ImmunoCAP assays: Pros and cons in allergology van Hage, Marianne, MD, PhD; Hamsten, Carl, PhD; Valenta, Rudolf, MD
Journal of allergy and clinical immunology,
10/2017, Letnik:
140, Številka:
4
Journal Article
Recenzirano
Odprti dostop
Allergen-specific IgE measurements and the clinical history are the cornerstones of allergy diagnosis. During the past decades, both characterization and standardization of allergen extracts and ...assay technology have improved. Here we discuss the uses, advantages, misinterpretations, and limitations of ImmunoCAP IgE assays (Thermo Fisher Scientific/Phadia, Uppsala, Sweden) in the field of allergology. They can be performed as singleplex (ImmunoCAP) and, for the last decade, as multiplex (Immuno Solid-phase Allergen Chip ISAC). The major benefit of ImmunoCAP is the obtained quantified allergen-specific IgE antibody level and the lack of interference from allergen-specific IgG antibodies. However, ImmunoCAP allergen extracts are limited to the composition of the extract. The introduction of allergen molecules has had a major effect on analytic specificity and allergy diagnosis. They are used in both singleplex ImmunoCAP and multiplex ImmunoCAP ISAC assays. The major advantage of ISAC is the comprehensive IgE pattern obtained with a minute amount of serum. The shortcomings are its semiquantitative measurements, lower linear range, and cost per assay. With respect to assay performance, ImmunoCAP allergen extracts are good screening tools, but allergen molecules dissect the IgE response on a molecular level and put allergy research on the map of precision medicine.
Background Isolated Ara h 8 sensitization is suggested to be associated with no or mild symptoms among peanut-sensitized subjects. Objective We sought to investigate the occurrence of systemic ...reactions in children with isolated sensitization to Ara h 8. Methods Participants were 144 children sensitized to Ara h 8 (≥0.35 kUA /L) but not to Ara h 1, Ara h 2, or Ara h 3 (<0.35 kUA /L). An open oral challenge with peanut was performed in those subjects who did not consume peanut regularly, and an extended IgE reactivity profile was obtained. If the child had a documented history of systemic reactions up to grade I anaphylaxis, double-blind, placebo-controlled food challenges were performed. Results One hundred twenty-nine (89.5%) children were either peanut consumers or did not react to peanut challenge. Another 14 (9.7%) children experienced oral cavity symptoms at the first 2 but not subsequent challenge doses. At the time of the double-blind, placebo-controlled food challenge, 1 boy with a previous mild systemic reaction to peanut experienced lip swelling, stomach cramping, and objective tiredness. Reanalysis of IgE levels showed an increase in peanut IgE levels from 1.5 to 8.8 kUA /L, but IgE levels to Ara h 8 remained stable and IgE levels to Ara h 1, Ara h 2, and Ara h 3 were all still less than 0.35 kUA /L. The IgE level to Ara h 6 was 0.45 kUA /L. Conclusion Isolated Ara h 8 sensitization indicates tolerance to peanuts in almost all cases. However, sensitization against thus far unidentified determinants in peanut might cause symptoms in rare cases.
Background Sensitization to individual cat and dog allergen molecules can contribute differently to development of allergy to these animals. Objective We sought to investigate the association between ...sensitization patterns to cat and dog allergen molecules during childhood and symptoms to these furry animals up to age 16 years. Methods Data from 779 randomly collected children from the Barn/Children Allergy/Asthma Milieu Stockholm Epidemiologic birth cohort at 4, 8, and 16 years were used. IgE levels to cat and dog were determined by using ImmunoCAP, and levels to allergen molecules were determined by using an allergen chip based on ISAC technology (Mechanisms for the Development of Allergy chip). Allergy was defined as reported rhinitis, conjunctivitis, or asthma at exposure to cat or dog. Results Cross-sectionally, IgE to Fel d 1 and cat extract had similar positive predictive values for cat allergy. IgE to Can f 1 showed a higher positive predictive value for dog allergy than dog extract IgE. Sensitizations to Fel d 1 and Can f 1 in childhood were significantly associated with symptoms to cat or dog at age 16 years. Polysensitization to 3 or more allergen molecules from cat or dog was a better longitudinal predictor of cat or dog symptoms than results of IgE tests with cat or dog allergen extract, respectively. Cross-sectionally, cat/dog-polysensitized children had higher IgE levels and more frequent symptoms to cat and dog than monosensitized children. Conclusions Sensitization to Fel d 1 and Can f 1 in childhood and polysensitization to either cat or dog allergen molecules predict cat and dog allergy cross-sectionally and longitudinally significantly better than IgE to cat or dog extract.
