The malarial blood transcriptome: translational applications

The blood transcriptome of malaria patients has been used extensively to elucidate the pathophysiological mechanisms and host immune responses to disease, identify candidate diagnostic and prognostic biomarkers, and reveal new therapeutic targets for drug discovery. This review gives a high-level overview of the three main translational applications of these studies (diagnostics, prognostics, and therapeutics) by summarising recent literature and outlining the main limitations and future directions of each application. It highlights the need for consistent and accurate definitions of disease states and subject groups and discusses how prognostic studies must distinguish clearly between analyses that attempt to predict future disease states and those which attempt to discriminate between current disease states (classification). Lastly it examines how many promising therapeutics fail due to the choice of imperfect animal models for pre-clinical testing and lack of appropriate validation studies in humans, and how future transcriptional studies may be utilised to overcome some of these limitations.

Stress and coping strategies in the general population of Greece and Cyprus in response to the COVID-19 pandemic: a cross-sectional study

The COVID-19 pandemic and the lockdown policy had a profound psychological impact on the general population worldwide. The aim of this study was to assess the level of stress and coping strategies used during the initial stage of the COVID-19 outbreak and their association. Secondary aims were to a) identify the most important coping strategies and b) investigate predictors of stress. A cross-sectional study was conducted by using an anonymous online questionnaire. The study was carried out from April 23 to May 4 2020. A snowball sampling method was conducted to recruit potential participants from the general population of Greece and Cyprus. Participants over 18 years old who were familiar with the Greek language were included. The psychological impact was assessed by the Impact of Event Scale-Revised (IES-R). Coping strategies were assessed using 15 statements detected from a review of the literature. Participants were asked to rate each one of the coping strategies according to how important it was to them, on a four-point likert scale. The sample consisted of 3941 participants (74.2% women, N=2926), with a mean age of 36.9 years old. The most important coping strategies adopted were 1) "Dealing the situation with a positive attitude" (96.5%), 2) "Follow strict personal protective measures" (95,9%), 3) "Acquiring knowledge about coronavirus" (94.6%), 4) "Engaging in health-promoting behaviors" (89.6%), 5) "Limiting the time spent on media" (75.5%). The highest and positive coefficients were recorded for the association of IES-R scales with 1) "Talking with family and friends to reduce stress", 2) "Seeking help from a mental health professional", 3) "Limiting the time spent on media", 4) "Relieving and managing emotions", 5) "Practicing relaxation techniques". 26.5% showed severe psychological impact. Conclusion: Addressing stress levels with the use of functional coping strategies can be beneficial to protect the general population from adverse psychological outcomes.

Potent Virustatic Polymer-Lipid Nanomimics Block Viral Entry and Inhibit Malaria Parasites In Vivo

Infectious diseases continue to pose a substantial burden on global populations, requiring innovative broad-spectrum prophylactic and treatment alternatives. Here, we have designed modular synthetic polymer nanoparticles that mimic functional components of host cell membranes, yielding multivalent nanomimics that act by directly binding to varied pathogens. Nanomimic blood circulation time was prolonged by reformulating polymer-lipid hybrids. Femtomolar concentrations of the polymer nanomimics were sufficient to inhibit herpes simplex virus type 2 (HSV-2) entry into epithelial cells, while higher doses were needed against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given their observed virustatic mode of action, the nanomimics were also tested with malaria parasite blood-stage merozoites, which lose their invasive capacity after a few minutes. Efficient inhibition of merozoite invasion of red blood cells was demonstrated both in vitro and in vivo using a preclinical rodent malaria model. We envision these nanomimics forming an adaptable platform for developing pathogen entry inhibitors and as immunomodulators, wherein nanomimic-inhibited pathogens can be secondarily targeted to sites of immune recognition.

Comparative transcriptomic analysis reveals translationally relevant processes in mouse models of malaria

Recent initiatives to improve translation of findings from animal models to human disease have focussed on reproducibility but quantifying the relevance of animal models remains a challenge. Here, we use comparative transcriptomics of blood to evaluate the systemic host response and its concordance between humans with different clinical manifestations of malaria and five commonly used mouse models. Plasmodium yoelii 17XL infection of mice most closely reproduces the profile of gene expression changes seen in the major human severe malaria syndromes, accompanied by high parasite biomass, severe anemia, hyperlactatemia, and cerebral microvascular pathology. However, there is also considerable discordance of changes in gene expression between the different host species and across all models, indicating that the relevance of biological mechanisms of interest in each model should be assessed before conducting experiments. These data will aid the selection of appropriate models for translational malaria research, and the approach is generalizable to other disease models.

Localised release of matrix metallopeptidase 8 in fatal cerebral malaria

OBJECTIVE

Cerebral malaria (CM) is a complication of Plasmodium falciparum malaria, in which progressive brain swelling is associated with sequestration of parasites and impaired barrier function of the cerebral microvascular endothelium. To test the hypothesis that localised release of matrix metallopeptidase 8 (MMP8) within the retina is implicated in microvascular leak in CM, we examined its expression and association with extravascular fibrinogen leak in a case-control study of post-mortem retinal samples from 13 Malawian children who met the clinical case definition of CM during life. Cases were seven children who were found on post-mortem examination to have 'true-CM' (parasite sequestration in brain blood vessels), whilst controls were six children who had alternative causes of death ('faux-CM', no parasite sequestration in blood vessels).

