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.