ABSTRACT
Anemia is common among young children infected with Plasmodium falciparum and severe malarial anemia (SMA) is a major cause of their mortality. Two major mechanisms cause malarial anemia: hemolysis of uninfected as well as infected erythrocytes and insufficient erythropoiesis. In a longitudinal birth cohort in Mali, we commonly observed marked hemoglobin reductions during P falciparum infections with a small proportion that progressed to SMA. We sought biomarkers of these processes using quantitative proteomic analysis on plasma samples from 9 P falciparum-infected children, comparing those with reduced hemoglobin (with or without SMA) vs those with stable hemoglobin. We identified higher plasma levels of circulating 20S proteasome and lower insulin-like growth factor-1 (IGF-1) levels in children with reduced hemoglobin. We confirmed these findings in independent enzyme-linked immunosorbent assay-based validation studies of subsets of children from the same cohort (20S proteasome, N = 71; IGF-1, N = 78). We speculate that circulating 20S proteasome plays a role in digesting erythrocyte membrane proteins modified by oxidative stress, resulting in hemolysis, whereas decreased IGF-1, a critical factor for erythroid maturation, might contribute to insufficient erythropoiesis. Quantitative plasma proteomics identified soluble mediators that may contribute to the major mechanisms underlying malarial anemia. This study was registered at www.clinicaltrials.gov as #NCT01168271.
Subject(s)
Anemia , Malaria, Falciparum , Malaria , Anemia/etiology , Biomarkers , Child , Child, Preschool , Hemoglobins , Hemolysis , Humans , Insulin-Like Growth Factor I , Malaria, Falciparum/complications , Plasmodium falciparum , Proteasome Endopeptidase Complex , ProteomicsABSTRACT
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.
Subject(s)
Malaria , Twins, Monozygotic , Child, Preschool , Humans , Bayes Theorem , Malaria/epidemiology , Twins, Monozygotic/geneticsABSTRACT
BACKGROUND: The extent of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) exposure and transmission in Mali and the surrounding region is not well understood. We aimed to estimate the cumulative incidence of SARS-CoV-2 in 3 communities and understand factors associated with infection. METHODS: Between July 2020 and January 2021, we collected blood samples and demographic, social, medical, and self-reported symptoms information from residents aged 6 months and older over 2 study visits. SARS-CoV-2 antibodies were measured using a highly specific 2-antigen enzyme-linked immunosorbent assay optimized for use in Mali. We calculated cumulative adjusted seroprevalence for each community and evaluated factors associated with serostatus at each visit by univariate and multivariate analysis. RESULTS: Overall, 94.8% (2533/2672) of participants completed both study visits. A total of 31.3% (837/2672) were aged <10 years, 27.6% (737/2672) were aged 10-17 years, and 41.1% (1098/2572) were aged ≥18 years. The cumulative SARS-CoV-2 exposure rate was 58.5% (95% confidence interval, 47.5-69.4). This varied between sites and was 73.4% in the urban community of Sotuba, 53.2% in the rural town of Bancoumana, and 37.1% in the rural village of Donéguébougou. Study site and increased age were associated with serostatus at both study visits. There was minimal difference in reported symptoms based on serostatus. CONCLUSIONS: The true extent of SARS-CoV-2 exposure in Mali is greater than previously reported and may now approach hypothetical "herd immunity" in urban areas. The epidemiology of the pandemic in the region may be primarily subclinical and within background illness rates.
ABSTRACT
BACKGROUND: In 2012, seasonal malaria chemoprevention (SMC) was recommended as policy for malaria control by the World Health Organization (WHO) in areas of highly seasonal malaria transmission across the Sahel sub-region in Africa along with monitoring of drug resistance. We assessed the long-term impact of SMC on Plasmodium falciparum resistance to sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) over a 3-year period of SMC implementation in the health district of Ouelessebougou, Mali. METHODS: In 8 randomly selected sub-districts of Ouelessebougou, Mali, children aged 0-5 years were randomly selected during cross-sectional surveys at baseline (August 2014) and 1, 2 and 3 years post-SMC, at the beginning and end of the malaria transmission season. Blood smears and blood spots on filter paper were obtained and frequencies of mutation in P. falciparum genes related to resistance to SP and AQ (Pfdhfr, Pfdhps, Pfmdr1, and Pfcrt) were assessed by PCR amplification on individual samples and PCR amplification followed by deep sequencing on pooled (by site and year) samples. RESULTS: At each survey, approximately 50-100 individual samples were analysed by PCR amplification and a total of 1,164 samples were analysed by deep sequencing with an average read depth of 18,018-36,918 after pooling by site and year. Most molecular markers of resistance did not increase in frequency over the period of study (2014-2016). After 3 years of SMC, the frequencies of Pfdhps 540E, Pfdhps 437G and Pfcrt K76T remained similar compared to baseline (4.0 vs 1.4%, p = 0.41; 74.5 vs 64.6%, p = 0.22; 71.3 vs 67.4%, p = 0.69). Nearly all samples tested carried Pfdhfr 59R, and this proportion remained similar 3 years after SMC implementation (98.8 vs 100%, p = 1). The frequency of Pfmdr1 N86Y increased significantly over time from 5.6% at baseline to 18.6% after 3 years of SMC (p = 0.016). Results of pooled analysis using deep sequencing were consistent with those by individual analysis with standard PCR, but also indicated for the first time the presence of mutations at the Pfdhps A581G allele at a frequency of 11.7% after 2 years of SMC, as well as the Pfdhps I431V allele at frequencies of 1.6-9.3% following 1 and 2 years of SMC, respectively. CONCLUSION: Two and 3 years of SMC implementation were associated with increased frequency of the Pfmdr1 N86Y mutation but not Pfdhps 540E, Pfdhps 437G and Pfcrt K76T. The first-time detection of the Pfdhps haplotype bearing the I431V and A581G mutations in Mali, even at low frequency, warrants further long-term surveillance.
