Selective Tropism of Dengue Virus for Human Glycoprotein Ib

Sepsis - it is all about the platelets

Sepsis is accompanied by thrombocytopenia and the severity of the thrombocytopenia is associated with mortality. This thrombocytopenia is characteristic of disseminated intravascular coagulation (DIC), the sepsis-associated coagulopathy. Many of the pathogens, both bacterial and viral, that cause sepsis also directly activate platelets, which suggests that pathogen-induced platelet activation leads to systemic thrombosis and drives the multi-organ failure of DIC. In this paper we review the mechanisms of platelet activation by pathogens and the evidence for a role for anti-platelet agents in the management of sepsis.

Transfusion-transmitted arboviruses: Update and systematic review

Background

The detection of the first cases of transfusion-transmitted West Nile virus in 2002 posed a new challenge for transfusion safety. Institutions like the World Health Organization have stated that blood transfusion centers need to know the epidemiology of the different emerging infectious agents and their impact on blood transfusion. The aim of the study is to review the published cases of arbovirus transmission through transfusion of blood or blood components and to analyze their main clinical and epidemiological characteristics.

Material and methods

Systematic literature searches were conducted in MEDLINE, Embase and Scopus. Pairs of review authors selected a variety of scientific publications reporting cases of transfusion-transmitted arboviruses. Main clinical and epidemiological characteristics were reviewed of the cases described. The study protocol was registered in PROSPERO CRD42021270355.

Results

A total of 74 cases of transfusion-transmitted infections were identified from 10 arboviruses: West Nile virus (n = 42), dengue virus (n = 18), Zika virus (n = 3), yellow fever vaccine virus (n = 3), tick-borne encephalitis virus (n = 2), Japanese encephalitis virus (n = 2), Powassan virus (n = 1), St. Louis encephalitis virus (n = 1), Ross River virus (n = 1) and Colorado tick fever virus (n = 1). The blood component most commonly involved was red blood cells (N = 35, 47.3%; 95% confidence interval [CI] 35.9% to 58.7%). In 54.1% (N = 40; 95% CI: 42.7%-65.47%) of the cases, the recipient was immunosuppressed. Transmission resulted in death in 18.9% (N = 14; 95% CI: 10.0%-27.8%) of the recipients. In addition, 18 additional arboviruses were identified with a potential threat to transfusion safety.

Discussion

In the last 20 years, the number of published cases of transfusion-transmitted arboviruses increased notably, implicating new arboviruses. In addition, a significant number of arboviruses that may pose a threat to transfusion safety were detected. In the coming years, it is expected that transmission of arboviruses will continue to expand globally. It is therefore essential that all responsible agencies prepare for this potential threat to transfusion safety.

The transfusion of blood and blood components entails some risks and potential complications, chief among them the transmission of infectious agents. Organizations like the American Association of Blood Banks have warned of the risks posed by emerging and re-emerging viruses for transfusion safety and have classified transmission of several arboviruses as a high or very high risk to the transfusion of blood and blood components. Following recommendations by the World Health Organization (WHO), this study aims to enable safe blood transfusion services, by making available the latest updated information of transfusion-transmitted arboviruses and comprehensive knowledge of the current epidemiology of reported cases.

Research revealed case reports of transfusion transmission of 10 arboviruses, with West Nile virus and dengue virus as the most prevalent. Main clinical characteristics of reported cases were collected, including the type of blood component transfused and the state of immunosuppression of the recipient. Research also revealed 18 additional arboviruses with potential risk of transmission through other direct transmission routes. This systematic review provides an updated overview of the clinical characteristics of reported cases of transfusion-transmitted arboviruses. It is the most complete record published to date that assesses the risk posed by arboviruses to blood transfusion.

