Effect Of Dengue Virus Infection Research Articles

Dengue virus infection in mice induces bone marrow myeloid cell differentiation and generates Ly6Glow immature neutrophils with modulated functions.

While neutrophil activation during dengue virus infection is known, the effect of dengue virus infection on neutrophil biogenesis has not been studied. We demonstrate that dengue virus serotype 2 induces the differentiation of mice progenitor cells ex vivo toward the CD11b+Ly6C+Ly6G+ granulocyte population. We further observed an expansion of CD11b+Ly6CintLy6Glow myeloid cells in the bone marrow of dengue virus serotype 2-infected AG129 mice with low CXCR2 expression, implying an immature population. Additionally, dengue virus serotype 2 alone could induce the differentiation of promyelocyte cell line HL-60 into neutrophil-like cells, as evidenced by increased expression of CD10, CD66b, CD16, CD11b, and CD62L, corroborating the preferential shift toward neutrophil differentiation by dengue virus serotype 2 in the mouse model of dengue infection. The functional analysis showed that dengue virus serotype 2-induced neutrophil-like cells exhibited reduced phagocytic activity and enhanced NETosis, as evidenced by the increased production of myeloperoxidase, citrullinated histones, extracellular DNA, and superoxide. These neutrophil-like cells lose their ability to proliferate irreversibly and undergo arrest in the G0 to G1 phase of the cell cycle. Further studies show that myeloperoxidase-mediated signaling operating through the reactive oxygen species axis may be involved in dengue virus serotype 2-induced proliferation and differentiation of bone marrow cells as ABAH, a myeloperoxidase inhibitor, limits cell proliferation in vitro and ex vivo, affects the cell cycle, and reduces reactive oxygen species production. Additionally, myeloperoxidase inhibitor reduced NETosis and vascular leakage in dengue virus serotype 2-infected AG129 mice. Our study thus provides evidence that dengue virus serotype 2 can accelerate the differentiation of bone marrow progenitor cells into neutrophils through myeloperoxidase and modulate their functions.

Dengue Infected Patients in Local Population of Lahore

Over the past 20 years, dengue fever's demographic characteristics have significantly altered in Pakistan. Different facets of particular epidemics have been covered in small-scale research from around the nation during this time. However, there is a dearth of information on the country's general trend of dengue virus infection. Objectives: To examine liver function test of dengue infected patients, age and gender wise distribution of dengue virus infected patients. Methods: During August-November 2011, patients with clinical presentation of DF, who came to Emergency department of Mayo Hospital Lahore, were included in this study. Total 64 patients were included in this study and LFTs were performed photometrically to see the effect of dengue virus infection on liver of affected patients during early days of infection from 2-7 days. Results: Out of 64 patients, 47 were males and 17 were females. Dengue fever was more common among the age group of 16-25 years and less common among children and older age group. All the patients had low platelet level with 29 patients had complaint of bleeding. Serum raised level of ALT and ALP was observed in some patients. Conclusions: Presently widespread throughout the year with a high frequency in the post-monsoon season, dengue fever is currently endemic in Pakistan. The median patient age for dengue has dropped, and younger patients, particularly men, may be more vulnerable. Total and differential leukocyte counts can assist identify individuals who are at risk for bleeding, and LFTs can show whether dengue virus infection has an impact on the liver.

Dengue Virus-2 Infection Affects Fecundity and Elicits Specific Transcriptional Changes in the Ovaries of Aedes aegypti Mosquitoes.

Dengue fever (DF), caused by the dengue virus (DENV), is the most burdensome arboviral disease in the world, with an estimated 400 million infections each year. The Aedes aegypti mosquito is the main vector of DENV and transmits several other human pathogens, including Zika, yellow fever, and chikungunya viruses. Previous studies have shown that the pathogen infection of mosquitoes can alter reproductive fitness, revealing specific vector-pathogen interactions that are key determinants of vector competence. However, only a handful of studies have examined the effect of DENV infection in A. aegypti, showing a reduction in lifespan and fecundity over multiple blood meals. To provide a more comprehensive analysis of the impact of DENV infection on egg laying and fecundity, we assessed egg laying timing in DENV-2 blood-fed mosquitoes (infected group) compared to mock blood-fed mosquitoes (control group). We confirmed a significant decrease in fecundity during the first gonadotrophic cycle. To further investigate this phenotype and the underlying DENV-2 infection-dependent changes in gene expression, we conducted a transcriptomic analysis for differentially expressed genes in the ovaries of A. aegypti infected with DENV-2 vs. mock-infected mosquitoes. This analysis reveals several DENV-2-regulated genes; among them, we identified a group of 12 metabolic genes that we validated using reverse transcription-quantitative PCR (RT-qPCR). Interestingly, two genes found to be upregulated in DENV-infected mosquito ovaries exhibited an antiviral role for DENV-2 in an Aedes cell line. Altogether, this study offers useful insights into the virus-vector interface, highlighting the importance of gene expression changes in the mosquito’s ovary during DENV-2 infection in the first gonadotrophic cycle, triggering antiviral responses that may possibly interfere with mosquito reproduction. This information is extremely relevant for further investigation of A. aegypti’s ability to tolerate viruses since virally infected mosquitoes in nature constitute a powerful source of supporting viruses during intra-epidemic periods, causing a huge burden on the public health system.

