Secretion of Functional Monocyte Chemotactic Protein 3 by Recombinant Mycobacterium bovis BCG Attenuates Vaccine Virulence and Maintains Protective Efficacy against M. tuberculosis Infection

A strain of Mycobacterium bovis BCG that secretes high levels of functional murine monocyte chemotactic protein 3 (BCGMCP-3) was developed. Mice vaccinated with BCGMCP-3displayed increased lymphocyte migration in vivo and augmented antigen-specific T-cell responses compared to mice vaccinated with BCG alone. The level of protection afforded by BCGMCP-3was equivalent to that with control BCG; however, immunodeficient mice infected with BCGMCP-3survived significantly longer than mice infected with the control BCG strain. Therefore, BCGMCP-3may be a safer alternative than conventional BCG for vaccination of immunocompromised individuals.