Vascular endothelium: the battlefield of dengue viruses

Vascular dysfunction in hemorrhagic viral fevers: opportunities for organotypic modeling

The hemorrhagic fever viruses (HFVs) cause severe or fatal infections in humans. Named after their common symptom hemorrhage, these viruses induce significant vascular dysfunction by affecting endothelial cells, altering immunity, and disrupting the clotting system. Despite advances in treatments, such as cytokine blocking therapies, disease modifying treatment for this class of pathogen remains elusive. Improved understanding of the pathogenesis of these infections could provide new avenues to treatment. While animal models and traditional 2D cell cultures have contributed insight into the mechanisms by which these pathogens affect the vasculature, these models fall short in replicatingin vivohuman vascular dynamics. The emergence of microphysiological systems (MPSs) offers promising avenues for modeling these complex interactions. These MPS or 'organ-on-chip' models present opportunities to better mimic human vascular responses and thus aid in treatment development. In this review, we explore the impact of HFV on the vasculature by causing endothelial dysfunction, blood clotting irregularities, and immune dysregulation. We highlight how existing MPS have elucidated features of HFV pathogenesis as well as discuss existing knowledge gaps and the challenges in modeling these interactions using MPS. Understanding the intricate mechanisms of vascular dysfunction caused by HFV is crucial in developing therapies not only for these infections, but also for other vasculotropic conditions like sepsis.

Distinct serum exosomal miRNA profiles detected in acute and asymptomatic dengue infections: A community-based study in Baiyun District, Guangzhou

Background

In recent years, research on exosomal miRNAs has provided new insights into exploring the mechanism of viral infection and disease prevention. This study aimed to investigate the serum exosomal miRNA expression profile of dengue-infected individuals through a community survey of dengue virus (DENV) infection.

Methods

A seroprevalence study of 1253 healthy persons was first conducted to ascertain the DENV infection status in Baiyun District, Guangzhou. A total of 18 serum samples, including 6 healthy controls (HC), 6 asymptomatic DENV infections (AsymptDI), and 6 confirmed dengue fever patients (AcuteDI), were collected for exosome isolation and then sRNA sequencing. Through bioinformatics analysis, we discovered distinct serum exosomal miRNA profiles among the different groups and identified differentially expressed miRNAs (DEMs). These findings were further validated by qRT-PCR.

Results

The community survey of DENV infection indicated that the DENV IgG antibody positivity rate among the population was 11.97 % in the study area, with asymptomatic infected individuals accounting for 93.06 % of the anti-DENV IgG positives. The age and Guangzhou household registration were associated with DENV IgG antibody positivity by logistic regression analysis. Distinct miRNA profiles were observed between healthy individuals and DENV infections. A total of 1854 miRNAs were identified in 18 serum exosome samples from the initial analysis of the sequencing data. Comparative analysis revealed 23 DEMs comprising 5 upregulated and 18 downregulated miRNAs in the DENV-infected group (mergedDI). In comparison to AcuteDI, 18 upregulated miRNAs were identified in AsymptDI. Moreover, functional enrichment of the predicted target genes of DEMs indicated that these miRNAs were involved in biological processes and pathways related to cell adhesion, focal adhesion, endocytosis, and ECM-receptor interaction. Eight DEMs were validated by qRT-PCR.

Conclusion

The Baiyun District of Guangzhou exhibits a notable proportion of asymptomatic DENV infections as suggested in other research, highlighting the need for enhanced monitoring and screening of asymptomatic persons and the elderly. Differential miRNA expression among healthy, symptomatic and asymptomatic DENV-infected individuals suggests their potential as biomarkers for distinguishing DENV infection and offers new avenues of investigating the mechanisms underlying DENV asymptomatic infections.

Extracellular Vesicles in Flaviviridae Pathogenesis: Their Roles in Viral Transmission, Immune Evasion, and Inflammation

The members of the Flaviviridae family are becoming an emerging threat for public health, causing an increasing number of infections each year and requiring effective treatment. The consequences of these infections can be severe and include liver inflammation with subsequent carcinogenesis, endothelial damage with hemorrhage, neuroinflammation, and, in some cases, death. The mechanisms of Flaviviridae pathogenesis are being actively investigated, but there are still many gaps in their understanding. Extracellular vesicles may play important roles in these mechanisms, and, therefore, this topic deserves detailed research. Recent data have revealed the involvement of extracellular vesicles in steps of Flaviviridae pathogenesis such as transmission, immune evasion, and inflammation, which is critical for disease establishment. This review covers recent papers on the roles of extracellular vesicles in the pathogenesis of Flaviviridae and includes examples of clinical applications of the accumulated data.

Molecular and Cellular Mechanisms Underlying Neurologic Manifestations of Mosquito-Borne Flavivirus Infections

Flaviviruses are a family of enveloped viruses with a positive-sense RNA genome, transmitted by arthropod vectors. These viruses are known for their broad cellular tropism leading to infection of multiple body systems, which can include the central nervous system. Neurologic effects of flavivirus infection can arise during both acute and post-acute infectious periods; however, the molecular and cellular mechanisms underlying post-acute sequelae are not fully understood. Here, we review recent studies that have examined molecular and cellular mechanisms that may contribute to neurologic sequelae following infection with the West Nile virus, Japanese encephalitis virus, Zika virus, dengue virus, and St. Louis encephalitis virus. Neuronal death, either from direct infection or due to the resultant inflammatory response, is a common mechanism by which flavivirus infection can lead to neurologic impairment. Other types of cellular damage, such as oxidative stress and DNA damage, appear to be more specific to certain viruses. This article aims to highlight mechanisms of cellular damage that are common across several flavivirus members and mechanisms that are more unique to specific members. Our goal is to inspire further research to improve understanding of this area in the hope of identifying treatment options for flavivirus-associated neurologic changes.

Liver immunopathogenesis in fatal cases of dengue in children: detection of viral antigen, cytokine profile and inflammatory mediators

Introduction

Dengue virus (DENV), the etiologic agent of dengue fever illness, represents a global public health concern, mainly in tropical and subtropical areas across the globe. It is well known that this acute viral disease can progress to severe hemorrhagic stages in some individuals, however, the immunopathogenic basis of the development of more severe forms by these patients is yet to be fully understood.

Objective

In this context, we investigated and characterized the histopathological features as well as the cytokine profile and cell subpopulations present in liver tissues from three fatal cases of DENV in children.

Methods

Hematoxylin and Eosin, Periodic Acid Schiff and Picro Sirius Red staining were utilized for the histopathological analysis. Immunohistochemistry assay was performed to characterize the inflammatory response and cell expression patterns.

Results

Vascular dysfunctions such as hemorrhage, vascular congestion and edema associated with a mononuclear infiltrate were observedin all three cases. Liver tissues exhibited increased presence of CD68+ and TCD8+ cells as well as high expression of MMP-9, TNF-a, RANTES, VEGFR-2 mediators. Viral replication was confirmed by the detection of NS3 protein.

Conclusion

Taken together, these results evidenced key factors that may be involved in the development of severe alterations in liver tissues of children in response to DENV infection.

Angiotensin II and dengue

Dengue is a disease caused by a flavivirus that is transmitted principally by the bite of an Aedes aegypti mosquito and represents a major public-health problem. Many studies have been carried out to identify soluble factors that are involved in the pathogenesis of this infection. Cytokines, soluble factors, and oxidative stress have been reported to be involved in the development of severe disease. Angiotensin II (Ang II) is a hormone with the ability to induce the production of cytokines and soluble factors related to the inflammatory processes and coagulation disorders observed in dengue. However, a direct involvement of Ang II in this disease has not been demonstrated. This review primarily summarizes the pathophysiology of dengue, the role of Ang II in various diseases, and reports that are highly suggestive of the involvement of this hormone in dengue.

Heart failure after dengue infection- a population-based self-controlled case-series study

BACKGROUND

Major cardiovascular events (MACEs) have been described with dengue infection. Among these MACEs, heart failure (HF) is the most common but has not been thoroughly assessed. This study aimed to evaluate the association between dengue and HF.

METHODS

Under the self-controlled case-series study design, we used the Notifiable Infectious Disease dataset linkage with the National Health Insurance claims data to obtain the study subjects. All laboratory-confirmed dengue cases who were hospitalized for HF after dengue infection within one year between 2009 and 2015 in Taiwan were included. We identified the first 7 and 14 days after dengue infection as the risk intervals. The incidence rate ratio (IRR) and 95% confidence interval (CI) for HF were estimated by conditional Poisson regression.

