Profilin is a relevant melon allergen susceptible to pepsin digestion in patients with oral allergy syndrome

Profiles of apple allergen components and its diagnostic value in Northern China

Background

Limited is known on the profiles of apple allergy in China.

Objective

To explore the clinical significance of apple allergen components in northern China.

Methods

This study recruited 40 participants and categorized into apple tolerance (n = 19) and allergy (n = 21) group. The latter was categorized into oral allergy symptoms (OAS, n = 14) and generalized symptoms (GS, n = 7). All participants underwent ImmunoCAP screening to assess sIgE levels of birch, apple, and their components.

Results

The sensitization rates were 90% for Bet v 1, 85% for Mal d 1, 35% for Bet v 2, and 20% for Mal d 3. The overall positive rate for apple allergens was 97.5%, with half demonstrating mono-sensitization to Mal d 1. Birch, Bet v 1 and Mal d 1 sIgE levels had consistent areas under the curve (AUC 0.747, p = 0.037; AUC 0.799, p = 0.012; AUC 0.902, p < 0.001 respectively) in diagnosing apple allergy. The optimal cut-off values were determined to be 22.85 kUA/L (63.6% sensitivity, 85.7% specificity), 6.84 kUA/L (81.8% sensitivity, 71.4% specificity) and 1.61 kUA/L (93.8% sensitivity, 75.0% specificity), respectively. No allergens or components demonstrated diagnostic value in distinguishing between OAS and GS. Mal d 3 sensitization was correlated with mugwort allergy and higher risk of peach, nuts or legumes generalized allergy.

Conclusion

Mal d 1 was major allergen and the best for diagnosing apple allergy. Mal d 3 does not necessarily indicate severe allergic reaction to apples in northern China but may indicate mugwort sensitization and an increased risk of peach, nuts or legumes allergy.

EAACI Molecular Allergology User's Guide 2.0

Since the discovery of immunoglobulin E (IgE) as a mediator of allergic diseases in 1967, our knowledge about the immunological mechanisms of IgE-mediated allergies has remarkably increased. In addition to understanding the immune response and clinical symptoms, allergy diagnosis and management depend strongly on the precise identification of the elicitors of the IgE-mediated allergic reaction. In the past four decades, innovations in bioscience and technology have facilitated the identification and production of well-defined, highly pure molecules for component-resolved diagnosis (CRD), allowing a personalized diagnosis and management of the allergic disease for individual patients. The first edition of the "EAACI Molecular Allergology User's Guide" (MAUG) in 2016 rapidly became a key reference for clinicians, scientists, and interested readers with a background in allergology, immunology, biology, and medicine. Nevertheless, the field of molecular allergology is moving fast, and after 6 years, a new EAACI Taskforce was established to provide an updated document. The Molecular Allergology User's Guide 2.0 summarizes state-of-the-art information on allergen molecules, their clinical relevance, and their application in diagnostic algorithms for clinical practice. It is designed for both, clinicians and scientists, guiding health care professionals through the overwhelming list of different allergen molecules available for testing. Further, it provides diagnostic algorithms on the clinical relevance of allergenic molecules and gives an overview of their biology, the basic mechanisms of test formats, and the application of tests to measure allergen exposure.

Development of mouse model for oral allergy syndrome to identify IgE cross-reactive pollen and food allergens: ragweed pollen cross-reacts with fennel and black pepper

Oral allergy syndrome (OAS) is an IgE-mediated immediate food allergy that is localized to the oral mucosa. Pollen food allergy syndrome (PFAS), a pollinosis-associated OAS, is caused by cross-reactivity between food and pollen allergens. However, we need to more precisely understand the underlying pathogenesis of OAS/PFAS. In the present study, we developed a method to comprehensively identify cross-reactive allergens by using murine model of OAS and protein microarray technology. We focused on lip angioedema, which is one of the most common symptoms of OAS, and confirmed that mast cells reside in the tissues inside the lower lip of the mice. Interestingly, when the food allergen ovalbumin (OVA) was injected inside the lower lip of mice with high levels of OVA-specific IgE followed by an intravenous injection of the Evans blue dye, we found immediate dye extravasation in the skin of the neck in a mast cell-dependent manner. In addition, the degree of mast cell degranulation in the oral cavity, reflecting the severity of oral allergic responses, can be estimated by measuring the amount of extravasated dye in the skin. Therefore, we used this model of OAS to examine IgE cross-reactive allergens in vivo. Protein microarray analysis showed that serum IgE from mice intraperitoneally sensitized with ragweed pollen, one of the major pollens causing pollinosis, bound highly to protein extracts from several edible plants including black peppercorn and fennel. We confirmed that the levels of black pepper-specific IgE and fennel-specific IgE were significantly higher in the serum from ragweed pollen-sensitized mice than in the serum from non-sensitized control mice. Importantly, analysis of murine model of OAS showed that the injection of black pepper or fennel extract induced apparent oral allergic responses in ragweed pollen-sensitized mice. These results indicate IgE cross-reactivity of ragweed pollen with black pepper and fennel. In conclusion, we developed mouse model of OAS to identify IgE cross-reactive pollen and food allergens, which will help understand the pathogenesis of OAS/PFAS.

Novel murine mAbs define specific and cross-reactive epitopes on the latex profilin panallergen Hev b 8

The production of specific antibodies able to recognize allergens from different sources or block interactions between allergens and antibodies mediating allergic reactions is crucial for developing successful tools for diagnostics and therapeutics. Panallergens are highly conserved proteins present in widely different species, implicated in relevant cross-reactions. The panallergen latex profilin (Hev b 8) has been associated with the latex-food-pollen syndrome. We generated five monoclonal IgGs and one IgE from murine hybridomas against recombinant Hev b 8 and evaluated their interaction with this allergen using ELISA and biolayer interferometry (BLI). Affinity purified mAbs exhibited high binding affinities towards rHev b 8, with K_D1 values ranging from 10^-10 M to 10^-11 M. Some of these antibodies also recognized the recombinant profilins from maize and tomato (Zea m 12 and Sola l 1), and the ash tree pollen (Fra e 2). Competition ELISA demonstrated that some mAb pairs could bind simultaneously to rHev b 8. Using BLI, we detected competitive, non-competitive, and partial-competition interactions between pairs of mAbs with rHev b 8, suggesting the existence of at least two non-overlapping epitopes on the surface of this allergen. Three-dimensional models of the Fv of 1B4 and 2D10 IgGs and docking simulations of these Fvs with rHev b 8 revealed these epitopes. Furthermore, these two mAbs inhibited the interaction of polyclonal IgE and IgG4 antibodies from profilin-allergic patients with rHev b 8, indicating that the mAbs and the antibodies present in sera from allergic patients bind to overlapping epitopes on the allergen. These mAbs can be useful tools for immune-localization studies, immunoassay development, or standardization of allergenic products.

Are Physicochemical Properties Shaping the Allergenic Potency of Plant Allergens?

This review searched for published evidence that could explain how different physicochemical properties impact on the allergenicity of food proteins and if their effects would follow specific patterns among distinct protein families. Owing to the amount and complexity of the collected information, this literature overview was divided in two articles, the current one dedicated to protein families of plant allergens and a second one focused on animal allergens. Our extensive analysis of the available literature revealed that physicochemical characteristics had consistent effects on protein allergenicity for allergens belonging to the same protein family. For example, protein aggregation contributes to increased allergenicity of 2S albumins, while for legumins and cereal prolamins, the same phenomenon leads to a reduction. Molecular stability, related to structural resistance to heat and proteolysis, was identified as the most common feature promoting plant protein allergenicity, although it fails to explain the potency of some unstable allergens (e.g. pollen-related food allergens). Furthermore, data on physicochemical characteristics translating into clinical effects are limited, mainly because most studies are focused on in vitro IgE binding. Clinical data assessing how these parameters affect the development and clinical manifestation of allergies is minimal, with only few reports evaluating the sensitising capacity of modified proteins (addressing different physicochemical properties) in murine allergy models. In vivo testing of modified pure proteins by SPT or DBPCFC is scarce. At this stage, a systematic approach to link the physicochemical properties with clinical plant allergenicity in real-life scenarios is still missing.

