Cloning and characterization of tropomyosin from the mite Chortoglyphus arcuatus.

Tropomyosin is a pan-allergen that shares a high homology among species. It is involved in cross-reactivity among mites, crustaceans, mollusks and insects. The objectives were to express and purify recombinant tropomyosin from the storage mite Chortoglyphus arcuatus, and to investigate the homology and cross-reactivity with tropomyosin from other invertebrates. Recombinant C. arcuatus tropomyosin (r-Cho a 10) was selected from a library by screening with a pool of patient sera. r-Cho a 10 (UniProt: H2DFL1) was sequenced, expressed in Escherichia coli and purified by ion exchange and affinity chromatography. Polyclonal anti-tropomyosin antibodies were produced in mice. IgE recognition of r-Cho a 10 was checked by immunoblot. Immunoblot inhibition assays were used to identify the native tropomyosin in the complete extract from C. arcuatus and study cross-reactivity between r-Cho a 10 and Der p 10. Identification of tropomyosin in other allergenic sources was performed by immunoblot. r-Cho a 10 showed a high homology (54-96%) with other tropomyosins from different allergenic sources. IgE recognition was observed using a pool of sera from sensitized individuals. Tropomyosins from different extracts were identified not only in the whole C. arcuatus extract but also in Dermatophagoides pteronyssinus, shrimp, mussel, cockroach and Anisakis extracts with polyclonal α-Cho a 10. r-Cho a 10 completely inhibited the recognition of Der p 10. Recombinant C. arcuatus tropomyosin maintained its capacity to recognize IgE. r-Cho a 10 was used to prove cross-reactivity among tropomyosins from other invertebrate species, including mites. This is the first C. arcuatus allergen included in the WHO/IUIS (World Health Organization/International Union of Immunological Societies) Allergen Nomenclature database.

Identification and expression of macrophage migration inhibitory factor in Sarcoptes scabiei.

Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine produced by many mammalian tissues including skin. It is also found in many invertebrate parasites of mammals including ticks and may function to aid the parasite to evade the innate and adaptive immune responses in the host. In this study, the cDNA for a MIF gene was sequenced from Sarcoptes scabiei, the scabies mite, using RT-PCR and RACE molecular techniques. The resulting nucleotide sequence had a length of 405 base pairs and the putative amino acid sequences for the mite and tick (Dermacentor variabilis) proteins were identical. The initial steps for the project resulted in the production of expressed scabies mite cDNAs. A real time (qPCR) assay was performed with MIF from scabies mites and various tick species. Results show that mRNA encoding MIF homologues was three times more abundant in the mite samples when compared to RNA prepared from D. variabilis salivary glands and 1.3 times more abundant when compared with RNA prepared from D. variabilis midgut.

Genetic epidemiology of Sarcoptes scabiei (Acari: Sarcoptidae) in northern Australia.

Utilising three hypervariable microsatellite markers we have previously shown that scabies mites on people are genetically distinct from those on dogs in sympatric populations in northern Australia. This had important ramifications on the formulation of public health control policies. In contrast phylogenetic analyses using mitochondrial markers on scabies mites infecting multiple animal hosts elsewhere in the world could not differentiate any genetic variation between mite haplotype and host species. Here we further analyse the intra-specific relationship of Sarcoptes scabiei var. hominis with S. scabiei var. canis by using both mitochondrial DNA and an expanded nuclear microsatellite marker system. Phylogenetic studies using sequences from the mitochondrial genes coding for 16S rRNA and Cytochrome Oxidase subunit I demonstrated significant relationships between S. scabiei MtDNA haplotypes, host species and geographical location. Multi-locus genotyping using 15 microsatellite markers substantiated previous data that gene flow between scabies mite populations on human and dog hosts is extremely rare in northern Australia. These data clearly support our previous contention that control programs for human scabies in endemic areas with sympatric S. scabiei var. hominis and var. canis populations must focus on human-to-human transmission. The genetic division of dog and human derived scabies mites also has important implications in vaccine and diagnostic test development as well as the emergence and monitoring of drug resistance in S. scabiei in northern Australia.

Characterization of allergens of Anisakis simplex.

