Dengue hemorrhagic fever in infants: a study of clinical and cytokine profiles

Angiotensin II and dengue

Dengue is a disease caused by a flavivirus that is transmitted principally by the bite of an Aedes aegypti mosquito and represents a major public-health problem. Many studies have been carried out to identify soluble factors that are involved in the pathogenesis of this infection. Cytokines, soluble factors, and oxidative stress have been reported to be involved in the development of severe disease. Angiotensin II (Ang II) is a hormone with the ability to induce the production of cytokines and soluble factors related to the inflammatory processes and coagulation disorders observed in dengue. However, a direct involvement of Ang II in this disease has not been demonstrated. This review primarily summarizes the pathophysiology of dengue, the role of Ang II in various diseases, and reports that are highly suggestive of the involvement of this hormone in dengue.

Dengue determinants: Necessities and challenges for universal dengue vaccine development

Dengue illness can range from mild illness to life-threatening haemorrhage. It is an Aedes-borne infectious disease caused by the dengue virus, which has four serotypes. Each serotype acts as an independent infectious agent. The antibodies against one serotype confer homotypic immunity but temporary protection against heterotypic infection. Dengue has become a growing health concern for up to one third of the world's population. Currently, there is no potent anti-dengue medicine, and treatment for severe dengue relies on intravenous fluid management and pain medications. The burden of dengue dramatically increases despite advances in vector control measures. These factors underscore the need for a vaccine. Various dengue vaccine strategies have been demonstrated, that is, live attenuated vaccine, inactivated vaccine, DNA vaccine, subunit vaccine, and viral-vector vaccines, some of which are at the stage of clinical testing. Unfortunately, the forefront candidate vaccine is less than satisfactory, and its performance depends on serostatus and age factors. The lessons from clinical studies depicted ambiguity concerning the efficacy of dengue vaccine. Our study highlighted that viral structural heterogeneity, epitope accessibility, autoimmune complications, genetic variants, genetic diversities, antigen competition, virulence variation, host-pathogen specific interaction, antibody-dependent enhancement, cross-reactive immunity among Flaviviruses, and host-susceptibility determinants not only influence infection outcomes but also hampered successful vaccine development. This review integrates dengue determinants allocated necessities and challenges, which would provide insight for universal dengue vaccine development.

Flaviviridae Nonstructural Proteins: The Role in Molecular Mechanisms of Triggering Inflammation

Members of the Flaviviridae family are posing a significant threat to human health worldwide. Many flaviviruses are capable of inducing severe inflammation in humans. Flaviviridae nonstructural proteins, apart from their canonical roles in viral replication, have noncanonical functions strongly affecting antiviral innate immunity. Among these functions, antagonism of type I IFN is the most investigated; meanwhile, more data are accumulated on their role in the other pathways of innate response. This review systematizes the last known data on the role of Flaviviridae nonstructural proteins in molecular mechanisms of triggering inflammation, with an emphasis on their interactions with TLRs and RLRs, interference with NF-κB and cGAS-STING signaling, and activation of inflammasomes.

The association between diabetes and obesity with Dengue infections

Dengue, an arboviral disease is a global threat to public health as the number of Dengue cases increases through the decades and this trend is predicted to continue. Non-communicable diseases such as diabetes and obesity are also on an upward trend. Moreover, past clinical studies have shown comorbidities worsen the clinical manifestation of especially Severe Dengue. However, discussion regarding the underlying mechanisms regarding the association between these comorbidities and dengue are lacking. The hallmark of Severe Dengue is plasma leakage which is due to several factors including presence of pro-inflammatory cytokines and dysregulation of endothelial barrier protein expression. The key factors of diabetes affecting endothelial functions are Th1 skewed responses and junctional-related proteins expression. Additionally, obesity alters the lipid metabolism and immune response causing increased viral replication and inflammation. The similarity between diabetes and obesity individuals is in having chronic inflammation resulting in endothelial dysfunction. This review outlines the roles of diabetes and obesity in severe dengue and gives some insights into the plausible mechanisms of comorbidities in Severe Dengue.

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.

Activation of the NLRP3 inflammasome and elevation of interleukin-1β secretion in infection by sever fever with thrombocytopenia syndrome virus

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging phlebovirus that causes a hemorrhagic fever known as the severe fever with thrombocytopenia syndrome (SFTS). Inflammasomes are a molecular platform that are assembled to process pro-caspase 1 and subsequently promote secretion of interleukin (IL)-1β/IL-18 for proinflammatory responses induced upon infection. We hypothesize that inflammasome activation and pyroptosis induced in SFTS results in elevated levels of IL-1β/IL-18 responsible for high fever and hemorrhage in the host, characteristic of SFTS. Here we report that IL-1β secretion was elevated in SFTS patients and infected mice and IL-1β levels appeared to be reversibly associated to disease severity and viral load in patients’ blood. Increased caspase-1 activation, IL-1β/IL-18 secretion, cell death, and processing of gasdermin D were detected, indicating that pyroptosis was induced in SFTSV-infected human peripheral blood monocytes (PBMCs). To characterize the mechanism of pyroptosis induction, we knocked down several NOD-like receptors (NLRs) with respective shRNAs in PBMCs and showed that the NLR family pyrin domain containing 3 (NLRP3) inflammasome was critical for processing pro-caspase-1 and pro-IL-1β. Our data with specific inhibitors for NLRP3 and caspase-1 further showed that activation of the NLRP3 inflammasome was key to caspase-1 activation and IL-1β secretion which may be inhibitory to viral replication in PBMCs infected with SFTSV. The findings in this study suggest that the activation of the NLPR3 inflammasome and pyroptosis, leading to IL-1β/IL-18 secretion during the SFTSV infection, could play important roles in viral pathogenesis and host protection. Pyroptosis as part of innate immunity might be essential in proinflammatory responses and pathogenicty in humans infected with this novel phlebovirus.

Role of cytokines produced by T helper immune-modulators in dengue pathogenesis: A systematic review and meta-analysis

BACKGROUND AND OBJECTIVES

Modulation of the immune reaction is essential in the development of various diseases, including dengue's "Cytokine Tsunami", an increase in vascular permeability with concomitant severe vascular leakage. We aim to identify the role of T-helper (Th) cells, Th2 and Th7, with their related cytokines in dengue pathogenesis.

