Novel recombinant BCG coexpressing Ag85B, ESAT-6 and mouse TNF-alpha induces significantly enhanced cellular immune and antibody responses in C57BL/6 mice

The recent emergence of multidrug-resistant and extensively drug-resistant strains of Mtb and the epidemic of TB in populations co-infected with human immunodeficiency virus demonstrate that TB remains a leading infectious disease. Moreover, the failure of BCG to protect against this disease indicates that new vaccines against TB are urgently needed. Experimental evidence has revealed that TNF plays a major role in host defense against Mtb in both active and latent phases of infection. Release of TNF, which would induce mycobacteria-mediated macrophage apoptosis and thus reduce the spread of mycobacteria, is one of the most important and early responses of macrophages challenged with Mtb. In order to identify the usefulness of TNF in improving the effectiveness of TB vaccine, in the current study a novel rBCG strain expressing the fusion gene of Ag85B-Esat6-TNF-alpha in BCG Danish strain was constructed, and its ability to induce an immune response in C57BL/6 mice evaluated. It was found that immunization with strains of rBCG-Ag85B-Esat6-TNF-alpha can induce a stronger immune response than does immunization with rBCG-Ag85B-Esat6 or parental BCG. The results indicate that rBCG-Ag85B-Esat6-TNF-alpha is a promising candidate for further study.