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An improved understanding of the Plasmodium vivax populations in the Great Mekong Subregion (GMS) is needed to monitor the progress of malaria elimination. This study aimed to use a P. vivax single nucleotide polymorphism (SNP) barcode to evaluate the population dynamics and explore the gene flow among P. vivax parasite populations in the western GMS (China, Myanmar and Thailand). A total of 315 P. vivax patient samples collected in 2011 and 2018 from four regions of the western GMS were genotyped for 42 SNPs using the high-throughput MassARRAY SNP genotyping technology. Population genetic analysis was conducted to estimate the genetic diversity, effective population size, and population structure among the P. vivax populations. Overall, 291 samples were successfully genotyped at 39 SNPs. A significant difference was observed in the proportion of polyclonal infections among the five P. vivax populations (P = 0.0012, Pearson Chi-square test, χ2 = 18.1), with western Myanmar having the highest proportion (96.2%, 50/52) in 2018. Likewise, the average complexity of infection was also highest in western Myanmar (1.31) and lowest in northeast Myanmar (1.01) in 2018. The older samples from western China in 2011 had the highest pairwise nucleotide diversity (π, 0.388 ± 0.046), expected heterozygosity (He, 0.363 ± 0.02), and the largest effective population size. In comparison, in the neighboring northeast Myanmar, the more recent samples in 2018 showed the lowest values (π, 0.224 ± 0.036; He, 0.220 ± 0.026). Furthermore, the 2018 northeast Myanmar parasites showed high and moderate genetic differentiation from other populations with FST values of 0.162-0.252, whereas genetic differentiation among other populations was relatively low (FST ≤ 0.059). Principal component analysis, phylogeny, and STRUCTURE analysis showed that the P. vivax population in northeast Myanmar in 2018 substantially diverged from other populations. Although the 42 SNP barcode is a valuable tool for tracking parasite origins of worldwide parasite populations, a more extended barcode with additional SNPs is needed to distinguish the more related parasite populations in the western GMS.
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Código de Barras del ADN Taxonómico , Malaria Vivax , Plasmodium vivax , Polimorfismo de Nucleótido Simple , Plasmodium vivax/genética , Plasmodium vivax/clasificación , Humanos , Malaria Vivax/parasitología , Malaria Vivax/epidemiología , Mianmar/epidemiología , Tailandia/epidemiología , Genotipo , China/epidemiología , Variación Genética , Flujo GénicoRESUMEN
Plasmodium falciparum 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.
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Recent reports from Thailand reveal a substantial surge in Plasmodium knowlesi cases over the past decade, with a more than eightfold increase in incidence by 2023 compared to 2018. This study investigates temporal changes in genetic polymorphism associated with the escalating transmission of P. knowlesi malaria in Thailand over the past two decades. Twenty-five P. knowlesi samples collected in 2018-2023 were sequenced for the 42-kDa region of pkmsp1 and compared with 24 samples collected in 2000-2009, focusing on nucleotide diversity, natural selection, recombination rate, and population differentiation. Seven unique haplotypes were identified in recent samples, compared to 15 in earlier samples. Nucleotide and haplotype diversities were lower in recent samples (π = 0.016, Hd = 0.817) than in earlier samples (π = 0.018, Hd = 0.942). Significantly higher synonymous substitution rates were observed in both sample sets (dS - dN = 2.77 and 2.43, p < 0.05), indicating purifying selection and reduced genetic diversity over time. Additionally, 8 out of 17 mutation points were located on B-cell epitopes, suggesting an adaptive response by the parasites to evade immune recognition. Population differentiation analysis using the fixation index (Fst) revealed high genetic differentiation between parasite populations in central and southern Thailand or Malaysia. Conversely, the relatively lower Fst value between southern Thailand and Malaysia suggests a closer genetic relationship, possibly reflecting historical gene flow. In conclusion, our findings highlight a decline in genetic diversity and evidence of purifying selection associated with the recently increased incidence of P. knowlesi malaria in Thailand. The minor genetic differentiation between P. knowlesi populations from southern Thailand and Malaysia suggests a shared recent ancestry of these parasites and underscores the need for coordinated efforts between the two countries for the elimination of P. knowlesi.
