ISOLATION AND CHARACTERIZATION OF A MAJOR ALLERGENIC COMPONENT (GP55)OF ASPERGILLUS-FUMIGATUS

IgE class antibodies specific for antigens in a water-soluble extract of Aspergillus fumigatus (strain NHL-5759) were analyzed by immunoblot ting with sera from patients with allergic bronchopulmonary aspergillo sis. All the sera tested were reactive with a major 50 to 60 kd protei n in the extract. This allergen, designated gp55, was purified by gel filtration and preparative sodium dodecyl sulfate-polyacrylamide gel e lectrophoresis. The antigen was found to be present in the water-solub le extract in the form of a complex composed of approximately eight mo lecules of gp55. The carbohydrate and phosphate content of the purifie d antigen were 23.1% and 0.46%, respectively. The molar ratio of manno se to galactose residues was 2.76:1, and the protein was glycosylated predominantly with N-linked oligosaccharides. The serologic activity o f the gp55 antigen was abolished by treatment with nonspecific proteas e (Pronase) but not by treatment with sodium metaperiodate or endoglyc osidases. Thus the major antigenic site of the glycoprotein is located within its peptide moiety. The antigen itself displayed no chymotrypt ic or tryptic activity. The amino acid sequence of the 20 N-terminal r esidues of the antigen (ATPHEPVFFSWDAGAVTSFP) is different from that o f any other protein previously reported.