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Resultados 1 - 20 de 20.041
1.

Larvicidal and pupicidal evaluation of silver nanoparticles synthesized using Aquilaria sinensis and Pogostemon cablin essential oils against dengue and zika viruses vector Aedes albopictus mosquito and its histopathological analysis.

Artif Cells Nanomed Biotechnol; : 1-9, 2017 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-28859534

Resumo

Mosquitoes pose a threat to humans and animals, causing millions of deaths every year. Vector control by effective eco-friendly pesticides of natural origin is a serious issue that requires urgent attention. The employment of green-reducing extracts for nanoparticles biosynthesis in a rapid and single-step process represents a promising strategy. In this study, silver nanoparticles (AgNPs) were biofabricated using an essential oil of Aquilaria sinensis (AsEO) and Pogostemonis Herba essential oil of Pogostemon cablin (PcEO) in one step and cost-effective manner. UV-vis spectrophotometry, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, X-ray diffraction analysis and energy-dispersive X-ray spectroscopy were used to confirm the AgNPs formation and their biophysical characterization. The larvicidal and pupicidal toxicity of AsEO, PcEO and biosynthesized AgNPs were evaluated against larvae and pupae of the dengue and Zika virus vector Aedes albopictus. Compared to the tested essential oils, the biofabricated AgNPs showed the highest toxicity against larvae and pupae of Ae.albopictus. In particular, the LC values of AsEO ranged from 44.23 (I) to 166 (pupae), LC values of PcEO ranged from 32.49 (I) to 90.05(IV), LC values of AsEO-AgNPs from 0.81 (I) to 1.12 (IV) and LC values of PcEO-AgPNs from 0.85 (I) to 1.19 (IV). Furthermore, histological analysis of the midgut cells of the control and treated larvae exhibited that the epithelial cells and brush border were highly affected by the fabricated AgNPs compared to the essential oils (AsEO and PcEO). Overall, the A. sinensis and P. cablin essential oils fabricated AgNPs have a potential of application as a biopesticide for mosquito control through safer and cost-effective approach.
2.

Random Forest-Based Evaluation of Raman Spectroscopy for Dengue Fever Analysis.

Appl Spectrosc; 71(9): 2111-2117, 2017 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-28862033

Resumo

This work presents the evaluation of Raman spectroscopy using random forest (RF) for the analysis of dengue fever in the infected human sera. A total of 100 dengue suspected blood samples, collected from Holy Family Hospital, Rawalpindi, Pakistan, have been used in this study. Out of these samples, 45 were dengue-positive based on immunoglobulin M (IgM) capture enzyme-linked immunosorbent assay (ELISA) tests. For highlighting the spectral differences between normal and infected samples, an effective machine learning system is developed that automatically learns the pattern of the shift in spectrum for the dengue compared to normal cases and thus is able to predict the unknown class based on the known example. In this connection, dimensionality reduction has been performed with the principal component analysis (PCA), while RF is used for automatic classification of dengue samples. For the determination of diagnostic capabilities of Raman spectroscopy based on RF, sensitivity, specificity, and accuracy have been calculated in comparison to normally performed IgM capture ELISA. According to the experiment, accuracy of 91%, sensitivity of 91%, and specificity of 91% were achieved for the proposed RF-based model.
3.

Genetic epidemiology of dengue viruses in phase III trials of the CYD tetravalent dengue vaccine and implications for efficacy.

Elife; 62017 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-28871961

Resumo

This study defined the genetic epidemiology of dengue viruses (DENV) in two pivotal phase III trials of the tetravalent dengue vaccine, CYD-TDV, and thereby enabled virus genotype-specific estimates of vaccine efficacy (VE). Envelope gene sequences (n = 661) from 11 DENV genotypes in 10 endemic countries provided a contemporaneous global snapshot of DENV population genetics and revealed high amino acid identity between the E genes of vaccine strains and wild-type viruses from trial participants, including at epitope sites targeted by virus neutralising human monoclonal antibodies. analysis of all CYD14/15 trial participants revealed a statistically significant genotype-level VE association within DENV-4, where efficacy was lowest against genotype I. In subgroup analysis of trial participants age 9-16 years, VE estimates appeared more balanced within each serotype, suggesting that genotype-level heterogeneity may be limited in older children. Post-licensure surveillance is needed to monitor vaccine performance against the backdrop of DENV sequence diversity and evolution.
4.