Food Allergy in Adults: Presentations, Evaluation, and Treatment

Food allergy presents in all ages and has a significant impact on an individual's quality of life. Some of the food allergies that start in childhood remain into adulthood and new-onset allergies can occur at any point of life. Health care providers caring for adult patients should be aware of various food allergy presentations and syndromes. In this article, the authors cover recent literature on food allergies in adults and discuss the epidemiology of adult food allergy as well as common clinical scenarios and presentations of various types of food allergies.

Identification and Characterization of β-Lathyrin, an Abundant Glycoprotein of Grass Pea ( Lathyrus sativus L.), as a Potential Allergen

Grass pea, a protein-rich, high-yielding, and drought-tolerant legume, is used as food and livestock feed in several tropical and subtropical regions of the world. The abundant seed proteins of grass pea are salt-soluble globulins, which can be separated into vicilins and legumins. In many other legumes, the members of vicilin seed proteins have been identified as major allergens. However, very little information is available on the allergens of grass pea. In this study, we have identified an abundant 47 kDa protein from grass pea, which was recognized by immunoglobulin E (IgE) antibodies from sera drawn from several peanut-allergic patients. The IgE-binding 47 kDa protein was partially purified by affinity chromatography on a Con-A sepharose column. Matrix-assisted laser desorption/ionization-time-of-flight mass spectrometry analysis of the 47 kDa grass pea protein revealed sequence homology to 47 kDa vicilin from pea and Len c 1 from lentil. Interestingly the grass pea vicilin was found to be susceptible to pepsin digestion in vitro. We have also isolated a cDNA encoding the grass pea 47 kDa vicilin (β-lathyrin), and the deduced amino acid sequence revealed extensive homology to several known allergens, including those from peanut and soybean. A homology model structure of the grass pea β-lathyrin, generated using the X-ray crystal structure of the soybean β-conglycinin β subunit as a template, revealed potential IgE-binding epitopes located on the surface of the molecule. The similarity in the three-dimensional structure and the conservation of the antigenic epitopes on the molecular surface of vicilin allergens explains the IgE-binding cross-reactivity.

Immunotherapy: Treating with Fewer Allergens?

Polysensitization, sensitization to more than one allergen, is a common feature of patients with allergic rhinitis, and may be a risk factor for subsequent development of allergic diseases, especially allergic asthma. However, a polysensitized patient does not necessarily have polyallergy, a documented, causal relationship between exposure to 2 or more specific, sensitizing allergens and the subsequent occurrence of relevant clinical symptoms of allergy. Allergen immunotherapy treatment strategy for the polysensitized patient in Europe is to treat the single or 2 most clinically relevant allergen(s), whereas patients in the United States are usually treated for all potential clinically relevant allergens.

Geographical differences in food allergy

BACKGROUND

Food allergy represents a health problem worldwide and leads to life-threatening reactions and even impairs quality of life. Epidemiological data during the past decades is very heterogeneous because of the use of different diagnostic procedures, and most studies have only been performed in specific geographical areas.

OBJECTIVES

The aim of this article is to review the available data on the geographical distribution of food allergies at the food source and molecular level and to link food allergy patterns to the aeroallergen influence in each area.

METHODS

Systematic reviews, meta-analysis, studies performed within the EuroPrevall Project and EAACI position papers regarding food allergy were analysed.

CONCLUSIONS

The prevalence of food allergy sensitization differs between geographical areas, probably as a consequence of differences among populations, their habits and the influence of the cross-reactivity of aeroallergens and other sources of allergens. Geographical differences in food allergy are clearly evident at the allergenic molecular level, which seems to be directly influenced by the aeroallergens of each region and associated with specific clinical patterns.

Application of phage peptide display technology for the study of food allergen epitopes

Phage peptide display technology has been used to identify IgE-binding mimotopes (mimics of natural epitopes) that mimic conformational epitopes. This approach is effective in the characterization of those epitopes that are important for eliciting IgE-mediated allergic responses by food allergens and those that are responsible for cross-reactivity among allergenic food proteins. Application of this technology will increase our understanding of the mechanisms whereby food allergens elicit allergic reactions, will facilitate the discovery of diagnostic reagents and may lead to mimotope-based immunotherapy.

EAACI Molecular Allergology User's Guide

The availability of allergen molecules ('components') from several protein families has advanced our understanding of immunoglobulin E (IgE)-mediated responses and enabled 'component-resolved diagnosis' (CRD). The European Academy of Allergy and Clinical Immunology (EAACI) Molecular Allergology User's Guide (MAUG) provides comprehensive information on important allergens and describes the diagnostic options using CRD. Part A of the EAACI MAUG introduces allergen molecules, families, composition of extracts, databases, and diagnostic IgE, skin, and basophil tests. Singleplex and multiplex IgE assays with components improve both sensitivity for low-abundance allergens and analytical specificity; IgE to individual allergens can yield information on clinical risks and distinguish cross-reactivity from true primary sensitization. Part B discusses the clinical and molecular aspects of IgE-mediated allergies to foods (including nuts, seeds, legumes, fruits, vegetables, cereal grains, milk, egg, meat, fish, and shellfish), inhalants (pollen, mold spores, mites, and animal dander), and Hymenoptera venom. Diagnostic algorithms and short case histories provide useful information for the clinical workup of allergic individuals targeted for CRD. Part C covers protein families containing ubiquitous, highly cross-reactive panallergens from plant (lipid transfer proteins, polcalcins, PR-10, profilins) and animal sources (lipocalins, parvalbumins, serum albumins, tropomyosins) and explains their diagnostic and clinical utility. Part D lists 100 important allergen molecules. In conclusion, IgE-mediated reactions and allergic diseases, including allergic rhinoconjunctivitis, asthma, food reactions, and insect sting reactions, are discussed from a novel molecular perspective. The EAACI MAUG documents the rapid progression of molecular allergology from basic research to its integration into clinical practice, a quantum leap in the management of allergic patients.

Clinical Relevance of IgE to Profilin and/or Polcalcin in Pollen-Sensitized Patients

BACKGROUND

Component-resolved diagnostics is gaining importance in allergy diagnostics. Allergen extracts contain components with different rates of prevalence and clinical relevance, which can be subdivided at molecular level into major and minor allergens. Clinical complaints are usually triggered by major allergens, while the role of sensitization to the panallergens profilin and polcalcin still remains unclear.

METHODS

Eighty-six patients from southern Bavaria with sensitization to the panallergens profilin (Bet v 2/Phl p 12) and/or polcalcin (Bet v 4/Phl p 7) were examined in regard to their sensitization to the 4 main botanic denominations Betulaceae, Oleaceae, Poaceae and Asteraceae by skin prick test and measurement of specific immunoglobulin E antibodies to natural allergen extracts as well as major allergen components rPhl p 1/5, rBet v 1, rOle e 1 and nArt v 1. Sensitization was rated as clinically relevant or irrelevant depending on anamnesis or intranasal allergen challenge.

RESULTS

Regarding the 4 botanic denominations, there was no significant difference in the incidence of sensitization to the panallergens profilin, polcalcin or both. The sensitization pattern does not alter when subdividing the cohort into clinically relevant and silent sensitization. We did not find clinically symptomatic sensitization to panallergens without cosensitization to a major allergen.

