Viral hemorrhagic fevers

Micro- and nanosystems for the detection of hemorrhagic fever viruses

Hemorrhagic fever viruses (HFVs) are virulent pathogens that can cause severe and often fatal illnesses in humans. Timely and accurate detection of HFVs is critical for effective disease management and prevention. In recent years, micro- and nano-technologies have emerged as promising approaches for the detection of HFVs. This paper provides an overview of the current state-of-the-art systems for micro- and nano-scale approaches to detect HFVs. It covers various aspects of these technologies, including the principles behind their sensing assays, as well as the different types of diagnostic strategies that have been developed. This paper also explores future possibilities of employing micro- and nano-systems for the development of HFV diagnostic tools that meet the practical demands of clinical settings.

Hemorrhagic fever viruses: Pathogenesis, therapeutics, and emerging and re-emerging potential

Hemorrhagic fever viruses (HFVs) pose a threat to global public health owing to the emergence and re-emergence of highly fatal diseases. Viral hemorrhagic fevers (VHFs) caused by these viruses are mostly characterized by an acute febrile syndrome with coagulation abnormalities and generalized hemorrhage that may lead to life-threatening organ dysfunction. Currently, the events underlying the viral pathogenicity associated with multiple organ dysfunction syndrome still underexplored. In this minireview, we address the current knowledge of the mechanisms underlying VHFs pathogenesis and discuss the available development of preventive and therapeutic options to treat these infections. Furthermore, we discuss the potential of HFVs to cause worldwide emergencies along with factors that favor their spread beyond their original niches.

Pathogenicity and virulence of Marburg virus

Marburg virus (MARV) has been a major concern since 1967, with two major outbreaks occurring in 1998 and 2004. Infection from MARV results in severe hemorrhagic fever, causing organ dysfunction and death. Exposure to fruit bats in caves and mines, and human-to-human transmission had major roles in the amplification of MARV outbreaks in African countries. The high fatality rate of up to 90% demands the broad study of MARV diseases (MVD) that correspond with MARV infection. Since large outbreaks are rare for MARV, clinical investigations are often inadequate for providing the substantial data necessary to determine the treatment of MARV disease. Therefore, an overall review may contribute to minimizing the limitations associated with future medical research and improve the clinical management of MVD. In this review, we sought to analyze and amalgamate significant information regarding MARV disease epidemics, pathophysiology, and management approaches to provide a better understanding of this deadly virus and the associated infection.

Arenaviral infection causes bleeding in mice due to reduced serotonin release from platelets

Bleeding correlates with disease severity in viral hemorrhagic fevers. We found that the increase in type I interferon (IFN-I) in mice caused by infection with the Armstrong strain of lymphocytic choriomeningitis virus (LCMV; an arenavirus) reduced the megakaryocytic expression of genes encoding enzymes involved in lipid biosynthesis (cyclooxygenase 1 and thromboxane A synthase 1) and a thrombopoietic transcription factor (Nf-e2). The decreased expression of these genes was associated with reduced numbers of circulating platelets and defects in the arachidonic acid synthetic pathway, thereby suppressing serotonin release from δ-granules in platelets. Bleeding resulted when severe thrombocytopenia and altered platelet function reduced the amount of platelet-derived serotonin below a critical threshold. Bleeding was facilitated by the absence of the activity of the kinase Lyn or the administration of aspirin, an inhibitor of arachidonic acid synthesis. Mouse platelets were not directly affected by IFN-I because they lack the receptor for the cytokine (IFNAR1), suggesting that transfusion of normal platelets into LCMV-infected mice could increase the amount of platelet-released serotonin and help to control hemorrhage.

Viral-induced inflammatory coagulation disorders: Preparing for another epidemic

A number of viral infectious diseases have emerged or reemerged from wildlife vectors that have generated serious threats to global health. Increased international traveling and commerce increase the risk of transmission of viral or other infectious diseases. In addition, recent climate changes accelerate the potential spread of domestic disease. The Coronavirus disease 2019 (COVID-19) pandemic is an important example of the worldwide spread, and the current epidemic will unlikely be the last. Viral hemorrhagic fevers, such as Dengue and Lassa fevers, may also have the potential to spread worldwide with a significant impact on public health with unpredictable timing. Based on the important lessons learned from COVID-19, it would be prudent to prepare for future pandemics of life-threatening viral diseases. Among the various threats, this review focuses on the coagulopathy of acute viral infections since hypercoagulability has been a major challenge in COVID-19, but represents a different presentation compared to viral hemorrhagic fever. However, both thrombosis and hemorrhage are understood as the result of thromboinflammation due to viral infections, and the role of anticoagulation is important to consider.

Simultaneous Detection of Ebola Virus and Pathogens Associated With Hemorrhagic Fever by an Oligonucleotide Microarray

Ebola virus infection causes severe hemorrhagic fever, and its mortality rates varied from 25 to 90% in the previous outbreaks. The highly infectious and lethal nature of this virus highlights the need for reliable and sensitive diagnostic methods to distinguish it from other diseases present with similar clinical symptoms. Based on multiplex polymerase chain reaction (PCR) and oligonucleotide microarray technology, a cost-effective, multipathogen and high-throughput method was developed for simultaneous detection of Ebola virus and other pathogens associated with hemorrhagic fever, including Marburg virus, Lassa fever virus, Junin virus, Machupo virus, Rift Valley fever virus, Crimean-Congo hemorrhagic fever virus, malaria parasite, hantavirus, severe fever with thrombocytopenia syndrome virus, dengue virus, yellow fever virus, Chikungunya virus, influenza A virus, and influenza B virus. This assay had an excellent specificity for target pathogens, without overlap signal between the probes. The limit of detection was approximately 10³ pathogen copies/μl. A total of 60 positive nucleic acid samples for different pathogens were detected, a concordance of 100% was observed between microarray assay and real-time PCR analysis. Consequently, the described oligonucleotide microarray may be specific and sensitive assay for diagnosis and surveillance of infections caused by Ebola virus and other species of hemorrhagic fever pathogens.

Clinical Update of Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) is an acute febrile illness characterized by fever, leukopenia, thrombocytopenia, and gastrointestinal symptoms such as diarrhea, nausea, and vomiting resulting from infection with the SFTS virus (SFTSV). The SFTSV is transmitted to humans by tick bites, primarily from Haemaphysalis longicornis, Amblyomma testudinarium, Ixodes nipponensis, and Rhipicephalus microplus. Human-to-human transmission has also been reported. Since the first report of an SFTS patient in China, the number of patients has also been increasing. The mortality rate of patients with SFTS remains high because the disease can quickly lead to death through multiple organ failure. In particular, an average fatality rate of approximately 20% has been reported for SFTS patients, and no treatment strategy has been established. Therefore, effective antiviral agents and vaccines are required. Here, we aim to review the epidemiology, clinical manifestations, laboratory diagnosis, and various specific treatments (i.e., antiviral agents, steroids, intravenous immunoglobulin, and plasma exchange) that have been tested to help to cope with the disease.

