IgE recognition patterns in peanut allergy are age dependent: perspectives of the EuroPrevall study.

BACKGROUND: We tested the hypothesis that specific molecular sensitization patterns correlate with the clinical data/manifestation in a European peanut-allergic population characterized under a common protocol. METHODS: Sixty-eight peanut-allergic subjects and 82 tolerant controls from 11 European countries were included. Allergy to peanut and lowest symptom-eliciting dose was established by double-blind placebo-controlled food challenge in all but anaphylactic subjects. Information of early or late (before or after 14 years of age) onset of peanut allergy was obtained from standardized questionnaires. IgE to peanut allergens rAra h 1-3, 6, 8-9, profilin and CCD was determined using ImmunoCAP. RESULTS: Seventy-eight percent of peanut allergics were sensitized to peanut extract and 90% to at least one peanut component. rAra h 2 was the sole major allergen for the peanut-allergic population. Geographical differences were observed for rAra h 8 and rAra h 9, which were major allergens for central/western and southern Europeans, respectively. Sensitization to rAra h 1 and 2 was exclusively observed in early-onset peanut allergy. Peanut-tolerant subjects were frequently sensitized to rAra h 8 or 9 but not to storage proteins. Sensitization to Ara h 2 ≥ 1.0 kUA /l conferred a 97% probability for a systemic reaction (P = 0.0002). Logistic regression revealed a significant influence of peanut extract sensitization and region on the occurrence of systemic reactions (P = 0.0185 and P = 0.0436, respectively). CONCLUSION: Sensitization to Ara h 1, 2 and 3 is usually acquired in childhood. IgE to Ara h 2 ≥ 1.0 kUA /l is significantly associated with the development of systemic reactions to peanut.

[Birch pollen allergy]. / Allergie au pollen de bouleau.

In the North-East of France, birch is the main tree responsible of spring pollen allergy. However, the epidemiology of sensitization to birch pollen remains unclear. Monosensitization to birch pollen seems rare because of the frequency of cross-reactions with other pollens of the same botanical family via the major allergen Bet v 1. Around one third of patients with allergic rhinoconjunctivitis due to birch pollen are also asthmatics and a half suffer from a food allergy, essentially an oral syndrome due to rosaceae fruits eaten raw. The molecular allergens of birch pollen are well-known and have been cloned. They are available for use in in vitro diagnostic tests and also in clinical trials of specific immunotherapy.

Nonallergic airway hyperresponsiveness and allergen-specific IgE levels are the main determinants of the early and late asthmatic response to allergen.

BACKGROUND: Conflicting results have been reported in studies of predictive factors for airway responsiveness to allergens during bronchial challenges. OBJECTIVE: The aim of this study was to assess determinants of airway responsiveness to 3 different allergens during standardized bronchial challenges. METHODS: Data were collected from asthmatic patients who participated in allergen challenge trials between 2000 and 2006 (cat, n = 37; house dust mite [HDM], n = 35; grass pollen, n = 27). PD20 (provocative dose causing a 20% fall in forced expiratory volume in the first second) methacholine, PD20 allergen, allergen skin test endpoint, allergen-specific immunoglobulin (Ig) E levels, and late asthmatic response were analyzed for each allergen group. RESULTS: During the early asthmatic response, a significant relationship was found between PD20 allergen and PD20 methacholine (P < .01 for cat, HDM, and grass pollen), as well as between PD20 allergen and allergen-specific IgE levels (P < .05 for cat and HDM). No relationship was observed between PD20 allergen and allergen skin test endpoint (P > .05). Late asthmatic response was significantly more frequent after HDM challenge than after cat or grass pollen challenges (57.1% vs16.2% and 33.3%, P < .01). Dual responders during HDM challenges had significantly higher allergen-specific IgE levels (P < .05) and higher nonallergic airway responsiveness (P < .05). CONCLUSION: Nonallergic airway hyperresponsiveness and allergen-specific IgE levels were the main determinants of early and late asthmatic responses. HDM challenges were the most interesting model with regard to the occurrence of late asthmatic response. In contrast to previous publications and to the official statement on standardized challenge testing with sensitizing stimuli, skin sensitivity appears to be a poor predictor of the early asthmatic response.

Comparison of genetically engineered hypoallergenic rBet v 1 derivatives with rBet v 1 wild-type by skin prick and intradermal testing: results obtained in a French population.

