DNA vaccination against Japanese cedar pollinosis in dogs suppresses type I hypersensitivity by controlling lesional mast cells

Sensitization to allergens of Japanese cedar pollen is known to cause canine atopic dermatitis as approximately 10% of atopic dogs in Japan were positive to the pollen allergen. Among the two major allergens of Japanese cedar pollen, since Cry j 1 is more important than Cry j 2 as an antigen to increase IgE in atopic dogs sensitized to Japanese cedar pollen, Cry j 1 can be a target for immunotherapy. In our study, efficacy of DNA vaccination with a plasmid containing the gene of a major allergen of Japanese cedar (Cryptomeria japnonica, CJ) pollen, Cry j 1, was examined using a dog model experimentally sensitized to CJ pollen allergen. Cry j 1 DNA plasmid and a vector plasmid (pCAGGS) were injected into six dogs and three dogs, respectively, five times with an interval of 1.5 month. After the treatment with Cry j 1 DNA plasmid, production of IgE against Cry j 1 decreased in four of the six dogs in the treatment group, whereas it increased in the three dogs of the control group. The reactivity to the pollen allergen in intradermal testing and provocation testing were obviously reduced in the treatment group, but not in the control group. The number of mast cells in alveolar area of the lung in the treatment group was smaller than that in the control group. Cry j 1 DNA plasmid was also injected into three atopic dogs sensitive to Cry j 1, resulting in improvement of clinical signs in the pollination season. These findings indicated that Cry j 1 DNA plasmid could regulate mast cell-mediated reaction against Cry j 1, which could be an alternative and effective treatment for CJ pollinosis.