Macrophage migration inhibitory factor induced by dengue virus infection increases vascular permeability

Japanese encephalitis virus NS1 and NS1' protein disrupts the blood-brain barrier through macrophage migration inhibitory factor-mediated autophagy

Flaviviruses in the Japanese encephalitis virus (JEV) serogroup, such as JEV, West Nile virus, and St. Louis encephalitis virus, can cause severe neurological diseases. The nonstructural protein 1 (NS1) is a multifunctional protein of flavivirus that can be secreted by infected cells and circulate in the host bloodstream. NS1' is an additional form of NS1 protein with 52 amino acids extension at its carboxy-terminal and is produced exclusively by flaviviruses in the JEV serogroup. In this study, we demonstrated that the secreted form of both NS1 and NS1' can disrupt the blood-brain barrier (BBB) of mice, with NS1' exhibiting a stronger effect. Using the in vitro BBB model, we found that treatment of soluble recombinant JEV NS1 or NS1' protein increases the permeability of human brain microvascular endothelial cells (hBMECs) and leads to the degradation of tight junction proteins through the autophagy-lysosomal pathway. Consistently, NS1' protein exhibited a more pronounced effect compared to NS1 in these cellular processes. Further research revealed that the increased expression of macrophage migration inhibitory factor (MIF) is responsible for triggering autophagy after NS1 or NS1' treatment in hBMECs. In addition, TLR4 and NF-κB signaling was found to be involved in the activation of MIF transcription. Moreover, administering the MIF inhibitor has been shown to decrease viral loads and mitigate inflammation in the brains of mice infected with JEV. This research offers a novel perspective on the pathogenesis of JEV. In addition, the stronger effect of NS1' on disrupting the BBB compared to NS1 enhances our understanding of the mechanism by which flaviviruses in the JEV serogroup exhibit neurotropism.IMPORTANCEJapanese encephalitis (JE) is a significant viral encephalitis worldwide, caused by the JE virus (JEV). In some patients, the virus cannot be cleared in time, leading to the breach of the blood-brain barrier (BBB) and invasion of the central nervous system. This invasion may result in cognitive impairment, behavioral disturbances, and even death in both humans and animals. However, the mechanism by which JEV crosses the BBB remains unclear. Previous studies have shown that the flavivirus NS1 protein plays an important role in causing endothelial dysfunction. The NS1' protein is an elongated form of NS1 protein that is particularly produced by flaviviruses in the JEV serogroup. This study revealed that both the secreted NS1 and NS1' of JEV can disrupt the BBB by breaking down tight junction proteins through the autophagy-lysosomal pathway, and NS1' is found to have a stronger effect compared to NS1 in this process. In addition, JEV NS1 and NS1' can stimulate the expression of MIF, which triggers autophagy via the ERK signaling pathway, leading to damage to BBB. Our findings reveal a new function of JEV NS1 and NS1' in the disruption of BBB, thereby providing the potential therapeutic target for JE.

Fingolimod (FTY720), an FDA-approved sphingosine 1-phosphate (S1P) receptor agonist, restores endothelial hyperpermeability in cellular and animal models of dengue virus serotype 2 infection

Extensive vascular leakage and shock is a major cause of dengue-associated mortality. At present, there are no specific treatments available. Sphingolipid pathway is a key player in the endothelial barrier integrity; and is mediated through the five sphingosine-1-phosphate receptors (S1PR1-S1PR5). Signaling through S1PR2 promotes barrier disruption; and in Dengue virus (DENV)-infection, there is overexpression of this receptor. Fingolimod (FTY720) is a specific agonist that targets the remaining barrier-protective S1P receptors, without targeting S1PR2. In the present study, we explored whether FTY720 treatment can alleviate DENV-induced endothelial hyperpermeability. In functional assays, in both in vitro systems and in AG129 animal models, FTY720 treatment was found effective. Upon treatment, there was complete restoration of the monolayer integrity in DENV serotype 2-infected human microvascular endothelial cells (HMEC-1). At the molecular level, the treatment reversed activation of the S1P pathway. It significantly reduced the phosphorylation of the key molecules such as PTEN, RhoA, and VE-Cadherin; and also, the expression levels of S1PR2. In DENV2-infected AG129 mice treated with FTY720, there was significant improvement in weight gain, in overall clinical symptoms, and in survival. Whereas 100% of the DENV2-infected, untreated animals died by day-10 post-infection, 70% of the FTY720-treated animals were alive; and at the end of the 15-day post-infection observation period, 30% of them were still surviving. There was a significant reduction in the Evan's-blue dye permeability in the organs of FTY720-treated, DENV-2 infected animals; and also improvement in the hemogram, with complete restoration of thrombocytopenia and hepatic function. Our results show that the FDA-approved molecule Fingolimod (FTY720) is a promising therapeutic intervention in severe dengue.

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.

Potential Protective Effect of Dengue NS1 Human Monoclonal Antibodies against Dengue and Zika Virus Infections

Due to the lack of an effective therapeutic treatment to flavivirus, dengue virus (DENV) nonstructural protein 1 (NS1) has been considered to develop a vaccine owing to its lack of a role in antibody-dependent enhancement (ADE). However, both NS1 and its antibody have shown cross-reactivity to host molecules and have stimulated anti-DENV NS1 antibody-mediated endothelial damage and platelet dysfunction. To overcome the pathogenic events and reactogenicity, human monoclonal antibodies (HuMAbs) against DENV NS1 were generated from DENV-infected patients. Herein, the four DENV NS1-specific HuMAbs revealed the therapeutic effects in viral neutralization, reduction of viral replication, and enhancement of cell cytolysis of DENV and zika virus (ZIKV) via complement pathway. Furthermore, we demonstrate that DENV and ZIKV NS1 trigger endothelial dysfunction, leading to vascular permeability in vitro. Nevertheless, the pathogenic effects from NS1 were impeded by 2 HuMAbs (D25-4D4C3 and D25-2B11E7) and also protected the massive cytokines stimulation (interleukin [IL-]-1b, IL-1ra, IL-2, IL-4, IL-5, IL-6, IL-8, IL-9, IL-13, IL-17, eotaxin, granulocyte colony-stimulating factor, granulocyte-macrophage colony-stimulating factor, Inducible protein-10, monocyte chemoattractant protein-1, macrophage inflammatory protein [MIP]-1 α, MIP-1β, tumor necrosis factor-α, platelet-derived growth factor, and RANTES). Collectively, our findings suggest that the novel protective NS1 monoclonal antibodies generated from humans has multiple therapeutic benefits against DENV and ZIKV infections.

Serum levels of matrix metalloproteinases as prognostic markers for severe dengue with plasma leakage

BACKGROUND

Plasma leakage is a major pathogenic manifestation of severe dengue and is a precursor of life-threatening complications associated with dengue. Accumulating evidence indicates the role of Matrix Metalloproteinases (MMPs) in mediating vascular permeability and plasma leakage following induction by the dengue virus. This study aims to investigate the utility of MMP-2, MMP-3, and MMP-9 in predicting the severity of dengue infection and further explore the relationship of these markers with the pathogenic factors associated with plasma leakage.

METHODS

The dengue-positive subjects were classified into mild and severe dengue groups based on the manifestation of warning signs. The samples in each group and healthy controls were quantified for basic laboratory characteristics. The levels of MMP-2, MMP-3, MMP-9, and Macrophage migration inhibitory factor (MIF) were estimated in all serum samples using a multiplex bead-based assay.

