Blomia tropicalis, a mite whose time has come

Frequent IgE recognition of Blomia tropicalis allergen molecules in asthmatic children and young adults in equatorial Africa

Background

Asthma is not well investigated in equatorial Africa and little is known about the disease-associated allergen molecules recognized by IgE from patients in this area. The aim was to study the molecular IgE sensitization profile of asthmatic children and young adults in a semi-rural area (Lambaréné) of an equatorial African country (Gabon), to identify the most important allergen molecules associated with allergic asthma in equatorial Africa.

Methods

Fifty-nine asthmatic patients, mainly children and few young adults, were studied by skin prick testing to Dermatophagoides pteronyssinus (Der p), D. farinae (Der f), cat, dog, cockroach, grass, Alternaria and peanut. Sera were obtained from a subset of 35 patients, 32 with positive and 3 with negative skin reaction to Der p and tested for IgE reactivity to 176 allergen molecules from different allergen sources by ImmunoCAP ISAC microarray technology and to seven recombinant Blomia tropicalis (Blo t) allergens by IgE dot blot assay.

Results

Thirty-three of the 59 patients (56%) were sensitized to Der p and 23 of them (39%) were also sensitized to other allergen sources, whereas 9 patients (15%) were only sensitized to allergen sources other than Der p. IgE serology analyses (n=35) showed high IgE-binding frequencies to the Blo t allergens Blo t 5 (43%), Blo t 21 (43%) and Blo t 2 (40%), whereas the Der p allergens rDer p 2, rDer p 21 and rDer p 5 (34%, 29% and 26%) were less frequently recognized. Only few patients showed IgE reactivity to allergens from other allergen sources, except to allergens containing carbohydrate determinants (CCDs) or to wasp venom allergens (i.e., antigen 5).

Conclusion

Our results thus demonstrate that IgE sensitization to mite allergens is very prevalent in asthmatics in Equatorial Africa with B. tropicalis allergen molecules representing the most important ones associated with allergic asthma.

Sharing a bed with mites: preferences of the house dust mite Dermatophagoides farinae in a temperature gradient

House dust mites inhabit bed mattresses contaminating them with allergens. A strong temperature/moisture gradient exists in mattresses when it is used by humans daily. Here, we studied migration patterns of the mite Dermatophagoides farinae in continuous and time-discontinuous temperature gradients consisting of five sectors with 19-23, 23-28, 28-32, 32-36 and 36-41 °C, containing dye-labeled diets as an indicator of mite presence and feeding. The mites migrated through the sectors and fed on the labeled diets or stayed unfed. The numbers of mites with the same coloration in their guts and the numbers of unfed mites in the sectors were recorded. Unfed mites provided information on short-term temperature preferences. Apart from a control trial, two experiments were performed: (i) a constant 19-41 °C gradient for 24 h, and (ii) alternating cycles of the same temperature gradient (19-41 °C, 8 h) and room temperature (16 h) for 5 days to model the typical daily occupancy of bed by humans. In both experiments, fed mites preferred a sector with 32-36 °C, suggesting that in mattresses, house dust mites prefer to stay as close as possible to the resting human, thus maximizing allergen exposure. However, the number of unfed mites decreased with increased temperatures in the gradient. Experiment (ii) showed that the fed mites remained at the same optimal distance from the heat source, suggesting that they stay at the upper surface of the regularly used mattress, even when human was temporarily absent during the day. Unfed mites apparently hide deeper in mattresses as suggested by their avoidance of increased temperatures.

Subcutaneous allergen immunotherapy for asthma: A randomized, double-blind, placebo-controlled study with a standardized Blomia tropicalis vaccine

BACKGROUND

Sensitization to Blomia tropicalis (Bt) is very frequent in the tropics, and particularly in Cuba, being a significant cause of allergic asthma. Allergen immunotherapy (AIT) with Bt can be a therapeutic option, however, placebo-controlled clinical trials have not been reported.

OBJECTIVE

To assess the therapeutic effect and safety of AIT for asthma using a standardized allergen vaccine of B. tropicalis by subcutaneous route, in allergic asthmatic patients exposed and sensitized to this mite species.

