Respiratory Allergy to Lipid Transfer Protein

Background Lipid transfer proteins (LTPs) are the most common cause of primary food allergy and food-induced anaphylaxis in Southern European countries (Mediterranean and Atlantic areas). They are widely distributed in the outer layer of plant-based foods as well as in the pollen of trees and herbaceous plants. Due to their biochemical and molecular characteristics, LTPs exhibit high resistance to enzymatic digestion, acidic pH, and heat, leading to immunological cross-reactivity with unrelated foods or pollens in patients sensitized to these proteins. LTPs are considered complete food allergens (Class I allergens) capable of sensitizing through the gastrointestinal tract, with peach LTP (Pru p 3) often acting as the primary sensitizer, subsequently directing the immune response towards recognizing other LTPs. The aim of this study was to determine the LTP sensitization profile and its association with food allergies in patients consulting the allergy department in our region. Methods Samples were collected from patients attending our allergy department with suspected LTP sensitization. Once sensitization was confirmed through a positive intradermal test for LTP, demographic data, clinical allergy history, and diagnostic test results were recorded. In vivo testing was conducted using intradermal skin tests, while in vitro testing involved specific IgE determination using LTP-RUO immunoblot assay strips from Euroimmun®, which include six recombinant allergens and four allergen mixtures. Results A total of 96 samples were collected, including 13 negative controls. The average patient age was 35 years, with a majority of female participants (55%). Among the specific IgE tests for LTP analyzed, 25 patients (30.1%) tested positive for all LTPs, 11 patients (13.3%) tested positive for between 1 and 5 of the studied LTPs, and 55 patients (66.3%) tested positive for more than 5. Seventeen participants (20.5%) tested negative for all LTPs but showed reactivity to aeroallergens (mainly pollen family) through intradermal skin testing. The Pru p 3 test (peach LTP), considered the primary sensitizer, was negative in 19 participants (22.9%), with no positive results for any of the other measured LTPs. We found two patients who tested negative for Pru p 3 but positive for other LTPs: one for X2 Pha v3 (green bean) and the other for both X4 Sola L (tomato) and X2 Pha v3 (green bean). Conclusion LTP sensitization in our geographic area is predominantly linked to Pru p 3 but it cannot be considered a prototypical marker of this syndrome. LTP allergy is very common in Mediterranean countries and can cause potentially life-threatening reactions. This highlights the need to understand the clinical and immunological characteristics that can help identify and prevent anaphylactic episodes in patients exposed to LTP-containing foods

A case of allergy to airborne, heat-labile shrimp allergens

Lipid-transfer proteins (LTPs) exist in all branches of the plant kingdom (panallergens) and are able to induce both IgE sensitization and allergic reactions of different severities, including anaphylaxis. The allergens have a molecular weight of 6–10 kDa and show both high thermal and proteolytic stability. In addition to foods (fruits and vegetables), LTPs can also be found in pollen. Sensitization toward LTPs seems to occur via food intake; the clinical relevance of cross-reactivities to pollen-derived LTPs is still unclear. Allergic reactions to LTPs occur predominantly in the Mediterranean areas and are rare in Northern and Central Europe. In Southern Europe IgE reactivity to peach LTP (Pru p 3) is frequently diagnosed. For this reason Pru p 3 is used as a marker allergen. For practical clinical issues, the improvement of allergy diagnosis (by component-resolved methods) has priority over the avoidance of LTPs in allergy-causing foods from the diet. At present, allergen-specific immunotherapy is not available.

We describe a case of a woman who developed three separate episodes of urticaria and ana-phylaxis during exercise after consuming an apple, with immunological evidence that nonspecific lipid transfer proteins (LTP) may have been responsible for these reactions. LTP sensitivity can cause life-threatening allergies and anaphylaxis. Although LTP sensitization is common in Mediterranean countries, the frequency of knowledge and diagnoses is increasing in Europe. Despite the geographic differences, LTP allergy should be kept on sight when facing severe anaphylaxis after consuming LTP-included food.