Subject(s)
Antimalarials , Malaria, Falciparum , Malaria , Amodiaquine/pharmacology , Antimalarials/pharmacology , Antimalarials/therapeutic use , Chemoprevention , Child , Child, Preschool , Cross-Sectional Studies , Drug Combinations , Drug Resistance/genetics , Humans , Infant , Infant, Newborn , Malaria/drug therapy , Malaria, Falciparum/drug therapy , Malaria, Falciparum/prevention & control , Mali , Plasmodium falciparum/genetics , Pyrimethamine/pharmacology , Seasons , Sulfadoxine/pharmacologyABSTRACT
Genetic polymorphisms within the IFNL3/IFNL4 genomic region, which encodes type III interferons, have been strongly associated with clearance of hepatitis C virus. We hypothesized that type III interferons might be important for the immune response to other pathogens as well. In a cohort of 914 Malian children, we genotyped functional variants IFNL4-rs368234815, IFNL4-rs117648444, and IFNL3-rs4803217 and analyzed episodes of malaria, gastrointestinal, and respiratory infections recorded at 30,626 clinic visits from birth up to 5 years of age. Compared to children with the rs368234815-TT/TT genotype (IFN-λ4-Null), rs368234815-dG allele was most strongly associated with an earlier time-to-first episode of gastrointestinal infections (p = 0.003). The risk of experiencing an infection episode during the follow-up was also significantly increased with rs368234815-dG allele, with OR = 1.53, 95%CI (1.13-2.07), p = 0.005 for gastrointestinal infections and OR = 1.30, 95%CI (1.02-1.65), p = 0.033 for malaria. All the associations for the moderately linked rs4803217 (r2 = 0.78 in this set) were weaker and lost significance after adjusting for rs368234815. We also analyzed all outcomes in relation to IFN-λ4-P70S groups. Our results implicate IFN-λ4 and not IFN-λ3 as the primary functional cause of genetic associations with increased overall risk and younger age at first clinical episodes but not with recurrence or intensity of several common pediatric infections.
Subject(s)
Hepatitis C , Interleukins , Alleles , Child , Genotype , Hepacivirus/genetics , Hepatitis C/genetics , Humans , Interferons/genetics , Interleukins/genetics , Polymorphism, Single NucleotideABSTRACT
BACKGROUND: In malaria-endemic areas, pregnant women and especially first-time mothers are more susceptible to Plasmodium falciparum. Malaria diagnosis is often missed during pregnancy, because many women with placental malaria remain asymptomatic or have submicroscopic parasitemia, masking the association between malaria and pregnancy outcomes. Severe maternal anemia and low birthweight deliveries are well-established sequelae, but few studies have confirmed the relationship between malaria infection and severe outcomes like perinatal mortality in high transmission zones. METHODS: Pregnant women of any gestational age enrolled at antenatal clinic into a longitudinal cohort study in Ouelessebougou, Mali, an area of high seasonal malaria transmission. Follow-up visits included scheduled and unscheduled visits throughout pregnancy. Blood smear microscopy and polymerase chain reaction (PCR) analysis were employed to detect both microscopic and submicroscopic infections, respectively. Intermittent preventative treatment in pregnancy with sulfadoxine-pyrimethamine (IPTp-SP) was documented and prompt treatment regardless of symptoms given upon malaria diagnosis. RESULTS: Of the 1850 women followed through delivery, 72.6% of women received 2 or more IPTp-SP doses, 67.2% of women experienced at least 1 infection between enrollment up to and including delivery. Malaria infection increased the risks of stillbirth (adjusted hazard ratio [aHR] 3.87, 95% confidence interval [CI]: 1.18-12.71) and preterm delivery (aHR 2.41, 95% CI: 1.35-4.29) in primigravidae, and early neonatal death (death within 7 days) in secundigravidae and multigravidae (aHR 6.30, 95% CI: 1.41-28.15). CONCLUSIONS: Malaria treatment after diagnosis, alongside IPTp-SP, is insufficient to prevent malaria-related stillbirth, early neonatal death and preterm delivery (PTD). Although IPTp-SP was beneficial in Mali during the study period, new tools are needed to improve pregnancy outcomes. CLINICAL TRIALS REGISTRATION: NCT01168271.