METHODS

A double-blind, placebo-controlled Phase II trial was conducted in 35 adults (18 with treatment and 17 with placebo), with mild to moderate asthma, predominantly sensitized to Bt. AIT was administered subcutaneously in increasing doses from 4 to 6000 Biological Units using a locally manufactured standardized extract (BIOCEN, Cuba). Patient assessment was performed using symptom-medication score (SMS), peak expiratory flow and skin reactivity relative to Histamine as measured by skin prick test (SPT).

RESULTS

The 12-month treatment achieved a significant (p < 0.001) decrease of SMS. Symptom score showed only 41% (CI: 26-61) of placebo values, whereas medication was 34.5% (22.4%-63.3%). Treatment was regarded clinically effective in 67% of patients (OR 32; 95%CI: 17 to 102). The effect size on symptoms and medication was higher than has been reported with equivalent allergen dosages of D. pteronyssinus and D. siboney in Cuban asthmatic patients. Skin reactivity to Bt was also significantly reduced (p = 0.0001), increasing 148-fold the allergen threshold to elicit a positive skin test. This desensitization effect was specific to Bt and did not modify the reactivity to Dermatophagoides. The change of specific skin reactivity was significantly (p < 0.05) correlated to clinical improvement. All adverse events were local with a frequency of 2.4% of injections.

CONCLUSIONS

Subcutaneous AIT with Blomia tropicalis was effective and safe in asthmatic adults exposed and sensitized to this mite species in a tropical environment.

TRIAL REGISTRATION

Cuban Public Registry of Clinical Trials: RPCEC00000026 (WHO International Clinical Trial Registry Platform ICTRP).

Proteomic Analysis Reveals Allergen Variability among Breeds of the Dust Mite Blomia tropicalis

BACKGROUND

The dawn of the "omics" technologies has changed allergy research, increasing the knowledge and identification of new allergens. However, these studies have been almost restricted to Dermatophagoides spp. Although Blomia tropicalis has long been established as a clinically important source of allergens, a thorough proteomic characterization is still lacking for this dust mite.

OBJECTIVE

To increase knowledge of B. tropicalis allergens through proteomic analysis.

METHODS

Eleven in-bred lineages of B. tropicalis were obtained from 11 unique different pregnant females. Their somatic extracts were analyzed and compared with a commercially available extract by liquid chromatography tandem mass spectrometry (LC-MS/MS).

RESULTS

Considerable differences in the protein expression profiles were found among the breeds, and most of them displayed higher expression levels of major allergens than the commercially available extract. Blo t 2 was the most prominent allergenic protein in the analyzed extracts. Six identified allergens and 14 isoforms have not yet been recognized by IUIS. Conversely, 3 previously recognized B. tropicalis allergens were not found.

CONCLUSIONS

The clear impact of inbreeding on allergen content shown by our study leads us to conclude that the quantification and/or identification of allergens from in-bred lines should be routinely considered for mite cultivation in order to select breeds with higher amounts of major allergens. In this sense, LC-MS/MS may be a useful method to achieve this quality control for research and commercial purposes.

Serum specific IgE responses to inhalant allergens sensitization

Background: Serum specific immunoglobulin E (ssIgE) sensitization to common inhalant allergens has not been studied in Indonesia. This study aimed to evaluate specific IgE production of common inhalant allergens in patients with asthma and/or allergic rhinitis in Jakarta, Indonesia.Methods: This was a cross-sectional study in adult patients with respiratory allergy from September to December 2016 at Cipto Mangunkusumo Hospital, Jakarta. Patients were included if they showed at least one positive skin prick test (SPT) to environmental allergens. Serum specific IgE was assayed by using multiple allergosorbent methods. Inhalant allergens tested were dust mites, pollen, cockroach, animal dander, and mould. Serum IgE level more than 0.35 kU/L was considered positive.Results: One hundred subjects were enrolled (76% women). Dust mites made up 75% of sensitization, followed by cat/dog (31%), cockroach (27%), pollen (24%), and mould (6%). Almost all patients sensitized to cockroach, pollen, cat/dog epithelia and mould were also co-sensitized with dust mites. Twenty two percent of patients were negative to all tested allergens.Conclusion: IgE-sensitization to inhalant allergens varies widely in respiratory allergic patients. House dust and storage mites are the most common allergens. About one-fifth of the subjects did not show specific-IgE sensitization. Thus, this test should always be combined with SPT to diagnose allergy.

