Objective  To investigate the effect of Mycobacterium bovis PtpA protein on NF-κB signaling pathway which is related to immune response, and reveal the role of PtpA protein in the body's response to immunity.

Method  The PtpA gene eukaryotic expression vector FLAG-PtpA was transfected into HEK293T for SDS-PAGE analysis and Western blot detection. After activation of NF-κB signaling pathway, the effects of PtpA protein on NF-κB signaling pathway were investigated by dual luciferase assay and qPCR.

Result  The eukaryotic expression vector FLAG-PtpA of PtpA gene was successfully constructed, transfected into HEK293T and analyzed by SDS-PAGE. The specific molecular band was visible with relative molecular mass of 22 000. Western blot results showed that the expression product specifically bound to the primary antibody, demonstrating that the protein was a PtpA protein. In the double luciferase assay, the ratios of the relative fluorescence intensities of firefly luciferase and Renilla luciferase in the test group and the control group were significantly different from 2 to 24 h after transfection (P<0.05). The relative fluorescence values of firefly luciferase and Renilla luciferase in the control group were 2.93 times higher than those in the experimental group 2 h after transfection, indicating that PtpA protein had a significant inhibitory effect on the early activation of NF-κB signaling pathway. qPCR results showed that the expression levels of IL-6, GM-CSF, BIRC-2 and BIRC-3 in the control group were 3.93, 3.42, 2.17 and 2.30 times respectively of those in the test group 2 h after transfection(P<0.01), and were 4.26, 3.93, 2.36 and 2.50 times respectively of those in the test group 4 h after transfection(P<0.01). These results indicated that PtpA protein had a significant inhibitory effect on NF-κB signaling pathway-associated cytokines (IL-6, GM-CSF, BIRC-2 and BIRC-3) in the early stage of immunization.

Conclusion  qPCR results are consistent with the results of dual luciferase assay, indicating that the effect of M. bovis PtpA on NF-κB signaling pathway mainly occurs in the early stage. This study provides a theoretical basis for the follow-up study of effective tuberculosis prevention and control drugs.