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At least 1,207 records · Page 67Linked to original sources
PubMed2004

Dengue virus surveillance: the co-circulation of DENV-1, DENV-2 and DENV-3 in the State of Rio de Janeiro, Brazil.

This study presents the results obtained in the monitoring of dengue virus (DENV) transmission in the Greater Metropolitan Region of the State of Rio de Janeiro, in the period 2000-2001. A total of 5324 serum samples from suspected cases of dengue were analysed in order to confirm dengue infection. The introduction of DENV-3 to the region in December 2000 resulted in the co-circulation of three serotypes: DENV-1, DENV-2 and DENV-3. In this study, virus isolation and/or reverse transcriptase PCR (RT-PCR) confirmed 52.3% (42/79) of DENV-3 cases, showing the importance of acute serum samples in the virological surveillance of the disease. Despite the introduction of a new serotype, an outbreak due to DENV-1 was observed in the municipality of Niteroi. The restriction site-specific PCR (RSS-PCR) patterns obtained for DENV-1 and DENV-2 isolated in that period showed that those strains belonged to the subtypes previously circulating in the state. DENV-3 RSS-PCR patterns confirmed that these viruses belonged to subtype C (Sri Lanka/India strains), represented by the strain circulating on the American continent. These data showed the importance of an active surveillance programme in countries where dengue is endemic.

Adolescent↗
PubMed2005

Immunogenicity and safety of two live-attenuated tetravalent dengue vaccine formulations in healthy Australian adults.

We conducted a Phase 1b study to evaluate the immunogenicity and safety of two live attenuated tetravalent dengue vaccines in healthy adult volunteers. After one injection, all subjects reported systemic reactions consistent with a mild dengue-like syndrome. Seven volunteers developed dengue 3 viraemia after vaccination. All subjects developed a neutralizing antibody response against serotype 3 with partial response against other serotypes. The trial was stopped early (after 10 subjects enrolled) due to formulation issues, which were related to the dengue 3 vaccine component. Managing viral interference and balancing attenuation to produce acceptable tetravalent immunogenicity with minimal reactogenicity may be a recurring problem for future multivalent live vaccines.

Adult↗
PubMed2004

Sustained transmission of dengue virus type 1 in the Pacific due to repeated introductions of different Asian strains.

Outbreaks of dengue due to dengue virus type 1 (DENV-1) occurred almost simultaneously in 2001 in Myanmar and at multiple sites almost 10,000 km away in the Pacific. Phylogenetic analyses of the E protein genes of DENV-1 strains recovered from Asia and the Pacific revealed three major viral genotypes (I, II, and III) with distinct clades within each. The majority of strains from the Pacific and Myanmar, and a number of other Asian strains fell into genotype I. Genotype II comprised a smaller set of Asian and Pacific strains, while genotype III contained viruses from diverse geographical localities. These analyses suggested that the continuing outbreak of dengue in the Pacific has been due to multiple, direct, introductions of dengue viruses from a variety of locations in Asia followed by local transmission. There was no evidence that the introduction of these viruses into the Pacific was associated with any adaptive changes in the E protein of the viruses.

Animals↗
PubMed1999

Diagnosis of dengue infection by detecting specific immunoglobulin M antibodies in saliva samples.

To investigate whether saliva could be used for diagnosis of recent dengue, serum and saliva samples were collected simultaneously from patients with suspected dengue infection. Sera (1:10 dilution) and saliva (undiluted) were tested by using an IgM capture enzyme linked immunosorbent assay (MAC-ELISA) with minor modifications (serum and saliva absorption for 3 h at 37 degrees C). The quality of saliva was evaluated by determining the IgG total concentration (enzyme immunoassay) which ranged from 2.7 to > 50 mg/l. Recent dengue infection was confirmed in 38 cases. Forty-six serum and saliva specimens were collected from these patients 1-30 days after the onset of symptoms. IgM was detected in 65.8% saliva samples. High rate of positivity ( > 80%) was observed for the saliva samples collected > or = 5 days after the onset of the disease. Fifty serum and saliva samples from other 32 patients with rash diseases were also tested and all the specimens were unreactive by MAC-ELISA. These results indicate that saliva may be a convenient non-invasive alternative to serum for diagnosis of recent dengue fever infection, especially for epidemiological studies during outbreaks of the disease.

Adolescent↗
PubMed2000

Evaluation of ELISA-based sero-diagnosis of dengue fever in travelers.

