.Expression and purification of Mycobacterium tuberculosis MPT83 protein and its application in tuberculosis immunological diagnosis / 中国热带医学

ABSTRACT

@#Abstract Objective To express and purify MPT83 protein of Mycobacterium tuberculosis and evaluate its application value in immunological diagnosis of tuberculosis (TB) using clinical samples. Methods Using Mycobacterium tuberculosis (Mtb) H37Rv genome as the template, Mtb mpt83 gene was amplified by PCR and connected to PET-21a (+) to construct prokaryotic expression vector, and then transferred into E.coli DH5α. The positive colonies were picked out and retained. The recombinant plasmid pET-mpt83 of the strain with positive colony PCR was extracted, identified by double digestion, and the samples of the positive colonies were sent for sequencing. The correctly sequenced plasmids then were transferred into BL21 competent cells for induction, expression and purification with nickel column affinity chromatography. The purified products were identified by 12 alkyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting. Mouse polyclonal antiserum was prepared by immunizing mice with purified protein. 8 patients clinically diagnosed as tuberculosis pleural effusion (TB group) and 8 adenocarcinomas patients (CA group) were enrolled and their pleural effusion and plasma were collected. 8 healthy people (HC group) were enrolled as the control group and their plasma were collected. An indirect ELISA was used to detect the level of specific antibodies recognizing MPT83 protein in the samples. Results Mtb MPT83 protein was successfully expressed and purified. The serum titer of MPT83 mouse polyclonal antibody was as high as 1∶1 280 000. The plasma levels of MPT83 antigen specific antibodies in TB group were significantly higher than those in HC group (P<0.05), while the plasma levels of MPT83 antigen specific antibodies in CA group were not significantly different from those in HC group (P>0.05). Compared with the HC group, there was no significant difference in pleural fluid in both the TB and CA groups (P>0.05). The ROC curve was used to analyze the OD values of plasma in TB group and HC group, and the area under the curve was greater than 0.7, showing high diagnostic efficacy. Conclusion　MPT83 protein has high antigen specificity and immunogenicity, which has great application value in the immunological diagnosis of tuberculosis.