Lipid transfer proteins and allergy to oranges

Lipid Transfer Proteins (LTPs)-Structure, Diversity and Roles beyond Antimicrobial Activity

Lipid transfer proteins (LTPs) are among the most promising plant-exclusive antimicrobial peptides (AMPs). They figure among the most challenging AMPs from the point of view of their structural diversity, functions and biotechnological applications. This review presents a current picture of the LTP research, addressing not only their structural, evolutionary and further predicted functional aspects. Traditionally, LTPs have been identified by their direct isolation by biochemical techniques, whereas omics data and bioinformatics deserve special attention for their potential to bring new insights. In this context, new possible functions have been identified revealing that LTPs are actually multipurpose, with many additional predicted roles. Despite some challenges due to the toxicity and allergenicity of LTPs, a systematic review and search in patent databases, indicate promising perspectives for the biotechnological use of LTPs in human health and also plant defense.

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.

The diagnosis and management of allergic reactions in patients sensitized to non-specific lipid transfer proteins

Sensitization to one or more non-specific lipid transfer proteins (nsLTPs), initially thought to exist mainly in southern Europe, is becoming accepted as a cause of allergic reactions to plant foods across Europe and beyond. The peach nsLTP allergen Pru p 3 is a dominant sensitizing allergen and peaches a common food trigger, although multiple foods can be involved. A frequent feature of reactions is the requirement for a cofactor (exercise, alcohol, non-steroidal anti-inflammatory drugs, Cannabis sativa) to be present for a food to elicit a reaction. The variability in the food and cofactor triggers makes it essential to include an allergy-focused diet and clinical history in the diagnostic workup. Testing on suspected food triggers should also establish whether sensitization to nsLTP is present, using purified or recombinant nsLTP allergens such as Pru p 3. The avoidance of known trigger foods and advice on cofactors is currently the main management for this condition. Studies on immunotherapy are promising, but it is unknown whether such treatments will be useful in populations where Pru p 3 is not the primary sensitizing allergen. Future research should focus on the mechanisms of cofactors, improving diagnostic accuracy and establishing the efficacy of immunotherapy.

Natural ingredients in cosmetic products-A suggestion for a screening series for skin allergy

BACKGROUND

Naturally derived cosmetic product ingredients of both plant and animal origin are being included increasingly in product formulations in order to cater to consumer preferences. They may be an overlooked cause of reactions to cosmetic products in some patients with dermatitis.

OBJECTIVES

To identify naturally derived cosmetic product ingredients with allergenic potential (type I and type IV) and propose a cosmetic screening test series.

METHODS

The study was conducted in two steps. The first step was a market survey using a nonprofit application helping consumers avoid problematic substances in cosmetic products. The application contained 10 067 cosmetic products that were label checked for naturally derived cosmetic product ingredients. The second step was a literature search to examine how frequently the naturally derived ingredients were described and related to allergic reactions in cosmetics or other topically administered products.

RESULTS

We identified 121 different naturally derived cosmetic product ingredients that were included in at least 30 cosmetic products. In total, 22 ingredients were selected for a screening test series.

CONCLUSIONS

We propose a supplemental patch test and a prick test screening series with naturally derived cosmetic product ingredients for patients with skin reactions to cosmetic products, aiming to identify a cause in more patients than is currently possible.

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.

Lipid Transfer Protein allergy in the United Kingdom: Characterization and comparison with a matched Italian cohort

BACKGROUND

Although pollen-related food allergy occurs in all European populations, lipid transfer protein (LTP) allergy is considered to manifest mainly in Mediterranean countries. We aimed to characterize adults presenting with LTP allergy in a northern European country.

METHOD

The clinical history and sensitization patterns of subjects born and residing in the United Kingdom (UK), with a prior diagnosis of LTP allergy and sensitization to the peach LTP allergen Pru p 3, were compared to UK subjects with pollen food syndrome (PFS). The sensitization patterns were also evaluated against a matched cohort of Italian subjects diagnosed with LTP allergy.

RESULTS

None of the 15 UK PFS subjects had a positive SPT to LTP-enriched peach reagent, compared to 91% of the 35 UK LTP subjects. The UK LTP cohort were also more likely to have positive skin prick tests to cabbage, lettuce and mustard and sensitization to the LTP allergens in peach, walnut, mugwort and plane tree These sensitization patterns to individual allergens were not significantly different to those obtained from the Italian LTP subjects, with significant correlations between Pru p 3 and the LTP allergens in peanuts, walnuts, plane tree and mugwort in both groups.

