Prevalence of allergic sensitization to storage mites in Northern Europe.

BACKGROUND: Allergic sensitization to storage mites has mostly been related to occupational exposures like farming, grain/cattle handling, whereas for non-occupational settings, storage mite sensitization has been attributed to cross-reactivity with house dust mite (HDM) allergens. OBJECTIVE: We aimed to describe the prevalence of allergic sensitization to storage mites, co-sensitization to HDM allergens and respiratory symptoms in Denmark, Iceland, Norway and Sweden. METHODS: The population comprised of 1180 participants born 1945-1972 of the third follow-up of the population-based cohort European Community Respiratory Health Survey (ECRHS) in Aarhus, Bergen, Reykjavik and Uppsala. A clinical examination included skin prick tests (SPT) to Lepidoglyphus destructor, Tyrophagus putrescentiae, Acarus siro and common inhalant allergens, as well as standardized interviews. RESULTS: 8% were sensitized to HDM and 10% to storage mite, with some variation by study centre: Reykjavik 13%, Bergen 8% and Aarhus 7%. In Uppsala, only L destructor (3%) was measured. Storage mite sensitization was higher among men (11%) than women (8%). Among storage mite sensitized, 44% were also sensitized to HDM. Storage mite sensitization was associated with asthma and nasal allergies, but not with age, education, pet keeping or place of upbringing. CONCLUSIONS AND CLINICAL RELEVANCE: In this Northern European population-based study, allergic sensitization to storage mite was as common as HDM sensitization. Storage mite sensitization was, independently of HDM sensitization, associated with respiratory symptoms and asthma. Our findings suggest that storage mite sensitization should be evaluated with regard to inclusion into the common inhalant allergen panel in Northern Europe.

Tyrophagus putrescentiae group 4 allergen allergenicity and epitope prediction.

INTRODUCTION AND OBJECTIVES: Allergen-specific immunotherapy (ASIT) is the only allergic disease-modifying therapy available for children and adults, and recombinant allergens are an interesting approach to improve allergy diagnosis and ASIT. Tyrophagus putrescentiae is a common storage mite that produces potent allergens. The aim of this study was to express and characterize recombinant group 4 allergen protein of T. putrescentiae (Tyr p 4), and to further investigate allergenicity and potential epitopes of Tyr p 4. MATERIALS AND METHODS: The cDNA encoding Tyr p 4 was generated by RT-PCR and subcloned into pET-28a(+) plasmid. The plasmid was then transformed into E. coli cells for expression. After purification by nickel affinity chromatography and identification by SDS-PAGE, recombinant Tyr p 4 protein was used for a skin prick test and an ELISA to determine the allergic response. RESULTS: Study participants' allergic response rate to Tyr p 4 protein was 13.3% (16/120). Eight B-cell epitopes and three T-cell epitopes of Tyr p 4 were predicted. CONCLUSIONS: Similar to group 4 allergens of other species of mite, allergenicity of Tyr p 4 is weak. The expression, characterization and epitope prediction of recombinant Tyr p 4 protein provide a foundation for further study of this allergen in the diagnosis and ASIT of storage mite allergy.

Blomia tropicalis-Specific TCR Transgenic Th2 Cells Induce Inducible BALT and Severe Asthma in Mice by an IL-4/IL-13-Dependent Mechanism.

Previous studies have highlighted the importance of lung-draining lymph nodes in the respiratory allergic immune response, whereas the lung parenchymal immune system has been largely neglected. We describe a new in vivo model of respiratory sensitization to Blomia tropicalis, the principal asthma allergen in the tropics, in which the immune response is focused on the lung parenchyma by transfer of Th2 cells from a novel TCR transgenic mouse, specific for the major B. tropicalis allergen Blo t 5, that targets the lung rather than the draining lymph nodes. Transfer of highly polarized transgenic CD4 effector Th2 cells, termed BT-II, followed by repeated inhalation of Blo t 5 expands these cells in the lung >100-fold, and subsequent Blo t 5 challenge induced decreased body temperature, reduction in movement, and a fall in specific lung compliance unseen in conventional mouse asthma models following a physiological allergen challenge. These mice exhibit lung eosinophilia; smooth muscle cell, collagen, and goblet cell hyperplasia; hyper IgE syndrome; mucus plugging; and extensive inducible BALT. In addition, there is a fall in total lung volume and forced expiratory volume at 100 ms. These pathophysiological changes were substantially reduced and, in some cases, completely abolished by administration of neutralizing mAbs specific for IL-4 and IL-13 on weeks 1, 2, and 3. This IL-4/IL-13-dependent inducible BALT model will be useful for investigating the pathophysiological mechanisms that underlie asthma and the development of more effective drugs for treating severe asthma.

