Optimization of the diagnosis and characterization of gibberellin-regulated protein sensitization: An Italian cohort study

BACKGROUND

Pru p 7 was the first gibberellin-regulated protein (GRP) to be identified as a food allergen as the basis of a pollen food allergy syndrome.

OBJECTIVE

To clinically and biologically characterize a group of patients with suspected allergy to Pru p 7 to optimize the diagnostic workup of GRP sensitization.

METHODS

Allergy to Pru p 7 was suspected in the presence of a systemic allergic reaction to plant food, positive skin prick test results for cypress pollen and lipid-transfer protein-enriched peach extract, and absence of Pru p 3-specific immunoglobulin E. Controls were patients with food allergies, patients sensitized to Pru p 3, and patients with cypress allergy without food allergy. Diagnostic workup included skin tests, basophil activation test, Western blot, and single and multiplex assays.

RESULTS

In total, 23 patients and 14 controls were enrolled. The most implicated food was peach (91.3%). Approximately 70% of patients reacted to multiple foods. Mueller 4 reactions were 8.7%. In 26.1% of cases, a cofactor triggered the reaction. The basophil activation test results were positive for rPru p 7 in 87% of the patients. Specific immunoglobulin E to Pru p 7 was detected in 95.7% by singleplex and in 73.9% by multiplex assays in patients with suspected allergies; 73.9% of them also reacted to cypress pollen GRP (Cup s 7) in Western blot analysis.

CONCLUSION

Patients with Pru p 7-Cup s 7 allergy in our cohort confirm a mild-to-severe clinical syndrome characterized by pollen and food allergy. The diagnosis may benefit from the proposed selection criteria that can be used as preliminary steps to further characterize the cross-reactive GRP sensitization.

Structural Basis for the IgE-Binding Cross-Reacting Epitopic Peptides of Cup s 3, a PR-5 Thaumatin-like Protein Allergen from Common Cypress (Cupressus sempervirens) Pollen

The present work was aimed at identifying the IgE-binding epitopic regions on the surface of the Cup s 3 allergen from the common cypress Cupressus sempervirens, that are possibly involved in the IgE-binding cross-reactivity reported between Cupressaceae species. Three main IgE-binding epitopic regions were mapped on the molecular surface of Cup s 3, the PR-5 thaumatin-like allergen of common cypress Cupressus sempervirens. They correspond to exposed areas containing either electropositive (R, K) or electronegative (D, E) residues. A coalescence occurs between epitopes #1 and #2, that creates an extended IgE-binding regions on the surface of the allergen. Epitope #3 contains a putative N-glycosylation site which is actually glycosylated and could therefore comprise a glycotope. However, most of the allergenic potency of Cup s 3 depends on non-glycosylated epitopic peptides. The corresponding regions of thaumatin-like allergens from other closely related Cupressaceae (Cryptomeria, Juniperus, Thuja) exhibit a very similar conformation that should account for the IgE-binding cross-reactivity observed among the Cupressaceae allergens.

Gibberellin-regulated proteins: Emergent allergens

About 10 years ago, a protein family was shown for the first time to contain allergenic members, gibberellin-regulated protein (GRP). The first reported member was from peach, Pru p 7. One can hypothesize that it was not detected before because its physicochemical characteristics overlap with those of lipid transfer protein (LTP), a well-known allergen, or because the exposure to GRP increased due to an increase in the gibberellin phythormone level in plant food, either exogenous or endogenous. Like LTPs, GRPs are small cationic proteins with disulfide bridges, are resistant to heat and proteolytic cleavage, and are involved in the defense of the plant. Besides peach, GRP allergens have been described in Japanese apricot (Pru m 7), sweet cherry (Pru av 7), orange (Cit s 7), pomegranate (Pun g 7), bell pepper (Cap a 7), strawberry (Fra a GRP), and also in pollen with a restriction to Cupressaceae tree family (Cup s 7, Cry j 7, and Jun a 7). IgE cross-reactivities were described between GRPs, and the reported peach/cypress and citrus/cypress syndromes may therefore be explained because of these GRP cross-reactivities. GRPs are clinically relevant, and severe adverse reactions may sometimes occur in association with cofactors. More than 60% and up to 95% sequence identities are calculated between various allergenic GRPs, and three-dimensional models show a cleft in the molecule and predict at least three epitopic regions. The structure of the protein and its properties and the matrix effect in the original allergenic source should be unraveled to understand why, despite the ubiquity of the protein family in plants, only a few members are able to sensitize patients.