Risk of Leukemia after Dengue Virus Infection: A Population-Based Cohort Study.

Infections account for about 15% of human cancers globally. Although abnormal hematologic profiles and bone marrow suppression are common in patients with dengue, whether dengue is associated with a higher risk of leukemia has not been investigated. We conducted a nationwide population-based cohort study by analyzing the National Health Insurance Research Databases in Taiwan. Laboratory-confirmed dengue patients between 2002 and 2011 were identified; five matched non-dengue controls were randomly selected for each patient. Follow-up ended on December 31, 2015. Multivariate Cox proportional hazard regression models were used to evaluate the effect of dengue virus infection on the risk of leukemia. Cancers other than leukemia were used as falsification endpoints to evaluate the validity of this study. We identified 12,573 patients with dengue and 62,865 non-dengue controls. Patients with dengue had a higher risk of leukemia [adjusted HR, 2.03; 95% confidence interval (CI), 1.16-3.53]. Stratified analyses by different follow-up periods showed that dengue virus infection was significantly associated with a higher risk of leukemia only between 3 and 6 years after infection (adjusted HR, 3.22; 95% CI, 1.25-8.32). There was no significant association between dengue and the risk of other cancers. This study provides the first epidemiologic evidence for the association between dengue virus infection and leukemia. Considering the rapidly increasing global incidence of dengue and the burden of leukemia, further studies are required to verify this association and to unravel the potential mechanisms of pathogenesis.

Aedes aegypti Immune Response and Its Potential Impact on Dengue Virus Transmission.

Dengue virus (DENV) transmission to human populations requires infection of vector mosquitoes as an essential component of the transmission process. DENV transmission leads to infections that range from asymptomatic to life-threatening pathologies, such as dengue hemorrhagic fever and dengue shock syndrome. Aedes aegypti is the principal vector of DENV, and its vector competence consists of the intrinsic factors, genes, molecules, and pathways that allow infection, replication, and dissemination of this virus throughout the cells of mosquito tissues. In the search for mosquito molecular targets to block DENV transmission, the effect of DENV infection on mosquitoes has been an important focus of research. In this study, we review the findings of research on the effect of DENV infection on mosquito tissue cells and the immunity pathways and molecules that are involved in this infection. We emphasize the relevance of recent findings to understand the relationship between Ae. aegypti immune response, vector competence, and DENV transmission to human hosts.

Neurological manifestations of dengue fever

Dengue fever is a highly endemic mosquito-borne viral infection with a wide range of neurological manifestations including encephalitis, neuromuscular and neuro-ophthalmic involvement. To explore the pleiotropic effects of dengue virus infection on the nervous system. Effect of the dengue virus on nervous system is pleiotropic. Direct central nervous system invasion by dengue virus is implicated in encephalitis whereas immune mediated release of cytokines may involve peripheral nerve constituents (myelin/axon), muscle fibres leading to myositis, and damage omnipause cells in the brainstem causing ocular flutter. Five patients of serologically confirmed Dengue fever (NS1 Antigen and Immunoglobulin M antibody positive) were included, who presented with the following uncommon neurological manifestations. Recently emerging evidence of neurotropism and neurovirulence by dengue virus emphasizes the need for neurologists to look for these associations while dealing with dengue infection. It also emphasizes the need for specific immunomodulation in addition to supportive measures for causing neurological recovery.