CONCLUSION

Native UK subjects with LTP allergy are not dissimilar to those with LTP allergy in southern Europe. Testing to LTP-enriched peach SPT reagent and/or LTP allergens in peach, walnut, mugwort and plane tree may enhance diagnostic accuracy.

Food Allergies Caused by Allergenic Lipid Transfer Proteins: What Is behind the Geographic Restriction?

PURPOSE OF REVIEW

To critically examine evidence suggesting that food allergy induced by lipid transfer proteins (LTPs) follows a geographic pattern.

RECENT FINDINGS

LTP syndrome remains most common in the Mediterranean basin, with a clear gradient seen in prevalence of LTP sensitization between northern and southern Europe. We hypothesize that high levels of birch pollen seem to protect against LTP allergy, as these higher levels correlate with a lower prevalence of LTP hypersensitivity. Nevertheless, LTP food allergy cases still appear in areas having a high environmental level of birch pollen. Food allergy caused by LTP may be related to (1) primary sensitization to a food LTP allergen in the absence of pollinosis, (2) primary sensitization to LTP from a pollen source, and (3) co-sensitization to LTP from pollen and food.

Evaluation of serum IgE in peach-allergic patients with systemic reaction by using recombinant Pru p 7 (gibberellin-regulated protein)

BACKGROUND

Lipid transfer protein (LTP) is a major fruit allergen. It has, however, recently been revealed that the systemic reaction in peach-allergic patients is related not only to LTP (Pru p 3) but also to gibberellin-regulated protein (Pru p 7). We investigated recombinant Pru p 7 (rPru p 7) for its potential use in worldwide standardization for the diagnosis of peach allergy.

METHODS

Natural Pru p 7 (nPru p 7) was purified from peach crude extract using a monoclonal antibody affinity column. Complementary DNA for Pru p 7 was cloned and expressed in Escherichia coli and Pichia pastoris. Serum immunoglobulin (Ig) E in peach-allergic patients was examined by enzyme-linked immunosorbent assay (ELISA) using nPru p 7 and rPru p 7 (E. coli product: erPru p 7 and P. pastoris product: prPru p 7).

RESULTS

Peach-allergic patients (n=27) were diagnosed and categorized into oral reaction (n=10) or systemic reaction (n=17). The nPru p 7 positivity based on serum IgE levels was 52% in the systemic-reaction group and 0% in the oral-reaction group (P<0.05). In the systemic-reaction group, there was no significant difference in reactivity between nPru p 7 and prPru p 7, but the reactivity of erPru p 7 was significantly lower than those of nPru p 7 and prPru p 7 (P<0.05).

CONCLUSIONS

We found that prPru p 7 exhibited reactivity in ELISA comparable to that of nPru p 7 for the diagnosis of peach allergy with systemic reaction.

Immunoblotting Quantification Approach for Identifying Potential Hypoallergenic Citrus Cultivars

The inherent allergens of citrus fruits, such as Cit s 1, Cit s 2, Cit s 3 can cause allergic reactions. A better understanding of the genetic factors (cultivar to cultivar) affecting the allergenic potential of citrus fruits would be beneficial for further identification of hypoallergenic genotypes. In the present study, an immunoblotting quantification approach was adopted to assess the potential allergenicity of 21 citrus cultivars, including nine subgroups (tangerine, satsuma, orange, pummelo, grapefruit, lemon, kumquat, tangor, and tangelo). To prepare highly sensitive and specific rabbit polyclonal antibodies, antigenicity of purified rCit s 1.01, rCit s 2.01, and rCit s 3.01 peptides were enhanced with high epitope density in a single protein molecule. The data integration of three citrus allergen quantifications demonstrated that the four pummelo cultivars (Kao Phuang Pummelo, Wanbai Pummelo, Shatian Pummelo, and Guanxi Pummelo) were potential hypoallergenic, compared with other 8 subgroups. Moreover, the immunological analyses with sera of allergic subjects revealed that Shatian Pummelo and Guanxi Pummelo showed the lowest immunoreactivity in 8 representative citrus cultivars. These potential hypoallergenic genotypes are of great significance to not only allergic consumers but also citrus breeders in the genetic improvement of hypoallergenic citrus as breeding resources.