CONCLUSIONS

Our results suggest that sole sensitization to panallergens seems to have no clinical relevance in allergic rhinoconjunctivitis. Clinical complaints seem to be triggered manly by major allergens. Thus, component-resolved allergy diagnostics is crucial in the diagnosis and treatment of polysensitized patients.

Major allergen from Amaranthus palmeri pollen is a profilin: Isolation, partial characterisation and IgE recognition

BACKGROUND

Pollens represent a rich source of proteins that are also potential elicitors of IgE-mediated pollen allergy. Sensitisation to panallergens could play an important role in diagnosis and specific immunotherapy, because these molecules are present in different plant pollens and plant foods and have marked structural similarity in different species. Profilins are one of the most common panallergens to be studied because they are responsible for a large number of sensitisations and are clearly related to cross-reactivity and co-sensitisation. This study aimed to isolate and characterise a new allergen of Amaranthus palmeri pollen and to determine its allergenicity.

METHODS

A. palmeri pollen profilin was purified using poly-l-proline-Sepharose affinity chromatography followed by anion exchanger chromatography. Identification of purified protein was carried out by mass spectrometry. Specific IgE was estimated in sera of patients with positive skin prick test to A. palmeri pollen extract, by enzyme-linked immunosorbent assay (ELISA).

PRINCIPAL FINDINGS

Purified protein appeared as a single band at 14 kDa in SDS-PAGE gel. Mass spectrometric analysis of the gel band identified two highly conserved peptides corresponding to allergenic profilins from pollen of other plants. Sera from about 60% of allergic patients have IgE that recognises the purified A. palmeri protein.

CONCLUSION

A 14 kDa protein of A. palmeri pollen was purified and identified as allergenic profilin, which was recognised by sera from pollen allergic patients.

Position paper of the EAACI: food allergy due to immunological cross-reactions with common inhalant allergens

In older children, adolescents, and adults, a substantial part of all IgE-mediated food allergies is caused by cross-reacting allergenic structures shared by inhalants and foods. IgE stimulated by a cross-reactive inhalant allergen can result in diverse patterns of allergic reactions to various foods. Local, mild, or severe systemic reactions may occur already after the first consumption of a food containing a cross-reactive allergen. In clinical practice, clinically relevant sensitizations are elucidated by skin prick testing or by the determination of specific IgE in vitro. Component-resolved diagnosis may help to reach a diagnosis and may predict the risk of a systemic reaction. Allergy needs to be confirmed in cases of unclear history by oral challenge tests. The therapeutic potential of allergen immunotherapy with inhalant allergens in pollen-related food allergy is not clear, and more placebo-controlled studies are needed. As we are facing an increasing incidence of pollen allergies, a shift in sensitization patterns and changes in nutritional habits, and the occurrence of new, so far unknown allergies due to cross-reactions are expected.

Profilin as a severe food allergen in allergic patients overexposed to grass pollen

BACKGROUND

Profilins are ubiquitous proteins that act as panallergens in sensitized patients, considered to be mild or incomplete food allergens. The aim of the study was to evaluate the role of profilins as severe food allergens in allergic patients overexposed to grass who were referred for severe food reactions and were sensitized to profilins.

METHODS

After a careful in vitro screening, 26 patients were included, classified into two groups, mild (17) and severe reactors (9), based on clinical history and subsequently provoked orally with purified profilin in a double-blind placebo-controlled food challenge setup.

RESULTS

A significant number of patients presented severe positive food challenge test reactions at low doses of the allergen profilin. Patients prone to suffer from severe reactions had lower IgG4/IgE ratio to major grass allergens than those who did not.

CONCLUSION

Profilins are complete food allergens in food-allergic patient populations that are exposed to high levels of grass pollen. This type of patient constitutes an optimal model to understand the link between respiratory and food allergies. The nature of the observed reactions and the low level of allergen eliciting the reactions suggest that intake through the oral mucosa might constitute a relevant route of exposure to food allergens.

Profilin sensitisation in a Mediterranean population

BACKGROUND

Sensitisation to pan-allergens has become an interesting tool for the study of the allergenic profile of different populations. Profilins are one of the most common pan-allergens to be studied because they are responsible for a large number of sensitisations and are clearly related to cross-reactivity and co-sensitisation.

OBJECTIVES

The objective of this study was to investigate the profile of sensitisation to profilins and to correlate it with sensitisation to foods and pollens.

METHODS

Six hundred and fifty-four consecutive patients were skin-prick tested with a battery of common allergens including pollens, epithelia, mites and moulds and profilin and divided into three groups depending on their sensitisation profile (non-atopic, atopic with pollinosis and atopic without pollinosis). Patients with symptoms were challenged and diagnosed with the offending food extracts. Profilin sensitisation was identified and analysed in detail.

RESULTS

According to the classification of the population, the prevalence of profilin sensitisation was estimated at 2.9% in patients suffering respiratory allergy, 4.2% in atopic patients, and 5.9% in pollen-sensitised individuals. Positive association was observed between pollen (except Cupressus and olive) and profilin but not with moulds, mites or epithelia. With respect to foods, positive association was only observed between profilin and melon sensitisation. Lastly, in terms of symptoms, positive association was only observed between profilin sensitisation and OAS.

CONCLUSION

Profilin sensitisation seems to be a marker of pollen-related poly-sensitisation in our area. Pan-allergen diagnosis seems to be an essential tool for developing and improving selection of the correct treatment for allergic patients.

Food allergies resulting from immunological cross-reactivity with inhalant allergens: Guidelines from the German Society for Allergology and Clinical Immunology (DGAKI), the German Dermatology Society (DDG), the Association of German Allergologists (AeDA) and the Society for Pediatric Allergology and Environmental Medicine (GPA)

A large proportion of immunoglobulin E (IgE)-mediated food allergies in older children, adolescents and adults are caused by cross-reactive allergenic structures. Primary sensitization is most commonly to inhalant allergens (e.g. Bet v 1, the major birch pollen allergen). IgE can be activated by various cross-reactive allergens and lead to a variety of clinical manifestations. In general, local and mild — in rare cases also severe and systemic — reactions occur directly after consumption of the food containing the cross-reactive allergen (e. g. plant-derived foods containing proteins of the Bet v 1 family). In clinical practice, sensitization to the primary responsible inhalant and/or food allergen can be detected by skin prick tests and/or in vitro detection of specific IgE. Component-based diagnostic methods can support clinical diagnosis. For individual allergens, these methods may be helpful to estimate the risk of systemic reactions. Confirmation of sensitization by oral provocation testing is important particulary in the case of unclear case history. New, as yet unrecognized allergens can also cause cross-reactions.

The therapeutic potential of specific immunotherapy (SIT) with inhalant allergens and their effect on pollen-associated food allergies is currently unclear: results vary and placebo-controlled trials will be necessary in the future. Pollen allergies are very common. Altogether allergic sensitization to pollen and cross-reactive food allergens are very common in our latitudes. The actual relevance has to be assessed on an individual basis using the clinical information.

