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

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

Cat sensitization according to cat window of exposure in adult asthmatics

Background In adults, there is limited information on tolerance to cat, which may be reflected by high IgG₄ without IgE sensitization. Early exposure to cat may play a critical role.
Objective The aim was to assess among adults the association of Fel d 1 IgG₄, Fel d 1 IgE, skin prick test (SPT) response to cat and pet-related symptoms in relation to exposure to cat considering the period of exposure.
Methods SPT response to cat, specific IgE and IgG₄ to Fel d 1 were assessed in 167 asthmatics recruited in chest clinics (40 years of age in average) from the French Epidemiological study on the Genetics and Environment of Asthma (EGEA). Childhood and/or current exposure to cat were studied retrospectively.
Results IgG₄ was higher in relation to current cat exposure (0.53 vs. 0.09 ng/mL; P <0.001) and higher in women than in men. The period of cat exposure was significantly related to Fel d 1 IgE, the IgE/IgG₄ pattern and cat weal size. The lowest values of Fel d 1 IgE, cat weal size, pet-related nasal or respiratory symptoms were observed in those with both childhood and current exposure as well as the highest proportion of the IgE⁻/IgG₄⁺ pattern observed in 1.4%, 4.0%, 38.1% and 12.5% of those with −/−, +/−, +/+, −/+ childhood/current exposure, respectively.
Conclusions Adult asthmatics exposed to cats since childhood present an immunologic pattern with high IgG₄ and low IgE. Continuous exposure may maintain a state of immunological tolerance to cat.     

Importance of including Blomia tropicalis in the routine diagnosis of Venezuelan patients with persistent allergic symptoms

Background:  Blomia tropicalis is a common mite found in the house dust of many tropical countries including Venezuela. The prevalence of skin test and specific serum immunoglobulin (Ig)E reactivity to B. tropicalis in Venezuela has not been previously evaluated.
Methods:  In the present study we evaluated the skin reactivity by skin prick test and specific IgE by a multiple antigen blot assay, against B. tropicalis and Dermatophagoides pteronyssinus , in a group of 115 subjects who attended the Allergy Clinic of the Institute of Biomedicine, Caracas, Venezuela, and we studied possible cross reactions between similar proteins of these two mites.
Results:  One hundred and six patients with persistent allergic respiratory symptoms showed a positive skin prick test to at least one of the mite extracts, with the frequency of positive reactions to B. tropicalis being as high as to D. pteronyssinus . Twelve patients reacted only to D. pteronyssinus and 13 different patients only to B. tropicalis . Specific IgE to each of the mite extracts was found with similar frequency, and the results coincided with the skin test reactivity.
Conclusions:  The study indicated the importance of including B. tropicalis in routine diagnostic testing in tropical and sub-tropical situations.     

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

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

Allergen sensitization and exposure to irritants in infancy

We investigated the relationship between residence in the neighbourhood of an aluminium smelter and the prevalence of atopy in schoolchildren (7–13 years of age). Atopy was assessed in 556 of the 620 participants by a skin prick test with eight common aeroallergens. The median exposures to sulphur dioxide and fluoride during the pollen season in the age interval 19–36 months were 24 and 3.1 μg/m³ in the spring and 20 and 3.3 μg/m³ in the summer, respectively. The odds ratio (OR) of having atopy was 2.0 (95% CI: 1.2–3.3) in those children who had lived in the index area for 7 years or more compared with those who had lived there less than 7 years (cumulative effect). The OR of atopy was 2.5 (1.44.4) in those who had lived in the index area during the age interval of 19–36 months compared with rural residence during this age-interval (age-specific effect). When the age-specific effect and the cumulative effect were compared in the same logistic model, the former decreased to 1.1 (0.43.0), whereas the latter was 2.2 (0.7–6.6). The results indicate that exposure to these low levels of irritants during early childhood increases allergen sensitization in children.     

