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Background: Plasmodium falciparum malaria is still a leading cause of child mortality in sub-Saharan Africa. The clinical manifestations of malaria range from asymptomatic infection to severe disease. The variation in clinical presentation is partly attributed to host genetic factors with estimated narrow-sense heritability of 23%. Here, we investigate the associations between candidate gene polymorphisms and the likelihood of severe malaria (SM) in a cohort of Malian children. Methods: Based on our previous genome-wide association studies (GWAS) analysis, candidate genes were selected for in-depth analysis using several criteria including gene-level GWAS scores, functional overlap with malaria pathogenesis, and evidence of association with protection or susceptibility to other infectious or inflammatory diseases. Single Nucleotide Polymorphisms (SNPs) residing within these genes were selected mainly based on p-values from previous severe malaria susceptibility GWAS studies and minor allele frequency (MAF) in West African populations. Results: Of 182 candidate genes reported in our previous study, 11 genes and 22 SNPs residing in these genes were selected. The selected SNPs were genotyped using KASP technology in 477 DNA samples (87 SM and 390 controls). Logistic regression analysis revealed that a common intron variant, rs13340578 in CUB and Sushi Multi Domain (CSMD1) gene, is associated with increased odds of SM in recessive mode of inheritance (MAF = 0.42, OR = 1.8, 95% CI = [1.78, 1.84], p = 0.029). The SNP is in linkage disequilibrium (LD) with multiple variants with regulatory features. Conclusion: Taken together, the current study showed that an intron variant rs13340578, residing in CSMD1 gene, is associated with increased susceptibility to malaria. This finding suggests that modified regulation of complement may contribute to malaria disease severity. Further studies are needed to identify the causal variants and the underlying molecular mechanisms.
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BACKGROUND: In patients with severe neutropenia, infections can rapidly become serious and life-threatening. It is essential to understand whether pregnancy induces changes in neutrophil levels thereby posing an increased threat to the health of gravidae. METHODOLOGY: This cross-sectional study was conducted in San Health District (Mali) and involved pregnant women infected or not by malaria parasites and non-pregnant healthy volunteers. Subjects were categorized as having neutropenia, normal neutrophil levels, and neutrophilia regarding their neutrophil levels. A logistic regression analysis was performed to determine factors associated with neutrophil level variation in pregnant women. RESULTS: Whether or not the pregnant women were infected with malaria, 98 of the 202 cases (48.5%) showed neutrophilia. Surprisingly, 67 of the 71 cases of neutropenia (94.4%) observed in this study concerned healthy people who were not pregnant. The mean percentage of neutrophil levels was significantly (p < 0.001) lower (49.9%) in the first trimester compared to the second trimester of pregnancy (62.0%). A logistic regression model showed that compared to early pregnancy, the second (OR = 12.9, 95% CI 2.2-248.1, p = 0.018) and the third trimesters (OR = 13.7, 95% CI 2.3-257.5, p = 0.016) were strongly associated with the increase of neutrophil levels. CONCLUSIONS: Pregnancy can induce the production of mature neutrophils that are continually released into circulation. Neutrophil levels were lower during the first trimester of the pregnancy compared to the second and third trimesters, but not affected by the presence or absence of malaria infection.
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Malaria , Neutrófilos , Humanos , Femenino , Embarazo , Malí/epidemiología , Estudios Transversales , Adulto , Adulto Joven , Malaria/sangre , Neutropenia/sangre , Adolescente , Complicaciones Infecciosas del Embarazo/sangre , Recuento de Leucocitos , Complicaciones Parasitarias del Embarazo/sangre , Complicaciones Parasitarias del Embarazo/epidemiologíaRESUMEN
BACKGROUND: Primaquine (PQ) is the prototype 8-aminoquinoline drug, a class which targets gametocytes and hypnozoites. The World Health Organization (WHO) recommends adding a single low dose of primaquine to the standard artemisinin-based combination therapy (ACT) in order to block malaria transmission in regions with low malaria transmission. However, the haemolytic toxicity is a major adverse outcome of primaquine in glucose-6-phosphate dehydrogenase (G6PD)-deficient subjects. This study aimed to characterize the pharmacokinetic properties of primaquine and its major metabolites in G6PD-deficient subjects. METHODS: A single low-dose of primaquine (0.4-0.5 mg/kg) was administered in twenty-eight African males. Venous and capillary plasma were sampled up to 24 h after the drug administration. Haemoglobin levels were observed up to 28 days after drug administration. Only PQ, carboxy-primaquine (CPQ), and primaquine carbamoyl-glucuronide (PQCG) were present in plasma samples and measured using liquid chromatography mass spectrometry. Drug and metabolites' pharmacokinetic properties were investigated using nonlinear mixed-effects modelling. RESULTS: Population pharmacokinetic properties of PQ, CPQ, and PQCG can be described by one-compartment disposition kinetics with a transit-absorption model. Body weight was implemented as an allometric function on the clearance and volume parameters for all compounds. None of the covariates significantly affected the pharmacokinetic parameters. No significant correlations were detected between the exposures of the measured compounds and the change in haemoglobin or methaemoglobin levels. There was no significant haemoglobin drop in the G6PD-deficient patients after administration of a single low dose of PQ. CONCLUSIONS: A single low-dose of PQ was haematologically safe in this population of G6PD-normal and G6PD-deficient African males without malaria. Trial registration NCT02535767.