Surface-Enhanced Raman Spectroscopy-Based Sandwich Immunoassays for Multiplexed Detection of Zika and Dengue Viral Biomarkers.

ACS Infect Dis; 2017 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-28875696

Resumo

Zika and dengue are mosquito-borne diseases that present similar nonspecific symptoms but possess dramatically different outcomes. The first line of defense in epidemic outbreaks are rapid point-of-care diagnostics. Because many outbreaks occur in areas that are resource poor, assays that are easy to use, inexpensive, and require no power have become invaluable in patient treatment, quarantining, and surveillance. Paper-based sandwich immunoassays such as lateral flow assays (LFAs) are attractive as point-of-care solutions as they have the potential for wider deployability than lab-based assays such as PCR. However, their low sensitivity imposes limitations on their ability to detect low biomarker levels and early diagnosis. Here, we exploit the high sensitivity of surface-enhanced Raman spectroscopy (SERS) in a multiplexed assay that can distinguish between Zika and dengue nonstructural protein 1 (NS1) biomarkers. SERS-encoded gold nanostars were conjugated to specific antibodies for both diseases and used in a dipstick immunoassay, which exhibited 15-fold and 7-fold lower detection limits for Zika NS1 and dengue NS1, respectively. This platform combines the simplicity of a LFA with the high sensitivity of SERS and could not only improve Zika diagnosis but also detect diseases sooner after infection when biomarker levels are low.
5.

Synthesis and structure-activity relationships of carbohydrazides and 1,3,4-oxadiazole derivatives bearing imidazolidine moiety against the yellow fever and dengue vector, Aedes aegypti.

Pest Manag Sci; 2017 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-28869331

Resumo

BACKGROUND: 1,3,4-oxadiazole and imidazolidine rings are important heterocyclic compounds exhibiting a variety of biological activities. In this study, novel compounds with oxadiazole and imidazolidine rings were synthesized from 3-(methylsulfonyl)-2-oxoimidazolidine-1-carbonyl chloride and screened for insecticidal activities. The proposed structures of the 17 synthesized compounds were confirmed using elemental analysis, IR, H-NMR, and mass spectroscopy. RESULTS: None of the compounds showed larvicidal activity at the tested concentrations against 1 instar Aedes aegypti larvae. However, nine compounds exhibited promising adulticidal activity with mortality rates of ≥80% at 5 µg/mosquito. Further dose-response bioassays were undertaken to determine LD values. Compounds 1, 2b, 2c, 2d, 2g, 3b, 3c, 3g, and 3h were effective, with typical LD s of about 5-10 µg/mosquito against female Ae. aegypti. Compounds 2c, bearing a nitro group on the aromatic ring, (LD = 2.80 ± 0.54 µg/mosquito) and 3h (double halogen groups at 2,4 position on the phenyl ring) (LD = 2.39 ± 0.15 µg/mosquito) were the most promising compounds. CONCLUSION: Preliminary mode of action studies failed to show consistent evidence of either neurotoxic or mitochondria-directed effects. Further chemical synthesis within this series may lead to the development of new effective insecticides.
6.

Presence of a predator image in potential breeding sites and oviposition responses of a dengue vector.