RESULTS

Among the 65,906 dengue patients, 230 had admission for HF after dengue infection within one year. The IRR of HF admission within the first week after dengue infection was 27.2456.50 (95% C.I. 43.88-72.75). This risk was highest in >60 years (IRR = 59.32, 95% C.I. 45.43-77.43) and lower in 0-40 years (IRR = 25.82, 95% C.I. 2.89-231.02). The risk was nearly nine times higher among admission (for dengue infection) than among nonadmission cases (IRR 75.35 vs. 8.61, p < 0.0001). The risks increased slightly in the second week 8.55 and became less obvious after the third and fourth week.

CONCLUSIONS

Patients with dengue infection have a risk of developing acute heart failure within one week, especially in >60 years, men, and dengue admission subjects. The findings emphasize the awareness of diagnosis and further appropriate treatment of HF.

Vitamin D modulates inflammatory response of DENV-2-infected macrophages by inhibiting the expression of inflammatory-liked miRNAs

Dengue disease caused by dengue virus (DENV) infection is the most common vector-borne viral disease worldwide. Currently, no treatment is available to fight dengue symptoms. We and others have demonstrated the antiviral and immunomodulatory properties of VitD3 as a possible therapy for DENV infection. MicroRNAs (miRNAs) are small non-coding RNAs responsible for the regulation of cell processes including antiviral defense. Previous transcriptomic analysis showed that VitD3 regulates the expression of genes involved in stress and immune response by inducing specific miRNAs. Here, we focus on the effects of VitD3 supplementation in the regulation of the expression of inflammatory-liked miR-182-5p, miR-130a-3p, miR125b-5p, miR146a-5p, and miR-155-5p during DENV-2 infection of monocyte-derived macrophages (MDMs). Further, we evaluated the effects of inhibition of these miRNAs in the innate immune response. Our results showed that supplementation with VitD3 differentially regulated the expression of these inflammatory miRNAs. We also observed that inhibition of miR-182-5p, miR-130a-3p, miR-125b-5p, and miR-155-5p, led to decreased production of TNF-α and TLR9 expression, while increased the expression of SOCS-1, IFN-β, and OAS1, without affecting DENV replication. By contrast, over-expression of miR-182-5p, miR-130a-3p, miR-125b-5p, and miR-155-5p significantly decreased DENV-2 infection rates and also DENV-2 replication in MDMs. Our results suggest that VitD3 immunomodulatory effects involve regulation of inflammation-linked miRNAs expression, which might play a key role in the inflammatory response during DENV infection.

The Role of Host-Cellular Responses in COVID-19 Endothelial Dysfunction

SARS-CoV2, Severe acute respiratory syndrome coronavirus 2, is a novel member of the human coronavirus family that has recently emerged worldwide to cause COVID-19 disease. COVID-19 disease has been declared a worldwide pandemic with over 270 million total cases, and >5 million deaths as of this writing. Although co-morbidities and preexisting conditions have played a significant role in the severity of COVID-19, the hallmark feature of severe disease associated with SARS-CoV2 is respiratory failure. Recent findings have demonstrated a key role for endothelial dysfunction caused by SARS-CoV2 in these clinical outcomes, characterized by endothelial inflammation, the persistence of a pro-coagulative state, and major recruitment of leukocytes and other immune cells to localized areas of endothelial dysfunction. Though it is generally recognized that endothelial impairment is a major contributor to COVID-19 disease, studies to examine the initial cellular events involved in triggering endothelial dysfunction are needed. In this article, we review the general strategy of pathogens to exploit endothelial cells and the endothelium to cause disease. We discuss the role of the endothelium in COVID-19 disease and highlight very recent findings that identify key signaling and cellular events that are associated with the initiation of SARS-CoV2 infection. These studies may reveal specific molecular pathways that can serve as potential means of therapeutic development against COVID-19 disease.

Endothelial Dysfunction, HMGB1, and Dengue: An Enigma to Solve

Dengue is a viral infection caused by dengue virus (DENV), which has a significant impact on public health worldwide. Although most infections are asymptomatic, a series of severe clinical manifestations such as hemorrhage and plasma leakage can occur during the severe presentation of the disease. This suggests that the virus or host immune response may affect the protective function of endothelial barriers, ultimately being considered the most relevant event in severe and fatal dengue pathogenesis. The mechanisms that induce these alterations are diverse. It has been suggested that the high mobility group box 1 protein (HMGB1) may be involved in endothelial dysfunction. This non-histone nuclear protein has different immunomodulatory activities and belongs to the alarmin group. High concentrations of HMGB1 have been detected in patients with several infectious diseases, including dengue, and it could be considered as a biomarker for the early diagnosis of dengue and a predictor of complications of the disease. This review summarizes the main features of dengue infection and describes the known causes associated with endothelial dysfunction, highlighting the involvement and possible relationship between HMGB1 and DENV.

Neurological Complications of Dengue Fever

PURPOSE OF REVIEW

To discuss the neurological complications of dengue virus (DENV) infection and their pathogenesis.

RECENT FINDINGS

Include recognition of the four different serotypes of DENV and their epidemiology as well as recognition of the expanded dengue syndrome encompassing multisystem involvement in the severe form of the disease including involvement of the central nervous system (CNS). DENV is a neurotropic virus with the ability to infect the supporting cells of the CNS. Neural injury during the acute stage of the infection results from direct neuro-invasion and/or the phenomenon of antibody-dependent enhancement, resulting in plasma leakage and coagulopathy. Immune mechanisms have been implicated in the development of the delayed neurological sequelae through molecular mimicry. A myriad of neurological syndromes has been described as a result of the involvement of the CNS, the peripheral nervous system (PNS), or both. Neurological manifestations in DENV infection are increasingly being recognized, some of which are potentially fatal if not treated promptly. DENV encephalopathy and encephalitis should be considered in the differential diagnosis of other acute febrile encephalopathies, autoimmune encephalitides, and in cases of encephalopathy/encephalitis related to SARS-CoV2 infection, especially in dengue-endemic areas. Acute disseminated encephalomyelitis (ADEM) may be occasionally encountered. Clinicians should be knowledgeable of the expanded dengue syndrome characterized by the concurrent compromise of cardiac, neurological, gastrointestinal, renal, and hematopopoietic systems. Isolated cranial nerve palsies occur rather uncommonly and are often steroid responsive. These neuropathies may result from the direct involvement of cranial nerve nuclei or nerve involvement or may be immune-mediated. Even if the diagnosis of dengue is confirmed, it is absolutely imperative to exclude other well-known causes of isolated cranial nerve palsies. Ischemic and hemorrhagic strokes may occur following dengue fever. The pathogenesis may be beyond the commonly observed thrombocytopenia and include cerebral vasculitis. Involvement of ocular blood vessels may cause maculopathy or retinal hemorrhages. Posterior reversible encephalopathy syndrome (PRES) is uncommon and possibly related to dysregulated cytokine release phenomena. Lastly, any patient developing acute neuromuscular weakness during the course or within a fortnight of remission from dengue fever must be screened for acute inflammatory demyelinating polyneuropathy (AIDP), hypokalemic paralysis, or acute myositis. Rarely, a Miller-Fisher-like syndrome with negative anti-GQ1b antibody may develop.

Self-association features of NS1 proteins from different flaviviruses

Flaviviruses comprise a large group of arboviral species that are distributed in several countries of the tropics, neotropics, and some temperate zones. Since they can produce neurological pathologies or vascular damage, there has been intense research seeking better diagnosis and treatments for their infections in the last decades. The flavivirus NS1 protein is a relevant clinical target because it is involved in viral replication, immune evasion, and virulence. Being a key factor in endothelial and tissue-specific modulation, NS1 has been largely studied to understand the molecular mechanisms exploited by the virus to reprogram host cells. A central part of the viral maturation processes is the NS1 oligomerization because many stages rely on these protein-protein assemblies. In the present study, the self-associations of NS1 proteins from Zika, Dengue, and West Nile viruses are examined through constant-pH coarse-grained biophysical simulations. Free energies of interactions were estimated for different oligomeric states and pH conditions. Our results show that these proteins can form both dimers and tetramers under conditions near physiological pH even without the presence of lipids. Moreover, pH plays an important role mainly controlling the regimes where van der Waals interactions govern their association. Finally, despite the similarity at the sequence level, we found that each flavivirus has a well-characteristic protein-protein interaction profile. These specific features can provide new hints for the development of binders both for better diagnostic tools and the formulation of new therapeutic drugs.