Seed storage proteins are extremely stable allergens in nuts, seeds, and legumes and are responsible for the most severe allergic reactions to these foods. The cross-reactivity between seed storage proteins from different sources has not been studied at a molecular level so far. This study aimed to ascertain the cross-reactivity between walnut and hazelnut seed storage proteins using recombinant allergens. Sera from 13 consecutive patients with severe primary walnut and/or hazelnut allergy and hypersensitive to both nuts were studied. IgE specific for rCor a 9, rCor a 14, and rJug r 1 was measured, and inhibition experiments were carried out by measuring IgE reactivity after absorption of patients’ sera with freshly prepared walnut extract. All 13 sera showed strong IgE reactivity against walnut 2S albumin, Jug r 1, 12 reacted to hazelnut 2S albumin, Cor a 14, and 8 to the hazelnut legumin, Cor a 9. In inhibition experiments, absorption of sera with whole walnut extract led to the complete disappearance of IgE reactivity to Jug r 1 in 12/13 cases, as expected, but also to the complete disappearance of specific IgE to Cor a 14 in 9/12 sera, and of IgE reactivity to Cor a 9 in 7/8. In the remaining cases a dramatic drop in IgE reactivity was observed. The study shows that patients primarily allergic to either walnut or hazelnut showing a skin or serological reactivity to the other nut also are potentially at risk of severe allergic reactions caused by cross-reactivity between 2S albumins and legumins.

Lipid transfer protein (LTP) has been documented as the dominant protein involved in food-induced anaphylaxis and food-dependent exercise-induced anaphylaxis (FDEIA) patients from Mediterranean European countries. To date, there is no report of FDEIA triggering by LTP in China. A 12-year-old Chinese boy experienced recurrent anaphylaxis during intense exercise for 3 months. Specific immunoglobulin E was performed using ImmunoCAP (Thermo Fisher Scientific, Sweden) and Euroline (EUROIMMUN, Germany). He was sensitized to several pollens, mainly mugwort (62 KUA/L), and was found to have detectable immunoglobulin E in multiple foods: cereal (wheat, barley, oat maize, rice, buckwheat, and common millet), fruits (peach, apple, grape, cherry, and orange), vegetables (lettuce, cabbage, broccoli, cauliflower, tomato, and celery), and legumes and nuts (soybean, peanut, and walnut). He also showed sensitization to LTP components from mugwort Art v3 (79.7 KUA/L) and wheat Tri a14 (12.4 KUA/L), but negative to gluten, gliadin, and omega-5 gliadin. We advised our patient to carry an epinephrine auto-injector, not to exercise alone, and to avoid wheat and fruit/vegetable ingestion for at least 4 hours before exercise or when taking non-steroidal anti-inflammatory drugs. After a 6-month follow-up, the patient has experienced no episode of anaphylaxis. We reported the first documented FDEIA case suspected triggered by LTP in a Chinese child. Clinicians should be aware of LTP sensitization when anaphylaxis occurs during exercise in individuals with multiple pollen and food sensitization.

IntroductionFood allergy affects 6–17% of Europeans and in 60% of the cases it is accompanied by inhalation allergy. This is due to two phenomena, namely co-sensitisation and cross-reactivity, which are caused by panallergens, such as lipid transfer proteins (LTP). These proteins are classified as defence proteins PR-14 and are responsible for protecting the plant from bacterial and fungal infections. Clinically, LTP allergy manifests with severe anaphylactic reactions or milder reactions, such as oral allergy syndrome.AimTo assess the incidence of specific IgE to components belonging to LTP based on molecular testing.Material and methodsThe study was conducted at the Department of Allergy, Clinical Immunology and Internal Diseases in Bydgoszcz, Poland. A total of 50 subjects participated in the study. Each subject had their asIgE levels determined with ImmunoCap ISAC.Results and ConclusionsAntigen-specific IgE antibodies to LTP components were identified in 24% of the subjects. In subjects with LTP allergy, adverse skin reactions were the most common after consumption of sensitising foods. Peach was the most common food allergen triggering these reactions. The Artemisia vulgaris component Art v 3 was the precursor of LTP allergy in our study population: the highest incidence and the highest mean levels of asIgE were demonstrated for this component.

