The present article aims to perform a comparative study whether the allergic ability of fish parvalbumin, shrimp tropomyosin, egg ovalbumin and milk β-lactoglobulin to BALB/c mice was associated with gut microbiota-sera metabolism. BALB/c mice were given the same amount of four allergens to establish an allergic model, and four allergens presented different allergic abilities to mice, which resulted in increased of IgE, IgG and IgG₁ levels, allergy symptom scores, spleen and thymus index. Meanwhile, these allergens reduced the relative abundance of allergy-associated gut microbiota, such as Lachnospiraceae_NK4A136_group, Lachnospiraceae, Blautia, Roseburia and Oscillibacter. Four allergens also downregulated the serotonin metabolic pathway, upregulated the indole and kynurenine pathways, and significantly affected the glycerophospholipid metabolic pathway. Overall, the disruption of the allergy-associated gut microbiota and regulating tryptophan and glycerophospholipid metabolic pathway were responsible for increasing the allergic ability of four allergens, which have different antigenic epitopes resulting in different allergic abilities.

The changes in antigenic epitopes and allergenicity of silver carp parvalbumin (PV) after glycation and phosphorylation were investigated by spectroscopy, mass spectrometry and KU812 cell assay. The results showed that glycation combined with phosphorylation increased the molecular mass, reduced the free amino acid content, and changed the secondary structure and conformation of PV. The modified PV had eight glycation sites (K33, K46, K55, K65, K84, K88, K97 and K108) and one phosphorylation site (S56). The modification significantly reduced the ability of PV to bind IgG and IgE, and decreased histamine and interleukin-6 release from KU812 cells. Thus, glycation combined with phosphorylation reduced PV allergencity by masking the linear epitopes and damaging the conformational epitopes at the glyclation and phosphorylation sites. The results of this study may provide an important theoretical basis for the development of hypoallergenic fish products.

Glycation is the initial stage of the Maillard reaction and plays an important role in food processing and storage. This study aimed to explore the effect of ultrasound pretreatment on the glycation characteristics of parvalbumin with galactose. The multilevel structure, glycation degree, glycated peptides and sites of glycated parvalbumin were characterized by high performance liquid chromatography (HPLC) combined with size exclusion chromatography (SEC), intrinsic fluorescence, ultraviolet absorption, synchronous fluorescence spectroscopy and high-resolution mass spectrometry (HR-MS). The results showed that glycation significantly increased the molecular mass, reduced the free amino content, intrinsic fluorescence and ultraviolet absorption intensity, and changed the tertiary structure of parvalbumin. This effect was further promoted by ultrasound pretreatment. The glycated parvalbumin without ultrasound pretreatment contained four glycation sites (K46, K55, K65 and K88), while the number of glycation sites increased to six (K46, K55, K65, K88, K97 and K108) after ultrasonic pretreatment combined with glycation. Therefore, ultrasound pretreatment can result in protein unfolding, increase the degree of glycation, and thereby improve the characteristics of protein glycation.

The rising incidence of food allergy attracts researchers to advocate that a high-fat diet (HFD) is an attention-grabbing trigger. However, the mechanism by which HFD aggravates food allergy remains largely unknown. In this context, intestinal epithelium dysfunction as a characteristic of food allergy is summarized. Specifically, we focus our attention on the microbiota-intestinal epithelium interactions and call attention to the underlying mechanism by which HFD promotes food allergy along the interactions. Escaped fat and excessed bile acids in the colon induced by HFD can disrupt gut microbiota, directly regulating intestinal epithelium function. Additionally, HFD contributes to indirectly destroying the intestinal epithelium and enhancing its permeability by altering the level of microbial metabolites. Consequently, these ways promote the influx of food allergens. Substantial quantities of food allergens traverse the intestinal epithelium, prompting heightened secretion of pro-inflammatory cytokines, thus favoring a Th2 immune response. In this situation, impaired differentiation of Treg and Th1 cells can aggravate food allergy. Clarifying the intricate relationship between HFD and food allergy from the microbiota-intestinal epithelium interactions may offer prevention strategies for food allergy.

Gut microbiota plays an important role in food allergy. The immunoglobulin G (IgG)/immunoglobulin E (IgE) binding capacity and human gut microbiota changes of digestion products derived from glycated ovalbumin (OVA) were investigated. Gastrointestinal digestion effectively destroyed the primary structure of glycated OVA, resulting in a significantly higher digestibility than gastric digestion, and more abundant peptides < 3 kDa. Moreover, gastric and gastrointestinal digestion products have different fluorescence quenching and red shift of fluorescence peaks, and possess different conformational structures. These changes resulted in a decrease in 28.7% of the IgE binding capacity of gastrointestinal digestion products beyond that of pepsin. Moreover, gastrointestinal digestion products of glycated OVA increased significantly the proportion of Subdoligranulum, Collinsella, and Bifidobacterium. Therefore, gastrointestinal digestion products of glycated OVA altered human intestinal microbiota, reducing the risk of potential allergy.

Bovine α-lactalbumin (BLA) induced severe cow's milk allergy. In this study, a novel strategy combining ultrasonication, performed before glycation, and phosphorylation was proposed to reduce BLA allergenicity. Result showed that IgE- and IgG-binding capacities and the release rates of histamine and interleukin-6 from RBL-2H3 were reduced. Moreover, intrinsic fluorescence intensity and surface hydrophobicity were decreased, whereas glycated sites (R10, N44, K79, K108, N102 and K114) and phosphorylated sites (Y36 and S112) of BLA were increased. Minimum allergenicity was detected during BLA treatment after ultrasonic prior to glycation and subsequent phosphorylation because of considerable increase in glycated and phosphorylated sites. Therefore, the decrease in allergenicity of BLA, the effect correlated well with the shielding effect of glycated sites combined with phosphorylated sites and the conformational changes. This study provides important theoretical foundations for improving and using the ultrasonic technology combined with protein modification in allergenic protein processing.