The prevalence of immediate positive skin tests to Dermatophagoides pteronyssinus and grass pollen in schoolchildren

The prevalence of immediate positive reactions to prick testing with house dust mite (Dermatophagoides pteronyssinus) and grass pollen allergens was determined in a random sample of 303 children aged between 8 and 14 years from two Southampton schools. One hundred and two (33.7%) showed positive reactions, fifty to both D. pteronyssinus and grass pollen, thirty to D. pteronyssinus only and twenty-two to pollen only. Allergic symptoms were present in fifty-one of the 102 children with positive skin tests; amongst thirty children with D. pteronyssinus skin sensitivity by itself, only six had symptoms suggestive of allergic disorder. Significantly more children with positive than with negative tests were reported by their parents to have suffered from recurrent bronchitis during early childhood.     

A comparison of mite populations in mattress dust from hospital and from private houses in Cardiff, Wales

Fifty mattress dust samples from private houses were examined—all were mite infested. Dermatophagoides pteronyssinus occurred in all samples and accounted for 81% of all mites. In thirty-two paired samples the total mite population of bedroom floor dust was only 10% of that found in the corresponding mattress dust. D. pteronyssinus was the dominant species in both and the population of this mite amounted to 7.5% of that found in the mattress dust. An analysis of mattress dust from 100 hospital beds showed that ninety-four mattresses were mite free; the other six contained only seven mites, all D. pteronyssinus. It is suggested that frequent changing and washing of bed linen and brushing and cleaning of mattresses were the main factors in preventing mite infestation in the Cardiff hospitals.     

Comparison of the levels of the major allergens Der p I and Der p II in standardized extracts of the house dust mite, Dermatophagoides pteronyssinus

Allergy to the house dust mite Dermatophagoides pteronyssinus is mediated by IgE to the major allergens Der p I and Der p II in the majority of mite-allergic patients. In recent years, standardized preparations of D. pteronyssinus, commercially available from several sources, have become widely used for the diagnosis and immunotherapy of mite allergy. As standardization implies uniformity of allergen composition and potency, we directly compared the absolute and relative quantities of Der p I and Der p II in six different commercial standardized extracts of D. pteronyssinus. Our findings reveal variability in levels of both Der p I and Der p II, producing ratios of Der p I/Der p II ranging from 1.1/1 to 6/1. Although the content of minor allergens in the extracts was not evaluated here, their contribution to the overall reactivity of mite-allergic patients to the commercial extracts was judged to be minimal. This was demonstrated by showing that plasma depleted of reactivity to both Der p I and Der p II had virtually no residual IgE directed against extract components. The variation in the proportion of Der p I and Der p II among different D. pteronyssinus extracts is likely to influence their biological effectiveness. Patients with reactivity against only Der p I or Der p II, who were found to comprise approximately one-third of the mite-allergic population, may not respond optimally to extracts containing relatively low levels of the allergen to which they are sensitive.     

Comparison of the stability of a mite and a pollen extract stored in normal conditions of use

Pollen extracts are stable in solutions containing 50% glycerol. The stability of Dermatophagoides pteronyssinus (Dp) extracts have not been determined. Two lyophilised extracts (Dp and cocksfoot pollen) were reconstituted in 50% glycerol and stored for up to 6 months at +4°C. Every day the extracts were placed at room temperature for 1 hr to mimic the natural use of allergen extracts by allergists. Every 2 months the extracts initially prepared were compared to freshly reconstituted extracts by means of prick skin tests in fifteen allergic patients. It was observed that cocksfoot pollen extract is stable but there appears a slight but significant (P > 0.05) decay in activity when the extract stored for up to 6 months was compared with a freshly prepared extract. On the other hand there is a significant (P > 0.01) decay in activity of the Dp extract after 2 months of storage. Dermatophagoides pteronyssinus and cocksfoot pollen extracts behave differently when stored. These findings have particular importance in the diagnosis and treatment of allergic disorders.     

