ReviewPerusal of food allergens analysis by mass spectrometry-based proteomics
Graphical abstract
Introduction
Food allergy is an adverse reaction to the antigens, defined as food allergens. In this view, the body reacts to certain foods as they are harmful substances and an immune reaction is elicited even though such antigens are innocuous in healthy people [1]. The immune system of non allergic (healthy or immune-tolerant) individuals is able to discriminate pathogenic antigens from innocuous ones and is, therefore, unresponsive to food antigens. On the contrary, in food allergic individuals, a process of sensitization occurs the first time the immune system interacts with food antigen and this inappropriate response determines the immune pathogenesis during the successive interactions with the food(s) [1].
Allergy is defined as “a hypersensitivity reaction initiated by proven or strongly suspected immunologic mechanisms” and, specifically for food allergy, this term is used when a causal relationship has been defined between a specific food and, ideally, with a specific immunological mechanism [2]. The elicited immune reaction could be IgE-mediated, non-IgE-mediated and mixed. The IgE-mediated reactions arise up to 2 h from the food ingestion (immediate onset symptoms) and may have a late-phase with prolonged or ongoing symptoms. After the sensitization phase, the subsequent exposure to the food allergen impacts the immune effector cells: food antigens attach to IgE molecules bound to FcεRI receptors on the surface of mast cells and basophils causing their degranulation and the release of histamine and other inflammatory mediators of the immediate allergic reaction (immediate phase of the response). The late-phase is characterized by de novo production of leukotrienes, platelet-activating factor and cytokines, such as interleukin-4 (IL-4), IL-5 and, IL-13. Different body districts are involved, like gastrointestinal (GI) tract, respiratory system, and the skin, and different may be the symptoms: oral tingling, pruritus, swelling, nausea, abdominal pain, vomiting, wheezing, asthma, angioedema. In acute cases, a serious explosive systemic response (anaphylaxis) may also occur that involves multiple organs and can often be life-threatening. Non-IgE-mediated reactions occur 4 to 28 h after ingestion of the offending food(s) and are believed to be generally T-cell-mediated. Although these immune reactions affect mostly the GI tract, details are poorly defined both clinically and scientifically. Food protein-induced enterocolitis syndrome (FPIES), food protein-induced proctocolitis (FPIP) and food protein enteropathy (FPE) are ascribed to non-IgE mediated food allergies. Mixed IgE and non-IgE mediated reaction involve both IgE- and non-IgE-mediated mechanisms; one example is eosinophilic oesophagitis (EoE), a GI disorder caused eosinophilic infiltration of tissues in presence of milk allergens [1,3]. Over the last few decades, food allergy prevalence has been dramatically increased, especially in children; they usually develop food allergy early in life and will eventually reach tolerance while growing (in case of milk allergy, approximately 80% by the fifth birthday resolved the allergy and 35% show new food allergy). Highly allergic children, which have the highest IgE levels and express the most serious clinical outcome like anaphylaxis and asthma, often develop hypersensitivity to other foods and are less likely to overgrowth their food allergy. It was assessed that food allergy affects up to 8% of young children and 6% of the adult population [4,5]. Due to these increasing numbers, food allergy is becoming a serious health problem and, so far, there is no treatment available beyond careful food avoidance [6]. Because of the extreme complexity of the pathogenesis, our understanding of food allergy is still partial and the science of food allergy is a dynamic, ever-growing field. The ultimate goal is to achieve deeper understanding of the biochemical and molecular basis of food allergy broad manifestation, more efficient diagnosis and management of patients and eventually better treatment strategies. Mass spectrometry (MS)-based proteomics has become an integral part of this continuous learning process acknowledged the recent and rapid technological advances: modern and up-to-date mass spectrometers have risen unprecedented specificity, sensitivity and capability to multiplex and parallelize the analyses of peptide/proteins. Proteomic approaches shed light on proteins structure, post-translational modifications (PTMs) and abundance, and protein-protein interactions, therefore proteomic investigations on food matrices have contributed, and it is still contributing, to the identification, the characterization and the quantification of food allergens. Approaches in a proteomic food allergen study involves: 1) extraction of proteins from food and food matrix, 2) detection and identification of target allergen(s), and eventually 3) quantification of allergens (Fig. 1). Each of these steps must be carefully addressed and may be accomplished with a wide range of operational choices reviewing related literature. Therefore, the purpose of this review is to provide a snapshot of the different methodologies adopted in the research on food allergens. Particular emphasis is given to proteomic approaches that are being employed in the last years, in order to help researchers in choosing the more suitable experimental workflow.
