Quantitative measurement of IgE antibodies to purified allergens using streptavidin linked to a high-capacity solid phase

BACKGROUND: Commercially available assays for IgE antibody provide results in international units per milliliter for many allergen extracts, but this is not easily achieved with purified or novel allergens. OBJECTIVE: To develop assays for IgE antibody suitable for purified or novel allergens by using a commercially available immunosorbent. METHODS: Streptavidin coupled to a high-capacity immunosorbent (CAP) was used to bind biotinylated purified allergens from mite (Der p 1 and Der p 2), cat (Fel d 1), and dog (Can f 1). Assays for IgE antibody to these allergens were performed on sera from children (asthma and control) as well as adults with atopic dermatitis. RESULTS: The results were validated by serial dilution of sera with high and low levels of IgE antibody and were quantitated in international units per milliliter by using a standard curve. Values for IgE antibody to Der p 1, Der p 2, and Fel d 1 correlated with values obtained with the allergen extracts (r2 = 0.80, 0.84, and 0.95, respectively; P < .001 in each case). Furthermore, the values for IgE antibody in sera from children with high exposure to mite and cat allergens demonstrated 10-fold higher levels of IgE antibody to Der p 1 and Der p 2 than to Fel d 1 (P < .001). CONCLUSION: The streptavidin immunosorbent technique provides a new method for quantifying IgE antibody to purified proteins. The results provide evidence about the high quantities of IgE antibody to purified inhalant allergens in patients with atopic dermatitis. In addition, the results demonstrate major differences in IgE antibodies specific for mite and cat allergens among children with high exposure to both allergens.