Plasmodium ovale wallikeri and P. ovale curtisi Infections and Diagnostic Approaches to Imported Malaria, France, 2013-2018.

We retrospectively analyzed epidemiologic, clinical, and biologic characteristics of 368 Plasmodium ovale wallikeri and 309 P. ovale curtisi infections treated in France during January 2013­December 2018. P. ovale wallikeri infections displayed deeper thrombocytopenia and shorter latency periods. Despite similar clinical manifestations, P. ovale wallikeri­infected patients were more frequently treated with artemisinin-based combination therapy. Although the difference was not statistically significant, P. ovale wallikeri­infected patients were 5 times more frequently hospitalized in intensive care or intermediate care and had a higher proportion of severe thrombocytopenia than P. ovale curtisi­infected patients. Rapid diagnostic tests that detect aldolase were more efficient than those detecting Plasmodium lactate dehydrogenase. Sequence analysis of the potra gene from 90 P. ovale isolates reveals an insufficient polymorphism for relapse typing.

Synthesis and antiplasmodial evaluation of 1H-1,2,3-triazole grafted 4-aminoquinoline-benzoxaborole hybrids and benzoxaborole analogues.

A library of 1H-1,2,3-triazole-tethered 4-aminoquinoline-benzoxaborole hybrids as well as aryl substituted benzoxaborole analogues was synthesized and screened for their anti-plasmodial efficacy against both chloroquine-susceptibility 3D7 and chloroquine-resistant W2 strains of P. falciparum. The inclusion of quinoline core among the synthesized analogues resulted in substantial enhancement of anti-plasmodial activities. Further, the spacer of a flexible alkyl chain is marginally preferred over piperazyl-ethyl in inhibiting growth of P. falciparum. The most potent 4-aminoquinoline-benzoxaborole conjugate with ethyl as spacer exhibited IC50 values of 4.15 and 3.78 µM against 3D7 CQ-susceptible and W2 CQ-resistant strains of P. falciparum with lower cross resistance with Chloroquine. There was no difference in anti-plasmodial activities between the CQ-susceptible 3D7 and CQ-resistant W2 strains of P. falciparum for the benzoxaborole derivatives lacking a quinoline core.

Baseline and multinormal distribution of ex vivo susceptibilities of Plasmodium falciparum to methylene blue in Africa, 2013-18.

BACKGROUND: Plasmodium falciparum resistance to most antimalarial compounds has emerged in Southeast Asia and spread to Africa. In this context, the development of new antimalarial drugs is urgent. OBJECTIVES: To determine the baseline in vitro activity of methylene blue (Proveblue®) on African isolates and to determine whether parasites have different phenotypes of susceptibility to methylene blue. METHODS: Ex vivo susceptibility to methylene blue was measured for 609 P. falciparum isolates of patients hospitalized in France for malaria imported from Africa. A Bayesian statistical analysis was designed to describe the distribution of median effective concentration (EC50) estimates. RESULTS: The EC50 ranged from 0.16 to 87.2 nM with a geometric mean of 7.17 nM (95% CI = 6.21-8.13). The 609 EC50 values were categorized into four components: A (mean = 2.5 nM; 95% CI = 2.28-2.72), B (mean = 7.44 nM; 95% CI = 7.07-7.81), C (mean = 16.29 nM; 95% CI = 15.40-17.18) and D (mean = 38.49 nM; 95% CI = 34.14-42.84). The threshold value for in vitro reduced susceptibility to methylene blue was estimated at 35 nM using the geometric mean of EC50 plus 2 SDs of the 609 isolates. This cut-off also corresponds to the lower limit of the 95% CI of the methylene blue EC50 of component D. Thirty-five isolates (5.7%) displayed EC50 values above this threshold. CONCLUSIONS: Methylene blue exerts a promising efficacy against P. falciparum and is a potential partner for triple combinations.

Prevalence of mutations in the Plasmodium falciparum chloroquine resistance transporter, PfCRT, and association with ex vivo susceptibility to common anti-malarial drugs against African Plasmodium falciparum isolates.