Update on pollen-food allergy syndrome

INTRODUCTION

Allergies affect 20-30% of the population and respiratory allergies are mostly due to pollen grains from anemophilous plants. One to 5% of people suffer from food allergies and clinicians report increasing numbers of pollen-food allergy syndrome (PFAS), such that the symptoms have broadened from respiratory to gastrointestinal, and even to anaphylactic shock in the presence of cofactors. Thirty to 60% of food allergies are associated with pollen allergy while the percentage of pollen allergies associated to food allergy varies according to local environment and dietary habits.

AREAS COVERED

Articles published in peer-reviewed journals, covered by PubMed databank, clinical data are discussed including symptoms, diagnosis, and management. A chapter emphasizes the role of six well-known allergen families involved in PFAS: PR10 proteins, profilins, lipid transfer proteins, thaumatin-like proteins, isoflavone reductases, and β-1,3 glucanases. The relevance in PFAS of three supplementary allergen families is presented: oleosins, polygalacturonases, and gibberellin-regulated proteins. To support the discussion a few original relevant results were added.

EXPERT OPINION

Both allergenic sources, pollen and food, are submitted to the same stressful environmental changes resulting in an increase of pathogenesis-related proteins in which numerous allergens are found. This might be responsible for the potential increase of PFAS.

Molecular approach to a patient's tailored diagnosis of the oral allergy syndrome

Oral allergy syndrome (OAS) is one of the most common IgE-mediated allergic reactions. It is characterized by a number of symptoms induced by the exposure of the oral and pharyngeal mucosa to allergenic proteins belonging to class 1 or to class 2 food allergens. OAS occurring when patients sensitized to pollens are exposed to some fresh plant foods has been called pollen food allergy syndrome (PFAS). In the wake of PFAS, several different associations of allergenic sources have been progressively proposed and called syndromes. Molecular allergology has shown that these associations are based on IgE co-recognition taking place between homologous allergens present in different allergenic sources. In addition, the molecular approach reveals that some allergens involved in OAS are also responsible for systemic reactions, as in the case of some food Bet v 1-related proteins, lipid transfer proteins and gibberellin regulated proteins. Therefore, in the presence of a convincing history of OAS, it becomes crucial to perform a patient's tailored molecule-based diagnosis in order to identify the individual IgE sensitization profile. This information allows the prediction of possible cross-reactions with homologous molecules contained in other sources. In addition, it allows the assessment of the risk of developing more severe symptoms on the basis of the features of the allergenic proteins to which the patient is sensitized. In this context, we aimed to provide an overview of the features of relevant plant allergenic molecules and their involvement in the clinical onset of OAS. The value of a personalized molecule-based approach to OAS diagnosis is also analyzed and discussed.

Gibberellin-regulated protein allergy: Clinical features and cross-reactivity

Gibberellin-regulated proteins (GRPs)/GASA proteins are members of cysteine-rich antimicrobial peptide families and are conserved in a broad range of plants. Some GRPs in fruits and pollens have been identified as allergens including peach Pru p 7, Japanese apricot Pru m 7, orange Cit s 7, pomegranate Pun g 7, and cypress pollen GRP. The clinical features of fruit-derived GRP allergies frequently include systemic reactions, multiple fruit allergies regardless of plant kingdom classifications and, less frequently, cofactor-dependence. Multiple fruit allergies might be related to cross-reactivity between GRPs. Clinical cross-reactivity, at least between the four fruit-derived GRPs, has been proven. In addition, GRP allergy induces peculiar clinical symptoms, such as laryngeal tightness and facial swelling, especially eyelid edema, which was proposed to be a predictive factor for Pru p 7 allergy. Fruit-derived GRPs have an unusually high content of cysteine, resulting in high stability to heat and resistance to digestive enzymes. Therefore, GRPs are considered "true" food allergens that induce severe allergic reactions. As an alternative mechanism of fruit-derived GRP allergies, cross-reactivity between fruit GRP and cypress pollen GRP, which might play a role as a sensitizer, is suspected. Taken together, these characteristics indicate GRPs are clinically relevant plant allergens. This review article summarizes our current knowledge of the clinical features and important aspects of GRP sensitization and allergy.

