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 μg, 3.0 μg, or 15.0 μg 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 IgG₄. 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-α and increase in secreted TGF-β. 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-γ, 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 μg Can f 1.

Key words: Immunotherapy, acetone-precipitated dog extract, Can f 1, cytokine, allergen-specific IgE, allergen-specific IgG₄, skin prick test, late cutaneous response

Abbreviations used: AP, Acetone-precipitated, cpm, Counts per minute, SPT, Skin prick test