Regional Difference of Causative Pollen in Children with Allergic Rhinitis

The aim of this study was to investigate role of common pollen in Korean school-aged children with allergic rhinitis (AR) in 5 provinces (Incheon Metropolitan City-Gyeonggi Province, Chungcheongbuk-do, Gwangju Metropolitan City, Busan Metropolitan City, and Jeju Special Self-Governing Province), using a questionnaire and skin prick test, and to assess the differences among the residential regions. Among the enrolled 14,678 total children, 1,641 (22.0%) had AR. The sensitization rate to pollen (38.7%) was the second highest among examined allergens and significant differences were in the sensitization rates to trees, weeds, and grasses among the 5 provinces (P < 0.05). The sensitization to trees (25.2%) was the highest common among the pollen types and significant differences also were observed in the sensitization rates to alder, birch, Japanese cedar, oak, and elm among the 5 provinces. The sensitization rate to weeds (19.9%) was the second highest and significant differences were observed in the sensitization rate to Japanese hop, mugwort, and ragweed among the 5 provinces. The sensitization rate to house dust mite was 86.8%, the highest among examined allergens and that to Dermatophagoides farinae exhibited regional differences (P = 0.003) but not to D. farinae (P = 0.584). The sensitization rate to mold (13.5%) was the highest in Jeju and lowest in Busan, and a statistically significant difference was detected among the 5 provinces. These results support that examined pollen allergens are strongly associated with residential region due to regional causative pollen differences among children with AR within Korea to investigate the main pollen allergens.

[Blomia tropicalis: A house dust mite in the tropics]

INTRODUCTION

Blomia tropicalis is a mite that belongs to the superfamily of Glycyphagidae. Initially described as a storage mite, it is now considered as a house dust mite of tropical and sub-tropical areas.

STATE OF THE ART

Sensitization to this mite is very common in South America and Southeast Asia. Epidemiological studies have also found sensitization to this mite in Africa and Central America. Blo t 5 is the major allergen of B. tropicalis. Co-sensitization to other house dust mites such as Dermatophagoides pteronyssinus (Der p) and Dermatophagoides farinae (Der f) is very common. Cross-reactivity has been described but recombinant allergens revealed by molecular biology techniques do not explain this cross-reactivity. Sensitization to B. tropicalis seems to begin at the age of 36 months, the incidence increases until adulthood, and decreases from the age of 50. The involvement of B. tropicalis in allergic rhinitis and asthma is well described. It is also implicated in other allergic diseases. Few studies have assessed the therapeutic strategies available against this mite but immunotherapy is widely used.

PERSPECTIVES

Studies are needed to better understand the role of B. tropicalis in human diseases and to develop specific treatments.

Particularities of allergy in the Tropics

Allergic diseases are distributed worldwide and their risk factors and triggers vary according to geographical and socioeconomic conditions. Allergies are frequent in the Tropics but aspects of their prevalence, natural history, risk factors, sensitizers and triggers are not well defined and some are expected to be different from those in temperate zone countries. The aim of this review is to investigate if allergic diseases in the Tropics have particularities that deserve special attention for research and clinical practice. Such information will help to form a better understanding of the pathogenesis, diagnosis and management of allergic diseases in the Tropics. As expected, we found particularities in the Tropics that merit further study because they strongly affect the natural history of common allergic diseases; most of them related to climate conditions that favor permanent exposure to mite allergens, helminth infections and stinging insects. In addition, we detected several unmet needs in important areas which should be investigated and solved by collaborative efforts led by the emergent research groups on allergy from tropical countries.

Current status and future perspectives of immunotherapy in Latin America and Cuba

