Antigens of Aspergillus fumigatus. II. Electrophoretic and clinical studies.

Cell sap (CS) and culture filtrate (CF) preparations of Aspergillus fumigatus strains Ag-507, Ag-515, and Ag-534 were analysed by two dimensional electrophoresis (2-DE; i.e., first dimension isoelectric focusing, second dimension sodium dodecyl sulphate gradient pore gel), which enabled detection of strain- and species-specific components. In CS preparations it was shown that CS2, a fraction isolated from strain Ag-507 by gel filtration, consists of the major protein components in the CS of the three A. fumigatus strains tested. Culture filtrate preparations of the three A. fumigatus strains analysed by 2-DE exhibited patterns dissimilar to the CS patterns, as well as to each other, presumably due to proteolysis. Culture filtrate preparations are therefore a less reliable source of standardized antigens than CS preparations. CS2 has a major component with a mol. wt. of approximately 150,000 and an sapp of 6.3 S. CS2 reacts on immunoelectrophoresis, producing one major precipitin arc with aspergilloma or allergic bronchopulmonary aspergillosis (ABPA) patient sera. Antibody titres of the IgG and IgA classes to CS2, as measured by enzyme-linked immunosorbent assay (ELISA), were demonstrated to be similar in aspergilloma and ABPA patients; IgG titres were higher than IgA. Similar titres were also obtained utilizing sera of patients that did or did not exhibit precipitating antibodies to CS2. In the diagnosis of ABPA, skin tests with CS2 were comparable in specificity to currently available commercial preparations. Importantly, CS2 is a standardized major antigenic preparation of the CS of three A. fumigatus strains which has been shown to be diagnostically useful.