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1.
Elife ; 102021 09 23.
Artigo em Inglês | MEDLINE | ID: mdl-34553687

RESUMO

The replication of Plasmodium falciparum parasites within red blood cells (RBCs) causes severe disease in humans, especially in Africa. Deleterious alleles like hemoglobin S are well-known to confer strong resistance to malaria, but the effects of common RBC variation are largely undetermined. Here, we collected fresh blood samples from 121 healthy donors, most with African ancestry, and performed exome sequencing, detailed RBC phenotyping, and parasite fitness assays. Over one-third of healthy donors unknowingly carried alleles for G6PD deficiency or hemoglobinopathies, which were associated with characteristic RBC phenotypes. Among non-carriers alone, variation in RBC hydration, membrane deformability, and volume was strongly associated with P. falciparum growth rate. Common genetic variants in PIEZO1, SPTA1/SPTB, and several P. falciparum invasion receptors were also associated with parasite growth rate. Interestingly, we observed little or negative evidence for divergent selection on non-pathogenic RBC variation between Africans and Europeans. These findings suggest a model in which globally widespread variation in a moderate number of genes and phenotypes modulates P. falciparum fitness in RBCs.


Assuntos
Eritrócitos/parasitologia , Malária Falciparum/genética , Plasmodium falciparum/fisiologia , África , Afro-Americanos/genética , Alelos , Grupo com Ancestrais do Continente Europeu/genética , Genótipo , Hemoglobina Falciforme/genética , Humanos , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Sequenciamento Completo do Exoma
2.
Nat Microbiol ; 6(9): 1163-1174, 2021 09.
Artigo em Inglês | MEDLINE | ID: mdl-34400833

RESUMO

Periodic fever is a characteristic clinical feature of human malaria, but how parasites survive febrile episodes is not known. Although the genomes of Plasmodium species encode a full set of chaperones, they lack the conserved eukaryotic transcription factor HSF1, which activates the expression of chaperones following heat shock. Here, we show that PfAP2-HS, a transcription factor in the ApiAP2 family, regulates the protective heat-shock response in Plasmodium falciparum. PfAP2-HS activates the transcription of hsp70-1 and hsp90 at elevated temperatures. The main binding site of PfAP2-HS in the entire genome coincides with a tandem G-box DNA motif in the hsp70-1 promoter. Engineered parasites lacking PfAP2-HS have reduced heat-shock survival and severe growth defects at 37 °C but not at 35 °C. Parasites lacking PfAP2-HS also have increased sensitivity to imbalances in protein homeostasis (proteostasis) produced by artemisinin, the frontline antimalarial drug, or the proteasome inhibitor epoxomicin. We propose that PfAP2-HS contributes to the maintenance of proteostasis under basal conditions and upregulates specific chaperone-encoding genes at febrile temperatures to protect the parasite against protein damage.


Assuntos
Febre/parasitologia , Malária Falciparum/parasitologia , Plasmodium falciparum/fisiologia , Proteínas de Protozoários/metabolismo , Fatores de Transcrição/metabolismo , Antimaláricos/farmacologia , Artemisininas/farmacologia , Regulação da Expressão Gênica/efeitos dos fármacos , Proteínas de Choque Térmico HSP70/genética , Proteínas de Choque Térmico HSP70/metabolismo , Proteínas de Choque Térmico HSP90/genética , Proteínas de Choque Térmico HSP90/metabolismo , Resposta ao Choque Térmico , Temperatura Alta , Humanos , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/genética , Plasmodium falciparum/crescimento & desenvolvimento , Proteostase/efeitos dos fármacos , Proteínas de Protozoários/genética , Fatores de Transcrição/genética
3.
Nat Commun ; 12(1): 4851, 2021 08 11.
Artigo em Inglês | MEDLINE | ID: mdl-34381047

RESUMO

Pathogens are thought to use host molecular cues to control when to initiate life-cycle transitions, but these signals are mostly unknown, particularly for the parasitic disease malaria caused by Plasmodium falciparum. The chemokine CXCL10 is present at high levels in fatal cases of cerebral malaria patients, but is reduced in patients who survive and do not have complications. Here we show a Pf 'decision-sensing-system' controlled by CXCL10 concentration. High CXCL10 expression prompts P. falciparum to initiate a survival strategy via growth acceleration. Remarkably, P. falciparum inhibits CXCL10 synthesis in monocytes by disrupting the association of host ribosomes with CXCL10 transcripts. The underlying inhibition cascade involves RNA cargo delivery into monocytes that triggers RIG-I, which leads to HUR1 binding to an AU-rich domain of the CXCL10 3'UTR. These data indicate that when the parasite can no longer keep CXCL10 at low levels, it can exploit the chemokine as a cue to shift tactics and escape.


