Showing papers on "Dengue fever published in 2007"
TL;DR: The unique immunological concerns in dengue virus vaccine development are discussed and the current prospects for the development of an acceptable vaccine are discussed, with a goal that is likely to be reached in the near future.
Abstract: The number of cases of severe dengue disease continues to grow in endemic areas of southeast Asia, Central and South America, and other subtropical regions. Children bear the greatest burden of disease, and the development of an effective vaccine remains a global public health priority. A tetravalent vaccine is urgently needed and must be effective against all four dengue virus serotypes, be cost-effective and provide long-term protection. In this Review we discuss the unique immunological concerns in dengue virus vaccine development and the current prospects for the development of an acceptable vaccine, a goal that is likely to be reached in the near future.
604 citations
TL;DR: The structure of the NS5 nuclear localization sequences, previously thought to fold into a separate domain, form an integral part of the polymerase subdomains and reveals the presence of two zinc ion binding motifs, which should inform and accelerate the structure-based design of antiviral compounds against dengue virus.
Abstract: Dengue fever, a neglected emerging disease for which no vaccine or antiviral agents exist at present, is caused by dengue virus, a member of the Flavivirus genus, which includes several important human pathogens, such as yellow fever and West Nile viruses. The NS5 protein from dengue virus is bifunctional and contains 900 amino acids. The S-adenosyl methionine transferase activity resides within its N-terminal domain, and residues 270 to 900 form the RNA-dependent RNA polymerase (RdRp) catalytic domain. Viral replication begins with the synthesis of minus-strand RNA from the dengue virus positive-strand RNA genome, which is subsequently used as a template for synthesizing additional plus-strand RNA genomes. This essential function for the production of new viral particles is catalyzed by the NS5 RdRp. Here we present a high-throughput in vitro assay partly recapitulating this activity and the crystallographic structure of an enzymatically active fragment of the dengue virus RdRp refined at 1.85-A resolution. The NS5 nuclear localization sequences, previously thought to fold into a separate domain, form an integral part of the polymerase subdomains. The structure also reveals the presence of two zinc ion binding motifs. In the absence of a template strand, a chain-terminating nucleoside analogue binds to the priming loop site. These results should inform and accelerate the structure-based design of antiviral compounds against dengue virus.
383 citations
TL;DR: This review compiles descriptions of atypical manifestations of dengue, such as d Dengue encephalitis, dengus myocarditis,dengue hepatitis and dengu cholecystitis.
Abstract: As the spread of dengue and dengue haemorrhagic fever is increasing, atypical manifestations are also on the rise, although they may be under reported because of lack of awareness. This review compiles descriptions of atypical manifestations of dengue, such as dengue encephalitis, dengue myocarditis, dengue hepatitis and dengue cholecystitis.
278 citations
TL;DR: Advances have underscored the fact that DHF/DSS pathogenesis is a complex, multifactorial process involving cocirculation of various dengue virus serotypes and the interplay of host and viral factors that influence disease severity.
Abstract: The past four decades has witnessed a consolidation of the original observations made in the 1970s that dengue haemorrhagic fever (DHF) and dengue shock syndrome (DSS) have an immunological basis. Following reinfection with a dengue virus of different serotype, severe disease is linked to high levels of antibody-enhanced viral replication early in illness which is followed by a cascade of memory T-cell activation and a 'storm' of inflammatory cytokines and other chemical mediators. These compounds are released mainly from T cells, monocytes/macrophages and endothelial cells, and ultimately cause an increase in vascular permeability. The consolidation of the evidence has been largely due to several important prospective sero-epidemiological studies in areas endemic for DHF/DSS, which have shown that risk of severe disease is significantly higher in secondary dengue infections. These advances have underscored the fact that DHF/DSS pathogenesis is a complex, multifactorial process involving cocirculation of various dengue virus serotypes and the interplay of host and viral factors that influence disease severity. The continued search to define risk factors in susceptible populations must be combined with the new techniques of molecular virology and innovative approaches in vaccine design to achieve the ultimate objective of developing a safe and effective vaccine.
