Lactococcus lactis carrying a DNA vaccine coding for the ESAT‐6 antigen increases IL‐17 cytokine secretion and boosts the BCG vaccine immune response

Aims A regimen utilizing Bacille Calmette—Guerin (BCG) and another vaccine system as a booster may represent a promising strategy for the development of an efficient tuberculosis vaccine for adults. In a previous work, we confirmed the ability of Lactococcus lactis fibronectin‐binding protein A (FnBPA+) (pValac:ESAT‐6), a live mucosal DNA vaccine, to produce a specific immune response in mice after oral immunization. In this study, we examined the immunogenicity of this strain as a booster for the BCG vaccine in mice. Methods and Results After immunization, cytokine and immunoglobulin profiles were measured. The BCG prime L. lactis FnBPA+ (pValac:ESAT‐6) boost group was the most responsive group, with a significant increase in splenic pro‐inflammatory cytokines IL‐17, IFN‐γ, IL‐6 and TNF‐α compared with the negative control. Conclusions Based on the results obtained here, we demonstrated that L. lactis FnBPA+ (pValac:ESAT‐6) was able to increase the BCG vaccine general immune response. Significance and Impact of the Study This work is of great scientific and social importance because it represents the first step towards the development of a booster to the BCG vaccine using L. lactis as a DNA delivery system.