Purification and partial characterization of two major allergens from the house dust mite Dermatophagoides pteronyssinus

Abstract

Two major allergens of the house dust mite, Dermatophagoides pteronyssinus (Dp), were purified, and their molecular weight and isoelectric points (pIs) were determined. Dp 42 was purified from an acetone-precipitated mite-excrement extract by a combination of hydrophobic interaction chromatography on phenyl Sepharose and copper-chelate chromatography. The molecular weight was determined to be 18,000 and 25,000 to 30,000 by gel filtration (G-75) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, respectively, and pI values of 4.6, 5.6, and 6.6 were obtained by sucrose gradient isoelectric focusing (IEF). These values correspond well with those described for the identical allergen, P 1. The pI 6.6 variant was considerably enriched in the purified material. Dp 42 constituted 6.4% of the dry weight of a reference whole mite-culture extract. Dp X was obtained partially purified by gel filtration (G-75), ammonium sulphate precipitation, and hydrophobic interaction chromatography. The molecular weight was 18,000 to 20,000 by gel filtration and sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Multiple pIs in the range 5 to 7 were found by sucrose gradient IEF and crossed IEF. The two purified allergens carried clearly distinct activities toward human IgE and appeared as potent allergens in crossed radioimmunoelectrophoresis, RAST, and RAST inhibition.