Systematic identification of substrates for profiling of secreted proteases from Aspergillus species

Reliable and early diagnosis of life-threatening invasive mycoses in neutropenic patients caused by fungi of the Aspergillus species remains challenging because current clinical diagnostic tools lack in sensitivity and/or specificity. During invasive growth a variety of fungal proteases are secreted into the bloodstream and protease profiling with reporter peptides might improve diagnosis of invasive aspergillosis in serum specimens. To characterise the specific protease activity of Aspergillus fumigatus and Aspergillus niger we analyzed Aspergillus culture supernatants, human serum and the mixture of both. A systematic screening for optimised protease substrates was performed using a random peptide library consisting of 360 synthetic peptides featuring fluorescence resonance energy transfer (FRET). We could identify numerous peptides that are selectively cleaved by fungus-specific proteases. These reporter peptides might be feasible for future protease profiling of serum specimens to improve diagnosis and monitoring of invasive aspergillosis.