Falciparum Parasitaemia Research Articles

Glucose-6-phosphate dehydrogenase deficiency and susceptibility to childhood diseases in Kilifi, Kenya

AbstractFew previous studies have reported the effects of glucose-6-phosphate dehydrogenase (G6PD)–deficiency on child health in Africa. We conducted a case-control study in which cases (n = 6829) were children admitted, for any reason, to Kilifi County Hospital, Kenya, while controls (n = 10 179) were recruited from the surrounding community. Cases were subclassified based on their clinical and laboratory findings at admission. We calculated the prevalence of specific diseases by G6PD c.202 genotype, the only significant cause of G6PD-deficiency in this area, then estimated the association between genotype and admission with specific conditions using logistic regression. Among neonates, the prevalence of jaundice was higher in both G6PD c.202T heterozygotes (40/88; 45.5%; P = .004) and homo/hemizygotes (81/134; 60.5%; P < .0001) than in wild-type homozygotes (157/526; 29.9%). Median bilirubin levels also increased across the groups, being highest (239 mmol/L; interquartile range 96-390 mmol/L) in G6PD c.202T homo/hemizygotes. No differences were seen in admission hemoglobin concentrations or the prevalence of anemia or severe anemia by G6PD c.202 genotype. On case control analysis, G6PD heterozygosity was negatively associated with all-cause hospital admission (odds ratio 0.81; 95% confidence interval 0.73-0.90; P < .0001) and, specifically, admission with either pneumonia or Plasmodium falciparum parasitemia; while, conversely, it was positively associated with Gram-positive bacteremia. G6PD c.202T homo/heterozygosity was positively associated with neonatal jaundice, severe pneumonia, the receipt of a transfusion, and in-patient death. Our study supports the conclusion that G6PD c.202T is a balanced polymorphism in which a selective advantage afforded to heterozygous females against malaria is counterbalanced by increased risks of neonatal jaundice, invasive bacterial infections, and anemia.

Relationship between selected circulating cytokines and haematological parameters in Plasmodium falciparum infected donor blood

Background: Plasmodium falciparum infection in donor blood has been severally reported. However, the impact of parasitaemia on cytokinaemia in stored blood has not been explored. This study, therefore, evaluated the impact of P. falciparum parasitaemia in donor blood on selected circulating cytokines and haematological parameters. Methods & Materials: Two groups of donor blood units were used for the study; those infected with P. falciparum parasites (n = 55) (range: 115–877 parasites/μl) and those without infection (n = 110). At day 0 (baseline), 7, 14, 21, 28 and 35, absolute leukocytes and erythrocytes counts and concentrations of circulating tumor necrosis factor alpha (TNF-α), interleukin (IL)-12, IL-10 and IL-6 levels in citrate-phosphate-dextrose-adenine (CPDA-1) anticoagulated donor blood were assessed using automated haematology analyzer and sandwich enzyme immunoassay respectively. Results: At baseline, the mean TNF-α (33.81 pg/mL vs 22.70 pg/mL), IL-12 (28.39 pg/mL vs 16.15 pg/mL), IL-10 (51.04 pg/mL vs 18.95 pg/mL), and IL-6 (71.03 pg/mL vs 30.89 pg/mL) levels were significantly higher in malaria-infected donor units. Significant rate of increases was observed in TNF-α (192.0%day-7 to 433.3%day-35), IL-12 (94.0%day-7 to 419.47%day-35) and TNF-α/IL-10 ratio (429.11%day 7 to 1883.54%day 35) in infected donor blood. Conceptually, transfusing a single 500 ml of malaria-infected blood stored for 21 days could lead to infusing 190 ng, 71.6 ng, or 48.2 ng of IL-6, TNF-α and IL-12 respectively. Significant changes in TNF-α, IL-12, IL-10, IL-6 and TNF-α/IL-10 ratio in infected donor blood were observed at day 7. Whereas, TNF-α and IL-12 negatively correlated with total absolute leukocytes, neutrophils and lymphocytes counts, it was positively related to monocytes at day 7 to day 35. Moreover, in malaria infected units, at days 7-35, TNF-α and IL-12 were significantly inversely related to RBC and RBC indices. Conclusion: Banking of malaria-infected donor units may lead to infusion of large quantities of inflammatory cytokines with potential adverse immunological response in recipients.