Subject(s)
Antimalarials , Malaria, Falciparum , Malaria , Perinatal Death , Pregnancy Complications, Parasitic , Premature Birth , Antimalarials/therapeutic use , Chemoprevention , Drug Combinations , Female , Humans , Infant, Newborn , Longitudinal Studies , Malaria/drug therapy , Malaria/epidemiology , Malaria/prevention & control , Malaria, Falciparum/drug therapy , Malaria, Falciparum/epidemiology , Malaria, Falciparum/prevention & control , Mali/epidemiology , Perinatal Mortality , Placenta , Pregnancy , Pregnancy Complications, Parasitic/drug therapy , Pregnancy Complications, Parasitic/epidemiology , Pregnancy Complications, Parasitic/prevention & control , Premature Birth/epidemiology , Premature Birth/prevention & control , Pyrimethamine/therapeutic use , Sulfadoxine/therapeutic useABSTRACT
BACKGROUND: More than 200 million people live in areas of highly seasonal malaria transmission where Seasonal Malaria Chemoprevention (SMC) with sulfadoxine-pyrimethamine (SP) and amodiaquine (AQ) was recommended in 2012 by WHO. This strategy is now implemented widely and protected more than 19 million children in 2018. It was previously reported that exposure to SMC reduced antibody levels to AMA1, MSP-142 and CSP, but the duration of exposure to SMC up to three 3 years, had no effect on antibody levels to MSP-142 and CSP. METHODS: In 2017, a cross-sectional survey was carried out 1 month after the last dose of SMC had been given to children aged 4-5 years randomly selected from areas where SMC had been given for 2 or 4 years during the malaria transmission season. A total of 461 children were enrolled, 242 children in areas where SMC had been implemented for 4 years and 219 children in areas where SMC had been implemented for 2 years. Antibody extracted from dry blood spots was used to measure IgG levels to the malaria antigens CSP, MSP-142 and AMA1 by ELISA. RESULTS: The prevalence of antibodies to MSP-142 was similar in children who had received SMC for 4 years compared to those who had received SMC for only 2 years (85.1 vs 86.0%, ajusted odd ratio (aOR) = 1.06, 95% confidence intervals (CI 0.62-1.80), p = 0.80). The prevalence of antibodies to AMA-1 and to CSP was not lower in children who received SMC for 4 years compared to those who had received SMC for only 2 years (95.3 vs 88.8%, aOR = 3.16, 95% CI 1.44-6.95, p = 0.004 for AMA-1; and 91.2 vs 81.9%, aOR = 3.14, 95% CI 1.70-5.76, p < 0.001 for CSP). Median antibody levels for anti-MSP-142 IgG were not significatively inferior in children who had received SMC for four rather than 2 years (0.88 (IQR: 0.64-1.15) and 0.95 ((0.68-1.15), respectively), anti-CSP (1.30 (1.00-1.56) and 1.17 (0.87-1.47)), and anti-AMA-1 (1.45 (1.24-1.68) and 1.41 (1.17-1.64)). CONCLUSION: In an area of high seasonal malaria transmission, children who had received SMC for 4 years did not had lower seropositivity or antibody levels to AMA1, MSP-142 and CSP compared to children who had received SMC for only 2 years suggesting that children who have received SMC for 4 years may not be more at risk of malaria after the cessation of SMC than children who have received SMC for a shorter period.
Subject(s)
Antibodies, Protozoan/immunology , Antigens, Protozoan/immunology , Antimalarials/therapeutic use , Chemoprevention/statistics & numerical data , Malaria/prevention & control , Plasmodium falciparum/immunology , MaliABSTRACT
BACKGROUND: Seasonal malaria chemoprevention (SMC) is a novel strategy to reduce malaria infections in children. Infection with Plasmodium falciparum results in immune dysfunction characterized by elevated expression of markers associated with exhaustion, such as PD1 and LAG3, and regulatory CD4+FOXP3+ T cells. METHODS: In the current study, the impact of seasonal malaria chemoprevention on malaria-induced immune dysfunction, as measured by markers associated with exhaustion and regulatory T cells, was explored by flow cytometry. RESULTS: Children that received seasonal malaria chemoprevention had fewer malaria episodes and showed significantly lower fold changes in CD4+PD1+ and CD4+PD1+LAG3+ compared to those that did not receive SMC. Seasonal malaria chemoprevention had no observable effect on fold changes in CD8 T cells expressing PD1 or CD160. However, children receiving SMC showed greater increases in CD4+FOXP3+ T regulatory cells compared to children not receiving SMC. CONCLUSIONS: These results provide important insights into the dynamics of malaria-induced changes in the CD4 T-cell compartment of the immune system and suggest that the reduction of infections due to seasonal malaria chemoprevention may also prevent immune dysfunction. CLINICAL TRIALS REGISTRATION: NCT02504918.