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Antimaláricos , Deficiencia de Glucosafosfato Deshidrogenasa , Primaquina , Adolescente , Adulto , Humanos , Masculino , Persona de Mediana Edad , Adulto Joven , Antimaláricos/farmacocinética , Antimaláricos/sangre , Antimaláricos/administración & dosificación , Primaquina/farmacocinética , Primaquina/sangre , Primaquina/administración & dosificaciónRESUMEN
BACKGROUND: Artemether-lumefantrine is widely used for uncomplicated Plasmodium falciparum malaria; sulfadoxine-pyrimethamine plus amodiaquine is used for seasonal malaria chemoprevention. We aimed to determine the efficacy of artemether-lumefantrine with and without primaquine and sulfadoxine-pyrimethamine plus amodiaquine with and without tafenoquine for reducing gametocyte carriage and transmission to mosquitoes. METHODS: In this phase 2, single-blind, randomised clinical trial conducted in Ouelessebougou, Mali, asymptomatic individuals aged 10-50 years with P falciparum gametocytaemia were recruited from the community and randomly assigned (1:1:1:1) to receive either artemether-lumefantrine, artemether-lumefantrine with a single dose of 0·25 mg/kg primaquine, sulfadoxine-pyrimethamine plus amodiaquine, or sulfadoxine-pyrimethamine plus amodiaquine with a single dose of 1·66 mg/kg tafenoquine. All trial staff other than the pharmacist were masked to group allocation. Participants were not masked to group allocation. Randomisation was done with a computer-generated randomisation list and concealed with sealed, opaque envelopes. The primary outcome was the median within-person percent change in mosquito infection rate in infectious individuals from baseline to day 2 (artemether-lumefantrine groups) or day 7 (sulfadoxine-pyrimethamine plus amodiaquine groups) after treatment, assessed by direct membrane feeding assay. All participants who received any trial drug were included in the safety analysis. This study is registered with ClinicalTrials.gov, NCT05081089. FINDINGS: Between Oct 13 and Dec 16, 2021, 1290 individuals were screened and 80 were enrolled and randomly assigned to one of the four treatment groups (20 per group). The median age of participants was 13 (IQR 11-20); 37 (46%) of 80 participants were female and 43 (54%) were male. In individuals who were infectious before treatment, the median percentage reduction in mosquito infection rate 2 days after treatment was 100·0% (IQR 100·0-100·0; n=19; p=0·0011) with artemether-lumefantrine and 100·0% (100·0-100·0; n=19; p=0·0001) with artemether-lumefantrine with primaquine. Only two individuals who were infectious at baseline infected mosquitoes on day 2 after artemether-lumefantrine and none at day 5. By contrast, the median percentage reduction in mosquito infection rate 7 days after treatment was 63·6% (IQR 0·0-100·0; n=20; p=0·013) with sulfadoxine-pyrimethamine plus amodiaquine and 100% (100·0-100·0; n=19; p<0·0001) with sulfadoxine-pyrimethamine plus amodiaquine with tafenoquine. No grade 3-4 or serious adverse events occurred. INTERPRETATION: These data support the effectiveness of artemether-lumefantrine alone for preventing nearly all mosquito infections. By contrast, there was considerable post-treatment transmission after sulfadoxine-pyrimethamine plus amodiaquine; therefore, the addition of a transmission-blocking drug might be beneficial in maximising its community impact. FUNDING: Bill & Melinda Gates Foundation.
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Amodiaquina , Antimaláricos , Combinación Arteméter y Lumefantrina , Combinación de Medicamentos , Fluorenos , Malaria Falciparum , Plasmodium falciparum , Primaquina , Pirimetamina , Sulfadoxina , Humanos , Antimaláricos/uso terapéutico , Antimaláricos/administración & dosificación , Pirimetamina/uso terapéutico , Pirimetamina/administración & dosificación , Amodiaquina/uso terapéutico , Amodiaquina/administración & dosificación , Sulfadoxina/uso terapéutico , Sulfadoxina/administración & dosificación , Masculino , Adulto , Femenino , Adolescente , Niño , Malaria Falciparum/transmisión , Malaria Falciparum/prevención & control , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/epidemiología , Método Simple Ciego , Persona de Mediana Edad , Primaquina/uso terapéutico , Primaquina/administración & dosificación , Combinación Arteméter y Lumefantrina/uso terapéutico , Combinación Arteméter y Lumefantrina/administración & dosificación , Adulto Joven , Fluorenos/administración & dosificación , Fluorenos/uso terapéutico , Malí/epidemiología , Plasmodium falciparum/efectos de los fármacos , Artemisininas/administración & dosificación , Artemisininas/uso terapéutico , Aminoquinolinas/administración & dosificación , Aminoquinolinas/uso terapéutico , Aminoquinolinas/efectos adversos , Etanolaminas/administración & dosificación , Etanolaminas/uso terapéutico , Animales , Quimioterapia CombinadaRESUMEN
BACKGROUND: The R21/Matrix-M vaccine has demonstrated high efficacy against Plasmodium falciparum clinical malaria in children in sub-Saharan Africa. Using trial data, we aimed to estimate the public health impact and cost-effectiveness of vaccine introduction across sub-Saharan Africa. METHODS: We fitted a semi-mechanistic model of the relationship between anti-circumsporozoite protein antibody titres and vaccine efficacy to data from 3 years of follow-up in the phase 2b trial of R21/Matrix-M in Nanoro, Burkina Faso. We validated the model by comparing predicted vaccine efficacy to that observed over 12-18 months in the phase 3 trial. Integrating this framework within a mathematical transmission model, we estimated the cases, malaria deaths, and disability-adjusted life-years (DALYs) averted and cost-effectiveness over a 15-year time horizon across a range of transmission settings in sub-Saharan Africa. Cost-effectiveness was estimated incorporating the cost of vaccine introduction (dose, consumables, and delivery) relative to existing interventions at baseline. We report estimates at a median of 20% parasite prevalence in children aged 2-10 years (PfPR2-10) and ranges from 3% to 65% PfPR2-10. FINDINGS: Anti-circumsporozoite protein antibody titres were found to satisfy the criteria for a surrogate of protection for vaccine efficacy against clinical malaria. Age-based implementation of a four-dose regimen of R21/Matrix-M vaccine was estimated to avert 181â825 (range 38â815-333â491) clinical cases per 100â000 fully vaccinated children in perennial settings and 202â017 (29â868-405â702) clinical cases per 100â000 fully vaccinated children in seasonal settings. Similar estimates were obtained for seasonal or hybrid implementation. Under an assumed vaccine dose price of US$3, the incremental cost per clinical case averted was $7 (range 4-48) in perennial settings and $6 (3-63) in seasonal settings and the incremental cost per DALY averted was $34 (29-139) in perennial settings and $30 (22-172) in seasonal settings, with lower cost-effectiveness ratios in settings with higher PfPR2-10. INTERPRETATION: Introduction of the R21/Matrix-M malaria vaccine could have a substantial public health benefit across sub-Saharan Africa. FUNDING: The Wellcome Trust, the Bill & Melinda Gates Foundation, the UK Medical Research Council, the European and Developing Countries Clinical Trials Partnership 2 and 3, the NIHR Oxford Biomedical Research Centre, and the Serum Institute of India, Open Philanthropy.