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BACKGROUND: Evidence suggests that coronavirus disease 2019 (COVID-19) is associated with the risk of cardiovascular diseases (CVDs). However, the results are inconsistent, and the causality remains to be established. We aimed to investigate the potential causal relationship between COVID-19 and CVDs by using two-sample Mendelian randomization (MR) analysis. METHODS: Summary-level data for COVID-19 and CVDs including myocarditis, heart failure (HF), acute myocardial infarction (AMI), arrhythmia and venous thromboembolism (VTE) were obtained from the IEU OpenGWAS project, a public genome-wide association study (GWAS). Single nucleotide polymorphisms (SNPs) were used as instrumental variables. Five complementary MR methods were performed, including inverse variance weighted (IVW), MR-Egger, weighted median, weighted mode and simple mode methods. IVW method was considered as the primary approach. Besides, sensitivity analyses, including Cochran's Q test, MR-Egger intercept test, and leave-one-out analysis, were performed to evaluate the robustness of the results. RESULTS: According to the IVW results, our MR study indicated that genetically predicted COVID-19 was not causally connected with the risk of CVDs [myocarditis: odds ratio (OR) = 1.407, 95% confidence interval (CI) = 0.761-2.602, p-value = 0.277; HF: OR = 1.180, 95% CI = 0.980-1.420, p-value = 0.080; AMI: OR = 1.002, 95% CI = 0.998-1.005, p-value = 0.241; arrhythmia: OR = 0.865, 95% CI = 0.717-1.044, p-value = 0.132; VTE: OR = 1.013, 95% CI = 0.997-1.028, p-value = 0.115]. The supplementary MR methods showed similar results. Sensitivity analyses suggested that the causal estimates were robust. CONCLUSION: This two-sample MR analysis did not provide sufficient evidence for a causal relationship between COVID-19 and the risk of acute CVDs, which may provide new insights into the prevention of acute CVDs in COVID-19 patients.
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COVID-19 , Enfermedades Cardiovasculares , Estudio de Asociación del Genoma Completo , Análisis de la Aleatorización Mendeliana , Polimorfismo de Nucleótido Simple , Humanos , COVID-19/diagnóstico , COVID-19/complicaciones , COVID-19/epidemiología , COVID-19/genética , Enfermedades Cardiovasculares/genética , Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/diagnóstico , Medición de Riesgo , Factores de Riesgo , SARS-CoV-2/genética , Predisposición Genética a la Enfermedad , Enfermedad AgudaRESUMEN
Host immune responses are tightly controlled by various immune factors during infection, and protozoan parasites also manipulate the immune system to evade surveillance, leading to an evolutionary arms race in hostâpathogen interactions; however, the underlying mechanisms are not fully understood. We observed that the level of superoxide dismutase 3 (SOD3) was significantly elevated in both Plasmodium falciparum malaria patients and mice infected with four parasite species. SOD3-deficient mice had a substantially longer survival time and lower parasitemia than control mice after infection, whereas SOD3-overexpressing mice were much more vulnerable to parasite infection. We revealed that SOD3, secreted from activated neutrophils, bound to T cells, suppressed the interleukin-2 expression and concomitant interferon-gamma responses crucial for parasite clearance. Overall, our findings expose active fronts in the arms race between the parasites and host immune system and provide insights into the roles of SOD3 in shaping host innate immune responses to parasite infection.
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Malaria Falciparum , Ratones Endogámicos C57BL , Ratones Noqueados , Neutrófilos , Superóxido Dismutasa , Animales , Superóxido Dismutasa/metabolismo , Superóxido Dismutasa/genética , Humanos , Ratones , Neutrófilos/inmunología , Malaria Falciparum/inmunología , Malaria Falciparum/parasitología , Inmunidad Celular , Linfocitos T/inmunología , Plasmodium falciparum/inmunología , Femenino , Interacciones Huésped-Parásitos/inmunología , Interacciones Huésped-Parásitos/genética , Interferón gamma/metabolismo , Interferón gamma/inmunología , Masculino , Inmunidad Innata , Interleucina-2/metabolismo , Interleucina-2/inmunología , Interleucina-2/genética , Parasitemia/inmunologíaRESUMEN
BACKGROUND: Malaria transmission-blocking vaccines (TBVs) aim to inhibit malaria parasite development in mosquitoes and prevent further transmission to the human host. The putative-secreted ookinete protein 25 (PSOP25), highly conserved in Plasmodium spp., is a promising TBV target. Here, we investigated PvPSOP25 from P. vivax as a TBV candidate using transgenic murine parasite P. berghei and clinical P. vivax isolates. METHODS AND FINDINGS: A transgenic P. berghei line expressing PvPSOP25 (TrPvPSOP25Pb) was generated. Full-length PvPSOP25 was expressed in the yeast Pichia pastoris and used to immunize mice to obtain anti-rPvPSOP25 sera. The transmission-blocking activity of the anti-rPvPSOP25 sera was evaluated through in vitro assays and mosquito-feeding experiments. The antisera generated by immunization with rPvPSOP25 specifically recognized the native PvPSOP25 antigen expressed in TrPvPSOP25Pb ookinetes. In vitro assays showed that the immune sera significantly inhibited exflagellation and ookinete formation of the TrPvPSOP25Pb parasite. Mosquitoes feeding on mice infected with the transgenic parasite and passively transferred with the anti-rPvPSOP25 sera showed a 70.7% reduction in oocyst density compared to the control group. In a direct membrane feeding assay conducted with five clinical P. vivax isolates, the mouse anti-rPvPSOP25 antibodies significantly reduced the oocyst density while showing a negligible influence on mosquito infection prevalence. CONCLUSIONS: This study supported the feasibility of transgenic murine malaria parasites expressing P. vivax antigens as a useful tool for evaluating P. vivax TBV candidates. Meanwhile, the moderate transmission-reducing activity of the generated anti-rPvPSOP25 sera necessitates further research to optimize its efficacy.
