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

Dengue virus-host interactions: Structural and mechanistic insights for future therapeutic strategies

Dengue pathogen, transmitted by mosquitoes, poses a growing threat as it is capable of inflicting severe illness in humans. Around 40% of the global population is currently affected by the virus, resulting in thousands of fatalities each year. The genetic blueprint of the virus comprises 10 proteins. Three proteins serve as structural components: the capsid (C), the precursor of the membrane protein (PrM/M), and the envelope protein (E). The other proteins serve as non-structural (NS) proteins, consisting of NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5. The virus relies on these NS proteins to expropriate host proteins for its replication. During their intracellular replication, these viruses engage with numerous host components and exploit the cellular machinery for tasks such as entry into various organs, propagation, and transmission. This review explores mainly the relationship between dengue viral protein and host proteins elucidating the development of viral-host interactions. These relationships between the virus and the host give important information on the processes behind viral replication and the etiology of disease, which in turn facilitates the creation of more potent treatment strategies.

Dengue virus infection: how platelet-leukocyte crosstalk shapes thrombotic events and inflammation

Dengue virus (DENV) poses a considerable threat to public health on a global scale, since about two-thirds of the world's population is currently at risk of contracting this arbovirus. Being transmitted by mosquitoes, this virus is associated with a range of illnesses and a small percentage of infected individuals might suffer from severe vascular leakage. This leakage leads to hypovolemic shock syndrome, generally known as dengue shock syndrome, organ failure, and bleeding complications. The severe form of this disease is believed to be, at least partially, associated with inflammatory and thrombotic states. These issues are significantly affected by the activation of platelets and leukocytes, as well as their interactions, which may influence its prognosis. The platelets present in a thrombus are able to attract leukocytes to the site of injury. The intricate process leads to the significant accumulation, activation, and migration of leukocytes, thereby promoting thrombotic events and triggering inflammatory responses. The occurrence of these events, combined with the direct viral infection of endothelial cells, leads to vascular endothelialitis, the disruption of cellular membranes, and the subsequent release of DAMPs. As a result, considerable damage occurs in the endothelium, which activates neutrophils and platelets; thisleads to their interaction and initiates the process of Netosis. Collectively, these processes exacerbate inflammatory and thrombotic conditions. In this respect, current research has focused on understanding whether effective anti-inflammatory protocols can prevent thrombotic events or, conversely, if efficient anticoagulant regimens may lead to a reduction in cytokine storms and tissue damage. This review article aims to illuminate the platelet leukocyte crosstalk, detailing the mechanisms through which platelets may play a role in the pathogenesis of DENV. The research outputs are particularly important in severe cases, in which case their interactions with leukocytes can exacerbate both inflammation and thrombosis in a mutually reinforcing manner.

Significance of diagnostic and therapeutic potential of serum endothelial and inflammatory biomarkers in defining disease severity of dengue infected patients

Dengue virus (DENV) mediated disease severity leads to fatality among infected patients. Immune sentinels recognize DENV thereby secreting inflammatory mediators, endothelial biomarkers and anticoagulation factors. Absence of any diagnostic biomarkers for early identification of severe dengue (SD) patients has hindered disease management. Present study is aimed to evaluate diagnostic potential of these biomarkers along with their therapeutic targets for disease severity. Dengue infection was screened among 214 symptomatic patients and 25 healthy individuals by qRT-PCR, NS1-antigen, anti-dengue-IgM, anti-dengue-IgG ELISA and categorized them according to WHO-classification, 2009. Dengue viral-load and serotypes were determined by qRT-PCR. Serum-protein concentrations of inflammatory mediators (MIF, PAF, MMP2, MMP9, MCP1, RANTES, STNFRI, ST2, EOTAXIN), endothelial biomarkers (SDC1, VEGF, ANGPT2), anticoagulation factors (sTM, vWF, TF, PAI) were determined by sandwich ELISA. Statistical, PPI-network, hub-proteins, drug prediction analysis were performed by GraphPad-Prism9, STRING, Cytoscape-cytoHubba, DrugBank online, TTD, respectively. Among 81 dengue infected patients, significantly higher levels of MIF, PAF, sTNFRI, MMP9, VEGF, ANGPT2, MMP2, RANTES, SDC1 were detected among SD patients compared to non-severe ones, with excellent and good diagnostic potential of first (> 77.11, > 57.57 ng/ml, > 3226 pg/ml) and next three (> 105.3 ng/ml, > 12,380, > 8284 pg/ml) biomarkers, respectively. Serum MIF, PAF, MMP9, sTNFRI levels were significantly higher among hospitalized (p-value: 0.0081-0.0499), high-viral-load (p-value: 0.0266-0.0466) and DENV-2, 4 (p-value: < 0.0001-0.0298) infected patients. PPI-network analysed MMP9, PAI, vWF, ANGPT2, sTM, sTNFRI, MIF as hub-proteins targeted by FDA-approved/experimental drugs. This study recognized serum-biomarkers: MIF, PAF, sTNFRI, MMP9, VEGF, ANGPT2 to have significant diagnostic potential for identification of SD cases.

