Role of Cytokines as Molecular Marker of Dengue Severity

Dengue overview: An updated systemic review

Dengue is caused by the dengue virus (DENVs) infection and clinical manifestations include dengue fever (DF), dengue hemorrhagic fever (DHF), or dengue shock syndrome (DSS). Due to a lack of antiviral drugs and effective vaccines, several therapeutic and control strategies have been proposed. A systemic literature review was conducted according to PRISMA guidelines to select proper references to give an overview of DENV infection. Results indicate that understanding the virus characteristics and epidemiology are essential to gain the basic and clinical knowledge as well as dengue disseminated pattern and status. Different factors and mechanisms are thought to be involved in the presentation of DHF and DSS, including antibody-dependent enhancement, immune dysregulation, viral virulence, host genetic susceptibility, and preexisting dengue antibodies. This study suggests that dissecting pathogenesis and risk factors as well as developing different types of therapeutic and control strategies against DENV infection are urgently needed.

Interferon-gamma gene diplotype (AA-rs2069716 / AG-rs2069727) may play an important role during secondary outcomes of severe dengue in Brazilian patients

Dengue is a global and growing health threat, especially in Southeast Asia, West Pacific and South America. Infection by the dengue virus (DENV) results in dengue fever, which can evolve to severe forms. Cytokines, especially interferons, are involved in the immunopathogenesis of dengue fever, and so may influence the disease outcomes. The aim of this study was to investigate the association between severe forms of dengue and two single nucleotide polymorphisms (SNPs) in the interferon-gamma gene (IFNG): A256G (rs2069716) and A325G (rs2069727). We included 274 patients infected with DENV serotype 3: 119 cases of dengue without warning signs (DWoWS), and 155 with warning signs (DWWS) or severe dengue (SD). DNA was extracted, and genotyped with Illumina Genotyping Kit or real time PCR (TaqMan probes). We estimated the adjusted Odds Ratios (OR) by multivariate logistic regression models. When comparing with the ancestral AA/AA diplotype (A256G/A325G), we found a protective association of the AA/AG against DWWS/SD among patients with secondary dengue (OR 0.51; 95% IC 0.24-1.10, p = 0.085), adjusting for age and sex. The variant genotype at locus A325G of the IFNG, in combination with the ancestral genotype at locus A256G, can protect against severe clinical forms of secondary dengue in Brazilian DENV3-infected patients.

Acute-phase Serum Cytokine Levels and Correlation with Clinical Outcomes in Children and Adults with Primary and Secondary Dengue Virus Infection in Myanmar between 2017 and 2019

The dengue virus (DENV) has been endemic in Myanmar since 1970, causing outbreaks every 2–3 years. DENV infection symptoms range from mild fever to lethal hemorrhage. Clinical biomarkers must be identified to facilitate patient risk stratification in the early stages of infection. We analyzed 45 cytokines and other factors in serum samples from the acute phase of DENV infection (within 3–5 days of symptom onset) from 167 patients in Yangon, Myanmar, between 2017 and 2019. All of the patients tested positive for serum DENV nonstructural protein 1 antigen (NS1 Ag); 78.4% and 62.9% were positive for immunoglobulin M (IgM) and G (IgG), respectively; and 18.0%, 19.8%, and 11.9% tested positive for serotypes 1, 3, and 4, respectively. Although the DENV-4 viral load was significantly higher than those of DENV-1 or DENV-3, disease severity was not associated with viral load or serotype. Significant correlations were identified between disease severity and CCL5, SCF, PDGF-BB, IL-10, and TNF-α levels; between NS1 Ag and SCF, CCL5, IFN-α, IL-1α, and IL-22 levels; between thrombocytopenia and IL-2, TNF-α, VEGF-D, and IL-6 levels; and between primary or secondary infection and IL-2, IL-6, IL-31, IL-12p70, and MIP-1β levels. These circulating factors may represent leading signatures in acute DENV infections, reflecting the clinical outcomes in the dengue endemic region, Myanmar.

Risk and predictive factors for severe dengue infection: A systematic review and meta-analysis

Background

Dengue is a major public health issue worldwide and severe dengue (SD) is life threatening. It is critical to triage patients with dengue infection in the early stage. However, there is limited knowledge on early indicators of SD. The objective of this study is to identify risk factors for the prognosis of SD and try to find out some potential predictive factors for SD from dengue fever (DF) in the early of infection.

