Proteomic profiles of bronchoalveolar lavage fluid from patients with ventilator-associated pneumonia by gel-assisted digestion and 2-D-LC/MS/MS

Development of ventilator-associated pneumonia (VAP) imposes a significant financial burden to the health care system, yet the therapeutic decisions rely on the conventional, less sensitive microbiological examination. Characterization of proteins secreted into bronchoalveolar lavage fluid (BALF) provides an opportunity for discovery of diagnostic marker candidates for accurate therapeutic decision-making. We report the first global description of the BALF proteome from patients with VAP. Our approach combining gel-assisted digestion followed by SCX fractionation and nano-LC-MS/MS effectively overcame the interference of high salt concentrations in BALF. Semi-quantitative analysis by a simple, label-free approach based on chromatographic peak area intensity revealed that the protein constituents were dramatically different between the non-VAP controls and the VAP group. To our knowledge, the 206 identified proteins present the most comprehensive global proteome map of BALF. The expression of four selected proteins with unique roles, including gelsolin, serum amyloid P-component, vitamin D-binding protein and pyruvate kinase, were significantly higher in BALF from patients with VAP (p <0.05). We demonstrate that this proteomic approach provides in-depth profiling of the BALF proteome, which comprises proteins functionally associated with the pathogenesis of VAP, including those expressed due to stress-induced injury and host immune response to local inflammation.