RESULTS

MMP-2 and MMP-9 were markedly elevated in severe dengue patients compared to mild dengue patients and healthy controls. No alteration in the circulating levels of MMP-3 was observed between the study groups. ROC curve analysis indicated that MMP-2 and MMP-9 exhibited good potential for predicting severe dengue. Notably, an increase in MMP-9 was associated with increased MIF and Hematocrit levels in severe dengue patients.

CONCLUSION

MMP-2 and MMP-9 could serve as prognostic biomarkers for severe dengue. These findings also identify the association of MMP-9 with markers of plasma leakage, thereby encouraging further studies to explore the therapeutic potential of targeting MMP-9 in managing plasma leakage in severe dengue.

The multifaceted roles of NLRP3-modulating proteins in virus infection

The innate immune response to viruses is critical for the correct establishment of protective adaptive immunity. Amongst the many pathways involved, the NLRP3 [nucleotide-binding oligomerisation domain (NOD)-like receptor protein 3 (NLRP3)] inflammasome has received considerable attention, particularly in the context of immunity and pathogenesis during infection with influenza A (IAV) and SARS-CoV-2, the causative agent of COVID-19. Activation of the NLRP3 inflammasome results in the secretion of the proinflammatory cytokines IL-1β and IL-18, commonly coupled with pyroptotic cell death. While this mechanism is protective and key to host defense, aberrant NLRP3 inflammasome activation causes a hyperinflammatory response and excessive release of cytokines, both locally and systemically. Here, we discuss key molecules in the NLRP3 pathway that have also been shown to have significant roles in innate and adaptive immunity to viruses, including DEAD box helicase X-linked (DDX3X), vimentin and macrophage migration inhibitory factor (MIF). We also discuss the clinical opportunities to suppress NLRP3-mediated inflammation and reduce disease severity.

Subsets of Cytokines and Chemokines from DENV-4-Infected Patients Could Regulate the Endothelial Integrity of Cultured Microvascular Endothelial Cells

Introduction: It is a consensus that inflammatory mediators produced by immune cells contribute to changes in endothelial permeability in dengue. We propose to relate inflammatory mediators seen in dengue patients with the in vitro alteration of endothelial cells (ECs) cultured with serum from these patients. Methods: Patients with mild (DF) to moderate and severe dengue (DFWS/Sev) were selected. ELISA quantified inflammatory mediators. Expression of adhesion molecules and CD147 were evaluated in the ECs cultured with the patient’s serum by flow cytometry. We assessed endothelial permeability by measuring transendothelial electrical resistance in cocultures of ECs with patient serum. Results: Dengue infection led to an increase in inflammatory mediators—the IL-10 distinguished DF from DFWS/Sev. There were no changes in CD31, CD54, and CD106 but decreased CD147 expression in ECs. DFWS/Sev sera induced a greater difference in endothelial permeability than DF sera. Correlation statistical test indicated that low IL-10 and IFN-γ and high CCL5 maintain the integrity of ECs in DF patients. In contrast, increased TNF, IFN-γ, CXCL8, and CCL2 maintain EC integrity in DFWS/Sev patients. Conclusions: Our preliminary data suggest that a subset of inflammatory mediators may be related to the maintenance or loss of endothelial integrity, reflecting the clinical prognosis.

Evaluation of a new NS1 rapid diagnostic test using a single acute-phase serum panel collected during the largest dengue outbreak in Taiwan history in 2015

Dengue virus (DENV) infection results mostly from the bites of virus-carrying Aedes mosquitoes, which results in dengue fever (DF) with or without warning signs, severe dengue, or asymptomatic infections in humans. For point-of care identification of DENV-infected patients, a rapid diagnostic test (RDT) for DENV nonstructural protein 1 (NS1) has been developed to achieve early diagnosis and timely clinical management. We evaluated the performance of a new commercially available dengue NS1 RDT AsiaGen Dengue NS1 Antigen Rapid Diagnosis Test using real-time qRT-PCR as a reference method and compared the results with SD BIOLINE Dengue NS1 Ag using a single acute-phase serum panel collected during the largest dengue outbreak in the history of Taiwan in 2015. The results suggested that the sensitivity and specificity of AsiaGen Dengue NS1 Antigen RDT (96.9% and 100%) were similar to those of SD BIOLINE Dengue NS1 RDT (100% and 100%) for detection in the acute phase of DENV-2 infection. The results suggested that the sensitivity of both RDTs was similar (95.4% ~ 100%) for the sera collected at less than or equal to three days postsymptom onset (PSO). Our results suggested that the two DENV NS1 RDTs used in this study were promising for the timely diagnosis of DENV infection during dengue outbreaks, at least for DENV-2 in areas where authorized medical laboratories are not available or medical resources are limited. However, the performance of AsiaGen DENV NS1 RDTs in the detection of primary/secondary infections and infection by serotypes of DENV other than DENV-2 requires further investigation.

Macrophage migration inhibitory factor (MIF): A multifaceted cytokine regulated by genetic and physiological strategies

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine encoded within a functionally polymorphic genetic locus. MIF was initially recognized as a cytokine generated by activated T cells, but in recent days it has been identified as a multipotent key cytokine secreted by many other cell types involved in immune response and physiological processes. MIF is a highly conserved 12.5 kDa secretory protein that is involved in numerous biological processes. The expression and secretion profile of MIF suggests that MIF to be ubiquitously and constitutively expressed in almost all mammalian cells and is vital for numerous physiological processes. MIF is a critical upstream mediator of host innate and adaptive immunity and survival pathways resulting in the clearance of pathogens thus playing a protective role during infectious diseases. On the other hand, MIF being an immune modulator accelerates detrimental inflammation, promotes cancer metastasis and progression, thus worsening disease conditions. Several reports demonstrated that genetic and physiological factors, including MIF gene polymorphisms, posttranslational regulations, and receptor binding control the functional activities of MIF. Taking into consideration the multi-faceted role of MIF both in physiology and pathology, we thought it is timely to review and summarize the expressional and functional regulation of MIF, its functional mechanisms associated with its beneficial and pathological roles, and MIF-targeting therapies. Thus, our review will provide an overview on how MIF is regulated, its response, and the potency of the therapies that target MIF.

Development of Bacteriophage Virus-Like Particle Vaccines Displaying Conserved Epitopes of Dengue Virus Non-Structural Protein 1

Dengue virus (DENV) is a major global health problem, with over half of the world's population at risk of infection. Despite over 60 years of efforts, no licensed vaccine suitable for population-based immunization against DENV is available. Here, we describe efforts to engineer epitope-based vaccines against DENV non-structural protein 1 (NS1). NS1 is present in DENV-infected cells as well as secreted into the blood of infected individuals. NS1 causes disruption of endothelial cell barriers, resulting in plasma leakage and hemorrhage. Immunizing against NS1 could elicit antibodies that block NS1 function and also target NS1-infected cells for antibody-dependent cell cytotoxicity. We identified highly conserved regions of NS1 from all four DENV serotypes. We generated synthetic peptides to these regions and chemically conjugated them to bacteriophage Qβ virus-like particles (VLPs). Mice were immunized two times with the candidate vaccines and sera were tested for the presence of antibodies that bound to the cognate peptide, recombinant NS1 from all four DENV serotypes, and DENV-2-infected cells. We found that two of the candidate vaccines elicited antibodies that bound to recombinant NS1, and one candidate vaccine elicited antibodies that bound to DENV-infected cells. These results show that an epitope-specific vaccine against conserved regions of NS1 could be a promising approach for DENV vaccines or therapeutics to bind circulating NS1 protein.