Diagnosis of dengue virus infection in travelers is often based on commercially available ELISA-based serological assays and not on the more difficult and costly procedures of Hemagglutination inhibition (HI), virus isolation or RT-PCR. These standard assays are not quantitative and are designed to diagnose primary and secondary dengue virus infections by testing for IgG and IgM antibodies. However, cross reactivity between various flaviviruses and the fact that most travelers today are prevaccinated against Japanese encelphalitis (JE) and yellow fever (YF) create a potential problem in such diagnosis. Our study was aimed at measuring the extent of false positive diagnosis in prevaccinated travelers which we have assessed by testing for dengue IgG and IgM antibodies in a group of prevaccinated healthy travelers using the PanBio indirect IgG ELISA and IgM capture ELISA kits. The IgM test was negative in all healthy vaccinees, thus, being highly specific. However, the kit had a disadvantage, which was recognized in other travelers clinically ill with dengue fever (DF), in which the IgM response was detected only 4-8 days after onset of the clinical symptoms. The IgG test yielded 11-17 and 15-44% positives in healthy travelers vaccinated against JE and YF, respectively. We conclude that the specificity of the IgG-ELISA assay in prevaccinated travelers is much lower than in unvaccinated populations. Thus, an IgG-positive results in a vaccinated traveler and IgM negative result during the 1st week of the illness period, are both inconclusive.

Adult↗
PubMed2002

Virus isolation as one of the diagnostic methods for dengue virus infection.

Virus isolation is the most reliable evidence of infection. In the present study, we isolated virus from serum samples collected from confirmed dengue cases. When data were analyzed based on disease days, dengue viruses were isolated from 28 of 32 serum samples collected on disease day 5 or earlier. When analyzed based on fever days, dengue viruses were isolated from all the serum samples collected on fever day -3 or earlier, and from 10 of 13 samples collected on fever days -2 and -1. Viruses were isolated from one each of the serum samples collected on fever days 0, 1, 2 and 3, respectively. Virus was not, however, isolated from those collected on fever day 4 or later. The results of virus isolation and reverse transcriptase-polymerase chain reaction were consistent in 78 of 82 serum samples. These results suggest that virus isolation is a useful and sensitive technique for confirmation of dengue virus infection, especially when serum samples are collected before fever subsides.

Adolescent↗
PubMed2000

Surveillance of dengue fever in French Guiana by monitoring the results of negative malaria diagnoses.

Surveillance of dengue fever is mainly based on specific laboratory tests. However non-specific systems, such as clinical surveillance, are also required. In French Guiana, we have tested a non-specific laboratory surveillance system where different biological examinations performed for other reasons than the diagnosis of dengue fever were analysed as methods for dengue fever surveillance. The number of negative malaria diagnoses in Cayenne and Kourou was found to be the best indicator of dengue fever infections in these towns. This surveillance system appears to be very simple and reliable, and a test which could serve as an indicator that is likely to be found everywhere.

Dengue↗
PubMed1997

Sequences of terminal non-coding regions from four dengue-2 viruses isolated from patients exhibiting different disease severities.

We have determined the 5' and 3' non-coding regions (NCR) of four dengue-2 viruses isolated from dengue patients with different clinical severities in Nakhon Phanom, Northeastern Thailand in 1993. The results were compared to prototype dengue-2 strains and were found to have highest homology with the New Guinea C strain. The sequence of the 5' NCR was completely conserved among all 4 isolates and were identical to the sequence of the New Guinea C strain. Homology of the 3' NCR sequence of the four isolates with the prototype strain ranged from 97.3 to 97.8%. Isolate ThNH-p11/93 from a mild dengue fever case showed the highest divergence from the prototype strain and the rest of the isolates from severe hemorrhagic cases, (1.11%). This includes a change in triad 297-299 nucleotides from the 3' terminus. Computer predicted secondary structures showed that isolate ThNHp-11/93 had significant structural differences from the other three isolates at this region.

Base Sequence↗
PubMed1998

An epidemic of dengue haemorrhagic fever/dengue shock syndrome in tropical India.

An epidemic of dengue haemorrhagic fever/dengue shock syndrome occurred in Chennai, South India in 1989 during and following the rainy season. Sixty-nine infants and children admitted to the Institute of Child Health and Hospital for Children with a brief febrile illness associated with skin and mucous membrane bleeds and/or shock were studied. Forty-nine had antibodies to dengue viruses. The specific serotype of the virus responsible could not be identified owing to cross-reacting antibodies. Primary infection occurred in 11 cases, secondary infection in 17 cases, antibodily titres were indicative of 'probable' dengue infection in 16 and were uninterpretable in five. In 11 cases, serology could not be done. The pattern of disease in these 60 cases was similar, with a high mortality. Haemoconcentration was not a feature in the majority and the Hess test was negative in all those tested. Nine cases with a similar but milder illness tested negative for dengue.

Blood Transfusion↗
PubMed2003

DC-SIGN (CD209) mediates dengue virus infection of human dendritic cells.

