Highly sensitive and specific ELISA with monoclonal antibody capture to measure Dermatophagoides farinae 1-specific IgE

Background: Dermatophagoides farinae (Der f) 1 is a major allergen in Der f extract. Measurement of Der f I-specific IgE has not been commonly used, because of the difficulty in obtaining large amounts of purified Der f 1. Objectives: To improve the diagnosis of dust mite allergy, we wanted to develop an ELISA to measure Der f 1-specific IgE in which purified Der f 1 is not required. Methods: Using a monoclonal antibody (mAb) against Der f 1, a mAb-capture ELISA was developed. Microplates coated with the mAb were sequentially incubated with crude Der f extract, serum samples, goat anti-human IgE, and conjugated rabbit anti-goat Igc. A conventional ELISA using purified Der f 1 as capture (Der f 1-ELISA) was developed to compare it with the mAb-capture ELISA. Results: There was a significant correlation between the two ELISAs (r = 0.89, P < .001) with a sensitivity of 0.8 U/mL. Both the assays were inhibited by the crude Der f extract in a dose-dependent manner. Using the two ELISAs, serum Der f 1-specific IgE was evaluated in 12 allergic patients with positive skin tests to Der f extract, 14 allergic patients with negative skin tests to Der f extract, and 15 healthy subjects. The mean Der f 1-IgE and the positivity rate of Der f I-IgE were higher in the mite-allergic group and lower in the healthy group when the mAb-ELISA was used (P < .01) than when the Der f 1-ELISA was used (P < .05). Conclusions: Der f 1-specific IgE can be measured by mAb-capture ELISA using crude Der f extract. The mAb-ELISA is more sensitive and specific than the conventional Der f 1-capture ELISA in diagnosing dust mite allergy.