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Análisis Costo-Beneficio , Vacunas contra la Malaria , Malaria Falciparum , Modelos Teóricos , Salud Pública , Humanos , Vacunas contra la Malaria/economía , Vacunas contra la Malaria/inmunología , Vacunas contra la Malaria/administración & dosificación , Malaria Falciparum/prevención & control , Malaria Falciparum/epidemiología , Malaria Falciparum/economía , Burkina Faso/epidemiología , Preescolar , Salud Pública/economía , Plasmodium falciparum/inmunología , Niño , Proteínas Protozoarias/inmunología , Anticuerpos Antiprotozoarios/sangre , Eficacia de las Vacunas , Lactante , Masculino , FemeninoRESUMEN
BACKGROUND: Recently, we found that a new malaria vaccine, R21/Matrix-M, had over 75% efficacy against clinical malaria with seasonal administration in a phase 2b trial in Burkina Faso. Here, we report on safety and efficacy of the vaccine in a phase 3 trial enrolling over 4800 children across four countries followed for up to 18 months at seasonal sites and 12 months at standard sites. METHODS: We did a double-blind, randomised, phase 3 trial of the R21/Matrix-M malaria vaccine across five sites in four African countries with differing malaria transmission intensities and seasonality. Children (aged 5-36 months) were enrolled and randomly assigned (2:1) to receive 5 µg R21 plus 50 µg Matrix-M or a control vaccine (licensed rabies vaccine [Abhayrab]). Participants, their families, investigators, laboratory teams, and the local study team were masked to treatment. Vaccines were administered as three doses, 4 weeks apart, with a booster administered 12 months after the third dose. Half of the children were recruited at two sites with seasonal malaria transmission and the remainder at standard sites with perennial malaria transmission using age-based immunisation. The primary objective was protective efficacy of R21/Matrix-M from 14 days after third vaccination to 12 months after completion of the primary series at seasonal and standard sites separately as co-primary endpoints. Vaccine efficacy against multiple malaria episodes and severe malaria, as well as safety and immunogenicity, were also assessed. This trial is registered on ClinicalTrials.gov, NCT04704830, and is ongoing. FINDINGS: From April 26, 2021, to Jan 12, 2022, 5477 children consented to be screened, of whom 1705 were randomly assigned to control vaccine and 3434 to R21/Matrix-M; 4878 participants received the first dose of vaccine. 3103 participants in the R21/Matrix-M group and 1541 participants in the control group were included in the modified per-protocol analysis (2412 [51·9%] male and 2232 [48·1%] female). R21/Matrix-M vaccine was well tolerated, with injection site pain (301 [18·6%] of 1615 participants) and fever (754 [46·7%] of 1615 participants) as the most frequent adverse events. Number of adverse events of special interest and serious adverse events did not significantly differ between the vaccine groups. There were no treatment-related deaths. 12-month vaccine efficacy was 75% (95% CI 71-79; p<0·0001) at the seasonal sites and 68% (61-74; p<0·0001) at the standard sites for time to first clinical malaria episode. Similarly, vaccine efficacy against multiple clinical malaria episodes was 75% (71-78; p<0·0001) at the seasonal sites and 67% (59-73; p<0·0001) at standard sites. A modest reduction in vaccine efficacy was observed over the first 12 months of follow-up, of similar size at seasonal and standard sites. A rate reduction of 868 (95% CI 762-974) cases per 1000 children-years at seasonal sites and 296 (231-362) at standard sites occurred over 12 months. Vaccine-induced antibodies against the conserved central Asn-Ala-Asn-Pro (NANP) repeat sequence of circumsporozoite protein correlated with vaccine efficacy. Higher NANP-specific antibody titres were observed in the 5-17 month age group compared with 18-36 month age group, and the younger age group had the highest 12-month vaccine efficacy on time to first clinical malaria episode at seasonal (79% [95% CI 73-84]; p<0·001) and standard (75% [65-83]; p<0·001) sites. INTERPRETATION: R21/Matrix-M was well tolerated and offered high efficacy against clinical malaria in African children. This low-cost, high-efficacy vaccine is already licensed by several African countries, and recently received a WHO policy recommendation and prequalification, offering large-scale supply to help reduce the great burden of malaria in sub-Saharan Africa. FUNDING: The Serum Institute of India, the Wellcome Trust, the UK National Institute for Health Research Oxford Biomedical Research Centre, and Open Philanthropy.
