Development of DNA vaccine therapy for allergic diseases in animals

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In order to establish an effective immunotherapy for allergic diseases using DNA vaccine, we examined the in vitro allergic reactions in spontaneously occurring allergic dogs and experimentally sensitized dogs and then explored in vivo efficacy of the immunotherapy using DNA vaccine.Allergic reactions directed to Japanese cedar (Cryptomeria japonica, CJ) pollen antigens were examined in atopic dogs sensitive to CJ pollen. Most of the dogs were shown to have IgE directed to Cry j1, a major allergen of CJ pollen, and the IgE level was found to be high in the pollenation season of CJ. Next, T-cell epitopes of CJ pollen antigen were identified from the blastogenesis response to its overlapping peptides in these dogs. In an experimental immunotherapy trial using Cry j1 DNA vaccine in 4 atopic dogs, suppression of intradermal reaction and blastogenesis of peripheral blood lymphocytes was observed in parallel to the partial improvement of the clinical sings of atopic dermatitis.On the other hand, CJ pollen-specific airway hypersensitivity could be induced in dogs experimentally sensitized with CJ pollen extract. After treatment of the dogs with Cry j1 DNA vaccine, threshold of the administered amount of CJ pollen extract in the intradermal reaction and airway provocation was shown to be increased in the treatment group, although the serum IgE level and lymphocyte blastogenesis response were not different between the treatment and control groups. Furthermore, the number of mast cells in the lung was smaller in the treatment group in comparison to the control group.The present study provided evidence to indicate that DNA vaccine immunotherapy can be considered as an effective therapy for allergic diseases.