Medicine and Health Sciences Commons^™

A Variant Pfcrt Isoform Can Contribute To Plasmodium Falciparum Resistance To The First-Line Partner Drug Piperaquine, Satish K. Dhingra, Devasha Redhi, Jill M. Combrinck, Tomas Yeo, John Okombo, Philipp P. Henrich, Ann N. Cowell, Purva Gupta, Matthew L. Stegman, Jonathan M. Hoke, Roland A. Cooper, Elizabeth Winzeler, Sachel Mok, Timothy J. Egan, David A. Fidock

Collected Faculty and Staff Scholarship

Current efforts to reduce the global burden of malaria are threatened by the rapid spread throughout Asia of Plasmodium falciparum resistance to artemisininbased combination therapies, which includes increasing rates of clinical failure with dihydroartemisinin plus piperaquine (PPQ) in Cambodia. Using zinc finger nucleasebased gene editing, we report that addition of the C101F mutation to the chloroquine (CQ) resistance-conferring PfCRT Dd2 isoform common to Asia can confer PPQ resistance to cultured parasites. Resistance was demonstrated as significantly higher PPQ concentrations causing 90% inhibition of parasite growth (IC90) or 50% parasite killing (50% lethal dose [LD50]). This mutation also reversed Dd2-mediated CQ …

Lack Of Resistance Of Plasmodium Falciparum To Dihydroartemisinin In Uganda Based On Parasitogolgical And Molecular Assays, Roland A. Cooper, Melissa D. Conrad, Quentin D. Watson, Stephanie J. Huezo, Harriet Ninsiima, Patrick Tumwebaze, Samuel L. Nsobya, Philip J. Rosenthal

Collected Faculty and Staff Scholarship

• Artemisinin-­‐based combination therapy is now standard treatment for falciparum malaria. However, this regimen is threatened by resistance to artemisinins, manifest as delayed clearance of parasitemia after therapy, in southeast Asia.

• Artemisinin resistance in southeast Asia is associated with increased parasitemias in culture, compared to those in sensi0ve parasites, 72 hours a=er a 6 hour pulse with 700 nM dihydroartemisinin (DHA), and with propeller domain polymorphisms in the Plasmodium falciparum kelch (K13; PF3D7_1343700) gene

• Given that artemether/lumefantrine has been adopted as standard therapy for malaria within the last decade in Uganda, we characterized artemisinin sensiBvity in fresh P. falciparum isolates from …

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Impact Of Antimalarial Treatment And Chemoprevention On The Drug Sensitivity Of Malaria Parasites Isolated From Ugandan Children, Patrick Tumwebaze, Melissa D. Conrad, Andrew Walakira, Norbert Leclair, Oswald Byaruhanga, Christine Nakazibwe, Benjamin Kozak, Jessica Bloome, Jaffer Okiring, Abel Kakuru, Victor Bigira, James Kapisi, Jennifer Legac, Jiri Gut, Roland A. Cooper, Moses R. Kamya, Diane V. Havlir, Grant Dorsey, Bryan Greenhouse, Samuel L. Nsobya, Philip J. Rosenthal

Collected Faculty and Staff Scholarship

Changing treatment practices may be selecting for changes in the drug sensitivity of malaria parasites. We characterized ex vivo drug sensitivity and parasite polymorphisms associated with sensitivity in 459 Plasmodium falciparum samples obtained from subjects enrolled in two clinical trials in Tororo, Uganda, from 2010 to 2013. Sensitivities to chloroquine and monodesethylamodiaquine varied widely; sensitivities to quinine, dihydroartemisinin, lumefantrine, and piperaquine were generally good. Associations between ex vivo drug sensitivity and parasite polymorphisms included decreased chloroquine and monodesethylamodiaquine sensitivity and increased lumefantrine and piperaquine sensitivity with pfcrt 76T, as well as increased lumefantrine sensitivity with pfmdr1 86Y, Y184, and 1246Y. …

Mutation In The Plasmodium Falciparum Crt Protein Determines The Stereospecific Activity Of Antimalarial Cinchona Alkaloids, Carol E. Griffin, Jonathan M. Hoke, Upeka Samarakoon, Junhui Duan, Jianbing Mu, Michael T. Ferdig, David C. Warhurst, Roland Cooper

Collected Faculty and Staff Scholarship

The Cinchona alkaloids are quinoline aminoalcohols that occur as diastereomer pairs, typified by (-)-quinine and (+)-quinidine. The potency of (+)-isomers is greater than the (-)-isomers in vitro and in vivo against Plasmodium falciparum malaria parasites. They may act by the inhibition of heme crystallization within the parasite digestive vacuole in a manner similar to chloroquine. Earlier studies showed that a K76I mutation in the digestive vacuole-associated protein, PfCRT (P. falciparum chloroquine resistance transporter), reversed the normal potency order of quinine and quinidine toward P. falciparum. To further explore PfCRT-alkaloid interactions in the malaria parasite, we measured the in vitro susceptibility …

Chloroquine Susceptibility And Reversibility In A Plasmodium Falciparum Genetic Cross, Jigar J. Patel, Drew Thacker, Jon C. Tan, Perri Pleeter, Lisa Checkley, Joseph M. Gonzales, Bingbing Deng, Paul D. Roepe, Roland A. Cooper, Michael T. Ferdig

Collected Faculty and Staff Scholarship

Mutations in the Plasmodium falciparum chloroquine (CQ) resistance transporter (PfCRT), are major determinants of verapamil (VP)-reversible CQ resistance (CQR). In the presence of mutant PfCRT, additional genes contribute to the wide range of CQ susceptibilities observed. It is not known if these genes influence mechanisms of chemosensitization by CQR reversal agents. Using quantitative trait locus (QTL) mapping of progeny clones from the HB3 × Dd2 cross, we show that the P. falciparum multidrug resistance gene 1 (pfmdr1) interacts with the Southeast Asiaderived mutant pfcrt haplotype to modulate CQR levels. A novel chromosome 7 locus is predicted to contribute with the …