Significant correlations between IgE to alpha-Gal and the different mammalian allergens were noted (see Fig E1 in this article's Online Repository at www.jacionline.org). Because the medical ...investigation revealed that all patients had been bitten by ticks, the majority more than 10 times (Table I), we investigated whether our patients were sensitized to the European tick I ricinus and whether they also recognized IgE epitopes in A americanum (described in the Methods section in this article's Online Repository at www.jacionline.org).
Background
Mammalian meat is the most common trigger of the allergic reactions in patients with α‐Gal syndrome (AGS). Milk and dairy, although less often, also cause a significant number of allergic ...manifestations. The aim of this study was to identify α‐Gal‐containing bovine milk proteins with allergenic properties among AGS patients.
Methods
Thirty‐eight AGS patients with IgE to milk were included in the study. Milk proteins were analyzed for the presence of α‐Gal and for binding by patients’ IgE using immunoblot, ImmunoCAP, and inhibition ELISA. Allergenicity of milk and milk proteins was assessed by basophil activation test.
Results
More than half of the AGS patients reported allergic reactions to milk or dairy products. Bovine γ‐globulin (BGG), lactoferrin (LF), and lactoperoxidase (LPO) were identified as α‐Gal carrying proteins which were recognized by AGS patients’ IgE. Whey mirrored the anti‐α‐Gal and IgE reactivity of BGG, LF, and LPO. Eighty‐nine percent of the patients displayed IgE to BGG, 91% to LF, and 57% to LPO. Inhibition of α‐Gal‐specific IgE binding was achieved by BGG, LF, LPO, and whey. These proteins also activated AGS patients’ basophils. Interestingly, at lower concentrations, LF was the most potent inhibitor of IgE binding, and the most potent activator of basophils.
Conclusion
BGG, LF, and LPO were all found to be relevant milk α‐Gal‐containing glycoproteins that bound AGS patients’ IgE antibodies and activated their basophils. These proteins are probably involved in the allergic reactions to milk in AGS patients. LPO was for the first time shown to be an allergen.
More than half of the AGS patients reported allergic reactions to milk or dairy products. Bovine γ‐globulin, lactoferrin, and lactoperoxidase were found to be relevant milk α‐Gal‐containing glycoproteins that bound AGS patients’ IgE antibodies and activated their basophils. These proteins are probably involved in the allergic reactions to milk and dairy products in AGS patients. Abbreviations: α‐Gal, galactose‐α‐1,3‐galactose; AGS, α‐Gal syndrome; kUA/L, kilo units of allergen‐specific IgE per liter.
Background
Factors predicting allergic sensitization in the first 6 months of life are poorly understood. We aimed to determine whether eczema, dry skin, and high transepidermal water loss (TEWL) at ...3 months were associated with allergic sensitization at 6 months of age and, secondarily, to establish whether these characteristics predicted sensitization from 3 to 6 months of age.
Methods
At 3 months of age, 1,994 infants from the population‐based PreventADALL birth cohort in Norway and Sweden were assessed for eczema and dry skin on the cheeks and/or extensors; impaired skin barrier function, defined as TEWL in the upper quartile (>9.4 g/m2/h), and allergen‐specific IgE levels <0.1 kUA/L, available in 830. At 6 months, we assessed allergic sensitization to any food (egg, cow's milk, peanut, wheat, soy) or inhalant (birch, timothy grass, dog, and cat) allergen by a skin prick test wheal diameter ≥2 mm larger than negative control.