Assuntos
Quimiocina CXCL10/metabolismo , Malária Falciparum/parasitologia , Plasmodium falciparum/fisiologia , Regiões 3' não Traduzidas , Quimiocina CXCL10/genética , Proteína DEAD-box 58/metabolismo , Proteína Semelhante a ELAV 1/metabolismo , Vesículas Extracelulares/metabolismo , Interações Hospedeiro-Parasita , Humanos , Estágios do Ciclo de Vida , Malária Falciparum/imunologia , Monócitos/metabolismo , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium falciparum/metabolismo , Biossíntese de Proteínas , RNA de Protozoário/metabolismo , Receptores Imunológicos/metabolismo , Ribossomos/metabolismo , Células THP-1
4.
Nucleic Acids Res ; 49(16): 9264-9279, 2021 09 20.
Artigo em Inglês | MEDLINE | ID: mdl-34365503

RESUMO

Gametocytogenesis, the process by which malaria parasites produce sexual forms that can infect mosquitoes, is essential for the transmission of malaria. A transcriptional switch of the pfap2-g gene triggers sexual commitment, but how the complex multi-step process is precisely programed remains largely unknown. Here, by systematic functional screening of a panel of ApiAP2 transcription factors, we identify six new ApiAP2 members associated with gametocytogenesis in Plasmodium falciparum. Among these, PfAP2-G5 (PF3D7_1139300) was found to be indispensable for gametocytogenesis. This factor suppresses the transcriptional activity of the pfap2-g gene via binding to both the upstream region and exonic gene body, the latter is linked to the maintenance of local heterochromatin structure, thereby preventing initiation of sexual commitment. Removal of this repressive effect through pfap2-g5 knockout disrupts the asexual replication cycle and promotes sexual commitment accompanied by upregulation of pfap2-g expression. However, the gametocytes produced fail to mature fully. Further analyses show that PfAP2-G5 is essential for gametocyte maturation, and causes the down-regulation of pfap2-g and a set of early gametocyte genes activated by PfAP2-G prior to gametocyte development. Collectively, our findings reveal a regulation cascade of gametocyte production in malaria parasites, and provide a new target for transmission blocking interventions.


Assuntos
Gametogênese/genética , Malária Falciparum/genética , Plasmodium falciparum/genética , Transcrição Genética , Animais , Culicidae/parasitologia , Regulação da Expressão Gênica/genética , Humanos , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Proteínas de Protozoários/genética , Fatores de Transcrição/genética
5.
PLoS Comput Biol ; 17(8): e1009257, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-34370724

RESUMO

Manual microscopic inspection of fixed and stained blood smears has remained the gold standard for Plasmodium parasitemia analysis for over a century. Unfortunately, smear preparation consumes time and reagents, while manual microscopy is skill-dependent and labor-intensive. Here, we demonstrate that deep learning enables both life stage classification and accurate parasitemia quantification of ordinary brightfield microscopy images of live, unstained red blood cells. We tested our method using both a standard light microscope equipped with visible and near-ultraviolet (UV) illumination, and a custom-built microscope employing deep-UV illumination. While using deep-UV light achieved an overall four-category classification of Plasmodium falciparum blood stages of greater than 99% and a recall of 89.8% for ring-stage parasites, imaging with near-UV light on a standard microscope resulted in 96.8% overall accuracy and over 90% recall for ring-stage parasites. Both imaging systems were tested extrinsically by parasitemia titration, revealing superior performance over manually-scored Giemsa-stained smears, and a limit of detection below 0.1%. Our results establish that label-free parasitemia analysis of live cells is possible in a biomedical laboratory setting without the need for complex optical instrumentation. We anticipate future extensions of this work could enable label-free clinical diagnostic measurements, one day eliminating the need for conventional blood smear analysis.


Assuntos
Malária Falciparum/parasitologia , Parasitemia/diagnóstico , Parasitemia/parasitologia , Plasmodium falciparum/classificação , Plasmodium falciparum/citologia , Biologia Computacional , Aprendizado Profundo , Diagnóstico por Computador , Eritrócitos/parasitologia , Humanos , Interpretação de Imagem Assistida por Computador , Malária Falciparum/diagnóstico por imagem , Microscopia Ultravioleta/instrumentação , Microscopia Ultravioleta/métodos , Redes Neurais de Computação , Parasitemia/diagnóstico por imagem , Plasmodium falciparum/crescimento & desenvolvimento
6.
J Biochem Mol Toxicol ; 35(9): e22860, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-34313355

