Arantxa Palacín

Mimotope mapping as a complementary strategy to define allergen IgE-epitopes : Peach Pru p 3 allergen as a model

Lipid transfer proteins (LTPs) are the major allergens of Rosaceae fruits in the Mediterranean area. Pru p 3, the LTP and major allergen of peach, is a suitable model for studying food allergy and amino acid sequences related with its IgE-binding capacity. In this work, we sought to map IgE mimotopes on the structure of Pru p 3, using the combination of a random peptide phage display library and a three-dimensional modelling approach. Pru p 3-specific IgE was purified from 2 different pools of sera from peach allergic patients grouped by symptoms (OAS-pool or SYS-pool), and used for screening of a random dodecapeptide phage display library. Positive clones were further confirmed by ELISA assays testing individual sera from each pool. Three-dimensional modelling allowed location of mimotopes based on analysis of electrostatic properties and solvent exposure of the Pru p 3 surface. Twenty-one phage clones were selected using Pru p 3-specific IgE, 9 of which were chosen using OAS-specific IgE while the other 12 were selected with systemic-specific IgE. Peptide alignments revealed consensus sequences for each pool: L37 R39 T40 P42 D43 R44 A46 P70 S76 P78 Y79 for OAS-IgE, and N35 N36 L37 R39 T40 D43 A46 S76 I77 P78 for systemic-IgE. These 2 consensus sequences were mapped on the same surface of Pru p 3, corresponding to the helix 2-loop-helix 3 region and part of the non-structured C-terminal coil. Thus, 2 relevant conformational IgE-binding regions of Pru p 3 were identified using a random peptide phage display library. Mimotopes can be used to study the interaction between allergens and IgE, and to accelerate the process to design new vaccines and new immunotherapy strategies.

Immunoglobulin E recognition patterns to purified Kiwifruit (Actinidinia deliciosa) allergens in patients sensitized to Kiwi with different clinical symptoms

Background Green kiwifruit allergy is on the rise. However, no surveys testing purified major kiwi allergens have been carried out in a large population, including both kiwi‐sensitized [skin prick test (SPT)‐positive] and truly kiwi‐allergic patients.

Characterization of peach thaumatin‐like proteins and their identification as major peach allergens

Background Peach is the most important fruit related to food allergy in the Mediterranean area. Pru p 3, its lipid transfer protein, has been described as the principal allergen responsible for cross‐reactivities with other foods and pollen and the severity of clinical symptoms. However, the involvement of other allergenic families cannot be ruled out. Thaumatin‐like proteins (TLPs) have been described as food allergen in several fruits, such as apple, cherry, kiwi and banana, and pollen.

The Involvement of Thaumatin-Like Proteins in Plant Food Cross-Reactivity: A Multicenter Study Using a Specific Protein Microarray

Cross-reactivity of plant foods is an important phenomenon in allergy, with geographical variations with respect to the number and prevalence of the allergens involved in this process, whose complexity requires detailed studies. We have addressed the role of thaumatin-like proteins (TLPs) in cross-reactivity between fruit and pollen allergies. A representative panel of 16 purified TLPs was printed onto an allergen microarray. The proteins selected belonged to the sources most frequently associated with peach allergy in representative regions of Spain. Sera from two groups of well characterized patients, one with allergy to Rosaceae fruit (FAG) and another against pollens but tolerant to food-plant allergens (PAG), were obtained from seven geographical areas with different environmental pollen profiles. Cross-reactivity between members of this family was demonstrated by inhibition assays. Only 6 out of 16 purified TLPs showed noticeable allergenic activity in the studied populations. Pru p 2.0201, the peach TLP (41%), chestnut TLP (24%) and plane pollen TLP (22%) proved to be allergens of probable relevance to fruit allergy, being mainly associated with pollen sensitization, and strongly linked to specific geographical areas such as Barcelona, Bilbao, the Canary Islands and Madrid. The patients exhibited >50% positive response to Pru p 2.0201 and to chestnut TLP in these specific areas. Therefore, their recognition patterns were associated with the geographical area, suggesting a role for pollen in the sensitization of these allergens. Finally, the co-sensitizations of patients considering pairs of TLP allergens were analyzed by using the co-sensitization graph associated with an allergen microarray immunoassay. Our data indicate that TLPs are significant allergens in plant food allergy and should be considered when diagnosing and treating pollen-food allergy.

Sensitization profiles to purified plant food allergens among pediatric patients with allergy to banana

To cite this article: Palacin A, Quirce S, Sanchez‐Monge R, Bobolea I, Diaz‐Perales A, Martin‐Muñoz F, Pascual C, Salcedo G. Sensitization profiles to purified plant food allergens among pediatric patients with allergy to banana. Pediatr Allergy Immunol 2011; 22: 186–195.

