Der p 2 isoallergens have different allergenicity, and quantification with 2-site ELISA using monoclonal antibodies is influenced by the isoallergens

Background: Der p 2 isoallergens have been reported and the possibility of different allergenicity has also been suggested. In addition, the quantification with 2-site ELISA may be affected by the isoallergens. Objectives: Two different recombinant Der p 2 (rDer p 2) isoallergens were compared in terms of human IgE responses and the reliability of quantification of them with two-site ELISA kits which use monoclonal antibodies (mAbs) as capture and detection of Der p 2. Methods: Seven different Der p 2 cDNA from the cultured Dermatophagoides pteronyssinus (DP) were cloned and polymorphism in nine amino acid residues was found. Two different recombinant isoallergens (rDer p 2A and rDer p 2B) were expressed and compared to their human IgE immune responses by ELISA and the ELISA inhibition test with 23 sera of DP-allergic patients. The reliability of quantification of two different available 2-site ELISA kits, which used mAbs for capture and detection of Der p 2, was evaluated. Results: The ELISA optical density of rDer p 2B-specific IgE (slgE) was higher than that of rDer p 2A (P < 0.001). The ELISA inhibition curve of rDer p 2B slgE in pool I sera (n = 5; high slgE both to rDer p 2A and rDer p 2B) did not show any differences in the 50% inhibition concentration and maximum inhibitory percentage of rDer p 2A and rDer p 2B slgE. However, with pool II sera (n = 5; markedly higher slgE to rDer p 2B than rDer p 2A), the 50% inhibitory concentrations (10 μg/mL vs. 40 ng/mL) and maximum inhibitory percentage (61% vs. 99%) of rDer p 2B slgE with the two recombinant isoallergens were quite different, rDer p 2B could be quantified with two different 2-site ELISA kits, but rDer p 2A was detected by only one kit. Conclusion: We conclude that isoallergens of Der p 2 may have different IgE immune responses. Quantification of Der p 2 with 2-site ELISA kits that adopted mAbs, might be affected by the prevalent form of the isoallergens in reservoir dust.