Dengue and Other Viral Hemorrhagic Fevers

How to cite this article: Shastri PS, Taneja S. Dengue and Other Viral Hemorrhagic Fevers. Indian J Crit Care Med 2021;25(Suppl 2):S130–S133.

Upregulation of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 in renal tissue in severe dengue in humans: Effects on endothelial activation/dysfunction

INTRODUCTION

Dengue is an important mosquito-borne disease in tropical and subtropical regions. Adhesion molecules have not been systematically characterized in the renal tissue of patients with severe dengue (SD). The objective of this study was to detect viral antigens in samples from patients that evolved with SD, correlating with the expression of ICAM-1, VCAM-1, VE-cadherin, and E-selectin to contribute to a better understanding of the pathophysiology of SD.

METHODS

Kidney specimens from patients with SD were selected according to clinical and laboratorial data and submitted to histological and immunohistochemistry analysis. A semiquantitative evaluation was performed considering positive immunostaining in 20 glomeruli.

RESULTS

Viral antigens were mainly detected in distal tubules. The intense immunostaining of VCAM-1 and ICAM-1 was observed. The expression of E-selectin was discrete, and VE-cadherin expression varied from mild to moderate. VCAM-1 was slightly intense in the glomerular capsule; the expression of ICAM-1 was diffuse. E-selectin was diffuse, and VE-cadherin varied from mild to moderate. The most frequent histological findings were glomerular congestion, mild glomerulitis, acute renal injury, and glomerular atrophy.

CONCLUSIONS

The results appear to demonstrate an imbalance between vascular endothelial permeability regulating events in renal lesions in SD. The increase in the expression of ICAM-1 and VCAM-1 is an in-situ indicator of higher permeability with a consequent influx of cells favoring the inflammation of the endothelium. These molecules are important in the pathophysiology of the disease and provide the possibility of developing new markers for the evaluation, clinical follow-up, and therapeutic response of patients with SD.

T-Cell Response to Viral Hemorrhagic Fevers

Viral hemorrhagic fevers (VHF) are a group of clinically similar diseases that can be caused by enveloped RNA viruses primarily from the families Arenaviridae, Filoviridae, Hantaviridae, and Flaviviridae. Clinically, this group of diseases has in common fever, fatigue, dizziness, muscle aches, and other associated symptoms that can progress to vascular leakage, bleeding and multi-organ failure. Most of these viruses are zoonotic causing asymptomatic infections in the primary host, but in human beings, the infection can be lethal. Clinical and experimental evidence suggest that the T-cell response is needed for protection against VHF, but can also cause damage to the host, and play an important role in disease pathogenesis. Here, we present a review of the T-cell immune responses to VHF and insights into the possible ways to improve counter-measures for these viral agents.

Molecular detection of viruses causing hemorrhagic fevers in rodents in the south-west of Korea

Many pathogens causing hemorrhagic fevers of medical and veterinary importance have been identified and isolated from rodents in the Republic of Korea (ROK). We investigated the occurrence of emerging viruses causing hemorrhagic fevers, such as hemorrhagic fever with renal syndrome (HFRS), severe fever with thrombocytopenia syndrome (SFTS), and flaviviruses, from wild rodents. Striped field mice, Apodemus agrarius (n = 39), were captured during 2014-2015 in the south-west of ROK. Using molecular methods, lung samples were evaluated for SFTS virus, hantavirus, and flavivirus, and seropositivity was evaluated in the blood. A high positive rate of hantavirus (46.2%) was detected in A. agrarius lungs by reverse transcription-nested polymerase chain reaction (RT-N-PCR). The monthly occurrence of hantavirus was 16.7% in October, 86.7% in November, and 25% in August of the following year (p < 0.001). Moreover, 17.9% of blood samples were serologically positive for hantavirus antibodies. The most prevalent strain in A. agrarius was Hantaan virus. All samples were positive for neither SFTS virus nor flavivirus. Hantaan virus was detected in 86.7% of A. agrarius in November (autumn), and thus, virus shedding from A. agrarius can increase the risk of humans contracting HFRS. These findings may help to predict and prevent disease outbreaks in ROK.

The Regulation of Seventeen Inflammatory Mediators are Associated with Patient Outcomes in Severe Fever with Thrombocytopenia Syndrome

Severe fever with thrombocytopenia syndrome (SFTS) as an emerging infection disease results in high morbidity and mortality in China. In this study, the circulating levels of 36 inflammatory mediators in 33 SFTS patients on days 3–7, 8–12 and 13–20 post-illness were measured by a multiplex Luminex® system dynamically. Among the patients, 15 severe patients recovered, 11 severe patients died within three weeks. We found IL-1RA, IL-6, IL-15, IL-10, TNF-α, IFN-γ, G-CSF, eotaxin, IL-8, IP-10, MCP-1, MIP-1α, MIP-1β and fractalkine were significantly upregulated in SFTS patients. Elevated IL-15 and eotaxin in SFTS patients were reported firstly. The highest levels of pro-inflammatory and anti-inflammatory cytokines coexisted in fatal patients during the first week. Inflammatory mediators remained high levels when death occurred in fatal patients, they were recovered within three weeks in nonfatal patients. Our results showed the occurrence of inflammatory storm in SFTS patients were associated with the severity of SFTS. RANTES and PDGF were down regulated and remained significantly lower levels in fatal patients throughout the course of disease, the concentrations of RANTES and PDGF were remarkably positively correlated with the platelet count. Our results demonstrated that dysregulated inflammatory response was associated with disease pathogenesis and mortality in SFTS patients.

Favipiravir pharmacokinetics in Ebola-Infected patients of the JIKI trial reveals concentrations lower than targeted

Background

In 2014–2015, we assessed favipiravir tolerance and efficacy in patients with Ebola virus (EBOV) disease (EVD) in Guinea (JIKI trial). Because the drug had never been used before for this indication and that high concentrations of the drugs were needed to achieve antiviral efficacy against EBOV, a pharmacokinetic model had been used to propose relevant dosing regimen. Here we report the favipiravir plasma concentrations that were achieved in participants in the JIKI trial and put them in perspective with the model-based targeted concentrations.

Methods and findings

Pre-dose drug concentrations were collected at Day-2 and Day-4 of treatment in 66 patients of the JIKI trial and compared to those predicted by the model taking into account patient’s individual characteristics. At Day-2, the observed concentrations were slightly lower than the model predictions adjusted for patient’s characteristics (median value of 46.1 versus 54.3 μg/mL for observed and predicted concentrations, respectively, p = 0.012). However, the concentrations dropped at Day-4, which was not anticipated by the model (median values of 25.9 and 64.4 μg/mL for observed and predicted concentrations, respectively, p<10⁻⁶). There was no significant relationship between favipiravir concentrations and EBOV viral kinetics or mortality.

