Prevalence of self-reported food allergy and IgE antibodies to food allergens in Swedish and Estonian schoolchildren

OBJECTIVE

To compare the prevalence of self-reported food allergy and IgE antibodies to food allergens in wheezing and non-wheezing Estonian and Swedish schoolchildren, in the light of the disparities in the standard of living, food consumption and prevalence of respiratory allergies that still exist between Estonia and the Scandinavian countries.

DESIGN AND SETTING

As a part of the ISAAC Phase II study, children from a random sample of schools in Tallinn in Estonia and Linköping and Ostersund in Sweden participated in skin prick tests to inhalant allergens and the parents replied to questionnaires. IgE antibodies against a panel of food allergens (egg white, milk, soy bean, fish, wheat and peanut) were taken from children with questionnaire-reported wheezing and a random sample of nonwheezing children.

SUBJECTS

Children aged 10-11 y.

RESULTS

The prevalence of self-reported food allergy was similar in Estonia and Sweden and about twice as high in wheezing children than in nonwheezing children. In Estonia, however, 3% of the children with perceived food allergy reported reactions from at least four different foods, as compared to 31% in Sweden. The prevalence of sensitisation to food allergens was similar in wheezing and nonwheezing children in Estonia (8%) while, in Swedish children, IgE antibodies to food allergens were more likely among wheezing children (Linköping 38 vs 11%, crude OR 5.1, 95% CI 2.2-11.6, and Ostersund 24 vs 7%, crude OR 4.1, 95% CI 1.9-8.5).

CONCLUSION

Our study suggests that IgE-mediated food reactions were less likely in Estonian schoolchildren. Moreover, the perception of food allergy and thereby the meaning of self-reported food allergy appears to be different in the two countries.

Rational design of hypoallergens applied to the major cat allergen Fel d 1

BACKGROUND

Allergen-specific immunotherapy is the only treatment for allergic disease providing long-lasting symptom relief. Currently, it is mainly based on the use of crude allergen extracts. The treatment may be improved by the use of genetically engineered allergens, hypoallergens, aiming at a more effective and safer therapy.

OBJECTIVE

The aim of this study was to provide a rational design of hypoallergen candidates for immunotherapy by using structural information and knowledge of B and T cell epitopes of an allergen.

METHODS

The three-dimensional structure of the major cat allergen Fel d 1 was systematically altered by duplication of selected T cell epitopes and disruption of disulphide bonds. Seven Fel d 1 derivatives were generated and screened for allergenic reactivity in comparison with recombinant Fel d 1 in competition-ELISA. The allergenicity was further evaluated in basophil activation experiments and T cell reactivity was assessed in a lymphoproliferation assay.

RESULTS

Three out of seven Fel d 1 derivatives, with two duplicated T cell epitopes and one or two disulphide bonds disrupted, were carefully evaluated. The three derivatives displayed a strong reduction in allergenicity with 400-900 times lower IgE-binding capacity than recombinant Fel d 1. In addition, they induced a lower degree of basophil activation and similar or stronger T cell proliferation than recombinant Fel d 1.

CONCLUSION

By a rational approach, we have constructed three Fel d 1 hypoallergens with reduced IgE-binding capacities and retained T cell reactivities. This strategy may be applied to any well-characterized allergen to improve immunotherapy for allergic patients.

Quantitative analysis of IgE antibodies to food and inhalant allergens in 4-year-old children reflects their likelihood of allergic disease

BACKGROUND

It is well established that early diagnosis of allergic disease is warranted.

METHODS

In a prospective birth cohort study (BAMSE) 3743 children at 4 years of age were included. Children were classified as having any allergic disease, e.g. asthma, suspected allergic rhinitis (suspAR), eczema or oro-gastro-intestinal symptoms with questionnaire. Blood was obtained from 2612 of these children and analysed for IgE antibodies (ab) towards 14 common food and airborne allergens.

RESULTS

Positive IgE ab results were found in 38% of the children with any allergic disease, whereas such IgE ab results were found in 17% among those without any allergic disease. Furthermore, among children with any allergic disease the median summated IgE ab levels were 10.7 kU(A)/l compared with 1.5 kU(A)/l among those without such symptoms. The highest IgE ab levels were found to birch, peanut, cat and horse. When the sum of the IgE-ab levels towards the selected allergens was at least 34 kU(A)/l, or, alternatively, more than four allergen tests were positive, there was a 75% likelihood of identifying the individual with any allergic disease. To identify those with asthma, as well as those with suspAR, a significant interaction was found for the combination of the sum of IgE-ab levels and number of allergens positive at test. For eczema only, the number of positive allergens at test was associated to the likelihood of such disease.

CONCLUSIONS

In children, 4 years of age, allergic disease was frequently not associated with the presence of single positive IgE antibody results, whereas increased IgE ab levels were significantly more prevalent among those with allergic disease. Thus, testing a certain profile of airborne and food allergens, and utilizing the sum of the IgE-ab levels in combination with the number of allergens positive at tests, may represent a more efficient diagnostic tool then to use just single positive IgE-ab results.

IgE-sensitization to predatory mites and respiratory symptoms in Swedish greenhouse workers

BACKGROUND

Predatory mites are used as biological pesticides worldwide for control of spider mites and other pests in greenhouses. The aim of this study was to evaluate the impact of occupational exposure to Phytoseiulus persimilis and Hypoaspis miles on IgE sensitization among a large group of Swedish greenhouse workers and to examine the relationship between exposure and allergic asthma and rhinoconjunctivitis.

METHODS

A total of 96 greenhouse workers from the southern part of Sweden, who were using the predatory mites for control of pests, were investigated with a questionnaire and a medical examination including lung function test. Blood samples were taken to test for allergen-specific IgE antibodies to Phytoseiulus persimilis and Hypoaspis miles as well as to Tetranychus urticae, Dermatophagoides pteronyssinus/farinae and Tyrophagus putrescentiae.

RESULTS

Seventeen of the 96 workers were positive in ImmunoCAP to predatory mites: 17 to P. persimilis (17.7%) and 14 to H. miles (14.6%). Subjects sensitized to predatory mites were significantly more often atopic (13/17), defined as a positive Phadiatop, than those who lacked IgE against these mite species (17/79) (P <0.01). IgE antibodies to the red spider mite T. urticae were present among 23 subjects. Thirty-five of the investigated subjects displayed a positive ImmunoCAP to at least one of the investigated mite species. Furthermore, sensitization to any of the mites tested was significantly associated with asthma (OR=9.3) and rhinoconjunctivitis (OR=4.3).

CONCLUSIONS

IgE sensitization to predatory mites, P. persimilis and H. miles, is common among greenhouse workers. The findings stress the importance of improved allergen avoidance in greenhouse environments.

Antibody profiles and self-reported symptoms to pollen-related food allergens in grass pollen-allergic patients from northern Europe

BACKGROUND

Most studies on pollen-related food allergy have so far focused on the association of birch/weed pollen allergens and plant food allergy. The aim of this study was to elucidate the allergen spectrum among a group of grass pollen-allergic patients from northern Europe and to relate the results to clinical histories of pollen-related food allergy.

METHODS

Fifty-eight grass pollen-allergic patients answered a questionnaire regarding allergy to foods. Blood samples were taken to test IgE-reactivity to a large panel of pollen allergens and pollen- and nonpollen-related food allergens using crude allergen extracts and recombinant and native allergens.

RESULTS

Three different groups of grass pollen-allergic patients were identified according to their IgE antibody profile: a grass pollen group only (19%), a grass and tree pollen group (29%) and a grass, tree and compositae (pan-) pollen group (48%). No sensitization to Bet v 1 as well as almost no IgE to plant food was observed in the grass pollen group. In contrast, nearly all patients in the two tree-related groups had IgE to Bet v 1, which reflected the high frequency of adverse reactions to typical birch-related food in these groups. Only four patients belonging to the pan-pollen group displayed IgE to profilin Phl p 12/Bet v 2. Patients in the pan-pollen group reported significantly more symptoms to food allergens compared with patients in the two other groups. The most frequently reported symptom was the oral allergy syndrome.

CONCLUSIONS

Sensitization to grass pollen alone is rare among grass pollen-allergic patients from northern Europe. The majority of patients are in addition sensitized to birch (Bet v 1), which seems to be closely related to their pollen-derived food allergy. The study highlights the advantage of using well-defined allergen molecules for the diagnosis of cross-reactivity between pollen and food allergens.