Expansion and Refinement of Deep Sequence-Coupled Biopanning Technology for Epitope-Specific Antibody Responses in Human Serum

Identifying the specific epitopes targeted by antibodies elicited in response to infectious diseases is important for developing vaccines and diagnostics. However, techniques for broadly exploring the specificity of antibodies in a rapid manner are lacking, limiting our ability to quickly respond to emerging viruses. We previously reported a technology that couples deep sequencing technology with a bacteriophage MS2 virus-like particle (VLP) peptide display platform for identifying pathogen-specific antibody responses. Here, we describe refinements that expand the number of patient samples that can be processed at one time, increasing the utility of this technology for rapidly responding to emerging infectious diseases. We used dengue virus (DENV) as a model system since much is already known about the antibody response. Sera from primary DENV-infected patients (n = 28) were used to pan an MS2 bacteriophage VLP library displaying all possible 10-amino-acid peptides from the DENV polypeptide. Selected VLPs were identified by deep sequencing and further investigated by enzyme-linked immunosorbent assay. We identified previously described immunodominant regions of envelope and nonstructural protein-1, as well as a number of other epitopes. Our refinement of the deep sequence-coupled biopanning technology expands the utility of this approach for rapidly investigating the specificity of antibody responses to infectious diseases.

Evaluation of rapid diagnostic tests to detect dengue virus infections in Taiwan

Early diagnosis is important for the clinical management of diseases caused by dengue virus (DENV) infections. We investigated the performance of three commercially available DENV nonstructural protein 1 (NS1) rapid diagnostic tests (RDTs) using 173 acute-phase sera collected from dengue fever-suspected patients during the 2012-2013 DENV outbreak in Taiwan. The results of the NS1 RDTs were compared with those of qRT-PCR to calculate the sensitivity and specificity of the NS1 RDTs. The anti-DENV IgM and IgG RDT results were included to increase the probability of detecting acute DENV infection. The anti-DENV IgM/IgG RDT results were also compared with those of IgM/IgG captured ELISA. The sera from DENV qRT-PCR-positive patients were subjected to NS1 RDTs, as well as IgM/IgG captured ELISA. These results suggested that there was no significant difference in the sensitivities of the three commercially available DNEV NS1 RDTs; the SD NS1 RDT results showed the highest agreement with the qRT-PCR reference results, followed in order by the Bio-Rad and CTK NS1 RDT results when the specificity was considered. Inclusion of the IgM or IgG RDT results increased the likelihood of diagnosing either a primary or secondary DENV infection. NS1 RDTs were more sensitive for the detection of primary infections than secondary infections, related to DENV viremia levels determined by qRT-PCR. These results suggested that anti-DENV antibodies reduced the sensitivity of NS1 rapid tests. We also analyzed the sensitivity for the detection of different DENV serotypes, and the results suggested that the NS1 RDTs used in this study were valuable for rapid screening of acute DENV infection with DENV-1, DENV-2 and DENV-3. Our results suggest that the NS1 RDT is a good alternative to qRT-PCR analysis for timely dengue disease management and prevention in dengue-endemic regions where medical resources are lacking or during large dengue outbreaks. However, the relatively low sensitivity for DENV-4 might miss the detection of DENV-4-infected cases.

Dengue virus-activated platelets modulate monocyte immunometabolic response through lipid droplet biogenesis and cytokine signaling

Dengue is characterized as one of the most important arthropod-borne human viral diseases, representing a public health problem. Increased activation of immune cells is involved in the progression of infection to severe forms. Recently, our group demonstrated the contribution of platelet-monocyte interaction to inflammatory responses in dengue, adding to evolving evidence that platelets have inflammatory functions and can regulate different aspects of innate immune responses. Furthermore, stimuli-specific-activated platelets can promote phenotypic changes and metabolic reprogramming in monocytes. Thus, this study aimed to evaluate the roles of dengue virus (DENV)-activated platelets on immunometabolic reprogramming of monocytes in vitro, focusing on lipid droplet (LD) biogenesis. We demonstrated that platelets exposed to DENV in vitro form aggregates with monocytes and signal to LD formation and CXCL8/IL-8, IL-10, CCL2, and PGE₂ secretion. Pharmacologic inhibition of LD biogenesis prevents PGE₂ secretion, but not CXCL8/IL-8 release, by platelet-monocyte complexes. In exploring the mechanisms involved, we demonstrated that LD formation in monocytes exposed to DENV-activated platelets is partially dependent on platelet-produced MIF. Additionally, LD formation is higher in monocytes, which have platelets adhered on their surface, suggesting that beyond paracrine signaling, platelet adhesion is an important event in platelet-mediated modulation of lipid metabolism in monocytes. Together, our results demonstrate that activated platelets aggregate with monocytes during DENV infection and signal to LD biogenesis and the secretion of inflammatory mediators, which may contribute to dengue immunopathogenesis.

Roles of Macrophage Migration Inhibitory Factor in Dengue Pathogenesis: From Pathogenic Factor to Therapeutic Target

Dengue virus (DENV) infection is the most prevalent mosquito-borne viral infection and can lead to severe dengue hemorrhagic fever (DHF) and even life-threatening dengue shock syndrome (DSS). Although the cytokine storm has been revealed as a critical factor in dengue disease, the limited understanding of dengue immunopathogenesis hinders the development of effective treatments. Macrophage migration inhibitory factor (MIF) is a pleiotropic proinflammatory cytokine that mediates diverse immune responses, and the serum level of MIF positively correlates with disease severity in patients with dengue. MIF is involved in DENV replication and many pathological changes, such as vascular leakage, during DENV infection. In this paper, the pathogenic roles of MIF and the regulation of MIF secretion during DENV infection are reviewed. Furthermore, whether MIF is a potential therapeutic target against DENV infection is also discussed.

Potential Role of Macrophage Migration Inhibitory Factor in the Pathogenesis of Marek's Disease

Introduction

Marek’s disease virus (MDV) can cause malignant T-cell lymphomas and immunosuppression in chickens. Macrophage migration inhibitory factor (MIF) not only plays a critical role in inhibiting T-cell responses, but also contributes to multiple aspects of tumour progression. The aim of this study was to reveal the potential role of MIF in the pathogenesis of MDV infection.

Material and Methods

MIF gene expression levels were measured by using real-time PCR. Expression was assayed at different times in chicken embryo fibroblast (CEF) cells and tissue samples of SPF chickens infected with different MDV strains and fold change was calculated by the 2^–△△CT method.

Results

The expression of MIF was significantly downregulated (p < 0.05 and FC > 2) in CEF cells infected with the very virulent MDV RB1B strain at 48 h post infection (hpi) and in the skin and spleen at 14 days post infection (dpi). The reduction of MIF expression was also found in CEF cells infected by reticuloendotheliosis virus (REV), avian leukosis virus subgroup J (ALV-J), and MDV vaccine strain CVI988 or in HD11 cells stimulated with TLR2, 3, 4, and 7 ligands. Interestingly, MIF expression decreased continuously from 7 to 28 dpi in the thymus after RB1B virus infection while it increased after CVI988 virus infection. Upregulated expression of MIF was found in CEF infected with RB1B at 96 hpi and in the spleen and skin at 21 and 28 dpi.

Conclusion

The present study revealed the different expression pattern of MIF in response to MDV infection and indicated that MIF level may be associated with MDV pathogenesis.