BACKGROUND: Anisakis simplex is an intestinal parasite of sea mammals. The larvae infect crustaceans, cephalopods and fish. Humans may consume A. simplex third stage larvae (L3) when eating infected raw or under-cooked fish. Consumed larvae cause an inflammatory reaction when they penetrate the digestive mucosa. The larvae or their secretory/excretory products can sensitize humans and induce an immunoglobulin E (IgE)-mediated allergic reaction. This parasite is now being implicated in numerous cases of allergic reactions after eating fish. The purpose of this study was to evaluate the allergenicity of proteins present in an extract of the third stage larva. METHODS: Rabbit antiserum raised to A. simplex somatic extract (L3) was reacted by crossed immunoelectrophoresis (CIE) with the same somatic extract. Crossed radioimmunoelectrophoresis (CRIE) was also performed by incubating CIE gels first in the sera of 13 individuals with positive immunoCAP to A. simplex and then in radiolabeled anti-human IgE. RESULTS: Twelve to 16 antigen-antibody precipitin peaks were visualized on Coomassie blue stained CIE gels in which somatic extract was reacted with somatic-antiserum. Autoradiography of CRIE gels showed that 18 different proteins bound IgE in patient sera. Individual patients had serum IgE directed at two to 10 different allergens. Five of these allergens were recognized by >/=50% of the patients. No allergen was recognized by every patient and no patient had serum IgE directed at all 18 allergens. CONCLUSION: Somatic extracts of A. simplex L3 larva contain a large number of allergenic molecules and there is significant variability between patients in their sensitivity and reactivity to these allergens.

Distribution and removal of cat, dog and mite allergens on smooth surfaces in homes with and without pets.

BACKGROUND: Removing allergen from the indoor environment should be a primary strategy for the management and treatment of allergic disease. OBJECTIVE: The aims of this study were to characterize the distribution of dog, cat, and mite allergen on hard surfaces in homes with and without pets and to evaluate the efficiency of removing allergen from hard surfaces by wiping with a dry dust cloth and by vacuum cleaning using the dustbrush attachment. METHODS: The amount of allergen collected from adjacent areas of two smooth floors, a wall, and finished furniture by wiping with a Pledge Grab-it dust cloth (S. C. Johnson & Son, Inc, Racine, WI) and by brush-vacuuming were compared for 24 homes with and without pets. In addition, the areas first wiped with the dust cloth were then brush-vacuumed and the amounts of allergen collected by the first and second cleaning were compared. RESULTS: A key finding was that 23 of the 24 homes had Can f 1 allergen on one or more of the sampled areas regardless of whether a dog was present. Most homes with pets and many homes without pets had Can f 1 and Fel d 1 allergens on walls, smooth floors, and finished furniture. Carpets were the major reservoir for pet allergens in homes with pets whereas allergen was more uniformly distributed in homes without pets. Little mite allergen was found on hard surfaces even when it was present in carpets. CONCLUSIONS: Dog and cat allergens are prevalent on walls, smooth floors, and finished furniture in homes with and without pets. Dry dusting with a Grab-it dust cloth was an effective cleaning method for removing allergen from hard smooth surfaces.

Characterization of house dust mite and scabies mite allergens by use of canine serum antibodies.

OBJECTIVE: To identify the major allergenic proteins from the 3 main species of dust mites to which dogs react (Dermatophagoides farinae, D. pteronyssinus, and Euroglyphus maynei) and evaluate the potential cross-reactivity of dust mite allergens with antigens from the ectoparasitic mite Sarcoptes scabiei var canis. SAMPLE POPULATION: Sera from 83 dogs with atopic dermatitis. PROCEDURE: Sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting using serum from atopic dogs was used to identify IgE-binding proteins in extracts of the 4 mite species. RESULTS: Sera of atopic dogs contained IgE against 23, 17, 25, and 17 allergens from D. farinae, D. pteronyssinus, E. maynei, and S. scabiei, respectively. Unlike the situation for humans, the major allergens for dogs are mostly proteins that are larger than 90 kd molecular weight. Dermatophagoides farinae and E. maynei appear to be more allergenic for dogs than is D. pteronyssinus. Some dogs with serum IgE against dust mites also had IgE against antigens of S. scabiei var canis. CONCLUSIONS AND CLINICAL RELEVANCE: Multiple dust mite allergens induce an IgE response in dogs. These allergens are mostly greater than 90 kd molecular weight.

