Saliva antibody profiles are associated with reaction threshold and severity of peanut allergic reactions

Background: Reaction threshold and severity in food allergy are difficult to predict, and noninvasive predictors are lacking. Objective: We sought to determine the relationships between pre-challenge levels of peanut (PN)-specific antibodies in saliva and reaction threshold, severity, and organ-specific symptoms during PN allergic reactions. Methods: We measured PN-specific antibody levels in saliva collected from 127 children with suspected PN allergy before double-blind, placebo-controlled PN challenges in which reaction threshold, severity, and symptoms were rigorously characterized. Low threshold (LT) PN allergy was defined as reaction to <300 mg of PN protein cumulatively consumed. A consensus severity grading system was used to grade severity. We analyzed associations between antibody levels and reaction threshold, severity, and organ-specific symptoms. Results: Among the 127 children, those with high pre-challenge saliva PN IgE had higher odds of LT PN allergy (odds ratio [OR] 3.9, 95% CI 1.6-9.5), while those with high saliva PN IgA:PN IgE ratio or PN IgG₄:PN IgE ratio had lower odds of LT PN allergy (OR 0.3, 95% CI 0.1-0.8; OR 0.4, 95% CI 0.2-0.9). Children with high pre-challenge saliva PN IgG₄ had lower odds of severe PN reactions (OR 0.4, 95% CI 0.2-0.9). Children with high saliva PN IgE had higher odds of respiratory symptoms (OR 8.0, 95% CI 2.2-26.8). Saliva PN IgE modestly correlated with serum PN IgE levels (Pearson r = 0.31, P = .0004). High and low saliva PN IgE levels further distinguished reaction threshold and severity in participants stratified by serum PN IgE, suggesting endotypes. Conclusions: Saliva PN antibodies could aid in noninvasive risk stratification of PN allergy threshold, severity, and organ-specific symptoms.