Chikungunya Virus Infection Outcome: A Systematic Review of Host Genetics

Background: Chikungunya virus (CHIKV) is a global concern, inducing chikungunya fever and trigging an arthritogenic chronic phase beyond some severe forms. Outcomes of CHIKV infections in humans are dependent on genetic variations. Here, a systematic review was performed to show evidence of genetic variations on infection outcomes of patients. Methods: Searches were performed in Scopus, SciELO, MEDLINE/PubMed, Web of Science, OneFile (GALE), Periódicos CAPES and ScienceDirect Journals databases. The PICOS approach was used to assess the eligibility of records. A meta-analysis was also conducted to show an association between described alleles/genes and CHIKV infection outcome. Results: Reviews of genetic variants were conducted on genes: CD 209, OAS1, OAS2, OAS3, MIF, TLR-3, TLR-7, TLR-8, MYD-88, KIR, HLA-B; HLA-C; DRB1 and DQB1. Studies were performed on Gabon, Singapore, and India, including Indians, Malay, Gabonese and Chinese ethnicities and published between 2009-2017. The meta-analysis was performed with DRB1 *01; *03; *04; *07; *10; *11; *13; *14 and *15 and DQB1 *02; *03; *05 and *06 alleles with Indian population sample. Sampling power was >80% and a significant positive association between DRB1*14 and CHIKV infection was found (OR = 1.67, 95% CI = 1.04-2.67; p = .03). Conclusion: Majority of the studies were conducted in India. Meta-analysis suggests that DRB1*14 is related to the susceptibility of symptomatic CHIKV infection in Indian population. The literature about CHIKV infection and genetic variations is scarce. The precise role of genetic variation in CHIKV is not clear yet. Further studies are necessary to provide more concrete evidences.

Significance of Autophagy in Dengue Virus Infection: A Brief Review

Dengue virus (DENV) causes asymptomatic to severe life-threatening infections and affects millions of people worldwide. Autophagy, a cellular degradative pathway, has both proviral and antiviral functions. Dengue virus triggers the autophagy pathway for the successful replication of its genome. However, the exact mechanism and the viral factors involved in activating this pathway remain unclear. This review summarizes the existing knowledge on the mechanism of autophagy induction and its significance during DENV infection.

Macrophage Migration Inhibitory Factor Triggers Inflammatory Responses During Very Virulent Infectious Bursal Disease Virus Infection

Infectious bursal disease (IBD) is one of the main threats to the poultry industry worldwide. In China, very virulent IBD virus (vvIBDV) is the main prevalent virus strain, causing inflammation, immunosuppression, and high mortality in young chickens. To determine whether this acute inflammation can trigger lesions or even death in chickens, it is important to study the mechanism of vvIBDV pathogenicity. Thus, in the current study, we investigated the inflammation response, bursal lesions, and mortality in chickens caused by vvIBDV at different time points postinfection. Results showed an upregulation of proinflammatory cytokines, including interleukin-1β and interleukin-18, and macrophage infiltration in bursa in response to vvIBDV infection. High-throughput proteomic sequencing based on isobaric tags for relative and absolute quantitation showed that chicken macrophage migration inhibitory factor (chMIF) was upregulated uniquely in primary bursal cells infected with vvIBDV compared with infection by nonpathogenic attenuated IBDV. We confirmed that chMIF was upregulated by vvIBDV infection both in vivo and in vitro. Moreover, chMIF was extracellularly secreted by infected DT40 and primary bursal cells. Further experiments revealed that the secreted chMIF could induce migration of peripheral blood mononuclear cells and promote transcription of proinflammatory cytokines in chicken primary macrophages. Notably, these effects of chMIF could be reduced by using an MIF specific inhibitor. Thus, our study elucidates critical molecular determinants underlying vvIBDV-mediated initiation of acute inflammation, which might be pivotal to understand the mechanism of vvIBDV pathogenicity.

Contemporary Strategies and Current Trends in Designing Antiviral Drugs against Dengue Fever via Targeting Host-Based Approaches

Dengue virus (DENV) is an arboviral human pathogen transmitted through mosquito bite that infects an estimated ~400 million humans (~5% of the global population) annually. To date, no specific therapeutics have been developed that can prevent or treat infections resulting from this pathogen. DENV utilizes numerous host molecules and factors for transcribing the single-stranded ~11 kb positive-sense RNA genome. For example, the glycosylation machinery of the host is required for viral particles to assemble in the endoplasmic reticulum. Since a variety of host factors seem to be utilized by the pathogens, targeting these factors may result in DENV inhibitors, and will play an important role in attenuating the rapid emergence of other flaviviruses. Many experimental studies have yielded findings indicating that host factors facilitate infection, indicating that the focus should be given to targeting the processes contributing to pathogenesis along with many other immune responses. Here, we provide an extensive literature review in order to elucidate the progress made in the development of host-based approaches for DENV viral infections, focusing on host cellular mechanisms and factors responsible for viral replication, aiming to aid the potential development of host-dependent antiviral therapeutics.

Combination of Modified NS1 and NS3 as a Novel Vaccine Strategy against Dengue Virus Infection

Dengue virus (DENV) causes a range of illness, including dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. DENV nonstructural protein (NS) 1 has been considered to be a desirable vaccine candidate for its ability to induce Ab and complement-dependent cytolysis of DENV-infected cells as well as to block the pathogenic effects of NS1. However a potential drawback of NS1 as a vaccine is that anti-DENV NS1 Abs can lead to endothelial cell damage and platelet dysfunction by antigenic cross-reactivity. Therefore, we modified the DENV NS1 by replacing the C-terminal cross-reactive epitopes with the corresponding region of Japanese encephalitis virus NS1 to generate a chimeric DJ NS1 protein. Active immunization with DJ NS1 induced a strong Ab response. To enhance cellular immunity, we further combined DJ NS1 with DENV NS3 to immunize mice and showed activation of Ag-specific CD4⁺ and CD8⁺ T cells in addition to Ab responses. We further detected NS3-specific CTL activities as well as CD107a expression of effector cells. Importantly, the protective effects attributed by DJ NS1 and NS3 immunization were demonstrated in a DENV-infected mouse model by reduced viral titers, soluble NS1 levels, mouse tail bleeding time, and vascular leakage at skin injection sites. Collectively, the results from this study reveal the humoral and cellular immune responses and the protective effects conferred by DJ NS1 and NS3 immunization in the mouse model of DENV infection and provide a potential strategy for dengue vaccine design.

Dengue virus or NS1 protein induces trans-endothelial cell permeability associated with VE-Cadherin and RhoA phosphorylation in HMEC-1 cells preventable by Angiopoietin-1

A transient increase in trans-endothelial cell permeability in dengue patients leads to vascular leakage and shock syndrome. Here, we analysed the molecular mechanisms that cause permeability changes in human dermal microvascular endothelial cells (HMEC-1) using a direct dengue virus (DENV) infection model or treatment with NS1, a secreted DENV non-structural protein. In HMEC-1 cells, both treatments increase permeability with a concordant increase in the secretion of angiopoietin-2 (Ang-2). There is phosphorylation and loss of the junction protein VE-Cadherin from the inter-endothelial cell junctions and phosphorylation of RhoA. Direct virus infection results in activation of Src by phosphorylation, whereas NS1 treatment alone does not lead to Src activation. Furthermore, treatment with recombinant Ang-1, a physiological antagonist of Ang-2, prevents Ang-2 release, VE-Cadherin phosphorylation and internalization, and phosphorylation of RhoA and Src, resulting in restoration of barrier function. The permeability increase could also be prevented by blocking the Ang1/2 signalling receptor, Tie-2, or using a Rho/ROCK-specific inhibitor. Dasatinib, a Src-family kinase (SFK) inhibitor that inhibits Src phosphorylation, prevents enhanced permeability induced by direct DENV infection whereas in NS1 protein-treated cells its effect is less significant. The results provide important insights on the mechanisms of increased trans-endothelial permeability in DENV infection, and suggest the therapeutic potential of using recombinant Ang-1 or targeting these key molecules to prevent vascular leakage in dengue.