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Vacunas contra la Malaria , Malaria , Nanopartículas , Saponinas , Preescolar , Femenino , Humanos , Lactante , Masculino , Anticuerpos Antivirales , Burkina Faso , Método Doble Ciego , Inmunización , Malaria/tratamiento farmacológico , Vacunas contra la Malaria/efectos adversosRESUMEN
BACKGROUND: Seasonal vaccination with the RTS,S/AS01E vaccine combined with seasonal malaria chemoprevention (SMC) prevented malaria in young children more effectively than either intervention given alone over a 3 year period. The objective of this study was to establish whether the added protection provided by the combination could be sustained for a further 2 years. METHODS: This was a double-blind, individually randomised, controlled, non-inferiority and superiority, phase 3 trial done at two sites: the Bougouni district and neighbouring areas in Mali and Houndé district, Burkina Faso. Children who had been enrolled in the initial 3-year trial when aged 5-17 months were initially randomly assigned individually to receive SMC with sulphadoxine-pyrimethamine and amodiaquine plus control vaccines, RTS,S/AS01E plus placebo SMC, or SMC plus RTS,S/AS01E. They continued to receive the same interventions until the age of 5 years. The primary trial endpoint was the incidence of clinical malaria over the 5-year trial period in both the modified intention-to-treat and per-protocol populations. Over the 5-year period, non-inferiority was defined as a 20% increase in clinical malaria in the RTS,S/AS01E-alone group compared with the SMC alone group. Superiority was defined as a 12% difference in the incidence of clinical malaria between the combined and single intervention groups. The study is registered with ClinicalTrials.gov, NCT04319380, and is complete. FINDINGS: In April, 2020, of 6861 children originally recruited, 5098 (94%) of the 5433 children who completed the initial 3-year follow-up were re-enrolled in the extension study. Over 5 years, the incidence of clinical malaria per 1000 person-years at risk was 313 in the SMC alone group, 320 in the RTS,S/AS01E-alone group, and 133 in the combined group. The combination of RTS,S/AS01E and SMC was superior to SMC (protective efficacy 57·7%, 95% CI 53·3 to 61·7) and to RTS,S/AS01E (protective efficacy 59·0%, 54·7 to 62·8) in preventing clinical malaria. RTS,S/AS01E was non-inferior to SMC (hazard ratio 1·03 [95% CI 0·95 to 1·12]). The protective efficacy of the combination versus SMC over the 5-year period of the study was very similar to that seen in the first 3 years with the protective efficacy of the combination versus SMC being 57·7% (53·3 to 61·7) and versus RTS/AS01E-alone being 59·0% (54·7 to 62·8). The comparable figures for the first 3 years of the study were 62·8% (58·4 to 66·8) and 59·6% (54·7 to 64·0%), respectively. Hospital admissions for WHO-defined severe malaria were reduced by 66·8% (95% CI 40·3 to 81·5), for malarial anaemia by 65·9% (34·1 to 82·4), for blood transfusion by 68·1% (32·6 to 84·9), for all-cause deaths by 44·5% (2·8 to 68·3), for deaths excluding external causes or surgery by 41·1% (-9·2 to 68·3), and for deaths from malaria by 66·8% (-2·7 to 89·3) in the combined group compared with the SMC alone group. No safety signals were detected. INTERPRETATION: Substantial protection against malaria was sustained over 5 years by combining seasonal malaria vaccination with seasonal chemoprevention, offering a potential new approach to malaria control in areas with seasonal malaria transmission. FUNDING: UK Joint Global Health Trials and PATH's Malaria Vaccine Initiative (through a grant from the Bill & Melinda Gates Foundation). TRANSLATION: For the French translation of the abstract see Supplementary Materials section.
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Vacunas contra la Malaria , Malaria Falciparum , Malaria , Niño , Humanos , Lactante , Preescolar , Malí/epidemiología , Burkina Faso/epidemiología , Estaciones del Año , Malaria/epidemiología , Malaria/prevención & control , Vacunación , Quimioprevención , Malaria Falciparum/epidemiología , Malaria Falciparum/prevención & controlRESUMEN
OBJECTIVES: The association between thrombocytopenia and parasite density or disease severity is described in numerous studies. In recent years, several studies described the protective role of platelets in directly killing Plasmodium parasites, mediated by platelet factor 4 (PF4) binding to Duffy antigen. This study aimed to evaluate the protective role of platelets in young children who are Duffy antigen-negative, such as those in sub-Saharan Africa. METHODS: A zero-inflated negative binomial model was used to relate platelet count and parasite density data collected in a longitudinal birth cohort. Platelet factors were measured by enzyme-linked immunosorbent assay in samples collected from malaria-infected children who participated in a cross-sectional study. RESULTS: We described that an increase of 10,000 platelets/µl was associated with a 2.76% reduction in parasite count. Increasing levels of PF4 and CXCL7 levels were also significantly associated with a reduction in parasite count. CONCLUSIONS: Platelets play a protective role in reducing parasite burden in Duffy-negative children, possibly mediated through activation of the innate immune system.