Acta Trop; 2017 Aug 30.
Artigo em Inglês | MEDLINE | ID: mdl-28865898

Resumo

In dengue vector control, attempts to minimize or replace the use of pesticides have mostly involved use of predators, but success has been severely impeded by difficulties associated with financial and environmental costs, predator mass production, and persistence in target habitats. Visual deterrents have been used successfully to control animal pests, in some cases in an effort to replace pesticide use. Despite evidence that visual signals are crucial in site choice for egg deposition by dengue vectors, and that female mosquitoes respond to artificial predation, the role of predator intimidation as it affects the oviposition behavior of dengue vectors remains largely unexplored. Here, we examined the oviposition responses of Aedes aegypti exposed to various mosquito predator pictures. Gravid females were presented with equal opportunities to oviposit in two cups with predator images [Toxorhynchites splendens-TXI, Goldfish (Carassius auratus)-small (SFI) and large (LFI) and Tx. splendens+Goldfish-TXFI] and two others without pictures. Differences in egg deposition were examined between sites with and without these images. When given a chance to oviposit in cups with and without TXI, Ae. aegypti females were similarly attracted to both sites. When provided an opportunity to oviposit in cups displaying pictures of fish (SFI or LFI) and blank cups, egg deposition rates were much lower in the fish picture sites. Females showed a preference for blank cups over TXFI for egg deposition. They also equally avoided cups with pictures of fish, regardless of the size of the picture. Our results indicate that the presence of images of goldfish and their association with Tx. larvae significantly reduced egg deposition by Ae. aegypti, and this was not the case with the predatory larvae alone. The observations that the images of natural predators can repel gravid females of a dengue vector provide novel possibilities to develop effective and inexpensive alternative tools to harmful insecticides.
7.

"We need people to collaborate together against this disease": A qualitative exploration of perceptions of dengue fever control in caregivers' of children under 5 years, in the Peruvian Amazon.

PLoS Negl Trop Dis; 11(9): e0005755, 2017 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-28873408

Resumo

BACKGROUND: Dengue Fever presents a significant and growing burden of disease to endemic countries, where children are at particular risk. Worldwide, no effective anti-viral treatment has been identified, thus vector control is key for disease prevention, particularly in Peru where no vaccine is currently available. This qualitative study aimed to explore the perceptions of dengue control in caregivers' of children under 5 years in Peru, to help direct future mosquito control programmes and strategy. METHODS: Eighteen semi-structured interviews were conducted in one health centre in Iquitos, Peru. Interviews were audio-recorded, transcribed and translated by an independent translator. Data were analysed using an inductive thematic approach. FINDINGS: Three core analytic themes were interpreted: (1) awareness of dengue and its control, (2) perceived susceptibility of children, rural riverside communities and city inhabitants, and (3) perceived responsibility of vector control. Participants were aware of dengue symptoms, transmission and larvae eradication strategies. Misconceptions about the day-time biting behaviour of the Aedes aegypti mosquito and confusion with other mosquito-borne diseases influenced preventative practice. Community-wide lack of cooperation was recognised as a key barrier. This was strengthened by attitudes that the government or health centre were responsible for dengue control and a belief that the disease cannot be prevented through individual actions. Participants felt powerless to prevent dengue due to assumed inevitability of infection and lack of faith in preventative practices. However, children and rural communities were believed to be most vulnerable. CONCLUSIONS: Perceptions of dengue control amongst caregivers to under 5's were important in shaping their likelihood to participate in preventative practices. There is a need to address the perceived lack of community cooperation through strategies creating a sense of ownership of community control and enhancing social responsibility. The belief that dengue cannot be prevented by individual actions in a community also warrants attention. Specific misconceptions about dengue should be addressed through the community health worker system and further research directed to identify the needs of certain vulnerable groups.
8.

Prospective study of patients with persistent symptoms of dengue in Brazil.