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Vacunas contra la Malaria , Malaria Vivax , Plasmodium berghei , Plasmodium vivax , Proteínas Protozoarias , Animales , Ratones , Plasmodium vivax/genética , Plasmodium vivax/inmunología , Vacunas contra la Malaria/inmunología , Vacunas contra la Malaria/administración & dosificación , Plasmodium berghei/genética , Plasmodium berghei/inmunología , Proteínas Protozoarias/genética , Proteínas Protozoarias/inmunología , Humanos , Malaria Vivax/transmisión , Malaria Vivax/parasitología , Malaria Vivax/prevención & control , Malaria Vivax/inmunología , Femenino , Antígenos de Protozoos/genética , Antígenos de Protozoos/inmunología , Anticuerpos Antiprotozoarios/sangre , Anticuerpos Antiprotozoarios/inmunología , Malaria/transmisión , Malaria/prevención & control , Malaria/parasitología , Malaria/inmunología , Ratones Endogámicos BALB CRESUMEN
Plasmodium falciparum 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.
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BACKGROUND: A challenge in achieving the malaria-elimination target in the Greater Mekong Subregion, including Thailand, is the predominance of Plasmodium vivax malaria, which has shown extreme resilience to control measures. OBJECTIVE: This proof-of-concept study aimed to provide evidence for implementing primaquine mass drug administration (pMDA) as a strategy for P. vivax elimination in low-endemicity settings. METHODS: The study employed a mixed-methods trial to thoroughly evaluate the effectiveness, safety, acceptability, and community engagement of pMDA. The quantitative part was designed as a 2-period cluster-crossover randomized controlled trial. The intervention was pMDA augmented to the national prevention and control standards with directly observed treatment (DOT) by village health volunteers. The qualitative part employed in-depth interviews and brainstorming discussions. The study involved 7 clusters in 2 districts of 2 southern provinces in Thailand with persistently low P. vivax transmission. In the quantitative part, 5 cross-sectional blood surveys were conducted in both the pMDA and control groups before and 3 months after pMDA. The effectiveness of pMDA was determined by comparing the proportions of P. vivax infections per 1000 population between the 2 groups, with a multilevel zero-inflated negative binomial model adjusted for cluster and time as covariates and the interaction. The safety data comprised adverse events after drug administration. Thematic content analysis was used to assess the acceptability and engagement of stakeholders. RESULTS: In the pre-pMDA period, the proportions of P. vivax infections in the pMDA (n=1536) and control (n=1577) groups were 13.0 (95% CI 8.2-20.4) and 12.0 (95% CI 7.5-19.1), respectively. At month 3 post-pMDA, these proportions in the pMDA (n=1430) and control (n=1420) groups were 8.4 (95% CI 4.6-15.1) and 5.6 (95% CI 2.6-11.5), respectively. No statistically significant differences were found between the groups. The number of malaria cases reduced in all clusters in both groups, and thus, the impact of pMDA was inconclusive. There were no major safety concerns. Acceptance among the study participants and public health care providers at local and national levels was high, and they believed that pMDA had boosted awareness in the community. CONCLUSIONS: pMDA was associated with high adherence, safety, and tolerability, but it may not significantly impact P. vivax transmission. As this was a proof-of-concept study, we decided not to scale up the intervention with larger clusters and samples. An alternative approach involving a targeted primaquine treatment strategy with primaquine and DOT is currently being implemented. We experienced success regarding effective health care workforces at point-of-care centers, effective collaborations in the community, and commitment from authorities at local and national levels. Our efforts boosted the acceptability of the malaria-elimination initiative. Community engagement is recommended to achieve elimination targets. TRIAL REGISTRATION: Thai Clinical Trials Registry TCTR20190806004; https://www.thaiclinicaltrials.org/show/TCTR20190806004.