Dengue virus is a single-stranded, enveloped RNA virus that productively infects human dendritic cells (DCs) primarily at the immature stage of their differentiation. We now find that all four serotypes of dengue use DC-SIGN (CD209), a C-type lectin, to infect dendritic cells. THP-1 cells become susceptible to dengue infection after transfection of DC-specific ICAM-3 grabbing nonintegrin (DC-SIGN), or its homologue L-SIGN, whereas the infection of dendritic cells is blocked by anti-DC-SIGN antibodies and not by antibodies to other molecules on these cells. Viruses produced by dendritic cells are infectious for DC-SIGN- and L-SIGN-bearing THP-1 cells and other permissive cell lines. Therefore, DC-SIGN may be considered as a new target for designing therapies that block dengue infection.

Antibodies, Monoclonal↗
PubMed1999

Early CD69 expression on peripheral blood lymphocytes from children with dengue hemorrhagic fever.

Recent reports have demonstrated immune activation in dengue hemorrhagic fever (DHF) by cytokine and soluble receptor detection in blood. The goal of this study was to determine which cell types are activated and likely to be responsible for cytokine production. Whole blood specimens from 51 Thai children presenting within 72 h of fever onset and with detectable plasma dengue viral RNA were studied by flow cytometry. Absolute CD4 T cell, CD8 T cell, NK cell, and gammadelta T cell counts were decreased in children with DHF compared with those with dengue fever (DF) early in the course of illness. The percent of cells expressing CD69 was increased on CD8 T cells and NK cells in children who developed DHF more than in those with DF. These data directly demonstrate that cellular immune activation is present early in acute dengue and is related to disease severity.

Antigens, CD↗
PubMed2002

Epidemiology and clinical features of imported dengue fever in Europe: sentinel surveillance data from TropNetEurop.

Travelers have the potential both to acquire and to spread dengue virus infection. The incidence of dengue fever (DF) among European travelers certainly is underestimated, because few centers use standardized diagnostic procedures for febrile patients. In addition, DF is currently not reported in most European public health systems. Surveillance has commenced within the framework of a European Network on Imported Infectious Disease Surveillance (TropNetEurop) to gain information on the quantity and severity of cases of dengue imported into Europe. Descriptions of 294 patients with DF were analyzed for epidemiological information and clinical features. By far the most infections were imported from Asia, which suggests a high risk of DF for travelers to that region. Dengue hemorrhagic fever occurred in 7 patients (2.4%) all of whom recovered. Data reported by member sites of the TropNetEurop can contribute to understanding the epidemiology and clinical characteristics of imported DF.

Adolescent↗
PubMed2004

Transmission of dengue virus without a mosquito vector: nosocomial mucocutaneous transmission and other routes of transmission.

We report a case of dengue fever in a Boston-area health care worker with no recent history of travel but with mucocutaneous exposure to infected blood from a febrile traveler who had recently returned from Peru. Serologic tests confirmed acute dengue virus infection in both the traveler and the health care worker. We believe that this is the first documented case of dengue virus transmission via the mucocutaneous route. We present case reports and review other ways that dengue virus has been transmitted without a mosquito vector.

Accidents, Occupational↗
PubMed1999

Effects of dengue fever during pregnancy in French Guiana.

To determine the effects of dengue fever (DF) during pregnancy, pregnant women presenting with a dengue-like syndrome at a hospital in Saint-Laurent du Maroni, French Guiana, from 1 January 1992 to 1 April 1998 were studied. The diagnosis of DF was made by serological tests, virus isolation on AP 61 mosquito cells, and/or reverse transcriptase polymerase chain reaction analysis. Twenty-two women had either probable or confirmed DF. Dengue virus serotype 2 was detected in four cases, and dengue virus serotype 1 was detected in one. Three fetuses died following the onset of the disease, and three cases of prematurity occurred. All infants appeared normal during physical examination, and no neonatal DF was diagnosed. In conclusion, DF in pregnant women did not cause any infant abnormality, but it may have been responsible for fetal death. The rate of fetal death associated with DF (13.6%) was much higher than the mean rate for the gynecology unit at the hospital (1.9%). However, these differences were not significant, and consequently these preliminary results need to be confirmed.

Dengue↗
PubMed2001

The heterogeneous nuclear ribonucleoprotein K (hnRNP K) interacts with dengue virus core protein.

