IGE AND MONOCLONAL-ANTIBODY BINDING BY THE MITE ALLERGEN DER-P-7

Background The recently characterized group 7 house dust mite allergen s give positive skin-test reactions in 53% of allergic patients. Objec tive This study was performed to compare the IgE binding activity of n atural and recombinant Der p 7, to measure the binding in allergic ser a in comparison to major allergen Der p 2 and characterize the respons e by competitive inhibition with monoclonal antibodies. Methods IgE an ti Der p 2 and Der p 7 antibodies against the recombinant allergens an d monoclonal binding activities were measured by a solid phase radioim mune assay. Results A competitive binding assay showed that rDer p 7 i nhibited 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 bi nding. All of the 19 sera which bound Der p 7 also bound Der p 2 but 1 1 (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 reacted with eac h allergen by enzyme linked immunosorbent assay (ELISA) and immunoblot ting. Two patterns of cross inhibition of monoclonal antibody binding were observed and of five monoclonal antibodies tested, four could inh ibit the binding of IgE (WH9, WH22, WP8 and HD19) while one (WH14) cou ld 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 importan t than the major Der p 2 allergen in a high percentage of subjects. Th e combined competitive inhibition experiments show the IgE response is directed at several specificities.