271 citations
TL;DR: Weather variability was identified as a meaningful and significant indicator for the increasing occurrence of dengue fever in this study, and it might be feasible to be adopted for predicting the influences of rising average temperature on the occurrence of infectious diseases of such kind at a city level.
270 citations
TL;DR: Oral administration of the antiviral compounds 7-deaza-2'-C-methyl-adenosine, N-nonyl-deoxynojirimycin, or 6-O-butanoyl castanospermine significantly reduced viremia in a dose-dependent manner, even after delayed treatment, leading to a reduction of splenomegaly and proinflammatory cytokine levels.
Abstract: Dengue fever is an emerging arboviral disease for which no vaccine or antiviral treatment exists and that causes thousands of fatalities each year. To develop an in vivo test system for antidengue drugs, AG129 mice, which are deficient for the interferon- alpha / beta and - gamma receptors, were injected with unadapted dengue virus, resulting in a dose-dependent transient viremia lasting several days and peaking on day 3 after infection. Additionally, nonstructural protein 1, increased levels of proinflammatory cytokines, and neutralizing IgM and IgG antibodies were found, and mice had splenomegaly. Oral administration of the antiviral compounds 7-deaza-2'-C-methyl-adenosine, N-nonyl-deoxynojirimycin, or 6-O-butanoyl castanospermine significantly reduced viremia in a dose-dependent manner, even after delayed treatment, leading to a reduction of splenomegaly and proinflammatory cytokine levels. The results validate this dengue viremia mouse model as a suitable system for testing antidengue drugs and indicate that antiviral treatment during the acute phase of dengue fever can reduce the severity of the disease.
248 citations
TL;DR: An analysis of the database of children admitted to the Queen Sirikit National Institute of Child Health and Kamphaeng Phet Provincial Hospital with suspected dengue illness revealed that the number of d Dengue admissions caused by a third or fourth DENV infection was extremely low.
Abstract: Immunity to a single dengue virus (DENV) infection does not provide heterologous immunity to subsequent infection. In fact, the greatest risk for dengue hemorrhagic fever (DHF) is with a second DENV serotype exposure. The risk for DHF with a third or fourth dengue infection relative to a first or second exposure is not known. An analysis of our database of children admitted to the Queen Sirikit National Institute of Child Health and Kamphaeng Phet Provincial Hospital with suspected dengue illness revealed that the number of dengue admissions caused by a third or fourth DENV infection was extremely low (0.08-0.8%). Once admitted, the risk for DHF relative to dengue fever was not different for those experiencing third or fourth DENV infections over those experiencing a second DENV infection. We document new dengue serotype infection sequences leading to DHF of 1-4, 2-3, 3-1, and 3-4.
223 citations
TL;DR: It is shown that both dengue and West Nile viruses enter HeLa cells by clathrin-dependent endocytosis and require vacuolar acidic pH, and inhibition of the GTPase Rab 5 or 7, which regulates transport to early or late endosomes, respectively, demonstrated that Rab 5 was essential for survival of both d Dengue andWest Nile virus.
Abstract: The mechanisms of cellular entry of dengue and West Nile viruses are not well characterized. We show that both these viruses enter HeLa cells by clathrin-dependent endocytosis and require vacuolar acidic pH. Inhibition of the GTPase Rab 5 or 7, which regulates transport to early or late endosomes, respectively, demonstrated that Rab 5 was essential for survival of both dengue and West Nile virus. These data broaden our understanding of the pathways required for productive dengue and West Nile virus infection and may facilitate new strategies for combating disease.
219 citations
TL;DR: Unbiased gene expression analysis has identified new host genes associated with dengue infection, which have been validated in functional studies and showed that some parts of the host response can be used as potential biomarkers for the disease while others can be use to control dengu viral replication, thus representing viable targets for drug therapy.
