Leishmania Eukaryotic Initiation Factor (LeIF) Inhibits Parasite Growth in Murine Macrophages

The leishmaniases constitute neglected global public health problems that require adequate control measures, prophylactic clinical vaccines and effective and non-toxic drug treatments. In this study, we explored the potential of Leishmania infantum eukaryotic initiation factor (LieIF), an exosomal protein, as a novel anti-infective therapeutic molecule. More specifically, we assessed the efficacy of recombinant LieIF, in combination with recombinant IFN-gamma, in eliminating intracellular L. donovani parasites in an in vitro macrophage model. J774A.1 macrophages were initially treated with LieIF/IFN-gamma prior to in vitro infection with L. donovani stationary phase promastigotes (pre-infection treatment), and resistance to infection was observed 72 h after infection. J774A.1 macrophages were also treated with LieIF/IFN-gamma after L. donovani infection (post-infection treatment), and resistance to infection was also observed at both time points tested (19 h and 72 h) after infection. To elucidate the LieIF/IFN-gamma-induced mechanism(s) that mediate the reduction of intracellular parasite growth, we examined the generation of potent microbicidal molecules, such as nitric oxide (NO) and reactive oxygen species (ROS), within infected macrophages. Furthermore, macrophages pre-treated with LieIF/IFN-gamma showed a clear up-regulation in macrophage inflammatory protein 1 alpha (MIP-1 alpha) as well as tumor necrosis factor alpha (TNF-alpha) expression. However, significant different protein levels were not detected. In addition, macrophages pre-treated with LieIF/IFN-gamma combined with anti-TNF-alpha monoclonal antibody produced significantly lower amounts of ROS. These data suggest that during the pre-treatment state, LieIF induces intramacrophage parasite growth inhibition through the production of TNF-alpha, which induces microbicidal activity by stimulating NO and ROS production. The mechanisms of NO and ROS production when macrophages are treated with LieIF after infection are probably different. Overall, these results indicate that LieIF is a good candidate for use as an anti-leishmanial molecule.