Malaria Disease Severity Research Articles

Epidemiological profile of severe malaria and sickle cell disease in children at the mother and child university hospital center Jeanne Ebori foundation of libreville from 2020 to 2021

Background: Hemoglobinopathies represent the most common genetic diseases worldwide. In Gabon, the clinico-biological profile of patients with homozygous hemoglobin S or those with AS sickle cell traits, faced with this prevalence of serious malaria, remains unknown today. The objective was to evaluate the complications of severe malaria in SS homozygous sickle cell patients and those carrying AS sickle cell traits. Methods: This is an observational, retrospective study, with descriptive and analytical aims which took place from January 2020 to October 2021. The parameters studied were socio-demographic, clinical and paraclinical data, the diagnosis chosen, therapeutic data and evolution. Results: severe neurological form of malaria was the most common criterion with a frequency of 41.7%, followed by parasitic forms 35.8% and anemic forms 21.8%. Among AS heterozygotes, the most widespread severe form was the neurological form with a frequency of 63.2%, the anemic form 26.3% and parasitic at 10.5%. In homozygous SS subjects, the most widespread severe form was the anemic form with a frequency of 68.1% followed by neurological forms 27.7% and parasitic forms 4.2%. Abdominal pain, prostration, respiratory distress were the main signs in SS homozygotes. In heterozygotes, prostration, convulsion and clinical jaundice were the main signs. A total of 99.8% of our patients were cured. Conclusions: All the electrophoretic profiles identified were subject to this infection which mainly affects heterozygous AS subjects and subjects with the AA electrophoretic profile in its severe neurological form and homozygous SS subjects in its anemic form.

Neutrophil activation, acute lung injury and disease severity in Plasmodium knowlesi malaria.

The risk of severe malaria from the zoonotic parasite Plasmodium knowlesi approximates that from P. falciparum. In severe falciparum malaria, neutrophil activation contributes to inflammatory pathogenesis, including acute lung injury. The role of neutrophil activation in the pathogenesis of severe knowlesi malaria has not been examined. We evaluated 213 patients with P. knowlesi mono-infection (138 non-severe, 75 severe) and 49 Plasmodium-negative controls from Malaysia. Markers of neutrophil activation (soluble neutrophil elastase [NE], citrullinated histone [CitH3] and circulating neutrophil extracellular traps [NETs]) were quantified in peripheral blood by microscopy and immunoassays. Findings were correlated with malaria severity, ALI clinical criteria, biomarkers of parasite biomass, haemolysis, and endothelial activation. Neutrophil activation increased with disease severity, with median levels higher in severe than non-severe malaria and controls for NE (380[IQR:210-930]ng/mL, 236[139-448]ng/mL, 218[134-307]ng/mL, respectively) and CitH3 (8.72[IQR:3.0-23.1]ng/mL, 4.29[1.46-9.49]ng/mL, 1.53[0.6-2.59]ng/mL, respectively)[all p<0.01]. NETs were higher in severe malaria compared to controls (126/μL[IQR:49-323] vs 51[20-75]/μL, p<0.001). In non-severe malaria, neutrophil activation fell significantly upon discharge from hospital (p<0.03). In severe disease, NETs, NE, and CitH3 were correlated with parasitaemia, cell-free haemoglobin and angiopoietin-2 (all Pearson's r>0.24, p<0.05). Plasma NE and angiopoietin-2 were higher in knowlesi patients with ALI than those without (p<0.008); neutrophilia was associated with an increased risk of ALI (aOR 3.27, p<0.01). In conclusion, neutrophil activation is increased in ALI and in proportion to disease severity in knowlesi malaria, is associated with endothelial activation, and may contribute to disease pathogenesis. Trials of adjunctive therapies to regulate neutrophil activation are warranted in severe knowlesi malaria.