MATERIAL AND METHODS

Nine electronic databases and manual search were applied to detect available publications. A meta-analysis using a fixed- or random-effect model was performed to measure standardized mean difference (SMD) with 95% confidence interval (CI). The National Institute of Health (NIH) tools for observational cohort, cross-sectional, and case-control studies were used to examine the risk of bias. The protocol was recorded in PROSPERO with CRD42017060230.

RESULTS

A total of 38 articles were found including 19 case-control, 11 cross-sectional and 8 prospective cohort studies. We indicated that Th2 cytokines (IL-4, IL-6, IL-8) and Th17 cytokine (IL-17) in dengue patients were notably higher than in a healthy control group in acute phase (SMD = 1.59, 95% CI [0.68, 2.51], p = 0.001; SMD = 1.24, 95% CI [0.41, 2.06], p = 0.003; SMD = 1.13, 95% CI [0.61, 1.66], p<0.0001; SMD = 1.74, 95% CI [0.87, 2.61], p<0.0001), respectively.

CONCLUSIONS

This study provides evidence of the significant roles of IL-4, IL-6, IL-8, IL-10 and IL-17 in the pathogenesis of developing a severe reaction in dengue fever. However, to fully determine the association of Th cytokines with dengue, it is necessary to perform further studies to assess kinetic levels during the duration of the illness.

Instability of the NS1 Glycoprotein from La Reunion 2018 Dengue 2 Virus (Cosmopolitan-1 Genotype) in Huh7 Cells Is Due to Lysine Residues on Positions 272 and 324

La Reunion island in the South West Indian Ocean is now endemic for dengue following the introduction of dengue virus serotype 2 (DENV-2) cosmopolitan-I genotype in 2017. DENV-2 infection causes a wide spectrum of clinical manifestations ranging from flu-like disease to severe dengue. The nonstructural glycoprotein 1 (NS1) has been identified as playing a key role in dengue disease severity. The intracellular NS1 exists as a homodimer, whereas a fraction is driven towards the plasma membrane or released as a soluble hexameric protein. Here, we characterized the NS1 glycoproteins from clinical isolates DES-14 and RUN-18 that were collected during the DENV-2 epidemics in Tanzania in 2014 and La Reunion island in 2018, respectively. In relation to hepatotropism of the DENV, expression of recombinant DES-14 NS1 and RUN-18 NS1 glycoproteins was compared in human hepatoma Huh7 cells. We observed that RUN-18 NS1 was poorly stable in Huh7 cells compared to DES-14 NS1. The instability of RUN-18 NS1 leading to a low level of NS1 secretion mostly relates to lysine residues on positions 272 and 324. Our data raise the issue of the consequences of a defect in NS1 stability in human hepatocytes in relation to the major role of NS1 in the pathogenesis of the DENV-2 infection.

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.

Clinical, Virological, and Cytokine Profiles of Children Infected with Dengue Virus during the Outbreak in Southern Vietnam in 2017

Dengue virus (DENV) infection is a major cause of morbidity and mortality in Vietnam, and the incidence is higher and more consistent in the southern part of the country. This study investigated the circulation of DENV serotypes, viremia levels, immunological status, and cytokine levels, with disease severities among children infected in 2017 in Ho Chi Minh City, Southern Vietnam. Acute and convalescent serum samples were collected from clinically diagnosed dengue children. They were confirmed to have DENV infection by NS1 antigen, IgM and IgG ELISAs, virus isolation, and conventional and real-time RT-PCR. Measurement of 10 cytokine levels was performed in the serum samples. All the children were dengue IgM positive; 28% and 72% of them had primary and secondary DENV infections, respectively, whereas 54% of those with secondary infection were children with dengue with warning signs and with severe dengue. Any or mixed infection of the four serotypes of DENV RNA was detected in 58 children. Twenty DENV strains (DENV-1 = 16 and DENV-4 = 4) were isolated. Levels of IFN-γ, TNF-α, MCP-1, IL-10, and IL-6 were significantly higher in severe dengue cases. We report the predominance of DENV-1 over other serotypes in the 2017 dengue outbreak in Southern Vietnam. Our data showed that cytokine expressions were correlated with dengue pathogenesis and may help in identifying an effective therapeutic strategy.

Impact of Climate Variability and Abundance of Mosquitoes on Dengue Transmission in Central Vietnam

Dengue fever is an important arboviral disease in many countries. Its incidence has increased during the last decade in central Vietnam. Most dengue studies in Vietnam focused on the northern area (Hanoi) and southern regions but not on central Vietnam. Dengue transmission dynamics and relevant environmental risk factors in central Vietnam are not understood. This study aimed to evaluate spatiotemporal patterns of dengue fever in central Vietnam and effects of climatic factors and abundance of mosquitoes on its transmission. Dengue and mosquito surveillance data were obtained from the Department of Vector Control and Border Quarantine at Nha Trang Pasteur Institute. Geographic Information System and satellite remote sensing techniques were used to perform spatiotemporal analyses and to develop climate models using generalized additive models. During 2005-2018, 230,458 dengue cases were reported in central Vietnam. Da Nang and Khanh Hoa were two major hotspots in the study area. The final models indicated the important role of Indian Ocean Dipole, multivariate El Niño-Southern Oscillation index, and vector index in dengue transmission in both regions. Regional climatic variables and mosquito population may drive dengue transmission in central Vietnam. These findings provide important information for developing an early dengue warning system in central Vietnam.

