Identification of antigenic sites destructed by high hydrostatic pressure (HHP) of the β subunit of β-conglycinin

Localization of G1A1a Allergenic Domain Destroyed by Thermal Processing

Glycinin is an important allergenic protein. A1a is the acidic chain of the G1 subunit in glycinin (G1A1a), and it has strong allergenicity. In this study, we used phage display technology to express the protein of G1A1a and its overlapping fragments and an indirect enzyme-linked immunosorbent assay (iELISA) to determine the antigenicity and allergenicity of the expressed protein. After three rounds of screening, it was determined that fragment A1a-2-B-I (151SLENQLDQMPRRFYLAGNQEQEFLKYQQEQG181) is the allergenic domain of G1A1a destroyed by thermal processing. In addition, three overlapping peptides were synthesized from fragments A1a-2-B-I, and a linear epitope was found in this domain through methods including dot blot and iELISA. Peptide 2 (157DQMPRRFYLANGNQE170) showed allergenicity, and after replacing it with alanine, it was found that amino acids D157, Q158, M159, and Y164 were the key amino acids that affected its antigenicity, while Q158, M159, R162, and N168 affected allergenicity.

Localization of an IgE epitope of glycinin A2 peptide chain

INTRODUCTION

One of the main allergens in soybeans is glycinin, which seriously impacts the normal lives of allergic people. Previous studies have confirmed that thermal processing and thermal processing combined with ultrahigh-pressure processing could significantly reduce the antigenicity of glycinin. The dominant antigen region of acidic peptide chain A2 of G2 subunit was located by phage display experiment.

METHODS

In this paper, overlapping peptides and alanine substitution techniques were used to explore the key amino acids that significantly affect the antigenicity of A2 peptide chain. The purity of peptide 1, peptide 2 and peptide 3 was identified by mass spectrometry and high-performance liquid chromatography, and the results showed that the purity of the synthesized overlapping peptide was more than 90%. SDS-PAGE showed that the peptide was successfully coupled with bovine serum albumin. The antigenicity of the coupling peptide was tested by ELISA and Dot-Blot, and the allergenicity was detected by reacting with the serum of patients with soybean globulin allergy.

CONCLUSION

The results showed that peptide 3 has stronger antigenicity and sensitization. Alanine substitution technology allowed one to perform site-directed mutagenesis on peptide 3. Dot-Blot and ELISA tests showed that D259, E260, E261, Q263 and C266 may be the key amino acids that significantly affect the antigenicity of peptide 3. The research presented is of great significance for correctly guiding the production of safe food and preventing the occurrence of food allergic diseases. © 2023 Society of Chemical Industry.

Localization and identification of denatured antigenic sites of glycinin A3 subunit after using two processing technologies

Glycinin is an important allergen in soybeans. In this study, molecular cloning and recombinant phage construction were performed to explore the antigenic sites of the glycinin A3 subunit that were denatured during processing. Next, the A-1-a fragment was located as the denatured antigenic sites by indirect ELISA. The combined UHP heat treatment showed better denaturation of this subunit than the single heat treatment assay. In addition, identification of the synthetic peptide showed that the A-1-a fragment was an amino acid sequence containing a conformational and linear IgE site, in which the first synthetic peptide (P1) being both an antigenic and allergenic site. The results of alanine-scanning showed that the key amino acids affecting antigenicity and allergenicity of A3 subunit were S²⁸, K²⁹, E³², L³⁵ and N¹³. Our results could provide the basis for further development of more efficient methods to reduce the allergenicity of soybeans.

Identification of allergenic epitopes destroyed by two processing technologies of glycinin A2 from soybean

BACKGROUND

Glycinin is one of the most highly allergenic proteins in soybeans, and G2 is one of the five allergenic subunits of glycinin. Compared with the alkaline chain, the acidic chain A2 of the G2 subunit has strong allergenicity. However, the precise epitopes of A2 and the epitopes destroyed during processing are still unknown.

