Last data update: Jul 01, 2024. (Total: 47134 publications since 2009)
Records 1-5 (of 5 Records) |
Query Trace: Ringwald P [original query] |
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Reply to Rasmussen and Ringwald, "Continued Low Efficacy of Artemether-Lumefantrine in Angola?"
Dimbu PR , Horth R , Cândido ALM , Ferreira CM , Caquece F , Garcia LEA , André K , Pembele G , Jandondo D , Bondo BJ , Nieto Andrade B , Labuda S , Ponce de León G , Kelley J , Patel D , Svigel SS , Talundzic E , Lucchi N , Morais JFM , Fortes F , Martins JF , Pluciński MM . Antimicrob Agents Chemother 12/28/2021 65 (6) We thank Rasmussen and Ringwald for further highlighting the importance of routine monitoring of antimalarial drug efficacy in sub-Saharan Africa, including Angola (1). Longitudinal monitoring is critical to identify potential new, persistent, and/or expanding foci of parasite resistance to available drugs. In 3 of the last 4 rounds, artemether-lumefantrine (AL) was estimated to have an efficacy of <90% at one of the three sentinel sites in Angola. To our knowledge, in sub-Saharan Africa, only Angola and Burkina Faso (2) have shown AL efficacy of <90% across multiple therapeutic efficacy study (TES) rounds. Thus, we chose a title to highlight this persistent concern. | | We concur that the significance of the high rates of day 2 slide positivity in Lunda Sul Province is not fully known, and as pointed out, there may be various explanations for this finding. Measuring drug levels is resource intensive and not feasible every year, but this could help rule out underdosing in future studies. However, we believe our study procedures, as described in this and previous studies, are robust and thus make systematic underdosing unlikely. We have always strictly adhered to WHO guidelines, including hemoglobin criteria and analysis of day 1 severe cases, to inform our classifications. |
Local emergence in Amazonia of Plasmodium falciparum k13 C580Y mutants associated with in vitro artemisinin resistance.
Mathieu LC , Cox H , Early AM , Mok S , Lazrek Y , Paquet JC , Ade MP , Lucchi NW , Grant Q , Udhayakumar V , Alexandre JS , Demar M , Ringwald P , Neafsey DE , Fidock DA , Musset L . Elife 2020 9 Antimalarial drug resistance has historically arisen through convergent de novo mutations in Plasmodium falciparum parasite populations in Southeast Asia and South America. For the past decade in Southeast Asia, artemisinins, the core component of first-line antimalarial therapies, have experienced delayed parasite clearance associated with several pfk13 mutations, primarily C580Y. We report that mutant pfk13 has emerged independently in Guyana, with genome analysis indicating an evolutionary origin distinct from Southeast Asia. Pfk13 C580Y parasites were observed in 1.6% (14/854) of samples collected in Guyana in 2016-2017. Introducing pfk13 C580Y or R539T mutations by gene editing into local parasites conferred high levels of in vitro artemisinin resistance. In vitro growth competition assays revealed a fitness cost associated with these pfk13 variants, potentially explaining why these resistance alleles have not increased in frequency more quickly in South America. These data place local malaria control efforts at risk in the Guiana Shield. | All recommended treatments against malaria include a drug called artemisinin or some of its derivatives. However, there are concerns that Plasmodium falciparum, the parasite that causes most cases of malaria, will eventually develop widespread resistance to the drug. A strain of P. falciparum partially resistant to artemisinin was seen in Cambodia in 2008, and it has since spread across Southeast Asia. The resistance appears to be frequently linked to a mutation known as pfk13 C580Y. Southeast Asia and Amazonia are considered to be hotspots for antimalarial drug resistance, and the pfk13 C580Y mutation was detected in the South American country of Guyana in 2010. To examine whether the mutation was still circulating in this part of the world, Mathieu et al. collected and analyzed 854 samples across Guyana between 2016 and 2017. Overall, 1.6% of the samples had the pfk13 C580Y mutation, but this number was as high as 8.8% in one region. Further analyses revealed that the mutation in Guyana had not spread from Southeast Asia, but that it had occurred in Amazonia independently. To better understand the impact of the pfk13 C580Y mutation, Mathieu et al. introduced this genetic change into non-resistant parasites from a country neighbouring Guyana. As expected, the mutation made P. falciparum highly resistant to artemisinin, but it also slowed the growth rate of the parasite. This disadvantage may explain why the mutation has not spread more rapidly through Guyana in recent years. Artemisinin and its derivatives are always associated with other antimalarial drugs to slow the development of resistance; there are concerns that reduced susceptibility to artemisinin leads to the parasites becoming resistant to the partner drugs. Further research is needed to evaluate how the pfk13 C580Y mutation affects the parasite's response to the typical combination of drugs that are given to patients. | eng |
Prevalence of molecular markers of artemisinin and lumefantrine resistance among patients with uncomplicated Plasmodium falciparum malaria in three provinces in Angola, 2015.