Immunodomination of Serotype-Specific CD4+ T-Cell Epitopes Contributed to the Biased Immune Responses Induced by a Tetravalent Measles-Vectored Dengue Vaccine

Dengue is an emerging mosquito-borne disease, and the use of prophylactic vaccines is still limited. We previously developed a tetravalent dengue vaccine (rMV-TDV) by a recombinant measles virus (MV) vector expressing envelope protein domain III (ED3). In this study, we used dengue-susceptible AG129 mice to evaluate the protective and/or pathogenic immune responses induced by rMV-TDV. Consistent with the previous study, rMV-TDV-immunized mice developed a significant neutralizing antibody response against all serotypes of DENV, as well as a significant IFN-γ response biased to DENV-3, compared to the vector controls. We further demonstrated that this DENV-3-specific IFN-γ response was dominated by one CD4⁺ T-cell epitope located in E_349-363. After DENV-2 challenge, rMV-TDV-immunized mice showed a significantly lower viremia and no inflammatory cytokine increase compared to the vector controls, which had an ~100 times higher viremia and a significant increase in IFN-γ and TNF-α. As a correlate of protection, a robust memory IFN-γ response specific to DENV-2 was boosted in rMV-TDV-immunized mice after challenge. This result suggested that pre-existing DENV-3-dominated T-cell responses did not cross-react, but a DENV-2-specific IFN-γ response, which was undetectable during immunization, was recalled. Interestingly, this recalled T-cell response recognized the epitope in the same position as the E_349-363 but in the DENV-2 serotype. This result suggested that immunodomination occurred in the CD4⁺ T-cell epitopes between dengue serotypes after rMV-TDV vaccination and resulted in a DENV-3-dominated CD4⁺ T-cell response. Although the significant increase in IgG against both DENV-2 and -3 suggested that cross-reactive antibody responses were boosted, the increased neutralizing antibodies and IgG avidity still remained DENV-2 specific, consistent with the serotype-specific T cell response post challenge. Our data reveal that immunodomination caused a biased T-cell response to one of the dengue serotypes after tetravalent dengue vaccination and highlight the roles of cross-reactive T cells in dengue protection.

The role of anti-flavivirus humoral immune response in protection and pathogenesis

Flavivirus infections are a public health threat in the world that requires the development of safe and effective vaccines. Therefore, the understanding of the anti-flavivirus humoral immune response is fundamental to future studies on flavivirus pathogenesis and the design of anti-flavivirus therapeutics. This review aims to provide an overview of the current understanding of the function and involvement of flavivirus proteins in the humoral immune response as well as the ability of the anti-envelope (anti-E) antibodies to interfere (neutralizing antibodies) or not (non-neutralizing antibodies) with viral infection, and how they can, in some circumstances enhance dengue virus infection on Fc gamma receptor (FcγR) bearing cells through a mechanism known as antibody-dependent enhancement (ADE). Thus, the dual role of the antibodies against E protein poses a formidable challenge for vaccine development. Also, we discuss the roles of antibody binding stoichiometry (the concentration, affinity, or epitope recognition) in the neutralization of flaviviruses and the "breathing" of flavivirus virions in the humoral immune response. Finally, the relevance of some specific antibodies in the design and improvement of effective vaccines is addressed.

Host-Based Prognostic Biomarkers to Improve Risk Stratification and Outcome of Febrile Children in Low- and Middle-Income Countries

Fever is one of the leading causes for pediatric medical consultation and the most common symptom at clinical presentation in low- and middle-income countries (LMICs). Most febrile episodes are due to self-limited infections, but a small proportion of children will develop life-threatening infections. The early recognition of children who have or are progressing to a critical illness among all febrile cases is challenging, and there are currently no objective and quantitative tools to do so. This results in increased morbidity and mortality among children with impending life-threatening infections, whilst contributing to the unnecessary prescription of antibiotics, overwhelming health care facilities, and harm to patients receiving avoidable antimicrobial treatment. Specific fever origin is difficult to ascertain and co-infections in LMICs are common. However, many severe infections share common pathways of host injury irrespective of etiology, including immune and endothelial activation that contribute to the pathobiology of sepsis (i.e., pathogen "agnostic" mechanisms of disease). Importantly, mediators of these pathways are independent markers of disease severity and outcome. We propose that measuring circulating levels of these factors can provide quantitative and objective evidence to: enable early recognition of severe infection; guide patient triage and management; enhance post-discharge risk stratification and follow up; and mitigate potential gender bias in clinical decisions. Here, we review the clinical and biological evidence supporting the clinical utility of host immune and endothelial activation biomarkers as components of novel rapid triage tests, and discuss the challenges and needs for developing and implementing such tools.

Insight into the Tropism of Dengue Virus in Humans

In tropical and subtropical zones, arboviruses are among the major threats to human life, affecting a large number of populations with serious diseases. Worldwide, over three hundred million people are infected with dengue virus (DENV) every year as per the World Health Organization (WHO). DENV-mediated disease severity ranges from a mild fever to hemorrhagic fever and shock syndrome. Patients suffering from severe infection might experience multi-organ failure, cardiomyopathy and even encephalopathy, further complicating the disease pathogenesis. In life-threatening cases, DENV has been reported to affect almost all organs of the human body. In this review, we discuss the organ tropism of DENV in humans in depth as detected in various autopsy studies. Keeping in mind the fact that there is currently no DENV-specific antiviral, it is of utmost importance to achieve a vivid picture of the susceptible cells in humans which might help in designing antivirals against DENV, especially targeting those tissues in which infection might lead to life-threatening conditions.

A clinical and epidemiological survey of the largest dengue outbreak in Southern Taiwan in 2015

OBJECTIVES

This study examined the epidemiological, clinical, and immunological characteristics of the 2015 dengue outbreak in Taiwan.

METHODS

Clinical data were collected from dengue fever (DF) and dengue hemorrhagic fever (DHF) patients. A phylogenetic tree was used to analyze the source of the outbreak strain. Paired plasma samples from DF/DHF patients were used for antibody-dependent enhancement (ADE) assay and cytokine multiplex biometric immunoassay to validate the immunological mechanism.

RESULTS

This outbreak mainly occurred in two of the southern cities of Taiwan: Tainan (n=22 777; 52%) and Kaohsiung (n=19 784; 45%). A high DHF death rate was noted (34.6%). The case (DHF) and control (DF) study indicated that older age (>60 years), type II diabetes, and hypertension were risk factors correlated with the development of DHF (p< 0.0001). The phylogenetic tree results suggested that the outbreak-associated strain was dengue virus serotype 2 and cosmopolitan genotype, forming a stable cluster with the isolates from Thailand and Indonesia (bootstrap value of 99%). Cytokine analyses demonstrated that levels of interleukin (IL)-6, IL-4, IL-13, IL-1β, interferon gamma (IFN-γ), and granulocyte-macrophage colony-stimulating factor (GM-CSF) were significantly higher in DHF patients compared to DF patients (p< 0.001). The ADE assay showed that diluted plasma containing preexisting dengue antibodies from DHF patients significantly enhanced dengue infection (p< 0.05).

