María Dolores Ibáñez

Peanut allergy: Clinical and immunologic differences among patients from 3 different geographic regions

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.

Greater epitope recognition of shrimp allergens by children than by adults suggests that shrimp sensitization decreases with age

BACKGROUND Shellfish allergy is a long-lasting disorder typically affecting adults. Despite its high prevalence, there is limited information about allergenic shrimp proteins and the epitopes implicated in such allergic reactions. OBJECTIVE We sought to identify the IgE-binding epitopes of the 4 shrimp allergens and to characterize epitope recognition profiles of children and adults with shrimp allergy. METHODS Fifty-three subjects, 34 children and 19 adults, were selected with immediate allergic reactions to shrimp, increased shrimp-specific serum IgE levels, and positive immunoblot binding to shrimp. Study subjects and 7 nonatopic control subjects were tested by means of peptide microarray for IgE binding with synthetic overlapping peptides spanning the sequences of Litopenaeus vannamei shrimp tropomyosin, arginine kinase (AK), myosin light chain (MLC), and sarcoplasmic calcium-binding protein (SCP). The Wilcoxon test was used to determine significant differences in z scores between patients and control subjects. RESULTS The median shrimp IgE level was 4-fold higher in children than in adults (47 vs 12.5 kU(A)/L). The frequency of allergen recognition was higher in children (tropomyosin, 81% [94% for children and 61% for adults]; MLC, 57% [70% for children and 31% for adults]; AK, 51% [67% for children and 21% for adults]; and SCP, 45% [59% for children and 21% for adults]), whereas control subjects showed negligible binding. Seven IgE-binding regions were identified in tropomyosin by means of peptide microarray, confirming previously identified shrimp epitopes. In addition, 3 new epitopes were identified in tropomyosin (epitopes 1, 3, and 5b-c), 5 epitopes were identified in MLC, 3 epitopes were identified in SCP, and 7 epitopes were identified in AK. Interestingly, frequency of individual epitope recognition, as well as intensity of IgE binding, was significantly greater in children than in adults for all 4 proteins. CONCLUSIONS Children with shrimp allergy have greater shrimp-specific IgE antibody levels and show more intense binding to shrimp peptides and greater epitope diversity than adults.

IgE antibody response to vertebrate meat proteins including tropomyosin

BACKGROUND Although meat is a main source of proteins in western diets, little information is available regarding allergy to vertebrate meats or the allergens implicated in these reactions. OBJECTIVE To evaluate the in vitro IgE antibody response to different vertebrate meats in suspected meat-allergic subjects, as well as the possible role of tropomyosin in meat allergy and to analyze the cross-reactivity between vertebrate meats and the effect of heating on the IgE-binding to meat proteins. METHODS Fifty-seven sera from suspected meat-allergic subjects were tested by grid blot to extracts of beef, lamb, pork, venison, chicken, and turkey and to four mammalian tropomyosins of different origins. RESULTS Meat-allergic subjects have IgE antibodies to proteins in different mammalian meats (43/57 subjects); cross-reactivity with avian meat was limited: less than 50% (19/43) of meat positive sera reacted to chicken. In contrast, most of the poultry-positive sera also reacted to different mammalian meats. In general, there was stronger IgE reactivity to raw meats in comparison to cooked meats; an exception was six cases in which IgE reactivity to cooked poultry was stronger. Weak IgE reactivity to tropomyosin was detected in only 2/57 sera tested. CONCLUSIONS Suspected meat-allergic subjects have serum IgE directed to meat proteins. In vitro cross-reactivity among mammalian meats appears to be important, while cross-reactivity to poultry is limited indicating mammalian-specific proteins. Although cooking in general denatures meat proteins rendering them less allergenic, in some cases the process of cooking may result in the formation of new allergenic moieties. The muscle protein tropomyosin is not an important vertebrate meat allergen.

Tropomyosin IgE-positive results are a good predictor of shrimp allergy.

To cite this article: Gámez C, Sánchez‐García S, Ibáñez MD, López R, Aguado E, López E, Sastre B, Sastre J, del Pozo V. Tropomyosin IgE‐positive results are a good predictor of shrimp allergy. Allergy 2011; 66: 1375–1383.

Safety of specific sublingual immunotherapy with SQ standardized grass allergen tablets in children

The aim of the study was to confirm the safety of an orodispersible grass allergen tablet 75,000 SQ‐T (Grazax®, ALK‐Abelló A/S, Hørsholm, Denmark) in children aged 5–12 yr. The study was randomized, double‐blinded and placebo‐controlled. Sixty children aged 5–12 yr suffering from grass pollen‐induced rhinoconjunctivitis (with or without asthma) from five centres in two countries (three in Germany and two in Spain) participated in the study. They were randomized at the ratio of 3:1 as receiving either Grazax or placebo tablet given sublingually once daily for 28 days outside the grass pollen season. A total of 810 treatment‐related adverse events were reported in the Grazax group. The majority of these were local reactions in the mouth or throat and were mostly mild (71%) to moderate (27%) in severity and resolved within days. Thirty‐five (78%) subjects treated with Grazax and five (33%) treated with placebo reported at least one treatment‐related adverse event. Oral pruritus, throat irritation, mouth oedema and ear pruritus appeared as the most frequently reported treatment‐related adverse events. 62% (28 of 45) of the actively treated subjects reported oral pruritus, 36% (16 of 45) throat irritation, 31% (14 of 45) mouth oedema and 22% (10 of 45) ear pruritus. Two actively treated subjects withdrew from the study: one subject due to four adverse events (moderate eye pruritus, moderate pharyngolaryngeal pain, moderate non‐cardiac chest pain and moderate dysphagia) and one subject due to a serious adverse event (asthmatic attack). The subjects recovered completely from the events. In conclusion, in the present study, Grazax was in general tolerated in a paediatric population and considered suitable for further clinical investigations in children.