The aim of this systematic review was to evaluate the diagnostic accuracy of molecular-based LTPs serum sIgE for the diagnosis of food allergies in patients with suspected allergy to one of the LTPs-containing foods. Cohort, prospective or retrospective cross-sectional studies were considered for inclusion in this review. Oral food challenge (both open and double-blind placebo-controlled) was the reference standard for the diagnosis. PubMed (MEDLINE), Web of Science, Scopus, and ClinicalTrial.org were searched for relevant papers. The risk of bias was assigned by the QUADAS-2 tool. Data were reported as the sensitivity and specificity. The study protocol was registered in the PROSPERO database (CRD42022321985). Fifteen articles, including 2395 individuals, were included. The sensitivity of Ara h 9 for peanut allergy diagnosis ranged from 6 to 61%; the specificity ranged from 57 to 100%. The Cor a 8 sensitivity ranged from 11 to 43%, with the specificity ranging from 59 to 94%. Ara h 9 and Cor a 8 serum sIgE may be useful for confirming the diagnosis of peanut and hazelnut allergy in symptomatic patients, although the diagnostic accuracy is limited by the low sensitivity. More investigation on other LTPs and in adult populations may be important to define the clinical role of this test in food allergy diagnostics.

2S albumins are relevant and often major allergens from several tree nuts and seeds, affecting mainly children and young people. The present study aims to assess how the structural features of 2S albumins could affect their immunogenic capacity, which is essential to comprehend the role of these proteins in food allergy. For this purpose, twelve 2S albumins were isolated from their respective extracts by chromatographic methods and identified by MALDI-TOF mass-spectrometry. Their molecular and structural characterization was conducted by electrophoretic, spectroscopic and in silico methods, showing that these are small proteins that comprise a wide range of isoelectric points, displaying a general high structure stability to thermal treatment. Despite low amino acid sequence identity, these proteins share structural features, pointing conformational epitopes to explain cross-reactivity between them. Immunoblotting with allergic patients’ sera revealed those possible correlations between evolutionarily distant 2S albumins from different sources. The availability of a well-characterized panel of 2S albumins from plant-derived sources allowed establishing correlations between their structural features and their allergenic potential, including their role in cross-reactivity processes.

Food allergy is a growing public health concern in industrialized countries. For individuals with food allergies, especially severe ones, inadvertently consuming even a small quantity of the allergenic food can lead to life-threatening and even fatal reactions 1. Currently, food allergy management involves eliminating the triggering food from the diet and for patients with a history of anaphylaxis also prescribing self-injectable adrenaline. The continuous vigilance regarding diet and the fear of accidentally ingesting the allergenic food can create anxiety and compromise the quality of life of both the patient and their family 1,2. Various specialized allergy services worldwide now offer oral immunotherapy (OIT), a treatment capable of increasing the tolerated dose of allergenic foods. Although effective, OIT exposes the patient to the risk of allergic reactions, including severe ones, and therefore is not appropriate for all patients. Furthermore, there are no standardized OIT products other than one for peanut allergy, which was recently approved by the U.S. Food and Drug Administration (FDA) for the American market 2. Small trials have shown that the anti-IgE monoclonal antibody omalizumab can reduce the occurrence and severity of allergic reactions, as well as the time needed to reach the maintenance dose if used in combination with OIT 2. Recently, it has been demonstrated that monotherapy with omalizumab, which is already approved for patients with severe allergic asthma and chronic spontaneous urticaria 3, may protect individuals with multiple food allergies from severe reactions if they accidentally ingest a small quantity of foods to which they are allergic 4. In a phase III, double-blind, randomized, placebo-controlled trial published on February 25 in the New England Journal of Medicine, Wood et al. 4 tested omalizumab on 3 adults and 177 children (ranging from 1 year old to 17 years old; median age 7 years) who were severely allergic to peanuts and at least two other foods. Doses and frequency of omalizumab administration were based on patients’ weight and baseline total IgE levels. After 16 to 20 weeks of treatment, 67% of those who received omalizumab were able to ingest at least 600 mg of peanut protein (equivalent to approximately to two or three peanuts) in a single dose without experiencing a significant reaction, compared to only 7% of those who received placebo (p < 0.001). Furthermore, omalizumab was equally effective in increasing participants’ tolerance to other allergenic foods (at least 1000 mg of protein from the respective food), including milk (66% in the active group vs 10% in placebo; p < 0.001), egg (67% in the active group vs 0% in placebo; p < 0.001), and cashew (41% in the active group vs 3% in placebo; p < 0.001). As commonly reported in trials with biologic agents, injection-site reactions were more frequent in the active group. However, no significant adverse effects were observed during the short treatment period with omalizumab 4. Also, the protective response to peanuts and other foods proved to be durable when omalizumab was continued for another 24 weeks in an open-label extension trial. Based on these results, the FDA approved omalizumab as a treatment for food allergies in the United States 5. The findings of the study by Wood et al. 4 represent a significant step forward in the treatment of food allergies. Although the drug does not offer a definitive cure for food allergies, it reduces the risk that inadvertently ingesting a small quantity or even traces of the food to which one is strongly allergic could cause anaphylactic reactions and even death. Perhaps the most important limitation of omalizumab is that it does not eliminate food allergies, but it only increases the amount of food a person can consume before experiencing a reaction. Additionally, although omalizumab increases the amount of food needed to trigger a reaction, it is unclear whether it can reduce the severity of a reaction if a person accidentally consumes a larger dose of food than the minimum amount tolerated. For this reason, the FDA has approved the drug with the recommendation that individuals using omalizumab for food allergy should continue to avoid the foods to which they are allergic. Also, it should be noted that 14% of peanut-allergic participants treated with omalizumab were not able to tolerate even a small amount of peanut. Understanding why some people do not respond well will be crucial for selecting those who will benefit most from this treatment. A definitive cure for food allergy is yet to be found. Several therapeutic options for food allergy are currently at various stages of development, including different biologics, pharmacological agents, and various forms of immunotherapy 2. A better understanding of the immune mechanisms underlying food allergy is pivotal to designing safe and long-term effective therapeutic interventions as well as early preventive strategies.

