Pathogenesis Of Severe Malaria Research Articles

The role of previously unmeasured organic acids in the pathogenesis of severe malaria.

IntroductionSevere falciparum malaria is commonly complicated by metabolic acidosis. Together with lactic acid (LA), other previously unmeasured acids have been implicated in the pathogenesis of falciparum malaria.MethodsIn this prospective study, we characterised organic acids in adults with severe falciparum malaria in India and Bangladesh. Liquid chromatography-mass spectrometry was used to measure organic acids in plasma and urine. Patients were followed until recovery or death.ResultsPatients with severe malaria (n=138), uncomplicated malaria (n=102), sepsis (n=32) and febrile encephalopathy (n=35) were included. Strong ion gap (mean±SD) was elevated in severe malaria (8.2 mEq/L±4.5) and severe sepsis (8.6 mEq/L±7.7) compared with uncomplicated malaria (6.0 mEq/L±5.1) and encephalopathy (6.6 mEq/L±4.7). Compared with uncomplicated malaria, severe malaria was characterised by elevated plasma LA, hydroxyphenyllactic acid (HPLA), α-hydroxybutyric acid and β-hydroxybutyric acid (all P<0.05). In urine, concentrations of methylmalonic, ethylmalonic and α-ketoglutaric acids were also elevated. Multivariate logistic regression showed that plasma HPLA was a strong independent predictor of death (odds ratio [OR] 3.5, 95 % confidence interval [CI] 1.6–7.5, P=0.001), comparable to LA (OR 3.5, 95 % CI 1.5–7.8, P=0.003) (combined area under the receiver operating characteristic curve 0.81).ConclusionsNewly identified acids, in addition to LA, are elevated in patients with severe malaria and are highly predictive of fatal outcome. Further characterisation of their sources and metabolic pathways is now needed.Electronic supplementary materialThe online version of this article (doi:10.1186/s13054-015-1023-5) contains supplementary material, which is available to authorized users.

Plasmodium Infection Is Associated with Impaired Hepatic Dimethylarginine Dimethylaminohydrolase Activity and Disruption of Nitric Oxide Synthase Inhibitor/Substrate Homeostasis.

Inhibition of nitric oxide (NO) signaling may contribute to pathological activation of the vascular endothelium during severe malaria infection. Dimethylarginine dimethylaminohydrolase (DDAH) regulates endothelial NO synthesis by maintaining homeostasis between asymmetric dimethylarginine (ADMA), an endogenous NO synthase (NOS) inhibitor, and arginine, the NOS substrate. We carried out a community-based case-control study of Gambian children to determine whether ADMA and arginine homeostasis is disrupted during severe or uncomplicated malaria infections. Circulating plasma levels of ADMA and arginine were determined at initial presentation and 28 days later. Plasma ADMA/arginine ratios were elevated in children with acute severe malaria compared to 28-day follow-up values and compared to children with uncomplicated malaria or healthy children (p<0.0001 for each comparison). To test the hypothesis that DDAH1 is inactivated during Plasmodium infection, we examined DDAH1 in a mouse model of severe malaria. Plasmodium berghei ANKA infection inactivated hepatic DDAH1 via a post-transcriptional mechanism as evidenced by stable mRNA transcript number, decreased DDAH1 protein concentration, decreased enzyme activity, elevated tissue ADMA, elevated ADMA/arginine ratio in plasma, and decreased whole blood nitrite concentration. Loss of hepatic DDAH1 activity and disruption of ADMA/arginine homeostasis may contribute to severe malaria pathogenesis by inhibiting NO synthesis.

