Longitudinal evaluation of immunological responses to allergen-specific immunotherapy in horses with IgE associated dermatological disease, a pilot study.

Abstract

BACKGROUND: The long-term effects of allergen specific immunotherapy (ASIT) on concentrations of circulating immunoglobulin E (IgE) and immunoglobulin G (IgG) in horses have not been reported. OBJECTIVES: To document changes in clinical severity of horses with atopic dermatitis (AD) and to monitor allergen-specific IgE and IgG concentrations during a two-year course of ASIT. ANIMALS: Nineteen client-owned horses with a conditional diagnosis of AD. METHODS AND MATERIALS: Three ASIT groups were randomly assigned based upon results obtained by either intradermal testing (IDT) for regional allergens (n&#xa0;=&#xa0;7); enzyme-linked immunosorbent assay (ELISA) for specific IgE (n&#xa0;=&#xa0;6); or a composite of results from both tests (n&#xa0;=&#xa0;6). Serum concentrations of IgE and IgG specific for allergens included in ASIT were measured at time zero and at four-month intervals. A visual analog scale (VAS) was used to record severity of clinical signs at times zero, 12 and 24&#xa0;months. RESULTS: Positive correlations were documented between IgE and both immediate and delayed IDT results (P&#xa0;<&#xa0;0.00001), and between immediate IDT and IgG results (P&#xa0;=&#xa0;0.003). Specific IgE in sera decreased significantly (P&#xa0;<&#xa0;0.05) for allergens that were included in ASIT, whereas IgG increased. Across all horses, the mean VAS score decreased by 1.2 units [95% CI: 1.28, 1.14; (P&#xa0;<&#xa0;0.0001)] during each 12-month period of ASIT therapy. Improvement in clinical signs was noted in 76.5% of the horses following 12&#xa0;months of ASIT and in 82% after 24&#xa0;months on ASIT. CONCLUSIONS AND CLINICAL IMPORTANCE: In this pilot study, ASIT in horses with AD provided significant clinical benefit associated with a concomitant reduction of allergen-specific IgE and elevation of IgG.