Total antioxidant status levels in malaria: a systematic review and meta-analysis

BackgroundMalaria, a severe health threat, significantly affects total antioxidant status (TAS) levels, leading to considerable oxidative stress. This systematic review and meta-analysis aimed to delineate differences in TAS levels between malaria patients and healthy controls, and assess correlations between disease severity and parasite density.MethodsThe systematic review was registered with the International Prospective Register of Systematic Reviews (PROSPERO) under registration number CRD42023448761. A comprehensive literature search was conducted in databases such as Embase, MEDLINE, Journals@Ovid, PubMed, Scopus, ProQuest, and Google Scholar to identify studies reporting data on TAS levels in malaria patients. Data from the included studies were analysed both qualitatively and quantitatively. Differences in TAS levels between malaria patients and controls were pooled using a random effects model, with Hedges' g as the effect size measure.ResultsOf 1796 identified records, 20 studies met the inclusion criteria. The qualitative synthesis of these studies revealed a marked decrease in TAS levels in patients with malaria compared to non-malaria cases. The meta-analysis results showed a significant decrease in TAS levels in patients with malaria compared to non-malaria cases (P < 0.01, Hedges’ g: − 2.75, 95% CI − 3.72 to −1.78, I2: 98.16%, 13 studies), suggesting elevated oxidative stress in these patients. Subgroup analyses revealed that TAS level variations were significantly influenced by geographical region, age group, Plasmodium species, and method for measuring TAS. Notably, TAS levels were significantly lower in severe malaria cases and those with high parasite density, indicating a potential relationship between oxidative stress and disease severity.ConclusionThis study highlights the potential utility of TAS as a biomarker for disease risk and severity in malaria. The significant decrease in TAS levels in malaria patients compared to controls implies increased oxidative stress. Further well-designed, large-scale studies are warranted to validate these findings and elucidate the intricate mechanisms linking TAS and malaria.

A novel locus in CSMD1 gene is associated with increased susceptibility to severe malaria in Malian children

BackgroundPlasmodium 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.MethodsBased 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.ResultsOf 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.ConclusionTaken 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.

Preventing malaria spread in the US.

Locally acquired malaria is rare in the US; however, in 2023, cases were reported in Florida, Texas, Maryland, and Arkansas. Prompt diagnosis and treatment of malaria are essential to prevent severe malaria disease. This article details malaria and offers treatment guidelines.

IL-15 Complex-Induced IL-10 Enhances Plasmodium-specific CD4+ T Follicular Helper Differentiation and Antibody Production.

Malaria, which results from infection with Plasmodium parasites, remains a major public health problem. Although humans do not develop long-lived, sterilizing immunity, protection against symptomatic disease develops after repeated exposure to Plasmodium parasites and correlates with the acquisition of humoral immunity. Despite the established role Abs play in protection from malaria disease, dysregulated inflammation is thought to contribute to the suboptimal immune response to Plasmodium infection. Plasmodium berghei ANKA (PbA) infection results in a fatal severe malaria disease in mice. We previously demonstrated that treatment of mice with IL-15 complex (IL-15C; IL-15 bound to an IL-15Rα-Fc fusion protein) induces IL-10 expression in NK cells, which protects mice from PbA-induced death. Using a novel MHC class II tetramer to identify PbA-specific CD4+ T cells, in this study we demonstrate that IL-15C treatment enhances T follicular helper (Tfh) differentiation and modulates cytokine production by CD4+ T cells. Moreover, genetic deletion of NK cell-derived IL-10 or IL-10R expression on T cells prevents IL-15C-induced Tfh differentiation. Additionally, IL-15C treatment results in increased anti-PbA IgG Ab levels and improves survival following reinfection. Overall, these data demonstrate that IL-15C treatment, via its induction of IL-10 from NK cells, modulates the dysregulated inflammation during Plasmodium infection to promote Tfh differentiation and Ab generation, correlating with improved survival from reinfection. These findings will facilitate improved control of malaria infection and protection from disease by informing therapeutic strategies and vaccine design.

Cish knockout mice exhibit similar outcomes to malaria infection despite altered hematopoietic responses.