Abstract: Background
Despite the seriousness of dengue-related disease, with an estimated 50–100 million cases of dengue fever and 250,000–500,000 cases of dengue hemorrhagic fever/dengue shock syndrome each year, a clear understanding of dengue pathogenesis remains elusive. Because of the lack of a disease model in animals and the complex immune interaction in dengue infection, the study of host response and immunopathogenesis is difficult. The development of genomics technology, microarray and high throughput quantitative PCR have allowed researchers to study gene expression changes on a much broader scale. We therefore used this approach to investigate the host response in dengue virus-infected cell lines and in patients developing dengue fever.
219 citations
TL;DR: It is understood that the process is initiated by infection with a virulent d Dengue virus, often in the presence of antibodies that enhance dengue virus infection in secondary infection, and then triggered by rapidly elevated cytokines and chemical mediators that were produced by intense immune activation.
Abstract: Dengue virus infections are a serious cause of morbidity and mortality in most tropical and subtropical areas of the world; Southeast and South Asia, Central and South America, and the Caribbean. Dengue virus infection can be asymptomatic or causes two forms of illness, dengue fever (DF) and dengue hemorrhagic fever (DHF), which is the severe form of dengue illness and often fatal. Pathogenesis of DHF has been analyzed, and two mechanisms are considered to be responsible. These include dengue serotype cross-reactive immune responses and virulence of the virus. The immunopathological mechanisms include a complex series of immune responses. Rapid increase in the levels of cytokines, especially TNF-alpha, and chemical mediators play a key role in inducing unique clinical manifestations of DHF such as plasma leakage, shock, and hemorrhagic manifestations. It is understood that the process is initiated by infection with a virulent dengue virus, often in the presence of antibodies that enhance dengue virus infection in secondary infection, and then triggered by rapidly elevated cytokines and chemical mediators that were produced by intense immune activation. However, complete understanding of the entire pathological mechanism is far from complete, and further studies are still needed.
208 citations
TL;DR: It is proposed that the Cuban, Caribbean Black and African populations share a common gene pool that could explain, at least partially, the low incidence of dengue hemorrhagic fever in Cuba and Caribbean and African countries.
Abstract: Cuban DHF/DSS outbreaks have provided evidence of a reduced risk of people of Negroid race for DHF/DSS compared to those of Caucasoid race. These observations from Cuban dengue outbreaks have significant epidemiological interest, as the differences in susceptibility to DHF/DSS among racial groups in Cuba coincide with that reported in African and Black Caribbean populations. In this article, we review the literature on race as a risk factor for DHF/DSS and discuss recent results from ongoing studies. Taking into consideration the origins of contemporary Cuban inhabitants, we propose that the Cuban, Caribbean Black and African populations share a common gene pool that could explain, at least partially, the low incidence of dengue hemorrhagic fever in Cuba and Caribbean and African countries. The central role played by immunological mechanisms in the pathogenesis of DHF/DSS has led us to consider that the polymorphic genes associated with the immune response must be carefully considered among those human genes regulating dengue disease severity that might be distributed unequally in Blacks and Whites.
TL;DR: The results indicate that the commercial dengue NS1 antigen-capture ELISA may be superior to virus isolation and RT-PCR for the laboratory diagnosis of acute d Dengue infection based on a single serum sample.
TL;DR: Different roles for the two glycans present at the E protein during d Dengue virus infection are defined, highlighting the involvement of distinct host functions from mammalian and mosquito cells during dengue virus propagation.
