Adjunct immunotherapies for tuberculosis.

The continued spread of multidrug-resistant (MDR) tuberculosis and extensively drug-resistant tuberculosis poses a major threat to global tuberculosis control. Treatment is complex and requires longer use of more-expensive, less effective, and toxic anti-tuberculosis drugs, which results in high morbidity and mortality. The poor treatment outcomes and the slow progress in the development and evaluation of new tuberculosis drugs have given rise to the development of adjunct immunotherapy. The host immune system is a critical factor both for containment and cure of Mycobacterium tuberculosis infection. Augmentation or dampening of proinflammatory responses can be of value in the treatment of individuals who have nonproductive M. tuberculosis infection with inflammation-induced tissue damage. The use of immunotherapy with interleukin 2, interferon γ, and interleukin 7 as an adjunct to drug treatment may improve success rates for treatment of MDR tuberculosis, shorten treatment time for drug-sensitive tuberculosis, and improve the immunity of individuals by enhancing M. tuberculosis elimination to prevent recurrence of disease. A broad range of immunological treatments, including cytokine treatment or cell-based therapy, is now available, although not all have been evaluated in humans. This review gives a critical overview of current adjunct immunotherapies for active tuberculosis, which are at various stages of development.