BACKGROUND: The Plasmodium falciparum chloroquine transporter gene (pfcrt) is known to be involved in chloroquine and amodiaquine resistance, and more particularly the mutations on the loci 72 to 76 localized within the second exon. Additionally, new mutations (T93S, H97Y, C101F, F145I, M343L, C350R and G353V) were recently shown to be associated with in vitro reduced susceptibility to piperaquine in Asian or South American P. falciparum strains. However, very few data are available on the prevalence of these mutations and their effect on parasite susceptibility to anti-malarial drugs, and more particularly piperaquine in Africa. METHODS: A molecular investigation of these mutations was performed in 602 African P. falciparum parasites collected between 2017 and 2018 on malaria patients hospitalized in France after a travel in African countries. Associations between genotypes and in vitro susceptibilities to piperaquine and standard antimalarial drugs were assessed. RESULTS: None of the mutations, previously described as associated with piperaquine resistance, was found in the 602 P. falciparum African isolates. The K76T mutation is associated with resistance to chloroquine (p < 0.0002) and desethylamodiaquine (p < 0.002) in Africa. The K76T mutation is not associated with in vitro reduced susceptibility to piperaquine. The mutation I356T, identified in 54.7% (n = 326) of the African isolates, was significantly associated with reduced susceptibility to quinine (p < 0.02) and increased susceptibility to mefloquine (p < 0.04). The K76T and I356T mutations were significantly associated in West African isolates (p = 0.008). CONCLUSION: None of the mutations in pfcrt found to be associated with piperaquine reduced susceptibility in Asia or South America (T93S, H97Y, C101F, F145I, M343L C350R and G353V) were found in the 602 African isolates including the three isolates with reduced susceptibility to piperaquine. The K76T mutation, involved in resistance to chloroquine and amodiaquine, and the I356T mutation were not associated with in vitro reduced susceptibility to piperaquine. Differences in mefloquine susceptibility between I356 and 356T isolates were, while statistically different, minimal. Further analyses are needed with a more important sample size from the same geographic area to confirm the role of the I356T mutation on quinine susceptibility.

Cytotoxic and Anti-Plasmodial Activities of Stephania dielsiana Y.C. Wu Extracts and the Isolated Compounds.

Natural products remain a viable source of novel therapeutics, and as detection and extraction techniques improve, we can identify more molecules from a broader set of plant tissues. The aim of this study was an investigation of the cytotoxic and anti-plasmodial activities of the methanol extract from Stephania dielsiana Y.C. Wu leaves and its isolated compounds. Our study led to the isolation of seven alkaloids, among which oxostephanine (1) is the most active against several cancer cell lines including HeLa, MDA-MB231, MDA-MB-468, MCF-7, and non-cancer cell lines, such as 184B5 and MCF10A, with IC50 values ranging from 1.66 to 4.35 µM. Morever, oxostephanine (1) is on average two-fold more active against cancer cells than stephanine (3), having a similar chemical structure. Cells treated with oxostephanine (1) are arrested at G2/M cell cycle, followed by the formation of aneuploidy and apoptotic cell death. The G2/M arrest appears to be due, at least in part, to the inactivation of Aurora kinases, which is implicated in the onset and progression of many forms of human cancer. An in-silico molecular modeling study suggests that oxostephanine (1) binds to the ATP binding pocket of Aurora kinases to inactivate their activities. Unlike oxostephanine (1), thailandine (2) is highly effective against only the triple-negative MDA-MB-468 breast cancer cells. However, it showed excellent selectivity against the cancer cell line when compared to its effects on non-cancer cells. Furthermore, thailandine (2) showed excellent anti-plasmodial activity against both chloroquine-susceptible 3D7 and chloroquine-resistant W2 Plasmodium falciparum strains. The structure-activity relationship of isolated compound was also discussed in this study. The results of this study support the traditional use of Stephania dielsiana Y.C. Wu and the lead molecules identified can be further optimized for the development of highly effective and safe anti-cancer and anti-plasmodial drugs.

In Vitro Antiviral Activity of Doxycycline against SARS-CoV-2.