Rev Inst Med Trop Sao Paulo; 59: e65, 2017 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-28876417

Resumo

Dengue is an arboviral infection clinically recognized as an acute and self-limited disease. Persistence of dengue symptoms is known, but it has been little studied. The aim of this study was to characterize persistent symptoms in 113 patients with dengue followed up clinically and by laboratory testing at a tertiary hospital. Symptoms that persisted for more than 14 days were observed in 61 (54.0%) patients, and six (6.2%) of them had symptoms for 6 months or more. The persistent symptoms identified were myalgia, weakness, hair loss, memory loss, reduced resistance to physical effort, headache, reasoning problems, arthralgia, sleepiness- and emotional lability. The progression to persistent symptoms was significantly associated with hospitalization, older age, more severe disease, the presence of bleeding and comorbidities upon univariate analysis. Upon multivariate analysis, the presence of persistent symptoms continued to be significantly associated only with increased age and dengue with warning signs. The platelet count during the acute phase of the disease was significantly lower in the group with persistent symptoms. In conclusion, the frequency of progression to persistent symptoms in dengue is relevant in patients seen at a tertiary hospital and the persistence of symptoms is more common in patients with dengue with warning signs.
9.

Circulating genotypes of Dengue-1 virus in South West India, 2014-2015.

Jpn J Infect Dis; 2017 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-28890510

Resumo

Dengue is found to be the most prevalent arboviral disease affecting humans. Tropical and subtropical regions are at high risk of dengue virus infections. The clinical manifestations often range from mild fever to fever with hemorrhagic manifestations and shock. Since 2010, India is witnessing a marked increase in the number of Dengue Virus Serotype 1(DENV-1) apart from Dengue Virus 2 (DENV-2) and Dengue Virus 3 (DENV-3) Serotypes. The present study was undertaken to understand the circulating genotypes of DENV-1 in South West India by sequencing the envelope gene of DENV-1 samples representative of the time period 2014-2015. The extracted RNA from Dengue NS1 antigen ELISA positive samples, archived at Manipal Centre for Virus Research (MCVR), National Vector Borne Disease Control Apex referral laboratory for arboviruses were employed for the study. The currently circulating genotypes of DENV-1 identified from the study area belonged to genotypes V and I. Multicentric laboratory-based studies analysing the envelope gene of all dengue serotypes are required from endemic countries like India.
10.

A case of imported dengue fever from Burkina Faso to Japan in October 2016.

Jpn J Infect Dis; 2017 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-28890518

Resumo

Dengue fever remains underreported in Africa due to lack of awareness among healthcare providers, the presence of other febrile illnesses, and insufficient laboratory testing. We present a case of imported dengue fever from Burkina Faso to Japan, where an outbreak of dengue was reported on October 18, 2016. The phylogenetic analysis revealed that the isolate from our patient belonged to a distinct of sylvatic dengue viruses, suggesting that dengue viruses have been maintained in the mosquitoes and human cycles in Burkina Faso for more than 30 years.
11.

Clinical application of modified bag-of-features coupled with hybrid neural-based classifier in dengue fever classification using gene expression data.

Med Biol Eng Comput; 2017 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-28891000

Resumo

Dengue fever detection and classification have a vital role due to the recent outbreaks of different kinds of dengue fever. Recently, the advancement in the microarray technology can be employed for such classification process. Several studies have established that the gene selection phase takes a significant role in the classifier performance. Subsequently, the current study focused on detecting two different variations, namely, dengue fever (DF) and dengue hemorrhagic fever (DHF). A modified bag-of-features method has been proposed to select the most promising genes in the classification process. Afterward, a modified cuckoo search optimization algorithm has been engaged to support the artificial neural (ANN-MCS) to classify the unknown subjects into three different classes namely, DF, DHF, and another class containing convalescent and normal cases. The proposed method has been compared with other three well-known classifiers, namely, multilayer perceptron feed-forward network (MLP-FFN), artificial neural network (ANN) trained with cuckoo search (ANN-CS), and ANN trained with PSO (ANN-PSO). Experiments have been carried out with different number of clusters for the initial bag-of-features-based feature selection phase. After obtaining the reduced dataset, the hybrid ANN-MCS model has been employed for the classification process. The results have been compared in terms of the confusion matrix-based performance measuring metrics. The experimental results indicated a highly statistically significant improvement with the proposed classifier over the traditional ANN-CS model.
12.

Effectiveness and economic assessment of routine larviciding for prevention of chikungunya and dengue in temperate urban settings in Europe.

