Report of a fatal case of dengue infection with hepatitis: demonstration of dengue antigens in hepatocytes and liver apoptosis

Early biomarkers for prediction of severe manifestations of dengue fever: a systematic review and a meta-analysis

Early identification of dengue patients at risk of adverse outcomes is important to prevent hospital overcrowding in low- to middle- income countries during epidemics. We performed a systematic review to identify which biomarkers measured in first 96 h of fever could predict dengue haemorrhagic fever (DHF, World Health Organization 1997 clinical classification) or severe dengue (SD, WHO 2009, clinical classification). PubMed, Scopus, CINAHL, Web of Science, and EMBASE databases were searched for prospective cohort and nested case-control studies published from 1997 to Feb 27, 2022. The protocol for the study was registered in PROSPERO (ID: CRD42021230053). After screening 6747 publications, and analysing 37 eligible studies reporting on 5925 patients, elevated C-reactive protein, aspartate aminotransferase, interleukin-8 and decreased albumin levels were strongly associated with dengue haemorrhagic fever (by meta-analyses of multiple studies, p < 0.05), while elevated vascular cell adhesion protein 1, syndecan-1, aspartate aminotransferase and C-reactive protein levels were strongly associated with severe dengue (by meta-analyses of multiple studies, p < 0.05). Further 44 and 28 biomarkers were associated with the risk of DHF and SD respectively, but only in a single study. The meta-analyses suggest the importance of early acute inflammation with hepatic involvement in determining the subsequent course of illness in dengue.

Diagnostic approaches for dengue infection

INTRODUCTION

Every year, a significant rise in dengue incidence observed is responsible for 10% of fever episodes in children and adolescents in endemic countries. Considering that the symptoms of dengue are similar to those of many other viruses, early diagnosis of the disease has long been difficult, and lack of sensitive diagnostic tools may be another factor contributing to a rise in dengue incidence.

AREAS COVERED

This review will highlight dengue diagnostics strategies and discuss other possible targets for dengue diagnosis. Understanding the dynamics of the immune response and how it affects viral infection has enabled informed diagnosis. As more technologies emerge, precise assays that include some clinical markers need to be included.

EXPERT OPINION

Future diagnostic strategies will require the use both viral and clinical markers in a serial manner with the use of artificial intelligence technology to determine from the first point of illness to better determine severity status and management. A definitive endpoint is not in the horizon as the disease as well as the virus is constantly evolving and hence many developed assays need to be constantly changing some of their reagents periodically as newer genotypes and probably too serotypes emerge.

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.

The Role of NS1 Protein in the Diagnosis of Flavivirus Infections

Nonstructural protein 1 (NS1) is a glycoprotein among the flavivirus genus. It is found in both membrane-associated and soluble secreted forms, has an essential role in viral replication, and modulates the host immune response. NS1 is secreted from infected cells within hours after viral infection, and thus immunodetection of NS1 can be used for early serum diagnosis of dengue fever infections instead of real-time (RT)-PCR. This method is fast, simple, and affordable, and its availability could provide an easy point-of-care testing solution for developing countries. Early studies show that detecting NS1 in cerebrospinal fluid (CSF) samples is possible and can improve the surveillance of patients with dengue-associated neurological diseases. NS1 can be detected postmortem in tissue specimens. It can also be identified using noninvasive methods in urine, saliva, and dried blood spots, extending the availability and effective detection period. Recently, an enzyme-linked immunosorbent assay (ELISA) assay for detecting antibodies directed against Zika virus NS1 has been developed and used for diagnosing Zika infection. This NS1-based assay was significantly more specific than envelope protein-based assays, suggesting that similar assays might be more specific for other flaviviruses as well. This review summarizes the knowledge on flaviviruses' NS1's potential role in antigen and antibody diagnosis.

The Current Landscape of Bioactive Molecules against DENV: A Systematic Review

With a 30-fold increase in incidence over the previous 50 years, dengue fever is now the most widespread viral disease transmitted by mosquitoes in the world. The intricate interaction of the human defense system, hereditary predisposition, and specific bitterness elements is more likely to be the pathogenesis of dengue. There are presently no viable treatments for dengue. Synthetic drugs which are used against this ailment also show major side effects. There must be a deeper understanding of the underlying mechanism generating severe symptoms to develop auguring markers, cutting-edge diagnostics, and treatments and finally a well-rounded and secure antiserum. Hence, the aim is to search for safer and more potent drugs derived from plants. Plants or herbs are mainly targeting replication or its enzyme or specific stereotypes, though an exact mechanism of phytoconstituents interfering with the viral replication is still undiscovered. The present attempt provided the update with the objective to bringing up forward pathophysiological eventualities involved in dengue virus along with the naturally derived treatment relevant to provide the impregnable therapy by evading the noxious symptoms for dengue fever. Governor's plum, Cryptocarya chartacea, magnolia berry, and Chinese ginger are such plants exhibiting many effective phytoconstituents against DENV and can be further explored for novel drug discovery by medicinal scientists.

Murine diabetic models for dengue virus infection

Dengue virus (DENV) is a critical public health concern in tropical and subtropical regions worldwide. Thus, immunocompetent murine models of DENV infection with robust viremia are required for vaccine studies. Diabetes is highly prevalent worldwide, making it frequent comorbidity in patients with dengue fever. Therefore, murine models are needed to understand viral pathogenesis and disease progression. Acquired-induced and inherently diabetic C57BL/6 and db/db mice were inoculated with DENV-3 via the tail vein. After infection, both the diabetic C57BL/6 and db/db mice showed obvious weight loss with clinical manifestations. Quantitative reverse-transcription polymerase chain reaction revealed robust and replicable viremia in the two types of diabetic mice. Immunohistochemical detection showed persistent DENV-3 infection in the liver. Enzyme-linked immunosorbent assay for cytokine detection revealed that diabetic mice showed more severe inflammatory responses than did nondiabetic mice, and significant histological alterations were observed in diabetic mice. Thus, the diabetic mice were more susceptible to DENV infection than the nondiabetic mice. Taken together, we established two types of immunocompetent diabetic mice for DENV infection, which can be used to further study the mechanisms of dengue pathogenesis in diabetes and to develop antiviral pharmaceuticals and treatments.

Dengue hemorrhagic fever and the liver

Dengue hemorrhagic fever (DHF) is one of the most rapidly emerging infections of tropical and subtropical regions worldwide. It affects more rural and urban areas due to many factors, including climate change. Although most people with dengue viral infection are asymptomatic, approximately 25% experience a self-limited febrile illness with mild to moderate biochemical abnormalities. Severe dengue diseases develop in a small proportion of these patients, and the common organ involvement is the liver. The hepatocellular injury was found in 60%-90% of DHF patients manifested as hepatomegaly, jaundice, elevated aminotransferase enzymes, and critical condition as an acute liver failure (ALF). Even the incidence of ALF in DHF is very low (0.31%-1.1%), but it is associated with a relatively high mortality rate (20%-68.3%). The pathophysiology of liver injury in DHF included the direct cytopathic effect of the DENV causing hepatocytes apoptosis, immune-mediated hepatocyte injury induced hepatitis, and cytokine storm. Hepatic hypoperfusion is another contributing factor in dengue shock syndrome. The reduction of morbidity and mortality in DHF with liver involvement is dependent on the early detection of warning signs before the development of ALF.

