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At least 19 recordsLinked to original sources
PubMed2002

Effect of dengue-1 antibodies on American dengue-2 viral infection and dengue haemorrhagic fever.

In Iquitos, Peru, no cases of dengue haemorrhagic fever have been recorded in individuals infected with dengue-1 virus followed by American genotype dengue-2 (American dengue-2) virus. We assayed serum samples collected in Iquitos that tested positive for antibodies of monotype dengue-1 and monotype dengue-2 using a plaque reduction neutralisation test to determine their ability to neutralise the infectivity of two dengue-1 viruses, two American dengue-2 viruses, and two Asian dengue-2 viruses. Sera positive for the dengue-1 antibody neutralised dengue-1 viruses and American dengue-2 viruses much more effectively than Asian dengue-2 viruses. Neutralisation of American dengue-2 virus by sera positive for dengue-1 antibodies may account for the absence of dengue haemorrhagic fever in individuals infected with dengue-1 in 1990-91 followed by American dengue-2 virus in 1995 in Iquitos, Peru.

Antibodies, Viral↗
PubMed2000

Isolation and partial characterization of dengue virus type 2 and 4 strains from dengue fever and dengue haemorrhagic fever patients from Mindanao, Republic of the Philippines.

OBJECTIVE: Isolation of dengue virus from dengue fever and dengue haemorrhagic fever cases from Mindanao, Republic of the Philippines. METHODS: 12 patients with clinically suspected dengue fever (DF) or dengue haemorrhagic fever (DHF) presenting in four regional hospitals between August and September 1995 on Minadano were enrolled in the study. Dengue virus was isolated by inoculation of Vero/E6 or C6/36 cells with patient serum. IgM antibodies were measured using a commercial test system. Up to 454 bp of the capsid region and 240 bp of the E/NS1 gene junction of different viral isolates were sequenced and phylogenetically analyzed. RESULTS: Virus could be isolated from seven patients, five isolates were typed as dengue virus type 2 and two as dengue virus type 4 by immunostaining with monoclonal antibodies or by RT/PCR. Phylogenetic analysis confirmed a close relationship of the dengue virus type 2 isolates with viruses isolated in the Philippines in 1983 and 1988. CONCLUSION: As observed in studies from other parts of South East Asia, dengue virus type 2 was readily isolated from dengue haemorrhagic fever cases. Dengue virus type 2 and 4 circulate in Mindanao, Philippines, with dengue type 2 being responsible for most of our severe DF or DHF cases.

Child↗
PubMed2000

Dengue virus specific T cell responses to live attenuated monovalent dengue-2 and tetravalent dengue vaccines.

The proliferative T cell responses to dengue vaccines were studied using the parental strains of dengue vaccines as antigens in 26 dengue immune individuals who resided in Bangkok which is the endemic area of dengue infection. The magnitude of the T cell responses in subjects with flavivirus cross-reactive neutralizing antibody was much higher and the cross-reactivity was broader than in those with dengue serotype-specific neutralizing antibodies, Japanese encephalitis (JE) specific antibodies or dengue cross-reactive antibodies. The T cell response in those with neutralizing antibody against a single serotype or in those who had dengue cross-reactive neutralizing antibody was relatively low, independent of the level or degree of cross-reactivity of the antibody. Evaluation of the proliferative T cell responses in 8 recipients of the monovalent dengue-2 (16681-PDK53) or the tetravalent dengue vaccines demonstrated that both vaccines induced high levels of neutralizing antibody as well as high levels of T cell responses to all serotypes of dengue virus. These results indicate that the evaluated dengue vaccines efficiently induced humoral and cell mediated immunity comparable to natural infection with dengue virus.

Adolescent↗
PubMed1999

Comparison of PanBio dengue duo enzyme-linked immunosorbent assay (ELISA) and MRL dengue fever virus immunoglobulin M capture ELISA for diagnosis of dengue virus infections in Southeast Asia.

The performances of the MRL dengue fever virus immunoglobulin M (IgM) capture enzyme-linked immunosorbent assay (ELISA) and the PanBio Dengue Duo IgM capture and IgG capture ELISA were compared. Eighty sera from patients with dengue virus infections, 24 sera from patients with Japanese encephalitis (JE), and 78 sera from patients with nonflavivirus infections, such as malaria, typhoid, leptospirosis, and scrub typhus, were used. The MRL test showed superior sensitivity for dengue virus infections (94 versus 89%), while the PanBio test showed superior specificity for JE (79 versus 25%) and other infections (100 versus 91%). The PanBio ELISA showed better overall performance, as assessed by the sum of sensitivity and specificity (F value). When dengue virus and nonflavivirus infections were compared, F values of 189 and 185 were obtained for the PanBio and MRL tests, respectively, while when dengue virus infections and JE were compared, F values of 168 and 119 were obtained. The results obtained with individual sera in the PanBio and MRL IgM ELISAs showed good correlation, but this analysis revealed that the cutoff value of the MRL test was set well below that of the PanBio test. Comparing the sensitivity and specificity of the tests at different cutoff values (receiver-operator analysis) revealed that the MRL and PanBio IgM ELISAs performed similarly in distinguishing dengue virus from nonflavivirus infections, although the PanBio IgM ELISA showed significantly better distinction between dengue virus infections and JE. The implications of these findings for the laboratory diagnosis of dengue are discussed.