CONCLUSION

The results suggest that older age, type II diabetes, hypertension, immunological cytokine dysregulation, and preexisting dengue antibodies inducing ADE infection are correlated with dengue severity. This study also indicates that the largest dengue outbreak in Taiwan might have been a result of imported DF from dengue epidemic regions.

Highlights for Dengue Immunopathogenesis: Antibody-Dependent Enhancement, Cytokine Storm, and Beyond

Infection with dengue virus (DENV) can lead to a wide spectrum of clinical presentations, ranging from asymptomatic infection to death. It is estimated that the disease manifests only in 90 million cases out of the total 390 million yearly infections. Even though research has not yet elucidated which are the precise pathophysiological mechanisms that trigger severe forms of dengue, the infection elicits a critical immune response significant for dengue pathogenesis development. Understanding how the immune response to DENV is established and how it can resolve the infection or turn into an immunopathology is of great importance in DENV research. Currently, studies have extensively debated 2 hypotheses involving immune response: antibody-dependent enhancement and cytokine storm. However, despite its undeniable importance in severe forms of the disease, these 2 hypotheses are based on a primed immune status resulting from previous heterologous infection, abstaining them from explaining the severe forms of dengue in naive immune subjects, for example. Thus, it seems that a more intricate arrangement of causes and conditions must be achieved to severe dengue to occur. Among them, the cytokine network signature elicited, in association with viral aspects deserves special attention regarding the establishment of infection and evolution to pathogenesis. In this work, we intend to shed light on how those elements contribute to severe dengue development.

Role of Interleukin-10 and Abdominopelvic Ultrasound as a Potential Predictor of Disease Severity in Dengue Hemorrhagic Fever

Introduction

Dengue viral infections are a major cause of morbidity and mortality in tropical/subtropical countries. Early and prompt detection of dengue hemorrhagic fever (DHF), though challenging, is helpful to identify an individual that would benefit from intensive therapy.

Objective

The goal of this study was to determine the plasma interleukin-10 (IL-10) levels in DHF patients at four to seven days of disease onset and 24 hours after the first sample. We also aimed to determine the association of plasma IL-10 levels and abdominopelvic ultrasound findings.

Methods

A total of 50 registered DHF patients aged 15 to 50 years were recruited. Plasma IL-10 concentration measurements and abdominopelvic ultrasounds were performed. Patients were also categorized based on ultrasound grading I to IV (based on severity). Outcomes were described as recovery and shock. Platelet count and hematocrit percentages were also recorded.

Results

Plasma IL-10 levels were elevated in DHF patients and associated with fatal outcomes (p = 0.00). Binary regression-coefficient showed the direct effect of high levels of plasma IL-10 on the fatal outcome of patients 24 hours after the first sample (p = 0.04). Disease severity was predicted by a positive correlation between ultrasound grades and outcomes (p = 0.00). Spearman’s correlation coefficient found a highly significant inverse relationship between plasma IL-10 levels and platelet count after 24 hours (p = 0.01). However, a significant positive relationship was observed between elevated plasma IL-10 levels and hematocrit percentage after 24 hours (p = 0.01).

Conclusion

Elevated plasma IL-10 levels and abdominopelvic ultrasonography are promising potential predictors of disease progression and fatal outcome in DHF patients.

Assessment of chemokine and cytokine signatures in patients with dengue infection: A hospital-based study in Kolkata, India

Dengue fever is an acute viral infection transmitted by arthropods but may evolve to severe clinical manifestations. Descriptions of the role of circulating immune modulators such as cytokines or chemokines in dengue immunopathogenesis have largely relied on data from South-east Asia and America, while India is poorly represented. This study characterizes dengue cases from West Bengal, eastern India, with respect to clinical profile and pro-inflammatory and inflammatory cytokines. We evaluated the profile of both inflammatory and anti-inflammatory cytokines (IFNγ, IL6, IL10, IL12 and TGFβ) and chemokines (IL8, CXCL9, CXCL10 and RANTES) in 100 hospitalized NS1/IgM confirmed Dengue patients during the epidemic in West Bengal during 2017. Additionally, all necessary blood investigations of the study subjects were performed. The patients mostly hailed from Kolkata, followed by Nadia, 24 Parganas (North and South), Murshidabad and Midnapore. The most common presentations apart from fever and bodyache were gastrointestinal symptoms. An elevated levels of cytokines IL6 and IL10 chemokine IL8 and CXCL10 along with decreased RANTES were found in the patients with Severe Dengue as compared to mild forms of dengue (p < 0.0001) during 3-6 days of infections. A significant association was obtained between most of cytokine and increased SGPT, haematocrit, albumin and decreased platelet count, whereas a negative correlation with the level of RANTES to haematocrit (r=-0.220 with p = 0.029) was found in severe dengue cases with altered liver function parameters. This is the first study demonstrating cytokine and chemokine association with dengue severity from the eastern part of India. Taken together, this study demonstrated that the altered expression levels of IL6, IL10, IL8, CXCL10 and RANTES had significant associations with dengue severity parameters.

Cytokine Signature Associated with Disease Severity in Dengue

Dengue is the most rapidly spreading viral disease transmitted by the bite of infected Aedes mosquitos. The pathogenesis of dengue is still unclear; although host immune responses and virus serotypes have been proposed to contribute to disease severity. In this study, we examined the circulating dengue virus (DENV) and measured plasma levels of inflammatory mediators. Ninety-eight patients during a dengue outbreak in eastern India in 2016 were included in the study. The presence of DENV was demonstrated by detecting NS1 antigen; IgM capture ELISA and serotypes were discriminated by type-specific RT-PCR and/or sequencing. Plasma samples were assayed for 41-plex cytokine/chemokines using multiplex Luminex assay. Eighty-five (87%) samples were positive by NS1/IgM capture ELISA/RT-PCR. All four serotypes of DENV were detected in this outbreak, with DENV-2 as the predominant type, seen in 55% of cases. Mixed infections were seen in 39% of subjects. Among the host inflammatory biomarkers, GM-CSF, IFN-γ, IL-10, IL-15, IL-8, MCP-1, IL-6, MIP-1β, and TNF-α levels were significantly increased in dengue with and without warning signs, in severe dengue patients in comparison to healthy controls. Four cytokines IFN-γ, GM-CSF, IL-10, and MIP-1β correlated significantly with disease severity and could serve as potential predictor for disease severity. Information on the host biomarkers and the dengue serotype may help guide in optimizing effective intervention strategies.