The Cytokine-inducible Src homology 2 domain-containing (CISH) protein is a negative feedback regulator induced by cytokines that play key roles in immunity and erythropoiesis. Single nucleotide polymorphisms (SNPs) in the human CISH gene have been associated with increased susceptibility to severe malaria disease. To directly assess how CISH might influence outcomes in the BALB/c model of malaria anemia, CISH knockout (Cish-/-) mice on this background were infected with Plasmodium berghei and their hematopoietic responses, cytokine production and ability to succumb to severe malaria disease evaluated. Despite basal erythrocytic disruption, upon P. berghei infection, the Cish -/- mice were better able to maintain peripheral blood cell counts, hemoglobin levels and a steady-state pattern of erythroid differentiation compared to wild-type (Cish+/+) mice. Ablation of CISH, however, did not influence the outcome of acute malaria infections in either the BALB/c model or the alternative C57BL/6 model of experimental cerebral malaria, with the kinetics of infection, parasite load, weight loss and cytokine responses being similar between Cish+/+ and Cish-/- mice, and both genotypes succumbed to experimental cerebral malaria within a comparable timeframe.

Renin as a Biomarker of Acute Kidney Injury and Mortality in Children With Severe Malaria or Sickle Cell Disease.

Globally, a very high percentage of acute kidney injury (AKI) occurs in low- and middle-income countries (LMICs) where late recognition contributes to increased mortality. There are challenges with using existing biomarkers of AKI in LMICs. Emerging evidence suggests renin may serve as a biomarker of kidney injury that can overcome limitations in creatinine-based diagnostics. Two study populations in Uganda were assessed. Cohort #1 was a two-site, prospective cohort study enrolling 600 children with severe malaria (SM). Cohort #2 was a prospective cohort study enrolling 185 children with sickle cell disease (SCD) hospitalized with a vaso-occlusive crisis. Plasma or serum renin concentrations were measured in both cohorts of children at the time of hospital admission using Luminex® (Luminex Corporation,Austin, Texas, United States) or enzyme-linked immunosorbent assay (ELISA), respectively. We assessed the ability of renin to discriminate between children with or without AKI and between children who survived and children who died using receiver operating characteristic curves. In both cohorts, renin concentrations were strongly associated with AKI and mortality. Renin was able to discriminate between children with or without AKI with an area under the curve (AUC) of 0.70 (95%CI, 0.65-0.74) in children with SM and 0.72 (95%CI, 0.6co3-0.81) in children with SCD. Renin was able to discriminate between children who survived and children who died with an AUC of 0.73 (95%CI, 0.63-0.83) in children with SM and 0.94 (95%CI, 0.89-0.99) in children with SCD. In Cohort #2, we compared renin against urine neutrophil gelatinase-associated lipocalin (NGAL) as the leading biomarker of AKI, and it had comparable performance in discriminating AKI and predicting mortality. In two independent populations of children at risk of AKI with key differences in the etiology of kidney injury, renin was strongly associated with AKI and mortality and had moderate to good diagnostic performance to predict mortality.

Circulating platelets and malaria severity: two sides of the same coin among inhabitants of a tropical savannah region, Nigeria.

Changes in circulating platelets during different grades of malaria are of major concerns, and its etiology is poorly understood. We appraised and evaluated the role of circulating platelets in the determination of the severity of malaria among a cohort of outpatients living in Ilorin, Nigeria. A hospital-based case-control study of outpatients visiting public health facilities within the locality voluntarily enrolled for this study. Blood samples from 1162 malaise patients were screened using routine microscopy for Plasmodium parasite species identification, and their respective circulating platelet levels were determined. Seven hundred and seventy-five individuals (775, 66.7%, p<0.001) were malaria-positive. Samples from 387 (33.3%) uninfected healthy individuals were used as controls. Individuals with uncomplicated malaria (UCM) and complicated malaria (CM) across age group were notable (p<0.05). Children ≤5 years had the highest number of individuals with CM (103, 45.2%) with a relative risk ratio of 4.005 (95% CI: 2.964-5.413). UCM (471, 40.5%) occurred more than CM (304, 26.2%) (p>0.05) across the groups. The geometric mean, 95% CI, median, and IQR of populations with malaria thrombocytopenia were higher (181, 110.94±2.207, 106.59-115.30, 118.00, and 39.00) than thrombocytosis (78, 624.64±13.131, 598.49-650.79, 623.00, and 208). Seemingly, health controls recorded insignificant morbidity with respect to platelet counts. High P. falciparum parasitemia is inversely correlated with platelet count, and its' morbidity is associated with the manifestation of several malaria pathogenesis. Thrombocytopenia is a silent pathophysiological attribute that can trigger other cofactors during severe malaria disease. Although further studies are pertinent in order to specifically clarify its relevance to clinical disease spectrum.