Clinical significance of differential serum-signatures for early prediction of severe dengue among Eastern Indian patients

Dengue infection can result in simple dengue fever or life-threatening severe dengue. Early identification of severe patients is needed for proper disease management. Dengue infection was screened among 168 symptomatic patients by qRT-PCR, anti-dengue IgM, and IgG ELISA. Dengue patients were categorized according to WHO classification. Viral load and dengue serotypes were determined by qRT-PCR. Levels of acute-phase-proteins (SAP, SAA2; CRP and ApoA1), endothelial (Ang2, VEGF), coagulation (fibrinogen) markers were determined by sandwich ELISA/immunoturbidimetry/western-blotting. Hepatic (ALT, AST, ALP) and other blood biochemical parameters were studied by autoanalyzer and haematology cell counter. Statistical analysis and protein-protein-interaction network were performed by GraphPad-Prism and STRINGS database, respectively. Among 87 dengue patients, significantly higher levels of Ang2, VEGF, CRP, SAA2, ApoA1, AST, ALT, and AST/ALT ratio and low level of fibrinogen were detected in severe-dengue cases compared to dengue without warning-signs, with seven of them severely altered during febrile-phase. Higher fold-change of Ang2 and VEGF as well as decreased fibrinogen were observed among patients with haemorrhagic-manifestation, clinical-fluid accumulation and thrombocytopenia. Functional network analysis predicted Ang2, VEGF, and CRP to be functionally and physically connected and SAA2 and ApoA1 to be functioning together. Correlation analyses also validated this connectivity by a strong positive correlation between Ang2, VEGF, and CRP. PCA analysis followed by hierarchical clustering heatmap analysis segregated severe-dengue patients from the rest, with VEGF, Ang2, ApoA1, AST, and ALT clearly distinguishing the severe-dengue group. Thus, serum levels of VEGF, Ang2, ApoA1, AST, and ALT might act as potential biomarkers for predicting dengue severity during the early stage.

Infection of Endothelial Cells by Dengue Virus Induces ROS Production by Different Sources Affecting Virus Replication, Cellular Activation, Death and Vascular Permeability

Exacerbated inflammatory response and altered vascular function are hallmarks of dengue disease. Reactive oxygen species (ROS) production has been associated to endothelial barrier disturbance and microvascular alteration in distinct pathological conditions. Increased ROS has been reported in in vitro models of dengue virus (DENV) infection, but its impact for endothelial cell physiology had not been fully investigated. Our group had previously demonstrated that infection of human brain microvascular endothelial cells (HBMEC) with DENV results in the activation of RNA sensors and production of proinflammatory cytokines, which culminate in cell death and endothelial permeability. Here, we evaluated the role of mitochondrial function and NADPH oxidase (NOX) activation for ROS generation in HBMEC infected by DENV and investigated whether altered cellular physiology could be a consequence of virus-induced oxidative stress. DENV-infected HBMECs showed a decrease in the maximal respiratory capacity and altered membrane potential, indicating functional mitochondrial alteration, what might be related to mtROS production. Indeed, mtROS was detected at later time points after infection. Specific inhibition of mtROS diminished virus replication, cell death, and endothelial permeability, but did not affect cytokine production. On the other hand, inhibition of NOX-associated ROS production decreased virus replication and cell death, as well as the secretion of inflammatory cytokines, including IL-6, IL-8, and CCL5. These results demonstrated that DENV replication in endothelial cells induces ROS production by different pathways, which impacts biological functions that might be relevant for dengue pathogenesis. Those data also indicate oxidative stress events as relevant therapeutical targets to avoid vascular permeability, inflammation, and neuroinvasion during DENV infection.

Optical Coherence Tomography Findings in Infectious Posterior Uveitis

PURPOSE

To describe and illustrate the main optical coherence tomography (OCT) findings of infectious uveitis.

METHODS

Narrative review.

RESULTS

Posterior segment OCT in patients with infectious uveitis reveals posterior hyaloid face precipitates, superficial retinal precipitates and infiltrates, foveolitis, retinitis, neuro-retinitis, choroidal granulomas, and choroiditis as main imaging biomarkers. Some of these features are specific to the underlying causing etiology and may support the diagnosis and the initiation of treatment. Some OCT features disappear completely with resolution; some others are associated with irreversible retinal damage.

CONCLUSIONS

OCT identifies different features of infectious uveitis into the vitreous, the retina, and the choroid. OCT characteristics, combined with other multimodal imaging features, are helpful in the differential diagnosis of infectious uveitis, the early detection of complications, and the assessment of the response to therapy.

Arenaviral infection causes bleeding in mice due to reduced serotonin release from platelets

Bleeding correlates with disease severity in viral hemorrhagic fevers. We found that the increase in type I interferon (IFN-I) in mice caused by infection with the Armstrong strain of lymphocytic choriomeningitis virus (LCMV; an arenavirus) reduced the megakaryocytic expression of genes encoding enzymes involved in lipid biosynthesis (cyclooxygenase 1 and thromboxane A synthase 1) and a thrombopoietic transcription factor (Nf-e2). The decreased expression of these genes was associated with reduced numbers of circulating platelets and defects in the arachidonic acid synthetic pathway, thereby suppressing serotonin release from δ-granules in platelets. Bleeding resulted when severe thrombocytopenia and altered platelet function reduced the amount of platelet-derived serotonin below a critical threshold. Bleeding was facilitated by the absence of the activity of the kinase Lyn or the administration of aspirin, an inhibitor of arachidonic acid synthesis. Mouse platelets were not directly affected by IFN-I because they lack the receptor for the cytokine (IFNAR1), suggesting that transfusion of normal platelets into LCMV-infected mice could increase the amount of platelet-released serotonin and help to control hemorrhage.

Evaluation of DENV-Induced Endothelial Cell Permeability by Measurements of Transendothelial Electrical Resistance (TEER) and Extravasation of Proteins and Virus

This chapter will discuss reliable and relatively easy and fast strategies to evaluate the integrity of endothelial cell monolayers when infected by dengue virus (DENV). Human brain microvascular endothelial cells (HBMEC) were exploited here as general model of vessel wall core, but it may also be used as an in vitro simplified model of blood brain barrier (BBB). The integrity of endothelial cells monolayer can be inferred using a transwell culture system by: (1) measuring transendothelial electrical resistance (TEER) using a Voltohmmeter; (2) analyzing the monolayer permeability to fluorescent-conjugated proteins and fluorimetric assay; (3) investigating virus extravasation by quantitative RT-PCR and plaque conventional assay. The rational to use those strategies is that vascular alterations are often observed during dengue infection, being associated to disease severity. The vasculature core consists of a barrier of endothelial cells, which are tightly adhered by the expression of adhesion molecules and tight junctions. This structure must be preserved in order to control the flux of cells and metabolites from the circulation to the tissues and to maintain vascular homeostasis. Therefore, experimental assays that allow evaluation of endothelial integrity can be useful platforms to further understand disease pathogenesis and screen pharmaceutical interventions to control vascular disturbance.

Measuring Transendothelial Electrical Resistance (TEER) for Dengue Infection Studies

A growing body of evidence demonstrates that endothelial cells (ECs) play a prominent role in immune-enhanced pathology seen in dengue virus (DENV) infection that might contribute to vascular permeability and hemorrhagic manifestations in severe dengue cases. However, it remains a question of whether DENV infection of ECs directly causes permeability or if extra-endothelial factors such as immune cell activation or antibody-dependent enhancement (ADE) are required. In this chapter, we detail the measurement of the transendothelial electrical resistance (TEER), a quantitative technique to measure the integrity of tight junction dynamics in cell culture models of endothelial monolayers and show that DENV infection of ECs does not cause endothelial permeability in vitro.

Brazilian Dengue Virus Type 2-Associated Renal Involvement in a Murine Model: Outcomes after Infection by Two Lineages of the Asian/American Genotype

Dengue virus type 2 (DENV-2) is, traditionally, the most studied serotype due to its association with explosive outbreaks and severe cases. In Brazil, almost 20 years after the first introduction in the 1990s, a new lineage (Lineage II) of the DENV-2 Asian/American genotype emerged and caused an epidemic with severe cases and hospitalizations. Severe dengue includes multiple organ failure, and renal involvement can be potentially related to increased mortality. In order to better understand the role of DENV infection in renal injury, here we aimed to investigate the outcomes of infection with two distinct lineages of DENV-2 Asian/American genotype in the kidney of a murine model. BALB/c mice were infected with Lineages I and II and tissues were submitted to histopathology, immunohistochemistry, histomorphometry and ultrastructural analysis. Blood urea nitrogen (BUN) was detected in blood sample accessed by cardiac puncture. A tendency in kidney weight increase was observed in mice infected with both lineages, but urea levels, on average, were increased only in mice infected with Lineage II. The DENV antigen was detected in the tissue of mice infected with Lineage II and morphological changes were similar to those observed in human dengue cases. Furthermore, the parameters such as organ weight, urea levels and morphometric analysis, showed significant differences between the two lineages in the infected BALB/c, which was demonstrated to be a suitable experimental model for dengue pathophysiology studies in kidneys.