The biology of dust mites and the remediation of mite allergens in allergic disease.

In most temperate humid areas of the world, house dust mites are a major source of multiple allergens in house dust. Mite allergens sensitize and induce perennial rhinitis, asthma, or atopic dermatitis in a large portion of patients with allergic disease. There is convincing evidence that avoidance of mite allergen can effectively reduce allergic symptoms. Patients can be moved to a mite allergen-free environment, or mite and mite allergen abatement can be performed to reduce exposure in existing residences. Some knowledge of the biology of house dust mites is essential to understand the basis of the recommendations for reducing mites and mite allergens in homes and to appreciate the difficulty of eliminating house dust mites and mite allergens from homes. This article reviews key aspects of the biology of dust mites, the properties of mite allergens, recommendations for reducing mite and mite allergen concentrations in homes, and practical recommendations for treatment.

Reducing relative humidity is a practical way to control dust mites and their allergens in homes in temperate climates.

BACKGROUND: Maintaining a relative humidity (RH) of less than 50% is one recommendation for reducing numbers of house dust mites and their allergens in homes. OBJECTIVE: The purpose of this study was to determine whether, in a humid temperate climate, indoor RH could be sufficiently lowered to control dust mites and their allergens. METHODS: During a period spanning 2 humid summers (May 1998 to October 1999), dust mite and allergen densities were determined in 3 groups of homes. One group (low RH group, n = 23) maintained an RH of less than 51%. Most of these homes used a high-efficiency dehumidifier and air conditioning. A second group of homes (group A) used air conditioning only (n = 19) or air conditioning and dehumidification (n = 5) but did not maintain an RH of less than 51%. A third group of homes (group C, n = 24) controlled climate by opening windows and had an RH of greater than 51%. Normal housecleaning was maintained in all homes during the study. RESULTS: The low RH group homes started in June with a mean +/- SE of 401 +/- 124 live mites and 17 +/- 3 microg of total Der 1 allergen per gram of dust. After 17 months of maintaining an RH of less than 51%, these declined significantly to 8 +/- 3 live mites per gram (P =. 004) and 4 +/- 1 microg of Der 1 per gram of dust (P <.001). In contrast, group A and C homes exhibited seasonal peaks of 500 to 1000 mites and 40 to 70 microg of Der 1 per gram of dust. At all time points after the baseline sample, the low RH group homes had significantly less (P <.001) allergen than the group A and C homes. After 17 months, allergen levels were more than 10 times lower in low RH homes compared with humid homes. CONCLUSION: This study showed that it is practical to maintain an indoor RH of less than 51% during the humid summer season in a temperate climate, and this resulted in significant reductions in mite and allergen levels.

Dust mites: update on their allergens and control.

Mites are ubiquitous organisms, and as a result, humans come into contact with mites and mite products in a variety of situations. Molecules from many mite species can induce IgE-mediated reactions. Best known among the allergy-causing mites are the house dust and storage mites. However, allergists should be aware that, in specific situations, contact with products of many other less-known species of mites also may cause IgE-mediated reactions.

Serum antibody to Sarcoptes scabiei and house dust mite prior to and during infestation with S. scabiei.

In this study, serum antibodies to Sarcoptes scabiei var. canis (SS), Dermatophagoides farinae (DF), and D. pteronyssinus (DP) were determined in 19 healthy, random-source dogs prior to infestation with scabies then again during a primary infestation, cure and challenge infestation with scabies. Prior to scabies infestation, serum of 11 dogs contained faintly detectable amounts of IgE and/or IgG to proteins in SS extract, probably resulting from sensitization to dust mites that share cross-reactive antigenic epitopes with SS. After becoming infested with scabies, the response to SS antigens became stronger with antibodies appearing to more antigens as the scabies infestation progressed. Three of the newly recognized proteins were 170, 155 and 142/133kD and could be used in a diagnostic test since antibodies to them appeared during the primary infestation. In addition, during the primary infestation, 14 of 15 dogs developed IgE to 1-11 new SS proteins in addition to an increase in IgE binding to those proteins recognized prior to infestation. Overall, the strongest antibody responses (IgE and IgG) were exhibited during cure of the first infestation, when dead mites were still present in the stratum corneum. As expected, the antibody response was strong and rapid during challenge when the infestation self-cured. The immunogenic SS proteins identified by serum antibody binding during challenge, when the hosts self-cured, are candidates for inclusion in a vaccine. These candidate proteins are 200, 185, 170, 155, 142/133, 112, 97, 74, 57, 45/42, 32 and 22kD. Some of the proteins in SS that exhibited new or increased antibody binding during the experiment also had IgE and IgG binding to proteins with similar molecular weights in DF and DP extracts. These results illustrate the difficulties involved in understanding and interpreting serum antibody for developing a serological test for the diagnosis of scabies, isolating relevant SS antigens that could be included in a vaccine for prevention of scabies, and for understanding the immune response mechanism to scabies.