Inflammatory cytokines as potential biomarkers for early diagnosis of severe malaria in children in Ghana

BackgroundSevere malaria (SM) is a fatal multi-system disease which accounted for an estimated 619,000 deaths in 2021. Less than 30% of children presenting with SM are diagnosed and treated promptly, resulting in increased mortality and neurologic impairments in survivors. Studies have identified cytokine profiles that differentiate the various clinical manifestations of malaria (severe and uncomplicated). However, the diagnostic capability of these cytokines in differentiating between the disease states in terms of cut-off values has not yet been determined.MethodsThe plasma levels of 22 pro-inflammatory cytokines (Eotaxin/CCL 11, interferon-gamma (IFN-γ), interleukin (IL)- 2, IL-6, IL-1β, IL-12p40/p70, IL-17A, RANTES, MCP-1, IL-15, IL-5, IL-1RA, IL-2R, IFN-α, IP-10, TNF, MIG, MIP-1α, MIP-1β, IL-7, IL-8 and Granulocyte Macrophage-Colony Stimulating Factor (GM-CSF), and 3 anti-inflammatory cytokines-(IL-4, IL-13 and IL-10) in patients with SM, uncomplicated malaria (UM) and other febrile conditions, were measured and compared using the Human Cytokine Magnetic 25-Plex Panel. The receiver operating characteristic (ROC) curve analysis was used to determine the diagnostic value of these cytokines.ResultsThe level of the pro-inflammatory cytokine, IL-17A, was significantly higher in the SM group as compared to the UM group. Levels of the anti-inflammatory cytokines however did not differ significantly among the SM and UM groups. Only IL-1β and IL-17A showed good diagnostic potential after ROC curve analysis.ConclusionThe data show that levels of pro-inflammatory cytokines correlate with malaria disease severity. IL-1β and IL-17A showed good diagnostic potentials and can be considered for use in clinical practice to target treatment.

The association of intraleucocytic malaria pigment and disease severity in Papua New Guinean children with severe P. falciparum malaria.

Plasmodium falciparum pigment-containing leucocytes (PCLs) are associated with adverse clinical manifestations of severe malaria in African children. However, limited data exist on the association of PCLs in settings outside of Africa. Thin films on peripheral blood slides obtained from children ages 6months-10y with severe malaria were examined for PCLs. The intraleucocytic pigment data were correlated with clinical phenotypic data such as severe anaemia, metabolic acidosis and coma to determine the association of PCLs with clinical phenotypes of severe malaria and outcome. Of the 169 children with severe P. falciparum malaria confirmed by microscopy, 76% (129/169) had PCLs. Compared with children without PCLs, the presence (adjusted odds ratio [AOR] 3.2 [95% confidence interval {CI} 1.5 to 6.9], p≤0.01) and quantity (AOR 1.0 [95% CI 1.0 to 1.1], p=0.04) of pigment-containing monocytes (PCMs) was significantly associated with severe anaemia, while the quantity of both PCMs (AOR 1.0 [95% CI 1.0 to 1.1], p≤0.01) and pigment-containing neutrophils (AOR 1.0 [95% CI 1.0 to 1.1], p=0.01) was significantly associated with metabolic acidosis. Plasma P. falciparum histidine-rich protein-2 level negatively correlated with the platelet count (r=-0.5, p≤0.01) in patients with PCLs and no PCLs. In Papua New Guinean children with severe P. falciparum malaria, the presence and quantity of PCLs are predictors of disease severity, severe anaemia and metabolic acidosis.

Abstract 2662: Identification of next-generation biomarkers of Vivax Malaria and understanding disease severity using proteomics

Abstract 2662: Identification of next-generation biomarkers of Vivax Malaria and understanding disease severity using proteomics

Seasonal targeting of the RTS,S/AS01 malaria vaccine: a complementary tool but sustained funding is required

In October 2021, WHO recommended the RTS,S/AS01 (RTS,S) malaria vaccine for widespread use for children living in regions with moderate to high Plasmodium falciparum malaria transmission.1 The recommendation received a positive reception worldwide as, despite being both preventable and treatable, malaria continues to affect the poorest nations, hampering population health, economic growth, and social wellbeing. The vaccine itself is not a silver bullet for malaria burden, offering only a 30% reduction in severe malaria disease when implemented in routine settings.

