BackgroundThere is currently no licensed antiviral drug for treatment of dengue. Chloroquine (CQ) inhibits the replication of dengue virus (DENV) in vitro.Methods and FindingsA double-blind, randomized, placebo-controlled trial of CQ in 307 adults hospitalized for suspected DENV infection was conducted at the Hospital for Tropical Diseases (Ho Chi Minh City, Vietnam) between May 2007 and July 2008. Patients with illness histories of 72 hours or less were randomized to a 3-day course of CQ (n = 153) or placebo (n = 154). Laboratory-confirmation of DENV infection was made in 257 (84%) patients. The primary endpoints were time to resolution of DENV viraemia and time to resolution of DENV NS1 antigenaemia. In patients treated with CQ there was a trend toward a longer duration of DENV viraemia (hazard ratio (HR) = 0.80, 95% CI 0.62–1.05), but we did not find any difference for the time to resolution of NS1 antigenaemia (HR = 1.07, 95% CI 0.76–1.51). Interestingly, CQ was associated with a significant reduction in fever clearance time in the intention-to-treat population (HR = 1.37, 95% CI 1.08–1.74) but not in the per-protocol population. There was also a trend towards a lower incidence of dengue hemorrhagic fever (odds ratio = 0.60, PP 95% CI 0.34–1.04) in patients treated with CQ. Differences in levels of T cell activation or pro- or anti-inflammatory plasma cytokine concentrations between CQ- and placebo-treated patients did not explain the trend towards less dengue hemorrhagic fever in the CQ arm. CQ was associated with significantly more adverse events, primarily vomiting.ConclusionsCQ does not reduce the durations of viraemia and NS1 antigenaemia in dengue patients. Further trials, with appropriate endpoints, would be required to determine if CQ treatment has any clinical benefit in dengue.Trial RegistrationCurrent Controlled Trials number ISRCTN38002730.

BackgroundDengue is a public health problem in many countries. Rapid diagnosis of dengue can assist patient triage and management. Detection of the dengue viral protein, NS1, represents a new approach to dengue diagnosis.Methodology/Principal FindingsThe sensitivity and specificity of the Platelia NS1 ELISA assay and an NS1 lateral flow rapid test (LFRT) were compared against a gold standard reference diagnostic algorithm in 138 Vietnamese children and adults. Overall, the Platelia NS1 ELISA was modestly more sensitive (82%) than the NS1 LFRT (72%) in confirmed dengue cases. Both ELISA and LFRT assays were more sensitive for primary than secondary dengue, and for specimens collected within 3 days of illness onset relative to later time points. The presence of measurable DENV-reactive IgG and to a lesser extent IgM in the test sample was associated with a significantly lower rate of NS1 detection in both assays. NS1 positivity was associated with the underlying viraemia, as NS1-positive samples had a significantly higher viraemia than NS1-negative samples matched for duration of illness. The Platelia and NS1 LFRT were 100% specific, being negative in all febrile patients without evidence of recent dengue, as well as in patients with enteric fever, malaria, Japanese encephalitis and leptospirosis.Conclusions/SignificanceCollectively, these data suggest NS1 assays deserve inclusion in the diagnostic evaluation of dengue patients, but with due consideration for the limitations in patients who present late in their illness or have a concomitant humoral immune response.

BackgroundDengue is a major public health problem in tropical and subtropical countries. Exploring the relationships between virological features of infection with patient immune status and outcome may help to identify predictors of disease severity and enable rational therapeutic strategies.MethodsClinical features, antibody responses and virological markers were characterized in Vietnamese adults participating in a randomised controlled treatment trial of chloroquine.ResultsOf the 248 patients with laboratory-confirmed dengue and defined serological and clinical classifications 29 (11.7%) had primary DF, 150 (60.5%) had secondary DF, 4 (1.6%) had primary DHF and 65 (26.2%) had secondary DHF. DENV-1 was the commonest serotype (57.3%), then DENV-2 (20.6%), DENV-3 (15.7%) and DENV-4 (2.8%). DHF was associated with secondary infection (Odds ratio = 3.13, 95% CI 1.04–12.75). DENV-1 infections resulted in significantly higher viremia levels than DENV-2 infections. Early viremia levels were higher in DENV-1 patients with DHF than with DF, even if the peak viremia level was often not observed because it occurred prior to enrolment. Peak viremias were significantly less often observed during secondary infections than primary for all disease severity grades (P = 0.001). The clearance of DENV viremia and NS1 antigenemia occurs earlier and faster in patients with secondary dengue (P<0.0001). The maximum daily rate of viremia clearance was significantly higher in patients with secondary infections than primary (P<0.00001).ConclusionsCollectively, our findings suggest that the early magnitude of viremia is positively associated with disease severity. The clearance of DENV is associated with immune status, and there are serotype dependent differences in infection kinetics. These findings are relevant for the rational design of randomized controlled trials of therapeutic interventions, especially antivirals.

BackgroundDengue is a major public health problem in tropical and subtropical countries. Rapid and easy diagnosis of dengue can assist patient triage and care-management. The detection of DENV NS1 on rapid lateral flow tests offers a fast route to a presumptive dengue diagnosis but careful evaluations are urgently needed as more and more people use them.MethodsThe sensitivity and specificity of the Bio-Rad NS1 Ag Strip and SD Dengue Duo (NS1/IgM/IgG) lateral flow rapid tests were evaluated in a panel of plasma samples from 245 Vietnamese patients with RT-PCR confirmed dengue and 47 with other febrile illnesses.ResultsThe NS1 rapid tests had similar diagnostic sensitivities (respectively 61.6% and 62.4%) in confirmed dengue cases but were 100% specific. When IgM/IgG results from the SD Dengue Duo were included in the test interpretation, the sensitivity improved significantly from 62.4% with NS1 alone to 75.5% when NS1 and/or IgM was positive and 83.7% when NS1 and/or IgM and/or IgG was positive. Both NS1 assays were significantly more sensitive for primary than secondary dengue. NS1 positivity was associated with the underlying viraemia as NS1-positive samples had a significantly higher viraemia than NS1-negative samples.ConclusionsThese data suggest that the NS1 test component of these assays are highly specific and have similar levels of sensitivity. The IgM parameter in the SD Duo test improved overall test sensitivity without compromising specificity. The SD Dengue Duo lateral flow rapid test deserves further prospective evaluation in dengue endemic settings.