Methods

The PubMed, Cochrane Library and Web of Science databases were searched for relevant studies from June 1999 to December 2020. The pooled odds ratio (OR) or standardized mean difference (SMD) with 95% confidence intervals (CI) of identified factors was calculated using a fixed or random effect model in the meta-analysis. Tests for heterogeneity, publication bias, subgroup analyses, meta-regression, and a sensitivity analysis were further performed.

Findings

A total of 6,848 candidate articles were retrieved, 87 studies with 35,184 DF and 8,173 SD cases met the eligibility criteria. A total of 64 factors were identified, including population and virus characteristics, clinical symptoms and signs, laboratory biomarkers, cytokines, and chemokines; of these factors, 34 were found to be significantly different between DF and SD, while the other 30 factors were not significantly different between the two groups after pooling the data from the relevant studies. Additionally, 9 factors were positive associated with SD within 7 days after illness when the timing subgroup analysis were performed.

Conclusions

Practical factors and biomarkers for the identification of SD were established, which will be helpful for a prompt diagnosis and early effective treatment for those at greatest risk. These outcomes also enhance our knowledge of the clinical manifestations and pathogenesis of SD.

Association Between a History of Dengue Fever and the Risk of Systemic Autoimmune Rheumatic Diseases: A Nationwide, Population-Based Case-Control Study

Purpose: To determine the association between a history of clinically diagnosed dengue infection and the risk of systemic autoimmune rheumatic diseases (SARDs). Methods: Using claims data from the 1997-2013 Taiwanese National Health Insurance Research Database, we included 74,422 patients who were diagnosed with SARDs and 297,688 patients without SARDs who were matched (in a 1:4 ratio) for age, sex, year of SARDs index date, and city of residence. The associations between the development of SARDs and a history of dengue infection (International Classification of Diseases, Ninth Revision, Clinical Modification code 061) were investigated using conditional logistic regression analysis shown as odds ratios (ORs) with 95% confidence intervals (CIs) after adjusting for potential confounders. Results: We included 17,126 patients with systemic lupus erythematosus (SLE), 15,531 patients with Sjogren's syndrome (SS), 37,685 patients with rheumatoid arthritis (RA), 1,911 patients with systemic sclerosis (SSc), 1,277 patients with dermatomyositis (DM), and 892 patients with polymyositis (PM). SLE (OR, 4.55; 95% CI, 2.77-7.46; p <0.001) risk was significantly associated with a history of dengue infection. However, no statistically significant association was found between dengue infection and SS (OR, 1.41; 95% CI, 0.88-2.26; p = 0.155), RA (OR, 1.03; 95% CI, 0.70-1.50; p = 0.888), SSc (OR, 1.97; 95% CI, 0.38-10.29; p = 0.420), DM (OR, 0.54; 95% CI, 0.04-7.27; p = 0.641), or PM (OR, 2.08; 95% CI, 0.23-18.79; p = 0.513). Conclusion: This study revealed that a history of dengue infection was significantly associated with the risk of SLE, but not SS, RA, SSc, DM, or PM.

Predictive markers for the early prognosis of dengue severity: A systematic review and meta-analysis

BACKGROUND

Predictive markers represent a solution for the proactive management of severe dengue. Despite the low mortality rate resulting from severe cases, dengue requires constant examination and round-the-clock nursing care due to the unpredictable progression of complications, posing a burden on clinical triage and material resources. Accordingly, identifying markers that allow for predicting disease prognosis from the initial diagnosis is needed. Given the improved pathogenesis understanding, myriad candidates have been proposed to be associated with severe dengue progression. Thus, we aim to review the relationship between the available biomarkers and severe dengue.

METHODOLOGY

We performed a systematic review and meta-analysis to compare the differences in host data collected within 72 hours of fever onset amongst the different disease severity levels. We searched nine bibliographic databases without restrictive criteria of language and publication date. We assessed risk of bias and graded robustness of evidence using NHLBI quality assessments and GRADE, respectively. This study protocol is registered in PROSPERO (CRD42018104495).

