RESUMEN
BACKGROUND: Severe Plasmodium falciparum malarial anemia is still the principal cause of death in children in underdeveloped countries. An imbalance between proinflammatory and anti-inflammatory cytokines is associated with malaria progression. This study evaluated circulating levels of selected inflammatory cytokines among malaria-infected children in Ghana. METHODS: This case-control study was conducted at Tamale Teaching Hospital, Ghana. One hundred and twenty children with malaria and 60 controls, aged 12-144 months were selected from April to July, 2023 for the study. Malaria was diagnosed through microscopy, full blood count was measured using hematology analyzer, and cytokines were measured using enzyme-linked immunosorbent assay. RESULTS: Malaria-infected children had higher tumor necrosis factor alpha (TNF-α) (p < .001), interferon-gamma (IFN-É£) (p < .001), interleukin (IL)-1ß (p < .001), IL-6 (p < .001), granulocyte macrophage-colony stimulating factor (GM-CSF) (p < .001), and IL-10 (p < .001) levels than controls. Participants with high parasitemia had raised TNF-α (p < .001), IFN-É£ (p < .001), IL-1ß (p < .001), IL-6 (p < .001), GM-CSF (p < .001), and IL-10 (p < .001), but reduced IL-3 (p < .001) and TGF-ß (p < .001) than those with low parasitemia. Severe malarial anemic children had elevated TNF-α (p < .001), IFN-É£ (p < .001), IL-1ß (p < .001), IL-6 (p < .001), GM-CSF (p < .001), and IL-10 (p < .001), but lower IL-3 (p < .001) and TGF-ß (p < .001) than those with uncomplicated malaria. CONCLUSION: Parasite density was the principal predictor of the cytokine levels, as parasitemia positively associated with IL-10, GM-CSF, IL-6, IL-1ß, IFN-É£, and TNF-α, but negatively associated with IL-3 and TGF-ß. Malaria is associated with enhanced secretion of pro- and anti-inflammatory cytokines in Ghanaian children. Inflammatory cytokines may be involved in the development of severe malarial anemia in children. However, IL-3 and TGF-ß may offer protection against severe malarial anemia.
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Anemia , Citocinas , Progresión de la Enfermedad , Malaria Falciparum , Humanos , Citocinas/sangre , Anemia/sangre , Anemia/inmunología , Anemia/parasitología , Masculino , Preescolar , Femenino , Estudios Prospectivos , Estudios de Casos y Controles , Lactante , Malaria Falciparum/sangre , Malaria Falciparum/inmunología , Malaria Falciparum/complicaciones , Malaria Falciparum/parasitología , Malaria Falciparum/epidemiología , Ghana/epidemiología , Niño , Parasitemia/sangre , Parasitemia/inmunología , Plasmodium falciparum/inmunología , Mediadores de Inflamación/sangreRESUMEN
Striking morphological transformations characterize the invasion of a red blood cell by the malaria parasite. Shortly after the infection, parasite-induced membranes appear in the cytosol of the affected host erythrocyte. One intensely investigated membrane type, commonly called Maurer's clefts, has a slit-like morphology and can be arranged in the form of extended three-dimensional membrane stacks or networks. Here we report the three-dimensional reconstruction of a second membrane type, giant or extended membrane rings/loops, that have only occasionally been described on single ultrathin sections, however that have never been systematically examined so far. Serial ultrathin sectioning of P. falciparum-infected red blood cells, subsequent three-dimensional reconstructions, and in addition examination of Giemsa-stained blood films revealed that intraerythrocytic membrane rings/loops are not isolated structures but are locally in contact with the parasite. They consist either of the parasitophorous vacuolar membrane alone or contain the parasitophorous vacuolar membrane including the plasma membrane of the parasite and small amounts of parasite cytoplasm. We demonstrate that membrane rings/loops represent surface extensions of the parasite that maybe involved in ring stage parasite formation and Maurer's cleft generation at least in a subset of infected red blood cells.
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Citosol , Eritrocitos , Plasmodium falciparum , Eritrocitos/parasitología , Plasmodium falciparum/fisiología , Citosol/parasitología , Citosol/química , Humanos , Membrana Eritrocítica/parasitología , Membrana Eritrocítica/ultraestructura , Malaria Falciparum/parasitología , Imagenología Tridimensional , Membrana Celular/parasitologíaRESUMEN
BACKGROUND: Asymptomatic carriage of infected red blood cells (iRBCs) can be prevalent in communities regardless of transmission patterns and can occur with infection of different Plasmodium species. Clinical immunity dampens the inflammatory responses leading to disease symptoms in malaria. The aim of this study was to define the immunological correlates of asymptomatic carriage of Plasmodium falciparum in a highly exposed population. METHODS: 142 asymptomatic Plasmodium-infected individuals greater than 2 years of age without fever (body temperature <37.5 â) were followed weekly for 10 weeks before being treated with artemisinin-based combination therapy (ACT). Plasma levels of 38 cytokines were measured at baseline by Luminex and the quantity and growth inhibitory activities of circulating parasite-reactive antibodies measured. The Plasmodium antigen tested included P. falciparum merozoite extract (ME) and schizont extract (SE), and the recombinant proteins erythrocyte binding antigen 175 (EBA-175) and merozoite surface protein 1 (MSP-119). RESULTS: Median levels of IgG against P. falciparum EBA-175 and MSP-119 at baseline were significantly higher in those older than 20 years of age compared with the younger age group and appeared to correlate with better parasite control. Amongst all participants there were no discernible changes in IgG levels over time. Parasite density was higher in the younger age group and associated with IL-10, TNF and MCP-1 levels. A balanced IL-10:TNF ratio was associated with asymptomatic malaria regardless of age, and balanced ratios of IL-10/TNF and IL-10/IFN-γ were the only significant correlate of maintenance of asymptomatic malaria over the course of the study in individuals 20 years of age and younger. CONCLUSION: The above findings indicate that asymptomatic carriage of P. falciparum in children living in a hyperendemic area occurs independently of IgG but is associated with a balanced inflammatory cytokine ratio.