Subject(s)
Antigens, CD/blood , Antimalarials/therapeutic use , CD4-Positive T-Lymphocytes/metabolism , Malaria, Falciparum/immunology , Malaria, Falciparum/prevention & control , Programmed Cell Death 1 Receptor/blood , Amodiaquine/therapeutic use , Biomarkers/blood , Child, Preschool , Drug Combinations , Female , Forkhead Transcription Factors/blood , Humans , Infant , Male , Pyrimethamine/therapeutic use , Seasons , Sulfadoxine/therapeutic use , T-Lymphocytes, Regulatory , Lymphocyte Activation Gene 3 ProteinABSTRACT
Plasmodium falciparum variant antigens named erythrocyte membrane protein 1 (PfEMP1) are important targets for developing a protective immunity to malaria caused by P. falciparum. One of the major challenges in P. falciparum proteomics studies is identifying PfEMP1s at the protein level due to antigenic variation. To identify these PfEMP1s using shotgun proteomics, we developed a pipeline that searches high-resolution mass spectrometry spectra against a custom protein sequence database. A local alignment algorithm, LAX, was developed as a part of the pipeline that matches peptide sequences to the most similar PfEMP1 and calculates a weight value based on peptide's uniqueness used for PfEMP1 protein inference. The pipeline was first validated in the analysis of a laboratory strain with a known PfEMP1, then it was implemented on the analysis of parasite isolates from malaria-infected pregnant women and finally on the analysis of parasite isolates from malaria-infected children where there was an increase of PfEMP1s identified in 27 out of 31 isolates using the expanded database.
Subject(s)
Mutant Proteins/metabolism , Plasmodium falciparum/metabolism , Proteome/metabolism , Proteomics/methods , Protozoan Proteins/metabolism , Amino Acid Sequence , Child , Chromatography, Liquid/methods , Female , Humans , Malaria, Falciparum/parasitology , Mutant Proteins/genetics , Plasmodium falciparum/isolation & purification , Plasmodium falciparum/physiology , Pregnancy , Pregnancy Complications, Parasitic/parasitology , Proteome/genetics , Protozoan Proteins/genetics , Sequence Homology, Amino Acid , Tandem Mass Spectrometry/methodsABSTRACT
BACKGROUND: Plasmodium falciparum-infected erythrocytes (IE) sequester in deep vascular beds where their adhesion is mediated by an array of endothelial surface receptors. Because parasite adhesion has been associated with disease, antibodies that block this activity may confer protective immunity. Here, levels of plasma anti-adhesion activity and surface reactivity against freshly collected IEs from malaria-infected children were measured in a Malian birth cohort and related to child age and malaria infection history. METHODS: Plasma samples from children enrolled at birth in a longitudinal cohort study of mother-infant pairs in Ouelessebougou, Mali were collected at multiple time points during follow-up visits. Anti-adhesion antibodies (i.e., inhibit IE binding to any of several endothelial receptors) and reactivity with surface IE proteins were measured using a binding inhibition assay and by flow cytometry, respectively. RESULTS: Levels of antibodies that inhibit the binding of children's IE to the receptors ICAM-1, integrin α3ß1 and laminin increased with age. The breadth of antibodies that inhibit ICAM-1 and laminin adhesion (defined as the proportion of IE isolates whose binding was reduced by ≥ 50%) also significantly increased with age. The number of malaria infections prior to plasma collection was associated with levels of plasma reactivity to IE surface proteins, but not levels of anti-adhesion activity. CONCLUSIONS: Age is associated with increased levels of antibodies that reduce adhesion of children's IE to three of the ten endothelial receptors evaluated here. These results suggest that anti-adhesion antibodies to some but not all endothelial receptors are acquired during the first few years of life.
