Immune response and protection by DNA vaccines expressing antigen 85B of Mycobacterium tuberculosis.

A plasmid DNA containing two different expression cassettes was prepared to independently drive antigen 85B (85B) of Mycobacterium tuberculosis and HIV-Tat in C57BL/6 mice. In vivo expression of the plasmid was demonstrated by efficient transcription of 85B and Tat mRNAs in mouse fibroblasts. DNA-85B or DNA-(85B-Tat) were immunogenic and protected mice to the same extent against M. tuberculosis infection, with a decrease in the numbers of CFU lung(-1) in comparison with nonimmunized animals down to levels (0.64 log10 CFU) not significantly different from protection conferred by bacillus Calmette-Guerin vaccine (0.97 log10 CFU decrease). Multipromoter plasmids, which permit the reduction of the total amount of DNA injected, can be useful for DNA vaccination against tuberculosis.