Provocation testing with recombinant allergens

In the past few decades, DNA technology has enabled the production of defined recombinant allergen molecules for diagnostic and therapeutic purposes. Recombinant allergens containing most of the relevant IgE epitopes present in natural allergen sources are now available and allergen proteins can be produced that are identical, without biological or batch-to-batch variation. A great advantage of recombinant allergens is that they can be used for component-resolved diagnostics, which makes it possible to establish the patient's individual IgE reactivity profile before therapy is selected. However, before recombinant allergens can be applied in clinical practice their biological activity has to be carefully investigated in vivo. We here describe the most commonly used provocation methods (skin tests (prick and intradermal), nasal, bronchial, and conjunctival provocations) and how they can be performed. We also discuss the results so far obtained with in vivo testing using recombinant allergens and envisage their future use for immunotherapy.

Vaccination with genetically engineered allergens prevents progression of allergic disease

IgE-mediated allergy affects >25% of the population in industrialized countries. Repeated contact with the disease-eliciting allergens induces rises of allergen-specific IgE Abs and progression of the disease to more severe manifestations. Our study uses a type of vaccine that is based on genetically modified allergen derivatives to treat allergic patients. We developed hypoallergenic derivatives of the major birch pollen allergen, Bet v 1, by genetic engineering and vaccinated birch pollen-allergic patients (n = 124) in a double-blind, placebo-controlled study. Active treatment induced protective IgG Abs that inhibited allergen-induced release of inflammatory mediators. We also observed a reduction of cutaneous sensitivity as well as an improvement of symptoms in actively treated patients. Most important, rises of allergen-specific IgE induced by seasonal birch pollen exposure were significantly reduced in vaccinated patients. Vaccination with genetically engineered allergen derivatives is a therapy for allergy that not only ameliorates allergic reactions but also reduces the IgE production underlying the disease.

No apparent association between periocular and ocular microcolonization and the degree of inflammation in patients with atopic keratoconjunctivitis

BACKGROUND

The cause of the chronic inflammation in atopic keratoconjunctivitis (AKC), the ocular manifestation of atopic eczema/dermatitis syndrome, is largely unknown.

OBJECTIVE

To investigate the possibility that microorganisms may be important in the inflammatory activity in AKC.

METHODS

Fifteen patients with AKC participated in the study. The presence of aerobic bacteria and fungi was related to the severity of clinical signs, the numbers of inflammatory cells in tears and conjunctival biopsies, and the concentration of various cytokines in tears. In addition, serological evidence for IgE sensitization to Staphylococcus aureus B antigen and Malassezia sympodialis antigen was investigated. Twelve healthy subjects were included for control purposes.

RESULTS

The patients exhibited moderate clinical signs of AKC. No relation was found between the severity of AKC and the presence of microorganisms, despite the fact that S. aureus was frequently isolated. AKC patients showed significantly higher levels of IFN-gamma, TNF-alpha (tumour necrosis factor-alpha), IL-2, IL-4, IL-5 and IL-10 than controls. An association was found between conjunctival signs and the levels of all cytokines except IL-5.

CONCLUSION

We found no evidence to suggest that periocular and ocular microcolonization are related to inflammatory parameters in AKC. However, confirmation of the present results in a longitudinal study with repeated clinical examinations and samplings in the same individual is required before the contribution of S. aureus to on-going inflammation in AKC can be dismissed.

Direct and indirect exposure to pets - risk of sensitization and asthma at 4 years in a birth cohort

INTRODUCTION

There are conflicting data on the association between early exposure to pets and allergic diseases. Bias related to retrospective information on pet ownership has been addressed as a reason for distorted study results.

OBJECTIVE

To elucidate how early exposure to cat and dog relates to IgE-sensitization and asthma in children at 2 and 4 years of age, in a prospective birth-cohort study.

METHODS

Four thousand and eighty-nine families with children born 1994-1996 in predefined areas of Stockholm answered questionnaires on environmental factors and symptoms of allergic disease at birth, one, two and four years of age. Dust samples collected from the mothers' beds at birth were analysed for Fel d 1 and Can f 1 in a subgroup of the cohort. Blood samples taken at four years from 2614 children were analysed for allergen-specific IgE to common airborne allergens. Risk associations were calculated with a multiple logistic regression model, with adjustment for potential confounders.

RESULTS

A correlation was seen between allergen levels and reported exposure to cat and dog. Exposure to cat seemed to increase the risk of cat sensitization, OR (odds ratio) 1.44 (95% confidence interval 1.03-2.01), whereas dog exposure did not have any effect on dog sensitization, OR 1.16 (0.79-1.72). Dog ownership was related to a reduced risk of sensitization to other airborne allergens, OR 0.36 (0.15-0.83), and a similar tendency was seen for cat ownership OR 0.63 (0.37-1.07). Early dog ownership seemed to be associated with a lower risk of asthma, OR 0.50 (0.24-1.03), with no corresponding effect after cat ownership, OR 0.88 (0.56-1.38).

CONCLUSION

Early exposure to cat seems to increase the risk of sensitization to cat but not of asthma at 4 years of age. Dog ownership, on the other hand, appears to be associated with lowered risk of sensitization to airborne allergens and asthma. Both aetiological relationships and selection effects have to be considered in the interpretation of these findings.

IgE-mediated sensitization to predatory mites in Swedish greenhouse workers

BACKGROUND

Predatory mites are used as biological pesticides worldwide for control of spider mites and other pests in greenhouses. The aim of this study was to investigate if predatory and spider mites give rise to sensitization among greenhouse workers who use biological pesticides.

METHODS

Blood samples were collected from 31 greenhouse workers from Stockholm area who were using the predatory mites Phytoseiulus persimilis and Hypoaspis miles for control of pesticides. Immunoglobulin E (IgE) binding to extracts of P. persimilis and H. miles and of the spider mite Tetranychus urticae was analysed with sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting.

RESULTS

A total of 16 workers displayed IgE antibodies to one or more of the three mite species, 32% (n = 10) to P. persimilis, 52% (n = 16) to H. miles and 26% (n = 8) to T. urticae. At least 17 IgE binding components in the molecular weight ranging from 28 to >94 kDa were identified in P. persimilis. In H. miles, at least 11 components were detected, among them at least one major component at about 70 kDa. Twenty-four IgE binding components were found in T. urticae.

CONCLUSIONS

In this study we have for the first time shown that the predatory mites P. persimilis and H. miles can cause IgE-mediated sensitization among greenhouse workers. The clinical relevance of sensitization to predatory mites needs to be investigated in further studies.

Nasal challenges with recombinant derivatives of the major birch pollen allergen Bet v 1 induce fewer symptoms and lower mediator release than rBet v 1 wild-type in patients with allergic rhinitis

BACKGROUND

Genetic engineering of the major birch pollen allergen (Bet v 1) has led to the generation of recombinant Bet v 1 derivatives with markedly reduced IgE-binding capacity, but with retained T cell activating ability.

OBJECTIVE

To compare the mucosal reactivity to rBet v 1 derivatives with rBet v 1 wild-type as basis for new therapeutic strategies for birch pollen allergy based on mucosal tolerance induction.

METHODS

Outside the pollen season, 10 patients with birch pollen allergic rhinitis and mild asthma underwent four nasal challenge-sessions in a randomized, double-blind, and cross-over design, employing increasing doses of rBet v 1 fragment mix, rBet v 1 trimer, rBet v 1 wild-type and diluent (albumin). Nasal lavage fluids (NAL) were collected before the challenge-series as well as 10 min, 4 and 24 h thereafter. Nasal lavage fluid levels of tryptase as well as EPO and ECP were measured as indices of mast cell and eosinophil activity, respectively.

RESULTS

All 10 patients tolerated the highest accumulated dose, 8.124 microg, when challenged with rBet v 1 trimer, eight with rBet v 1 fragments compared to one when challenged with rBet v 1 wild-type. No late phase reactions were observed. The change in tryptase levels (pre-challenge vs. 10 min) was significantly lower after challenges with rBet v 1 trimer and rBet v 1 fragments than with rBet v 1 wild-type. The change in EPO/ECP concentration pre-challenge versus 4 h post-challenge was lower for rBet v 1 trimer and the change was significantly lower when pre-challenge versus 24 h post-challenge to rBet v 1 fragments and rBet v 1 wild-type was examined.

CONCLUSION

The derivatives induced significantly fewer symptoms and lower mast cell and eosinophil activation than rBet v 1 wild-type upon application to the nasal mucosa. They could in the future be candidates for immunotherapy based on mucosal tolerance induction.

Associations of Fc epsilon R1-beta polymorphisms with immunoglobin E antibody responses to common inhalant allergens in a rural population

BACKGROUND

Polymorphisms within the beta subunit of the high-affinity receptor for IgE (Fc epsilon R1-beta ) on chromosome 11q13 have been related to atopy and asthma and the lymphotoxin alpha (LT alpha) gene on chromosome 6 is implicated in asthma.