In December 2019, a new severe acute respiratory syndrome coronavirus (SARS-CoV-2), causing coronavirus disease 2019 (COVID-19), emerged in Wuhan, China. Despite containment measures, SARS-CoV-2 spread in Asia, Southern Europe, then in America and currently in Africa. Identifying effective antiviral drugs is urgently needed. An efficient approach to drug discovery is to evaluate whether existing approved drugs can be efficient against SARS-CoV-2. Doxycycline, which is a second-generation tetracycline with broad-spectrum antimicrobial, antimalarial and anti-inflammatory activities, showed in vitro activity on Vero E6 cells infected with a clinically isolated SARS-CoV-2 strain (IHUMI-3) with median effective concentration (EC50) of 4.5 ± 2.9 µM, compatible with oral uptake and intravenous administrations. Doxycycline interacted both on SARS-CoV-2 entry and in replication after virus entry. Besides its in vitro antiviral activity against SARS-CoV-2, doxycycline has anti-inflammatory effects by decreasing the expression of various pro-inflammatory cytokines and could prevent co-infections and superinfections due to broad-spectrum antimicrobial activity. Therefore, doxycycline could be a potential partner of COVID-19 therapies. However, these results must be taken with caution regarding the potential use in SARS-CoV-2-infected patients: it is difficult to translate in vitro study results to actual clinical treatment in patients. In vivo evaluation in animal experimental models is required to confirm the antiviral effects of doxycycline on SARS-CoV-2 and more trials of high-risk patients with moderate to severe COVID-19 infections must be initiated.

Baseline Ex Vivo and Molecular Responses of Plasmodium falciparum Isolates to Piperaquine before Implementation of Dihydroartemisinin-Piperaquine in Senegal.

Dihydroartemisinin-piperaquine, which was registered in 2017 in Senegal, is not currently used as the first-line treatment against uncomplicated malaria. A total of 6.6% to 17.1% of P. falciparum isolates collected in Dakar in 2013 to 2015 showed ex vivo-reduced susceptibility to piperaquine. Neither the exonuclease E415G mutation nor the copy number variation of the plasmepsin II gene (Pfpm2), associated with piperaquine resistance in Cambodia, was detected in Senegalese parasites.

Are k13 and plasmepsin II genes, involved in Plasmodium falciparum resistance to artemisinin derivatives and piperaquine in Southeast Asia, reliable to monitor resistance surveillance in Africa?

Mutations in the propeller domain of Plasmodium falciparum kelch 13 (Pfk13) gene are associated with artemisinin resistance in Southeast Asia. Artemisinin resistance is defined by increased ring survival rate and delayed parasite clearance half-life in patients. Additionally, an amplification of the Plasmodium falciparum plasmepsin II gene (pfpm2), encoding a protease involved in hemoglobin degradation, has been found to be associated with reduced in vitro susceptibility to piperaquine in Cambodian P. falciparum parasites and with dihydroartemisinin-piperaquine failures in Cambodia. The World Health Organization (WHO) has recommended the use of these two genes to track the emergence and the spread of the resistance to dihydroartemisinin-piperaquine in malaria endemic areas. Although the resistance to dihydroartemisinin-piperaquine has not yet emerged in Africa, few reports on clinical failures suggest that k13 and pfpm2 would not be the only genes involved in artemisinin and piperaquine resistance. It is imperative to identify molecular markers or drug resistance genes that associate with artemisinin and piperaquine in Africa. K13 polymorphisms and Pfpm2 copy number variation analysis may not be sufficient for monitoring the emergence of dihydroartemisinin-piperaquine resistance in Africa. But, these markers should not be ruled out for tracking the emergence of resistance.

Low polymorphisms in pfact, pfugt and pfcarl genes in African Plasmodium falciparum isolates and absence of association with susceptibility to common anti-malarial drugs.

