Purification and characterization of a new peptide antigen extracted from dermatophyte mycelia

Abstract

A highly purified peptide antigen was produced from the cultured mycelia of Trichophyton mentagrophytes. Mycelia were extracted with 0.1 N-HCl at 37 degrees C repeatedly. The protein fraction was precipitated with picric acid and the final product was tentatively designated as Trichophyton mentagrophytes peptide (TMP). Total yield of TMP was about 3% of the original mycelia. When skin tests were done on sensitized guinea pigs, TMP showed a delayed-type reaction. The minimal dose which gave a positive reaction was 3 micrograms (0.1 ml of 30 micrograms/ml solution). Chemical analyses showed that TMP was almost exclusively of a peptide nature and digestion with bacterial peptidase (pronase) completely destroyed its skin test activity, thereby suggesting that protein fraction carried the entire antigenic activity. With chemical and/or physical processings, TMP showed firm stability; the skin test activity was unchanged after heating to 120 degrees C or after processing with HCl or NaOH. Fractionation of TMP by gel filtration demonstrated a considerable heterogeneity in its molecular size, while the antigenic activity was virtually the same in all the fractions. Disc electrophoresis also showed a wide-spread heterogeneous pattern. In the MIF test using peritoneal exudate cells from sensitized guinea pigs, 100 micrograms/ml of TMP had definite inhibitory effect on cell migration.