An IRF-3-, IRF-5-, and IRF-7-Independent Pathway of Dengue Viral Resistance Utilizes IRF-1 to Stimulate Type I and II Interferon Responses

Interferon-regulatory factors (IRFs) are a family of transcription factors (TFs) that translate viral recognition into antiviral responses, including type I interferon (IFN) production. Dengue virus (DENV) and other clinically important flaviviruses are suppressed by type I IFN. While mice lacking the type I IFN receptor (Ifnar1^-/-) succumb to DENV infection, we found that mice deficient in three transcription factors controlling type I IFN production (Irf3^-/-Irf5^-/-Irf7^-/- triple knockout [TKO]) survive DENV challenge. DENV infection of TKO mice resulted in minimal type I IFN production but a robust type II IFN (IFN-γ) response. Using loss-of-function approaches for various molecules, we demonstrate that the IRF-3-, IRF-5-, IRF-7-independent pathway predominantly utilizes IFN-γ and, to a lesser degree, type I IFNs. This pathway signals via IRF-1 to stimulate interleukin-12 (IL-12) production and IFN-γ response. These results reveal a key antiviral role for IRF-1 by activating both type I and II IFN responses during DENV infection.

Assessing the effects of daily commuting in two-patch dengue dynamics: A case study of Cali, Colombia

There are many infectious diseases that can be spread by daily commuting of people and dengue fever is one of them. The absence of vaccine and irregularities in ongoing vector control programs make this disease the most frequent and persistent in many tropical and subtropical regions of the world. This paper targets to access the effects of daily commuting on dengue transmission dynamics by using a deterministic two-patch model fitted to observed data gathered in Cali, Colombia where dengue fever is highly persistent and exhibits endemo-epidemic patterns. The two-patch dengue transmission model with daily communing of human residents between patches (that is, between the city and its suburban areas) is presented using the concept of residence times, which certainly affect the disease transmission rates by inducing variability in human population sizes and vectorial densities at each patch. The same modeling framework is applied to two primary scenarios (epidemic outbreaks and endemic persistence of the disease) and for each scenario two coupling cases (one-way and asymmetric commuting) with different inflow and outflow intensities are analyzed. The concept of effective vectorial density, introduced in this paper, allows to explain in very simple terms why the daily commuting affects quite differently the dengue morbidity among human residents in both patches. In particular, residents of the patch with a greater share of incoming than outgoing commuters may actually "benefit" from inflow of daily commuter by avoiding a considerable number of infections. However, residents of the patch with a greater share of outgoing than incoming commuters, especially those who stay at home patch, incur more risk of getting infected. Additionally, the model shows that daily commuting enhance the total number of human infections acquired in both patches and may even provoke an epidemic outbreak in one patch while moderately lowering the level of the disease persistence in another patch.

Modulation of Dengue/Zika Virus Pathogenicity by Antibody-Dependent Enhancement and Strategies to Protect Against Enhancement in Zika Virus Infection

Antibody-dependent enhancement (ADE) is a phenomenon in which preexisting poorly neutralizing antibodies leads to enhanced infection. It is a serious concern with mosquito-borne flaviviruses such as Dengue virus (DENV) and Zika virus (ZIKV). In vitro experimental evidences have indicated the preventive, as well as a pathogenicity-enhancing role, of preexisting DENV antibodies in ZIKV infections. ADE has been confirmed in DENV but not ZIKV infections. Principally, the Fc region of the anti-DENV antibody binds with the fragment crystallizable gamma receptor (FcγR), and subsequent C1q interactions and immune effector functions are responsible for the ADE. In contrast to normal DENV infections, with ADE in DENV infections, inhibition of STAT1 phosphorylation and a reduction in IRF-1 gene expression, NOS2 levels, and RIG-1 and MDA-5 expression levels occurs. FcγRIIA is the most permissive FcγR for DENV-ADE, and under hypoxic conditions, hypoxia-inducible factor-1 alpha transcriptionally enhances expression levels of FcγRIIA, which further enhances ADE. To produce therapeutic antibodies with broad reactivity to different DENV serotypes, as well as to ZIKV, bispecific antibodies, Fc region mutants, modified Fc regions, and anti-idiotypic antibodies may be engineered. An in-depth understanding of the immunological and molecular mechanisms of DENV-ADE of ZIKV pathogenicity will be useful for the design of common and safe therapeutics and prophylactics against both viral pathogens. The present review discusses the role of DENV antibodies in modulating DENV/ZIKV pathogenicity/infection and strategies to counter ADE to protect against Zika infection.

A predictive score for hypotension in patients with confirmed dengue fever in Cayenne Hospital, French Guiana

Background

Identifying patients at risk of developing severe dengue is challenging. The objective of the present study was to determine the incidence of hypotension and its predictive factors during the Dengue 2 epidemic in 2013.

Methods

In 2013, a longitudinal study was performed using data from all confirmed cases of dengue seen in Cayenne General Hospital. The analysis used Cox proportional modeling to obtain adjusted hazards ratios for hypotension.

Results

A total of 806 confirmed patients were included 78 (9.6%) of whom developed hypotension. Extensive purpura, cutaneomucous hemorrhage, serous effusion and age 1-15 years were associated with subsequent hypotension whereas 'aches' and a rash were associated with a lower incidence of hypotension. The biological variables independently associated with hypotension were: increase of hematocrit, low protein concentrations, low sodium concentration and lymphocytes over 1400/ml. A risk score was computed from the scaled Cox model coefficient.