Asunto(s)
Portador Sano , Citocinas , Inmunoglobulina G , Malaria Falciparum , Plasmodium falciparum , Humanos , Plasmodium falciparum/inmunología , Plasmodium falciparum/fisiología , Niño , Inmunoglobulina G/sangre , Preescolar , Malaria Falciparum/epidemiología , Malaria Falciparum/inmunología , Malaria Falciparum/parasitología , Citocinas/sangre , Adolescente , Masculino , Femenino , Portador Sano/epidemiología , Adulto Joven , Infecciones Asintomáticas/epidemiología , Anticuerpos Antiprotozoarios/sangre , Enfermedades Endémicas/estadística & datos numéricosRESUMEN
Plasmodium falciparum apical membrane antigen-1 (PfAMA-1) is a major candidate for the blood-stage malaria vaccine. Genetic polymorphisms of global pfama-1suggest that the genetic diversity of the gene can disturb effective vaccine development targeting this antigen. This study was conducted to explore the genetic diversity and gene structure of pfama-1 among P. falciparum isolates collected in the Khyber Pakhtunkhwa (KP) province of Pakistan. A total of 19 full-length pfama-1 sequences were obtained from KP-Pakistan P. falciparum isolates, and genetic polymorphism and natural selection were investigated. KP-Pakistan pfama-1 exhibited genetic diversity, wherein 58 amino acid changes were identified, most of which were located in ectodomains, and domains I, II, and III. The amino acid changes commonly found in the ectodomain of global pfama-1 were also detected in KP-Pakistan pfama-1. Interestingly, 13 novel amino acid changes not reported in the global population were identified in KP-Pakistan pfama-1. KP-Pakistan pfama-1 shared similar levels of genetic diversity with global pfama-1. Evidence of natural selection and recombination events were also detected in KP-Pakistan pfama-1.
Asunto(s)
Antígenos de Protozoos , Malaria Falciparum , Proteínas de la Membrana , Plasmodium falciparum , Polimorfismo Genético , Proteínas Protozoarias , Pakistán , Plasmodium falciparum/genética , Antígenos de Protozoos/genética , Antígenos de Protozoos/inmunología , Antígenos de Protozoos/química , Proteínas Protozoarias/genética , Proteínas Protozoarias/química , Proteínas de la Membrana/genética , Humanos , Malaria Falciparum/parasitología , Malaria Falciparum/epidemiología , Variación Genética/genética , Selección Genética , Filogenia , Recombinación Genética/genéticaRESUMEN
BACKGROUND: Endemic African malaria vectors are poorly adapted to typical urban ecologies. However, Anopheles stephensi, an urban malaria vector formerly confined to South Asia and the Persian Gulf, was recently detected in Africa and may change the epidemiology of malaria across the continent. Little is known about the public health implications of An. stephensi in Africa. This study is designed to assess the relative importance of household exposure to An. stephensi and endemic malaria vectors for malaria risk in urban Sudan and Ethiopia. METHODS: Case-control studies will be conducted in 3 urban settings (2 in Sudan, 1 in Ethiopia) to assess the association between presence of An. stephensi in and around households and malaria. Cases, defined as individuals positive for Plasmodium falciparum and/or P. vivax by microscopy/rapid diagnostic test (RDT), and controls, defined as age-matched individuals negative for P. falciparum and/or P. vivax by microscopy/RDT, will be recruited from public health facilities. Both household surveys and entomological surveillance for adult and immature mosquitoes will be conducted at participant homes within 48 hours of enrolment. Adult and immature mosquitoes will be identified by polymerase chain reaction (PCR). Conditional logistic regression will be used to estimate the association between presence of An. stephensi and malaria status, adjusted for co-occurrence of other malaria vectors and participant gender. CONCLUSIONS: Findings from this study will provide evidence of the relative importance of An. stephensi for malaria burden in urban African settings, shedding light on the need for future intervention planning and policy development.
