1∣INTRODUCTION
Allergen-specific immunotherapy (ASIT) remains the only treatment that is capable of inducing immune tolerance to the corresponding allergen and potentially treating the root cause of the allergic disease.1-3 Currently available vaccines for ASIT, either by subcutaneous injection or sublingual administration, are all protein-based. As the treatment course of protein-based vaccines for ASIT is time-consuming, an easily administered epicutaneous anti-allergic DNA-based vaccine is not only an attractive alternative, but also important in patient care, especially during the COVID-19 pandemic.4,5
The skin has been known for centuries to be a unique site for immunization. Delivering a vaccine via the skin has been shown to elicit similar or even higher immune responses compared to intramuscular injection.6,7 Several epicutaneous protein-based placebo-controlled clinical studies have been conducted to investigate the effectiveness and safety of treatment for grass pollen rhino-conjunctivitis, cow’s milk allergy, and peanut allergy. Though the exact protocol of this new delivery method varies among studies, the results of pilot studies of this convenient delivery system are generally positive.8-10
The biting midge, Forcipomyia taiwana , is the most prevalent cause of biting insect allergy in Taiwan. It is a tiny hematophagous midge that attacks en masse. As many as 60% of exposed individuals develop intense itchy reactions to the bites.11,12 The midge is widely distributed throughout Taiwan and southern China. The hematophagous midges of the same genus have also been reported worldwide, from tropical to temperate places.13-17Among the 11 identified allergens, For t 2 is the most predominant allergen for F. taiwana, with 75% of midge-allergic patients showing specific IgE to For t 2.18,19
A previous study by the authors showed that a DNA vaccine encoding the For t 2 midge allergen was able to prevent the development of biting midge allergy in a mouse model.20 We also demonstrated in recent studies that a DNA vaccine is able to treat mice with an established midge allergy.21
Though only two injections are required for the For t 2 DNA vaccine developed in our previous studies, a vaccine that could be delivered via the skin would be more practical and would make self-administration at home a possibility. A convenient delivery system also potentially reduces the total cost of treatment as patients do not need to go to the hospital for this specific therapy.
In this study, we demonstrate the first needle-free epicutaneous DNA vaccine patch that is effective in preventing as well as treating biting midge allergy in a murine model.