Predictors of plasma leakage among dengue patients in Thailand: A plasma-leak score analysis

Delayed plasma leakage recognition could lead to improper fluid administration resulting in dengue shock syndrome, subsequently, multi-organ failure, and death. This prospective observational study was conducted in Bangkok, Thailand, between March 2018 and February 2020 to determine predictors of plasma leakage and develop a plasma leakage predictive score among dengue patients aged ≥15 years. Of 667 confirmed dengue patients, 318 (47.7%) developed plasma leakage, and 349 (52.3%) had no plasma leakage. Multivariate analysis showed three independent factors associated with plasma leakage, including body mass index ≥25.0 kg/m2 (odds ratio [OR] = 1.784; 95% confidence interval [CI] = 1.040-3.057; P = 0.035), platelet count <100,000/mm3 on fever days 3 to 4 (OR = 2.151; 95% CI = 1.269-3.647; P = 0.004), and aspartate aminotransferase or alanine aminotransferase ≥100 U/l on fever days 3 to 4 (OR = 2.189; 95% CI = 1.231-3.891; P = 0.008). Because these three parameters had evidence of equality, each independent factor was weighted to give a score of 1 with a total plasma-leak score of 3. Higher scores were associated with increased plasma leakage occurrence, with ORs of 2.017 (95% CI = 1.052-3.869; P = 0.035) for score 1, 6.158 (95% CI = 2.914-13.015; P <0.001) for score 2, and 6.300 (95% CI = 2.419-16.407; P <0.001) for score 3. The area under the receiver operating characteristics curves for predicting plasma leakage was good (0.677 [95% CI = 0.616-0.739]). Patients with a plasma-leak score ≥1 had high sensitivity (88.8%), and those with a plasma-leak score of 3 had high specificity (93.4%) for plasma leakage occurrence. This simple and easily accessible clinical score might help physicians provide early and timely appropriate clinical dengue management in endemic areas.

Two Cases of Natural Infection of Dengue-2 Virus in Bats in the Colombian Caribbean

Dengue, a mosquito-borne zoonotic disease, is the most common vector-borne disease in tropical and subtropical areas. In this study, we aim to demonstrate biological evidence of dengue virus infection in bats. A cross-sectional study was carried out in the departments of Cordoba and Sucre, Colombia. A total of 286 bats were captured following the ethical protocols of animal experimentation. The specimens were identified and euthanized using a pharmacological treatment with atropine, acepromazine and sodium pentobarbital. Duplicate samples of brain, heart, lung, spleen, liver, and kidney were collected with one set stored in Trizol and the other stored in 10% buffered formalin for histopathological and immunohistochemical analysis using polyclonal antibodies. Brain samples from lactating mice with an intracranial inoculation of DENV-2 were used as a positive control. As a negative control, lactating mouse brains without inoculation and bats brains negative for RT-PCR were included. Tissue sections from each specimen of bat without conjugate were used as staining control. In a specimen of Carollia perspicillata captured in Ayapel (Cordoba) and Phylostomus discolor captured in San Carlos (Cordoba), dengue virus was detected, and sequences were matched to DENV serotype 2. In bats RT-PCR positive for dengue, lesions compatible with viral infections, and the presence of antigens in tissues were observed. Molecular findings, pathological lesions, and detection of antigens in tissues could demonstrate viral DENV-2 replication and may correspond to natural infection in bats. Additional studies are needed to elucidate the exact role of these species in dengue epidemics.

Dengue Infections and the Surgical Patient

Dengue infections are increasing globally and account for significant morbidity and mortality. Severe dengue results in microvascular changes and coagulopathy that may make surgical intervention risky and the overall surgical management challenging. We outline the potential surgical manifestations and complications following dengue infections and describe the clinical, pathogenetic, diagnostic, and treatment aspects of dengue and surgical patients. The main surgical presentations were acute cholecystitis, acute pancreatitis, acute appendicitis, splenic rupture, bowel perforation, gastrointestinal bleeding, and hematomas. Dengue may also mimic an acute abdomen without any true surgical complications. A majority were treated nonoperatively. Misdiagnosis and unnecessary surgical intervention resulted in poor outcomes. Better knowledge of the potential surgical complications would help in early diagnosis, treatment, and referral to specialized centers and thus improve outcomes. A high degree of suspicion of dengue fever is necessary when patients in a dengue-epidemic area present with acute abdomen or bleeding manifestations. In endemic areas, early dengue antigen testing and abdominal imaging before surgical intervention may help in the diagnoses. Multidisciplinary team involvement with case-by-case decision-making is needed for optimal care.

Immortalized stem cell-derived hepatocyte-like cells: An alternative model for studying dengue pathogenesis and therapy

Suitable cell models are essential to advance our understanding of the pathogenesis of liver diseases and the development of therapeutic strategies. Primary human hepatocytes (PHHs), the most ideal hepatic model, are commercially available, but they are expensive and vary from lot-to-lot which confounds their utility. We have recently developed an immortalized hepatocyte-like cell line (imHC) from human mesenchymal stem cells, and tested it for use as a substitute model for hepatotropic infectious diseases. With a special interest in liver pathogenesis of viral infection, herein we determined the suitability of imHC as a host cell target for dengue virus (DENV) and as a model for anti-viral drug testing. We characterized the kinetics of DENV production, cellular responses to DENV infection (apoptosis, cytokine production and lipid droplet metabolism), and examined anti-viral drug effects in imHC cells with comparisons to the commonly used hepatoma cell lines (HepG2 and Huh-7) and PHHs. Our results showed that imHC cells had higher efficiencies in DENV replication and NS1 secretion as compared to HepG2 and Huh-7 cells. The kinetics of DENV infection in imHC cells showed a slower rate of apoptosis than the hepatoma cell lines and a certain similarity of cytokine profiles to PHHs. In imHC, DENV-induced alterations in levels of lipid droplets and triacylglycerols, a major component of lipid droplets, were more apparent than in hepatoma cell lines, suggesting active lipid metabolism in imHC. Significantly, responses to drugs with DENV inhibitory effects were greater in imHC cells than in HepG2 and Huh-7 cells. In conclusion, our findings suggest superior suitability of imHC as a new hepatocyte model for studying mechanisms underlying viral pathogenesis, liver diseases and drug effects.

