Animal models to detect allergenicity to foods and genetically modified products: workshop summary

Identification of Allergic Epitopes of Soybean β-Conglycinin in Different Animal Species

Soybean can cause allergy in both humans and animals. The herein study aims to identify the antigenic determinants (epitopes) of β-conglycinin that lead to allergy in different animal species (swine, bovine, and rats). The epitopes of β-conglycinin were identified through co-immunoprecipitation and mass spectrometry. The binding abilities of seven identified epitope peptides to allergic sera of three animal species were compared by ELISA and dot-blot techniques. Some epitope peptides could be recognized by the three animal allergic sera, while most epitopes showed some differences in binding abilities to the different animal sera. The strongest reaction using swine sera was detected with peptides α2, β2, and β3, but the biggest sensitive regions for bovine and rats were peptides α2, β1, and β4. Most epitopes of β-conglycinin exhibited different binding abilities to the three animal sera, in which the biggest sensitive regions were peptides α2, β2, and β3 for swine, but peptides α2, β1, and β4 were detected for bovine and rats.

The structural properties and antigenicity of soybean glycinin by glycation with xylose

BACKGROUND

Soybean glycinin is considered a major allergenic protein, and glycation is widely used to reduce the allergenic potential of present allergens. Glycation of soybean glycinin with xylose at 55 °C for different lengths of time was investigated. The extent of Maillard reaction was reflected through the content changing of free amino groups, color analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Alteration in the structural properties of glycinin was characterized by Fourier transform infrared spectroscopy, and antigenicity was evaluated by indirect competitive enzyme-linked immunosorbent assay.

RESULTS

The changes in the color of glycinin-xylose samples and the reduction of free amino group content in proteins indicated that the Maillard reaction occurred. The degree of glycation increased in glycated samples with the increase in reaction time. Glycation induced the changes in the secondary structure of glycinin and the ordered structure of proteins increased during the glycation reaction. The antigenicity of glycinin was reduced with the increase in reaction time. After glycation for 12 h, the antigenicity of glycinin declined about 18% compared with native glycinin.

CONCLUSION

The application of glycation may be an efficient method to reduce the antigenicity of soybean glycinin. © 2016 Society of Chemical Industry.

Determination of glycinin in soybean and soybean products using a sandwich enzyme-linked immunosorbent assay

This study performs a sandwich ELISA for detection of trace amounts of glycinin in soybean products. We designed a soy-free mouse model to produce anti-glycinin monoclonal antibodies with high affinity and specificity. Using the monoclonal antibody as coating antibody, with the rabbit anti-glycinin polyclonal antibody as a detected antibody, the established sandwich ELISA showed high specificity for glycinin with minimum cross-reactions with other soy proteins. The practical working range of the determination was 3-200 ng/mL with detection limit of 1.63 ng/mL. The regaining of glycinin in spiked soybean samples were between 93.8% and 103.3% with relative standard deviation less than 8.3% (intra-day) and 10.5% (inter-day). The developed assay was used in analysing 469 soybean samples and five soybean products under different processing. The assay provides a specific and sensitive method for screening of glycinin and allows for further investigation into hypersensitive mechanisms to soybean proteins.

Determination of beta-conglycinin in soybean and soybean products using a sandwich enzyme-linked immunosorbent assay

Soybean protein has long been recognized as a source of dietary allergens for humans and animals with β-conglycinin being the major allergen. This paper presents a sandwich enzyme-linked immunosorbent assay (ELISA) that allows for the detection of trace amount of β-conglycinin in soybean and soybean products. In the sandwich ELISA, mouse anti-β-conglycinin monoclonal antibody (Mab 5C5) was used as coating antibody, and rabbit anti-β-conglycinin polyclonal antibody (Pab) was used as secondary antibody. The assay showed high specificity for β-conglycinin with minimum cross-reactions with other soy proteins. The practical working range for the determination of β-conglycinin using the developed assay was 3-100ngmL(-1) and the limit of determination (LOD) was 1.63 ng mL(-1). The recoveries of β-conglycinin in spiked soybean samples were between 88.1% and 106.6% with relative standard deviation less than 8.9% (intra-day) and 13.1% (inter-day). The developed method was used to analyze 469 soybean seed samples from different sources as well as five soybean products treated with different processing techniques. The data showed that the concentration of β-conglycinin decreased significantly after processing, especially for soybean protein isolation, where the concentration of β-conglycinin dropped to nearly zero. The assay provides a specific and sensitive method for the screening of β-conglycinin and allows for further investigation into hypersensitive mechanisms of soybean proteins and development of soybean processing techniques to reduce their negative effects.

Immune effector mechanisms against schistosomiasis: looking for a chink in the parasite's armour

A recombinant antigen vaccine against Schistosoma mansoni remains elusive, in part because the parasite deploys complex defensive and offensive strategies to combat immune attack. Nevertheless, research on rodent and primate models has shown that schistosomes can be defeated when appropriate responses are elicited. Acquired protection appears to involve protracted inhibition of larval migration or key molecular processes at the adult surfaces, not rapid cytolytic killing mechanisms. A successful vaccine will likely require a cocktail of antigens rather than a single recombinant protein. In addition, ways need to be found of keeping the immune system on permanent alert, either to achieve adequate inhibition of protein function in adults, or because a trickle of incoming parasites does not amplify the secondary response.

