DNA Subunit Vaccine and Recombinant BCG Based on Mycobacterial Lipoprotein LprO Enhance Anti-Tuberculosis Protection in the Lungs of Mice

Background/Objectives: Over the past two centuries, tuberculosis (TB) has been responsible for approximately one billion deaths and continues to represent a significant global health challenge. Despite extensive research efforts, fully effective strategies for the prevention or eradication of TB remain elusive, highlighting the urgent demand for novel vaccines with enhanced safety profiles and efficacy. Lipoproteins, integral surface proteins of mycobacteria, are frequently associated with virulence and display notable immunogenicity, rendering them promising candidates for vaccine development. This study investigates the potential of the mycobacterial lipoprotein, LprO, as a vaccine antigen against TB. Methods: A pcDNA-lprO DNA vaccine was constructed, and its immunogenicity was evaluated using a murine model. Its protective efficacy was further assessed using a Mycobacterium marinum (M. marinum)-infected zebrafish model. Additionally, a recombinant BCG vaccine strain, BCG Japan::pNBV1-lprO, was generated. Its immunogenicity was tested in mice, and its safety was evaluated in SCID mice. Both vaccine candidates were further assessed in regard to their protective efficacy in a murine Mycobacterium tuberculosis (M. tb) infection model. Results: The pcDNA-lprO vaccine increased the M. tb-specific IFN-γ-secreting lymphocytes in murine spleens and prolonged the survival of zebrafish infected with M. marinum. The recombinant BCG Japan::pNBV1-lprO vaccine elicited M. tb-specific Th1-type immune responses in mice compared to the standard BCG Japan strain. Both vaccines effectively reduced the bacterial burden of M. tb in murine lungs, offering superior protection relative to the control groups. Conclusions: These findings establish LprO as a compelling candidate for TB vaccine development, with both LprO-based DNA and recombinant BCG vaccines demonstrating robust protective effects against TB.