Dengue virus non-structural protein 1: a pathogenic factor, therapeutic target, and vaccine candidate

Dengue virus (DENV) infection is the most common mosquito-transmitted viral infection. DENV infection can cause mild dengue fever or severe dengue hemorrhagic fever (DHF)/dengue shock syndrome (DSS). Hemorrhage and vascular leakage are two characteristic symptoms of DHF/DSS. However, due to the limited understanding of dengue pathogenesis, no satisfactory therapies to treat nor vaccine to prevent dengue infection are available, and the mortality of DHF/DSS is still high. DENV nonstructural protein 1 (NS1), which can be secreted in patients’ sera, has been used as an early diagnostic marker for dengue infection for many years. However, the roles of NS1 in dengue-induced vascular leakage were described only recently. In this article, the pathogenic roles of DENV NS1 in hemorrhage and vascular leakage are reviewed, and the possibility of using NS1 as a therapeutic target and vaccine candidate is discussed.

An hPSC-Derived Tissue-Resident Macrophage Model Reveals Differential Responses of Macrophages to ZIKV and DENV Infection

Zika virus (ZIKV) and dengue virus (DENV) are two closely related flaviviruses that lead to different clinical outcomes. The mechanism for the distinct pathogenesis of ZIKV and DENV is poorly understood. Here, we investigate ZIKV and DENV infection of macrophages using a human pluripotent stem cell (hPSC)-derived macrophage model and discover key virus-specific responses. ZIKV and DENV productively infect hPSC-derived macrophages. DENV, but not ZIKV, infection of macrophages strongly activates macrophage migration inhibitory factor (MIF) secretion and decreases macrophage migration. Neutralization of MIF leads to improved migratory ability of DENV-infected macrophages. In contrast, ZIKV-infected macrophages exhibit prolonged migration and express low levels of pro-inflammatory cytokines and chemokines. Mechanistically, ZIKV disrupts the nuclear factor κB (NF-κB)-MIF positive feedback loop by inhibiting the NF-κB signaling pathway. Our results demonstrate the utility of hPSC-derived macrophages in infectious disease modeling and suggest that the distinct impact of ZIKV and DENV on macrophage immune response may underlie different pathogenesis of Zika and dengue diseases.

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An hPSC-derived tissue-resident macrophage model for ZIKV and DENV infection

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ZIKV-, but not DENV-, infected macrophages maintain migratory capacity

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ZIKV, but not DENV, inhibits pro-inflammatory cytokines and chemokines expression

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ZIKV disrupts NF-κB-MIF positive feedback loop by inhibiting NF-κB pathway

Upsetting the Balance: When Viruses Manipulate Cell Polarity Control

The central importance of cell polarity control is emphasized by the frequency with which it is targeted by many diverse viruses. It is clear that in targeting key polarity control proteins, viruses affect not only host cell polarity, but also influence many cellular processes, including transcription, replication, and innate and acquired immunity. Examination of the interactions of different virus proteins with the cell and its polarity controls during the virus life cycles, and in virally‐induced cell transformation shows ever more clearly how intimately all cellular processes are linked to the control of cell polarity.

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Multiple viruses target cell polarity.

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Viral targeting of polarity frequently occurs through PDZ recognition.

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Biological effects include immune-avoidance, cell proliferation and apoptosis inhibition.

Macrophage migration inhibitory factor is critical for dengue NS1-induced endothelial glycocalyx degradation and hyperpermeability

Vascular leakage is one of the salient characteristics of severe dengue. Nonstructural protein 1 (NS1) of dengue virus (DENV) can stimulate endothelial cells to secrete endothelial hyperpermeability factor, macrophage migration inhibitory factor (MIF), and the glycocalyx degradation factor heparanase 1 (HPA-1). However, it is unclear whether MIF is directly involved in NS1-induced glycocalyx degradation. In this study, we observed that among NS1, MIF and glycocalyx degradation-related molecules, the HPA-1, metalloproteinase 9 (MMP-9) and syndecan 1 (CD138) serum levels were all increased in dengue patients, and only NS1 and MIF showed a positive correlation with the CD138 level in severe patients. To further characterize and clarify the relationship between MIF and CD138, we used recombinant NS1 to stimulate human cells in vitro and challenge mice in vivo. Our tabulated results suggested that NS1 stimulation could induce human endothelial cells to secrete HPA-1 and immune cells to secrete MMP-9, resulting in endothelial glycocalyx degradation and hyperpermeability. Moreover, HPA-1, MMP-9, and CD138 secretion after NS1 stimulation was blocked by MIF inhibitors or antibodies both in vitro and in mice. Taken together, these results suggest that MIF directly engages in dengue NS1-induced glycocalyx degradation and that targeting MIF may represent a possible therapeutic approach for preventing dengue-induced vascular leakage.

Porphyromonas gingivalis ATCC 33277 promotes intercellular adhesion molecule-1 expression in endothelial cells and monocyte-endothelial cell adhesion through macrophage migration inhibitory factor

BACKGROUND

Porphyromonas gingivalis (P. gingivalis), one of the main pathogenic bacteria involved in periodontitis, induces the expression of intercellular adhesion molecule - 1 (ICAM-1) and monocyte-endothelial cell adhesion. This effect plays a pivotal role in atherosclerosis development. Macrophage migration inhibitory factor (MIF) is a multifunctional cytokine and critically affects atherosclerosis pathogenesis. In this study, we tested the involvement of MIF in the P. gingivalis ATCC 33277-enhanced adhesive properties of endothelial cells.

RESULTS

Endothelial MIF expression was enhanced by P. gingivalis ATCC 33277 infection. The MIF inhibitor ISO-1 inhibited ICAM-1 production in endothelial cells, and monocyte-endothelial cell adhesion was induced by P. gingivalis ATCC 33277 infection. However, the addition of exogenous human recombinant MIF to P. gingivalis ATCC 33277-infected endothelial cells facilitated monocyte recruitment by promoting ICAM-1 expression in endothelial cells.

CONCLUSIONS

These experiments revealed that MIF in endothelial cells participates in the pro-atherosclerotic lesion formation caused by P. gingivalis ATCC 33277 infection. Our novel findings identify a more detailed pathological role of P. gingivalis ATCC 33277 in atherosclerosis.

Development of a chimeric Zika vaccine using a licensed live-attenuated flavivirus vaccine as backbone

The global spread of Zika virus (ZIKV) and its unexpected association with congenital defects necessitates the rapid development of a safe and effective vaccine. Here we report the development and characterization of a recombinant chimeric ZIKV vaccine candidate (termed ChinZIKV) that expresses the prM-E proteins of ZIKV using the licensed Japanese encephalitis live-attenuated vaccine SA14-14-2 as the genetic backbone. ChinZIKV retains its replication activity and genetic stability in vitro, while exhibiting an attenuation phenotype in multiple animal models. Remarkably, immunization of mice and rhesus macaques with a single dose of ChinZIKV elicits robust and long-lasting immune responses, and confers complete protection against ZIKV challenge. Significantly, female mice immunized with ChinZIKV are protected against placental and fetal damage upon ZIKV challenge during pregnancy. Overall, our study provides an alternative vaccine platform in response to the ZIKV emergency, and the safety, immunogenicity, and protection profiles of ChinZIKV warrant further clinical development.