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Malaria Falciparum , Malaria , Parásitos , Niño , Animales , Humanos , Preescolar , Plasmodium falciparum , Recuento de Plaquetas , Estudios Transversales , Malaria Falciparum/parasitologíaRESUMEN
INTRODUCTION: Polymorphonuclear neutrophils (PMN) are involved in pathogen clearance by phagocytosis. However, the role of PMNs in the efficacy of artemisinin-based combination therapy (ACT) is poorly understood. METHODOLOGY: In a prospective longitudinal in vivo study, neutrophil rates were compared with malaria carriage after treatment with different ACTs: Artemether - lumefantrine (AL), Artesunate - amodiaquine (ASAQ), Dihydroartemisinin - piperaquine (DP) or Pyronaridine artesunate (PA). The study cases were classified as having neutropenia, normal neutrophil levels or neutrophilia depending on the level of neutrophils in the blood. This study included 3148 patients and was analyzed using R. RESULTS: On day 7, only four patients in the neutropenia group and treated with AL had a malaria positive blood smear based on microscopy. On day 28, the rate of recurrent parasitemia in the AL arm was significantly higher in neutropenia patients (50.9%) than in patients with normal rates of neutrophils (43.1%) or in those with neutrophilia (6.0%) (p < 0.001). In ASAQ arm, the rate of recurrent Plasmodium falciparum parasitemia was 58.8% in the neutropenia group versus 29.4% in patients with normal rates of neutrophils and 11.8% in patients with neutrophilia (p < 0.001). No patient treated with DP with normal neutrophil counts or neutrophilia was carrying malaria parasites on day 28. Among the 15 patients with parasitemia on day 28 in the PA arm, 11 (73.33%) had neutropenia while 4 (26.67%) had a normal neutrophil count (p < 0.001). CONCLUSIONS: Patients with neutropenia had higher rates of recurrent P. falciparum parasitemia after ACT.
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Antimaláricos , Artemisininas , Malaria Falciparum , Malaria , Neutropenia , Humanos , Artesunato/uso terapéutico , Antimaláricos/uso terapéutico , Neutrófilos , Malaria Falciparum/tratamiento farmacológico , Parasitemia/tratamiento farmacológico , Estudios Prospectivos , Combinación Arteméter y Lumefantrina/uso terapéutico , Amodiaquina/uso terapéutico , Artemisininas/uso terapéutico , Malaria/tratamiento farmacológico , Combinación de Medicamentos , Neutropenia/inducido químicamente , África , Plasmodium falciparum , Etanolaminas/uso terapéuticoRESUMEN
INTRODUCTION: Malaria, a devastating febrile illness caused by protozoan parasites, sickened 247,000,000 people in 2021 and killed 619,000, mostly children and pregnant women in sub-Saharan Africa. A highly effective vaccine is urgently needed, especially for Plasmodium falciparum (Pf), the deadliest human malaria parasite. AREAS COVERED: Sporozoites (SPZ), the parasite stage transmitted by Anopheles mosquitoes to humans, are the only vaccine immunogen achieving >90% efficacy against Pf infection. This review describes >30 clinical trials of PfSPZ vaccines in the U.S.A., Europe, Africa, and Asia, based on first-hand knowledge of the trials and PubMed searches of 'sporozoites,' 'malaria,' and 'vaccines.' EXPERT OPINION: First generation (radiation-attenuated) PfSPZ vaccines are safe, well tolerated, 80-100% efficacious against homologous controlled human malaria infection (CHMI) and provide 18-19 months protection without boosting in Africa. Second generation chemo-attenuated PfSPZ are more potent, 100% efficacious against stringent heterologous (variant strain) CHMI, but require a co-administered drug, raising safety concerns. Third generation, late liver stage-arresting, replication competent (LARC), genetically-attenuated PfSPZ are expected to be both safe and highly efficacious. Overall, PfSPZ vaccines meet safety, tolerability, and efficacy requirements for protecting pregnant women and travelers exposed to Pf in Africa, with licensure for these populations possible within 5 years. Protecting children and mass vaccination programs to block transmission and eliminate malaria are long-term objectives.
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Vacunas contra la Malaria , Malaria Falciparum , Malaria , Embarazo , Niño , Animales , Humanos , Femenino , Esporozoítos , Ciencia Traslacional Biomédica , Vacunas Atenuadas , Malaria/prevención & control , Malaria Falciparum/prevención & control , Plasmodium falciparum , InmunizaciónRESUMEN
Sequence analysis of Plasmodium falciparum parasites is informative in ensuring sustained success of malaria control programmes. Whole-genome sequencing technologies provide insights into the epidemiology and genome-wide variation of P. falciparum populations and can characterise geographical as well as temporal changes. This is particularly important to monitor the emergence and spread of drug resistant P. falciparum parasites which is threatening malaria control programmes world-wide. Here, we provide a detailed characterisation of genome-wide genetic variation and drug resistance profiles in asymptomatic individuals in South-Western Mali, where malaria transmission is intense and seasonal, and case numbers have recently increased. Samples collected from Ouélessébougou, Mali (2019-2020; n = 87) were sequenced and placed in the context of older Malian (2007-2017; n = 876) and African-wide (n = 711) P. falciparum isolates. Our analysis revealed high multiclonality and low relatedness between isolates, in addition to increased frequencies of molecular markers for sulfadoxine-pyrimethamine and lumefantrine resistance, compared to older Malian isolates. Furthermore, 21 genes under selective pressure were identified, including a transmission-blocking vaccine candidate (pfCelTOS) and an erythrocyte invasion locus (pfdblmsp2). Overall, our work provides the most recent assessment of P. falciparum genetic diversity in Mali, a country with the second highest burden of malaria in West Africa, thereby informing malaria control activities.
