Are Physicochemical Properties Shaping the Allergenic Potency of Animal Allergens?

Abstract

Key determinants for the development of an allergic response to an otherwise 'harmless' food protein involve different factors like the predisposition of the individual, the timing, the dose, the route of exposure, the intrinsic properties of the allergen, the food matrix (e.g. lipids) and the allergen modification by food processing. Various physicochemical parameters can have an impact on the allergenicity of animal proteins. Following our previous review on how physicochemical parameters shape plant protein allergenicity, the same analysis was proceeded here for animal allergens.We found that each parameter can have variable effects, ranging on an axis from allergenicity enhancement to resolution, depending on its nature and the allergen. While glycosylation and phosphorylation are common, both are not universal traits of animal allergens. High molecular structures can favour allergenicity, but structural loss and uncovering hidden epitopes, can also have a similar impact. We discovered that there are important knowledge gaps in regard to physicochemical parameters shaping protein allergenicity both from animal and plant origin, mainly because the comparability of the data is poor. Future biomolecular studies of exhaustive, standardized design together with strong validation part in the clinical context, together with data integration model systems will be needed to unravel causal relationships between physicochemical properties and the basis of protein allergenicity.

Maillard Reaction Induced Changes in Allergenicity of Food

“…In practice, given that the most common type of FA is IgE-mediated, which involves the mechanism of IgE-FcεRI-mast cell/basophil axis, the IgE binding ability test is usually introduced [ 14 ]. Under most circumstances, the IgE reactivity test in food research uses in vitro assays such as ELISA and Western blot [ 10 ]. Nevertheless, allergens after ingestion would confront a series of events such as degradation and digestion, so finally it is not the original allergens ingested that crosslink with IgE.…”

“…This paper reviews the effects of the MR on the allergenicity of common allergenic foods from a food science point of view. There have been several reviews concerning the MR and allergenicity of foods; however, they either include various processings, and MR is just a minor part containing limited information [ 10 , 11 ], or they are written from a more clinical perspective [ 8 , 12 , 13 ]. Moreover, because the MR occurs during heating, this review not only describes MR-induced changes in allergenicity but also differentiates it from heating-induced changes.…”

An overview of tropomyosin as an important seafood allergen: Structure, cross‐reactivity, epitopes, allergenicity, and processing modifications

“…The corresponding mechanisms are mainly divided into two ways: (1) TM can be hydrolyzed by proteases into polypeptides or amino acids or other small molecular, thus changing the spatial conformation; (2) intermolecular or intramolecular cross‐linking caused by enzymes results in the destruction of protein conformation (Figure 3b; Khan et al., 2019; Meng et al., 2020). In general, the enzymatic hydrolysis process seems to decrease the IgE‐binding capacity of animal allergens (Costa et al., 2021).…”

The Effector Function of Allergens

“…Arguably, all of these aspects must be present for an allergen to be clinically relevant although there are exceptions due to cross-reactivity when IgE sensitization is primarily induced by a different allergen (2,3). The concept of "allergenicity" in general or in a specific context has been reviewed previously, most often focusing on the ability of allergens to elicit an IgE response but also acknowledging the importance of clinical reactions (4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16). This review is focused solely on the effector function of allergens and the ability of an allergen to elicit an allergic reaction by cross-linking of IgE/FcεR1complexes to activate mast cells and basophils.…”

“…The mechanism whereby one allergenic protein may sensitize and thus generate an IgE response that allows a different but homologous allergen to cause an effector response, likely involves cross-reactive linear and/or conformational epitopes (23,24). However, for proteins displaying low overall identity such as between Ara h 1 and Ara h 2 or between peanut and treenut proteins, the mechanism is less well-understood and may involve discrete sequences similar in physicochemical properties (16,(25)(26)(27).…”