The Role of Platelets in Malarial Acute Lung Injury and Acute Respiratory Distress Syndrome: A World of Possibilities

In recent decades our understanding of platelets' role in immune response has increased. Traditionally platelets were considered as bleeding-stopping and thrombosis-causing cells. In recent years the platelets' role in malarial innate and adaptive immune responses is being recognized. Platelets play critical role in pathogenesis of malaria infection leading to variety of outcomes. It is being realized that platelets play dual role in case of malaria (i) by preventing early stage exponential growth of parasitemia (ii) promoting exaggerated immune responses later. Platelets role in pathogenesis of severe and cerebral malaria has been widely studied. However their role in malaria related acute lung injury and respiratory distress has gained less attention. Recently the presence of active megakaryocytes and proplatelets have been explained in human lungs. Simultaneously, the platelets role in pathogenesis of acute lung injury and respiratory distress (ALI/ARDS) was also recognized. This gives a hint that there is a possible association of platelets with malaria related respiratory diseases as well. ALI/ARDS are characterized by lung edema due to increased permeability of the alveolar-capillary barrier and subsequent impairment of arterial oxygenation. In this review we have attempted to establish the importance of role of platelets in malaria related acute lungs injury and malaria acute respiratory distress syndrome and try to explain the underlying mechanism of this process. In ALI/ARDS, including those caused by malaria, platelets participate sequestration to the vascular bundle facilitating the recruitment of immune cells viz. neutrophils. Additionally, they secrete or induce the secretion of chemokines that result into vascular damage.

Investigating the Pathogenesis of Severe Malaria: A Multidisciplinary and Cross-Geographical Approach.

More than a century after the discovery of Plasmodium spp. parasites, the pathogenesis of severe malaria is still not well understood. The majority of malaria cases are caused by Plasmodium falciparum and Plasmodium vivax, which differ in virulence, red blood cell tropism, cytoadhesion of infected erythrocytes, and dormant liver hypnozoite stages. Cerebral malaria coma is one of the most severe manifestations of P. falciparum infection. Insights into its complex pathophysiology are emerging through a combination of autopsy, neuroimaging, parasite binding, and endothelial characterizations. Nevertheless, important questions remain regarding why some patients develop life-threatening conditions while the majority of P. falciparum-infected individuals do not, and why clinical presentations differ between children and adults. For P. vivax, there is renewed recognition of severe malaria, but an understanding of the factors influencing disease severity is limited and remains an important research topic. Shedding light on the underlying disease mechanisms will be necessary to implement effective diagnostic tools for identifying and classifying severe malaria syndromes and developing new therapeutic approaches for severe disease. This review highlights progress and outstanding questions in severe malaria pathophysiology and summarizes key areas of pathogenesis research within the International Centers of Excellence for Malaria Research program.

Binding of subdomains 1/2 of PfEMP1-DBL1α to heparan sulfate or heparin mediates Plasmodium falciparum rosetting.

The capacity of Plasmodium falciparum parasitized erythrocytes (pRBC) to adhere to the endothelial lining in the microvasculature and to red blood cells (RBC) is associated with the virulence of the parasite, the pathogenesis and development of severe malaria. Rosetting, the binding of uninfected RBC to pRBC, is frequently observed in individuals with severe malaria and is mediated by the N-terminal NTS-DBL1α domain of the adhesin Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) expressed at the surface of the pRBC. Heparan sulfate has been suggested to be an important receptor for the NTS-DBL1α variant IT4var60 expressed by the parasite FCR3S1.2. Here, we have determined the binding site of NTS-DBL1α (IT4var60) to the RBC and heparin using a set of recombinant, mutated proteins expressed in and purified from E. coli. All the variants were studied for their ability to bind to RBC, their capacities to disrupt FCR3S1.2 rosettes, their affinities for heparin and their binding to rosette-disruptive mAbs. Our results suggest that NTS-DBL1α mediates binding to RBC through a limited number of basic amino acid residues localized on the surface of subdomains 1 (SD1) and 2 (SD2). The SD2-binding site is localized in close proximity to one of two previously identified binding sites in the rosetting PfEMP1 of the parasite PaloAlto-varO. The binding site in SD2 of NTS-DBL1α could represent a template for the development of anti-rosetting drugs.