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Malaria Falciparum , Plasmodium falciparum , Humanos , Malí , Antiparasitarios , Variación GenéticaRESUMEN
BACKGROUND: Seasonal vaccination with the RTS,S/AS01E malaria vaccine given alongside seasonal malaria chemoprevention (SMC) substantially reduces malaria in young children. The WHO has recommended the use of RTS,S/AS01E, including seasonal vaccination, in areas with seasonal malaria transmission. This study aimed to identify potential strategies to deliver RTS,S/AS01E, and assess the considerations and recommendations for delivery of seasonal malaria vaccination in Mali, a country with highly seasonal malaria. METHODS: Potential delivery strategies for RTS,S/AS01E in areas with seasonal malaria were identified through a series of high level discussions with the RTS,S/AS01E plus SMC trial investigators, international and national immunisation and malaria experts, and through the development of a theory of change. These were explored through qualitative in-depth interviews with 108 participants, including national-level, regional-level and district-level malaria and immunisation programme managers, health workers, caregivers of children under 5 years of age, and community stakeholders. A national-level workshop was held to confirm the qualitative findings and work towards consensus on an appropriate strategy. RESULTS: Four delivery strategies were identified: age-based vaccination delivered via the Essential Programme on Immunisation (EPI); seasonal vaccination via EPI mass vaccination campaigns (MVCs); a combination of age-based priming vaccination doses delivered via the EPI clinics and seasonal booster doses delivered via MVCs; and a combination of age-based priming vaccination doses and seasonal booster doses, all delivered via the EPI clinics, which was the preferred strategy for delivery of RTS,S/AS01E in Mali identified during the national workshop. Participants recommended that supportive interventions, including communications and mobilisation, would be needed for this strategy to achieve required coverage. CONCLUSIONS: Four delivery strategies were identified for administration of RTS,S/AS01E alongside SMC in countries with seasonal malaria transmission. Components of these delivery strategies were defined as the vaccination schedule, and the delivery system(s) plus the supportive interventions needed for the strategies to be effective. Further implementation research and evaluation is needed to explore how, where, when and what effective coverage is achievable via these new strategies and their supportive interventions.
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Vacunas contra la Malaria , Malaria Falciparum , Malaria , Niño , Humanos , Preescolar , Vacunas contra la Malaria/uso terapéutico , Malaria Falciparum/prevención & control , Estaciones del Año , Malaria/prevención & control , VacunaciónRESUMEN
BACKGROUND: The WHO recommends use of the RTS,S/AS01E (RTS,S) malaria vaccine for young children living in areas of moderate to high Plasmodium falciparum malaria transmission and suggests countries consider seasonal vaccination in areas with highly seasonal malaria. Seasonal vaccination is uncommon and may require adaptations with potential cost consequences. This study prospectively estimates cost of seasonal malaria vaccine delivery in Mali and Burkina Faso. METHODS: Three scenarios for seasonal vaccine delivery are costed (1) mass campaign only, (2) routine Expanded Programme on Immunisation (EPI) and (3) mixed delivery (mass campaign and routine EPI)), from the government's perspective. Resource use data are informed by previous new vaccine introductions, supplemented with primary data from a sample of health facilities and administrative units. FINDINGS: At an assumed vaccine price of US $5 per dose, the economic cost per dose administered ranges between $7.73 and $8.68 (mass campaign), $7.04 and $7.38 (routine EPI) and $7.26 and $7.93 (mixed delivery). Excluding commodities, the cost ranges between $1.17 and $2.12 (mass campaign), $0.48 and $0.82 (routine EPI) and $0.70 and $1.37 (mixed delivery). The financial non-commodity cost per dose administered ranges between $0.99 and $1.99 (mass campaign), $0.39 and $0.76 (routine EPI) and $0.58 and $1.28 (mixed delivery). Excluding commodity costs, service delivery is the main cost driver under the mass campaign scenario, accounting for 36% to 55% of the financial cost. Service delivery accounts for 2%-8% and 12%-23% of the total financial cost under routine EPI and mixed delivery scenarios, respectively. CONCLUSION: Vaccine delivery using the mass campaign approach is most costly followed by mixed delivery and routine EPI delivery approaches, in both countries. Our cost estimates provide useful insights for decisions regarding delivery approaches, as countries plan the malaria vaccine rollout.
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Vacunas contra la Malaria , Malaria , Niño , Humanos , Preescolar , Burkina Faso , Malí , Estaciones del Año , Malaria/prevención & controlRESUMEN
BACKGROUND: Addressing persistent and pervasive health inequities is a global moral imperative, which has been highlighted and magnified by the societal and health impacts of the COVID-19 pandemic. Observational studies can aid our understanding of the impact of health and structural oppression based on the intersection of gender, race, ethnicity, age and other factors, as they frequently collect this data. However, the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE) guideline, does not provide guidance related to reporting of health equity. The goal of this project is to develop a STROBE-Equity reporting guideline extension. METHODS: We assembled a diverse team across multiple domains, including gender, age, ethnicity, Indigenous background, disciplines, geographies, lived experience of health inequity and decision-making organizations. Using an inclusive, integrated knowledge translation approach, we will implement a five-phase plan which will include: (1) assessing the reporting of health equity in published observational studies, (2) seeking wide international feedback on items to improve reporting of health equity, (3) establishing consensus amongst knowledge users and researchers, (4) evaluating in partnership with Indigenous contributors the relevance to Indigenous peoples who have globally experienced the oppressive legacy of colonization, and (5) widely disseminating and seeking endorsement from relevant knowledge users. We will seek input from external collaborators using social media, mailing lists and other communication channels. DISCUSSION: Achieving global imperatives such as the Sustainable Development Goals (e.g., SDG 10 Reduced inequalities, SDG 3 Good health and wellbeing) requires advancing health equity in research. The implementation of the STROBE-Equity guidelines will enable a better awareness and understanding of health inequities through better reporting. We will broadly disseminate the reporting guideline with tools to enable adoption and use by journal editors, authors, and funding agencies, using diverse strategies tailored to specific audiences.