Conclusions

Favipiravir plasma concentrations in the JIKI trial failed to achieve the target exposure defined before the trial. Furthermore, the drug concentration experienced an unanticipated drop between Day-2 and Day-4. The origin of this drop could be due to severe sepsis conditions and/or to intrinsic properties of favipiravir metabolism. Dose-ranging studies should be performed in healthy volunteers to assess the concentrations and the tolerance that could be achieved with high doses.

Trial registration

ClinicalTrials.gov NCT02329054

In 2014–2015, the JIKI trial was conducted in Guinea to test favipiravir tolerance and efficacy in patients with Ebola virus disease (EDV). The main results of the trial were previously published without drug concentrations which were not available at the time of publication. The purpose of this study was to report favipiravir concentrations achieved in participants in the JIKI trial and to compare them with the targeted concentrations. We analyzed drug concentrations obtained at Day-2 and Day-4 and compared them to the targeted concentrations. At Day-2, favipiravir concentrations were significantly below but still close to the targeted concentration. At Day-4, a significant and unanticipated drop of concentrations as compared to Day-2 was observed. The origin of the lower-than-targeted concentrations and the unexpected drop could be due to severe sepsis conditions and/or to intrinsic properties of favipiravir metabolism. No significant correlation was found between the drug exposure and the virological response, indicating that it is possible that the favipiravir concentrations in the JIKI trial were not sufficient to strongly inhibit the viral replication. These findings suggest the necessity of performing dose-ranging studies with high doses of favipiravir in healthy volunteers to inform any further development of favipiravir for treatment of EVD.

Pathological Characterization Of IFNAR(-/-) Mice Infected With Bluetongue Virus Serotype 4

Bluetongue virus (BTV) replicates in lymphoid tissues where infected mononuclear leukocytes secrete proinflammatory and vasoactive mediators that can contribute to bluetongue (BT) pathogenesis. Using the well-characterized IFNAR(-/-) mice animal model, we have now studied the histopathology and dynamics of leukocyte populations in different target tissues (spleen, thymus, and lung) during BTV-4 infection by histological and immunohistochemical techniques. The spleen and thymus of BTV-4 infected mice showed severe lymphoid depletion on H&E stained sections. This finding was confirmed by IHC, showing moderate decreased immunopositivity against CD3 in the thymus, and scarce immunoreactivity against CD3 and CD79 in the rest of the white pulp in the spleen, together with an increase in MAC387 immunostaining. BTV-4 infection also induced the expression of active caspase-3 in the spleen, where apoptotic debris was observed by H&E. A dramatic increase in iNOS immunoreactivity associated to necrotic areas of the white pulp was observed, being less noticeable in the thymus and the lung. The induction of pro-inflammatory cytokines in tissues where BTV replicates was evaluated by measuring transcript levels by RT-qPCR. BTV-4 infection led to enhance transcription of IFN-γ, TNF, IL-6, IL-12-p40, and IL-1β mRNA in the thymus, spleen and lung, correlating with the level of virus replication in these tissues. Disease progression and pathogenesis in IFNAR(-/-) mice closely mimics hallmarks of bluetongue disease in ruminants. IFNAR(-/-) mice are a good choice to facilitate a faster advance in the field of orbiviruses.

Estimating Time of Infection Using Prior Serological and Individual Information Can Greatly Improve Incidence Estimation of Human and Wildlife Infections

Diseases of humans and wildlife are typically tracked and studied through incidence, the number of new infections per time unit. Estimating incidence is not without difficulties, as asymptomatic infections, low sampling intervals and low sample sizes can introduce large estimation errors. After infection, biomarkers such as antibodies or pathogens often change predictably over time, and this temporal pattern can contain information about the time since infection that could improve incidence estimation. Antibody level and avidity have been used to estimate time since infection and to recreate incidence, but the errors on these estimates using currently existing methods are generally large. Using a semi-parametric model in a Bayesian framework, we introduce a method that allows the use of multiple sources of information (such as antibody level, pathogen presence in different organs, individual age, season) for estimating individual time since infection. When sufficient background data are available, this method can greatly improve incidence estimation, which we show using arenavirus infection in multimammate mice as a test case. The method performs well, especially compared to the situation in which seroconversion events between sampling sessions are the main data source. The possibility to implement several sources of information allows the use of data that are in many cases already available, which means that existing incidence data can be improved without the need for additional sampling efforts or laboratory assays.

Association of the Serum Angiotensin II Level with Disease Severity in Severe Fever with Thrombocytopenia Syndrome Patients

OBJECTIVE

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging infectious disease caused by a novel Bunyavirus. Recent data suggest that the physiological balance of multiple proinflammatory cytokines is substantially changed in cases of severe fever with thrombocytopenia syndrome virus (SFTSV) infection, and the inflammatory response probably plays an important role in disease progression. Angiotensin II is an important active substance of the renin-angiotensin system, and studies have demonstrated that angiotensin II is involved in key events in the inflammatory process and can regulate inflammatory cell responses.

METHODS

In order to elucidate the role of angiotensin II in the pathogenesis of SFTS, we collected serum samples from SFTS patients in the acute or convalescent phase and tested the angiotensin II levels using an enzyme-linked immunosorbent assay as well as SFTSV viral RNA with real-time reverse-transcriptase polymerase chain reaction. Furthermore, we explored possible correlations between the angiotensin II levels and clinical parameters in SFTS patients.

RESULTS

Our data showed that the serum level of angiotensin II was significantly increased in the acute phase compared with that seen in the convalescent phase and the healthy controls, while there were no significant differences between the convalescent cases and healthy controls (p>0.05). A correlation analysis demonstrated that the level of angiotensin II positively correlated with the SFTS viral RNA load. The angiotensin II levels were also found to be correlated with clinical parameters indicating impairments in organ functions. Moreover, we also found that the angiotensin II levels were significantly increased in the severe cases versus the non-severe cases (p<0.001).

CONCLUSION

The serum angiotensin II levels in SFTS patients may be used to stratify the disease severity and are possibly predictive of disease outcomes.

Decreased monocyte subsets and TLR4-mediated functions in patients with acute severe fever with thrombocytopenia syndrome (SFTS)

OBJECTIVES

The role of a newly discovered bunyavirus, the severe fever with thrombocytopenia syndrome virus (SFTSV), in the pathogenesis of severe fever with thrombocytopenia syndrome (SFTS) is poorly understood. In this study, it was hypothesized that peripheral monocytes, which are constantly exposed to viral infection in the blood, are likely targeted by the causative virus in SFTS patients.

METHODS

Fifty-three patients and 25 healthy volunteers were enrolled in the study. Monocyte counts in the peripheral blood of all human subjects were monitored throughout the progress of the disease. SFTSV viral load and the expression of monocyte genes were investigated by real-time RT-PCR. Cytokine production of monocytes in SFTS patients upon lipopolysaccharide (LPS) stimulation was examined by ELISA.

RESULTS

In comparison to SFTS patients in the convalescent stage and healthy controls, monocyte cell counts and percentages in patients at the acute stage were significantly lower. Decreased monocyte cell counts and subsets were positively correlated with SFTSV viral loads in the serum samples from SFTS patients. Despite their higher basal toll-like receptor 4 (TLR4) expression, monocytes from patients in the acute phase were shown to be compromised regarding the production of tumor necrosis factor alpha, but not interleukin 10, upon LPS stimulation.

