An integrative in silico and in vitro study identifies Leishmania donovani MAP kinase12 as a probable virulence factor.

Visceral leishmaniasis (VL), a potentially fatal vector-borne disease caused by the intracellular protozoan parasite Leishmania donovani, remains a major health problem due to restricted repertoire of drugs, deleterious side effects, high cost and increasing drug resistance. Therefore, identifying newer drug targets and developing efficacious affordable treatments with minimal or no side effects are pressing needs. Being regulators of diverse cellular processes, Mitogen-Activated Protein Kinases (MAPKs) are potential drug targets. Herein, we report L.donovani MAPK12 (LdMAPK12) as a probable virulence factor implying it as a plausible target. LdMAPK12 sequence is distinct from human MAPKs and is highly conserved in different Leishmania species. LdMAPK12 is expressed in both promastigotes and amastigotes. In comparison with the avirulent and procyclic promastigotes, the virulent and metacyclic promastigotes have higher expression of LdMAPK12. Pro-inflammatory cytokines reduced, whereas anti-inflammatory cytokines increased LdMAPK12 expression in macrophages. These data suggest a probable novel role of LdMAPK12 in parasite virulence and identifies it as a plausible drug target.

Immunotherapy for visceral leishmaniasis: A trapeze of balancing counteractive forces.

The protozoan parasite Leishmania donovani, residing and replicating within the cells of the monocyte-macrophage (mono-mac) lineage, causes visceral leishmaniasis (VL) in humans. While, Leishmania infantum, is the main causative agent for zoonotic VL, where dogs are the main reservoirs of the disease. The chemotherapy is a serious problem because of restricted repertoire of drugs, drug-resistant parasites, drug-toxicity and the requirement for parenteral administration, which is a problem in resource-starved countries. Moreover, immunocompromised individuals, particularly HIV-1 infected are at higher risk of VL due to impairment in T-helper cell and regulatory cell responses. Furthermore, HIV-VL co-infected patients report poor response to conventional chemotherapy. Recent efforts are therefore directed towards devising both prophylactic and therapeutic immunomodulation. As far as prophylaxis is concerned, although canine vaccines for the disease caused by Leishmania infantum or Leishmania chagasi are available, no vaccine is available for use in humans till date. Therefore, anti-leishmanial immunotherapy triggering or manipulating the host's immune response is gaining momentum during the last two decades. Immunomodulators comprised of small molecules, anti-leishmanial peptides, complex ligands for host receptors, cytokines or their agonists and antibodies have been given trials both in experimental models and in humans. However, the success of immunotherapy in humans remains a far-off target. We, therefore, propose that devising a successful immunotherapy is an act of balancing enhanced beneficial Leishmania-specific responses and deleterious immune activation/hyperinflammation just as the swings in a trapeze.

The HIV - 1 protease inhibitor Amprenavir targets Leishmania donovani topoisomerase I and induces oxidative stress-mediated programmed cell death.

The global prevalence of HIV is a major challenge for the control of visceral leishmaniasis. Although the effectiveness and usefulness of amprenavir (APV) are well studied in anti-retroviral regimens, very little is known on HIV/VL-co-infected patients. In the present study, we report for the first time the protective efficacy of APV against visceral leishmaniasis by inhibition of DNA Topoisomerase I (LdTOP1LS) and APV-induced downstream pathway in programmed cell death (PCD). During the early phase of activation, reactive oxygen species (ROS) is increased inside the cells, which causes subsequent elevation of lipid peroxidation. Endogenous ROS formation and lipid peroxidation cause eventual depolarization of mitochondrial membrane potential (ΔΨm). Furthermore, the release of cytochrome c and activation of CED3/CPP32 group of proteases lead to the formation of oxidative DNA lesions followed by DNA fragmentation. The promising in vitro and ex vivo results promoted to substantiate further by in vivo animal experiment, which showed a significant reduction of splenic and hepatic parasites burden compared to infected controls. Interestingly, APV selectively targets LdTOPILS and does not inhibit the catalytic activity of human topoisomerase I (hTopI). Moreover, based on the cytotoxicity test APV is not toxic for host macrophage cells, which is correlated with non-responsiveness of inhibition of catalytic activity of hTopI. Taken together, this study provides the opportunity for discovering and evaluating newer potential molecular therapeutic targets for drug designing. The present study might be exploited in future as important therapeutics, which will be useful for treatment of VL as well as HIV-VL co-infection.