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Inequidades en Salud , Estudios Observacionales como Asunto , Justicia Social , Humanos , COVID-19 , Pandemias , Proyectos de Investigación , Desarrollo Sostenible , Pueblos IndígenasRESUMEN
Host immunity has been suggested to clear drug-resistant parasites in malaria-endemic settings. However, the immunogenetic mechanisms involved in parasite clearance are poorly understood. Characterizing the host's immunity and genes involved in controlling the parasitic infection can inform the development of blood-stage malaria vaccines. This study investigates host regulatory cytokines and immunogenomic factors associated with the clearance of Plasmodium falciparum carrying a chloroquine resistance genotype. Biological samples from participants of previous drug efficacy trials conducted in two Malian localities were retrieved. The P. falciparum chloroquine resistance transporter (Pfcrt) gene was genotyped using parasite DNA. Children carrying parasites with the mutant allele (Pfcrt-76T) were classified based on their ability to clear their parasites. The levels of the different cytokines were measured in serum. The polymorphisms of specific human genes involved in malaria susceptibility were genotyped using human DNA. The prevalence of the Pfcrt-76T was significantly higher in Kolle than in Bandiagara (81.6 % vs 38.6 %, p < 10-6). The prevalence of children who cleared their mutant parasites was significantly higher in Bandiagara than in Kolle (82.2 % vs 67.4 %, p < 0.05). The genotyping of host genes revealed that IFN-γ -874 T and TNF-α -308A alleles were positively associated with parasite clearance. Cytokine profiling revealed that IFN-γ level was positively associated with parasite clearance (p = 0.04). This study highlights the role of host's immunity and immunogenetic factors to clear resistant parasites, suggesting further characterization of these polymorphisms may help to develop novel approaches to antiparasitic treatment strategies.
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Antimaláricos , Malaria Falciparum , Malaria , Humanos , Niño , Antimaláricos/farmacología , Factor de Necrosis Tumoral alfa/genética , Factor de Necrosis Tumoral alfa/uso terapéutico , Resistencia a Medicamentos/genética , Proteínas Protozoarias/genética , Cloroquina/farmacología , Malaria Falciparum/genética , Malaria Falciparum/tratamiento farmacológico , Malaria Falciparum/parasitología , Plasmodium falciparum/genética , Proteínas de Transporte de Membrana/genética , Proteínas de Transporte de Membrana/uso terapéutico , Malaria/tratamiento farmacológicoRESUMEN
BACKGROUND: The frequency and clinical presentation of malaria infections show marked heterogeneity in epidemiological studies. However, deeper understanding of this variability is hampered by the difficulty in quantifying all relevant factors. Here, we report the history of malaria infections in twins, who are exposed to the same in utero milieu, share genetic factors, and are similarly exposed to vectors. METHODS: Data were obtained from a Malian longitudinal birth cohort. Samples from 25 twin pairs were examined for malaria infection and antibody responses. Bayesian models were developed for the number of infections during follow-up. RESULTS: In 16 of 25 pairs, both children were infected and often developed symptoms. In 8 of 25 pairs, only 1 twin was infected, but usually only once or twice. Statistical models suggest that this pattern is not inconsistent with twin siblings having the same underlying infection rate. In a pair with discordant hemoglobin genotype, parasite densities were consistently lower in the child with hemoglobin AS, but antibody levels were similar. CONCLUSIONS: By using a novel design, we describe residual variation in malaria phenotypes in naturally matched children and confirm the important role of environmental factors, as suggested by the between-twin pair heterogeneity in malaria history.
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Malaria , Gemelos Monocigóticos , Preescolar , Humanos , Teorema de Bayes , Malaria/epidemiología , Gemelos Monocigóticos/genéticaRESUMEN
BACKGROUND: Seasonal malaria chemoprevention is used in 13 countries in the Sahel region of Africa to prevent malaria in children younger than 5 years. Resistance of Plasmodium falciparum to seasonal malaria chemoprevention drugs across the region is a potential threat to this intervention. METHODS: Between December, 2015, and March, 2016, and between December, 2017, and March, 2018, immediately following the 2015 and 2017 malaria transmission seasons, community surveys were done among children younger than 5 years and individuals aged 10-30 years in districts implementing seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine in Burkina Faso, Chad, Guinea, Mali, Nigeria, Niger and The Gambia. Dried blood samples were collected and tested for P falciparum DNA by PCR. Resistance-associated haplotypes of the P falciparum genes crt, mdr1, dhfr, and dhps were identified by quantitative PCR and sequencing of isolates from the collected samples, and survey-weighted prevalence and prevalence ratio between the first and second surveys were estimated for each variant. FINDINGS: 5130 (17·5%) of 29 274 samples from 2016 and 2176 (7·6%) of 28 546 samples from 2018 were positive for P falciparum on quantitative PCR. Among children younger than 5 years, parasite carriage decreased from 2844 of 14 345 samples (19·8% [95% CI 19·2-20·5]) in 2016 to 801 of 14 019 samples (5·7% [5·3-6·1]) in 2018 (prevalence ratio 0·27 [95% CI 0·24-0·31], p<0·0001). Genotyping found no consistent evidence of increasing prevalence of amodiaquine resistance-associated variants of crt and mdr1 between 2016 and 2018. The dhfr haplotype IRN (consisting of 51Ile-59Arg-108Asn) was common at both survey timepoints, but the dhps haplotype ISGEAA (431Ile-436Ser-437Gly-540Glu-581Ala-613Ala), crucial for resistance to sulfadoxine-pyrimethamine, was always rare. Parasites carrying amodiaquine resistance-associated variants of both crt and mdr1 together with dhfr IRN and dhps ISGEAA occurred in 0·05% of isolates. The emerging dhps haplotype VAGKGS (431Val-436Ala-437Gly-540Lys-581Gly-613Ser) was present in four countries. INTERPRETATION: In seven African countries, evidence of a significant reduction in parasite carriage among children receiving seasonal malaria chemoprevention was found 2 years after intervention scale-up. Combined resistance-associated haplotypes remained rare, and seasonal malaria chemoprevention with sulfadoxine-pyrimethamine and amodiaquine is expected to retain effectiveness. The threat of future erosion of effectiveness due to dhps variant haplotypes requires further monitoring. FUNDING: Unitaid.