Cite this as Worm M, Jappe U, Kleine-Tebbe J, Schäfer C, Reese I, Saloga J, Treudler R, Zuberbier T, Wassmann A, Fuchs T, Dölle S, Raithel M, Ballmer-Weber B, Niggemann B, Werfel T. Food allergies resulting from immunological cross-reactivity with inhalant allergens. Allergo J Int 2014; 23: 1–16 DOI 10.1007/s40629-014-0004-6

Analysis of the structural and immunological stability of 2S albumin, nonspecific lipid transfer protein, and profilin allergens from mustard seeds

This work investigates the resistance to proteolysis and heating of the yellow mustard (Sinapis alba L.) allergens Sin a 1 (2S albumin), Sin a 3 (nonspecific lipid transfer protein, LTP), and Sin a 4 (profilin) to explain their potential capability to induce primary sensitization at the gastrointestinal level. Sin a 1 and Sin a 3 resisted gastric digestion showing no reduction of the IgE reactivity. Intestinal digestion of Sin a 1 and Sin a 3 produced a limited proteolysis but retained significant IgE-binding reactivity. Sin a 1 was stable after heating, and although Sin a 3 was modified, most of its structure was recovered after cooling back. These two allergens would be therefore able to sensitize by ingestion. Sin a 4 was completely digested by gastric treatment and its conformational structure markedly modified at 85 °C. Thus, this allergen can be described as a nonsensitizing mustard allergen.

Correlation of anti-Pru p 3 IgE levels with severity of peach allergy reactions in children

BACKGROUND

Peach allergy is regarded as one of the most important fresh fruit allergies. Data are available on the state-of-the-art diagnosis, including food challenges, and a component-resolved diagnosis. However, the roles played by different peach allergens with respect to symptom severity are not completely understood.

OBJECTIVE

To evaluate the role of serum specific IgE to peach and recombinant allergens in the diagnosis of peach allergies in Italian children.

METHODS

Forty-four children with peach allergy confirmed by a placebo-controlled food challenge were divided into 2 groups based on their symptom severity: patients with mild oral allergy syndrome (OAS) and patients with systemic symptoms (SS). The presence of specific IgE to peach and rPru p 1, rPru p 3, and rPru p 4 was determined.

RESULTS

The presence of specific IgE to Pru p 4 and Pru p 1 was found significantly more frequently in patients with OAS, whereas specific IgE to Pru p 3 was not found significantly more frequently in patients with SS. Only anti-rPru p 4 IgE levels were significantly higher in patients with OAS, whereas no significant differences were found in anti-rPru p 1 and anti-rPru p 3 IgE levels between patients with OAS compared with patients with SS.

CONCLUSION

In Italian children with peach allergies, the presence of specific IgE to Pru p 3 is not associated with SS, and the levels of specific IgE to Pru p 3 do not correlate with the severity of the reactions.

Molecular cloning and expression of Cucumisin (Cuc m 1), a subtilisin-like protease of Cucumis melo in Escherichia coli

BACKGROUND

Oral allergy syndrome resulted from plant-derived foods is frequent among adults. Allergy to melon (cucumis melo) is one of the most frequent fruit allergies in Iran. Three different major allergens have been found in Cucumis melo that Cuc m 1 (cucumisin) has been identified as the major allergen of melon. Cucumisin is an alkaline serine protease that it is found as a 78kDa protein in precursor form. The aim of this study was production of recombinant Cuc m 1 in Escherichia coli (E. coli) cells and characterization of its allergenicity property.

METHODS

Production of recombinant Cuc m 1 was carried out by cDNA cloning technique into the pET32b(+) vector using specific primers designed based on cucumisin nucleotide sequence available in Genebank database, cucumisin encoding gene and directional cloning method. Cloned plasmid into E. coli TOP10 was transformed into E. coli BL21 and expression of the protein was induced by IPTG. The recombinant protein was purified via Ni-NTA affinity chromatography using histidine tag in recombinant protein. IgE binding of this protein was assessed by IgE-immunoblotting, ELISA and inhibition ELISA.

RESULTS

The directional cloning was resulted in expression of a fusion Cuc m 1. Immunoblotting with sera of patients allergic to melon showed strong reactivity with purified protein band. Inhibition assays demonstrated that purified rCuc m 1 could be the same with natural form of Cuc m 1 in total extract.

CONCLUSIONS

In the present study, we have provided a functional recombinant cucumisin allergen, rCuc m 1 with 86kDa, which may be used as a standard allergen for clinical diagnosis and study of allergy to melon.

Profilins: mimickers of allergy or relevant allergens?

Profilins are ubiquitous proteins, present in all eukaryotic cells and identified as allergens in pollen, latex and plant foods. The highly conserved structure justifies the cross-reactive nature of IgE antibodies against plant profilins and their designation as pan-allergens. Primary sensitization to profilin seems to arise from pollen sensitization with later development of cross-reactive IgE antibodies against plant food (and possibly latex) profilins. The role of profilin in inducing allergic symptoms needs to be evaluated and raises important issues in allergy diagnosis due to cross-reactivity. IgE cross-reactivity among profilins is associated with multiple pollen sensitization and with various pollen-food syndromes. In respiratory allergy, sensitization to pollen to which the patient has virtually no environmental exposure has been identified as a manifestation of profilin sensitization. As a food allergen, profilin usually elicits mild reactions, such as oral allergy syndrome, is not modified by processing and is especially important in allergy to some fruits, such as melon, watermelon, banana, tomato, citrus fruit and persimmon. Purified natural and recombinant profilins for in vitro and in vivo allergy tests are helpful in the diagnostic work-up. Herein we review the current state of knowledge about the allergen profilin and its implications in the diagnosis and treatment of allergic diseases. We conclude that, although its role in triggering allergic symptoms is still controversial, profilin is undoubtedly a relevant allergen. As a pan-allergen, profilin is associated with multiple pollen sensitization and pollen-food-latex syndromes that the allergist has to be aware of in order to accomplish an accurate diagnosis and successful treatment of allergic diseases.

Gal d 6 is the second allergen characterized from egg yolk

Only one allergen from the egg yolk, alpha-livetin (Gal d 5) has been described thus far. A new egg yolk allergen was detected studying 27 egg allergic patients. The study was performed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and IgE-immunoblotting and IgE-immunoblotting-inhibition assays. An egg yolk extract was fractioned by reverse-phase high-performance liquid chromatography (RP-HPLC), and the new allergen detected was characterized by N-terminal amino acid analysis. A total of 5 of the 27 patients (18%) detected a yolk allergen of an apparent molecular weight of 35 kDa by SDS-PAGE. Heating and reduction treatments did not affect its allergenicity, although digestion with simulated gastric fluid diminished the IgE-binding capacity of the allergen. The N-terminal amino acid sequence corresponded with the YGP42 protein, a fragment of the vitellogenin-1 precursor. Thus, a second egg yolk allergen has been described and designated Gal d 6 by the World Health Organization (WHO)/International Union of Immunological Societies (IUIS) Allergen Nomenclature Subcommittee.

Panallergens and their impact on the allergic patient

The panallergen concept encompasses families of related proteins, which are involved in general vital processes and thus, widely distributed throughout nature. Plant panallergens share highly conserved sequence regions, structure, and function. They are responsible for many IgE cross-reactions even between unrelated pollen and plant food allergen sources. Although usually considered as minor allergens, sensitization to panallergens might be problematic as it bears the risk of developing multiple sensitizations. Clinical manifestations seem to be tightly connected with geographical and exposure factors. Future population- and disease-based screenings should provide new insights on panallergens and their contribution to disease manifestations. Such information requires molecule-based diagnostics and will be valuable for developing patient-tailored prophylactic and therapeutic approaches. In this article, we focus on profilins, non-specific lipid transfer proteins, polcalcins, and Bet v 1-related proteins and discuss possible consequences of panallergen sensitization for the allergic patient. Based on their pattern of IgE cross-reactivity, which is reflected by their distribution in the plant kingdom, we propose a novel classification of panallergens into ubiquitously spread "real panallergens" (e.g. profilins) and widespread "eurallergens" (e.g. polcalcins). "Stenallergens" display more limited distribution and cross-reactivity patterns, and "monallergens" are restricted to a single allergen source.

