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Vaccines May 2024While two circumsporozoite protein-based pre-erythrocytic vaccines (PEV), RTS,S and R21, have been approved by the WHO, no blood-stage vaccine (BSV) or... (Review)
Review
While two circumsporozoite protein-based pre-erythrocytic vaccines (PEV), RTS,S and R21, have been approved by the WHO, no blood-stage vaccine (BSV) or transmission-blocking vaccine (TBV) has reached a phase 3 trial. One of the major obstacles that slows down malaria vaccine development is the shortage (or lack) of in vitro assays or animal models by which investigators can reasonably select the best vaccine formulation (e.g., antigen, adjuvant, or platform) and/or immunization strategy (e.g., interval of inoculation or route of immunization) before a human phase 2 trial. In the case of PEV, RTS,S and R21 have set a benchmark, and a new vaccine can be compared with (one of) the approved PEV directly in preclinical or early clinical studies. However, such an approach cannot be utilized for BSV or TBV development at this moment. The focus of this review is in vitro assays or in vivo models that can be used for BSV or TBV development, and I discuss important considerations during assay selection, standardization, qualification, validation, and interpretation of the assay results. Establishment of a robust assay/model with proper interpretation of the results is the one of key elements to accelerate future vaccine development.
PubMed: 38932315
DOI: 10.3390/vaccines12060586 -
Microorganisms Jun 2024Malaria parasites increase their host erythrocyte's permeability to obtain essential nutrients from plasma and facilitate intracellular growth. In the human pathogen,...
Malaria parasites increase their host erythrocyte's permeability to obtain essential nutrients from plasma and facilitate intracellular growth. In the human pathogen, this increase is mediated by the plasmodial surface anion channel (PSAC) and has been linked to CLAG3, a protein integral to the host erythrocyte membrane and encoded by a member of the conserved multigene family. Whether paralogs encoded by other genes also insert at the host membrane is unknown; their contributions to PSAC formation and other roles served are also unexplored. Here, we generated transfectant lines carrying epitope-tagged versions of each CLAG. Each paralog is colocalized with CLAG3, with concordant trafficking via merozoite rhoptries to the host erythrocyte membrane of newly invaded erythrocytes. Each also exists within infected cells in at least two forms: an alkaline-extractable soluble form and a form integral to the host membrane. Like CLAG3, CLAG2 has a variant region cleaved by extracellular proteases, but CLAG8 and CLAG9 are protease resistant. Paralog knockout lines, generated through CRISPR/Cas9 transfection, exhibited uncompromised growth in PGIM, a modified medium with higher physiological nutrient levels; this finding is in marked contrast to a recently reported CLAG3 knockout parasite. CLAG2 and CLAG8 knockout lines exhibited compensatory increases in the transcription of the remaining and associated genes, yielding increased PSAC-mediated uptake for specific solutes. We also report on the distinct transport properties of these knockout lines. Similar membrane topologies at the host membrane are consistent with each CLAG paralog contributing to PSAC, but other roles require further examination.
PubMed: 38930554
DOI: 10.3390/microorganisms12061172 -
Life (Basel, Switzerland) May 2024Plakortinic acids C () and D (), an unseparable pair of endoperoxide polyketides isolated and purified from the symbiotic association of Caribbean Sea sponges ,...
Probing the Antiplasmodial Properties of Plakortinic Acids C and D: An Uncommon Pair of Marine Peroxide-Polyketides Isolated from a Two-Sponge Association of and Collected near Puerto Rico.
Plakortinic acids C () and D (), an unseparable pair of endoperoxide polyketides isolated and purified from the symbiotic association of Caribbean Sea sponges , underwent in vitro evaluation for antiplasmodial activity against the malaria parasite using a drug luminescence assay. Initial screening at 10 µM revealed 50% in vitro parasite growth inhibition. The title compounds displayed antiplasmodial activity with an EC of 5.3 µM toward parasites. The lytic activity against erythrocytes was assessed through an erythrocyte cell lysis assay, which showed non-lytic activity at lower concentrations ranging from 1.95 to 3.91 µM. The antiplasmodial activity and the absence of hemolytic activity support the potential of plakortinic acids C () and D () as promising lead compounds. Moreover, drug-likeness (ADMET) properties assessed through the pkCSM server predicted high intestinal absorption, hepatic metabolism, and volume of distribution, indicating favorable pharmacokinetic profiles for oral administration. These findings suggest the potential suitability of these metabolites for further investigations of antiplasmodial activity in multiple parasitic stages in the mosquito and Notably, this study represents the first report of a marine natural product exhibiting the unique 7,8-dioxatricyclo[4.2.2.0]dec-9-ene motif being evaluated against malaria.