Plant food allergy: Influence of chemicals on plant allergens

Plant-derived foods are the most common allergenic sources in adulthood. Owing to the rapidly increasing prevalence of plant food allergies in industrialized countries, the environmental factors are suspected to play a key role in development of allergic sensitization. The present article provides an overview of ways by which chemicals may influence the development and severity of allergic reactions to plant foods, with especial focus on plant allergens up-regulated under chemical stress. In plants, a substantial part of allergens have defense-related function and their expression is highly influenced by environmental stress and diseases. Pathogenesis-related proteins (PR) account for about 25% of plant food allergens and some are responsible for extensive cross-reactions between plant-derived foods, pollen and latex allergens. Chemicals released by anthropogenic sources such as agriculture, industrial activities and traffic-related air pollutants are potential drivers of the increasing sensitization to allergenic PRs by elevating their expression and by altering their immunogenicity through post-translational modifications. In addition, some orally-taken chemicals may act as immune adjuvants or directly trigger non-IgE mediated food allergy. Taken together, the current literature provides an overwhelming body of evidence supporting the fact that plant chemical exposure and chemicals in diet may enhance the allergenic properties of certain plant-derived foods.

Identification of a polygalacturonase (Cup s 2) as the major CCD-bearing allergen in Cupressus sempervirens pollen

As IgE glyco-epitopes, also referred to as cross-reactive carbohydrate determinants (CCDs), can share significant structural homologies between different plants, they are prone to extensive cross-reactivity among allergen pollen extracts. Here, cypress pollen allergens, especially a polygalacturonase (PG), were further characterized using double one-dimensional electrophoresis (D1-DE). The presence of specific IgE directed against CCDs was investigated by bromelain IgE inhibition and concanavalin A binding assays using sera of cypress pollen-sensitized patients. Our results showed that IgE reactivity to CCDs in Cupressus sempervirens pollen extracts is mainly related to bromelain-type epitopes of a newly identified cypress PG. This glycoprotein has been further characterized through an immunoproteomic approach and officially indexed as Cup s 2 by the WHO/IUIS allergen nomenclature. Cup s 2 could thus be associated with the increased prevalence of IgE reactivity to cypress pollen extracts because of CCD interference.

Immunoproteomics of tree of heaven (Ailanthus atltissima) pollen allergens

Ailanthus altissima pollen (AAP) is considered as an emerging cause of respiratory allergy in United States, Italy and Iran. However, the allergenic composition of AAP is still unknown and has yet to be characterized. The present study aimed to identify AAP allergens using a proteomics-based approach. For this purpose, optimized AAP protein extracts were analyzed using 1D- and 2D- gel electrophoresis and confronted to twenty sera from individuals with respiratory allergy during the AAP season. Candidate allergens were detected using the serum from an allergic patient with clinical history of AAP pollinosis. IgE-binding spots were identified using MALDI-TOF/TOF mass spectrometry and database searching. According to our results, AAP extracts were rich in proteins (up to 16.25mg/ml) with a molecular-weight distribution ranging from 10 to 175kDa. Two-D electrophoresis of AAP extracts revealed 125 protein spots from which 13 were IgE reactive. These IgE-binding proteins were identified as enolase, calreticulin, probable pectate lyase 6, conserved hypothetical protein and ras-related protein RHN1-like. By our knowledge, this study is the first report identifying AAP allergens. These findings will open up further avenues for the diagnosis and immunotherapy of the AAP allergy as well as for the cloning and molecular characterization of relevant allergens.

