Intralymphatic injections as a new administration route for allergen-specific immunotherapy.

Background: IgE-mediated allergy can be treated by subcutaneous allergen-specific immunotherapy (SIT). However, the percentage of allergic patients undergoing SIT is low, mainly due to the long duration of the therapy and the risk of severe systemic allergic reactions associated with the allergen administration. To improve the safety and attractiveness of SIT for patients, alternative routes of allergen administration are being explored, such as sub-lingual or oral administration.

Methods: The present study evaluated direct intralymphatic allergen administration as a means to enhance SIT with bee venom and cat fur allergens in mice. Allergen-specific antibody and T-cell responses were analysed by ELISA and flow cytometry. The therapeutic potential of intralymphatic immunisation in sensitised mice was analysed using an anaphylaxis model.

Results: Direct injection of the major bee venom allergen phospholipase A(2) or the major cat fur allergen Fel d 1 into inguinal lymph nodes enhanced allergen-specific IgG and T-cell responses when compared with subcutaneous injections. Moreover, only intralymphatic immunisation stimulated the production of the Th1-dependent subclass IgG2a, which is associated with improved protection against allergen-induced anaphylaxis. Biodistribution studies showed that injection into the lymph node delivered antigen more efficiently to subcutaneous lymph nodes than subcutaneous injection.

Conclusions: As intralymphatic immunisation induced more than 10-fold higher IgG2a responses with 100-fold lower allergen doses than subcutaneous immunisation, this approach should allow to reduce both the number of allergen injections as well as the allergen dose, improving both efficacy and safety of SIT.