PubMed: 38929667
DOI: 10.3390/life14060684 -
Medicina (Kaunas, Lithuania) Jun 2024: Malaria continues to be a significant global health challenge. The efficacy of artemisinin-based combination therapies (ACTs) has declined in many parts of the Greater...
: Malaria continues to be a significant global health challenge. The efficacy of artemisinin-based combination therapies (ACTs) has declined in many parts of the Greater Mekong Subregion, including Vietnam, due to the spread of resistant malaria strains. This study was conducted to assess the efficacy of the Dihydroartemisinin (DHA)-Piperaquine (PPQ) regimen in treating uncomplicated malaria and to conduct molecular surveillance of antimalarial drug resistance in Binh Phuoc and Dak Nong provinces. : The study included 63 uncomplicated malaria falciparum patients from therapeutic efficacy studies (TES) treated following the WHO treatment guidelines (2009). Molecular marker analysis was performed on all 63 patients. Methods encompassed Sanger sequencing for mutations and quantitative real-time PCR for the gene. : This study found a marked decrease in the efficacy of the DHA-PPQ regimen, with an increased rate of treatment failures at two study sites. Genetic analysis revealed a significant presence of mutations and amplifications, indicating emerging resistance to artemisinin and its partner drug. : The effectiveness of the standard DHA-PPQ regimen has sharply declined, with rising treatment failure rates. This decline necessitates a review and possible revision of national malaria treatment guidelines. Importantly, molecular monitoring and clinical efficacy assessments together provide a robust framework for understanding and addressing detection drug resistance in malaria.
Topics: Humans; Artemisinins; Quinolines; Vietnam; Antimalarials; Malaria, Falciparum; Male; Female; Adult; Plasmodium falciparum; Drug Resistance; Adolescent; Middle Aged; Drug Therapy, Combination; Young Adult; Protozoan Proteins; Real-Time Polymerase Chain Reaction; Mutation; Piperazines
PubMed: 38929629
DOI: 10.3390/medicina60061013 -
International Journal of Environmental... May 2024Multidrug- and artemisinin-resistant (ART-R) parasites represent a challenge for malaria elimination worldwide. Molecular monitoring in the Kelch domain region gene...
Multidrug- and artemisinin-resistant (ART-R) parasites represent a challenge for malaria elimination worldwide. Molecular monitoring in the Kelch domain region gene allows tracking mutations in parasite resistance to artemisinin. The increase in illegal miners in the Roraima Yanomami indigenous land (YIL) could favor ART-R parasites. Thus, this study aimed to investigate ART-R in patients from illegal gold mining areas in the YIL of Roraima, Brazil. A questionnaire was conducted, and blood was collected from 48 patients diagnosed with or mixed malaria (). The DNA was extracted and the gene was amplified by PCR. The amplicons were subjected to DNA-Sanger-sequencing and the entire amplified fragment was analyzed. Among the patients, 96% (46) were from illegal mining areas of the YIL. All parasite samples carried the wild-type genotypes/ART-sensitive phenotypes. These data reinforce the continued use of artemisinin-based combination therapies (ACTs) in Roraima, as well as the maintenance of systematic monitoring for early detection of parasite populations resistant to ART, mainly in regions with an intense flow of individuals from mining areas, such as the YIL. This is especially true when the achievement of falciparum malaria elimination in Brazil is planned and expected by 2030.
Topics: Artemisinins; Brazil; Plasmodium falciparum; Humans; Antimalarials; Drug Resistance; Malaria, Falciparum; Male; Mining; Adult; Female; Middle Aged; Young Adult; Adolescent; Genotype
PubMed: 38928926
DOI: 10.3390/ijerph21060679 -
Genes May 2024Malaria results in more than 550,000 deaths each year due to drug resistance in the most lethal () species . A full genome was published in 2002, yet 44.6% of its...
BACKGROUND
Malaria results in more than 550,000 deaths each year due to drug resistance in the most lethal () species . A full genome was published in 2002, yet 44.6% of its genes have unknown functions. Improving the functional annotation of genes is important for identifying drug targets and understanding the evolution of drug resistance.
RESULTS
Genes function by interacting with one another. So, analyzing gene co-expression networks can enhance functional annotations and prioritize genes for wet lab validation. Earlier efforts to build gene co-expression networks in have been limited to a single network inference method or gaining biological understanding for only a single gene and its interacting partners. Here, we explore multiple inference methods and aim to systematically predict functional annotations for all genes. We evaluate each inferred network based on how well it predicts existing gene-Gene Ontology (GO) term annotations using network clustering and leave-one-out crossvalidation. We assess overlaps of the different networks' edges (gene co-expression relationships), as well as predicted functional knowledge. The networks' edges are overall complementary: 47-85% of all edges are unique to each network. In terms of the accuracy of predicting gene functional annotations, all networks yielded relatively high precision (as high as 87% for the network inferred using mutual information), but the highest recall reached was below 15%. All networks having low recall means that none of them capture a large amount of all existing gene-GO term annotations. In fact, their annotation predictions are highly complementary, with the largest pairwise overlap of only 27%. We provide ranked lists of inferred gene-gene interactions and predicted gene-GO term annotations for future use and wet lab validation by the malaria community.