Comparative analysis of liver involvement caused by two DENV-2 lineages using an immunocompetent murine model

Dengue (DEN) is the most prevalent arbovirus among humans, and four billion people live at risk of infection. The clinical manifestations of DEN are variable, and the disease may present subclinically or asymptomatically. A quarter of patients develop classical dengue (CD) or severe dengue (SD), which is potentially lethal and involves vascular permeability changes, severe hemorrhage and organ damage. The involvement of the liver is a fairly common feature in DEN, and alterations range from asymptomatic elevation of transaminases to acute liver failure. Since its introduction in Brazil in 1990, two strains of Dengue virus (DENV) serotype 2 (DENV-2) have been detected: Lineage I, which is responsible for an outbreak in 1991, and Lineage II, which caused an epidemic greater than the previous one and had a different epidemiological profile. To date, studies on different strains of the same serotype/genotype and their association with disease severity are scarce. In addition, one of the greatest challenges regarding the study of DEN pathogenesis and the development of drug and vaccine therapies is the absence of an animal model that reproduces the disease as it occurs in humans. The main goals of this study were to assess BALB/c mouse susceptibility experimentally infected by two distinct DENV-2 strains and characterize possible differences in the clinical signs and alterations induced in the liver resulting from those infections. Mice infected by the two DENV-2 lineages gained less weight than uninfected mice; however, their livers were slightly heavier. Increased AST and AST levels were observed in infected mice, and the number of platelets increased in the first 72 h of infection and subsequently decreased. Mice infected with both lineages presented leukocytosis but at different times of infection. The histopathological changes induced by both lineages were similar and comparable to the changes observed in DEN fatal cases. The viral genome was detected in two liver samples. The results demonstrate the susceptibility of BALB/c mice to both DENV-2 lineages and suggest that the changes induced by those strains are similar, although for some parameters, they are manifested at different times of infection.

Role of cytokines produced by T helper immune-modulators in dengue pathogenesis: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Modulation of the immune reaction is essential in the development of various diseases, including dengue's "Cytokine Tsunami", an increase in vascular permeability with concomitant severe vascular leakage. We aim to identify the role of T-helper (Th) cells, Th2 and Th7, with their related cytokines in dengue pathogenesis.

MATERIAL AND METHODS

Nine electronic databases and manual search were applied to detect available publications. A meta-analysis using a fixed- or random-effect model was performed to measure standardized mean difference (SMD) with 95% confidence interval (CI). The National Institute of Health (NIH) tools for observational cohort, cross-sectional, and case-control studies were used to examine the risk of bias. The protocol was recorded in PROSPERO with CRD42017060230.

RESULTS

A total of 38 articles were found including 19 case-control, 11 cross-sectional and 8 prospective cohort studies. We indicated that Th2 cytokines (IL-4, IL-6, IL-8) and Th17 cytokine (IL-17) in dengue patients were notably higher than in a healthy control group in acute phase (SMD = 1.59, 95% CI [0.68, 2.51], p = 0.001; SMD = 1.24, 95% CI [0.41, 2.06], p = 0.003; SMD = 1.13, 95% CI [0.61, 1.66], p<0.0001; SMD = 1.74, 95% CI [0.87, 2.61], p<0.0001), respectively.

CONCLUSIONS

This study provides evidence of the significant roles of IL-4, IL-6, IL-8, IL-10 and IL-17 in the pathogenesis of developing a severe reaction in dengue fever. However, to fully determine the association of Th cytokines with dengue, it is necessary to perform further studies to assess kinetic levels during the duration of the illness.

Clinical characteristics and risk factors for intracranial hemorrhage or infarction in patients with dengue

BACKGROUND

Intracranial hemorrhage (ICH) or infarction in dengue cases is rare but very challenging for clinicians. We report these uncommon complications of dengue patients and focused on the significant factors associated with ICH or infarction in dengue patients.

METHODS

This investigation was a retrospective study of 182 adult dengue patients who received brain computed tomography at three Taiwan hospitals during the 2014 and 2015 dengue outbreaks. This included 13 hemorrhage cases, 26 infarction cases and 143 cases without brain infarction or hemorrhage.

RESULTS

Among them, 13 (7.14%) suffered from ICH (6 had subdural hemorrhage, 3 had subarachnoid hemorrhage, 1 had subdural and subarachnoid hemorrhage, and 3 had intracerebral hemorrhage) and 26 (14.3%) had brain infarction. The overall mortality rate was 4/13 (30.8%) in the ICH group and 3/26 (11.5%) in the infarction group. The significant variables from the univariate analysis, including difference between 2014 and 2015, age, history of cerebrovascular accident, bone pain, arthralgia, dizziness, altered consciousness, and a higher Charlson comorbidity score. Multivariate analysis revealed that significant risk factors for ICH/infarction in dengue cases were the year of occurrence, 2014 vs. 2015 (p < 0.0001, OR = 25.027, 95% CI = 8.205-76.336), Charlson score >4 (p = 0.01, OR = 3.764, 95% CI = 1.364-10.386) and altered consciousness (p < 0.0001, OR = 6.3, 95% CI = 2.242-17.7). The factors physicians should notice in dengue endemic regions for brain infarction or ICH include altered consciousness and a Charlson score >4, especially in the year that a higher frequency of infarction/ICH was observed.

Contact System Activation in Plasma from Dengue Patients Might Harness Endothelial Virus Replication through the Signaling of Bradykinin Receptors

Since exacerbated inflammation and microvascular leakage are hallmarks of dengue virus (DENV) infection, here we interrogated whether systemic activation of the contact/kallikrein-kinin system (KKS) might hamper endothelial function. In vitro assays showed that dextran sulfate, a potent contact activator, failed to generate appreciable levels of activated plasma kallikrein (PKa) in the large majority of samples from a dengue cohort (n = 70), irrespective of severity of clinical symptoms. Impaired formation of PKa in dengue-plasmas correlated with the presence of cleaved Factor XII and high molecular weight kininogen (HK), suggesting that the prothrombogenic contact system is frequently triggered during the course of infection. Using two pathogenic arboviruses, DENV or Zika virus (ZIKV), we then asked whether exogenous BK could influence the outcome of infection of human brain microvascular endothelial cells (HBMECs). Unlike the unresponsive phenotype of Zika-infected HBMECs, we found that BK, acting via B2R, vigorously stimulated DENV-2 replication by reverting nitric oxide-driven apoptosis of endothelial cells. Using the mouse model of cerebral dengue infection, we next demonstrated that B2R targeting by icatibant decreased viral load in brain tissues. In summary, our study suggests that contact/KKS activation followed by BK-induced enhancement of DENV replication in the endothelium may underlie microvascular pathology in dengue.

Association of single nucleotide polymorphisms in TNF-α (-308G/A and -238G/A) to dengue: Case-control and meta-analysis study

Dengue is an acute viral disease whose clinical condition is related to the interaction of factors related to the Dengue virus (DENV), environment and the host, with the immunity of the human host contributing a substantial role in the pathogenesis of DENV infection. Studies have demonstrated that single nucleotide polymorphisms (SNPs) in the promoter regions of cytokine genes such as tumor necrosis factor (TNF-α) affect transcription and/or expression; and therefore, may influence the pathogenesis of infectious diseases, such as dengue. Consequently, the objective of this study was to assess through a case-control study whether there was an association between the presence of SNPs -308G/A and -238G/A in the TNF-α gene and 158 patients with dengue and 123 controls. No association was found between the SNPs and the dengue cases in the study population. We then performed a meta-analysis, retrieving data from case-control studies in the literature for the same polymorphisms. For SNP-308G/A, the GG genotype was associated with dengue fever (DF) risk (OR = 1.24, 1.00-1.53; p = 0.05; I² = 0%), while the GA genotype (OR = 0.75, 0.60-0.93; p = 0.01; I² = 0%) and allele A (OR = 0.75, 0.60-0.93; p = 0.01; I² = 0%) were associated with protection. The genotype GG population in the Asian continent (OR = 1.81 [1.06, 3.09], p = 0.03, I² = 0%) and American (OR = 1.29 [1.00, 1.65], p = 0.05, I² = 0%) was also associated with protection in the comparison between the cases versus the control group. In each comparison, the dominant model AA + GA (p < 0.00001) conferred protection. For SNP-238G/A the GA genotype was associated with risk for dengue hemorrhagic fever (DHF; OR = 2.17, 1.28-3.67; p = 0.004; I² = 0%)), and the dominant AA + GA model (p < 0.00001) was associated with protection in each comparison. In summary, our results did not associate SNPs in the TNF-α gene to dengue in the Brazilian northeast population. However, combined literature data suggested the effect of the GG and GA genotypes of the SNP-308G/A on risk and protection, respectively, in Asian and American populations.