BACKGROUND: Resistance to all available anti-malarial drugs has emerged and spread including artemisinin derivatives and their partner drugs. Several genes involved in artemisinin and partner drugs resistance, such as pfcrt, pfmdr1, pfK13 or pfpm2, have been identified. However, these genes do not properly explain anti-malarial drug resistance, and more particularly clinical failures observed in Africa. Mutations in genes encoding for Plasmodium falciparum proteins, such as P. falciparum Acetyl-CoA transporter (PfACT), P. falciparum UDP-galactose transporter (PfUGT) and P. falciparum cyclic amine resistance locus (PfCARL) have recently been associated to resistance to imidazolopiperazines and other unrelated drugs. METHODS: Mutations on pfugt, pfact and pfcarl were characterized on 86 isolates collected in Dakar, Senegal and 173 samples collected from patients hospitalized in France after a travel in African countries from 2015 and 2016 to assess their potential association with ex vivo susceptibility to chloroquine, quinine, lumefantrine, monodesethylamodiaquine, mefloquine, dihydroartemisinin, artesunate, doxycycline, pyronaridine and piperaquine. RESULTS: No mutations were found on the genes pfugt and pfact. None of the pfcarl described mutations were identified in these samples from Africa. The K784N mutation was found in one sample and the K734M mutation was identified on 7.9% of all samples for pfcarl. The only significant differences in ex vivo susceptibility according to the K734M mutation were observed for pyronaridine for African isolates from imported malaria and for doxycycline for Senegalese parasites. CONCLUSION: No evidence was found of involvement of these genes in reduced susceptibility to standard anti-malarial drugs in African P. falciparum isolates.

Absence of a High Level of Duplication of the Plasmepsin II Gene in Africa.

Resistance to piperaquine has been associated with the amplification of the plasmepsin II gene in Cambodia. None of the 175 African isolates that we analyzed had plasmepsin II gene amplification (piperaquine 50% inhibitory concentration ranged from 0.94 to 137.5 nM), suggesting there is a low prevalence of piperaquine reduced susceptibility in Africa. Additionally, the few isolates with reduced susceptibility to piperaquine did not harbor amplification of the plasmepsin II gene.

The D113N mutation in the RING E3 ubiquitin protein ligase gene is not associated with ex vivo susceptibility to common anti-malarial drugs in African Plasmodium falciparum isolates.

BACKGROUND: Plasmodium falciparum resistance to artemisinin-based combination therapy has emerged and spread in Southeast Asia. In areas where artemisinin resistance is emerging, the efficacy of combination is now based on partner drugs. In this context, the identification of novel markers of resistance is essential to monitor the emergence and spread of resistance to these partner drugs. The ubiquitylation pathway could be a possible target for anti-malarial compounds and might be involved in resistance. Polymorphisms in the E3 ubiquitin-protein ligase (PF3D7_0627300) gene could be associated with decreased in vitro susceptibility to anti-malarial drugs. METHODS: Plasmodium falciparum isolates were collected from patients hospitalized in France with imported malaria from a malaria-endemic country from January 2015 to December 2016 and, more particularly, from African French-speaking countries. In total, 215 isolates were successfully sequenced for the E3 ubiquitin-protein ligase gene and assessed for ex vivo susceptibility to anti-malarial drugs. RESULTS: The D113N mutation in the RING E3 ubiquitin-protein ligase gene was present in 147 out of the 215 samples (68.4%). The IC50 values for the ten anti-malarial drugs were not significantly different between the wild-type and mutant parasites (p values between 0.225 and 0.933). There was no significant difference in terms of the percentage of parasites with decreased susceptibility between the D113 wild-type and the 133N mutated P. falciparum strains (p values between 0.541 and 1). CONCLUSION: The present data confirmed the absence of the association between polymorphisms in the RING E3 ubiquitin-protein ligase gene and the ex vivo susceptibility to common anti-malarial drugs in African P. falciparum isolates.

Association between Polymorphisms in the Pfmdr6 Gene and Ex Vivo Susceptibility to Quinine in Plasmodium falciparum Parasites from Dakar, Senegal.

Polymorphisms and the overexpression of transporter genes, especially of the ATP-binding cassette superfamily, have been involved in antimalarial drug resistance. The objective of this study was to use 77 Senegalese Plasmodium falciparum isolates to evaluate the association between the number of Asn residues in the polymorphic microsatellite region of the Plasmodium falciparum multidrug resistance 6 gene (Pfmdr6) and the ex vivo susceptibility to antimalarials. A significant association was observed between the presence of 7 or 9 Asn repeats and reduced susceptibility to quinine.

