Protective immunotherapy against seasonal allergy in horses (834.2)

Abstract

The study objective was to evaluate the effectiveness of active and passive immunotherapy in horses affected with recurrent airway obstruction (RAO), using a newly developed peptide and antibodies to the peptide. This peptide is part of an endogenous protein and has a sequence homology to some common environmental allergens. RAO is a type‐I immediate hypersensitivity response involving reaginic antibodies (IgE and IgG), and is a model for human asthma. Our hypothesis is that a protective immune response to asthma can be induced by active vaccination or by passive immunotherapy. Five RAO‐affected horses with a history of seasonal RAO, transpulmonary pressure >15 cm of H2O, and a clinical score (CS) of 5 and above were selected. Either of the two doses of the antibody, 0.1 mg/kg or 0.2 mg/kg, was administered subcutaneously to 2 horses each. A third dose 0.3 mg/kg was given to the fifth horse. The peptide (0.1 mg/kg) was used to vaccinate two additional RAO‐horses. After closely watching them for 2 days, they were returned to the pasture. Blood samples were collected on day 0 (pre‐immune sample), day 1 and every 7th day for two months along with clinical scores. A dose related decrease in CS was observed in horses that received antibodies. The serum antibody titer was below detection levels by ELISA. The vaccinated horses showed significant protective antibody titer when the season arrived. The study suggests that protective immunotherapy early in the season has some therapeutic potential for RAO‐affected horses.Grant Funding Source: Supported by EHSP, LSU‐SVM