Subject(s)
Antibodies, Protozoan/immunology , Erythrocytes/parasitology , Integrin alpha3beta1/metabolism , Intercellular Adhesion Molecule-1/metabolism , Malaria, Falciparum/physiopathology , Plasmodium falciparum/immunology , Cell Adhesion , Child, Preschool , Humans , Infant , Infant, Newborn , Laminin/metabolism , Longitudinal Studies , MaliABSTRACT
BACKGROUND: Maternal malaria is a tropical scourge associated with poor pregnancy outcomes. Women become resistant to Plasmodium falciparum pregnancy malaria as they acquire antibodies to the variant surface antigen VAR2CSA, a leading vaccine candidate. Because malaria infection may increase VAR2CSA antibody levels and thereby confound analyses of immune protection, gravidity-dependent changes in antibody levels during and after infection, and the effect of VAR2CSA antibodies on pregnancy outcomes were evaluated. METHODS: Pregnant women enrolled in a longitudinal cohort study of mother-infant pairs in Ouelessebougou, Mali provided plasma samples at enrollment, gestational week 30-32, and delivery. Antibody levels to VAR2CSA domains were measured using a multiplex bead-based assay. RESULTS: Antibody levels to VAR2CSA were higher in multigravidae than primigravidae. Malaria infection was associated with increased antibody levels to VAR2CSA domains. In primigravidae but not in secundigravidae or multigravidae, antibodies levels sharply declined after an infection. A relationship between any VAR2CSA antibody specificity and protection from adverse pregnancy outcomes was not detected. CONCLUSIONS: During malaria infection, primigravidae acquire short-lived antibodies. The lack of an association between VAR2CSA domain antibody reactivity and improved pregnancy outcomes suggests that the recombinant proteins may not present native epitopes targeted by protective antibodies.
Subject(s)
Antibodies, Protozoan/blood , Antigens, Protozoan/immunology , Malaria, Falciparum/pathology , Parasitemia/pathology , Pregnancy Complications, Infectious/pathology , Adolescent , Adult , Female , Gestational Age , Humans , Infant, Newborn , Longitudinal Studies , Mali , Middle Aged , Pregnancy , Pregnancy Outcome , Young AdultABSTRACT
BACKGROUND: Pregnancy malaria (PM) is associated with a proinflammatory immune response characterized by increased levels of cytokines and chemokines such as tumor necrosis factor-α, interferon-γ, interleukin 10 (IL-10), and CXCL9. These changes are associated with poor outcomes including low birthweight delivery and maternal anemia. However, it is unknown if inflammatory pathways during malaria are related to pregnancy loss and preterm delivery (PTD). METHODS: Cytokine and chemokine levels were measured in maternal peripheral blood at enrollment, gestational week 30-32, and delivery, and in placental blood, of 638 women during a longitudinal cohort study in Ouelessebougou, Mali. Plasmodium falciparum infection was assessed by blood smear microscopy at all visits. RESULTS: PM was associated with increased levels of cytokines and chemokines including IL-10 and CXCL9. In a competing risks model adjusted for known covariates, high CXCL9 levels measured in the peripheral blood during pregnancy were associated with increased risk of pregnancy loss and PTD. At delivery, high IL-10 levels in maternal blood were associated with an increase in pregnancy loss, and increased IL-1ß levels in placental blood were associated with pregnancy loss and PTD. CONCLUSIONS: PM is associated with increased proinflammatory cytokine and chemokine levels in placental and maternal peripheral blood. Systemic inflammatory responses to malaria during pregnancy predict increased risk of pregnancy loss and PTD. CLINICAL TRIALS REGISTRATION: NCT01168271.
Subject(s)
Abortion, Spontaneous/epidemiology , Malaria, Falciparum/epidemiology , Pregnancy Complications, Parasitic/epidemiology , Premature Birth/epidemiology , Systemic Inflammatory Response Syndrome/epidemiology , Abortion, Spontaneous/etiology , Adolescent , Adult , Cytokines/blood , Female , Humans , Longitudinal Studies , Malaria, Falciparum/complications , Mali/epidemiology , Middle Aged , Pregnancy , Premature Birth/etiology , Systemic Inflammatory Response Syndrome/complications , Young AdultABSTRACT
BACKGROUND: Seasonal malaria chemoprevention (SMC) is a new strategy to reduce malaria burden in young children in Sahelian countries. It consists of the administration of full treatment courses of sulfadoxine-pyrimethamine plus amodiaquine to children at monthly intervals during the malaria season. However, it is not clear if there is a cumulative effect of SMC over time on acquisition of antibodies to malaria antigens. METHODS: A cross-sectional serosurvey was carried out 1 month after the last dose of SMC in 2016. Children aged 3-4 years were randomly selected from areas where SMC was given for 1, 2 or 3 years during the malaria season. Children in the areas where SMC had been implemented for 1 year but who failed to receive SMC were used as comparison group. Antibody extracted from dry blood spots was used to measure IgG levels to CSP, MSP-142 and AMA1. RESULTS: The prevalence of antibodies to AMA-1 were high and similar in children who received SMC for 1, 2 or 3 years and also when compared to those who never received SMC (96.3 vs 97.5%, adjusted OR = 0.99, 95% CI 0.33-2.97, p = 0.99). The prevalence of antibodies to MSP-142 and to CSP were similar in children that received SMC for 1, 2 or 3 years, but were lower in these children compared to those who did not receive SMC (87.1 vs 91.2%, adjusted OR = 0.55, 95% CI 0.29-1.01, p = 0.05 for MSP-142; 79.8 vs 89.2%, adjusted OR = 0.52, 95% CI 0.30-0.90, p = 0.019 for CSP). CONCLUSIONS: SMC reduced seropositivity to MSP-142 and CSP, but the duration of SMC did not further reduce seropositivity. Exposure to SMC did not reduce the seropositivity to AMA1.