Flavivirus Infection Associated with Cerebrovascular Events

Arthropod-borne viruses (arboviruses) of the genus Flavivirus are distributed globally and cause significant human disease and mortality annually. Flavivirus infections present a spectrum of clinical manifestations, ranging from asymptomatic to severe manifestations, including hemorrhage, encephalitis and death. Herein, we describe 3 case reports of cerebrovascular involvement in patients infected by dengue and Zika viruses in Sao Jose do Rio Preto, São Paulo State, Brazil, a hyperendemic area for arbovirus circulation, including dengue, yellow fever, chikungunya and Saint Louis encephalitis viruses. Our findings highlight the potential threat that unusual clinical manifestations may pose to arbovirus disease management and recovery.

Multivariate time-series analysis of biomarkers from a dengue cohort offers new approaches for diagnosis and prognosis

Dengue is a major public health problem worldwide with distinct clinical manifestations: an acute presentation (dengue fever, DF) similar to other febrile illnesses (OFI) and a more severe, life-threatening form (severe dengue, SD). Due to nonspecific clinical presentation during the early phase of dengue infection, differentiating DF from OFI has remained a challenge, and current methods to determine severity of dengue remain poor early predictors. We present a prospective clinical cohort study conducted in Caracas, Venezuela from 2001-2005, designed to determine whether clinical and hematological parameters could distinguish DF from OFI, and identify early prognostic biomarkers of SD. From 204 enrolled suspected dengue patients, there were 111 confirmed dengue cases. Piecewise mixed effects regression and nonparametric statistics were used to analyze longitudinal records. Decreased serum albumin and fibrinogen along with increased D-dimer, thrombin-antithrombin complex, activated partial thromboplastin time and thrombin time were prognostic of SD on the day of defervescence. In the febrile phase, the day-to-day rates of change in serum albumin and fibrinogen concentration, along with platelet counts, were significantly decreased in dengue patients compared to OFI, while the day-to-day rates of change of lymphocytes (%) and thrombin time were increased. In dengue patients, the absolute lymphocytes to neutrophils ratio showed specific temporal increase, enabling classification of dengue patients entering the critical phase with an area under the ROC curve of 0.79. Secondary dengue patients had elongation of Thrombin time compared to primary cases while the D-dimer formation (fibrinolysis marker) remained always lower for secondary compared to primary cases. Based on partial analysis of 31 viral complete genomes, a high frequency of C-to-T transitions located at the third codon position was observed, suggesting deamination events with five major hot spots of amino acid polymorphic sites outside in non-structural proteins. No association of severe outcome was statistically significant for any of the five major polymorphic sites found. This study offers an improved understanding of dengue hemostasis and a novel way of approaching dengue diagnosis and disease prognosis using piecewise mixed effect regression modeling. It also suggests that a better discrimination of the day of disease can improve the diagnostic and prognostic classification power of clinical variables using ROC curve analysis. The piecewise mixed effect regression model corroborated key early clinical determinants of disease, and offers a time-series approach for future vaccine and pathogenesis clinical studies.

Transcutaneous Administration of Dengue Vaccines

In the present study, we evaluated the immunological responses induced by dengue vaccines under experimental conditions after delivery via a transcutaneous (TC) route. Vaccines against type 2 Dengue virus particles (DENV2 New Guinea C (NGC) strain) combined with enterotoxigenic Escherichia coli (ETEC) heat-labile toxin (LT) were administered to BALB/c mice in a three-dose immunization regimen via the TC route. As a control for the parenteral administration route, other mouse groups were immunized with the same vaccine formulation via the intradermic (ID) route. Our results showed that mice vaccinated either via the TC or ID routes developed similar protective immunity, as measured after lethal challenges with the DENV2 NGC strain. Notably, the vaccine delivered through the TC route induced lower serum antibody (IgG) responses with regard to ID-immunized mice, particularly after the third dose. The protective immunity elicited in TC-immunized mice was attributed to different antigen-specific antibody properties, such as epitope specificity and IgG subclass responses, and cellular immune responses, as determined by cytokine secretion profiles. Altogether, the results of the present study demonstrate the immunogenicity and protective properties of a dengue vaccine delivered through the TC route and offer perspectives for future clinical applications.

Role of RNA-binding proteins during the late stages of Flavivirus replication cycle

The genus Flavivirus encompasses several worldwide-distributed arthropod-borne viruses including, dengue virus, Japanese encephalitis virus, West Nile virus, yellow fever virus, Zika virus, and tick-borne encephalitis virus. Infection with these viruses manifest with symptoms ranging from febrile illness to life- threatening hypotensive shock and encephalitis. Therefore, flaviviruses pose a great risk to public health. Currently, preventive measures are falling short to control epidemics and there are no antivirals against any Flavivirus.Flaviviruses carry a single stranded positive-sense RNA genome that plays multiple roles in infected cells: it is translated into viral proteins, used as template for genome replication, it is the precursor of the subgenomic flaviviral RNA and it is assembled into new virions. Furthermore, viral RNA genomes are also packaged into extracellular vesicles, e.g. exosomes, which represent an alternate mode of virus dissemination.Because RNA molecules are at the center of Flavivirus replication cycle, viral and host RNA-binding proteins (RBPs) are critical determinants of infection. Numerous studies have revealed the function of RBPs during Flavivirus infection, particularly at the level of RNA translation and replication. These proteins, however, are also critical participants at the late stages of the replication cycle. Here we revise the function of host RBPs and the viral proteins capsid, NS2A and NS3, during the packaging of viral RNA and the assembly of new virus particles. Furthermore, we go through the evidence pointing towards the importance of host RBPs in mediating cellular RNA export with the idea that the biogenesis of exosomes harboring Flavivirus RNA would follow an analogous pathway.

ZIKV-Specific NS1 Epitopes as Serological Markers of Acute Zika Virus Infection

BACKGROUND

Zika virus (ZIKV) infections have reemerged as a global health issue due to serious clinical complications. Development of specific serological assays to detect and differentiate ZIKV from other cocirculating flaviviruses for accurate diagnosis remains a challenge.

METHODS

We investigated antibody responses in 51 acute ZIKV-infected adult patients from Campinas, Brazil, including 7 pregnant women who later delivered during the study. Using enzyme-linked immunosorbent assays, levels of antibody response were measured and specific epitopes identified.

RESULTS

Several antibody-binding hot spots were identified in ZIKV immunogenic antigens, including membrane, envelope (E) and nonstructural protein 1 (NS1). Interestingly, specific epitopes (2 from E and 2 from NS1) strongly recognized by ZIKV-infected patients' antibodies were identified and were not cross-recognized by dengue virus (DENV)-infected patients' antibodies. Corresponding DENV peptides were not strongly recognized by ZIKV-infected patients' antibodies. Notably, ZIKV-infected pregnant women had specific epitope recognition for ZIKV NS1 (amino acid residues 17-34), which could be a potential serological marker for early ZIKV detection.

CONCLUSIONS

This study identified 6 linear ZIKV-specific epitopes for early detection of ZIKV infections. We observed differential epitope recognition between ZIKV-infected and DENV-infected patients. This information will be useful for developing diagnostic methods that differentiate between closely related flaviviruses.