RESUMO

The present manuscript deals with the development of novel p-aminobenzoic acid (PABA) associated 1,3,5-triazine derivatives as antimalarial agents. The molecules were developed via microwave-assisted synthesis and structures of compounds were ascertained via numerous analytical and spectroscopic techniques. The synthesized compounds were also subjected to ADMET analysis. In a docking analysis, the title compounds showed high and diverse binding affinities towards wild (-162.45 to -369.38 kcal/mol) and quadruple mutant (-165.36 to -209.47 kcal/mol) Pf-DHFR-TS via interacting with Phe58, Arg59, Ser111, Ile112, Phe116. The in vitro antimalarial activity suggested that compounds 4e, 4b, and 4h showed IC50 ranging from 4.18 to 8.66 µg/ml against the chloroquine-sensitive (3D7) strain of Plasmodium falciparum. Moreover, compounds 4g, 4b, 4e, and 4c showed IC50 ranging from 8.12 to 12.09 µg/ml against chloroquine-resistant (Dd2) strain. In conclusion, our study demonstrated the development of hybrid PABA substituted 1,3,5-triazines as a novel class of Pf-DHFR inhibitor for antimalarial drug discovery.


Assuntos
Antimaláricos , Micro-Ondas , Plasmodium falciparum/crescimento & desenvolvimento , Triazinas , Antimaláricos/síntese química , Antimaláricos/química , Antimaláricos/farmacologia , Humanos , Triazinas/síntese química , Triazinas/química , Triazinas/farmacologia
7.
Malar J ; 20(1): 303, 2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34225761

RESUMO

BACKGROUND: Plasmodium falciparum parasites cause malaria and co-exist in humans together with B-cells for long periods of time. Immunity is only achieved after repeated exposure. There has been a lack of methods to mimic the in vivo co-occurrence, where cells and parasites can be grown together for many days, and it has been difficult with long time in vitro studies. METHODS AND RESULTS: A new method for growing P. falciparum in 5% CO2 with a specially formulated culture medium is described. This knowledge was used to establish the co-culture of live P. falciparum together with human B-cells in vitro for 10 days. The presence of B-cells clearly enhanced parasite growth, but less so when Transwell inserts were used (not allowing passage of cells or merozoites), showing that direct contact is advantageous. B-cells also proliferated more in presence of parasites. Symbiotic parasitic growth was verified using CESS cell-line and it showed similar results, indicating that B-cells are indeed the cells responsible for the effect. In malaria endemic areas, people often have increased levels of atypical memory B-cells in the blood, and in this assay it was demonstrated that when parasites were present there was an increase in the proportion of CD19 + CD20 + CD27 - FCRL4 + B-cells, and a contraction of classical memory B-cells. This effect was most clearly seen when direct contact between B-cells and parasites was allowed. CONCLUSIONS: These results demonstrate that P. falciparum and B-cells undoubtedly can affect each other when allowed to multiply together, which is valuable information for future vaccine studies.


Assuntos
Linfócitos B/metabolismo , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Linfócitos B/parasitologia , Técnicas de Cocultura , Humanos
8.
Molecules ; 26(13)2021 Jun 30.
Artigo em Inglês | MEDLINE | ID: mdl-34208832

RESUMO

The rapid emergence of drug resistance to the current antimalarial agents has led to the urgent need for the discovery of new and effective compounds. In this work, a series of 5-phenoxy primaquine analogs with 8-aminoquinoline core (7a-7h) was synthesized and investigated for their antimalarial activity against Plasmodium falciparum. Most analogs showed improved blood antimalarial activity compared to the original primaquine. To further explore a drug hybrid strategy, a conjugate compound between tetraoxane and the representative 5-phenoxy-primaquine analog 7a was synthesized. In our work, the hybrid compound 12 exhibited almost a 30-fold increase in the blood antimalarial activity (IC50 = 0.38 ± 0.11 µM) compared to that of primaquine, with relatively low toxicity against mammalian cells (SI = 45.61). Furthermore, we found that these 5-phenoxy primaquine analogs and the hybrid exhibit significant heme polymerization inhibition, an activity similar to that of chloroquine, which could contribute to their improved antimalarial activity. The 5-phenoxy primaquine analogs and the tetraoxane hybrid could serve as promising candidates for the further development of antimalarial agents.


Assuntos
Antimaláricos , Eritrócitos/parasitologia , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/crescimento & desenvolvimento , Primaquina , Tetraoxanos , Adulto , Antimaláricos/síntese química , Antimaláricos/química , Antimaláricos/farmacologia , Eritrócitos/metabolismo , Eritrócitos/patologia , Feminino , Humanos , Malária Falciparum/metabolismo , Malária Falciparum/patologia , Masculino , Pessoa de Meia-Idade , Primaquina/análogos & derivados , Primaquina/síntese química , Primaquina/química , Primaquina/farmacologia , Tetraoxanos/síntese química , Tetraoxanos/química , Tetraoxanos/farmacologia
9.
Molecules ; 26(13)2021 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-34201912