RESULTS

In the present study, preparation of two specific antibodies damaged by processing and phage display techniques were applied to locate the antigenic epitopes of glycinin A2 polypeptide chains disrupted by two processing techniques (thermal processing and ultra-high pressure combined thermal processing). Bioinformatics methods were used to predict the possible epitopes of the A2 chain. The A2 chain and its overlapping segments were introduced into T7 phages and expressed on phage shell by phage display. An indirect enzyme-linked immunosorbent assay was used to screen for antigenic epitopes that had been disrupted by the two processing technologies. The results showed that the dominant antigenic region disrupted by processing was located mainly in the A2-3-B fragment. The reacting experiment with the serum of allergic patients showed that the A2-3-B fragment protein was not only an antigenic region, but also an allergenic region. The two processing technologies destroyed the allergenic epitopes of A2 chain, thereby reducing the allergenicity of protein. The amino acids where the dominant allergenic region disrupted by processing was located were: ²³³ AIVTVKGGLRVTAPAMRKPQQEEDDDDEEEQPQCVE²⁶⁸ .

CONCLUSION

Precise epitopes of the acidic chain A2 in glycinin were identified and epitopes destroyed in two common processing methods were also obtained. The application products of rapid detection of de-allergenicity effect of processed food can be developed according to the location of processed destruction allergenic region, which is of great significance with respect to preventing the occurrence of soybean allergenic diseases. © 2022 Society of Chemical Industry.

Establishment of DAS-ELISA for the detection of antigenic changes in glycinin after heat processing

In this study, a double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) method was established to detect the antigenic changes of thermally processed products containing glycinin. The proposed DAS-ELISA method used heat-treated antigen-absorbing antiserum as the coating antibody, and horseradish peroxidase (HRP)-labeled rabbit anti-glycinin polyclonal antibody as the detection antibody. The specificity test results which were obtained using the proposed method indicated that good specificity had been achieved. The cut-off value was 0.388, and the LOD was determined to be 19.53 ng/mL. The coefficient of variation was less than 5.25% (intra-day) and 9.50% (inter-day). In this study's milk powder addition test, the recovery rate of the glycinin ranged between 83.65% and 90.13%. The established DAS-ELISA method was also used to detect soybean thermal processing products, such as soy sauce, steamed fish and soy sauce, soybean paste, beef sauce, soy milk powder, and tofu. The results showed that the OD450 values of the aforementioned products were lower than the OD450 values of the glycinin in defatted soybean flour. Therefore, it was indicated that the above products has undergone different degrees of thermal processing. In other words, the majority of the epitopes of glycinin in the products had been destroyed by the thermal processing and could not be combined with heat-treated antigen-absorbing antiserum.

Effect of high hydrostatic pressure on the edible quality, health and safety attributes of plant-based foods represented by cereals and legumes: a review

Consumers today are increasingly willing to reduce their meat consumption and adopt plant-based alternatives in their diet. As a main source of plant-based foods, cereals and legumes (CLs) together could make up for all the essential nutrients that humans consume daily. However, the consumption of CLs and their derivatives is facing many challenges, such as the poor palatability of coarse grains and vegetarian meat, the presence of anti-nutritional factors, and allergenic proteins in CLs, and the vulnerability of plant-based foods to microbial contamination. Recently, high hydrostatic pressure (HHP) technology has been used to tailor the techno-functionality of plant proteins and induce cold gelatinization of starch in CLs to improve the edible quality of plant-based products. The nutritional value (e.g., the bioavailability of vitamins and minerals, reduction of anti-nutritional factors of legume proteins) and bio-functional properties (e.g., production of bioactive peptides, increasing the content of γ-aminobutyric acid) of CLs were significantly improved as affected by HHP. Moreover, the food safety of plant-based products could be significantly improved as well. HHP lowered the risk of microbial contamination through the inactivation of numerous microorganisms, spores, and enzymes in CLs and alleviated the allergy symptoms from consumption of plant-based foods.