Results
Any sensitization was found in 198 of the 1,994 infants (9.9%), the majority to food allergens (n = 177, 8.9%). Eczema, dry skin, and high TEWL at 3 months increased the risk of sensitization at 6 months; adjusted odds ratios 4.20 (95% CI 2.93–6.04), 2.09 (95% CI 1.51–2.90) and 3.67 (95% CI 2.58–5.22), respectively. Eczema predicted sensitization with 55.6% sensitivity and 68.1% specificity; dry skin with 65.3% sensitivity and 57.3% specificity; and high TEWL with 61.7% sensitivity and 78.1% specificity.
Conclusion
Eczema, dry skin, and high TEWL at 3 months predicted allergic sensitization at 6 months of age.
At 6 months, 198/1994 infants (9.9%) had any sensitization, the majority to food. Eczema, dry skin, and high TEWL at 3 months increased the risk of sensitization at 6 months of age. Eczema, dry skin, and high TEWL at 3 months predicted incident sensitization at 6 months of age (n = 87/830, 10.5%). Abbreviations: Adj, adjusted; kUA/L, kilounits of allergen‐specific IgE per liter; OR, odds ratio; SPT, skin prick test; TEWL, transepidermal water loss.
Background
Understanding differences in sensitization profiles at the molecular allergen level is important for diagnosis, personalized treatment and prevention strategies in allergy.
Methods
...Immunoglobulin E (IgE) sensitization profiles were determined in more than 2800 sera from children in nine population‐based cohorts in different geographical regions of Europe; north BAMSE (Sweden), ECA (Norway), west/central PIAMA (the Netherlands), BiB (the United Kingdom), GINIplus (Germany), and south INMA Sabadell and Gipuzkoa (Spain) and ROBBIC Rome and Bologna (Italy) using the MeDALL‐allergen chip.
Results
Sensitization to grass pollen allergen, Phl p 1, and to major cat allergen, Fel d 1, dominated in most European regions whereas sensitization to house dust mite allergens Der p 1, 2 and 23 varied considerably between regions and were lowest in the north. Less than half of children from Sabadell which has a hot and dry climate were sensitized to respiratory allergens, in particular house dust mite allergens as compared to Gipuzkoa nearby with a more humid climate. Peanut allergen Ara h 1 was the most frequently recognized class 1 food allergen in Northern/Western Europe, while the fruit allergens Pru p 3, Act d 1 and 2 were prominent in Southern and Western/Central Europe. Ves v 5‐sensitization dominated in North and West/Central Europe.
Conclusion
We show regional, exposome‐ and climate‐dependent differences in molecular IgE‐reactivity profiles in Northern, Western/Central and Southern Europe which may form a molecular basis for precision medicine‐based approaches for treatment and prevention of allergy.
Sera from nine population‐based birth cohorts representing Northern, West/Central, and Southern Europe were analyzed for IgE to more than 170 micro‐arrayed allergen molecules. The sensitization map revealed exposome‐ and climate‐dependent sensitization profiles, with strong regional differences. The results form a molecular basis for precision medicine‐based approaches for prevention and treatment of allergy. Abbreviations: IgE, immunoglobulin E; ISAC, multiplex specific IgE test
Background Peanut allergy affects persons from various geographic regions where populations are exposed to different dietary habits and environmental pollens. Objective We sought to describe the ...clinical and immunologic characteristics of patients with peanut allergy from 3 countries (Spain, the United States, and Sweden) using a molecular component diagnostic approach. Methods Patients with peanut allergy from Madrid (Spain, n = 50), New York (United States, n = 30), Gothenburg, and Stockholm (both Sweden, n = 35) were enrolled. Clinical data were obtained either from a specific questionnaire or gathered from chart reviews. IgE antibodies to peanut extract and the peanut allergens rAra h 1, 2, 3, 8 and 9, as well as to cross-reactive birch (rBet v 1) and grass (rPhl p 1, 5, 7, and 12) pollen allergens, were analyzed. Results American patients frequently had IgE antibodies to rAra h 1 to 3 (56.7% to 90.0%) and often presented with severe symptoms. Spanish patients recognized these 3 recombinant peanut allergens less frequently (16.0% to 42.0%), were more often sensitized to the lipid transfer protein rAra h 9 (60.0%), and typically had peanut allergy after becoming allergic to other plant-derived foods. Swedish patients detected rAra h 1 to 3 more frequently than Spanish patients (37.1% to 74.3%) and had the highest sensitization rate to the Bet v 1 homologue rAra h 8 (65.7%), as well as to rBet v 1 (82.9%). Spanish and Swedish patients became allergic to peanut at 2 years or later, whereas the American children became allergic around 1 year of age. Conclusions Peanut allergy has different clinical and immunologic patterns in different areas of the world. Allergen component diagnostics might help us to better understand this complex entity.