Absence of Association between Polymorphisms in the RING E3 Ubiquitin Protein Ligase Gene and Ex Vivo Susceptibility to Conventional Antimalarial Drugs in Plasmodium falciparum Isolates from Dakar, Senegal.

The RING E3 ubiquitin protein ligase is crucial for facilitating the transfer of ubiquitin. The only polymorphism identified in the E3 ubiquitin protein ligase gene was the D113N mutation (62.5%) but was not significantly associated with the 50% inhibitory concentration (IC50) of conventional antimalarial drugs. However, some mutated isolates (D113N) present a trend of reduced susceptibility to piperaquine (P = 0.0938). To evaluate the association of D113N polymorphism with susceptibility to antimalarials, more isolates are necessary.

Analysis of trapped mosquito excreta as a noninvasive method to reveal biodiversity and arbovirus circulation.

Emerging and endemic mosquito-borne viruses can be difficult to detect and monitor because they often cause asymptomatic infections in human or vertebrate animals or cause nonspecific febrile illness with a short recovery waiting period. Some of these pathogens circulate into complex cryptic cycles involving several animal species as reservoir or amplifying hosts. Detection of cases in vertebrate hosts can be complemented by entomological surveillance, but this method is not adapted to low infection rates in mosquito populations that typically occur in low or nonendemic areas. We identified West Nile virus circulation in Camargue, a wetland area in South of France, using a cost-effective xenomonitoring method based on the molecular detection of virus in excreta from trapped mosquitoes. We also succeeded at identifying the mosquito species community on several sampling sites, together with the vertebrate hosts on which they fed prior to being captured using amplicon-based metabarcoding on mosquito excreta without processing any mosquitoes. Mosquito excreta-based virus surveillance can complement standard surveillance methods because it is cost-effective and does not require personnel with a strong background in entomology. This strategy can also be used to noninvasively explore the ecological network underlying arbovirus circulation.

Methylene Blue-Based Combination Therapy with Amodiaquine Prevents Severe Malaria in an Experimental Rodent Model.

Untreated malaria can progress rapidly to severe forms (<24 h). Moreover, resistance to antimalarial drugs is a threat to global efforts to protect people from malaria. Given this, it is clear that new chemotherapy must be developed. We contribute new data about using methylene blue (MB) to cure malaria and cerebral malaria in a combined therapy with common antimalarial drugs, including mefloquine (MQ) and amodiaquine (AQ). A C57BL6/J mouse model was used in an experimental cerebral malaria model. Mice were infected with Plasmodium berghei ANKA on Day 0 (D0) and the treatment started on D3 (nearly 1% parasitaemia) with AQ, MQ or MB alone or in combination with AQ or MQ. AQ, MQ and MB alone were unable to prevent cerebral malaria as part of a late chemotherapy. MB-based combination therapies were efficient even if treatment began at a late stage. We found a significant difference in survival rate (p < 0.0001) between MBAQ and the untreated group, but also with the AQ (p = 0.0024) and MB groups (p < 0.0001). All the infected mice treated with MB in combination with AQ were protected from cerebral malaria. Partial protection was demonstrated with MB associated with MQ. In this group, a significant difference was found between MBMQ and the untreated group (p < 0.0001), MQ (p = 0.0079) and MB (p = 0.0039). MB associated with AQ would be a good candidate for preventing cerebral malaria.

Comparative Assessment of the Sensitivity of Ten Commercial Rapid Diagnostic Test Kits for the Detection of Plasmodium.