Abstract: Dengue virus envelope protein (E) contains two N-linked glycosylation sites, at Asn-67 and Asn-153. The glycosylation site at position 153 is conserved in most flaviviruses, while the site at position 67 is thought to be unique for dengue viruses. N-linked oligosaccharide side chains on flavivirus E proteins have been associated with viral morphogenesis, infectivity, and tropism. Here, we examined the relevance of each N-linked glycan on dengue virus E protein by removing each site in the context of infectious viral particles. Dengue viruses lacking Asn-67 were able to infect mammalian cells and translate and replicate the viral genome, but production of new infectious particles was abolished. In addition, dengue viruses lacking Asn-153 in the E showed reduced infectivity. In contrast, ablation of one or both glycosylation sites yielded viruses that replicate and propagate in mosquito cells. Furthermore, we found a differential requirement of N-linked glycans for E secretion in mammalian and mosquito cells. While secretion of E lacking Asn-67 was efficient in mosquito cells, secretion of the same protein expressed in mammalian cells was dramatically impaired. Finally, we found that viruses lacking the carbohydrate at position 67 showed reduced infection of immature dendritic cells, suggesting interaction between this glycan and the lectin DC-SIGN. Overall, our data defined different roles for the two glycans present at the E protein during dengue virus infection, highlighting the involvement of distinct host functions from mammalian and mosquito cells during dengue virus propagation.
TL;DR: Use of prospective data to estimate the burden of disease shows that most DALYs lost to dengue illness were the result of non-hospitalised illnesses of long duration, thus, inclusion ofNon- hospitalised cases is critical to accurately assess the total burden of denge illness.
TL;DR: This work brought large-scale laboratory life table techniques to bear on the question of age-dependent mortality in the mosquito vector of dengue virus, Aedes aegypti, and found that mortality was highly age dependent in both sexes.
Abstract: Although variation in mortality is considered by virtually all vector-borne disease specialists to be one of the most important determinants of an arthropod's capacity to transmit pathogens, the operational assumption often is that insect vector mortality is independent of age. Acceptance of the non-senescence assumption leads to the erroneous conclusion that mosquito age is unimportant, results in misleading predictions regarding disease reductions after vector control, and represses study of other aspects of mosquito biology that change with age. We brought large-scale laboratory life table techniques (N > 100,000) to bear on the question of age-dependent mortality in the mosquito vector of dengue virus, Aedes aegypti. Mortality was highly age dependent in both sexes. Mortality was low at young ages (< 10 days old), steadily increased at middle ages, and decelerated at older ages. A newly derived age-dependent model of pathogen transmission shows the importance of young mosquitoes and population age structure to transmission dynamics. Departure from the age-independent mortality paradigm encourages research on overlooked complexities in mosquito biology, the need for innovative methods to study mosquito population dynamics, and the need to study age-dependent changes for an accurate understanding of mosquito biology and pathogen transmission.
TL;DR: Historical data provided useful details concerning serotype differences in the natural history of primary DENV infections, and incubation period was negatively correlated with disease severity, potentially reflecting a dose-response mechanism.
Abstract: Background. The natural history of wild-type dengue virus (DENV) infections of humans, including incubation and infectious periods, requires further study. Methods. Two experimental studies in the Philippines of DENV-4 (1924-1925) and DENV-1 (1929-1930) were reexamined. The intrinsic incubation periods were fitted to log-normal distribution using the maximum likelihood method, and the infectious and extrinsic incubation periods were assessed by proportions of successful transmissions causing clinically apparent dengue. Correlations between the intrinsic incubation period and other variables and univariate associations between clinical severity and serotype were also examined. Results. Mean ± SD incubation periods were 6.0 ± 1.4 and 5.7 ± 1.5 days for DENV-4 and DENV-1, respectively. Significant negative correlations were observed between the incubation period and duration of fever (r = -0.43 and -0.33). Even 1 and 2 days before the onset of fever, 80.0% (95% confidence interval [CI], 44.9%-100%) and 25.0% (CI, 0%-67.4%) of biting experiments caused clinically apparent dengue. DENV-1 infections resulted in a significantly longer duration of fever than DENV-4 infections (P<.01). Conclusions. Incubation period was negatively correlated with disease severity, potentially reflecting a dose-response mechanism. The historical data provided useful details concerning serotype differences in the natural history of primary DENV infections.
TL;DR: Serial ultrasound examination detected plasma leakage in multiple body compartments around the time of defervescence and was detectable before changes in hematocrits, indicating that ultrasound is a useful tool for detecting plasma leaking in dengue infection.
