An iTRAQ approach to quantitative proteome analysis of cerebrospinal fluid from patients with tuberculous meningitis

To study the cerebrospinal fluid (CSF) protein profiles of tuberculous meningitis (TBM) and discover potential biomarkers for TBM, differential expression of proteins in the CSF of patients with TBM, patients with cryptococcal meningitis, and a control group were compared using isobaric tags for relative and absolute quantitation labelling (iTRAQ) coupled with 2-dimensional liquid chromatography-tandem mass spectrometry (LC-MS). As a result, a total of 208 unique proteins with a molecular weight ranging from 10 KD to 135 KD were identified and quantified in CSF samples from patients with TBM. Of the proteins, 9 were expressed at levels differing 2.0 fold, 6 were up-regulated, and 3 were down-regulated. These proteins appear to be involved in calcium ion binding, lipoprotein metabolism, immune response, and signal conduction. Two differentially expressed proteins were identified using ELISA. The present study represents the successful use of iTRAQ to examine CSF from patients with TBM. The differentially expressed proteins identified may be potential diagnostic biomarkers and provide valuable insight into the underlying mechanisms of TBM. This study also demonstrated that the differential protein profiles of diseases can be quickly determined using iTRAQ-LC-MS, a potential method for quantitative comparative proteomics.