Potential correlates of BCG induced protection against tuberculosis detected in a mouse aerosol model using gene expression profiling.

Tuberculosis (TB) is responsible for more than 2 million deaths per year with the incidence of new cases rising throughout the world. Mycobacterium bovis bacillus Calmette Guerin (BCG) is currently the only available licensed vaccine against M. tuberculosis. Despite the variable protective efficacy in different populations it affords some protection, particularly against childhood and disseminated forms of the disease. BCG remains the gold standard for assessing other prospective TB vaccines, yet there is a lack of information on the mechanisms of BCG protection and consequently there are no definitive correlates of protection for this vaccine. In order to further studies in this area we assessed lung RNA homogenates from naïve, BCG vaccinated and aerosol challenged mice. We found increased IFN-gamma levels in lungs of aerosol challenged mice previously vaccinated with BCG and a number of transcripts regulated by IFN-gamma were also increased in the lungs of these animals. These transcripts represent a cluster of IFN-gamma related transcripts that may assist in determining if BCG and maybe other potential vaccines will elicit protection against M. tuberculosis.