Abstract: Background: Although plasma leakage is the major cause of mortality and morbidity in patients with dengue hemorrhagic fever (DHF), a detailed assessment of the natural course of this process is still lacking. We employed serial ultrasound examination to delineate the locations and the timing of plasma leakage and to evaluate the usefulness of ultrasound in detecting plasma leakage in DHF. Method: Daily ultrasound examinations of the abdomen and right thorax were performed in 158 suspected dengue cases to detect ascites, thickened gall bladder wall and pleural effusions. Cases were classified into dengue fever (DF), DHF or other febrile illness (OFI) based on serology and evidence of plasma leakage including hemoconcentration and pleural effusion detected by chest radiograph. Results: Ultrasonographic evidence of plasma leakage was detected in DHF cases starting from 2 days before defervescence and was detected in some cases within 3 days after fever onset. Pleural effusion was the most common ultrasonographic sign of plasma leakage (62% of DHF cases one day after defervescence). Thickening of the gallbladder wall and ascites were detected less frequently (43% and 52% of DHF cases respectively) and resolved more rapidly than pleural effusions. The size of pleural effusions, ascites and gall bladder wall thickness in DHF grade I and II were smaller than those of grade III patients. Ultrasound detected plasma leakage in 12 of 17 DHF cases who did not meet the criteria for significant hemoconcentration. Conclusions: Ultrasound examinations detected plasma leakage in multiple body compartments around the time of defervescence. Ultrasonographic signs of plasma leakage were detectable before changes in hematocrits. Ultrasound is a useful tool for detecting plasma leakage in dengue infection.
TL;DR: It is suggested that viral burden may not solely explain severe dengue in infants and that neutralizing antibody is a reasonable but not absolute marker of protective immunity in infants.
Abstract: The pathogenesis of dengue in infants is poorly understood. We postulated that dengue severity in infants would be positively associated with markers of viral burden and that maternally derived, neutralizing anti-dengue antibody would have decayed before the age at which infants with dengue presented to the hospital. In 75 Vietnamese infants with primary dengue, we found significant heterogeneity in viremia and NS1 antigenemia at hospital presentation, and these factors were independent of disease grade or continuous measures of disease severity. Neutralizing antibody titers, predicted in each infant at the time of their illness, suggested that the majority of infants (65%) experienced dengue hemorrhagic fever when the maternally derived neutralizing antibody titer had declined to <1 : 20. Collectively, these data have important implications for dengue vaccine research because they suggest that viral burden may not solely explain severe dengue in infants and that neutralizing antibody is a reasonable but not absolute marker of protective immunity in infants.
TL;DR: In the early years of the 21st century the authors are collectively failing to meet the threat posed by dengue as the disease spreads unabated and almost 40% of the worlds population now live at risk of contracting it.
Abstract: Dengue is the most rapidly advancing vector-borne disease with an estimated 50 million dengue infections occurring annually. As a result of major demographic changes rapid urbanization on a massive scale global travel and environmental change the world - particularly the tropical world - faces enormous challenges from emerging infectious diseases. Dengue epitomizes these challenges. In the early years of the 21st century we are collectively failing to meet the threat posed by dengue as the disease spreads unabated and almost 40% of the worlds population now live at risk of contracting it. Because of the rapidly increasing public health importance of dengue the 2002 World Health Assembly Resolution (WHA55.17) urged greater commitment among Member States and WHO to dengue control; of particular significance is the 2005 Revision of the International Health Regulations (WHA58.3) which includes dengue fever as an example of a disease that may constitute an international public health emergency. (excerpt)
TL;DR: These data provide the first snapshot of gene-expression patterns in peripheral blood during acute dengue and suggest that DSS is associated with attenuation of selected aspects of the innate host response.