RESUMO

Ethnobotanical surveys indicate that the Masai and Kikuyu in Kenya, the Venda in South Africa, and the Gumuz people of Ethiopia use Pappea capensis for the treatment of malaria. The present study aimed to investigate the phytochemical and antiplasmodial properties of the plant leaves. The bioactive compounds were isolated using chromatographic techniques. The structures were established using NMR, HRMS, and UV spectroscopy. Antiplasmodial activity of P. capensis leaf extract and isolated compounds against chloroquine-sensitive 3D7 P. falciparum was evaluated using the parasite lactate dehydrogenase assay. Cytotoxicity against HeLa (human cervix adenocarcinoma) cells was determined using the resazurin assay. The extract inhibited the viability of Plasmodium falciparum by more than 80% at 50 µg/mL, but it was also cytotoxic against HeLa cells at the same concentration. Chromatographic purification of the extract led to the isolation of four flavonoid glycosides and epicatechin. The compounds displayed a similar activity pattern with the extract against P. falciparum and HeLa cells. The results from this study suggest that the widespread use of P. capensis in traditional medicine for the treatment of malaria might have some merits. However, more selectivity studies are needed to determine whether the leaf extract is cytotoxic against noncancerous cells.


Assuntos
Antimaláricos , Apiaceae/química , Citotoxinas , Flavonoides , Malária Falciparum/tratamento farmacológico , Folhas de Planta/química , Plasmodium falciparum/crescimento & desenvolvimento , Antimaláricos/química , Antimaláricos/isolamento & purificação , Antimaláricos/farmacologia , Citotoxinas/química , Citotoxinas/isolamento & purificação , Citotoxinas/farmacologia , Flavonoides/química , Flavonoides/isolamento & purificação , Flavonoides/farmacologia , Células HeLa , Humanos , Malária Falciparum/metabolismo
10.
Nature ; 595(7866): 289-294, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34194041

RESUMO

The global decline in malaria has stalled1, emphasizing the need for vaccines that induce durable sterilizing immunity. Here we optimized regimens for chemoprophylaxis vaccination (CVac), for which aseptic, purified, cryopreserved, infectious Plasmodium falciparum sporozoites (PfSPZ) were inoculated under prophylactic cover with pyrimethamine (PYR) (Sanaria PfSPZ-CVac(PYR)) or chloroquine (CQ) (PfSPZ-CVac(CQ))-which kill liver-stage and blood-stage parasites, respectively-and we assessed vaccine efficacy against homologous (that is, the same strain as the vaccine) and heterologous (a different strain) controlled human malaria infection (CHMI) three months after immunization ( https://clinicaltrials.gov/ , NCT02511054 and NCT03083847). We report that a fourfold increase in the dose of PfSPZ-CVac(PYR) from 5.12 × 104 to 2 × 105 PfSPZs transformed a minimal vaccine efficacy (low dose, two out of nine (22.2%) participants protected against homologous CHMI), to a high-level vaccine efficacy with seven out of eight (87.5%) individuals protected against homologous and seven out of nine (77.8%) protected against heterologous CHMI. Increased protection was associated with Vδ2 γδ T cell and antibody responses. At the higher dose, PfSPZ-CVac(CQ) protected six out of six (100%) participants against heterologous CHMI three months after immunization. All homologous (four out of four) and heterologous (eight out of eight) infectivity control participants showed parasitaemia. PfSPZ-CVac(CQ) and PfSPZ-CVac(PYR) induced a durable, sterile vaccine efficacy against a heterologous South American strain of P. falciparum, which has a genome and predicted CD8 T cell immunome that differs more strongly from the African vaccine strain than other analysed African P. falciparum strains.


Assuntos
Anticorpos Neutralizantes/imunologia , Fígado/imunologia , Fígado/parasitologia , Vacinas Antimaláricas/imunologia , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/imunologia , Vacinas Atenuadas/imunologia , Adulto , Animais , Formação de Anticorpos/imunologia , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Estágios do Ciclo de Vida/imunologia , Malária/sangue , Malária/imunologia , Malária/parasitologia , Malária/prevenção & controle , Vacinas Antimaláricas/administração & dosagem , Vacinas Antimaláricas/efeitos adversos , Vacinas Antimaláricas/química , Masculino , Pessoa de Meia-Idade , Plasmodium falciparum/crescimento & desenvolvimento , Linfócitos T/citologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , Fatores de Tempo , Vacinação/efeitos adversos , Vacinas Atenuadas/administração & dosagem , Vacinas Atenuadas/efeitos adversos , Vacinas Atenuadas/química
11.
Int J Mol Sci ; 22(13)2021 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-34281290

