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Scientific Articles

Chemoprotective Antimalarial Activity of P218 against Plasmodium falciparum: A Randomized, Placebo-Controlled Volunteer Infection Study

February 10, 2021 - 09:44 -- Open Access
Author(s): 
Chughlay MF, El Gaaloul M, Chalon S, et al.
Reference: 
Am J Trop Med Hyg. 2021 Feb 8:tpmd201165

P218 is a highly selective dihydrofolate reductase inhibitor with potent in vitro activity against pyrimethamine-resistant Plasmodium falciparum. This single-center, randomized, double-blind, placebo-controlled phase Ib study evaluated P218 safety and chemoprotective efficacy in a P. falciparum sporozoite (PfSPZ) volunteer infection study (VIS). Consecutive dose safety and tolerability were evaluated (cohort 1), with participants receiving two oral doses of P218 1,000 mg 48 hours apart (n = 6), or placebo (n = 2). P218 chemoprotective efficacy was assessed (cohorts 2 and 3) with direct venous inoculation of 3,200 aseptic, cryopreserved PfSPZ (NF54 strain) followed 2 hours later with two P218 doses of 1,000 mg (cohort 2, n = 9) or 100 mg (cohort 3, n = 9) administered 48 hours apart, or placebo (n = 6).

Multi-Indicator and Multistep Assessment of Malaria Transmission Risks in Western Kenya

February 10, 2021 - 09:41 -- Open Access
Author(s): 
Zhou G, Zhong D, Lee MC, Wang X, Atieli HE, Githure JI, Githeko AK, Kazura J, Yan G
Reference: 
Am J Trop Med Hyg. 2021 Feb 8:tpmd201211

Malaria risk factor assessment is a critical step in determining cost-effective intervention strategies and operational plans in a regional setting. We develop a multi-indicator multistep approach to model the malaria risks at the population level in western Kenya. We used a combination of cross-sectional seasonal malaria infection prevalence, vector density, and cohort surveillance of malaria incidence at the village level to classify villages into malaria risk groups through unsupervised classification. Generalized boosted multinomial logistics regression analysis was performed to determine village-level risk factors using environmental, biological, socioeconomic, and climatic features.

Bioactivities of rose-scented geranium nanoemulsions against the larvae of Anopheles stephensi and their gut bacteria

February 10, 2021 - 09:38 -- Open Access
Author(s): 
Dehghankar M, Maleki-Ravasan N, Tahghighi A, Karimian F, Karami M
Reference: 
PLoS One. 2021 Feb 8;16(2):e0246470

Anopheles stephensi with three different biotypes is a major vector of malaria in Asia. It breeds in a wide range of habitats. Therefore, safer and more sustainable methods are needed to control its immature stages rather than chemical pesticides. The larvicidal and antibacterial properties of the Pelargonium roseum essential oil (PREO) formulations were investigated against mysorensis and intermediate forms of An. stephensi in laboratory conditions. A series of nanoemulsions containing different amounts of PREO, equivalent to the calculated LC50 values for each An. stephensi form, and various quantities of surfactants and co-surfactants were developed. The physical and morphological properties of the most lethal formulations were also determined. PREO and its major components, i.e. citronellol (21.34%), L-menthone (6.41%), linalool (4.214%), and geraniol (2.19%), showed potent larvicidal activity against the studied mosquitoes.

NOT Open Access | The challenges of a circumsporozoite protein-based malaria vaccine

February 10, 2021 - 09:33 -- NOT Open Access
Author(s): 
Chatterjee D, Cockburn IA
Reference: 
Expert Rev Vaccines. 2021 Feb 7:1-13

A safe and effective vaccine will likely be necessary for the control or eradication of malaria which kills 400,000 annually. Our most advanced vaccine candidate to date is RTS,S which is based on the Plasmodium falciparum circumsporozoite protein (PfCSP) of the malaria parasite. However, protection by RTS,S is incomplete and short-lived.

Direct Comparison of Standard and Ultrasensitive PCR for the Detection of Plasmodium falciparum from Dried Blood Spots in Bagamoyo, Tanzania

February 9, 2021 - 10:35 -- Open Access
Author(s): 
Markwalter CF, Ngasala B, Mowatt T, Basham C, Park Z, Loya M, Muller M, Plowe C, Nyunt M, Lin JT
Reference: 
Am J Trop Med Hyg. 2021 Feb 8:tpmd201233

Ultrasensitive PCR used in low-transmission malaria-endemic settings has revealed a much higher burden of asymptomatic infections than that detected by rapid diagnostic tests (RDTs) or standard PCR, but there is limited evidence as to whether this is the case in higher transmission settings.