Subject(s)
Antibodies, Protozoan/blood , Chemoprevention/methods , Malaria, Falciparum/epidemiology , Seasons , Child, Preschool , Communicable Disease Control/standards , Cross-Sectional Studies , Female , Humans , Malaria, Falciparum/prevention & control , Male , Mali/epidemiology , Prevalence , Seroepidemiologic StudiesABSTRACT
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.
ABSTRACT
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.
Subject(s)
Malaria, Falciparum , Malaria , Parasites , Child , Animals , Humans , Child, Preschool , Plasmodium falciparum , Platelet Count , Cross-Sectional Studies , Malaria, Falciparum/parasitologyABSTRACT
BACKGROUND: Plasmodium falciparum parasitaemia during pregnancy causes maternal, fetal, and infant mortality. Poor pregnancy outcomes are related to blood-stage parasite sequestration and the ensuing inflammatory response in the placenta, which decreases over successive pregnancies. A radiation-attenuated, non-replicating, whole-organism vaccine based on P falciparum sporozoites (PfSPZ Vaccine) has shown efficacy at preventing infection in African adults. Here, we aimed to examine vaccine safety and efficacy of the PfSPZ Vaccine in adults and women who anticipated conception. METHODS: Two randomised, double-blind, placebo-controlled trials (phase 1 MLSPZV3 and phase 2 MLSPZV4) were conducted at a clinical research centre in Mali. MLSPZV3 included adults aged 18-35 years and MLSPZV4 included non-pregnant women aged 18-38 years who anticipated conception within a year of enrolment. In MLSPZV3, participants were stratified by village and randomly assigned (2:1) using block randomisation to receive three doses of 9â×â105 PfSPZ Vaccine or saline placebo at weeks 0, 1, and 4 (4-week schedule) or at weeks 0, 8, and 16 (16-week schedule) and a booster dose around 1 year later. In MLSPZV4, women received presumptive artemether-lumefantrine twice per day for 3 days 2 weeks before dose one and were randomly assigned (1:1:1) using block randomisation to receive three doses of 9â×â105 or 1·8â×â106 PfSPZ Vaccine or saline placebo all administered at weeks 0, 1, and 4 (4-week schedule). Participants in both studies received artemether-lumefantrine 2 weeks before dose three and additionally 2 weeks before dose four (booster dose) in MLSPZV3. Investigators and participants were masked to group assignment. The primary outcome, assessed in the as-treated population, was PfSPZ Vaccine safety and tolerability within 7 days after each dose. The secondary outcome, assessed in the modified intention-to-treat population, was vaccine efficacy against P falciparum parasitaemia (defined as the time-to-first positive blood smear) from dose three until the end of transmission season. In exploratory analyses, MLSPZV4 evaluated incidence of maternal obstetric and neonatal outcomes as safety outcomes, and vaccine efficacy against P falciparum parasitaemia during pregnancy (defined as time-to-first positive blood smear post-conception). In MLSPZV4, women were followed at least once a month with human chorionic gonadotropin testing, and those who became pregnant received standard of care (including intermittent presumptive sulfadoxine-pyrimethamine antimalarial drugs after the first trimester) during routine antenatal visits. These studies are registered with ClinicalTrials.gov, NCT03510481 and NCT03989102. FINDINGS: Participants were enrolled for vaccination during the onset of malaria seasons for two sequential studies conducted from 2018 to 2019 for MLSPZV3 and from 2019 to 2021 for MLSPZV4, with follow-up during malaria seasons across 2 years. In MLSPZV3, 478 adults were assessed for eligibility, of whom 220 were enrolled between May 30 and June 12, 2018, and then between Aug 13 and Aug 18, 2018, and 210 received dose one. 66 (96%) of 69 participants who received the 16-week schedule and 68 (97%) of 70 who received the 4-week schedule of the 9â×â105 PfSPZ Vaccine and 70 (99%) of 71 who received saline completed all three doses in year 1. In MLSPZV4, 407 women were assessed for eligibility, of whom 324 were enrolled from July 3 to July 27, 2019, and 320 received dose one of presumptive artemether-lumefantrine. 