Identification of M. tuberculosis antigens in the sera of tuberculosis patients using biomimetic affinity chromatography in conjunction with ESI-CID-MS/MS.

The profiling of abnormally-expressed proteins in host cells using mass spectrometry (MS) analysis is a classical approach for screening disease-associated biomarkers in clinical diagnosis. However, few pathogen-specific antigens can currently be detected in serum using this proteomic approach, since these are very low-abundant proteins that are easily masked by host high-abundant proteins. Identification of pathogen-specific antigens in the sera of tuberculosis patients is crucial for the clinical diagnosis of this infectious disease, especially in immune-compromised patients. In the present study, two biomimetic affinity chromatography (BiAC) media, At-23 and A115-94, were selected from a library of BiAC media and used to selectively fractionate Albumin and Immunoglobulin from sera, respectively, prior to MS analyses. Each fraction was collected and screened against the proteomic database of M. tuberculosis complex. Three antigens, FbpA, FbpB and BfrB, were identified with two distinct peptides in BiAC-fractionated sera from tuberculosis patients, which were confirmed by Western blotting. Moreover, the identification of pathogen-specific antigens in sera by BiAC in conjunction with ESI-CID-MS/MS represents a promising strategy for the discovery of disease-associated biomarkers in other diseases.