Targeting multidrug-resistant tuberculosis (MDR-TB) by therapeutic vaccines.

Tuberculosis (TB) has scourged humankind for millennia, and latent infection affects nearly one-third of today's world population. The emergence of multidrug-resistant (MDR)-TB is a major global threat and reflects treatment failure of drug-sensitive disease. MDR-TB management is a burden for patients and society; success rates are unacceptably low with prolonged treatment duration. Mycobacterium tuberculosis (Mtb) possesses the ability to transform into a dormant state in which it can persist in the face of antimicrobial treatment and host defense. This sub-population of persisters is largely responsible for lengthy and difficult treatment. Targeting persistent bacilli could eventually improve the treatment success rate (currently 50-65 %) and shorten duration of treatment. A subset of therapies in the pipeline, termed therapeutic vaccines, use the host immune response to attack Mtb. The historical occurrence of an exacerbated host response has resulted in a negative perception of therapeutic vaccines. Thus, a renewed concept of immunotherapy is needed. We review current perspectives of immunotherapy in MDR-TB based on the knowledge of TB immunology and briefly discuss the profiles of several therapeutic vaccine products.