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Antimicrobial Agents and Chemotherapy Jun 2024In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and...
In response to the spread of artemisinin (ART) resistance, ART-based hybrid drugs were developed, and their activity profile was characterized against drug-sensitive and drug-resistant parasites. Two hybrids were found to display parasite growth reduction, stage-specificity, speed of activity, additivity of activity in drug combinations, and stability in hepatic microsomes of similar levels to those displayed by dihydroartemisinin (DHA). Conversely, the rate of chemical homolysis of the peroxide bonds is slower in hybrids than in DHA. From a mechanistic perspective, heme plays a central role in the chemical homolysis of peroxide, inhibiting heme detoxification and disrupting parasite heme redox homeostasis. The hybrid exhibiting slow homolysis of peroxide bonds was more potent in reducing the viability of ART-resistant parasites in a ring-stage survival assay than the hybrid exhibiting fast homolysis. However, both hybrids showed limited activity against ART-induced quiescent parasites in the quiescent-stage survival assay. Our findings are consistent with previous results showing that slow homolysis of peroxide-containing drugs may retain activity against proliferating ART-resistant parasites. However, our data suggest that this property does not overcome the limited activity of peroxides in killing non-proliferating parasites in a quiescent state.
PubMed: 38899927
DOI: 10.1128/aac.00143-24 -
BMC Infectious Diseases Jun 2024the mortality associated with severe malaria due to Plasmodiun falciparum remains high despite improvements in malaria management. Case prensentation: this case series...
BACKGROUND
the mortality associated with severe malaria due to Plasmodiun falciparum remains high despite improvements in malaria management. Case prensentation: this case series aims to describe the efficacy and safety of the exchange transfusion combined with artesunate (ET-AS) regimen in severe P. falciparum malaria. Eight patients diagnosed with severe P. falciparum malaria were included. All patients underwent ET using the COBE Spectra system. The aimed for a post-exchange hematocrit of 30%. Half the estimated blood volume was removed and replaced using fresh frozen plasma. The regimen was well-tolerated without complications. The parasite clearance time ranged from 1 ~ 5 days. Five patients with cerebral malaria exhibited full improved consciousness within 3 days, while patient2 with hemolysis improved on day 2. Liver function improved within 1 ~ 6 days, and patient 1 and patient 6 showed improvements renal function on days 18 and 19, respectively. The length of intensive care unit stay range from 2 ~ 10 days, and all patients treated with ET-AS remained in the hospital for 3 ~ 19 days.
CONCLUSIONS
these preliminary results suggest that ET-AS regimens are a safe and effective therapy for severe P. falciparum malaria and can benefit patients in clinical settings.
Topics: Humans; Artesunate; Malaria, Falciparum; Male; Adult; Female; Antimalarials; Middle Aged; Exchange Transfusion, Whole Blood; Artemisinins; Treatment Outcome; Young Adult; Plasmodium falciparum; Aged; Combined Modality Therapy
PubMed: 38898395
DOI: 10.1186/s12879-024-09381-2 -
International Journal of Biological... Jun 2024Artemisinin and its derivatives have been commonly used to treat malaria. However, the emergence of resistance against artemisinin derivatives has posed a critical...
Artemisinin and its derivatives have been commonly used to treat malaria. However, the emergence of resistance against artemisinin derivatives has posed a critical challenge in malaria management. In the present study, we have proposed a combinatorial approach, utilizing pH-responsive acetal-dextran nanoparticles (Ac-Dex NPs) as carriers for the delivery of withaferin-A (WS-3) and artesunate (Art) to improve treatment efficacy of malaria. The optimized WS-3 and Art Ac-Dex NPs demonstrated enhanced pH-responsive release profiles under parasitophorous mimetic conditions (pH 5.5). Computational molecular modeling reveals that Ac-Dex's polymeric backbone strongly interacts with merozoite surface protein-1 (MSP-1), preventing erythrocyte invasion. In-vitro antimalarial activity of drug-loaded Ac-Dex NPs reveals a 1-1.5-fold reduction in IC values compared to pure drug against the 3D7 strain of Plasmodium falciparum. Treatment with WS-3 Ac-Dex NPs (100 mg/kg) and Art Ac-Dex NPs (30 mg/kg) to Plasmodium berghei-infected mice resulted in 78.11 % and 100 % inhibition of parasitemia. Notably, the combination therapy comprised of Art and WS-3 Ac-Dex NPs achieved complete inhibition of parasitemia even at a half dose of Art, indicating the synergistic potential of the combinations. However, further investigations are necessary to confirm the safety and effectiveness of WS-3 and Art Ac-Dex NPs for their successful clinical implications.
PubMed: 38897506
DOI: 10.1016/j.ijbiomac.2024.133220 -
Parasitology Research Jun 2024Human toxocariasis is a neglected anthropozoonosis with global distribution. Treatment is based on the administration of anthelmintics; however, their effectiveness at...