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Antimaláricos , Malaria Vivax , Administración Masiva de Medicamentos , Primaquina , Humanos , Primaquina/uso terapéutico , Primaquina/administración & dosificación , Tailandia/epidemiología , Administración Masiva de Medicamentos/métodos , Administración Masiva de Medicamentos/estadística & datos numéricos , Masculino , Femenino , Adulto , Adolescente , Malaria Vivax/tratamiento farmacológico , Antimaláricos/uso terapéutico , Antimaláricos/administración & dosificación , Persona de Mediana Edad , Adulto Joven , Prueba de Estudio Conceptual , Niño , Estudios Cruzados , Estudios Transversales , Aceptación de la Atención de Salud/estadística & datos numéricos , Aceptación de la Atención de Salud/psicologíaRESUMEN
In malaria parasites, the regulation of mRNA translation, storage and degradation during development and life-stage transitions remains largely unknown. Here, we functionally characterized the DEAD-box RNA helicase PfDOZI in P. falciparum. Disruption of pfdozi enhanced asexual proliferation but reduced sexual commitment and impaired gametocyte development. By quantitative transcriptomics, we show that PfDOZI is involved in the regulation of invasion-related genes and sexual stage-specific genes during different developmental stages. PfDOZI predominantly participates in processing body-like mRNPs in schizonts but germ cell granule-like mRNPs in gametocytes to impose opposing actions of degradation and protection on different mRNA targets. We further show the formation of stress granule-like mRNPs during nutritional deprivation, highlighting an essential role of PfDOZI-associated mRNPs in stress response. We demonstrate that PfDOZI participates in distinct mRNPs to maintain mRNA homeostasis in response to life-stage transition and environmental changes by differentially executing post-transcriptional regulation on the target mRNAs.
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ARN Helicasas DEAD-box , Plasmodium falciparum , Proteínas Protozoarias , ARN Mensajero , ARN Helicasas DEAD-box/metabolismo , ARN Helicasas DEAD-box/genética , Plasmodium falciparum/genética , Plasmodium falciparum/metabolismo , Plasmodium falciparum/crecimiento & desarrollo , ARN Mensajero/metabolismo , ARN Mensajero/genética , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/genética , Ribonucleoproteínas/metabolismo , Ribonucleoproteínas/genética , Estadios del Ciclo de Vida/genética , ARN Protozoario/metabolismo , ARN Protozoario/genética , Estabilidad del ARN , Humanos , Malaria Falciparum/parasitologíaRESUMEN
Histone lysine acetyltransferase MYST-associated NuA4 complex is conserved from yeast to humans and plays key roles in cell cycle regulation, gene transcription, and DNA replication/repair. Here, we identified a Plasmodium falciparum MYST-associated complex, PfNuA4, which contains 11 of the 13 conserved NuA4 subunits. Reciprocal pulldowns using PfEAF2, a shared component between the NuA4 and SWR1 complexes, not only confirmed the PfNuA4 complex but also identified the PfSWR1 complex, a histone remodeling complex, although their identities are low compared to the homologs in yeast or humans. Notably, both H2A.Z/H2B.Z were associated with the PfSWR1 complex, indicating that this complex is involved in the deposition of H2A.Z/H2B.Z, the variant histone pair that is enriched in the activated promoters. Overexpression of PfMYST resulted in earlier expression of genes involved in cell cycle regulation, DNA replication, and merozoite invasion, and upregulation of the genes related to antigenic variation and DNA repair. Consistently, PfMYST overexpression led to high basal phosphorylated PfH2A (γ-PfH2A), the mark of DNA double-strand breaks, and conferred protection against genotoxic agent methyl methanesulfonate (MMS), X-rays, and artemisinin, the first-line antimalarial drug. In contrast, the knockdown of PfMYST caused a delayed parasite recovery upon MMS treatment. MMS induced the gradual disappearance of PfMYST in the cytoplasm and concomitant accumulation of PfMYST in the nucleus, suggesting cytoplasm-nucleus shuttling of PfMYST. Meanwhile, PfMYST colocalized with the γ-PfH2A, indicating PfMYST was recruited to the DNA damage sites. Collectively, PfMYST plays critical roles in cell cycle regulation, gene transcription, and DNA replication/DNA repair in this low-branching parasitic protist.IMPORTANCEUnderstanding gene regulation and DNA repair in malaria parasites is critical for identifying targets for antimalarials. This study found PfNuA4, a PfMYST-associated, histone modifier complex, and PfSWR1, a chromatin remodeling complex in malaria parasite Plasmodium falciparum. These complexes are divergent due to the low identities compared to their homologs from yeast and humans. Furthermore, overexpression of PfMYST resulted in substantial transcriptomic changes, indicating that PfMYST is involved in regulating the cell cycle, antigenic variation, and DNA replication/repair. Consistently, PfMYST was found to protect against DNA damage caused by the genotoxic agent methyl methanesulfonate, X-rays, and artemisinin, the first-line antimalarial drug. Additionally, DNA damage led to the relocation of cytoplasmic PfMYST to the nucleus and colocalization of PfMYST with γ-PfH2A, the mark of DNA damage. In summary, this study demonstrated that the PfMYST complex has critical functions in regulating cell cycle, antigenic variation, and DNA replication/DNA repair in P. falciparum.