Most Latin-American countries use subcutaneous immunotherapy (SCIT) extracts from the United States and Europe and sublingual immunotherapy (SLIT) from Europe, with the exception of Argentina, Brazil, Cuba and Mexico. The number of researches on immunotherapy (IT) in Latin America has increased extensively in the last years. Only few Latin American countries have their own guidelines on IT, and, in general, the economic resources for medical research on IT are still low in the area. A global approach for the future of IT in Latin America includes to improve standardization, quality control and the production of allergen products, to develop IT guidelines and clinical investigation by the highest number of countries, to improve the regulatory status for allergens products in the area, and to expand IT accessibility for low-income patients. In Cuba, the first registered allergen vaccines were developed and registered in 2006: a standardized (in biologic units) and freeze dried product for SCIT, with a sublingual version developed in 2009. As much as 23.000 IT treatments were applied in 2011, all provided to patients free of charge. In 2012, Cuban researchers developed an IT vaccine with adjuvant for subcutaneous route, which uses Neisseria meningitidis proteoliposome as an adjuvant, added to the purified Dermatophagoides siboney major allergens: Der s1 and Der s2. Since December 2012, this vaccine is in Phase I clinical trial, evaluating its safety, tolerability and immunogenicity in asthmatic patients sensitized to this allergen. Cuban perspectives on IT includes to work on new indications for IT, to investigate the preventive effect and cost-effectiveness for the current vaccines, to develop new products with mixed formulas of house dust mites for SLIT, to complete the phase I and II clinical study for dust mite plus adjuvant vaccine, to develop allergen vaccines for fungi allergy and to complete the Cuban guideline for allergen IT management.

[Sensitization to Blomia tropicalis among asthmatic patients in Yaoundé, Cameroon]

INTRODUCTION

The aim of this study was to determine the prevalence and investigate associated factors for Blomia tropicalis (BT) sensitization in adolescent and adult patients with asthma in Yaoundé (Cameroon).

METHODS

We performed a cross-sectional study of 18 months duration (January 2012 to June 2013). All asthmatic patients who were seen for a consultation during the study period and who had a skin prick testing for perennial aeroallergens were included in the study.

RESULTS

Two hundred and one asthmatic patients (132 female patients, 65.7%) with median age (1st-3rd quartiles) of 35 (20-51.5) years were included in the study. Ninety-six (47.8%) patients had positive skin tests to BT. BT sensitization was associated with sensitization to two other dust mites (Dermatophagoides pteronyssinus [DP] and Dermatophagoides farinae [DF]) in 75 (86.2%) patients. The only clinical factor associated with BT sensitization was the presence of persistent rhinitis (odds ratio [confidence interval 95%]: 2.06 [1.12-3.81]). The independent allergenic factors associated with BT sensitization were sensitization to DP (3.49 [CI 95%: 1.49-8.19]), to DF (4.88 [CI 95%: 2.10-11.36]) and to German cockroach (4.16 [CI 95%: 1.72-10.09]).

CONCLUSION

Blomia tropicalis sensitization is common in asthmatic patients in Yaoundé. It occurs most often in the context of sensitization to multiple aeroallergens, particularly with sensitization to other dust mites and German cockroach.

Respiratory allergy to moth: the importance of sensitization to Bombyx mori in children with asthma and rhinitis

OBJECTIVE

this study aimed to prepare a silkworm moth (Bombyx mori) antigenic extract and to perform skin prick tests with this extract in patients with allergic respiratory diseases; to evaluate serum specific immunoglobulin E (IgE) to Bombyx mori using ImmunoCAP® system and to report the frequency of positivity between the two methods and with clinical data.

METHODS

this was a cross-sectional study with 99 children and adolescents diagnosed with asthma and/or allergic rhinitis, who had skin reactivity to at least one of the six aeroallergens tested. Clinical data were evaluated: skin prick tests with Bombyx mori in-house extract, and total and specific IgE analysis using ImmunoCAP® were performed.

RESULTS

the frequency of Bombyx mori specific IgE was found to be 52.5% and 60% using the skin prick test and ImmunoCAP®, respectively. An association between a positive skin test for Bombyx mori and the presence of allergic rhinitis, atopic dermatitis, and urticaria was observed, but the same was not true for asthma or allergic conjunctivitis. There was no relation with the severity of asthma or rhinitis symptoms.

CONCLUSIONS

a high frequency of sensitization to Bombyx mori was observed in a selected population of patients with respiratory allergic diseases in the city of Curitiba, state of Paraná, Brazil. The extract prepared from the wings of this moth species is effective in demonstrating this sensitivity.