Prevalence of sickle cell disorders and malaria infection in children aged 1\u201312\xa0years in the Volta Region, Ghana: a community-based study

BackgroundAlterations in the structure of haemoglobin (Hb) are usually brought about by point mutations affecting one or, in some cases, two codons encoding amino acids of the globin chains. One in three Ghanaians are said to have sickle cell disorders, whereas malaria continues to be one of the leading causes of mortality among children. This study determined the prevalence of sickle cell disorders and malaria infection among children aged 1–12 years in the Volta Region.MethodsThis was a community-based cross-sectional survey that involved 938 children aged 1–12 years selected from three districts, one each from the 3 geographical zones of the Volta Region using a multistage sampling method. Demographic information was collected using a standard questionnaire and anthropometric indices were measured. Isoelectric focusing (IEF) electrophoresis was used to determine the Hb genotypes and sub-microscopic parasites were determined by PCR.ResultsThe prevalence of sickling screening positive was 16.0% with an overall prevalence of sickle cell disorders being 2.0%. Among the individual genotypes making up the sickle cell disorders, genotype HbSF was the highest (0.9% as compared to 0.2%; HbSS, 0.6%; HbSC and 0.3%; HbSCF). Microscopic Plasmodium falciparum parasitaemia was detected among 5.5% of the children and 14.2% sub-microscopic prevalence by PCR. Children with sickle cell disorders were more likely to have sub-microscopic parasitaemia (AOR = 5.51 95%CI (2.15, 14.10), p < 0.001) as well as anaemia (AOR = 3.03 95% CI (1.04, 8.82), p = 0.042), compared to those with normal genotypes. There was no significant difference observed between sickle cell disorders and growth and development of the children screened.ConclusionsSickle cell disorders were significantly associated with sub-microscopic parasitaemia as well as anaemia in this study. Establishment of sickle cell clinics in the district and regional hospitals will help in the management of children with the disorder and also generate a national database on sickle cell disorders. National neonatal screening policies must also be put in place to help in early detection and management of these disorders.

Association of Inhibitory Killer Cell Immunoglobulin-like Receptor Ligands With Higher Plasmodium falciparum Parasite Prevalence.

Killer cell immunoglobulin-like receptors (KIRs) and their HLA ligands influence the outcome of many infectious diseases. We analyzed the relationship of compound KIR-HLA genotypes with risk of Plasmodium falciparum infection in a longitudinal cohort of 890 Ugandan individuals. We found that presence of HLA-C2 and HLA-Bw4, ligands for inhibitory KIR2DL1 and KIR3DL1, respectively, increased the likelihood of P. falciparum parasitemia in an additive manner. Individuals homozygous for HLA-C2, which mediates strong inhibition via KIR2DL1, had the highest odds of parasitemia, HLA-C1/C2 heterozygotes had intermediate odds, and individuals homozygous for HLA-C1, which mediates weaker inhibition through KIR2DL2/3, had the lowest odds of parasitemia. In addition, higher surface expression of HLA-C, the ligand for inhibitory KIR2DL1/2/3, was associated with a higher likelihood of parasitemia. Together these data indicate that stronger KIR-mediated inhibition confers a higher risk of P. falciparum parasitemia and suggest that KIR-expressing effector cells play a role in mediating antiparasite immunity.

Elevated IL-12, TNF-α, and TNF-α/IL-10 Ratios in Stored Plasmodium falciparum-Infected Whole Blood: Implications for Safe Haemotransfusion.

Although Plasmodium falciparum infections in blood donors have been reported, the impact of parasitaemia on cytokine levels in stored whole blood has not been explored. This study evaluated the effect of P. falciparum parasitaemia on circulating cytokines and their relationship with haematological parameters in banked blood. In this case-control study, two groups of donor whole blood were recruited: P. falciparum-infected donors (parasitaemia: 515–1877 parasites/μL) and noninfected blood donors (control). At day 0 (baseline), 7, 14, 21, and 35 of banking circulating cytokine levels of tumor necrosis factor alpha (TNF-α), interleukin- (IL-) 12, IL-10, and IL-6 levels and haematological parameters were determined. Kruskal-Wallis test determined differences in weekly cytokine levels while Dunn's post hoc test determined exact significant points. At baseline, the mean TNF-α (33.81 pg/mL vs. 22.70 pg/mL), IL-12 (28.39 pg/mL vs. 16.15 pg/mL), IL-10 (51.04 pg/mL vs. 18.95 pg/mL), and IL-6 (71.03 pg/mL vs. 30.89 pg/mL) levels were significantly higher in infected donor whole blood. Significant rate of increase was observed in TNF-α, IL-12 levels, and TNF-α/IL-10 ratios in infected blood, while decreased levels were observed in IL-10. IL-6 peaked at day 21 and fell below baseline level at day 35. Significant changes in TNF-α, IL-12, IL-10, IL-6 levels, and TNF-α/IL-10 ratios in infected donor blood were observed 7 days after storage. Unlike in noninfected stored whole blood, TNF-α, IL-6, IL-12, and TNF-α/IL-10 ratio levels in infected stored whole blood related inversely to haematological parameters (white cells, red cells, platelets, and haemoglobin levels) during storage. However, in both groups, significant direct relationship was observed in IL-10 and haematological parameters. In conclusion, banking of P. falciparum-infected donor whole blood may lead to infusion of large quantities of inflammatory cytokines with potential adverse immunological response in recipients.

