Screening novel diagnostic marker of Mycobacterium tuberculosis

Abstract

The aim of present study was to screen and evaluate the serodiagnostic value of the purified fusion antigens of Mycobacterium tuberculosis (Mtb) by enzyme-linked immunosorbent assay (ELISA). A group of vector system which was constructed by cloning Rv1908c, Rv0733, Rv0899, Rv1411c and Rv3914 gene of Mtb into the prokaryotic expression plasmid pET-32b was transformed into E. coli for induction and expression fusion antigens to determine their potentiality in diagnostic application. Following purification with the His-select nickel magnetic agarose beads, the expressed fusion proteins showed purity via sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot technique. The ELISA plates were coated with these fusion antigens. Through ELISA, the antigen binding with specific IgG levels between active TB patients and healthy controls was compared. The purity and the size of the expressed fusion antigens were confirmed by the Western blot. The ELISA results indicated that IgG levels against Rv1411c-6His, Rv3914-6His and Rv2031c-6His were significantly higher in serum of active TB patients than in that of healthy controls. More interesting, the AUC value of Rv3914-6His (0.7867) was higher than that of Rv2031c-6His (0.754) which was widely used in clinic. The results implied that Rv3914-6His might be a useful candidate antigen in the diagnosis of Mtb infection, especially for active pulmonary TB diagnosis. Its role in serodiagnosis of extra-pulmonary TB is still needed to be validated.