Small Study Provides Big Implications for Long-Term Walnut Immunotherapy

Amy Scurlock, MD, of University of Arkansas for Medical Sciences & Arkansas Children’s Hospital, and colleagues conducted a study on long-term walnut oral immunotherapy (WOIT) and presented the findings at the annual meeting of the American Academy of Allergy, Asthma, and Immunology (AAAAI 2017) in Atlanta, Georgia.

Among the most common food allergens are the proteins found in cow’s milk, eggs, wheat, soy, fish, and shellfish. Peanuts and tree nuts—including walnuts, cashews, and pecans—are also common allergies, impacting around three million people in the United States, according to Food Allergy Research & Education. Allergies to nuts tend to last a lifetime, so identifying long-term treatment outcomes is crucial.

The aim of the research was to evaluate “the impact of long-term WOIT on desensitization and sustained unresponsiveness to both walnut and a test tree nut,” Scurlock explained.

The study cohort included children who had allergy to walnut as well as another test tree nut (tTN)--including pecan, cashew, hazelnut, and pistachio--with a median age of 9. All of the participants completed a 38-week blinded, placebo-controlled treatment before being enrolled in WOIT.

“Walnut and tTN desensitization oral food challenge (dOFC, 5g) were performed by 142 weeks; if passed, suOFC was performed after four weeks off WOIT,” the report said. In addition, data was collected from skin prick testing (SPT) and TN specific IgE, IgG4.

By week 142, eight participants underwent OFC. The Wilcoxon rank sum test revealed that seven of those eight patients (88%) were desensitized to both walnut and tTN. Those seven patients moved on to suOFC after four weeks off of WOIT. The team documented various other observations:

• Four out of the seven patients had sustained unresponsiveness to both walnut and tTN
• Six out of the seven patients had sustained unresponsiveness to just walnut
• Five out the seven patients had sustained unresponsiveness to just tTN

From baseline to the study’s end at 142 weeks, there were significant decreases in walnut SPT (8.5mm (7.5-11.8) vs. 5.5mm (1.2-6.2), P = 0.004). In addition, there were significant increases in walnut-specific IgG4 (0.1 kU/I (0 -1) vs. 11.1 kU/I (2.9-19.7), P = 0.007).

The team also observed a decrease in tTN SPT from baseline to 142 weeks (13.5 mm (10.1-13.5) vs. 5.5 mm (3.2-10), P = 0.069).

There are three additional patients who are currently undergoing WOIT, the researchers noted, but they did not say when or if those results will be released.

Preceding this research was another study conducted by Scurlock and her colleagues. In 2016, they released findings showing that WOIT induces clinical desensitization to both walnut and tTN after 38 weeks. The development of sustained unresponsiveness was supported by observed mechanistic changes.

The study, “Long-term Walnut Oral Immunotherapy Induces Clinically Relevant Treatment Responses in Tree Nut Allergic Children,” was published in The Journal of Allergy and Clinical Immunology.

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