Opsonized antigen activates Vδ2+ T cells via CD16/FCγRIIIa in individuals with chronic malaria exposure.

Vγ9Vδ2 T cells rapidly respond to phosphoantigens produced by Plasmodium falciparum in an innate-like manner, without prior antigen exposure or processing. Vδ2 T cells have been shown to inhibit parasite replication in vitro and are associated with protection from P. falciparum parasitemia in vivo. Although a marked expansion of Vδ2 T cells is seen after acute malaria infection in naïve individuals, repeated malaria causes Vδ2 T cells to decline both in frequency and in malaria-responsiveness, and to exhibit numerous transcriptional and phenotypic changes, including upregulation of the Fc receptor CD16. Here we investigate the functional role of CD16 on Vδ2 T cells in the immune response to malaria. We show that CD16+ Vδ2 T cells possess more cytolytic potential than their CD16- counterparts, and bear many of the hallmarks of mature NK cells, including KIR expression. Furthermore, we demonstrate that Vδ2 T cells from heavily malaria-exposed individuals are able to respond to opsonized P.falciparum-infected red blood cells through CD16, representing a second, distinct pathway by which Vδ2 T cells may contribute to anti-parasite effector functions. This response was independent of TCR engagement, as demonstrated by blockade of the phosphoantigen presenting molecule Butyrophilin 3A1. Together these results indicate that Vδ2 T cells in heavily malaria-exposed individuals retain the capacity for antimalarial effector function, and demonstrate their activation by opsonized parasite antigen. This represents a new role both for Vδ2 T cells and for opsonizing antibodies in parasite clearance, emphasizing cooperation between the cellular and humoral arms of the immune system.

Integrative genomic analysis reveals mechanisms of immune evasion in P. falciparum malaria

The mechanisms behind the ability of Plasmodium falciparum to evade host immune system are poorly understood and are a major roadblock in achieving malaria elimination. Here, we use integrative genomic profiling and a longitudinal pediatric cohort in Burkina Faso to demonstrate the role of post-transcriptional regulation in host immune response in malaria. We report a strong signature of miRNA expression differentiation associated with P. falciparum infection (127 out of 320 miRNAs, B-H FDR 5%) and parasitemia (72 miRNAs, B-H FDR 5%). Integrative miRNA-mRNA analysis implicates several infection-responsive miRNAs (e.g., miR-16-5p, miR-15a-5p and miR-181c-5p) promoting lymphocyte cell death. miRNA cis-eQTL analysis using whole-genome sequencing data identified 1,376 genetic variants associated with the expression of 34 miRNAs (B-H FDR 5%). We report a protective effect of rs114136945 minor allele on parasitemia mediated through miR-598-3p expression. These results highlight the impact of post-transcriptional regulation, immune cell death processes and host genetic regulatory control in malaria.

Bacteraemia, Malaria, and Case Fatality Among Children Hospitalized With Fever in Dar es Salaam, Tanzania.

BackgroundFebrile illness is the commonest cause of hospitalization in children <5 years in sub-Saharan Africa, and bacterial bloodstream infections and malaria are major causes of death.MethodsFrom March 2017 to July 2018, we enrolled 2,226 children aged 0–5 years hospitalized due to fever in four major public hospitals of Dar es Salaam, namely, Amana, Temeke, and Mwananyamala Regional Hospitals and Muhimbili National Hospital. We recorded social demographic and clinical data, and we performed blood-culture and HIV-antibody testing. We used qPCR to quantify Plasmodium falciparum parasitaemia and Matrix-Assisted Laser Desorption/Ionization-Time of Flight (MALDI-TOF) to identify bacterial isolates. Disk diffusion method was used for antimicrobial susceptibility testing.ResultsNineteen percent of the children (426/2,226) had pathogens detected from blood. Eleven percent (236/2,226) of the children had bacteraemia/fungaemia and 10% (204/2,063) had P. falciparum malaria. Ten children had concomitant malaria and bacteraemia. Gram-negative bacteria (64%) were more frequent than Gram-positive (32%) and fungi (4%). Over 50% of Gram-negative bacteria were extended-spectrum beta-lactamase (ESBL) producers and multidrug resistant. Methicillin resistant Staphylococcus aureus (MRSA) was found in 11/42 (26.2%). The most severe form of clinical malaria was associated with high parasitaemia (>four million genomes/μL) of P. falciparum in plasma. Overall, in-hospital death was 4% (89/2,146), and it was higher in children with bacteraemia (8%, 18/227) than malaria (2%, 4/194, p = 0.007). Risk factors for death were bacteraemia (p = 0.03), unconsciousness at admission (p < 0.001), and admission at a tertiary hospital (p = 0.003).ConclusionCompared to previous studies in this region, our study showed a reduction in malaria prevalence, a decrease in in-hospital mortality, and an increase in antimicrobial resistance (AMR) including ESBLs and multidrug resistance. An increase of AMR highlights the importance of continued strengthening of diagnostic capability and antimicrobial stewardship programs. We also found malaria and bacteraemia contributed equally in causing febrile illness, but bacteraemia caused higher in-hospital death. The most severe form of clinical malaria was associated with P. falciparum parasitaemia.

