title: Functional protease profiling for laboratory based diagnosis of invasive aspergillosis.
abstract: Invasive aspergillosis (IA) remains difficult to diagnose in immunocompromised patients, because diagnostic criteria according to EORTC/MSG guidelines are often not met and have low sensitivity. Hence there is an urgent need to improve diagnostic procedures by developing novel approaches. In the present study, we present a proof of concept experiment for the monitoring of Aspergillus associated protease activity in serum specimens for diagnostic purpose. Synthetic peptides that are selectively cleaved by proteases secreted from Aspergillus species were selected from our own experiments and published data. These so called reporter peptides (RP, n=5) were added to serum specimens from healthy controls (HC, n=101) and patients with proven (IA, n=9) and possible (PIA, n=144) invasive aspergillosis. Spiked samples were incubated ex vivo under strictly standardized conditions. Proteolytic fragments were analyzed using MALDI-TOF mass spectrometry. Spiked specimens of IA patients had highest concentrations of RP-fragments followed by PIA and HC. The median signal intensity was 116.546 (SD, 53.063) for IA and 5.009 (SD, 8.432) for HC. A cut-off >36.910 was chosen that performed with 100% specificity and sensitivity. Patients with PIA had either values above [53% (76/144)] or below [47% (67/144)] this chosen cut-off. The detection of respective reporter peptide fragments can easily be performed by MALDI TOF mass spectrometry. In this proof of concept study we were able to demonstrate that serum specimens of patients with IA have increased proteolytic activity towards selected reporter peptides. However, the diagnostic value of functional protease profiling has to be validated in further prospective studies. It is likely that a combination of existing and new methods will be required to achieve optimal performance for diagnosis of IA in the future.
authors.affiliation: Institute for Clinical Chemistry, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Bassel
authors.initials: B
authors.lastname: Sabbagh
authors.affiliation: Institute for Clinical Chemistry, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Victor
authors.initials: V
authors.lastname: Costina
authors.affiliation: Department of Haematology and Oncology, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Dieter
authors.initials: D
authors.lastname: Buchheidt
authors.affiliation: Department of Haematology and Oncology, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Mark
authors.initials: M
authors.lastname: Reinwald
authors.affiliation: Institute for Clinical Chemistry, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Neumaier
authors.affiliation: Institute for Clinical Chemistry, Medical Faculty Mannheim of the University of Heidelberg, University Hospital Mannheim, D-68167 Mannheim, Germany.
authors.forename: Peter
authors.initials: P
authors.lastname: Findeisen
mesh_terms: D000328:Adult; D000368:Aged; D001228:Aspergillosis / Q000097:blood / Q000175:diagnosis* / Q000382:microbiology; D001230:Aspergillus / Q000201:enzymology*; D005260:Female; D005656:Fungal Proteins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D010447:Peptide Hydrolases / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D012680:Sensitivity and Specificity; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods
chemical_list: D005656:Fungal Proteins; D010455:Peptides; D010447:Peptide Hydrolases