Procalcitonin as a Candidate Biomarker for Malarial Infection and Severe Malaria: A Meta-Analysis.

Procalcitonin (PCT), as a marker of malaria severity, remains to be investigated. The present study collated and compared the levels of PCT between patients with severe malaria, uncomplicated malaria, and control participants to assess their role in predicting malaria infection and disease severity. The systematic review was registered at PROSPERO with registration number CRD42021297243. The search for relevant studies that reported PCT in patients with malaria was performed in PubMed, Scopus, and Web of Science. The following meta-analyses were conducted; (1) the pooled mean PCT levels in patients with severe and uncomplicated malaria, and (2) the pooled mean difference in PCT levels between patients with severe and uncomplicated malaria. Fifteen studies were included for qualitative and quantitative syntheses. The meta-analysis results show that the pooled mean PCT levels in patients with uncomplicated malaria were 3.92 ng/mL (95% CI: 2.26–5.58 ng/mL, I2: 96.5, five studies), whereas the pooled mean PCT levels in patients with severe malaria were 14.13 ng/mL (95% CI: 8.75–19.5 ng/mL, I2: 92.6, six studies). The meta-analysis showed that patients with severe malaria had an equal mean of PCT compared to those with uncomplicated malaria when the random-effects model was used (p: 0.055, weighted mean difference: 6.93, 95% CI: −0.16–14.02, I2: 84.6%, four studies). There were probable correlations between the level of parasitemia, immunity level, and possibly bacterial or other parasitic co-infection that could affect the PCT level among different clinical severities of malaria. Therefore, the PCT level alone does not seem to be a suitable biomarker to discriminate the severe/uncomplicated or infected/uninfected cases. Further studies should investigate the increased PCT levels in combination with other markers in association with malaria infection and severity.

Epstein-Barr Virus and Malaria Interactions: Immunology Perspective

Epstein-Barr Virus can cause various diseases, from acute inflammatory diseases such as fatal or chronic EBV infection, infectious mononucleosis as well as lymphoid and epithelial cancer, various autoimmune diseases, and also could interact with malaria. As EBV infects 95% of the world population, and more than 30% are infected with the protozoan parasite, with more than 500,000 deaths due to malaria cases. It is important to understand how EBV dysregulates the immune system, especially when the virus is interacting with other pathogens such as malaria parasites, causing more severe conditions in certain people like Burkitt Lymphoma. This review will be informative about the mechanism of how EBV interacts with malaria parasites and how it affects the immune system. Knowledge of various cytokines triggering the immune system which may provide links to control/minimize malaria disease severity.

NK cell-derived IL-10 enhances Plasmodium-specific CD4+ Tfh differentiation and IL-27 production in mice

Abstract Malaria, which results from infection with Plasmodium parasites, remains a major public health problem with over 200 million cases and nearly 500,000 deaths annually. Although long-lived, sterilizing immunity does not develop in humans following repeated exposure to Plasmodium parasites, protection against symptomatic disease correlates with the acquisition of humoral immunity. Despite the established role antibodies play in protection to malaria disease, excessive inflammation is thought to contribute to the ineffective immune response to Plasmodium infection. Plasmodium berghei ANKA (PbA) infection results in a fatal severe malaria disease in mice. We previously showed that treatment of mice with IL-15 complex (IL-15C; IL-15 bound to an IL-15Rα-Fc fusion protein) induces IL-10 expression in NK cells, which protects mice from PbA-induced death by dampening the fatal inflammatory response. Interestingly, IL-15C treatment promotes Tfh differentiation at 7 days post-PbA infection (dpi), and genetic deletion of NK cell-derived IL-10 or antibody blockade of IL-10R prevents IL-15C-induced Tfh differentiation. Additionally, IL-15C treatment enhances CD4 T cell-derived IL-27p28 production at 7 dpi and results in increased anti-PbA IgG antibody levels at 42 dpi. These data suggest that IL-15C treatment, via its induction of IL-10 from NK cells, modulates the inflammatory milieu to promote Tfh differentiation, IL-27 production, and PbA-specific antibody generation. These findings will facilitate improved control of malaria infection and protection from disease by informing therapeutic strategies and vaccine design. Supported by grants from NIH (K22 AI143969-01A1, K08 AI141761-01)