Abstract: Responses by peripheral blood leukocytes may contribute to the pathogenesis of dengue hemorrhagic fever (DHF). We used DNA microarrays to reveal transcriptional patterns in the blood of 14 adults with DHF. Acute DHF was defined by an abundance of transcripts from cell cycle- and endoplasmic reticulum (ER)-related genes, suggesting a proliferative response accompanied by ER stress. Transcript-abundance levels for immunoresponse-associated genes, including cell surface markers, immunoglobulin, and innate response elements, were also elevated. Twenty-four genes were identified for which transcript abundance distinguished patients with dengue shock syndrome (DSS) from those without DSS. All the gene transcripts associated with DSS, many of which are induced by type I interferons, were less abundant in patients with DSS than in those without DSS. To our knowledge, these data provide the first snapshot of gene-expression patterns in peripheral blood during acute dengue and suggest that DSS is associated with attenuation of selected aspects of the innate host response.
01 Jan 2007
TL;DR: Aedes albopictus, a secondary dengue vector related to the classical vector, Aedes aegypti, has been expanding globally at an alarming rate, perhaps aided by global warming as discussed by the authors.
Abstract: MOST INDIVIDUALS IN THE UNITED STATES ARE AS little concerned about dengue fever as they were a decade ago about West Nile fever. That situation could change if dengue continues its expansion as one of the world’s most aggressive reemerging infections. After decades of absence in the United States, the sometimes deadly disease is again striking US individuals, causing an epidemic in Hawaii in 2001, appearing with increasing frequency along the Texas-Mexico border, returning with unprecedented severity in US tropical territories and commonwealths such as Puerto Rico, and striking overseas travelers. Widespread appearance of dengue in the continental United States is a real possibility. The range of Aedes albopictus (“Asian tiger mosquito”), a secondary dengue vector related to the classical vector, Aedes aegypti, has been expanding globally at an alarming rate, perhaps aided by global warming. Since its introduction into the United States in 1985, Aedes albopictus has spread to 36 states, bringing with it an increased risk of dengue outbreaks. Moreover, as dengue has reemerged throughout South and Central America and the Caribbean, its fatal form, dengue hemorrhagic fever (DHF), has appeared in many countries as well as in Puerto Rico. Between January 1, 2007, and November 30, 2007, the Pan American Health Organization received reports of 760 846 cases of dengue and 19 976 cases of DHF in the Americas. Globally, dengue and DHF case counts have been increasing steadily for more than 50 years. In the mid-1950s, annual case reports to the World Health Organization (WHO) totaled only approximately 900; by 2005, annual case reports had increased to nearly a million, submitted by more than 60 nations. Worldwide, dengue is among the most important reemerging infectious diseases with an estimated 50 million to 100 million annual cases, 500 000 hospitalizations (often requiring intensive care), and, by WHO estimates, 22 000 deaths, mostly in children. Fortunately, standardized therapy coupled with intensive education in many countries, most notably in Thailand, has greatly reduced casefatality rates. The economic and social effects of dengue are also enormous because the disease tends to occur in explosive epidemics that paralyze communities and sometimes entire nations. An explanation for why a group of viruses so well adapted to humans, having caused debilitating but nonfatal influenzalike illnesses for centuries, should suddenly expand geographically into new areas, and also turn more deadly, has proved elusive. The formidable challenges of understanding dengue pathogenesis and of developing effective therapies and vaccines must be met to effectively fight this important reemerging disease.
TL;DR: Some clinical presentations of dengue disease and laboratory findings in adults are different from those in children, and adults as well as pediatric cases of DHF need appropriate and prompt case management to reduce the mortality rate ofDHF.
TL;DR: High seroprevalence of dengue was found on both sides of the border.
Abstract: Reported autochthonous dengue fever transmission in the United States has been limited to 5 south Texas border counties since 1980. We conducted a cross-sectional serosurvey in Brownsville, Texas, and Matamoros, Tamaulipas, Mexico (n = 600), in 2004 to assess dengue seroprevalence. Recent dengue infection was detected in 2% (95% confi dence interval [CI] 0.5%–3.5%) and 7.3% (95% CI 4.3%–10.3%) of residents in Brownsville and Matamoros, respectively. Past infection was detected in 40% (95% CI 34%–45%) of Brownsville residents and 78% (95% CI 74%–83%) of Matamoros residents. For recent infection, only weekly family income <$100 was a signifi cant predictor (adjusted odds ratio 3.2, 95% CI 1.3–8.0). Risk factors that predicted past dengue infection were presence of larval habitat, absence of air-conditioning and street drainage, and weekly family income <$100. Mosquito larvae were present in 30% of households in both cities. Our results show that dengue fever is endemic in this area of the southern Texas–Mexico border.
