The immunogenicity of recombinant Mycobacterium smegmatis bearing BCG genes

Specific pathogen-free C57BL/6 mice infected with recombinant Mycobacterium smegmatis (rM. smegmatis) bearing BCG genes showed increased splenic survival compared to those receiving the vector control (plasmid DNA only). The mouse-passaged rM. smegmatis (J3R) survived in peritoneal macrophages better than the vector control, regardless of whether the macrophages were infected in vivo or in vitro. When rM. smegmatis J3R was cultured in synthetic Proskauer-Beck-Tween medium, protein bands characteristic of BCG culture filtrates and not present in the vector control preparation were observed. Mice immunized with two doses of heat-killed J3R suspended in Freund's adjuvant were able to limit the growth of virulent Mycobacterium tuberculosis within the lung and spleen compared to that observed in control mice receiving adjuvanted vector control or Freund's adjuvant alone.