Browsing by Author "Suman Gupta"

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Characterization of natural antimony resistance in Leishmania donovani isolates
(American Society of Tropical Medicine and Hygiene, 2007) Mukul K. Mittal; Smita Rai; Ashutosh; Ravinder; Suman Gupta; Shyam Sundar; Neena Goyal
Clinical resistance to pentavalent antimonial compounds has long been recognized as a major problem in the treatment of visceral leishmaniasis in India. However, mechanisms of natural resistance are unclear. In this study, we observed that Leishmania donovani clinical isolates not responsive to sodium stibogluconate showed resistance to antimony treatment in both in vitro and in vivo laboratory conditions. The resistant isolates have increased levels of intracellular thiols. This increase in thiol levels was not mediated by the amplification of γ-glutamylcysteine synthetase, but was accompanied by amplification of trypanothione reductase and an intracellular ATP-binding cassette transporter gene MRPA. The resistance of parasites to antimony could be reversed by the glutathione biosynthesis-specific inhibitor, buthionine sulfoximine, which resulted in increased drug susceptibility. These results suggest the possible role of thiols and MRPA in antimony resistance in field isolates. Copyright © 2007 by The American Society of Tropical Medicine and Hygiene.
Use of Leishmania donovani field isolates expressing the luciferase reporter gene in in vitro drug screening
(2005) Ashutosh; Suman Gupta; Ramesh; Shyam Sundar; Neena Goyal
Currently available primary screens for the selection of candidate antileishmanial compounds are not ideal. These techniques are time-consuming, laborious, and difficult to scale and require macrophages, which limit their use for high-throughput screening. We have developed Leishmania donovani field isolates that constitutively express the firefly luciferase reporter gene (luc) as a part of an episomal vector. An excellent correlation between parasite number and luciferase activity was observed. luc expression was stable, even in the absence of drug selection, for 4 weeks. The transfectants were infective to macrophages, and intracellular amastigotes exhibited luciferase activity. The suitability of these recombinant field isolates for in vitro screening of antileishmanial drugs was established. The luciferase-expressing sodium stibogluconate-resistant cell lines offer a model for the screening of compounds for resistance. The system is in routine use at the Central Drug Research Institute, Lucknow, India, for high-throughput screening of newly synthesized compounds. Copyright © 2005, American Society for Microbiology. All Rights Reserved.