In Vitro Activity of Cocoa Powder Extracts on Some Biomarkers Implicated in P. falciparum Malaria Pathogenesis

Malaria is a public health concern in many developing countries, including Ghana, and efforts are being made to eradicate it. Extracts from natural products have been used in several malaria endemic areas for malaria prophylaxis and treatment. Natural cocoa powder has been reported to possess in vitro direct inhibitory on P. falciparum. This study investigated the effect of natural cocoa powder on inducible nitric oxide, TNF-α and IL-10, biomarkers that play different roles in malaria pathogenesis. Chloroform and ethylacetate fractions of cocoa powder were cultured together with phytohemagglutinin-stimulated peripheral blood mononuclear cells (PBMCs) for 24 hours at 37°C with 5% CO2. Cell free supernatants were harvested and assayed for iNO, TNF-α and IL-10. Inducible NO was determined by diazotization reaction developed by Griess. TNF-α and IL-10 were determined by ELISA. This study showed that TNF-α and iNO in phytohemagglutinin-stimulated PBMCs were significantly reduced by cocoa fractions (p &lt; 0.05), but IL-10 levels did not change significantly (p &gt; 0.05), although TNF-α is known to up-regulate IL-10.Apart from the documented direct inhibitory effect of cocoa powder on P. falciparum, it can be hypothesized that the antiplasmodial activity of unsweetened cocoa powder could also be due to its ability to significantly inhibit iNO and TNF-α, inflammatory substances implicated in severe malaria pathogenesis.

Role of the lipoperoxidation product 4-hydroxynonenal in the pathogenesis of severe malaria anemia and malaria immunodepression.

Oxidative stress plays an important role in the pathogenesis of falciparum malaria, a disease still claiming close to 1 million deaths and 200 million new cases per year. Most frequent complications are severe anemia, cerebral malaria, and immunodepression, the latter being constantly present in all forms of malaria. Complications are associated with oxidative stress and lipoperoxidation. Its final product 4-hydroxynonenal (4-HNE), a stable yet very reactive and diffusible molecule, forms covalent conjugates with proteins, DNA, and phospholipids and modulates important cell functions at very low concentrations. Since oxidative stress plays important roles in the pathogenesis of severe malaria, it appears important to explore the role of 4-HNE in two important malaria complications such as malaria anemia and malaria immunodepression where oxidative stress is considered to be involved. In this review we will summarize data about 4-HNE chemistry, its biologically relevant chemical properties, and its role as regulator of physiologic processes and as pathogenic factor. We will review studies documenting the role of 4-HNE in severe malaria with emphasis on malaria anemia and immunodepression. Data from other diseases qualify 4-HNE both as oxidative stress marker and as pathomechanistically important molecule. Further studies are needed to establish 4-HNE as accepted pathogenic factor in severe malaria.

Targeted Disruption of a Ring-infected Erythrocyte Surface Antigen (RESA)-like Export Protein Gene in Plasmodium falciparum Confers Stable Chondroitin 4-Sulfate Cytoadherence Capacity

The Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) family proteins mediate the adherence of infected erythrocytes to microvascular endothelia of various organs, including the placenta, thereby contributing to cerebral, placental, and other severe malaria pathogenesis. Several parasite proteins, including KAHRP and PfEMP3, play important roles in the cytoadherence by mediating the clustering of PfEMP1 in rigid knoblike structures on the infected erythrocyte surface. The lack of a subtelomeric region of chromosome 2 that contains kahrp and pfemp3 causes reduced cytoadherence. In this study, microarray transcriptome analysis showed that the absence of a gene cluster, comprising kahrp, pfemp3, and four other genes, results in the loss of parasitized erythrocytes adhering to chondroitin 4-sulfate (C4S). The role of one of these genes, PF3D7_0201600/PFB0080c, which encodes PHISTb (Plasmodium helical interspersed subtelomeric b) domain-containing RESA-like protein 1 expressed on the infected erythrocyte surface, was investigated. Disruption of PFB0080c resulted in increased var2csa transcription and VAR2CSA surface expression, leading to higher C4S-binding capacity of infected erythrocytes. Further, PFB0080c-knock-out parasites stably maintained the C4S adherence through many generations of growth. Although the majority of PFB0080c-knock-out parasites bound to C4S even after culturing for 6 months, a minor population bound to both C4S and CD36. These results strongly suggest that the loss of PFB0080c markedly compromises the var gene switching process, leading to a marked reduction in the switching rate and additional PfEMP1 expression by a minor population of parasites. PFB0080c interacts with VAR2CSA and modulates knob-associated Hsp40 expression. Thus, PFB0080c may regulate VAR2CSA expression through these processes. Overall, we conclude that PFB0080c regulates PfEMP1 expression and the parasite's cytoadherence.

