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.     

<Emphasis Type="Italic">Dermatophagoides pteronyssinus</Emphasis> and <Emphasis Type="Italic">Tyrophagus putrescentiae</Emphasis> Allergy in Allergic Rhinitis Caused by Cross-reactivity Not Dual-Sensitization

Tyrophagus putrescentiae and Dermatophagoides pteronyssinus are causative factors for the development of airway hypersensitivity. The main objective in this study was to identify the cross-reactive allergens between T. putrescentiae and D. pteronyssinus and investigate their sensitization in patients with allergic rhinitis. The prevalence of sensitization to mites was determined by skin prick tests and histamine release assays. Both immunoblot and ELISA inhibition assays were performed by using the recombinant allergens of T. putrescentiae and D. pteronyssinus. The cross-reactive allergens were identified by using IgE-binding inhibition analysis. The correlations of specific IgE between T. putrescentiae and D. pteronyssinus to group 2 and group 3 mite allergens were compared. A total of 117 allergic rhinitis patients, aged between 16 and 40 years old were recruited to be included in this study. The results showed that 70% (82/117) of allergic rhinitis subjects had skin test positive reactions to D. pteronyssinus or T. putrescentiae. Among these mite-sensitive subjects, there were 81 subjects (81/82) sensitive to D. pteronyssinus and 34 subjects (34/82) sensitive to T. putrescentiae. Among the T. putrescentiae hypersensitive subjects, 97% (33/34) were also sensitized to D. pteronyssinus. In the IgE-binding inhibition analysis, 59% (13/22) subjects had IgE-binding activity of T. putrescentiae that was completely absorbed by D. pteronyssinus, especially components with MW at 16 kDa. In ELISA inhibition testing, 69% of IgE-binding was inhibited by rTyr p 2, and 45% inhibited by rTyr p 3. The titers of IgE antibodies to rTyr p 2 and rDer p 2 were well correlated, but not rTyr p 3 and rDer p 3. In conclusion, most T. putrescentiae sensitized subjects were also sensitized to D. pteronyssinus in young adult allergic rhinitis patients. The complete absorption of IgE binding activity by D. pteronyssinus indicates that T. putrescentiae hypersensitivity might be due to the cross-reactivity, not dual-sensitization of D. pteronyssinus and T. putrescentiae. The IgE-binding titers of group 2 allergens were well correlated and the binding activity of Tyr p 2 could be absorbed by Der p 2, suggesting that group 2 allergens are the major cross-reactive allergen of D. pteronyssinus and T. putrescentiae.     

Mite fauna, Der p I, Der f I and Blomia tropicalis allergen levels in a tropical environment

Fifty dust samples were collected from the mattresses and bedroom floors of 25 subjects with allergic asthma in Cartagena, Colombia, in order to identify house dust mites and quantitate Der p I, Derf I and Blomia tropicalis allergens. The geometric mean of the total mite density per gram of dust was 418 (range, 40–2280). Twenty-two samples (44%) had more than 500 mites and four, less than 100. B. tropicalis and Dermatopha-goides pteronyssinus were found in 96% and 90% of the samples, accounting for 40.1% and 35.7% of the total mites, respectively. Cheyletus malaccensis, Chortoglyphus arcuatus, Pyroglyphus africanus, Orihatids, Grallacheles bakeri. Tarsonemus spp., Suidasia spp., Dermatophagoides farinae and unidentified mites accounted for the rest. The geometric mean of the total mites/gram of dust in mattresses (563.9) was significantly higher than in floor dust (309. 1), P < 0.01. Allergen concentrations and mite numbers were analysed by Spearman rank correlations: B. tropicalis mites vs B. tropicalis allergen, r= 0.54, P<0.001; D. pteronyssinus mites vs Der p I, r= 0.52, P< 0.001. A negative correlation was obtained between B. tropicalis mites and Der p I. Allergens derived from B. tropicalis and other domestic mite species may play an important role in sensitization and allergic symptoms in Cartagena, Colombia.     

