Irradiation does not impact the immunogenicity of food flours used for oral immunotherapy

Peanut and tree nut flours are considered drug products by the US Food and Drug Administration when used during oral immunotherapy clinical trials and oral food challenges and must meet specific standards for microbial contamination and allergen content. Gamma irradiation of food flours can reduce microbial contamination, but its effects on food allergen content and immunogenicity remain unclear.

We sought to investigate whether gamma irradiation of peanut and tree nut flours alters allergen content and immunogenicity.

Commercially available peanut, cashew, walnut, hazelnut, and almond flours underwent gamma irradiation. Allergen content and stability, as well as microbial contamination, in irradiated and nonirradiated flours were measured over a 12-month period. The immunogenicity of flour extracts was assessed by basophil activation tests, T-cell activation-induced marker assays, and T_H cytokine production using whole blood or PBMCs from peanut- or tree nut-sensitized individuals.

Irradiation of peanut and tree nut flours decreased microbial contamination while not affecting allergen content or stability for 12 months. Irradiated and nonirradiated flours were similar in their ability to activate basophils and allergen-reactive CD4⁺ effector and regulatory T cells from sensitized individuals. Irradiated and nonirradiated flours induced comparable T_H1, T_H2, T_H17, and regulatory T- cell cytokine production by PBMCs from sensitized individuals.

Irradiation of peanut and tree nut flours decreases microbial contamination without significantly altering allergen content or immunogenicity. Irradiated food flours are likely effective for use in oral immunotherapy studies and oral food challenges.