Purification and characterization of the major allergen from Dermatophagoides pteronyssinus-antigen P1.

Abstract

A purified allergen was obtained from D. pteronyssinus culture by gel filtration, block electrophoresis, and preparative isoelectricfocusing (IEF). The antigenic activity on IEF was predominantly distributed in two peaks (pI 4.7 to 5.4 and pI 6.6 to 7.1), which were completely cross-reactive on immunodiffusion and by cross-inhibition of radioimmunoassay. These fractions had the same m.w. (24,000) and a very similar amino acid composition. The common antigen in each fraction was designated Derma tophagoides pteronyssinus antigen P1. In seven, symptomatic mite allergic subjects skin test reactivity to antigen P1 and crude mite extract was closely correlated. There was also a very good correlation between IgE-binding activity (BA) for P1 measured by antigen-binding radioimmunoassay and IgE antibody (ab) to D. pteronyssinus measured by using the radioallergosorbent test (RAST) (r = 0.82, p < 0.001). RAST experiments showed that up to three-quarters of the IgE ab to D. pteronyssinus was directed against P1, and that IgE ab to P1 accounted for on average 12% of the total serum IgE. These data strongly suggest that P1 is the major allergen of D. pteronyssinus. By immunodiffusion, SDS-PAGE, and radioimmunoassay antigen P1 appeared to be present as a large proportion (10 to 20%) of the protein in crude mite extract. Our results support the view that the importance of an inhalant allergen is largely determined by its physical properties, and by the quantities inhaled during natural exposure.