Allergies to fruits and vegetables

Allergic reactions to fruits and vegetables are frequently observed in older children and adolescents. They can result from a primary sensitization to food allergens or from a primary sensitization to inhalant allergens such as pollens or latex. In the case of fruit allergies, the stability of the allergens involved is crucial to the sensitization pathway and in the clinical presentation of the food allergy. Two patients allergic to fruits are presented and discussed in the light of the allergens involved. Patient 1 was a 14 yr-old girl with a grass and olive pollen allergy who developed oropharyngeal symptoms typical of the oral allergy syndrome (OAS) with multiple fruits from taxonomically unrelated families, and who was sensitized to profilin. Patient 2 was an 8 yr-old girl, with no pollen allergies, who developed systemic reactions to peach and apple, and who was sensitized to non-specific lipid transfer proteins (LTP). Profilins are labile allergens present in pollens and foods, and sensitization occurs through the respiratory route to pollen profilin. The cross-reactive IgE antibodies generated can elicit local reactions in the oropharyngeal mucosa (OAS) when exposed to fruit profilins. In contrast, LTPs are a family of stable allergens that resist thermal treatment and enzymatic digestion, and can thus behave as true food allergens inducing primary (non-pollen related) sensitizations and triggering systemic reactions. These two cases represent two distinct patterns of sensitization and clinical expression of fruit allergies that are determined by the panallergens involved (LTPs and profilins) and their intrinsic physicochemical properties. Additionally, these two cases also show the improved diagnostic value of Component Resolved Diagnosis, and strengthen its utility in the routine diagnosis and management of patients.

The effect of digestion and pH on the allergenicity of kiwifruit proteins

It is suggested that patients with oral allergy syndrome (OAS) respond to pepsin-sensitive allergens, and systemic reactors identify pepsin-resistant allergens. We sought to assess the digestibility of kiwifruit proteins in simulated gastric fluid (SGF), and to compare the immunogenicity of the digests in patients with isolated oral and systemic reactions to kiwifruit. In addition, the effect of pH on digestibility of kiwifruit proteins was investigated. The in vitro resistance of kiwifruit proteins to digestion was determined using SGF. G-immunoglobulin (IgE) binding to digested proteins was investigated by Western blotting using sera from children and adults (aged 5-72 yr) with systemic reactions and patients with isolated oral symptoms. To determine whether pH conditions influence digestion of kiwifruit extracts, digestion at pHs 1.5-7 were compared by SDS-PAGE. Patients with systemic reactions showed IgE binding to digestion-resistant allergens, but patients with oral symptoms reacted only to digestion-labile allergens. An increase in pH from 1.5 to 2.5 significantly reduced pepsin breakdown of kiwifruit allergens. Immunoreactive digested protein fragments were detectable by immunoblot but not Coomassie stain. This study confirms a difference in the lability of food allergens recognized by patients with systemic reactions and those with OAS. Pepsin digestion of kiwifruit proteins was impaired by hypoacidic conditions suggesting that patients with hypoacidic gastric conditions are at increased risk of systemic absorption of allergens. The data indicate that commonly used methods for predicting allergenicity of novel proteins using Coomassie stains may be flawed.

Profilin sensitization detected in the office by skin prick test: a study of prevalence and clinical relevance of profilin as a plant food allergen

BACKGROUND

Profilin, a pan-allergen present in all eukaryotic cells, is one of the main causes of cross-sensitization between pollen and plant-derived foods, but its clinical relevance as a food allergen is still debated.

OBJECTIVE

To investigate the prevalence of profilin sensitization in a pollen-allergic population and its clinical relevance as a food allergen.

METHODS

Two hundred consecutive patients with pollen allergy underwent skin prick tests (SPT) with purified natural date palm profilin (Pho d 2; 50 microg/mL; Alk Abello, Madrid, Spain). Those reporting adverse reactions to foods (confirmed by SPT with either commercial food extracts or fresh foods) underwent SPT with an apple extract containing uniquely Mal d 1 (2 microg/mL; ALK-Abello), and with a commercial peach extract containing uniquely lipid transfer protein (LTP 30 microg/mL; ALK-Abello).

RESULTS

Sixty patients (30%) showed skin reactivity to date palm profilin, Pho d 2. All were sensitized to grass pollen, and most of them reacted to birch, mugwort, ragweed and plantain pollen as well. SPT with pellitory and cypress scored negative in a high proportion of profilin reactors [26/60 (43%) and 33/60 (55%), respectively]. More than one half (34/60 [57%]) of profilin reactors had food allergy; 21 of these were monosensitized to profilin, 11 were sensitized to both profilin and Bet v 1 homologous protein, one to both profilin and LTP, and one to all the three allergens. The large majority of profilin-allergic patients reported oral allergy syndrome as the only food-induced symptom and were able to tolerate the offending foods if they were cooked or otherwise processed. Twenty-eight of 34 reported reactivity to two or more plant-derived foods. Rosaceae, tree nuts, melon and watermelon, tomato, pineapple, citrus fruits and banana were the more frequently offending foods.

CONCLUSION

Profilin should be considered a clinically relevant food allergen. Allergy to melon, watermelon, tomato, banana, pineapple and orange may be considered as a marker of profilin hypersensitivity. This study underlines the clinical importance of being able to diagnose hypersensitivity to single food allergenic proteins by SPT, particularly when the relevant food allergen sources contain several allergens that show different chemical/physical features and, hence, completely different risk profiles.

A hypoallergenic vaccine obtained by tail-to-head restructuring of timothy grass pollen profilin, Phl p 12, for the treatment of cross-sensitization to profilin

Profilins are highly cross-reactive allergens in pollens and plant food. In a paradigmatic approach, the cDNA coding for timothy grass pollen profilin, Phl p 12, was used as a template to develop a new strategy for engineering an allergy vaccine with low IgE reactivity. Non-IgE-reactive fragments of Phl p 12 were identified by synthetic peptide chemistry and restructured (rs) as a new molecule, Phl p 12-rs. It comprised the C terminus of Phl p 12 at its N terminus and the Phl p 12 N terminus at its C terminus. Phl p 12-rs was expressed in Escherichia coli and purified to homogeneity. Determination of secondary structure by circular dichroism indicated that the restructuring process had reduced the IgE-reactive alpha-helical contents of the protein but retained its beta-sheet conformation. Phl p 12-rs exhibited reduced IgE binding capacity and allergenic activity but preserved T cell reactivity in allergic patients. IgG Abs induced by immunization of mice and rabbits with Phl p 12-rs cross-reacted with pollen and food-derived profilins. Recombinant Phl p 12-rs, rPhl p 12-rs, induced less reaginic IgE to the wild-type allergen than rPhl p 12. However, the rPhl p 12-rs-induced IgGs inhibited allergic patients' IgE Ab binding to profilins to a similar degree as those induced by immunization with the wild type. Phl p 12-rs specific IgG inhibited profilin-induced basophil degranulation. In conclusion, a restructured recombinant vaccine was developed for the treatment of profilin-allergic patients. The strategy of tail-to-head reassembly of hypoallergenic allergen fragments within one molecule represents a generally applicable strategy for the generation of allergy vaccines.