Severe Anemia Is Associated with Systemic Inflammation in Young Children Presenting to a Tertiary Hospital in Uganda.

.The role of inflammation in severe anemia (SA) in African children has not been well characterized. We conducted a study to evaluate risk factors for SA in young children admitted at a tertiary unit in Uganda. Clinical, infectious, and micronutrient risk factors for anemia, along with markers of inflammation, were evaluated in children aged < 5 years in Jinja Hospital, Uganda. Participants included 284 children with SA (Hemoglobin [Hb] < 5.0 g/dL), and two control groups: 63 children admitted with acute illness without SA (Hb > 9.3 g/dL) and 53 asymptomatic community control children. Appropriate logistic analysis was performed to determine factors associated with SA. Of the 284 children with SA, 36.5% had Plasmodium falciparum parasitemia, 32.7% had blackwater fever (one of the types of severe malaria), and 15.5% had vitamin B12 deficiency. HIV infection, bacteremia, hookworm infection, severe acute malnutrition, and folate deficiency were relatively uncommon (each accounting for < 8%). Factors independently associated with SA compared with the combined control groups included (adjusted odds ratio [OR]; 95% CI) the following: P. falciparum parasitemia (OR: 4.3; 95% CI: 1.4–13.8), total white blood count (OR: 1.3; 95% CI: 1.1–1.4), C-reactive protein (OR: 1.8; 95% CI: 1.3–2.4), and ferritin (OR: 2.7; 95% CI: 1.9–4.0). In this area of Uganda, malaria and markers of inflammation were independently associated with SA in children. Additional studies are required to determine the role of inflammation in children with SA in this population.

CML-004: Imatinib is Protective Against Falciparum Malaria: A Case Control Study from a Tertiary Care Centre in West Bengal

Context Rising evidence of artemisin resistant malaria in Indian subcontinent and South America has prompted researchers to search for alternative antimalarials. In the last few decades, few reports and subsequent in vitro results have emerged showing dependence of malarial parasites, particularly P falciparum, on RBC tyrosine kinases for its maturation and egress. As there were no clinical data to support the hypothesis, we conducted a case control study with patients of CML-CP on fixed dose imatinib (TKI) as cases and a representative healthy population as control. Objective To compare the prevalence of asymptomatic falciparum and vivax infections in study cases with the prevalence of matched control taken from healthy blood donors. Methods A standard questionnaire and rapid diagnostic test (RDT) for plasmodium antigens from the blood of cases attending CML clinic were used as study tools. 191 CML patients who are on imatinib 400mg/d for a minimum period of 1 year were analysed. Controls were healthy voluntary blood donors attending the hospital during the same time-frame. Study time was April-September (peak malaria season). All RDT +ve cases were internally validated with PCR using two species specific forward primers. Results Out of 54 febrile episodes among cases during the study period, one had vivax malaria. RDT testing on non-febrile participants revealed two samples positive for dual vivax-falciparum antigens and the other two for vivax antigen. PCR showed three cases positive for vivax and one positive for both vivax and falciparum. Among 205 controls, three had vivax infections, three had falciparum infections and four were found to have infections with both. The concordance for positive results among the diagnostic modalities (RDT and PCR) was found to be 93.3%. The prevalence of malarial infections in cases and controls were found to be 2.05% and 4.87% respectively while falciparum parasitemia in cases and controls were found to be 0.51% and 3.41% respectively. Conclusion Analysis showed that the difference of asymptomatic falciparum carriage among cases and control was statistically significant suggesting a protective effect of imatinib against falciparum infections. The association of vivax positivity with imatinib exposure was however not statistically significant.