A model system resembling normal human liver cells is needed for advancement of hepatotropic infectious disease research. Here we show that immortalized cells (imHC) derived from human stem cells have a higher efficiency of DENV replication and a lower rate of cell death in response to DENV infection than the cancer cell-derived model systems currently used. The imHC also have active fat metabolism and respond well to anti-viral drug treatment, making them an attractive model for the initial stage of drug discovery and testing.

Infectivity and viability of dengue virus infected hepatocytes cocultured with peripheral blood mononuclear cells from a healthy subject

BACKGROUND Dengue virus (DENV) can infect and replicate in monocytes, resulting in antibody-dependent enhancement. The liver is the main target of DENV, and the infection mechanisms of DENV include direct cytopathic effects (CPEs) of the virus, mitochondrial dysfunction, and effect of cellular and humoral immune factors in the liver. This study was aimed to explore the infectivity of DENV and viability of human hepatocytes using Huh 7it-1 cells cocultured with peripheral blood mononuclear cells (PBMCs). METHODS Huh 7it-1 cells were infected with dengue virus serotype-2 (DENV-2) New Guinea C strain at multiplicity of infection of 0.5 and 1 FFU/cell, and cocultured in vitro with and without adherent PBMCs. The infectivity of DENV was assessed by immunoperoxidase staining. The viability of Huh 7it-1 cells was assessed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT, a tetrazole) assay and trypan blue staining. Data were statistically analyzed by Shapiro–Wilk and analysis of variance for normality significances. RESULTS The result showed that addition of PBMCs to DENV-2 infected Huh 7it-1 cells decreased the infectivity of DENV (15–37%). DENV-2 infection decreased the viability of Huh 7it-1 cells (15.5–20.8%). Despite the decrease in infectivity of DENV, the addition of PBMCs increased the Huh 7it-1 cells viability (4.5–10.2%). CONCLUSIONS Addition of PBMCs to Huh 7it-1 cells that are infected with DENV-2 decreased the infectivity of DENV and increased Huh 7it-1 cells viability.

Crocetin Improves Dengue Virus-Induced Liver Injury

Dengue virus (DENV) infection is one of the most widespread mosquito-borne viral infections. Liver injury is commonly observed in severe DENV infection, and the present study aimed to examine the efficacy of crocetin treatment in an immunocompetent mouse model of DENV infection exhibiting liver injury. The efficacy of crocetin treatment in DENV-induced liver injury was assessed via both transaminase levels and histopathology analysis. A real-time polymerase chain reaction array was then used to describe the expression of 84 apoptosis-related genes. Using real-time RT-PCR and Western blot analysis, the gene expressions of host factors were investigated. Additionally, the effect of crocetin in NF-kB signaling during DENV infection was studied. We did not observe any significant reduction in virus production when DENV-infected mice were treated with crocetin. However, DENV-infected mice treated with crocetin showed reduced DENV-induced apoptosis. The real-time polymerase chain reaction array revealed pro-inflammatory cytokine expressions to be significantly reduced in the crocetin-treated DENV-infected mice. We also found that crocetin could effectively modulate antioxidant status in DENV-infected mice. Moreover, crocetin demonstrated the ability to reduce the nuclear translocation of NF-kB in DENV-infected mice. Our results suggest that crocetin treatment does not inhibit DENV replication in the liver of DENV-infected mice; however, we did find that crocetin improves host responses that reduce liver injury.

Coronavirus Disease of 2019: a Mimicker of Dengue Infection?

At the beginning of 2020, the national health system and medical communities are faced with unprecedented public health challenges. A novel strain of coronavirus, later identified as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally, marking another pandemic of coronaviruses. This viral disease is responsible for devastating pneumonia, named coronavirus disease of 2019 (COVID-19), and projected to persist until the end of the year. In tropical countries, however, concerns arise regarding the similarities of COVID-19 with other infectious diseases due to the same chief complaint, which is fever. One of the infectious disease of a primary concern is dengue infection, which its peak season is approaching. Others report that there are cases of serological cross-reaction of COVID-19 and dengue infection. In this comprehensive review, we underscore the importance of knowing similar clinical presentations of both diseases and emphasize why excluding COVID-19 in the differentials in the setting of a pandemic is imprudent.

Dengue hepatitis with acute liver failure: Clinical, biochemical, histopathological characteristics and predictors of outcome

BACKGROUND

Hepatitis infection from non-hepatotropic viruses such as dengue virus (DENV) is increasing worldwide. There is increasing recognition of the changing epidemiology and atypical presentations of DENV infection including acute liver failure (ALF). There is paucity of data regarding incidence, disease characteristics, and markers of prognosis in patients who develop DENV-related ALF.

METHODS

We aimed to study the incidence, clinical features, laboratory characteristics, and determinants of outcome in patients of DENV presenting with ALF. We reviewed all patients with DENV infection and focused on DENV-related ALF from 2014 to 2017. Diagnosis of DENV and ALF was confirmed by serological tests and standard criteria, respectively.

RESULTS

Thirty-six patients (20 men, mean age 32.3) developed ALF among 10 108 patients with DENV infection (0.35%). Twenty-one patients died (58.3%). Although bilirubin, aspartate and alanine aminotransferase, and international normalized ratio were markedly elevated in all patients with DENV ALF, there was no statistically significant difference between survivors and non-survivors. Lactate levels, pH at admission, and model for end-stage liver disease (MELD) score were the only predictors of mortality. Lactate levels were significantly higher in non-survivors (11.5 ± 4.2 mmol/L) than survivors (6.3 ± 3.6 mmol/L) (P < 0.001). MELD score in non-survivors (26.7 ± 10.2) was significantly higher than in survivors (20 ± 7.2) (P = 0.039). Receiver operator characteristic curve showed lactate or pH to be a superior prognostic marker than MELD with an area under the curve of 0.80, 0.79, and 0.70, respectively.

CONCLUSION

Dengue hepatitis progressed to ALF in 0.35%. Development of ALF was associated with a high mortality (> 50%). Lactate level, pH, and MELD score at admission were significant determinants of outcome.

Severe dengue and liver involvement: an overview and review of the literature

Introduction: Two billion population are at risk of dengue fever and by 2080, over six billion population will be at risk. Hepatitis is common in dengue and the liver is invariably involved in severe cases. We conducted a literature review using the PubMed database on articles covering a broad range of issues related to dengue and hepatitis.Areas covered: This article overviews available literature on changes in the definition of severe dengue, pathogenesis of liver involvement in dengue, clinical manifestations, and predictors of mortality in severe dengue with liver involvement, impact of viral hepatitis co-infections and hepatotoxic drugs, and hemophagocytic lymphohistiocytosis.Expert commentary: Hepatitis is commonly seen in dengue however the degree of elevation of transaminases did not correlate well with severity of illness in observational studies, except in the elderly. The underlying pathogenesis of liver injury is still being elucidated and further studies are required to fully understand the cellular pathways. Acute or chronic viral hepatitis does not appear to affect dengue outcomes. Commonly used medications such as paracetamol and statins may influence dengue outcomes.

