The 19-kD antigen and protective immunity in a murine model of tuberculosis

The 19-kD antigen is a cell wall-associated lipoprotein present in Mycobact erium tuberculosis and in bacille Calmette-Guerin (BCG) vaccine strains. Ex pression of the 19-kD antigen as a recombinant protein in two saprophytic m ycobacteria-M. vaccae and M. smegmatis-resulted in abrogation of their abil ity to confer protection against M. tuberculosis in a murine challenge mode l, and in their ability to prime a DTH response to cross-reactive mycobacte rial antigens. Induction of an immune response to the 19-kD antigen by an a lternative approach of DNA vaccination had no effect on subsequent M. tuber culosis challenge. These results are consistent with a model in which the p resence of the 19-kD protein has a detrimental effect on the efficacy of va ccination with live mycobacteria. Targeted inactivation of genes encoding s elected antigens represents a potential route towards development of improv ed vaccine candidates.