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Anopheles , Mosquitos Vectores , Anopheles/parasitología , Etiopía/epidemiología , Sudán/epidemiología , Animales , Humanos , Estudios de Casos y Controles , Mosquitos Vectores/parasitología , Composición Familiar , Malaria/epidemiología , Malaria/transmisión , Malaria Falciparum/epidemiología , Malaria Falciparum/transmisión , Plasmodium falciparum/aislamiento & purificación , Femenino , MasculinoRESUMEN
BACKGROUND: Primaquine (PQ) has activity against mature P. falciparum gametocytes and proven transmission blocking efficacy (TBE) between humans and mosquitoes. WHO formerly recommended a single transmission blocking dose of 0.75 mg/kg but this was little used. Then in 2012, faced with the emergence of artemisinin-resistant P. falciparum (ARPf) in SE Asia, the WHO recommended a lower dose of 0.25 mg/kg to be added to artemisinin-based combination therapy in falciparum-infected patients in low transmission areas. This dose was considered safe in glucose-6-phosphate dehydrogenase deficiency (G6PDd) and not requiring G6PD testing. Subsequent single low-dose primaquine (SLDPQ) studies have demonstrated safety in different G6PD variants. Dosing remains challenging in children under the age of 5 because of the paucity of PQ pharmacokinetic (PK) data. We plan to assess the anti-infectivity efficacy of SLDPQ using an allometrically scaled, weight-based regimen, with a target dose of 0.25 mg/kg, in children with acute uncomplicated falciparum malaria. METHODS: This study is an open label, randomised 1:1, phase IIb study to assess TBE, tolerability, pharmacokinetics and acceptability of artesunate pyronaridine (ASPYR) administered alone or combined with SLDPQ in 56 Burkinabe children aged ≥ 6 months- < 5 years, with uncomplicated P. falciparum and a haemoglobin (Hb) concentration of ≥ 5 g/dL. We will assess TBE, using direct membrane feeding assays (DMFA), and further investigate PQ pharmacokinetics, adverse events, Hb dynamics, G6PD, sickle cells, thalassaemia and cytochrome 2D6 (CYP2D6) status, acceptability of flavoured PQ [CAST-ClinSearch Acceptability Score Test®], and the population's knowledge, attitude and practices on malaria. EXPECTED RESULTS AND DISCUSSION: We expect children to accept tablets, confirm the TBE and gametocytocidal effects of SLDPQ and then construct a PK infectivity model (including age, sex, baseline Hb, G6PD and CYP2D6 status) to define the dose response TBE relationship that may lead to fine tuning our SLDPQ regimen. Our study will complement others that have examined factors associated with Hb dynamics and PQ PK. It will provide much needed, high-quality evidence of SLDPQ in sick African children and provide reassurance that SLDPQ should be used as a strategy against emerging ARPf in Africa. TRIAL REGISTRATION: ISRCTN16297951. Registered on September 26, 2021.
Asunto(s)
Antimaláricos , Malaria Falciparum , Plasmodium falciparum , Primaquina , Ensayos Clínicos Controlados Aleatorios como Asunto , Humanos , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/parasitología , Primaquina/farmacocinética , Primaquina/administración & dosificación , Primaquina/efectos adversos , Burkina Faso , Antimaláricos/farmacocinética , Antimaláricos/administración & dosificación , Antimaláricos/efectos adversos , Preescolar , Plasmodium falciparum/efectos de los fármacos , Masculino , Resultado del Tratamiento , Femenino , Lactante , Ensayos Clínicos Fase II como Asunto , Artemisininas/farmacocinética , Artemisininas/administración & dosificación , Artemisininas/efectos adversos , Artemisininas/uso terapéuticoRESUMEN
The selection and combination of dose regimens for antimalarials involve complex considerations including pharmacokinetic and pharmacodynamic interactions. In this study, we use immediate ex vivo P. falciparum field isolates to evaluate the effect of cabamiquine and pyronaridine as standalone treatments and in combination therapy. We feed the data into a pharmacometrics model to generate an interaction map and simulate meaningful clinical dose ratios. We demonstrate that the pharmacometrics model of parasite growth and killing provides a detailed description of parasite kinetics against cabamiquine-susceptible and resistant parasites. Pyronaridine monotherapy provides suboptimal killing rates at doses as high as 720 mg. In contrast, the combination of a single dose of 330 mg cabamiquine and 360 mg pyronaridine provides over 90% parasite killing in most of the simulated patients. The described methodology that combines a rapid, 3R-compliant in vitro method and modelling to set meaningful doses for new antimalarials could contribute to clinical drug development.
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Antimaláricos , Malaria Falciparum , Naftiridinas , Plasmodium falciparum , Plasmodium falciparum/efectos de los fármacos , Antimaláricos/farmacología , Antimaláricos/administración & dosificación , Antimaláricos/farmacocinética , Humanos , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/parasitología , Naftiridinas/administración & dosificación , Naftiridinas/farmacología , Naftiridinas/farmacocinética , Quimioterapia Combinada , Relación Dosis-Respuesta a Droga , Resistencia a Medicamentos/efectos de los fármacosRESUMEN
The Plasmodium falciparum mitochondrial electron transport chain (mETC) is responsible for essential metabolic pathways such as de novo pyrimidine synthesis and ATP synthesis. The mETC complex III (cytochrome bc1 complex) is responsible for transferring electrons from ubiquinol to cytochrome c and generating a proton gradient across the inner mitochondrial membrane, which is necessary for the function of ATP synthase. Recent studies have revealed that the composition of Plasmodium falciparum complex III (PfCIII) is divergent from humans, highlighting its suitability as a target for specific inhibition. Indeed, PfCIII is the target of the clinically used anti-malarial atovaquone and of several inhibitors undergoing pre-clinical trials, yet its role in parasite biology has not been thoroughly studied. We provide evidence that the universally conserved subunit, PfRieske, and the new parasite subunit, PfC3AP2, are part of PfCIII, with the latter providing support for the prediction of its divergent composition. Using inducible depletion, we show that PfRieske, and therefore, PfCIII as a whole, is essential for asexual blood stage parasite survival, in line with previous observations. We further found that depletion of PfRieske results in gametocyte maturation defects. These phenotypes are linked to defects in mitochondrial functions upon PfRieske depletion, including increased sensitivity to mETC inhibitors in asexual stages and decreased cristae abundance alongside abnormal mitochondrial morphology in gametocytes. This is the first study that explores the direct role of the PfCIII in gametogenesis via genetic disruption, paving the way for a better understanding of the role of mETC in the complex life cycle of these important parasites and providing further support for the focus of antimalarial drug development on this pathway.