Different sensitization to storage mites depending on the co-exposure to house dust mites.

BACKGROUND: Co-sensitization to house dust mites (HDMs) and storage mites (SMs) is very frequent, although the clinical relevance is not well established. OBJECTIVE: To describe the pattern of sensitization and immunologic characterization of patients with positive skin prick test reactions to HDMs and SMs in 4 areas of Spain, selected according to high exposure to HDMs and variable exposure to SMs. METHODS: One hundred sixty-nine individuals with positive skin prick test reactions to HDMs and SMs were included. Specific IgE levels to different mite species and to Der p 1, Der p 2, and Der p 10 were determined. Immunoblots to Dermatophagoides pteronyssinus, Lepidoglyphus destructor, and Tyrophagus putrescentiae extracts were carried out, and allergograms were obtained. Results of different areas were compared. RESULTS: A high rate of polysensitization to SMs was observed, although 12% of participants did not have specific IgE to any SM species. Sensitization to Dermatophagoides species, Der p 2, and L destructor were predominant, although significant differences were observed among areas depending on the grade of exposure to SMs. In areas with high exposure, the SM allergogram showed greater recognition of group 2 allergen. CONCLUSION: Sensitization patterns to SMs in patients sensitized to HDMs and SMs differ depending on the exposure to SMs. Sensitization, mainly to L destructor, seems to exist in areas with high exposure, possibly with group 2 allergens mainly involved. However, in areas with low SM populations, sensitizations observed by skin prick testing appear to be related to HDM exposure.

Atopy patch test with Aleuroglyphus ovatus antigen in patients with atopic dermatitis.

BACKGROUND: Epicutaneous test made with dust mite antigens. OBJECTIVE: Evaluation of the response of the epicutaneous test with Aleuroglyphus ovatus antigen in atopic patients. METHODS: We patch tested 119 individuals, 48 with atopic dermatitis, 50 with respiratory allergy and 21 healthy controls. We compare the positive response frequency to a closed patch test using Aleuroglyphus ovatus antigen in different concentrations and 48 and 96h reading times among those individuals. RESULTS: Six patients with atopic dermatitis (12.5%) and 4 with respiratory atopy (8.0%) had positive reactions. None of the non-atopic controls had a positive response. As the antigen concentration raised, the number of positive reactions to epicutaneous test raised as well. CONCLUSION: Our data suggest a positive relation between Atopy Patch Test positive responses and Aleuroglyphus ovatus antigen concentration, no matter the kind of the atopic clinical expression.

Comparison of IgE test results with intradermal skin tests for dust mites and storage mites in atopic dogs.

Atopic dermatitis is one of the most frequent allergic diseases in dogs. There are many methods of treating its symptoms but specific immunotherapy has recently gained high popularity. Before the application of specific immunotherapy, it is necessary to identify the allergens provoking the reaction of hypersensitivity in the selected animal. This raises a question about the method of allergen identification the medical practitioner decides to use in order to obtain the most credible result. The authors of the present study decided to compare the results of intradermal allergic tests and the results of an IgE screening test carried out using the FcɛRIα receptor method. The aim of the study was to compare the results of both tests directed to dust and storage mites. The study proves that in case of the IgE screening tests (for a group of allergens), the sensitivity is quite high (85 to 90.69%) but the specificity of these tests is insufficient (25 to 50%). In case of antibodies for the selected mites the sensitivity and specificity was too low (65.1 to 89.4% for the sensitivity, with only 14.2 to 33.3% for the specificity). Only in case of D. petronyssinus the results were higher with the sensitivity calculated at 65.1% and the specificity at 80%. The IgE screening test carried out using the FcɛRIα receptor method is reliable only in case of screening test for mites and the intradermal allergic test remains the gold standard for allergy testing.

Effect of different diets on Tyrophagus putrescentiae population and amelioration of their immunological disorder by garlic.