Antigenic interrelationships among mite allergens (Blomia andDermatophagoides spp)

Conclusions Asthma can occur as a result of allergy to both house dust mites and to storage mites. Many people worldwide are exposed to more than one mite species in the domestic environment. The most common domestic mites areD. pteronyssinus, D. farinae, E. maynei, andB. tropicalis; other storage mites are found in homes much less frequently, even in tropical climates. Because of the ready availability of allergen extracts for skin testing and immunotherapy, patients with respiratory symptoms are generally evaluated for sensitization toD. pteronyssinus andD. farinae only. The evidence reviewed here suggests, however, that, although there are crossreactive allergens between many mite species, most species have specific allergens that can be an important cause of IgE responses. Therefore, the role ofB. tropicalis andE. maynei in the etiology of asthma merits further investigation. Identification of species-specific and crossreactive allergens and production of recombinant allergens would be useful tools in allergy practice. By skin-testing patients, physicians would then be able to evaluate whether patients recognize crossreactive allergens or species-specific allergens and whether or not there is a need for immunotherapy to more than one mite species.     

Impact of specific sensitization on asthma and rhinitis in young Brazilian and Chilean adults

Background The pattern of associations and the attributable fractions (AF) of atopic conditions due to specific sensitizations vary between countries. Objective To assess the level of associations and AF between sensitization to five allergens and atopic conditions in two settings. Methods We studied 2063 Brazilians and 1231 Chileans of both sexes using representative samples selected at birth in the 1970s. Information on asthma and rhinitis was based on the European Community Respiratory Health Survey questionnaire. We assessed bronchial hyperresponsiveness (BHR) to methacholine and sensitization to Dermatophagoides pteronyssinus, cat, dog, grass blend and Alternaria alternata. Results The prevalence of sensitization to one or more allergens was 50% in Brazilians and 22% in Chileans. The level of associations varied according to the outcome used. Strong associations between sensitization and asthma, defined as wheeze or awakening with breathlessness at night and positive BHR, were found for each of the five allergens in Chileans [varying from odds ratio (OR) 3.24, 95% confidence interval (CI) 1.47, 7.15 for D. pteronyssinus to 8.44, 95% CI 3.82, 18.66 for cat], whereas the level of associations was restricted to D. pteronyssinus, cat and dog in Brazilians and was somewhat weaker (highest OR 3.90, 95% CI 2.80–5.44). The AF of sensitization on asthma was 54% in Brazil and 44% in Chile. D. pteronyssinus and cat made an independent contribution to asthma in the two samples. The patterns of associations between sensitization and rhino‐conjunctivitis were similar to those for asthma. Conclusion The associations between sensitization, and asthma and rhinitis were high in Chile and moderately high in Brazil, but the AF were higher in Brazil, reflecting a higher prevalence of sensitization. In Brazil, dust mite had the greatest impact on atopic conditions while in Chile several allergens had an impact. Sensitization is as serious a problem in Chile and Brazil as in developed countries.     

The incidence and causative factors of atopic asthma and rhinitis in an Orkney farming community

Fifty farming families on the mainland (the largest island) of Orkney were surveyed to assess the amount of allergic respiratory disease and the principal causative factor. This account deals with only type I allergy and demonstrates a prevalence of asthma and rhinitis of 17.3% and of extrinsic asthma and rhinitis, in which definite allergic causes can be identified, of 12.7%. In addition it is shown that over one-fifth of the farming community are ‘atopic’ in that they demonstrate positive prick tests to one or more allergens. Less than 50% of those with allergic respiratory disease have attended the doctor with their complaint, a fact which calls in question the validity of epidemiological studies of allergic disease based on hospital and clinic attendances. Sex distribution confirms the finding that males suffer from asthma more frequently than females, however more females than males give positive skin tests without exhibiting symptoms of allergy. Pollens, animal danders and fungi all have a part to play in the aetiology of asthma and rhinitis among Orkney farmers, although the incidence of grass pollenosis is well below average. The two commonest allergens are hay dust and Dermatophagoides pteronyssinus which are found frequently to affect the same subject.     