RESUMO

Plasmodium falciparum's resistance to available antimalarial drugs highlights the need for the development of novel drugs. Pyrimidine de novo biosynthesis is a validated drug target for the prevention and treatment of malaria infection. P. falciparum dihydroorotate dehydrogenase (PfDHODH) catalyzes the oxidation of dihydroorotate to orotate and utilize ubiquinone as an electron acceptor in the fourth step of pyrimidine de novo biosynthesis. PfDHODH is targeted by the inhibitor DSM265, which binds to a hydrophobic pocket located at the N-terminus where ubiquinone binds, which is known to be structurally divergent from the mammalian orthologue. In this study, we screened 40,400 compounds from the Kyoto University chemical library against recombinant PfDHODH. These studies led to the identification of 3,4-dihydro-2H,6H-pyrimido[1,2-c][1,3]benzothiazin-6-imine and its derivatives as a new class of PfDHODH inhibitor. Moreover, the hit compounds identified in this study are selective for PfDHODH without inhibition of the human enzymes. Finally, this new scaffold of PfDHODH inhibitors showed growth inhibition activity against P. falciparum 3D7 with low toxicity to three human cell lines, providing a new starting point for antimalarial drug development.


Assuntos
Antimaláricos/farmacologia , Inibidores Enzimáticos/farmacologia , Iminas/farmacologia , Oxirredutases atuantes sobre Doadores de Grupo CH-CH/antagonistas & inibidores , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/enzimologia , Proteínas de Protozoários/antagonistas & inibidores , Pirimidinas/farmacologia , Animais , Antimaláricos/química , Antimaláricos/toxicidade , Linhagem Celular , Avaliação Pré-Clínica de Medicamentos , Inibidores Enzimáticos/química , Inibidores Enzimáticos/toxicidade , Humanos , Iminas/química , Iminas/toxicidade , Plasmodium falciparum/crescimento & desenvolvimento , Pirimidinas/química , Pirimidinas/toxicidade , Proteínas Recombinantes/efeitos dos fármacos , Relação Estrutura-Atividade , Triazóis/farmacologia
12.
Parasitol Int ; 85: 102420, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34265466

RESUMO

Malaria is a haemato-protozoan disease which causes thousands of deaths every year. Due to the alarming increase of drug resistant strains of P. falciparum, malaria is now becoming more deadly. Helicases are the most important components of the cellular machinery without which cells are unable to survive. The importance of helicases has been proven in variety of organisms. In this study we have reported detailed biochemical characterization of human homologue of DDX3X from Plasmodium falciparum (PfDDX3X). Our study revealed that PfDDX3X is ATP- dependent DNA helicase whereas in human host it is ATP-dependent RNA helicase. We show that N-terminal is essential for its activity and it is present in nucleus and cytoplasm in intraerythrocytic developmental stages of P. falciparum 3D7 strain. Also, it is highly expressed in the schizont stage of P. falciparum 3D7strain. The present study suggests that a protein can perform different functions in different systems. The present study will help to understand the basic biology of malaria parasite P. falciparum.


Assuntos
DNA Helicases/genética , Plasmodium falciparum/genética , Proteínas de Protozoários/genética , Sequência de Aminoácidos , DNA Helicases/química , DNA Helicases/metabolismo , Malária Falciparum/metabolismo , Filogenia , Plasmodium falciparum/enzimologia , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium falciparum/metabolismo , Proteínas de Protozoários/química , Proteínas de Protozoários/metabolismo , Esquizontes/enzimologia , Esquizontes/genética , Esquizontes/crescimento & desenvolvimento , Esquizontes/metabolismo , Alinhamento de Sequência
13.
Front Immunol ; 12: 690348, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34305923

RESUMO

The hurdles to effective blood stage malaria vaccine design include immune evasion tactics used by the parasite such as redundant invasion pathways and antigen variation among circulating parasite strains. While blood stage malaria vaccine development primarily focuses on eliciting optimal humoral responses capable of blocking erythrocyte invasion, clinically-tested Plasmodium falciparum (Pf) vaccines have not elicited sterile protection, in part due to the dramatically high levels of antibody needed. Recent development efforts with non-redundant, conserved blood stage antigens suggest both high antibody titer and rapid antibody binding kinetics are important efficacy factors. Based on the central role of helper CD4 T cells in development of strong, protective immune responses, we systematically analyzed the class II epitope content in five leading Pf blood stage antigens (RH5, CyRPA, RIPR, AMA1 and EBA175) using in silico, in vitro, and ex vivo methodologies. We employed in silico T cell epitope analysis to enable identification of 67 HLA-restricted class II epitope clusters predicted to bind a panel of nine HLA-DRB1 alleles. We assessed a subset of these for HLA-DRB1 allele binding in vitro, to verify the in silico predictions. All clusters assessed (40 clusters represented by 46 peptides) bound at least two HLA-DR alleles in vitro. The overall epitope prediction to in vitro HLA-DRB1 allele binding accuracy was 71%. Utilizing the set of RH5 class II epitope clusters (10 clusters represented by 12 peptides), we assessed stimulation of T cells collected from HLA-matched RH5 vaccinees using an IFN-γ T cell recall assay. All clusters demonstrated positive recall responses, with the highest responses - by percentage of responders and response magnitude - associated with clusters located in the N-terminal region of RH5. Finally, a statistically significant correlation between in silico epitope predictions and ex vivo IFN-γ recall response was found when accounting for HLA-DR matches between the epitope predictions and donor HLA phenotypes. This is the first comprehensive analysis of class II epitope content in RH5, CyRPA, RIPR, AMA1 and EBA175 accompanied by in vitro HLA binding validation for all five proteins and ex vivo T cell response confirmation for RH5.


