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Notes: 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 × 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 µg/ml. Positive intradermal tests to Blomia tropicalis were seen in 12/19 patients at concentrations of 0.002 to 2 µg/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.

Notes: 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.

Notes: Asp f I is a major allergen produced by the mycelia of Aspergillus fumigatus. It is not present in spores and can be used as a specific marker for the detection of germination of this fungus. We investigated the domestic and outdoor concentration of Asp f I in Poole, U.K. and Charlottesville, VA, U.S.A. Asp f I was undetectable in 95% (281/296) of house dust extracts and present at low levels (〈 0.17 μg/g of sieved dust, mean 0.038 μg/g) in the remainder. In contrast, Asp f I could be detected in 65% (15/23) of cultures of house dust, suggesting the presence of viable, but ungerminated, A. fumigatus in the majority of homes. Asp f I was detectable in 80% (28/35) of extracts of leaves and compost, but present in these outdoor samples at low levels (〈0.11 μg/g, mean 0.27 μg/g). Air sampling for Asp f I was undertaken before and after vigorous disturbances at indoor (n= 5) and outdoor (n= 6) sites. Airborne Asp f I was not detected in domestic samples or in undisturbed outdoor samples. Following disturbance it could be measured in outdoor samples (range 7.6–29 ng/m3). The results suggest that while exposure to A. fumigatus is common, exposure to Asp f I and germinating A. fumigatus is uncommon. It is probable that those individuals who develop antibody responses to Asp f I have been exposed to A. fumigatus which has germinated in their respiratory tract.

Notes: Background Sensitization to indoor allergens, particularly to dust mites, is a strong risk factor for asthma in children and adults. Assessment of sensitization is carried out using in vivo and in vitro tests to detect specific IgE antibodies.Objective To investigate IgE antibody responses to mites in patients with asthma, wheezing and/or rhinitis, using chimeric ELISA to measure specific IgE antibodies to mite allergens Der p 1 and Der p 2.Methods Specific IgE antibodies to Der p 1 and Der p 2 were quantified by chimeric ELISA, and compared with IgE to Dermatophagoides pteronyssinus (Dpt) measured using the CAP system (Pharmacia). A panel of sera from 212 patients with asthma, wheezing and/or rhinitis and 11 controls was analysed.Results There was a significant correlation between IgE to Dpt measured by CAP and IgE to Der p 1 (r = 0.81, P 〈 0.001), Der p 2 (r = 0.79, P 〈 0.001) and combined Der p 1 and Der p 2 (r = 0.86, P 〈 0.001). Seventy per cent of all patients had IgE to Dpt, and of those, 76.5% had IgE to Der p 1, 79.2% had IgE to Der p 2 and 83.1% had IgE to Der p 1 and Der p 2 combined. Considering the cut-off level of 2 IU/mL of IgE to either Der p 1 or Der p 2, the predictive value for a positive IgE to Dpt by CAP was greater than 95%.Conclusions The chimeric ELISA allowed accurate quantification of IgE antibodies to Dpt allergens Der p 1 and Der p 2, and it could be useful for studying immune responses to mites in patients with asthma and/or rhinitis.

Notes: The introduction of molecular cloning techniques has led to advances in allergen identification and sequencing, production of recombinant allergens, identification of B-cell and T-cell epitopes, and tertiary structural analysis of allergen molecules. Over 10 groups of mite allergens have been cloned from Dermatophagoides spp., as well as several homologous allergens from Euroglyphus maynei, Lepidoglyphus destructor, and Blomia tropicalis. The availability of these allergens has made it feasible to consider their use for both diagnostic and therapeutic purposes. Several recombinant Dermatophagoides allergens show comparable reactivity on skin testing and in serologic assays to natural allergens, and cocktails of the recombinant proteins could be used as diagnostic reagents. New technologies have been developed for detection of allergen-specific IgE and for environmental allergen detection using rapid diagnostic tests. Novel approaches to immunotherapy are also being investigated, including T-cell-peptide-based vaccines, allergen variants which lack IgE reactivity, and naked DNA vaccines. The application of allergen biotechnology should lead to improvements in the management of mite-allergic patients with asthma and represents a logical step toward reducing asthma mortality and morbidity.