Asunto(s)
Antimaláricos , Atovacuona , Complejo III de Transporte de Electrones , Malaria Falciparum , Mitocondrias , Plasmodium falciparum , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/crecimiento & desarrollo , Plasmodium falciparum/metabolismo , Plasmodium falciparum/genética , Atovacuona/farmacología , Complejo III de Transporte de Electrones/metabolismo , Complejo III de Transporte de Electrones/genética , Complejo III de Transporte de Electrones/antagonistas & inhibidores , Antimaláricos/farmacología , Mitocondrias/metabolismo , Mitocondrias/efectos de los fármacos , Malaria Falciparum/parasitología , Malaria Falciparum/tratamiento farmacológico , Humanos , Proteínas Protozoarias/metabolismo , Proteínas Protozoarias/genética , Proteínas Protozoarias/antagonistas & inhibidores , Estadios del Ciclo de Vida/efectos de los fármacosRESUMEN
Cerebral malaria in young African children is associated with high mortality, and persisting neurological deficits often remain in survivors. Sequestered Plasmodium-infected red blood cells lead to cerebrovascular inflammation and subsequent neuroinflammation. Brain inflammation can play a role in the pathogenesis of neurologic sequelae. Therefore, we assessed a select set of proinflammatory analytes (IP10, IL23, MIP3α, GRO, MCP-1, and osteopontin in both the plasma and cerebrospinal fluid(CSF) of Zambian children with cerebral malaria and compared this with children with neurological symptoms that were negative for Plasmodium falciparum (non-cerebral malaria). Several similarities in plasma and CSF levels were found, as were some striking differences. We confirmed that IP10 levels were higher in the plasma of cerebral malaria patients, but this was not found in CSF. Levels of osteopontin were elevated in both the plasma and CSF of CM patients compared to the non-CM patients. These results show again a highly inflammatory environment in both groups but a different profile for CM when compared to non-cerebral malaria. Osteopontin may play an important role in neurological inflammation in CM and the resulting sequelae. Therefore, osteopontin could be a valid target for further biomarker research and potentially for therapeutic interventions in neuroinflammatory infections.
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Biomarcadores , Malaria Cerebral , Osteopontina , Humanos , Malaria Cerebral/líquido cefalorraquídeo , Malaria Cerebral/sangre , Malaria Cerebral/parasitología , Osteopontina/líquido cefalorraquídeo , Osteopontina/sangre , Masculino , Femenino , Preescolar , Biomarcadores/líquido cefalorraquídeo , Biomarcadores/sangre , Inflamación/líquido cefalorraquídeo , Inflamación/sangre , Niño , Plasmodium falciparum/patogenicidad , Lactante , Malaria Falciparum/líquido cefalorraquídeo , Malaria Falciparum/sangre , Malaria Falciparum/parasitologíaRESUMEN
To achieve malaria eradication, new preventative agents that act differently to front-line treatment drugs are needed. To identify potential chemoprevention starting points we screened a sub-set of the CSIRO Australia Compound Collection for compounds with slow-action in vitro activity against Plasmodium falciparum. This work identified N,N-dialkyl-5-alkylsulfonyl-1,3,4-oxadiazol-2-amines as a new antiplasmodial chemotype (e.g., 1 96 h IC50 550 nM; 3 96 h IC50 160 nM) with a different action to delayed-death slow-action drugs. A series of analogues were synthesized from thiotetrazoles and carbomoyl derivatives using Huisgen 1,3,4-oxadiazole synthesis followed by oxidation of the resultant thioethers to target sulfones. Structure activity relationship analysis of analogues identified compounds with potent and selective in vitro activity against drug-sensitive and multi-drug resistant Plasmodium parasites (e.g., 31 and 32 96 h IC50 <40 nM; SI > 2500). Subsequent studies in mice with compound 1, which had the best microsomal stability of the compounds assessed (T1/2 >255 min), demonstrated rapid clearance and poor oral in vivo efficacy in a P. berghei murine malaria model. These data indicate that while N,N-dialkyl-5-alkylsulfonyl-1,3,4-oxadiazol-2-amines are a novel class of slow-acting antiplasmodial agents, the further development of this chemotype for malaria chemoprophylaxis will require pharmacokinetic profile improvements.