Reducing relative humidity to control the house dust mite Dermatophagoides farinae.

BACKGROUND: Indoor relative humidity (RH) is the key factor that determines the survival and population development of the house dust mite Dermatophagoides farinae. Maintaining RH below 50% is one recommendation in a comprehensive plan to reduce house dust mites and mite allergen levels in homes. Even when mean daily RH is reduced below 50%, RH may rise above 50% intermittently for brief periods because of activities in the home (eg, cooking, bathing, and ventilation). OBJECTIVE: The purpose of this study was to determine how brief daily periods of moist air alternating with long spells of low ambient RH (0% or 35%) influence population survival and growth of D farinae. METHODS: Population growth was determined for D farinae at daily RH regimens of 2, 4, 6, and 8 hours at 75% or 85% RH alternating with 22, 20, 18, and 16 hours at 0% or 35% RH. RESULTS: D farinae populations declined at daily regimens of 2 hours at 75% or 85% RH alternating with 22 hours at 0% or 35% RH. Daily regimens of 4, 6, and 8 hours at 75% RH alternating with 20, 18, and 16 hours, respectively, at 35% RH provided sufficient moisture for small growths in population size. These growths after 10 weeks were reduced by 98.2%, 98.0%, and 97.3% for daily regimens of 4, 6, and 8 hours, respectively, at 75% RH (with the remainder of the day at 35% RH) compared with the growth of populations continuously exposed to 75% RH. Continuous exposure to 85% RH inhibited population growth, but alternating daily regimens of 16, 18, and 20 hours at 35% RH allowed small populations to develop, although they were reduced by 99.4%, 98.8%, and 99.1% compared with population growth at a continuous 75% RH. CONCLUSION: This study indicates that maintaining mean daily RH below 50%, even when RH rises above 50% for 2 to 8 hours daily, effectively restricts population growth of these mites and thus the production of allergen. To completely prevent population growth of D farinae, RH must be maintained below 35% for at least 22 hours per day when the daily RH is 75% or 85% for the remainder of the day.

Fluctuating hydrating and dehydrating relative humidities effects on the life cycle of Dermatophagoides farinae (Acari: Pyroglyphidae).

Reducing relative humidity to < 50% in homes is recommended as one means of reducing dust mite populations in the homes of those who suffer allergies to house dust mites. Because of some activities in the home (e.g., bathing, cooking, opening windows), it may not be possible to keep relative humidity constantly < 50%. We determined how the fluctuating daily regimes of hydrating (75%) and dehydrating (35%) relative humidities affected the development of Dermatophagoides farinae Hughes. The life cycle was completed (egg to adults) when mites were given regimes of 24 h at 75% RH, 8 h at 75% and 16 h at 35% RH, 6 h at 75% and 18 h at 35% RH, and 4 h at 75% and 20 h at 35% RH. The time required to complete development was inversely related to the amount of moist air given daily. Development took 58.3 +/- 1.44, 64.7 +/- 1.87, and 82.4 +/- 2.39 d for 8, 6, and 4 h of moist air daily, respectively. In comparison, the life cycle was completed in 41.1 +/- 0.50 d when development occurred at a constant 75% RH. Egg incubation time was significantly longer for fluctuating ambient relative humidity compared to a continuous 75 or 35% RH. Of the emerging larvae 53.8, 72.7, 62.7, and 85.0% completed the life cycle when given 4, 6, 8, and 24 h 75% RH daily and 35% RH for the remainder of the day. This study revealed that D. farinae can complete development when given only short periods of moist air daily but the rate of development is much slower than development at a constant 75% RH. Therefore, reducing ambient relative humidity does reduce the rate of development of mite populations and the accumulation of dust mite allergen.