TL;DR: In travelers, severe dengue virus infections are not uncommon but may be missed if the WHO classification is strictly applied, and high liver enzyme levels and low platelet counts could serve as indicators of disease severity.
Abstract: BACKGROUND Dengue fever is the most common arboviral disease in travelers. In countries where dengue virus is endemic, sequential (secondary) infections with different dengue virus serotypes are associated with disease severity. Data on severity and secondary infection rates in a population of travelers are lacking. METHODS Intensified surveillance of dengue fever in travelers was performed within the European Network on Surveillance of Imported Infectious Diseases. Data were collected at 14 European clinical referral centers between 2003 and 2005. RESULTS A total of 219 dengue virus infections imported from various regions of endemicity were reported. Serological analysis revealed a secondary immune response in 17%. Spontaneous bleeding was observed in 17 (8%) patients and was associated with increased serum alanine and aspartate aminotransferase levels and lower median platelet counts. Two (0.9%) patients fulfilled the World Health Organization (WHO) case definition for dengue hemorrhagic fever. However, 23 (11%) travelers had severe clinical manifestations (internal hemorrhage, plasma leakage, shock, or marked thrombocytopenia). A secondary immune response was significantly associated with both spontaneous bleeding and other severe clinical manifestations. CONCLUSIONS In travelers, severe dengue virus infections are not uncommon but may be missed if the WHO classification is strictly applied. High liver enzyme levels and low platelet counts could serve as indicators of disease severity.
TL;DR: Validation of the assays with local clinical samples collected from 2004 to 2006 revealed that there was an 88% positive correlation between virus isolation and RT-PCR with regard to dengue virus detection and a 100% correlation with seroconversion in subsequent samples.
Abstract: Virus detection methodology provides detection of dengue virus in the early phase of the disease. PCR, targeting cDNA derived from viral RNA, has been used as a laboratory-based molecular tool for the detection of Dengue virus. We report the development and use of three real-time one-step reverse transcriptase PCR (RT-PCR) assays to detect dengue cases and serotype the virus involved. The first RT-PCR assay uses SYBR green I as the reporting dye for the purpose of cost-effective screening for dengue virus. The detection limit of the SYBR green I assay was 10 PFU/ml (0.01 equivalent PFU per assay) for all four dengue virus serotypes. The second RT-PCR assay is a duplex fluorogenic probe-based real-time RT-PCR for serotyping clinical samples for dengue viruses. The detection threshold of the probe-based RT-PCR format was 0.1 PFU for serotypes Dengue-1 and Dengue-2, 1 PFU for serotype Dengue-3, and 0.01 PFU for serotype Dengue-4. The third is a fourplex assay that detects any of the four serotypes in a single closed tube with comparable sensitivity. Validation of the assays with local clinical samples collected from 2004 to 2006 revealed that there was an 88% positive correlation between virus isolation and RT-PCR with regard to dengue virus detection and a 100% correlation with seroconversion in subsequent samples. The serotyping results derived from duplex and fourplex assays agree fully with each other and with that derived from immunofluorescence assays.
TL;DR: Dengue is associated with severe disease, and deaths do occur despite current supportive management, and Fatal DHF/dengue shock syndrome (DSS) does occur in adults and in primary dengue infection.
TL;DR: It is found that the initial cellular tropism of DENV in mice is similar to that reported in humans, thereby paving the way for investigation of cellular Tropism and pathogenesis ofDENV in primary and secondary infections.