Anaphylaxis to Wheat Flour-Derived Foodstuffs and the Lipid Transfer Protein Syndrome: A Potential Role of Wheat Lipid Transfer Protein Tri a 14

Background: Food allergy to wheat-derived foodstuffs is on the rise. Tri a 14, a wheat flour lipid transfer protein (LTP) allergen, has been described as a major allergen associated with baker’s asthma and wheat food allergy. Cross-reactivity among LTP allergens leads to the so-called ‘LTP syndrome’. Methods: Eight adult patients showing anaphylaxis after ingestion of wheat-derived foodstuffs were selected. A homemade wheat extract, purified natural (n) and recombinant (r) Tri a 14, and peach fruit and Artemisia pollen LTP allergens Pru p 3 and Art v 3 were subjected to skin prick test, specific IgE determination (ELISA) and IgE immunodetection assays. Results: All tests were positive in the 8 selected patients with the homemade extract. Positive skin prick test responses to nTri a 14, Pru p 3 and Art v 3 were found in 5/8, 6/8 and 4/4 patients, respectively. Specific IgE determined by ELISA assays was detected in 6 to nTri a 14 and rTri a 14, in 4 to Pru p 3 and in 3 to Art v 3 out of 8 individual sera tested, whereas all these sera showed IgE binding to nTri a 14 and Pru p 3 in immunodetection after SDS-PAGE separation. Conclusions: Tri a 14 seems to be a relevant allergen in patients with anaphylaxis after ingestion of wheat flour foodstuffs, according to in vitro and in vivo results. Clinical history of the analyzed patients, together with sensitization to peach Pru p 3 and Artemisia pollen Art v 3, suggests that 6 of them suffer from LTP syndrome.

Characterization of IgE epitopes of Cuc m 2, the major melon allergen, and their role in cross-reactivity with pollen profilins

Background Plant profilins are described as minor allergens, although with some exceptions in foods such as melon, watermelon or orange. In fact, they could be responsible for many cross‐reactions among distantly related species. This is likely to be a consequence of the presence of common epitopes.

Graph based study of allergen cross-reactivity of plant lipid transfer proteins (LTPs) using microarray in a multicenter study.

The study of cross-reactivity in allergy is key to both understanding. the allergic response of many patients and providing them with a rational treatment In the present study, protein microarrays and a co-sensitization graph approach were used in conjunction with an allergen microarray immunoassay. This enabled us to include a wide number of proteins and a large number of patients, and to study sensitization profiles among members of the LTP family. Fourteen LTPs from the most frequent plant food-induced allergies in the geographical area studied were printed into a microarray specifically designed for this research. 212 patients with fruit allergy and 117 food-tolerant pollen allergic subjects were recruited from seven regions of Spain with different pollen profiles, and their sera were tested with allergen microarray. This approach has proven itself to be a good tool to study cross-reactivity between members of LTP family, and could become a useful strategy to analyze other families of allergens.

Transport of Pru p 3 across gastrointestinal epithelium – an essential step towards the induction of food allergy?

Since intestinal absorption of food protein can trigger an allergic reaction, the effect of plant food allergen on intestinal epithelial cell permeability and its ability to cross the epithelial monolayer was evaluated.

Salt-soluble proteins from wheat-derived foodstuffs show lower allergenic potency than those from raw flour.

Salt-soluble proteins from wheat flour have been described as main allergens associated with both bakers asthma and food allergy. However, most studies have used raw flour as starting material, thus not considering potential changes in allergenic properties induced by the heat treatment and other industrial processing to produce wheat-derived foodstuffs. Salt extracts from different commercial wheat-derived products were obtained and their allergenic properties investigated by IgE-immunodetection, ELISA assays, and skin prick test. The IgE-binding capacity of salt-soluble proteins from commercial breads and cooked pastas was reduced around 50% compared with that of raw flour, the reduction being less dramatic in noncooked pastas and biscuits. Several wheat-derived foodstuffs showed major IgE-binding components of 20 and 35 kDa, identified as avenin-like and globulin proteins, respectively. These proteins, as well as most flour and bread salt-soluble proteins, were hydrolyzed when subjected to simulated gastrointestinal digestion. However, the digested products still exhibited a residual IgE-binding capacity. Therefore, processing of wheat flour to obtain derived foodstuffs decreases the IgE binding-capacity of the major salt-soluble wheat proteins. Moreover, simulated gastric fluid digestion further inactivates some heat-resistant IgE-binding proteins.