Sensitization to Dermatophagoides pteronyssinus and Blomia tropicalis extracts and recombinant mite allergens in atopic Thai patients

Mite surveys in Thailand indicated that Dermatophagoides pteronyssinus (Dp) is predominant, but so far there were no data available on Blomia tropicalis (Bt), which is prevalent in the Asia Pacific region. Skin prick testing (SPT) was performed in 40 atopic children, 45 atopic adults and 17 non-atopic volunteers. Skin reactions to Dp were found in 25/40 (62.5%) and 23/45 (51.1%); skin reactions to Bt were found in 15/40 (37.5%) and 18/45 (40%) in atopic children and adults, respectively. SPT to the major sensitizing allergens Der p 1, Der p 2, Der p 5, and Blo t 5 showed positive results in 14/40 (35%), 12/40 (30%), 1/40 (2.5%) and 4/40 (10%) of atopic children, and in 12/45 (26.7%), 13/45 (28.9%), 5/45 (11.1%), 6/45 (13.3%) of atopic adults, respectively. The results indicate that Dp is one of the major sources of allergy, while Bt is a minor one and that Der p 1 and Der p 2 are important mite allergens in Chiang Mai, Thailand.     

Allergenic differences between the domestic mites Blomia tropicalis and Dermatophagoides pteronyssinus

BACKGROUND: House dust mite allergens are the most important indoor allergens associated with asthma and rhinitis in Singapore and the tropics. Recent data to suggest that besides the Dermatophagoides spp., the domestic mite Blomia tropicalis (Bt) is also an important source of allergens in these regions. OBJECTIVE: To evaluate the degree of allergenic cross-reactivity between Bt and D. pteronyssinus (Dp). METHODS: Cross-reactivity between extracts of Bt and Dp was evaluated by fluorescent allergosorbent (FAST) inhibition studies and cross enzyme immunoelectrophoresis. Additionally, the major Dp allergens - Der p 1, Der p 2 and Der p 5, were also compared with the Bt extract by dot blot inhibition. Skin prick and intradermal end-point titration were then carried out to compare the homologous allergens of the mite species, Blo t 5 and Der p 5. RESULTS: FAST inhibition studies showed low to moderate cross-reactivity between the two dust mite extracts (maximum cross-inhibition, 60%). Native allergens studied by cross enzyme immunoelectrophoresis using mite allergic sera also showed similar results but with at least four cross-reactive IgE binding antigens. Dot blot inhibition studies using allergens of Dp, Der p 1, Der p 2, and Der p 5, showed little cross-reactivity between these allergens with components of the crude Bt extracts. Further, evaluation of a recombinant allergen of Bt, Blo t 5, showed low levels of cross-reactivity even with its homologous Dp counterpart, Der p 5. CONCLUSION: These results provide evidence that Bt allergens are distinct and have relatively low to moderate cross-reactivity with Dermatophagoides spp. allergens. Bt allergens should therefore be included in the diagnostic panel for the evaluation of allergic disorders in the tropics, and the development of new diagnostic and therapeutic strategies should include allergens of Bt.     

Correlates of sensitization to Blomia tropicalis and Dermatophagoides pteronyssinus in asthma in Barbados

BACKGROUND: Sensitivity to the mite Blomia tropicalis is related to asthma in tropical climates, but correlates of sensitivity to B. tropicalis and its relationship to Dermatophagoides pteronyssinus sensitivity have not been widely examined in families with asthma. The main objective of this study was to determine prevalence and correlates of sensitivity to these mites in families with asthma and characteristics of persons sensitized to both. METHODS: Antibodies to major antigens (Blo t 5 and Der p 1) of these mites were measured by immunochemiluminescent assay in 481 members of 29 families from Barbados ascertained through two asthmatic siblings. RESULTS: Blo t 5 sensitivity was present in 261 subjects (46%) and was associated with younger age, higher total serum IgE level, and more than a three-fold increased prevalence of asthma (42 vs. 13%). Der p 1 sensitivity was less common (27%) and showed similar associations with age, IgE, and asthma. Of the 261 subjects sensitized to Blo t 5, 116 were also sensitized to Der p 1; they were younger, had higher total and Blo t 5 specific IgE levels, and had more than twice the asthma prevalence as those sensitized to Blo t 5 alone (59 vs. 29%). Der p 1 sensitivity without Blo t 5 sensitivity was uncommon; 90% of those sensitized to Der p 1 were also sensitized to Blo t 5. Geometric mean total IgE levels were lowest in the 207 participants without any mite sensitization (102 U/ml), intermediate in 158 sensitized to either Blo t 5 OR Der p 1 (609 U/ml), and highest in 116 sensitized to both (1,869 U/ml). CONCLUSIONS: Blo t 5 is the predominant sensitizing mite allergen in these Barbadian families with correlates similar to Der p 1. Concomitant sensitization to Der p 1 appears to identify a more reactive subgroup of individuals at a higher risk of asthma.     

