Evaluation of the applicability of the Immuno‐solid‐phase allergen chip (ISAC) assay in atopic patients in Singapore
Amelia SantosaAnand Kumar AndiappanOlaf RötzschkeHung Chew WongAmanda ChangMei Bigliardi‐QiDe Yun WangPaul L. Bigliardi
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Atopy
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<i>Background:</i> Genetic studies of atopy rely upon evidence of abnormal IgE production, usually elevated total IgE or skin prick test (SPT) reactions. However, these measures may change with subject age. <i>Methods:</i> We screened 1,099 members of atopic families (aged 6–87 years) by serum total IgE and SPT for 14 allergens. For those SPT negative, we screened for Amb a 1- and Der p 1-specific IgE. Der p 1 IgE-Der p 1 allergen binding affinities were done on randomly selected subjects. <i>Results:</i> There were significantly fewer atopics ≤10 years old (69.1%) compared to those >10 years old (75.8%) based upon any SPT-positive result. Children ≤10 years had fewer SPT-positive reactions and smaller SPT wheal reaction areas. Yet, mean total IgE values were comparable to those of the older group. Screens for specific IgE showed no differences in proportions of atopics (≤10 years old = 83.1% and >10 years old = 82.3%). Among those SPT-positive for house dust mite extract, there was a positive correlation between Der p 1 binding affinity and the wheal area of the house dust mite extract. There was a positive correlation between the number of SPT-positive reactions and total IgE for both age groups. However, there was only a significant relationship between SPT-positive wheal area and total IgE for those >10 years old and no apparent relationship between wheal area and total IgE for those ≤10 years old. <i>Conclusion:</i> These results suggest that atopy-specific physiological mechanisms, primarily those involving allergen-IgE binding, change during the earliest years of life.
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Our examination of 225 subjects who had been exposed to the insect allergen Chi t I involved the degree of allergen exposure, the exposure-associated symptoms, and their relationship to the presence of specific IgE and IgG antibodies as well as sensitization to ubiquitous allergens. It could be shown that specific IgE antibodies found in 34% of these subjects were closely associated with symptoms (P < 0.01), whereas no relationship between IgG antibodies and complaints could be observed. Conjunctivitis (63%) and rhinitis (62%) were predominant, followed by asthma (45%) and urticaria (37%). Antibody levels of patients suffering from asthma were highest. In addition, symptoms were associated with the degree of exposure. While nearly all IgE-sensitized subjects of the medium-, high-, and very high-exposure group were symptomatic, only 57% of the sensitized individuals of the low-exposure group reported complaints. Furthermore, specific IgE antibodies were most frequently present in the groups with medium (46%) and high (54.5%) exposure, whereas IgG antibodies predominated in individuals with very high exposure (69.1%). In the low-exposure group, most subjects (73.6%) had neither IgE nor IgG antibodies. In addition, within Chi t I sensitized subjects, sensitization to common allergens and elevated total IgE levels were more frequently present than within non-Chi t I sensitized individuals, indicating a predisposition to allergy.
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Background: We examined the role of fish intake in the development of atopic disease with particular reference to the possibility of differential effects on allergen‐specific subgroups of sensitization. Methods: The exposure of interest was parental report of fish intake by children aged 8 years at the 1997 Childhood Allergy and Respiratory Health Study ( n = 499). The outcomes of interest were subgroups of atopy: house dust mite (HDM)‐pure sensitization [a positive skin‐prick test (SPT) ≥2 mm to Der p or Der f only], ryegrass‐pure sensitization (a positive SPT ≥2 mm to ryegrass only); asthma and hay fever by allergen‐specific sensitization. Results: A significant association between fish intake and ryegrass‐pure [adjusted odds ratio (AOR) 0.37 (0.15–0.90)] but not HDM‐pure sensitization [AOR 0.87 (0.36–2.13)] was found. Fish consumption significantly decreased the risk for ryegrass‐pure sensitization in comparison with HDM‐pure sensitization [AOR 0.20 (0.05–0.79)]. Conclusions: We have demonstrated a differential effect of fish intake for sensitization to different aeroallergens. This may be due to the different timing of allergen exposure during early life. Further investigation of the causes of atopic disease should take into account allergen‐specific subgroups.