Plasmodium berghei histamine-releasing factor favours liver-stage development via inhibition of IL-6 production and associates with a severe outcome of disease.

Plasmodium spp., which causes malaria, produces a histamine-releasing factor (HRF), an orthologue of mammalian HRF. Histamine-releasing factor produced by erythrocytic stages of the parasite is thought to play a role in the pathogenesis of severe malaria. Here, we show in a rodent model that HRF is not important during the erythrocytic but pre-erythrocytic phase of infection, which mainly consists in the transformation in the liver of the mosquito-injected parasite form into the erythrocyte-infecting form. Development of P. berghei ANKA cl15cy1 liver stages lacking HRF is impaired and associated with an early rise in systemic IL-6, a cytokine that strongly suppresses development of Plasmodium liver stages. The defect is rescued by injection of anti-IL-6 antibodies or infection in IL-6-deficient mice and parasite HRF is sufficient to decrease IL-6 synthesis, indicating a direct role of parasite HRF in reducing host IL-6. The target cells modulated by HRF for IL-6 production at early time points during liver infection are neutrophils. Parasite HRF is thus used to down-regulate a cytokine with anti-parasite activity. Our data also highlight the link between a prolonged transition from liver to blood-stage infection and reduced incidence of experimental cerebral malaria.

Secretory group V phospholipase A2: a new player in thrombosis?

The protein C anticoagulant system plays a critical role in the regulation of haemostasis and inflammation. Binding of protein C to endothelial cell protein C receptor (EPCR) and the subsequent activation of EPCR-bound protein C by thrombin/thrombomodulin are the key steps in the protein C anticoagulant system. Activated protein C (APC) -mediated cell signalling, supported by its binding to EPCR or independent of EPCR, activates anti-inflammatory and cytoprotective pathways [1]. Therefore, pathophysiologic conditions that impair the interaction of protein C with EPCR have the potential to decrease APC generation. Such reduced binding to EPCR may not only contribute to thrombotic disorders, but also result in the loss of endogenous APC-mediated cytoprotection..

Prognostic value of Serum C-Reactive Protein in Malaria

Introduction: C-Reactive protein is known as a marker of morbidity and mortality in malaria. It correlates closely with other complications in malaria and can be used to predict severity. Thus, measurement of CRP can be useful in understanding the pathogenesis of severe malaria. However, studies regarding CRP in malaria are very rare from India. Aims & objectives: The present study aimed to study CRP levels in patients with malarial infection and to find out the usefulness of CRP in assessment of disease severity. Material and Methods: The study population consisted of 50 patients with malarial infection, of them 29 were Plasmodium falciparum, 21 were P. vivax-infected and no patient found with dual infection in our study. Out of 50 patients, 17 patients required admission for various reasons and of them 5 patients died. Serum C-reactive protein concentrations were measured in all the patients. Percentage parasitemia, platelet count and Liver function tests were measured on the day of admission. Statistical tests included were Students t-test, chi-square test and Pearson correlation coefficient. Results: Serum C-reactive protein concentration was significantly elevated in all the malaria patients and it was significantly higher (P<0.01) in Plasmodium falciparum (28.81 10.91 mg/L) as compared to P. Vivax malaria (15.91 8.73 mg/L ). Admitted patients had higher CRP levels (47.80 12.73 mg/L) compared to patients treated on OPD basis (24.14 12.17 mg/L) (P < 0.0001). Also CRP levels were higher in patients with multiple complications and in the patients who died compared to survivors. A significant positive correlation was found between serum CRP and percentage parasitemia, serum bilirubin, serum alanine aminotransferase and serum aspartate aminotransferase in P. falciparum infected patients but not in P. Vivax. Conclusion: There is significant increase in C-reactive protein in malaria infected patients and can be considered a cost - effective and reliable tool in assessment of prognosis in malaria.

