Prevalence of mutations in the cysteine desulfurase IscS (Pfnfs1) gene in recurrent Plasmodium falciparum infections following artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) treatment in Matayos, Western Kenya.

BACKGROUND: Malaria remains a public health concern globally. Resistance to anti-malarial drugs has consistently threatened the gains in controlling the malaria parasites. Currently, artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP) are the treatment regimens against Plasmodium falciparum infections in many African countries, including Kenya. Recurrent infections have been reported in patients treated with AL or DP, suggesting the possibility of reinfection or parasite recrudescence associated with the development of resistance against the two therapies. The Plasmodium falciparum cysteine desulfurase IscS (Pfnfs1) K65 selection marker has previously been associated with decreased lumefantrine susceptibility. This study evaluated the frequency of the Pfnfs1 K65 resistance marker and associated K65Q resistant allele in recurrent infections collected from P. falciparum-infected individuals living in Matayos, Busia County, in western Kenya. METHODS: Archived dried blood spots (DBS) of patients with recurrent malaria infection on clinical follow-up days after treatment with either AL or DP were used in the study. After extraction of genomic DNA, PCR amplification and sequencing analysis were employed to determine the frequencies of the Pfnfs1 K65 resistance marker and K65Q mutant allele in the recurrent infections. Plasmodium falciparum msp1 and P. falciparum msp2 genetic markers were used to distinguish recrudescent infections from new infections. RESULTS: The K65 wild-type allele was detected at a frequency of 41% while the K65Q mutant allele was detected at a frequency of 22% in the recurrent samples. 58% of the samples containing the K65 wild-type allele were AL treated samples and while 42% were DP treated samples. 79% of the samples with the K65Q mutation were AL treated samples and 21% were DP treated samples. The K65 wild-type allele was detected in three recrudescent infections (100%) identified from the AL treated samples. The K65 wild-type allele was detected in two recrudescent DP treated samples (67%) while the K65Q mutant allele was identified in one DP treated (33%) recrudescent sample. CONCLUSIONS: The data demonstrate a higher frequency of the K65 resistance marker in patients with recurrent infection during the study period. The study underscores the need for consistent monitoring of molecular markers of resistance in regions of high malaria transmission.

Amodiaquine drug pressure selects nonsynonymous mutations in pantothenate kinase 1, diacylglycerol kinase, and phosphatidylinositol-4 kinase in Plasmodium berghei ANKA.

Background: Lumefantrine (LM), piperaquine (PQ), and amodiaquine (AQ), the long-acting components of the artemisinin-based combination therapies (ACTs), are a cornerstone of malaria treatment in Africa. Studies have shown that PQ, AQ, and LM resistance may arise independently of predicted modes of action. Protein kinases have emerged as mediators of drug action and efficacy in malaria parasites; however, the link between top druggable Plasmodium kinases with LM, PQ, and AQ resistance remains unclear. Using LM, PQ, or AQ-resistant Plasmodium berghei parasites, we have evaluated the association of choline kinase (CK), pantothenate kinase 1 (PANK1), diacylglycerol kinase (DAGK), and phosphatidylinositol-4 kinase (PI4Kß), and calcium-dependent protein kinase 1 (CDPK1) with LM, PQ, and AQ resistance in Plasmodium berghei ANKA. Methods: We used in silico bioinformatics tools to identify ligand-binding motifs, active sites, and sequence conservation across the different parasites. We then used PCR and sequencing analysis to probe for single nucleotide polymorphisms (SNPs) within the predicted functional motifs in the CK, PANK1, DAGK, PI4Kß, and CDPK1. Using qPCR analysis, we measured the mRNA amount of PANK1, DAGK, and PI4Kß at trophozoites and schizonts stages. Results: We reveal sequence conservation and unique ligand-binding motifs in the CK, PANK1, DAGK, PI4Kß, and CDPK1 across malaria species. DAGK, PANK1, and PI4Kß possessed nonsynonymous mutations; surprisingly, the mutations only occurred in the AQr parasites. PANK1 acquired Asn394His, while DAGK contained K270R and K292R mutations. PI4Kß had Asp366Asn, Ser1367Arg, Tyr1394Asn and Asp1423Asn. We show downregulation of PANK1, DAGK, and PI4Kß in the trophozoites but upregulation at the schizonts stages in the AQr parasites. Conclusions: The selective acquisition of the mutations and the differential gene expression in AQ-resistant parasites may signify proteins under AQ pressure. The role of the mutations in the resistant parasites and their impact on drug responses require investigations using reverse genetics techniques in malaria parasites.