In vitro digestion of soluble cashew proteins and characterization of surviving IgE-reactive peptides

Authors

  • Christopher P. Mattison,

    Corresponding author
    1. U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, USA
    • Correspondence: Dr. Christopher P. Mattison, United States Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, 1100 Robert E Lee Blvd., New Orleans, LA 70124, USA

      E-mail: chris.mattison@ars.usda.gov

      Fax: +1-504-286-4419

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  • Casey C. Grimm,

    1. U.S. Department of Agriculture, Agricultural Research Service, Southern Regional Research Center, New Orleans, LA, USA
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  • Richard L. Wasserman

    1. Allergy Immunology Research Center of North Texas, Department of Pediatrics, University of Texas Southwestern Medical School, Dallas, TX, USA
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Abstract

Scope

The stability of food allergens to digestion varies. We characterized the stability of cashew allergens to digestion by pepsin and trypsin and identified IgE-binding epitopes that survive digestion.

Methods and results

The ability of pepsin and trypsin to digest cashew allergens was assessed with an in vitro digestion model. Samples were evaluated by SDS-PAGE, MS, ELISA, and immunoblotting to compare IgE binding. Increasing amount of protease resulted in greater degradation of higher molecular weight cashew proteins. Among cashew proteins, the 2S albumin, Ana o 3, was most resistant to digestion by both pepsin and trypsin. MS identified digestion resistant Ana o 3 protein fragments that retained reported IgE-binding epitopes. Pretreatment of extracts or purified Ana o 3 with reducing agent increased the sensitivity of Ana o 3 to protease digestion. Circular dichroism revealed the structure of purified Ana o 3 was largely alphahelical and was disrupted following reduction. Ana o 3 reduction followed by protease digestion decreased binding of serum IgE from cashew allergic patients. Our results indicate that the Ana o 3 disulfide bond dependent structure protects the protein from proteolysis.

Conclusion

Ana o 3 is the cashew allergen most likely to survive gastrointestinal digestion intact.

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