Development of monoclonal antibody-based ELISA for the quantification of orange allergen Cit s 2 in fresh and processed oranges

The aim of this study was to develop a monoclonal antibody (mAb)-based enzyme-linked immunosorbent assay (ELISA) for the quantification of a major allergen (Cit s 2) in fresh and processed oranges. Purified recombinant Cit s 2 (rCit s 2)-small ubiquitin-like modifier (SUMO) was used for the production of mAbs. In the optimized ELISA, the recovery of rCit s 2 from Navel oranges or orange juice was 107-132%, and the intra- and inter-assay coefficients of variation were 3.1-8.8% and 4.4-11%, respectively. The Cit s 2 content in fresh oranges was determined to be 1,800±430ng/g, while this content was much lower in the processed foods. The developed ELISA demonstrated high reproducibility, sensitivity, and accuracy, and this assay may help individuals with orange allergy by determining Cit s 2 quantities in food products and controlling their Cit s 2 intake.

Development and Application of a Multiplex Real-Time PCR Assay as an Indicator of Potential Allergenicity in Citrus Fruits

The effects of tissue type, harvest maturity, and genetic factors on the expression of genes that related to citrus fruit allergies remain poorly understood. In the present study, a multiplex real-time PCR assay was developed to monitor the expression of citrus allergen genes individually with the advantages of much fewer sample requirements and simultaneously multiple target genes detection. Gene specific primer pairs and Taqman probes of three citrus allergen genes Cit s 1.01, Cit s 2.01, and Cit s 3.01 and the house-keeping gene β-actin were designed based on gene sequence differences. The PCR results showed that differential expression patterns were found during the ripening process. The expression levels of Cit s 3.01 were much higher than those of Cit s 1.01 and Cit s 2.01 in both peel and pulp tissues among 10 citrus cultivars. Data suggested that Kao Phuang Pummelo could be safely consumed with a potential low risk in allergenicity. Considering that assessing allergenicity is one of the tests in food safety, this assay might also facilitate the breeding and production of "allergy-friendly" citrus fruits.

Volunteer study and serum protein profiling to understand inflammatory response induced by Satsuma mandarin

It has been observed that consumption of a certain amount of Satsuma, lychee, and longan often caused a symptom characterized by dry or sore throat, gum swelling and even mouth ulcer, which significantly impaired the life quality of a large population. We define the adverse reaction to Satsuma as Satsuma-induced syndrome (SIS). Volunteers were assigned to oral Satsuma challenge in an open manner. The results showed that SIS was characterized with symptoms affecting the throat, oral cavity, face, gastrointestinal system and eye either individually or in combination. A comparative proteomic study was performed to investigate the differences of serum proteins in the Post-SC (after Satsuma challenge) and Pre-SC (before Satsuma challenge) serum samples of 15 volunteers with severe SIS. Ten proteins were identified to be differentially expressed (P<0.05). Of these, levels of complement component C9 precursor were elevated significantly in the Post-SC serum samples and were further verified by enzyme-linked immunosorbent assay, indicating that the complement system may be activated and plays a significant role in inflammatory response. Meanwhile, serum samples were subjected to immobilized metal affinity capture (IMAC3) protein chip surfaces and tested by surface-enhanced laser desorption/ionization-time of flight-mass spectrometry. The data were analyzed by Ciphergen ProteinChip Software. A diagnostic model was constructed to discriminate the SIS from normal samples, using principal component analysis. A total of 50 detected biomarkers were found to be different with statistical significance (P<0.05). The multivariate logistic analysis demonstrates a complete distinction between the two groups. Our findings suggest that these assays may provide potential biomarkers for the diagnosis of SIS.

The biochemical basis and clinical evidence of food allergy due to lipid transfer proteins: a comprehensive review

Plant lipid transfer proteins (LTPs) are ubiquitous proteins that are found in divergent plant species. Although the exact function of LTPs is not fully understood, LTPs are conserved across a broad range of plant species. Because LTPs share structural features, there is an increased probability for significant allergic cross-reactivity. The molecular features of LTPs also decrease the probability of degradation due to cooking or digestion, thereby increasing the probability of systemic absorption and severe allergic reactions. LTP allergy, unlike other forms of anaphylaxis, tends to occur more frequently in areas of lower latitude. The geographic distribution of LTP allergy, along with evidence of increased sensitization after respiratory exposure, has led to the hypothesis that LTP-related food allergy may be secondary to sensitization via the respiratory route. Clinical reactions associated with LTPs have broad clinical phenotypes and can be severe in nature. Life-threatening clinical reactions have been associated with ingestion of a multitude of plant products. Component-resolved diagnosis has played a significant role in research applications for LTP allergy. In the future, component-resolved diagnosis may play a significant role in day-to-day clinical care. Also, quantitative analysis of LTPs in foodstuffs may allow for the identification and/or production of low-LTP foods, thereby decreasing the risk to patients with LTP allergy. Furthermore, sublingual immunotherapy may provide a therapeutic option for patients with LTP allergy.

