3 research outputs found
Drug susceptibility of Plasmodium falciparum in eastern Uganda: a longitudinal phenotypic and genotypic study
Background: Treatment and control of malaria depends on artemisinin-based combination therapies (ACTs) and is challenged by drug resistance, but thus far resistance to artemisinins and partner drugs has primarily occurred in southeast Asia. The aim of this study was to characterise antimalarial drug susceptibility of Plasmodium falciparum isolates from Tororo and Busia districts in Uganda.
Methods: In this prospective longitudinal study, P falciparum isolates were collected from patients aged 6 months or older presenting at the Tororo District Hospital (Tororo district, a site with relatively low malaria incidence) or Masafu General Hospital (Busia district, a high-incidence site) in eastern Uganda with clinical symptoms of malaria, a positive Giemsa-stained blood film for P falciparum, and no signs of severe disease. Ex-vivo susceptibilities to ten antimalarial drugs were measured using a 72-h microplate growth inhibition assay with SYBR Green detection. Relevant P falciparum genetic polymorphisms were characterised by molecular methods. We compared results with those from earlier studies in this region and searched for associations between drug susceptibility and parasite genotypes.
Findings: From June 10, 2016, to July 29, 2019, 361 P falciparum isolates were collected in the Busia district and 79 in the Tororo district from 440 participants. Of 440 total isolates, 392 (89%) successfully grew in culture and showed excellent drug susceptibility for chloroquine (median half-maximal inhibitory concentration [IC50] 20路0 nM [IQR 12路0-26路0]), monodesethylamodiaquine (7路1 nM [4路3-8路9]), pyronaridine (1路1 nM [0路7-2路3]), piperaquine (5路6 nM [3路3-8路6]), ferroquine (1路8 nM [1路5-3路3]), AQ-13 (24路0 nM [17路0-32路0]), lumefantrine (5路1 nM [3路2-7路7]), mefloquine (9路5 nM [6路6-13路0]), dihydroartemisinin (1路5 nM [1路0-2路0]), and atovaquone (0路3 nM [0路2-0路4]). Compared with results from our study in 2010-13, significant improvements in susceptibility were seen for chloroquine (median IC50 288路0 nM [IQR 122路0-607路0]; p\u3c0路0001), monodesethylamodiaquine (76路0 nM [44路0-137]; p\u3c0路0001), and piperaquine (21路0 nM [7路6-43路0]; p\u3c0路0001), a small but significant decrease in susceptibility was seen for lumefantrine (3路0 nM [1路1-7路6]; p\u3c0路0001), and no change in susceptibility was seen with dihydroartemisinin (1路3 nM [0路8-2路5]; p=0路64). Chloroquine resistance (IC50\u3e100 nM) was more common in isolates from the Tororo district (11 [15%] of 71), compared with those from the Busia district (12 [4%] of 320; p=0路0017). We showed significant increases between 2010-12 and 2016-19 in the prevalences of wild-type P falciparum multidrug resistance protein 1 (PfMDR1) Asn86Tyr from 60% (391 of 653) to 99% (418 of 422; p\u3c0路0001), PfMDR1 Asp1246Tyr from 60% (390 of 650) to 90% (371 of 419; p\u3c0路0001), and P falciparum chloroquine resistance transporter (PfCRT) Lys76Thr from 7% (44 of 675) to 87% (364 of 417; p\u3c0路0001).
Interpretation: Our results show marked changes in P falciparum drug susceptibility phenotypes and genotypes in Uganda during the past decade. These results suggest that additional changes will be seen over time and continued surveillance of susceptibility to key ACT components is warranted.
Funding: National Institutes of Health and Medicines for Malaria Venture
Development of a Highly Selective Plasmodium falciparum Proteasome Inhibitor with Anti-malaria Activity in Humanized Mice.
Plasmodium falciparum proteasome (Pf20S) inhibitors are active against Plasmodium at multiple stages-erythrocytic, gametocyte, liver, and gamete activation stages-indicating that selective Pf20S inhibitors possess the potential to be therapeutic, prophylactic, and transmission-blocking antimalarials. Starting from a reported compound, we developed a noncovalent, macrocyclic peptide inhibitor of the malarial proteasome with high species selectivity and improved pharmacokinetic properties. The compound demonstrates specific, time-dependent inhibition of the 尾5 subunit of the Pf20S, kills artemisinin-sensitive and artemisinin-resistant P.鈥協alciparum isolates in鈥卾itro and reduces parasitemia in humanized, P.鈥協alciparum-infected mice
Recommended from our members
Susceptibilities of Ugandan Plasmodium falciparum Isolates to Proteasome Inhibitors
The proteasome is a promising target for antimalarial chemotherapy. We assessed ex vivo susceptibilities of fresh Plasmodium falciparum isolates from eastern Uganda to seven proteasome inhibitors: two asparagine ethylenediamines, two macrocyclic peptides, and three peptide boronates; five had median IC50 values <100鈥塶M. TDI8304, a macrocylic peptide lead compound with drug-like properties, had a median IC50 of 16鈥塶M. Sequencing genes encoding the 尾2 and 尾5 catalytic proteasome subunits, the predicted targets of the inhibitors, and five additional proteasome subunits, identified two mutations in 尾2 (I204T, S214F), three mutations in 尾5 (V2I, A142S, D150E), and three mutations in other subunits. The 尾2 S214F mutation was associated with decreased susceptibility to two peptide boronates, with IC50s of 181鈥塶M and 2635鈥塶M against mutant versus 62鈥塶M and 477鈥塶M against wild type parasites for MMV1579506 and MMV1794229, respectively, although significance could not be formally assessed due to the small number of mutant parasites with available data. The other 尾2 and 尾5 mutations and mutations in other subunits were not associated with susceptibility to tested compounds. Against culture-adapted Ugandan isolates, two asparagine ethylenediamines and the peptide proteasome inhibitors WLW-vinyl sulfone and WLL-vinyl sulfone (which were not studied ex vivo) demonstrated low nM activity, without decreased activity against 尾2 S214F mutant parasites. Overall, proteasome inhibitors had potent activity against P. falciparum isolates circulating in Uganda, and genetic variation in proteasome targets was uncommon