Proteomic analysis of the secretome of HepG2 cells indicates differential proteolytic processing after infection with dengue virus

Secretome analysis can be described as a subset of proteomics studies consisting in the analysis of the molecules secreted by cells or tissues. Dengue virus (DENV) infection can lead to a broad spectrum of clinical manifestations, with the severe forms of the disease characterized by hemostasis abnormalities and liver injury. The hepatocytes are a relevant site of viral replication and a major source of plasma proteins. Until now, we had limited information on the small molecules secreted by hepatic cells after infection by DENV. In the present study, we analysed a fraction of the secretome of mock- and DENV-infected hepatic cells (HepG2 cells) containing molecules with <10kDa, using different proteomic approaches. We identified 175 proteins, with 57 detected only in the samples from mock-infected cells, 59 only in samples from DENV-infected cells, and 59 in both conditions. Most of the peptides identified were derived from proteins larger than 10kDa, suggesting a proteolytic processing of the secreted molecules. Using in silico analysis, we predicted consistent differences between the proteolytic processing occurring in mock and DENV-infected samples, raising, for the first time, the hypothesis that differential proteolysis of secreted molecules would be involved in the pathogenesis of dengue. Biological significanceSince the liver, one of the targets of DENV infection, is responsible for producing molecules involved in distinct biological processes, the identification of proteins and peptides secreted by hepatocytes after infection would help to a better understanding of the physiopathology of dengue. Proteomic analyses of molecules with <10kDa secreted by HepG2 cells after infection with DENV revealed differential proteolytic processing as an effect of DENV infection.

1H Nuclear Magnetic Resonance Metabolomics of Plasma Unveils Liver Dysfunction in Dengue Patients.

Dengue, due to its global burden, is the most important arthropod-borne flavivirus disease, and early detection lowers fatality rates to below 1%. Since the metabolic resources crucial for viral replication are provided by host cells, detection of changes in the metabolic profile associated with disease pathogenesis could help with the identification of markers of prognostic and diagnostic importance. We applied (1)H nuclear magnetic resonance exploratory metabolomics to study longitudinal changes in plasma metabolites in a cohort in Recife, Brazil. To gain statistical power, we used innovative paired multivariate analyses to discriminate individuals with primary and secondary infection presenting as dengue fever (DF; mild) and dengue hemorrhagic fever (DHF; severe) and subjects with a nonspecific nondengue (ND) illness (ND subjects). Our results showed that a decrease in plasma low-density lipoprotein (LDL) and very-low-density lipoprotein (VLDL) discriminated dengue virus (DENV)-infected subjects from ND subjects, and also, subjects with severe infection even presented a decrease in lipoprotein concentrations compared to the concentrations in subjects with mild infection. These results add to the ongoing discussion that the manipulation of lipid metabolism is crucial for DENV replication and infection. In addition, a decrease in plasma glutamine content was characteristic of DENV infection and disease severity, and an increase in plasma acetate levels discriminated subjects with DF and DHF from ND subjects. Several other metabolites shown to be altered in DENV infection and the implications of these alterations are discussed. We hypothesize that these changes in the plasma metabolome are suggestive of liver dysfunction, could provide insights into the underlying molecular mechanisms of dengue virus pathogenesis, and could help to discriminate individuals at risk of the development of severe infection and predict disease outcome. Dengue, due to its global burden, is the most important mosquito-borne viral disease. There is no specific treatment for dengue disease, and early detection lowers fatality rates to below 1%. In this study, we observed the effects of dengue virus infection on the profile of small molecules in the blood of patients with mild and severe infection. Variations in the profiles of these small molecules reflected the replication of dengue virus in different tissues and the extent of tissue damage during infection. The results of this study showed that the molecules that changed the most were VLDL, LDL, and amino acids. We propose that these changes reflect liver dysfunction and also that they can be used to discriminate subjects with mild dengue from those with severe dengue.

Lower IgG somatic hypermutation rates during acute dengue virus infection is compatible with a germinal center-independent B cell response.