Health risks of genetically modified foods

As genetically modified (GM) foods are starting to intrude in our diet concerns have been expressed regarding GM food safety. These concerns as well as the limitations of the procedures followed in the evaluation of their safety are presented. Animal toxicity studies with certain GM foods have shown that they may toxically affect several organs and systems. The review of these studies should not be conducted separately for each GM food, but according to the effects exerted on certain organs it may help us create a better picture of the possible health effects on human beings. The results of most studies with GM foods indicate that they may cause some common toxic effects such as hepatic, pancreatic, renal, or reproductive effects and may alter the hematological, biochemical, and immunologic parameters. However, many years of research with animals and clinical trials are required for this assessment. The use of recombinant GH or its expression in animals should be re-examined since it has been shown that it increases IGF-1 which may promote cancer.

Utility of animal models for predicting human allergenicity

The biochemical characterization of protein structures has led to a better understanding of allergens, their structure/function relationship, and can be very powerful in identifying protein sequences with significant structural similarity to known allergens. However, for scientists, regulators and food manufacturers there exists a need for acquiring additional data on potential allergenicity of proteins, particularly, biotechnology derived molecules in food products for which minimal or no prior human exposure information is available. Since human exposure testing, while direct, is unacceptable, understanding allergy in animals has been used to investigate the allergic response on a molecular level as well as test the potential in vivo allergenicity of food proteins. Rodents seem to be the most likely candidate for assessing allergenicity. For development of an animal test system for allergenicity characterization and testing, a number of criteria are required for qualification for a model of human allergy including acceptable immunization protocols, allergic response measurements, and for standardization and validation of materials and procedures. If an animal test system can minimally provide a basis for measuring the relative physiological response to known allergens, this should be enough to establish a model that produces a relative measure of potential allergenicity. Our article will consider development of an adequate animal model for allergenicity determination that can be validated as a tool in safety assessments.

Identification, characterization, epitope mapping, and three-dimensional modeling of the alpha-subunit of beta-conglycinin of soybean, a potential allergen for young pigs

Soybean meal (SBM), the major byproduct of soybean oil extraction, is the main protein source for swine diets globally. In the United States, 8.6 million metric tons of SBM was used in swine rations in 2004. The pathological effect and immunological response of SBM feeding have been demonstrated in swine. In this study, we have utilized plasma collected from piglet feed with SBM in immunoblot analysis to detect proteins that elicited antigenic responses. We have identified soybean beta-conglycinin alpha-subunit as being a potential allergen for young piglets. Characterization of this protein indicated that deglycosylation and pepsin digestion did not eliminate immunoreactivity of this protein. Epitope mapping utilizing planar cellulose supports technology (SPOT) showed that three peptides spanning amino acids S185-R231 were critical for the allergenicity. A computer-generated three-dimensional structure model of the alpha-subunit of beta-conglycinin indicated that the antigenic epitopes were located on the surface of the protein. Information from this study may assist in the construction of recombinant nonallergenic soybean protein useable for both immunotherapy and the potential production of hypoallergenic soybean plants.

Genetically modified plants and food hypersensitivity diseases: usage and implications of experimental models for risk assessment

The recent advances in biotechnology in the plant industry have led to increasing crop production and yield that in turn has increased the usage of genetically modified (GM) food in the human food chain. The usage of GM foods for human consumption has raised a number of fundamental questions including the ability of GM foods to elicit potentially harmful immunological responses, including allergic hypersensitivity. To assess the safety of foods derived from GM plants including allergenic potential, the US FDA, Food and Agriculture Organization of the United Nations (FAO)/World Health Organization (WHO), and the EU have developed approaches for evaluation assessment. One assessment approach that has been a very active area of research and debate is the development and usage of animal models to assess the potential allergenicity of GM foods. A number of specific animal models employing rodents, pigs, and dogs have been developed for allergenicity assessment. However, validation of these models is needed and consideration of the criteria for an appropriate animal model for the assessment of allergenicity in GM plants is required. We have recently employed a BALB/c mouse model to assess the potential allergenicity of GM plants. We have been able to demonstrate that this model is able to detect differences in antigenicity and identify aspects of protein post-translational modifications that can alter antigenicity. Furthermore, this model has also enabled us to examine the usage of GM plants as a therapeutic approach for the treatment of allergic diseases. This review discusses the current approaches to assess the allergenic potential of GM food and particularly focusing on the usage of animal models to determine the potential allergenicity of GM foods and gives an overview of our recent findings and implications of these studies.

Allergenic Proteins in Soybean: Processing and Reduction of P34 Allergenicity

Soybean ranks among the "big 8" of the most allergenic foods, and with increasing consumption of soybean products, the incidence of soy-caused allergies is expected to escalate. Soybean and its derivatives have become ubiquitous in vegetarian and many meat-based food products, and as a result, dietary avoidance has become difficult. However, soybeans can be manipulated in a variety of ways to alter their allergenicity. Several studies have focused on reducing the allergenicity of soybeans by changing the structure of the immunodominant allergen P34 using food processing, agronomic, or genetic manipulation techniques. A review of the literature pertaining to these studies is presented here.