Dengue virus: pathogenesis and potential for small molecule inhibitors

Dengue, caused by dengue virus (DENV), is now endemic in nearly 100 countries and infection incidence is reported in another 30 countries. Yearly an estimated 400 million cases and 2200 deaths are reported. Effective vaccines against DENV are limited and there has been significant focus on the development of effective antiviral against the disease. The World Health Organization has initiated research programs to prioritize the development and optimization of antiviral agents against several viruses including Flaviviridae. A significant effort has been taken by the researchers to develop effective antivirals against DENV. Several potential small-molecule inhibitors like efavirenz, tipranavir and dasabuvir have been tested against envelope and non-structural proteins of DENV, and are in clinical trials around the world. We recently developed one small molecule, namely 7D, targeting the host PF4-CXCR3 axis. 7D inhibited all 4 serotypes of DENV in vitro and specifically DENV2 infection in two different mice models. Although the development of dengue vaccines remains a high priority, antibody cross reactivity among the serotypes and resulting antibody-dependent enhancement (ADE) of infection are major concerns that have limited the development of effective vaccine against DENV. Therefore, there has been a significant emphasis on the development of antiviral drugs against dengue. This review article describes the rescue effects of some of the small molecule inhibitors to viral/host factors associated with DENV pathogenesis.

Clinacanthus nutans (Burm. f.) Lindau Extract Inhibits Dengue Virus Infection and Inflammation in the Huh7 Hepatoma Cell Line

Dengue virus (DENV) infection has emerged as a global health problem, with no specific treatment available presently. Clinacanthus nutans (Burm. f.) Lindau extract has been used in traditional medicine for its anti-inflammatory and antiviral properties. We thus hypothesized C. nutans had a broad-ranged activity to inhibit DENV and the liver inflammation caused by DENV infection. The study showed that treatment using C. nutans extract during DENV infection (co-infection step) showed the highest efficiency in lowering the viral antigen concentration to 22.87 ± 6.49% at 31.25 μg/mL. In addition, the virus-host cell binding assay demonstrated that C. nutans treatment greatly inhibited the virus after its binding to Huh7 cells. Moreover, it could remarkably lower the expression of cytokine and chemokine genes, including TNF-α, CXCL10, IL-6, and IL-8, in addition to inflammatory mediator COX-2 genes. Interestingly, the activation of the NF-κB signaling cascade after C. nutans extract treatment was dramatically decreased, which could be the underlying mechanism of its anti-inflammatory activity. The HPLC profile showed that gallic acid was the bioactive compound of C. nutans extract and might be responsible for the antiviral properties of C. nutans. Taken together, our results revealed the potential of C. nutans extract to inhibit DENV infection and lower inflammation in infected cells.

