Immunologic response to administration of standardized dog allergen extract at differing doses

Background: The immunologic response to immunotherapy with dog extract is not well characterized. Objective: The purpose of this study was to examine the immunologic response to 3 doses of dog extract expressed as their Can f 1 content. Methods: Cluster immunotherapy was administered to 28 patients with dog allergy who were randomly assigned to 1 of 4 treatment arms: placebo or acetone-precipitated extract containing 0.6 mu g, 3.0 mu g, or 15.0 mu g Can f 1 per 0.5 mL maintenance dose. Studies included titrated skin prick tests, the late cutaneous response, titrated nasal challenge with dog extract, and serum allergen-specific IgE and IgG(4). Dog allergen-stimulated lymphocyte proliferation was performed with measurement of secreted cytokines by ELISA and of intracellular cytokines by flow cytometry. Results: There was a significant dose-dependent response in suppression of titrated skin prick tests and suppression of the late cutaneous response. There was a significant increase from baseline in dog-specific IgG4 in both the high-dose and low-dose groups and a dose-dependent suppression of secreted TNF-alpha and increase in secreted TGF-beta. There was a dose-dependent trend in suppression of secreted IL-4 with a significant decrease from baseline in the high-dose group. There were no significant changes in symptom scores; lymphocyte proliferation; secreted IFN-gamma, IL-10, or IL-5; or intracellular cytokine production. Conclusion: The dose-response in immunologic parameters after immunotherapy with dog extract is similar to that previously demonstrated with cat extract. Clinical implications: The greatest and most consistent response is seen with a dose containing 15 mu g Can f 1.