Human toxocariasis is a neglected anthropozoonosis with global distribution. Treatment is based on the administration of anthelmintics; however, their effectiveness at the tissue level is low to moderate, necessitating the discovery of new drug candidates. Several groups of synthetic compounds, including coumarin derivatives, have demonstrated bioactivity against fungi, bacteria, and even parasites, such as Dactylogyrus intermedius, Leishmania major, and Plasmodium falciparum. The aim of this study was to evaluate the effect of ten coumarin-derived compounds against Toxocara canis larvae using in vitro, cytotoxicity, and in silico tests for selecting new drug candidates for preclinical tests aimed at evaluating the treatment of visceral toxocariasis. The compounds were tested in vitro in duplicate at a concentration of 1 mg/mL, and compounds with larvicidal activity were serially diluted to obtain concentrations of 0.5 mg/mL; 0.25 mg/mL; 0.125 mg/mL; and 0.05 mg/mL. The tests were performed in a microculture plate containing 100 T. canis larvae in RPMI-1640 medium. One compound (COU 9) was selected for cytotoxicity analysis using J774.A1 murine macrophages and it was found to be non-cytotoxic at any concentration tested. The in silico analysis was performed using computational models; the compound presented adequate results of oral bioavailability. To confirm the non-viability of the larvae, the contents of the microplate wells of COU 9 were inoculated intraperitoneally (IP) into female Swiss mice at 7-8 weeks of age. This confirmed the larvicidal activity of this compound. These results show that COU 9 exhibited larvicidal activity against T. canis larvae, which, after exposure to the compound, were non-viable, and that COU 9 inhibited infection in a murine model. In addition, COU 9 did not exhibit cytotoxicity and presented adequate bioavailability in silico, similar to albendazole, an anthelmintic, which is the first choice for treatment of human toxocariasis, supporting the potential for future investigations and preclinical tests on COU 9.
Topics: Animals; Larva; Toxocara canis; Coumarins; Anthelmintics; Biological Availability; Mice; Computer Simulation; Toxocariasis
PubMed: 38896311
DOI: 10.1007/s00436-024-08272-4 -
Parasite (Paris, France) 2024Anopheles coustani has long been recognized as a secondary malaria vector in Africa. It has recently been involved in the transmission of both Plasmodium falciparum and...
Anopheles coustani has long been recognized as a secondary malaria vector in Africa. It has recently been involved in the transmission of both Plasmodium falciparum and P. vivax in Madagascar. As most secondary malaria vectors, An. coustani mainly bites outdoors, which renders the control of this mosquito species difficult using classical malaria control measures, such as the use of bed nets or indoor residual spraying of insecticides. For a better understanding of the biology and vector competence of a vector species, it is useful to rear the species in the laboratory. The absence of a colony hinders the assessment of the bionomics of a species and the development of adapted control strategies. Here, we report the first successful establishment of an An. coustani colony from mosquitoes collected in Madagascar. We used a forced copulation procedure as this mosquito species will not mate in cages. We describe our mosquito colonization procedure with detailed biological features concerning larval to adult development and survival, recorded over the first six critical generations. The procedure should be easily applicable to An. coustani from different African countries, facilitating local investigation of An. coustani vector competence and insecticide resistance using the colony as a reference.
Topics: Animals; Anopheles; Madagascar; Mosquito Vectors; Female; Male; Malaria; Larva
PubMed: 38896103
DOI: 10.1051/parasite/2024032 -
BioRxiv : the Preprint Server For... Jun 2024acetyl-CoA synthetase (PfACAS) protein is an important source of acetyl-CoA. We detected the mutations S868G and V949I in PfACAS by whole-genome sequencing analysis in...
acetyl-CoA synthetase (PfACAS) protein is an important source of acetyl-CoA. We detected the mutations S868G and V949I in PfACAS by whole-genome sequencing analysis in some recrudescent parasites after antimalarial treatment with artesunate and dihydroartemisinin-piperaquine, suggesting that they may confer drug resistance. Using CRISPR/Cas9 technology, we engineered parasite lines carrying the PfACAS S868G and V949I mutations in two genetic backgrounds and evaluated their susceptibility to antimalarial drugs in vitro. The results demonstrated that PfACAS S868G and V949I mutations alone or in combination were not enough to provide resistance to antimalarial drugs.
PubMed: 38895343
DOI: 10.1101/2024.06.03.597226 -
BioRxiv : the Preprint Server For... Jun 2024Rodent malaria models serve as important preclinical antimalarial and vaccine testing tools. Evaluating treatment outcomes in these models often requires manually...
Rodent malaria models serve as important preclinical antimalarial and vaccine testing tools. Evaluating treatment outcomes in these models often requires manually counting parasite-infected red blood cells (iRBCs), a time-consuming process, which can be inconsistent between individuals and labs. We have developed an easy-to-use machine learning (ML)-based software, Malaria Screener R, to expedite and standardize such studies by automating the counting of iRBCs in rodents. This software can process Giemsa-stained blood smear images captured by any camera-equipped microscope. It features an intuitive graphical user interface that facilitates image processing and visualization of the results. The software has been developed as a desktop application that processes images on standard Windows and Mac OS computers. A previous ML model created by the authors designed to count -infected human RBCs did not perform well counting -infected mouse RBCs. We leveraged that model by loading the pre-trained weights and training the algorithm with newly collected data to target and mouse iRBCs. This new model reliably measured both and parasitemia (R = 0.9916). Additional rounds of training data to incorporate variances due to length of Giemsa staining, microscopes etc, have produced a generalizable model, meeting WHO Competency Level 1 for the sub-category of parasite counting using independent microscopes. Reliable, automated analyses of blood-stage parasitemia will facilitate rapid and consistent evaluation of novel vaccines and antimalarials across labs in an easily accessible malaria model.