Identification of allergenic component Tyr p 8 from Tyrophagus putrescentiae and cross-reactivity with Der p 8

Group 8 mite allergens exhibit sequence homology to glutathione S-transferases (GSTs), such as that from Dermatophagoides pteronyssinus (Der p 8). GSTs have been identified as important allergens in studies of allergens from house dust mites, cockroaches, and fungi. Our objective was to purify the native group 8 allergen from Tyrophagus putrescentiae (nTyr p 8) and generate recombinant Tyr p 8 (rTyr p 8) for immunological characterization. The allergenicity was determined by antibody recognition, IgE inhibition, and triggering of the basophil-sensitized release of histamine, using T. putrescentiae hypersensitivity sera. The results showed that the mRNA transcript of nTyr p 8 is 657 bp long, contains 218 amino acids with a molecular mass of 26 kDa, and exhibits 83% sequence homology to Der p 8. Serum samples from the allergic patients with an IgE-positive response to T. putrescentiae were analyzed to determine their IgE response to rTyr p 8. The results showed that the sera of 48 subjects (45.3%) had specific IgE against rTyr p 8. However, sera of only 19 subjects (17.9%) had specific IgE against rTyr p 8 after D. pteronyssinus absorption. Histamine release was observed from T. putrescentiae-allergic subjects in the presence of rTyr p 8. Both the nTyr p 8 and T. putrescentiae crude extract had been demonstrated to possess GST enzymatic activity. Although the specific binding of serum IgE to rTyr p 8 was only 17.9%, which indicates that rTyr p 8 was not a major allergen, the positive response to rTyr p 8 was due to the cross-reactivity with Der p 8. The group 8 mite allergen might be of use in the design of a suitable allergen for diagnosis and for the development of novel immunotherapies.

Prevalence of sensitization to Blomia tropicalis among young adults in a temperate climate

BACKGROUND

There are no previous population-based studies assessing the prevalence of Blomia tropicalis (BT). This investigation analyzes the prevalence of sensitization to BT and its contribution to asthma and related diseases among young adults in the Canary Islands.

MATERIAL AND METHODS

From a random sample of 9506 adults, aged between 20 and 44, who had previously answered a short respiratory questionnaire, a further 20% random sample was drawn. All participants filled in an extensive questionnaire, and they underwent spirometry and bronchial hyperresponsiveness (BHR) test and skin testing to several allergens as well as the determination of total IgE and specific IgE.

RESULTS

The prevalence of positive skin tests to BT was 13.8% (95% confidence interval [CI] 10.6-17.9%) and that of BT-specific IgE 17.9% (95% CI 14.2-24.5%). Sensitization to BT (positive skin tests or positive specific IgE) was 20.9% (95% CI 16.9-25.5%). Most of the subjects sensitized to BT were also sensitized to Dermatophagoides pteronissimus; however, only 7% displayed monosensitization to BT. Among subjects who exhibited BHR, sensitization to BT reached 46.7% (95% CI 32.7-60.9%), among those with asthma 50% (95% CI 26.8-73.2%), in subjects with rhinitis 37.2% (95% CI 28.1-47.6%), and in those suffering from dermatitis 25.9% (95% CI 18.7-34.5%). A strong association of BT sensitization with BHR and asthma before and after 15 years was found.

CONCLUSION

The prevalence of sensitization to BT among young adults in the Canary Islands is high, and it displays a close relationship with allergic respiratory diseases and dermatitis.

Impact of Dermatophagoides pteronyssinus mite body raw material on house dust mite allergy diagnosis in a Serbian population

House dust mite (HDM) allergy has different clinical and immunological patterns in different geographic regions. The impact of raw material of commercial Dermatophadoides pteronyssinus (Acari: Pyroglyphidae) mite bodies on the quality of allergen extracts for allergy diagnosis in the Serbian population has not been previously evaluated. House dust mite bodies obtained from manufacturers in Europe, South America and Australia were used in the preparation of allergen extracts for in vivo diagnosis and serological analysis in a group of 14 HDM-allergic adults. In the group of mite-allergic patients, there was no statistically significant difference in skin test reactivity (Wilcoxon matched pairs test) among the three HDM body extract preparations. In a CAP inhibition assay, two extracts (A and C) achieved maximum inhibition of >90%, whereas extract B demonstrated a different inhibition slope and lower inhibition potential (80%). However, a remarkable difference in immunoglobulin E reactivity using Western blot analysis with individual patients' sera was observed in one of the preparations (extract B). These findings emphasize the need for the careful selection of starting material for the preparation of HDM diagnostic reagents intended for use in patients from geographically distinct regions as these preparations can have implications on the selection criteria for patient-tailored immunotherapy of HDM allergy.

