Sequence polymorphisms and antibody binding to the group 2 dust mite allergens

Background: The group 2 allergens Der p 2, Der f 2 and fur m 2 are 14-kD pr oteins with >80% sequence identity. Isoforms within each genus have been id entified which differ by 3-4 amino acids. The aim of this study was to inve stigate the importance of these substitutions to antibody binding. Methods: Recombinant allergens were expressed and purified from Escherichia coli. E LISA and skin testing were used to evaluate antibody binding. Molecular mod eling of the tertiary structure was preformed to examine the location of su bstitutions. Results: The th ree Der f 2 isoforms and two of th ree of the Der p 2 isoforms reacted with all monoclonal antibodies (mAb). Der p 2.0101 , the isoform with aspartate at position 114, bound all mAb except 1D8. Sub stitution of asparagine for aspartate restored binding of rDer p 2.0101 to mAb 1D8 and increased the correlation coefficient for IgE binding from 0.72 to 0.77. The three Der p 2 isoforms showed comparable skin test reactivity to nDer p 2 and commercial extract. rEur m 2.0101 bound to all mAb except 7A1 and when compared with rDer p 2 for IgE binding, r(2) = of 0.58 (n = 72 ). Lep d 2 did not react with mAb or with Dermatophagoides spp. allergic se ra. Modeling revealed that fur m 2, Lep d 2 and Tyr p 2 retain the tertiary fold of Der p 2 and the substitutions are on the surface. Conclusions: mAb could distinguish isoform substitutions. IgE binding showed a good correla tion among ail isoforms, thus the recombinant allergens are useful for diag nosis. Copyright (C) 2001 S. Karger AG. Basel.