Antigens of alternaria. I. Isolation and partial characterization of a basic peptide allergen

A basic peptide allergen has been isolated from Alternaria extracts. Flat-bed gel preparative isoelectric focusing followed by dialysis and lyophilization allowed for concentration of substantial quantities of this heretofore unrecognized allergen. Rocket immunoelectrophoresis and autoradiography (using a 2 X concentrated, IgE serum fraction from Alternaria patient sera and 125I-anti human IgE), a RAST inhibition assay, and skin testing of Alternaria-sensitive patients were used to demonstrate the allergenicity of this fraction. The allergenicity of this protein was sufficient to give 50% RAST inhibition at a concentration of 100 micrograms/ml using standard RAST procedures. The immunoelectrophoresis autoradiography also indicated allergenicity. Skin tests indicated that over 90% of patients hypersensitive to Alternaria crude extracts were also hypersensitive to the basic allergen fraction.