Plasmodium falciparum population dynamics during the early phase of anti-malarial drug treatment in Tanzanian children with acute uncomplicated malaria

BACKGROUND\ud \ud This study aimed to explore Plasmodium falciparum population dynamics during the early phase of anti-malarial drug treatment with artemisinin-based combination therapy in children with clinical malaria in a high transmission area in Africa.\ud \ud METHODS\ud \ud A total of 50 children aged 1-10 years with acute uncomplicated P. falciparum malaria in Bagamoyo District, Tanzania, were enrolled. Participants were hospitalized and received supervised standard treatment with artemether-lumefantrine according to body weight in six doses over 3 days. Blood samples were collected 11 times, i.e. at time of diagnosis (-2 h) and 0, 2, 4, 8, 16, 24, 36, 48, 60 and 72 h after initiation of treatment. Parasite population dynamics were assessed using nested polymerase chain reaction (PCR)-genotyping of merozoite surface protein (msp) 1 and 2.\ud \ud RESULTS\ud \ud PCR-analyses from nine sequential blood samples collected after initiation of treatment identified 20 and 21 additional genotypes in 15/50 (30%) and 14/50 (28%) children with msp1 and msp2, respectively, non-detectable in the pre-treatment samples (-2 and 0 h combined). Some 15/20 (75%) and 14/21 (67%) of these genotypes were identified within 24 h, whereas 17/20 (85%) and 19/21 (90%) within 48 h for msp1 and msp2, respectively. The genotype profile was diverse, and varied considerably over time both within and between patients, molecular markers and their respective families.\ud \ud CONCLUSION\ud \ud PCR analyses from multiple blood samples collected during the early treatment phase revealed a complex picture of parasite sub-populations. This underlines the importance of interpreting PCR-outcomes with caution and suggests that the present use of PCR-adjustment from paired blood samples in anti-malarial drug trials may overestimate assessment of drug efficacy in high transmission areas in Africa.The study is registered at http://www.clinicaltrials.gov with identifier NCT00336375

Polymorphisms in Plasmodium falciparum chloroquine resistance transporter and multidrug resistance 1 genes: parasite risk factors that affect treatment outcomes for P. falciparum malaria after artemether-lumefantrine and artesunate-amodiaquine.

Adequate clinical and parasitologic cure by artemisinin combination therapies relies on the artemisinin component and the partner drug. Polymorphisms in the Plasmodium falciparum chloroquine resistance transporter (pfcrt) and P. falciparum multidrug resistance 1 (pfmdr1) genes are associated with decreased sensitivity to amodiaquine and lumefantrine, but effects of these polymorphisms on therapeutic responses to artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) have not been clearly defined. Individual patient data from 31 clinical trials were harmonized and pooled by using standardized methods from the WorldWide Antimalarial Resistance Network. Data for more than 7,000 patients were analyzed to assess relationships between parasite polymorphisms in pfcrt and pfmdr1 and clinically relevant outcomes after treatment with AL or ASAQ. Presence of the pfmdr1 gene N86 (adjusted hazards ratio = 4.74, 95% confidence interval = 2.29 - 9.78, P < 0.001) and increased pfmdr1 copy number (adjusted hazards ratio = 6.52, 95% confidence interval = 2.36-17.97, P < 0.001 : were significant independent risk factors for recrudescence in patients treated with AL. AL and ASAQ exerted opposing selective effects on single-nucleotide polymorphisms in pfcrt and pfmdr1. Monitoring selection and responding to emerging signs of drug resistance are critical tools for preserving efficacy of artemisinin combination therapies; determination of the prevalence of at least pfcrt K76T and pfmdr1 N86Y should now be routine

Role of PfATP6 and pfMRP1 in Plasmodium falciparum resistance to antimalarial drugs

Half of the world s population live at risk for malaria and nearly one million people die from the disease every year. The malaria burden is greatest in children and pregnant women in sub-Saharan Africa. As effective treatment is crucial for malaria control, the spread of antimalarial drug resistance has contributed significantly to malaria attributed morbidity and mortality. The current cornerstones in malaria treatment are artemisininbased combination therapy (ACT) for treatment of uncomplicated Plasmodium falciparum malaria and sulfadoxine-pyrimethamine (SP) for intermittent preventive treatment of pregnant women. While resistance to SP is already established, recent advances have provided the first evidence of decreased susceptibility or resistance to the ACT components; artemisinins (ART) and the key ACT partner drugs lumefantrine, amodiaquine and mefloquine. Development of resistance to ACTs and aggravation of SP resistance could be devastating, as there are presently no further well established treatment options. This stresses the importance to understand the molecular mechanism of resistance in order to potentially prevent its emergence and spread. The sarco/endoplasmic reticulum Ca2+-ATPase orthologue of P. falciparum (PfATP6) has been suggested to be a target for ART. Multidrug resistance proteins (MRPs) are known to be related with multidrug resistance in many organisms. The P. falciparum Multidrug Resistance Protein 1 (pfMRP1) has been suggested to have a role in the parasite response to several antimalarial drugs through drug efflux The aim of this thesis is to understand the role of PfATP6 and pfMRP1 in decreased susceptibility/resistance to ACTs and SP in vivo and in vitro. In two comprehensive studies the global biodiversity of PfATP6 and pfmrp1 was determined, resulting in the identification of a large number of SNPs suggesting that both genes harbor significant diversity. The contribution of the identified pfmrp1 polymorphisms in the parasite drug response in vivo was studied in P. falciparum infected patients from clinical drug trials. We observed a selection of parasites harboring pfmrp1 I876 in patients with recurrent infections after treatment with artemether-lumefantrine and of pfmrp1 K1466 in recrudescent infections after SP treatment, providing the first indications ever that pfMRP1 may have a role in P. falciparum drug response in vivo. In vitro associations between pfmrp1 SNPs and decreased susceptibility to a large number of structurally unrelated antimalarial drugs, including artemisinin, lumefantrine, amodiaquine and mefloquine, were observed in P. falciparum fresh isolates. However, we could not detect any association with PfATP6 SNPs. In conclusion, in this work no further evidence was found supporting the hypothesis of PfATP6 as a target of ART. Nevertheless it was demonstrated that PfATP6 harbors considerable sequence biodiversity which can be the basis for following studies investigating the association of PfATP6 polymorphisms with artemisinin resistant or tolerant phenotypes, as they emerge. The association of pfmrp1 polymorphism with P. falciparum response to a number of structurally unrelated drugs suggests that pfMRP1 may be a true multidrug resistance factor. Potential pfMRP1-based cross-resistance between ART and the partner drugs may have implications for development of resistance to ACTs