BACKGROUND: The storage mite, Tyrophagus putrescentiae, detected in the samples collected from stored products and house dust, is one of the major causes of allergic disorders. OBJECTIVE: The purpose of this study was to ameliorate the T. putrescentiae faeces allergic immunological disorder by garlic. METHODS: Albino experimental rats were classified into control, inhaled and treated groups. Mass rearing of T. putrescentiae on different diets, and ELISA of some cytokines and IgE techniques were used. RESULTS: The results obtained showed the highest population of T. putrescentiae reared in four from thirteen tested diets. In addition, significantly higher serum levels of INF-γ and IgE were found in rats treated with faeces than the other groups; especially the garlic-treated group. In contrast, IL-4 was lower in faeces-treated rats than the others; however, the control group had the highest level of IL-4. Statistical analysis of data showed a significant difference between the garlic-treated group and either control or faeces-treated groups (P<0.05). CONCLUSIONS: The population of T. putrescentiae mites peaked in four from thirteen tested diets. The immunological disorder caused by repeated exposure to T. putrescentiae faeces might be modulated by garlic.

Ascaris lumbricoides infection in urban schoolchildren: specific IgE and IL-10 production.

BACKGROUND: Helminth infections and allergies are diseases with intense Th2 lymphocytes participation and characterised by a high IgE and Interleukin-(IL) IL-4, IL-5 production and eosinophilia. However, helminths also induce IL-10 production, which may alter the outcome of allergic diseases in infected patients. OBJECTIVE: This experimental study analyses the relationship between IL-10 production by cell culture from geohelminth infected and non-infected children and specific IgE to Ascaris lumbricoides (Asc) or Blomia tropicalis (BT). METHODS: IL-10 content in supernatant from peripheral blood mononuclear cell culture from nine helminth infected and eleven non-infected patients was determined by ELISA after in vitro stimulation with Asc or BT extracts. RESULTS: A positive association was observed between total IgE levels and anti-Ascaris and anti-Blomia tropicalis specific IgE, independent of infection status. For both helminth-infected and non-infected groups, there was no difference in IL-10 production in response to Asc extract, even though anti-Ascaris IgE levels were higher in the latter group. In response to BT stimulus, a lower production of IL-10 by the geohelminth-infected group was observed, but with no relationship between IL-10 production and specific IgE to BT. CONCLUSION: The results suggest that anti-Ascaris IgE in non-infected patients may be associated to a resistance to parasites. Levels of specific IgE to parasite antigens or B. tropicalis allergen were not impaired by IL-10 production in children from an urban area in which geohelminthiasis is endemic.

Equine intradermal test threshold concentrations for house dust mite and storage mite allergens and identification of stable acari fauna.

BACKGROUND: House dust mite (HDM) and storage mite (SM) stable fauna and their associated equine intradermal test (IDT) threshold concentrations (TCs) for the midwestern region of the USA are unknown. HYPOTHESIS/OBJECTIVES: To determine IDT TCs and serum IgE concentrations for two HDM and three SM species in clinically normal horses over two seasons, and to identify the mite taxa and habitats in a stable. ANIMALS: Thirty-eight clinically normal horses. METHODS: Threshold concentrations for HDMs and SMs were determined using IDT subjective measurements and a statistical model. An enzyme-linked immunosorbent assay was used to quantify serum IgE concentrations for the same mite species. A modified flotation method was used to identify morphologically HDMs and SMs. RESULTS: Subjective IDT TCs were as follows: 1:80,000 w/v for Dermatophagoides farinae in both seasons; 1:80,000 w/v in spring and 1:160,000 w/v in late summer for Dermatophagoides pteronyssinus; 1:40,000 w/v in spring and 1:20,000 w/v in late summer for Acarus siro; 1:20,000 w/v for Lepidoglyphus destructor in both seasons; and 1:20,000 w/v in spring and 1:10,000 w/v in late summer for Tyrophagus putrescentiae. Statistically significant associations for increased serum IgE and a positive IDT reaction were evident for D. farinae in the spring and D. pteronyssinus in both seasons. One mite from all four genera specific to this study was identified; however,two HDM and A. siro species were not detected.Conclusions and clinical importance ­ This study established HDM and SM IDT dilution concentrations for the horses in this region. Exposure to diverse acaridae fauna may contribute to the pathogenesis of equine allergic disease.

Enzymatic activity of allergenic house dust and storage mite extracts.