Exposure and sensitization to dust mite allergens among asthmatic children in Sao Paulo, Brazil

A group of 20 mite allergic asthmatic children aged 6-12 years old. living in Sao Paulo, Brazil, was studied regarding their degree of sensitization to house dust mites and exposure to mite allergens in their homes. In 18 out of 20 houses at least one dust sample was obtained which contained > 10 μg Der p I/g of dust. The highest levels of Dermatophagoides pteronyssinm allergens, Der p I and Group II, were measured in bedding samples (geometric mean 38.4 and 36.6 μg/g, respectively), followed by bedroom floor, TV room and kitchen. Mite allergen levels in Brazilian houses were as high as those reported to be associated with sensitization and acute attacks of asthma in other parts of the world. In keeping with previous reports that D. farinae is rarely found in Brazil, Der fl was undetectable or found in very low levels (<0.5 μg/g). Levels of cat allergen Pel d I of > 8 μg/g of dust were obtained only in 2 houses only. Cockroach allergen Bia g I was detected in five out of 20 houses. Levels of IgE antibodies to D. pteronyssinus were > 200 RAST U/ml in 19 out of 20 children (geometric mean 1588 RAST U/ml). IgE antibodies to cat, cockroach, A. fumigatus, ragweed and rye grass pollens were undetectable or <80 RAST U/ml. IgE antibodies to the mite Blomia tropicalix were also measured, and levels >200 RAST U/ml were observed in 13 out of 20 sera. Immunoabsorption studies demonstrated that the bulk of the IgE- antibody to B. tropicafis (64%) was to species-specific allergens and that 36% were cross-reactive with D. pteronyssinus. The implication of our results is that management of children with asthma in São Paulo should include skin testing for allergy to both Dermatophagoides and B. tropicalis as well as recommendations about environmental control of house dust mite exposure.     

Cloning,bioinformatics analysis,and expression of the dust mite allergen Der f 5 of Dermatophagoides farinae

Crude extracts of house dust mites are used clinically for diagnosis and immunotherapy of allergic diseases, including bronchial asthma, perennial rhinitis, and atopic dermatitis. However, crude extracts are complexes with non-allergenic antigens and lack effective concentrations of important allergens, resulting in several side effects. Dermatophagoides farinae (Hughes; Acari: Pyroglyphidae) is one of the predominant sources of dust mite allergens, which has more than 30 groups of allergen. The cDNA coding for the group 5 allergen of D. farinae from China was cloned, sequenced and expressed. According to alignment using the VECTOR NTI 9.0 software, there were eight mismatched nucleotides in five cDNA clones resulting in seven incompatible amino acid residues, suggesting that the Der f 5 allergen might have sequence polymorphism. Bioinformatics analysis revealed that the matured Der f 5 allergen has a molecular mass of 13604.03 Da, a theoretical pI of 5.43 and is probably hydrophobic and cytoplasmic. Similarities in amino acid sequences between Der f 5 and allergens of other domestic mite species, viz. Der p 5, Blo t 5, Sui m 5, and Lep d 5, were 79, 48, 53, and 37%, respectively. Phylogenetic analysis indicated that Der f 5 and Der p 5 clustered together. Blo t 5 and Ale o 5 also clustered together, although Blomia tropicalis and Aleuroglyphus ovatus belong to different mite families, viz. Echimyopodidae and Acaridae, respectively.     

Mites and house dust allergy

279 patients, most of whom had perennial asthma or perennial rhinitis, were tested intradermally with extracts of Dermatophagoides pteronyssinus and D. farinae in order to ascertain the incidence of positive skin reactions. The great majority of house dust sensitive patients had positive skin reactions to both mite extracts. However, the concordance between house dust and mite extract positive skin reactions, though statistically significant, did not reach the extent found in other countries. Of the three extracts employed, D. pteronyssinus appeared to contain the most potent allergen while its culture medium extract yielded a low percentage of positive skin reactions. These results suggest that, in italy also, mites seem to represent the most important allergenic source of house dust.     