Allergenicity of the mite Hemisarcoptes cooremani.

BACKGROUND: A researcher experienced allergic symptoms while working with the astigmatid mite Hemisarcoptes cooremani cultured on scale insects. This mite is a predator of scale insects that often parasitize many perennial vascular plants in orchards, gardens, and ornamental nurseries worldwide; therefore, orchard and ornamental nursery workers and gardeners may be exposed to this mite. OBJECTIVE: We investigated the possible allergenicity of H. cooremani and the cross-reactivity between it and other allergy-causing astigmatid mites. METHODS: Serum from a subject who experienced allergic symptoms while working with H. cooremani was analyzed for IgE and IgG to proteins in an extract of this mite and of other astigmatid mites known to cause allergic reactions. The serum was used to probe proteins fractionated by SDS-PAGE or precipitated by CIE using rabbit antiserum. In addition, the subject's serum was used to directly precipitate proteins in extracts of H. cooremani and other mite species. RESULTS: SDS-PAGE and immunoblotting of proteins in an H. cooremani extract showed the reference serum contained IgE directed at 16-kD and 19-kD proteins. Crossed radioimmunoelectrophoresis reaction showed that the subject's serum contained antibody that precipitated a protein in an H. cooremani extract and that IgE bound to this protein. The proteins in an extract of H. cooremani did not precipitate when reacted with rabbit antisera against the dust mites D. farinae, D. pteronyssinus, and E. maynei, or the storage mites B. tropicalis, L. destructor, and T. putrescentiae. This indicated there was no cross-reactivity between H. cooremani and these mites. CONCLUSION: These results indicated that an extract of the mite H. cooremani contained at least two prominent IgE binding proteins that were not present in the other astigmatid mites. Thus, H. cooremani is the source of unique allergenic proteins and allergy to this mite may develop in orchard and ornamental nursery workers and gardeners.

Survival, fecundity, and development of Dermatophagoides farinae (Acari: Pyroglyphidae) at fluctuating relative humidity.

We determined the survival, development, and fecundity of Dermatophagoides farinae Hughes exposed to fluctuating daily regimes of hydrating and dehydrating relative humidity. Larva emerged from 84, 92, and 94% of eggs incubated at a regime of 2, 4, and 8 h at 75% RH and 22, 20, and 16 h at 0% RH, respectively. No emerging offspring completed the life cycle when exposed to the 2 and 4 h of moist air daily but 44 and 53% survived for 70 d in the larval or nymphal stages, respectivley, and these completed development to adults when subsequently held at a constant 75% RH. Given 8 h of moist air daily, 41% of emerging offspring completed the life cycle but development was 1.6 times longer compared with development at a constant 75% RH. For all daily hydrating and dehydrating regimes, a greater percentage of offspring became males than females. Overall, survival of immatures was remarkable at these daily long periods of dehydrating conditions when a short period of hydrating moisture was provided. When exposed to a daily regime of 4 h of moist air (75% RH) and 20 h of dry air (0% RH), 84% of females survived 28 d and produced approximately 1/3 of the number of eggs produced at constant 75% RH (control).

Population dynamics of the house dust mites Dermatophagoides farinae, D. pteronyssinus, and Euroglyphus maynei (Acari: Pyroglyphidae) at specific relative humidities.