CONCLUSIONS
The different networks seem to capture different aspects of the biology in terms of both inferred interactions and predicted gene functional annotations. Thus, relying on a single network inference method should be avoided when possible.
SUPPLEMENTARY DATA
Attached.
Topics: Plasmodium falciparum; Gene Regulatory Networks; Malaria, Falciparum; Humans; Gene Ontology; Molecular Sequence Annotation; Protozoan Proteins
PubMed: 38927622
DOI: 10.3390/genes15060685 -
Malaria Journal Jun 2024Although Tanzania adopted and has been implementing effective interventions to control and eventually eliminate malaria, the disease is still a leading public health...
High prevalence and risk of malaria among asymptomatic individuals from villages with high prevalence of artemisinin partial resistance in Kyerwa district of Kagera region, north-western Tanzania.
BACKGROUND
Although Tanzania adopted and has been implementing effective interventions to control and eventually eliminate malaria, the disease is still a leading public health problem, and the country experiences heterogeneous transmission. Recent studies reported the emergence of parasites with artemisinin partial resistance (ART-R) in Kagera region with high prevalence (> 10.0%) in two districts of Karagwe and Kyerwa. This study assessed the prevalence and predictors/risk of malaria infections among asymptomatic individuals living in a hyperendemic area where ART-R has emerged in Kyerwa District of Kagera region, north-western Tanzania.
METHODS
This was a community-based cross-sectional survey which was conducted in July and August 2023 and involved individuals aged ≥ 6 months from five villages in Kyerwa district. Demographic, anthropometric, clinical, parasitological, type of house inhabited and socio-economic status (SES) data were collected using electronic capture tools run on Open Data Kit (ODK) software. Predictors/risks of malaria infections were determined by univariate and multivariate logistic regression, and the results were presented as crude (cORs) and adjusted odds ratios (aORs), with 95% confidence intervals (CIs).
RESULTS
Overall, 4454 individuals were tested using rapid diagnostic tests (RDTs), and 1979 (44.4%) had positive results. The prevalence of malaria infections ranged from 14.4% to 68.5% and varied significantly among the villages (p < 0.001). The prevalence and odds of infections were significantly higher in males (aOR = 1.28, 95% CI 1.08 -1.51, p = 0.003), school children (aged 5-≤10 years (aOR = 3.88, 95% CI 3.07-4.91, p < 0.001) and 10-≤15 years (aOR = 4.06, 95% CI 3.22-5.13, p < 0.001)) and among individuals who were not using bed nets (aOR = 1.22, 95% CI 1.03-1.46, p = 0.024). The odds of malaria infections were also higher in individuals with lower SES (aOR = 1.42, 95% CI 1.17-1.72, p < 0.001), and living in houses without windows (aOR = 2.08, 95% CI 1.46-2.96, p < 0.001), partially open (aOR = 1.33, 95% CI 1.11-1.58, p = 0.002) or fully open windows (aOR = 1.30, 95%CI 1.05-1.61, p = 0.015).
CONCLUSION
The five villages had a high prevalence of malaria infections and heterogeneity at micro-geographic levels. Groups with higher odds of malaria infections included school children, males, and individuals with low SES, living in poorly constructed houses or non-bed net users. These are important baseline data from an area with high prevalence of parasites with ART-R and will be useful in planning interventions for these groups, and in future studies to monitor the trends and potential spread of such parasites, and in designing a response to ART-R.
Topics: Tanzania; Male; Prevalence; Female; Humans; Artemisinins; Cross-Sectional Studies; Child; Child, Preschool; Adolescent; Adult; Young Adult; Antimalarials; Middle Aged; Infant; Drug Resistance; Malaria; Aged; Malaria, Falciparum; Risk Factors; Plasmodium falciparum
PubMed: 38926854
DOI: 10.1186/s12936-024-05019-5 -
The Journal of Biological Chemistry Jun 2024Emerging Artemisinin (ART) resistance in Plasmodium falciparum (Pf) poses challenges for discovery of novel drugs to tackle ART resistant parasites. Concentrated efforts...