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Antimaláricos , Malaria Falciparum , Malaria , Niño , Humanos , Plasmodium falciparum , Amodiaquina/uso terapéutico , Haplotipos , Antimaláricos/uso terapéutico , Estaciones del Año , Prevalencia , Pirimetamina/uso terapéutico , Sulfadoxina/uso terapéutico , Malaria/tratamiento farmacológico , Malaria Falciparum/tratamiento farmacológico , Combinación de Medicamentos , Quimioprevención , Nigeria , Tetrahidrofolato Deshidrogenasa/genética , Tetrahidrofolato Deshidrogenasa/uso terapéutico , Genómica , Resistencia a Medicamentos/genéticaRESUMEN
In malaria-endemic areas, pregnant women are more susceptible to Plasmodium falciparum infection, especially primigravidae. During pregnancy, parasites sequester in the placenta and bind to the receptor chondroitin sulfate (CSA). This unique adhesion is mediated by the parasite protein VAR2CSA expressed on the surface of infected erythrocytes (IE). Placental malaria is associated with poor pregnancy outcomes including perinatal mortality, preterm delivery, small for gestational age (SGA) and low birthweight deliveries. Over successive pregnancies, women acquire functional antibodies that inhibit IE adhesion to CSA. Here, we examine the development of anti-adhesion activity and the breadth of anti-adhesion activity as a function of number of previous pregnancies, using samples collected from pregnant women living in an area with high seasonal malaria transmission. Women reached plateau levels of anti-adhesion activity and breadth of anti-adhesion activity after 5 pregnancies. We related the level of anti-adhesion activity and reactivity with surface IE to SGA 19/232 pregnancies resulted in SGA, and report that an increase of 10% in median anti-adhesion activity reduced the odds of SGA by 13% and this relationship approached significance. Further, at an anti-adhesion activity level of 43.7%, an increase of 10% in the breadth of activity significantly reduced the odds of SGA by 21.5%. Antibodies that recognize IE surface increased over successive pregnancies, but were not associated with a reduction in SGA. These results can serve as a guideline for assessing vaccine candidates aiming to reduce poor pregnancy outcomes associated with placental malaria.
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Malaria , Plasmodium falciparum , Recién Nacido , Femenino , Humanos , Embarazo , Placenta/metabolismo , Sulfatos de Condroitina , Número de Embarazos , Antígenos de Protozoos , Anticuerpos AntiprotozoariosRESUMEN
BACKGROUND: In some settings, sensitive field diagnostic tools may be needed to achieve elimination of falciparum malaria. To this end, rapid diagnostic tests (RDTs) based on the detection of the Plasmodium falciparum protein HRP-2 are being developed with increasingly lower limits of detection. However, it is currently unclear how parasite stages that are unaffected by standard drug treatments may contribute to HRP-2 detectability and potentially confound RDT results even after clearance of blood stage infection. This study assessed the detectability of HRP-2 in periods of post-treatment residual gametocytaemia. METHODS: A cohort of 100 P. falciparum infected, gametocyte positive individuals were treated with or without the gametocytocidal drug primaquine (PQ), alongside standard artemisinin-based combination therapy (ACT), in the context of a randomised clinical trial in Ouelessebougou, Mali. A quantitative ELISA was used to measure levels of HRP-2, and compared time to test negativity using a standard and ultra-sensitive RDT (uRDT) between residual gametocyte positive and negative groups. RESULTS: Time to test negativity was longest by uRDT, followed by ELISA and then standard RDT. No significant difference in time to negativity was found between the treatment groups with and without residual gametocytes: uRDT (HR 0.79 [95% CI 0.52-1.21], p = 0.28), RDT (HR 0.77 [95% CI 0.51-1.15], p = 0.20) or ELISA (HR 0.88 [95% CI 0.59-1.32], p = 0.53). Similarly, no difference was observed when adjusting for baseline asexual parasite density. Quantified levels of HRP-2 over time were similar between groups, with differences attributable to asexual parasite densities. Furthermore, no difference in levels of HRP-2 was found between individuals who were or were not infectious to mosquitoes (OR 1.19 [95% CI 0.98-1.46], p = 0.077). CONCLUSIONS: Surviving sexual stage parasites after standard ACT treatment do not contribute to the persistence of HRP-2 antigenaemia, and appear to have little impact on RDT results.
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Plasmodium falciparum , Humanos , MalíRESUMEN
In Sub-Saharan Africa, malaria continues to be associated with adverse pregnancy outcomes including stillbirth, early neonatal death, preterm delivery, and low birth weight. Current preventive measures are insufficient and new interventions are urgently needed. However, before such interventions can be tested in pregnant women, background information on pregnancy outcomes in this target population must be collected. We conducted an observational study in Ouélessébougou, Mali, a malaria-endemic area where first antenatal visit commonly occurs during the second trimester of pregnancy, hindering calculation of miscarriage rate in the population. To accurately determine the rate of miscarriage, 799 non-pregnant women of child-bearing age were enrolled and surveyed via monthly follow up visits that included pregnancy tests. Out of 505 women that completed the study, 364 became pregnant and 358 pregnancies were analyzed: 43 (12%) resulted in miscarriage, 28 (65.1%) occurred during the first trimester of pregnancy. We also determined rates of stillbirth, neonatal death, preterm delivery, and small for gestational age. The results showed high rate of miscarriage during the first trimester and established a basis to evaluate new interventions to prevent pregnancy malaria. This survey design enabled identification of first trimester miscarriages that are often missed by studies conducted in antenatal clinics. Clinical trial registration: [https://clinicaltrials.gov/], identifier [NCT0297 4608].