Identification and Deconvolution of Cross-Resistance Signals from Antimalarial Compounds Using Multidrug-Resistant Plasmodium falciparum Strains

Abstract

h Plasmodium falciparum, the most deadly agent of malaria, displays a wide variety of resistance mechanisms in the field. The ability of antimalarial compounds in development to overcome these must therefore be carefully evaluated to ensure uncompromised activity against real-life parasites. We report here on the selection and phenotypic as well as genotypic characterization of a panel of sensitive and multidrug-resistant P. falciparum strains that can be used to optimally identify and deconvolute the cross-resistance signals from an extended panel of investigational antimalarials. As a case study, the effectiveness of the selected panel of strains was demonstrated using the 1,2,4-oxadiazole series, a newly identified antimalarial series of compounds with in vitro activity against P. falciparum at nanomolar concentrations. This series of compounds was to be found inactive against several multidrug-resistant strains, and the deconvolution of this signal implicated pfcrt, the genetic determinant of chloroquine resistance. Targeted mode-of-action studies further suggested that this new chemical series might act as falcipain 2 inhibitors, substantiating the suggestion that these compounds have a site of action similar to that of chloroquine but a distinct mode of action. New antimalarials must overcome existing resistance and, ideally, prevent its de novo appearance. The panel of strains reported here, which includes recently collected as well as standard laboratory-adapted field isolates, is able to efficiently detect and precisely characterize cross-resistance and, as such, can contribute to the faster development of new, effective antimalarial drugs.

A Method for Amplicon Deep Sequencing of Drug Resistance Genes in Plasmodium falciparum Clinical Isolates from India

“…Indeed, during data analysis, we detected two variants, N86Y (36%) and N86F (64%), at Pfmdr1 codon 86 in our Dd2 sample obtained from MR4. The N86F variant has been reported in field isolates from Africa and Afghanistan ( 69 , 70 ), as well as the South Asian reference isolate Dd2 ( 11 , 71 ). It appears that the two allelic variants observed in our Dd2 sample represent two copies of Pfmdr1 , which have been observed in previous studies ( 11 ).…”

Use of a highly specific kinase inhibitor for rapid, simple and precise synchronization of Plasmodium falciparum and Plasmodium knowlesi asexual stage parasites

“…To investigate whether the 25 nM working concentration used for 3D7 would be widely applicable to other P. falciparum isolates, we determined the EC 50 of ML10 in three additional P. falciparum laboratory isolates from different parts of the world and with different drug resistance phenotypes [49]: Dd2 (originally from Southeast Asia, has increased resistance to chloroquine, cycloguanil and pyrimethamine), HB3 (originally from Honduras, has increased resistance to cycloguanil and pyrimethamine) and NF54 (isolated from a case of ‘airport malaria’; this strain has similarities to African parasite strains [50]) from which 3D7 is derived. The EC 50 values obtained for these strains were 5.14 nM (±SD 1.5 nM) for Dd2, 4.86 nM (±SD 2.9 nM) for HB3 and 6.87 nM (±SD 2.0 nM) for NF54 (Figures 2A, 2B and 2C, Table 1, Supp.…”

Síntesis y Actividad Antimalárica de Estirilquinolinas sobre Plasmodium falciparum

“…Actualmente, debido a los problemas de resistencia que presentan los parásitos a algunos de los medicamentos utilizados para su tratamiento (Vicente et al, 2007;Arroyabe et al, 2014), se hace necesario buscar nuevos agentes antimaláricos ya sean de origen natural o sintético, dado que la diversidad y complejidad genética presente en el parasito le confiere a Plasmodium la capacidad de evadir la respuesta inmune del hospedador, produciendo así variantes resistentes a los medicamentos y vacunas, originándose la supervivencia del parásito en la historia evolutiva, así como del fracaso de las estrategias empleadas con el objetivo de erradicarlo (Jiménez et al, 2005), convirtiendo esta resistencia en uno de los mayores retos que enfrenta el control de la malaria (Chugh et al, 2015).…”