House dust mite allergens in asthma and allergy

IgE antibodies in house dust mite (HDM) allergy follow a predictable pattern. Half are directed against two dominant allergens and the remainder largely against four midpotency allergens. This hierarchical pattern is not changed by the titre of the IgE response or severity of disease. The structures of these allergens are known and they can be produced as authentic recombinant allergens. There is also evidence that the allergenicity is augmented by the biological activity of the key allergens, validating them as targets for vaccination. Collectively, these developments should facilitate the development of new diagnostics, improve immunotherapy and allow vaccination with defined reagents. Highly purified recombinant polypeptides representing the important mite allergens are now available so that informative and reproducible experiments can be performed with mite allergens in place of poorly defined and variable extracts.

Household arthropod allergens in Korea

Arthropods are important in human health, which can transmit pathogens to humans, parasitize, or produce important allergens. Allergy prevalence becomes higher in Korea recently as well as other developed countries in contrast to a decrease of infectious diseases. Allergic diseases caused by household arthropods have increased dramatically during the last few decades since human beings spend more their time for indoor activities in modernized life style. Household arthropods are one of the most common causes of allergic diseases. Biological characterization of household arthropods and researches on their allergens will provide better understanding of the pathogenesis of allergic diseases and suggest new therapeutic ways. Therefore, studies on arthropods of allergenic importance can be considered one of the major research areas in medical arthropodology and parasitology. Here, the biology of several household arthropods, including house dust mites and cockroaches, the 2 most well known arthropods living indoor together with humans worldwide, and characteristics of their allergens, especially the research activities on these allergens performed in Korea, are summarized.

The alimentary canal of Blomia tropicalis (Acari: Astigmata: Echymopodidae): the application of three-dimensional reconstruction technology

The domestic mite species Blomia tropicalis is an important indoor allergen source related to asthma and other allergic diseases in tropical and subtropical regions. Here, we describe the alimentary canal of B. tropicalis with the particular application of three-dimensional reconstruction technology. The alimentary canal of B. tropicalis resembles the typical acarid form consisting of the cuticle-lined foregut and hindgut separated by a cuticle-free midgut. The foregut is divided into a muscular pharynx and an esophagus. The midgut is composed of a central ventriculus, two lateral caeca, a globular colon and a postcolon with two tubiform postcolonic diverticula. The most common cells forming the epithelium of ventriculus and caeca are squamous and cuboidal. The globular cells contain a big central vacuole in the posterior region of the caeca. The epithelium of the colon and postcolon has significantly longer microvilli. The anal atrium is a simple tube with flattened epithelial cells. The spatial measurements of the three-dimensional model suggest that the paired caeca and central ventriculus occupy 55.1 and 34.6%, respectively, of the total volume of the alimentary canal and may play the key role in food digestion.

Characterization of Der p 21, a new important allergen derived from the gut of house dust mites

BACKGROUND

The house dust mite (HDM) Dermatophagoides pteronyssinus is a major allergen source eliciting allergic asthma. The aim of the study was to identify new important HDM allergens associated with allergic asthma.

METHODS

A cDNA coding for a new mite allergen, designated Der p 21, was isolated using immunoglobulin E (IgE) antibodies from patients with allergic asthma out of a D. pteronyssinus expression cDNA library and expressed in Escherichia coli.

RESULTS

Circular dichroism analysis of the purified allergen showed that rDer p 21 (14 726 Da) is one of the few mite allergens with an alpha-helical secondary structure. The protein exhibited high thermal stability and refolding capacity, and, as determined by small angle X-ray scattering, formed a dimer consisting of two flat triangles. rDer p 21 bound high levels of patients' IgE antibodies and showed high allergenic activity in basophil activation experiments. Rabbit anti-Der p 21 IgG antibodies inhibited mite-allergic patients' IgE binding and allowed the ultrastructural localization of the allergen in the midgut (epithelium, lumen and faeces) of D. pteronyssinus by immunogold electron microscopy. Der p 21 revealed sequence homology with group 5 mite allergens, but IgE and IgG reactivity data and cross-inhibition studies identified it as a new mite allergen.