METHODS

We used immunofluorescence microscopy and independent scoring, by two assessors blinded to the CM status, to assess MMP8 expression, extravascular fibrinogen as an indicator of vascular leak and their co-localisation in the retinal microvasculature.

RESULTS

In 'true-CM' subjects, MMP8 staining was invariably associated with sequestered parasites and a median of 88% (IQR = 74-91%) of capillaries showed MMP8 staining, compared with 14% (IQR = 3.8-24%) in 'faux-CM' (P-value = 0.001). 41% (IQR = 28-49%) of capillaries in 'true-CM' subjects showed co-localisation of extravascular fibrinogen leak and MMP8 staining, compared with 1.8% of capillaries in 'faux-CM' (IQR = 0-3.9%, P-value = 0.01). Vascular leak was rare in the absence of MMP8 staining.

CONCLUSION

Matrix metallopeptidase 8 was extensively expressed in retinal capillaries of Malawian children with malarial retinopathy and strongly associated with vascular leak. Our findings implicate MMP8 as a cause of the vascular endothelial barrier disruption in CM, which may precipitate fatal brain swelling.

Immunopathology of Acute Kidney Injury in Severe Malaria

Acute kidney injury (AKI) is a common feature of severe malaria, and an independent risk factor for death. Previous research has suggested that an overactivation of the host inflammatory response is at least partly involved in mediating the kidney damage observed in P. falciparum patients with AKI, however the exact pathophysiology of AKI in severe malaria remains unknown. The purpose of this mini-review is to describe how different aspects of malaria pathology, including parasite sequestration, microvascular obstruction and extensive intravascular hemolysis, may interact with each other and contribute to the development of AKI in severe malaria, by amplifying the damaging effects of the host inflammatory response. Here, we highlight the importance of considering how the systemic effects and multi-organ involvement of malaria are intertwined with the localized effects on the kidney.

Neutrophil extracellular traps drive inflammatory pathogenesis in malaria

Neutrophils are essential innate immune cells that extrude chromatin in the form of neutrophil extracellular traps (NETs) when they die. This form of cell death has potent immunostimulatory activity. We show that heme-induced NETs are essential for malaria pathogenesis. Using patient samples and a mouse model, we define two mechanisms of NET-mediated inflammation of the vasculature: activation of emergency granulopoiesis via granulocyte colony-stimulating factor production and induction of the endothelial cytoadhesion receptor intercellular adhesion molecule-1. Soluble NET components facilitate parasite sequestration and mediate tissue destruction. We demonstrate that neutrophils have a key role in malaria immunopathology and propose inhibition of NETs as a treatment strategy in vascular infections.

Integrated pathogen load and dual transcriptome analysis of systemic host-pathogen interactions in severe malaria

The pathogenesis of infectious diseases depends on the interaction of host and pathogen. In Plasmodium falciparum malaria, host and parasite processes can be assessed by dual RNA sequencing of blood from infected patients. We performed dual transcriptome analyses on samples from 46 malaria-infected Gambian children to reveal mechanisms driving the systemic pathophysiology of severe malaria. Integrating these transcriptomic data with estimates of parasite load and detailed clinical information allowed consideration of potentially confounding effects due to differing leukocyte proportions in blood, parasite developmental stage, and whole-body pathogen load. We report hundreds of human and parasite genes differentially expressed between severe and uncomplicated malaria, with distinct profiles associated with coma, hyperlactatemia, and thrombocytopenia. High expression of neutrophil granule-related genes was consistently associated with all severe malaria phenotypes. We observed severity-associated variation in the expression of parasite genes, which determine cytoadhesion to vascular endothelium, rigidity of infected erythrocytes, and parasite growth rate. Up to 99% of human differential gene expression in severe malaria was driven by differences in parasite load, whereas parasite gene expression showed little association with parasite load. Coexpression analyses revealed interactions between human and P. falciparum, with prominent co-regulation of translation genes in severe malaria between host and parasite. Multivariate analyses suggested that increased expression of granulopoiesis and interferon-γ-related genes, together with inadequate suppression of type 1 interferon signaling, best explained severity of infection. These findings provide a framework for understanding the contributions of host and parasite to the pathogenesis of severe malaria and identifying new treatments.