Dengue, the most common mosquito-borne viral infection of humans, is endemic across much of the world, including much of tropical Asia and is increasing in its geographical range. Here, we present a mathematical model of dengue virus dynamics within infected individuals, detailing the interaction between virus and a simple immune response. We fit this model to measurements of plasma viral titre from cases of primary and secondary DENV 1 infection in Vietnam. We show that variation in model parameters governing the immune response is sufficient to create the observed variation in virus dynamics between individuals. Estimating model parameter values, we find parameter differences between primary and secondary cases consistent with the theory of antibody-dependent enhancement (namely enhanced rates of viral entry to target cells in secondary cases). Finally, we use our model to examine the potential impact of an antiviral drug on the within-host dynamics of dengue. We conclude that the impact of antiviral therapy on virus dynamics is likely to be limited if therapy is only started at the onset of symptoms, owing to the typically late stage of viral pathogenesis reached by the time symptoms are manifested and thus treatment is started.

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Background Takeda’s live attenuated tetravalent dengue vaccine candidate (TAK-003) is under evaluation in a long-term clinical trial across eight dengue-endemic countries. Previously, we have reported its efficacy and safety in both seronegative and seropositive participants and that its performance varies by serotype, with some decline in efficacy from first to second year post-vaccination. This exploratory analysis provides an update with cumulative and third year data. Methods Healthy 4–16 year-olds (n=20,099) were randomized 2:1 to receive TAK-003 or placebo (0, 3 month schedule). The protocol included baseline serostatus testing of all participants and detection of all symptomatic dengue throughout the trial with a serotype specific RT-PCR. Results Cumulative efficacy after three years was 62.0% (95% confidence interval: 56.6%, 66.7%) against virologically-confirmed dengue (VCD) and 83.6% (76.8%, 88.4%) against hospitalized VCD. Efficacy was 54.3% (41.9%, 64.1%) against VCD and 77.1% (58.6%, 87.3%) against hospitalized VCD in baseline seronegatives, and 65.0% (58.9%, 70.1%) against VCD and 86.0% (78.4%, 91.0%) against hospitalized VCD in seropositives. Efficacy against VCD during the third year declined to 44.7% (32.5%, 54.7%), while efficacy against hospitalized VCD was sustained at 70.8% (49.6%, 83.0%). Rates of serious adverse events were 2.9% in TAK-003 group and 3.5% in placebo group during the ongoing long-term follow-up (i.e. second half of the three years following vaccination), but none were related. No important safety risks were identified. Conclusions TAK-003 was efficacious against symptomatic dengue over three years. Efficacy declined over time but remained robust against hospitalized dengue. A booster dose evaluation is planned.

Little is known about the rate at which genetic variation is generated within intrahost populations of dengue virus (DENV) and what implications this diversity has for dengue pathogenesis, disease severity, and host immunity. Previous studies of intrahost DENV variation have used a low frequency of sampling and/or experimental methods that do not fully account for errors generated through amplification and sequencing of viral RNAs. We investigated the extent and pattern of genetic diversity in sequence data in domain III (DIII) of the envelope (E) gene in serial plasma samples (n ‫؍‬ 49) taken from 17 patients infected with DENV type 1 (DENV-1), totaling some 8,458 clones. Statistically rigorous approaches were employed to account for artifactual variants resulting from amplification and sequencing, which we suggest have played a major role in previous studies of intrahost genetic variation. Accordingly, nucleotide sequence diversities of viral populations were very low, with conservative estimates of the average levels of genetic diversity ranging from 0 to 0.0013. Despite such sequence conservation, we observed clear evidence for mixed infection, with the presence of multiple phylogenetically distinct lineages present within the same host, while the presence of stop codon mutations in some samples suggests the action of complementation. In contrast to some previous studies we observed no relationship between the extent and pattern of DENV-1 genetic diversity and disease severity, immune status, or level of viremia. Dengue virus (DENV) is a single-strand positive-sense RNA virus of the family Flaviviridae and exists as four closely related antigenically distinct serotypes denoted DENV-1 to DENV-4. These serotypes differ at the consensus level by 25 to 40% at the amino acid level (15, 30). Genetic variation within each of the four serotypes is defined as a series of "genotypes" (or "subtypes"), which can vary from one another by up to ϳ6 to 8% and 3% at the nucleotide and amino acid levels, respectively (15,25,32). For example, at least four major genotypes of DENV-1 exist, each with a different geographical distribution (9, 38). The basis for the genetic diversity in DENV is its error-prone RNA polymerase (10), such that mutations commonly occur during viral replication and on which a combination of genetic drift and negative and/or positive natural selection is able to act. This high rate of replication error results in DENV existing as a population of closely related variants within an individually infected host (33, 34), and this intrahost genetic diversity has been proposed to have implications for pathogenesis of DENV infection, variable disease outcomes, virus evolution, and host immunity (6).Several previous studies have confirmed that the population of DENV in humans and within individual Aedes mosquitoes contains measurable genetic variation (8,19,33,34). Levels of withinhost genetic diversity have been previously shown to vary among patients. Reported levels of intrahost genetic diversity ranged from ...