Screening and identification of putative allergens in berry fruits of the Rosaceae family: technical challenges

Cross-reactive proteins in small fruits of the Rosaceae family like strawberry, raspberry and blackberry revealed an unexpected complex IgE-reactivity pattern. Several copies of PR-10 and PR-14 proteins were detected by Southern blots in strawberry, raspberry and blackberry. In raspberry, the highest similarity at the DNA level for PR-10 and PR-14 (Rub i 1 and Rub i 3) was detected to strawberry sequences of Fra a 1 and Fra a 3. At the protein level, Rub i 1 and Rub i 3 showed more than 70% identity with homologous proteins of rosaceous fruits. Furthermore, raspberries contained additional putative allergens, e.g. class III acidic chitinases and cyclophilins. Blackberries were shown to share at least two well-known major fruit allergens with other rosaceous fruits, namely PR-10s and PR-14s homologous proteins. However the IgE-reactive proteins of small fruits are still not extensively investigated. The main challenges in studying small fruit allergens are the complexity of the fruit matrix, the diversity of physico-chemical properties of fruit proteins, the lack of appropriate protein extraction procedures and the missing information about the influence of processing treatments on food components.

Immunology

The concept of forbidden foods that should not be eaten goes back to the Garden of Eden and apart from its religious meanings it may also have foreshadowed the concept of foods that can provoke adverse reactions. Thus we could say that allergic diseases have plagued mankind since the beginning of life on earth. The prophet Job was affected by a condition that following the rare symptoms described by the Holy Bible might be identified as a severe form of atopic dermatitis (AD). The earliest record of an apparently allergic reaction is 2621 B.C., when death from stinging insects was first described by hieroglyphics carved into the walls of the tomb of Pharaoh Menes depicting his death following the sting of a wasp. In 79 A.D., the death of the Roman admiral Pliny the Elder was ascribed to the SO₂-rich gases emanating from the eruption of Mount Vesuvius. Hippocrates (460–377 B.C.) was probably the first to describe how cow’s milk (CM) could cause gastric upset and hives, proposing dietetic measures including both treatment and prevention for CM allergy.

Detection of Some Safe Plant-Derived Foods for LTP-Allergic Patients

BACKGROUND

Lipid transfer protein (LTP) is a widely cross-reacting plant pan-allergen. Adverse reactions to Rosaceae, tree nuts, peanut, beer, maize, mustard, asparagus, grapes, mulberry, cabbage, dates, orange, fig, kiwi, lupine, fennel, celery, tomato, eggplant, lettuce, chestnut and pineapple have been recorded.

OBJECTIVE

To detect vegetable foods to be regarded as safe for LTP-allergic patients.

METHODS

Tolerance/intolerance to a large spectrum of vegetable foods other than Rosaceae, tree nuts and peanut was assessed by interview in 49 subjects monosensitized to LTP and in three distinct groups of controls monosensitized to Bet v 1 (n = 24) or Bet v 2 (n = 18), or sensitized to both LTP and birch pollen (n = 16), all with a history of vegetable food allergy. Patients and controls underwent skin prick test (SPT) with a large spectrum of vegetable foods. The absence of IgE reactivity to foods that were negative in both clinical history and SPT was confirmed by immunoblot analysis and their clinical tolerance was finally assessed by open oral challenge (50 g per food).

RESULTS

All patients reported tolerance and showed negative SPT to carrot, potato, banana and melon; these foods scored positive in SPT and elicited clinical symptoms in a significant proportion of patients from all three control groups. All patients tolerated these four foods on oral challenge. Immunoblot analysis confirmed the lack of IgE reactivity to these foods by LTP-allergic patients.

CONCLUSION

Carrot, potato, banana and melon seem safe for LTP-allergic patients. This finding may be helpful for a better management of allergy to LTP.

Characterization of recombinant Mal d 4 and its application for component-resolved diagnosis of apple allergy

BACKGROUND

Profilins are ubiquitous panallergens that have been extensively characterized; yet, their clinical relevance is still unclear.

OBJECTIVE

The aim of the present study was to produce recombinant apple profilin (rMal d 4) and to evaluate its allergenic activity and its potency for component-resolved allergy diagnosis.

METHODS

Complementary DNA-derived Mal d 4 was cloned, expressed in Escherichia coli and subsequently purified via poly (l-proline) sepharose. A total of 28 sera from apple-allergic patients were used for IgE-ELISA, immunoblot, RAST and basophil histamine release (BHR) test. In addition, skin prick tests (SPTs) were performed in five patients.

RESULTS

Four different complementary DNA coding for apple profilin, Mal d 4, each with an open reading frame of 393 nucleotides, were identified. One isoform Mal d 4.0101 was expressed in Escherichia coli and subsequently purified. Mass spectroscopy revealed the expected mass of 13.826 for rMal d 4.0101, and circular dichroism analysis data were typical for a folded protein and small-angle X-ray scattering measurement identified the protein as a monomer. All the serum samples displayed IgE binding to rMal d 4.0101 in IgE ELISA, immunoblot and RAST. In immunoblotting, IgE binding to natural Mal d 4 was partially/completely inhibited by preincubation with rMal d 4.0101, and RAST values to apple extract were significantly reduced upon serum pretreatment with rMal d 4.0101. SPTs and BHR assays using purified rMal d 4.0101 were positive. Purified rMal d 4.0101 was destroyed within seconds when subjected to pepsin digestion.

CONCLUSIONS

Apple profilin complementary DNAs were identified. The physicochemical and allergenic properties of purified recombinant Mal d 4.0101 were evaluated showing that the recombinant protein was equal to the natural protein as shown by inhibition assays. Thus, Mal d 4 represents another example suitable for component-resolved diagnosis of food allergy.

Gastrointestinal digestion of food allergens: effect on their allergenicity

This paper reviews the in vitro digestion models developed to assess the stability digestion of food allergens, as well as the factors derived from the methodology and food structure that may affect the assay results. The adequacy of using the digestion stability of food allergens as a criterion for assessing potential allergenicity is also discussed. Data based on the traditional pepsin digestibility test in simulated gastric fluid are discussed in detail, with special attention to the influence of the pH and pepsin: allergen ratio in the pepsinolysis rate. This review points out the importance of using physiologically relevant in vitro digestion systems for evaluating digestibility of allergens. This would imply the sequential use of digestive enzymes in physiological concentrations, simulation of the stomach/small intestine environment (multi-phase models) with addition of surfactants such as phospholipids or bile salts, as well as the consideration of the gastrointestinal transit and the effect of the food matrices on the allergen digestion and subsequent absorption through the intestinal mucosa. In vitro gastrointestinal digestion protocols should be preferably combined with immunological assays in order to elucidate the role of large digestion-resistant fragments and the influence of the food matrix on the stimulation of the immune system.

Allergenic reactivity of the melon profilin Cuc m 2 and its identification as major allergen

BACKGROUND

Melon allergy is commonly associated with oral allergy syndrome (OAS) and with hypersensitivity to pollens and other plant foods. No melon allergen responsible for these clinical characteristics has yet been isolated, although profilin has been proposed as a potential target.

OBJECTIVE

To isolate natural and recombinant melon profilin, to evaluate its in vivo and in vitro reactivity, and to analyse its behaviour in simulated gastric fluid (SGF) and heat treatments.

METHODS

A pool or individual sera from 23 patients, and an additional group of 10 patients, all of them with melon allergy, were analysed by in vitro and in vivo tests, respectively. Natural melon profilin (nCuc m 2) and its recombinant counterpart (rCuc m 2) were isolated by poly-l-proline affinity chromatography, and characterized by N-terminal amino acid sequencing, matrix-assisted laser desorption/ionization analysis, DNA sequencing of cDNAs encoding rCuc m 2, and immunodetection with anti-profilin antibodies. In vitro analysis included IgE immunodetection, specific IgE determination, ELISA-inhibition assays, and histamine release (HR) tests. In vivo activity of nCuc m 2 was established by skin prick testing (SPT). The effect of SGF and heat treatment on rCuc m 2 was followed by immunodetection, ELISA inhibition, and HR assays.