Ljolje D , Dimbu PR , Kelley J , Goldman I , Nace D , Macaia A , Halsey ES , Ringwald P , Fortes F , Udhayakumar V , Talundzic E , Lucchi NW , Plucinski MM . Malar J 2018 17 (1) 84 BACKGROUND: Artemisinin-based combination therapy is the first-line anti-malarial treatment for uncomplicated Plasmodium falciparum infection in Angola. To date, the prevalence of polymorphisms in the pfk13 gene, associated with artemisinin resistance, and pfmdr1, associated with lumefantrine resistance, have not been systematically studied in Angola. METHODS: DNA was isolated from pretreatment and late treatment failure dried blood spots collected during the 2015 round of therapeutic efficacy studies in Benguela, Lunda Sul, and Zaire Provinces in Angola. The pfk13 propeller domain and pfmdr1 gene were sequenced and analysed for polymorphisms. Pfmdr1 copy number variation was assessed using a real-time PCR method. The association between pfmdr1 and pfk13 mutations and treatment failure was investigated. RESULTS: The majority of pretreatment (99%, 466/469) and all late treatment failure (100%, 50/50) samples were wild type for pfk13. Three of the pretreatment samples (1%) carried the A578S mutation commonly observed in Africa and not associated with artemisinin resistance. All 543 pretreatment and day of late treatment failure samples successfully analysed for pfmdr1 copy number variation carried one copy of pfmdr1. The NYD haplotype was the predominant pfmdr1 haplotype, present in 63% (308/491) of pretreatment samples, followed by NFD, which was present in 32% (157/491) of pretreatment samples. The pfmdr1 N86 allele was overrepresented in day of late treatment failure samples from participants receiving artemether-lumefantrine (p value 0.03). CONCLUSIONS: The pretreatment parasites in patients participating in therapeutic efficacy studies in 2015 in Angola's three sentinel sites showed genetic evidence of susceptibility to artemisinins, consistent with clinical outcome data showing greater than 99% day 3 clearance rates. The lack of increased pfmdr1 copy number is consistent with previous reports from sub-Saharan Africa. Although pfmdr1 NYD and NFD haplotypes were overrepresented in artemether-lumefantrine late treatment failure samples, their role as markers of resistance was unclear given that these haplotypes were also present in the majority of successfully treated patients in the artemether-lumefantrine treatment arms. |
Efficacy of artemether-lumefantrine, artesunate-amodiaquine, and dihydroartemisinin-piperaquine for treatment of uncomplicated Plasmodium falciparum malaria in Angola, 2015.
Plucinski MM , Dimbu PR , Macaia AP , Ferreira CM , Samutondo C , Quivinja J , Afonso M , Kiniffo R , Mbounga E , Kelley JS , Patel DS , He Y , Talundzic E , Garrett DO , Halsey ES , Udhayakumar V , Ringwald P , Fortes F . Malar J 2017 16 (1) 62 BACKGROUND: Recent anti-malarial resistance monitoring in Angola has shown efficacy of artemether-lumefantrine (AL) in certain sites approaching the key 90% lower limit of efficacy recommended for artemisinin-based combination therapy. In addition, a controversial case of malaria unresponsive to artemisinins was reported in a patient infected in Lunda Sul Province in 2013. METHODS: During January-June 2015, investigators monitored the clinical and parasitological response of children with uncomplicated Plasmodium falciparum infection treated with AL, artesunate-amodiaquine (ASAQ), or dihydroartemisinin-piperaquine (DP). The study comprised two treatment arms in each of three provinces: Benguela (AL, ASAQ), Zaire (AL, DP), and Lunda Sul (ASAQ, DP). Samples from treatment failures were analysed for molecular markers of resistance for artemisinin (K13) and lumefantrine (pfmdr1). RESULTS: A total of 467 children reached a study endpoint. Fifty-four treatment failures were observed: four early treatment failures, 40 re-infections and ten recrudescences. Excluding re-infections, the 28-day microsatellite-corrected efficacy was 96.3% (95% CI 91-100) for AL in Benguela, 99.9% (95-100) for ASAQ in Benguela, 88.1% (81-95) for AL in Zaire, and 100% for ASAQ in Lunda Sul. For DP, the 42-day corrected efficacy was 98.8% (96-100) in Zaire and 100% in Lunda Sul. All treatment failures were wild type for K13, but all AL treatment failures had pfmdr1 haplotypes associated with decreased lumefantrine susceptibility. CONCLUSIONS: No evidence was found to corroborate the specific allegation of artemisinin resistance in Lunda Sul. The efficacy below 90% of AL in Zaire matches findings from 2013 from the same site. Further monitoring, particularly including measurement of lumefantrine blood levels, is recommended. |
The threat of artemisinin-resistant malaria
Dondorp AM , Fairhurst RM , Slutsker L , Macarthur JR , M DJg , Guerin PJ , Wellems TE , Ringwald P , Newman RD , Plowe CV . N Engl J Med 2011 365 (12) 1073-5 In the 1970s, Chinese government scientists working on a secret “Project 523” developed a new class of potent antimalarial drugs, the artemisinins or qinghaosu derivatives. In mostly unpublished work that has just been recognized by a 2011 Lasker Award to Tu Youyou, researchers in China isolated the active compounds from the plant Artemisia annua, tested them in mice, analyzed the chemical structure of the artemisinins, and demonstrated their high potency and rapid efficacy in human trials. Although they were widely used in China during the 1980s, only in the 1990s did the artemisinins come to wider global attention in the form of artemisinin-based combination therapies. Over the past decade, these highly efficacious treatments, along with other malaria-control measures, have contributed to significant reductions of the malaria burden in many areas of the world, including parts of Africa. | Together, these successes and increased funding have revived the bold aspiration to eradicate malaria. About one quarter of malaria-afflicted countries are already shifting their focus from malaria control to elimination. Past successful malaria-elimination schemes have all depended on reliable curative drugs, used in conjunction with vector-control methods. Similarly, current elimination plans rely on the long-term availability of effective antimalarial drugs — a requirement that is pivotally dependent on the efficacy of artemisinins. The artemisinin derivative artesunate has also proven to be the best drug against severe falciparum malaria. Losing the artemisinins to resistance would be a disaster for the control and treatment of malaria and would bring eradication efforts to a standstill. |
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