CONCLUSIONS

These data strongly suggest that monocytes could be a major target during SFTSV infection. The decreased population and dysfunction of monocytes in acute SFTS patients may contribute to the disease severity.

Viral Hemorrhagic Fever Diagnostics

There are 4 families of viruses that cause viral hemorrhagic fever (VHF), including Filoviridae. Ebola virus is one virus within the family Filoviridae and the cause of the current outbreak of VHF in West Africa. VHF-endemic areas are found throughout the world, yet traditional diagnosis of VHF has been performed in large reference laboratories centered in Europe and the United States. The large amount of capital needed, as well as highly trained and skilled personnel, has limited the availability of diagnostics in endemic areas except in conjunction with governmental and nongovernmental entities. However, rapid diagnosis of VHF is essential to efforts that will limit outbreaks. In addition, increased global travel suggests VHF diagnoses may be made outside of the endemic areas. Thus, understanding how to diagnose VHF is imperative for laboratories worldwide. This article reviews traditional and current diagnostic modalities for VHF.

Activation of TLR2 and TLR6 by Dengue NS1 Protein and Its Implications in the Immunopathogenesis of Dengue Virus Infection

Dengue virus (DV) infection is the most prevalent mosquito-borne viral disease and its manifestation has been shown to be contributed in part by the host immune responses. In this study, pathogen recognition receptors, Toll-like receptor (TLR) 2 and TLR6 were found to be up-regulated in DV-infected human PBMC using immunofluorescence staining, flow cytometry and Western blot analyses. Using ELISA, IL-6 and TNF-α, cytokines downstream of TLR2 and TLR6 signaling pathways were also found to be up-regulated in DV-infected PBMC. IL-6 and TNF-α production by PBMC were reduced when TLR2 and TLR6 were blocked using TLR2 and TLR6 neutralizing antibodies during DV infection. These results suggested that signaling pathways of TLR2 and TLR6 were activated during DV infection and its activation contributed to IL-6 and TNF-α production. DV NS1 protein was found to significantly increase the production of IL-6 and TNF-α when added to PBMC. The amount of IL-6 and TNF-α stimulated by DV NS1 protein was reduced when TLR2 and TLR6 were blocked, suggesting that DV NS1 protein is the viral protein responsible for the activation of TLR2 and TLR6 during DV infection. Secreted alkaline phosphatase (SEAP) reporter assay was used to further confirm activation of TLR2 and TLR6 by DV NS1 protein. In addition, DV-infected and DV NS1 protein-treated TLR6^-/- mice have higher survivability compared to DV-infected and DV NS1 protein-treated wild-type mice. Hence, activation of TLR6 via DV NS1 protein could potentially play an important role in the immunopathogenesis of DV infection.

Despite the prevalence of dengue virus infection and the heavy economic burden it puts on the endemic countries, the immunopathogenesis of dengue virus infection remains unclear. Plasma leakage in dengue hemorrhagic fever (DHF) develops not when the viremia is at its peak in infected patients but when viremia has been significantly reduced or cleared. This suggests that host immune response is responsible for the development DHF. The interactions of the viral factors with host factors which trigger the host immune responses are likely to play a significant role in the development of dengue diseases, thus are of great interests. In this study, we found that dengue NS1 protein activates TLR2 and TLR6, leading to increase proinflammatory cytokine production. In addition, the interaction of viral factor with TLR6 was found to play an important role in the manifestation of dengue virus infection. Our study provides new insights into the involvement of TLR6 in dengue virus infection and the potential of using TLR6 anatagonist in therapeutic treatment for DV infection.

Shedding dynamics of Morogoro virus, an African arenavirus closely related to Lassa virus, in its natural reservoir host Mastomys natalensis

Arenaviruses can cause mild to severe hemorrhagic fevers. Humans mainly get infected through contact with infected rodents or their excretions, yet little is known about transmission dynamics within rodent populations. Morogoro virus (MORV) is an Old World arenavirus closely related to Lassa virus with which it shares the same host species Mastomys natalensis. We injected MORV in its host, and sampled blood and excretions at frequent intervals. Infection in adults was acute; viral RNA disappeared from blood after 18 days post infection (dpi) and from excretions after 39 dpi. Antibodies were present from 7 dpi and never disappeared. Neonatally infected animals acquired a chronic infection with RNA and antibodies in blood for at least 3 months. The quantified excretion and antibody patterns can be used to inform mathematical transmission models, and are essential for understanding and controlling transmission in the natural rodent host populations.

Serum levels of IL-8, IFNγ, IL-10, and TGF β and their gene expression levels in severe and non-severe cases of dengue virus infection

Increased serum and mRNA levels of cytokines in patients with dengue virus (DV) infection suggest that cytokines are one of the key factors in the pathogenesis of disease caused by this virus. Here, we tested 211 serum and 56 mRNA samples from an equal number of dengue cases to determine the levels of interleukin-8 (IL-8), interferon gamma (IFN-γ), interleukin-10 (IL-10) and transforming growth factor beta (TGF-β). A total 70 serum and 15 mRNA samples from healthy individual were also tested for cytokines and served as controls. Serum and mRNA levels of IL-8 were highest in the earlier days of dengue infection. IFNγ levels peaked one or two days before defervescence. Levels of IL-10 and TGF-β were highest later in dengue infection, and TGF-β levels peaked on the day of defervescence. Mean levels of IFNγ, TGF β and IL-10 were higher in samples from dengue cases, irrespective of severity, than in healthy controls. In contrast, the level of IL-8 was significantly higher in samples from severe dengue cases and lower in cases of dengue without warning signs than in healthy controls. Children (82.2 % of 101 paediatric cases) commonly had severe dengue illness. Samples that were positive for anti-DV IgG antibody had higher levels of IL-8 and TGF β. DV-2 infections were associated with severe dengue illness. IL-8 and IFNγ levels were higher in the presence of warning signs of severe dengue. Levels of IL-8, IL-10 and TGF β were independently associated with disease outcome. These data provide evidence of an association of IL-8, IFNγ, TGF β and IL-10 levels with the severity of dengue illness. Especially, IL-8 levels can be used as a predictor of severe DV infection.

Increased risk of acute myocardial infarction and stroke during hemorrhagic fever with renal syndrome: a self-controlled case series study

BACKGROUND

We recently observed that cardiovascular causes of death are common in patients with hemorrhagic fever with renal syndrome (HFRS), which is caused by hantaviruses. However, it is not known whether HFRS is a risk factor for the acute cardiovascular events of acute myocardial infarction (AMI) and stroke.