Allergy to cockroaches in patients with asthma and rhinitis in an urban area (Madrid)

Previous studies have established that cockroach allergens are important sensitizing agents in the induction of rhinitis and asthma principally in urban areas. This study was undertaken to assess skin test reactivity and specific IgE antibody reactivity to extracts of Periplaneta americana (Pa.), Blattella germanica (B.g.), B. orientalis (B.o.), and a fecal extract of B. germanica (FEB.g.) in a group of patients with rhinitis and asthma living in an urban area in Europe. We examined clinical characteristics and aeroallergen sensitivities of 171 consecutive Madrid urban patients with rhinitis and asthma who met the criteria for the study. A comprehensive clinical evaluation was followed by skin prick test with common allergens and saline extracts of P.a., B.g., B.o., and FEB.g. and measurement of serum specific IgE antibody to cockroach extracts. The age of patients ranged from 7 to 68 years (mean 20.4 ± 16). A total of 153 (90.5%) subjects were atopic and 19 (10%) were considered nonallergic. Pollen sensitivity (66.5%) was most prevalent, distantly followed by sensitivity to cockroach (25.7%), mite (20%), cat (15.5%), Alternaria alternata (14.5%), dog (14%), and food (2%). Skin test reactivity to cockroach extracts was 37 (21.6%) to B.o., 20 (11.6%) to Pa., 19 (11.1%) to B.g. and five (2.9%) to FEB.g. Twenty-one of these patients had rhinitis, 19 rhinitis and asthma, and one only asthma; 26 had perennial symptoms, while 16 had seasonal (spring) symptoms; three (1.7%) patients had only positive prick test to cockroach; all had perennial rhinitis and/or asthma. Eighteen (10.5%) patients had specific serum IgE (RAST 1 or 2) to B.o., 13 (7.6%) to Pa., and six (3.5%) to B.g. Eighty (46.7%) patients had visual evidence of cockroach infestation in their home, mostly B.o.; 31 had positive prick test to cockroach (P< 0.0003). The results indicate that sensitivity to outdoor allergens (pollen) is more prevalent than to indoor allergens. Cockroach sensitization is the most important indoor allergen in our area, and B.o. accounts for most cockroach sensitization.     

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.     

Lack of evidence of a significant association between HLA-DR, DQ and DP genotypes and atopy in families with HDM allergy

Background HLA class II genetic polymorphism has been variably implicated in susceptibility to specific immune responsiveness to house dust mite (HDM) allergens, and may also influence the development of atopy. Objective In order to assess accurately the influence of HLA alleles in the atopic immune response, we typed 22 families selected from 131 previously obtained randomly selected families (i.e. without regard to atopy or asthma), chosen on the basis of two or more members having skin prick reactivity to HDM. Methods Each individual was fully typed for HLA-DRB1, DQA1, DQB1 and DPB1 class II alleles using a combination of sequence-specific oligonucleotide probes (SSOP) and sequence-specific primer (SSP) polymerase chain reaction (PCR) typing and direct sequencing. Results Using appropriate statistical tests, no significant allelic associations were found between any DRBl, DQB1 or DPBl alleles and atopy or skin prick reactivity to Dermataphagoides pteronyssinus (Der p) or D. farinae (Der f). However, positive associations were found between DQA 1*0301 and skin prick reactivity to Der f (P= 0.009) and atopy (P= 0.027). Sib-pair analysis revealed no significant sharing of alleles between affected sib pairs for any of the phenotypes studied. Conclusion These results fail to confirm a previously reported association between the DRB1*04 and 07 haplotypes and atopy, and suggest that HLA class II restriction does not play a major role in the development of the IgE response to domestic house dust mite allergens in the British population.     

The prevalence of immediate positive skin tests to Dermatophagoides pteronyssinus and grass pollen in schoolchildren

The prevalence of immediate positive reactions to prick testing with house dust mite (Dermatophagoides pteronyssinus) and grass pollen allergens was determined in a random sample of 303 children aged between 8 and 14 years from two Southampton schools. One hundred and two (33.7%) showed positive reactions, fifty to both D. pteronyssinus and grass pollen, thirty to D. pteronyssinus only and twenty-two to pollen only. Allergic symptoms were present in fifty-one of the 102 children with positive skin tests; amongst thirty children with D. pteronyssinus skin sensitivity by itself, only six had symptoms suggestive of allergic disorder. Significantly more children with positive than with negative tests were reported by their parents to have suffered from recurrent bronchitis during early childhood.     

