Simultaneous detection of IgG and IgM antibodies against a recombinant polyprotein PstS1-LEP for tuberculosis diagnosis

Abstract

Background: Commercial serological tests for the diagnosis of tuberculosis (TB) show poor sensitivity and specificity, and a new approach to antigen screening is required to improve the accuracy of serodiagnosis. Methods: Using an indirect enzyme-linked immunosorbent assay (ELISA), we evaluated the responses of IgG and IgM antibodies to the recombinant PstS1-LEP protein expressed in Escherichia coli, a polyprotein of PstS1 and line multi-epitopes polypeptide (LEP). Results: The mixture of anti-human IgG and IgM added to a well [Ig(G + M)], which was different from the combination of IgG and IgM (IgG + IgM), had a stronger immunoreactivity to PstS1-LEP than the single antibody. IgG and Ig(G + M), but not IgM against the PstS1-LEP protein effectively distinguished TB patients from patients with nontuberculous pulmonary disease (NTBPD) and healthy controls (HCs). Compared with IgG, the sensitivities of Ig(G + M) and IgG + IgM varied from 71.4% to 77.6% and 72.7% in pulmonary TB (PTB) patients and from 42.1% to 64.0% and 55.8% in extrapulmonary TB (EPTB) patients, respectively. The specificity of Ig(G + M) did not decrease, and was higher than that provided by IgG + IgM in HCs with positive tuberculin skin test. Conclusion: These findings suggest that PstS1-LEP can act as a candidate for detecting Ig(G + M) in serum from PTB and EPTB patients.

Keywords::

• Line multi-epitope polypeptide
• ELISA
• tuberculosis
• Ig(G + M)

Acknowledgments

This study was supported by funding from the National Mega Projects on Key Infectious Disease Control of Ministry of Science and Technology, China (2013ZX10003006-003-001).

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.