Developmental stimuli and stress factors affect expression of ClGLP1, an emerging allergen-related gene in Citrus limon

Germins and germin-like proteins (GLPs) constitute an ubiquitous family of plant proteins that seem to be involved in many developmental and stress related processes. A novel GLP cDNA was isolated from Citrus limon and structural features and genomic organization were investigated by in silico and Southern blots analysis. In lemon, the ClGLP1 encodes a 24.38 kDa which possesses a conserved motif of plant GLPs proteins. A phylogetic analysis mapped ClGLP1 as belonging to the GER3 subfamily into the GLP1 group of large GLP family. ClGLP1 was differentially expressed in the various organs and was highest in mature fruit. Moreover, expression in the fruit was tissue- and stage-related as well as dependent on agricultural practice (organic vs conventional). ClGLP1 transcripts increased during the transition from the green (180 days after blooming) to the yellow (240 days after blooming) mature fruit and were strongly enhanced in yellow mature fruit from organic compared with conventional culture. A sudden and systemic increase in ClGLP1 expression level was observed in leaves injured by wounding, together with an increase of endogenous H2O2 amount. Notably, an enhancement of H202 was observed in fruit peel during transition from green to yellow fruit stage. All together our data showed that ClGLP1 expression can be modulated in relation to both developmental stimuli and culture practices; evidence is also provided that through an oxidase activity this gene could play a role in fruit maturation as well as in stress responses.

The Citrus clementina putative allergens: from proteomic analysis to structural features

Several allergens have been identified and characterized in the genus Citrus, which belongs to the germin-like proteins (GPLs), profilins, and non-specific lipid transfer proteins (nsLTPs). In this work, in silico sequence analysis, protein purification, mass spectrometry identification, and the spectral counting method were integrated to identify new putative allergens of Citrus clementina and their expression level in the fruit peel. The in silico analysis revealed fifteen new sequences belonging to GLPs (Cit cl 1), and two more belonging to nsLTPs (Cit cl 3). No other new sequences were found as regards profilins (Cit cl 2). Each putative allergen from fruit peel was obtained using different protein extraction methods, and the protein sequences of the putative allergens were identified by means of LTQ-Orbitrap XL mass spectrometer. The spectral counting strategy revealed that Cit cl 1 had a higher expression level than Cit cl 2 and Cit cl 3. To predict the quaternary structure and deduced function of Cit cl 1, its primary sequence was used as a template to search a homologous protein structure in the RCSB PDB Database, getting high correspondence with the oxalate oxidase protein in barley.

Citrus allergy from pollen to clinical symptoms

Allergy to citrus fruits is often associated with pollinosis and sensitization to other plants due to a phenomenon of cross-reactivity. The aims of the present study were to highlight the cross-reactivity among citrus and the major allergenic pollens/fruits, throughout clinical and molecular investigations, and to evaluate the sensitization frequency to citrus fruits in a population of children and adults with pollinosis. We found a relevant percentage of sensitisation (39%) to citrus fruits in the patients recruited and in all of them the IgE-mediated mechanism has been confirmed by the positive response to the prick-to-prick test. RT-PCR experiments showed the expression of Cit s 1, Cit s 3 and a profilin isoform, already described in apple, also in Citrus clementine pollen. Data of multiple sequence alignments demonstrated that Citrus allergens shared high percentage identity values with other clinically relevant species (i.e. Triticum aestivum, Malus domestica), confirming the possible cross-allergenicity citrus/grasses and citrus/apple. Finally, a novelty of the present work has been the expression of two phospholipaseA2 isoforms (PLA2 α and β) in Citrus as well as in Triticum pollens; being PLA2 able to generate pro-inflammatory factors, this enzyme could participate in the activation of the allergenic inflammatory cascade.

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.