Cabbage lipid transfer protein Bra o 3 is a major allergen responsible for cross-reactivity between plant foods and pollens

Background Lipid Transfer Protein (LTP) allergy constitutes the first cause of food allergy to vegetables in Southern Europe. LTPs are highly stable proteins, resistant to both gastric digestion and high temperatures. Allergic reactions to multiples vegetables, not phylogenetically related, are produced based on the cross-reactivity among these proteins, a phenomenon that has been named LTP syndrome. Tri a 14, the wheat LTP, is involved in baker s asthma and anaphylactic reaction. In the present work, we studied Weetabix ® foodstuff tolerance in four patients with wheat allergy, characterized by oral food challenge (OFC) and skin tests, trying to identify the source of this tolerance in wheat-based foodstuff.

Expression and purification of recombinant Pru p 3 and Mal d 3 in Escherichia coli

Nonspecific lipid transfer proteins (nsLTPs) represent a major cause of systemic food allergic reactions in the Mediterranean area. This study investigate hierarchical patterns and cluster relationships of IgE sensitization to different nsLTPs, and the relationship to clinical allergy in a large Italian cohort. A total of 568 nsLTP-positive subjects after IgE ImmunoCAP-ISAC microarray analysis with Ara h 9, Art v 3, Cor a 8, Jug r 3, Pla a 3, Pru p 3 and Tri a 14 allergens were studied. IgE inhibition experiments were carried out with mugwort and plane tree pollen extracts. Eighty-two per cent of nsLTP-positive participants (94% if <6years old) were Pru p 3(pos) , and 71% were Jug r 3(pos) . Participants who reacted to >5 nsLTPs reported a higher incidence of food-induced systemic reactions. Only Art v 3 and Pla a 3 (mugwort and plane tree nsLTPs, respectively) were associated with respiratory symptoms, and a correlation was observed between sensitization to pollen and plant food nsLTPs, particularly between Pla a 3 and tree nut/peanut nsLTPs. Co-sensitization to Par j 2 and PR-10 or profilin pan-allergens was associated with a lower prior prevalence of severe food-induced reactions. In inhibition assays, plane and mugwort pollen extracts inhibited 50-100% of IgE binding to food nsLTPs in microarrays. Testing IgE reactivity to a panel of nsLTP allergens unveils important associations between nsLTP sensitization profiles and clinical presentation and allows the identification of novel cluster patterns indicating likely cross-reactivities and highlighting potential allergens for nsLTP immunotherapy.

Almond is one of the tree nuts listed by U.S. FDA as a food allergen source. A food allergen identified with patient sera has been debated to be the 2S albumin or the 7S vicilin. However, neither of these proteins has been defined as a food allergen. The purpose of this study was to clone, express, and purify almond vicilin and test whether it is a food allergen. Western blot experiment was performed with 18 individual sera from patients with double-blind, placebo-controlled clinical almond allergy. The results showed that 44% of the sera contained IgE antibodies that recognized the recombinant almond vicilin, indicating that it is an almond allergen. Identifying this and additional almond allergens will facilitate the understanding of the allergenicity of seed proteins in tree nuts and their cross-reactivity.