An analysis of the binding characteristics of a panel of recently selected ICAM-1 binding Plasmodium falciparum patient isolates.

The basis of severe malaria pathogenesis in part includes sequestration of Plasmodium falciparum-infected erythrocytes (IE) from the peripheral circulation. This phenomenon is mediated by the interaction between several endothelial receptors and one of the main parasite-derived variant antigens (PfEMP1) expressed on the surface of the infected erythrocyte membrane. One of the commonly used host receptors is ICAM-1, and it has been suggested that ICAM-1 has a role in cerebral malaria pathology, although the evidence to support this is not conclusive. The current study examined the cytoadherence patterns of lab-adapted patient isolates after selecting on ICAM-1. We investigated the binding phenotypes using variant ICAM-1 proteins including ICAM-1Ref, ICAM-1Kilifi, ICAM-1S22/A, ICAM-1L42/A and ICAM-1L44/A using static assays. The study also examined ICAM-1 blocking by four anti-ICAM-1 monoclonal antibodies (mAb) under static conditions. We also characterised the binding phenotypes using Human Dermal Microvascular Endothelial Cells (HDMEC) under flow conditions. The results show that different isolates have variant-specific binding phenotypes under both static and flow conditions, extending our previous observations that this variation might be due to variable contact residues on ICAM-1 being used by different parasite PfEMP1 variants.

Autoimmunity, phospholipid-reacting antibodies and malaria immunity.

Several questions regarding the production and functioning of autoantibodies (AAb) during malaria infection remain open. Here we provide an overview of studies conducted in our laboratory that shed some light on the questions of whether antiphospholipid antibodies (aPL) and other AAb associated with autoimmune diseases (AID) can recognize Plasmodia antigens and exert anti-parasite activity; and whether anti-parasite phospholipid antibodies, produced in response to malaria, can inhibit phospholipid-induced inflammatory responses and protect against the pathogenesis of severe malaria. Our work showed that sera from patients with AID containing AAb against dsDNA, ssDNA, nuclear antigens (ANA), actin, cardiolipin (aCL) and erythrocyte membrane antigens recognize plasmodial antigens and can, similarly to monoclonal AAb of several specificities including phospholipid, inhibit the growth of P. falciparum in vitro. However, we did not detect a relationship between the presence of anti-glycosylphosphatidylinositol (GPI) antibodies in the serum and asymptomatic malaria infection, although we did register a relationship between these antibodies and parasitemia levels in infected individuals. Taken together, these results indicate that autoimmune responses mediated by AAb of different specificities, including phospholipid, may have anti-plasmodial activity and protect against malaria, although it is not clear whether anti-parasite phospholipid antibodies can mediate the same effect. The potential effect of anti-parasite phospholipid antibodies in malarious patients that are prone to the development of systemic lupus erythematosus or antiphospholipid syndrome, as well as the (possibly protective?) role of the (pathogenic) aPL on the malaria symptomatology and severity in these individuals, remain open questions.

Parasite physiology: RNase silences Plasmodium antigens.

A newly discovered Plasmodium falciparum exoribonuclease silences the expression of var gene transcripts, which are involved in the pathogenesis of severe malaria.