The Role of Macrophage Migration Inhibitory Factor (MIF) and D-Dopachrome Tautomerase (D-DT/MIF-2) in Infections: A Clinical Perspective

Macrophage migration inhibitory factor (MIF) and its homolog, D-dopachrome tautomerase (D-DT), are cytokines that play critical roles in the immune response to various infectious diseases. This review provides an overview of the complex involvement of MIF and D-DT in bacterial, viral, fungal, and parasitic infections. The role of MIF in different types of infections is controversial, as it has either a protective function or a host damage-enhancing function depending on the pathogen. Depending on the specific role of MIF, different therapeutic options for MIF-targeting drugs arise. Human MIF-neutralizing antibodies, anti-parasite MIF antibodies, small molecule MIF inhibitors or MIF-blocking peptides, as well as the administration of exogenous MIF or MIF activity-augmenting small molecules have potential therapeutic applications and need to be further explored in the future. In addition, MIF has been shown to be a potential biomarker and therapeutic target in sepsis. Further research is needed to unravel the complexity of MIF and D-DT in infectious diseases and to develop personalized therapeutic approaches targeting these cytokines. Overall, a comprehensive understanding of the role of MIF and D-DT in infections could lead to new strategies for the diagnosis, treatment, and management of infectious diseases.

Recent two-year advances in anti-dengue small-molecule inhibitors

Dengue is an acute tropical infectious disease transmitted by mosquitoes, which has posed a major challenge to global public health. Unfortunately, there is a lack of clinically proven dengue-specific drugs for its prevention and treatment. As the pathogenesis of dengue has not been fully elucidated, the development of specific drugs is seriously hindered. This article briefly describes the pathogenesis of dengue fever, the molecular characteristics, and epidemiology of dengue virus, and focuses on the potential small-molecule inhibitors of dengue virus, including on-target and multi-targeted inhibitors, which have been reported in the past two years.

HIF Prolyl Hydroxylase Inhibitors for COVID-19 Treatment: Pros and Cons

The review analyzes the potential advantages and problems associated with using HIF prolyl hydroxylase inhibitors as a treatment for COVID-19. HIF prolyl hydroxylase inhibitors are known to boost endogenous erythropoietin (Epo) and activate erythropoiesis by stabilizing and activating the hypoxia inducible factor (HIF). Recombinant Epo treatment has anti-inflammatory and healing properties, and thus, very likely, will be beneficial for moderate to severe cases of COVID-19. However, HIF PHD inhibition may have a significantly broader effect, in addition to stimulating the endogenous Epo production. The analysis of HIF target genes reveals that some HIF-targets, such as furin, could play a negative role with respect to viral entry. On the other hand, HIF prolyl hydroxylase inhibitors counteract ferroptosis, the process recently implicated in vessel damage during the later stages of COVID-19. Therefore, HIF prolyl hydroxylase inhibitors may serve as a promising treatment of COVID-19 complications, but they are unlikely to aid in the prevention of the initial stages of infection.

Role of Platelet Cytokines in Dengue Virus Infection

Platelets are anucleated blood cells derived from bone marrow megakaryocytes and play a crucial role in hemostasis and thrombosis. Platelets contain specialized storage organelles, called alpha-granules, contents of which are rich in cytokines such as C-X-C Motif Chemokine Ligand (CXCL) 1/4/7, (C-C motif) ligand (CCL) 5/3, CXCL8 (also called as interleukin 8, IL-8), and transforming growth factor β (TGF-β). Activation of platelets lead to degranulation and release of contents into the plasma. Platelet activation is a common event in many viral infections including human immunodeficiency virus (HIV), H1N1 influenza, Hepatitis C virus (HCV), Ebola virus (EBV), and Dengue virus (DENV). The cytokines CXCL8, CCL5 (also known as Regulated on Activation, Normal T Expressed and Secreted, RANTES), tumor necrosis factor α (TNF-α), CXCL1/5 and CCL3 released, promote development of a pro-inflammatory state along with the recruitment of other immune cells to the site of infection. Platelets also interact with Monocytes and Neutrophils and facilitate their activation to release different cytokines which further enhances inflammation. Upon activation, platelets also secrete factors such as CXCL4 (also known as platelet factor, PF4), CCL5 and fibrinopeptides which are critical regulators of replication and propagation of several viruses in the host. Studies suggest that CXCL4 can both inhibit as well as enhance HIV1 infection. Data from our lab show that CXCL4 inhibits interferon (IFN) pathway and promotes DENV replication in monocytes in vitro and in patients significantly. Inhibition of CXCL4 mediated signaling results in increased IFN production and suppressed DENV and JEV replication in monocytes. In this review, we discuss the role of platelets in viral disease progression with a focus on dengue infection.