Conclusions

From a clinician's perspective, extensive purpura, cutaneomucous hemorrhage, serous effusion, age 1-15 years, hematocrit increase, low protein, low sodium, lymphocytosis and the absence of aches or of a rash, may be important warning signs to predict subsequent hypotension and shock. Over half of the patients with the highest risk score subsequently developed hypotension. The prognostic score had a 48.2% sensitivity with less than 10% of false positives. This score requires external validation before its impact on clinical practice is evaluated.

Plugging the Leak in Dengue Shock

Recent structural and functional advances provide fresh insight into the biology of the dengue virus non-structural protein, NS1 and suggest new avenues of research. The work of our lab and others have shown that the secreted, hexameric form of NS1 has a systemic toxic effect, inducing inflammatory cytokines and acting directly on endothelial cells to produce the hallmark of dengue disease, vascular leak. We also demonstrated that NS1 exerts its toxic activity through recognition by the innate immune receptor TLR4, mimicking the bacterial endotoxin LPS. This monograph covers the background underpinning these new findings and discusses new avenues for antiviral and vaccine intervention.

Host genetics and dengue fever

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

Neurological Manifestations of Dengue Infection

Dengue counts among the most commonly encountered arboviral diseases, representing the fastest spreading tropical illness in the world. It is prevalent in 128 countries, and each year >2.5 billion people are at risk of dengue virus infection worldwide. Neurological signs of dengue infection are increasingly reported. In this review, the main neurological complications of dengue virus infection, such as central nervous system (CNS), peripheral nervous system, and ophthalmic complications were discussed according to clinical features, treatment and possible pathogenesis. In addition, neurological complications in children were assessed due to their atypical clinical features. Finally, dengue infection and Japanese encephalitis were compared for pathogenesis and main clinical manifestations.

Gefitinib and pyrrolidine dithiocarbamate decrease viral replication and cytokine production in dengue virus infected human monocyte cultures

AIMS

The epidermal growth factor receptor (EGFR) and nucleotide-binding and oligomerization-domain containing 2 (NOD2) are important in cancer and in microbial recognition, respectively. These molecules trigger intracellular signaling pathways inducing the expression of inflammatory genes by NF-kB translocation. Gefitinib (GBTC) and pyrrolidine dithiocarbamate (PDTC) are capable of inhibiting EGFR/NOD2 and NF-kB, respectively. In earlier stages of dengue virus (DENV) infection, monocytes are capable of sustaining viral replication and increasing cytokine production, suggesting that monocyte/macrophages play an important role in early DENV replication. GBTC and PDTC have not been used to modify the pathogenesis of DENV in infected cells. This study was aimed to determine the effect of GBTC and PDTC on viral replication and cytokine production in DENV serotype 2 (DENV2)-infected human monocyte cultures.

MAIN METHODS

GBTC and PDTC were used to inhibit EGFR/NOD2 and NF-kB, respectively. Cytokine production was measured by ELISA and viral replication by plaque forming unit assay.

KEY FINDINGS

Increased DENV2 replication and anti-viral cytokine production (IFN-α/β, TNF-α, IL-12 and IL-18) in infected cultures were found. These parameters were decreased after EGFR/NOD2 or NF-kB inhibitions.

SIGNIFICANCE

The inhibitory effects of GBTC and PDTC on viral replication and cytokine production can be beneficial in the treatment of patients infected by dengue and suggest a possible role of EGFR/NOD2 receptors and NF-kB in dengue pathogenesis.

Alpha-mangostin inhibits both dengue virus production and cytokine/chemokine expression

Since severe dengue virus (DENV) infection in humans associates with both high viral load and massive cytokine production - referred to as "cytokine storm", an ideal drug for treatment of DENV infection should efficiently inhibit both virus production and cytokine expression. In searching for such an ideal drug, we discovered that α-mangostin (α-MG), a major bioactive compound purified from the pericarp of the mangosteen fruit (Garcinia mangostana Linn), which has been used in traditional medicine for several conditions including trauma, diarrhea, wound infection, pain, fever, and convulsion, inhibits both DENV production in cultured hepatocellular carcinoma HepG2 and Huh-7 cells, and cytokine/chemokine expression in HepG2 cells. α-MG could also efficiently inhibit all four serotypes of DENV. Treatment of DENV-infected cells with α-MG (20μM) significantly reduced the infection rates of four DENV serotypes by 47-55%. α-MG completely inhibited production of DENV-1 and DENV-3, and markedly reduced production of DENV-2 and DENV-4 by 100 folds. Furthermore, it could markedly reduce cytokine (IL-6 and TNF-α) and chemokine (RANTES, MIP-1β, and IP-10) transcription. These actions of α-MG are more potent than those of antiviral agent (ribavirin) and anti-inflammatory drug (dexamethasone). Thus, α-MG is potential to be further developed as therapeutic agent for DENV infection.

Transcriptional Profiling Confirms the Therapeutic Effects of Mast Cell Stabilization in a Dengue Disease Model

There are no approved therapeutics for the treatment of dengue disease despite the global prevalence of dengue virus (DENV) and its mosquito vectors. DENV infections can lead to vascular complications, hemorrhage, and shock due to the ability of DENV to infect a variety of immune and nonimmune cell populations. Increasingly, studies have implicated the host response as a major contributor to severe disease. Inflammatory products of various cell types, including responding T cells, mast cells (MCs), and infected monocytes, can contribute to immune pathology. In this study, we show that the host response to DENV infection in immunocompetent mice recapitulates transcriptional changes that have been described in human studies. We found that DENV infection strongly induced metabolic dysregulation, complement signaling, and inflammation. DENV also affected the immune cell content of the spleen and liver, enhancing NK, NKT, and CD8⁺ T cell activation. The MC-stabilizing drug ketotifen reversed many of these responses without suppressing memory T cell formation and induced additional changes in the transcriptome and immune cell composition of the spleen, consistent with reduced inflammation. This study provides a global transcriptional map of immune activation in DENV target organs of an immunocompetent host and supports the further development of targeted immunomodulatory strategies to treat DENV disease.IMPORTANCE Dengue virus (DENV), which causes febrile illness, is transmitted by mosquito vectors throughout tropical and subtropical regions of the world. Symptoms of DENV infection involve damage to blood vessels and, in rare cases, hemorrhage and shock. Currently, there are no targeted therapies to treat DENV infection, but it is thought that drugs that target the host immune response may be effective in limiting symptoms that result from excessive inflammation. In this study, we measured the host transcriptional response to infection in multiple DENV target organs using a mouse model of disease. We found that DENV infection induced metabolic dysregulation and inflammatory responses and affected the immune cell content of the spleen and liver. The use of the mast cell stabilization drug ketotifen reversed many of these responses and induced additional changes in the transcriptome and immune cell repertoire that contribute to decreased dengue disease.

