A lipid transfer protein involved in occupational sensitization to spelt

Diagnostic management of patients reporting symptoms after wheat ingestion

Many patients report symptoms after wheat ingestion experiencing a wide spectrum of clinical manifestations. Three possible diagnoses have been recognized: celiac disease (CD), wheat allergy (WA), and non-celiac (gluten) wheat sensitivity (NCGS/NCWS). CD is a chronic immune-mediated disease of the small bowel caused by exposure to dietary gluten in genetically predisposed individuals, with a prevalence of approximately 1%. It is characterized by mucosal inflammation and atrophy following exposure to gluten and improvement after gluten withdrawal. Food allergies are immunological responses to a food antigen. WA is the expression of an immunologically mediated process that can be immunoglobulin E (IgE) or non-IgE mediated; its many symptoms include urticaria/angioedema, asthma, rhinitis, and anaphylaxis. NCGS/NCWS is characterized by gastrointestinal and/or extra-intestinal symptoms after ingestion of gluten-containing food in subjects not affected by CD or WA. The aim of this review is to help physicians and nutritionists diagnose the cause of symptoms reported after wheat ingestion, thus avoiding patient frustration, inappropriate testing, and incorrect or missed diagnoses. An algorithm for the diagnostic approach in these patients is provided, to help to diagnose CD, WA, NCGS/NCWS or to identify possible functional disorders as the wheat-sensitive irritable bowel syndrome. A personalized approach, regular follow-up, and the help of a skilled healthcare professional are mandatory for patients with symptoms following wheat ingestion is provided. A gluten-free-diet is often recommended for patients with self-reported gluten/wheat-dependent symptoms; for patients with symptoms similar to those of functional diseases while there is evidence that a low-FODMAP diet could be the first option.

Lipid transfer protein allergy: A review of current controversies

Sensitization to lipid transfer protein (LTP), the most frequent cause of food allergy in southern Europe, still shows several controversial, but also intriguing, aspects. Some of these include the degree of cross-reactivity between LTPs from botanically distant sources, the definition of risk factors, the role of some cofactors, clinical outcomes, geographical differences and the identification of the primary sensitizer in different areas. This review article tries to analyse and comment on these aspects point by point suggesting some explanatory hypotheses with the final scope to stimulate critical thoughts and elicit the scientific discussion about this issue in the readership.

Non-specific lipid-transfer proteins: Allergen structure and function, cross-reactivity, sensitization, and epidemiology

Background

Discovered and described 40 years ago, non‐specific lipid transfer proteins (nsLTP) are present in many plant species and play an important role protecting plants from stressors such as heat or drought. In the last 20 years, sensitization to nsLTP and consequent reactions to plant foods has become an increasing concern.

Aim

The aim of this paper is to review the evidence for the structure and function of nsLTP allergens, and cross‐reactivity, sensitization, and epidemiology of nsLTP allergy.

Materials and Methods

A Task Force, supported by the European Academy of Allergy & Clinical Immunology (EAACI), reviewed current evidence and provide a signpost for future research. The search terms for this paper were “Non‐specific Lipid Transfer Proteins”, “LTP syndrome”, “Pru p 3”, “plant food allergy”, “pollen‐food syndrome”.

Results

Most nsLTP allergens have a highly conserved structure stabilised by 4‐disulphide bridges. Studies on the peach nsLTP, Pru p 3, demonstrate that nsLTPs are very cross‐reactive, with the four major IgE epitopes of Pru p 3 being shared by nsLTP from other botanically related fruits. These nsLTP allergens are to varying degrees resistant to heat and digestion, and sensitization may occur through the oral, inhaled or cutaneous routes. In some populations, Pru p 3 is the primary and sole sensitizing allergen, but many are poly‐sensitised both to botanically un‐related nsLTP in foods, and non‐food sources of nsLTP such as Cannabis sativa, Platanus acerifolia, (plane tree), Ambrosia artemisiifolia (ragweed) and Artemisia vulgaris (mugwort). Initially, nsLTP sensitization appeared to be limited to Mediterranean countries, however more recent studies suggest clinically relevant sensitization occurs in North Atlantic regions and also countries in Northern Europe, with nsLTP sensitisation profiles being broadly similar.