Extracellular vesicles of U937 macrophage cell line infected with DENV-2 induce activation in endothelial cells EA.hy926

Endothelial activation and alteration during dengue virus (DENV) infection are multifactorial events; however, the role of extracellular vesicles (EVs) in these phenomena is not known. In the present study, we characterized the EVs released by DENV-2 infected U937 macrophage cell line and evaluated the changes in the physiology and integrity of the EA.hy926 endothelial cells exposed to them. U937 macrophages were infected, supernatants were collected, and EVs were purified and characterized. Then, polarized endothelial EA.hy926 cells were exposed to the EVs for 24 h, and the transendothelial electrical resistance (TEER), monolayer permeability, and the expression of tight junction and adhesion proteins and cytokines were evaluated. The isolated EVs from infected macrophages corresponded to exosomes and apoptotic bodies, which contained the viral NS3 protein and different miRs, among other products. Exposure of EA.hy926 cells to EVs induced an increase in TEER, as well as changes in the expression of VE-cadherin and ICAM in addition leads to an increase in TNF-α, IP-10, IL-10, RANTES, and MCP-1 secretion. These results suggest that the EVs of infected macrophages transport proteins and miR that induce early changes in the physiology of the endothelium, leading to its activation and eliciting a defense program against damage during first stages of the disease, even in the absence of the virus.

Inflammation During Virus Infection: Swings and Roundabouts

Inflammation constitutes a concerted series of cellular and molecular responses that follow disturbance of systemic homeostasis, by either toxins or infectious organisms. Leukocytes modulate inflammation through production of secretory mediators, like cytokines and chemokines, which work in an autocrine and/or paracrine manner. These mediators can either promote or attenuate the inflammatory response and depending on differential temporal and spatial expression play a crucial role in the outcome of infection. Even though the objective is clearance of the pathogen with minimum damage to host, the pathogenesis of multiple human pathogenic viruses has been suggested to emanate from a dysregulation of the inflammatory response, sometimes with fatal consequences. This review discusses the nature and the outcome of inflammatory response, which is triggered in the human host subsequent to infection by single-sense plus-strand RNA viruses. In view of such harmful effects of a dysregulated inflammatory response, an exogenous regulation of these reactions by either interference or supplementation of critical regulators has been suggested. Currently multiple such factors are being tested for their beneficial and adverse effects. A successful use of such an approach in diseases of viral etiology can potentially protect the affected individual without directly affecting the virus life cycle. Further, such approaches whenever applicable would be useful in mitigating death and/or debility that is caused by the infection of those viruses which have proven particularly difficult to control by either prophylactic vaccines and/or therapeutic strategies using specific antiviral drugs.

Effect of high doses of vitamin D supplementation on dengue virus replication, Toll-like receptor expression, and cytokine profiles on dendritic cells

Dengue, caused by dengue virus (DENV) infection, is a public health problem worldwide. Although DENV pathogenesis has not yet been fully elucidated, the inflammatory response is a hallmark feature in severe DENV infection. Although vitamin D (vitD) can promote the innate immune response against virus infection, no studies have evaluated the effects of vitD on DENV infection, dendritic cells (DCs), and inflammatory response regulation. This study aimed to assess the impact of oral vitD supplementation on DENV-2 infection, Toll-like receptor (TLR) expression, and both pro- and anti-inflammatory cytokine production in monocyte-derived DCs (MDDCs). To accomplish this, 20 healthy donors were randomly divided into two groups and received either 1000 or 4000 international units (IU)/day of vitD for 10 days. During pre- and post-vitD supplementation, peripheral blood samples were taken to obtain MDDCs, which were challenged with DENV-2. We found that MDDCs from donors who received 4000 IU/day of vitD were less susceptible to DENV-2 infection than MDDCs from donors who received 1000 IU/day of vitD. Moreover, these cells showed decreased mRNA expression of TLR3, 7, and 9; downregulation of IL-12/IL-8 production; and increased IL-10 secretion in response to DENV-2 infection. In conclusion, the administration of 4000 IU/day of vitD decreased DENV-2 infection. Our findings support a possible role of vitD in improving the innate immune response against DENV. However, further studies are necessary to determine the role of vitD on DENV replication and its innate immune response modulation in MDDCs.

Ubiquitin-based modifications in endothelial cell-cell contact and inflammation

Endothelial cell-cell contacts are essential for vascular integrity and physiology, protecting tissues and organs from edema and uncontrolled invasion of inflammatory cells. The vascular endothelial barrier is dynamic, but its integrity is preserved through a tight control at different levels. Inflammatory cytokines and G-protein-coupled receptor agonists, such as histamine, reduce endothelial integrity and increase vascular leakage. This is due to elevated myosin-based contractility, in conjunction with phosphorylation of proteins at cell-cell contacts. Conversely, reducing contractility stabilizes or even increases endothelial junctional integrity. Rho GTPases are key regulators of such cytoskeletal dynamics and endothelial cell-cell contacts. In addition to signaling-induced regulation, the expression of junctional proteins, such as occludin, claudins and vascular endothelial cadherin, also controls endothelial barrier function. There is increasing evidence that, in addition to protein phosphorylation, ubiquitylation (also known as ubiquitination) is an important and dynamic post-translational modification that regulates Rho GTPases, junctional proteins and, consequently, endothelial barrier function. In this Review, we discuss the emerging role of ubiquitylation and deubiquitylation events in endothelial integrity and inflammation. The picture that emerges is one of increasing complexity, which is both fascinating and promising given the clinical relevance of vascular integrity in the control of inflammation, and of tissue and organ damage.

Significance of RANTES-CCR5 axis and linked downstream immunomodulation in Dengue pathogenesis: A study from Guwahati, India

We aimed to evaluate the significance of the RANTES-CCR5 axis and resulting immunomodulatory status in Dengue pathogenesis involving a Guwahati, India based population where Dengue cases have increased alarmingly. An increased CC-chemokine receptor type 5 (CCR5) messenger RNA expression and CCR5 positive cell count profile was observed in Dengue cases, the highest being in severe cases. CCR5 ligand RANTES expression was significantly decreased in Dengue cases and inversely correlated with Dengue viremia fold change in severe cases. Monocytes are involved in Dengue virus homing and replication. Its levels and activation profile were higher in Dengue cases. A hyper Th1-biased immunomodulatory profile with upregulated tumor necrosis factor-α levels, and downregulated expression of antiviral cytokine interferon-γ and key regulatory Th2 anti-inflammatory cytokine interleukin 10 was observed in severe Dengue cases compared with mild Dengue cases and controls. The results, therefore, suggest the significance of RANTES-CCR5 axis deregulation and resulting altered immunomodulation in Dengue pathogenesis, and holds prognostic and therapeutic significance.

Risk of stroke in patients with dengue fever: a population-based cohort study

BACKGROUND

Stroke is a severe neurologic complication of dengue fever, described in only a few case reports. The incidence and risk factors for stroke in patients with dengue remain unclear. We conducted a population-based retrospective cohort study to investigate the risk of stroke in patients with dengue.

METHODS

Using data from the Taiwan National Health Insurance Research Database, we included a total of 13 787 patients with dengue newly diagnosed between 2000 and 2012. The control cohort consisted of patients who did not have dengue, matched 1:1 by demographic characteristics and stroke-related comorbidities. We calculated the cumulative incidences and hazard ratios (HRs) of stroke in both cohorts using Kaplan-Meier curves and Cox proportional hazards regression.

RESULTS

The overall incidence rate of stroke was 5.33 per 1000 person-years in the dengue cohort and 3.72 per 1000 person-years in the control cohort, with an adjusted HR of 1.16 (95% confidence interval [CI] 1.01-1.32). The risk of stroke among patients with dengue was highest in the first 2 months after diagnosis (25.53 per 1000 person-years, adjusted HR 2.49, 95% CI 1.48-4.18).

INTERPRETATION

Dengue fever was associated with an increased risk of stroke in the first few months after diagnosis. The effect of dengue on stroke may be acute rather than chronic.

Dengue Virus Infection of Blood-Brain Barrier Cells: Consequences of Severe Disease

More than 500 million people worldwide are infected each year by any of the four-dengue virus (DENV) serotypes. The clinical spectrum caused during these infections is wide and some patients may develop neurological alterations during or after the infection, which could be explained by the cryptic neurotropic and neurovirulent features of flaviviruses like DENV. Using in vivo and in vitro models, researchers have demonstrated that DENV can affect the cells from the blood-brain barrier (BBB) in several ways, which could result in brain tissue damage, neuronal loss, glial activation, tissue inflammation and hemorrhages. The latter suggests that BBB may be compromised during infection; however, it is not clear whether the damage is due to the infection per se or to the local and/or systemic inflammatory response established or activated by the BBB cells. Similarly, the kinetics and cascade of events that trigger tissue damage, and the cells that initiate it, are unknown. This review presents evidence of the BBB cell infection with DENV and the response established toward it by these cells; it also describes the consequences of this response on the nervous tissue, compares these evidence with the one reported with neurotropic viruses of the Flaviviridae family, and shows the complexity and unpredictability of dengue and the neurological alterations induced by it. Clinical evidence and in vitro and in vivo models suggest that this virus uses the bloodstream to enter nerve tissue where it infects the different cells of the neurovascular unit. Each of the cell populations respond individually and collectively and control infection and inflammation, in other cases this response exacerbates the damage leaving irreversible sequelae or causing death. This information will allow us to understand more about the complex disease known as dengue, and its impact on a specialized and delicate tissue like is the nervous tissue.

