

The American house dust mite, Dermatophagoidesfarinae Hughes, and European house dust mite, Dermatophagoides pteronyssinus Trouessart, are major pests of medical importance throughout the developed world, causing atopic diseases such as asthma, rhinitis, and atopic dermatitis. Previous studies in our laboratory have shown that the behavioral responses of house dust mites toward volatiles from food sources could be assessed using a Y-tube olfactometer assay. The current study used this Y-tube assay to investigate house dust mite pheromones. A hexane extract of D.farinae, along with fractions of the extract prepared by microscale liquid chromatography over Florisil, were tested for behavioral activity. One of the chromatographic fractions was shown to be significantly attractive (P < 0.05) for D. farinae, compared with a solvent control. Coupled gas chromatography-mass spectrometry analysis of this behaviorally active fraction indicated that neryl or geranyl formate was the major component. Peak enhancement by gas chromatography, using authentic samples of the neryl and geranyl isomers prepared in high purity by chemical synthesis, confirmed the identity of the major peak as neryl formate. In Y-tube assays, male and female D. farinae and D. pteronyssinus both were significantly attracted to synthetic neryl formate at doses of 100 and 10 ng, respectively (P < 0.05). No significant differences were found for D. farinae and D. pteronyssinus when synthetic neryl formate and house dust mite extracts containing natural neryl formate were tested at the same level. Dynamic headspace collection of D. farinae and D. pteronyssinus colonies showed that neryl formate was released as a volatile organic compound by both species. Our study shows that neryl formate is an aggregation pheromone for D. farinae and D. pteronyssinus, and has the potential to be used as part of a novel lure-and-kill system for house dust mite control.     

Biology, ecology, and prevalence of dust mites

The house dust mites D. farinae, D. pteronyssinus, and E. maynei are sources of multiple potent allergens in the indoor environment. They are common inhabitants in homes worldwide. Many biologically significant studies have revealed how well adapted these mites are to the microhabitats in homes. Ambient RH is a key factor in determining where these mites are found. Many aspects of the biology of house dust mites are not understood. A greater understanding of the biology of dust mites may reveal new strategies for controlling dust mites and their allergens in homes.     

The chitinase allergens Der p 15 and Der p 18 from Dermatophagoides pteronyssinus

BACKGROUND: House dust mites Dermatophagoides pteronyssinus and Dermatophagoides farinae cause allergic disease in humans as well as in dogs. In geographical regions where the two mite species coexist, they both elicit specific immunoglobulin (Ig E) responses in humans whereas dogs preferentially react to D. farinae extracts. In dogs the main IgE binding is directed to the D. farinae chitinase allergens Der f 15 and Der f 18 and not to the groups 1 and 2 allergens as found for humans. Although the IgE response of humans to Der f 18 has been investigated there is no report on Der f 15-specific IgE in humans. OBJECTIVE: This study aimed to characterize the chitinase allergens Der p 15 and Der p 18 of D. pteronyssinus and to find out whether they are important allergens for humans. METHODS: cDNA was cloned by a polymerase chain reaction strategy from D. pteronyssinus libraries using primers based on conserved chitinase sequences. IgE binding to the recombinant polypeptides was measured by immunosorbent assay. Mice were immunized with the polypeptides and cross-reactivity examined. RESULTS: Two variants of Der p 15 were isolated, encoding mature proteins of 58.8 and 61.4 kDa. The amino acid sequences had 90% identity to Der f 15. The cDNA for Der p 18 encoded a mature protein of 49.2 kDa with 88% sequence identity to Der f 18. Der p 15-specific IgE was detected in 70% and Der p 18-specific IgE in 63% of a panel of 27 human allergic sera. CONCLUSIONS: The D. pteronyssinus chitinases Der p 15 and Der p 18 show a high frequency of binding to IgE in allergic human sera. They are therefore potentially important allergens for humans as well as dogs.