PRINCIPAL FINDINGS

Of 4000 records found, 40 studies for qualitative synthesis, 19 for meta-analysis. We identified 108 host and viral markers collected within 72 hours of fever onset from 6160 laboratory-confirmed dengue cases, including hematopoietic parameters, biochemical substances, clinical symptoms, immune mediators, viral particles, and host genes. Overall, inconsistent case classifications explained substantial heterogeneity, and meta-analyses lacked statistical power. Still, moderate-certainty evidence indicated significantly lower platelet counts (SMD -0.65, 95% CI -0.97 to -0.32) and higher AST levels (SMD 0.87, 95% CI 0.36 to 1.38) in severe cases when compared to non-severe dengue during this time window.

CONCLUSION

The findings suggest that alterations of platelet count and AST level-in the first 72 hours of fever onset-are independent markers predicting the development of severe dengue.

Emergence of Dengue 4 as Dominant Serotype During 2017 Outbreak in South India and Associated Cytokine Expression Profile

Dengue virus (DENV) infection is prevalent in tropical and subtropical regions of the world, which is fatal if untreated symptomatically. Emergence of new genotype within serotypes led to enhanced severity. The objective of the study is to identify the molecular characteristics of the DENV circulated during 2017 outbreak in Tamil Nadu, India, and to investigate the role of inflammatory cytokines in different “serotypes” and in “dengue severity”. A total of 135 suspected samples were tested for DENV infection using IgM, IgG, and qPCR assay; where 76 samples were positive for DENV and analyzed for 12 inflammatory cytokines using ELISA. Serotyping shows 14 DENV-1, 22 DENV-2, 7 DENV-3, and 33 DENV-4, where DENV-4 was predominant. Among 76, 42 isolates were successfully sequenced for C-prM region and grouped. A lineage shift was observed in DENV-4 genotype. Irrespective of serotypes, IFNγ was significantly elevated in all serotypes than control as well as in primary infection than secondary, indicating its role in immune response. GM-CSF and IP-10 were significantly elevated in secondary infection and could be used as prognostic biomarkers for secondary infection. Our observation shows differential cytokine expression profile varied with each serotype, indicating serotype/genotype-specific viral proteins might play a major role in dengue severity. DENV-4 as dominant serotype was reported in Tamil Nadu for the first time during an outbreak with a mixed Th1/Th17 cytokine expression profile that correlated with disease severity. We conclude it is essential to identify circulating viral genotype and their fitness by mutational analysis to correlate with disease severity and immune status, as this correlation will be helpful in diagnostics and therapeutics applications.

Acute monocyte pro inflammatory response predicts higher positive to negative acute phase reactants ratio and severe hemostatic derangement in dengue fever

PURPOSE

The present study was intended to investigate whether monocyte immune activation shapes plasma positive to negative acute phase reactants (APRs) ratio and predicts disease severity in dengue infection.

METHODS

Serum level of ferritin, ceruloplasmin and transferrin was measured by means of electrochemiluminescence and immunoturbidimetry, respectively. Gene expression and plasma level for TNF-α, IL-6 and IL1-β was measured by means of RT-qPCR and ELISA.

RESULTS

A significant increased serum ferritin to transferrin [6.6 (3-11.7) vs 3.4 (1.9-6.1)] and ceruloplasmin to transferrin ratio [0.48 (0.21-0.87) vs 0.22 (0.13-0.43)] has been detected among the subjects with secondary dengue infection (SDENI) compared to primarily infected (PDENI) subjects (P < 0.001). Significant increased expression for CD14⁺ monocyte TNF-α, IL-6 and IL-1β has been detected in SDENI patients (vs PDENI and control, P < 0.001). Plasma ferritin to transferrin ratio was found in a significant association with high level of plasma TNF-α [ρ = 0.6522, 95% CI (0.4714-0.7805)], IL-6 [ρ = 0.6181, 95% CI (0.4257-0.7571)] and IL- 1β [ρ = 0.4119, 95% CI (0.1689-0.6077)] level among SDENI patients at 5th day time point after progression of the disease, with significantly low platelet [P < 0.001] and prolonging prothrombin time [P < 0.001] compared to control and PDENI subjects, respectively.

CONCLUSION

Acute proinflammatory cytokine response is significantly associated with increased positive to negative APRs ratio in SDENI patients, which predicts intense immune activation, and renders SDENI patients extremely susceptible to hemostatic derangement.

ILC1 and NK cells are sources of IFN-γ and other inflammatory cytokines associated to distinct clinical presentation in early dengue infection

BACKGROUND

Increased levels of inflammatory cytokines are associated to severe dengue evolution, but the source of such hypercytokinemia is elusive. We investigated the contribution of innate lymphocytes, innate lymphoid cells (ILC) and NK cells in cytokine production in early dengue infection.