Heterogeneous nuclear ribonucleoprotein K (hnRNP K), a component of hnRNP particles, is involved in several steps of gene expression regulation. Dengue (DEN) virus, a member of the Flaviviridae, is the primary cause of illnesses such as dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. In mature DEN virus particles, the core protein is a structural protein that forms a nucleocapsid complex with genomic RNA. Very little of its biologic functions is known. Here, using an in vitro binding assay and coimmunoprecipitation analysis, we report a protein-protein interaction between the DEN virus core protein and hnRNP K. The C-terminal hydrophilic region of the DEN virus core protein, spanning amino acid residues 73 to 100, is required for such interaction. Results of glutathione-S transferase binding assays indicated that the core protein-hnRNP K interaction might be abolished in the presence of hnRNP K cognate nucleic acids. Furthermore, in a cotransfection experiment, the repressive effect of hnRNP K on C/EBPbeta-mediated transcription activation could be reversed by full-length DEN virus core protein but not by a truncated form containing amino acids 1-72. Our results suggest that, on DEN virus infection, the multiple functions of cellular hnRNP K may be affected by the virus core protein.

Amino Acid Sequence↗
PubMed2005

Infectivity of West Nile/dengue chimeric viruses for West Nile and dengue mosquito vectors.

West Nile virus (WN), an agent of significant human and veterinary disease, is endemic in the Old World and rapidly spreading throughout the Americas. Vaccines are needed to halt the geographic expansion of this virus and prevent disease where it is established. However, to preclude introduction of a vaccine virus into the environment, a live attenuated WN vaccine should have low potential for transmission by mosquitoes. A chimeric WN vaccine candidate was previously generated by replacing the membrane and envelope structural protein genes of recombinant dengue type 4 virus (rDEN4) with those of WN; a derivative of this virus, WN/DEN4-3'delta30, contains a 30-nucleotide deletion in the 3' untranslated region. To assess the potential for transmission by mosquitoes of these vaccine candidates, the ability of each chimeric virus to infect the mosquito midgut, disseminate to the head, and pass into the saliva was compared to that of their wild-type parental WN and DEN4 viruses in three vector species. The WN/DEN4 chimeric viruses were significantly attenuated in both Culex tarsalis, a vector able to transmit WN but not dengue, and in Ae. aegypti, a vector able to transmit dengue but not WN. However, the chimeric viruses were as infectious as either wild-type virus for Ae. albopictus, a vector able to transmit both dengue and WN. These results indicate that chimerization caused a contraction in vector host range rather than universal attenuation for mosquitoes per se. This restriction in potential vectors renders it less likely that WN/DEN4 and WN/DEN4-3'delta30 would be transmitted from vaccinees to mosquitoes.

Aedes↗
PubMed2005

DNA priming E and NS1 constructs--homologous proteins boosting immunization strategy to improve immune response against dengue in mice.

DNA priming-protein boosting is a strategy used to establish strong immunity to a specific pathogen by the use of two different antigens through sequential delivery systems. In this work, two recombinant plasmids were used, one encoding for the dengue virus E protein, which is know to induce neutralizing antibodies (pcDNA 3.1/E), and the other encoding for the Dengue virus nonstructural protein 1 (pcDNA 3.1/NS1), as a source of B- and T-cell epitopes possibly involved in protective immunity. We showed that immunization of BALB/c mice with three priming doses of both plasmids pcDNA 3.1/E and/or pcDNA 3.1/NS1 were able to induce antibody responses to E protein with a single plasmid; in contrast to the antibody response to NS1 protein we observed an additive effect in terms of antibody response. Moreover, using a prime-boost protocol in which both plasmid constructs were co-administrated followed by a boost of homologous GST-E and GST-NS1 recombinant proteins, we observed an increased antibody response to NS1 and to E protein compared to animals vaccinated with the proteins or with dengue constructs alone. If neutralizing antibodies play an important role in dengue infection, antibodies generated with this regimen was also significantly better than the administration of the mix of proteins alone. These results suggest that NS1 and E proteins together could be considered in a design of subunit recombinant vaccines.

Animals↗
PubMed1988

Dengue epidemics on the Pacific Coast of Mexico.

Dengue epidemics in three Mexican cities were investigated with retrospective surveys and virus isolations from acute cases. These epidemics were part of the continuing extension of dengue in Mexico since 1978 after 15 years without transmission. Serotype 1 dengue infection predominated in all epidemics, but in one city, type 2 strains were also isolated. The following findings were consistent in all three cities: 1) illness history provided evidence of presence of infection months before the epidemic became evident, 2) there was a very sharp and progressive increase of dengue illness attack rates by age, 3) there were no interpretable relationships between illness and the presence of different types of breeding sights in the home, 4) socioeconomic status was strongly negatively related to illness, and 5) geographical factors not related to the other measured variables had a strong effect on illness rates reflecting the focality of transmission. In addition, there was evidence of a strong protective effect against illness by the use of mosquito netting or the presence of screens on houses, but these relationships were not universal to all three cities.

Adolescent↗