Bermuda Grass Allergen Immunotherapy Exerts Cross Protection in House Dust Mite Sensitized Cats with Experimental Asthma
Allergen-specific immunotherapy relies on identification of the specific allergen(s) to which animals have been sensitized. Administration of Bermuda grass allergen-specific rush immunotherapy (BGA-RIT) in cats sensitized and challenged with BGA has previously been shown to confer protection (i.e., dampen eosinophilic airway inflammation). Since it may be difficult to determine which specific allergen(s) are responsible for inducing the asthmatic phenotype in cats with naturally developing asthma, we undertook a study to evaluate if administration of RIT using a different allergen to which the animal has been sensitized would have beneficial effects on the asthmatic phenotype. We hypothesized that administration of BGA-RIT to cats sensitized to house dust mite allergen (HDMA) would at least in part blunt eosinophilic airway inflammation. Nine cats were enrolled: group 1 (n=3) sensitized to BGA, group 2 (n=4) sensitized to HDMA, group 3 (n=2) placebo (saline) sensitized. Cats received weekly aerosol challenges of BGA, HDMA, and saline, respectively for the duration of the study. All cats received subcutaneous BGA RIT over a 2 day period (dose escalation to 200mcg BGA), followed by weekly sc injections of BGA (200mcg). Bronchoalveolar lavage fluid (BALF) was collected prior to BGA-RIT (D0) and at month 1 (M1). Cytospins of the BALF were made and differential counts performed. Results showed that the BALF eosinophil % decreased in cats sensitized to both BGA and to HDMA (mean±SEM, group 1 D0 26±12, M1 4±1; group 2 D047±15, M1 16±3; group 3, D0 1±1, M1 1±1). Additional cats are being enrolled into this study. Preliminary results suggest that immunotherapy using one allergen exerts beneficial cross protection to asthmatic cats sensitized to an unrelated allergen.