Recombinant BCG vaccine expressing multistage antigens of Mycobacterium tuberculosis provides long-term immunity against tuberculosis in BALB/c mice

ABSTRACT

Tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) persistently kills nearly 1.5 million lives per year in the world, whereas the only licensed TB vaccine BCG exhibits unsatisfactory efficacy in adults. Taking BCG as a vehicle to express Mtb antigens is a promising way to enhance its efficacy against Mtb infection. In this study, the immune efficacy of recombination BCG (rBCG-ECD003) expressing specific antigens ESAT-6, CFP-10, and nDnaK was evaluated at different time points after immunizing BALB/c mice. The results revealed that rBCG-ECD003 induced multiple Th1 cytokine secretion including IFN-γ, TNF-α, IL-2, and IL-12 when compared to the parental BCG. Under the action of PPD or ECD003, rBCG-ECD003 immunization resulted in a significant increase in the proportion of IL-2⁺ and IFN-γ⁺IL-2⁺ CD4⁺T cells. Importantly, rBCG-ECD003 induced a stronger long-term humoral immune response without compromising the safety of the parental BCG vaccine. By means of the protective efficacy assay in vitro, rBCG-ECD003 showed a greater capacity to inhibit Mtb growth in the long term. Collectively, these features of rBCG-ECD003 indicate long-term protection and the promising effect of controlling Mtb infection.

KEYWORDS:

• Tuberculosis
• Mycobacterium tuberculosis
• recombinant BCG vaccine
• multicomponent fusion antigen
• cytokine

Acknowledgments

We would like to thank the collaboration of the Laboratory Animal Center, Chinese Center for Disease Control and Prevention, for their help and support in the animal experiments.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

DF, RW, and KW designed the study. HL contributed to the epitope prediction. DF, XF, RW, BC, and CQ performed experiments. DF and ML analyzed and interpreted data. KW provided reagents. DF and KW wrote the manuscript. All authors contributed to the article and approved the submitted version.

Additional information

Funding

This work was financially supported by the projects of 2018ZX10731301-002. The funders had no role in the study design, data collection and analysis, manuscript preparation or decision to publish.