EFFECT OF VACCINES IN A MURINE MODEL OF DORMANT TUBERCULOSIS

Setting: The value of Mycobacterium vaccae vaccine in immunotherapy is of current interest. Objective: A series of 3 experiments was carried out using the Cornell model of dormant tuberculosis in the mouse to s ee whether M. vaccae and BCG vaccines would alter the rate of relapse to active disease. Design: In each experiment, BALB/c mice were infect ed intravenously with M. tuberculosis strain H37Rv and the disease was allowed to progress for 2 weeks to the point where the spleens yielde d about 10(7) colony forming units (cfu). Treatment with 25 mg isoniaz id/kg and 1000 mg pyrazinamide/kg in the diet was given for 14 weeks w hen the spleens and lungs usually yielded negative cultures only (the sterile state). The mice were then divided into 3 groups each of 30-49 mice, one of which received a heat-killed M. vaccae vaccine, another BCG vaccine and the third a control saline injection. The mice were ki lled 3 months later and the spleens and lungs cultured. Results: Neith er of the vaccines altered the relapse rate from the sterile state. Co nclusion: Immunotherapy does not influence relapse from the dormant st ate and probably therefore human endogenous reactivation. However, vac cine dosage was not studied, nor do mice necessarily model human respo nse.