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Summary Background Almost no information is available regarding the prevalence of IgE‐mediated allergies and the disease‐eliciting allergens in tropical Africa. Objective To study IgE‐mediated allergies and the allergen profile in allergic patients from Zimbabwe. Methods The frequency of sensitization to common environmental allergen sources was determined by skin prick testing in 650 allergic patients from Zimbabwe. Fifty representative sera were analysed for IgE reactivity to 20 respiratory and 20 food allergen extracts by multiallergen extract testing. The IgE reactivity profiles to recombinant pollen and mite allergens were compared between grass pollen‐ and mite‐sensitized patients from Zimbabwe and central Europe. Sera from grass pollen‐allergic patients were also analysed for IgE reactivity to nitrocellulose‐blotted natural timothy grass and Bermuda grass pollen allergens. Results IgE‐mediated allergies were found to be common in Zimbabwe. Similar to the situation in central Europe, mites and grass pollens represented the most prevalent allergen sources. However, the IgE reactivity profiles determined with single recombinant pollen and mite allergens revealed interesting differences between the European and African patients, which most likely reflect the local allergen exposure. Conclusions The striking differences regarding sensitization to grass pollen and mite allergens between African and European patients revealed by recombinant allergen‐based testing emphasize the need for component‐resolved allergy testing to optimize allergy prevention and therapy in different populations.
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We subjected seven asthmatic children to two bronchial allergen challenges, first with an extract from the house dust mite Dermatophagoides pteronyssinus (Der p) and then Dermatophagoides farinae (Der f), or vice versa. All children had elevated specific serum IgE to both species as well as reactions by crossed radioimmuno/electrophoresis (CRIE) to both group I and II allergens from both species. Immunoabsorption and subsequent analysis by CRIE showed a considerable concentration of serum IgE with specificity for epitopes common to the two species of house dust mite. Home dust sampling established that all children were exposed to Der f and only two to Der p. On bronchial provocation tests, all responded to Der f with an immediate reaction and five with a late reaction, only three of seven showed an immediate response to Der p, with four of the seven showing a late reaction. Our data could indicate that the local allergic immune reaction in the respiratory tract is sustained by ongoing exposure, and may thus have a different species specificity than the response reflected in the serum. In conclusion, our data indicates a lack of association between in vitro and in vivo tests for house dust mite allergy, which supports the continuing need for monitoring current clinical sensitization by allergen provocation tests and by measuring domestic exposure to the corresponding allergen. Extended studies are needed to support our findings.
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Summary Background There is evidence that the specificity of the IgE binding in allergy tests can vary for different populations. Objective We aimed to examine the allergenic specificity of IgE binding in sera from house dust mite (HDM)‐atopic subjects in a tropical Australian Aboriginal community. Methods Sera shown to contain IgE antibodies to an HDM extract of Dermatophagoides pteronyssinus were examined for IgE binding to a panel of nine purified HDM allergens from this mite species by quantitative microtitre assays. IgG antibody binding (IgG1 and IgG4) was also measured. Results The IgE‐binding activity in the sera from the Aboriginal community was not directed to the expected major groups 1 and 2 HDM allergens but instead to the group 4 amylase allergen. There was also little IgE binding to the potentially cross‐reactive tropomyosin (Der p 10) or arginine kinase (Der p 20) allergens. The IgG4 antibody was rarely detected and limited to the Der p 4 allergen. IgG1 antibody binding was frequently measured to all the allergens regardless of an individual's atopic status, whereas in urban communities it is restricted to the major allergens and to atopic subjects. Conclusion The high IgE anti‐HDM response of Australian Aboriginals predominantly bound Der p 4 and not the Der p 1 and 2 allergens, showing a distinctive allergy that could affect the disease outcome and diagnosis.
Pyroglyphidae
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Abstract Background House dust mites (HDM) Dermatophagoides pteronyssinus are a frequent indoor allergen source. Our aim was to determine the frequencies of IgE reactivity to purified HDM allergen molecules in mite allergic patients from different parts of Europe in order to establish an allergen panel for diagnosis of HDM allergy. Materials and methods Populations of D. pteronyssinus ‐allergic patients from Austria ( n = 56), France ( n = 55), Italy ( n = 67) and Sweden ( n = 65) and storage mite allergic patients from Sweden ( n = 31) were analysed for IgE reactivity to eight purified natural (n) and recombinant (r) D. pteronyssinus allergens (nDer p 1, rDer p 2, nDer p 4, rDer p 5, rDer p 7, rDer p 8, rDer p 10 and rDer p 14) in RAST‐based dot blot assays. Results Using a combination of Der p 1 and Der p 2, at least 97% of the D. pteronyssinus ‐allergic patients could be diagnosed in each of the HDM allergic populations. However, more than 50% of the patients also reacted with other allergens and significant variabilities regarding the frequencies of IgE reactivity to individual allergen molecules were found. Patients with a predominant storage mite allergy showed none or only very weak IgE reactivity to purified D. pteronyssinus allergens. Conclusions Purified Der p 1 and Der p 2 are sufficient for the diagnosis of ≥ 97% of D. pteronyssinus allergic patients in Europe, but other allergens may also play an important role for the diagnosis and treatment of HDM allergy.
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