Determination of the stability of diluted allergen extracts using a concentration step prior to EAST inhibition

Background Generally the stability of diluted allergen extracts, as used for skin testing, provocation testing und immunotherapy can not be tneasured using a normal enzyme allergosorbent test (EAST) inhibition method. Objective The aim of this study was to determine the stability of diluted allergen extracts using an ultrafiltration step prior to the standard EAST inhibition procedure, in which the allergen extract was concentrated 100-fold. Methods This eoncentration procedure was validated for Dermatophagoides pteronyssinus, timothy pollen, birch pollen and cat dander extraets and used in a stability study in which three batches were stored for 1 year al 6° C and 25° C. Results There was no difference in relative potency before and after concentration of birch and timothy pollen extracts. D. pteronyssinus and cat dander extracts showed a significant decrease of 25% and 35% of the relative potency after concentration. The mean coeffieient of variation of 12 determinations of the stability study was 11.8%. Conclusion For all allergens the 30BU/mL or approximately 0.00025 mg/mL solution was stable for 12 months at both temperatures, except for D. pteronyssinus which declined rapidly at 25°C.     

Seasonal asthma and the house-dust mite in tropical Africa

The relationship between seasonal asthma and sensitivity to the house-dust mite has been investigated in a country with large seasonal variations in relative humidity. Of seventy-eight African asthmatics, 64.1% gave a history probably suggestive of sensitivity to house-dust, and 55.1% a history strongly suggestive of such sensitivity. On skin testing, 35.9% had strong reactions to the house-dust mite Dermatophagoides Pteronyssinus, compared with 1.9% of fifty-one matched controls without symptoms of chest disease. Few had either a history or skin tests suggestive of pollen or mould sensitivity. Most of the asthmatics were worse during the hot, wet season when the humidity is highest. This is also the time when in-patient asthmatics are most numerous. D. pteronyssinus grows well in warm, damp conditions and it is suggested that sensitivity to this mite may play a significant role in the marked seasonal changes seen in our asthmatic patients.     

In vitro investigations in asthmatic children undergoing hyposensitization with tyrosine-adsorbed Dermatophagoides pteronyssinus antigen

Successful hyposensitization to Dermatophagoides pteronyssinus in perennial childhood asthma was associated with a slight mean rise of serum IgG antibody to the mite antigen in contrast to a placebo group in whom this antibody fell slightly. No relationship was detected between the effect on asthma and the magnitude of this change, Nor was there any consistent effect on IgE or IgA antibody. There was a wide range of total serum IgE and IgE, IgG and IgA antibody to D. pteronyssinus before treatment; this level did not predict the effect of treatment. Some patients lacked IgA antibody. IgE antibody to timothy grass pollen was raised in some but not others. These levels did not change systematically during the study and improvement occurred in those who had this antibody as well as IgE antibody to D. pteronyssinus. IgG and IgE antibodies to D. pteronyssinus were significantly correlated in the pre-treatment samples. Lymphocyte thymidine uptake was lower after 8 weeks of treatment than in the control group, not only after stimulus with D. pteronyssinus antigen, in vitro, but also with antigen from Candida albicans. This was not a serum effect. The late bronchial provocation response was lost only in those with serum IgA less than the log mean for age.     

Mites and house dust allergy

279 patients, most of whom had perennial asthma or perennial rhinitis, were tested intradermally with extracts of Dermatophagoides pteronyssinus and D. farinae in order to ascertain the incidence of positive skin reactions. The great majority of house dust sensitive patients had positive skin reactions to both mite extracts. However, the concordance between house dust and mite extract positive skin reactions, though statistically significant, did not reach the extent found in other countries. Of the three extracts employed, D. pteronyssinus appeared to contain the most potent allergen while its culture medium extract yielded a low percentage of positive skin reactions. These results suggest that, in italy also, mites seem to represent the most important allergenic source of house dust.     

A clinical evaluation in children of the Pharmacia ImmunoCAP system for inhalant allergens