Proteases are involved in the pathogenicity of allergy, increasing epithelial permeability and acting as adjuvants. Enzymatic activity is therefore important for the allergenicity of an extract and also affects its stability and safety. However, the enzymatic activity of extracts is not usually evaluated. The objective of this study was to evaluate the enzymatic activity of the most allergenic mite extracts and to investigate their allergenic properties. Extracts from nine allergenic mite species (Dermatophagoides pteronyssinus, Dermatophagoides farinae Hughes, Euroglyphus maynei, Lepidoglyphus destructor, Tyrophagus putrescentiae (Schrank), Glycyphagus domesticus (DeGeer), Acarus siro L., Chortoglyphus arcuatus, and Blomia tropicalis) were characterized. Protein and allergen profiles were characterized by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and western-blot, respectively. Gelatinolytic activity was evaluated with a zymogram and the activity of other enzymes (cysteine, serine proteases, and esterases) was evaluated individually or with the API-ZYM system. The main differences in protease activity were found between house dust mites and storage mites. House dust mites presented higher cysteine protease activity while storage mites presented higher serine protease activity. These differences are in line with their trophic specialization. A wide range of different activities was found in all the extracts analyzed, reflecting the fact that the extracts preserve the activity of many enzymes, this being necessary for a correct diagnosis. However, enzymes may act as adjuvants and, therefore, could lead to undesirable effects in immunotherapies, making this activity not suitable for treatment products. Modified extracts with lower enzymatic activity could be more appropriate for immunotherapy.

Immune responses to tyrophagus putrescentiae-induced airway inflammation in mice.

BACKGROUND: Storage mites are a source of aeroallergens that affect patients with allergic rhinitis and asthma. Tyrophagus putrescentiae is a causative factor of airway hypersensitivity, but the mechanisms and pathogenesis of Tputrescentiae-induced allergy are not well understood. OBJECTIVE: This study aimed to develop a murine model of T putrescentiae-induced allergic asthma. METHODS: Immune responses and physiologic variations in immunoglobulins (Ig), leukocyte subpopulations, cytokines, gene expression, pulmonary function, and lung pathology were evaluated after intraperitoneal sensitization and intratracheal challenge with crude extract of T putrescentiae. RESULTS: After sensitization with aluminum hydroxide and challenge with T putrescentiae in mice, levels of T putrescentiae-specific IgE and IgG1 in sera increased significantly compared to the normal saline group (P < .01): Values for inflammatory leukocytes (neutrophils and eosinophils) and cytokines (interleukin [IL] 4, IL-5, and IL-13) increased significantly after sensitization. In terms of pulmonary function, pause values were significantly enhanced in T putrescentiae-sensitized mice after intratracheal challenge with T putrescentiae (P < .05). Expression of type 2 helper T cell (T(H)2)-related genes (IL4, IL5, IL13, and RANTES), T(H)2-specific transcription factor (GATA-3), and proinflammatory genes (IL6), and T(H)(H)17-related genes (IL17F) increased significantly after airway challenge. Sensitization with T putrescentiae crude extract led to inflammation of lung tissue, thickening of the tracheal wall, and tracheal rupture. CONCLUSIONS: Intraperitoneal sensitization followed by intratracheal challenge with crude extract of T putrescentiae can induce airway inflammation in BALB/c mice. The symptoms observed in a mouse model of allergic asthma, in terms of immune and clinical parameters, are reminiscent of the symptoms of allergic asthma in humans. A mouse model can be used to evaluate the therapeutic effectiveness of drugs on T putrescentiae-induced airway inflammation in humans.

Enzymatic activity and immunoreactivity of Aca s 4, an alpha-amylase allergen from the storage mite Acarus siro.

BACKGROUND: Enzymatic allergens of storage mites that contaminate stored food products are poorly characterized. We describe biochemical and immunological properties of the native alpha-amylase allergen Aca s 4 from Acarus siro, a medically important storage mite. RESULTS: A. siro produced a high level of alpha-amylase activity attributed to Aca s 4. This enzyme was purified and identified by protein sequencing and LC-MS/MS analysis. Aca s 4 showed a distinct inhibition pattern and an unusual alpha-amylolytic activity with low sensitivity to activation by chloride ions. Homology modeling of Aca s 4 revealed a structural change in the chloride-binding site that may account for this activation pattern. Aca s 4 was recognized by IgE from house dust mite-sensitive patients, and potential epitopes for cross-reactivity with house dust mite group 4 allergens were found. CONCLUSIONS: We present the first protein-level characterization of a group 4 allergen from storage mites. Due to its high production and IgE reactivity, Aca s 4 is potentially relevant to allergic hypersensitivity.

Effect of stored product mite extracts on human dermal microvascular endothelial cells.