Proteome from lemon fruit flavedo reveals that this tissue produces high amounts of the Cit s1 germin-like isoforms

A multistep procedure has been developed and applied to extract and purify proteins from lemon fruit flavedo. 2DE, LC-ESI-MS/MS, and bioinformatics were used to detect the high abundance of the germin-like glycoprotein Cit s1, a powerful allergen in humans. Peptide alignments against Citrus EST repositories gave the best scores with the C. sinensis cDNA (gi|188354270/EY710037), annotated as unknown sweet orange fruit protein; additional BLAST of peptides against NCBI databases gave high sequence identities with sequence of orange Cit s1 (gi|52782810/P84159), suggesting that the unknown sweet orange fruit protein is consistent with the Cit s1 protein. Peptides of Cit s1 were detected in 17 spots ranging from 120 to 20 kDa, pointing out that in the flavedo of lemon the Cit s1 may be expressed as several isoforms of which the 120 kDa isoform is the largest monomer and the 20 kDa is the smallest one. This finding adds information about the features of Cit s1, because it has been previously reported as a unique monomeric glycoprotein of 24 kDa.

Maternal diet during pregnancy and allergic sensitization in the offspring by 5 yrs of age: a prospective cohort study

To examine the effect of maternal diet during pregnancy on allergic sensitization in the offspring by 5 yrs of age. The Finnish type 1 Diabetes Prediction and Prevention Nutrition Study. A population-based cohort study with 5-yr follow-up. A total of 931 children with human leukocyte antigen-conferred susceptibility to type 1 diabetes for whom maternal pregnancy food frequency questionnaire data and allergen-specific immunoglobulin E measurement at 5 yrs were available. Increasing maternal consumption of citrus fruits [odds ratio (OR) = 1.14, 95% confidence interval (CI) = 1.05-1.25] and total fruit (OR = 1.36, 95% CI = 1.09-1.70) were positively associated with sensitization to inhalant allergens, after adjustment for potential confounders. Maternal intake of vitamin D (OR = 0.56, 95% CI = 0.35-0.91) was inversely associated with sensitization to food allergens. Maternal consumption of citrus fruits during pregnancy may increase the risk to allergic sensitization in the offspring, whereas vitamin D intake may have a beneficial effect. Further studies are required to define more closely the putative effect of maternal intake of polyunsaturated fatty acids on development of allergic diseases in the offspring.

Comparative proteomical analysis of zygotic embryo and endosperm from Coffea arabica seeds

During coffee seed development, proteins are predominantly deposited in cotyledons and in the endosperm. Reserve proteins of the 11S family are the most abundant globulins in coffee seeds, acting as a nitrogen source during roasting and guaranteeing flavor and aroma. The aim of the present study was to compare the protein profiles of endosperm and zygotic embryos of coffee seeds. Proteins were extracted from whole seed as well as from embryo and endosperm, separately. Total proteins were analyzed by two-dimensional electrophoresis (2-DE) followed by identification by mass spectrometry (MS). The most abundant spots observed in the gels of coffee seeds were excised, digested with trypsin, and identified by MS as subunits of the 11S globulin. Spots with identical pI and molecular masses were also observed in the protein profiles of coffee endosperm and embryo, indicating that 11S protein is also highly expressed in those tissues. Peptide sequence coverage of about 20% of the entire 11S globulin was obtained. Three other proteins were identified in the embryo and endosperm 2-DE profiles as a Cupin superfamily protein, an allergenic protein (Pru ar 1), exclusive to the endosperm 2D map, and a hypothetical protein, observed only in the zygotic embryo profile.

A structural basis for food allergy: the role of cross-reactivity

PURPOSE OF REVIEW

Immunologic cross-reactivity, which is important in many aspects of host defense and immune-mediated diseases, is a prominent feature of allergic disorders. The goal of this article is to define allergenic cross-reactivity and its role in food allergy, review current understanding of mechanisms of cross-reactivity, and consider how advances in our ability to predict cross-reactivity can impact diagnosis and treatment of food allergy.

RECENT FINDINGS

Recent evidence suggests that specific T cells, in addition to IgE, developed in response to inhaled allergens can cross-react with related food allergens, leading to distinct clinical reactions. Several new cross-reactivities have been identified, including food-food, pollen-food, and latex-venom associations. Debate continues regarding prediction of allergenicity based on protein structure, and clinical relevance of in-vitro testing. Cross-reactivity is also being used to develop specific immunotherapy for treatment of food allergy.

SUMMARY

A thorough understanding of immunologic cross-reactivity is essential to advancing our knowledge about food allergy. This knowledge will help elucidate the pathogenesis of the disorder and prevent exposures to allergenic, genetically engineered foods. New insight will allow for better utilization of current diagnostic tools and the development of more accurate tests and therapies for food allergy.

Lipid transfer protein allergy: primary food allergy or pollen/food syndrome in some cases

PURPOSE OF REVIEW

To summarize recent findings on non-specific lipid transfer proteins in food allergy, with a specific focus on the localization, stability and route of sensitization.