Insight into the Tropism of Dengue Virus in Humans

In tropical and subtropical zones, arboviruses are among the major threats to human life, affecting a large number of populations with serious diseases. Worldwide, over three hundred million people are infected with dengue virus (DENV) every year as per the World Health Organization (WHO). DENV-mediated disease severity ranges from a mild fever to hemorrhagic fever and shock syndrome. Patients suffering from severe infection might experience multi-organ failure, cardiomyopathy and even encephalopathy, further complicating the disease pathogenesis. In life-threatening cases, DENV has been reported to affect almost all organs of the human body. In this review, we discuss the organ tropism of DENV in humans in depth as detected in various autopsy studies. Keeping in mind the fact that there is currently no DENV-specific antiviral, it is of utmost importance to achieve a vivid picture of the susceptible cells in humans which might help in designing antivirals against DENV, especially targeting those tissues in which infection might lead to life-threatening conditions.

Unusual clinical manifestations of dengue disease - Real or imagined?

The disease caused by each of the four serotypes of dengue virus (DENV) have plagued humans since last century. Symptoms of dengue virus (DENV) infection range from asymptomatic to dengue fever (DF) to severe dengue disease (SDD). One third of the world's population lives in regions with active urban DENV transmission, and thousands of serologically naïve travelers visit these areas annually, making a significant portion of the human population at risk of being infected. Even though lifelong immunity to the homotypic serotype is achieved after a primary DENV infection. Heterotypic DENV infections may be exacerbated by a pre-existing immune memory to the primary infection and can result in an increased probability of severe disease. Not only, age, comorbidities and presence of antibodies transferred passively from dengue-immune mother to infants are considered risk factors to dengue severe forms. Plasma leakage and multiple organ impairment are well documented in the literature, affecting liver, lung, brain, muscle, and kidney. However, unusual manifestation, severe or not, have been reported and may require medical attention. This review will summarize and discuss the increasing reports of unusual manifestations in the clinical course of dengue infection.

Zika Virus Induced More Severe Inflammatory Response Than Dengue Virus in Chicken Embryonic Livers

Dengue (DENV) and Zika virus (ZIKV) are important flaviviruses in tropical and subtropical regions, causing severe Dengue Hemorrhagic Fever (DHF)/Dengue Shock Syndrome (DSS) and microcephaly, respectively. The infection of both viruses during pregnancy were reported with adverse fetal outcomes. To investigate the effects of ZIKV and DENV infections on fetal development, we established an infection model in chicken embryos. Compared with DENV-2, the infection of ZIKV significantly retarded the development of chicken embryos. High viral loads of both DENV-2 and ZIKV was detected in brain, eye and heart 7 and 11 days post-infection, respectively. Interestingly, only ZIKV but not DENV-2 was detected in the liver. Even both of them induced apparent liver inflammation, ZIKV infection showed a more severe inflammatory response than DENV-2 infection based on the inflammation scores and the gene expression levels of IL-1β, TNF, IL-6, and TGFβ-2 in liver. Our results demonstrated that ZIKV induced more severe inflammatory response in chicken embryo liver compared to DENV-2, which might partially attribute to viral replication in liver cells. Clinicians should be aware of the potential liver injury associated with ZIKV infection in patients, especially in perinatal fetuses.

Effect of freeze-dried Carica papaya leaf juice on inflammatory cytokines production during dengue virus infection in AG129 mice

Background

Carica papaya leaves have been used for traditional treatment of dengue fever and have been reported to exhibit an immunomodulatory activity by affecting the level of cytokine production in vitro and in vivo. Due to the lack of adequate in vivo evidence in dengue disease model, the present study was initiated to screen and identify the cytokines affected by freeze-dried C. papaya leaf juice (FCPLJ) treatment in AG129 mice infected with DEN-2 dengue virus.

Methods

The AG129 mice were fed orally with FCPLJ for 3 consecutive days after 24 h of dengue virus inoculation. Plasma cytokines were screened by using ProcartaPlex immunoassay. The gene expression in the liver was analyzed by using RT² Profiler PCR Array.

Results

The results showed that FCPLJ treatment has increased the plasma CCL2/MCP-1 level during peak of viremia. Gene expression study has identified 8 inflammatory cytokine genes which were downregulated in the liver of infected AG129 mice treated with FCPLJ. The downregulated inflammatory cytokine genes were CCL6/MRP-1, CCL8/MCP-2, CCL12/MCP-5, CCL17/TARC, IL1R1, IL1RN/IL1Ra, NAMPT/PBEF1 and PF4/CXCL4.

Conclusion

The findings indicated the possible immunomodulatory role of FCPLJ during dengue virus infection in AG129 mice.

Electronic supplementary material

The online version of this article (10.1186/s12906-019-2438-3) contains supplementary material, which is available to authorized users.

Genome-wide profiling of mRNA and lncRNA expression in dengue fever and dengue hemorrhagic fever

Dengue fever (DF) and dengue hemorrhagic fever (DHF) are recurrent diseases that are widespread in the tropics. Here, we identified candidate genes associated with these diseases by performing integrated analyses of DF (GSE51808) and DHF (GSE18090) microarray datasets in the Gene Expression Omnibus (GEO). In all, we identified 7635 differentially expressed genes (DEGs) in DF and 8147 DEGs in DHF as compared to healthy controls (P < 0.05). In addition, we discovered 215 differentially expressed long non-coding RNAs (DElncRNAs) in DF and 225 DElncRNAs in DHF. There were 1256 common DEGs and eight common DElncRNAs in DHF vs DF, DHF vs normal control, and DF vs normal control groups. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis revealed that signal transduction (false discovery rate = 8.33E-10), 'toxoplasmosis', and 'protein processing in endoplasmic reticulum' were significantly enriched pathways for common DEGs. We conclude that the MAGED1,STAT1, and IL12A genes may play crucial roles in DF and DHF, and suggest that our findings may facilitate the identification of biomarkers and the development of new drug design strategies for DF and DHF treatment.

Systematic review of spontaneous splenic rupture in dengue-infected patients

Dengue infection varies from a mild febrile form to more severe disease with plasma leakage, shock, and multiorgan failure. Several serious complications such as cardiomyopathy, encephalopathy, encephalitis, hepatic damage, and neural manifestations cause organ damage in dengue infection. Splenic rupture, a less well known but life-threatening complication, can occur in dengue. The mechanism of splenic rupture in dengue is still unclear. Optimal therapeutic management is required to save the lives of patients with this complication. The objective of this study was to conduct a systematic review of studies documenting the development of spontaneous nontraumatic splenic rupture in patients with dengue infection. In March 2018, a search was conducted systematically in nine electronic databases, in addition to hand- searching. A total of 127 references were exported to Endnote; 47 references remained after removing duplicates. Finally, 16 reports met the inclusion criteria and represented 17 cases. All articles were evaluated and data extracted according to predefined criteria: number of cases, age, sex, severity of dengue disease, days of illness before admission, methods of definitive diagnosis, timing of the event, and management and outcome. A total of 17 individual patients including 13 males and four females were found. Most of the patients were young adults (ranging from 20 to 52 years) and diagnosed with computed tomography scan and managed with splenectomy. Four cases were fatal. Pathological splenic rupture in dengue is a rare, life-threatening condition where timely management can achieve a favorable outcome.

