Baseline basophil activation and early suppression is associated with clinical outcome after peanut sublingual immunotherapy.

BACKGROUND Sublingual immunotherapy (SLIT) was recently shown to safely induce desensitization and remission of peanut allergy in 1-to 4-year-old children. OBJECTIVE Basophil activation has been shown to be suppressed in allergen-specific immunotherapy. We aimed to evaluate the timing of basophil suppression during peanut SLIT and its impact on clinical outcomes. METHODS Fifty peanut-allergic children were enrolled in a peanut SLIT trial and randomized to active peanut or placebo SLIT for 36 months followed by a three-month avoidance period to evaluate remission. Blood was collected at baseline, 12, 24, 36, and 39 months to measure basophil activation by CD63 and CD203c. RESULTS For participants on peanut SLIT, basophil activation based on CD63 expression was significantly reduced by 12 months and continued to decrease throughout peanut SLIT, whereas CD63 activation in participants receiving placebo remained unchanged from 0-36 months. CD203c expression remained unchanged for both peanut SLIT and placebo participants throughout the trial. Actively treated participants who achieved remission had lower CD63 expression at baseline and significant suppression of CD63 expression by 12 months, while treatment failures had higher CD63 expression at baseline and lack of suppression by 12 months. Lower basophil activation in those achieving remission, compared to those that failed treatment, remained present for up to 3 years. CONCLUSIONS Following peanut SLIT, participants who achieved remission had significantly suppressed basophils by 12 months, compared to unsuccessful participants that were not desensitized, suggesting that early suppression of basophils may be indicative of peanut SLIT efficacy.