PLoS Negl Trop Dis; 11(9): e0005918, 2017 Sep 11.
Artigo em Inglês | MEDLINE | ID: mdl-28892499

Resumo

In the last decades, several European countries where arboviral infections are not endemic have faced outbreaks of diseases such as chikungunya and dengue, initially introduced by infectious travellers from tropical endemic areas and then spread locally via mosquito bites. To keep in check the epidemiological risk, interventions targeted to control vector abundance can be implemented by local authorities. We assessed the epidemiological effectiveness and economic costs and benefits of routine larviciding in European towns with temperate climate, using a mathematical model of Aedes albopictus populations and viral transmission, calibrated on entomological surveillance data collected from ten municipalities in Northern Italy during 2014 and 2015.We found that routine larviciding of public catch basins can limit both the risk of autochthonous transmission and the size of potential epidemics. Ideal larvicide interventions should be timed in such a way to cover the month of July. Optimally timed larviciding can reduce locally transmitted cases of chikungunya by 20% - 33% for a single application (dengue: 18-22%) and up to 43% - 65% if treatment is repeated four times throughout the season (dengue: 31-51%). In larger municipalities (>35,000 inhabitants), the cost of comprehensive larviciding over the whole urban area overcomes potential health benefits related to preventing cases of disease, suggesting the adoption of more localized interventions. Small/medium sized towns with high mosquito abundance will likely have a positive cost-benefit balance. Involvement of private citizens in routine larviciding activities further reduces transmission risks but with disproportionate costs of intervention. International travels and the incidence of mosquito-borne diseases are increasing worldwide, exposing a growing number of European citizens to higher risks of potential outbreaks. Results from this study may support the planning and timing of interventions aimed to reduce the probability of autochthonous transmission as well as the nuisance for local populations living in temperate areas of Europe.
14.

Prior Exposure to Zika Virus Significantly Enhances Peak Dengue-2 Viremia in Rhesus Macaques.

Sci Rep; 7(1): 10498, 2017 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-28874759

Resumo

Structural and functional homologies between the Zika and Dengue viruses' envelope proteins raise the possibility that cross-reactive antibodies induced following Zika virus infection might enhance subsequent Dengue infection. Using the rhesus macaque model we show that prior infection with Zika virus leads to a significant enhancement of Dengue-2 viremia that is accompanied by neutropenia, lympocytosis, hyperglycemia, and higher reticulocyte counts, along with the activation of pro-inflammatory monocyte subsets and release of inflammatory mediators. Zika virus infection induced detectable Dengue cross-reactive serum IgG responses that significantly amplified after Dengue-2 virus infection. Serum from Zika virus immune animals collected prior to Dengue-2 infection showed significant capacity for in vitro antibody dependent enhancement of Dengue-1, 2, 3 and 4 serotypes suggesting that pre-existing immunity to Zika virus could potentially enhance infection by heterologous Dengue serotypes. Our results provide first in vivo evidence that prior exposure to Zika virus infection can enhance Dengue infection, which has implications for understanding pathogenesis and the development of vaccines.
15.

The Clinical and Serological Profile of Pediatric Dengue.

Indian J Pediatr; 2017 Sep 08.
Artigo em Inglês | MEDLINE | ID: mdl-28887788

Resumo

OBJECTIVE: To classify suspected dengue into dengue, dengue with warning signs and severe dengue, based on clinical features as per the revised WHO guidelines with special emphasis on serology. METHODS: It was a prospective cross-sectional study for five years from 2011-2016 in a tertiary care medical college hospital in Bangalore. All cases of fever of three to five days duration with symptoms like dengue were enrolled for the study. They were categorized into three groups as per the Revised WHO 2012 criteria. Laboratory parameters, serology, ultrasound abdomen and X-ray were done in almost all patients. Data was analysed by SPSS software, version 16, and different groups were compared with Chi square test. RESULTS: Five hundred sixty eight children were diagnosed to have dengue fever; 4.2% of the sample belonged to infancy. Majority were in the age group of 5-10 y (42.6%). Fever and flushing were present in majority of the children. Gastrointestinal bleed was more commonly seen in the severe dengue group. Dengue nonstructural protein antigen (NS1Ag) was positive in 78%, immunoglobulin M (IgM) in 15.8% and immunoglobulin G (IgG) in 14.6%. Children with IgG had more complications, though not statistically significant. Mortality was reported in 1.2%. Dengue serology helped to confirm the diagnosis, however did not help in patient management. CONCLUSIONS: There is a considerable overlap in the symptomatology of dengue with warning signs and severe dengue. More studies are required on the severity and type of response to treatment in infants and obese adoloscents with severe dengue.
16.