Background Not much data are available from large, unselected, birth cohort studies on the natural course and comorbidities of rhinitis in children. Objective To study phenotypes of rhinitis in ...relation to the natural course and comorbidities of allergic diseases in preschool-age and early school-age children. Methods We analyzed data from a birth cohort of 2024 children, for whom information on IgEs against 8 common inhaled allergens was available, collected at age 4 and 8 years. The children were assigned to groups of allergic rhinitis (rhinitis with sensitization to allergens), nonallergic rhinitis (rhinitis without sensitization), allergic sensitization but no rhinitis, or neither rhinitis nor sensitization. Results The proportion of children with allergic rhinitis increased from 5% to 14% from age 4 to 8 years, whereas the proportion of children with nonallergic rhinitis decreased slightly over the same period of development, from 8% to 6%. Of the children with allergic rhinitis when they were 4 years old, 12% underwent remission by the time they were 8 years old; of the children with nonallergic rhinitis, 73% underwent remission during this period of development. Among 4-year-olds without rhinitis who were sensitized to allergen, 56% had allergic rhinitis when they were 8 years old. Among 4- and 8-year-olds, allergic rhinitis and nonallergic rhinitis were associated with asthma, eczema, and food hypersensitivity. Twenty-five percent of 8-year-olds with allergic rhinitis also had oral allergy syndrome. Conclusions Fewer preschool-age children with allergic rhinitis undergo remission than do those with nonallergic rhinitis. Sensitization to inhaled allergens at an early age (4 years) precedes the development of allergic rhinitis, whereas symptoms of rhinitis do not. Oral allergy syndrome is common among 8-year-olds with allergic rhinitis.
Background The role of exposure to air pollution in the development of allergic sensitization remains unclear. Objective We sought to assess the development of sensitization until school age related ...to longitudinal exposure to air pollution from road traffic. Methods More than 2500 children in the birth cohort BAMSE (Children, Allergy, Milieu, Stockholm, Epidemiological Survey) from Stockholm, Sweden, were followed with repeated questionnaires and blood sampling until 8 years of age. Outdoor concentrations of nitrogen oxides, as a marker of exhaust particles, and particles with an aerodynamic diameter of less than 10 μm (PM10 ), mainly representing road dust, were assigned to residential, day care, and school addresses by using dispersion models. Time-weighted average exposures were linked to levels of IgE against common inhalant and food allergens at 4 and 8 years of age. Results Air pollution exposure during the first year of life was associated with an increased risk of pollen sensitization at 4 years of age (odds ratio, 1.83; 95% confidence interval, 1.02-3.28) for a 5th to 95th difference in exposure to nitrogen oxides. At 8 years, there was no general increase in the risk of sensitization; however, the risk of food sensitization was increased, particularly among children free of sensitization at 4 years of age (odds ratio, 2.30; 95% confidence interval, 1.10-4.82). Results were similar by using PM10 . No associations between air pollution exposure after the first year of life and sensitization were seen. Conclusion Traffic-related air pollution exposure does not seem to increase the overall risk of sensitization to common inhalant and food allergens up to school age, but sensitization to certain allergens might be related to exposure during infancy.
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