Establishment and characterization of murine models of asthma and subcutaneous immunotherapy for Humulus pollen allergy

Humulus pollen is an important cause of allergic asthma in East Asia. There have been some murine models for Humulus pollen allergy established by intraperitoneal (IP) sensitization and nasal drip stimulation, but they were not comprehensive enough. Here, we used atomized inhalation for challenge and compared the subcutaneous (SC) and IP sensitization routes to determine the optimal method to establish a model of asthma induced by Humulus pollen. Subsequently, we tried to develop a rapid subcutaneous immunotherapy (SCIT) model. Mice were sensitized through the SC or IP route and challenged with Humulus pollen extract to induce asthma. To compare the two sensitization methods, airway hyperresponsiveness (AHR), inflammatory cell infiltration, allergen-specific serum immunoglobulin (Ig)E (sIgE) levels, cytokine levels, and lung histopathology were assessed. The effects of SCIT (once every other day for 16 days) on airway inflammation, AHR, sIgE, and allergen-specific serum IgG2a (sIgG2a) levels were evaluated by using the model established. Although mice sensitized by the SC or IP routes both showed AHR and airway inflammation, the SC route elicited significantly higher levels of sIgE, eosinophil inflammation, and T helper type 2 cytokines, compared with the IP route. SCIT in the treatment group significantly reduced the titers of sIgE, enhanced the titers of sIgG2a, and effectively alleviated pulmonary inflammation and AHR, compared with the vehicle group. These observations indicate that the SC route can be a better sensitization route than IP route for establishing a murine model of Humulus pollen allergy; short-term SCIT improved symptoms and pathophysiology in asthmatic mice.