Sensitization to Blomia tropicalis and Lepidoglyphus destructor in Dermatophagoides spp-allergic individuals.

Serum was collected from 77 atopic subjects from Cartagena, Colombia, who had a positive skin test (greater than or equal to 3 mm) to either Dermatophagoides farinae (Df) (73) or D. pteronyssinus (Dp) (70). Twenty-nine healthy volunteers with negative allergy histories and negative skin tests were used as control subjects. RAST and RAST-inhibition assays were used to study the prevalence of specific IgE to Blomia tropicalis (Bt), Lepidoglyphus destructor (Ld), and Df. RAST results were considered positive when a serum bound greater than or equal to 1% of the total counts added; 69 atopic subjects (89.6%) were positive to Df, 66 (85.5%) to Bt, and 46 subjects (59.7%) were positive to Ld. RAST results, analyzed by regression analysis, revealed the following correlation coefficients: Df versus Bt, r = 0.59; Df versus Ld, r = 0.44; and Bt versus Ld, r = 0.52. RAST-inhibition assays with a serum pool of 11 individuals highly allergic to all three mites (mean specific IgE to all mites, greater than or equal to 18.2 percent total counts bound) demonstrated considerable cross-reactivity between Bt and Ld and moderate cross-reactivity between Df and Bt and Ld. Bt, Df, and Ld possess unique, as well as common, allergens. Sensitization to Bt and Ld is very common in mite-allergic individuals in Cartagena, Colombia.     

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.     

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.     

Oral tolerance induction to Dermatophagoides pteronyssinus and Blomia tropicalis in sensitized mice: occurrence of natural autoantibodies to immunoglobulin E

BACKGROUND: The dust mites Dermatophagoides pteronyssinus (Dp) and Blomia tropicalis (Bt) are important sources of indoor allergens in tropical and subtropical countries. Murine models allow the analysis of the immune response and regulation of IgE production to Dp and Bt allergens. Oral tolerance induces unresponsiveness in naive animals, but its application in sensitized animals can provide useful information to improve allergy therapy. OBJECTIVE: To study the profile of IgE and IgG subclasses antibody upon oral administration with Bt and Dp extract in previously sensitized mice. Further, the occurrence of autoantibodies IgG anti-IgE in the immunization and in the oral tolerance was investigated. METHODS: A/Sn mice were immunized with Bt or Dp extract in alum, orally administrated with 0.25 mg of Bt or Dp extract or PBS at the 6th, 7th and 8th days after immunization and boosted twice with their respective allergens. To analyse the mice groups, specific IgE antibodies were measured by passive anaphylaxis reaction and specific IgG subclasses and anti-IgE IgG autoantibody by ELISA assay. RESULTS: IgE levels were markedly increased in Bt-immunized mice compared with Dp-immunized mice. A distinct profile of the specific isotypes was verified in Bt-immunized mice with a preferential production of IgG3 and IgA antibodies, whereas Dp-immunized mice developed high titres of anti-Dp IgG1, IgG2a and IgG2b antibodies. The antigen feeding inhibited IgE response in both fed-mice groups but only Dp-fed mice presented decreased levels of IgG antibodies. Free anti-IgE IgG autoantibodies were detected mainly in the Dp-immunization and they correlated with the antibody isotypes found against the allergen. CONCLUSIONS: This is the first time that the murine-type I hypersensitivity is employed to study Bt-immunization, showing a marked IgE production, associated with IgG response, which is at least in part driven by T-independent antigens. The oral tolerance protocol in previously sensitized animals was able to down-modulate IgE response and points out this route as a strategy for allergy therapy.     