BackgroundThe study of human B cell response to dengue virus (DENV) infection is critical to understand serotype-specific protection and the cross-reactive sub-neutralizing response. Whereas the first is beneficial and thus represents the ultimate goal of vaccination, the latter has been implicated in the development of severe disease, which occurs in a small, albeit significant, fraction of secondary DENV infections. Both primary and secondary infections are associated with the production of poly-reactive and cross-reactive IgG antibodies.MethodsTo gain insight into the effect of DENV infection on the B cell repertoire, we used VH region high-throughput cDNA sequencing of the peripheral blood IgG B cell compartment of 19 individuals during the acute phase of infection. For 11 individuals, a second sample obtained 6 months later was analyzed for comparison. Probabilities of sequencing antibody secreting cells or memory B cells were estimated using second-order Monte Carlo simulation.ResultsWe found that in acute disease there is an increase in IgG B cell diversity and changes in the relative use of segments IGHV1-2, IGHV1-18, and IGHV1-69. Somewhat unexpectedly, an overall low proportion of somatic hypermutated antibody genes was observed during the acute phase plasmablasts, particularly in secondary infections and those cases with more severe disease.ConclusionsOur data are consistent with an innate-like antiviral recognition system mediated by B cells using defined germ-line coded B cell receptors, which could provide a rapid germinal center-independent antibody response during the early phase of infection. A model describing concurrent T-dependent and T-independent B cell responses in the context of DENV infection is proposed, which incorporates the selection of B cells using hypomutated IGHV segments and their potential role in poly/cross-reactivity. Its formal demonstration could lead to a definition of its potential implication in antibody-dependent enhancement, and may contribute to rational vaccine development efforts.Electronic supplementary materialThe online version of this article (doi:10.1186/s13073-016-0276-1) contains supplementary material, which is available to authorized users.

DENGUE DURING PREGNANCY: ASSOCIATION WITH LOW BIRTH WEIGHT AND PREMATURITY.

The aim of this study was to evaluate the effects of dengue virus infection during pregnancy and its correlation with low birth weight, prematurity, and asphyxia. A non-concurrent cohort study reveals the association of dengue during pregnancy with prematurity and low birth weight, when birth occurred during the maternal-fetal viremia period (p = 0.016 and p < 0.0001, respectively).

Roles for Endothelial Cells in Dengue Virus Infection

Dengue viruses cause two severe diseases that alter vascular fluid barrier functions, dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). The endothelium is the primary fluid barrier of the vasculature and ultimately the effects of dengue virus infection that cause capillary leakage impact endothelial cell (EC) barrier functions. The ability of dengue virus to infect the endothelium provides a direct means for dengue to alter capillary permeability, permit virus replication, and induce responses that recruit immune cells to the endothelium. Recent studies focused on dengue virus infection of primary ECs have demonstrated that ECs are efficiently infected, rapidly produce viral progeny, and elicit immune enhancing cytokine responses that may contribute to pathogenesis. Furthermore, infected ECs have also been implicated in enhancing viremia and immunopathogenesis within murine dengue disease models. Thus dengue-infected ECs have the potential to directly contribute to immune enhancement, capillary permeability, viremia, and immune targeting of the endothelium. These effects implicate responses of the infected endothelium in dengue pathogenesis and rationalize therapeutic targeting of the endothelium and EC responses as a means of reducing the severity of dengue virus disease.

Metabolomics Approach for Investigation of Effects of Dengue Virus Infection Using the EA.hy926 Cell Line

This paper describes a multiplatform analytical approach combining proton nuclear magnetic resonance ((1)H NMR) spectroscopy and mass spectrometry (MS), together with pattern recognition tools in a metabolomic study used to investigate the effects of dengue virus infection. The four serotypes of dengue, DEN-1, DEN-2, DEN-3, and DEN-4, were inoculated into the EA.hy926 cell line, which was then incubated for various time intervals. Principal component analysis (PCA) of the (1)H NMR and MS data revealed metabolic profile patterns or fingerprint patterns that can be attributed to specific virus serotypes. Distinct effects of infection by each serotype were demonstrated, and these differences were attributed to changes in levels of metabolites (including amino acids, dicarboxylic acids, fatty acids, and organic acids related to the tricarboxylic acid (TCA) cycle). The study demonstrated application of metabolomics to improve understanding of the effect of dengue infection on endothelial cells' metabolome.