Identification of bovine IgG as a major cross-reactive vertebrate meat allergen.

Background: Although beef is a main source of protein in Western diets, very little has been published on allergic reactions to beef or the main allergens implicated in these reactions. The aim was to evaluate the IgE antibody response to beef in suspected meat‐allergic subjects and assess cross‐reactivity of beef with other vertebrate meats.

Reactividad cruzada de las legumbres

Legumes are dicotyledonous plants belonging to the Fabales order. The main distinctive characteristic of which is their fruit (legumen, seeds contained in pods). This botanical order is formed by three families: Mimosaceae, Caesalpiniaceae and Papilionaceae or Fabacea. The Papilionaceae family includes the most important allergenic species: Lens culinaris (lentil), Cicer arietinum (chick-pea), Pisum sativum (pea), Arachis hipogea (peanut), Phaseolus vulgaris (bean) y Glycine max (soy). Legumes are an important ingredient in the Mediterranean diet. Among Spanish children, sensitivity to legumes is the fifth most prevalent food allergy. Lentil and chick-pea are the most frequent cause of allergic reactions to legumes in Spanish children. Legumes could be involved in severe allergic symptoms. The different legumes have structurally homologous proteins, but they are not all equally allergenic, thus making it difficult to distinguish in vitro and in vivo cross-reactivity. We have demonstrated by skin tests and CAP that most of the patients are sensitised to more than one species. We have demonstrated a great degree of cross-reactivity among lentil, chick-pea, pea and peanut by ELISA inhibition (> 50 % max. inhibition). Unlike the Anglo-Saxons population, this phenomenon implies clinical sensitisation for many Spanish children. The majority of our patients have had symptoms with more than one legume (median 3 legumes). Thirty-nine patients were challenged (open or simple blind) with two or more legumes and 32 (82 %) reacted to two or more legumes: 43,5 % to 3, 25,6 % to 2, 13 % to 4 legumes. Seventy three per cent of the patients challenged with lentil and pea had positive challenge to both, 69,4 % to lentil and chick-pea, 60 % to chick-pea and 64,3 % to lentil, chick-pea and pea simultaneously. Peanut allergy peanut can be associated to allergy to lentil, chick-pea and pea but less frequently. Contrarily, white bean and overall green bean and soy are well tolerated by children allergic to other legumes. In our study, 82 % of the children allergic to legumes had a sensitisation to pollen. Pea and bean are the legumes with more in vitro cross-reactivity with Lolium perenne, Olea europea and Betula alba. This cross-reactivity could be because of common antigenic determinants or due to the coexistence of pollen and legume allergy. Panallergens implication seems to be less probable. It is important to emphasize that in spite of an evident clinical and immunological cross-reactivity, the diagnosis of legume allergy should not be based only on specific IgE tests. The decision to eliminate one legume from the diet should be based on a positive oral food challenge.

Occupational asthma caused by cellulase

Inhalation of enzyme dusts can cause occupational asthma, and the list of enzymes able to induce asthma is increasing. We report two patients with asthma induced by occupational exposure to cellulase powder derived from Aspergillus niger. A type I hypersensitivity to this enzyme was demonstrated by means of skin test reactivity, positive passive transfer test, positive reverse enzyme immunoassay for specific IgE, and immediate bronchial provocation test response to cellulase dust. Skin tests with an A. niger extract were positive. Cross-reactivity between cellulase dust and an entire A. niger extract was also demonstrated.

Identification of IgE sequential epitopes of lentil (Len c 1) by means of peptide microarray immunoassay.

BACKGROUND Lentils are often responsible for allergic reactions to legumes in Mediterranean children. Although the primary sequence of the major allergen Len c 1 is known, the location of the IgE-binding epitopes remains undefined. OBJECTIVE We sought to identify IgE-binding epitopes of Len c 1 and relate epitope binding to clinical characteristics. METHODS One hundred thirty-five peptides corresponding to the primary sequence of Len c 1 were probed with sera from 33 patients with lentil allergy and 15 nonatopic control subjects by means of microarray immunoassay. Lentil-specific IgE levels, skin prick test responses, and clinical reactions to lentil were determined. Epitopes were defined as overlapping signal above interslide and intraslide cutoffs and confirmed by using inhibition assays with a peptide from the respective region. Hierarchic clustering of microarray data was used to correlate binding patterns with clinical findings. RESULTS The patients with lentil allergy specifically recognized IgE-binding epitopes located in the C-terminal region between peptides 107 and 135. Inhibition experiments confirmed the specificity of IgE binding in this region, identifying different epitopes. Linkage of cluster results with clinical data and lentil-specific IgE levels displayed a positive correlation between lentil-specific IgE levels, epitope recognition, and respiratory symptoms. Modeling based on the 3-dimensional structure of a homologous soy vicilin suggests that the Len c 1 epitopes identified are exposed on the surface of the molecule. CONCLUSION Several IgE-binding sequential epitopes of Len c 1 have been identified. Epitopes are located in the C-terminal region and are predicted to be exposed on the surface of the protein. Epitope diversity is positively correlated with IgE levels, pointing to a more polyclonal IgE response.

Early sustained unresponsiveness after short‐course egg oral immunotherapy: a randomized controlled study in egg‐allergic children

No studies have evaluated the potential of egg oral immunotherapy (egg‐OIT) to induce sustained unresponsiveness after discontinuing therapy following short‐term treatments.