Identification of immunogenic epitopes of the soybean a and ß unit of ß -conglycinin in chickens

Authors: Taliercio, Earl; Loveless, Telisa

Submitted to: Journal of Food and Agriculture Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/26/2021
Publication Date: 4/23/2021
Citation: Taliercio, E.W., Loveless, T.M. 2021. Identification of immunogenic epitopes of the soybean a and ß unit of ß -conglycinin in chickens. Journal of Food and Agriculture Immunology. 32:174-183. https://doi.org/10.1080/09540105.2021.1911960.
DOI: https://doi.org/10.1080/09540105.2021.1911960

Interpretive Summary: The protein content of soybeans comprises a significant amount of the value of the US soybean crop. Much of the soybean crop provides protein for animal feeds and any aspect of the protein the detract from it value as an animal feed reduce the value of soybean. We have identified immunogenic regions of two subunits of the soybean seed storage protein conglycinin that cause an immune response in chickens. Seed storage proteins account for much of the protein present in soybean seeds. An inappropriate immune response to proteins is a necessary but not sufficient step in causing an animal to be allergic to soybean protein. These allergies compromise the ability of the animal to grow when soybean proteins are present in feed. To develop a strategy to mitigate the allergic response of chickens to conglycinin we have identified specific regions of the conglycinin subunits that are consistently immunogenic. Identification of natural variants of these immunogenic regions or modifying these regions by molecular manipulations may provide insight into ways to improve the growth and egg production of chickens when fed soybean protein.

Technical Abstract: Soybean meal is a valuable food crop in the United States and worldwide. Soy meal is what remains after oil is removed from soybean and is a valuable protein supplement for humans and animals. One of the most abundant proteins in soy meal is the seed storage protein ß -conglycinin (conglycinin). Conglycinin is a 7S trimer composed of different combinations of ß, a and a’ subunits. Allergic responses to the protein in soy meal have been associated with poor performance in animals that reduce its value as a feed. Allergies begin with an inappropriate immune response to food. To assess this response, we isolated Immunoglobulins (Ig) Y, M and A from chicken eggs. Chicken eggs provide a concentrated source of Ig and represent the Ig repertoire of the hen. We established correlations between amounts of total IgA and IgM with the immunogenic response of IgA and IgM to conglycinin, respectively. Total amounts of IgY were not correlated with the response of IgY to conglycinin. We identified specific immunogenic epitopes in the ß and a subunits of conglycinin that were commonly antigenic in multiple eggs. Generally, the same epitopes bound multiple types of Ig. Comparison of the protein sequences suggest that immunogenic epitopes are conserved between subunits. We propose ways that these immunogenic regions could be mitigated to develop test lines to improve soybean meal.