A modified two-color flow cytometry assay to quantify in-vitro reinvasion and determine invasion phenotypes at low Plasmodium falciparum parasitemia

Invasion of human red blood cells (RBCs) by Plasmodium parasites is a crucial yet poorly characterised phenotype. Two-color flow cytometry (2cFCM) promises to be a very sensitive and high throughput method for phenotyping parasite invasion. However, current protocols require high (~1.0%) parasitemia for assay set-up and need to be adapted for low parasitemia samples, which are becoming increasingly common in low transmission settings. Background fluorescence from nuclei-containing uninfected RBCs and high autologous reinvasion rates (merozoite invasion of donor uninfected RBCs present at 50% assay volume) are some of the limitations to the method's sensitivity to enumerate low parasitemia (<0.5%) with nucleic acid-based stains. Here, we describe modifications for plating unlabeled donor to labeled target RBCs per assay well and for gating parasitemia, that produces accurate quantifications of low reinvasion parasitemia. Plasmodium falciparum 3D7, Dd2 and field isolates at various low and high parasitemia (0.05%–2.0%) were used to set-up SyBr Green 1-based 2cFCM invasion assays. Target RBCs were labeled with CTFR proliferation dye. We show that this dye combination allowed for efficient parasite invasion into target RBCs and that a 1:3 ratio of unlabeled to labeled RBCs per assay greatly skewed autologous reinvasion (p < 0.001). Accuracy of quantifying reinvasion was limited to an assay parasitemia of 0.02% with minimal background interference. Invasion inhibition by enzymatic treatments increased averagely by 10% (p<0.05) across the entire parasitemia range. The effect was greater for samples with <0.5% parasitemia. Overall, a more sensitive method for phenotyping invasion of low P. falciparum parasitemia is described.

Diagnostic and prognostic value of thrombocytopenia severity in Sudanese children with Falciparum malaria

Malaria remains one of the most significant global public health challenges, with more than 200 million clinical cases worldwide each year. Falciparum malaria accounting for up to 87.6 % of malaria cases in Sudan. Platelets abnormalities as thrombocytopenia especially severe thrombocytopenia have been associated with mortality in patients with P. falciparum infection. The aim of this study was to study the relationships between thrombocytopenia and their severity with falciparum malaria severity, parasitemia and parasite count. This study was case-control hospital based study conducted among 200 Sudanese children admitted to Wad Medani Pediatric Hospital, Wad Medani, Sudan during period September to December 2018. The study population was divided into two groups. Group 1 (UM) was 100 children with uncomplicated falciparum malaria. Group 2 (SM) was 100 children with severe falciparum malaria were diagnosed by WHO criteria. A 2.5 ml venous blood sample was collected from each children. The malaria parasitemia was determined from thick blood films using plus system. The parasite count (% of parasitized red cells counting) was counted from thin blood film. Platelets count was determined using the Sysmex XP 300 N automated hematology analyzer (Sysmex, Kobe, Japan) and confirmed and assessed using stained thin blood film. The data were analyzed using SPSS software (V 20.0) and Stat disk software (V 13.0). The mean age and male: female ratio of Group 1 (UM) were 8.83 ± 4.20 years and 1:1.22 respectively and for Group 2 (SM) were 8.63 ± 3.40 years and 1.56:1 respectively. Group 2 (61 %) associated with thrombocytopenia (mean PLTs 160.91 ± 186.24 × 109/) more than Group 1 (25 %) (mean PLTs 221.10 ± 98.69 × 109/L) (P value = 0.000). The mild, moderate and severe thrombocytopenia account for 19 %, 5 % and 1 % respectively among Group 1; and 22 %, 28 % and 11 % respectively among Group 2 (P value 0.003). Malaria thrombocytopenia was significantly associated (P value = 0.000) and negatively correlated (P value = 0.000; r = - 0.341) with malaria parasitemia. The mean parasite count in malaria thrombocytopenia (0.77 ± 0.51 %) was higher than malaria without thrombocytopenia (0.53 ± 0.36 %) (P value 0.000). Thrombocytopenia severity was significantly positive correlated with malaria parasitemia (r = 258; P value = 0.017) and parasite count (r = 0.229; P value = 0.034). The study concluded that the severe thrombocytopenia associated commonly with severe falciparum malaria and falciparum malaria hyperparasitemia.

Droplet Digital PCR for the Detection of Plasmodium falciparum DNA in Whole Blood and Serum: A Comparative Analysis with Other Molecular Methods.