Heart and liver are infected in fatal cases of dengue: three PCR based case studies

Background

Dengue is a global problem mainly in the tropics. Meticulous clinical management of cases has reduced the death rate significantly, but large numbers of people still succumb to severe complications of the infection. Presence of myocarditis is often overlooked leading to a poor outcome. Clinical management guidelines of dengue do not stress the importance of myocarditis as a manifestation in dengue infection. Severe hepatic dysfunction also needs emphasis.

Case presentation

We present three patients who had come to hospital on the 3rd day of fever. Two of them (case 1 and 3) were in shock on admission and case 2, who was stable on the3^rd day, went into the critical phase and developed shock while in the hospital on the 4^thday. All three had tachycardia on admission that got worse with time. The clinical course was unstable with fluctuations in urine output and deterioration of organ function. Despite frequent monitoring and life support they survived only 2–3 days in hospital. All three patients had myocarditis during the critical phase. In the first case, myocarditis was confirmed by troponin estimation and echocardiogram. In the second and third cases, histopathology confirmed myocarditis. Haemorrhagic necrosis of the liver was found in case 2 and 3 with exponential rise of transaminases. In all three cases, viral RNA was detected in both heart and liver tissues by PCR amplification.

Conclusions

We stress that detection of myocarditis and liver involvement in any dengue patient is important from the onset of the illness where treatment should be tailored to prevent development of hypotension. Our findings are novel as PCR and histology are rarely done on tissues of deceased dengue patients in the world. Studies are needed to find therapeutic interventions to reverse cardiac and hepatic dysfunction in dengue infection.

Subverting the mechanisms of cell death: flavivirus manipulation of host cell responses to infection

Viruses exploit host metabolic and defence machinery for their own replication. The flaviviruses, which include Dengue (DENV), Yellow Fever (YFV), Japanese Encephalitis (JEV), West Nile (WNV) and Zika (ZIKV) viruses, infect a broad range of hosts, cells and tissues. Flaviviruses are largely transmitted by mosquito bites and humans are usually incidental, dead-end hosts, with the notable exceptions of YFV, DENV and ZIKV. Infection by flaviviruses elicits cellular responses including cell death via necrosis, pyroptosis (involving inflammation) or apoptosis (which avoids inflammation). Flaviviruses exploit these mechanisms and subvert them to prolong viral replication. The different effects induced by DENV, WNV, JEV and ZIKV are reviewed. Host cell surface proteoglycans (PGs) bearing glycosaminoglycan (GAG) polysaccharides — heparan/chondroitin sulfate (HS/CS) — are involved in initial flavivirus attachment and during the expression of non-structural viral proteins play a role in disease aetiology. Recent work has shown that ZIKV-infected cells are protected from cell death by exogenous heparin (a GAG structurally similar to host cell surface HS), raising the possibility of further subtle involvement of HS PGs in flavivirus disease processes. The aim of this review is to synthesize information regarding DENV, WNV, JEV and ZIKV from two areas that are usually treated separately: the response of host cells to infection by flaviviruses and the involvement of cell surface GAGs in response to those infections.

Divergent Role of Sphingosine 1-Phosphate in Liver Health and Disease

Two decades ago, sphingosine 1-phosphate (S1P) was discovered as a novel bioactive molecule that regulates a variety of cellular functions. The plethora of S1P-mediated effects is due to the fact that the sphingolipid not only modulates intracellular functions but also acts as a ligand of G protein-coupled receptors after secretion into the extracellular environment. In the plasma, S1P is found in high concentrations, modulating immune cell trafficking and vascular endothelial integrity. The liver is engaged in modulating the plasma S1P content, as it produces apolipoprotein M, which is a chaperone for the S1P transport. Moreover, the liver plays a substantial role in glucose and lipid homeostasis. A dysfunction of glucose and lipid metabolism is connected with the development of liver diseases such as hepatic insulin resistance, non-alcoholic fatty liver disease, or liver fibrosis. Recent studies indicate that S1P is involved in liver pathophysiology and contributes to the development of liver diseases. In this review, the current state of knowledge about S1P and its signaling in the liver is summarized with a specific focus on the dysregulation of S1P signaling in obesity-mediated liver diseases. Thus, the modulation of S1P signaling can be considered as a potential therapeutic target for the treatment of hepatic diseases.

Immune Response to Dengue and Zika

Flaviviruses such as dengue (DENV), yellow fever (YFV), West Nile (WNV), and Zika (ZIKV) are human pathogens of global significance. In particular, DENV causes the most prevalent mosquito-borne viral diseases in humans, and ZIKV emerged from obscurity into the spotlight in 2016 as the etiologic agent of congenital Zika syndrome. Owing to the recent emergence of ZIKV as a global pandemic threat, the roles of the immune system during ZIKV infections are as yet unclear. In contrast, decades of DENV research implicate a dual role for the immune system in protection against and pathogenesis of DENV infection. As DENV and ZIKV are closely related, knowledge based on DENV studies has been used to prioritize investigation of ZIKV immunity and pathogenesis, and to accelerate ZIKV diagnostic, therapeutic, and vaccine design. This review discusses the following topics related to innate and adaptive immune responses to DENV and ZIKV: the interferon system as the key mechanism of host defense and viral target for immune evasion, antibody-mediated protection versus antibody-dependent enhancement, and T cell-mediated protection versus original T cell antigenic sin. Understanding the mechanisms that regulate the balance between immune-mediated protection and pathogenesis during DENV and ZIKV infections is critical toward development of safe and effective DENV and ZIKV therapeutics and vaccines.

Plugging the Leak in Dengue Shock

Recent structural and functional advances provide fresh insight into the biology of the dengue virus non-structural protein, NS1 and suggest new avenues of research. The work of our lab and others have shown that the secreted, hexameric form of NS1 has a systemic toxic effect, inducing inflammatory cytokines and acting directly on endothelial cells to produce the hallmark of dengue disease, vascular leak. We also demonstrated that NS1 exerts its toxic activity through recognition by the innate immune receptor TLR4, mimicking the bacterial endotoxin LPS. This monograph covers the background underpinning these new findings and discusses new avenues for antiviral and vaccine intervention.