Mite allergen content in mattress dust of Dermatophagoides-allergic asthmatics/rhinitics and matched controls

It has been suggested that the mites Dermatophagoides pteronyssinus and D.farinae are important indoor environmental factors facilitating both the sensitization of atopic subjects and asthmatic attacks of house dust-sensitive patients. Contradictory results have been reported about the current exposure to mites or their allergens among patients and control groups of atopic or non-atopic subjects. In order to determine whether there is a difference in mite exposure levels between D. pteronyssinus-sensitized asthmatics and/or rhinitis and control subjects we considered a case-control study of 70 patients with asthma and/or rhinitis and positive skin test reactions to D. pteronyssinus and twice as many control subjects who were matched as to age and sex. The first control subject for each patient was an immediate neighbour of the patient and the second was a patient arbitrarily chosen among hospitalized patients. Mite allergen exposure was measured in mattress dust collected under standardized conditions, by measuring Der p I +Derf I content and by performing a semiquantitative guanine determination (Acarex-test^R). The content of Der p I and Der f I was very high both in the homes of patients and those of healthy individuals: 69% of the total samples contained more than 10 μg Der p I + Der f I/g of dust. There was no significant difference between cases and controls with respect to Der p I, Der f I, Der p I + Der f I content and Acarex^R class distributions. The calculated odds-ratios associated with the Acarex test^R and the mite allergens did not differ significantly from the level 1.0. Our findings show that in a Rhine valley city such as Strasbourg with a high mite allergen load there is no difference in mite exposure between D. pteronyssinus-sensitized patients and controls who can be considered not to differ from the general population with respect to atopy.     

Comparative degree and type of sensitization to common indoor and outdoor allergens in subjects with allergic rhinitis and/or asthma

Background and objectives The determinants of variability in the clinical expression of atopy are still to be documented. The goals of this study were to determine, in subjects with a clinical diagnosis of symptomatic asthma or rhinitis, what is the possible contribution of different types of indoor and outdoor allergens to the development of their disease, by looking at the prevalence and degree of sensitization to these allergens according to age and gender. Subjects and methods We analysed allergy skin prick tests to common airborne indoor and outdoor allergens in 3371 consecutive patients, grouped according to diagnosis of allergic asthma, rhinitis, or both. For each of these three groups, we calculated the prevalence of sensitization to indoor/outdoor allergens, the atopic index (Al), the number of positive responses to allergy skin prick test and the mean wheal diameter (MWD) of these responses. Results The prevalence of atopy and the values of Al and MWD peaked in subjects aged 16 to 25 years, declining afterwards; in subjects ± 18 years old, atopic indices were slightly higher in men than in women. In atopic subjects, the prevalence of sensitization was, in decreasing order: housedust (84.2%), cat hair-epithelium (76.5%), dog hair-dander (63.0%), house dust mite (54.2%), grasses (51.9%), trees (47.2%) and ragweed pollens (44.9%) and finally, moulds (25.4%). Among subjects sensitized only to outdoor allergens (n= 195), 73.8% had a rhinitis, 11.8% had asthma and 14.4% had both diagnoses; for those sensitized only to indoor allergens (n= 710), these values were respeetively 48.6, 24.5 and 26.9%, and for those sensitized to both indoor and outdoor allergens (n= 1793), the comparable values were 55.5, 14.6 and 29.9%. Conclusion These data show that in our population of subjects with respiratory allergic symptoms, indoor allergen sensitization is strongly associated with asthma, while exclusive sensitization to pollens is associated primarily with rhinitis. Sensitization was more prevalent for indoor allergens than for outdoor allergens in all groups determined according to diagnosis or age. Indices of atopy were higher in men in the group ± 18 years old. Prevalence and degree of sensitization were shown to peak in young adults, regardless of the allergen, and to diminish with age. This study stresses the role of indoor allergens in the development of asthma and shows the variability of allergic manifestations according to the type of sensitization.     

