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PubMed2000

Silent spread of dengue and dengue haemorrhagic fever to Coimbatore and Erode districts in Tamil Nadu, India, 1998: need for effective surveillance to monitor and control the disease.

Dengue fever (DF) or dengue haemorrhagic fever (DHF) has not previously been reported in Coimbatore and Erode districts in Tamil Nadu in India. In 1998, 20 hospitalized cases of fever tested positive for dengue virus IgM and/or IgG antibodies. All of them had dengue-compatible illness, and at least four had DHF. Two of them died. Sixteen cases were below 10 years of age. The cases were scattered in 15 distantly located villages and 5 urban localities that had a high Aedes aegypti population. Although the incidence of dengue-like illness has not increased recently, almost 89% (95/107) of samples from healthy persons in the community tested positive for dengue IgG antibodies. The study showed that dengue has been endemic in the area, but was not suspected earlier. A strong laboratory-based surveillance system is essential to monitor and control DF/DHF.

Adolescent↗
PubMed2006

Immunopathological mechanisms in dengue and dengue hemorrhagic fever.

PURPOSE OF REVIEW: The continued emergence of dengue virus infection and its severe disease manifestation, dengue hemorrhagic fever, is a growing public health problem. The majority of severe infections occur upon secondary encounters with heterologous dengue virus serotypes, suggesting an immune-mediated process. RECENT FINDINGS: Significant findings in the past year include a greater understanding of dengue virus interactions with target cells such as dendritic cells, hepatocytes and endothelial cells. Infection of these cells results in the production of immune mediators that then shape the adaptive humoral and cellular immune response. The circulation of high levels of secreted NS1 in the presence of pre-existing heterologous non-neutralizing antibody may mediate complement activation and trigger plasma leakage. The role of enhancing antibodies in disease pathogenesis remains unclear. Recent studies demonstrate low avidity crossreactive T cells, which may produce an altered profile of cytokines leading to plasma leakage. Ongoing prospective studies that include epidemiological, virological and immunological risk factors are crucial to our understanding of the mechanisms of immunopathogenesis of dengue hemorrhagic fever. SUMMARY: The immune mechanisms that lead to dengue hemorrhagic fever are complex and need to be elucidated further for the development of therapeutics as well as safe and efficacious dengue vaccines.

Antibodies, Viral↗
PubMed2002

Epidemiology of dengue in Sri Lanka before and after the emergence of epidemic dengue hemorrhagic fever.

Before 1989, dengue epidemiology in Sri Lanka was characterized by frequent transmission of all four dengue serotypes but a low incidence of dengue hemorrhagic fever (DHF). After 1989, cases of DHF dramatically increased. Here we present the results of epidemiologic studies conducted in Colombo, Sri Lanka before and after epidemic emergence of DHF in 1989. We compared the proportion of dengue cases among people with fever attending clinics from 1980 to 1984 and in 1997 and 1998 to determine if an increase in dengue transmission was associated with more DHF cases being reported. We also compared the relative distribution of dengue virus serotypes circulating in Colombo before and after the emergence of DHF. We detected no significant differences in dengue as a proportion of fever cases or in serotype distribution between the pre and post-DHF periods. We conclude that an increase in virus transmission or a change in circulating serotypes does not explain the epidemic emergence of DHF in Sri Lanka.

Antibodies, Viral↗
PubMedDate not supplied

Comparison of immunoglobulin G enzyme-linked immunosorbent assay (IgG-ELISA) and haemagglutination inhibition (HI) test for the detection of dengue antibodies. Prevalence of dengue IgG-ELISA antibodies in Tahiti.

An immunoglobulin G enzyme-linked immunosorbent assay (IgG-ELISA) for the detection of dengue antibodies is described and compared to the haemagglutination inhibition test (HI). The sensitivity, specificity and agreement rate between the 2 techniques were good. The coefficients of correlation between IgG-ELISA and HI results, using dengue 1-4 antigens, were highly significant (P less than 0.001 for either antigen). IgG-ELISA was rapid, and easy to perform and suitable for large-scale studies. Between April and June 1987, a baseline serosurvey of the prevalence of dengue antibodies in age-stratified samples of children was carried out in Tahiti using IgG-ELISA. 327 children were tested against each dengue serotype. There was no significant difference between sex. Overall rates ranged from 7.4% in children under 5 years to 83.1% in those aged 15-19 years. Dengue 4 being the only serotype involved since 1979, specific responses to dengue 4 were found in higher proportion among children under 8 years old, while the IgG-ELISA responses were more widely reactive among children aged above 8 years (P less than 0.001). The acquisition rate of dengue 4 antibodies was 2.95% on average per year in children under 8 years of age.