METHODS AND RESULTS

Personal identification numbers from the Swedish HFRS patient database (1997-2012; n=6643) were cross-linked with the National Patient Register from 1987 to 2011. Using the self-controlled case series method, we calculated the incidence rate ratio of AMI/stroke in the 21 days after HFRS against 2 different control periods either excluding (analysis 1) or including (analysis 2) fatal AMI/stroke events. The incidence rate ratios for analyses 1 and 2 for all AMI events were 5.53 (95% confidence interval [CI], 2.6-11.8) and 6.02 (95% CI, 2.95-12.3) and for first AMI events were 3.53 (95% CI, 1.25-9.96) and 4.64 (95% CI, 1.83-11.77). The incidence rate ratios for analyses 1 and 2 for all stroke events were 12.93 (95% CI, 5.62-29.74) and 15.16 (95% CI, 7.21-31.87) and for first stroke events were 14.54 (95% CI, 5.87-36.04) and 17.09 (95% CI, 7.49-38.96). The majority of stroke events occurred in the first week after HFRS. Seasonal effects were not observed, and apart from 1 study, neither sex nor age interacted with the associations observed in this study.

CONCLUSIONS

There is a significantly increased risk for AMI and stroke in the immediate time period after HFRS. Therefore, HFRS patients should be carefully monitored during the acute phase of disease to ensure early recognition of symptoms of impending AMI or stroke.

Crimean-Congo hemorrhagic fever: an overview

Crimean-Congo hemorrhagic fever (CCHF) is a zoonotic viral infection that is a serious threat to humans. The disease is widely distributed in Africa, Asia, and Europe and has developed into a serious public health concern. Humans become infected through the bites of ticks, by contact with a patient with CCHF, or by contact with blood or tissues from viremic livestock. Microvascular instability and impaired hemostasis are the hallmarks of the infection. Infection in human begins with nonspecific febrile symptoms, but may progress to a serious hemorrhagic syndrome with high mortality rates. Enzyme-linked immunoassay (ELISA) and polymerase chain reaction (PCR) are the most used and specific tests for the diagnosis. The mainstay of treatment is supportive. Although definitive studies are not available, ribavirin is suggested to be effective especially at the earlier phase of the infection. Uses of universal protective measures are the best way to avoid the infection. In this review, all aspects of CCHF are overviewed in light of the current literature.

Review: Viral infections and mechanisms of thrombosis and bleeding

Viral infections are associated with coagulation disorders. All aspects of the coagulation cascade, primary hemostasis, coagulation, and fibrinolysis, can be affected. As a consequence, thrombosis and disseminated intravascular coagulation, hemorrhage, or both, may occur. Investigation of coagulation disorders as a consequence of different viral infections have not been performed uniformly. Common pathways are therefore not fully elucidated. In many severe viral infections there is no treatment other than supportive measures. A better understanding of the pathophysiology behind the association of viral infections and coagulation disorders is crucial for developing therapeutic strategies. This is of special importance in case of severe complications, such as those seen in hemorrhagic viral infections, the incidence of which is increasing worldwide. To date, only a few promising targets have been discovered, meaning the implementation in a clinical context is still hampered. This review discusses non‐hemorrhagic and hemorrhagic viruses for which sufficient data on the association with hemostasis and related clinical features is available. This will enable clinicians to interpret research data and place them into a perspective. J. Med. Virol. 84:1680–1696, 2012. © 2012 Wiley Periodicals, Inc.

The Baboon (Papio spp.) as a model of human Ebola virus infection

Baboons are susceptible to natural Ebola virus (EBOV) infection and share 96% genetic homology with humans. Despite these characteristics, baboons have rarely been utilized as experimental models of human EBOV infection to evaluate the efficacy of prophylactics and therapeutics in the United States. This review will summarize what is known about the pathogenesis of EBOV infection in baboons compared to EBOV infection in humans and other Old World nonhuman primates. In addition, we will discuss how closely the baboon model recapitulates human EBOV infection. We will also review some of the housing requirements and behavioral attributes of baboons compared to other Old World nonhuman primates. Due to the lack of data available on the pathogenesis of Marburg virus (MARV) infection in baboons, discussion of the pathogenesis of MARV infection in baboons will be limited.

Host cytokine storm is associated with disease severity of severe fever with thrombocytopenia syndrome

BACKGROUND

Severe fever with thrombocytopenia syndrome (SFTS) is an emerging viral disease in China, caused by SFTS virus (SFTSV). Severe SFTS patients can quickly proceed to multiorgan dysfunction and death; however, underlying pathogenic mechanisms remain unclear.

METHODS

Serum samples from 15 fatal and 44 nonfatal SFTS cases were subjected to multiplex-microbead immunoassays to detect a broad spectrum of cytokines. The viral load and virus-specific IgG titers were also tested by real-time PCR and ELISA, respectively.

RESULTS

Cytokines IL-1RA, IL-6, IL-10, G-CSF, IP-10, and MCP-1 were elevated in SFTS patients and produced at robust levels in fatal cases. In contrast, cytokines PDGF-BB and RANTES decreased in SFTS patients. These cytokines reverted to normal ranges during the convalescent phase of SFTSV infection. Cytokines IL-1β, IL-8, MIP-1α, and MIP-1β showed a unique pattern of elevation in fatal cases but not in nonfatal cases. However, these cytokines increased in the convalescent phase of nonfatal SFTS cases. Our regression analysis revealed that the serum viral load correlated with these cytokines. Moreover, levels of these cytokines correlated with various clinical parameters and virus-specific IgG titers.

CONCLUSION

The study demonstrates that SFTSV infection induces a cytokine storm with abnormally expressed cytokine profiles, which are associated with the disease severity.

Platelets support a protective immune response to LCMV by preventing splenic necrosis

Severe arenaviral infections in humans are characterized by clinical findings common to other viral hemorrhagic fevers (VHFs), including thrombocytopenia, leukopenia, skin and internal organ hemorrhages, high viral replication, splenic necrosis, and death. Host responses, rather than direct damage by the arenaviral replication, account for most of the observed pathology, but it is not known what protective roles platelets may have in each of the manifestations. To address this issue in an animal model, we compared nondepleted (100%), partially depleted (15%), and profoundly (< 2.5%) platelet depleted mice infected with the mouse arenavirus lymphocytic choriomeningitis virus (LCMV). Here, we describe that systemic bleedings and death were seen only in those animals receiving the stronger depletion treatment. Furthermore, we showed that the nonhemorrhagic but partially platelet-depleted mice were unable to control the viral replication because of generalized splenic necrosis, affecting innate and adaptive immune cells.These data suggest that, by their supportive roles in hemostasis, platelets may be preventing the severe pathology observed in human arenaviral infections.

A family cluster of infections by a newly recognized bunyavirus in eastern China, 2007: further evidence of person-to-person transmission

BACKGROUND

Seven persons in one family living in eastern China developed fever and thrombocytopenia during May 2007, but the initial investigation failed to identify an infectious etiology. In December 2009, a novel bunyavirus (designated severe fever with thrombocytopenia syndrome bunyavirus [SFTSV]) was identified as the cause of illness in patients with similar clinical manifestations in China. We reexamined this family cluster for SFTSV infection.

