Background The recently characterized group 7 house dust mite allergens give positive skin-test reactions in 53% of allergie patients.
Objective This study was performed to compare the IgE bindinig activity of natural and recombinant Der p 7, to measure the binding in allergic sera in comparison to major allergen Der p 2 and characterize the response by competitive inhibition with monoclonal antibodies.
Methods IgE anti Der p 2 and Der p 7 antibodies against the recombinant allergens and monoclonal binding activities were measured by a solid phase radioimmune assay. Reslts A competitive binding assay showed that rDer p 7 inhibited 91% of IgE-binding to natural Der p 7 in 2 sera and 73% in a further two. The IgE binding of rDer p 2 and Der p 7 from 41 sera was then compared. Of the sera 88% and 46% respectively showed positive binding. All of the 19 sera which bound Der p 7 also bound Der p 2 but 11 (58%) had bound IgE to Der p 7 as high or higher than the binding to Der p 2. These sera were mostly high responders to both allergens. A panel of six monoclonal antibodies produced against either rDer p 7 or rDer f 7 was used for epitope analysis. All of these reaeted with eaeh allergen by enzyme linked immunosorbent assay (ELISA) and immunoblotting. Two patterns of cross inhibition of monoclonal antibody binding were observed and of five monoclonal antibodies tested, lour could inhibit the binding of IgE (WH9, WH22. WPS and HD19) while one (WH14) could not.
Conclusions Although Der p 7 only reacts with 50% of allergic sera it often has a high IgE binding activity and may be more important than the major Der p 2 allergen in a high percentage of subjects. The combined competitive inhibition experiments show the IgE response is directed at several specilieities.