RESULTS

Both purified forms of melon profilin were recognized by rabbit anti-profilin antibodies and IgE of sera from allergic patients, and showed molecular sizes typical of the profilin family. nCuc m 2 had a blocked N-terminus, whereas rCuc m 2 rendered the expected N-terminal amino acid sequence, its full protein sequence being highly similar (98--71% identity) to those of profilins from plant foods and pollens. The natural allergen displayed a slightly higher IgE-binding capacity than its recombinant counterpart. Specific IgE to nCuc m 2 and rCuc m 2 was found in 100% and 78% of the 23 individual sera analysed, respectively. nCuc m 2 evoked positive SPT responses in all (10/10) patients tested, and rCuc m 2 induced HR in two out of three sera assayed. SGF treatment readily inactivated rCuc m 2, as shown by its loss of recognition by anti-profilin antibodies, lack of IgE binding, and inability to induce HR. In contrast, heat treatment did not affect the IgE-binding capacity of rCuc m 2.

CONCLUSIONS

Profilin is highly prevalent in melon-allergic patients, and promptly inactivated by SGF, as expected for an allergen mainly linked to OAS.

Isolation, cloning and allergenic reactivity of natural profilin Cit s 2, a major orange allergen

BACKGROUND

Orange is among the most widely consumed fruits, and among the plant food sources causing allergic reactions according to popular perception. However, its relevant allergenic components are virtually unknown. Profilin is a well-defined minor plant panallergen, showing prevalences around 30% in fruits and vegetables.

METHODS

Twenty-three orange-allergic patients were studied. Natural orange profilin, named Cit s 2, was purified by affinity chromatography and characterized by N-terminal amino acid sequencing, matrix-assisted laser desorption/ionization mass spectrometry analysis and isolation of its coding cDNA. Reactivity to Cit s 2 was analyzed in vivo by skin prick tests (SPT) and in vitro by IgE immunodetection, specific IgE determination in individual sera and enzyme-linked immunosorbent assay-inhibition assays.

RESULTS

The N-terminal amino acid sequence and molecular mass of natural Cit s 2, both fully in agreement with the complete amino acid sequence deduced from its coding cDNA, demonstrated its profilin nature. An unexpectedly high reactivity to Cit s 2 was found in vivo (78% of positive SPT responses) and in vitro (87% of sera from orange allergic patients had specific IgE to Cit s 2). The purified allergen inhibited around 50% of the IgE binding to an orange pulp extract.

CONCLUSION

Orange profilin Cit s 2, unlike other plant food profilins, is a major and highly prevalent allergen.

Sequence homology: a poor predictive value for profilins cross-reactivity

BACKGROUND

Profilins are highly cross-reactive allergens which bind IgE antibodies of almost 20% of plant-allergic patients. This study is aimed at investigating cross-reactivity of melon profilin with other plant profilins and the role of the linear and conformational epitopes in human IgE cross-reactivity.

METHODS

Seventeen patients with melon allergy were selected based on clinical history and a positive skin prick test to melon extract. Melon profilin has been cloned and expressed in E. coli. The IgE binding and cross-reactivity of the recombinant profilin were measured by ELISA and inhibition ELISA. The amino acid sequence of melon profilin was compared with other profilin sequences. A combination of chemical cleavage and immunoblotting techniques were used to define the role of conformational and linear epitopes in IgE binding. Comparative modeling was used to construct three-dimensional models of profilins and to assess theoretical impact of amino acid differences on conformational structure.

RESULTS

Profilin was identified as a major IgE-binding component of melon. Alignment of amino acid sequences of melon profilin with other profilins showed the most identity with watermelon profilin. This melon profilin showed substantial cross-reactivity with the tomato, peach, grape and Cynodon dactylon (Bermuda grass) pollen profilins. Cantaloupe, watermelon, banana and Poa pratensis (Kentucky blue grass) displayed no notable inhibition. Our experiments also indicated human IgE only react with complete melon profilin. Immunoblotting analysis with rabbit polyclonal antibody shows the reaction of the antibody to the fragmented and complete melon profilin. Although, the well-known linear epitope of profilins were identical in melon and watermelon, comparison of three-dimensional models of watermelon and melon profilins indicated amino acid differences influence the electric potential and accessibility of the solvent-accessible surface of profilins that may markedly affect conformational epitopes.

CONCLUSION

Human IgE reactivity to melon profilin strongly depends on the highly conserved conformational structure, rather than a high degree of amino acid sequence identity or even linear epitopes identity.

Pho d 2, a major allergen from date palm pollen, is a profilin: cloning, sequencing, and immunoglobulin E cross-reactivity with other profilins

BACKGROUND

Up to now, some date palm pollen (DPP) allergens have been described but very few data are available about their molecular nature. The aim of this study was to identify and characterize Pho d 2, a major allergen from this pollen.

METHODS

Sera from 25 patients allergic to DPP were analysed by immunoblotting. Purification of DPP profilin was performed by poly-l-proline affinity chromatography. Profilin-encoding cDNA from DPP was cloned by using a RT-PCR strategy and recombinant allergen was expressed as a non-fusion protein in Escherichia coli. Natural and recombinant Pho d 2 were investigated by means of enzyme allergosorbent test to compare the immunologic properties of both allergens and to analyse cross-reactivity with other profilins.

RESULTS

A 14.4 kDa protein was identified as a major allergen in DPP extract. Purification, cloning, heterologous expression, and inhibition experiments identified it as profilin (Pho d 2). Pho d 2 comprises 131 amino acids and has high sequence identity with other allergenic food and pollen profilins. The prevalence of specific IgE antibody reactivity to natural Pho d 2 by ELISA was 56% and 64% by skin prick test (SPT). Pho d 2 is an important allergen as it is responsible for more than 70% of the IgE reactivity to the pollen extract. IgE directed against Pho d 2 showed a strong cross-reactivity with other profilins such as those from olive tree and grass pollens.

CONCLUSION

Pho d 2, a 14.4 kDa protein identified as profilin, is a major and relevant allergen in DPP, as confirmed by SPT and thereby may elicit clinical symptoms in sensitized patients.

Plant food allergies: a suggested approach to allergen-resolved diagnosis in the clinical practice by identifying easily available sensitization markers

BACKGROUND

Molecular biology techniques have led to the identification of a number of allergens in vegetable foods, but due to the lack of purified food proteins for routine diagnostic use, the detection of sensitizing allergens remains a nearly impossible task in most clinical settings. The allergen-resolved diagnosis of food allergy is essential because each plant-derived food may contain a number of different allergens showing different physical/chemical characteristics that strongly influence the clinical expression of allergy; moreover, many allergens may cross-react with homologue proteins present in botanically unrelated vegetable foods.

OBJECTIVE

Through a review of the available literature, this study aimed to detect "markers" of sensitization to specific plant food allergens that are easily accessible in the clinical practice.

RESULTS

There are several "markers" of sensitization to different allergenic proteins in vegetable foods that can be helpful in the clinical practice. Specific algorithms for patients allergic to Rosaceae and to tree nuts were built.

CONCLUSION

Clinical allergologists lacking the assistance of an advanced molecular biology lab may take advantage of some specific clinical data as well as of some "markers" in the difficult task of correctly diagnosing patients with plant food allergy and to provide them the best preventive advice.

The oral allergy syndrome: improved diagnostic and treatment methods

PURPOSE OF REVIEW

The aim of this article is to review recent clinical and molecular findings related to the oral allergy syndrome in order to define its relevance in the field of food allergy, describe current diagnostic approaches and discuss attempts to use specific immunotherapy for treatment.