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Antimaláricos , Oxadiazoles , Plasmodium falciparum , Oxadiazoles/química , Oxadiazoles/farmacología , Oxadiazoles/síntesis química , Plasmodium falciparum/efectos de los fármacos , Antimaláricos/farmacología , Antimaláricos/química , Antimaláricos/síntesis química , Animales , Relación Estructura-Actividad , Ratones , Pruebas de Sensibilidad Parasitaria , Estructura Molecular , Relación Dosis-Respuesta a Droga , Descubrimiento de Drogas , Humanos , Malaria Falciparum/tratamiento farmacológicoRESUMEN
BACKGROUND: Reactive case detection (RCD) aims to reduce malaria transmission stemming from asymptomatic carriers. Symptomatic individuals diagnosed with malaria at a health centre are followed to their households, where members of the index case and neighbouring households are tested and treated for malaria. An RCD programme was tested in the Ashanti region of Ghana in order to study diagnostic accuracy in the hospital and household settings, assess the prevalence of subclinical infections and possible clustering in index case households, and identify operational challenges for future RCD programmes. Currently, transmission in this region is high, but reactive interventions might become an option once transmission is reduced. METHODS: 264 febrile individuals were enrolled at the Mankranso Government Hospital and tested for malaria using rapid diagnostic tests (RDT). From the pool of RDT-positive febrile index cases, 14 successful RCD follow-ups were conducted, and 233 individuals were enrolled from the index case, neighbour, and control households. The sensitivity of diagnostic tools for clinical and subclinical cases was compared, including RDT, expert microscopy by World Health Organization-certified microscopists, field microscopy, and qPCR. RESULTS: Poor diagnosis and low receptivity to RCD-style follow-ups were major limitations to a successful and effective RCD programme. Field microscopy detected only 49% of clinical infections compared to RDT. 54% of individuals did not agree to a follow-up, and 66% of attempted follow-ups failed. The system effectiveness of RCD, calculated as the product of correctly diagnosed index cases, successful follow-ups, and proportion of asymptomatic infections detected by RDT, was very low at 4.0%. CONCLUSIONS: Due to low system effectiveness and the endemic nature of the disease setting in which asymptomatic prevalence is high and infections are not clustered around index case households, RCD is currently not a feasible option for malaria control in this region. The operational challenges identified through this study may help inform future reactive intervention programme designs once transmission is reduced.
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Infecciones Asintomáticas , Pruebas Diagnósticas de Rutina , Malaria Falciparum , Ghana/epidemiología , Humanos , Malaria Falciparum/diagnóstico , Malaria Falciparum/epidemiología , Malaria Falciparum/prevención & control , Infecciones Asintomáticas/epidemiología , Femenino , Masculino , Preescolar , Niño , Adolescente , Pruebas Diagnósticas de Rutina/métodos , Pruebas Diagnósticas de Rutina/estadística & datos numéricos , Adulto , Adulto Joven , Lactante , Persona de Mediana Edad , Plasmodium falciparum/aislamiento & purificación , Prevalencia , Sensibilidad y Especificidad , AncianoRESUMEN
BACKGROUND: Human serum is a major component of Plasmodium falciparum culture medium, and can be replaced with AlbuMAX™ II, a lipid-rich bovine serum albumin, for asexual cultures. However, gametocytes produced without serum are poorly infective to mosquitoes. Serum suffers from high cost, limited availability, and variability in quality. METHODS: Several commercially-available media supplements were tested for their ability to support parasite growth and production of P. falciparum (3D7) gametocytes in standard RPMI1640 medium containing 0.5% AlbuMAX. The impact on asexual growth and gametocyte production with each supplement was assessed and compared to standard RPMI1640 medium containing 10% human serum, as well as to medium containing 0.5% AlbuMAX alone. The infectivity of gametocytes produced with one supplement to Anopheles gambiae sensu stricto was assessed by standard membrane feeding assay and measuring both prevalence of infection and oocyst intensity. RESULTS: Supplementation of medium containing 0.5% AlbuMAX with five supplements did not affect asexual growth of P. falciparum, and four of the five supplements supported early gametocyte production. The supplement producing the highest number of gametocytes, ITS-X, was further investigated and was found to support the production of mature gametocytes. Infection prevalence and oocyst intensity did not differ significantly between mosquitoes given a membrane feed containing gametocytes grown in medium with 0.5% AlbuMAX + ITS-X and those grown in medium with 10% human serum. Infection prevalence and oocyst intensity was significantly higher in case of ITS-X supplementation when compared to AlbuMAX alone. Infectious gametocytes were also produced from two field clones using ITS-X supplementation. CONCLUSIONS: Serum-free medium supplemented with ITS-X was able to support the growth of gametocytes of P. falciparum that were as infectious to An. gambiae as those grown in medium with 10% serum. This is the first fully serum-free culture system able to produce highly infectious gametocytes, thereby removing the requirement for access to serum for transmission assays.
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Anopheles , Plasmodium falciparum , Plasmodium falciparum/fisiología , Plasmodium falciparum/efectos de los fármacos , Plasmodium falciparum/crecimiento & desarrollo , Animales , Anopheles/parasitología , Medio de Cultivo Libre de Suero , Humanos , Malaria Falciparum/parasitología , Malaria Falciparum/prevención & controlRESUMEN
Australian Defence Force (ADF) personnel train and operate in malarious regions that include neighboring countries with high burden and species with latent hepatic parasites.1 We summarized longitudinal malaria case data, following a prior 10-year period review to 2007.2 Malaria case entries within the ADF Malaria and Infectious Diseases Institute (ADFMIDI)-managed Central Malaria Register (CMR) were examined. Data from cases confirmed between January 1, 2008 through December 31, 2022 were analyzed. Sixty ADF members were diagnosed with malaria, including 1 with a mixed Plasmodium falciparum and P. vivax infection. Of 61 malaria infections, 69% (42 of 61) were P. vivax. P. vivax infection resulted in delayed initial case presentation (more than 4 weeks after exposure) in at least 36% (15 of 42) of cases, and 5 personnel experienced further relapse. Most P. vivax infections were acquired in the U.S. Indo-Pacific Command (INDOPACOM) and P. falciparum in the U.S. Africa Command (AFRICOM) regions. The ADF experienced ongoing reduced malaria case incidence following high rates in the early 2000s. Maintenance of prophylactic vigilance, both for eradicating dormant hypnozoites and preventing P. vivax relapse, remains important, however.