IL-10 and socs3 Are Predictive Biomarkers of Dengue Hemorrhagic Fever

Background

Cytokines play important roles in the physiopathology of dengue infection; therefore, the suppressors of cytokine signaling (socs) that control the type and timing of cytokine functions could be involved in the origin of immune alterations in dengue.

Objective

To explore the association of cytokine and socs levels with disease severity in dengue patients.

Methods

Blood samples of 48 patients with confirmed dengue infection were analyzed. Amounts of interleukins IL-2, IL-4, IL-6, and IL-10, interferon- (IFN-) γ, and tumor necrosis factor- (TNF-) α were quantified by flow cytometry, and the relative expression of socs1 and socs3 mRNA was quantified by real-time RT-PCR.

Results

Increased levels of IL-10 and socs3 and lower expression of socs1 were found in patients with dengue hemorrhagic fever (DHF) with respect to those with dengue fever (DF) (p < 0.05). Negative correlations were found between socs1 and both IL-10 and socs3 (p < 0.01). The cutoff values of socs3 (>199.8-fold), socs1 (<1.94-fold), and IL-10 (>134 pg/ml) have the highest sensitivity and specificity to discriminate between DF and DHF.

Conclusion

Simultaneous changes in IL-10 and socs1/socs3 could be used as prognostic biomarkers of dengue severity.

Association of rs1285933 single nucleotide polymorphism in CLEC5A gene with dengue severity and its functional effects

Outbreaks of the Zika, dengue, and chikungunya viruses, especially in the Americas, pose a global threat due to their rapid spread and difficulty controlling the vector. Extreme phenotypes are often observed, from asymptomatic to severe clinical manifestations, which are well-studied in dengue. Host variations are also important contributors to disease outcomes, and many case-control studies have associated single nucleotide polymorphisms (SNPs) with severe dengue. Here, we found that the TC genotype and T-carriers for SNP rs1285933 in the C-type lectin superfamily member 5 (CLEC5A) gene was associated with severe dengue in a Northern Brazilian population (OR=2.75 and p-value=0.01, OR=2.11 and p-value=0.04, respectively). We also tested the functional effect of the CLEC5A protein and found that it is upregulated on the surface of human monocytes after in vitro dengue infection. CLEC5A was correlated with viral load inside the monocytes (Spearman r=0.55, p=0.008) and TNF production in culture supernatants (Spearman r=0.72, p=0.03). Analysis of mRNA in blood samples from DENV4-infected patients exhibiting mild symptoms showed that CLEC5A mRNA expression is correlated with TNF (r=0.67, p=0.0001) and other immune mediators. Monocytes from rs1285933 TT/TC individuals showed lower CLEC5A expression compared to CC genotypes. However, in these cells, CLEC5A was not correlated with TNF production. In summary, we confirmed that CLEC5A is genetically associated with dengue severity outcome, playing a central role during the immune response triggered by a dengue viral infection, and rs1285933 is a relevant SNP that is able to regulate signaling pathways after interactions between the dengue virus and CLEC5A receptors.

The Role of Heterotypic DENV-specific CD8+T Lymphocytes in an Immunocompetent Mouse Model of Secondary Dengue Virus Infection

Dengue is the most prevalent arthropod-borne viral disease worldwide and is caused by the four dengue virus serotypes (DENV-1-4). Sequential heterologous DENV infections can be associated with severe disease manifestations. Here, we present an immunocompetent mouse model of secondary DENV infection using non mouse-adapted DENV strains to investigate the pathogenesis of severe dengue disease. C57BL/6 mice infected sequentially with DENV-1 (strain Puerto Rico/94) and DENV-2 (strain Tonga/74) developed low platelet counts, internal hemorrhages, and increase of liver enzymes. Cross-reactive CD8⁺ T lymphocytes were found to be necessary and sufficient for signs of severe disease by adoptively transferring of DENV-1-immune CD8⁺T lymphocytes before DENV-2 challenge. Disease signs were associated with production of tumor necrosis factor (TNF)-α and elevated cytotoxicity displayed by heterotypic anti-DENV-1 CD8⁺ T lymphocytes. These findings highlight the critical role of heterotypic anti-DENV CD8⁺ T lymphocytes in manifestations of severe dengue disease.

Serum cytokine/chemokine profiles in patients with dengue fever (DF) and dengue hemorrhagic fever (FHD) by using protein array

BACKGROUND

DENV infection can induce different clinical manifestations varying from mild forms to dengue fever (DF) or the severe hemorrhagic fever (DHF). Several factors are involved in the progression from DF to DHF. No marker is available to predict this progression. Such biomarker could allow a suitable medical care at the beginning of the infection, improving patient prognosis.

OBJECTIVES

The aim of this study was to compare the serum expression levels of acute phase proteins in a well-established cohort of dengue fever (DF) and dengue hemorrhagic fever (DHF) patients, in order to individuate a prognostic marker of diseases severity.

STUDY DESIGN

The serum levels of 36 cytokines, chemokines and acute phase proteins were determined in DF and DHF patients and compared to healthy volunteers using a multiplex protein array and near-infrared (NIR) fluorescence detection. Serum levels of IL-1ra, IL-23, MIF, sCD40 ligand, IP-10 and GRO-α were also determined by ELISA.

RESULTS

At the early stages of infection, GRO-α and IP-10 expression levels were different in DF compared to DHF patients. Besides, GRO-α was positively correlated with platelet counts and IP-10 was negatively correlated with total protein levels.

