Investigation of Sensitization Potential of the Soybean Allergen Gly m 4 by Using Caco-2/Immune Cells Co-Culture Model

Study on Immunoregulatory Effects of Fucoidan from Sargassum graminifolium In Vivo and Immunoactivation Activity of Its Fecal Fermentation Products Using Co-Culture Model

Fucoidan, brown seaweed-derived dietary fibers (DFs), can be considered a promising candidate for modulating immune responses. Due to its structural complexity and diversity, it is unclear whether Sargassum graminifolium fucoidans (SGFs) also show marvelous immunoregulatory effects. In the present study, two fractions, SGF-1 and SGF-2, were purified from SGFs by DEAE-Sepharose Fast Flow and Sephacryl S-400 HR column chromatography. We investigated the in vivo immune regulatory activity of SGF-2 and explored the immune activation of SGF-2 fecal fermentation products with in vitro fecal fermentation combined with a Caco-2/RAW264.7 co-culture system. In vivo results exhibited that SGF-2 could elevate the thymus/spleen indices, CD8+ splenic T lymphocyte subpopulations, and CD4+ Foxp3+ splenic Tregs. The 16S high-throughput sequencing results showed that SGF-2 administration significantly increased the relative abundance of Lactobacillus, Alloprevotella, Ruminococcus, and Akkermansia. In addition, it was found that SGF-2 fermented by feces could significantly improve the phagocytosis, NO, and cytokine (TNF-α, IL-6, and IL-10) production of macrophages in the co-culture system. These results indicated that SGFs have the potential to modulate immunity and promote health by affecting the gut microbiota.

The epithelial barrier: The gateway to allergic, autoimmune, and metabolic diseases and chronic neuropsychiatric conditions

Since the 1960 s, our health has been compromised by exposure to over 350,000 newly introduced toxic substances, contributing to the current pandemic in allergic, autoimmune and metabolic diseases. The "Epithelial Barrier Theory" postulates that these diseases are exacerbated by persistent periepithelial inflammation (epithelitis) triggered by exposure to a wide range of epithelial barrier-damaging substances as well as genetic susceptibility. The epithelial barrier serves as the body's primary physical, chemical, and immunological barrier against external stimuli. A leaky epithelial barrier facilitates the translocation of the microbiome from the surface of the afflicted tissues to interepithelial and even deeper subepithelial locations. In turn, opportunistic bacterial colonization, microbiota dysbiosis, local inflammation and impaired tissue regeneration and remodelling follow. Migration of inflammatory cells to susceptible tissues contributes to damage and inflammation, initiating and aggravating many chronic inflammatory diseases. The objective of this review is to highlight and evaluate recent studies on epithelial physiology and its role in the pathogenesis of chronic diseases in light of the epithelial barrier theory.

A comprehensive review on glycation and its potential application to reduce food allergenicity

Food allergens are a major concern for individuals who are susceptible to food allergies and may experience various health issues due to allergens in their food. Most allergenic foods are subjected to heat treatment before being consumed. However, thermal processing and prolonged storage can cause glycation reactions to occur in food. The glycation reaction is a common processing method requiring no special chemicals or equipment. It may affect the allergenicity of proteins by altering the structure of the epitope, revealing hidden epitopes, concealing linear epitopes, or creating new ones. Changes in food allergenicity following glycation processing depend on several factors, including the allergen's characteristics, processing parameters, and matrix, and are therefore hard to predict. This review examines how glycation reactions affect the allergenicity of different allergen groups in allergenic foods.