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Reparación del ADN , Plasmodium falciparum , Proteínas Protozoarias , Plasmodium falciparum/genética , Plasmodium falciparum/efectos de los fármacos , Proteínas Protozoarias/genética , Proteínas Protozoarias/metabolismo , Histona Acetiltransferasas/genética , Histona Acetiltransferasas/metabolismo , Humanos , Replicación del ADN , Histonas/genética , Histonas/metabolismo , Regulación de la Expresión GénicaRESUMEN
BACKGROUND: Ghana is among the top 10 highest malaria burden countries, with about 20,000 children dying annually, 25% of which were under five years. This study aimed to produce interactive web-based disease spatial maps and identify the high-burden malaria districts in Ghana. METHODS: The study used 2016-2021 data extracted from the routine health service nationally representative and comprehensive District Health Information Management System II (DHIMS2) implemented by the Ghana Health Service. Bayesian geospatial modelling and interactive web-based spatial disease mapping methods were employed to quantify spatial variations and clustering in malaria risk across 260 districts. For each district, the study simultaneously mapped the observed malaria counts, district name, standardized incidence rate, and predicted relative risk and their associated standard errors using interactive web-based visualization methods. RESULTS: A total of 32,659,240 malaria cases were reported among children < 5 years from 2016 to 2021. For every 10% increase in the number of children, malaria risk increased by 0.039 (log-mean 0.95, 95% credible interval = - 13.82-15.73) and for every 10% increase in the number of males, malaria risk decreased by 0.075, albeit not statistically significant (log-mean - 1.82, 95% credible interval = - 16.59-12.95). The study found substantial spatial and temporal differences in malaria risk across the 260 districts. The predicted national relative risk was 1.25 (95% credible interval = 1.23, 1.27). The malaria risk is relatively the same over the entire year. However, a slightly higher relative risk was recorded in 2019 while in 2021, residing in Keta, Abuakwa South, Jomoro, Ahafo Ano South East, Tain, Nanumba North, and Tatale Sanguli districts was associated with the highest malaria risk ranging from a relative risk of 3.00 to 4.83. The district-level spatial patterns of malaria risks changed over time. CONCLUSION: This study identified high malaria risk districts in Ghana where urgent and targeted control efforts are required. Noticeable changes were also observed in malaria risk for certain districts over some periods in the study. The findings provide an effective, actionable tool to arm policymakers and programme managers in their efforts to reduce malaria risk and its associated morbidity and mortality in line with the Sustainable Development Goals (SDG) 3.2 for limited public health resource settings, where universal intervention across all districts is practically impossible.
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Malaria , Masculino , Niño , Humanos , Ghana/epidemiología , Teorema de Bayes , Malaria/epidemiología , Servicios de Salud , RiesgoRESUMEN
During May-July 2023, a cluster of 7 patients at local hospitals in Florida, USA, received a diagnosis of Plasmodium vivax malaria. Whole-genome sequencing of the organism from 4 patients and phylogenetic analysis with worldwide representative P. vivax genomes indicated probable single parasite introduction from Central/South America.