RNAi screen reveals a role of SPHK2 in dengue virus-mediated apoptosis in hepatic cell lines

Hepatic dysfunction is a feature of dengue virus (DENV) infection. Hepatic biopsy specimens obtained from fatal cases of DENV infection show apoptosis, which relates to the pathogenesis of DENV infection. However, how DENV induced liver injury is not fully understood. In this study, we aim to identify the factors that influence cell death by employing an apoptosis-related siRNA library screening. Our results show the effect of 558 gene silencing on caspase 3-mediated apoptosis in DENV-infected Huh7 cells. The majority of genes that contributed to apoptosis were the apoptosis-related kinase enzymes. Tumor necrosis factor superfamily member 12 (TNFSF12), and sphingosine kinase 2 (SPHK2), were selected as the candidate genes to further validate their influences on DENV-induced apoptosis. Transfection of siRNA targeting SPHK2 but not TNFSF12 genes reduced apoptosis determined by Annexin V/PI staining. Knockdown of SPHK2 did not reduce caspase 8 activity; however, did significantly reduce caspase 9 activity, suggesting its involvement of SPHK2 in the intrinsic pathway of apoptosis. Treatment of ABC294649, an inhibitor of SPHK2, reduced the caspase 3 activity, suggesting the involvement of its kinase activity in apoptosis. Knockdown of SPHK2 significantly reduced caspase 3 activity not only in DENV-infected Huh7 cells but also in DENV-infected HepG2 cells. Our results were consistent across all of the four serotypes of DENV infection, which supports the pro-apoptotic role of SPHK2 in DENV-infected liver cells.

The Differential Expression and Possible Function of Long Noncoding RNAs in Liver Cells Infected by Dengue Virus

The function of long noncoding RNAs (lncRNAs) in liver injury resulted by dengue virus (DENV) infection have not yet been explored. The differential expression profiles of lncRNAs (as well as mRNAs) in the L-02 liver cells infected by DENV1, DENV2, or uninfected were compared and analyzed after a high throughput RNA seq. The significantly up-regulated and down-regulated lncRNAs (or mRNAs) resulted by DENV infection were identified with a cutoff value at log2 (ratio) ≥ 1.5 and log2 (ratio) ≤ -1.5 (ratio = the reads of the lncRNAs or mRNAs from the infection groups divided by the reads from the control group). Several differentially expressed lncRNAs were verified with reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR). Target gene analysis, pre-miRNA prediction, and the lncRNA-mRNA co-expression network construction were performed to predict the function of the differentially expressed lncRNAs. The differentially expressed lncRNAs were associated with biosynthesis, DNA/RNA related processes, inhibition of estrogen signaling pathway, sterol biosynthetic process, protein dimerization activity, vesicular fraction in DENV1 infection group; and with protein secretion, methyltransferase process, host cell cytoskeleton reorganization and the small GTPase Ras superfamily, inhibition of cell proliferation, induction of apoptosis in DENV2 infection. LncRNAs might be novel diagnostic markers and targets for further researches on dengue infection and liver injury resulted by dengue virus.

Alpha-mangostin inhibits both dengue virus production and cytokine/chemokine expression

Since severe dengue virus (DENV) infection in humans associates with both high viral load and massive cytokine production - referred to as "cytokine storm", an ideal drug for treatment of DENV infection should efficiently inhibit both virus production and cytokine expression. In searching for such an ideal drug, we discovered that α-mangostin (α-MG), a major bioactive compound purified from the pericarp of the mangosteen fruit (Garcinia mangostana Linn), which has been used in traditional medicine for several conditions including trauma, diarrhea, wound infection, pain, fever, and convulsion, inhibits both DENV production in cultured hepatocellular carcinoma HepG2 and Huh-7 cells, and cytokine/chemokine expression in HepG2 cells. α-MG could also efficiently inhibit all four serotypes of DENV. Treatment of DENV-infected cells with α-MG (20μM) significantly reduced the infection rates of four DENV serotypes by 47-55%. α-MG completely inhibited production of DENV-1 and DENV-3, and markedly reduced production of DENV-2 and DENV-4 by 100 folds. Furthermore, it could markedly reduce cytokine (IL-6 and TNF-α) and chemokine (RANTES, MIP-1β, and IP-10) transcription. These actions of α-MG are more potent than those of antiviral agent (ribavirin) and anti-inflammatory drug (dexamethasone). Thus, α-MG is potential to be further developed as therapeutic agent for DENV infection.

Immune-mediated cytokine storm and its role in severe dengue

Dengue remains one of the most important mosquito-borne diseases worldwide. Infection with one of the serologically related dengue viruses (DENVs) can lead to a wide range of clinical manifestations and severity. Severe dengue is characterized by plasma leakage and abnormal bleeding that can lead to shock and death. There is currently no specific treatment for severe dengue due to gaps in understanding of the underlying mechanisms. The transient period of vascular leakage is usually followed by a rapid recovery and is suggestive of the effects of short-lived biological mediators. Both the innate and the adaptive immune systems are activated in severe dengue and contribute to the cytokine production. We discuss the immunological events elicited during a DENV infection and identify candidate cytokines that may play a key role in the severe manifestations of dengue and possible interventions.

HELZ2 Is an IFN Effector Mediating Suppression of Dengue Virus

Flaviviral infections including dengue virus are an increasing clinical problem worldwide. Dengue infection triggers host production of the type 1 IFN, IFN alpha, one of the strongest and broadest acting antivirals known. However, dengue virus subverts host IFN signaling at early steps of IFN signal transduction. This subversion allows unbridled viral replication which subsequently triggers ongoing production of IFN which, again, is subverted. Identification of downstream IFN antiviral effectors will provide targets which could be activated to restore broad acting antiviral activity, stopping the signal to produce endogenous IFN at toxic levels. To this end, we performed a targeted functional genomic screen for IFN antiviral effector genes (IEGs), identifying 56 IEGs required for antiviral effects of IFN against fully infectious dengue virus. Dengue IEGs were enriched for genes encoding nuclear receptor interacting proteins, including HELZ2, MAP2K4, SLC27A2, HSP90AA1, and HSP90AB1. We focused on HELZ2 (Helicase With Zinc Finger 2), an IFN stimulated gene and IEG which encodes a promiscuous nuclear factor coactivator that exists in two isoforms. The two unique HELZ2 isoforms are both IFN responsive, contain ISRE elements, and gene products increase in the nucleus upon IFN stimulation. Chromatin immunoprecipitation-sequencing revealed that the HELZ2 complex interacts with triglyceride-regulator LMF1. Mass spectrometry revealed that HELZ2 knockdown cells are depleted of triglyceride subsets. We thus sought to determine whether HELZ2 interacts with a nuclear receptor known to regulate immune response and lipid metabolism, AHR, and identified HELZ2:AHR interactions via co-immunoprecipitation, found that AHR is a dengue IEG, and that an AHR ligand, FICZ, exhibits anti-dengue activity. Primary bone marrow derived macrophages from HELZ2 knockout mice, compared to wild type controls, exhibit enhanced dengue infectivity. Overall, these findings reveal that IFN antiviral response is mediated by HELZ2 transcriptional upregulation, enrichment of HELZ2 protein levels in the nucleus, and activation of a transcriptional program that appears to modulate intracellular lipid state. IEGs identified in this study may serve as both (1) potential targets for host directed antiviral design, downstream of the common flaviviral subversion point, as well as (2) possible biomarkers, whose variation, natural, or iatrogenic, could affect host response to viral infections.