Assuntos
Antígenos de Protozoários/farmacologia , Linfócitos T CD4-Positivos/efeitos dos fármacos , Epitopos de Linfócito T/imunologia , Vacinas Antimaláricas/farmacologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum/imunologia , Antígenos de Protozoários/imunologia , Linfócitos T CD4-Positivos/imunologia , Linfócitos T CD4-Positivos/metabolismo , Linfócitos T CD4-Positivos/parasitologia , Proteínas de Transporte/imunologia , Proteínas de Transporte/farmacologia , Antígenos HLA-DR/imunologia , Interações Hospedeiro-Parasita , Humanos , Interferon gama/metabolismo , Vacinas Antimaláricas/imunologia , Malária Falciparum/sangue , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium falciparum/patogenicidade , Proteínas de Protozoários/imunologia , Proteínas de Protozoários/farmacologia
14.
Trends Parasitol ; 37(10): 922-932, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34119440

RESUMO

Epidemiological indicators describing population-level malaria transmission dynamics are widely used to guide policy recommendations. However, the determinants of malaria outcomes within individuals are still poorly understood. This conceptual gap partly reflects the fact that there are few indicators that robustly predict the trajectory of individual infections or clinical outcomes. The parasite multiplication rate (PMR) is a widely used indicator for the Plasmodium intraerythrocytic development cycle (IDC), for example, but its relationship to clinical outcomes is complex. Here, we review its calculation and use in P. falciparum malaria research, as well as the parasite and host factors that impact it. We also provide examples of metrics that can help to link within-host dynamics to malaria clinical outcomes when used alongside the PMR.


Assuntos
Plasmodium falciparum , Proteínas de Protozoários , Animais , Eritrócitos/parasitologia , Interações Hospedeiro-Parasita , Humanos , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Proteínas de Protozoários/metabolismo
15.
Mol Biochem Parasitol ; 244: 111385, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34062177

RESUMO

The sexual blood stages of the human malaria parasite Plasmodium falciparum undergo a remarkable transformation from a roughly spherical shape to an elongated crescent or "falciform" morphology from which the species gets its name. In this review, the molecular events that drive this spectacular shape change are discussed and some questions that remain regarding the mechanistic underpinnings are posed. We speculate on the role of the shape changes in promoting sequestration and release of the developing gametocyte, thereby facilitating parasite survival in the host and underpinning transmission to the mosquito vector.


Assuntos
Culicidae/parasitologia , Gametogênese , Insetos Vetores/parasitologia , Estágios do Ciclo de Vida/genética , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Animais , Fenômenos Biomecânicos , Eritrócitos/parasitologia , Feminino , Hepatócitos/parasitologia , Interações Hospedeiro-Parasita/genética , Humanos , Malária Falciparum/transmissão , Masculino , Microtúbulos/parasitologia , Microtúbulos/ultraestrutura , Plasmodium falciparum/citologia , Plasmodium falciparum/genética , Plasmodium falciparum/metabolismo , Reprodução Assexuada
16.
Mol Biochem Parasitol ; 244: 111390, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34087264

RESUMO

The present study aimed to examine the genetic diversity of human malaria parasites (i.e., P. falciparum, P. vivax and P. knowlesi) in Malaysia and southern Thailand targeting the 19-kDa C-terminal region of Merozoite Surface Protein-1 (MSP-119). This region is essential for the recognition and invasion of erythrocytes and it is considered one of the leading candidates for asexual blood stage vaccines. However, the genetic data of MSP-119 among human malaria parasites in Malaysia is limited and there is also a need to update the current sequence diversity of this gene region among the Thailand isolates. In this study, genomic DNA was extracted from 384 microscopy-positive blood samples collected from patients who attended the hospitals or clinics in Malaysia and malaria clinics in Thailand from the year 2008 to 2016. The MSP-119 was amplified using PCR followed by bidirectional sequencing. DNA sequences identified in the present study were subjected to Median-joining network analysis with sequences of MSP-119 obtained from GenBank. DNA sequence analysis revealed that PfMSP-119 of Malaysian and Thailand isolates was not genetically conserved as high number of haplotypes were detected and positive selection was prevalent in PfMSP-119, hence questioning its suitability to be used as a vaccine candidate. A novel haplotype (Q/TNG/L) was also detected in Thailand P. falciparum isolate. In contrast, PvMSP-119 was highly conserved, however for the first time, a non-synonymous substitution (A1657S) was reported among Malaysian isolates. As for PkMSP-119, the presence of purifying selection and low nucleotide diversity indicated that it might be a potential vaccine target for P. knowlesi.