Background The Pharmacia ImmunoCAP system (CAP) for assaying serum IgE specific antibodies was evaluated in a clinical setting against skin-prick test (SPT) perfonncd using Dome/Hollister-Steir allergen extracts. The five cotnmon inhalant allergens D. pteronyssinus. D. farinae, mould mix, grass mix and cat epithelium were tested concurrently by both methods in 167 children aged 7.5–12 years. The specific SPT for D. pteronyssinus and D. farinae were also tested against the CAP house dust mite (HDM) mix. Objective The purpose of the study was to determine the sensitivity and specificity of the Pharmacia ImmunoCAP system Tor detecting serum IgE specific antibodies to inhalant allergens in a clinical setting, using the SPT result as the ‘gold standard’. Methods The SPTs were performed using Dome/Hollister-Steir allergen extracts. The serum IgE specific antibodies were quantitated using the radioimmunoassay version of the Pharmacia ImmunoCAP system. A history of allergic disease was assessed using a validated questionnaire. Results SPT gave more positive reactions than CAP with the exception of cat epithelium. The concordance between SPT and CAP results was 91% over all the tests. The concordance with SPT was slightly higher for the specific CAP for D. pteronyssinus and D. farinae (93% and 95% respectively) than for the CAP HDM mix (86% and 90% respectively). There was a higher proportion of positive results for both SPT and CAP in the 115 children defined as having a history of allergic disease. Using SPT defined allergy as the gold standard, the sensitivity of the CAP system was 87% for the two specific house dust mites but was lower for cat epithelium (67%), mould mix (59%) and grass mix (46%). The sensitivity of the CAP system improved for D. pteronyssinus (96%) and the HDM mix (91%) when tested in subjects defined as having a history of allergy associated disease. The specificity of the CAP system showed less variation between allergens and ranged from 90–99%. Conclusion The results of this study of children aged 7.5–12 years demonstrate that, for the inhalent allergens tested, the Pharmacia ImmunoCAP system perfoms well in the setting of known allergic disease.     

The importance of mites in house dust sensitivity in Barbadian asthmatics

House dust sensitivity is a common precipitating cause of naso-respiratory allergy in Barbados. A high degree of correlation between skin tests to house dust and to mite extracts was found. The pyroglyphid species Dermatophagoides pteronyssinus occurred in high densities in samples of mattress and bedroom dust. Twenty-two other species of mites were identified in the dust samples and in certain cases some of these species were more abundant than D. pter. Skin tests were positive in a high proportion of dust sensitive asthmatics tested with extracts prepared from five species of mite in addition to D. pter. and D. farinae. There appears to be a relationship between the density of D. pter. in mattress dust and allergy to house dust.     

Mites and house dust allergy. IV. Antigen and allergen(s) of Dermatophagoides pteronyssinus extract

The antigenic composition of D. pteronyssinus extract was investigated by using antisera raised in rabbits by injection of the mile extract in Freund's adjuvant. Immunodiffusion analysis revealed the presence in the mite extract of many antigenic constituents, most of which were also common to human dander and house dust extracts. Four antigenic components not shared by human dander appeared to be common to D.farinae extract. D. pteronyssinus extract was then fractionated on Sephadex G-75 and DEAE-Sephadex. Immunodiffusion analysis of the most active fraction revealed, after heat-treatment, the presence of three precipitin lines, one of which appeared not to be shared by nutrient medium or by D. farinae extract constituents. When the anti-mite rabbit serum was fixed to an immunosorbent and incubated with a house dust extract it was constantly able to induce a strong decrease or a complete loss of the allergenicity of the dust extract in man. These results suggest that mite allergen(s) are immunogenic in the rabbit and provide more direct evidence for identity of the allergens in house dust and mite.     

Estimation of Der p and Der f I quantities in the reference preparations of Dermatophagoides mite extracts

A monoclonal antibody-based enzyme-linked immunosorbent assay (MoAb-ELISA) was developed to measure the major Dermatophagoides mite allergens, Der p I and Der f I, The assay was highly species-specific and sensitive. Using this assay system, the absolute mass unit of Der p I and Der fI in the reference preparations of the extracts was estimated. The primary standards used were the purified Der p I and Der f I preparations. The reference preparations of the D. pteronyssinus and D. farinae extracts (92-Dp) and 92-Df), which had been prepared from the same amount of mite bodies of both species, were found to contain the same levels of the Der I allergens, 10.1 μg/ml of Der p I and 10.0 μg/ml of Der f I, respectively. A histamine release assay with leucocytes from mite-allergic donors showed that the total allergenic potency of 92-Dp and 92-Df was comparable. This result indicates that the estimated Der I levels in these extracts seem to be valid, at least, in the balanece between the two species, although further comparisons of the absolute quantities by several different laboratories are needed. The Der I levels in the WHO/IUIS international reference preparation of D. pteronyssinus and the CBER standard mite extracts, E4-Dp and E5-Df, were also estimated using this assay system. They were found to contain 4.4 μg/viaI and 13.3 μg/ml of Der p I and 9.5 μg/ml of Der f I, respectively.     