Age Factors↗
PubMed2006

Dengue fever with papilledema: a case of dengue-3 virus infection in central nervous system.

BACKGROUND AND OBJECTIVES: Neurological manifestations of dengue fever are rarely reported during acute illness and clinical presentation commonly observed is of acute encephalitis or one of the post-infectious immune mediated manifestations. We describe a case of dengue fever having mild encephalopathy and papilledema at presentation. CASE REPORT: Twenty-year-old female presented with fever, headache and vomiting. On examination she did not have classical signs of dengue fever and was found to have bilateral papilledema on fundus examination. Detailed work-up did not reveal any other cause of papilledema. Diagnosis of dengue fever was established by blood IgM antibody test on day 7 of illness. Retrospective analysis of CSF (drawn on day 5 of illness) by RT-PCR assay showed a characteristic band of dengue-3 virus. Papilledema was transient and subsided following symptomatic treatment. The patient recovered from acute illness and follow-up was unremarkable. CONCLUSION: Especially in dengue endemic areas, in the patients having acute febrile illness with subtle signs and symptoms suggestive of CNS involvement, dengue virus infection should also be ruled out early in the clinical course.

Adult↗
PubMed2005

Tetravalent neutralizing antibody response against four dengue serotypes by a single chimeric dengue envelope antigen.

We employed DNA shuffling and screening technologies to develop a single recombinant dengue envelope (E) antigen capable of inducing neutralizing antibodies against all four antigenically distinct dengue serotypes. By DNA shuffling of codon-optimized dengue 1-4 E genes, we created a panel of novel chimeric clones expressing C-terminal truncated E antigens that combined epitopes from all four dengue serotypes. DNA vaccines encoding these novel chimeras induced multivalent T cell and neutralizing antibody responses against all four dengue serotypes in mice. By contrast, a mixture of four unshuffled, parental DNA vaccines failed to produce tetravalent neutralizing antibodies in mice. The neutralizing antibody titers for some of these antigens could be further improved by extending the sequences to express full-length pre-membrane and envelope proteins. The chimeric antigens also protected mice against a lethal dengue-2 virus challenge. These data demonstrate that DNA shuffling and associated screening can lead to the selection of multi-epitope antigens against closely related dengue virus serotypes and suggest a broad utility for these technologies in optimizing vaccine antigens.

Animals↗
PubMed2000

Immunization of rhesus monkeys with a recombinant of modified vaccinia virus Ankara expressing a truncated envelope glycoprotein of dengue type 2 virus induced resistance to dengue type 2 virus challenge.

Dengue epidemics increasingly pose a public health problem in most countries of the tropical and subtropical areas. Despite decades of research, development of a safe and effective live dengue virus vaccine is still at the experimental stage. To explore an alternative vaccine strategy, we employed the highly attenuated, replication-deficient modified vaccinia Ankara (MVA) as a vector to construct recombinants for expression of the major envelope glycoprotein of one or more dengue virus serotypes. MVA recombinants expressing the highly immunogenic C-terminally truncated dengue type 2 virus (DEN2) or dengue type 4 virus (DEN4) envelope protein (E), approx. 80% of the full-length, were evaluated for their protective immunity in animal models. Each of these recombinants elicited an elevated antibody response to DEN2 or DEN4 E in mice following the booster inoculation, as detected by radio-immunoprecipitation. Recombinant MVA-DEN2 80%E, but not MVA-DEN4 80%E, induced a neutralizing antibody response. The MVA-DEN2 80%E recombinant was chosen to further evaluate its ability to induce resistance to wild type DEN2 challenge in monkeys. Monkeys immunized twice with recombinant MVA-DEN2 80%E developed a low to moderate antibody response and were partially protected against DEN2 challenge, as determined by the viremia pattern. Importantly, the subsequent study showed that all four monkeys immunized with the recombinant in a three dose schedule developed an increased level of antibodies and were completely protected against DEN2 challenge. The potential efficacy of recombinant MVA-DEN2 80%E to protect primates against dengue infection suggests that construction and evaluation of MVA recombinants expressing other serotypes of dengue virus E for use in a tetravalent vaccine strategy might be warranted.

Animals↗
PubMed1999

Dengue: an evaluation of dengue severity in French Polynesia based on an analysis of 403 laboratory-confirmed cases.