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Malaria Vivax , Filogenia , Plasmodium vivax , Humanos , Malaria Vivax/epidemiología , Malaria Vivax/parasitología , Malaria Vivax/diagnóstico , Florida/epidemiología , Plasmodium vivax/genética , Masculino , Secuenciación Completa del Genoma , Femenino , Adulto , Persona de Mediana EdadRESUMEN
Artemether-lumefantrine (AL) is the most widely used antimalarial drug for treating uncomplicated falciparum malaria. This study evaluated whether the K65Q mutation in the Plasmodium falciparum cysteine desulfurase IscS (Pfnfs1) gene was associated with alternated susceptibility to lumefantrine using clinical parasite samples from Ghana and the China-Myanmar border area. Parasite isolates from the China-Myanmar border had significantly higher IC50 values to lumefantrine than parasites from Ghana. In addition, the K65 allele was significantly more prevalent in the Ghanaian parasites (34.5%) than in the China-Myanmar border samples (6.8%). However, no difference was observed in the lumefantrine IC50 value between the Pfnfs1 reference K65 allele and the non reference 65Q allele in parasites from the two regions. These data suggest that the Pfnfs1 K65Q mutation may not be a reliable marker for reduced susceptibility to lumefantrine.
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Antimaláricos , Artemisininas , Malaria Falciparum , Humanos , Lumefantrina/farmacología , Antimaláricos/farmacología , Antimaláricos/uso terapéutico , Plasmodium falciparum , Combinación Arteméter y Lumefantrina/uso terapéutico , Ghana , Artemisininas/farmacología , Artemisininas/uso terapéutico , Arteméter/uso terapéutico , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/parasitología , Mutación , Etanolaminas/farmacología , Etanolaminas/uso terapéutico , Resistencia a Medicamentos/genéticaRESUMEN
Adjuvants are critical components for vaccines, which enhance the strength and longevity of the antibody response and influence the types of immune response. Limited research has been conducted on the immunogenicity and protective efficacy of various adjuvants in malaria transmission-blocking vaccines (TBVs). In this study, we formulated a promising TBV candidate antigen, the P. berghei ookinete surface antigen PSOP25, with different types of adjuvants, including the TLR4 agonist monophosphoryl lipid A (MPLA), the TLR9 agonist cytosine phosphoguanosine oligodeoxynucleotides (CpG ODN 1826) (CpG), a saponin adjuvant QS-21, aluminum hydroxide (Alum), and two combination adjuvants MPLA + QS-21 and QS-21 + CpG. We demonstrated that adjuvanted vaccines results in elevated elicited antibody levels, increased proliferation of plasma cells, and efficient formation of germinal centers (GCs), leading to enhanced long-term protective immune responses. Furthermore, CpG group exhibited the most potent inhibition of ookinete formation and transmission-blocking activity. We found that the rPSOP25 with CpG adjuvant was more effective than MPLA, QS-21, MPLA + QS-21, QS-21 + CpG adjuvants in dendritic cells (DCs) activation and differentiation. Additionally, the CpG adjuvant elicited more rubust immune memory response than Alum adjuvant. CpG and QS-21 adjuvants could activate the Th1 response and promote the secretion of IFN-γ and TNF-α. PSOP25 induced a higher number of Tfh cells in splenocytes when combined with MPLA, CpG, and QS-21 + CpG; and there was no increase in these cell populations when PSOP25 was administered with Alum. In conclusion, CpG may confer enhanced efficacy for the rPSOP25 vaccine, as evidenced by the ability of the elicited antisera to induce protective immune responses and improved transmission-blocking activity.
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Vacunas contra la Malaria , Malaria , Humanos , Adyuvantes Inmunológicos , Compuestos de Alumbre , Hidróxido de Aluminio , Malaria/prevención & control , OligodesoxirribonucleótidosRESUMEN
BACKGROUND: The effect of clothing colour on the biting rates of different vector mosquito species is not well understood. Studies under tropical field conditions are lacking. This study aimed to determine the influence of clothing colours on mosquito biting rates in rural and suburban settings in West Africa. METHODS: We performed a simulated field study in a suburban and a rural site in Mali using Mosquito-Magnet traps utilizing CO2 and other attractants, which were covered with black, white, and black/white striped textile sheets covers. These targets operated continuously for 10 consecutive days with bright nights (around full moon) and 10 consecutive days with dark nights (around new moon). Trapped mosquitoes were collected and catch rates counted hourly. Mosquitoes were morphologically identified to the species complex level (Anopheles gambiae s.l. and Culex pipiens s.l.) or species level (Aedes aegypti). A subset of Anopheles specimens were further identified by molecular methods. RESULTS: Under bright-night conditions, An. gambiae s.l. was significantly more attracted to black targets than to white and striped targets; during dark nights, no target preference was noted. During bright nights, Cx. pipiens s.l. was significantly more attracted to black and striped targets than to white targets; a similar trend was noted during dark nights (not significant). For day-active Ae. aegypti, striped targets were more attractive than the other targets and black were more attractive than white targets. CONCLUSIONS: The study firstly demonstrated that under field conditions in Mali, West Africa, mosquito catch rates were influenced by different clothing colours, depending on mosquito species and light conditions. Overall, light colours were least attractive to host-seeking mosquitoes. Using white or other light-coloured clothing can potentially reduce bite exposure and risk of disease transmission in endemic tropical regions.
