Background: Dust mites are important inducers of allergic disease. Group 2 allergens are recognized as major allergens in several mite species, including Dermatophagoides pteronyssinus, Lepidoglyphus destructor, and Tyrophagus putrescentiae. No allergens have thus far been characterized on the molecular level from the dust mite Glycyphagus domesticus.
Objective: We sought to examine the cross-reactivity among group 2 allergens of G domesticus, L destructor, T putrescentiae, and D pteronyssinus.
Methods: A group 2 allergen from G domesticus, Gly d 2, was cloned and expressed as a recombinant protein. Cross-reactivity between Gly d 2 and 3 other group 2 allergens, Lep d 2, Tyr p 2, and Der p 2, was studied by using individual sera and a serum pool RAST-positive to G domesticus, L destructor, T putrescentiae, and D pteronyssinus. Recombinant allergens were used as inhibitors of IgE binding in immunoblotting experiments. Molecular modeling on the basis of the Der p 2 structure was carried out for Gly d 2, Lep d 2, and Tyr p 2.
Results: Two cDNAs encoding isoforms of Gly d 2 were isolated, but only the Gly d 2.02 isoform was used in this study. Sixteen of 17 subjects had IgE to Gly d 2. The protein sequence of Gly d 2 revealed 79% identity to Lep d 2 and 46% and 41% identity to Tyr p 2 and Der p 2, respectively. Extensive cross-reactivity was demonstrated among Gly d 2, Lep d 2, and Tyr p 2, but little cross-reactivity was found between these allergens and Der p 2. According to the tertiary structure of Der p 2 and 3-dimensional models of Gly d 2, Lep d 2, and Tyr p 2, differences reside mainly in surface-exposed residues.
Conclusion: Gly d 2 showed high sequence homology to Lep d 2. Cross-reactivity was observed between Gly d 2, Lep d 2, and Tyr p 2, but only limited cross-reactivity was demonstrated between these 3 allergens and Der p 2.