300 women were randomly assigned with 100 per group (PfSPZ Vaccine 9â×â105, 1·8â×â106, or saline) receiving dose one. First trimester miscarriages were the most commonly reported serious adverse event but occurred at a similar rate across study groups (eight [15%] of 54 with 9â×â105 PfSPZ Vaccine, 12 [21%] of 58 with 1·8â×â106 PfSPZ Vaccine, and five [12%] of 43 with saline). One unrelated maternal death occurred 425 days after the last vaccine dose in the 1·8â×â106 PfSPZ Vaccine group due to peritonitis shortly after childbirth. Most related adverse events reported in MLSPZV3 and MLSPZV4 were mild (grade 1) and frequency of adverse events in the PfSPZ Vaccine groups did not differ from that in the saline group. Two unrelated serious adverse events occurred in MLSPZV3 (one participant had appendicitis in the 9â×â105 PfSPZ Vaccine group and the other in the saline group died due to a road traffic accident). In MLSPZV3, the 9â×â105 PfSPZ Vaccine did not show vaccine efficacy against parasitaemia with the 4-week (27% [95% CI -18 to 55] in year 1 and 42% [-5 to 68] in year 2) and 16-week schedules (16% [-34 to 48] in year 1 and -14% [-95 to 33] in year 2); efficacies were similar or worse against clinical malaria compared with saline. In MLSPZV4, the PfSPZ Vaccine showed significant efficacy against parasitaemia at doses 9â×â105 (41% [15 to 59]; p=0·0069 in year 1 and 61% [36 to 77]; p=0·0011 in year 2) and 1·8â×â106 (54% [34 to 69]; p<0·0001 in year 1 and 45% [13 to 65]; p=0·029 in year 2); and against clinical malaria at doses 9â×â105 (47% [20 to 65]; p=0·0045 in year 1 and 56% [22 to 75]; p=0·0081 in year 2) and 1·8â×â106 (48% [22 to 65]; p=0·0013 in year 1 and 40% [2 to 64]; p=0·069 in year 2). Vaccine efficacy against post-conception P falciparum parasitaemia during first pregnancies that arose in the 2-year follow-up was 57% (14 to 78; p=0·017) in the 9 × 105 PfSPZ Vaccine group versus 49% (3 to 73; p=0·042) in the 1·8â×â106 PfSPZ Vaccine group. Among 55 women who became pregnant within 24 weeks after dose three, vaccine efficacy against parasitaemia was 65% (23 to 84; p=0·0088) with the 9â×â105 PfSPZ Vaccine and 86% (64 to 94; p<0·0001) with the 1·8â×â106 PfSPZ Vaccine. When combined in a post-hoc analysis, women in the PfSPZ Vaccine groups had a non-significantly reduced time-to-first pregnancy after dose one compared with those in the saline group (log-rank test p=0·056). Exploratory maternal obstetric and neonatal outcomes did not differ significantly between vaccine groups and saline. INTERPRETATION: PfSPZ Vaccine was safe and well tolerated in adults in Mali. The 9â×â105 and 1·8â×â106 doses of PfSPZ Vaccine administered as per the 4-week schedule, which incorporated presumptive antimalarial treatment before the first vaccine dose, showed significant efficacy against P falciparum parasitaemia and clinical malaria for two malaria transmission seasons in women of childbearing age and against pregnancy malaria. PfSPZ Vaccine without presumptive antimalarial treatment before the first vaccine dose did not show efficacy. FUNDING: National Institute of Allergy and Infectious Diseases, National Institutes of Health, and Sanaria.
ABSTRACT
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.
Subject(s)
Malaria , Plasmodium falciparum , Infant, Newborn , Female , Humans , Pregnancy , Placenta/metabolism , Chondroitin Sulfates , Gravidity , Antigens, Protozoan , Antibodies, ProtozoanABSTRACT
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].