Background: The estimation of Plasmodium falciparum parasitaemia can vary according to the method used. Recently, droplet digital PCR (ddPCR) has been proposed as a promising approach in the molecular quantitation of Plasmodium, but its ability to predict the actual parasitaemia on clinical samples has not been largely investigated. Moreover, the possibility of applying the ddPCR-sensitive method to serum samples has never been explored. Methods: We used, for the first time, ddPCR on both blood and serum to detect the DNA of P. falciparum in 52 paired samples from 26 patients. ddPCR was compared with loop-mediated isothermal amplification (LAMP) and rtPCR. The correlation between the ddPCR results, microscopy, and clinical parameters was examined. Results: ddPCR and microscopy were found to be strongly correlated (ρ(26) = 0.83111, p < 0.0001) in blood. Samples deviating from the correlation were partially explained by clinical parameters. In serum samples, ddPCR revealed the best performance in detecting P. falciparum DNA, with 77% positive samples among malaria subjects. Conclusion: Absolute quantitation by ddPCR can be a flexible technique for Plasmodium detection, with potential application in the diagnosis of malaria. In particular, ddPCR is a powerful approach for Plasmodium DNA analysis on serum when blood samples are unavailable.

Iron Deficiency Is Associated With Reduced Levels of Plasmodium falciparum-specific Antibodies in African Children.

BackgroundIron deficiency (ID) and malaria are common causes of ill-health and disability among children living in sub-Saharan Africa. Although iron is critical for the acquisition of humoral immunity, little is known about the effects of ID on antibody responses to Plasmodium falciparum malaria.MethodsThe study included 1794 Kenyan and Ugandan children aged 0–7 years. We measured biomarkers of iron and inflammation, and antibodies to P. falciparum antigens including apical merozoite antigen 1 (anti-AMA-1) and merozoite surface antigen 1 (anti-MSP-1) in cross-sectional and longitudinal studies.ResultsThe overall prevalence of ID was 31%. ID was associated with lower anti-AMA-1 and anti-MSP-1 antibody levels in pooled analyses adjusted for age, sex, study site, inflammation, and P. falciparum parasitemia (adjusted mean difference on a log-transformed scale (β) −0.46; 95 confidence interval [CI], −.66, −.25 P < .0001; β −0.33; 95 CI, −.50, −.16 P < .0001, respectively). Additional covariates for malaria exposure index, previous malaria episodes, and time since last malaria episode were available for individual cohorts. Meta-analysis was used to allow for these adjustments giving β −0.34; −0.52, −0.16 for anti-AMA-1 antibodies and β −0.26; −0.41, −0.11 for anti-MSP-1 antibodies. Low transferrin saturation was similarly associated with reduced anti-AMA-1 antibody levels. Lower AMA-1 and MSP-1-specific antibody levels persisted over time in iron-deficient children.ConclusionsReduced levels of P. falciparum-specific antibodies in iron-deficient children might reflect impaired acquisition of immunity to malaria and/or reduced malaria exposure. Strategies to prevent and treat ID may influence antibody responses to malaria for children living in sub-Saharan Africa.

Plasma levels of interleukin 27 in falciparum malaria is increased independently of co-infection with HIV: potential immune-regulatory role during malaria

BackgroundThe immune response during falciparum malaria mediates both harmful and protective effects on the host; however the participating molecules have not been fully defined. Interleukin (IL)-27 is a pleiotropic cytokine exerting both inflammatory and anti-inflammatory effects, but data on IL-27 in malaria patients are scarce.MethodsClinical data and blood samples were collected from adults in Mozambique with P. falciparum infection, with (n = 70) and without (n = 61) HIV-1 co-infection, from HIV-infected patients with similar symptoms without malaria (n = 58) and from healthy controls (n = 52). In vitro studies were performed in endothelial cells and PBMC using hemozoin crystals. Samples were analyzed using enzyme immunoassays and quantitative PCR.Results(i) IL-27 was markedly up-regulated in malaria patients compared with controls and HIV-infected patients without malaria, showing no relation to HIV co-infection. (ii) IL-27 was correlated with P. falciparum parasitemia and von Willebrand factor as a marker of endothelial activation, but not with disease severity. (iii) In vitro, IL-27 modulated the hemozoin-mediated cytokine response in endothelial cells and PBMC with enhancing effects on IL-6 and attenuating effects on IL-8.ConclusionOur findings show that IL-27 is regulated during falciparum malaria, mediating both inflammatory and anti-inflammatory effects, potentially playing an immune-regulatory role during falciparum malaria.