Transcytosis Involvement in Transport System and Endothelial Permeability of Vascular Leakage during Dengue Virus Infection

The major role of endothelial cells is to maintain homeostasis of vascular permeability and to preserve the integrity of vascular vessels to prevent fluid leakage. Properly functioning endothelial cells promote physiological balance and stability for blood circulation and fluid components. A monolayer of endothelial cells has the ability to regulate paracellular and transcellular pathways for transport proteins, solutes, and fluid. In addition to the paracellular pathway, the transcellular pathway is another route of endothelial permeability that mediates vascular permeability under physiologic conditions. The transcellular pathway was found to be associated with an assortment of disease pathogeneses. The clinical manifestation of severe dengue infection in humans is vascular leakage and hemorrhagic diatheses. This review explores and describes the transcellular pathway, which is an alternate route of vascular permeability during dengue infection that corresponds with the pathologic finding of intact tight junction. This pathway may be the route of albumin transport that causes endothelial dysfunction during dengue virus infection.

Host genetics and dengue fever

Dengue is a major worldwide problem in tropical and subtropical areas; it is caused by four different viral serotypes, and it can manifest as asymptomatic, mild, or severe. Many factors interact to determine the severity of the disease, including the genetic profile of the infected patient. However, the mechanisms that lead to severe disease and eventually death have not been determined, and a great challenge is the early identification of patients who are more likely to progress to a worse health condition. Studies performed in regions with cyclic outbreaks such as Cuba, Brazil, and Colombia have demonstrated that African ancestry confers protection against severe dengue. Highlighting the host genetics as an important factor in infectious diseases, a large number of association studies between genetic polymorphisms and dengue outcomes have been published in the last two decades. The most widely used approach involves case-control studies with candidate genes, such as the HLA locus and genes for receptors, cytokines, and other immune mediators. Additionally, a Genome-Wide Association Study (GWAS) identified SNPs associated with African ethnicity that had not previously been identified in case-control studies. Despite the increasing number of publications in America, Africa, and Asia, the results are quite controversial, and a meta-analysis is needed to assess the consensus among the studies. SNPs in the MICB, TNF, CD209, FcγRIIA, TPSAB1, CLEC5A, IL10 and PLCE1 genes are associated with the risk or protection of severe dengue, and the findings have been replicated in different populations. A thorough understanding of the viral, human genetic, and immunological mechanisms of dengue and how they interact is essential for effectively preventing dengue, but also managing and treating patients.

Decrease in Dengue virus-2 infection and reduction of cytokine/chemokine production by Uncaria guianensis in human hepatocyte cell line Huh-7

BACKGROUND

Dengue fever may present hemorrhages and cavitary effusions as result of exacerbated immune responses. We investigated hydro-alcoholic extracts from leaves (UGL) and bark (UGB) of the medicinal species Uncaria guinanensis with respect to antiviral effects in Dengue virus (DENV) infection and in immunological parameters associated with in vivo physiopathological features.

METHODS

Chemical profiles from UGB or UGL were compared in thin layer chromatography and ¹H nuclear magnetic resonance using flavonoid compounds and a pentacyclic oxindole alkaloid-enriched fraction as references. DENV-2-infected hepatocytes (Huh-7) were treated with extracts. Cell viability, DENV antigens and immunological factors were detected by enzyme-linked immunosorbent assay (ELISA) or flow cytometry.

FINDINGS

The UGL mainly differed from UGB by selectively containing the flavonoid kaempferitrin. UGB and UGL improved hepatocyte viability. Both extracts reduced intracellular viral antigen and inhibited the secretion of viral non-structural protein (NS1), which is indicative of viral replication. Reduction in secretion of macrophage migration inhibitory factor was achieved by UGB, of interleukin-6 by UGL, and of interleukin-8 by both UGB and UGL. MAIN

CONCLUSIONS

The U. guianensis extracts presented, antiviral and immunomodulatory effects for DENV and possibly a hepatocyte-protective activity. Further studies may be performed to consider these products as potential candidates for the development of an herbal product for the future treatment of dengue.

Garlic Organosulfur Compounds Reduce Inflammation and Oxidative Stress during Dengue Virus Infection

Dengue virus (DENV) is a mosquito-borne flavivirus that causes significant global human disease and mortality. One approach to develop treatments for DENV infection and the prevention of severe disease is through investigation of natural medicines. Inflammation plays both beneficial and harmful roles during DENV infection. Studies have proposed that the oxidative stress response may be one mechanism responsible for triggering inflammation during DENV infection. Thus, blocking the oxidative stress response could reduce inflammation and the development of severe disease. Garlic has been shown to both reduce inflammation and affect the oxidative stress response. Here, we show that the garlic active compounds diallyl disulfide (DADS), diallyl sulfide (DAS) and alliin reduced inflammation during DENV infection and show that this reduction is due to the effects on the oxidative stress response. These results suggest that garlic could be used as an alternative treatment for DENV infection and for the prevention of severe disease development.

Aberrant monocyte responses predict and characterize dengue virus infection in individuals with severe disease

BACKGROUND

Currently, several assays can diagnose acute dengue infection. However, none of these assays can predict the severity of the disease. Biomarkers that predicts the likelihood that a dengue patient will develop a severe form of the disease could permit more efficient patient triage and allows better supportive care for the individual in need, especially during dengue outbreaks.

METHODS

We measured 20 plasma markers i.e. IFN-γ, IL-10, granzyme-B, CX3CL1, IP-10, RANTES, CXCL8, CXCL6, VCAM, ICAM, VEGF, HGF, sCD25, IL-18, LBP, sCD14, sCD163, MIF, MCP-1 and MIP-1β in 141 dengue patients in over 230 specimens and correlate the levels of these plasma markers with the development of dengue without warning signs (DWS-), dengue with warning signs (DWS+) and severe dengue (SD).

RESULTS

Our results show that the elevation of plasma levels of IL-18 at both febrile and defervescence phase was significantly associated with DWS+ and SD; whilst increase of sCD14 and LBP at febrile phase were associated with severity of dengue disease. By using receiver operating characteristic (ROC) analysis, the IL-18, LBP and sCD14 were significantly predicted the development of more severe form of dengue disease (DWS+/SD) (AUC = 0.768, P < 0.0001; AUC = 0.819, P < 0.0001 and AUC = 0.647, P = 0.014 respectively). Furthermore, we also found that the levels of VEGF were directly correlated and sCD14 was inversely correlated with platelet count, suggesting that the endothelial activation and microbial translocation may played a role in pathogenesis of dengue disease.

CONCLUSIONS

Given that the elevation IL-18, LBP and sCD14 among patients with severe form of dengue disease, our findings suggest a pathogenic role for an aberrant inflammasome and monocyte activation in the development of severe form of dengue disease.

In vitro Assays for Measuring Endothelial Permeability byTranswells and Electrical Impedance Systems

Vascular leakage is an important feature in several diseases, such as septic shock, viral hemorrhagic fever, cancer metastasis and ischemia-reperfusion injuries. Thus establishing assays for measuring endothelial permeability will provide insight into the establishment or progression of such diseases. Here, we provide transwell permeability assay and electrical impedance sensing assay for studying endothelial permeability in vitro. With these methods, the effect of a molecule on endothelial permeability could be defined.

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.

