Subcutaneous allergen-specific immunotherapy (SCIT) qualifies as a promising approach for the permanent cure of IgE-mediated airway allergies, which can often manifest into allergic rhinitis and other allergic respiratory diseases. SCIT entails repeated administration of a high allergen dose into the subcutaneous (sc) region using a hypodermic needle for many (3-5) years, which is inconvenient and painful and reduces patient compliance. To overcome these limitations, we hypothesized that microneedles (MNs), which are minimally invasive and painless, could provide a novel approach for allergen desensitization by depositing the allergen into the superficial layers of the skin. To test this hypothesis, we compared MNs and SCIT for allergen desensitization in a mouse model of ovalbumin (Ova)-induced airway allergy. Mice were first made allergic to Ova and then treated with MNs coated with Ova (with or without CpG as an adjuvant) or via SCIT-Ova + alum (subcutaneous Ova + alum injections) for comparison. Treatment with coated MNs significantly induced Ova-specific serum IgG antibodies in a manner comparable to SCIT-Ova + alum-treated group. To test the efficacy against allergen challenge, treated mice were challenged with Ova via the nasal route. Coated MNs with Ova and CpG (MN-Ova + CpG) considerably suppressed the airway inflammation in allergic mice, evidenced by downregulation of proinflammatory cytokines (IL-5 and IL-13), upregulation of anti-inflammatory cytokine IL-10, and activation of Ova-specific immune response in bronchoalveolar (BAL) fluid. The therapeutic capacity of MN-based allergy treatment was further validated by the reduction in eosinophil and mast cell infiltration in the lung tissues of mice treated with MN-Ova + CpG, and low deposition of mucus inside their lung bronchioles. Overall, coated MNs ameliorated the symptoms of airway allergy in mice similar to SCIT and could provide a novel means of painless allergen-specific immunotherapy.
Keywords: allergen immunotherapy; allergy treatment; cutaneous allergen immunotherapy; microneedles; ovalbumin-induced allergy; subcutaneous allergen-specific immunotherapy.