Profound Alteration of Host Response in Severe Malarial Anemia By Sickle Cell Disease: Reduction of Parasite Sequestration and Inflammation, Upregulation of Angiopoietin-2

Introduction. Plasmodium falciparum malaria is a major cause of morbidity in African children with sickle cell anemia (SCA). Factors associated with severe disease and mortality in malaria, including tumor necrosis factor (TNF)-alpha and components of the angiopoietin (Angpt)-Tie-2 system, have also been implicated in the pathogenesis and clinical severity of SCA. However, there is no data on how these factors are altered in children with SCA during severe malaria. Methods. A total of 232 children who presented with severe malarial anemia (hemoglobin &lt; 5 g/dL with Plasmodium parasitemia on peripheral blood smear) were enrolled in a prospective study of severe malaria at Mulago National Referral Hospital in Kampala, Uganda. No child had known SCA at the time of severe malarial anemia diagnosis. Samples from enrolled children were subsequently tested by genotyping for the presence of hemoglobin S (HbS) using a TaqMan assay at rs334. Clinical and laboratory parameters, plasma markers of inflammation and endothelial activation, and the estimated total, sequestered, and circulating parasite biomass were compared in children with HbSS compared to HbAA. Results. The study cohort included 208 children with HbAA (90.4%), 22 children with HbSS (9.6%), and 2 with HbAS. Children with HbSS were older than children with HbAA (Table 1), so all comparisons were adjusted for age. Children with HbSS versus HbAA did not differ significantly in duration of symptoms, clinical signs, disease severity, or degree of peripheral P. falciparum parasitemia. However, children with HbSS had significantly lower concentrations of PfHRP2, a marker of total parasite biomass, and lower levels of estimated sequestered parasite biomass (Table 1). Children with HbSS had pronounced leukocytosis, a feature of chronic inflammation in SCA, but had significantly lower concentrations of the inflammatory biomarkers C-reactive protein and alpha-1-acid glycoprotein and the pro-inflammatory cytokine TNF-alpha than children with HbAA (Table 1). In contrast, concentrations of angiopoietin-2 (Angpt-2), a marker of endothelial dysregulation that has been associated with mortality in severe malaria, were 3-fold greater in children with HbSS than HbAA (Table 1), and were associated with an increased risk of post-discharge recurrent malaria in the cohort, after adjustment for age, sex, and hemoglobin S genotype (odds ratio per log-10 increase in Angpt-2 [95% confidence interval], 2.11 [1.01, 4.38]). Conclusion. In this population, undiagnosed SCA is common in children with severe malarial anemia. During episodes of severe malarial anemia, children with SCA suppress parasite sequestration and inflammation but upregulate Angpt-2, which may increase risk of recurrence of malaria. Disclosures Conroy: ALC: Patents &amp; Royalties: angiopoietin-1, angiopoietin-2. Ware:Addmedica: Other: Research Drug Donation; Global Blood Therapeutics: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; Nova Laboratories: Membership on an entity's Board of Directors or advisory committees; CSL Behring: Membership on an entity's Board of Directors or advisory committees; Novartis: Other: DSMB; Bristol Myers Squibb: Other: Research Drug Donation.

A validation study of microscopy versus quantitative PCR for measuring Plasmodium falciparum parasitemia

Microscopy and 18S qPCR are the most common and field-friendly methods for quantifying malaria parasite density, and it is important that these methods can be interpreted as giving equivalent results. We compared results of quantitative measurement of Plasmodium falciparum parasitemia by microscopy and by 18S qPCR in a phase 2a study. Microscopy positive samples (n = 355; median 810 parasites/μL [IQR 40–10,471]) showed close agreement with 18S qPCR in mean log10/mL transformed parasitemia values by paired t test (difference 0.04, 95%CI − 0.01–0.10, p = 0.088). Excellent intraclass correlation (0.97) and no evidence of systematic or proportional differences by Passing–Bablok regression were observed. 18S qPCR appears to give equivalent parasitemia values to microscopy, which indicates 18S qPCR is an appropriate alternative method to quantify parasitemia in clinical trials.

Impact of Submicroscopic Plasmodium falciparum Parasitaemia on Maternal Anaemia and Low Birth Weight in Blue Nile State, Sudan.