PubMed: 38895284
DOI: 10.1101/2024.06.05.597554 -
BioRxiv : the Preprint Server For... Jun 2024infections elicit strong humoral immune responses to two main groups of antigens expressed by blood-stage parasites: merozoite antigens that are involved in the...
infections elicit strong humoral immune responses to two main groups of antigens expressed by blood-stage parasites: merozoite antigens that are involved in the erythrocyte invasion process and variant surface antigens that mediate endothelial sequestration of infected erythrocytes. Long-lived B cells against both antigen classes can be detected in the circulation for years after exposure, but have not been directly compared. Here, we studied the phenotype of long-lived memory and atypical B cells to merozoite antigens (MSP1 and AMA1) and variant surface antigens (the CIDRα1 domain of PfEMP1) in Ugandan adults before and after local reduction of transmission. After a median of 1.7 years without infections, the percentage of antigen-specific activated B cells declined, but long-lived antigen-specific B cells were still detectable in all individuals. The majority of MSP1/AMA1-specific B cells were CD95CD11c memory B cells, which are primed for rapid differentiation into antibody-secreting cells, and FcRL5T-bet atypical B cells. On the other hand, most CIDRα1-specific B cells were CD95CD11c memory B cells. CIDRα1-specific B cells were also enriched among a subset of atypical B cells that seem poised for antigen presentation. These results point to differences in how these antigens are recognized or processed by the immune system and how -specific B cells will respond upon re-infection.
PubMed: 38895251
DOI: 10.1101/2024.06.01.596978 -
Communications Biology Jun 2024Aminoacyl-tRNA synthetases (aaRSs) play a central role in the translation of genetic code, serving as attractive drug targets. Within this family, the lysyl-tRNA...
Aminoacyl-tRNA synthetases (aaRSs) play a central role in the translation of genetic code, serving as attractive drug targets. Within this family, the lysyl-tRNA synthetase (LysRS) constitutes a promising antimalarial target. ASP3026, an anaplastic lymphoma kinase (ALK) inhibitor was recently identified as a novel Plasmodium falciparum LysRS (PfLysRS) inhibitor. Here, based on cocrystal structures and biochemical experiments, we developed a series of ASP3026 analogues to improve the selectivity and potency of LysRS inhibition. The leading compound 36 showed a dissociation constant of 15.9 nM with PfLysRS. The inhibitory efficacy on PfLysRS and parasites has been enhanced. Covalent attachment of L-lysine to compound 36 resulted in compound 36K3, which exhibited further increased inhibitory activity against PfLysRS but significantly decreased activity against ALK. However, its inhibitory activity against parasites did not improve, suggesting potential future optimization directions. This study presents a new example of derivatization of kinase inhibitors repurposed to inhibit aaRS.
Topics: Plasmodium falciparum; Lysine-tRNA Ligase; Protein Kinase Inhibitors; Anaplastic Lymphoma Kinase; Antimalarials; Structure-Activity Relationship; Humans; Protozoan Proteins
PubMed: 38890421
DOI: 10.1038/s42003-024-06455-4 -
Nature Communications Jun 2024With resistance to most antimalarials increasing, it is imperative that new drugs are developed. We previously identified an aryl acetamide compound, MMV006833 (M-833),...
With resistance to most antimalarials increasing, it is imperative that new drugs are developed. We previously identified an aryl acetamide compound, MMV006833 (M-833), that inhibited the ring-stage development of newly invaded merozoites. Here, we select parasites resistant to M-833 and identify mutations in the START lipid transfer protein (PF3D7_0104200, PfSTART1). Introducing PfSTART1 mutations into wildtype parasites reproduces resistance to M-833 as well as to more potent analogues. PfSTART1 binding to the analogues is validated using organic solvent-based Proteome Integral Solubility Alteration (Solvent PISA) assays. Imaging of invading merozoites shows the inhibitors prevent the development of ring-stage parasites potentially by inhibiting the expansion of the encasing parasitophorous vacuole membrane. The PfSTART1-targeting compounds also block transmission to mosquitoes and with multiple stages of the parasite's lifecycle being affected, PfSTART1 represents a drug target with a new mechanism of action.
Topics: Plasmodium falciparum; Acetamides; Protozoan Proteins; Antimalarials; Animals; Carrier Proteins; Mutation; Malaria, Falciparum; Humans; Drug Resistance; Life Cycle Stages
PubMed: 38890312
DOI: 10.1038/s41467-024-49491-8