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Anopheles , Color , Mosquitos Vectores , Animales , Malí , Mosquitos Vectores/fisiología , Humanos , Anopheles/fisiología , Culex/fisiología , Vestuario , Textiles , Mordeduras y Picaduras de Insectos/prevención & control , Control de Mosquitos/métodos , Conducta Alimentaria , Aedes/fisiología , Culicidae/fisiologíaRESUMEN
BACKGROUND: Artemisinin-based combination therapy (ACT) has been effective in the supervised treatment of uncomplicated malaria in Ghana. Since ACT usage is primarily unsupervised, this study aimed to determine the effectiveness of artemether-lumefantrine (AL) for treating malaria patients in two transmission settings in Ghana. METHODS: Eighty-four individuals with uncomplicated Plasmodium falciparum malaria were recruited from Lekma Hospital (LH) in Accra (low-transmission area; N = 28), southern Ghana, and King's Medical Centre (KMC) in Kumbungu (high-transmission area; N = 56), northern Ghana. Participants were followed up for 28 days after unsupervised treatment with AL. The presence of asexual parasites was determined by microscopic examination of Giemsa-stained blood smears. Plasmodium species identification was confirmed using species-specific primers targeting the 18S rRNA gene. Parasite recrudescence or reinfection was determined by genotyping the Pfmsp 1 and Pfmsp 2 genes. RESULTS: After AL treatment, 3.6% (2/56) of the patients from KMC were parasitaemic on day 3 compared to none from the LH patients. One patient from KMC with delayed parasite clearance on day 3 remained parasite-positive by microscopy on day 7 but was parasite-free by day 14. While none of the patients from LH experienced parasite recurrence during the 28-day follow-up, three and two patients from KMC had recurrent parasitaemia on days 21 and 28, respectively. Percentage reduction in parasite densities from day 1, 2, and 3 for participants from the KMC was 63.2%, 89.5%, and 84.5%. Parasite densities for participants from the LH reduced from 98.2%, 99.8% on day 1, and 2 to 100% on day 3. The 28-day cumulative incidence rate of treatment failure for KMC was 12.8% (95% confidence interval: 1.9-23.7%), while the per-protocol effectiveness of AL in KMC was 89.47%. All recurrent cases were assigned to recrudescence after parasite genotyping by Pfmsp 1 and Pfmsp 2. CONCLUSION: While AL is efficacious in treating uncomplicated malaria in Ghana, when taken under unsupervised conditions, it showed an 89.4% PCR-corrected cure rate in northern Ghana, which is slightly below the WHO-defined threshold.
Asunto(s)
Antimaláricos , Artemisininas , Malaria Falciparum , Humanos , Combinación Arteméter y Lumefantrina/uso terapéutico , Antimaláricos/uso terapéutico , Ghana , Artemisininas/uso terapéutico , Combinación de Medicamentos , Arteméter/uso terapéutico , Malaria Falciparum/tratamiento farmacológico , Recurrencia , Parasitemia/tratamiento farmacológico , Etanolaminas/uso terapéutico , Fluorenos/uso terapéutico , Plasmodium falciparum/genéticaRESUMEN
BACKGROUND: Clothianidin, an insecticide with a novel mode of action, has been deployed in the annual indoor residual spraying programme in northern Ghana since March 2021. To inform pragmatic management strategies and guide future studies, baseline data on local Anopheles gambiae sensu lato (s.l.) susceptibility to the clothianidin insecticide were collected in Kpalsogu, a village in the Northern region, Ghana. METHODS: Phenotypic susceptibility of An. gambiae mosquitoes to clothianidin was assessed using the World Health Organization (WHO) insecticide resistance monitoring bioassay. The WHO cone bioassays were conducted on mud and cement walls sprayed with Sumishield 50 wettable granules (WG) (with clothianidin active ingredient). Daily mortalities were recorded for up to 7 days to observe for delayed mortalities. Polymerase chain reaction (PCR) technique was used to differentiate the sibling species of the An. gambiae complex and also for the detection of knock down resistance genes (kdr) and the insensitive acetylcholinesterase mutation (ace-1). RESULTS: The WHO susceptibility bioassay revealed a delayed killing effect of clothianidin. Mosquitoes exposed to the cone bioassays for 5 min died 120 h after exposure. Slightly higher mortalities were observed in mosquitoes exposed to clothianidin-treated cement wall surfaces than mosquitoes exposed to mud wall surfaces. The kdr target-site mutation L1014F occurred at very high frequencies (0.89-0.94) across all vector species identified whereas the ace-1 mutation occurred at moderate levels (0.32-0.44). Anopheles gambiae sensu stricto was the most abundant species observed at 63%, whereas Anopheles arabiensis was the least observed at 9%. CONCLUSIONS: Anopheles gambiae s.l. mosquitoes in northern Ghana were susceptible to clothianidin. They harboured kdr mutations at high frequencies. The ace-1 mutation occurred in moderation. The results of this study confirm that clothianidin is an effective active ingredient and should be utilized in malaria vector control interventions.
