Comparison of the Allergenic Potency of House Dust Extract and House Dust Mite Allergen Extract for Subcutaneous Allergen Immunotherapy.

Subcutaneous allergen immunotherapy (SCIT) with non-standardized house dust (HD) extracts has been used in Japan since 1963 for house dust mite (HDM)-allergic patients. Since the potencies of HD extracts are unknown, the allergenic potency of HD extracts was examined by comparing with a standardized HDM allergen extracts. The major allergen content of HDM in the extracts was measured using a sandwich enzyme linked immunosorbent assay (ELISA). The immunoglobulin E (IgE) inhibitory activities of the extracts were measured by a competitive ELISA. The extract concentrations giving 50% inhibition of IgE binding (log IC50) were determined from dose response curves and defined as inhibitory activities. A linear regression line was constructed from the log(10) IC50 values of the standardized HDM extract to interpolate the relative potency of the HD extract with strength of 1 :10w/v (HD 1:10). The amounts of major allergens (Der f 1, Der p 1 and Der 2) were 116.3 mu g/mL in the HDM allergen extract (100000 Japanese Allergy Units [JAU]/mL) and 0.77 mu g/mL in the HD 1:10. The inhibitory activity (log(10) IC50 values) of HD 1 :10 was 2.389 +/- 0.078, indicating the allergenic potency was between 200 and 2000JAU/mL. Based on regression analysis (R-2 >0.99), the allergenic potency of HD 1:10 was estimated to be 842 +/- 128 JAU/mL. The present study determined the major allergen content of HD extract, which contributes to its allergenic potency. The allergenic potency of HD 1 :10 was ca. 100-fold less than that of HDM allergen extract.