METHODS

We analyzed epidemiological and clinical data for the index patient and 6 secondary patients. We tested stored blood specimens from the 6 secondary patients using real time reverse transcription polymerase chain reaction (RT-PCR), viral culture, genetic sequencing, micro-neutralization assay (MNA), and indirect immunofluorescence assay (IFA).

RESULTS

An 80-year-old woman with fever, leucopenia, and thrombocytopenia died on 27 April 2007. Between 3 and 7 May 2007, another 6 patients from her family were admitted to a local county hospital with fever and other similar symptoms. Serum specimens collected in 2007 from these 6 patients were positive for SFTS viral RNA through RT-PCR and for antibody to SFTSV through MNA and IFA. SFTSV was isolated from 1 preserved serum specimen. The only shared characteristic between secondary patients was personal contact with the index patient; none reported exposure to suspected animals or vectors.

CONCLUSIONS

Clinical and laboratory evidence confirmed that the patients of fever and thrombocytopenia occurring in a family cluster in eastern China in 2007 were caused by a newly recognized bunyavirus, SFTSV. Epidemiological investigation strongly suggests that infection of secondary patients was transmitted to family members by personal contact.

Clinical aspects of Marburg hemorrhagic fever

Marburg virus belongs to the genus Marburgvirus in the family Filoviridae and causes a severe hemorrhagic fever, known as Marburg hemorrhagic fever (MHF), in both humans and nonhuman primates. Similar to the more widely known Ebola hemorrhagic fever, MHF is characterized by systemic viral replication, immunosuppression and abnormal inflammatory responses. These pathological features of the disease contribute to a number of systemic dysfunctions including hemorrhages, edema, coagulation abnormalities and, ultimately, multiorgan failure and shock, often resulting in death. A detailed understanding of the pathological processes that lead to this devastating disease remains elusive, a fact that contributes to the lack of licensed vaccines or effective therapeutics. This article will review the clinical aspects of MHF and discuss the pathogenesis and possible options for diagnosis, treatment and prevention.

Minigenomes, transcription and replication competent virus-like particles and beyond: reverse genetics systems for filoviruses and other negative stranded hemorrhagic fever viruses

Reverse-genetics systems are powerful tools enabling researchers to study the replication cycle of RNA viruses, including filoviruses and other hemorrhagic fever viruses, as well as to discover new antivirals. They include full-length clone systems as well as a number of life cycle modeling systems. Full-length clone systems allow for the generation of infectious, recombinant viruses, and thus are an important tool for studying the virus replication cycle in its entirety. In contrast, life cycle modeling systems such as minigenome and transcription and replication competent virus-like particle systems can be used to simulate and dissect parts of the virus life cycle outside of containment facilities. Minigenome systems are used to model viral genome replication and transcription, whereas transcription and replication competent virus-like particle systems also model morphogenesis and budding as well as infection of target cells. As such, these modeling systems have tremendous potential to further the discovery and screening of new antivirals targeting hemorrhagic fever viruses. This review provides an overview of currently established reverse genetics systems for hemorrhagic fever-causing negative-sense RNA viruses, with a particular emphasis on filoviruses, and the potential application of these systems for antiviral research.

Modulation of cytokine and cytokine receptor/antagonist by treatment with doxycycline and tetracycline in patients with dengue fever

Dengue virus infection can lead to dengue fever (DF) or dengue hemorrhagic fever (DHF). Disease severity has been linked to an increase in various cytokine levels. In this study, we evaluated the effectiveness of doxycycline and tetracycline to modulate serum levels of IL-6, IL-1B, and TNF and cytokine receptor/receptor antagonist TNF-R1 and IL-1RA in patients with DF or DHF. Hospitalized patients were randomized to receive standard supportive care or supportive care combined with doxycycline or tetracycline therapy. Serum cytokine and cytokine receptor/antagonist levels were determined at the onset of therapy and after 3 and 7 days. Cytokine and cytokine receptor/antagonist levels were substantially elevated at day 0. IL-6, IL-1β, and TNF remained at or above day 0 levels throughout the study period in untreated patients. Treatment with tetracycline or doxycycline resulted in a significant decline in cytokine levels. Similarly, IL-1RA and TNF-R1 serum concentrations were elevated at baseline and showed a moderate increase among untreated patients. Both drugs resulted in a significant rise in IL-1Ra levels by day 3 in patients. In contrast, treatment did not affect a similar result for TNF-R1. When compared to the control group, however, a significant rise post-treatment was seen upon intragroup analysis. Further analysis demonstrated that doxycycline was significantly more effective at modulating cytokine and cytokine receptor/antagonist levels than tetracycline.

Hantaviruses

Hantaviruses affect people worldwide, yet they remain poorly understood. This article explores the known history of hantaviruses. It describes diagnostic methods and potential options for treatment and prevention.

Bluetongue virus infection activates bovine monocyte-derived macrophages and pulmonary artery endothelial cells

Bluetongue virus (BTV) is the cause of bluetongue (BT), an emerging, arthropod-transmitted disease of ungulates. The cellular tropism of BTV in ruminants includes macrophages, dendritic cells and endothelial cells (ECs), and fulminant infection is characterized by lesions consistent with those of so-called viral hemorrhagic fevers. Specifically, BT is characterized by vascular injury with hemorrhage, tissue infarction and widespread edema. To further investigate the pathogenesis of vascular injury in BT, we evaluated the responses of cultured bovine pulmonary artery EC (bPAEC) and monocyte-derived macrophages (bMDM) to BTV infection by measuring transcript levels of genes encoding molecules important in mediating EC activation and/or endothelial barrier dysregulation. The data confirm that BTV infection of bPAEC resulted in increased transcription of genes encoding chemokine ligand 2 (CCL2) and E-selectin, and BTV infection of bMDM resulted in increased transcription of genes encoding TNF-alpha, IL-1beta, IL-8, and inducible nitric oxide synthase (iNOS). The data from these in vitro studies provide further evidence that cytokines and other vasoactive substances produced in macrophages potentially contribute to vascular injury in BTV-infected ruminants, along with direct effects of the virus itself on ECs.

Infectious Lassa virus, but not filoviruses, is restricted by BST-2/tetherin

Bone marrow stromal antigen 2 (BST-2/tetherin) is a cellular membrane protein that inhibits the release of HIV-1. We show for the first time, using infectious viruses, that BST-2 also inhibits egress of arenaviruses but has no effect on filovirus replication and spread. Specifically, infectious Lassa virus (LASV) release significantly decreased or increased in human cells in which BST-2 was either stably expressed or knocked down, respectively. In contrast, replication and spread of infectious Zaire ebolavirus (ZEBOV) and Lake Victoria marburgvirus (MARV) were not affected by these conditions. Replication of infectious Rift Valley fever virus (RVFV) and cowpox virus (CPXV) was also not affected by BST-2 expression. Elevated cellular levels of human or murine BST-2 inhibited the release of virus-like particles (VLPs) consisting of the matrix proteins of multiple highly virulent NIAID Priority Pathogens, including arenaviruses (LASV and Machupo virus [MACV]), filoviruses (ZEBOV and MARV), and paramyxoviruses (Nipah virus). Although the glycoproteins of filoviruses counteracted the antiviral activity of BST-2 in the context of VLPs, they could not rescue arenaviral (LASV and MACV) VLP release upon BST-2 overexpression. Furthermore, we did not observe colocalization of filoviral glycoproteins with BST-2 during infection with authentic viruses. None of the arenavirus-encoded proteins rescued budding of VLPs in the presence of BST-2. Our results demonstrate that BST-2 might be a broad antiviral factor with the ability to restrict release of a wide variety of human pathogens. However, at least filoviruses, RVFV, and CPXV are immune to its inhibitory effect.