Stored product mites commonly occur in agricultural work environments and sometimes in homes in significant numbers. They are a source of allergens that sensitize and induce allergic reactions. This may include atopic dermatitis. The purpose of this investigation was to determine if the common species of storage mites are the sources of molecules that influence the function of human dermal microvascular endothelial cells that regulate the trafficking of inflammatory and immune cells into the dermis during allergic reactions and other skin diseases. Human dermal microvascular endothelial cells were challenged with varying doses of extracts of the storage mites Acarus siro L., Chortoglyphus arcuatus (Troupeau), Lepidoglyphus destructor (Schrank), or Tyrophagus putrescentiae (Schrank) and the secretion of cytokines and expression of adhesion molecules were measured. The role of endotoxin and protein in inducing these responses was evaluated. These stored product mite extracts induced secretion of interleukin-6, interleukin-8, monocyte chemotactic protein-1, and granulocyte/monocyte colony stimulating factor. Some of these effects were induced by protein present in the extracts, some were induced by endotoxin, and some were induced by other substances. C. arcuatus and T. putrescentiae extracts also down-regulated tumor necrosis factor a-induced vascular cell adhesion molecule-1 expression. Stored product mite extracts contain an assortment of molecules, including endotoxins and proteins, which modulate the expression of cell adhesion molecules and the secretion of cytokines by microvascular endothelial cells. These modulating properties varied among mite species indicating that each mite species has a unique set of molecules that is responsible for its activity.

Seasonal population of Acarus siro mites and effects of their faeces on allergenic immunological disorder modulated by garlic in albino rat.

BACKGROUND: Mites are the main factor involved in respiratory disorder. Acarus siro is the most allergenic species of mite detected in the samples collected from flour mills. OBJECTIVE: This work aimed to ameliorate the A. siro faeces allergenic disorder by garlic extract. METHODS: Albino experimental rats were classified into three groups (native, inhaled and treated). Mites extract, ELISA and leukocytes differential counts techniques were used. RESULTS: The data obtained showed that the highest densities of A. siro in the samples collected from flour mills in El-Minia governorate during the period of February 2009 to January 2010 were recorded during the spring and autumn seasons. In addition, significantly higher serum levels of INF-γ and IgE were found in rats treated with faeces than the other groups, especially the garlic-treated group. In contrast, IL-4 was lower in faeces-treated rats than the others; however, the native group had the highest level of IL-4. The leukocytes differential count showed that eosinophil and basophil percentages in faeces-inhaled group are higher than both the native group and the garlic-treated group. Statistical analysis of data showed significant difference between garlic-treated group and either control or faeces-treated group (P<0.05). CONCLUSIONS: The population of A. siro mites peaked in spring and autumn. The immunological disorder caused by repeated exposure to A. siro faeces might be modulated by garlic.

Antagonism of Protease Activated Receptor-2 by GB88 Reduces Inflammation Triggered by Protease Allergen Tyr-p3.

The occurrence of allergic diseases induced by aeroallergens has increased in the past decades. Among inhalant allergens, mites remain the important causal agent of allergic diseases. Storage mites- Tyrophagus putrescentiae are found in stored products or domestic environments. Major allergen Tyr-p3 plays a significant role in triggering IgE-mediated hypersensitivity. However, its effects on pulmonary inflammation, internalization, and activation in human epithelium remain elusive. Protease-activated receptors (PARs) are activated upon cleavage by proteases. A549 cells were used as an epithelial model to examine the PAR activation by Tyr-p3 and therapeutic potential of PAR-2 antagonist (GB88) in allergic responses. Enzymatic properties and allergen localization of Tyr-p3 were performed. The release of inflammatory mediators, phosphorylation of mitogen-activated protein kinase (MAPK), and cell junction disruptions were evaluated after Tyr-p3 challenge. Enzymatic properties determined by substrate digestion and protease inhibitors indicated that Tyr-p3 processes a trypsin-like serine protease activity. The PAR-2 mRNA levels were significantly increased by nTyr-p3 but inhibited by protease inhibitors or GB88. Protease allergen of nTyr-p3 significantly increased the levels of pro-inflammatory cytokines (IL-6 and TNF-α), chemokine (IL-8), and IL-1ß in epithelial cells. nTyr-p3 markedly increased phosphorylation of extracellular signal-regulated kinase (ERK)1/2 and MAP kinase. When cells were pretreated with GB88 then added nTyr-p3, the phosphorylated ERK1/2 did not inhibit by GB88. GB88 increased ERK1/2 phosphorylation in human epithelium cells. GB88 is able to block PAR-2-mediated calcium signaling which inhibits the nTyr-p3-induced Ca2+ release. Among the pharmacologic inhibitors, the most effective inhibitor of the nTyr-p3 in the induction of IL-8 or IL-1ß levels was GB88 followed by SBTI, MAPK/ERK, ERK, and p38 inhibitors. Levels of inflammatory mediators, including GM-CSF, VEGF, COX-2, TSLP, and IL-33 were reduced by treatment of GB88 or SBTI. Further, GB88 treatment down-regulated the nTyr-p3-induced PAR-2 expression in allergic patients with asthma or rhinitis. Tight junction and adherens junction were disrupted in epithelial cells by nTyr-p3 exposure; however, this effect was avoided by GB88. Immunostaining with frozen sections of the mite body showed the presence of Tyr-p3 throughout the intestinal digestive system, especially in the hindgut around the excretion site. In conclusion, our findings suggest that Tyr-p3 from domestic mites leads to disruption of the airway epithelial barrier after inhalation. Proteolytic activity of Tyr-p3 causes the PAR-2 mRNA expression, thus leading to the release of numerous inflammatory mediators. Antagonism of PAR2 activity suggests GB88 as the therapeutic potential for anti-inflammation medicine, especially in allergy development triggered by protease allergens.

