Identification and characterization of Mycobacterium tuberculosis antigens in urine of patients with active pulmonary tuberculosis: an innovative and alternative approach of antigen discovery of useful microbial molecules.

Despite the clear need to control tuberculosis, the diagnosis and prevention of this serious disease are poorly developed and have remained fundamentally unchanged for more than 50 years. Here, we introduce an innovative approach to directly identify Mycobacterium tuberculosis antigens produced in vivo in humans with tuberculosis. We combined reversed phase high performance liquid chromatography and mass spectrometry and categorize four distinct M. tuberculosis proteins produced presumably in lung lesions and excreted in the urine of patients with pulmonary tuberculosis. The genes (MT_1721, MT_1694, MT_2462 and MT_3444) coding for these proteins were cloned and the recombinant molecules were produced in Escherichia coli. The proteins were recognized by immunoglobulin G antibodies from tuberculosis patients but not from non-diseased subjects. In addition, the recombinant proteins were recognized strongly by peripheral blood mononuclear cells from healthy purified protein derivative of tuberculin-positive individuals and to a lesser extent from patients with tuberculosis. These molecules are the only proteins reported to date that are derived directly from bodily fluids of tuberculosis patients, therefore are interesting candidate antigens for the development of vaccine and/or antigen detection assay for accurate diagnosis of active tuberculosis.