Critical features of an in vitro intestinal absorption model to study the first key aspects underlying food allergen sensitization

New types of protein sources will enter our diet in a near future, reinforcing the need for a straightforward in vitro (cell-based) screening model to test and predict the safety of these novel proteins, in particular their potential risk for de novo allergic sensitization. The Adverse Outcome Pathway (AOP) for allergen sensitization describes the current knowledge of key events underlying the complex cellular interactions that proceed allergic food sensitization. Currently, there is no consensus on the in vitro model to study the intestinal translocation of proteins as well as the epithelial activation, which comprise the first molecular initiation events (ME1-3) and the first key event of the AOP, respectively. As members of INFOGEST, we have highlighted several critical features that should be considered for any proposed in vitro model to study epithelial protein transport in the context of allergic sensitization. In addition, we defined which intestinal cell types are indispensable in a consensus model of the first steps of the AOP, and which cell types are optional or desired when there is the possibility to create a more complex cell model. A model of these first key aspects of the AOP can be used to study the gut epithelial translocation behavior of known hypo- and hyperallergens, juxtaposed to the transport behavior of novel proteins as a first screen for risk management of dietary proteins. Indeed, this disquisition forms a basis for the development of a future consensus model of the allergic sensitization cascade, comprising also the other key events (KE2-5).

Structural and Immunologic Properties of the Major Soybean Allergen Gly m 4 Causing Anaphylaxis

Gly m 4 is the major soybean allergen, causing birch pollen cross allergic reactions. In some cases, Gly m 4-mediated anaphylaxis takes place, but the causative factors are still unknown. Here, we studied the structural and immunologic properties of Gly m 4 to shed light on this phenomenon. We showed that Gly m 4 retained its structure and IgE-binding capacity after heating. Gly m 4 was cleaved slowly under nonoptimal gastric conditions mimicking duodenal digestion, and IgE from the sera of allergic patients interacted with the intact allergen rather than with its proteolytic fragments. Similar peptide clusters of Bet v 1 and Gly m 4 were formed during allergen endolysosomal degradation in vitro, but their sequence identity was insignificant. Animal polyclonal anti-Gly m 4 and anti-Bet v 1 IgG weakly cross-reacted with Bet v 1 and Gly m 4, respectively. Thus, we supposed that not only conserved epitopes elicited cross-reactivity with Bet v 1, but also variable epitopes were present in the Gly m 4 structure. Our data suggests that consumption of moderately processed soybean-based drinks may lead to the neutralizing of gastric pH as a result of which intact Gly m 4 can reach the human intestine and cause IgE-mediated system allergic reactions.

How Do Pollen Allergens Sensitize?

Plant pollen is one of the main sources of allergens causing allergic diseases such as allergic rhinitis and asthma. Several allergens in plant pollen are panallergens which are also present in other allergen sources. As a result, sensitized individuals may also experience food allergies. The mechanism of sensitization and development of allergic inflammation is a consequence of the interaction of allergens with a large number of molecular factors that often are acting in a complex with other compounds, for example low-molecular-mass ligands, which contribute to the induction a type 2-driven response of immune system. In this review, special attention is paid not only to properties of allergens but also to an important role of their interaction with lipids and other hydrophobic molecules in pollen sensitization. The reactions of epithelial cells lining the nasal and bronchial mucosa and of other immunocompetent cells will also be considered, in particular the mechanisms of the activation of B and T lymphocytes and the formation of allergen-specific antibody responses.

Do Lipids Influence Gastrointestinal Processing: A Case Study of Major Soybean Allergen Gly m 4

Previously, we have demonstrated that Gly m 4, one of the major soybean allergens, could pass through the Caco-2 epithelial barrier and have proposed a mechanism of sensitization. However, it is not known yet whether Gly m 4 can reach the intestine in its intact form after digestion in stomach. In the present work, we studied an influence of various factors including lipids (fatty acids and lysolipids) on digestibility of Gly m 4. Using fluorescent and CD spectroscopies, we showed that Gly m 4 interacted with oleic acid and LPPG (lyso-palmitoyl phosphatidylglycerol), but its binding affinity greatly decreased under acidic conditions, probably due to the protein denaturation. The mimicking of gastric digestion revealed that Gly m 4 digestibility could be significantly reduced with the change of pH value and pepsin-to-allergen ratio, as well as by the presence of LPPG. We suggested that the protective effect of LPPG was unlikely associated with the allergen binding, but rather connected to the pepsin inhibition due to the lipid interaction with its catalytic site. As a result, we assumed that, under certain conditions, the intact Gly m 4 might be able to reach the human intestine and thereby could be responsible for allergic sensitization.