Immune response to Blomia kulagini and Dermatophagoides pteronyssinus in Sweden and Brazil

The immune responses to the non-pyroglyphid mite Blomia kulagini and the pyroglyphid mite Dermatophagoides pteronyssinus were compared in 440 Swedish farmers and 34 allergic subjects from Brazil using the radioallergosorbent test (RAST). Both B. kulagini and D. pteronyssinus were shown to be a common cause of sensitization, particularly in Brazil. The highest RAST scores were found against D. pteronyssinus in sera from both countries. Allergenic cross-reactivity between the two mites was studied by the RAST inhibition technique. Both B. kulagini and D. pteronyssinus possess their own unique allergens as well as allergens in common. Thus, besides mites belonging to the Dermatophagoides genus, other pyroglyphid and non-pyroglyphid mites in different countries should be taken into consideration before starting hyposensitization treatments.     

Identification of shared and unique immunoglobulin E epitopes of the highly conserved tropomyosins in Blomia tropicalis and Dermatophagoides pteronyssinus

BACKGROUND: Tropomyosin belongs to a class of highly conserved proteins in invertebrates and vertebrates. The invertebrate tropomyosins are allergenic in man with high IgE cross-reactivity and have been therefore referred to as pan-allergens. OBJECTIVES: This study aimed to clone and identify the IgE epitopes of tropomyosin from Blomia tropicalis (Blo t 10) mite. Cross-reactivity between the IgE epitopes of Blo t 10 and Der p 10 was also evaluated. METHODS: Blo t 10 was isolated using mouse anti-Der p 10 antibodies. Allergenicity of the cloned Blo t 10 was confirmed by skin prick test (SPT) and enzyme-linked immunosorbent assay (ELISA). Dose-dependent inhibition assay was performed to determine the degree of IgE cross-reactivity between Blo t 10 and Der p 10. Overlapping polymerase chain reaction-derived cDNA were generated and expressed as glutathione-S-transferase (GST) recombinant proteins in Escherichia coli and used to identify shared and unique IgE epitopes of Blo t 10 and Der p 10. RESULTS: The cloned Blo t 10 shared up to 96% amino acid identity to tropomyosin of other mites. SPT and ELISA IgE-immunoassay showed recombinant Blo t 10 sensitization rates of between 20% and 29% in atopic subjects. Results of SPT and dose-dependent inhibition assays showed that some allergic individuals had unique IgE epitopes for Blo t 10. IgE epitope mapping of Blo t 10 revealed that the epitopes were mainly located at N- and C-termini of the molecule. The results of ELISA inhibition assays of overlapping recombinant fragments indicated that the unique IgE epitopes of Blo t 10 were located at the C-terminal. CONCLUSION: Although Blo t 10 and Der p 10 are highly conserved (shared 95% amino acids identity) and significantly cross-reactive, unique IgE epitopes do exist. The results suggest the potential deficiency of using only one of these highly conserved allergens as diagnostic or therapeutic reagents.     

Blomia tropicalis and Dermatophagoides pteronyssinus Mites Evoke Distinct Patterns of Airway Cellular Influx in Type I Hypersensitivity Murine Model

Murine models of hypersensitivity to allergens are useful tools for the evaluation of strategies to downmodulate IgE response. We sought to compare allergen inflammatory pulmonary response in previously sensitized mice orally administered with dust mites Blomia tropicalis (Bt) or Dermatophagoides pteronyssinus (Dp). Sensitized A/Sn mice fed with Bt or Dp showed a significant decrease in the IgE response compared to control-immunized mice. Bt-immunized mice demonstrated an accumulation of neutrophils in the bronchoalveolar lavage fluid, while Dp-immunized mice revealed an intense influx of eosinophils in the airway. Bt oral administration did not attenuate cell influx in the airway and Dp-fed mice showed a significant decrease of neutrophils and lymphocytes in the bronchoalveolar lavage fluid. These findings demonstrated that oral tolerance induction to Bt and Dp extract in sensitized mice decrease IgE response, but does not interfere in local inflammatory pulmonary response. The distinct profile of airway cellular infiltration between mites immunization suggest an interesting model to study allergic inflammation.     

