Effect of vaccines in a murine model of dormant tuberculosis

The value of Mycobacterium vaccae vaccine in immunotherapy is of current interest.

A series of 3 experiments was carried out using the Cornell model of dormant tuberculosis in the mouse to see whether M. vaccae and BCG vaccines would alter the rate of relapse to active disease.

In each experiment, BALB/c mice were infected intravenously with M. tuberculosis strain H37Rv and the disease was allowed to progress for 2 weeks to the point where the spleens yielded about 10(7) colony forming units (cfu). Treatment with 25 mg isoniazid/kg and 1000 mg pyrazinamide/kg in the diet was given for 14 weeks when 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 killed 3 months later and the spleens and lungs cultured.

Neither of the vaccines altered the relapse rate from the sterile state.

Immunotherapy does not influence relapse from the dormant state and probably therefore human endogenous reactivation. However, vaccine dosage was not studied, nor do mice necessarily model human response.