We conducted a retrospective study of 403 laboratory-confirmed dengue cases hospitalized in Tahiti between August 1989 and March 1997. According to standard WHO criteria, 337 of these cases were dengue fever (DF) and 64 were dengue haemorrhagic fever (DHF). Of the 10 fatal cases, 6 were DF and 4 were DHF. As an alternative, we used a correspondence analysis procedure to define dengue severity based on basic clinical and biological criteria for which we assigned a severity score, and then selected the 50 most severe cases from this analysis. Of the latter, 17 patients had been classified as DF and 33 as DHF by the WHO criteria. From this analysis, haemorrhages and decreased platelets counts associated with hepatic disorders are the main criteria associated with the severe dengue cases. Thus in our study population, the WHO classification does not account for the overall severity of dengue; hepatic failure should be considered as a specific severe form of dengue since plasma leakage, which is the pathophysiological hallmark of DHF, is only one of the pathogenic mechanisms leading to severity.

Adolescent↗
PubMed2001

Development of dengue virus replicons expressing HIV-1 gp120 and other heterologous genes: a potential future tool for dual vaccination against dengue virus and HIV.

BACKGROUND: Toward the goals of providing an additional vector to add to the armamentarium available to HIV vaccinologists and of creating a bivalent vaccine effective against dengue virus and HIV, we have attempted to create vectors which express dengue virus non-structural proteins and HIV immunogens. Previously we reported the successful construction of dengue virus replicons which lack structural genes necessary for virion release and spreading infection in culture but which can replicate intracellularly and abundantly produce dengue non-structural proteins. Here we attempted to express heterologous genetic material from these replicons. RESULTS: We cloned into a Deltapre-M/E dengue virus replicon genes for either green fluorescent protein (GFP), HIV gp160 or HIV gp120 and tested the ability of these constructs to express dengue virus proteins as well as the heterologous proteins in tissue culture after transfection of replicon RNA. CONCLUSIONS: Heterologous proteins were readily expressed from these constructs. GFP and gp120 demonstrated minimal or no toxicity. Gp160 expressing replicons were found to express proteins abundantly at 36 hours post transfection, but after 50 hrs of transfection, few replicon positive cells could be found despite the presence of cellular debris positive for replicon proteins. This suggested that gp160 expressed from dengue virus replicons is considerably more toxic than either GFP or gp120. The successful expression of heterologous proteins, including HIV gp120 for long periods in culture suggests this vector system may be useful as a vaccine vector, given appropriate delivery methods.

Dengue↗
PubMed2006

[Economic impact of dengue and dengue hemorrhagic fever in the State of Zulia, Venezuela, 1997-2003].

OBJECTIVES: To determine the direct and indirect costs of medical care provided to cases of dengue and dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) between 1997 and 2003 in Zulia State, Venezuela. METHODS: The total number of patients with dengue and DHF/DSS was obtained from records belonging to the Regional Epidemiology Office of the state of Zulia and from reports of cases that were confirmed in the Virology Section of Dr. Americo Negrette's Clinical Research Institute, Zulia University, Maracaibo, Venezuela, between 1 January 1997 and 31 December 2003. Direct costs included the cost of emergency medical care for all cases and hospital costs for cases with DHF/DSS (cost per bed-day and laboratory expenses). The costs connected to absence from work among patients over 15 years of age and mothers who accompanied their children under 15 years of age comprised the indirect costs, which were adjusted for the proportion of men and women in the labor force. Calculations were based on the minimum yearly wage, and results were given in United States dollars, converted according to each year's average exchange rate. RESULTS: During the study period, 33,857 cases of dengue and DHF/DSS were seen. Of them, 30 251 (89.35%) were cases of dengue, and 3606 (10.65%) were cases of DHF/DSS. Six cases of DHF/DSS died (lethality rate: 0.2 per 100 cases of DHF/DSS). Direct costs were 474,251.70 US dollars; of these costs, 132,042.30 US dollars were spent on emergency medical care and 342,209.40 US dollars on the hospital costs of DHF/DSS cases. Indirect costs were 873,825.84 US dollars and comprised 64.8% of overall expenditures (1 ,48,077.54 US dollars) connected to this disease during the study years. CONCLUSIONS: This is the first study on the economic impact of dengue in the state of Zulia and in Venezuela. In spite of some limitations, results show that dengue is an important public health problem that causes great expense because of temporary absenteeism from work and that undermines regional and national economic development.

Adolescent↗
PubMed1982

Reintroduction of dengue fever into the continental United States. I. Dengue surveillance in Texas, 1980.

