The role of toll-like receptor agonists in the immunotherapy of leishmaniosis. An update and proposal for a new form of anti-leishmanial therapy.

The use of toll-like receptor agonists in immunotherapy is a new approach in the prevention of immunosuppression during fatal Leishmania parasite infection. The objective of such immunotherapy is to activate specific cell-mediated immune responses, macrophage activation and antigen-responsive inflammation, to kill intracellular amastigotes. Toll-like receptor agonist-based treatment in immunocompetent hosts can be effective either by selective use of the agonists alone or in combination with the anti-leishmanial drug stibanate. Recent investigations suggest that toll-like receptor signal pathways constitute a possible new mode of anti-leishmanial treatment. This article describes the prospect of toll-like receptor - mediated signal pathways in the immunotherapy of cutaneous and visceral leishmaniosis, as well as post kala-azar dermal leishmaniosis (PKADL), a skin-sequel of visceral infection. Suitable synthetic agonists need to be developed for toll-like receptors to overcome immunosuppression.