OBJECTIVE

To elucidate the association of polymorphisms in the Fc epsilon R1-beta and LT alpha genes to IgE responses and asthma in a family-orientated rural population.

METHODS

A total of 461 adult farmers, who participated in an epidemiological follow-up study on respiratory symptoms among farmers on the Swedish island of Gotland, were examined. The traits assessed included serum total IgE, IgE antibody responses to 21 common inhalant allergens and asthma.

RESULTS

The 237G mutation was only detected in seven persons. Atopy was found to be associated with the RsaI-ex7 AB-genotype (OR = 1.9; P = 0.04). The RsaI-ex7 B allele had a significant influence on IgE responses to pollens and dust mites (OR = 5.5; P = 0.03 and OR = 5.2; P = 0.049, respectively). The influence of this allele was stronger when the association towards single dust mite species (Lepidoglyphus destructor) was estimated (OR = 7.1, P = 0.03) and the association increased even more when the major allergen of L. destructor (rLep d 2) was analysed (OR = 11.2, P = 0.02). These associations were independent of sex, age and smoking, and the estimates of RsaI-in2 independent of RsaI-ex7. RsaI-in2, RsaI-ex7 and LT alpha genotypes were unassociated with total serum IgE. No significant difference in the distribution of RsaI-in2, RsaI-ex7 and LT alpha genotypes was found among subjects with atopy or asthma compared to healthy controls.

CONCLUSION

This study supports the notion that polymorphisms in the Fc epsilon R1-beta gene have significant effects on IgE responsiveness. Secondly, dust mites in rural populations influence the expression of genes on chromosome 11q13.

An ELISA for recombinant Lepidoglyphus destructor, Lep d 2, and the monitoring of exposure to dust mite allergens in farming households

BACKGROUND

Exposure to indoor allergens, such as dust mites, has been recognized as a risk factor for sensitization and symptoms.

OBJECTIVE

To develop a two-site ELISA for the determination of Lep d 2 in the reservoir, to measure dust mite allergen exposure (Lep d 2, Der p 1, Der f 1 and Der 2) in farm households, and to investigate whether exposure to these allergens is associated with sensitization, asthma and rhinoconjunctivitis.

METHODS

Monoclonal antibodies to recombinant (r)Lep d 2 were produced with standard hybridoma technique. Dust samples from 393 households were analysed for allergen content by two-site ELISA methods.

RESULTS

A two-site Lep d 2 ELISA was developed with a detection limit of 0.09 microg/g. The assay was highly reproducible and levels of Lep d 2 showed a strong correlation with the number of Lepidoglyphus mites (r(s): 0.7; P = 0.0002). Lep d 2 was detected in 20% of the homes; levels ranged from 0.09 to 1.7 microg/g of dust. Der p 1 was recorded in 59% of the samples, ranging from 0.055 to 139 microg/g, and Der f 1 and Der 2 in 40% and 50% of the samples, ranging from 0.055 to 24.5 microg/g and 24.3 microg/g, respectively. Dermatophagoides allergens were significantly higher in mattresses than in carpets (P < 0.0001), but this difference was not observed with Lep d 2. A strong relationship between immunoglobulin (Ig)E to rLep d 2 and asthma (OR = 10.4) and rhinoconjunctivitis (OR = 7.5) was seen. Furthermore, sensitization to D. pteronyssinus was significantly associated with asthma (OR: 13.7) and rhinoconjunctivitis (OR: 5.7).

CONCLUSION

When assessing mite allergen exposure in rural homes, not only the Der p 1, Der f 1 and Der 2 allergens, but also the Lep d 2 allergen should be taken into consideration.

A revised nomenclature for allergy. An EAACI position statement from the EAACI nomenclature task force

This report has been prepared by an EAACI task force representing the five EAACI Sections and the EAACI Executive Committee composed of specialists that reflect the broad opinion on allergy expressed by various clinical and basic specialties dealing with allergy. The aim of this report is to propose a revised nomenclature for allergic and related reactions that can be used independently of target organ or patient age group. The nomenclature is based on the present knowledge of the mechanisms which initiate and mediate allergic reactions. However, the intention has not been to revise the nomenclature of nonallergic hypersensitivity.

Working with male rodents may increase risk of allergy to laboratory animals

BACKGROUND

Our aim was to study the risk of laboratory animal allergy (LAA) among research staff working in laboratories separate from the animal confinement area. The roles of atopy and exposure intensity in LAA were studied with special regard to exposure to male rodents, who excrete higher levels of urinary allergens than female rodents.

METHODS

Eighty rodent-exposed subjects gave blood samples for the analysis of total IgE, Phadiatop, and specific IgE against rat (RUA) and mouse urinary allergens (MUA), and answered questionnaires. Air samples were collected for RUA and MUA aeroallergen measurement in both laboratories and animal confinement facilities.

RESULTS

Twenty percent of the subjects had IgE >0.35 kU/l to RUA and/or MUA, and 32% had experienced animal work-related symptoms, although 90% of aeroallergen samples from the research department laboratories were below the detection limit (<0.26 ng RUA per m(3) and <0.8 ng MUA per m(3)). Atopy (positive Phadiatop), total IgE >100 kU/l, other allergies (especially to other animals), or more than 4 years of exposure significantly increased laboratory animal sensitization and symptoms. Working with mainly male rodents gave odds ratios (95% CI) of 3.8 (0.97-15) for sensitization and 4.4 (1.4-14) for symptoms. Subjects with both exposure to mainly male rodents and atopy or elevated total IgE had a 10-fold higher frequency of sensitization than exposed subjects with neither risk factor.

CONCLUSION

A majority of subjects with a combination of exposure to mainly male rodents and atopy or elevated total IgE developed sensitization to and symptoms from laboratory animals. Current low exposure seems to maintain the presence of specific IgE. Further measures must be undertaken to provide a safe workplace for laboratory animal workers.

A hypoallergenic derivative of the major allergen of the dust mite Lepidoglyphus destructor, Lep d 2.6Cys, induces less IgE reactivity and cellular response in the skin than recombinant Lep d 2

BACKGROUND

The major allergen of the dust mite Lepidoglyphus destructor, Lep d 2, has been produced as a recombinant allergen (rLep d 2) with IgE reactivity both in vivo and in vitro. A modified form of rLep d 2 (rLep d 2.6Cys) obtained by site-directed mutagenesis has been shown to have a reduced IgE reactivity in vitro. In this study we have compared the ability of rLep d 2 and rLep d 2.6Cys to elicit positive skin prick tests and cellular responses among L. destructor-sensitized subjects.

METHODS

Seventeen subjects were skin prick-tested with rLep d 2, rLep d 2.6Cys, histamine and negative controls and 17-20 h later skin biopsy specimens were taken from the skin prick-tested sites. The biopsy specimens were stained immunohistochemically for EG2+, CD3+, CD1a+, mast cell tryptase+, and IgE+ cells. Dermal cell infiltrates were judged in hematoxylin and eosin staining. Total IgE and allergen-specific IgE were determined by CAP-RAST.

RESULTS

Compared to rLep d 2, rLep d 2.6Cys induced significantly smaller and fewer skin prick test reactions (p < 0.001) and dermal cell infiltrates (p < 0.05). Further, rLep d 2.6Cys induced fewer EG2+ cells (p < 0.001) but more tryptase+ cells (p < 0.05) than rLep d 2. A positive RAST to rLep d 2 was obtained for 88.2% of the subjects, while only 35.2% displayed a positive RAST to rLep d 2.6Cys.

CONCLUSION

This study demonstrates that rLep d 2.6Cys is less able to evoke IgE-mediated reactions and cellular responses, as measured both in skin and in serum, than rLep d 2. In the future this hypoallergenic derivative may be a promising candidate molecule for immunotherapy of L. destructor-allergic patients.

A revised nomenclature for allergy. An EAACI position statement from the EAACI nomenclature task force

This report has been prepared by an EAACI task force representing the five EAACI Sections and the EAACI Executive Committee composed of specialists that reflect the broad opinion on allergy expressed by various clinical and basic specialties dealing with allergy. The aim of this report is to propose a revised nomenclature for allergic and related reactions that can be used independently of target organ or patient age group. The nomenclature is based on the present knowledge of the mechanisms which initiate and mediate allergic reactions. However, the intention has not been to revise the nomenclature of nonallergic hypersensitivity.