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Malaria Falciparum , Malaria Vivax , Personal Militar , Humanos , Personal Militar/estadística & datos numéricos , Australia/epidemiología , Masculino , Femenino , Adulto , Malaria Vivax/epidemiología , Malaria Falciparum/epidemiología , Adulto Joven , Incidencia , Persona de Mediana Edad , Plasmodium vivax/aislamiento & purificación , Malaria/epidemiología , Plasmodium falciparum/aislamiento & purificación , Sistema de RegistrosRESUMEN
BACKGROUND: Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) proteins are expressed on the surface of infected erythrocytes, mediating parasite sequestration in the vasculature. PfEMP1 is a major target of protective antibodies, but the features of the antibody response are poorly defined. METHODS: In Malawian children with cerebral or uncomplicated malaria, we characterized the antibody response to 39 recombinant PfEMP1 Duffy binding like (DBL) domains or cysteine-rich interdomain regions (CIDRs) in detail, including measures of antibody classes, subclasses, and engagement with Fcγ receptors and complement. Using elastic net regularized logistic regression, we identified a combination of seven antibody targets and Fc features that best distinguished between children with cerebral and uncomplicated malaria. To confirm the role of the selected targets and Fc features, we measured antibody-dependent neutrophil and THP-1 cell phagocytosis of intercellular adhesion molecule-1 (ICAM-1) and endothelial protein C (EPCR) co-binding infected erythrocytes. RESULTS: The selected features distinguished between children with cerebral and uncomplicated malaria with 87% accuracy (median, 80-96% interquartile range) and included antibody to well-characterized DBLß3 domains and a less well-characterized CIDRγ12 domain. The abilities of antibodies to engage C1q and FcγRIIIb, rather than levels of IgG, correlated with protection. In line with a role of FcγRIIIb binding antibodies to DBLß3 domains, antibody-dependent neutrophil phagocytosis of ICAM-1 and EPCR co-binding IE was higher in uncomplicated malaria (15% median, 8-38% interquartile range) compared to cerebral malaria (7%, 30-15%, p < 0.001). CONCLUSIONS: Antibodies associated with protection from cerebral malaria target a subset of PfEMP1 domains. The Fc features of protective antibody response include engagement of FcγRIIIb and C1q, and ability to induce antibody-dependent neutrophil phagocytosis of infected erythrocytes. Identifying the targets and Fc features of protective immunity could facilitate the development of PfEMP1-based therapeutics for cerebral malaria.
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Anticuerpos Antiprotozoarios , Malaria Cerebral , Plasmodium falciparum , Proteínas Protozoarias , Humanos , Malaria Cerebral/inmunología , Malaui , Anticuerpos Antiprotozoarios/inmunología , Anticuerpos Antiprotozoarios/sangre , Proteínas Protozoarias/inmunología , Preescolar , Plasmodium falciparum/inmunología , Masculino , Femenino , Niño , Lactante , Molécula 1 de Adhesión Intercelular/inmunología , Receptor de Proteína C Endotelial/inmunología , Fagocitosis , Eritrocitos/parasitología , Eritrocitos/inmunología , Malaria Falciparum/inmunología , Antígenos de Protozoos/inmunologíaRESUMEN
BACKGROUND: Accurate diagnosis and timely treatment are crucial in combating malaria. METHODS: A total of 449 samples were screened for Plasmodium falciparum infection by expert microscopy, qPCR, and three RDTs, namely Rapigen Biocredit Malaria Ag Pf (detecting HRP2 and pLDH on separate bands), Abbott NxTek Eliminate Malaria Ag Pf (detecting HRP2), and SD Bioline Malaria Ag Pf (detecting HRP2). hrp2/3 deletion typing was done by digital PCR. RESULTS: 45.7% (205/449) individuals tested positive by qPCR for P. falciparum with a mean parasite density of 12.5 parasites/µL. Using qPCR as reference, the sensitivity of microscopy was 28.3% (58/205), the Biocredit RDT was 52.2% (107/205), the NxTek RDT was 49.3% (101/205), and the Bioline RDT was 39.5% (81/205). When only samples with densities > 20 parasites/µL were included (n = 89), sensitivity of 62.9% (56/89) by microscopy, 88.8% (79/89) by Biocredit, 88.8% (79/89) by NxTek, and 78.7% (70/89) by Bioline were obtained. All three RDTs demonstrated specificities > 95%. The limits of detection (95% probability that a sample tested positive) was 4393 parasites/µL (microscopy), 56 parasites/µL (Biocredit, considering either HRP2 or pLDH), 84 parasites/µL (NxTek), and 331 parasites/µL (Bioline). None of the three qPCR-confirmed P. falciparum positive samples, identified solely through the pLDH target, or eight samples negative for all RDTs but qPCR-positive at densities > 20 parasites/µL carried hrp2/3 deletions. CONCLUSION: The Biocredit and NxTek RDTs demonstrated comparable diagnostic efficacies. All three RDTs performed better than microscopy.