Assuntos
DNA de Protozoário/genética , Malária/parasitologia , Proteína 1 de Superfície de Merozoito/genética , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium knowlesi/crescimento & desenvolvimento , Plasmodium vivax/crescimento & desenvolvimento , Seleção Genética , Animais , Sequência de Bases , Culicidae/parasitologia , Eritrócitos/parasitologia , Feminino , Expressão Gênica , Variação Genética , Haplótipos , Humanos , Insetos Vetores/parasitologia , Malária/epidemiologia , Malária/transmissão , Malásia/epidemiologia , Masculino , Proteína 1 de Superfície de Merozoito/classificação , Filogenia , Plasmodium falciparum/genética , Plasmodium falciparum/metabolismo , Plasmodium knowlesi/genética , Plasmodium knowlesi/metabolismo , Plasmodium vivax/genética , Plasmodium vivax/metabolismo , Reprodução Assexuada/genética , Análise de Sequência de DNA , Tailândia/epidemiologia
17.
Mol Biochem Parasitol ; 244: 111392, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-34171456

RESUMO

Plasmodium falciparum gametocytes modify the mechanical properties of their erythrocyte host to persist for several weeks in the blood circulation and to be available for mosquitoes. These changes are tightly regulated by the plasmodial phosphodiesterase delta that decreases both the stiffness and the permeability of the infected host cell. Here, we address the effect of the phosphodiesterase inhibitor tadalafil on deformability and permeability of gametocyte-infected erythrocytes. We show that this inhibitor drastically increases isosmotic lysis of gametocyte-infected erythrocytes and impairs their ability to circulate in an in vitro model for splenic retention. These findings indicate that tadalafil represents a novel drug lead potentially capable of blocking malaria parasite transmission by impacting gametocyte circulation.


Assuntos
Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/genética , Gametogênese/efeitos dos fármacos , Estágios do Ciclo de Vida/efeitos dos fármacos , Inibidores da Fosfodiesterase 5/farmacologia , Plasmodium falciparum/efeitos dos fármacos , Proteínas de Protozoários/antagonistas & inibidores , Tadalafila/farmacologia , Fenômenos Biomecânicos , Permeabilidade da Membrana Celular/efeitos dos fármacos , Nucleotídeo Cíclico Fosfodiesterase do Tipo 5/metabolismo , Deformação Eritrocítica/efeitos dos fármacos , Eritrócitos/efeitos dos fármacos , Eritrócitos/parasitologia , Eritrócitos/ultraestrutura , Feminino , Expressão Gênica , Interações Hospedeiro-Parasita/efeitos dos fármacos , Interações Hospedeiro-Parasita/genética , Humanos , Estágios do Ciclo de Vida/genética , Masculino , Plasmodium falciparum/enzimologia , Plasmodium falciparum/genética , Plasmodium falciparum/crescimento & desenvolvimento , Proteínas de Protozoários/genética , Proteínas de Protozoários/metabolismo , Reprodução Assexuada/efeitos dos fármacos
18.
Nat Commun ; 12(1): 3820, 2021 06 21.
Artigo em Inglês | MEDLINE | ID: mdl-34155201

RESUMO

Our current understanding of mitochondrial functioning is largely restricted to traditional model organisms, which only represent a fraction of eukaryotic diversity. The unusual mitochondrion of malaria parasites is a validated drug target but remains poorly understood. Here, we apply complexome profiling to map the inventory of protein complexes across the pathogenic asexual blood stages and the transmissible gametocyte stages of Plasmodium falciparum. We identify remarkably divergent composition and clade-specific additions of all respiratory chain complexes. Furthermore, we show that respiratory chain complex components and linked metabolic pathways are up to 40-fold more prevalent in gametocytes, while glycolytic enzymes are substantially reduced. Underlining this functional switch, we find that cristae are exclusively present in gametocytes. Leveraging these divergent properties and stage dynamics for drug development presents an attractive opportunity to discover novel classes of antimalarials and increase our repertoire of gametocytocidal drugs.