Malaria is one of the most common tropical diseases encountered by members of the French military who are deployed in operations under constrained conditions in malaria-endemic areas. Blood smear microscopy-the gold standard for malaria diagnosis-is often not available in such settings, where the detection of malaria relies on rapid diagnostic tests (RDTs). Ten RDTs (from Biosynex, Carestart, Humasis, SD Bioline, and CTK Biotech), based on the detection of the Plasmodium falciparum histidine-rich protein 2 (HRP2) or lactate dehydrogenase (pLDH, PfLDH, or PvLDH), were assessed against 159 samples collected from imported malaria cases, including 79 P. falciparum, 37 P. vivax, 22 P. ovale, and 21 P. malariae parasites. Samples had been previously characterised using microscopy and real-time PCR. The overall sensitivities for the Plasmodium test ranged from 69.8% (111/159) to 95% (151/159). There was no significant difference for the specific detection of P. falciparum (96.2% to 98.7%, p = 0.845). No significant difference was found between sensitivities to P. vivax by pan LDH or pvLDH (81.1% (30/37) to 94.6% (35/37) (p = 0.845)). Some of the RDTs missed most of P. ovale and P. malariae, with sensitivities for all RDTs ranging respectively from 4.5% (1/22) to 81.8% (18/22) and 14.3% (3/21) to 95.2% (20/21). Carestart Malaria Pf/Pan (pLDH) Ag G0121, a pLDH-based RDT (PfLDH and pLDH), showed the highest sensitivities to P. falciparum (98.7%, 78/79), P. vivax (94.6%, 35/37), P. ovale (81.8%, 18/22), and P. malariae (95.2%, 20/21) and meets the requirements for military deployments in malaria-endemic areas.

Repurposing of Doxycycline to Hinder the Viral Replication of SARS-CoV-2: From in silico to in vitro Validation.

Since the rapid spread of coronavirus disease (COVID-19) became a global pandemic, healthcare ministries around the world have recommended specific control methods such as quarantining infected peoples, identifying infections, wearing mask, and practicing hand hygiene. Since no effective treatment for COVID-19 has yet been discovered, a variety of drugs approved by Food and Drug Administration (FDA) have been suggested for repurposing strategy. In the current study, we predicted that doxycycline could interact with the nucleotide triphosphate (NTP) entry channel, and is therefore expected to hinder the viral replication of SARS-CoV-2 RNA-dependent RNA-polymerase (RdRp) through docking analysis. Further, the molecular dynamics results revealed that the RdRp-Doxycycline complex was structurally relatively stable during the dynamic period (100 ns), and its complex maintained close contact with their active catalytic domains of SARS-CoV-2 RdRp. The molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) calculation of binding free energy also showed that the doxycycline has worthy affinities with SARS-CoV-2 RdRp. As expected, doxycycline effectively inhibited the viral replication of IHU strains of SARS-CoV-2 (IHUMI-3 and IHUMI-6), identified from the hospitalized patients in IHU Méditerranée Infection (IHUMI), Marseille, France. Moreover, doxycycline inhibited the viral load in vitro at both on-entry and after viral entry of IHU variants of SARS-CoV-2. The results suggest that doxycycline exhibits strains-dependant antiviral activity against COVID-19. As a result, the current study concludes that doxycycline may be more effective in combination with other drugs for better COVID-19 treatment efficacy.

Antiviral Activity of Repurposing Ivermectin against a Panel of 30 Clinical SARS-CoV-2 Strains Belonging to 14 Variants.

Over the past two years, several variants of SARS-CoV-2 have emerged and spread all over the world. However, infectivity, clinical severity, re-infection, virulence, transmissibility, vaccine responses and escape, and epidemiological aspects have differed between SARS-CoV-2 variants. Currently, very few treatments are recommended against SARS-CoV-2. Identification of effective drugs among repurposing FDA-approved drugs is a rapid, efficient and low-cost strategy against SARS-CoV-2. One of those drugs is ivermectin. Ivermectin is an antihelminthic agent that previously showed in vitro effects against a SARS-CoV-2 isolate (Australia/VI01/2020 isolate) with an IC50 of around 2 µM. We evaluated the in vitro activity of ivermectin on Vero E6 cells infected with 30 clinically isolated SARS-CoV-2 strains belonging to 14 different variants, and particularly 17 strains belonging to six variants of concern (VOC) (variants related to Wuhan, alpha, beta, gamma, delta and omicron). The in vitro activity of ivermectin was compared to those of chloroquine and remdesivir. Unlike chloroquine (EC50 from 4.3 ± 2.5 to 29.3 ± 5.2 µM) or remdesivir (EC50 from 0.4 ± 0.3 to 25.2 ± 9.4 µM), ivermectin showed a relatively homogeneous in vitro activity against SARS-CoV-2 regardless of the strains or variants (EC50 from 5.1 ± 0.5 to 6.7 ± 0.4 µM), except for one omicron strain (EC50 = 1.3 ± 0.5 µM). Ivermectin (No. EC50 = 219, mean EC50 = 5.7 ± 1.0 µM) was, overall, more potent in vitro than chloroquine (No. EC50 = 214, mean EC50 = 16.1 ± 9.0 µM) (p = 1.3 × 10-34) and remdesivir (No. EC50 = 201, mean EC50 = 11.9 ± 10.0 µM) (p = 1.6 × 10-13). These results should be interpreted with caution regarding the potential use of ivermectin in SARS-CoV-2-infected patients: it is difficult to translate in vitro study results into actual clinical treatment in patients.