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Pruebas Diagnósticas de Rutina , Malaria Falciparum , Plasmodium falciparum , Sensibilidad y Especificidad , Malaria Falciparum/diagnóstico , Malaria Falciparum/parasitología , Humanos , Plasmodium falciparum/aislamiento & purificación , Plasmodium falciparum/genética , Ghana , Pruebas Diagnósticas de Rutina/métodos , Preescolar , Adolescente , Adulto , Niño , Adulto Joven , Femenino , Persona de Mediana Edad , Masculino , Microscopía/métodos , Lactante , Reacción en Cadena en Tiempo Real de la Polimerasa/métodos , Anciano , Anciano de 80 o más Años , Prueba de Diagnóstico RápidoRESUMEN
Intervention efforts against falciparum malaria in high-transmission regions remain challenging, with rapid resurgence typically following their relaxation. Such resilience co-occurs with incomplete immunity and a large transmission reservoir from high asymptomatic prevalence. Incomplete immunity relates to the large antigenic variation of the parasite, with the major surface antigen of the blood stage of infection encoded by the multigene and recombinant family known as var. With a stochastic agent-based model, we investigate the existence of a sharp transition in resurgence ability with intervention intensity and identify molecular indicators informative of its proximity. Their application to survey data with deep sampling of var sequences from individual isolates in northern Ghana suggests that the transmission system was brought close to transition by intervention with indoor residual spraying. These results indicate that sustaining and intensifying intervention would have pushed malaria dynamics to a slow-rebound regime with an increased probability of local parasite extinction.
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Variación Antigénica , Malaria Falciparum , Plasmodium falciparum , Malaria Falciparum/inmunología , Malaria Falciparum/transmisión , Malaria Falciparum/prevención & control , Malaria Falciparum/epidemiología , Malaria Falciparum/parasitología , Humanos , Plasmodium falciparum/inmunología , Plasmodium falciparum/genética , Ghana/epidemiología , Antígenos de Protozoos/inmunología , Antígenos de Protozoos/genética , Proteínas Protozoarias/inmunología , Proteínas Protozoarias/genética , AnimalesRESUMEN
BACKGROUND: Despite the successful efforts in controlling malaria in Vietnam, the disease remains a significant health concern, particularly in Central Vietnam. This study aimed to assess correlations between environmental, climatic, and socio-economic factors in the district with malaria cases. METHODS: The study was conducted in 15 provinces in Central Vietnam from January 2018 to December 2022. Monthly malaria cases were obtained from the Institute of Malariology, Parasitology, and Entomology Quy Nhon, Vietnam. Environmental, climatic, and socio-economic data were retrieved using a Google Earth Engine script. A multivariable Zero-inflated Poisson regression was undertaken using a Bayesian framework with spatial and spatiotemporal random effects with a conditional autoregressive prior structure. The posterior random effects were estimated using Bayesian Markov Chain Monte Carlo simulation with Gibbs sampling. RESULTS: There was a total of 5,985 Plasmodium falciparum and 2,623 Plasmodium vivax cases during the study period. Plasmodium falciparum risk increased by five times (95% credible interval [CrI] 4.37, 6.74) for each 1-unit increase of normalized difference vegetation index (NDVI) without lag and by 8% (95% CrI 7%, 9%) for every 1ºC increase in maximum temperature (TMAX) at a 6-month lag. While a decrease in risk of 1% (95% CrI 0%, 1%) for a 1 mm increase in precipitation with a 6-month lag was observed. A 1-unit increase in NDVI at a 1-month lag was associated with a four-fold increase (95% CrI 2.95, 4.90) in risk of P. vivax. In addition, the risk increased by 6% (95% CrI 5%, 7%) and 3% (95% CrI 1%, 5%) for each 1ºC increase in land surface temperature during daytime with a 6-month lag and TMAX at a 4-month lag, respectively. Spatial analysis showed a higher mean malaria risk of both species in the Central Highlands and southeast parts of Central Vietnam and a lower risk in the northern and north-western areas. CONCLUSION: Identification of environmental, climatic, and socio-economic risk factors and spatial malaria clusters are crucial for designing adaptive strategies to maximize the impact of limited public health resources toward eliminating malaria in Vietnam.