RECENT FINDINGS

Plant non-specific lipid transfer proteins are major food allergens, especially in the Mediterranean area. They have been identified as allergens in a number of foods and the list grows ever longer. As non-specific lipid transfer proteins are considered to be "true" food allergens that sensitize directly via the gastrointestinal tract their stability during food processing and gastric digestion has been studied in more detail. In addition, several groups have tried to determine the sensitization patterns of lipid transfer protein-reactive patients, to determine and possibly clarify the observed geographical differences in sensitization. Different sensitization routes (via the respiratory tract or even transdermally) have been suggested.

SUMMARY

As the structure and molecular properties of non-specific lipid transfer proteins are resolved and more purified non-specific lipid transfer proteins become available for diagnostic purposes, detailed studies on the sensitization pattern and route are becoming feasible. Continuing studies on the pattern of lipid transfer protein sensitization will give more insight into the development and possible treatment of lipid transfer protein-related food 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.

Anaphylaxis from mandarin (Citrus reticulata): identification of potential responsible allergens

We report on a patient with anaphylaxis from mandarin. Temporal relationship between consumption of the fruit, the presence of positive specific IgE, the positive skin test and the basophil activation test for mandarin strongly supported the diagnosis of an IgE-mediated allergy from mandarin. The lipid transfer protein allergen from mandarin fruit was isolated and characterized. Specific IgE levels and IgE immunodetection data indicated the patient's sensitization to orange (Cit s 3) and mandarin (Cit r 3) lipid transfer protein allergens, as well as to germin-like (Cit s 1) allergen. These results were fully confirmed by skin prick test and basophil activation test (BAT) for lipid transfer proteins, and a BAT for Cit s 1. This case report has several particularities. First, in Central and Northern Europe, it is not widely appreciated that citrus fruits, particularly mandarin, can elicit anaphylaxis. Second, this case report re-emphasizes sensitization from lipid transfer proteins to predispose for severe allergic reactions. Finally, it provides an opportunity to summarize the applications of flow cytometry-assisted analysis and quantification of in vitro activated basophils in the diagnostic approach of anaphylaxis from food.

Anaphylaxis to lemon soap: citrus seed and peanut allergen cross-reactivity

BACKGROUND

Many individuals allergic to peanuts have multiple allergen sensitivity.

OBJECTIVE

To report the first case, to our knowledge, of a peanut allergic patient who exhibited cosensitivity to citrus seeds and who had experienced anaphylaxis to lemon soap.

METHODS

Extracts of peanut and seeds from different varieties of citrus fruit (orange, lemon, and mandarin) were prepared and resolved with 14% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Direct and inhibition immunoblotting of the patient's serum on the extracts was used to examine the pattern of IgE reactivity and the presence of cross-reactive allergens.

RESULTS

Numerous IgE reactive proteins were demonstrated in each citrus seed extract and the peanut extract. Complete IgE cross-reactivity was demonstrated among the different citrus seed extracts. Partial cross-reactivity was demonstrated between the peanut and orange seed extracts.

CONCLUSIONS

Citrus seeds contain numerous IgE reactive proteins that are completely cross-reactive among orange, lemon, and mandarin. When peanut allergy coexists with citrus seed allergy, IgE cross-reactivity between peanut and citrus seed proteins can be demonstrated, suggesting a basis to this cosensitivity.

Maternal diet during pregnancy in relation to eczema and allergic sensitization in the offspring at 2 y of age

BACKGROUND

Maternal diet during pregnancy might be one of the factors that influences fetal immune responses associated with childhood allergy.

OBJECTIVE

We analyzed the association between maternal diet during the last 4 wk of pregnancy and allergic sensitization and eczema in the offspring at 2 y of age.

DESIGN

Data from 2641 children at 2 y of age were analyzed within a German prospective birth cohort study (LISA). Maternal diet during the last 4 wk of pregnancy was assessed with a semiquantitative food-frequency questionnaire, which was administered shortly after childbirth.

RESULTS

High maternal intake of margarine [adjusted odds ratio (aOR): 1. 49; 95% CI: 1.08, 2.04] and vegetable oils (aOR: 1.48; 95% CI: 1.14, 1.91) during the last 4 wk of pregnancy was positively associated and high maternal fish intake (aOR: 0.75; 95% CI: 0.57, 0.98) was inversely associated with eczema during the first 2 y in the offspring. High celery (aOR: 1.85; 95% CI: 1.18, 2.89) and citrus fruit (aOR: 1.73; 95% CI: 1.18, 2.53) intakes increased the risk of sensitization against food allergens. In turn, sensitization against inhalant allergens was positively related to a high maternal intake of deep-frying vegetable fat (aOR: 1.61; 95% CI: 1.02, 2.54), raw sweet pepper (aOR: 2.16; 95% CI: 1.20, 3.90), and citrus fruit (aOR: 1.72; 95% CI: 1.02, 2.92).