The effect of the dengue non-structural 1 protein expression over the HepG2 cell proteins in a proteomic approach

Dengue is an important mosquito borne viral disease in the world. Dengue virus (DENV) encodes a polyprotein, which is cleaved in ten proteins, including the non-structural protein 1 (NS1). In this work, we analyzed the effect of NS1 expression in one hepatic cell line, HepG2, through a shotgun proteomic approach. Cells were transfected with pcENS1 plasmid, which encodes the DENV2 NS1 protein, or the controls pcDNA3 (negative control) and pMAXGFP (GFP, a protein unrelated to dengue). Expression of NS1 was detected by immunofluorescence, western blot and flow cytometry. We identified 14,138 peptides that mapped to 4,756 proteins in all analyzed conditions. We found 41 and 81 differentially abundant proteins when compared to cells transfected with plasmids pcDNA3 and pMAXGFP, respectively. Besides, 107 proteins were detected only in the presence of NS1. We identified clusters of proteins involved mainly in mRNA process and viral RNA replication. Down regulation expression of one protein (MARCKS), identified by the proteomic analysis, was also confirmed by real time PCR in HepG2 cells infected with DENV2. Identification of proteins modulated by the presence of NS1 may improve our understanding of its role in virus infection and pathogenesis, contributing to development of new therapies and vaccines.

BIOLOGICAL SIGNIFICANCE

Dengue is an important viral disease, with epidemics in tropical and subtropical regions of the world. The disease is complex, with different manifestations, in which the liver is normally affected. The NS1 is found in infected cells associated with plasma membrane and secreted into the circulation as a soluble multimer. This protein is essential for virus viability, although its function is not elucidated. Some reports indicate that the NS1 can be used as a protective antigen for the development of a dengue vaccine, while others suggest its involvement in viral pathogenesis. In this work, we report an in-depth comprehensive proteomic profiling resulting from the presence of NS1 in HepG2 cells. These results can contribute to a better understanding of the NS1 role during infection.

Cloning, characterization, and expression of the macrophage migration inhibitory factor gene from the black tiger shrimp (Penaeus monodon)

Macrophage migration inhibitory factor (MIF) is an ancient cytokine that engages in innate immune system of vertebrates and invertebrates. In this study, the MIF gene homologue (PmMIF) was cloned from the black tiger shrimp, Penaeus monodon. The full-length cDNA sequence of PmMIF was 838 bp and contained 78 bp 5' untranslated region (UTR) and 397 bp 3' UTR, and an open reading frame (ORF) of 363 bp which coded 120 amino acids (aa). Multiple alignment analysis showed that the deduced amino acid sequence shared 98% identities with MIF from closely related species of Litopenaeus vannamei. Quantitative real-time PCR (qRT-PCR) analysis indicated that PmMIF was highly expression observed in hepatotpancreas and gills. After Vibrio harveyi challenge, PmMIF mRNA level in hepatopancreas and gills were sharply up-regulated at 6 h post-injection, and reached the maximum at 12 h. PmMIF expression level in the hepatopancreas and gills were up-regulated markedly under low (2.3%) and high (4.3%) salinity exposure, respectively. PmMIF expression level in gills increased significantly at 12 h and reached peak values (2.5- fold, 6.4-fold and 1.8-fold compared with the control) at 12 h, 48 h and 12 h after zinc, cadmium and copper exposure, respectively. In the hepatopancreas, the expression of PmMIF reached maximum levels (8.5- fold, 6.2-fold and 2.1-fold compared with the control) at 24 h, 6 h and 48 h after zinc, cadmium and copper exposure, respectively. All the results indicate that PmMIF plays an important role in responding in the innate immune system of shrimps.

Dengue Virus Nonstructural Protein 1 Induces Vascular Leakage through Macrophage Migration Inhibitory Factor and Autophagy

Dengue virus (DENV) is the most common mosquito-borne flavivirus; it can either cause mild dengue fever or the more severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). One of the characteristic features of DHF/DSS is vascular leakage; although DENV nonstructural protein 1 (NS1) has been proved to induce vascular leakage after binding to Toll-like receptor 4, the down-stream mechanism has not yet been fully understood. In the sera of DENV-infected patients, the concentrations of DENV NS1 and inflammatory cytokine macrophage migration inhibitory factor (MIF) are positively correlated with disease severity, but whether DENV NS1 induces vascular leakage through MIF secretion remains unknown. We demonstrated that recombinant NS1 induced vascular leakage and MIF secretion both in human endothelial cell line HMEC-1 and in mice. Furthermore, these phenomena were inhibited in the presence of anti-NS1 antibodies both in vitro and in vivo. DENV NS1 also induced LC3-I to LC3-II conversion and p62 degradation in endothelial cell line, which indicated the formation of autophagy. To clarify whether MIF or autophagy mediated DENV NS1-induced vascular leakage, various inhibitors were applied. The results showed that DENV NS1-induced vascular leakage and VE-cadherin disarray were blocked in the presence of MIF inhibitors, anti-MIF-antibodies or autophagy inhibitors. An Atg5 knockdown clone further confirmed that autophagy formation of endothelial cells was required in NS1-induced vascular leakage. Furthermore, DENV NS1-induced LC3 puncta were also decreased in the presence of MIF inhibitors, indicating that MIF mediated DENV NS1-induced autophagy. Taken together, the results suggest a potential mechanism of DENV-induced vascular leakage and provide possible therapeutic targets against DHF/DSS.

Vitamin D-Regulated MicroRNAs: Are They Protective Factors against Dengue Virus Infection?

Over the last few years, an increasing body of evidence has highlighted the critical participation of vitamin D in the regulation of proinflammatory responses and protection against many infectious pathogens, including viruses. The activity of vitamin D is associated with microRNAs, which are fine tuners of immune activation pathways and provide novel mechanisms to avoid the damage that arises from excessive inflammatory responses. Severe symptoms of an ongoing dengue virus infection and disease are strongly related to highly altered production of proinflammatory mediators, suggesting impairment in homeostatic mechanisms that control the host's immune response. Here, we discuss the possible implications of emerging studies anticipating the biological effects of vitamin D and microRNAs during the inflammatory response, and we attempt to extrapolate these findings to dengue virus infection and to their potential use for disease management strategies.

Macrophage migration inhibitory factor has a permissive role in concanavalin A-induced cell death of human hepatoma cells through autophagy

Concanavalin A (ConA) is a lectin and T-cell mitogen that can activate immune responses. In recent times, ConA-induced cell death of hepatoma cells through autophagy has been reported and its therapeutic effect was confirmed in a murine in situ hepatoma model. However, the molecular mechanism of ConA-induced autophagy is still unclear. As macrophage migration inhibitory factor (MIF), which is a proinflammatory cytokine, can trigger autophagy in human hepatoma cells, the possible involvement of MIF in ConA-induced autophagy was investigated in this study. We demonstrated that cell death is followed by an increment in MIF expression and secretion in the ConA-stimulated human hepatoma cell lines, HuH-7 and Hep G2. In addition, ConA-induced autophagy and cell death of hepatoma cells were blocked in the presence of an MIF inhibitor. Knockdown of endogenous MIF by small hairpin RNA confirmed that MIF is required for both ConA-induced autophagy and death of hepatoma cells. Furthermore, signal pathway studies demonstrated that ConA induces signal transducer and activator of transcription 3 (STAT3) phosphorylation to trigger MIF upregulation, which in turn promotes Bcl-2/adenovirus E1B 19 kDa-interacting protein 3 (BNIP3)-dependent autophagy. By using a murine in situ hepatoma model, we further demonstrated that MIF contributes to anti-hepatoma activity of ConA by regulating STAT3-MIF-BNIP3-dependent autophagy. In summary, our findings uncover a novel role of MIF in lectin-mediated anti-hepatoma activities by regulating autophagy.

