Project description:Induction of parasite-specific CD4+ Th1 cell responses is a promising strategy for designing effective blood-stage malaria vaccines; however, the underlying regulatory mechanisms remain largely unknown. This study demonstrated that ATG5 deficiency in myeloid cells can significantly inhibit the growth of rodent blood-stage malarial parasites by enhancing parasite-specific CD4+ Th1 cell responses. This effect was independent of ATG5-mediated canonical and non-canonical autophagy. Mechanistically, ATG5 deficiency promoted myeloid cell (Ly6G-CD11b+F4/80-) survival and subsequently increased MCP-1 production in parasite-infected mice. Ly6G-CD11b+F4/80- cell-derived MCP-1 interacted with CCR2 on CD4+ Th1 cells for their optimized responses through the JAK2/STAT4 pathway. Notably, recombinant MCP-1 significantly improved parasite-specific CD4+ Th1 responses of the whole-killed blood-stage vaccine. Conclusively, our study highlights the previously unrecognized role of ATG5 in modulating myeloid cell survival via MCP-1 production, which selectively promotes CD4+ Th1 cell responses. Our findings provide new insights into the development of effective antimalarial vaccines.
Project description:BackgroundDespite noticeable improvement in anti-malarial treatment, rapid growth of resistant malaria strains points out the need for continuous development of novel anti-malarials to fight the disastrous infection. Haemozoin is considered as a novel inhibitory pathway for new anti-malarial drugs, therefore, this study aimed to systematically review all articles investigating the correlation between anti-malarial and anti-haemozoin activities of anti-malarial compounds.MethodsA literature search was conducted on 22 October 2017 in eight databases for relevant in vitro articles reporting the correlation between anti-malarial and anti-haemozoin of anti-malarial compounds, based on the constructed search terms and inclusion criteria. ToxRtool was used to assess quality of each study.ResultsA total of ten articles were included in the review. In vitro anti-malarial and anti-haemozoin activity had a good correlation for quinolines for sensitive strains (R2 ranging from 0.66 to 0.95) and xanthones (Spearman ρ = 0.886). However, these correlations were reached after removing some compounds which had non-detectable anti-malarial or anti-haemozoin effects. Other structures (acridines, pyrolidines) showed negligible correlation with Spearman ρ ranging from 0.095 to 0.381 for acridines, and r varying from 0.54 to 0.62 for pyrolidines. Some good correlations were only shown in a logarithmic manner or when the anti-malarial activity was normalized.ConclusionThe results raised a relative relationship between anti-haemozoin and in vitro anti-malarial activities. Some studies reported compounds that were effective in the inhibition of haemozoin formation, but failed to inhibit the parasite survival and vice versa. The correlation results in these studies were calculated after these compounds were removed from their analysis. The ability of anti-malarial compounds to accumulate inside the reaction site might strengthen their anti-malarial activity.
Project description:RNA sequencing on TSWV transfected protoplast made of Nicotiana benthamiana plants silenced for subunits of the mitochondrial cytochrome bc1 complex.
Project description:Following up the open initiative of anti-malarial drug discovery, a GlaxoSmithKline (GSK) phenotypic screening hit was developed to generate hydroxyethylamine based plasmepsin (Plm) inhibitors exhibiting growth inhibition of the malaria parasite Plasmodium falciparum at nanomolar concentrations. Lead optimization studies were performed with the aim of improving Plm inhibition selectivity versus the related human aspartic protease cathepsin D (Cat D). Optimization studies were performed using Plm IV as a readily accessible model protein, the inhibition of which correlates with anti-malarial activity. Guided by sequence alignment of Plms and Cat D, selectivity-inducing structural motifs were modified in the S3 and S4 sub-pocket occupying substituents of the hydroxyethylamine inhibitors. This resulted in potent anti-malarials with an up to 50-fold Plm IV/Cat D selectivity factor. More detailed investigation of the mechanism of action of the selected compounds revealed that they inhibit maturation of the P. falciparum subtilisin-like protease SUB1, and also inhibit parasite egress from erythrocytes. Our results indicate that the anti-malarial activity of the compounds is linked to inhibition of the SUB1 maturase plasmepsin subtype Plm X.