CONCLUSIONS

We suggest that the intake of allergenic foods and foods rich in n-6 polyunsaturated fatty acids during pregnancy may increase and foods rich in n-3 polyunsaturated fatty acids may decrease the risk of allergic diseases in the offspring.

Plant non-specific lipid transfer proteins: an interface between plant defence and human allergy

Plant non-specific LTPs (lipid transfer proteins) form a protein family of basic polypeptides of 9 kDa ubiquitously distributed throughout the plant kingdom. The members of this family are located extracellularly, usually associated with plant cell walls, and possess a broad lipid-binding specificity closely related to their three-dimensional structure. The nsLTP fold is characterized by a compact domain composed of 4 alpha-helices, firmly held by a network of 4 conserved disulphide bridges. This fold presents a large internal tunnel-like cavity, which can accommodate different types of lipids. nsLTPs are involved in plant defence mechanisms against phytopathogenic bacteria and fungi, and, possibly, in the assembly of hydrophobic protective layers of surface polymers, such as cutin. In addition, several members of the nsLTP family have been identified as relevant allergens in plant foods and pollens. Their high resistance to both heat treatment and digestive proteolytic attack has been related with the induction by these allergens of severe symptoms in many patients. Therefore, they are probably primary sensitizers by the oral route. nsLTP sensitization shows an unexpected pattern throughout Europe, with a high prevalence in the Mediterranean area, but a low incidence in Northern and Central European countries.

Molecular and immunological characterization of the glycosylated orange allergen Cit s 1

The IgE of sera from patients with a history of allergy to oranges (Citrus sinensis) binds a number of proteins in orange extract, including Cit s 1, a germin-like protein. In the present study, we have analyzed its immunological cross-reactivity and its molecular nature. Sera from many of the patients examined recognize a range of glycoproteins and neoglycoconjugates containing beta1,2-xylose and core alpha1,3-fucose on their N-glycans. These reagents also inhibited the interaction of Cit s 1 with patients' sera, thus underlining the critical role of glycosylation in the recognition of this protein by patients' IgE and extending previous data showing that deglycosylated Cit s 1 does not possess IgE epitopes. In parallel, we examined the peptide sequence and glycan structure of Cit s 1, using mass spectrometric techniques. Indeed, we achieved complete sequence coverage of the mature protein compared with the translation of an expressed sequence tag cDNA clone and demonstrated that the single N-glycosylation site of this protein carries oligosaccharides with xylose and fucose residues. Owing to the presumed requirement for multivalency for in vivo allergenicity, our molecular data showing that Cit s 1 is monovalent as regards glycosylation and that the single N-glycan is the target of the IgE response to this protein explain the immunological cross-reactive properties of Cit s 1 as well as its equivocal nature as a clinically relevant allergen.

Component-resolved diagnostics in food allergy

PURPOSE OF REVIEW

The purpose of this paper is to review and discuss recent studies on component-resolved diagnostics in food allergy, involving panels of pure allergen molecules or arrays of peptides derived from allergen sequences, and to summarize the reporting of new food allergens during the past 2 years.

RECENT FINDINGS

Several component-resolved diagnostic studies in food allergy suggest that the use of panels of allergen molecules may allow refined clinical information to be obtained on the likelihood or severity of an allergic food reaction and regarding diagnostic specificity. Further, in some studies the use of pure allergen molecules has led to a clearly higher sensitivity of the immunoglobulin E immunoassay compared with conventional allergen extracts.

SUMMARY

While common diagnostic methods in allergy assess the presence or absence of allergen-specific sensitization, to date, no in-vitro or in-vivo test exists which exhibits full correlation with clinical food allergy. A multitude of recently reported findings and observations indicate that molecular analysis of allergen sensitization pattern may serve to enhance the clinical utility of immunoglobulin E antibody-based allergy diagnostics. Pure natural and recombinant allergen molecules as well as panels of synthetic peptides have been used for this purpose.

