Therapeutic DNA vaccine attenuates itching and allergic inflammation in mice with established biting midge allergy

Forcipomyia taiwana is a tiny hematophagous midge that attacks en masse. It is responsible for the most prevalent biting insect allergy in Taiwan. For t 2 is its major allergen. The intense itchy reactions can prevent allergic individuals from performing their regular daily outdoor activities. This study aimed to investigate whether the For t 2 DNA vaccine was effective in treating mice with established biting midge allergy. Mice were sensitized with recombinant For t 2 proteins or whole midge extracts. Two to four consecutive shots of various concentrations of For t 2 DNA vaccine, with or without CpG adjuvants, were then administered to midge-sensitized mice. Mice that received two shots of 50-100 μg For t 2 DNA vaccine showed a significant reduction in allergen-induced bouts of scratching, For t 2-specific IgE, specific IgG1/IgG2a ratio in sera, skin eosinophil infiltration, and IL-31 production, as well as IL-4 and IL-13 production by splenocytes. Two doses of For t 2 DNA vaccine one week apart was sufficient to treat mice with established biting midge allergy. The treatment resulted in clinical, immunological, and histopathological improvements. We recommend that this low-cost, convenient treatment strategy be developed for use in humans who are allergic to biting midges.