BACKGROUND: Bet v 1, the major allergen in birch pollen, is recognized by more than 90% of patients allergic to birch in northern and central Europe. Immunotherapy is commonly performed with birch pollen extracts. Recently, hypoallergenic derivatives of Bet v 1 (rBet v 1 fragments, rBet v 1 dimer and trimer) were constructed and purified. OBJECTIVE: Our aim was to compare the allergenic activity of wild-type rBet v 1 with recombinant Bet v 1 derivatives (rBet v 1 fragments, dimer and trimer) with potentially reduced anaphylactic activity by skin testing in a French population. METHODS: Among the 36 birch pollen allergic patients included in the study, 29 were tested by skin prick testing and 30 by intradermal injections with purified monosubstances: rBet v 1 fragments (F1: aa1-74 and F2: aa75-160), Bet v 1 dimer and trimer. Intradermal tests were performed by the end-point intradermal titration method. Eight of the intradermally-tested patients were previously hyposensitized. Tests were performed over a period of 6 months (before, during and after birch pollen season); Bet v 1-specific IgE and IgG4 subclass responses were measured by immunoblotting and ELISA. RESULTS: All patients showed lower reactivity with the modified rBet v 1 allergens, both in skin prick and intradermal tests. In 25 and 23 out of 29 patients the lowest concentration of fragment 1 and 2, respectively, resulting in a positive prick test was 100-fold higher than the lowest concentration of monomer resulting in a positive prick test. For dimer it was 100-fold or more in 25 out of 29 patients, and for trimer it was 100-fold or superior in 26 out of 29 patients. By intradermal testing, the end-point concentration was 160-fold higher for trimer than for monomer in 24 patients and 40-fold higher in five patients. For the two fragments the end-point concentration was 160-fold higher in 20 out of 22 patients. CONCLUSION: Genetically modified hypoallergenic derivatives of the major birch pollen allergen, Bet v 1 showed reduced capacity to induce immediate type skin reactions. They may represent candidate molecules for immunotherapy of birch pollen allergy with reduced risk of anaphylactic side-effects.

Serum eosinophil cationic protein measurements in the management of perennial and periodic asthma: a prospective study.

We performed a prospective study in order: 1) to determine whether a correlation could be found between serum eosinophil cationic protein (ECP) levels and clinical and functional status in perennial asthmatics during a 5 month prospective study; and 2) to evaluate the relationship between allergic exposure and ECP levels in periodic asthmatics. Two groups of asthmatic patients were selected: a group of acutely ill perennial asthmatics and a group of periodic asthmatics. The acutely ill perennial asthmatics (n=22, mean age=39.4 yrs) were included on the basis of hospitalization for acute asthma. At the end of the hospitalization, there was a 5 month follow-up of clinical, functional and medication scores, as well as eosinophil counts and ECP levels. The periodic asthmatic group was composed of asthmatics sensitized to birch and tree pollens (n=10, mean age=33.8 yrs). The same measurement were performed on this group, before, during and after the pollen season. Under corticosteroid treatment in the acutely ill patients, there was a significant decrease in serum ECP levels between the first day of hospitalization and the day of discharge (mean: 23.2 microg x L(-1) and 9.5 microg x L(-1), respectively; p=0.006). No correlation was found between the clinical status, functional status and serum ECP levels during the 5 month follow-up. A significant increase in ECP levels was found in periodic asthmatics during the pollen season. Our results suggest that serum eosinophil cationic protein is a useful marker of allergen exposure and of acute asthma treatment. This could be of importance in the prevention and follow-up of allergic asthma; the value of serum eosinophil cationic protein measurements in the day-to-day management of adult asthmatics needs to be further clarified.

Cross-reactions between respiratory and food allergens.

Cross-reactions between inhaled and food allergens are usually attributed to pollen hypersensitivity associated with fruit and vegetable allergy. However, other allergens are involved in these types of cross-reactions. In a few cases, there is a complete similarity between the inhaled and food allergens (garlic, crustacea proteins). More frequently, partial similarity has been demonstrated: whole inhaled allergens are included in ingested substances. Moreover, immunological techniques can demonstrate common antigenic epitopes in organic substances without any apparent relationship. This has been demonstrated by RAST-inhibition and/or immunoblot techniques, using sera from patients cross-sensitized to (1) pollens and fruits or vegetables or (2) avian sera and eggs. Respiratory sensitization always seems to precede food allergy symptoms.