A Hybrid of Amodiaquine and Primaquine Linked by Gold(I) Is a Multistage Antimalarial Agent Targeting Heme Detoxification and Thiol Redox Homeostasis.

Hybrid-based drugs linked through a transition metal constitute an emerging concept for Plasmodium intervention. To advance the drug design concept and enhance the therapeutic potential of this class of drugs, we developed a novel hybrid composed of quinolinic ligands amodiaquine (AQ) and primaquine (PQ) linked by gold(I), named [AuAQPQ]PF6. This compound demonstrated potent and efficacious antiplasmodial activity against multiple stages of the Plasmodium life cycle. The source of this activity was thoroughly investigated by comparing parasite susceptibility to the hybrid's components, the annotation of structure-activity relationships and studies of the mechanism of action. The activity of [AuAQPQ]PF6 for the parasite's asexual blood stages was influenced by the presence of AQ, while its activity against gametocytes and pre-erythrocytic parasites was influenced by both quinolinic components. Moreover, the coordination of ligands to gold(I) was found to be essential for the enhancement of potency, as suggested by the observation that a combination of quinolinic ligands does not reproduce the antimalarial potency and efficacy as observed for the metallic hybrid. Our results indicate that this gold(I) hybrid compound presents a dual mechanism of action by inhibiting the beta-hematin formation and enzymatic activity of thioredoxin reductases. Overall, our findings support the potential of transition metals as a dual chemical linker and an antiplasmodial payload for the development of hybrid-based drugs.

Prevalence of Mutations in the pfcoronin Gene and Association with Ex Vivo Susceptibility to Common Quinoline Drugs against Plasmodium falciparum.

BACKGROUND: Artemisinin-based combination therapy (ACT) was recommended to treat uncomplicated falciparum malaria. Unlike the situation in Asia where resistance to ACT has been reported, artemisinin resistance has not yet emerged in Africa. However, some rare failures with ACT or patients continuing to be parasitaemic on day 3 after ACT treatment have been reported in Africa or in travellers returning from Africa. Three mutations (G50E, R100K, and E107V) in the pfcoronin gene could be responsible for artemisinin resistance in Africa. METHODS: The aims of this study were first to determine the prevalence of mutations in the pfcoronin gene in African P. falciparum isolates by Sanger sequencing, by targeting the 874 samples collected from patients hospitalised in France after returning from endemic areas in Africa between 2018 and 2019, and secondly to evaluate their association with in vitro reduced susceptibility to standard quinoline antimalarial drugs, including chloroquine, quinine, mefloquine, desethylamodiaquine, lumefantrine, piperaquine, and pyronaridine. RESULTS: The three mutations in the pfcoronin gene (50E, 100K, and 107V) were not detected in the 874 P. falciparum isolates. Current data show that another polymorphism (P76S) is present in many countries of West Africa (mean prevalence of 20.7%) and Central Africa (11.9%) and, rarely, in East Africa (4.2%). This mutation does not appear to be predictive of in vitro reduced susceptibility to quinolines, including artemisinin derivative partners in ACT such as amodiaquine, lumefantrine, piperaquine, pyronaridine, and mefloquine. Another mutation (V62M) was identified at low prevalence (overall prevalence of 1%). CONCLUSIONS: The 76S mutation is present in many African countries with a prevalence above 10%. It is reassuring that this mutation does not confer in vitro resistance to ACT partners.