BIOLOGICAL SIGNIFICANCE

Ailanthus altissima colonizes new areas every year in Iran and is spreading aggressively worldwide. According to USDA, the tree of heaven is now present as an invasive plant in 30 states in US (www.invasivespeciesinfo.gov/plants/treeheaven.shtml) and come to dominate large areas in many regions. Up to now, several cases of allergy to A. altissima pollen have been reported in United States, Italy and Iran [1-4]. However, there is still no information on the sensitizing allergens and the molecular origin of these clinical symptoms, which constitutes a serious threat to patients suffering from respiratory allergies in these regions. To our knowledge, the current study describes, therefore, the first panel of proteins responsible for IgE-mediated A. altissima pollinosis by using a gel-based proteomic approach. This work represents the pioneer proteomic investigation on Simaroubaceae spp. and provides useful insights for further studies on the allergens of this widely distributed plant family.

Urtica dioica pollen allergy: Clinical, biological, and allergomics analysis

BACKGROUND

The most emblematic members of Urticaceae at allergic risk level are wall pellitories (Parietaria), whereas nettle (Urtica) pollen is considered as poorly allergenic. No allergen from nettle pollen has yet been characterized, whereas 4 are listed for Parietaria pollen by the International Union of Immunological Societies. Clinical and biological profiles of 2 adult men who developed symptoms against nettle pollen and/or leaves were studied.

OBJECTIVE

To characterize the allergic reaction and identify the potential nettle pollen sensitizing allergens.

METHODS

IgE-mediated reaction to nettle pollen extract was evaluated by skin prick test, immunoassay, nasal provocation, and basophil activation test. To characterize specific nettle pollen allergens, an allergomic (IgE immunoproteomic) analysis was performed combining 1- and 2-dimensional electrophoresis, IgE immunoblots of nettle pollen extract, identification of allergens by mass spectrometry, and database queries.

RESULTS

The results of biological and immunochemical analyses revealed that the allergic rhinitis was due to Urtica dioica pollen in both patients. The allergomic analysis of nettle pollen extract allowed the characterization of 4 basic protein allergens: a thaumatin-like protein (osmotin) with a relative molecular mass of 27 to 29 kDa, a pectinesterase (relative molecular mass, 40 kDa), and 2 other basic proteins with relative molecular masses of 14 to 16 kDa and 43 kDa. There is no or only very weak allergen associations between pellitory and nettle pollen.

CONCLUSION

Exposure to nettle pollen can be responsible of allergic symptoms, and several allergens were characterized. Unravelling the allergens of this underestimated allergy might help to improve diagnosis and care for patients, to predict cross-reactivities and design adapted specific immunotherapy.

Prevalence of allergic sensitization to conifer pollen in a high cypress exposure area

Background:

Sensitization to Pinales (Cupressaceae and Pinaceae) has increased dramatically in recent years. The prevalence of sensitization in different geographic areas is related to exposure to specific pollens.

Objectives:

To investigate the prevalence of allergy to different conifer pollens, describe the characteristics of patients with such allergy, and identify the involved allergens.

Methods:

Patients were recruited at five hospitals near Madrid. Extracts from conifer pollen were prepared and used in skin-prick testing. Wheal sizes were recorded, and serum samples obtained from patients with positive reactions to Cupressus arizonica and/or Pinus pinea. The specific immunoglobulin E value to C. arizonica and Cup a 1 was determined. Individual immunoblots for each patient and with a pool of sera were performed. Allergenic proteins were sequenced by using liquid chromatography-tandem mass spectrometry.

Results:

Of 499 individuals included in the study, 17 (14%) had positive skin-prick test results to some conifer pollen extracts. Sixty-four patients had positive results to C. arizonica (prevalence 12.8%) and 11 had positive results to P. pinea (2.2%). All the patients had respiratory symptoms (61.4% during the C. arizonica pollination period), and 62.9% had asthma. Approximately 86% of the patients had positive specific immunoglobulin E results to C. arizonica and 92.3% had positive results to Cup a 1. Fourteen different bands were recognized by immunoblot; the most frequent bands were those detected at 43, 18, 16, and 14 kDa. All sequenced proteins corresponded to Cup a 1.

Conclusion:

Allergy to conifer pollen could be considered a relevant cause of respiratory allergy in central Spain. Asthma was more frequent than in other studies. We only identified Cup a 1 as involved in sensitization.