Evaluation of subcutaneous versus mucosal (intranasal) allergen-specific rush immunotherapy in experimental feline asthma

Abstract

Rush immunotherapy (RIT) is effective for the treatment of experimental feline allergic asthma. In humans, the safety profile of immunotherapy is improved by delivering allergen by a mucosal route. We hypothesized that mucosal (intranasal) RIT would have similar efficacy to subcutaneous RIT with improved safety. Twelve cats sensitized and challenged with Bermuda grass allergen (BGA) were randomized to receive subcutaneous (SC) or intranasal (IN) RIT. Increasing doses of BGA (20–200 μg) were administered over 24 h followed by 200 μg BGA weekly as maintenance. Adverse reactions were recorded. Clinical respiratory scores after BGA aerosol challenge, bronchoalveolar lavage fluid (BALF) % eosinophils, and cytokine concentrations were measured before RIT (day 1) and at months 1, 3 and 6 (M1, M3, M6). More adverse events were recorded with SC RIT ( n = 12) compared with IN RIT ( n = 6). Respiratory scores were lower by M6 compared with D1 in both the groups. The % BALF eosinophils declined significantly after RIT for both groups (mean ± SEM, SC RIT D1 62 ± 12, M6 9 ± 4; IN RIT D1 54 ± 9, M6 14 ± 6). The BALF IL-4:IFN-γ ratio significantly decreased over time in the IN RIT group (mean ± SEM, D1 2.4 ± 0.2, M6 1.0 ± 0.2). While both protocols decreased eosinophilic airway inflammation, the SC RIT protocol did not cause life-threatening adverse events and demonstrated more consistent resolution of clinical signs after allergen challenge. Either protocol could be considered for the treatment of feline allergic asthma.