Pathogenic roles of macrophage migration inhibitory factor during dengue virus infection

Dengue virus (DENV) infection is the most common cause of viral hemorrhagic fever, which can lead to life-threatening dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). Hemorrhage and plasma leakage are two major hallmarks of DHF/DSS. Because the mechanisms causing these pathogenic changes are unclear, there is no effective therapy against DHF/DSS. In this review, we focus on the possible pathogenic effects of a pleiotropic cytokine, macrophage migration inhibitory factor (MIF), on the pathogenesis of DENV infection. MIF is a critical mediator of the host immune response and inflammation, and there is a correlation between the serum levels of MIF and disease severity in dengue patients. Furthermore, MIF knock-out mice exhibit less severe clinical disease and lethality. However, the role of MIF in the pathogenesis of DHF/DSS is not limited to immune cell recruitment. Recent evidence indicates that DENV infection induced MIF production and may contribute to vascular hyperpermeability and viral replication during DENV infection. The expression of both adhesion and coagulation molecules on MIF-stimulated monocytes and endothelial cells is also increased, which may contribute to inflammatory and anticoagulatory states during DHF/DSS. Therefore, blocking MIF production or its function may provide a solution for the treatment and prevention of DHF/DSS.

Culture medium from TNF-α-stimulated mesenchymal stem cells attenuates allergic conjunctivitis through multiple antiallergic mechanisms

BACKGROUND

The immunomodulatory and anti-inflammatory functions of mesenchymal stem cells (MSCs) have been demonstrated in several autoimmune/inflammatory diseases, but their contribution to allergic conjunctivitis and underlying antiallergic mechanisms remain elusive.

OBJECTIVE

We sought to explore the clinical application of MSCs to experimental allergic conjunctivitis (EAC) and its underlying antiallergic mechanisms.

METHODS

Culture medium from TNF-α-stimulated, bone marrow-derived MSCs (MSC-CMT) was administered topically to mice with EAC, and the related allergic symptoms and biological changes were evaluated. Murine spleen-derived B cells, bone marrow-derived mast cells (MCs), and lung vascular endothelial cells were cultured in vitro to investigate the antiallergic MSC-CMT mechanisms.

RESULTS

Topical instillation of MSC-CMT significantly attenuated the clinical symptoms of short ragweed pollen-induced EAC, with a significant decrease in inflammatory cell frequency, nuclear factor κB p65 expression, and TNF-α and IL-4 production. In vitro MSC-CMT significantly inhibited the activation of MCs and B-cell IgE release and reduced histamine-induced vascular hyperpermeability. During EAC, MSC-CMT treatment also decreased IgE production, histamine release, enrichment and activation of MCs, and conjunctival vascular hyperpermeability. The MSC-CMT-mediated inhibition of B cells, MCs, and histamine and its antiallergic effects during EAC were abrogated when MSCs were pretreated with COX2 small interfering RNA.

CONCLUSIONS

Our findings provide compelling evidence that MSC-CMT inhibits EAC through COX2-dependent multiple antiallergic mechanisms and support the use of MSC-CMT as a novel strategy for treating allergic conjunctivitis.

Macrophage migration inhibitory factor induces vascular leakage via autophagy

Vascular leakage is an important feature of acute inflammatory shock, which currently has no effective treatment. Macrophage migration inhibitory factor (MIF) is a pro-inflammatory cytokine that can induce vascular leakage and plays an important role in the pathogenesis of shock. However, the mechanism of MIF-induced vascular leakage is still unclear. In this study, using recombinant MIF (rMIF), we demonstrated that MIF induced disorganization and degradation of junction proteins and increased the permeability of human endothelial cells in vitro. Western blotting analysis showed that rMIF treatment induced LC3 conversion and p62 degradation. Inhibition of autophagy with a PI3K inhibitor (3-MA), a ROS scavenger (NAC) or autophagosomal-lysosomal fusion inhibitors (bafilomycin A1 and chloroquine) rescued rMIF-induced vascular leakage, suggesting that autophagy mediates MIF-induced vascular leakage. The potential involvement of other signaling pathways was also studied using different inhibitors, and the results suggested that MIF-induced vascular leakage may occur through the ERK pathway. In conclusion, we showed that MIF triggered autophagic degradation of endothelial cells, resulting in vascular leakage. Inhibition of MIF-induced autophagy may provide therapeutic targets against vascular leakage in inflammatory shock.

Macrophage migration inhibitory factor triggers chemotaxis of CD74+CXCR2+ NKT cells in chemically induced IFN-γ-mediated skin inflammation

IFN-γ mediates chemically induced skin inflammation; however, the mechanism by which IFN-γ-producing cells are recruited to the sites of inflammation remains undefined. Secretion of macrophage migration inhibitory factor (MIF), a proinflammatory cytokine, from damaged cells may promote immune cell recruitment. We hypothesized that MIF triggers an initial step in the chemotaxis of IFN-γ-producing cells in chemically induced skin inflammation. Using acute and chronic models of 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced skin inflammation in mouse ears, MIF expression was examined, and its role in this process was investigated pharmacologically. The cell populations targeted by MIF, their receptor expression patterns, and the effects of MIF on cell migration were examined. TPA directly caused cytotoxicity accompanied by MIF release in mouse ear epidermal keratinocytes, as well as in human keratinocytic HaCaT cells. Treatment with the MIF antagonist (S,R)-3-(4-hydroxyphenyl)-4,5-dihydro-5-isoxazole acetic acid methyl ester considerably attenuated TPA-induced ear swelling, leukocyte infiltration, epidermal cell proliferation, and dermal angiogenesis. Inhibition of MIF greatly diminished the dermal infiltration of IFN-γ(+) NKT cells, whereas the addition of exogenous TPA and MIF to NKT cells promoted their IFN-γ production and migration, respectively. MIF specifically triggered the chemotaxis of NKT cells via CD74 and CXCR2, and the resulting depletion of NKT cells abolished TPA-induced skin inflammation. In TPA-induced skin inflammation, MIF is released from damaged keratinocytes and then triggers the chemotaxis of CD74(+)CXCR2(+) NKT cells for IFN-γ production.

Clinical and immunological markers of dengue progression in a study cohort from a hyperendemic area in Malaysia

Background

With its elusive pathogenesis, dengue imposes serious healthcare, economic and social burden on endemic countries. This study describes the clinical and immunological parameters of a dengue cohort in a Malaysian city, the first according to the WHO 2009 dengue classification.

Methodology and Findings

This longitudinal descriptive study was conducted in two Malaysian hospitals where patients aged 14 and above with clinical symptoms suggestive of dengue were recruited with informed consent. Among the 504 participants, 9.3% were classified as non-dengue, 12.7% without warning signs, 77.0% with warning signs and 1.0% with severe dengue based on clinical diagnosis. Of these, 37% were misdiagnosed as non-dengue, highlighting the importance of both clinical diagnosis and laboratory findings. Thrombocytopenia, prolonged clotting time, liver enzymes, ALT and AST served as good markers for dengue progression but could not distinguish between patients with and without warning signs. HLA-A*24 and -B*57 were positively associated with Chinese and Indians patients with warning signs, respectively, whereas A*03 may be protective in the Malays. HLA-A*33 was also positively associated in patients with warning signs when compared to those without. Dengue NS1, NS2A, NS4A and NS4B were found to be important T cell epitopes; however with no apparent difference between with and without warning signs patients. Distinction between the 2 groups of patients was also not observed in any of the cytokines analyzed; nevertheless, 12 were significantly differentially expressed at the different phases of illness.

Conclusion

The new dengue classification system has allowed more specific detection of dengue patients, however, none of the clinical parameters allowed distinction of patients with and without warning signs. While the HLA-A*33 may be predictive marker for development of warning signs; larger studies will be needed to support this findings.