Reproducibility of prick skin tests to five common allergens

Thirty-five asthmatic patients had prick skin tests to the common allergens Candida aibicans, Aspergillus fumigatus, grass pollen, horse dander and Dermatophagoides pteronyssinus performed on a regular basis from Autumn 1973 to Autumn 1975. Specific IgE to the same allergens (except C. albicans) was determined at the time of skin testing for the first five seasons. It was found that the position on the volar aspect of the forearm on which the test was performed did not affect the reaction. There was a significant variation in the percentage of patients with positive skin tests to A. fumigatus, grass pollen and horse dander with the latter showing a significant decrease with time. There was evidence of variation in weal size for all but C. albicans, and for grass pollen, horse dander and D. pteronyssinus there were reductions in weal size with time. Significant differences were found for results of Log specific IgE for grass pollen and D. pteronyssinus over the study, but there was no trend. A good correlation between weal size and Log specific IgE for grass pollens and D. pteronyssinus was observed. For the four allergens, the coefficient of concordance between IgE levels within patients for the five seasons was highly significant.     

Passive cutaneous anaphylaxis (PCA) and specific IgE in cystic fibrosis and their heterozygotes

The serum from 75% of the patients with cystic fibrosis (C.F.) who had a positive prick test in their skin to at least one or more antigens, together with elevated concentrations of total serum IgE, also gave strong immediate PCA reactions in the baboon skin to Aspergillus fumigatus, bovine serum albumin and egg albumin. Of the C.F. patients, 37% also had elevated serum specific IgE to A. fumigatus whereas only 8–10% had either raised specific IgE or PCA reaction to Dermatophagoides pteronyssinus. Abolition of the PCA activity by incubating the C.F. sera or sputum at 56°C suggested that the reaginic antibody was IgE rather than IgG4. PCA reactions to a number of allergens could be detected in both the C.F. sputum and saliva. Several of the C.F. heterozygotes had a strongly positive history of allergy and a significant number of these heterozygotes had an elevated serum total IgE as well as positive PCA to Timothy grass pollen or to D. pteronyssinus similar to the patients with asthma or hay fever. Three C.F. patients who died gave strong prick test reactions to several allergens and their sera also had raised serum IgE and positive PCA to at least three different allergens, suggesting that immediate hypersensitivity is of some significance in patients with C.F.     

Skin test reactivity to natural and recombinant Blomia and Dermatophagoides spp. allergens among mite allergic patients in the UK

BACKGROUND: Many asthmatics in tropical and subtropical areas have positive skin prick tests to both Dermatophagoides spp. and to the mite Blomia tropicalis. This may be due to recognition by IgE of cross-reactive allergens between the different mite species or because of sensitization to species-specific allergens. A 14-kDa Blomia tropicalis allergen, Blo t 5, has been cloned and shows 40% sequence homology with Der p 5. The aim of this study was to investigate reactivity to B. tropicalis in patients known to be sensitized to D. pteronyssinus and to assess allergenic activity and cross-reactivity of recombinant (r) Group 5 allergens amongst these patients, who live in the UK and who are not exposed to B. tropicalis in their homes. METHODS: Patients (n = 19) with asthma and/or rhinitis were selected based on clinical history and a positive skin prick test to D. pteronyssinus extract and were compared with non-allergic skin test negative controls (n = 10). IgE antibody responses to Blomia tropicalis, Dermatophagoides pteronyssinus, rDer p 5 and rBlo t 5 were compared by quantitative intradermal skin testing using serial 10-fold dilutions of each allergen. End point titre was the highest dilution giving an 8 x 8 mm wheal at 15 min. IgE antibodies to Blomia tropicalis, Dermatophagoides pteronyssinus, rDer p 5 and rBlo t 5 were measured using RAST, CAP and RIA, respectively. RESULTS: All 19 patients had positive skin tests to D. pteronyssinus at concentrations of 0.001 to 1 AU/ml and 10 were skin test positive to rDer p 5 at concentrations of 10-4 to 5 micro g/ml. Positive intradermal tests to Blomia tropicalis were seen in 12/19 patients at concentrations of 0.002 to 2 micro g/ml. However none of the patients had positive skin tests to rBlo t 5. Non-allergic controls were all skin test negative at the highest concentration of each allergen tested. All subjects had quantifiable specific IgE to D. pteronyssinus, but only two had IgE to B. tropicalis. IgE to Der p 5 was found in six patients, but no patients had IgE to Blo t 5. CONCLUSIONS: This study of patients naturally exposed to D. pteronyssinus but not to Blomia tropicalis, provides evidence for IgE mediated cross-reactivity between allergens produced by both mite species. The results suggest that the Group 5 allergens of D. pteronyssinus and B. tropicalis are species-specific.     

