Scientific Study

BACKGROUND: Allergic reactions to tree nuts are often severe and are outgrown in less than 10% of diagnosed patients. OBJECTIVES: To determine whether treatment of underlying tree nut sensitization will prevent allergic reactions to cross-reacting tree nuts and to determine the effects of single-tree nut immunotherapy on true multi-tree nut sensitization. METHODS: Cross-reactivity model: Cashew-sensitized mice underwent immunotherapy with cashew and were subsequently challenged with cashew and pistachio. Multisensitization model: Cashew plus walnut-sensitized mice were treated with cashew alone; walnut alone; or both cashew and walnut and then underwent challenges to cashew and walnut. Challenges were assessed on the basis of symptoms; changes in body temperature; and mouse mast cell protease-1 release. RESULTS: In the cross-reactivity model; cashew immunotherapy completely prevented allergic reactions on challenges with cashew or the cross-reactive pistachio. In the multisensitization model; mice with cashew plus walnut allergy were significantly protected from anaphylactic reactions on cashew challenge in both the cashew-alone and walnut-alone immunotherapy groups. Results from the walnut challenge demonstrated significantly decreased allergic responses in the walnut immunotherapy group; whereas mice in the cashew immunotherapy group experienced significantly lower symptoms. In the cross-reactivity model; immunotherapy effectively decreased IL-4 and IL-5 production and increased IL-12 relative to placebo while also inducing a 5-fold increase in specific IgG(1). CONCLUSION: Single-tree nut immunotherapy can effectively decrease allergic responses in both the cross-reactivity and multisensitization mouse models. Further studies are needed to determine which single-tree nut immunotherapies will be most effective for specific multi-tree nut allergy profiles.