Project description:The Plasmodium proteasome (Pf20S) emerged as a target for antimalarials. Pf20S inhibitors are active at multiple stages of the parasite life cycle and synergize with artemisinins, suggesting that Pf20S inhibitors have potential to be prophylactic, therapeutic, and transmission blocking as well as are useful for combination therapy. We recently reported asparagine ethylenediamines (AsnEDAs) as immunoproteasome inhibitors and modified AsnEDAs as selective Pf20S inhibitors. Here, we report further a structure-activity relationship study of AsnEDAs for selective inhibition of Pf20S over human proteasomes. Additionally, we show new mutation that conferred resistance to AsnEDAs and collateral sensitivity to an inhibitor of the Pf20S β2 subunit, the same as previously identified resistant mutation. This resistance could be overcome through the use of the structure-guided inhibitor design. Collateral sensitivity to inhibitors among respective proteasome subunits underscores the potential value of treating malaria with combinations of inhibitors of different proteasome subunits to minimize the emergence of drug resistance.
Project description:Exploration and Characterization of the Antimalarial Activity of Cyclopropyl Carboxamides that Target the Mitochondrial Protein, Cytochrome b
Project description:Malaria parasite egress from host erythrocytes (RBCs) is regulated by discharge of a parasite serine protease called SUB1 into the parasitophorous vacuole (PV). There, SUB1 activates a PV-resident cysteine protease called SERA6, enabling host RBC rupture through SERA6-mediated degradation of the RBC cytoskeleton protein beta-spectrin. Here we show that activation of Plasmodium falciparum SERA6 involves a second, autocatalytic step that is triggered by SUB1 cleavage. Unexpectedly, autoproteolytic maturation of SERA6 requires interaction in multimolecular complexes with a distinct PV-located protein cofactor, MSA180, that is itself a SUB1 substrate. Genetic ablation of MSA180 mimics SERA6 disruption, producing a fatal block in beta-spectrin cleavage and RBC rupture. Drug-like inhibitors of SERA6 autoprocessing similarly prevent beta-spectrin cleavage and egress in both P. falciparum and the emerging zoonotic pathogen P. knowlesi. Our results elucidate the egress pathway and identify SERA6 as a target for a new class of antimalarial drugs designed to prevent disease progression.
Project description:Plasmodium falciparum, the causative agent of the most deadly form of human malaria, is unable to salvage pyrimidines and must rely on de novo biosynthesis for survival. Dihydroorotate dehydrogenase (DHODH) catalyzes the rate-limiting step in the pyrimidine biosynthetic pathway and represents a potential target for anti-malarial therapy. A high throughput screen and subsequent medicinal chemistry program identified a series of N-alkyl-5-(1H-benzimidazol-1-yl)thiophene-2-carboxamides with low nanomolar in vitro potency against DHODH from P. falciparum, P. vivax, and P. berghei. The compounds were selective for the parasite enzymes over human DHODH, and x-ray structural data on the analog Genz-667348, demonstrated that species selectivity could be attributed to amino acid differences in the inhibitor-binding site. Compounds from this series demonstrated in vitro potency against the 3D7 and Dd2 strains of P. falciparum, good tolerability and oral exposure in the mouse, and ED(50) values in the 4-day murine P. berghei efficacy model of 13-21 mg/kg/day with oral twice-daily dosing. In particular, treatment with Genz-667348 at 100 mg/kg/day resulted in sterile cure. Two recent analogs of Genz-667348 are currently undergoing pilot toxicity testing to determine suitability as clinical development candidates.
Project description:Two PfHsp90-binding molecules, BX2819 and HS292 that have and do not have (respectively) biological activity against the blood and liver stages of Plasmodium Falciparum, were subjected to a Thermal Proteome Profiling analysis to identify the direct and indirect protein target of these molecules.