Platelets mediate inflammatory monocyte activation by SARS-CoV-2 Spike protein

Infection with SARS-CoV-2, the causative agent of COVID-19, causes mild to moderate disease in most patients but carries a risk of morbidity and mortality. Seriously affected individuals manifest disorders of hemostasis and a cytokine storm, but it is not understood how these manifestations of severe COVID-19 are linked. Here, we showed that the SARS-CoV-2 spike protein engaged the CD42b receptor to activate platelets via 2 distinct signaling pathways and promoted platelet-monocyte communication through the engagement of P selectin/PGSL-1 and CD40L/CD40, which led to proinflammatory cytokine production by monocytes. These results explain why hypercoagulation, monocyte activation, and a cytokine storm are correlated in patients severely affected by COVID-19 and suggest a potential target for therapeutic intervention.

Platelets in the pathogenesis of flavivirus disease

Research on the role of platelets in modulating innate and adaptive host immune responses has gaining importance in the last two decades. Since the virus can directly interact with platelet receptors and modulate the host immune response, understanding the role of platelets in viral pathogenesis would pave way for novel therapeutic means. The present review aims at presenting the important molecular aspects of platelet-flavivirus interactions and how it leads to platelet activation, thrombocytopenia, and vascular endothelial leakage. Besides, the role of some of the platelet-derived factors as biomarkers for the early prediction of disease outcome taking dengue infection as an example is reviewed.

Exposure of Platelets to Dengue Virus and Envelope Protein Domain III Induces Nlrp3 Inflammasome-Dependent Platelet Cell Death and Thrombocytopenia in Mice

In tropical and subtropical regions, mosquito-borne dengue virus (DENV) infections can lead to severe dengue, also known as dengue hemorrhage fever, which causes bleeding, thrombocytopenia, and blood plasma leakage and increases mortality. Although DENV-induced platelet cell death was linked to disease severity, the role of responsible viral factors and the elicitation mechanism of abnormal platelet activation and cell death remain unclear. DENV and virion-surface envelope protein domain III (EIII), a cellular binding moiety of the virus particle, highly increase during the viremia stage. Our previous report suggested that exposure to such viremia EIII levels can lead to cell death of endothelial cells, neutrophils, and megakaryocytes. Here we found that both DENV and EIII could induce abnormal platelet activation and predominantly necrotic cell death pyroptosis. Blockages of EIII-induced platelet signaling using the competitive inhibitor chondroitin sulfate B or selective Nlrp3 inflammasome inhibitors OLT1177 and Z-WHED-FMK markedly ameliorated DENV- and EIII-induced thrombocytopenia, platelet activation, and cell death. These results suggest that EIII could be considered as a virulence factor of DENV, and that Nlrp3 inflammasome is a feasible target for developing therapeutic approaches against dengue-induced platelet defects.

Exposure to Dengue Envelope Protein Domain III Induces Nlrp3 Inflammasome-Dependent Endothelial Dysfunction and Hemorrhage in Mice

Typically occurring during secondary dengue virus (DENV) infections, dengue hemorrhagic fever (DHF) causes abnormal immune responses, as well as endothelial vascular dysfunction, for which the responsible viral factor remains unclear. During peak viremia, the plasma levels of virion-associated envelope protein domain III (EIII) increases to a point at which cell death is sufficiently induced in megakaryocytes in vitro. Thus, EIII may constitute a virulence factor for endothelial damage. In this study, we examined endothelial cell death induced by treatment with DENV and EIII in vitro. Notably, pyroptosis, the major type of endothelial cell death observed, was attenuated through treatment with Nlrp3 inflammasome inhibitors. EIII injection effectively induced endothelial abnormalities, and sequential injection of EIII and DENV-NS1 autoantibodies induced further vascular damage, liver dysfunction, thrombocytopenia, and hemorrhage, which are typical manifestations in DHF. Under the same treatments, pathophysiological changes in the Nlrp3 inflammasome–deficient mice were notably reduced compared with those in the wild-type mice. These results suggest that the Nlrp3 inflammasome constitutes a potential therapeutic target for treating DENV-induced hemorrhage in DHF.