Adolescent↗
PubMed1999

Dynamics of susceptibility and transmissibility of the live, attenuated, candidate vaccines dengue-1 PDK13, dengue-3 PGMK30F3, and dengue-4 PDK48 after oral infection in Aedes aegypti.

Dengue-1 virus PDK13 and isolates from vaccinees (dengue-1 Ib1 and dengue-1 Ib 10), dengue-3 PGMK30F3, and dengue-4 PDK48 were studied for their abilities to infect, disseminate, and replicate in Aedes aegypti mosquitoes by the oral route. In general, infection and dissemination rates were poorer for the vaccine compared with the parent viruses. The transmissibility was also lower for dengue-1 PDK13 than the parent virus, whereas it was not detected for isolates from vaccinees and dengue-3 PGMK30F3. Transmissibility of dengue-4 PDK48 was not determined because no dissemination occurred. Replication rates of vaccine strains were also found to be less efficient than the parent viruses. These imply that vaccination with the candidate vaccine is safe. Moreover, vector attenuation of vaccine viruses was consistent with its phenotypic markers of attenuation, which remained stable after a mosquito passage or after human and mosquito passage.

Administration, Oral↗
PubMed2002

The reappearance of dengue-3 and a subsequent dengue-4 and dengue-1 epidemic in Puerto Rico in 1998.

In January 1998, dengue-3 (DEN)-3 (group III genotype) was detected in Puerto Rico after an absence of 20 years. Public health officials intensified education efforts to promote community participation in dengue control. Virologic surveillance revealed an unexpected paradox: DEN-4 and DEN-1 produced a large epidemic overlaying the DEN-3 epidemic. In 1998 there were 17,000 reported cases of dengue (4.8/1,000 persons), and among all virus isolations (n = 960), DEN-4 (419, 43.6%), DEN-1 (337, 35.1%), and DEN-2 (143, 14.9%) were detected much more frequently than DEN-3 (61, 6%). Age group-specific attack rates were highest for persons 10-19 years old, followed by infants less than a year of age. Nineteen fatal cases (median = 37 years old, range = 8 months to 90 years) had a positive laboratory diagnosis of dengue. Among DEN-3 cases no fatalities were documented, 50 were hospitalized, and 10 of 48 (21%) fulfilled the criteria for dengue hemorrhagic fever (four had primary infections and six had secondary infections). During 1999, DEN-3 became the predominant serotype isolated (182 of 310 isolations, 59%). The reappearance of DEN-3 and its subsequent circulation from 1999 to 2001 produced no changes in dengue incidence that could have been detected in the absence of virologic surveillance.

Adolescent↗
PubMed1998

Possible dengue sequential infection: dengue spread in a neighbourhood during the 1996/97 dengue-2 epidemic in French Polynesia.

A DEN-2 epidemic occurred in French Polynesia from August 1996 to April 1997 after 7 years of DEN-3 circulation. The susceptible population constituted all expatriates and Polynesians under 21. In August 1996, two successive DEN-2 cases occurred in Teroma, a Tahitian neighbourhood close to the international airport of Tahiti. A serological prospective study of persons < 21 years living in Teroma was conducted. The study population was bled in September 1996, October 1996 and June 1997. Analysis of dengue spread in Teroma confirmed that dengue transmission occurs primarily in the house, thus vector control campaigns should incorporate focal insecticide spraying and systematic daily use of insecticide in houses. The evolution in time of the disease demonstrated that among a susceptible population, prevalence and incidence rates are related to the time of exposure, and consequently to age. Comparison of dengue incidence or dengue prevalence between populations therefore requires adjusted age rates. Most studies did not adjust for age, leading to the conclusion that DHF is more frequent during secondary than during primary dengue infection. Prospective studies taking into account the time of dengue exposure are necessary to confirm the sequential infection hypothesis.

Adolescent↗
PubMed2002

High circulating levels of the dengue virus nonstructural protein NS1 early in dengue illness correlate with the development of dengue hemorrhagic fever.

Infection with any 1 of 4 dengue viruses produces a spectrum of clinical illness ranging from a mild undifferentiated febrile illness to dengue fever (DF) to dengue hemorrhagic fever (DHF), a potentially life-threatening disease. The morbidity and mortality of DHF can be reduced by early hospitalization and careful supportive care. To determine its usefulness as a predictor of DHF, plasma levels of the secreted dengue virus nonstructural protein NS1 (sNS1) were measured daily in 32 children with dengue-2 virus infections participating in a prospective, hospital-based study. Free sNS1 levels in plasma correlated with viremia levels and were higher in patients with DHF than in those with DF. An elevated free sNS1 level (> or =600 ng/mL) within 72 h of illness onset identified patients at risk for developing DHF.