METHODS

PBMCs of individuals with DWS- (dengue without warning signs) and DWS+ (dengue with warning signs and severe dengue presentation combined) were obtained between 2 and 7 days since fever onset and submitted to flow cytometry without specific antigen stimulation to evaluate cytokines in ILC and NK cells subpopulations.

RESULTS

ILCs and NK cells were found to be important sources of cytokines during dengue. ILCs of DWS+/SD group displayed higher production of IFN-γand IL-4/IL-13 when compared to DWS- individuals. On the other hand, NK EOMES+ cells of DWS- patients displayed higher IFN-γ production levels, when compared to DWS+/SD group. Interestingly, when NK cells were identified by CD56 expression, DWS+/SD displayed higher frequency of IL-17 production when compared to DWS- group.

CONCLUSION

These results indicate that ILCs and NK cells are important sources of inflammatory cytokines during acute dengue infection and display distinct profiles associated with different clinical forms.

Identification of a Direct-Acting Antiviral Agent Targeting RNA Helicase via a Graphene Oxide Nanobiosensor

Dengue virus (DENV), an arbovirus transmitted by mosquitoes, causes infectious diseases such as dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. Despite the dangers posed by DENV, there are no approved antiviral drugs for treatment of DENV infection. Considering the potential for a global dengue outbreak, rapid development of antiviral agents against DENV infections is crucial as a preemptive measure; thus, the selection of apparent drug targets, such as the viral enzymes involved in the viral life cycle, is recommended. Helicase, a potential drug target in DENV, is a crucial viral enzyme that unwinds double-stranded viral RNA, releasing single-stranded RNA genomes during viral replication. Therefore, an inhibitor of helicase activity could serve as a direct-acting antiviral agent. Here, we introduce an RNA helicase assay based on graphene oxide, which enables fluorescence-based analysis of RNA substrate-specific helicase enzyme activity. This assay demonstrated high reliability and ability for high-throughput screening, identifying a new helicase inhibitor candidate, micafungin (MCFG), from an FDA-approved drug library. As a direct-acting antiviral agent targeting RNA helicase, MCFG inhibits DENV proliferation in cells and an animal model. Notably, in vivo, MCFG treatment reduced viremia, inflammatory cytokine levels, and viral loads in several tissues and improved survival rates by up to 40% in a lethal mouse model. Therefore, we suggest MCFG as a potential direct-acting antiviral drug candidate.

Current Understanding of the Pathogenesis of Dengue Virus Infection

The pathogenesis of dengue virus infection is attributed to complex interplay between virus, host genes and host immune response. Host factors such as antibody-dependent enhancement (ADE), memory cross-reactive T cells, anti-DENV NS1 antibodies, autoimmunity as well as genetic factors are major determinants of disease susceptibility. NS1 protein and anti-DENV NS1 antibodies were believed to be responsible for pathogenesis of severe dengue. The cytokine response of cross-reactive CD4+ T cells might be altered by the sequential infection with different DENV serotypes, leading to further elevation of pro-inflammatory cytokines contributing a detrimental immune response. Fcγ receptor-mediated antibody-dependent enhancement (ADE) results in release of cytokines from immune cells leading to vascular endothelial cell dysfunction and increased vascular permeability. Genomic variation of dengue virus and subgenomic flavivirus RNA (sfRNA) suppressing host immune response are viral determinants of disease severity. Dengue infection can lead to the generation of autoantibodies against DENV NS1antigen, DENV prM, and E proteins, which can cross-react with several self-antigens such as plasminogen, integrin, and platelet cells. Apart from viral factors, several host genetic factors and gene polymorphisms also have a role to play in pathogenesis of DENV infection. This review article highlights the various factors responsible for the pathogenesis of dengue and also highlights the recent advances in the field related to biomarkers which can be used in future for predicting severe disease outcome.

