Nanoparticle tracking analysis of natural hemozoin from Plasmodium parasites.

BACKGROUND: Hemozoin is a byproduct of hemoglobin digestion crucial for parasite survival. It forms crystals that can be of interest as drug targets or biomarkers of malaria infection. However, hemozoin has long been considered as an amorphous crystal of simple morphology. Studying the consequences of biomineralization of this crystal during the parasite growth may provide more comprehensive evidence of its role during malaria. OBJECTIVES: This study aimed to investigate the interest of nanoparticles tracker analysis for measuring the concentration and size of hemozoin particles produced from different parasite sources and conditions. METHODS: Hemozoin was extracted from several clones of Plasmodium falciparum both asexual and sexual parasites. Hemozoin was also extracted from blood samples of malaria patients and from saliva of asymptomatic malaria carriers. Nanoparticles tracking analysis (NTA) was performed to assess the size and concentration of hemozoin. RESULTS: NTA data showed variation in hemozoin concentration, size, and crystal clusters between parasite clones, species, and stages. Among parasite clones, hemozoin concentration ranged from 131 to 2663 particles/infected red blood cell (iRBC) and size ranged from 149.6 ± 6.3 nm to 234.8 ± 40.1 nm. The mean size was lower for Plasmodium vivax (176 ± 79.2 nm) than for Plasmodium falciparum (254.8 ± 74.0 nm). Sexual NF54 parasites showed a 7.5-fold higher concentration of hemozoin particles (28.7 particles/iRBC) compared to asexual parasites (3.8 particles/iRBC). In addition, the mean hemozoin size also increased by approximately 60 % for sexual parasites. Compared to in vitro cultures of parasites, blood samples showed low hemozoin concentrations. CONCLUSIONS: This study highlights the potential of NTA as a useful method for analyzing hemozoin, demonstrating its ability to provide detailed information on hemozoin characterization. However, further research is needed to adapt the NTA for hemozoin analysis.

Protocols for Plasmodium gametocyte production in vitro: an integrative review and analysis.

BACKGROUND: The production of Plasmodium gametocytes in vitro is a real challenge. Many protocols have been described, but few have resulted in the production of viable and infectious gametocytes in sufficient quantities to conduct research on-but not limited to-transmission-blocking drug and vaccine development. The aim of this review was to identify and discuss gametocyte production protocols that have been developed over the last two decades. METHODS: We analyzed the original gametocyte production protocols published from 2000 onwards based on a literature search and a thorough review. A systematic review was performed of relevant articles identified in the PubMed, Web of Sciences and ScienceDirect databases. RESULTS: A total 23 studies on the production of Plasmodium gametocytes were identified, 19 involving in vitro Plasmodium falciparum, one involving Plasmodium knowlesi and three involving ex vivo Plasmodium vivax. Of the in vitro studies, 90% used environmental stressors to trigger gametocytogenesis. Mature gametocytemia of up to 4% was reported. CONCLUSIONS: Several biological parameters contribute to an optimal production in vitro of viable and infectious mature gametocytes. The knowledge gained from this systematic review on the molecular mechanisms involved in gametocytogenesis enables reproducible gametocyte protocols with transgenic parasite lines to be set up. This review highlights the need for additional gametocyte production protocols for Plasmodium species other than P. falciparum.

Pre-referral intranasal artesunate powder for cerebral malaria: a proof-of-concept study.

BACKGROUND: Malaria still kills young children in rural endemic areas because early treatment is not available. Thus, the World Health Organization recommends the administration of artesunate suppositories as pre-referral treatment before transportation to the hospital in case of severe symptoms with an unavailable parenteral and oral treatment. However, negative cultural perception of the rectal route, and limited access to artesunate suppositories, could limit the use of artesunate suppositories. There is, therefore, a need for an alternative route for malaria pre-referral treatment. The aim of this study was to assess the potential of intranasal route for malaria pre-referral treatment. METHODS: The permeability of artesunate through human nasal mucosa was tested in vitro. The Transepithelial Electrical Resistance (TEER) of the nasal mucosa was followed during the permeation tests. Beside, regional deposition of artesunate powder was assessed with an unidose drug delivery device in each nostril of a nasal cast. Artesunate quantification was performed using Liquid Chromatography coupled to tandem Mass Spectrometry. RESULTS: The experimental model of human nasal mucosa was successfully implemented. Using this model, artesunate powder showed a much better passage rate through human nasal mucosa than solution (26.8 ± 6.6% versus 2.1 ± 0.3%). More than half (62.3%) of the artesunate dose sprayed in the nostrils of the nasal cast was recovered in the olfactory areas (44.7 ± 8.6%) and turbinates (17.6 ± 3.3%) allowing nose-to-brain and systemic drug diffusion, respectively. CONCLUSION: Artesunate powder showed a good permeation efficiency on human nasal mucosa. Moreover it can be efficiently sprayed in the nostrils using unidose device to reach the olfactory area leading to a fast nose-to-brain delivery as well as a systemic effect. Taken together, those results are part of the proof-of-concept for the use of intranasal artesunate as a malaria pre-referral treatment.