RECENT FINDINGS

New allergenic sources causing the oral allergy syndrome have been reported. Their allergenic molecules have been identified. In most of those studies oral allergy syndrome is reported as a clinical manifestation among more severe ones. Some of the molecules generally considered not to be at risk for severe reactions have been demonstrated to pose a threat for inducing generalized reactions. Some studies tried to assess the usefulness of immunotherapy with birch pollen extract by either subcutaneous or sublingual routes for the treatment of associated food allergies. In most of the cases, a well defined study design and a molecular approach at different study levels are lacking and thus the value of the obtained results is limited. To date, no final conclusion can be drawn on the basis of reported results.

SUMMARY

The knowledge about the highly prevalent phenomenon of oral allergy syndrome is still incomplete, in respect to both, epidemiology and foods inducing symptoms. It is very important to reach consensus on several aspects of this food-induced allergic disease. Further studies are required to highlight whether immunotherapy using co-recognized inhalant allergens is an effective way of curative treatment, or if co-treatment with purified pollen-related food allergens will be required to obtain a long-lasting effect.

Lipid transfer proteins and allergy to oranges

BACKGROUND

Lipid transfer proteins (LTPs) are relevant fruit allergens, recently proposed as model plant food allergens. No citrus fruit allergen has been characterized to date. We sought to identify and isolate citrus fruit LTPs and to explore their relevance in orange allergy.

METHODS

Twenty-seven patients, showing mainly oral allergy syndrome after orange ingestion, as well as positive prick responses and serum-specific IgE levels to orange, were selected. Natural orange and lemon LTPs, as well as a recombinant orange LTP isoform expressed in Pichia pastoris, were isolated by chromatographic methods and characterized by N-terminal amino acid sequencing and matrix-assisted laser desorption/ionizaion mass spectrometry, and DNA sequencing of the corresponding cDNA in the case of the recombinant allergen. Specific IgE determination, immunodetection, ELISA-inhibition assays and in vivo skin prick tests (SPTs) were performed with all three purified allergens and with the major peach LTP allergen, Pru p 3.

RESULTS

The natural allergens purified from orange (nCit s 3) and lemon (nCit l 3) showed very similar N-terminal amino acid sequences (18 out of 20 identical residues), typical of LTPs, and molecular masses of 9,610 and 9,618 Da, respectively. The recombinant orange isoform (rCit s 3) expressed in P. pastoris (16 out of 20 residues identical to its natural counterpart in the N-terminal region) presented 92 amino acid residues and 9,463 Da, and 67% sequence identity with rPru p 3. Of the 27 sera analyzed, specific IgE to the purified allergens was found in 54% for nCit l 3, 48% for nCit s 3, 46% for rCit s 3 and 37% for rPru p 3. Positive SPT responses were obtained in 7 out of 26 patients tested for nCit s 3, 3 out of 8 for nCit l 3 and 10 out of 26 for nPru p 3. ELISA-inhibition assays showed an equivalent IgE-binding pattern for the natural and recombinant orange LTPs, and IgE cross-reactivity among the purified orange, lemon and peach LTP allergens.

CONCLUSIONS

Members of the LTP allergen family are involved in allergy to oranges, displaying positive in vitro and in vivo reactions in 30-50% of the patients studied. Both orange and lemon allergens show cross-reactivity with the major peach allergen Pru p 3.

Severe allergy to sharon fruit caused by birch pollen

BACKGROUND

Allergy to sharon fruit (persimmon) has been only rarely reported. Cross-reactivity with pollen (profilin and Bet v 6) appeared to be involved, but Bet v 1 has not been implicated previously.

OBJECTIVE

It is our aim to identify whether Bet v 1 sensitization is linked to sharon fruit allergy.

METHODS

Two patients with a reaction upon first exposure to sharon fruit were included in the study, as well as 7 patients with birch-pollen-related apple allergy. Sensitivity was assessed by skin prick testing (SPT), a radio-allergosorbent test (RAST) and immunoblotting. RAST analysis was performed for Bet v 1, Bet v 2 and Bet v 6. Cross-reactivity was evaluated by RAST and immunoblot inhibitions. Biological activity of IgE was measured by basophil histamine release. Sharon fruit allergy was evaluated by double-blind placebo-controlled food challenge (DBPCFC) or open challenge (OC).

RESULTS

Both sharon-fruit-allergic patients demonstrated positive reactions in the RAST (8.6 and 6.2 IU/ml, respectively) and SPT (wheal area 37 and 36 mm2). Sharon fruit allergy was confirmed by DBPCFC in 1 patient. The second patient refused a challenge because of the severe initial reaction. Sera from both patients were reactive to Bet v 1 and Bet v 6, which was cross-reactive with sharon fruit by inhibition assays. The patient with the severest reactions was reactive to profilin on immunoblotting. However, profilin did not induce significant histamine release, nor did Bet v 6. Bet v 1 induce approximately 60% histamine release. An OC with sharon fruit in 7 patients allergic to birch pollen and apple, who had not eaten sharon fruit previously, was positive in 6/7 cases.

CONCLUSIONS

Birch-pollen-related allergy to sharon fruit is mediated by the known cross-reactive pollen allergens including Bet v 1 and may become more of a problem should sharon fruit consumption increase.

Allergenic potency of spices: hot, medium hot, or very hot

Spices are the most attractive ingredients to confer an authentic taste to food. As they are derived from plants, they harbour allergenic potency and can induce symptoms ranging from mild local to severe systemic reactions. Due to the content of pharmacologically active substances of spices, the diagnosis of allergy and the differentiation from intolerance reactions may be difficult. Association with inhalative allergies via IgE cross-reactivity, but also direct gastrointestinal sensitization plays a role. This article is a botanical and allergological overview of the most important spices and molecules responsible for eliciting IgE-mediated reactions or cross-reactions. As no curative treatments are known at present, strict avoidance is recommended and, therefore, accurate labelling of pre-packed food is necessary.

Characterization of cross-reactive bell pepper allergens involved in the latex-fruit syndrome

BACKGROUND

Between 30% and 50% of individuals who are allergic to latex products are also allergic to specific plant foods, a fact that is well documented as the latex-fruit syndrome. Simultaneous sensitization to latex and bell pepper has been previously reported. Although bell pepper fruits are frequently consumed raw, cooked or as a spice, little is known about the cross-reactive allergens.

OBJECTIVE

In this study we wished to identify bell pepper allergens involved in the latex-fruit syndrome.

METHODS

Sera of four patients who displayed clinical symptoms to latex and bell pepper were used in immunoblot studies on protein extracts of three different cultivars of fresh bell pepper and fresh Hevea latex. Cross-reactive allergens were identified by inhibition experiments using recombinant Hev b 8 (latex profilin), and natural Hev b 2 (latex beta-1,3-glucanase) in addition to the protein extracts. A novel cross-reactive IgE-reactive 30 kDa protein was subjected to sequence analysis.

RESULTS

Three patients displayed IgE to profilins from bell pepper fruits and latex. Two patients possessed IgE to Hev b 2, a latex beta-1,3-glucanase, and a homologous protein in bell pepper. One patient possessed IgE reactive with a protein of 30 kDa identified by N-terminal sequencing as an l-ascorbate peroxidase and another patient to a protein of 38 kDa. Additionally, IgE binding proteins in two higher molecular weight ranges showed cross-reactive capacities.

CONCLUSION

Our findings show on the molecular level that bell pepper is part of the latex-fruit syndrome. For the first time we have identified the major latex allergen Hev b 2, a beta-1,3-glucanase, and the bell pepper l-ascorbate peroxidase as cross-reactive allergens. We were also able to show that profilins are responsible for some of the IgE cross-reactivity.