CONCLUSIONS

These findings suggest that high levels of GRO-α during acute DENV infection may be associated with a good prognosis, while high levels of IP-10 may be a warning sign of infection severity.

Primary dengue haemorrhagic fever in patients from northeast of Brazil is associated with high levels of interferon-β during acute phase

Dengue is an acute febrile disease caused by the mosquito-borne dengue virus (DENV) that according to clinical manifestations can be classified as asymptomatic, mild or severe dengue. Severe dengue cases have been associated with an unbalanced immune response characterised by an over secretion of inflammatory cytokines. In the present study we measured type I interferon (IFN-I) transcript and circulating levels in primary and secondary DENV infected patients. We observed that dengue fever (DF) and dengue haemorrhagic fever (DHF) patients express IFN-I differently. While DF and DHF patients express interferon-α similarly (52,71 ± 7,40 and 49,05 ± 7,70, respectively), IFN- β were associated with primary DHF patients. On the other hand, secondary DHF patients were not able to secrete large amounts of IFN- β which in turn may have influenced the high-level of viraemia. Our results suggest that, in patients from our cohort, infection by DENV serotype 3 elicits an innate response characterised by higher levels of IFN- β in the DHF patients with primary infection, which could contribute to control infection evidenced by the low-level of viraemia in these patients. The present findings may contribute to shed light in the role of innate immune response in dengue pathogenesis.

Lactate based optical screening of dengue virus infection in human sera using Raman spectroscopy

This study presents the screening of dengue virus (DENV) infection in human blood sera based on lactate concentration using Raman spectroscopy. A total of 70 samples, 50 from confirmed DENV infected patients and 20 from healthy volunteers have been used in this study. Raman spectra of all these samples have been acquired in the spectral range from 600 cm^-1 to 1800 cm^-1 using a 532 nm laser as an excitation source. Spectra of all these samples have been analyzed for assessing the biochemical changes resulting from infection. In DENV infected samples three prominent Raman peaks have been found at 750, 830 and 1450 cm^-1. These peaks are most probably attributed to an elevated level of lactate due to an impaired function of different body organs in dengue infected patients. This has been proven by an addition of lactic acid solution to the healthy serum in a controlled manner. By the addition of lactic acid solution, the intense Raman bands at 1003, 1156 and 1516 cm^-1 found in the spectrum of healthy serum got suppressed when the new peaks appeared around 750, 830, 925, 950, 1123, 1333, 1450, 1580 and 1730 cm^-1. The current study predicts that lactate may possibly be a potential biomarker for the diagnosis of DENV infection.

Primary dengue virus infections induce differential cytokine production in Mexican patients

Severe dengue pathogenesis is not fully understood, but high levels of proinflammatory cytokines have been associated with dengue disease severity. In this study, the cytokine levels in 171 sera from Mexican patients with primary dengue fever (DF) and dengue haemorrhagic fever (DHF) from dengue virus (DENV) 1 (n = 116) or 2 (n = 55) were compared. DF and DHF were defined according to the patient’s clinical condition, the primary infections as indicated by IgG enzymatic immunoassay negative results, and the infecting serotype as assessed by real-time reverse transcription-polymerase chain reaction. Samples were analysed for circulating levels of interleukin (IL)-12p70, interferon (IFN)-γ, tumour necrosis factor (TNF)-α, IL-6, and IL-8 using a commercial cytometric bead array. Significantly higher IFN-γ levels were found in patients with DHF than those with DF. However, significantly higher IL-12p70, TNF-α, and IL-6 levels were associated with DHF only in patients who were infected with DENV2 but not with DENV1. Moreover, patients with DF who were infected with DENV1 showed higher levels of IL-12p70, TNF-α, and IL-6 than patients with DHF early after-fever onset. The IL-8 levels were similar in all cases regardless of the clinical condition or infection serotype. These results suggest that the association between high proinflammatory cytokine levels and dengue disease severity does not always stand, and it once again highlights the complex nature of DHF pathogenesis.

Aspects of T Cell-Mediated Immunity Induced in Mice by a DNA Vaccine Based on the Dengue-NS1 Antigen after Challenge by the Intracerebral Route

Dengue disease has emerged as a major public health issue across tropical and subtropical countries. Infections caused by dengue virus (DENV) can evolve to life-threatening forms, resulting in about 20,000 deaths every year worldwide. Several animal models have been described concerning pre-clinical stages in vaccine development against dengue, each of them presenting limitations and advantages. Among these models, a traditional approach is the inoculation of a mouse-brain adapted DENV variant in immunocompetent animals by the intracerebral (i.c.) route. Despite the historical usage and relevance of this model for vaccine testing, little is known about the mechanisms by which the protection is developed upon vaccination. To cover this topic, a DNA vaccine based on the DENV non-structural protein 1 (pcTPANS1) was considered and investigations were focused on the induced T cell-mediated immunity against i.c.-DENV infection. Immunophenotyping assays by flow cytometry revealed that immunization with pcTPANS1 promotes a sustained T cell activation in spleen of i.c.-infected mice. Moreover, we found that the downregulation of CD45RB on T cells, as an indicator of cell activation, correlated with absence of morbidity upon virus challenge. Adoptive transfer procedures supported by CFSE-labeled cell tracking showed that NS1-specific T cells induced by vaccination, proliferate and migrate to peripheral organs of infected mice, such as the liver. Additionally, in late stages of infection (from the 7th day onwards), vaccinated mice also presented reduced levels of circulating IFN-γ and IL-12p70 in comparison to non-vaccinated animals. In conclusion, this work presented new aspects about the T cell-mediated immunity concerning DNA vaccination with pcTPANS1 and the i.c. infection model. These insights can be explored in further studies of anti-dengue vaccine efficacy.

Dengue fever in infants: report of three cases

Dengue fever has classically been described as a disease of children and young adults. Infants are naturally protected by virtue of maternally derived immunoglobulins, especially in endemic countries. The resurgence of dengue, coupled with the availability of early and sensitive diagnostic methods and a high degree of clinical suspicion, has led to an increasing number of infants being diagnosed. There is a wide spectrum of clinical manifestations, particularly in infancy. Here we describe three cases presenting with diverse clinical features, their subsequent management and outcome.