Impact of dengue virus (serotype DENV-2) infection on liver of BALB/c mice: A histopathological analysis

In this research, we characterized the histopathological impact of dengue virus (serotype DENV-2) infection in livers of BALB/c mice. The mice were infected with different doses of DENV-2 via intraperitoneal injection and liver tissues were processed for histological analyses and variation was documented. In the BALB/c mouse model, typical liver tissues showed regular hepatocyte architecture, with normal endothelial cells surrounding sinusoid capillary. Based on histopathological observations, the liver sections of BALB/c mice infected by DENV-2 exhibited a loss of cell integrity, with a widening of the sinusoidal spaces. There were marked increases in the infiltration of mononuclear cells. The areas of hemorrhage and micro- and macrovesicular steatosis were noted. Necrosis and apoptosis were abundantly present. The hallmark of viral infection, i.e., cytopathic effects, included intracellular edema and vacuole formation, cumulatively led to sinusoidal and lobular collapse in the liver. The histopathological studies on autopsy specimens of fatal human DENV cases are important to shed light on tissue damage for preventive and treatment modalities, in order to manage future DENV infections. In this framework, the method present here on BALB/c mouse model may be used to study not only the effects of infections by other DENV serotypes, but also to investigate the effects of novel drugs, such as recently developed nano-formulations, and the relative recovery ability with intact immune functions of host.

Dengue virus induces mitochondrial elongation through impairment of Drp1-triggered mitochondrial fission

Mitochondria are highly dynamic organelles that undergo continuous cycles of fission and fusion to maintain essential cellular functions. An imbalance between these two processes can result in many pathophysiological outcomes. Dengue virus (DENV) interacts with cellular organelles, including mitochondria, to successfully replicate in cells. This study used live-cell imaging and found an increase in mitochondrial length and respiration during DENV infection. The level of mitochondrial fission protein, Dynamin-related protein 1 (Drp1), was decreased on mitochondria during DENV infection, as well as Drp1 phosphorylated on serine 616, which is important for mitochondrial fission. DENV proteins NS4b and NS3 were also associated with subcellular fractions of mitochondria. Induction of fission through uncoupling of mitochondria or overexpression of Drp1 wild-type and Drp1 with a phosphomimetic mutation (S616D) significantly reduced viral replication. These results demonstrate that DENV infection causes an imbalance in mitochondrial dynamics by inhibiting Drp1-triggered mitochondrial fission, which promotes viral replication.

Dengue infection

Dengue is widespread throughout the tropics and local spatial variation in dengue virus transmission is strongly influenced by rainfall, temperature, urbanization and distribution of the principal mosquito vector Aedes aegypti. Currently, endemic dengue virus transmission is reported in the Eastern Mediterranean, American, South-East Asian, Western Pacific and African regions, whereas sporadic local transmission has been reported in Europe and the United States as the result of virus introduction to areas where Ae. aegypti and Aedes albopictus, a secondary vector, occur. The global burden of the disease is not well known, but its epidemiological patterns are alarming for both human health and the global economy. Dengue has been identified as a disease of the future owing to trends toward increased urbanization, scarce water supplies and, possibly, environmental change. According to the WHO, dengue control is technically feasible with coordinated international technical and financial support for national programmes. This Primer provides a general overview on dengue, covering epidemiology, control, disease mechanisms, diagnosis, treatment and research priorities.

Outcome of Severe Dengue Viral Infection-caused Acute Liver Failure in Thai Children

To determine clinical course and outcomes of liver functions in children with dengue viral infection-caused acute liver failure (ALF), the records of patients aged <15 years attending our institution during 1989-2011 were reviewed. Of the 41 ALF patients, 2, 6 and 33 patients had dengue hemorrhagic fever grade II, III and IV, respectively. Multiorgan failure including respiratory failure, massive bleeding and acute kidney injury occurred in 80.0%, 96.0% and 84.0% of the ALF cases, respectively, with an overall fatality rate of 68.3%. Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels were highest on the day that the patient developed ALF. Lactate dehydrogenase levels had positive correlations with AST (r = 0.95) and ALT (r = 0.87) (all p < 0.01). The median (interquartile range) days before the AST and ALT levels returned to lower than 200 U/L after the ALF were 10.5 (8.8, 12.8) and 10.5 (7.8, 14.0) days, respectively.

Mass spectrometric analysis of host cell proteins interacting with dengue virus nonstructural protein 1 in dengue virus-infected HepG2 cells

Dengue virus (DENV) infection is a leading cause of the mosquito-borne infectious diseases that affect humans worldwide. Virus-host interactions appear to play significant roles in DENV replication and the pathogenesis of DENV infection. Nonstructural protein 1 (NS1) of DENV is likely involved in these processes; however, its associations with host cell proteins in DENV infection remain unclear. In this study, we used a combination of techniques (immunoprecipitation, in-solution trypsin digestion, and LC-MS/MS) to identify the host cell proteins that interact with cell-associated NS1 in an in vitro model of DENV infection in the human hepatocyte HepG2 cell line. Thirty-six novel host cell proteins were identified as potential DENV NS1-interacting partners. A large number of these proteins had characteristic binding or catalytic activities, and were involved in cellular metabolism. Coimmunoprecipitation and colocalization assays confirmed the interactions of DENV NS1 and human NIMA-related kinase 2 (NEK2), thousand and one amino acid protein kinase 1 (TAO1), and component of oligomeric Golgi complex 1 (COG1) proteins in virus-infected cells. This study reports a novel set of DENV NS1-interacting host cell proteins in the HepG2 cell line and proposes possible roles for human NEK2, TAO1, and COG1 in DENV infection.

Peripheral effects induced in BALB/c mice infected with DENV by the intracerebral route

The lack of an immunocompetent animal model for dengue mimicking the disease in humans is a limitation for advances in this field. Inoculation by intracerebral route of neuroadapted dengue strains in mice is normally lethal and provides a straightforward readout parameter for vaccine testing. However, systemic effects of infection and the immune response elicited in this model remain poorly described. In the present work, BALB/c mice infected by the intracerebral route with neuroadapted DENV2 exhibited several evidences of systemic involvement. DENV-inoculated mice presented virus infective particles in the brain followed by viremia, especially in late stages of infection. Infection induced cellular and humoral responses, with presence of activated T cells in spleen and blood, lymphocyte infiltration and tissue damages in brain and liver, and an increase in serum levels of some pro-inflammatory cytokines. Data highlighted an interplay between the central nervous system commitment and peripheral effects under this experimental condition.