The epidemiological and allergic features of asthma in the New Guinea Highlands

Asthma in the New Guinea Highlands is of interest because of its reported rarity. In the Eastern Highlands, seventy-one cases of asthma were investigated over a 12 month period. In addition, a whole village community of 2000 people was examined for wheezing illness. In children and adolescents asthma was extremely uncommon with no case being identified in the community study and the youngest hospital case being 10 years old. The prevalence of active asthma in adults was estimated to be 0.2–0.3%. Compared with European countries, the age at onset was much later with 58% starling after the age of 30 years. The sex ratio was almost equal. Cutaneous sensitivity to allergens was assessed using the prick lest. In asthmatics, reactions to D. pteronyssinus were positive in all cases. Multiple sensitivities were common and did not diminish with increasing age at onset. In 335 unselected controls of all ages, 19% were positive to allergens, 14% of them to D. pteronyssinus. D. pteronyssinus was identified in ail house dust samples from both village and urban dwellings. Asthma occurred in both traditional and European-influenced environments, but the importance of social change remains uncertain.     

Sensitization to local dust-mite fauna in Singapore

BACKGROUND: Recent studies showed the presence of a unique dust-mite fauna in the indoor environment of Singapore. Immediate hypersensitivity to these dust mites, along with other known indoor allergens, may play a role in the pathogenesis of allergic respiratory diseases. This study evaluated the sensitization rates of the local atopic population to these allergens. METHODS: The skin prick test was performed on a total of 391 individuals (289 patients with asthma and/or allergic rhinitis and 102 healthy controls) using extracts of six species of local dust mites (Austroglycyphagus malaysiensis, Blomia tropicalis, Dermatophagoides pteronyssinus, D. farinae, Sturnophagoides brasiliensis, and Tyrophagus putrescentiae) and 10 other common indoor allergens. Total serum IgE and specific IgE to these dust mites were also quantified with the fluorescence allergosorbent test (FAST). RESULTS: The sensitization rates among patients with asthma and/or allergic rhinitis to dust mites and other inhalant allergens tested (via skin prick tests) were as follow: B. tropicalis (96.2%), D. pteronyssinus (93.4%), D. farinae (92.3%), A. malaysiensis (78.2%), S. brasiliensis (71.6%), T. putrescentiae (71.3%), canary feathers (69.9%), Periplaneta americana (cockroach) (59.5%), Blattella germanica (cockroach) (56.4%), mosquito (Aedes sp.) (46.4%), dog epithelia (mixed breed) (34.3%), kapok seed (31.8%), cat hair (29.1%), Aspergillus fumigatus (20.8%), Penicillium notatum (18.0%), and Candida (Monilia) albicans (9.3%). All patients were observed to react to at least three of the six dust-mite extracts, with 254/289 (87.9%) reacting to at least five or to all six. Skin prick responses to the dust mites were found to correlate with the corresponding specific IgE levels quantified by FAST (P<0.001). In addition, specific IgE levels to D. pteronyssinus and D. farinae were highly correlated (Spearman's rank coefficient = 0.76, P<0.001), as were those to B. tropicalis and A. malaysiensis (r = 0.60, P<0.001). CONCLUSIONS: Asthma and/or allergic rhinitis patients were highly sensitized to the local dust-mite fauna. Thus, these dust mites should be considered important allergenic sources of this region.