Serum Ferritin As a Prognostic Indicator in Adult Dengue Patients

Dengue virus (DENV) infection is increasing with rapid urbanization in India. Treatment of DENV infection is mainly supportive with no specific antiviral therapy. Although most patients show mild illness, some have a severe disease course such as dengue hemorrhagic syndrome, dengue shock, multi-organ failure, and death. The cause for severity is not fully understood. Currently, there are no methods available to predict the course of the illness. Hence, it is crucial to develop an early biomarker to predict the course of dengue illness which can aid in vigorous monitoring and early intervention. Here, we tried to establish a correlation between serum ferritin and severity of dengue illness. We measured ferritin levels in 100 dengue-positive cases on day 1 (D1) (febrile phase) and day 4 (D4) (defervescence or convalescent) of admissions to compare the levels with the severity of the disease. On D1, the serum ferritin level was a "good" predictor of severe dengue, with an area under the curve (AUC) of 0.863 with standard error (SE) = 0.043 and a 95% CI from 0.778 to 0.947 (P < 0.05). On D4, serum ferritin was an "excellent" predictor of severe dengue, with an AUC of 0.947 with SE = 0.021 and a 95% CI from 0.907 to 0.988 (P < 0.05). Serum ferritin is an inexpensive and easily accessible biomarker that can assist in monitoring and prognosticating the dengue-positive patients. This biomarker also directs us to explore the underlying pathogenetic mechanism in severe dengue, which can lay a foundation for future targeted therapeutic options to combat severe illness.

Correlation of host inflammatory cytokines and immune-related metabolites, but not viral NS1 protein, with disease severity of dengue virus infection

Severe dengue can be lethal caused by manifestations such as severe bleeding, fluid accumulation and organ impairment. This study aimed to investigate the role of dengue non-structural 1 (NS1) protein and host factors contributing to severe dengue. Electrical cell-substrate impedance sensing system was used to investigate the changes in barrier function of microvascular endothelial cells treated NS1 protein and serum samples from patients with different disease severity. Cytokines and metabolites profiles were assessed using a multiplex cytokine assay and liquid chromatography mass spectrometry respectively. The findings showed that NS1 was able to induce the loss of barrier function in microvascular endothelium in a dose dependent manner, however, the level of NS1 in serum samples did not correlate with the extent of vascular leakage induced. Further assessment of host factors revealed that cytokines such as CCL2, CCL5, CCL20 and CXCL1, as well as adhesion molecule ICAM-1, that are involved in leukocytes infiltration were expressed higher in dengue patients in comparison to healthy individuals. In addition, metabolomics study revealed the presence of deregulated metabolites involved in the phospholipid metabolism pathway in patients with severe manifestations. In conclusion, disease severity in dengue virus infection did not correlate directly with NS1 level, but instead with host factors that are involved in the regulation of junctional integrity and phospholipid metabolism. However, as the studied population was relatively small in this study, these exploratory findings should be confirmed by expanding the sample size using an independent cohort to further establish the significance of this study.

Cytokine Expression in Dengue Fever and Dengue Hemorrhagic Fever Patients with Bleeding and Severe Hepatitis

Dengue is the most common mosquito-borne flaviviral infection in the world today. Several factors contribute and act synergistically to cause severe infection. One of these is dysregulated host immunological mediators that cause transient pathophysiology during infection. These mediators act on the endothelium to increase vascular permeability, which leads to plasma leakage compromising hemodynamics and coagulopathy. We conducted a prospective study to explore the expression of pro- and anti-inflammatory cytokines and how they relate to clinical dengue manifestations, by assessing their dynamics through acute dengue infection in adults admitted to the Hospital for Tropical Diseases, Bangkok, Thailand. We performed cytokine analysis at three phases of infection for 96 hospitalized adults together with serotyping of confirmed dengue infection during the outbreaks of 2015 and 2016. The serum concentrations of seven cytokines (interleukin [IL]-2, IL-4, IL-6, IL-8, IL-10, tumor necrosis factor alpha, and interferon gamma) were measured in duplicate using a commercial kit (Bio-Plex Human Cytokine Assay). In this study, the cytokine profile was suggestive of a T-helper 2 response. Most patients had secondary infection, and the levels of viremia were higher in patients with plasma leakage than those without plasma leakage. In addition, we observed that bleeding and hepatitis were associated with significantly higher levels of IL-8 during the early phases of infection. Furthermore, IL-6 levels in the early phase of infection were also elevated in bleeding patients with plasma leakage. These results suggest that IL-6 and IL-8 may act in synergy to cause bleeding in patients with plasma leakage.