Emerging Artemisinin (ART) resistance in Plasmodium falciparum (Pf) poses challenges for discovery of novel drugs to tackle ART resistant parasites. Concentrated efforts towards ART resistance mechanism indicated a strong molecular link of ART resistance with up-regulated expression of unfolded protein response pathways involving Prefoldins (PFDs). However, a complete characterization of PFDs as molecular players taking part in ART resistance mechanism, and discovery of small molecule inhibitors to block this process have not been identified to date. Here, we functionally characterized all Pf Prefoldin subunits (PFD1-6), and established a causative role played by PFDs in ART resistance by demonstrating their expression in intra-erythrocytic parasites along with their interactions with Kelch13 protein through immunoprecipitation coupled MS/MS analysis. Systematic biophysical interaction analysis between all subunits of PFDs revealed their potential to form a complex. The role of PFDs in ART resistance was confirmed in orthologous yeast PFD6 mutants, where PfPFD6 expression in yeast mutants reverted phenotype to ART resistance. We identified an FDA approved drug 'Biperiden' that restricts the formation of Prefoldin complex and inhibits its interaction with its key parasite protein substrates, MSP-1 and α-tubulin-I. Moreover, Biperiden treatment inhibits the parasite growth in ART sensitive Pf3D7 and resistant Pf3D7k13 strains. Ring survival assays that are clinically relevant to analyse ART resistance in Pf3D7k13 parasites demonstrate the potency of BPD to inhibit growth of survivor parasites. Overall, our study provides first evidence towards the role of PfPFDs in ART resistance mechanism, and opens new avenues for the management of resistant parasite.
PubMed: 38925325
DOI: 10.1016/j.jbc.2024.107496 -
Biotechnology and Applied Biochemistry Jun 2024In spite of 150 years of studying malaria, the unique features of the malarial parasite, Plasmodium, still perplex researchers. One of the methods by which the parasite...
In spite of 150 years of studying malaria, the unique features of the malarial parasite, Plasmodium, still perplex researchers. One of the methods by which the parasite manages its gene expression is epigenetic regulation, the champion of which is PfGCN5, an essential enzyme responsible for acetylating histone proteins. PfGCN5 is a ∼170 kDa chromatin-remodeling enzyme that harbors the conserved bromodomain and acetyltransferase domain situated in its C-terminus domain. Although the PfGCN5 proteolytic processing is essential for its activity, the specific protease involved in this process still remains elusive. Identification of PfGCN5 interacting proteins through immunoprecipitation (IP) followed by LC-tandem mass spectrometry analysis revealed the presence of food vacuolar proteins, such as the cysteine protease Falcipain 3 (FP3), in addition to the typical members of the PfGCN5 complex. The direct interaction between FP3 and PfGCN5 was further validated by in vitro pull-down assay as well as IP assay. Subsequently, use of cysteine protease inhibitor E64d led to the inhibition of protease-specific processing of PfGCN5 with concomitant enrichment and co-localization of PfGCN5 and FP3 around the food vacuole as evidenced by confocal microscopy as well as electron microscopy. Remarkably, the proteolytic cleavage of the nuclear protein PfGCN5 by food vacuolar protease FP3 is exceptional and atypical in eukaryotic organisms. Targeting the proteolytic processing of GCN5 and the associated protease FP3 could provide a novel approach for drug development aimed at addressing the growing resistance of parasites to current antimalarial drugs.
PubMed: 38924147
DOI: 10.1002/bab.2630 -
Chembiochem : a European Journal of... Jun 2024The human malaria parasite Plasmodium falciparum (P. falciparum) continues to pose a significant public health challenge, leading to millions of fatalities globally....
The human malaria parasite Plasmodium falciparum (P. falciparum) continues to pose a significant public health challenge, leading to millions of fatalities globally. Halofuginone (HF) has shown a significant anti-P. falciparum effect, suggesting its potential as a therapeutic agent for malaria treatment. In this study, we synthesized a photoaffinity labeling probe of HF to identify its direct target in P. falciparum. Our results reveal that ubiquitin carboxyl-terminal hydrolase 3 (PfUCHL3) acts as a crucial target protein of HF, which modulates parasite growth in the intraerythrocytic cycle. In particular, we discovered that HF potentially forms hydrogen bonds with the Leu10, Glu11, and Arg217 sites of PfUCHL3, thereby inducing an allosteric effect by promoting the embedding of the helix 6' region on the protein surface. Furthermore, HF disrupts the expression of multiple functional proteins mediated by PfUCHL3, specifically those that play crucial roles in amino acid biosynthesis and metabolism in P. falciparum. Taken together, this study highlights PfUCHL3 as a previously undisclosed druggable target of HF, which contributes to the development of novel anti-malarial agents in the future.
PubMed: 38923255
DOI: 10.1002/cbic.202400269