Abstract: Dengue fever is a mosquitoborne viral illness caused by 4 dengue viruses (DENV-1-4). The cellular tropism of DENV has not been definitively determined, despite its importance for understanding viral pathogenesis and identifying therapeutic targets. To define DENV cellular tropism in a small animal model, 129/Pas mice lacking interferon-alpha/beta and/or-gamma receptors were infected with DENV via a subcutaneous route. During the first week after infection, virus was present in lymph nodes, spleen, bone marrow, and circulating white blood cells. F4/80+CD11b+ macrophages and CD11c+ dendritic cells were demonstrated to be targets for DENV-2 infection in the spleen by flow cytometry directed to structural and nonstructural DENV proteins and by magnetic bead separation followed by strand-specific reverse-transcriptase polymerase chain reaction. We find that the initial cellular tropism of DENV in mice is similar to that reported in humans, thereby paving the way for investigation of cellular tropism and pathogenesis of DENV in primary and secondary infections.
TL;DR: Evidence is provided that Dengue infection induces and regulates the three branches of the UPR signaling cascades, a basis for the understanding of the viral regulation and conditions beneficial to the viral infection.
Abstract: Dengue and Dengue hemorrhagic fever have emerged as some of the most important mosquito-borne viral diseases in the tropics. The mechanisms of pathogenesis of Dengue remain elusive. Recently, virus-induced apoptosis mediated by the Unfolded Protein Response (UPR) has been hypothesised to represent a crucial pathogenic event in viral infection. In an attempt to evaluate the contribution of the UPR to virus replication, we have characterized each component of this signalling pathway following Dengue virus infection. We find that upon Dengue virus infection, A549 cells elicit an UPR which is observed at the level of translation attenuation (as visualized by the phosphorylation of eIF2alpha) and activation of specific pathways such as nuclear translocation of ATF-6 and splicing of XBP-1. Interestingly, we find that specific serotype of virus modulate the UPR with different selectivity. In addition, we demonstrate that perturbation of the UPR by preventing the dephosphorylation of the translation initiation factor eIF2alpha using Salubrinal considerably alters virus infectivity. This report provides evidence that Dengue infection induces and regulates the three branches of the UPR signaling cascades. This is a basis for our understanding of the viral regulation and conditions beneficial to the viral infection. Furthermore, modulators of UPR such as Salubrinal that inhibit Dengue replication may open up an avenue toward cell-protective agents that target the endoplasmic reticulum for anti-viral therapy.
TL;DR: It is suggested that VEGF regulates vascular permeability and its activity is controlled by binding to soluble VEGFR2, which may be an important mechanism of plasma leakage in DHF.
Abstract: Some individuals infected with dengue virus develop dengue hemorrhagic fever (DHF), a viral hemorrhagic disease characterized by a transient period of localized plasma leakage. To determine the importance of vascular endothelial growth factor A (VEGF-A) in this syndrome, we compared plasma levels of VEGF-A and the soluble forms of its receptors in patients with DHF to patients with dengue fever (DF), a milder form of dengue virus infection without plasma leakage. We observed a rise in the plasma levels of free, but not total VEGF-A in DHF patients at the time of plasma leakage. This was associated with a decline in the soluble form of VEGF receptor 2 (VEGFR2) and VEGF-soluble VEGFR2 complexes, but not the soluble form of VEGFR1. The severity of plasma leakage in patients inversely correlated with plasma levels of soluble VEGFR2. In vitro, dengue virus suppressed soluble VEGFR2 production by endothelial cells but up-regulated surface VEGFR2 expression and promoted response to VEGF stimulation. In vivo, plasma viral load correlated with the degree of decline in plasma soluble VEGFR2. These results suggest that VEGF regulates vascular permeability and its activity is controlled by binding to soluble VEGFR2. Dengue virus-induced changes in surface and soluble VEGFR2 expression may be an important mechanism of plasma leakage in DHF.
TL;DR: It is demonstrated for the first time that humanized mice are capable of dengue viral primary human immune responses thus paving the way for new d Dengue immunopathogenesis and vaccine studies.