VIPR: A probabilistic algorithm for analysis of microbial detection microarrays

BACKGROUND

All infectious disease oriented clinical diagnostic assays in use today focus on detecting the presence of a single, well defined target agent or a set of agents. In recent years, microarray-based diagnostics have been developed that greatly facilitate the highly parallel detection of multiple microbes that may be present in a given clinical specimen. While several algorithms have been described for interpretation of diagnostic microarrays, none of the existing approaches is capable of incorporating training data generated from positive control samples to improve performance.

RESULTS

To specifically address this issue we have developed a novel interpretive algorithm, VIPR (Viral Identification using a PRobabilistic algorithm), which uses Bayesian inference to capitalize on empirical training data to optimize detection sensitivity. To illustrate this approach, we have focused on the detection of viruses that cause hemorrhagic fever (HF) using a custom HF-virus microarray. VIPR was used to analyze 110 empirical microarray hybridizations generated from 33 distinct virus species. An accuracy of 94% was achieved as measured by leave-one-out cross validation.

CONCLUSIONS

VIPR outperformed previously described algorithms for this dataset. The VIPR algorithm has potential to be broadly applicable to clinical diagnostic settings, wherein positive controls are typically readily available for generation of training data.

Interacting roles of immune mechanisms and viral load in the pathogenesis of crimean-congo hemorrhagic fever

Until now, the pathogenesis of Crimean-Congo hemorrhagic fever (CCHF) has not been well described. However, it has been hypothesized that it could be a result of the direct injury of virus-infected tissues in combination with the indirect effects of host immune responses, including cytokines. To shed more light on the role of viral load and cytokines, differential influences of CCHF virus (CCHFV) RNA load, antibody response, and cytokine production on severity and outcome of the disease were studied in sera of 46 patients with confirmed acute CCHF from Kosovo. In this study, viral load proved to be strongly related to the severity and outcome of the disease, with higher viral loads detected in patients with fatal outcomes than in surviving patients. Also, patients with fatal outcome had on average a weaker antibody response, if one was present at all. High levels of interleukin-10 (IL-10), gamma interferon (IFN-gamma), and tumor necrosis factor alpha (TNF-alpha) were associated with poor outcome, since detected concentrations were highest in patients with fatal outcome and lowest in patients with moderate disease course. Additionally, a positive linear dependence between viral load and these cytokines was observed. Interestingly, reduced levels of IL-12 were detected in all CCHF patients. Our study favors the hypothesis that CCHF could be a result of a delayed and downregulated immune response caused by IL-10, which leads to an increased replication and spread of CCHFV throughout the body. This consequently triggers increased production of IFN-gamma and TNF-alpha, cytokines mediating vascular dysfunction, disseminated intravascular coagulation, organ failure, and shock.

Junín virus infection of human hematopoietic progenitors impairs in vitro proplatelet formation and platelet release via a bystander effect involving type I IFN signaling

Argentine hemorrhagic fever (AHF) is an endemo-epidemic disease caused by Junín virus (JUNV), a member of the arenaviridae family. Although a recently introduced live attenuated vaccine has proven to be effective, AHF remains a potentially lethal infection. Like in other viral hemorrhagic fevers (VHF), AHF patients present with fever and hemorrhagic complications. Although the causes of the bleeding are poorly understood, impaired hemostasis, endothelial cell dysfunction and low platelet counts have been described. Thrombocytopenia is a common feature in VHF syndromes, and it is a major sign for its diagnosis. However, the underlying pathogenic mechanism has not yet been elucidated. We hypothesized that thrombocytopenia results from a viral-triggered alteration of the megakaryo/thrombopoiesis process. Therefore, we evaluated the impact of JUNV on megakaryopoiesis using an in vitro model of human CD34⁺ cells stimulated with thrombopoietin. Our results showed that CD34⁺ cells are infected with JUNV in a restricted fashion. Infection was transferrin receptor 1 (TfR1)-dependent and the surface expression of TfR1 was higher in infected cultures, suggesting a novel arenaviral dissemination strategy in hematopoietic progenitor cells. Although proliferation, survival, and commitment in JUNV-infected cultures were normal, viral infection impaired thrombopoiesis by decreasing in vitro proplatelet formation, platelet release, and P-selectin externalization via a bystander effect. The decrease in platelet release was also TfR1-dependent, mimicked by poly(I:C), and type I interferon (IFN α/β) was implicated as a key paracrine mediator. Among the relevant molecules studied, only the transcription factor NF-E2 showed a moderate decrease in expression in megakaryocytes from either infected cultures or after type I IFN treatment. Moreover, type I IFN-treated megakaryocytes presented ultrastructural abnormalities resembling the reported thrombocytopenic NF-E2^−/− mouse phenotype. Our study introduces a potential mechanism for thrombocytopenia in VHF and other diseases associated with increased bone marrow type I IFN levels.

Argentine hemorrhagic fever (AHF) is an endemo-epidemic disease caused by Junín virus (JUNV). Although a recently introduced live attenuated vaccine has proven to be effective, AHF remains a potentially lethal infection and JUNV is considered to be a potential biological weapon. Like other viral hemorrhagic fevers (VHF), AHF patients present fever with a combination of neurological and bleeding complications. Although the causes of the bleeding are poorly understood, impaired hemostasis and endothelial cell function as well as low platelet counts have been described. In this study, we have examined the impact of JUNV on an in vitro model of platelet production. We found that neither infection of hematopoietic progenitors with JUNV nor poly(I:C) (a double-stranded RNA that mimics viral infection) affected cell survival or megakaryocyte generation. However, these treatments triggered the main anti-viral cytokines produced by host type I IFN (IFN α/β), which acted in a paracrine fashion and led to abnormal platelet formation. Thus, this study identifies type I IFN as a new regulator that selectively affects the last steps of megakaryocyte lifespan, and it suggests a potential mechanism for thrombocytopenia in AHF and other diseases associated with increased bone marrow type I IFN levels.

Evaluation of the association of serum levels of hyaluronic acid, sICAM-1, sVCAM-1, and VEGF-A with mortality and prognosis in patients with Crimean-Congo hemorrhagic fever

BACKGROUND

Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral hemorrhagic disease. Pathogenesis of the disease has not been well described yet. A well-known pathogenic feature of CCHF virus is its capability to damage endothelium. Increased hyaluronic acid (HA) levels indicate liver sinusoidal endothelial damage. Soluble intercellular adhesion molecule-1 (sICAM-1), soluble vascular cell adhesion molecule-1 (sVCAM-1) and vascular endothelial growth factor-A (VEGF-A) play a role in the inflammatory process, vascular damage and plasma leakage.