The aim of the present study was to investigate the prevalence of submicroscopic infections and to assess its impact on maternal anaemia and low birth weight. A cross-sectional study was carried out with 1149 consented pregnant women who delivered at 3 main hospitals in the Blue Nile State, between January 2012 and December 2015. From a matched maternal peripheral, placental maternal side, and cord blood sample, blood films and dried spots were prepared for microscopic examination and nested polymerase chain reaction (n-PCR), respectively. 107 out of 447 negative blood films were found to have submicroscopic infection detected using n-PCR in any of the three compartments. Placental samples had a significantly higher prevalence (142) of submicroscopic infections compared with the peripheral (6.5%) and cord (8.1%) samples. The mean (SD) of the maternal haemoglobin (Hb) was significantly lower in cases with submicroscopic parasitaemia (10.9 (0.8) vs. 12.1 (0.7) g/dl, P < 0.001) compared with those who had no submicroscopic parasitaemia. Submicroscopic malaria infection was associated with anaemia (OR 19.7, (95% CI, 10.3–37.8)). Thirty-eight babies born to women with submicroscopic infections were low birth weight (LBW) and was significantly lower in submicroscopic parasitaemia (2.663 (0.235) vs. 2.926 (0.341) kg, P < 0.001). Submicroscopic malaria infection was associated with LBW (OR = 2.7, (95% CI, 1.2–5.6)). There is a high incidence of submicroscopic infections in any of the three compartments regardless of age or parity. Submicroscopic infection is a risk of maternal anaemia and low birth weight in women in this area of high seasonal malaria transmission.

Influence of infant feeding practices on the occurrence of malnutrition, malaria and anaemia in children ≤5 years in the Mount Cameroon area: A cross sectional study.

BackgroundThe objective of this study was to evaluate the influence of different infant feeding habits on the occurrence of malnutrition, Plasmodium falciparum parasitaemia and anaemia in children ≤5 years in the Mount Cameroon area.MethodologyA total of 1227 children ≤5 years of age were recruited in a descriptive cross-sectional study. Socio demographic data and information on the different infant feeding habits was obtained by the use of semi-structured questionnaire. Nutritional status was assessed by the use of anthropometric measurements. Plasmodium was detected by light microscopy and haemoglobin was measured by use of an auto-haematology analyser. Anaemia as well as its severity was classified based on WHO standards. The associations between variables were assessed using logistic regression analysis.ResultsThe prevalence of exclusive breast feeding (EBF) was 22.6%, mixed feeding (MF) was 60.1% and those not breastfed (NBF) at all was 17.3%. The prevalence of malnutrition, P. falciparum parasitaemia and anaemia was 32.6%, 30.4% and 77.3% respectively. Children who had EBF had significantly lower (P <0.001) prevalence of malaria parasite (16.2%) than those NBF at all (61.3%). The prevalence of anaemia was significantly higher (P <0.001) in children who had MF (80.5%) while, severe and moderate anaemia was highest in those NBF at all (6.6%, 67.1% respectively; P = 0.029) than their counterparts. The significant predictors of anaemia were age group (P <0.001), marital status (P <0.001) and educational level of parent (P <0.001), that for malaria parasitaemia was infant feeding habit (MF: P< 0.001 and NBF: P <0.001) and malnutrition was age group (≤2 years: P <0.008 and 2.1–4.0 years: P = 0.028).ConclusionThe infant feeding habit significantly influenced the occurrence of malaria parasite infection and not malnutrition and anaemia, hence EBF should be encouraged in malaria endemic zones.

Measuring malaria morbidity in an area of seasonal transmission: Pyrogenic parasitemia thresholds based on a 20-year follow-up study.

IntroductionAsymptomatic carriage of P. falciparum is frequent in areas endemic for malaria and individual diagnosis of clinical malaria attacks is still difficult. We investigated the impact of changes in malaria endemicity on the diagnostic criteria for malaria attacks in an area of seasonal malaria transmission.MethodsWe analyzed the longitudinal data collected over 20 years from a daily survey of all inhabitants of Ndiop, a rural community in central Senegal, in a logistic regression model to investigate the relationship between the level of Plasmodium falciparum parasitemia and the risk of fever, with the aim of determining the best parasitemia thresholds for attributing to malaria a fever episode.ResultsA total of 34,136 observations recorded from July 1993 to December 2013 from 850 individuals aged from 1 day to 87 years were included. P. falciparum asymptomatic carriage declined from 36% to 1% between 1993 and 2013. A total of 9,819 fever episodes were associated with a positive blood film for P. falciparum. Using age-dependent parasitemia thresholds for attributing to malaria a fever episode, we recorded 6,006 malaria attacks during the study period. Parasitemia thresholds seemed to be lower during the low-to-zero transmission season and tended to decrease with changes in control policies. The number of clinical malaria attacks was overestimated for all age groups throughout the study when all fever episodes associated with P. falciparum parasitemia were defined as malaria attacks.ConclusionPyrogenic thresholds are particularly sensitive to changes in malaria epidemiology and are therefore an interesting tool to accurately assess the burden of malaria in the context of declining transmission.