Date Published: February 13, 2015
Publisher: Public Library of Science
Author(s): Juliana Q. Reimão, Jordana C. Oliveira, Cristiana T. Trinconi, Paulo C. Cotrim, Adriano C. Coelho, Silvia R. B. Uliana, Anne-Laure Bañuls. http://doi.org/10.1371/journal.pntd.0003556
Abstract: BackgroundThe only oral drug available for the treatment of leishmaniasis is miltefosine, described and approved for visceral leishmaniasis in India. Miltefosine is under evaluation for the treatment of cutaneous leishmaniasis in the Americas although its efficacy for the treatment of human visceral leishmaniasis caused by Leishmania infantum chagasi has not been described. Drug efficacy for visceral leishmaniasis is ideally tested in hamsters, an experimental model that mimics human disease. Luciferase has been validated as a quantitative tool for the determination of parasite burden in experimental leishmaniasis. However, there are no reports of luciferase detection in the model of progressive visceral leishmaniasis in hamsters. Therefore, the aims of this study were to generate recombinant Leishmania infantum chagasi expressing the luciferase gene (Lc-LUC), characterize the biological properties of this transgenic line as compared with the wild-type parasites and evaluate miltefosine effectiveness in Lc-LUC infected hamsters.Methodology/Principal FindingsA transgenic line containing a luciferase encoding gene integrated into the ribosomal DNA locus was obtained and shown to produce bioluminescence which correlated with the number of parasites. Lc-LUC growth curves and susceptibility to pentavalent antimony and miltefosine in vitro were indistinguishable from the wild-type parasites. The effectiveness of pentavalent antimony was evaluated in Lc-LUC infected hamsters through bioimaging and determination of Leishman Donovan Units. Both methods showed concordant results. Miltefosine was effective in the treatment of Lc-LUC-infected hamsters, as demonstrated by the reduction in parasite burden in a dose-dependent manner and by prolongation of animal survival.Conclusions/SignificanceLuciferase expressing parasites are a reliable alternative for parasite burden quantification in hamsters with advantages such as the possibility of estimating parasite load before drug treatment and therefore allowing distribution of animals in groups with equivalent mean parasite burden. Miltefosine was effective in vivo in an L. infantum chagasi experimental model of infection.
Partial Text: Visceral leishmaniasis (VL) is a neglected vector borne disease that manifests with fever, fatigue, weight loss, anemia and hepatosplenomegaly in humans. Untreated, VL is almost 100% fatal . VL is transmitted by phlebotomine sand flies and is caused by Leishmania infantum and Leishmania donovani. L. infantum chagasi  is the etiological agent of VL in Latin America. L. infantum is found in the Mediterranean Basin, while L. donovani is prevalent in the Indian subcontinent, South Asia and East Africa .
We report here the generation of recombinant luciferase-expressing L. infantum chagasi parasites and their use to quantify parasite load in vivo in infected hamsters. The hamster model is used to study VL because it reproduces the clinical course and pathology of the disease, as seen in humans and dogs . Results presented here contribute to the study of new alternatives for VL treatment through the use of a chronic infection model.