The allergenic importance of house dust and storage mites in asthmatics in Brunei, S.E. Asia

Examination of dust from sleeping areas showed that storage mites, especially Glycyphagid species, were predominant in Brunei house dust. On skin testing sixty asthmatics with 1% extracts of six mite species, Dermatophagoides pteronyssinus was found to provoke the greatest number of positive skin reactions (66.7%), but positive reactions for Tyrophagus putrescentiae (50%), Acarus siro (35%), Glycyphagus domesticus (40%), and Lepidoglyphus destructor (45%) demonstrated that storage mites are also significant allergens. The role of storage mites in the causation of asthma in the tropics may have been underestimated.     

Skin test and crossreactivity studies with Euroglyphus maynei and Dermatophagoides pteronyssinus

Background The prevalence of sensitization to Euroglyphus maynei (E. maynei) in the United States has not been reported previously. Objectives To determine: (l) the prevalence of skin-test reactivity in allergic subjects to E. maynei compared to D. pteronyssinus, D. farinae, and B. tropicalis and (2) the allergenic crossreactivity between D. pteronyssinus and E. maynei. Methods Skin testing with extracts of B. tropicalis and E. maynei (1:50 w/v) and standardized D. pteronyssinus and D. farinae extracts (1:50 w/v; 10000 AU/mL) provided data on 250 subjects (87 males and 163 females) aged 9–77 years (mean age, 39.8 years) with possible allergic respiratory diseases. RAST inhibition assays were used to study crossreactivity between D. pteronyssinus and E. maynei. Results One hundred (40%) of 250 subjects had insignificant or no allergic diseases. Of the 150 allergic subjects (53 males, 97 females), 101 (67.3%) had a positive test (a percutaneous test with a weal diameter ≥ 3 mm larger than the saline control) to at least one mite species; 60.7%, 60.0%, 28.7%, and 52.0% reacted to D. farinae, D. pteronyssinus, B. tropicalis, and E. maynei, respectively; 40(26.7%) reacted to the four mite species. Positive tests to D. farinae, D. pteronyssinus, B. tropicalis, or E. maynei alone occurred in six (4.0%), four (2.7%), two (1.3%), and 0%, respectively. D. pteronyssinus and E. maynei showed moderately high crossreactivity in RAST inhibition assays. Conclusion There is a high rate of skin-test reactivity to E. maynei in Florida. Moderately high crossreactivity exists between E. maynei and D. pteronyssinus.     

Identification of allergen-specific IgE antibodies in the sera of African asthmatics

Of eighty African asthmatics, sixty-three had significant levels of specific IgE against the house dust mite Dermatophagoides pteronyssinus. By contrast, grass-specific IgE was found in six patients and mould-specific IgE in none. Sixty-three patients also had symptoms predominantly during the rainy season. Positive skin tests against D. pteronyssinus correlated well with the presence of mite-specific IgE, as did the size of these skin test weals with the amount of specific IgE. For grass pollen and moulds there was no such relationship. There was no correlation between a history of sensitivity to house dust and either skin tests or specific IgE against D. pteronyssinus. The results support previous findings that it is allergy to house dust mite and not to grass pollens or moulds which is important in producing the seasonal symptoms in our patients.     

Sensitivity to house dust mite and grass pollen in adults

A comparison was made between the birth month of a control population and a sample of 240 adult patients with bronchial asthma or rhinitis and positive skin test towards house dust mite (Dermatophagoides pteronyssinus). The patients were born more frequently (P < 0.005) in the summer and autumn months than in the other seasons. A similar comparison of 336 allergic patients with a positive skin test towards grass pollen (Phlemt pratense) but no consistent seasonal preference in the birth months was revealed. This was possibly explained by the age of the patient group studied. The increased incidence of house-dust mite allergy in patients born in the months of May to September inclusive when house dust mites are supposed to be most abundant corresponds to a relative risk of 1.44. It is important lo diminish the exposure to house dust mites in early childhood because exposure to allergens may influence the development of allergic disease in later life.     