Perforated gastric ulcer in severe dengue infection: A case report.

Med J Malaysia; 72(4): 244-245, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28889137

Resumo

Abdominal pain is one of the common presentations in severe dengue infection. We report a rare case of perforated gastric ulcer in a young man diagnosed with severe dengue infection and the challenges we faced in managing this patient. Perforated gastric ulcer need to be considered if there are signs of peritonitis and persistent abdominal pain that does not conform to the natural history of dengue. Proper imaging and early surgical intervention in perforated gastric ulcer is vital in preventing further complication and reducing the risk of mortality.
17.

Dengue shock syndrome with retroperitoneal haematoma requiring repeated artery angioembolization.

Med J Malaysia; 72(4): 254-256, 2017 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-28889142

Resumo

Eyelid reconstruction is complex and challenging since it is not only for structural and functional restoration, but also for an acceptable aesthetic result. In full thickness eyelid injuries, it will involve both anterior and posterior lamella. Therefore, when reconstructing the defect, it requires at least two layers; one will be a flap with blood supply, and the other can be a free graft. In this case, a rotational advancement cheek flap and composite graft were used to reconstruct the lower eyelid.
18.

Abundance and distribution of sylvatic dengue virus vectors in three different land cover types in Sarawak, Malaysian Borneo.

Parasit Vectors; 10(1): 406, 2017 Aug 31.
Artigo em Inglês | MEDLINE | ID: mdl-28859676

Resumo

BACKGROUND: Mosquito-borne dengue virus (DENV) is maintained in a sylvatic, enzootic cycle of transmission between canopy-dwelling non-human primates and Aedes mosquitoes in Borneo. Sylvatic DENV can spill over into humans living in proximity to forest foci of transmission, in some cases resulting in severe dengue disease. The most likely vectors of such spillover (bridge vectors) in Borneo are Ae. albopictus and Ae. niveus. Borneo is currently experiencing extensive forest clearance. To gauge the effect of this change in forest cover on the likelihood of sylvatic DENV spillover, it is first necessary to characterize the distribution of bridge vectors in different land cover types. In the current study, we hypothesized that Ae. niveus and Ae. albopictus would show significantly different distributions in different land cover types; specifically, we predicted that Ae. niveus would be most abundant in forests whereas Ae. albopictus would have a more even distribution in the landscape. RESULTS: Mosquitoes were collected from a total of 15 sites using gravid traps and a backpack aspirator around Kampong Puruh Karu, Sarawak, Malaysian Borneo, where sylvatic DENV spillover has been documented. A total of 2447 mosquitoes comprising 10 genera and 4 species of Aedes, were collected over the three years, 2013, 2014 and 2016, in the three major land cover types in the area, homestead, agriculture and forest. Mosquitoes were identified morphologically, pooled by species and gender, homogenized, and subject to DNA barcoding of each Aedes species and to arbovirus screening. As predicted, Ae. niveus was found almost exclusively in forests whereas Ae. albopictus was collected in all land cover types. Aedes albopictus was significantly (P = 0.04) more abundant in agricultural fields than forests. Sylvatic DENV was not detected in any Aedes mosquito pools, however genomes of 14 viruses were detected using next generation sequencing. CONCLUSIONS: Land cover type affects the abundance and distribution of the most likely bridge vectors of sylvatic DENV in Malaysia Borneo. Conversion of forests to agriculture will likely decrease the range and abundance of Ae. niveus but enhance the abundance of Ae. albopictus.
19.