Assuntos
Estágios do Ciclo de Vida , Mitocôndrias/metabolismo , Plasmodium falciparum/metabolismo , Complexo de Proteínas da Cadeia de Transporte de Elétrons/metabolismo , Complexo de Proteínas da Cadeia de Transporte de Elétrons/ultraestrutura , Evolução Molecular , Mitocôndrias/ultraestrutura , Proteínas Mitocondriais/metabolismo , Proteínas Mitocondriais/ultraestrutura , Complexos Multiproteicos/metabolismo , Complexos Multiproteicos/ultraestrutura , Fosforilação Oxidativa , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium falciparum/ultraestrutura , Proteínas de Protozoários/metabolismo , Proteínas de Protozoários/ultraestrutura , Especificidade da Espécie
19.
Sci Rep ; 11(1): 13419, 2021 06 28.
Artigo em Inglês | MEDLINE | ID: mdl-34183715

RESUMO

Malaria remains a public health problem in Thailand, especially along its borders where highly mobile populations can contribute to persistent transmission. This study aimed to determine resistant genotypes and phenotypes of 112 Plasmodium falciparum isolates from patients along the Thai-Cambodia border during 2013-2015. The majority of parasites harbored a pfmdr1-Y184F mutation. A single pfmdr1 copy number had CVIET haplotype of amino acids 72-76 of pfcrt and no pfcytb mutations. All isolates had a single pfk13 point mutation (R539T, R539I, or C580Y), and increased % survival in the ring-stage survival assay (except for R539I). Multiple copies of pfpm2 and pfcrt-F145I were detected in 2014 (12.8%) and increased to 30.4% in 2015. Parasites containing either multiple pfpm2 copies with and without pfcrt-F145I or a single pfpm2 copy with pfcrt-F145I exhibited elevated IC90 values of piperaquine. Collectively, the emergence of these resistance patterns in Thailand near Cambodia border mirrored the reports of dihydroartemisinin-piperaquine treatment failures in the adjacent province of Cambodia, Oddar Meanchey, suggesting a migration of parasites across the border. As malaria elimination efforts ramp up in Southeast Asia, host nations militaries and other groups in border regions need to coordinate the proposed interventions.


Assuntos
Antimaláricos/farmacologia , Resistência a Medicamentos/genética , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Quinolinas/farmacologia , Adolescente , Adulto , Idoso , Antimaláricos/administração & dosagem , Antimaláricos/uso terapêutico , Artemisininas/administração & dosagem , Artemisininas/uso terapêutico , Variações do Número de Cópias de DNA , DNA de Protozoário/genética , Quimioterapia Combinada , Doenças Endêmicas , Feminino , Estudos de Associação Genética , Genótipo , Haplótipos/genética , Humanos , Malária Falciparum/epidemiologia , Masculino , Pessoa de Meia-Idade , Parasitemia/tratamento farmacológico , Parasitemia/epidemiologia , Plasmodium falciparum/genética , Plasmodium falciparum/crescimento & desenvolvimento , Plasmodium falciparum/isolamento & purificação , Proteínas de Protozoários/genética , Proteínas de Protozoários/fisiologia , Quinolinas/administração & dosagem , Quinolinas/uso terapêutico , Tailândia/epidemiologia , Adulto Jovem
20.
Commun Biol ; 4(1): 600, 2021 05 20.
Artigo em Inglês | MEDLINE | ID: mdl-34017052

RESUMO

The eukaryotic signal recognition particle (SRP) contains an Alu domain, which docks into the factor binding site of translating ribosomes and confers translation retardation. The canonical Alu domain consists of the SRP9/14 protein heterodimer and a tRNA-like folded Alu RNA that adopts a strictly 'closed' conformation involving a loop-loop pseudoknot. Here, we study the structure of the Alu domain from Plasmodium falciparum (PfAlu), a divergent apicomplexan protozoan that causes human malaria. Using NMR, SAXS and cryo-EM analyses, we show that, in contrast to its prokaryotic and eukaryotic counterparts, the PfAlu domain adopts an 'open' Y-shaped conformation. We show that cytoplasmic P. falciparum ribosomes are non-discriminative and recognize both the open PfAlu and closed human Alu domains with nanomolar affinity. In contrast, human ribosomes do not provide high affinity binding sites for either of the Alu domains. Our analyses extend the structural database of Alu domains to the protozoan species and reveal species-specific differences in the recognition of SRP Alu domains by ribosomes.


Assuntos
Elementos Alu , Plasmodium falciparum/metabolismo , Ribossomos/metabolismo , Partícula de Reconhecimento de Sinal/química , Sítios de Ligação , Cristalografia por Raios X , Humanos , Modelos Moleculares , Conformação de Ácido Nucleico , Plasmodium falciparum/genética , Plasmodium falciparum/crescimento & desenvolvimento , Ribossomos/genética , Espalhamento a Baixo Ângulo
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