CONCLUSIONS

Der p 21 is a new important mite allergen which is liberated into the environment via faecal particles and hence may be associated with allergic asthma.

In vivo and in vitro allergenicity of the domestic mite Chortoglyphus arcuatus

BACKGROUND

Chortoglyphus arcuatus is frequently identified in mattress dust samples in coastal areas of northern Spain.

OBJECTIVES

To establish the prevalence of positive skin test reactions to C. arcuatus and to analyze its allergenicity and cross-reactivity.

METHODS

One hundred thirty-eight consecutive patients entered the study. The main referred symptoms were rhinoconjunctivitis and asthma. Skin tests were performed with extracts of Dermatophagoides pteronyssinus, Lepidoglyphus destructor, Tyrophagus putrescentiae, C. arcuatus, and Glycyphagus domesticus. Enzyme-linked immunosorbent assay inhibition experiments were conducted with the different mite species and immunoblots with serum samples from 31 sensitized patients. Conjunctival provocation tests were performed in 10 patients with C. arcuatus-positive skin test reactions and in 9 with negative results; all the patients had positive skin test reactions to D. pteronyssinus.

RESULTS

The prevalence of positive skin test reactions to D. pteronyssinus was 94.2% and to C. arcuatus was 58%. There was a significant correlation between the number of mites to which patients were sensitized and the time of disease evolution (P = .02). Results of enzyme-linked immunosorbent assay inhibition experiments suggested minimal cross-reactivity between C. arcuatus and D. pteronyssinus. Immunoblot results confirmed specific IgE binding to several bands. Conjunctival test results were positive in 9 of 10 C. arcuatus-positive individuals and slightly positive in 2 of 9 C. arcuatus-negative, D. pteronyssinus-positive individuals.

CONCLUSIONS

There is a high prevalence of sensitization to C. arcuatus in northern Spain. Sensitization to this species should be considered of clinical significance. There is minimal cross-reactivity between C. arcuatus and D. pteronyssinus.

Mite allergens

There is an increasing awareness of the health implications of mite sensitivity, as it is closely related to asthma. Mite allergy constitutes a complex worldwide problem, with sanitary and economical implications. Not only are mite species present in house dust, producing potent allergens, but other, less studied species are also responsible for significant allergic reactions in occupational settings. In this review, we focus on the growing number of mite species that are implicated in allergic cutaneous and respiratory diseases in humans. Mite allergy is not restricted only to the human "indoor" environment, because numerous reports clearly demonstrate that many species that can induce sensitization and symptoms are encountered in occupational settings. An important component of allergy research is the evaluation of the allergenic cross-reactivity to verify to what extent different mite species have unique, species-specific, or cross-reactive allergens. The results of these investigations have important clinical consequences for the diagnosis and treatment of allergic diseases. Internationally standardized mite extracts are needed to compare sensitization rates around the world and clearly establish risk factors associated with sensitization and asthma. In spite of recent controversial results, a significant reduction in the exposure to mite allergens continues to be an important challenge and one of the main goals in the treatment of mite-induced respiratory symptoms. In many cases, this reduction must be achieved in the workplace as well as in the home environment.

Risk factors of allergic rhinitis: genetic or environmental?

Allergic diseases such as allergic rhinitis represent a global health problem, affecting 10%-25% of the world population. There is clear evidence to support the concept that allergic diseases are influenced by genetic predisposition and environmental exposure. Polymorphisms of candidate genes have been associated with clinical expression of these diseases. However, characterization of these susceptibility markers in discriminating an "allergic individual" from the general population has not yet been achieved, and the value of how this genetic insight leading to recognition of specific subtypes of these disorders still needs to be confirmed. Environmental factors (eg, air pollution and bacterial/viral infection) also play an important role in the development of the diseases. A number of epidemiologic studies have supported the "hygiene hypothesis", which is based on the observations that Th1 responses induced by microbial stimulation can counterbalance allergen-induced Th2 responses. Future studies are needed to identify the key genes or their haplotypes for atopic phenotypes and to investigate the interactions between genetic and environmental factors that influence the complex trait of allergic diseases. This will help us to further understand the etiology of the diseases and develop new avenues for genetically oriented diagnosis and more effective measures of prevention and intervention.