Tuberculosis infection is a leading cause of death worldwide. The emergence of multi-drug resistant strains of Mycobacterium tuberculosis (Mtb) and the increased prevalence of immunocompromised individuals create the conditions for an explosive epidemic of tuberculosis. Recognition of the limitations in the effectiveness of the M. bovis (BCG) vaccine make developing an improved Mtb vaccine imperative. One new approach to a Mtb vaccine is genetic immunization (aka. DNA immunization). This technique involves directly inoculating simple plasmids encoding a protein of the pathogen into the host cells of the living animal. Since its first demonstration in 1992, it remains a viable vaccine delivery system against a wide variety of pathogens. However, as with the more classical protein vaccines, the problem of selecting appropriate DNA fragments encoding for proteins that induce a protective immune response remains. Expression library immunization (ELI), is a mechanism for the rapid screening for immuno-protective epitopes that combines recombinant DNA technology with in vivo infection models. Expression libraries containing the total genome of a pathogen are created and introduced into naive mice. The DNA-inoculated mice are then challenged with the pathogen and tested for increased resistance compared to control animals which have received DNA-libraries from an irrelevant organism. Resistant mice identify libraries that contain plasmids encoding for protective antigenic epitopes. The libraries are divided and the procedure repeated until individual protective plasmids are identified. It is an unbiased, systematic approach for isolating vaccine candidates which can be used as genetic vaccines or in other forms. The investigators have proven the feasibility of this technique with Mycoplasma pulmonis and now propose to use it to make and characterize an effective Mtb vaccine. Specifically, the investigators will: 1. Apply ELI to Mtb using a mouse pulmonary infection model to isolate up to nine protective new genes from the genome. 2. compare the genes, the proteins corresponding to them and BCG as vaccines. 3. determine whether the protective genes have non-additive effects, whether unique vectors can influence the antigen processing of the expressed proteins to influence the immune response and whether they confer cross protection against other species of Mycobacteria. The ELI approach may provide a new and rapid method for developing a Mtb vaccine as well as for other emerging pathogens.
