Walnut oral immunotherapy induced walnut, additional tree nut desensitization

ATLANTA — Walnut oral immunotherapy effectively induced walnut desensitization, as well as cross-desensitization to a secondary tree nut, in a majority of tree nut-allergic patients, according to early data presented at the annual meeting of the American Academy of Allergy, Asthma & Immunology.

Additionally, walnut oral immunotherapy induced sustained unresponsiveness to both walnut and a second tree nut in approximately half the patients.

Robbie D. Pesesk

“Although tree nut allergy is not the most common allergy seen, it is certainly becoming more common, affecting about 1% of the US population,” Robbie D. Pesesk, MD, from Arkansas Children’s Hospital, said during a press conference. “However, not even 10% of patients with tree nut allergy will outgrow it so there is definitely a growing need for some kind of intervention for that population. We also know that patients are usually sensitized or allergic to multiple tree nuts at one time so avoidance is more difficult than with allergies involving a single food.”

Based on previous data, the researchers wanted to determine whether patients could be safely desensitized using walnut oral immunotherapy, and if this immunotherapy could also induce sensitization to a secondary tree nut. Pesek and colleagues enrolled patients with an allergy to walnut and another tree nut (pecan, cashew, hazelnut or pistachio) to receive walnut oral immunotherapy following 38-weeks of blinded, placebo-controlled treatment.

The researchers performed walnut and tree nut desensitization oral food challenges (5 grams) by 142 weeks; if the patients passed, an oral food challenge testing sustained unresponsiveness was performed following a 4-week break in walnut immunotherapy. Eight patients received an oral food challenge by week 142.

The researchers also evaluated skin prick testing and tree nut-specific IgE and IgG levels, and analyzed outcomes using Wilcoxon rank sum test.

According to study results, desensitization to both walnut and a second tree nut was observed in 88% of patients. An oral food challenge testing sustained unresponsiveness of 7 patients following 4 weeks without walnut oral immunotherapy demonstrated sustained unresponsiveness to both walnut and a second tree nut in 4 patients, sustained unresponsiveness to walnut only in 6 patients, and sustained unresponsiveness to tree nut only in 5 patients.

The researchers observed significant decreases in walnut skin prick test [baseline 8.5 mm (7.5-11.8) vs. 142 weeks 5.5mm (1.2-6.2), P=0.004] as well as significant increases in walnut-specific IgG4 [baseline 0.1 kU/l (0-1) vs. 142 weeks 11.1 kU/l (2.9-19.7), P=0.007] were observed.

Pesek and colleagues noted that skin prick tests for secondary tree nut was also decreased [baseline 13.5 mm (10.1-13.5) vs. 5.5 (3.2-10), P=0.069]; walnut immunotherapy remains ongoing in 3 other patients.

“Walnut oral immunotherapy appears safe and seems to be effective in desensitizing patients to a significant dose, which makes it clinically relevant,” Pesek said. “We were also able to show desensitization for patients who have a second tree nut allergy, as well as sustained unresponsiveness in a significant number of patients. Moving forward, we will need larger studies to determine if this will be applicable to a larger group of patients as well.” – by Bob Stott

Reference:

Pesek R, et al. Abstract 558. Presented at: American Academy of Allergy, Asthma & Immunology Annual Meeting; March 3-6, 2017; Atlanta.

Disclosure: The researchers report no relevant financial disclosures.