Effect of dengue virus infection on the host signal transduction pathways

Background: Dengue virus (DENV) is a single, positive-stranded RNA virus from the family Flaviviridae. Dengue infection is a medically important infectious disease affecting many tropical and subtropical countries. To date, vaccine and anti-viral drugs for DENV infection is still not available. This is mainly due to the incomplete understanding of the pathogenesis and the underlying molecular mechanism involved during infection. This project aims to study the virus-host interplay by investigating the signal transduction pathways that are activated during DENV infection. Methods: RT2 Profiler PCR array from SABiosciences was employed to screen for the pathways that were affected during DENV infection on Human Embryonic Kidney (HEK)-293 cells. A panel of 84 genes from 18 biological pathways were analyzed and quantified simultaneously. The HEK293 cells were infected with DENV at multiplicity of infection of 1 and the total RNA were extracted after 12hr, 24hr, and 48hr post infection (p.i.). The RNA of infected cells and mock infected cells were reverse-transcribed into cDNA which were then served as templates for real-time polymerase chain reaction in a 96-well plate containing predispensed gene specific primer sets. The gene expression profiling of DENV-infected cells were compared to that of mock-infected cells. Results: The PCR array data showed that there was no significant change in the gene expression profile of infected cells at 12hr p.i. as compared to mock infected cells. Nevertheless, the number of activated genes increased from 24hr p.i. to 48hr p.i. Among 18 signal transduction pathways, the most affected pathways are NFκB, CREB, Jak-Stat, phospholipase C, insulin and low density lipoprotein pathways. Besides, there are also novel genes identified to be activated in this study. All the activated genes were analyzed and an interactome map was generated. It provides a better understanding of the virus-host interplay during different stages of DENV infection. Conclusion: PCR array allows fast and convenient analysis of many gene expression profiles simultaneously for different samples. Therefore, the comparison of the gene expression profiles of all four different DENV serotypes can be carried out to study the similarities and differences in virus-host interaction. Abstracts for SupplementInternational Journal of Infectious DiseasesVol. 14Preview Full-Text PDF Open Archive

Dengue during Pregnancy: A Study of Thirteen Cases

Problem statement: The principal aim was to evaluate the effects of dengue virus infection by dengue during pregnancy and analyze the histopathology of the placenta. Approach: A retrospective study was conducted with 13 pregnant women with dengue confirmed in the period from January-December 2002, during a widespread dengue type 3 epidemic in Rio de Janeiro. Maternal and newborn data were collected from patient files and medical records during hospitalization for research for identification of dengue IgM antibodies (PanBio, Australia). Virus isolation was performed on all fatal cases and anathomopathological studies and immunohistochemistry of the placenta were carried out in three cases. Results: Among the 13 women, 11 (84, 6%) were infected in the third quarter of pregnancy, 6 (54, 5%) of which resulting in premature birth and 4 cases (30, 7%) were classified as DHF, causing 2 deaths. Intense abdominal pain afflicted 6 patients (46, 2%) and 5 newborns presented low weight, however appropriate for the gestacional age. Conclusion: Dengue virus infection in pregnancy increases premature birth risk, especially if the infection occurs in the last quarter of pregnancy.

RNA interference mediated silencing of Hsp60 gene in human monocytic myeloma cell line U937 revealed decreased dengue virus multiplication

Heat shock proteins (Hsps) or stress proteins are highly conserved molecules and expressed in all cell types under stressful conditions like heat, cold, hypoxia and infections. The objective of the present study was to determine the effect of dengue virus infection on relative expression of stress proteins and their role in the progression of the infection. As macrophages are the primary host for dengue, human promonocytic myeloblastoma U937 cells were infected with dengue virus type 2 New Guinea C strain for the evaluation of Hsps expression. A significant expression of Hsp60 was observed in virally infected U937 cells as compared to controls. In order to determine the correlation between Hsp60 expression and viral multiplication in infected cells, expression of Hsp60 was down regulated by RNA interference. Viral multiplication was determined by quantification of viral RNA copy number using Real Time PCR and plaque formation assay in cellular supernatants of Hsp60 silenced cells. Intracellular quantification of viral load was also determined by flow cytometry. It was observed that down regulation of Hsp60 in virally infected cells resulted into decrease in viral RNA copy number, plaque forming units and intracellular viral load. At the same time down regulation also resulted in increased IFN-α level. These observations suggest that, elevated levels of Hsp60 expression in virally infected cells may help in viral multiplication and could be possible therapeutic targets for the management of dengue virus infection.

Effects of Dengue Virus Infection on the Spleen of Male Mice Given Hexavalent Chromium with Drinking Water

The present study was undertaken to investigate the effects of dengue virus (DV) infection in male mice given drinking water containing 250 ppm Cr (VI) and the normal control male mice given plain water to drink. On the basis of intake of water in 24 h, the average dose of Cr (VI) in each mouse was 14.8 mg/kg. After 3, 6, and 9 weeks of drinking Cr (VI), a set of five mice from each group were inoculated intracerebrally (ic) with a 1000 × LD50 (100 times the lethal dose that kills 50% mice) dose of DV, and the effects on the spleen were studied at the fourth and eightth day postinoculation. It was observed that Cr (VI) drinking and DV infection led to reduction in the weight of the spleen, but the peak reduction was seen in Cr (VI)-fed mice infected with DV, being 30, 34, and 61% at 3, 6, and 9 weeks respectively. A similar response was seen with respect to the cytotoxic activity of spleen homogenates, phagocytic activity of macrophages, and the mitogenic response of spleen cells to concanavalin A from different groups of animals, being most marked (58 to 60%) at the ninth week of Cr (VI) drinking. This shows a summation of adverse effects of DV infection in mice preexposed to Cr (VI).