Two surveillance systems were initiated in Texas in 1980 to detect cases of dengue fever. Physicians throughout the state were requested to report cases of dengue (passive surveillance), and 27 out-patient facilities serving geographically and ethnically high risk populations were asked to report cases of dengue-like illness weekly (active surveillance). Additionally, two clinics participating in active surveillance submitted acute-phase blood specimens weekly for dengue virus isolation. Sixty-three cases of illness due to dengue type 1 infection (dates of onset 2 August-10 November) were documented by virus isolation or serologic testing; 52 of them (83%) occurred n countries adjacent to the Texas-Mexico border. Fifty-six patients (89%) were Hispanic; 46 (73%) were females. Twenty-seven patients (43%) had not traveled outside the U.S. before becoming ill. Since no clinically apparent outbreak of dengue was ever recognized by public health officials in Texas in 1980, the active surveillance system in other Gulf Coast states should be considered when the risk of introduction of dengue is considered high.

Adolescent↗
PubMed1992

Use of dengue blot in dengue diagnosis: the Malaysian experience.

Dengue fever/Dengue haemorrhagic fever (DF/DHF) has been a public health problem in Malaysia with an endemic level of about 7 per 100,000 population per year. In 1990, Malaysia experienced its most severe outbreak of DF/DHF with a record total of 5,590 cases referred to the Division of Virology, Institute for Medical Research (IMR). Of these, 1,880 were confirmed serologically to be DF/DHF. The conventional serological procedure, the Haemagglutination Inhibition (HI) test, for the diagnosis of DF/DHF is cumbersome and causes delay in diagnosis. Another problem associated with the HI test has been that it has often been difficult to obtain a second convalescent serum sample for an accurate diagnosis. This has raised an urgent need to establish a "rapid" test for diagnosis of DF/DHF. As such the authors recently carried out an evaluation of a newly available commercial rapid test, namely, the Dengue Blot Assay (Diagnostic Biotechnology Singapore Pte Ltd). The test is intended for use in laboratory confirmation of dengue virus infection. The evaluation was to determine if the test could be utilised as a routine laboratory test and to establish its sensitivity and specificity. Over 400 samples were tested against the Dengue Blot Assay. Results were checked against an in-house Dengue IgM ELISA and HI assay. Preliminary results indicate that the sensitivity and specificity of the Dengue Blot is satisfactory. Our results also indicate that the Dengue Blot has a useful role to play in a routine laboratory especially since it provides rapid results on single serum samples thereby reducing the workload in a busy diagnostic laboratory.

Dengue↗
PubMed1989

[MAC-ELISA for the detection of IgM antibodies to dengue type I virus (rapid diagnosis of dengue type I virus infection)].

The commercial rapid diagnostic reagents for Dengue virus infection is still not available at present. An ABC MAC-ELISA (Avidin Biotin Complex IgM Antibody Capture Enzyme Linked Immunosorbent Assay) for the detection of Dengue type I virus infection has been described. IgG purified from high titer (HI = 2560) human anti-flavivirus serum is labelled with biotin for the rapid diagnosis of Dengue type I virus infection. 389 serum specimens of suspected Dengue Fever patients including 226 HI(+) paired sera and 163 HI(-) paired sera which were collected from 1 to 150 days after onset of the disease in 1988 have been assayed for IgM antibodies to Dengue type I virus. Cut off value is based on the mean of OD490 of 162 Dengue negative serum specimens plus 4 SD. The positivity of IgM antibody increased as the viremia disappeared and IgM antibody for Dengue-1 serum specimens collected 9 days after onset of the disease is 100% detectable.

Antibodies, Viral↗
PubMed1996

Primary sequence of the envelope glycoprotein of a dengue type 2 virus isolated from patient with dengue hemorrhagic fever and encephalopathy.

Dengue viruses exist in nature as a collection of highly similar but not identical members (quasispecies). In order to correlate the presence of viral quasispecies with rare occurrence of unusual clinical manifestations in dengue-infected individuals, a dengue type 2 virus was isolated from the peripheral blood of a 12-year-old boy who presented with fever, headache, drowsiness and tonic seizure of the left arm, and subsequently manifested symptoms and signs of dengue hemorrhagic fever. Analysis of the envelope glycoprotein sequence of the encephalopathy-associated virus and two other dengue type 2 viruses from the same epidemic season in Chiang Mai, Thailand revealed that all three viruses belonged to the subtype IIIa of the five-subtype phylogenetic nomenclature system for dengue type 2 virus. The encephalopathy-associated dengue virus was more divergent from the others and was characterized by an Ala-->Val substitution at the position 173 of the envelope glycoprotein. This substitution mapped to the central domain 1 which was not known to be involved directly in envelope-receptor interaction.

Amino Acid Sequence↗
PubMed1997

Comparison of dengue virus antigens in sera and peripheral blood mononuclear cells from dengue infected patients.