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Teorema de Bayes , Clima , Malaria Falciparum , Malaria Vivax , Factores Socioeconómicos , Análisis Espacio-Temporal , Vietnam/epidemiología , Malaria Falciparum/epidemiología , Malaria Vivax/epidemiología , Humanos , Ambiente , Plasmodium falciparum , Plasmodium vivax/fisiologíaRESUMEN
BACKGROUND: Plasmodium falciparum infection is associated with the human ABO blood group. However, there is a paucity of data on the role that ABO and Rhesus blood groups play in malaria clinical presentations. Therefore, the objective of this study was to assess the association of human ABO blood groups and the Rhesus blood (Rh) types with the severity of malaria. METHODS: This cross-sectional study was carried out at the Suhum Government Hospital in the Eastern region of Ghana. Conveniently, study participants with malaria, diagnosed by microscopy, were selected into the study. Subsequently, their ABO and Rh blood groups were determined (Accucare ABO/Rh monoclonal antibodies, Chennai, India). Malaria severity was assessed using the criteria for assessing severe malarial anaemia published by the World Health Organization. According to the criteria, severe malarial anaemia was classified as having haemoglobin (Hb) < 5 g/dL for children < 12 years and in patients ≥ 12 years, Hb level < 7 g/dL, with parasitaemia > 10,000/µL in both cases. Severe malarial anaemia was also classified as having plasma bilirubin > 50 µmol/L with parasitaemia ≥ 100,000/µL, for all ages. Chi square statistical analysis was used to test the association between the blood groups and the clinical or laboratory findings, while multivariate analysis was performed to identify which blood groups were more vulnerable to develop severe malarial anaemia. RESULTS: Of the total number of the study participants (n = 328), most of the patients had blood group O Rh positive (35.7%) while few of them had blood group AB Rh negative (2.1%). The types of Rhesus did not associate with malaria. However, compared to blood group O, the odds of developing severe malarial anaemia, in children < 12 years and in patients ≥ 12 years, were 16 times and 17.8 times higher among patients with blood group A, respectively. Furthermore, the odds of having bilirubin level > 50 µmol/L with parasitaemia ≥ 100,000 /µL was 10 times higher among patients with blood groups A and 2.6 times higher in patients with blood group B, compared to blood group O. Finally, in patients with blood group A majority (71.6%) of them developed high temperature (> 37.5 °C) while 43.3% of them vomited and had diarrhoea. However, pallor (group B = 46.2% vs group A = 37.3%), fever (group B = 84.6% vs group A = 79.1%) and nausea (group B = 46.2% vs group A = 25.4%) were more frequent in patients with blood group B than A. CONCLUSIONS: This study found that people with blood groups A and B were severely affected by malaria, with group A being the most vulnerable. It is recommended that blood group assessment be performed for all patients with malaria. Patients found to have blood group A or B must be promptly and efficiently managed to avoid the development of severe malaria anaemia.
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Sistema del Grupo Sanguíneo ABO , Anemia , Malaria Falciparum , Sistema del Grupo Sanguíneo Rh-Hr , Humanos , Estudios Transversales , Masculino , Femenino , Preescolar , Niño , Ghana/epidemiología , Adulto , Malaria Falciparum/complicaciones , Malaria Falciparum/epidemiología , Malaria Falciparum/sangre , Anemia/etiología , Anemia/sangre , Anemia/epidemiología , Adolescente , Adulto Joven , Lactante , Persona de Mediana Edad , AncianoRESUMEN
East African countries accounted for ~ 10% of all malaria prevalence worldwide in 2022, with an estimated 23.8 million cases and > 53,000 deaths. Despite recent increases in malaria incidence, high-resolution genome-wide analyses of Plasmodium parasite populations are sparse in Kenya, Tanzania, and Uganda. The Kenyan-Ugandan border region is a particular concern, with Uganda confirming the emergence and spread of artemisinin resistant P. falciparum parasites. To establish genomic surveillance along the Kenyan-Ugandan border and analyse P. falciparum population dynamics within East Africa, we generated whole-genome sequencing (WGS) data for 38 parasites from Bungoma, Western Kenya. These sequences were integrated into a genomic analysis of available East African isolate data (n = 599) and revealed parasite subpopulations with distinct genetic structure and diverse ancestral origins. Ancestral admixture analysis of these subpopulations alongside isolates from across Africa (n = 365) suggested potential independent ancestral populations from other major African populations. Within isolates from Western Kenya, the prevalence of biomarkers associated with chloroquine resistance (e.g. Pfcrt K76T) were significantly reduced compared to wider East African populations and a single isolate contained the PfK13 V568I variant, potentially linked to reduced susceptibility to artemisinin. Overall, our work provides baseline WGS data and analysis for future malaria genomic surveillance in the region.
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Resistencia a Medicamentos , Malaria Falciparum , Plasmodium falciparum , Plasmodium falciparum/genética , Plasmodium falciparum/efectos de los fármacos , Kenia/epidemiología , Humanos , Uganda/epidemiología , Malaria Falciparum/epidemiología , Malaria Falciparum/parasitología , Resistencia a Medicamentos/genética , Secuenciación Completa del Genoma , Dinámica Poblacional , Antimaláricos/farmacología , Antimaláricos/uso terapéutico , Genómica/métodos , África Oriental/epidemiología , Genoma de ProtozoosRESUMEN
Plasmodium falciparum malaria remains a dominant infectious disease that affects Africa than the rest of the world, considering its associated cases and death rates. It's a febrile illness that produces several reliable biomarkers, for example, P. falciparum lactate dehydrogenase (PfLDH), P. falciparum Plasmodium glutamate dehydrogenase (PfGDH), and P. falciparum histidine-rich proteins (HRP-II) in blood circulatory system that can easily be employed as targets in rapid diagnostic tests (RDTs). In recent times, several DNA aptamers have been developed via SELEX technology to detect some specific malaria biomarkers (PfLDH, PvLDH, HRP-II, PfGDH) in a biosensor mode with good binding affinity properties to overcome the trend of cross-reactivity, limited sensitivity and stability problems that have been observed with immunodiagnostics. In this review, we summarized existing diagnostic methods and relevant biomarkers to suggest promising approaches to develop sensitive and species-specific multiplexed diagnostic devices enabling effective detection of malaria in complex biological matrices and surveillance in the endemic region.