Parasite Burden and Severity of Malaria in Tanzanian Children

BackgroundSevere Plasmodium falciparum malaria is a major cause of death in children. The contribution of the parasite burden to the pathogenesis of severe malaria has been controversial.MethodsWe documented P. falciparum infection and disease in Tanzanian children followed from birth for an average of 2 years and for as long as 4 years.ResultsOf the 882 children in our study, 102 had severe malaria, but only 3 had more than two episodes. More than half of first episodes of severe malaria occurred after a second infection. Although parasite levels were higher on average when children had severe rather than mild disease, most children (67 of 102) had high-density infection (>2500 parasites per 200 white cells) with only mild symptoms before severe malaria, after severe malaria, or both. The incidence of severe malaria decreased considerably after infancy, whereas the incidence of high-density infection was similar among all age groups. Infections before and after episodes of severe malaria were associated with similar parasite densities. Nonuse of bed nets, placental malaria at the time of a woman's second or subsequent delivery, high-transmission season, and absence of the sickle cell trait increased severe-malaria risk and parasite density during infections.ConclusionsResistance to severe malaria was not acquired after one or two mild infections. Although the parasite burden was higher on average during episodes of severe malaria, a high parasite burden was often insufficient to cause severe malaria even in children who later were susceptible. The diverging rates of severe disease and high-density infection after infancy, as well as the similar parasite burdens before and after severe malaria, indicate that naturally acquired resistance to severe malaria is not explained by improved control of parasite density. (Funded by the National Institute of Allergy and Infectious Diseases and others.)

Association of the endothelial protein C receptor (PROCR) rs867186-G allele with protection from severe malaria

BackgroundCytoadhesion of Plasmodium falciparum-infected erythrocytes to endothelial cells in microvessels is a remarkable characteristic of severe malaria. The endothelial protein C receptor (EPCR), encoded by the endothelial protein C receptor gene (PROCR), has recently been identified as an endothelial receptor for specific P. falciparum erythrocyte membrane protein 1 (PfEMP1) subtypes containing domain cassettes (DCs) 8 and 13. The PROCR rs867186-G allele (serine-to-glycine substitution at position 219 of EPCR; 219Gly) has been shown to be associated with higher levels of plasma soluble EPCR (sEPCR). In this study, the association of PROCR rs867186 with severe malaria is examined in Thai population.MethodsA total of 707 Thai patients with P. falciparum malaria (341 with severe malaria and 336 with mild malaria) were genotyped for rs867186. To assess the association of PROCR rs867186 with severe malaria, three models (dominant, recessive and allelic) were evaluated. The rates of non-synonymous and synonymous substitutions were estimated for the coding sequence of the PROCR gene.ResultsThe rs867186-GG genotype was significantly associated with protection from severe malaria (P-value = 0.026; odds ratio = 0.33; 95% confidence interval = 0.12–0.90). Evolutionary analysis provided no evidence of strong positive selection acting on the PROCR gene.ConclusionThe rs867186-GG genotype showed significant association with protection from severe malaria. The present results suggest that PfEMP1–EPCR interaction, which can mediate cytoadhesion and/or reduce cytoprotective and anti-inflammatory effects, is crucial to the pathogenesis of severe malaria.

Plasmodium falciparum Specific IgE, IgG and Anti-GPI IgG Antibodies in Cameroonian Children with Severe and Uncomplicated Malaria

Aims: We investigated the role of antibodies in the pathogenesis of severe malaria in children by measuring and comparing plasma levels of antibodies to glycosyl phosphatidy linositol (GPI) and crude Plasmodium falciparum extract. Study Design: Cross-sectional case-control study. Place and Duration of Study: Five health institutions in two towns and seven primary schools in the South West region of Cameroon between April 2003 and December 2005. Methodology: A total of 649 children including 25, 156 and 233 cases of cerebral malaria (CM), severe malaria anaemia (SMA) and uncomplicated malaria (UM) respectively were recruited from health institutions and 233 apparently healthy controls (HC) from schools using predefined inclusion criteria. Malaria parasitaemia was determined by light microscopy using Giemsa-stained thick blood smears, haemoglobin level using a haemoglobinometer and blood cell count using a haemocytometer. The levels of total IgE,