Age-dependency of sensitization to aero-allergens in asthmatics

Skin reactivity (intracutaneous test) to histamine and allergens was studied cross-sectionally in a Dutch asthmatic patient population from childhood to old age (4–75 years). It was found that the histamine skin reactivity rose significantly (p<0.05) during childhood, was significantly higher in the 10–15-year age group, and was constant between 20 and 75 years of age. The mean wheal index (histamine ratio) of all allergens was constant during childhood, and decreased after the age of 25 for grass pollen and house-dust mite and after the age of 15 for the other allergens. The prevalence of a positive skin test decreased with age, except for grass pollen. During childhood the indoor allergens, cat dander and house-dust mite, were the most important, while after the age of 15 sensitivity to an outdoor allergen, grass pollen, increased markedly. At all ages house-dust mite was the most important allergen. After the age of 25 the prevalence of every allergen declines. The prevalence of a positive skin test to Cladosporium was unexpectedly high in childhood (10–40%). It can be concluded that the prevalence of a positive skin test declines with age, except for grass pollen. The degree of sensitization in asthmatics peaked in the age groups between 20 and 40 and sensitivity to indoor allergens developed earlier than sensitivity to outdoor allergens. Clinical aspects Skin tests producing immediate wheal and flare reactions are widely used for the detection of allergy in patients referred for asthmatic prohlems. For good evaluation of a skin test it is important to know the influence of age on skin reactivity. In this study we evaluated the wheal index (histamine ratio) of the skin test and the prevalence of a positive skin test using a set of 6 standardized common aero-allergens and one non-standardized, cross-sectionally, in a Dutch asthmatic patient population (4–75 years). Since standardized allergens were used, the prevalences hetween the different allergens could be compared. It was found that the histamine skin reactivity peaked at the age of 15 and was lower in all other age groups. Therefore, when comparing skin test results in different age groups, it may be important to use wheal indices instead of absolute values. Except for grass pollen the prevalence of a positive skin test decreased with age. During childhood indoor allergens are the most important, while after the age of 15 sensitivity towards outdoor allergens increases. Honse-dust mite is the most important allergen at all ages. Surprisingly, a fungal allergen (Cladosporium herharuni) was found to he of significance in young children (prevalence 10–40%). The prevalence of at least one positive skin test in asthmatics declined with age, while the degree of sensitization (expressed as the mean wheal index) peaked in young adults (20–40 years of age).     

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

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

Sensitization to Dermatophagoides siboney, Blomia tropicalis, and other domestic mites in asthmatic patients

Mite species adapted to warm, humid climates are commonly found in house dust in the tropics. In Cuba, Dermatophagoides pteronyssinus, D. siboney , and Blomia tropicalis are the most common and abundant mite species in house dust. To investigate the pattern of Sensitization of Cuban asthmatic patients to common mite species, we skin-prick-tested (SPT) 148 patients with a clinical history of asthma and possible mite allergy, and determined specific IgE antibodies against mite allergens ( D. pteronyssinus, D. farinae, D. siboney, B. tropicalis, Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae , and Glycyphagus domesticus ). The prevalence of positive SPT was high to D. siboney (88%), D. pteronyssinus (87%), A. siro (85%), B. tropicalis (85%), and D. farinae (83%). The largest skin reactions were obtained with D. siboney and B. tropicalis extracts. The skin test response to the D. siboney extract correlated to those of D. farinae, D. pteronyssinus, B. tropicalis , and A. siro. The highest IgE levels were found to Dermatophagoides species and B. tropicalis. IgE to D. siboney and B. tropicalis were found in 97% and 96% of the patients, respectively. The prevalence of specific IgE to the other mites studied varied from 46 to 65%. D. siboney and B. tropicalis are important sensitizers among asthmatic patients in Cuba.     

A comparison of the prevalence of sensitization to Aspergillus antigens among asthmatics in Cleveland and London

A survey of the frequency of sensitization to Aspergillus antigens was conducted in a group of asthmatics in Cleveland and compared with a group of asthmatics in London, using common antigens for testing purposes. The two groups were comparable except for earlier onset, longer duration of asthma, and a larger number of males in the London group. Twenty-eight per cent of the asthmatics from Cleveland and 23% from London had immediate skin reactivity to Aspergillus. Seven and one-half percent from the Cleveland group and 10.5% of the London group had Aspergillus precipitins in the serum. Aspergillus skin test reactivity was related to the severity of airways obstruction (p < 0.01) but was not influenced by other factors. We conclude that sensitization to Aspergillus antigens occur with equal frequency in both the United States and the United Kingdom.     

