The identification of tuberculosis biomarkers in human urine samples

We aimed to determine whether shotgun proteomic approaches could be used to identify tuberculosis (TB)-specific biomarkers in the urine of well-characterised patients with active TB versus no TB. Patients with suspected TB (n=63) were classified as: definite TB ( Mycobacterium tuberculosis positive culture, n=21); presumed latent-TB infection (LTBI) ( M. tuberculosis negative culture, no radiological features of active TB, a positive QuantiFERON-TB Gold In-Tube (QFT-IT) test and a positive T-SPOT.TB test, n=24); and presumed non-TB/non-LTBI ( M. tuberculosis negative culture, no radiological features of active TB, a negative QFT-IT test and a negative T-SPOT.TB test, n=18). Urine proteins, in the range of 3–50 kDa, were collected, separated by a one-dimensional SDS-PAGE gel and digested using trypsin, after which high-performance liquid chromatography-tandem mass spectrometry was used to identify the urinary proteome. 10 mycobacterial proteins were observed exclusively in the urine of definite TB patients, while six mycobacterial proteins were found exclusively in the urine of presumed LTBI patients. In addition, a gene ontology enrichment analysis identified a panel of 20 human proteins that were significant discriminators (p<0.05) for TB disease compared to no TB disease. Furthermore, seven common human proteins were differentially over- or under-expressed in the TB versus the non-TB group. These biomarkers hold promise for the development of new point-of-care diagnostics for TB.