Toll-Like Receptors and Malaria – Sensing and Susceptibility

Toll-Like Receptors (TLRs) are important mediators of the innate immune response to pathogens, including malaria. Of the ten human and twelve mouse TLRs, TLR2, TLR4, TLR7 and TLR9 are known to detect malarial antigens and induce anti-malarial immune responses. Multiple immune cell populations express TLRs, and much has been done to elucidate the TLR-mediated immune response to malaria infections, in particular the involvement of TLRs in severe malaria pathogenesis. Here we review the role TLRs play in parasite detection, immune response, and severe malaria, with a focus on recent findings. Furthermore, the use of TLR ligands as malarial vaccine adjuvants is discussed, as this could have great potential in improving efficacy of vaccine candidates

Low Antibody Levels to Pregnancy-specific Malaria Antigens and Heightened Cytokine Responses Associated With Severe Malaria in Pregnancy

Pregnant women living in unstable malaria transmission settings may develop severe malaria (SM). The pathogenesis of SM in pregnancy is poorly understood. To determine whether SM in pregnancy is associated with lower malarial antibody responses and higher cytokine responses, plasma samples were collected from 121 Sudanese pregnant women of whom 39 were diagnosed with SM. Antibodies to pregnancy-specific and non-pregnancy-specific Plasmodium falciparum variant surface antigens (VSA) and concentrations of cytokines TNF, IFNγ, IL-1β, IL-6, IL-8 and IL-10 were measured. Pregnant women with SM demonstrated significantly lower antibody levels to pregnancy-specific VSA (P = .020) and higher plasma IFNγ (P = .020), IL-10 (P = .0002) and IL-6 levels (P < .0001) than uninfected pregnant women. Concentrations of inflammatory cytokines IL-1β (P = .001), IL-6 (P = .004) and IL-8 (P = .020) were inversely correlated with antibodies to VAR2CSA-DBL5 in pregnant women with SM. Lower haemoglobin levels and higher parasite densities were associated with lack of pregnancy-specific antibodies (P = .028) and higher levels of inflammatory cytokines, in particular IL-6 and IL-8. Pregnant women with SM lack pregnancy-specific malaria immunity, and this correlates with heightened inflammatory cytokine concentrations, low haemoglobin levels and high parasite density, suggesting that failure of antibody to control parasitaemia may contribute to SM pathogenesis.

Randomized controlled trial of levamisole hydrochloride as adjunctive therapy in severe falciparum malaria with high parasitemia.

Background. Cytoadherence and sequestration of erythrocytes containing mature stages of Plasmodium falciparum are central to the pathogenesis of severe malaria. The oral anthelminthic drug levamisole inhibits cytoadherence in vitro and reduces sequestration of late-stage parasites in uncomplicated falciparum malaria treated with quinine.Methods. Fifty-six adult patients with severe malaria and high parasitemia admitted to a referral hospital in Bangladesh were randomized to receive a single dose of levamisole hydrochloride (150 mg) or no adjuvant to antimalarial treatment with intravenous artesunate.Results. Circulating late-stage parasites measured as the median area under the parasite clearance curves were 2150 (interquartile range [IQR], 0–28 025) parasites/µL × hour in patients treated with levamisole and 5489 (IQR, 192–25 848) parasites/µL × hour in controls (P = .25). The “sequestration ratios” at 6 and 12 hours for all parasite stages and changes in microvascular blood flow did not differ between treatment groups (all P > .40). The median time to normalization of plasma lactate (<2 mmol/L) was 24 (IQR, 12–30) hours with levamisole vs 28 (IQR, 12–36) hours without levamisole (P = .15).Conclusions. There was no benefit of a single-dose of levamisole hydrochloride as adjuvant to intravenous artesunate in the treatment of adults with severe falciparum malaria. Rapid parasite killing by intravenous artesunate might obscure the effects of levamisole.