The upper and lower airway responses to nasal challenge with house-dust mite Blomia tropicalis

BACKGROUND: The house dust mite Blomia tropicalis (B. tropicalis) was found to be the most prevalent domestic mite in Singapore. However, its pathogenicity in allergic airway diseases remains to be investigated. METHODS: Twenty adults with persistent allergic rhinitis (PAR) were studied. Five had a history of asthma, and all were asymptomatic except one who was under treatment with low-dose inhaled corticosteroid. Nasal challenge was carried out by nasal spray with phosphate-buffered saline (PBS) and with increasing concentrations of crude B. tropicalis extracts (0.6, 6.0 and 60 micro g/ml) at 15 min intervals. Subjective symptom scores and absolute number of sneezes were recorded together with objective measurements of spirometry (forced expiratory volume in 1 s, FEV1) and acoustic rhinomanometry (volume of the nasal cavity). These were performed at baseline, 5 min after each incremental challenge, and 30 min, 1 h, 3 h, 5 h and 7 h after the last challenge. Meanwhile, concentrations of mediators in nasal secretions (tryptase, leukotriene C4 (LTC4) and eosinophil cationic protein (ECP)) were measured in nasal aspirate samples at similar time intervals. An identical (control) challenge procedure with PBS alone was repeated in seven patients after a washout period of at least 2 weeks. RESULTS: Significant increases in the subjective and objective nasal symptoms, together with a significant increase of tryptase and LTC4 concentrations in nasal secretion, were found 5 min after each challenge with B. tropicalis, but not with PBS. There was no definitive pattern of the late-phase nasal response in either subjective symptoms or objective measurements. Three patients (3/5) with a history of asthma showed a fall in FEV1 readings (33%, 22% and 11% from baseline, respectively) at 7 h post challenge with concomitant mild wheezing in the night. CONCLUSIONS: Our study demonstrates direct evidence of allergic nasal response to B. tropicalis in sensitized adults. It shows that nasal provocation may also provoke concomitant asthmatic symptoms during the late-phase reaction, especially in people with a history of asthma.     

Sensitization profiles of Malaysian and Singaporean subjects to allergens from Dermatophagoides pteronyssinus and Blomia tropicalis

BACKGROUND: The house dust mites Dermatophagoides pteronyssinus (Der p) and Blomia tropicalis (Blo t) are the most common house dust mite species in Southeast Asia. To date, there have only been a few studies on the sensitization profile of the general populations in Southeast Asia to house dust mites. The aim of this study was to determine the profiles of Der p and Blo t sensitization among Singaporean and Malaysian subjects. METHODS: Enzyme-linked immunosorbent assay was used to detect specific IgE to Der p and Blo t mite crude extracts as well as purified Der p 1, Der p 2 and Blo t 5 allergens. Sera used were from 229 Singaporean subjects (124 with rhinitis, 105 without rhinitis) and 143 Malaysian subjects (94 adults and 49 children with asthma). RESULTS: The sensitization profile of rhinitis subjects to the dust mite allergens used in this study was as follows: Blo t extract positive: 91/124 (73%); Blo t 5 positive: 62/124 (50%); Der p extract positive: 61/124 (49%); Der p 1 positive: 53/124 (43%); Der p 2 positive: 45/124 (36%). The nonrhinitis subjects' sensitization profile was as follows: Blo t extract positive: 60/105 (57%); Blo t 5 positive: 24/105 (23%); Der p extract positive: 38/105 (36%); Der p 1 positive: 14/105 (13%); Der p 2 positive: 17/105 (16%). The study of Malaysian asthmatic adults showed that 39% of them were sensitized to Der p 1, 32% to Der p 2 and 37% to Blo t 5. Among the asthmatic children, sensitization to Blo t 5, Der p 1 and Der p 2 was 90, 57 and 39%, respectively. CONCLUSION: This study clearly revealed that dual sensitization to B. tropicalis and D. pteronyssinus is common in the general populations of Singapore and Malaysia. Sensitization to Blo t 5 is more prevalent than to Der p 1 and Der p 2.     

IgE, IgG1, and IgG4 antibody responses to Blomia tropicalis in atopic patients

BACKGROUND: Allergens from house dust mites (HDMs), Dermatophagoides pteronyssinus and Blomia tropicalis are clinically relevant in atopic respiratory diseases in tropical countries. AIMS OF THE STUDY: To evaluate immunoglobulin (Ig)E, IgG1, and IgG4 antibody responses to B. tropicalis in Brazilian atopic patients. METHODS: About 110 patients with allergic rhinitis with/without asthma and 33 control subjects underwent skin prick testing (SPT) with HDM extracts, and their sera were tested for IgE and IgG subclass antibodies to D. pteronyssinus and B. tropicalis by enzyme-linked immunosorbent assay (ELISA) and immunoblotting. RESULTS: Most patients (56%) had positive SPT to B. tropicalis extract (B. tropicalis+ group), although 51% were reactive to both B. tropicalis and D. pteronyssinus and 6% were sensitized to B. tropicalis only. IgE-ELISA detected 43%B. tropicalis positivity with high-specific IgE levels in B. tropicalis+ patients. Specific IgG4 levels were higher in B. tropicalis+ than B. tropicalis- groups and correlated with specific IgE levels. The IgG1 levels to B. tropicalis were higher in patients than controls. The major allergenic B. tropicalis components recognized by B. tropicalis+ patient sera were the 54, 66, and 68 kDa proteins. The IgG4-binding protein profiles closely resembled that of IgE. The IgG1 antibodies recognizing multiple B. tropicalis protein species were detected in sera of all three patient groups. CONCLUSIONS: A large percentage of our allergic patients are B. tropicalis+. They are more frequently sensitized to high-molecular weight (HMW) B. tropicalis components than the major low-molecular weight (11-15 kDa) allergens detected in other studies. The results suggest that HMW B. tropicalis antigenic components are potential candidates for evaluating allergen exposure and sensitization, and for immunotherapy treatment.     