Germin-like protein Cit s 1 and profilin Cit s 2 are major allergens in orange (Citrus sinensis) fruits

Oranges are clinically relevant allergenic foods. To date, orange allergens have not been characterized in detail. The study is aimed at analyzing the sensitization profile in orange-sensitized subjects with and without clinical allergy, and to identify orange allergens. Fifty-six sensitized subjects with self-reported reactions to orange were grouped into reactors (anaphylaxis or multiple episodes of immediate reactions and/or positive challenge tests) and non-reactors (negative open food challenge tests). Allergens were characterized by IgE immunoblotting, N-terminal sequencing, IgE-inhibition assays, and mediator release assays were performed to determine the allergenic potency of orange profilin. Of 56 subjects, 23 were classified as orange allergic showing mainly an oral allergy syndrome. Of 23 subjects classified as orange allergic, 22 were sensitized to profilin, Cit s 2. In patients with mono-sensitization to profilin in vitro histamine releases up to 75% from basophils were induced using orange extract and purified plant profilins. Of the allergic patients 78% were sensitized to germin-like protein, Cit s 1. Both allergens showed retained IgE reactivity in heat-processed orange juice. Interestingly, subjects with and without clinical allergy showed a comparable sensitization profile. Profilin and germin-like proteins are major orange allergens. The potential clinical relevance of orange profilin was indicated by its strong capacity to release histamine from basophils. However, a predominant sensitization to both allergens in subjects without symptoms also indicates a high frequency of clinically insignificant sensitization.

Orange Germin-Like Glycoprotein Cit s 1: An Equivocal Allergen

BACKGROUND

Orange allergens are virtually unknown, in spite of the large consumption of this fruit. Germin-like proteins, together with vicilins and legumins, form the cupin superfamily of plant proteins, which includes many seed allergens.

METHODS

Twenty-nine patients with allergy to oranges were studied. A major IgE-binding protein from orange extracts was isolated by means of a two-step cation-exchange chromatographic protocol. The allergen was characterized by N-terminal amino acid sequencing and MALDI analysis, and its reactivity explored by specific IgE determination in individual sera, ELISA inhibition assays and in vivo skin prick tests (SPT). Chemical deglycosylation of the purified allergen was achieved by trifluoromethylsulfonate acid treatment.

RESULTS

The 24-kDa purified allergen, designated Cit s 1, was identified as a germin-like glycoprotein, based on its N-terminal amino acid sequence, molecular size and recognition by rabbit anti-complex N-linked glycan antibodies. Specific IgE to Cit s 1 was detected in 62% of 29 individual sera from orange-allergic patients, whereas positive SPT responses to the purified allergen were obtained in only 10% of such patients. Deglycosylation of Cit s 1 resulted in a loss of its IgE-binding capacity. Moreover, the unrelated plant glycoprotein horseradish peroxidase inhibited over 70% the IgE-binding to Cit s 1.

CONCLUSIONS

Over 60% of patients with allergy to oranges show specific IgE to Cit s 1. However, the purified allergen exerts a low in vivo reactivity. Complex N-linked glycans seem to play a prominent role in the IgE-binding capacity of Cit s 1. This characteristic of Cit s 1, as well as of other orange glycoproteins, could lead to false positives if the diagnosis of allergy to oranges is mainly based on in vitro specific IgE determination.

Crystal structure of peach Pru p 3, the prototypic member of the family of plant non-specific lipid transfer protein pan-allergens

This study describes the three-dimensional crystal structure of a non-specific lipid transport protein (ns-LTP) from Rosaceae. Whilst ns-LTPs from species other than Rosaceae, such as nuts, cereals, grape, oranges and vegetables are also responsible for plant food allergies, this is less frequent compared with ns-LTPs from Rosaceae in the Mediterranean area. In this heterologously expressed peach Pru p3, a ligand is present inside the central cavity of the protein, presumably a fatty acid that was present or produced in the culture medium of the expression organism Escherichia coli. Moreover, the two molecules of ns-LTP present in the asymmetric unit bind this ligand in a different way, suggesting a significant degree of plasticity for the peach ns-LTP binding cavity, despite the presence of four disulphide bridges. Two molecules are present in the asymmetric unit: molecule A is a fully liganded protein, while molecule B apparently represents a partially liganded state. Also, molecular dynamics simulation, along with other evidence, suggests that these two molecular conformations represent different states in solution. Comparison of the 3D models of different ns-LTPs justifies the evidence of a high degree of conservation of the putative IgE binding epitopes among proteins of the Rosaceae family and the presence of significant amino acid replacements in correspondence of the same regions in ns-LTPs of botanical species unrelated to Rosaceae.