WALNUT AND PECAN CROSS-DESENSITIZATION: EPITOPE DETERMINATION

Abstract

Introduction Clinical trials using oral immunotherapy (OIT) for the treatment of walnut food allergy have shown promising results. In a randomized, double-blind, placebo-controlled, clinical trial participants with walnut and pecan food allergies underwent treatment with walnut OIT (n=12). Participants allergic to both walnut and pecan received only walnut oral immunotherapy. Participants receiving walnut oral immunotherapy passed food challenges against both walnut and pecan, suggesting possible cross-desensitization in individuals with pecan and walnut allergies. We sought to test the hypothesis that cross-desensitization occurs due to a common epitope in walnut and pecan allergens proteins following walnut oral immunotherapy, subjects allergic to walnut and pecan will become desensitized to both allergens. Methods Walnut and pecan proteins were separated using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-Page), blotted onto a nitrocellulose membrane, and probed with plasma and secondary antibodies. IgE and IgG4binding were examined for walnut and pecan allergic plasma at two time points: baseline and 1-2 years post-oral immunotherapy. Results In blots probed with baseline serum and anti-IgE, binding appeared with a 9 kDa walnut allergen protein. As expected this binding was not present in blots probed with post-OIT serum and anti-IgE. This band was not seen in blots probed with baseline serum and anti-IgG4. In blots probed with post OIT and anti-IgG4, binding appeared with 9 Da walnut and pecan allergen proteins. Conclusions Results indicate a common epitope between walnut and pecan allergen proteins. In addition, an IgG4-recognized allergen protein not observed at baseline, unexpectedly appeared following walnut OIT.