Purification of two allergens from Dermatophagoides pteronyssinus using monoclonal antibodies

Fractionation of soluble extracts from the house dust mite Dermatophagoides pteronyssinus (DP) by SDS-PAGE and crossed immunoelectrophoresis (CIE) revealed at least fifty distinct protein components. Western blotting and crossed radioimmunoelectrophoresis (CRIE) indicated that fewer than one quarter of these components were allergens as determined by their ability to bind IgE from allergic individuals. Following immunization with a crude extract, two monoclonal antibodies were raised against distinct components which exhibited IgE binding capacities in Western blot and CRIE. Affinity chromatography using these monoclonal antibodies yielded components which elicited positive skin test reactions in patients allergic to DP.     

Sensitization to major Dermatophagoides pteronyssinus allergens in house dust mite allergic patients from North Eastern Poland developing rhinitis or asthma

PurposeRecognition of individual allergens by IgE is crucial for triggering symptoms in allergic rhinitis (AR) or asthmatic (AA) patients. House dust mite (HDM) allergy is frequent around the world, the sensitization profile to individual HDM allergens varies in individual HDM-allergic patients (APs). The aim of this study was to evaluate the pattern of IgE sensitization to three major Dermatophagoides pteronyssinus (Dp) allergens among patients from North Eastern Poland suffering from HDM-AR and/or AA.Patients and methodsThe study was performed on 323 HDM-AR and/or AA patients and 106 controls (CG) including 30 healthy non-atopic subjects, 32 AR patients not sensitized to Dp and 44 non-atopic asthmatics. IgE levels to natural (n)Der p 1, nDer p 2, recombinant (r)Der p 2.0101 and rDer p 23 allergens were measured by ELISA.ResultsThe majority of HDM-APs were sensitized to nDer p 1 (72.1%), nDer p 2 (81.7%), rDer p 2.0101 (78.3%) and rDer p 23 (70.9%). The frequency of positive results to individual allergens depended on clinical manifestations and the level of IgE to the whole Dp extract. In HDM-AA patients, reactivity to nDer p 1 and rDer p 23 was detected more frequently than in HDM-AR patients. The whole Dp extract completely inhibited IgE binding to nDer p 1 and nDer p 2 but only partially to rDer p 23.ConclusionsHDM-APs from North-Eastern Poland display sensitization profile to major allergens which is similarly observed in western Europe. HDM-based diagnostic and therapeutic products should include all major allergens.     

Comparative analysis of physicochemical and immunochemical properties of the two major allergens from Dermatophagoides pteronyssinus and the corresponding allergens from Dermatophagoides farinae

Two major allergens, DP1 (Der p I) and DP2 (Der p II), were isolated from the whole culture extract of Dermatophagoides pteronyssinus, and the physicochemical and immunochemical properties of these allergens were compared with those of the corresponding allergens from Dermatophagoides farinae, DF1 (Der fI) and DF2 (Der fII). On sodium dodecyl sulfate-polyacrylamide gel electrophoresis, polyacrylamide gel isoelectric focusing and amino acid analysis, both DP1 and DP2 were demonstrated to have close physicochemical similarity with DF1 and DF2, respectively. On immunodiffusion with the use of rabbit antisera, the two Der I allergens showed the reaction of typical partial identity, while the two Der II allergens showed the reaction of almost complete identity. Radioallergosorbent test (RAST) and RAST absorption experiments with the use of sera from mite-allergic patients showed that human IgE antibody response to the Der I allergens was directed against both cross-reactive and species-specific determinants. In contrast, IgE antibodies to the Der II allergens were demonstrated to react almost completely to cross-reactive determinants.     