OBJECTIVES

To investigate whether or not there is a relationship between HA, sICAM-1, sVCAM-1 and VEGF-A serum levels and fatality in CCHF.

STUDY DESIGN

Sixty-one patients who were confirmed by RT-PCR and serological tests for CCHF, included in the current study. HA, sICAM-1, sVCAM-1, VEGF-A levels in serum samples were analyzed by ELISA.

RESULTS

There were statistically significant differences between fatal and non-fatal CCHF patients in terms of HA, sICAM-1, sVCAM-1, and VEGF-A levels. In addition, AST and ALT levels were positively correlated with HA, sICAM-1, sVCAM-1, and VEGF-A levels.

CONCLUSION

HA, sICAM-1, sVCAM-1, and VEGF-A levels of the patients that died during hospitalization were statistically significantly higher than the patients that survived, and this finding suggests that the level of these molecules could be used as a prognostic marker in CCHF.

Serum angiopoietin-1 and -2 levels discriminate cerebral malaria from uncomplicated malaria and predict clinical outcome in African children

BACKGROUND

Limited tools exist to identify which individuals infected with Plasmodium falciparum are at risk of developing serious complications such as cerebral malaria (CM). The objective of this study was to assess serum biomarkers that differentiate between CM and non-CM, with the long-term goal of developing a clinically informative prognostic test for severe malaria.

METHODOLOGY/PRINCIPAL FINDINGS

Based on the hypothesis that endothelial activation and blood-brain-barrier dysfunction contribute to CM pathogenesis, we examined the endothelial regulators, angiopoietin-1 (ANG-1) and angiopoietin-2 (ANG-2), in serum samples from P. falciparum-infected patients with uncomplicated malaria (UM) or CM, from two diverse populations--Thai adults and Ugandan children. Angiopoietin levels were compared to tumour necrosis factor (TNF). In both populations, ANG-1 levels were significantly decreased and ANG-2 levels were significantly increased in CM versus UM and healthy controls (p<0.001). TNF was significantly elevated in CM in the Thai adult population (p<0.001), but did not discriminate well between CM and UM in African children. Receiver operating characteristic curve analysis showed that ANG-1 and the ratio of ANG-2:ANG-1 accurately discriminated CM patients from UM in both populations. Applied as a diagnostic test, ANG-1 had a sensitivity and specificity of 100% for distinguishing CM from UM in Thai adults and 70% and 75%, respectively, for Ugandan children. Across both populations the likelihood ratio of CM given a positive test (ANG-1<15 ng/mL) was 4.1 (2.7-6.5) and the likelihood ratio of CM given a negative test was 0.29 (0.20-0.42). Moreover, low ANG-1 levels at presentation predicted subsequent mortality in children with CM (p = 0.027).

CONCLUSIONS/SIGNIFICANCE

ANG-1 and the ANG-2/1 ratio are promising clinically informative biomarkers for CM. Additional studies should address their utility as prognostic biomarkers and potential therapeutic targets in severe malaria.

A key role for Toll-like receptor-3 in disrupting the hemostasis balance on endothelial cells

Various virus infections cause dysfunctional hemostasis and in some instances lead to the development of viral hemorrhagic fever syndrome. How do diverse viruses induce the expression of tissue factor on vascular cells? We hypothesize that a direct stimulation of pattern recognition receptors (PRR) by viral nucleic acids may be the key. Double-stranded RNA (dsRNA) is produced by many viruses and is recognized by various PRR, including Toll-like receptor-3 (TLR3). We have investigated whether poly I:C, a model for viral dsRNA, can influence cellular hemostasis. Poly I:C could up-regulate tissue factor and down-regulate thrombomodulin expression on endothelial cells but not on monocytes. The response to poly I:C was diminished upon small interfering RNA (siRNA)-mediated inhibition of TLR3, but not other PRR. In vivo, application of poly I:C induced similar changes in the aortic endothelium of mice as determined by enface microscopy. D-dimer, a circulating marker for enhanced coagulation and fibrinolysis, and tissue fibrin deposition was elevated. All the hemostasis-related responses to poly I:C, but not cytokine secretion, were blunted in TLR3(-/-) mice. Hence, the activation of TLR3 can induce the procoagulant state in the endothelium, and this could be relevant for understanding the mechanisms of viral stimulation of hemostasis.

Multiplex cytokine profile from dengue patients: MIP-1beta and IFN-gamma as predictive factors for severity

BACKGROUND

Dengue virus pathogenesis is not yet fully understood and the identification of patients at high risk for developing severe disease forms is still a great challenge in dengue patient care. During the present study, we evaluated prospectively the potential of cytokines present in plasma from patients with dengue in stratifying disease severity.

METHODS

Seventeen-cytokine multiplex fluorescent microbead immunoassay was used for the simultaneous detection in 59 dengue patients. GLM models using bimodal or Gaussian family were determined in order to associate cytokines with clinical manifestations and laboratory diagnosis.

RESULTS

IL-1beta, IFN-gamma, IL-4, IL-6, IL-13, IL-7 and GM-CSF were significantly increased in patients with severe clinical manifestations (severe dengue) when compared to mild disease forms (mild dengue). In contrast, increased MIP-1beta levels were observed in patients with mild dengue. MIP-1beta was also associated with CD56+NK cell circulating rates. IL-1beta, IL-8, TNF-alpha and MCP-1 were associated with marked thrombocytopenia. Increased MCP-1 and GM-CSF levels correlated with hypotension. Moreover, MIP-1beta and IFN-gamma were independently associated with both dengue severity and disease outcome.

CONCLUSION

Our data demonstrated that the use of a multiple cytokine assay platform was suitable for identifying distinct cytokine profiles associated with the dengue clinical manifestations and severity. MIP-beta is indicated for the first time as a good prognostic marker in contrast to IFN-gamma that was associated with disease severity.

Experimental Reproduction of Severe Bluetongue in Sheep

Sheep inoculated with a virulent South African strain of bluetongue (BT) virus serotype 4 developed severe clinical signs and lesions characteristic of fulminant BT, including coronitis, hemorrhage and ulceration of the mucosal lining of the oral cavity and forestomaches, hemorrhage in the wall of the pulmonary artery, and focally extensive necrosis of skeletal muscle, especially of the neck. At necropsy, up to 14 days after infection, the infected sheep exhibited striking pulmonary edema, edema of the subcutaneous tissues and fascial planes of the head and neck, and pleural and pericardial effusion of varying severity. A reliable model for experimental reproduction of fulminant BT in sheep will facilitate future studies to better characterize the pathogenesis of this disease, particularly as it regards the mechanisms responsible for the increased vascular permeability that characterizes BT and related orbiviral diseases such as African horse sickness.