Exploration of some new secretory proteins to be employed for companion diagnosis of Mycobacterium tuberculosis

Abstract Tuberculosis (TB) is a highly infectious disease and its early and precise diagnosis is essential to reduce morbidity and mortality of patients. Since the routine diagnostic tests (like Monteux, AFB smear microscopy, chest X-Ray) do not give infallible results, additional tests are always recommended. Therefore to address the concerns about non-specificity of the present battery of diagnostic tests, we have attempted to analyze some unique secretory antigens which could be able to identify the stage specific infection of MTB. In this study, we have used recombinant proteins CFP-10, ESAT-6, Ag85 A, Ag85B, Ag85C, PE3, PE4 and Mycp1 to eliminate heterogeneity and cross reactivity in clinical diagnosis. Amplified genes were cloned and over-expressed in Escherichia coli BL21 (DE3). The recombinantly purified proteins were used as antigens against 158 sera samples of TB patients. Secretory proteins showed better response than the PPD control. Among all the used antigens PE3 and PE4 proteins showed better reactivity levels among all the groups of TB patients. The secretions of CFP-10 and ESAT-6 were also higher as compared to other secretory proteins like Ag85 A, Ag85B, Ag85C and MycP1.The clinical use of these newly identified secretory antigens could be of significant value for the confirmatory, rapid, simple and low-cost diagnosis of TB patients.