Discussion

These robust allergens have the potential to sensitize and provoke symptoms to a large number of plant foods, including those which are raw, cooked or processed. It is unknown why some sensitized individuals develop clinical symptoms to foods whereas others do not, or indeed what other allergens besides Pru p 3 may be primary sensitising allergens. It is clear that these allergens are also relevant in non‐Mediterranean populations and there needs to be more recognition of this.

Conclusion

Non‐specific LTP allergens, present in a wide variety of plant foods and pollens, are structurally robust and so may be present in both raw and cooked foods. More studies are needed to understand routes of sensitization and the world‐wide prevalence of clinical symptoms associated with sensitization to these complex allergens.

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.

Nonspecific lipid-transfer proteins in plant foods and pollens: an important allergen class

PURPOSE OF REVIEW

Here we focus our attention on the structural stability and physicochemical properties of plant nonspecific lipid-transfer proteins (nsLTPs) as keys to their allergenicity. We further present the current opinions on the route of sensitization and include the latest additions to the nsLTP allergen family.

RECENT FINDINGS

Plant nsLTPs are small cysteine-rich lipid-binding proteins that play a key role in plant resistance to biotic and abiotic stress. Besides their relevance for plant-pathogen interactions, nsLTPs have attracted interest as true food allergens which are of high importance to atopics in Mediterranean countries. It is now becoming clear that their molecular properties such as the remarkable stability to proteolysis and thermal denaturation are intrinsically linked to their allergenicity. These properties also facilitate sensitization via the gastrointestinal tract which allows these molecules to act as allergens independently of prior exposure to pollen. In addition, a group of allergenic pollen nsLTPs exists which seem to be only partially linked to the food nsLTPs by cross-reactivity.

SUMMARY

Research into the family of nsLTPs will continue to provide insights about the particular molecular properties that make an nsLTP an allergen and how primary sensitization occurs.

Respiratory allergy to peach leaves and lipid-transfer proteins

BACKGROUND

Several lipid-transfer proteins (LTPs) have been identified as important food allergens, especially in fruits of the Rosaceae family. The major peach (Prunus persica) allergen has been identified, sequenced and designated Pru p 3.

OBJECTIVE

To present Pru p 3 as an aeroallergen able to induce occupational asthma.

METHODS

A thorough investigation was performed in a fruit grower with occupational asthma. Skin prick-prick tests with peach leaves and prick tests with perennial respiratory allergens and pollens, fruits and peach leaf extracts were done. Serum-specific IgE was tested for peach leaf, peach fruit, peach skin and respiratory allergens that were positive in skin prick tests. Specific bronchial provocation tests (BPTs) with extracts of peach leaf were also done. Before and 24 h after the BPT, BPTs with methacholine and sputum induction were done. The IgE reactivity pattern to peach leaf and fruit extracts and to Pru p 3 was identified by using SDS-PAGE and immunoblotting. Blotting inhibition of peach leaf extract by Pru p 3 was also performed. The putative allergen was quantified in leaf and fruit skin extracts with ELISA based on an anti-Pru p 3 antibody.

RESULTS

Skin tests were positive for peach leaf and fruit. The BPT was positive, with immediate and delayed response. This test induced a decrease in PD20 (dose of agonist that induces a 20% fall in FEV1) methacholine and an increase in eosinophils and eosinophil cationic protein in sputum. Peach leaf extract contained concentrations of Pru p 3 similar to those found in peach skin. Specific IgE immunodetection showed that patient's sera reacted with Pru p 3, and with a single major band from the peach leaf extract fully inhibited by Pru p 3.

CONCLUSION

Pru p 3 from peach leaves can act as a respiratory allergen and cause occupational rhinoconjunctivitis and asthma.