The presence of dengue virus antigens in acute sera and peripheral blood mononuclear cells (PBMC) from dengue infected patients were determined by a biotin-streptavidin enzyme-linked immunosorbent assay (BS-ELISA). The frequency of the antigens detected in PBMC was higher than that in sera (53.8% vs 18.9%). In comparison with sera, the detection rate in PBMC was greater than six times: 7 cases were positive only in sera whereas 44 cases were positive only in PBMC, p < 0.001. The presence of the antigens in the sera did not depend on the severity of the disease, i.e. dengue fever, dengue hemorrhagic fever (grades I and II) or dengue shock syndrome (grades III and IV). In contrast, the presence of the antigens in PBMC increased from 36.8% to 100% when the infection was more severe. The dengue virus antigens could be detected in the samples collected between day 2 and day 7 after onset of the disease with the highest rate of detection (68.8%) in PBMC collected on day 4. The data suggest the use of PBMC with access to the appropriate acute-phase specimen for detection of dengue virus antigens.

Antigens, Viral↗
PubMed1993

Comparative analysis of the NS 1 gene sequences of dengue-1 viruses prototype Hawaii strain and Thai isolate TH-Sman, and determination of the intratypic variation of NS 1 protein among dengue-1 viruses.

In view of a previous report on significant antigenic and biophysical differences between the purified soluble complement-fixing antigens of dengue-1 virus strains Hawaii and TH-Sman, the NS 1 genes of both virus isolates were cloned, sequenced, and compared in an attempt to define the genetic basis for the observed differences. Sequence comparison revealed ten encoded amino acid differences between the NS 1 genes of both viruses. Three of these amino acid differences, which are associated with a change in charge distribution, are clustered within the major antigenic region previously defined by studies of recombinant dengue-1 NS 1 protein expressed in E. coli. In parallel, the NS 1 sequences of both Hawaii and TH-Sman isolates were also aligned and compared with two other published dengue-1 NS 1 protein sequences to determine the intratypic variation of dengue-1 NS 1 antigen. Pairwise comparisons between the encoded amino acid sequences revealed a variability of 1.1% to 3.1% difference in the NS 1 protein among dengue-1 strains, which is comparable to that reported for dengue-1 envelope protein (0.2% to 3.6% difference) but less than that of dengue-2 NS 1 protein (0.6% to 7.4% difference).

Amino Acid Sequence↗
PubMed1998

Analysis of antibody-independent binding of dengue viruses and dengue virus envelope protein to human myelomonocytic cells and B lymphocytes.

The identification of cell surface receptor molecules for the dengue viruses, one of the leading causes of morbidity and mortality in tropical and subtropical parts of the world, remains controversial. Both glycoproteins and glycosaminoglycans have been identified as likely candidates on various cell types. However, most of these studies have used cell types other than those thought to be the main target cells in humans: monocyte-macrophages, B lymphocytes and bone marrow cells. In this report characterization of dengue virus binding to two human leukocyte cell lines, the myelo-monocytic cell line HL60 and a non-EBV transformed B cell line, BM13674, is described. The results corroborate earlier descriptions of the presence of virus-binding protein(s), different from the FcR, on the surface of human leukocytes, and further suggest that the proteins may have differential affinity for the four dengue virus serotypes in the order dengue 2 > or = dengue 3 > dengue 1 > dengue 4 virus.

Aedes↗
PubMed1991

Production of dimer-specific and dengue virus group cross-reactive mouse monoclonal antibodies to the dengue 2 virus non-structural glycoprotein NS1.

A panel of mouse monoclonal antibodies (MAbs) raised against the non-structural glycoprotein NS1 of dengue 2 virus (PR159) was studied for cross-reactivity with the NS1 protein of other dengue virus serotypes and other members of the Flaviviridae using immunoblotting. Most of the 35 anti-NS1 MAbs were found to be specific for dengue 2 virus NS1 (some of which were specific for the native, dimeric form of this protein), but others were found to cross-react within the dengue virus group. This latter group of MAbs, although dominated by MAbs defining a dengue 2 and 4 virus subgroup, also contained some MAbs that were shown to cross-react with both linear (sequential) and conformational epitopes common to the NS1 glycoproteins of all four dengue virus serotypes. Several of these MAbs were also able to cross-react with other flaviviruses, most notably viruses from the Japanese encephalitis antigenic complex. Although cross-reactive epitopes were previously demonstrated on this glycoprotein using polyclonal sera from dengue virus-infected animals and human, this is the first report of the isolation of MAbs which define these determinants and which will allow their further analysis.

Animals↗