IgG1, IgG4 and IgE antibody reactivity to mutant forms of the major dust mite allergen Lep d 2 among atopic and nonatopic subjects naturally exposed to Lepidoglyphus destructor

BACKGROUND

Lepidoglyphus destructor is a common dust mite causing IgE-mediated sensitization. The major allergen, Lep d 2, has previously been cloned and expressed as several double Cys to Ser mutants with the purpose of producing hypoallergenic variants for immunotherapy. Our aim was to investigate the reactivity pattern of IgG1, IgG4 and IgE antibodies to wild-type (wt) rLep d 2 and four mutants among atopic and nonatopic subjects in relation to sensitization and exposure to L. destructor.

METHODS

Inhibition and sandwich ELISA were used to compare IgG1, IgG4 and IgE antibody reactivities to rLep d 2 variants in serum of 20 atopic and 18 nonatopic farmers naturally exposed to L. destructor. A group of 22 urban subjects served as controls.

RESULTS

Atopic farmers demonstrated correlating IgE and IgG4 levels to rLep d 2(wt) (rs = 0.70; p < 0.0001) which were significantly (p < 0.0001) higher than those of nonatopic farmers and urban controls. No IgG4 antibodies were detected in nonatopic farmers despite chronic allergen exposure. A parallel reactivity pattern of IgE and IgG4 to all rLep d 2 mutants was observed. The mutant lacking all 3 disulfide bonds, rLep d 2.6Cys, demonstrated neither any IgE nor IgG4 reactivity. In contrast, IgG1 antibodies had a different reactivity pattern and were detected among most subjects irrespective of atopy, exposure to L. destructor or disulfide impairments in rLep d 2. Moreover, IgG1 levels to rLep d 2(wt) and rLep d 2.6Cys correlated (n = 60; rs = 0.65; p < 0.0001).

CONCLUSIONS

IgE/IgG4 Ab to rLep d 2 were restricted to atopic farmers and demonstrated parallel recognition patterns of conformational epitopes. In contrast, IgG1 antibodies are ubiquitously found and mainly recognize sequential structures. The observed isotypic difference and interindividual variation in antibody specificities among atopic and nonatopic subjects imply careful investigation of hypoallergenic variants destined for immunotherapy.

Allergenic cross-reactivity between the nematode Anisakis simplex and the dust mites Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, and Dermatophagoides pteronyssinus

BACKGROUND

The nematode Anisakis simplex is a common parasite on fish and other seafood. It is considered to be a food allergen and to induce IgE-mediated reactions. Allergenic cross-reactivity between A. simplex and other nematodes has been reported, as has cross-reactivity with arthropods: red mosquito larvae and German cockroach. We have here studied the allergenic relationship between A. simplex and four different dust-mite species.

METHODS

Serum samples collected from 69 farmers allergic to dust mites were analyzed for IgE to A. simplex by CAP FEIA. Allergenic cross-reactivity between A. simplex and dust mites was studied in two of the sera by CAP FEIA and immunoblotting inhibition.

RESULTS

We found that 14/69 farmers had detectable levels of IgE antibodies to A. simplex. The IgE response in CAP FEIA to A. simplex was inhibited to various degrees in the two studied sera by extracts of the dust mites Acarus siro, Lepidoglyphus destructor, Tyrophagus putrescentiae, and Dermatophagoides pteronyssinus. In the reverse inhibition experiment, extract of A. simplex inhibited the response in both sera to A. siro and T. putrescentiae, but not to L. destructor. The IgE binding to D. pteronyssinus was inhibited in one of the two sera. In blotting inhibition experiments, the IgE binding to several allergens in A. simplex was inhibited by each of the four mite extracts, especially by A. siro and T. putrescentiae, which completely inhibited the IgE binding to several allergens.

CONCLUSION

The results show allergenic cross-reactivity between several allergens in A. simplex and four dust-mite species. The clinical significance of this cross-reactivity remains to be evaluated.

Influence of early and current environmental exposure factors on sensitization and outcome of asthma in pre-school children

BACKGROUND

Exposure to furred pets in early life has been considered to increase the risk of allergic sensitization and consequent development of asthma later in children. However, recently, it has been suggested that early exposure to pets prevents sensitization. The aim of this study was to evaluate the importance of early exposure to pets and other environmental risk factors in asthmatic children.

METHODS

This is a follow-up study after 2 years of a previously investigated group of 193 asthmatic children, aged 1-4 years. The study was completed by 181 children, who were clinically examined; serum IgE antibodies were also measured and a questionnaire was answered.

RESULTS

Children with reported exposure to cats during the first 2 years of life were more likely to have developed sensitization to cat by 4 years of age than unexposed children. High levels of cat allergen (Fel d 1> or =8 microg/g dust) were associated with an increased risk of sensitization to cat and, in combination with tobacco smoke, also with the development of more severe asthma.

CONCLUSION

In young asthmatic children, early exposure to cat and tobacco smoke increased the risk of allergic sensitization and further development of more severe asthma later in childhood.

Fewer allergic respiratory disorders among farmers' children in a closed birth cohort from Sweden

The aim of this study was to investigate the prevalence of respiratory allergy, eczema and atopic sensitization in a closed birth cohort of Swedish schoolchildren, 7-8 yrs of age (n=707), of farmers and nonfarmers on the island of Gotland, in the Baltic Sea. All children were born and raised on the island. The survey comprised a questionnaire on atopic diseases and lifestyle factors. Atopic sensitization was assessed by the skin-prick test (SPT) with 15 standardized allergens. The risk ratio (RR) for ever having asthma and/or allergic rhinoconjunctivitis was significantly lower among children of farmers compared to children of nonfarmers (RR=0.38, confidence interval (CI) 95% 0.19-0.77). SPTs (test rate 92%) showed that 32% of the children had at least one positive test. Although the number of positive SPTs did not differ between the groups, there was a reduced risk among children of farmers for having both respiratory symptoms and sensitization to any International Study on Asthma and Allergy in Childhood allergen (RR=0.28, CI 95% 0.09-0.88). The present indicate that living in a farming population seems to protect against development of respiratory allergic disorders but not against allergic sensitization.

The molecular basis of antigenic cross-reactivity between the group 2 mite allergens

BACKGROUND

Mite group 2 allergens Der p 2, Der f 2, and Eur m 2 are 14-kDa proteins of unknown function that share 83% to 85% amino acid sequence identity. Isoforms of the allergens within each genus have been identified which differ by 3 or 4 amino acids, but little is known of the influence of group 2 polymorphisms on human IgE antibody binding.

OBJECTIVE

The purpose of this study was to investigate the importance of interspecies and isoform substitutions on murine mAb and IgE antibody binding and on the molecular structure of the group 2 allergens.

METHODS

Site-directed mutagenesis was used to incorporate the isoform amino acid substitutions onto the Der p 2.0101 sequence. Recombinant allergens were expressed and purified from Escherichia coli and used to evaluate antibody binding by enzyme-linked immunosorbent assay (ELISA). Molecular modeling of the tertiary structure was used to analyze structural differences between the various group 2 allergens.

RESULTS

The substitution of asparagine for aspartic acid at position 114 restored mAb binding of rDer p 2.0101; the other Der p 2 isoforms and the 3 rDer f 2 isoforms also reacted in the 2-site ELISA. The correlation of IgE binding to the Der p 2 isoforms was excellent and tended to be higher in the isoforms with the asparagine 114 substitution (r (2) = 0.87 vs r (2) = 0.95). rEur m 2.0101 bound to all mAb except 7A1; when compared with rDer p 2 for IgE binding, rEur m 2.0101 gave a correlation coefficient of r (2) = 0.68. Molecular modeling revealed that Eur m 2 and the storage mite homologs Lep d 2 and Tyr p 2 retain the tertiary fold of Der p 2. Eur m 2 has a conserved surface, whereas Lep d 2 and Tyr p 2 present most of the amino acid substitutions on this surface. Lep d 2 and Tyr p 2 did not react with mAb or with sera from patients with IgE to Dermatophagoides species.

CONCLUSION

The isoform substitutions of rDer p 2 can be distinguished by mAb. The allergenic cross-reactivity between Der p 2, Der f 2, and Eur m 2 is a direct result of the conserved antigenic surface, whereas the lack of cross-reactivity with Lep d 2 and Tyr p 2 is a result of the multiple substitutions across this surface.

Cross-reactivity studies of a new group 2 allergen from the dust mite Glycyphagus domesticus, Gly d 2, and group 2 allergens from Dermatophagoides pteronyssinus, Lepidoglyphus destructor, and Tyrophagus putrescentiae with recombinant allergens

BACKGROUND

Dust mites are important inducers of allergic disease. Group 2 allergens are recognized as major allergens in several mite species, including Dermatophagoides pteronyssinus, Lepidoglyphus destructor, and Tyrophagus putrescentiae. No allergens have thus far been characterized on the molecular level from the dust mite Glycyphagus domesticus.