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

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

Allergen sensitization evaluation and allergen avoidance education in an inner-city adult cohort with persistent asthma

BACKGROUND: Asthma morbidity, mortality, and health services utilization are highest among inner-city populations. The National Asthma Education and Prevention Program Expert Panel recommends that all patients with moderate and severe persistent asthma be evaluated for sensitization to environmental allergens. OBJECTIVE: This study examined whether a cohort of inner-city adults hospitalized with asthma had been evaluated for allergen sensitization, received avoidance counseling, and followed through on these recommendations. METHODS: One hundred sixty-nine eligible patients who were part of a prospective cohort of all adults hospitalized in an inner-city hospital over a consecutive 12-month period completed a questionnaire to assess allergen sensitization evaluation, avoidance education, and adherence. RESULTS: Overall, 60% of patients had ever been evaluated for allergen sensitization. Among those who were evaluated, 94.0% were sensitized to at least one antigen: 91.5% to dust mites, 90.5% to outdoor allergens, 77.9% to cats, 69.5% to dogs, 68.4% to molds, and 61% to cockroaches. Approximately half of the patients sensitized to dust mite (55.1%) or mold (52.8%) were given any avoidance-abatement advice. Patient adherence to this advice was highly variable. Allergen sensitization evaluation was more likely among women (odds ratio, 3.05; CI, 1.64-8.64) and those who use oral steroids most or all of the time (odds ratio, 7.14; CI, 2.25-22.56) and less likely among smokers (odds ratio, 0.26; CI, 0.11-0.61). CONCLUSION: In this population of inner-city adults hospitalized with asthma, the quality of allergen sensitization evaluation, avoidance education, and patient adherence with these recommendations was suboptimal.     

Allergen sensitization and bronchial hyper-responsiveness to adenosine monophosphate in asthmatic patients

BACKGROUND: Indirect bronchoprovocation using adenosine monophosphate (AMP) is related to atopic phenotype expression. OBJECTIVE: To evaluate the putative relationship between skin prick allergen sensitization and bronchial hyper-responsiveness to AMP in a retrospective cross-sectional database analysis. METHODS: We retrospectively evaluated two groups of non-smoking asthmatics (forced expiratory volume in 1 s (FEV)1>/=60% predicted) who were reactive (responders) or unreactive (controls) to inhaled AMP. The main outcome measure was the difference in sensitization to individual allergens and the total atopic load according to the presence or absence of bronchial hyper-responsiveness. RESULTS: We initially identified 180 (44%) non-smoking asthmatics with PC20/=1600 mg/mL. For those who had a skin prick test, the responders (n=151) and controls (n=151) were found to be matched for age, sex, inhaled corticosteroid dose and number of patients using inhaled corticosteroids. There were significant differences in the number of responders vs. controls in terms of sensitization to house dust mite (77% vs. 62%, P=0.004), aspergillus (19% vs. 9%, P=0.014), cat (61% vs. 48%, P=0.028), total atopic load (493 vs. 380 positive tests, P<0.001) and forced mid-expiratory flow (60% vs. 68% predicted, P<0.001). CONCLUSION: Sensitization to common aeroallergens increased the likelihood of bronchial inflammation as reflected by bronchial hyper-responsiveness to inhaled AMP, independently of both FEV1 or inhaled corticosteroid use. This in turn suggests an association between allergen exposure and AMP responsiveness in asthmatics. Further prospective long-term evaluation is indicated to assess whether allergen avoidance strategies can modify the airway response.     