Sensitization to Blomia tropicalis and dermatophagoides pteronyssinus-a comparative study between Singapore and Taiwan

Blomia tropicalis (Bt) and Dermatophagoides pteronyssinus (Dp) are the predominant domestic mites species in Singapore and Taiwan. This study aims to characterize and compare the mite sensitization profiles in both countries. Skin prick tests were performed on 203 Singaporeans with Dp and Bt crude extracts. In vitro IgE and IgG4 reactivity to extracts and specific allergens (Der p 1, Der p 2 Der p 5 and Blo t 5) were determined by immunoassays. Approximately 91% of the tested Singaporeans were skin test positive for both Bt and Dp. Both populations share similar frequencies of in vitro IgE reactivity to all the allergens tested, but they differ in the pattern and magnitude of allergen sensitization. Although Der p 1, Der p 2 and Blo t5 are major sensitizing allergens in both countries, Blo t 5 is a more potent one in Singapore, probably reflecting the high level of exposure to Bt. The unique major Bt and Dp allergens should be included for precise diagnosis and effective immuno-therapeutic treatment of mite allergy in both countries.     

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.     

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.     

Identification of major allergens from the house dust mites, Dermatophagoides farinae and Dermatophagoides pteronyssinus, by electroblotting

The allergens were separated from the extracts of house dust mites by SDS-polyacrylamide gel electrophoresis (SDS-PAGE) and identified by autoradiography. Over 30 protein bands of the whole body extract of Dermatophagoides farinae were apparent on 10-20% gradient SDS-PAGE, and 13 bands with MW between 93KD and 12KD bound with specific IgE antibodies in patients' sera sensitive to house dust mites. The major allergenic component of the whole body extract of D. farinae was the protein of MW 14-15KD, which was detected in 95.7% of 47 patients' sera sensitive to house dust mites. The extract of Dermatophagoides pteronyssinus supplied by Bencard Company, England was thought to contain feces enriched material as noted in a few broad protein bands on SDS-PAGE. Seven allergenic components were shown by autoradiography. The protein band of MW 14-15KD was one of the most frequently revealed allergens on autoradiography, which has appeared in 32.5% of 40 patients' sera sensitive to house dust mites. The electrobotting technique used in the present study was fast, convenient and highly useful for both the identification of allergen components and the screening of specific IgE antibody. The individual variations of IgE immune responses to the allergenic components of the two house dust mites were discussed.     

Skin tests and conjunctival and bronchial challenges with extracts of Blomia tropicalis and Dermatophagoides pteronyssinus in patients with allergic asthma and/or rhinoconjunctivitis

BACKGROUND: Blomia tropicalis and Dermatophagoides pteronyssinus are important mite species in Tenerife, Canary Islands, Spain. Several studies have demonstrated a variable degree of allergenic cross-reactivity in vitro. However, only a few have addressed their allergenic cross-reactivity using challenge tests. OBJECTIVE: The objective of this study was to conduct conjunctival and bronchial challenge tests with B. tropicalis and D. pteronyssinus extracts in a group of 42 patients with allergic asthma and/or rhinoconjunctivitis sensitised to house dust mites (31 females, 11 males; mean age 21.7 +/- 7.02 years). METHODS: Prick tests using standardised extracts and specific IgE determinations using the CAP system were performed. Bronchial and/or conjunctival challenges were conducted using freeze-dried extracts of both mite species. A patient was considered sensitive to a mite species if she/he had a positive prick and/or CAP test result. A total of 32 conjunctival and 15 bronchial challenges were performed with both mite species. RESULTS: Prick tests were positive to B. tropicalis in 23 patients (54.7%) and to D. pteronyssinus in 41 (97.6%). One patient (2.4%) was exclusively sensitive to B. tropicalis. The CAP test was positive for B. tropicalis in 28 patients and for D. pteronyssinus in 41. Conjunctival challenges to B. tropicalis were positive in 20 patients (18 sensitised and 2 non-sensitised) and negative in 12 (5 sensitised and 7 non-sensitised patients). Conjunctival challenges with D. pteronyssinus were positive in all 31 D. pteronyssinus-sensitised patients who underwent conjunctival challenges. Bronchial challenges with B. tropicalis were positive in 9 sensitised patients and negative in 6 patients (2 sensitised and 4 non-sensitised). Bronchial challenges with D. pteronyssinus were positive in all patients except 1, who only reacted to B. tropicalis. CONCLUSIONS: Allergens of the mite species B. tropicalis induce positive conjunctival and bronchial challenges in B. tropicalis-sensitised individuals. Our results suggest that although there is a low to moderate degree of in vivo cross-reactivity between B. tropicalis and D. pteronyssinus, B. tropicalis seems to be a relevant source of allergens in areas where patients are exposed.