Investigation of Heterochromatin Protein 1 Function in the Malaria Parasite Plasmodium falciparum Using a Conditional Domain Deletion and Swapping Approach

February 9, 2021 - 10:16 -- Open Access
Author(s): 
Bui HTN, Passecker A, Brancucci NMB, Voss TS
Reference: 
mSphere. 2021 Feb 3;6(1):e01220-20

The human malaria parasite Plasmodium falciparum encodes a single ortholog of heterochromatin protein 1 (PfHP1) that plays a crucial role in the epigenetic regulation of various survival-related processes. PfHP1 is essential for parasite proliferation and the heritable silencing of genes linked to antigenic variation, host cell invasion, and sexual conversion. Here, we employed CRISPR/Cas9-mediated genome editing combined with the DiCre/loxP system to investigate how the PfHP1 chromodomain (CD), hinge domain, and chromoshadow domain (CSD) contribute to overall PfHP1 function. We show that the 76 C-terminal residues are responsible for targeting PfHP1 to the nucleus.

Biochemical and cellular characterisation of the Plasmodium falciparum M1 alanyl aminopeptidase (PfM1AAP) and M17 leucyl aminopeptidase (PfM17LAP)

February 9, 2021 - 10:11 -- Open Access
Author(s): 
Mathew R, Wunderlich J, Thivierge K, Cwiklinski K, Dumont C, Tilley L, Rohrbach P, Dalton JP
Reference: 
Sci Rep. 2021 Feb 3;11(1):2854

The Plasmodium falciparum M1 alanyl aminopeptidase and M17 leucyl aminopeptidase, PfM1AAP and PfM17LAP, are potential targets for novel anti-malarial drug development. Inhibitors of these aminopeptidases have been shown to kill malaria parasites in culture and reduce parasite growth in murine models. The two enzymes may function in the terminal stages of haemoglobin digestion, providing free amino acids for protein synthesis by the rapidly growing intra-erythrocytic parasites.

Not Open Access | Dolutegravir pharmacokinetics during co-administration with either artemether/lumefantrine or artesunate/amodiaquine

February 9, 2021 - 10:05 -- NOT Open Access
Author(s): 
Kawuma AN, Walimbwa SI, Pillai GC, Khoo S, Lamorde M, Wasmann RE, Denti P
Reference: 
J Antimicrob Chemother. 2021 Feb 7:dkab022

In sub-Saharan Africa, artemisinin-containing therapies for malaria treatment are regularly co-administered with ART. Currently, dolutegravir-based regimens are recommended as first-line therapy for HIV across most of Africa.

A redox-active crosslinker reveals an essential and inhibitable oxidative folding network in the endoplasmic reticulum of malaria parasites

February 9, 2021 - 10:02 -- Open Access
Author(s): 
Cobb DW, Kudyba HM, Villegas A, Hoopmann MR, Baptista RP, Bruton B, Krakowiak M, Moritz RL, Muralidharan V
Reference: 
PLoS Pathog. 2021 Feb 3;17(2):e1009293

Malaria remains a major global health problem, creating a constant need for research to identify druggable weaknesses in P. falciparum biology. As important components of cellular redox biology, members of the Thioredoxin (Trx) superfamily of proteins have received interest as potential drug targets in Apicomplexans. However, the function and essentiality of endoplasmic reticulum (ER)-localized Trx-domain proteins within P. falciparum has not been investigated.

The Role of the Histone Methyltransferase PfSET10 in Antigenic Variation by Malaria Parasites: a Cautionary Tale

February 9, 2021 - 09:57 -- Open Access
Author(s): 
Ngwa CJ, Gross MR, Musabyimana JP, Pradel G, Deitsch KW
Reference: 
mSphere. 2021 Feb 3;6(1):e01217-20

The virulence of the malaria parasite Plasmodium falciparum is due in large part to its ability to avoid immune destruction through antigenic variation. This results from changes in expression within the multicopy var gene family that encodes the surface antigen P. falciparum erythrocyte protein one (PfEMP1). Understanding the mechanisms underlying this process has been a high-profile research focus for many years. The histone methyltransferase PfSET10 was previously identified as a key enzyme required both for parasite viability and for regulating var gene expression, thus making it a prominent target for developing antimalarial intervention strategies and the subject of considerable research focus. Here, however, we show that disruption of the gene encoding PfSET10 is not lethal and has no effect on var gene expression, in sharp contrast with previously published reports. The contradictory findings highlight the importance of reevaluating previous conclusions when new technologies become available and suggest the possibility of a previously unappreciated plasticity in epigenetic gene regulation in P. falciparum.

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