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Targeted Phenotypic Screening in Plasmodium falciparum and Toxoplasma gondii Reveals Novel Modes of Action of Medicines for Malaria Venture Malaria Box Molecules

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dc.contributor.advisor Shanmugam, Dhanasekaran
dc.contributor.advisor Chandramohandas, Rajesh
dc.contributor.author Subramanian, Gowtham
dc.contributor.author Belekar, Meenakshi Anil
dc.contributor.author Shukla, Anurag
dc.contributor.author Tong, Jie Xin
dc.contributor.author Sinha, Ameya
dc.contributor.author Chu, Trang T T
dc.contributor.author Kulkarni, Akshay S
dc.contributor.author Preiser, Peter R
dc.contributor.author Reddy, D. Srinivasa
dc.contributor.author Tan, Kevin S W
dc.contributor.author Shanmugam, Dhanasekaran
dc.contributor.author Chanramohandas, Rajesh
dc.date.accessioned 2019-08-28T00:19:38Z
dc.date.available 2019-08-28T00:19:38Z
dc.date.issued 2018-01
dc.identifier.citation mSphere. 2018 Jan 17;3(1). pii: e00534-17. doi: 10.1128/mSphere.00534-17. eCollection 2018 Jan-Feb en_US
dc.identifier.uri http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/4597
dc.description.abstract The Malaria Box collection includes 400 chemically diverse small molecules with documented potency against malaria parasite growth, but the underlying modes of action are largely unknown. Using complementary phenotypic screens against Plasmodium falciparum and Toxoplasma gondii, we report phenotype-specific hits based on inhibition of overall parasite growth, apicoplast segregation, and egress or host invasion, providing hitherto unavailable insights into the possible mechanisms affected. First, the Malaria Box library was screened against tachyzoite stage T. gondii and the half-maximal effective concentrations (EC50s) of molecules showing ≥80% growth inhibition at 10 µM were determined. Comparison of the EC50s for T. gondii and P. falciparum identified a subset of 24 molecules with nanomolar potency against both parasites. Thirty molecules that failed to induce acute growth inhibition in T. gondii tachyzoites in a 2-day assay caused delayed parasite death upon extended exposure, with at least three molecules interfering with apicoplast segregation during daughter cell formation. Using flow cytometry and microscopy-based examinations, we prioritized 26 molecules with the potential to inhibit host cell egress/invasion during asexual developmental stages of P. falciparum. None of the inhibitors affected digestive vacuole integrity, ruling out a mechanism mediated by broadly specific protease inhibitor activity. Interestingly, five of the plasmodial egress inhibitors inhibited ionophore-induced egress of T. gondii tachyzoites. These findings highlight the advantage of comparative and targeted phenotypic screens in related species as a means to identify lead molecules with a conserved mode of action. Further work on target identification and mechanism analysis will facilitate the development of antiparasitic compounds with cross-species efficacy. IMPORTANCE The phylum Apicomplexa includes many human and animal pathogens, such as Plasmodium falciparum (human malaria) and Toxoplasma gondii (human and animal toxoplasmosis). Widespread resistance to current antimalarials and the lack of a commercial vaccine necessitate novel pharmacological interventions with distinct modes of action against malaria. For toxoplasmosis, new drugs to effectively eliminate tissue-dwelling latent cysts of the parasite are needed. The Malaria Box antimalarial collection, managed and distributed by the Medicines for Malaria Venture, includes molecules of novel chemical classes with proven antimalarial efficacy. Using targeted phenotypic assays of P. falciparum and T. gondii, we have identified a subset of the Malaria Box molecules as potent inhibitors of plastid segregation and parasite invasion and egress, thereby providing early insights into their probable mode of action. Five molecules that inhibit the egress of both parasites have been identified for further mechanistic studies. Thus, the approach we have used to identify novel molecules with defined modes of action in multiple parasites can expedite the development of pan-active antiparasitic agents en_US
dc.description.sponsorship CSIR, DST/ASTAR Singapore en_US
dc.format.extent 22 en_US
dc.language.iso en_US en_US
dc.publisher mSphere en_US
dc.subject MMV Malaria Box; Plasmodium falciparum; Toxoplasma gondii; apicoplast; chemical phenotyping; egress; flow cytometry; invasion; malaria; merozoites; tachyzoites; toxoplasmosis en_US
dc.title Targeted Phenotypic Screening in Plasmodium falciparum and Toxoplasma gondii Reveals Novel Modes of Action of Medicines for Malaria Venture Malaria Box Molecules en_US
dc.type Article en_US
local.division.division Biochemical Sciences Division en_US
dc.description.university AcSIR en_US

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