Dengue en el embarazo: efectos en el feto y el recién nacido.

The risk of dengue virus infection during pregnancy has increased due to the current rash of frequent and severe dengue epidemics. The effects of dengue virus in the fetus and newborn children have been studied only superficially and with contradictory results. Therefore, a retrospective cohort study was conducted in Medellin, Colombia, to describe the fetal and postnatal effects of dengue virus infection acquired during pregnancy. Twenty-two babies born from mothers who suffered dengue during the epidemics of 1998 were compared with babies from non-infected mothers. In the exposed cohort, three premature births occurred, three children suffered from fetal anomalies and four children were born with low weight. In the non-exposed children, none of these problems were found. Psychomotor development was normal in both groups. Only the low weight subgroup was statistically significant (Fisher test, p = 0.045). These results suggested that the children from women with dengue during pregnancy present low weight, greater frequency of premature birth and increased fetal distress. A larger sample is necessary to confirm these results.

Dengue virus selectively induces human mast cell chemokine production.

Severe dengue virus infections usually occur in individuals who have preexisting anti-dengue virus antibodies. Mast cells are known to play an important role in host defense against several pathogens, but their role in viral infection has not yet been elucidated. The effects of dengue virus infection on the production of chemokines by human mast cells were examined. Elevated levels of secreted RANTES, MIP-1alpha, and MIP-1beta, but not IL-8 or ENA-78, were observed following infection of KU812 or HMC-1 human mast cell-basophil lines. In some cases a >200-fold increase in RANTES production was observed. Cord blood-derived cultured human mast cells treated with dengue virus in the presence of subneutralizing concentrations of dengue virus-specific antibody also demonstrated significantly (P < 0.05) increased RANTES production, under conditions which did not induce significant degranulation. Chemokine responses were not observed when mast cells were treated with UV-inactivated dengue virus in the presence or absence of human dengue virus-specific antibody. Neither antibody-enhanced dengue virus infection of the highly permissive U937 monocytic cell line nor adenovirus infection of mast cells induced a RANTES, MIP-1alpha, or MIP-1beta response, demonstrating a selective mast cell response to dengue virus. These results suggest a role for mast cells in the initiation of chemokine-dependent host responses to dengue virus infection.

Increased production of interleukin-8 in primary human monocytes and in human epithelial and endothelial cell lines after dengue virus challenge.

The more severe form of dengue virus infection, dengue hemorrhagic fever, is characterized by plasma leakage and derangements in hemostasis. As elevated interleukin-8 (IL-8) levels have been observed in sera from patients with more severe disease manifestations, a study was initiated to look at the effect of dengue virus infection in vitro on proinflammatory cytokine secretion and expression. A significant increase in IL-8 levels in the culture supernatant of primary human monocytes infected with dengue 2 virus (D2V) New Guinea C (NGC) was found by enzyme-linked immunosorbent assay. Additionally, by reverse transcriptase PCR, the mRNA was also augmented. Among the proinflammatory cytokines and their mRNAs measured (IL-6, IL-1 beta, IL-8, and tumor necrosis factor alpha), IL-8 showed the greatest change following D2V infection. Similarly, two cell lines, 293T (a human epithelial cell line) and ECV304 (an endothelial cell line), were permissive to D2V NGC and responded to the infection by increasing the synthesis of IL-8. Nuclear factor kappa B (NF-kappa B) and nuclear factor IL-6 (NFIL-6) are primary mediators of IL-8 expression. We studied the transcriptional regulation of IL-8 in the ECV304 and 293T cell lines and found that the induction of IL-8 gene expression involved the activation of NF-kappa B (P = 0.001) and, to a lesser extent, the activation of NFIL-6 in ECV304 cells only. We next observed by the chromatin immunoprecipitation procedure in vivo acetylation of core histones bound to the IL-8 promoter after D2V infection. IL-8 produced by infected monocytes and also IL-8 that may be produced by endothelial or other epithelial cells is associated with the hyperacetylation of histones bound to the IL-8 promoter in addition to the activation of transcription by NF-kappa B. We hypothesize that the overall increase in IL-8 synthesis observed in this in vitro study may play a role in the pathogenesis of the plasma leakage seen in dengue hemorrhagic fever and dengue shock syndrome.