Thrombocytopenia in Virus Infections

Thrombocytopenia, which signifies a low platelet count usually below 150 × 10⁹/L, is a common finding following or during many viral infections. In clinical medicine, mild thrombocytopenia, combined with lymphopenia in a patient with signs and symptoms of an infectious disease, raises the suspicion of a viral infection. This phenomenon is classically attributed to platelet consumption due to inflammation-induced coagulation, sequestration from the circulation by phagocytosis and hypersplenism, and impaired platelet production due to defective megakaryopoiesis or cytokine-induced myelosuppression. All these mechanisms, while plausible and supported by substantial evidence, regard platelets as passive bystanders during viral infection. However, platelets are increasingly recognized as active players in the (antiviral) immune response and have been shown to interact with cells of the innate and adaptive immune system as well as directly with viruses. These findings can be of interest both for understanding the pathogenesis of viral infectious diseases and predicting outcome. In this review, we will summarize and discuss the literature currently available on various mechanisms within the relationship between thrombocytopenia and virus infections.

Role of Platelets in Detection and Regulation of Infection

Platelets are classically known as essential mediators of hemostasis and thrombosis. However, in recent years, platelets have gained recognition for their inflammatory functions, which modulate the immune response during infectious diseases. Platelets contain various immunoreceptors that enable them to act as sentinels to recognize intravascular pathogens. Upon activation, platelets directly limit pathogen growth through the release of AMPs (antimicrobial proteins) and ensure pathogen clearance through activation of immune cells. However, aberrant platelet activation can lead to inflammation and thrombotic events.

Identification and characterization of permissive cells to dengue virus infection in human hematopoietic stem and progenitor cells

BACKGROUND

Dengue virus (DENV) is a significant threat to public health in tropical and subtropical regions, where the frequency of human migration is increasing. Transmission of DENV from donors to recipients after hematopoietic stem cell transplantation has been steadily described. However, the underlying mechanisms remain unclear.

STUDY DESIGN AND METHODS

Freshly isolated bone marrow (BM) was subjected to DENV infection, followed by multicolor fluorescence-activated cell sorting (FACS) analysis. Virus in supernatants was collected and analyzed by plaque assay.

RESULTS

DENV-1 to DENV-4 could effectively infect freshly obtained BM and produced infectious virus. DENV infection did not change the quantitative population of hematopoietic stem and progenitor cells (HSPCs), megakaryocytic progenitor cells (MkPs) and megakaryocytes. Additionally, DENV antigen, nonstructural protein 1, was enriched in HSPCs and MkPs of DENV infected marrow cells. CD34+, CD133+, or CD61+ cells sorted out from BM were not only the major contributing targets facilitating the DENV infection directly but also facilitated the spread of DENV into other cells when cocultured.

CONCLUSION

Results suggest that DENV can efficiently infect HSPCs, which might jeopardize the recipients if DENV-infected cells were subsequently used. We therefore raise the need for DENV screening for both the donors and recipients of hematopoietic stem cell transplantation, especially for donors exposed to endemic areas, to mitigate DENV infection in immunocompromised recipients.

Viral Metagenomics of Blood Donors and Blood-Derived Products Using Next-Generation Sequencing

Transfusion-transmitted infections remain a permanent threat in medicine. It keeps the burden of the past, marked by serious infections transmitted by transfusion, and is constantly threatened by emerging viruses. The global rise of immunosuppression among patients undergoing frequent transfusions exacerbates this problem. Over the past decade, criteria for donor selection have become increasingly more stringent. Although routine nucleic acid testing (NAT) for virus-specific detection has become more sensitive, these safety measures are only valuable for a limited number of select viruses. The scientific approach to this is however changing, with the goal of trying to identify infectious agents in donor units as early as possible to mitigate the risk of a clinically relevant infection. To this end, and in addition to an epidemiological surveillance of the general population, researchers are adopting new methods to discover emerging infectious agents, while simultaneously screening for an extended number of viruses in donors. Next-generation sequencing (NGS) offers the opportunity to explore the entire viral landscape in blood donors, the so-called metagenomics, to investigate severe transfusion reactions of unknown etiology. In the not too distant future, one could imagine this platform being used for routine testing of donated blood products.