Asunto(s)
Anopheles , Insecticidas , Malaria , Animales , Anopheles/genética , Insecticidas/farmacología , Acetilcolinesterasa , Ghana , Mosquitos VectoresRESUMEN
BACKGROUND: Imported cerebral malaria (CM) cases in non-endemic areas are often misdiagnosed, which delays treatment. Post-malaria neurological syndrome (PMNS) after recovery from severe malaria can also complicate diagnosis. CASE: We report an imported malaria case from West Africa with two sequential episodes with neurological syndromes within about a month. The first episode was diagnosed as CM with microscopy-positive Plasmodium falciparum infection. The second episode, occurring a month after the recovery from the first CM episode, was consistent with PMNS, since malaria parasites were not detected by microscopy in peripheral blood smears. However, this diagnosis was complicated by the detection of Plasmodium vivax in peripheral blood by PCR, suggesting a potential cause of the second episode by P. vivax. CONCLUSION: This study suggests that PMNS often occurs after severe falciparum malaria. Concurrent P. vivax infection with pathogenic biomass being predominantly extravascular further complicates accurate diagnosis.
Asunto(s)
Malaria Cerebral , Malaria Falciparum , Malaria Vivax , Plasmodium , Humanos , Plasmodium falciparum , Malaria Falciparum/complicaciones , Malaria Falciparum/diagnóstico , Malaria Falciparum/parasitología , Malaria Vivax/complicaciones , Malaria Vivax/diagnóstico , Malaria Vivax/parasitología , Plasmodium vivax/genética , Malaria Cerebral/complicaciones , Malaria Cerebral/diagnósticoRESUMEN
BACKGROUND: Despite years of effort to develop an effective vaccine against malaria infection, a vaccine that provides individuals with sufficient protection against malaria illness and death in endemic areas is not yet available. The development of transmission-blocking vaccines (TBVs) is a promising strategy for malaria control. A dual-antigen malaria vaccine targeting both pre- and post-fertilization antigens could effectively improve the transmission-blocking activity of vaccines against the sexual stages of the parasite. METHODS: A chimeric recombinant protein Pb22-Pbg37 (Plasmodium berghei 22-P. berghei G37) composed of 19-218 amino acids (aa) of Pb22 and the N-terminal 26-88 aa of Pbg37 was designed and expressed in the Escherichia coli expression system. The antibody titers of the fusion (Pb22-Pbg37) and mixed (Pb22+Pbg37) antigens, as well as those of Pb22 and Pbg37 single antigens were evaluated by enzyme-linked immunosorbent assay. Immunofluorescence and western blot assays were performed to test the reactivity of the antisera with the native proteins in the parasite. The induction of transmission-blocking activity (TBA) by Pb22-Pbg37 and Pb22+Pbg37 were evaluated by in vitro gametocyte activation, gamete and exflagellation center formation, ookinete conversion, and in the direct mosquito feeding assay. RESULTS: The Pb22-Pbg37 fusion protein was successfully expressed in vitro. Co-administration of Pb22 and Pbg37 as a fusion or mixed protein elicited comparable antibody responses in mice and resulted in responses to both antigens. Most importantly, both the mixed and fusion antigens induced antibodies with significantly higher levels of TBA than did each of the individual antigens when administered alone. In addition, the efficacy of vaccination with the Pb22-Pbg37 fusion protein was equivalent to that of vaccination with the mixed single antigens. CONCLUSIONS: Dual-antigen vaccines, which expand/lengthen the period during which the transmission-blocking antibodies can act during sexual-stage development, can provide a promising higher transmission-reducing activity compared to single antigens.