Gender and Politeness in Friends: : An investigation of politeness markers across gender in the TV series Friends

Slutgiltigt godkännandedatum: 2022-06-05</p

Gender and Politeness in Friends: : An investigation of politeness markers across gender in the TV series Friends

Slutgiltigt godkännandedatum: 2022-06-05</p

Att ändra negativ gruppdynamik : samarbetsövningar i förskolan

Denna studie hade syftet att undersöka om det går att förändra gruppdynamiken i en barngrupp i förskolan. Vi valde att utgå från olika tillitsövningar och samarbetsövningar. Vi har använt oss av observationer för att kunna se resultaten. Det resultat studien visade är att det kan ske förändringar med hjälp av olika aktiviteter. Studien genomfördes på en förskola där vi observerade barn i åldern 5 år. Av resultatet hade vi svårt att dra en slutsats dock kunde vi se en liten förändring med de barn som deltagit under båda tillfällena eftersom de börjat samarbeta mer. För att få ett tydligare resultat behöver övningarna dock genomföras under en längre tid då samarbete och självförtroende utvecklas

Polymorphism in PfMRP1 (Plasmodium falciparum Multidrug Resistance Protein 1) Amino Acid 1466 Associated with Resistance to Sulfadoxine-Pyrimethamine Treatment▿

Sulfadoxine-pyrimethamine (SP) remains widely recommended for intermittent preventive treatment against Plasmodium falciparum malaria for pregnant women and infants in Africa. Resistance to SP is increasing and associated primarily with mutations in the P. falciparum dhfr (Pfdhfr) and Pfdhps genes. This study aimed to explore the hypothetical association of genetic alterations in the P. falciparum multidrug resistance protein gene (Pfmrp1) with the in vivo response to SP by detecting the selection of single nucleotide polymorphisms (SNPs) following standard single-dose treatment administered to children with acute uncomplicated P. falciparum malaria in Tanzania. We detected significant selection of parasites carrying the Pfmrp1 1466K allele in samples from children with recrudescent infections, with 12 (100%) of 12 such samples being positive for this allele, compared to 52 (67.5%) of 77 baseline samples (P = 0.017), in parallel with the selection of the Pfdhfr Pfdhps quintuple mutant haplotype in cases of recrudescence (P = 0.001). There was no association between the 1466K SNP and the Pfdhfr Pfdhps quintuple mutation, indicating independent selections. Our data point for the first time to a role for a P. falciparum multidrug resistance protein homologue in the antimalarial activity of SP. Moreover, they add to the growing evidence of the potential importance of Pfmrp1 in antimalarial drug resistance

An online mapping database of molecular markers of drug resistance in Plasmodium falciparum: the ACT Partner Drug Molecular Surveyor

Abstract Background Prior to this project, only a handful of online visualizations existed for exploring the published literature on molecular markers of antimalarial drug resistance, and none specifically for the markers associated with Plasmodium falciparum resistance to the partner drugs in artemisinin-based combination therapy (ACT). Molecular information is collected in studies with different designs, using a variety of molecular methodologies and data analysis strategies, making it difficult to compare across studies. The purpose of this project was to develop a free online tool, which visualizes the widely published data on molecular markers of antimalarial drug resistance, starting with the two genes pfcrt and pfmdr-1, associated with resistance to the three most common partner drugs; amodiaquine, lumefantrine and mefloquine. Methods A literature review was conducted, and a standardized method was used to extract data from publications, and critical decisions on visualization were made. A global geospatial database was developed of specific pfmdr1 and pfcrt single nucleotide polymorphisms and pfmdr1 copy number variation. An informatics framework was developed that allowed flexibility in development of the tool over time and efficient adaptation to different source data. Results The database discussed in this paper has pfmdr1 and pfcrt marker prevalence information, from 579 geographic sites in 76 different countries, including results from over 86,000 samples from 456 articles published January 2001–May 2017. The ACT Partner Drugs Molecular Surveyor was launched by the WorldWide Antimalarial Resistance Network (WWARN) in March 2015 and it has attracted over 3000 unique visitors since then. Presented here is a demonstration of how the Surveyor database can be explored to monitor local, temporal changes in the prevalence of molecular markers. Here publications up to May 2017 were included, however the online ACT partner drug Molecular Surveyor is continuously updated with new data and relevant markers. Conclusions The WWARN ACT Partner Drugs Molecular Surveyor summarizes data on resistance markers in the pfmdr1 and pfcrt genes. The database is fully accessible, providing users with a rich resource to explore and analyze, and thus utilize a centralized, standardized database for different purposes. This open-source software framework can be adapted to other data, as demonstrated by the subsequent launch of the Artemisinin Molecular Surveyor and the Vivax Surveyor