OBJECTIVE

We sought to examine the cross-reactivity among group 2 allergens of G domesticus, L destructor, T putrescentiae, and D pteronyssinus.

METHODS

A group 2 allergen from G domesticus, Gly d 2, was cloned and expressed as a recombinant protein. Cross-reactivity between Gly d 2 and 3 other group 2 allergens, Lep d 2, Tyr p 2, and Der p 2, was studied by using individual sera and a serum pool RAST-positive to G domesticus, L destructor, T putrescentiae, and D pteronyssinus. Recombinant allergens were used as inhibitors of IgE binding in immunoblotting experiments. Molecular modeling on the basis of the Der p 2 structure was carried out for Gly d 2, Lep d 2, and Tyr p 2.

RESULTS

Two cDNAs encoding isoforms of Gly d 2 were isolated, but only the Gly d 2.02 isoform was used in this study. Sixteen of 17 subjects had IgE to Gly d 2. The protein sequence of Gly d 2 revealed 79% identity to Lep d 2 and 46% and 41% identity to Tyr p 2 and Der p 2, respectively. Extensive cross-reactivity was demonstrated among Gly d 2, Lep d 2, and Tyr p 2, but little cross-reactivity was found between these allergens and Der p 2. According to the tertiary structure of Der p 2 and 3-dimensional models of Gly d 2, Lep d 2, and Tyr p 2, differences reside mainly in surface-exposed residues.

CONCLUSION

Gly d 2 showed high sequence homology to Lep d 2. Cross-reactivity was observed between Gly d 2, Lep d 2, and Tyr p 2, but only limited cross-reactivity was demonstrated between these 3 allergens and Der p 2.

Effectiveness of occlusive bedding in the treatment of atopic dermatitis--a placebo-controlled trial of 12 months' duration

BACKGROUND

Several studies on avoidance of house-dust-mite (HDM) and cat allergens have been carried out, most of them in asthmatic patients and only a few in patients with atopic dermatitis (AD). No study so far has focused on which subgroup of AD patients benefits from avoidance measures.

METHODS

Forty adult patients with AD completed the 12-month avoidance study. They were divided into an active treatment (n = 22) and a placebo (n = 18) group. Active treatment comprised use of polyurethane-coated cotton encasings for bedding, and placebo use of cotton covers. Patients came for regular checkups during the 12-month period, when eczema severity was assessed and blood samples were analyzed for total IgE, HDM- and cat-specific IgE and soluble CD30 (sCD30) in serum. Dust samples were collected from mattresses before treatment and after 3, 6, and 12 months, and analyzed for content of HDM and cat allergen.

RESULTS

Eczema severity decreased significantly in both groups (P < 0.001), with a more pronounced decrease in patients with active covers. The HDM exposure decreased significantly in the active treatment group (P < 0.001), and the levels of HDM-specific IgE were reduced (P<0.05). Exposure to cat allergens was unchanged in the active treatment group but decreased, albeit not significantly (P=0.19), in the placebo group. sCD30 levels were significantly reduced in both groups (P<0.001). Patients not sensitized to HDM allergens benefited from the bedcovers as much as sensitized patients.

CONCLUSIONS

Occlusive bedding significantly reduced HDM exposure in bed (P<0.001) and eczema severity, and sCD30 levels decreased significantly (P<0.001). Patients not sensitized to HDM and not exposed to HDM allergens benefited equally from use of the bedcovers, a result which could be due to a reduction of other important allergens, superantigens, or irritants in bed. We therefore recommend the use of bedcovers as part of treatment for AD.

Cloning of three new allergens from the dust mite Lepidoglyphus destructor using phage surface display technology

The dust mite Lepidoglyphus destructor is a common species in Europe and a major cause of dust mite allergy in rural surroundings, but it also contributes to dust mite allergy in urban areas. One major allergen, Lep d 2, has been expressed as a recombinant protein and evaluated both in vivo and in vitro and shown to detect 60% or more of L. destructor-sensitized subjects. Additional recombinant allergens are needed to obtain a reliable diagnostic tool for L. destructor allergy. The aim of this study was to clone and express new allergens from L. destructor and determine their recognition frequency among sensitized individuals. A phage display cDNA expression library was constructed and screened with sera from L. destructor-sensitized individuals. The cDNAs encoding the allergens were cloned into the pET17b vector and subsequently expressed in Escherichia coli as C-terminal His6-tagged proteins. Immunoblotting of the recombinant proteins was performed using sera from 45 subjects allergic to L. destructor. Three new allergens from L. destructor, Ld 5 (originating from a partial Lep d 5 clone), Lep d 7 and Lep d 13, were identified and recognized by 4/45 (9%), 28/45 (62%) and 6/45 (13%) sera from L. destructor-sensitized subjects, respectively.

A new method for collecting airborne allergens

BACKGROUND

Measurement of airborne allergens has hitherto been done with the use of fixed-location pumps or personal air samplers. Our objective was to find out whether ionizers could be good tools for collecting airborne allergens. As a model we have used cat allergen (Fel d l). We have compared Fel d l levels collected by the ionizer at different time periods, as well as comparing Fel d l levels obtained with the ionizer with those of low- and high-volume pumps.

METHODS

Dust samples from floors and air samples collected with ionizers and pumps, obtained in 31 homes with cat, 23 homes without cats, and 28 day-care centres, were analysed for cat allergen content (Fel d I) by ELISA.

RESULTS

Fel d l was present in the reservoir in all homes with cats, ranging from 660 to 375,000 ng/g (GM 75,000) and in the air collected by the ionizer from 2.0 to 204 ng/24 h (GM 19.3). The allergen in homes without cat varied from < 55 to 1,800 ng/g (GM 166). Corresponding levels in air were found in two of these homes (2.3 and 7.3 ng/24 h). There was a correlation between the number of cats and the amount of airborne cat allergen (r: 0.47; P < 0.05). The levels in day-care centres were < 55 to 3,070 ng/g in dust (GM 360) and < 1.1 to 7.9 ng/24 h in the air (GM 1.6). We obtained a moderately strong correlation between air and dust samples in homes with cats (rs: 0.64; P< 0.001) and in day-care centres (rs: 0.49; P<0.05). We found that a collection period of 24 h is preferable for the ionizer. The intrahome reliability coefficient was nearly two times higher for the ionizer (r: 0.69) than the pump (r: 0.39).

CONCLUSIONS

The ionizer seems to be a good tool for monitoring the environment. It is easy to use and silent and does not disturb the airflow in the room.

Skin prick test and serological analysis with recombinant group 2 allergens of the dust mites L. destructor and T. putrescentiae

BACKGROUND

The dust mites Lepidoglyphus destructor and Tyrophagus putrescentiae are important sources of allergen in farming environments. The major allergens of the dust mites L. destructor and T. putrescentiae have been cloned and expressed as recombinant proteins.

OBJECTIVE

To evaluate the use of recombinant group 2 allergens of L. destructor (rLep d 2) and T. putrescentiae (rTyr p 2) in skin prick test (SPT), and serological analysis in sensitized and non-sensitized farmers chronically exposed to dust mites.

METHODS

Skin prick test with rLep d 2, rTyr p 2 and the corresponding commercial extracts was performed in 44 farmers sensitized to L. destructor and/or T. putrescentiae, and 38 control farmers. IgE and IgG subclass antibodies to the recombinant allergens were analysed by RAST and ELISA, respectively.

RESULTS

Out of the 44 subjects positive in SPT to L. destructor and/or T. putrescentiae extract, 26 (59%) displayed a positive SPT to one or the other of the recombinant allergens, whereas 21 (48%) were positive to both. Significant correlations were registered between the sizes of the weals induced by rLep d 2 and rTyr p 2 and the corresponding RAST values (P < 0.001). A majority of subjects positive in SPT to the recombinant allergens had detectable IgG4 antibodies, and the levels were significantly higher in the dust mite sensitized group than in the controls (P < 0.05). No such differences were found in the IgG1 values (P > 0.05). The results obtained with rLep d 2 and rTyr p 2 correlated relatively well with each other with respect to SPT, RAST and IgG4, suggesting that the allergens have similar or shared IgE epitopes. All the control subjects had a negative SPT and RAST to rLep d 2 and rTyr p 2.

CONCLUSION

Recombinant group 2 allergens from the dust mite L. destructor and T. putrescentiae represent useful tools for diagnosis of dust mite allergy.

Risk factors associated with asthma and rhinoconjunctivitis among Swedish farmers

BACKGROUND

Earlier studies have shown a high prevalence of respiratory symptoms in farming communities and that storage mites constitute important allergens. We examined risk factors associated with asthma and rhinoconjunctivitis among Swedish farmers.