MCP-1 LEVELS AND ATYPICAL LYMPHOCYTES IN EARLY FEVER OF DENGUE VIRUS INFECTION WITH NON-STRUCTURAL PROTEIN 1 (NS-1) ANTIGEN TEST IN dr DARSONO HOSPITAL, PACITAN

Dengue infection caused by DENV and transmitted by mosquitoes Aedes aegypti and Aedes albopictus is a major health problem in the world, including Indonesia. Clinical manifestations of dengue infection are very widely, from asymptomatic until dengue shock syndrome (DSS). DENV will attack macrophages and dendritic cells (DC) and replicate them. Monocytes are macrophages in the blood (±10% leukocytes). Macrophages produce cytokines and chemokines such as monocyte chemotactic protein-1 (MCP-1)/CCL2. The monocytes that are infected with DENV will express MCP-1, which will increase the permeability of vascular endothelial cells so that they have a risk of developing DHF/DSS. Macrophages and DC secrete NS1 proteins, which are the co-factors that are needed for viral replication and can be detected in the early phase of fever. The increased MCP-1 levels in dengue infection followed by an increase in the number of atypical lymphocytes indicate the arrival of macrophages and monocytes to the site of inflammation which triggers proliferation rather than lymphocytes. This is an observational analytical study with a cross-sectional design to determine the MCP-1 level in dengue infection patients with 1st until the 4th day of fever and the presence of atypical lymphocytes. Dengue infection was determined by rapid tests NS1 positive or negative and MCP-1 levels were measured using by ELISA sandwich method.MCP-1 level of sixty patients dengue infection NS-1 rapid positive or negative with 2nd until 4rt fever were significantly higher than healthy subjects (420.263±158,496vs29, 475±23.443;p=0.000), but there was no significant difference in subjects with DF, DHF or DSS (436,47±225,59 vs422,77±170,55vs 448,50±117,39; p =0.844). Atypicallymphosite differs significantly in healthy  subjects than subjects infected with DENV an average of 2% (p= 0,000). In conclusion, this shows the arrival of macrophages and monocytes to the site of inflammation, which triggers the proliferation of lymphocytes.

Inflammation During Virus Infection: Swings and Roundabouts

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

Dengue viruses infect human megakaryocytes, with probable clinical consequences

One of the most important clinical signs of dengue virus infection is the reduction of white blood cells and platelets in human peripheral blood (leukopenia and thrombocytopenia, respectively), which may significantly impair the clearance of dengue virus by the immune system. The cause of thrombocytopenia and leukopenia during dengue infection is still unknown, but may be related to severe suppression of bone marrow populations including hematopoietic stem cells and megakaryocytes, the progenitors of white blood cells and platelets respectively. Here, we explored the possibility that bone marrow suppression, including ablation of megakaryocyte populations, is caused by dengue virus infection of megakaryocytes. We used three different models to measure dengue virus infection and replication: in vitro, in a human megakaryocyte cell line with viral receptors, ex vivo, in primary human megakaryocytes, and in vivo, in humanized mice. All three systems support dengue virus infection and replication, including virus strains from serotypes 1, 2, and 3, and clinical signs, in vivo; all assays showed viral RNA and/or infectious viruses 7–14 days post-infection. Although we saw no significant decrease in cell viability in vitro, there was significant depletion of mature megakaryocytes in vivo. We conclude that megakaryocytes can produce dengue viruses in the bone marrow niche, and a reduction of cell numbers may affect bone marrow homeostasis.

Dengue virus is the most common cause of viral hemorrhagic fever in humans. Over half of the world’s population lives in an at risk area for dengue virus infection, and this number will continue to grow as climate change allows the mosquito vectors of dengue virus to expand their breeding ranges to more temperate climates. Currently, there are no specific treatments for dengue virus infection. Understanding how dengue virus causes hemorrhagic fever could inform the development of these much needed treatments. Populations of important immune system mediators, such as white blood cells and platelets, are significantly dysregulated during dengue virus infection. These cells originate in the bone marrow, which experiences significant suppression, including a complete ablation of megakaryocytes (platelet progenitor cells), during DENV infection. Here, we add to the knowledge on how dengue virus induces bone marrow suppression by investigating whether dengue virus infects human megakaryocytes. We discovered that dengue virus infects human megakaryocytes in vitro, ex vivo, and in vivo models of dengue virus infection; however, dengue virus infection does not appear to directly affect viability of human megakaryocytes. Future studies will investigate whether infected megakaryocytes are still able to perform their functions of producing platelets and maintaining bone marrow homeostasis.