Association between severity of atopic eczema and degree of sensitization to aeroallergens in schoolchildren

BACKGROUND: A subgroup of patients with atopic eczema exhibits aggravation through contact with aeroallergens. Little is known from population-based studies, however, about the association between the severity of eczematous skin disease and the degree of aeroallergen sensitization. OBJECTIVE: We sought to investigate the relationship between IgE-mediated allergic sensitization to aeroallergens and severity of atopic eczema in schoolchildren. METHODS: A nested case-control analysis on atopic eczema was performed on the basis of a cross-sectional study of 2201 East German schoolchildren aged 5 to 14 years. Atopic eczema and its severity was identified by dermatologic examination. Total and allergen-specific IgE antibodies to grass and birch pollen, Cladosporium herbarum, Dermatophagoides pteronyssinus, and cat epithelium in serum were determined, and additional information was obtained by means of standardized questionnaire. RESULTS: The overall prevalence of actual atopic eczema was 2.5%. Thirty-seven percent of the children were sensitized to at least one allergen. Children with atopic eczema were significantly more often sensitized than those without skin disease (75.0% vs 36.3%; odds ratio, 5.27; 95% confidence interval, 2.54-11.15). This was observed for each single allergen. The prevalence of atopic eczema increased significantly with increasing RAST class (chi(2) trend test for each allergen, P <.0001). Also, the prevalence of sensitization increased with the severity of the disease (chi(2) trend test for each allergen, P <.0001). This association was pronounced for house dust mite and cat allergen. Multiple linear regression analyses showed significant associations between the severity score of atopic eczema and concentrations of allergen-specific IgE to dust mite (P =.032) and cat (P =.014) allergens after adjustment for sex, age, location, and parental predisposition. CONCLUSIONS: The degree of sensitization is directly associated with the severity of atopic eczema. We speculate that early epicutaneous sensitization to aeroallergens may be enhanced by damage of the skin barrier function. The specific IgE response seems to contribute to the severity of the disease in a dose-dependent fashion.     

cDNA cloning and expression of Blo t 11, the Blomia tropicalis allergen homologous to paramyosin

Blomia tropicalis is an important mite species in many parts of the world and the most predominant mite species in tropical countries. The prevalence of sensitization to this species has probably been underestimated because commercial extracts are largely unavailable. Identification and characterization of B. tropicalis allergens is an important step toward understanding the role of this species in allergic sensitization and could provide appropriate reagents for diagnostic and therapeutic procedures. This paper describes the isolation, sequence analysis, expression and allergenicity of a cDNA gene coding for a B. tropicalis allergen with homology to paramyosin, a high-molecular-weight allergen previously identified in Dermatophagoides farinae. The full-length Blo t 11 cDNA gene was isolated by cDNA library screening, 5'-rapid amplification of cDNA ends and long-distance PCR. Sequence analysis was performed with a combination of CLUSTAL W, CGC and BLAST program packages. The cDNA gene was expressed as a GST fusion protein in Escherichia coli and purified by affinity chromatography using the glutathione Sepharose column. Allergenicity of the rBlo t 11 was tested by human IgE dot blot immunoassay. Blo t 11 is a 3,111-bp cDNA gene with a 2,625-bp open reading frame coding for an 875-amino acid protein, exhibiting significant homology with different invertebrate paramyosins. The human IgE dot blot immunoassay showed that the rBlo t 11 reacted positively to 52% (33/63) of sera from asthmatic patients. Blo t 11 is the homolog of Der f 11 exhibiting potentially important allergenic activity.     

Dynamic changes in sensitization to specific aeroallergens in children raised in a desert environment

BACKGROUND: Allergen skin test reactivity and total serum IgE are objective measures used to characterize and help diagnose allergic diseases. Cross-sectional studies have shown that overall aeroallergen skin test reactivity increases throughout childhood. However, little attention has been paid to whether individual aeroallergen remittance occurs, which could distort or mask relationships to disease. OBJECTIVE: To access the incidence and remittance of skin test reactions to individual allergens in children aged 6-11 years. METHODS: Longitudinal sensitization to six aeroallergens and total IgE were assessed in 828 children raised in the semi-arid US southwest at ages 6 and 11 years. RESULTS: New sensitization (to any allergen) between 6 and 11 years occurred in 30.2% of children compared with 39.7% before age 6 years. The rate of complete remittance from positive to negative between ages 6 and 11 years was 8.2%, and total IgE at age 6 years was not predictive. Remittance rates for individual allergens were high and variable (19-49%). The perennial allergens Bermuda and Alternaria were early sensitizers and had low remittance rates. Early sensitization to the four seasonal allergens was less common and more subject to remittance with the bulk of sensitization occurring between 6 and 11 years. CONCLUSION: This study shows that sensitization to individual aeroallergens in childhood is dynamic and indicates the limitation of single point assessment of skin test reactivity.