METHODS

A population of 1015 small-scale dairy farmers was part of an epidemiologic survey. After selection based on symptom reports in a questionnaire, 461 of the farmers attended a medical examination, which comprised SPT, RAST analyses, and lung-function measurements. Risk factors for sensitization to different allergens, and development of asthma and rhinoconjunctivitis were assessed by multiple logistic regression.

RESULTS

The prevalence of atopy was 26.7% among the farmers. For both asthma and rhinoconjunctivitis, sensitization to mites (OR = 5.8 vs. OR = 3.8) and pollens (OR = 10.3 vs. OR=5.8) was a significant risk factor. There was a significant relationship between sensitization to mites and working time (OR = 5.2). Environmental tobacco smoke and exposure to different animal species at the farm did not appear to affect the risk of allergen sensitization or respiratory symptoms. Farmers smoked less than the general population, but they more frequently had reduced FEV1.

CONCLUSIONS

Allergen sensitization, especially to mites and pollens, was significantly associated with asthma and rhinoconjunctivitis in a farming community. The results point to allergen avoidance as a major goal for the prevention of occupational respiratory diseases among the farming population.

Skin test evaluation of genetically engineered hypoallergenic derivatives of the major birch pollen allergen, Bet v 1: results obtained with a mix of two recombinant Bet v 1 fragments and recombinant Bet v 1 trimer in a Swedish population before the birch pollen season

BACKGROUND

More than 95% of birch pollen-allergic subjects react with the major birch pollen allergen, Bet v 1, and almost 60% of them are sensitized exclusively to this allergen.

OBJECTIVE

The aim of this study was to compare the in vivo biologic activity of genetically engineered hypoallergenic derivatives of Bet v 1 (an equimolar mixture of 2 recombinant [r] Bet v 1 fragments and of rBet v 1 trimer) with that of rBet v 1 wild-type by skin prick and intradermal testing.

METHODS

Birch pollen-allergic patients who had not received immunotherapy (n = 23), a group of allergic patients without birch pollen allergy (n = 12), and nonatopic persons (n = 8) from northern Europe (Sweden) underwent skin prick and intradermal testing with different concentrations of the recombinant allergens and commercial birch pollen extract before the birch pollen season. Immediate and late-phase reactions were recorded and allergen-specific IgE and IgG subclass responses were determined by CAP radioallergosorbent test and ELISA, respectively.

RESULTS

Atopic persons without birch pollen allergy and nonatopic individuals did not have skin reactions to rBet v 1 wild-type and genetically engineered hypoallergenic derivatives. By intradermal testing, 8 of 23 and 13 of 23 birch pollen-allergic patients did not react with the highest concentration (1 microg/mL) of the rBet v 1 fragment mix and rBet v 1 trimer, respectively, compared with 1 with rBet v 1 wild type. Likewise, the highest concentration (100 microg/mL) of fragment mix or trimer failed to elicit a positive skin prick test in 18 of 23 and 15 of 23 patients in comparison with 0/23 with the monomer. No late reactions were observed.

CONCLUSION

The recombinant hypoallergenic birch pollen allergens can probably be used for patient-tailored immunotherapy with a reduced risk to induce anaphylactic reactions.

Characterization of eosinophils and detection of eotaxin in skin chamber fluid after challenge with relevant allergen in patients with mild asthma

BACKGROUND

A selective recruitment of eosinophils to sites of allergic inflammation is suggested to be controlled by regulation of cytokines, chemokines and adhesion molecules.

OBJECTIVE

The aim of this study was to examine whether allergen challenge in skin chambers, applied on patients with allergic rhinitis and mild asthma, results in a selective influx of activated eosinophils and detectable levels of cytokines/chemokines related to eosinophil recruitment, such as interleukin (IL)-5 and eotaxin.

METHODS

A skin blister was induced on the volar aspect of each forearm; one contained PBS-heparin buffer (control) and the other was challenged with relevant allergen. Peripheral blood was drawn before the allergen was applied to the skin chamber, and the expression of CD9, CD11b and EG2-epitope on intracellular eosinophil cationic protein (ECP) was analysed in eosinophils. Chamber fluid was collected 8 h after allergen application and analysed for differential cell counts, expression of eosinophil activity markers, the presence of ECP, eotaxin, and IL-5.

RESULTS

The number of recruited leucocytes was equal in the allergen-challenged chambers and in controls. However, the number of eosinophils was significantly increased in the allergen-challenged chambers, and elevated levels of released ECP were measured. Moreover, the eosinophils recruited were activated, as shown by increased expression of EG2 and CD11b, and decreased expression of CD9, in comparison with blood eosinophils. In the skin chamber fluids, higher levels of eotaxin were detected in the allergen-challenged chambers than in controls, but there were no detectable levels of IL-5.

CONCLUSION

We have demonstrated a selective recruitment of eosinophils, and higher levels of released ECP and eotaxin, in skin chambers stimulated with allergen, as compared with control chambers. Allergen challenge in skin chambers is a useful tool for studies of eosinophil recruitment, their state of activation, and their involvement in the allergic inflammatory response.

Influence of interaction of environmental risk factors and sensitization in young asthmatic children

BACKGROUND

The increasing prevalence of asthma and allergy in many countries demands evaluation of potential risk factors to improve the possibility of prevention.

OBJECTIVE

We studied the association between exposure to cat and dog allergen and allergic sensitization in young children with asthma and interactions with potential environmental risk factors.

METHODS

One hundred eighty-nine young children with asthma were evaluated. IgE antibodies to cat and dog were analyzed. Questionnaires were filled in focusing on exposure to cats and dogs, environmental tobacco smoke (ETS), and signs of home dampness as indicated by window pane condensation (WPC) during the first years of life. House dust was analyzed for content of cat (Fel d 1) and dog (Can f 1) allergen.

RESULTS

There was a strong association between the degree of reported exposure to cat and dog and the concentration of the respective allergens in floor dust. A dose-response relationship was found between cat exposure, measured as either reported degree of cat exposure or cat allergen levels in dust, and sensitization both to cat and dog. No such relationship was found between exposure and sensitization to dog. WPC increased the risk for sensitization to cat (odds ratio = 2.6, 95% confidence interval 1.2-5.8), whereas ETS strongly tended to do so both to cat and dog. Interaction was found between exposure to ETS, WPC, and high levels of cat allergen (>8 microg/g dust). The presence of all 3 risk factors revealed a multiplicative interaction with a high risk of sensitization to cat (odds ratio = 42.0, 95% confidence interval 3.7-472.8).

CONCLUSIONS

Keeping cats indoors may be a health hazard for infants and young children at risk for development of asthma, particularly when they live in a damp house and their parents smoke.

Vernal keratoconjunctivitis in a Stockholm ophthalmic centre--epidemiological, functional, and immunologic investigations

PURPOSE

To classify a cohort of 62 patients with vernal keratoconjunctivitis (VKC) in immunologic, functional, and epidemiological terms.

METHODS

A retrospective chart review was conducted to establish the patients' ethnic origin and to ascertain the results of standard in vitro and in vivo testing for atopic allergy. The latter data were compared with tear Phadiatop, an allergy screening test, in 31 subjects. Further subgroup analyses included methacholine bronchial provocations, serum screening for chlamydial antibodies and epidemiological calculations of the observed prevalence of VKC in the Stockholm area in 1994.

RESULTS

Thirty-seven subjects (59.7%) were sensitised to common allergens. No additional allergic subjects were diagnosed with the tear Phadiatop test. The serology for ocular chlamydial disease was negative. Only 6 out of 17 subjects displayed bronchial reactivity to methacholine of whom 4 had a history of asthma. VKC was clearly more common in individuals with an Asian and African origin.

CONCLUSIONS

Sensitivity to allergens is a strong determinant for the disease but in a large proportion of the subjects this immunologic abnormality is absent. The varying prevalence of the condition in different ethnic groups indicates a genetic predisposing factor.

Evaluation of specific IgE to the recombinant group 2 mite allergens Lep d 2 and Tyr p 2 in the Pharmacia CAP system

BACKGROUND

Several recombinant allergens have been shown to be potentially useful for diagnosis of IgE-mediated allergy, but only a few recombinant allergens are at present commercially available in serological assays for detection of specific IgE. The aim of this study was to evaluate the IgE binding to the recombinant major dust mite allergens rLep d 2 and rTyr p 2 and compare it with the IgE binding to the commercial mite extracts Lepidoglyphus destructor and Tyrophagus putrescentiae in the Pharmacia RAST CAP System.

METHODS

The recombinant allergens rLep d 2 and rTyr p 2 were immobilised on ImmunoCAPs, and sera from 461 Swedish farmers who are frequently exposed to mites were analysed for specific IgE antibodies. Immunoblotting was performed to evaluate discrepancies between the results obtained with the recombinant and the commercial CAP assays.