Experiments were conducted to determine the effects of relative humidity on the population dynamics of single and mixed species of Dermatophagoides farinae Hughes, D. pteronyssinus (Trouessart), and Euroglyphus maynei (Cooreman) at specific relative humidities maintained at 20 degrees C, with unlimited food. The population density of single and mixed species (D. farinae and D. pteronyssinus) increased exponentially when cultured at 65, 70, and 75% RH. The mean population growth rates were 17.3 +/- 4.4 SD and 32.5% +/- 4.7/wk for D. farinae and D. pteronyssinus, respectively. Mean population doubling times were 2.2 +/- 0.3 and 4.2 +/- 1.3 wk for D. pteronyssinus and D. farinae, respectively. Mixed species cultures, started with equal numbers of D. farinae and D. pteronyssinus, resulted in higher percentages of D. farinae than D. pteronyssinus. In cultures started with 75% of one species and 25% of the other, the more numerous species remained dominant and in similar ratios throughout the experiment. Both D. farinae and D. pteronyssinus population densities maintained at 85% RH declined over a 12-wk culture period because of mold growth. E. maynei were unable to survive at 65, 70, 75, and 85% RH, which indicated that their climatic requirements were different from those of D. farinae and D. pteronyssinus. Population densities of D. farinae and D. pteronyssinus cultures declined when held at 21-22 degrees C and relative humidities of < or = 50%; however, at 50% RH, significant proportions of the populations survived for 10 wk. Half-life for desiccation of D. farinae and D. pteronyssinus at 45% RH was 11.5 and 1.2 wk, respectively, but at 50% RH was 86.3 and 4.0 wk, respectively. The data indicated that a < or = 50% RH would have to be maintained for long periods to reduce both D. farinae and D. pteronyssinus by desiccation procedures. The results of this study show that D. farinae and D. pteronyssinus have high reproductive potentials and population growth rates, which indicate that mite reduction procedures must be thorough or mite densities will return to high levels quickly following remediation if adequate food and suitable microclimatic conditions exist.

Characterization of the allergens of the house dust mite Euroglyphus maynei.

BACKGROUND: The house dust mite Euroglyphus maynei inhabits homes in many parts of the world and is the source of many allergens. OBJECTIVE: The purpose of this study was to biochemically and immunologically characterize the major allergens of E. maynei. METHODS: Proteins in an extract of E. maynei were separated into 20 fractions by using preparative isoelectric focusing. Most proteins and allergens were contained in fractions 7 to 17 with pH of 4.8 to 8.0. The fractions were further characterized by nonreducing sodium dodecylsulfate-polyacrylamide gel electrophoresis and immunoblotting with the serum of 16 individuals sensitive to E. maynei. RESULTS: Molecular weights and isoelectric points were assigned to 47 IgE-binding proteins in an E. maynei extract, and the frequency of IgE binding to each allergen was determined. Twenty-two of the allergens were recognized by more than 50% of the 16 sera, and all but one of the subjects had IgE that bound to more than 10 allergens (range, 0 to 32). One of the proteins was identified as the allergen Eur m 2. CONCLUSION: E. maynei is the source of at least 47 individual allergens that have been characterized by molecular weight, isoelectric point, and IgE-binding properties.

Skin test and radioallergosorbent test characteristics of scabietic patients.

The scabies mite Sarcoptes scabiei and the Dermatophagoides house dust mites (HDM) are related phylogenetically and are the sources of several cross-reactive antigens. The purpose of this study was to investigate the immune response to S. scabiei and HDM in scabietic patients. Skin test sensitivity and serum IgE to both S. scabiei and HDM were determined for patients who had or previously had confirmed ordinary scabies. A retrospective group included nine subjects who had received successful treatment three weeks to one year prior to the study. A prospective group included 16 subjects with active scabies. Allergic histories were obtained, serum was collected, and skin prick tests (SPTs) were performed at enrollment for all and periodically over the next 12 months for the prospective patients. None of the individuals in either group reported a known sensitivity to HDM. Six of the nine retrospective patients were SPT positive to both S. scabiei and HDM and two of these showed circulating IgE specific for these antigens. At diagnosis, 13 of 16 patients with active scabies were SPT positive to S. scabiei and 12 of these were also SPT and/or radioallergosorbent test positive to HDM. Six patients had circulating IgE directed at both S. scabiei and HDM antigens while one subject had IgE to S. scabiei only and another had IgE directed at HDM only. Twelve of the 15 subjects tested also showed IgE and/or IgG binding to one or more bands on Western blots of an S. scabiei-specific protein fraction. This study indicated that approximately half of the patients with active scabies had S. scabiei- and HDM-specific circulating IgE while most patients cured of scabies lacked S. scabiei- and HDM-specific serum IgE. The data also suggested that antibodies to S. scabiei in scabietic patients also recognize HDM; however, some antibodies were directed at scabies-specific antigens.

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: (1) 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; 10,000 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 > or = 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.