Zika Virus Infection Induces Elevation of Tissue Factor Production and Apoptosis on Human Umbilical Vein Endothelial Cells

Zika virus (ZIKV) infection is typically characterized by a mild disease presenting with fever, maculopapular rash, headache, fatigue, myalgia, and arthralgia. A recent animal study found that ZIKV-infected pregnant Ifnar ^-/-mice developed vascular damage in the placenta and reduced amount of fetal capillaries. Moreover, ZIKV infection causes segmental thrombosis in the umbilical cord of pregnant rhesus macaques. Furthermore, several case reports suggest that ZIKV infection cause coagulation disorders. These results suggest that ZIKV could cause an alteration in the host hemostatic response, however, the mechanism has not been investigated thus far. This paper aims to determine whether ZIKV infection on HUVECs induces apoptosis and elevation of tissue factor (TF) that leads to activation of secondary hemostasis. We infected HUVECs with two ZIKV strains and performed virus titration, immunostaining, and flow cytometry to confirm and quantify infection. We measured TF concentrations with flow cytometry and performed thrombin generation test (TGT) as a functional assay to assess secondary hemostasis. Furthermore, we determined the amount of cell death using flow cytometry. We also performed enzyme-linked immunosorbent assay (ELISA) to determine interleukin (IL)-6 and IL-8 production and conducted blocking experiments to associate these cytokines with TF expression. Both ZIKV strains infected and replicated to high titers in HUVECs. We found that infection induced elevation of TF expressions. We also showed that increased TF expression led to shortened TGT time. Moreover, the data revealed that infection induced apoptosis. In addition, there was a significant increase of IL-6 and IL-8 production in infected cells. Here we provide in vitro evidence that infection of HUVECs with ZIKV induces apoptosis and elevation of TF expression that leads to activation of secondary hemostasis.

Jaw Osteonecrosis Preceded by Dengue Fever - Possible Pathogenetic Mechanism

Introduction:

Osteonecrosis of jaw (ONJ) is a debilitating condition which can lead to compromised dentition. Various causes for ONJ are suggested in the literature such as drugs, trauma, radiation, chemicals, bacterial, and fungal infections. Knowing etiology for particular case of ONJ is important to prevent further progression of this debilitating condition. It is the first case of ONJ reported with dengue virus as a possible etiology.

Case Report:

This article presents a case of 46-year-old male patient with extensive osteonecrosis of maxilla preceded by dengue fever. In the present case, all known causes for osteonecrosis were ruled out. The present article discusses dengue infection as a possible etiologic agent for ONJ.

Conclusion:

In the present case, probable cause for ONJ can be established as a dengue virus necessitating the need for proper preventive methods to avoid further complication of osteonecrosis.

Expression of Four Cytokine/Chemokine Genes in Peripheral Blood Mononuclear Cells infected with Dengue Virus

Overproduction of numerous pro-inflammatory cytokines, during dengue virus (DENV) infection, has been related to plasma leakage in the vascular endothelium and studied elsewhere with conflicting results. The current study objective is to evaluate the expression of four cytokine/chemokine genes following DENV-2 infection within peripheral blood mononuclear cells (PBMC) isolated from a healthy donor. Venous blood was drawn,  and PBMCs were isolated using Ficoll density gradient centrifugation. Cells were maintained in culture medium and infected with Indonesian isolate of DENV-2. Cells were harvested and followed by total RNA extraction and reverse-transcription into cDNA using oligo d(T) primers and Reverse Transcriptase enzyme system. The SYBR Green-based quantitative qRT-PCR was used to calculate the relative expression of IL-6, IL-8, IP-10 and MIP-1β- encoding genes during infection time points, compared to uninfected cell controls. The observation of the cytokine was on the 6 and 18 hours post-infection. The different expression profiles of cytokines/chemokines were observed. The up-regulation of gene expression was observed for IL-8 and IP-10. In contrast, the down-regulatory of IL-6 and MIP-1β genes expression was documented during the infection period. The cytokine IL-8 and IP-10 are potent chemoattractants  in the recruitment  of neutrophil, basophil, and lymphocytes in response to an infection. The highlight of this study is on the up-regulation of IL-8 and IP-10 genes expression which may confirm the roles of these chemokines in the pathogenesis of dengue infection.

Dengue haemorrhagic fever: a job done via exosomes?

Dengue fever is one of those unique diseases where host immune responses largely determine the pathogenesis and its severity. Earlier studies have established the fact that dengue virus (DENV) infection causes haemorrhagic fever and shock syndrome, but it is not directly responsible for exhibiting these clinical symptoms. It is noteworthy that clinically, vascular leakage syndrome does not develop for several days after infection despite a robust innate immune response that elicits the production of proinflammatory and proangiogenic cytokines. The onset of hyperpermeability in severe cases of dengue disease takes place around the time of defervescence and after clearance of viraemia. Extracellular vesicles are known to carry biological information (mRNA, miRNA, transcription factors) from their cells of origin and have emerged as a significant vehicle for horizontal transfer of stress signals. In dengue virus infection, the relevance of exosomes can be instrumental since the majority of the immune responses in severe dengue involve heavy secretion and circulation of pro-inflammatory cytokines and chemokines. Here, we present an updated review which will address the unique and puzzling features of hyperpermeability associated with DENV infection with a special focus on the role of secreted extracellular vesicles.

Endothelins in inflammatory neurological diseases

Endothelins were discovered more than thirty years ago as potent vasoactive compounds. Beyond their well-documented cardiovascular properties, however, the contributions of the endothelin pathway have been demonstrated in several neuroinflammatory processes and the peptides have been reported as clinically relevant biomarkers in neurodegenerative diseases. Several studies report that endothelin-1 significantly contributes to the progression of neuroinflammatory processes, particularly during infections in the central nervous system (CNS), and is associated with a loss of endothelial integrity at the blood brain barrier level. Because of the paucity of clinical trials with endothelin-1 antagonists in several infectious and non-infectious neuroinflammatory diseases, it remains an open question whether the 21 amino acid peptide is a mediator/modulator rather than a biomarker of the progression of neurodegeneration. This review focuses on the potential roles of endothelins in the pathology of neuroinflammatory processes, including infectious diseases of viral, bacterial or parasitic origin in which the synthesis of endothelins or its pharmacology have been investigated from the cell to the bedside in several cases, as well as in non-infectious inflammatory processes such as neurodegenerative disorders like Alzheimers Disease or central nervous system vasculitis.

Unique Francisella Phosphatidylethanolamine Acts as a Potent Anti-Inflammatory Lipid

Virulent Francisella tularensis subsp. tularensis (Ftt) is a dynamic, intracellular, bacterial pathogen. Its ability to evade and rapidly suppress host inflammatory responses is considered a key element for its profound virulence. We previously established that Ftt lipids play a role in inhibiting inflammation, but we did not determine the lipid species mediating this process. Here, we show that a unique, abundant, phosphatidylethanolamine (PE), present in Francisella, contributes to driving the suppression of inflammatory responses in human and mouse cells. Acyl chain lengths of this PE, C24: 0 and C10: 0, were key to the suppressive capabilities of Francisella PE. Addition of synthetic PE 24: 0-10: 0 resulted in the accumulation of PE in host cells for up to 24 h of incubation, and recapitulated the inhibition of inflammatory responses observed with native Ftt PE. Importantly, this novel PE significantly inhibited inflammatory responses driven by a medically and globally important flavivirus, dengue fever virus. Thus, targeting these lipids and/or the pathways that they manipulate represents a new strategy to combat immunosuppression engendered by Ftt, but they also show promise as a novel therapeutic intervention for significant viral infections.