Increased interleukin-6 levels associated with malaria infection and disease severity: a systematic review and meta-analysis

Interleukin-6 (IL-6) is generated by immune cells during infection with malaria parasites and they are associated with the immunopathogenesis of malaria. The present systematic review and meta-analysis aimed to compare the differences in IL-6 levels between several groups of patients with malaria and healthy control groups. The systematic review was registered at PROSPERO with a registration number: CRD42021290753. Systematic literature searches were conducted in PubMed, Web of Science, and Scopus until November 7, 2021 to obtain studies that documented IL-6 levels in patients with malaria. The quality of the included studies was assessed using critical appraisal tools from the Joanna Briggs Institute. Differences in the mean IL-6 levels among patients with: (1) severe and non-severe malaria, (2) uncomplicated malaria and controls, (3) uncomplicated and asymptomatic malaria, (4) asymptomatic malaria and healthy controls, and (5) those that died or survived were estimated using a random-effects model. Forty-three of 1,969 studies were included in the systematic review. Results of the meta-analysis showed that patients with severe malaria had higher mean IL-6 levels than those with non-severe malaria [P = 0.04, weight mean difference (WMD) = 96.63 pg/mL, 95% confidence interval (CI) = 0.88 − 19.38 pg/mL, I2 = 99.9%, 13 studies]. Patients with uncomplicated malaria had higher mean IL-6 levels than the controls (P < 0.001, WMD = 42.86 pg/mL, 95% CI = 30.17 − 55.56 pg/mL, I2 = 100%, 17 studies). No differences in the mean levels of IL-6 were found between patients with uncomplicated malaria and those with asymptomatic malaria (P = 0.063, WMD = 42.07 pg/mL, 95% CI = − 2.23 pg/mL to − 86.37 pg/mL, I2 = 99.1%, 8 studies), or between patients with asymptomatic malaria and healthy controls (P = 0.45, WMD = 1.67 pg/mL, 95% CI = − 2.73 pg/mL to − 6.07 pg/mL, I2 = 98.1%, 2 studies). A higher mean level of IL-6 was observed in patients who died compared with the levels of those who survived (P = 0.007, WMD = 1,399.19 pg/mL, 95% CI = 384.16 − 2,414.2 pg/mL, I2 = 93.1%, 4 studies). Our meta-analysis of the pooled evidence can be used to guide future studies in which IL-6 levels are measured during malaria outbreaks to monitor malaria severity. Heterogeneity of the effect estimate among the included studies was the main limitation of this analysis. In conclusion, significantly increased levels of IL-6 were observed in patients with severe malaria compared with those in patients with non-severe malaria, which indicates that IL-6 is a candidate marker for severe malaria. Future studies should investigate the sensitivity and specificity of increased IL-6 levels to determine the effectiveness of assessments of IL-6 levels monitoring of malaria infection and severity.

The Role of PCSK9 in Infectious Diseases.

In recent years, many aspects of the physiological role of PCSK9 have been elucidated, in particular regarding its role in lipid metabolism, cardiovascular risk but also its role in innate immunity. Increasing evidence is available on the involvement of PCSK9 in the pathogenesis of viral infections, mainly HCV, as well as in the regulation of host response to bacterial infections, mainly sepsis and septic shock. Moreover, the action of PCSK9 has been investigated as a crucial step in the pathogenesis of malaria infection and disease severity. Aim of this paper is to review available published literature on the role of PCSK9 in a wide array of infectious diseases. Besides the ongoing investigation on PCSK9 inhibition among HIV-infected patients for the treatment of HIV- and ART-related hyperlipidemia, preclinical studies indicate how PCSK9 is involved in reducing the replication of HCV. Moreover, a protective role of PCSK9 inhibition has also been proposed against dengue and SARS-CoV-2 viral infections. Interestingly, high plasmatic PCSK9 levels have been described in patients with sepsis. Finally, a loss of function in the PCSK9-encoding gene has been reported to possibly reduce mortality in malaria infection.