Prevalence of Tyrophagus putrescentiae hypersensitivity in subjects over 70 years of age in a veterans' nursing home in Taiwan.

BACKGROUND: Domestic mites are present in house dust samples throughout the world. Reports have shown a high prevalence of Tyrophagus putrescentiae (Tp) sensitization in Europe and Asia, and its importance and clinical relevance in elderly subjects have grown rapidly. The main objective of this study was to investigate the prevalence of Tp sensitization in elderly subjects in a veterans' nursing home using mite allergen extracts and recombinant allergens. METHODS: A total of 199 subjects were enrolled in this study: 112 elderly subjects from a nursing home and 87 healthy young adults from the hospital staff as controls. The prevalence of Tp hypersensitivity was determined by specific IgE measurements and basophil histamine release. Immunoblotting with or without inhibition with Dermatophagoides pteronyssinus (Dp) was performed to identify the major allergens and species-specific allergen to Tp. RESULTS: It was determined that 39.3% (44/112) of the elderly population were sensitized to Tp and 17.9% (20/112) to Tp alone. There was a significantly higher prevalence of Tp hypersensitivity in elderly subjects in comparison with the young adult population. In the age association study of Tp and Dp sensitization, the elderly subjects were more sensitized to Tp than to Dp (p = 0.02). Among the elderly subjects with chronic obstructive pulmonary disease (COPD) 45.8% (11/24) were Tp sensitive. The major allergens, Tyr p 2 and Tyr p 3, were identified with molecular weights of 16 kDa (53%) and 26 kDa (50%) as determined by ELISA and immunoblot inhibition analyses. CONCLUSION: The prevalence of Tp sensitization was higher in elderly subjects, especially in patients with COPD. The high percentage of IgE-binding components to the allergens Tyr p 2 and Tyr p 3 indicated that both allergens may play a role in the pathogenesis of IgE-mediated allergic diseases in elderly populations.

Allergenicity of recombinant troponin C from Tyrophagus putrescentiae.

BACKGROUND: The storage mite, Tyrophagus putrescentiae, produces potent allergens, many of which have not been characterized. This study was undertaken to characterize the allergenicity of troponin C from T. putrescentiae. METHODS: A cDNA encoding 17.7 kDa troponin C, with homology to cockroach allergen Bla g 6, was identified from T. putrescentiae-expressed sequence tags. Recombinant troponin C was expressed and IgE responses to the recombinant protein were assessed in the presence and absence of 10 mM CaCl(2). Cross-reactivity between T. putrescentiae troponin C and Bla g 6 was tested using an inhibition ELISA. RESULTS: Recombinant T. putrescentiae troponin C shares 62.7-85.5% homology with troponin C from various arthropods. Sera from 5 of 47 subjects in our study group (10.6%) showed IgE binding to the recombinant protein. Interestingly, addition of 10 mM CaCl(2) increased the intensity of IgE binding approximately 2-fold. In an immune-inhibition ELISA with these sera, T. putrescetiae troponin C and Bla g 6 did not cross-react significantly. CONCLUSIONS: Troponin C is a new mite allergen with calcium-dependent IgE reactivity.