Dengue Virus Induces Increased Activity of the Complement Alternative Pathway in Infected Cells

Severe dengue virus (DENV) infection is associated with overactivity of the complement alternative pathway (AP) in patient studies. Here, the molecular changes in components of the AP during DENV infection in vitro were investigated. mRNA for factor H (FH), a major negative regulator of the AP, was significantly increased in DENV-infected endothelial cells (EC) and macrophages, but, in contrast, production of extracellular FH protein was not. This discord was not seen for the AP activator factor B (FB), with DENV induction of both FB mRNA and protein, nor was it seen with Toll-like receptor 3 or 4 stimulation of EC and macrophages, which induces both FH and FB mRNA and protein. Surface-bound and intracellular FH protein was, however, induced by DENV, but only in DENV antigen-positive cells, while in two other DENV-susceptible immortalized cell lines (ARPE-19 and human retinal endothelial cells), FH protein was induced both intracellularly and extracellularly by DENV infection. Regardless of the cell type, there was an imbalance in AP components and an increase in markers of complement AP activity associated with DENV-infected cells, with lower FH relative to FB protein, an increased ability to promote AP-mediated lytic activity, and increased deposition of complement component C3b on the surface of DENV-infected cells. For EC in particular, these changes are predicted to result in higher complement activity in the local cellular microenvironment, with the potential to induce functional changes that may result in increased vascular permeability, a hallmark of dengue disease.IMPORTANCE Dengue virus (DENV) is a significant human viral pathogen with a global medical and economic impact. DENV may cause serious and life-threatening disease, with increased vascular permeability and plasma leakage. The pathogenic mechanisms underlying these features remain unclear; however, overactivity of the complement alternative pathway has been suggested to play a role. In this study, we investigate the molecular events that may be responsible for this observed alternative pathway overactivity and provide novel findings of changes in the complement system in response to DENV infection in primary cell types that are a major target for DENV infection (macrophages) and pathogenesis (endothelial cells) in vivo Our results suggest a new dimension of cellular events that may influence endothelial cell barrier function during DENV infection that could expand strategies for developing therapeutics to prevent or control DENV-mediated vascular disease.

NS1 Antigenemia and Viraemia Load: Potential Markers of Progression to Dengue Fatal Outcome?

Dengue is a worldwide problem characterized by a multifactorial pathogenesis. Considering the viral components, it is known that high viremia or high levels of the secreted nonstructural protein 1 (NS1) may be associated with a more severe disease. We aimed to characterize the NS1 antigenemia and viremia in dengue fatal and non-fatal cases, as potential markers of progression to a fatal outcome. NS1 antigenemia and viremia were determined in Brazilian dengue fatal cases (n = 40) and non-fatal cases (n = 40), representative of the four dengue virus (DENV) serotypes. Overall, the fatal cases presented higher NS1 levels and viremia. Moreover, the fatal cases from secondary infections showed significantly higher NS1 levels than the non-fatal ones. Here, irrespective of the disease outcome, DENV-1 cases presented higher NS1 levels than the other serotypes. However, DENV-2 and DENV-4 fatal cases had higher NS1 antigenemia than the non-fatal cases with the same serotype. The viremia in the fatal cases was higher than in the non-fatal ones, with DENV-3 and DENV-4 presenting higher viral loads. Viral components, such as NS1 and viral RNA, may be factors influencing the disease outcome. However, the host immune status, comorbidities, and access to adequate medical support cannot be ruled out as interfering in the disease outcome.

Evaluation of concurrent malaria and dengue infections among febrile patients

CONTEXT

Despite a wide overlap between endemic areas for two important vector-borne infections, malaria and dengue, published reports of co-infections are scarce till date.

AIMS

To find the incidence of dengue and malaria co-infection as well as to ascertain the severity of such dengue and malaria co-infection based on clinical and haematological parameters.

SETTING AND DESIGN

Observational, retrospective cross-sectional study was designed including patients who consulted the tertiary care hospital of Ahmedabad seeking treatment for fever compatible with malaria and/or dengue.

SUBJECTS AND METHODS

A total of 8364 serum samples from clinically suspected cases of fever compatible with malaria and/or dengue were collected. All samples were tested for dengue NS-1 antigen before 5 days of onset of illness and for dengue IgM after 5 days of onset of illness. In all samples, malaria diagnosis was based on the identification of Plasmodium parasites on a thin and thick blood films microscopy.

RESULTS

Only 10.27% (859) patients with fever were tested positive for dengue and 5.1% (434) were tested positive for malaria. 3.14% (27) dengue cases show concurrent infection with malarial parasites. Hepatomegaly and jaundice 37.03% (10), haemorrhagic manifestations 18.51% (5) and kidney failure 3.7% (1), haemoglobin <12 g/dl 100% (27) and thrombocytopenia (platelet count <150,000/cmm) 96.29% (26) were common in malaria and dengue co-infections and were much more common in Plasmodium falciparum infections.

CONCLUSION

All febrile patients must be tested for malaria and dengue, both otherwise one of them will be missed in case of concurrent infections which could lead to severe diseases with complications.

The Tolerability and Efficacy of Oral Isotonic Solution versus Plain Water in Dengue Patients: A Randomized Clinical Trial

Background

Plasma leakage plays an important role in dengue infection, and this condition can lead to hemoconcentration, hypovolemia, and shock. Fluid replacement is the main treatment for dengue. There is a lack of evidence to support certain oral fluid therapy as a treatment for dengue patients.

Objectives

The objective of this study is to evaluate tolerability and efficacy of oral isotonic solution (OIS) compared to plain water as a fluid replacement in dengue patients.

Materials and Methods

A randomized, clinical trial with single-blinded groups was conducted to compare tolerability and efficacy of OIS and plain water in dengue patients. We evaluated gastrointestinal disturbances (nausea, vomiting, and bloating), body temperature, mean arterial pressure (MAP), fluid balance, hematocrit, Na⁺, and K⁺ levels. Data were analyzed with SPSS 20.0, and figures were made with GraphPad Prism version 5.01.

Results

Twenty four subjects were included and divided equally into two groups. Our results showed that there are no significant differences but indicate several noteworthy trends. The intervention group (OIS) experienced less nausea, less vomiting, had positive fluid balance and higher MAP, and became afebrile faster compared to the control group (plain water).

Conclusion

Although not statistically significant, this study shows the trend that OIS is well-tolerated and effective for dengue patients compared to plain water.

High dengue virus load differentially modulates human microvascular endothelial barrier function during early infection

Plasma leakage is the main pathophysiological feature in severe dengue, resulting from altered vascular barrier function associated with an inappropriate immune response triggered upon infection. The present study investigated functional changes using an electric cell-substrate impedance sensing system in four (brain, dermal, pulmonary and retinal) human microvascular endothelial cell (MEC) lines infected with purified dengue virus, followed by assessment of cytokine profiles and the expression of inter-endothelial junctional proteins. Modelling of changes in electrical impedance suggests that vascular leakage in dengue-infected MECs is mostly due to the modulation of cell-to-cell interactions, while this loss of vascular barrier function observed in the infected MECs varied between cell lines and DENV serotypes. High levels of inflammatory cytokines (IL-6 and TNF-α), chemokines (CXCL1, CXCL5, CXCL11, CX3CL1, CCL2 and CCL20) and adhesion molecules (VCAM-1) were differentially produced in the four infected MECs. Further, the tight junctional protein, ZO-1, was down-regulated in both the DENV-1-infected brain and pulmonary MECs, while claudin-1, PECAM-1 and VE-cadherin were differentially expressed in these two MECs after infection. Non-purified virus stock was also studied to investigate the impact of virus stock purity on dengue-specific immune responses, and the results suggest that virus stock propagated through cell culture may include factors that mask or alter the DENV-specific immune responses of the MECs. The findings of the present study show that high DENV load differentially modulates human microvascular endothelial barrier function and disrupts the function of inter-endothelial junctional proteins during early infection with organ-specific cytokine production.

Neurological Manifestations of Dengue Infection

Dengue counts among the most commonly encountered arboviral diseases, representing the fastest spreading tropical illness in the world. It is prevalent in 128 countries, and each year >2.5 billion people are at risk of dengue virus infection worldwide. Neurological signs of dengue infection are increasingly reported. In this review, the main neurological complications of dengue virus infection, such as central nervous system (CNS), peripheral nervous system, and ophthalmic complications were discussed according to clinical features, treatment and possible pathogenesis. In addition, neurological complications in children were assessed due to their atypical clinical features. Finally, dengue infection and Japanese encephalitis were compared for pathogenesis and main clinical manifestations.