Systematic review of Plasmodium knowlesi in Indonesia: a risk of emergence in the context of capital relocation to Borneo?

BACKGROUND: The Indonesian Republic plans to relocate its capital from Jakarta to East Kalimantan, Borneo Island, in the next few years. This relocation may be associated with deforestation, decreased biodiversity, and an increased risk of emerging zoonotic infections, including Plasmodium knowlesi malaria. The Malaysian part of Borneo Island is one of the main hotspots of P. knowlesi malaria. METHODS: Considering this risk, we evaluated the transmission dynamics of P. knowlesi in the Indonesian Archipelago based on a literature search and extensive review of data from the Indonesian Ministry of Health. RESULTS: We report that 545 P. knowlesi cases were documented in Indonesia, mainly in the Aceh and North Sumatra provinces, with 95% of these occurring in the last 4 years. CONCLUSIONS: The main P. knowlesi vectors are present in the area of the future capital, requiring strengthened surveillance to reduce the risk of emerging cases in a rapidly growing population.

Assessment of quantitative and semi-quantitative biological test methods of artesunate in vitro.

Artesunate is the current most potent antimalarial drug widely used for the treatment of malaria. Considering the emergence of artemisinin resistance, several situations may require a simple method for artesunate quantification. We thus developed a quantitative and a semi-quantitative biological method for the determination of artesunate in liquid samples. The tests are based on the measurement of samples' antimalarial activity on Plasmodium falciparum 3D7 using a modified SYBR Green I drug susceptibility test. For the quantitative test, we established a standard curve that resulted from a dose-response curve and evaluated its performances using controls samples. Whereas the linear regression analysis between artesunate concentration and antimalarial activity showed promising results (linearity range 1.5-24.6 ng/mL, r2 = 0.9373), we found that artesunate content of the controls was significantly overestimated (p = 0.0313). For the semi-quantitative test, we compared the antimalarial activities of samples collected during permeation studies of artesunate to that of a reference (artesunate IC50) by statistical analysis. We demonstrated that antimalarial activities of samples from permeation tests using a powder formulation of artesunate were greater than those of samples from tests using a solution formulation. Bioassays can be simple techniques to assess artesunate in liquid samples, particularly in resource-limited settings. Comparison with reference methods is still recommended when accurate drug quantification is required.

Title: Évaluation de méthodes de tests biologiques quantitatives et semi-quantitatives de l'artésunate in vitro. Abstract: L'artésunate est le médicament antipaludique le plus puissant actuellement, largement utilisé pour le traitement du paludisme. Compte tenu de l'émergence de la résistance à l'artémisinine, plusieurs situations peuvent nécessiter une méthode simple de quantification de l'artésunate. Nous avons ainsi développé un test biologique quantitatif et un test semi-quantitatif pour le dosage de l'artésunate dans des échantillons liquides. Les méthodes sont basées sur la mesure de l'activité antipaludique des échantillons sur Plasmodium falciparum 3D7 à l'aide d'un test de sensibilité aux médicaments SYBR Green I modifié. Pour le test quantitatif, nous avons établi une courbe standard issue d'une courbe dose-réponse et évalué ses performances à l'aide d'échantillons témoins. Alors que l'analyse de régression linéaire entre la concentration d'artésunate et l'activité antipaludique a montré des résultats prometteurs (gamme de linéarité de 1,5 à 24,6 ng/mL, r2 = 0,9373), nous avons constaté que la teneur en artésunate des témoins était significativement surestimée (p = 0,0313). Pour le test semi-quantitatif, nous avons comparé les activités antipaludiques d'échantillons collectés lors des études de perméation de l'artésunate à celle d'une référence (artésunate IC50) par analyse statistique. Nous avons démontré que les activités antipaludiques des échantillons provenant de tests de perméation utilisant une formulation en poudre d'artésunate étaient supérieures à celles des échantillons provenant de tests utilisant une formulation en solution. Les dosages biologiques peuvent être des techniques simples pour évaluer l'artésunate dans des échantillons liquides, en particulier dans les milieux à ressources limitées. La comparaison avec des méthodes de référence est toujours recommandée lorsqu'une quantification précise du médicament est requise.