Characterization of Dengue Virus Infections Among Febrile Children Clinically Diagnosed With a Non-Dengue Illness, Managua, Nicaragua.

J Infect Dis; 215(12): 1816-1823, 2017 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-28863466

Resumo

Background: We sought to characterize dengue virus (DENV) infections among febrile children enrolled in a pediatric cohort study who were clinically diagnosed with a non-dengue illness ("C cases"). Methods: DENV infections were detected and viral load quantitated by real-time reverse transcription-polymerase chain reaction in C cases presenting between January 2007 and January 2013. Results: One hundred forty-one of 2892 C cases (4.88%) tested positive for DENV. Of all febrile cases in the study, DENV-positive C cases accounted for an estimated 52.0% of patients with DENV viremia at presentation. Compared with previously detected, symptomatic dengue cases, DENV-positive C cases were significantly less likely to develop long-lasting humoral immune responses to DENV, as measured in healthy annual serum samples (79.7% vs 47.8%; P < .001). Humoral immunity was associated with viral load at presentation: 40 of 43 patients (93.0%) with a viral load ≥7.0 log10 copies/mL serum developed the expected rise in anti-DENV antibodies in annual samples versus 13 of 68 (19.1%) patients with a viral load below this level (P < .001). Conclusions: Antibody responses to DENV-positive C cases differ from responses to classic symptomatic dengue. These findings have important implications for DENV transmission modeling, immunology, and epidemiologic surveillance.
20.

Potent Plasmablast-Derived Antibodies Elicited by the NIH Dengue Vaccine.

J Virol; 2017 Sep 06.
Artigo em Inglês | MEDLINE | ID: mdl-28878078

Resumo

Exposure to dengue virus (DENV) is thought to elicit lifelong immunity, mediated by DENV-neutralizing antibodies (nAbs). However, Abs generated by primary infections confer serotype-specific protection, and immunity against other serotypes only develops after subsequent infections. Accordingly, the induction of these nAb responses acquired after serial DENV infections has been a long sought-after goal for vaccination. Nonetheless, it is still unclear if tetravalent vaccines can elicit or recall nAbs. Here, we have characterized the responses from a volunteer who had been previously exposed to DENV and was immunized with the live attenuated tetravalent vaccine Butantan-DV, developed by the NIH and Butantan. Eleven days after vaccination, we observed a ∼70-fold expansion of the plasmablast population. We generated 21 monoclonal (m)Abs from singly-sorted plasmablasts. These mAbs were the result of clonal expansions and had significant levels of somatic hypermutation (SHM). Nineteen mAbs (90.5%) neutralized at least one DENV serotype at concentrations of 1 µg/ml or less; six of the 21 mAbs neutralized three or more serotypes. Despite the tetravalent composition of the vaccine, we observed a neutralization bias in the induced repertoire: DENV3 was targeted by 18 of the 19 neutralizing (n)mAbs. Furthermore, the P3D05 nmAb neutralized DENV3 with extraordinary potency (Neut 0.03 µg/ml). Thus, the Butantan-DV vaccine engendered a mature, antigen-selected B cell repertoire. Our results suggest that pre-existing responses elicited by a previous DENV3 infection were recalled by immunization. The dengue epidemic presents a global public health challenge that causes widespread economic burden and remains largely unchecked by existing control strategies. Successful control of the dengue epidemic will require effective prophylactic and therapeutic interventions. Several vaccine clinical efficacy trials are approaching completion, and the chances that one or more live attenuated tetravalent vaccines (LATVs) will be introduced worldwide is higher than ever. While it is widely accepted that dengue virus (DENV)-neutralizing antibody (nAb) titers are associated with protection, the Ab repertoire induced by LATVs remain uncharacterized. Here, we describe the isolation of potent (Neut < 0.1 µg/ml) nAbs from a DENV-seropositive volunteer immunized with the tetravalent vaccine Butantan-DV, which is currently in Phase III trials.
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