Purification and characterization of Lep d I, a major allergen from the mite Lepidoglyphus destructor

A major allergen of the storage mite Lepidoglyphus destructor (Lep d I) has been purified by affinity chromatography using an anti-Lep d I monoclonal antibody. The purity of the protein obtained by this procedure was assessed by reverse-phase HPLC. Lep d I displayed a molecular weight of 14 kD on SDS-PAGE under non-reducing conditions, and 16 kD in the presence of a reducing agent. Analytical IEF revealed a little charge microheterogeneity, showing three bands with pIs 7.6-7.8. Purified Lep d I retained IgE-binding ability, as proved by immunoblotting experiments after SDS-PAGE and RAST with individual sera from L. destructor-sensitive patients. Results from the latter technique demonstrated that 87% of L. destructor-allergic patients had specific IgE to Lep d I, and a good correlation between IgE reactivity with L. destructor extract and Lep d I was found. In addition, RAST inhibition experiments showed that IgE-binding sites on Lep d I are major L. destructor-allergenic determinants, since Lep d I could inhibit up to 75% the binding of specific IgE to L. destructor extract; on the other hand, Lep d I did not cross-react with D. pteronyssinus allergens.