Differential replicative ability of clinical dengue virus isolates in an immunocompetent C57BL/6 mouse model

BACKGROUND

Several experimental animal models have been used to study the pathogenesis of dengue disease; however, most of the studies used laboratory-adapted viruses, which lack the virulence of viruses circulating in humans. The aim of this study was to analyze the ability of clinical Dengue virus (DENV) isolates (D2/BR/RP/RMB/09 and D3/BR/SL3/02) to infect immunocompetent C57BL/6 mice.

METHODS

Two strategies of intraperitoneal infection, which were based on the concept of the antibody dependent enhancement phenomenon, were used. In one strategy, the animals were inoculated with macrophages infected in vitro with dengue viruses, which were incubated with enhancing antibodies, and in the other strategy, the animals were inoculated with a complex of enhancing antibodies and dengue viruses.

RESULTS

The D3/BR/SL3/08 isolate showed a higher ability of infection (virus RNA was more frequently detected in the serum and in several organs) in the experimental model compared to both the D2/BR/RP/RMB/2009 isolate and a laboratory adapted DENV-1 strain (Mochizuki strain), regardless of the infection strategy used. The main features of the D3/BR/SL3/08 isolate were its neuroinvasiveness and the induction of an extended period of viremia. Enhancing antibodies did not influence on the infection of animals when macrophages were used, but the level of viremia was increased when they were used as a complex with a D3/BR/SL3/02 isolate.

DISCUSSION

We showed that DENV isolates could infect immunocompetent C57BL/6 mice, which have has been previously used to study some aspect of dengue disease when infected with laboratory adapted strains. DENV genome was detected in the same organs found in humans when autopsy and biopsy samples were analyzed, showing that C57BL/6 mice reproduce some aspects of the DENV tropism observed in humans. The main difference observed between the D3/BR/SL3/02 and D2/BR/RP/RMB/2009 clinical isolates was the neuroinvasive ability of the first one. Neuroinvasiveness has been described in some DENV infected cases and is common for other members of the Flavivirus genus.

CONCLUSIONS

These results suggest that C57BL/6 mice can be used as an experimental model to evaluate virulence differences among DENV clinical isolates.

Circulating cytokines and chemokines associated with plasma leakage and hepatic dysfunction in Brazilian children with dengue fever

Dengue fever is usually a benign acute viral infection transmitted by arthropods but may evolve to severe clinical manifestations such as coagulation and/or hemodynamic disorders, caused mainly by an increase of vascular permeability. Deregulated circulating immunological factors have been associated with severity. In Brazil severe cases appeared in children only recently and we evaluated the profile of cytokine/chemokine kinetics in 134 hospitalized young patients during the epidemic in Rio de Janeiro in 2008. Inflammatory cytokines TNF and IFNγ were found elevated during the acute phase in children as well as the anti-inflammatory IL10 and chemokines MIF and CXCL10/IP10, all last three persisting longer during the recovery phase. Severe disease fitting the dengue hemorrhagic fever pattern (WHO, 1997) was associated with higher IL10 and CXCL10/IP10 circulating levels (peak levels at seven days with P<0.01 and P<0.001 respectively as compared to DF). These factors were higher in patients pulmonary effusion or ascites (P<0.05 for IL10 and P<0.01 for CXCL10/IP10). Both factors were also associated with liver changes such as AST increase correlated with CXCL10/IP10 (r=0.4300 with P<0.0001) and patients presenting painful hepatomegaly showed higher circulating levels of IL10 (P<0.01, at 7-9 days) and of CXCL10/IP10 (P<0.05, 4-6 days and P<0.001, 7-9 days) when compared to patients without apparent liver alterations. Most cases presented a history of prior infection (93%). This is the first study demonstrating cytokine and chemokine association with severity during dengue fever in Brazilian children. IL10 and CXCL10/IP10 play a role in the disease severity associated with induction of vascular leakage and a novel association with changes in liver dysfunction.

Dengue and its effects on liver

Dengue has emerged as an important arboviral disease with significant impact on the disease burden in population residing in tropical countries. Dengue is spread by the bite of Aedes mosquito. The virus seems to have some hepatotoxic effects. Affliction of liver in form of derangements in the liver function tests is common and may include mild elevations in serum bilirubin, elevated transaminases and derangements in serum albumin. Although asymptomatic in most cases, clinical manifestations like jaundice, and acute liver failure (ALF) may occasionally complicate the clinical picture. Indeed, dengue has been implicated as an important cause of ALF in endemic countries. The present review focuses on the hepatic manifestations and the pathogenesis of the liver injury in dengue.

Phosphatidylserine receptors: enhancers of enveloped virus entry and infection

A variety of both RNA and DNA viruses envelop their capsids in a lipid bilayer. One of the more recently appreciated benefits this envelope is incorporation of phosphatidylserine (PtdSer). Surface exposure of PtdSer disguises viruses as apoptotic bodies; tricking cells into engulfing virions. This mechanism is termed apoptotic mimicry. Several PtdSer receptors have been identified to enhance virus entry and we have termed this group of proteins PtdSer-mediated virus entry enhancing receptors or PVEERs. These receptors enhance entry of a range of enveloped viruses. Internalization of virions by PVEERs provides a broad mechanism of entry with little investment by the virus itself. PVEERs may allow some viruses to attach to cells, thereby making viral glycoprotein/cellular receptor interactions more probable. Alternatively, other viruses may rely entirely on PVEERs for internalization into endosomes. This review provides an overview of PtdSer receptors that serve as PVEERs and the biology behind virion/PVEER interaction.

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Phosphatidylserine (PtdSer) receptors can mediate entry of enveloped viruses.

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PtdSer is present on the outer leaflet of the virion envelope.

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PtdSer receptors are expressed on a variety of primary cells and cell lines.

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Characteristics of PtdSer receptors that mediate virus entry are defined.

Distribution of fitness in populations of dengue viruses

Genetically diverse RNA viruses like dengue viruses (DENVs) segregate into multiple, genetically distinct, lineages that temporally arise and disappear on a regular basis. Lineage turnover may occur through multiple processes such as, stochastic or due to variations in fitness. To determine the variation of fitness, we measured the distribution of fitness within DENV populations and correlated it with lineage extinction and replacement. The fitness of most members within a population proved lower than the aggregate fitness of populations from which they were drawn, but lineage replacement events were not associated with changes in the distribution of fitness. These data provide insights into variations in fitness of DENV populations, extending our understanding of the complexity between members of individual populations.

Endothelial cells in dengue hemorrhagic fever

Therapies to prevent or reverse endothelial dysfunction and vascular leak found in dengue hemorrhagic fever (DHF) have not been identified. In this review we summarize dengue viruses and the spectrum of human disease and highlight evidence of endothelial cell dysfunction in DHF based on studies in patients and mouse and tissue culture models. Evidence suggests that both virus antigen and host immune response, can cause endothelial cell dysfunction and weaken endothelial barrier integrity. We suggest possible therapeutic interventions and highlight how therapies targeting altered endothelial function might be evaluated in animal models and in patients with DHF.