RESULTS

The IgE values of each recombinant assay significantly correlated with the IgE values of the corresponding commercial CAP assay. The sensitivity of the rLep d 2 assay was 73.3% and that of the rTyr p 2 assay, 60.5% of that provided by the commercial L. destructor and T. putrescentiae assays. Two subjects out of 416, who tested negative in the commercial L. destructor assay, were positive to rLep d 2. The corresponding figures for rTyr p 2 and the T. putrescentiae extract were 5/418. The possibility that these subjects were sensitised to L. destructor and T. putrescentiae could not be excluded.

CONCLUSIONS

The data suggest that it may be possible to use rLep d 2 and rTyr p 2 on ImmunoCAPs to detect and quantify IgE antibodies to these, the major allergens of L. destructor and T. putrescentiae. It appears likely that the addition of just a few more recombinant L. destructor and T. putrescentiae allergens in the CAP assay will be sufficient for in vitro diagnosis of IgE mediated allergy to L. destructor and T. putrescentiae.

Identification and characterisation of two allergens from the dust mite Acarus siro, homologous with fatty acid-binding proteins

BACKGROUND

Dust mites are a major cause of allergic disease worldwide. The dust mite Acarus siro is an inducer of occupational allergy among farmers, but sensitisation has also been found in non-farming populations.

METHODS

A degenerate primer was designed to the N-terminal amino acid sequence of a 15-kD IgE-binding protein in A. siro extract. The cDNA sequence was obtained by using reverse transcriptase polymerase chain reaction, standard cloning and sequencing techniques. The protein was expressed in Escherichia coli with a 6-histidine tag at its C-terminus. Immunoblotting of the recombinant protein and whole extract was performed using patient sera.

RESULTS AND CONCLUSION

15 and 17-kD allergens were identified in a fraction of A. siro extract. The cDNA of the 15-kD allergen was isolated, cloned and sequenced and the allergen was expressed as a recombinant protein. The calculated molecular weight of the cDNA-encoded protein is 14.2 kD. The predicted amino acid sequence has one potential N-glycosylation site at position 4-6 and a cytosolic fatty acid-binding protein signature at position 5-22. The protein has 64% sequence identity with Blo t 13, an allergen from the dust mite Blomia tropicalis, as well as homology with several other fatty acid-binding proteins (FABPs) from different organisms. The allergen was named Aca s 13 and was recognised strongly by 3 of 13 (23%) of the subjects investigated. The amino acid sequence of the 17-kD protein was partly determined and it also showed high sequence homology with Blo t 13 and FABPs.

Sensitization to allergens of house-dust mite in adults with atopic dermatitis in a cold temperature region

BACKGROUND

An IgE-mediated contact reaction to airborne allergens has been suggested as one important pathogenetic mechanism in atopic dermatitis (AD). The house-dust mite (HDM) might be a common allergen involved. In Scandinavia, sensitization to HDM has been rare, probably because of the cold, dry climate. However, recent studies indicate high levels of domestic mites and HDM allergen in 15-20% of homes in central and northern Sweden.

METHODS

To evaluate the importance of the HDM in patients with AD in the Stockholm region, we screened 81 adult Stockholm residents with AD, for the prevalence and degree of sensitization to the HDM, according to specific IgE (RAST), skin prick test (SPT), and atopy patch test (APT). We also assessed the HDM exposure in their homes and correlated the results with clinical history, severity of the dermatitis, and type of residence during childhood and today.

RESULTS

The sensitization rate to HDM was high (56% according to RAST, 24% according to SPT, and 47% according to APT), and 20% of the patients were exposed to HDM allergens in their beds. Mite exposure seemed to aggravate the dermatitis in highly sensitized patients.

CONCLUSIONS

The results indicate that we have to take the HDM into account when discussing aggravating factors in adult patients with AD in the Stockholm region.

Allergen-induced accumulation of eosinophils and lymphocytes in skin chambers is associated with increased levels of interleukin-4 and sVCAM-1

BACKGROUND

The aim of the study was to characterize the kinetic accumulation of various inflammatory mediators in allergen-challenged skin chambers applied on patients with pollen-related allergic rhinitis/mild asthma.

METHODS

Skin blisters were induced on the forearms and challenged with allergen or phosphate-buffered saline (PBS). Peripheral blood was drawn before and 8 h after challenge for analysis of differential cell counts, sVCAM-1, and alpha2-macroglobulin. Chamber fluids, collected at 1, 4, and 8 h after allergen application, were analyzed for differential cell counts, histamine, interleukin (IL)-4, sVCAM-1, and alpha2-macroglobulin.

RESULTS

The number of recruited leukocytes was equal in allergen and PBS chambers; however, the numbers of eosinophils and lymphocytes were significantly (P< or =0.05) elevated in allergen-challenged chambers at 8 h. Compared to PBS chambers, allergen chambers contained significantly (P<0.01-0.05) higher levels of histamine (at 1 and 4 h), IL-4 (at 4 and 8 h), alpha2-macroglobulin (at 1 and 8 h), and sVCAM-1 (at 1 and 8 h). In contrast to alpha2-macroglobulin, levels of sVCAM-1 in peripheral blood were significantly (P<0.05) increased at 8 h.

CONCLUSIONS

Increased levels of sVCAM-1 and IL-4 in allergen-challenged chambers, in parallel with increased recruitment of eosinophils and lymphocytes, points to the participation of IL-4 and VCAM-1 in the development of the late-phase reaction. Increased levels of sVCAM-1 in allergen-challenged chambers probably reflects a combination of leakage and local production.

Clinical and immunologic aspects of storage mite allergy

Exposure to storage (nonpyroglyphid) mites has been increasingly recognized as a cause of asthma and rhinitis. Several species have been identified in Europe; e.g., Lepidoglyphus destructor, Acarus farris/siro, Tyrophagus spp., Glycyphagus domesticus, and Blomia tjibodas. Blomia tropicalis, on the other hand, predominates in subtropical and tropical areas. Studies from several countries have shown that IgE-mediated allergy in rural populations is of considerable importance and that storage mites are major allergens. Since these mites are found in homes, especially in regions with damp housing conditions, urban populations are at risk of becoming sensitized. Therefore, sensitization is not restricted only to those with occupational exposure. Several major allergens from storage mites have been identified and characterized. There seems to be a limited allergenic cross-reactivity between storage- and house dust mites. Molecular cloning has demonstrated that the Group 2 allergens from storage mites (Lep d 2 and Tyr p 2) show more than 40% sequence identity with the Group 2 allergens from Dermatophagoides spp. The availability of a large number of recombinant dust mite allergens will make it possible to investigate their homology and the number of allergens required for the diagnosis and treatment of storage mite allergy.

Exposure to an abundance of cat (Fel d 1) and dog (Can f 1) allergens in Swedish farming households

BACKGROUND

Earlier studies have shown that farmers are to a low degree sensitized to animal allergens. We have measured the amount of cat (Fel d 1) and dog (Can f 1) in farm households and examined the relationship between exposure and sensitization to cat and dog allergens.

METHODS

Dust samples from the homes of 403 farmers who had participated in an epidemiologic follow-up study on respiratory symptoms were analyzed for allergen content by two-site ELISA methods.

RESULTS

Fel d 1 was detected in 99.5% of the farmers' households ranging from 0.055 to 1455 microg/g dust in mattresses (GM 13.2) and to 3775 microg/g dust in living-room carpets (GM 17.1). Can f 1 was detected in 90.6% of the households from 0.2 to 116 microg/g dust in mattresses (GM 2.0) and to 504 microg/g dust in carpets (GM 4.3). Homes with pets present had the highest levels of the allergens (P<0.001). A total of 8.4% and 7.4% of the farmers were sensitized to cat and dog, respectively. A significant correlation was noted between exposure to the allergens and specific IgE to cat and dog, respectively (P<0.001). Sensitization to cat (OR = 4.9) and dog (OR = 17.8) was significantly associated with asthma.

CONCLUSIONS

In spite of the abundance of Fel d 1 and Can f 1, farmers are only to a low degree sensitized to cats and dogs.