Transcriptomic Studies of Malaria: a Paradigm for Investigation of Systemic Host-Pathogen Interactions

Transcriptomics, the analysis of genome-wide RNA expression, is a common approach to investigate host and pathogen processes in infectious diseases. Technical and bioinformatic advances have permitted increasingly thorough analyses of the association of RNA expression with fundamental biology, immunity, pathogenesis, diagnosis, and prognosis. Transcriptomic approaches can now be used to realize a previously unattainable goal, the simultaneous study of RNA expression in host and pathogen, in order to better understand their interactions. This exciting prospect is not without challenges, especially as focus moves from interactions in vitro under tightly controlled conditions to tissue- and systems-level interactions in animal models and natural and experimental infections in humans. Here we review the contribution of transcriptomic studies to the understanding of malaria, a parasitic disease which has exerted a major influence on human evolution and continues to cause a huge global burden of disease. We consider malaria a paradigm for the transcriptomic assessment of systemic host-pathogen interactions in humans, because much of the direct host-pathogen interaction occurs within the blood, a readily sampled compartment of the body. We illustrate lessons learned from transcriptomic studies of malaria and how these lessons may guide studies of host-pathogen interactions in other infectious diseases. We propose that the potential of transcriptomic studies to improve the understanding of malaria as a disease remains partly untapped because of limitations in study design rather than as a consequence of technological constraints. Further advances will require the integration of transcriptomic data with analytical approaches from other scientific disciplines, including epidemiology and mathematical modeling.

Study of key resonances in the 30P(p,γ)31S reaction in classical novae

Among reactions with strong impact on classical novae model predictions, 30P(p,γ)31S is one of the few remained that are worthy to be measured accurately, because of their rate uncertainty, as like as 18F(p,α)15O and 25Al(pγ)26Si. To reduce the nuclear uncertainties associated to this reaction, we performed an experiment at ALTO facility of Orsay using the 31P(3He,t)31S reaction to populate 31S excited states of astrophysical interest and detect in coincidence the protons coming from the decay of the populated states in order to extract the proton branching ratios. After a presentation of the astrophysical context of this work, the current situation of the 30P(p,γ)31S reaction rate will be discussed. Then the experiment set-up of this work and the analysis of the single events will be presented.

Analysis of expired air of fasting male monks at Mount Athos

Expired air chemical analysis is investigated as a search and locate method for the early detection of entrapped people under the ruins of collapsed buildings after an earthquake. Fasting individuals were examined as a group that simulates the medical status of some of such victims. Exhaled air from seven fasting male monks (after 63 h) was analysed using thermal desorption-gas chromatography-mass spectrometry (TD-GC-MS) analysis. Over 150 volatile organic compounds (VOCs) were identified and the 43 most frequent are presented. Acetone showed by far the highest "positive alveolar gradient". Other compounds included phenol, di-limonene, 2-pentanone, isoprene and acetaldehyde. Quantitative results showed a 30-fold increase of acetone concentration (5.8 ppmv) compared to control measurements of a volunteer. Breath acetone was also identified through a portable gas chromatography-ion mobility spectrometer showing possible, under certain conditions, effectiveness of the method in the field.

Preliminary investigation of using volatile organic compounds from human expired air, blood and urine for locating entrapped people in earthquakes

A preliminary investigation on the possibility of using volatile organic compounds (VOCs) determination of expired air, blood and urine, for the early location of entrapped people in earthquakes, has been carried out. A group of 15 healthy subjects has been sampled. The identification of a common "core" of substances might provide indications of human presence that can be used for the development of a real time field analytical method for the on site detection of entrapped people. Expired air samples have been analyzed by thermal desorption GC/MS and VOCs from blood and urine by headspace SPME-GC/MS. Acetone was the only compound found common in all three matrices. Isoprene was found in both expired air and blood samples. Acetone and isoprene along with a number of saturated hydrocarbons were among the major constituents identified in expired air analysis. Various ketones (2-pentanone, 4-heptanone, 2-butanone) were also determined over urine specimens. Using the techniques and methods of field analytical chemistry and technology appears to be the proper approach for applying the results of the present study in real situations.

Cortical bone density is normal in prepubertal children with growth hormone (GH) deficiency, but initially decreases during GH replacement due to early bone remodeling

Dual energy x-ray absorptiometry (DEXA) has revealed that GH- deficient adults gain in bone mineral density during GH therapy. Measurements of volumetric bone density (grams per cubic centimeter vs. grams per square centimeter) and structure, however, are achieved through peripheral quantitative computed tomography (pQCT). In 45 prepubertal GH-deficient children, we studied pQCT measurements before the start and for 12 months of GH treatment. Serum alkaline phosphatase (AP), procollagen I carboxyl-terminal propeptide (PICP), and deoxypyridinoline reflected bone metabolism status. Findings at the start of GH treatment were (mean SD score): bone area, -0.44; cortical density, -0.03; cortical area, -1.32; cortical thickness, -1.41; and marrow area, +0.66. At 12 months, cortical density had fallen to -0.73 (P < 0.001), whereas cortical area and thickness, and marrow area did not change. AP, PICP, and deoxypyridinoline increased significantly within the first 3 months (increase: AP, 66.5 U/liter; PICP, 72 microg/liter; DPD, 11.4 nmol/mmol creatinine). The pQCT showed that cortical density is not reduced in GH-deficient patients. Higher bone metabolism explains the lower cortical density after GH therapy commenced. Thus, the manifestation of GH deficiency is evidently similar in children and adults, and pQCT provides important information in addition to DEXA measurements, as DEXA does not take bone structure into account.