Amanda Luisa da Fonseca

Public Knowledge about and Detection of Canine Visceral Leishmaniasis in Urban Divinópolis, Brazil.

Background. Leishmaniases are diseases with a wide spectrum of clinical manifestations including cutaneous (CL) and visceral (VL) forms. Many factors may affect their occurrence and expansion including environmental, geographic, and social conditions. In the past two decades, Divinópolis, Minas Gerais State, Brazil, has exhibited the potential for a disease outbreak, with the appearance of CL, and VL cases (human and canine). Hence, this study was initiated to monitor public knowledge of the disease. Questionnaires were administered in four neighborhoods (Jardim Belvedere, Esplanada, Danilo Passos I and II) where most of the human and canine cases have been reported. The analyses demonstrated that public knowledge of the disease is sparse and fragmented. A strong perception of the dog as the main reservoir was observed. Five veterinary clinics were evaluated for the presence of canine VL using serological (RIFI and ELISA) and molecular (PCR-RFLP) techniques. This is the first study demonstrating the occurrence of Leishmania infantum in Divinópolis, suggesting a possible urbanization of VL.

Successful application of virtual screening and molecular dynamics simulations against antimalarial molecular targets

The main challenge in the control of malaria has been the emergence of drug-resistant parasites. The presence of drug-resistant Plasmodium sp. has raised the need for new antimalarial drugs. Molecular modelling techniques have been used as tools to develop new drugs. In this study, we employed virtual screening of a pyrazol derivative (Tx001) against four malaria targets: plasmepsin-IV, plasmepsin-II, falcipain-II, and PfATP6. The receiver operating characteristic curves and area under the curve (AUC) were established for each molecular target. The AUC values obtained for plasmepsin-IV, plasmepsin-II, and falcipain-II were 0.64, 0.92, and 0.94, respectively. All docking simulations were carried out using AutoDock Vina software. The ligand Tx001 exhibited a better interaction with PfATP6 than with the reference compound (-12.2 versus -6.8 Kcal/mol). The Tx001-PfATP6 complex was submitted to molecular dynamics simulations in vacuum implemented on an NAMD program. The ligand Tx001 docked at the same binding site as thapsigargin, which is a natural inhibitor of PfATP6. Compound TX001 was evaluated in vitro with a P. falciparum strain (W2) and a human cell line (WI-26VA4). Tx001 was discovered to be active against P. falciparum (IC50 = 8.2 µM) and inactive against WI-26VA4 (IC50 > 200 µM). Further ligand optimisation cycles generated new prospects for docking and biological assays.

Structure-based drug design studies of the interactions of ent-kaurane diterpenes derived from Wedelia paludosa with the Plasmodium falciparum sarco/endoplasmic reticulum Ca²⁺-ATPase PfATP6.

Malaria is responsible for more deaths around the world than any other parasitic disease. Due to the emergence of strains that are resistant to the current chemotherapeutic antimalarial arsenal, the search for new antimalarial drugs remains urgent though hampered by a lack of knowledge regarding the molecular mechanisms of artemisinin resistance. Semisynthetic compounds derived from diterpenes from the medicinal plant Wedelia paludosa were tested in silico against the Plasmodium falciparum Ca2+-ATPase, PfATP6. This protein was constructed by comparative modelling using the three-dimensional structure of a homologous protein, 1IWO, as a scaffold. Compound 21 showed the best docking scores, indicating a better interaction with PfATP6 than that of thapsigargin, the natural inhibitor. Inhibition of PfATP6 by diterpene compounds could promote a change in calcium homeostasis, leading to parasite death. These data suggest PfATP6 as a potential target for the antimalarial ent-kaurane diterpenes.

Docking, QM/MM, and molecular dynamics simulations of the hexose transporter from Plasmodium falciparum (PfHT).

Malaria is the most prevalent parasitic disease in the world. Currently, an effective vaccine for malaria does not exist, and chemotherapy must be used to treat the disease. Because of increasing resistance to current antimalarial drugs, new treatments must be developed. Among the many potential molecular targets, the hexose transporter of Plasmodium falciparum (PfHT) is particularly promising because it plays a vital role in glucose transport for the parasite. Thus, this study aims to determine the three-dimensional structure of PfHT and to describe the intermolecular interactions between active glycoside derivatives and PfHT. Such information should aid in the development of new antimalarial drugs. The receptor PfHT was constructed from primary sequences deposited in the SWISS MODEL database. Next, molecular docking simulations between O-(undec-10-en)-l-D-glucose and the constructed active site models were performed using Autodock Vina. The glycoside derivative-PfHT complexes were then refined using the hybrid QM/MM (PM3/ff03) method within the AMBER package. The models were then evaluated using Ramachandran plots, which indicated that 93.2% of the residues in the refined PfHT models (P5) were present in favorable regions. Furthermore, graphical plots using ANOLEA showed that the potential energies of interaction for atoms unbonded to P5 were negative. Finally, the O-(undec-10-en)-l-D-glucose-PfHT complex was evaluated using 20-ns Molecular Dynamics simulations with an ff03 force field. Docking and QM/MM studies revealed the amino acids essential for molecular recognition of and activity on glycosides. Inhibition of glucose transporters may prevent the development and metabolism of P. falciparum, so a description of the receptors structure is a critical step towards rational drug design.

Co-nanoencapsulation of antimalarial drugs increases their in vitro efficacy against Plasmodium falciparum and decreases their toxicity to Caenorhabditis elegans

&NA; Drugs used for the treatment and prevention of malaria have resistance‐related problems, making them ineffective for monotherapy. If properly associated, many of these antimalarial drugs may find their way back to the treatment regimen. Among the therapeutic arsenal, quinine (QN) is a second‐line treatment for uncomplicated malaria but has side effects that limit its use. Curcumin (CR) is a natural compound with anti‐plasmodial activities and low bioavailability. In this context, the aim of this work was to develop and characterize co‐encapsulated QN+CR‐loaded polysorbate‐coated polymeric nanocapsules (NC‐QC) to evaluate their activity on Plasmodium falciparum and the safety of the nanoformulations for Caenorhabditis elegans. NC‐QC displayed a diameter of approximately 200nm, a negative zeta potential and a slightly basic pH. The drugs are homogeneously distributed in the NCs in the amorphous form. Co‐encapsulated NCs exhibited a significant reduction in P. falciparum parasitemia, better than QN/CR. The worms exposed to NC‐QC showed higher survival and longevity and no decrease in their reproductive capacity compared to free and associated drugs. It was possible to prove that the NCs were absorbed orally by the worms using fluorescence microscopy. Co‐encapsulation of QN and CR was effective against P. falciparum, minimizing the toxic effects caused by chronic exposure of the free drugs in C. elegans. Graphical abstract: Symbol. No Caption available. Highlights:Quinine and curcumin loaded P80‐coated PCL nanocapsules was developed as a strategy against monotherapy‐resistant malaria.Polymeric walls protect quinine and curcumin from ultraviolet‐induced degradation.The co‐encapsulation of quinine and curcumin depicted antimalarial effects on the W2 and 3D7 Plasmodium falciparum strains.Quinine + curcumin‐loaded nanocapsules minimized the toxic effects of free drugs in Caenorhabditis elegans.