Allergenic characterization of Acarus siro and Tyrophagus putrescentiae and their crossreactivity with Lepidoglyphus destructor and Dermatophagoides pteronyssinus

Allergenic components in extracts of Acarus siro and Tyrophagus putrescentiae were identified by sodium dodecyl sulphate-polyacrylamide (SDS-PAGE) and immuno-blotting. Five and four allergenic components, respectively, were visualized with sera from farmers sensitized to storage mites. The highest frequency of IgE-binding was to a 15kDa component of A. siro (7/9 sera) and a 16kDa component of T. putrescentiae (23/29 sera). The allergenic crossreactivity of A. siro and T. putrescentiae with Lepidoglyphus destructor and Dermatophagoides pteronyssinus was studied with an immunoblotting inhibition technique. Crossreactivity between D. pteronyssinus on the one hand and A. siro and T. putrescentiae on the other, was shown, as the IgE reactivity to a 25 kDa component of D. ptertonyssinus was inhibited to the same degree by extracts of A. siro, T. putrescentiae and D. pteronyssinus. However, D. pteronyssinus was a poor inhibitor of the allergenic components of A. siro and T. putrescentiae. Strong cross-reactivity was also shown between L. destructor and the allergenic components of A. siro and T. putrescentiae, while the latter mite species only to a very low degree inhibited the allergenic components of L. destructor.     

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 α‐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.     

Immunological features of asthma (Part II)

A serological comparison was made of two groups of 120 matched asthmatic and healthy subjects, between the ages of 20 and 49 years and matched for age and sex, in terms of serum total levels of IgG, IgM, IgA. IgD and IgE and of specific antibody levels in each immunoglobulin class to five common UK allergens. The relationship of clinical features to the serological tests was also examined in the asthmatic subjects. The following statistically significant findings were shown. The patients had higher levels than the controls of total globulins and of IgG, IgA and IgD but not IgM. In both patients and controls the females had higher IgM levels than the males. The total IgE levels were higher in patients than in the controls and the male patients had higher levels than the female patients. Total IgE levels were also related, to the numbers of first degree relatives with asthma, hay fever and eczema, to the severity of hay fever and to the amount of time off work in the male patients. In those male patients with exercise induced asthma the total IgE levels were lower than in those not showing this reaction. As for the other iminunoglobulins, the only significant differences were a higher [gG level in patients with FEV, or PFR>50% predicted and a higher IgD level in patients with hay fever. Radio-immunodiffusion tests for specific precipitins were positive for Dermatophagoldes pteronyssinus in comparable numbers of asthmatics (25.8%) and controls (21.7%). Positive precipitin tests were uncommon in tests with extracts of grass pollen, Aspergillus fumigatus, cat and dog hair in the patients and even less so in the controls. Positive RAST tests for specific IgE antibodies were obtained in patients and controls respectively, against D. pteronyssinus 59% and 11% grass pollen 37.0 and 12%, and A. fumigatus 6% and 4%. The male patients showed the closest significant relationship of specific IgE to D pteronyssinus and the history of house dust allergy, positive skin test and nasal test. in the females only the skin and specific IgE tests were related. Both sexes showed a significant association between specific IgE to grass pollen and positive skin tests and nasal tests, but only the males showed an association with the history. The size of skin test weal to D. pteronyssinus were related to the levels of specific IgE antibody, Correspondence: Professor J. Pepys, Cardiothoracic Institute, Brompton, London SW3 6HP. No differences were found between the four skin test groups and between the asthmatics and the control subjects in the incidence of bacterial precipitins and auin-antibodies.     

Reproducibility of prick skin tests to five common allergens

Thirty-five asthmatic patients had prick skin tests to the common allergens Candida aibicans, Aspergillus fumigatus, grass pollen, horse dander and Dermatophagoides pteronyssinus performed on a regular basis from Autumn 1973 to Autumn 1975. Specific IgE to the same allergens (except C. albicans) was determined at the time of skin testing for the first five seasons. It was found that the position on the volar aspect of the forearm on which the test was performed did not affect the reaction. There was a significant variation in the percentage of patients with positive skin tests to A. fumigatus, grass pollen and horse dander with the latter showing a significant decrease with time. There was evidence of variation in weal size for all but C. albicans, and for grass pollen, horse dander and D. pteronyssinus there were reductions in weal size with time. Significant differences were found for results of Log specific IgE for grass pollen and D. pteronyssinus over the study, but there was no trend. A good correlation between weal size and Log specific IgE for grass pollens and D. pteronyssinus was observed. For the four allergens, the coefficient of concordance between IgE levels within patients for the five seasons was highly significant.