Markers of inflammation and bronchial reactivity in children with asthma, exposed to animal dander in school dust

Several studies have confirmed the presence of animal dander allergens in school dust but the effect of this indirect animal exposure on health has not been evaluated. In this study we investigated bronchial reactivity and markers of eosinophil activity and inflammation during two separate weeks of school in 10 children with mild asthma and a positive skin prick test to cat and dog. At the beginning and the end of the first week the children underwent bronchial challenges with methacholine, and at the beginning and the end of the second week they underwent nasal lavages (NAL) and induced sputum samplings. Blood and urine samples for analysis of inflammatory markers were obtained before and after both school weeks. Peak expiratory flow (PEF) and symptoms of asthma and allergy were recorded daily, and spirometry was performed on each visit. The exposure to animal dander allergens was estimated from dust samples obtained in the subjects' schools and homes. Bronchial sensitivity to methacholine increased in the week when this was measured. The proportion of eosinophils in peripheral blood, and urinary eosinophil protein X (EPX), decreased in both weeks. There was a trend towards an increase of eosinophil peroxidase (EPO) and myeloperoxidase (MPO) in sputum in the week when these proteins were measured. The concentrations of cat (Fel d1) and dog (Can f1) allergens were higher in dust collected in schools than in homes. Our results show that in children with mild asthma and animal dander allergy, there is a significantly increased bronchial sensitivity to methacholine after one school week. There is also a significant decrease in the number of circulating eosinophils and a trend towards an increase of sputum EPO, which could correlate with the early phase of eosinophil recruitment to the lungs. These effects may be related to the continuous exposure to animal allergens in school dust.

Increasing prevalence of asthma over 12 years among dairy farmers on Gotland, Sweden: storage mites remain dominant allergens

BACKGROUND

Earlier studies from several countries have shown that IgE-mediated allergy in rural populations is of considerable importance and that storage mites are dominant allergens.

OBJECTIVE

In an epidemiological follow-up study among farmers on the island of Gotland, Sweden in 1996 we wished to investigate the prevalence of respiratory allergy and to find out whether storage mites are still important allergens in a farming environment.

METHODS

A questionnaire concerning airway symptoms, social and working conditions and smoking habits was distributed to all Gotland farmers aged 15-65 years and was completed by 1577 (86.7%), of whom 1015 were dairy farmers. Based on the answers, 500 dairy farmers were invited to undergo a medical examination which included a skin-prick test (SPT) and blood sampling for RAST analyses. Prevalence figures (symptoms, RAST and SPT) given for the whole population (n = 1015) were based on the investigation of the 461 farmers who took part in the examination.

RESULTS

Immediate onset hypersensitivity was present in 41.7% of the 1015 farmers studied, which is almost the same figure as in 1984 (40.0%). The prevalence of asthma had increased significantly during the previous 12 years (5.3% vs 9.8%), as had asthma in combination with rhinoconjunctivitis (3.7% vs 7.0%). Rhinoconjunctivitis, on the other hand, had not changed significantly (36.5% vs 33.1%) and remained one of the most common symptoms. The prevalence of storage mite allergy in the farming population in 1996 was 6.5% and constituted an important cause of allergic symptoms.

CONCLUSION

Over 12 years, Gotland dairy farmers have developed significantly more respiratory symptoms from the lower airways, although the proportion with atopy is unchanged. Storage mites are still dominant allergens for developing allergic disease.

IgE binding capacity of synthetic and recombinant peptides of the major storage mite (Lepidoglyphus destructor) allergen, Lep d 2

BACKGROUND

Lepidoglyphus destructor is an important non-pyroglyphid mite species in Europe and a dominant allergen in farming environments. The major allergen of L. destructor, Lep d 2, is a protein of 13.2 kD that is recognised by about 90% of sera RAST positive to this mite species.

METHODS

The cDNA of two isoallergens of the Lep d 2 has previously been sequenced and the protein expressed in different protein expression systems. In order to map the B-cell epitopes, the full length protein and the truncated forms of the protein have been expressed in Escherichia coli as glutathione-S-transferase (GST) fusion proteins. Recombinant Lep d 2 fragments and synthetic overlapping 15 mer peptides spanning Lep d 2 were probed with sera from patients allergic to storage mite.

RESULTS

The full-length (125 amino acids) GST fusion protein reacted strongly with patient IgE in Western blots and dot blots. Synthetic peptides failed to react with IgE antibodies from mite-allergic patients and the truncated fusion proteins displayed weak IgE-binding capacity.

CONCLUSION

We conclude that there are no dominant linear IgE-binding epitopes in Lep d 2. Recombinant or synthetic Lep d 2 fragments may, however, be further evaluated as hypoallergenic candidate molecules for specific immunotherapy.

Contribution of disulphide bonds to antigenicity of Lep d 2, the major allergen of the dust mite Lepidoglyphus destructor

To study the contribution of the 3 disulphide bonds in the major allergen Lep d 2 to the antigenic structure, site-directed mutagenesis was performed. Mutants with one or more cysteine residues altered were constructed with a histidine residue tag for purification purposes and expressed as recombinant proteins in E. coli. Seven mutants were analysed: 3 single mutants (Cys 8, Cys 21 and Cys 72), 3 double mutants (Cys 8-117, Cys 21-16 and Cys 72 77) and one mutant with all 6 cysteines altered (6 Cys). The evaluation of IgE reactivity in 10 allergic patients showed that the disulphide bond formed by cysteine 72 and 77 was the single most contributing bond to IgE binding. Mutants with disruption of the Cys 8-117 bond had a lesser reduction in IgE binding, even though this alteration seemed to influence the compact nature of Lep d 2. However, to abolish the IgE reactivity almost completely, all 6 cysteines had to be altered. A monoclonal antibody previously raised against Lepidoglyphus destructor showed a similar binding as human IgE with no reactivity to the Cys 72 77 or the 6 Cys mutant. Using skin prick test we found no reaction to the 6 Cys mutant at the concentrations tested (1-100 microg/ml) in an Lepidoglyphus destructor allergic patient, while the T-cell reactivity was preserved. The 6 Cys mutant of Lep d 2 may, after further evaluation, be a candidate molecule for improved immunotherapy of Lepidoglyphus destructor allergy.

IgG subclass antibody responses to birch pollen in sibling pairs discordant for atopy

Birch pollen allergen specific IgG and IgE antibodies were analysed in the sera of fourteen sibling pairs discordant for atopy. In addition, eight unrelated children free of atopic disease were included in the study. The presence of Bet v 1 specific antibodies in the sera were analysed by an immunoblotting assay. All but one (13/14) of the atopic children had detectable anti-Bet v 1 antibodies of the IgG1 and IgG4 subclasses. The child lacking IgG1 and IgG4 antibodies to Bet v 1 was the only allergic child lacking IgE to Bet v 1. In contrast, only one of the non-atopic siblings (1/14) displayed detectable IgG1 antibodies to Bet v 1. Furthermore, among the non-atopic siblings none (0/14), had detectable IgG4 antibodies to Bet v 1. In the unrelated control group no detectable IgG1 or IgG4 anti-Bet v 1 were detected (0/8). Thus of the non-atopic children only one out of 22 children displayed IgG1 anti-Bet v 1 antibodies. Taken together, it appears that the non-atopic children in general have no/low allergen specific IgG to birch pollen.

Expression of two isoforms of Lep d 2, the major allergen of Lepidoglyphus destructor, in both prokaryotic and eukaryotic systems

BACKGROUND

The dust mite Lepidoglyphus destructor is a major cause of allergic diseases among farmers. We have previously cloned and sequenced two isoforms of the major allergen Lep d 2 (formerly designated Lep d 1) and found significant homology to group 2 allergens of the house dust mite species Dermatophagoides. We now report on the production and characterization of recombinant Lep d 2.

OBJECTIVE

We have expressed both isoforms in two different expression systems; a eukaryotic system, baculovirus in insect cells and a prokaryotic system, E. coli. We have compared the two systems in regard to production yields and immunoreactivity of the recombinant allergens.

METHODS

The complete cDNA including the natural leader sequence was cloned into the pBlueBacIII transfer vector, and the rLep d 2 was produced as a secreted protein in baculovirus. For the expression in E. coli, the cDNA was cloned into the pET vector, and the rLep d 2 was produced with six C-terminal histidine residues. The purified recombinant allergens were tested for immunoreactivity with 10 sera from subjects allergic to Lepidoglyphus destructor and were compared with native Lep d 2 using inhibition immunoblotting. The ability of the recombinant allergens to release histamine from basophils was evaluated using a histamine release assay.

RESULTS

Both expression systems produced immunoreactive recombinant allergens. They inhibited the binding of human sera to native Lep d 2 confirming their retained IgE binding properties. The yield of pure recombinant protein from the prokaryotic system was approximately 1 mg/L compared to the eukaryotic system which produced up to 4 mg/L in an adherent cell culture system.

CONCLUSIONS

We have produced recombinant Lep d 2 in prokaryotic and eukaryotic expression systems which are comparable to the native allergen. Recombinant Lep d 2 might now be included in more extensive clinical studies to confirm its usefulness in the in vitro and the in vivo diagnosis of Lepidoglyphus destructor.