ABSTRACT
BACKGROUND: Tafenoquine was recently approved as a prophylaxis and radical cure for Plasmodium vivax infection, but its Plasmodium falciparum transmission-blocking efficacy is unclear. We aimed to establish the efficacy and safety of three single low doses of tafenoquine in combination with dihydroartemisinin-piperaquine for reducing gametocyte density and transmission to mosquitoes. METHODS: In this four-arm, single-blind, phase 2, randomised controlled trial, participants were recruited at the Clinical Research Unit of the Malaria Research and Training Centre of the University of Bamako in Mali. Eligible participants were aged 12-50 years, with asymptomatic P falciparum microscopy-detected gametocyte carriage, had a bodyweight of 80 kg or less, and had no clinical signs of malaria defined by fever. Participants were randomly assigned (1:1:1:1) to standard treatment with dihydroartemisinin-piperaquine, or dihydroartemisinin-piperaquine plus a single dose of tafenoquine (in solution) at a final dosage of 0·42 mg/kg, 0·83 mg/kg, or 1·66 mg/kg. Randomisation was done with a computer-generated randomisation list and concealed with sealed, opaque envelopes. Dihydroartemisinin-piperaquine was administered as oral tablets over 3 days (day 0, 1, and 2), as per manufacturer instructions. A single dose of tafenoquine was administered as oral solution on day 0 in parallel with the first dose of dihydroartemisinin-piperaquine. Tafenoquine dosing was based on bodyweight to standardise efficacy and risk variance. The primary endpoint, assessed in the per-protocol population, was median percentage change in mosquito infection rate 7 days after treatment compared with baseline. Safety endpoints included frequency and incidence of adverse events. The final follow-up visit was on Dec 23, 2021; the trial is registered with ClinicalTrials.gov, NCT04609098. FINDINGS: From Oct 29 to Nov 25, 2020, 1091 individuals were screened for eligibility, 80 of whom were enrolled and randomly assigned (20 per treatment group). Before treatment, 53 (66%) individuals were infectious to mosquitoes, infecting median 12·50% of mosquitoes (IQR 3·64-35·00). Within-group reduction in mosquito infection rate on day 7 was 79·95% (IQR 57·15-100; p=0·0005 for difference from baseline) following dihydroartemisinin-piperaquine only, 100% (98·36-100; p=0·0005) following dihydroartemisinin-piperaquine plus tafenoquine 0·42 mg/kg, 100% (100-100; p=0·0001) following dihydroartemisinin-piperaquine plus tafenoquine 0·83 mg/kg, and 100% (100-100; p=0·0001) following dihydroartemisinin-piperaquine plus tafenoquine 1·66 mg/kg. 55 (69%) of 80 participants had a total of 94 adverse events over the course of the trial; 86 (92%) adverse events were categorised as mild, seven (7%) as moderate, and one (1%) as severe. The most common treatment-related adverse event was mild or moderate headache, which occurred in 15 (19%) participants (dihydroartemisinin-piperaquine n=2; dihydroartemisinin-piperaquine plus tafenoquine 0·42 mg/kg n=6; dihydroartemisinin-piperaquine plus tafenoquine 0·83 mg/kg n=3; and dihydroartemisinin-piperaquine plus tafenoquine 1·66 mg/kg n=4). No serious adverse events occurred. No significant differences in the incidence of all adverse events (p=0·73) or treatment-related adverse events (p=0·62) were observed between treatment groups. INTERPRETATION: Tafenoquine was well tolerated at all doses and accelerated P falciparum gametocyte clearance. All tafenoquine doses showed improved transmission reduction at day 7 compared with dihydroartemisinin-piperaquine alone. These data support the case for further research on tafenoquine as a transmission-blocking supplement to standard antimalarials. FUNDING: Bill & Melinda Gates Foundation. TRANSLATIONS: For the French, Portuguese, Spanish and Swahili translations of the abstract see Supplementary Materials section.
Subject(s)
Artemisinins , Malaria, Falciparum , Malaria , Aminoquinolines , Animals , Artemisinins/adverse effects , Humans , Malaria/drug therapy , Malaria, Falciparum/drug therapy , Mali/epidemiology , Piperazines , Plasmodium falciparum , Quinolines , Single-Blind MethodABSTRACT
Malaria has been hypothesized as a factor that may have reduced the severity of the COVID-19 pandemic in sub-Saharan Africa. To evaluate the effect of recent malaria on COVID-19 we assessed a subgroup of individuals participating in a longitudinal cohort COVID-19 serosurvey that were also undergoing intensive malaria monitoring as part of antimalarial vaccine trials during the 2020 transmission season in Mali. These communities experienced a high incidence of primarily asymptomatic or mild COVID-19 during 2020 and 2021. In 1314 individuals, 711 were parasitemic during the 2020 malaria transmission season; 442 were symptomatic with clinical malaria and 269 had asymptomatic infection. Presence of parasitemia was not associated with new COVID-19 seroconversion (29.7% (211/711) vs. 30.0% (181/603), p=0.9038) or with rates of reported symptomatic seroconversion during the malaria transmission season. In the subsequent dry season, prior parasitemia was not associated with new COVID-19 seroconversion (30.2% (133/441) vs. 31.2% (108/346), p=0.7499), with symptomatic seroconversion, or with reversion from seropositive to seronegative (prior parasitemia: 36.2% (64/177) vs. no parasitemia: 30.1% (37/119), p=0.3842). After excluding participants with asymptomatic infection, clinical malaria was also not associated with COVID-19 serostatus or symptomatic seroconversion when compared to participants with no parasitemia during the monitoring period. In communities with intense seasonal malaria and a high incidence of asymptomatic or mild COVID-19, we did not demonstrate a relationship between recent malaria and subsequent response to COVID-19. Lifetime exposure, rather than recent infection, may be responsible for any effect of malaria on COVID-19 severity.