Section snippets
Food allergens identification and detection
Food allergy prevalence is increasing over time becoming a significant public health problem. Unfortunately, no treatment beyond careful food avoidance exists to date, and for the most sensitive patients, ingestion of even tiny load of allergens may be life-threatening in absence of rapid treatment with epinephrine for food-induced anaphylaxis. Therefore, each country has put in place mandatory labelling that regulates the list of allergenic ingredients present in any food and processed food
Food allergens quantification
Allergens accurate quantification represents one of the major challenges for food science mass spectrometrists. MS analytical pipelines capable of multiplexed absolute quantification are routinely adopted for small molecules and therapeutic drug monitoring in human plasma and urine samples. Nevertheless, dealing with proteins in different matrices, such as food ones, is much more demanding [77].
Determining the exact reference doses of the allergens below which even the most sensitive
Immunoproteomics
Besides allergen detection and quantitation into complex food matrixes, research efforts are also being performed in discovering novel allergenic proteins and epitopes to target an efficient diagnostic model. In addition, gained knowledge might also be useful in understanding the molecular mechanisms governing the allergic reactions provoked by a wide variety of food allergens, thus propose effective treatments in both prophylactic and therapeutic terms.
It is defined as “Immunoproteomics” the
Practical challenges in food allergen detection
Nowadays, MS-based proteomics is widely accepted as the best approach for a fair food allergen assessment. Besides general issues common to all allergen detection methods such as the choice of the analyte, matrix effect and allergen protein recovery, several issues of practical concern are still unsolved, keeping proteomics away from being adopted in the routine proceedings for food allergen evaluation [53]. Development of novel proteomics-based methods relies on preliminary tests performed
Allergen proteomics for the food industry
The high sensitivity of the MS-based investigations makes proteomics an extremely powerful tool, and it is believed that an increasing number of studies will be performed in the Research and Development (R&D) sector of food industry, in the next future. Among the diverse facets of proteomics investigation in food science, MS-proteomics applied to fruits and vegetables packed under controlled atmosphere demonstrated an altered profile of allergenic proteins [108]. Proteomics investigations have
Conclusions
The increasing technological advances in the field of MS makes proteomics a powerful and versatile omic science. Mass spectrometer vendors are developing faster and more sensitive instruments which are able to perform sophisticated experiments and multiplexed analysis in a high throughput fashion. Nowadays, proteomics investigations are being performed in diverse research field, contributing to expanding the overall knowledge of the “protein world” with enormous advantages also for the food
Funding
This work was supported by RC2018 of Italian Ministry of Health to Lorenza Putignani and Alessandro Giovanni Fiocchi.
The authors declare that there are no financial and/or personal relationships with any people or organizations that could inappropriately influence their work.
Declaration of Competing Interest
The authors declare that there exist no conflicts of interest with regard to the present study.
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2022, Future FoodsCitation Excerpt :Mass spectrometry (MS)-based proteomics analysis has developed into a cornerstone of biotechnological and biomedical research (Armengaud, 2016; Noor et al., 2021), but is still in its infancy for food protein analysis and characterization. In the food context, MS-based proteomics has primarily been employed to investigate food safety, food quality, allergenicity, as well as organism and cellular responses to exogenous stimuli in relation to e.g. crop breeding (Agrawal et al., 2013; Andjelković and Josić, 2018; Mora et al., 2018; Lexhaller, Colgrave and Scherf, 2019; Marzano et al., 2020). Such studies have also been performed for red seaweeds (Beaulieu, 2019).
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Authors contributed equally.