Vascular Dysfunction in Malaria: Understanding the Role of the Endothelial Glycocalyx.

Malaria caused by Plasmodium falciparum results in over 400,000 deaths annually, predominantly affecting African children. In addition, non-falciparum species including vivax and knowlesi cause significant morbidity and mortality. Vascular dysfunction is a key feature in malaria pathogenesis leading to impaired blood perfusion, vascular obstruction, and tissue hypoxia. Contributing factors include adhesion of infected RBC to endothelium, endothelial activation, and reduced nitric oxide formation. Endothelial glycocalyx (eGC) protects the vasculature by maintaining vessel integrity and regulating cellular adhesion and nitric oxide signaling pathways. Breakdown of eGC is known to occur in infectious diseases such as bacterial sepsis and dengue and is associated with adverse outcomes. Emerging studies using biochemical markers and in vivo imaging suggest that eGC breakdown occurs during Plasmodium infection and is associated with markers of malaria disease severity, endothelial activation, and vascular function. In this review, we describe characteristics of eGC breakdown in malaria and discuss how these relate to vascular dysfunction and adverse outcomes. Further understanding of this process may lead to adjunctive therapy to preserve or restore damaged eGC and reduce microvascular dysfunction and the morbidity/mortality of malaria.

Hemoglobin Variants Influence Plasmodium Falciparum Sexual Differentiation

It has long been recognized that individuals who express variations of the hemoglobin-A (HbA) protein experience less severe malaria disease. As malaria remains to be one of the most significant infectious diseases in history, this human adaptation has led to the persistence of HbA variants (HbVARs) in the population. The intricate lifecycle of the parasite which causes the most cases of clinical malaria, Plasmodium falciparum, relies on both asexual and sexual reproductive cycles, with host to vector transmission reliant on sexual stage gametocyte formation. Multiple epidemiological studies have shown that HbVARs may influence gametocyte production during P. falciparum infection, with greater gametocyte numbers reported in individuals with hemoglobin variant containing erythrocytes (Hb VAR-Ery) when compared to hemoglobin A containing erythrocytes (Hb A-Ery). Here we provide experimental support for these studies by showing significantly higher sexual differentiation rates among parasites grown in Hb S containing erythrocytes (Hb S-Ery) obtained from sickle cell patients than those differentiated in Hb A-Ery (p=0.038). Because the digestion of hemoglobin is such an integral part of the intraerythrocytic cycle, we then sought to determine whether there was a difference between the hydrolysis efficiencies of HbA and other hemoglobin variants (HbVAR). By using a prominent recombinant P. falciparum hemoglobinase we found the hydrolysis efficiency of HbA to be significantly (p=0.0058) more efficient after 24 hours compared to a HbVAR sample containing mixed amounts of HbA, HbF, and HbS. To further determine whether there is a link between hemoglobin digestion efficiency and sexual differentiation, we therapeutically inhibited the hemoglobin digestion and hemozoin formation process in a culture of P. falciparum using sub-optimal doses of chloroquine diphosphate. We found a significant difference (p<0.001) among gametocyte conversion rates between treated and non-treated cultures, as well as a moderate negative correlation between hemozoin formation and gametocyte conversion rate (Pearson r=0.72, p=0.008). Gene expression analysis also revealed patterns of expression that were consistent with increased gametocytogenesis. We conclude that hemoglobin type plays a significant role in the process of sexual conversion in P. falciparum. Though further studies should be completed in order to confirm these results, these findings may suggest hemoglobin digestion efficiency as a causative factor for sexual differentiation. As individuals with hemoglobinopathies make up approximately 7% of the global population, and malaria infection rates have been shown to differ depending on these genetic dynamics, these findings may support the creation of targeted initiatives to reduce transmission specifically in areas where there is a high percentage of hemoglobinopathy carriage. DisclosuresNo relevant conflicts of interest to declare.