Adolescent↗
PubMed1993

Dengue epidemic in the stage of Rio de Janeiro, Brazil, 1990-1: co-circulation of dengue 1 and dengue 2 serotypes.

During 1990 and 1991, dengue fever was detected in the State of Rio de Janeiro, Brazil. It occurred in two epidemic waves; one, from January to August 1990, caused predominantly by dengue virus type 1 (DEN-1) the other from October 1990 to May 1991 caused by type 2 virus (DEN-2). Dengue was confirmed by virus isolation and/or IgM capture enzyme-linked immunosorbent assay (MAC-ELISA) in 2109/5964 (35.4%) of the cases. DEN-2 virus was isolated from 180 patients. HAI tests indicated that of these previous infection with DEN-1 had occurred in 130 (72%). The epidemic was classified as dengue fever, but severe and even fatal cases occurred in association with secondary infection.

Antibodies, Viral↗
PubMed1991

Dengue surveillance in French Polynesia: an attempt to use the excess number of laboratory requests for confirmation of dengue diagnosis as an indicator of dengue activity.

The excess number of weekly laboratory requests for confirmation of dengue diagnosis over the expected number of requests forecasted by the modified Serfling method is proposed for the surveillance of dengue in French Polynesia, in addition to conventional methods. Retrospective analysis of the seasonal curves of dengue activity related to the number of laboratory requests is described for the years 1982-1987 where dengue type 4 was the only active flavivirus at the time when the forecast was initiated. By using past epidemic data, the probability of failing to recognize an increase in excess of requests as possibly epidemic was of 13.2% and 5.8%, respectively, when the criterion for epidemic increase was set respectively at 2 and 3 successive weeks during which the epidemic threshold is exceeded. A weekly surveillance was set up prospectively for 1988 using these criteria.

Clinical Laboratory Techniques↗
PubMed2000

Dengue NS1-specific antibody responses: isotype distribution and serotyping in patients with Dengue fever and Dengue hemorrhagic fever.

To understand the antibody responses to dengue (DEN) nonstructural 1 (NS1) glycoprotein and their roles in protective immunity or pathogenesis of dengue fever (DF) and dengue hemorrhagic fever (DHF), we have analyzed the NS1-speccific IgM, IgA and IgG antibodies from patients with DF and DHF. An isotype-specific, indirect enzyme-linked immunosorbent assay (ELISA) was established by coating a NS1-specific monoclonal antibody (MAb), D2/8-1, to capture soluble NS1 antigens secreted in the culture supernatants of Vero cells infected with DEN virus. We observed strong anti-NS1 antibody responses in all of the convalescent sera of patients with DF and DHF. Similar NS1-specific isotypic and serotypic antibody responses were found in the sera from DF and DHF patients. The results showed that all DEN infections induced significant NS1-specific IgG, whereas 75% and 60% of primary DF patients vs. 40% and 90% of secondary DF patients produced IgM and IgA antibodies, respectively. Specificity analysis showed that DEN NS1-specific IgG and IgA antibodies cross-react strongly to Japanese encephalitis (JE) virus NS1 glycoprotein, whereas DEN NS1-specific IgM antibodies do not cross-react to JE virus NS1 glycoprotein at all. The serotype specificity of NS1-specific IgM, IgA and IgG were found to be 80%, 67% and 75% for primary infections, and 50%, 22% and 30% for secondary infections in positive samples of DF patients. Similar pattern was found in DHF patients. The results showed that all of the DF and DHF patients produced significant NS1-specific antibodies. We did not observe direct correlation between the anti-NS1 antibody responses and DHF because sera from patients with DF and DHF showed similar anti-NS1 antibody responses.

Antibodies, Monoclonal↗
PubMed1998

[Basic standards in handling patients with dengue fever, hemorrhagic dengue and dengue shock].

The Dengue epidemic in Venezuela has increase dramatically during the last years. There is a rise in the number of cases as well as in the severity of the disease. The fact that it circulates more than one serotype of the virus (1, 2 and 4), from the four described turn us into a hyperendemic region. The symptoms produce in the patient as a consequence of the infection with the Dengue virus, varies from a mild fever to the severe Dengue Shock. Here, the characteristics and classification of the different clinical manifestation are presented as well as the basic procedures in the management of the patient in every case.

Ambulatory Care↗
PubMed1993

Molecular epidemiology of dengue 3 viruses and genetic relatedness among dengue 3 strains isolated from patients with mild or severe form of dengue fever in French Polynesia.

The nucleotide sequences of a short fragment of the envelope protein gene encoding amino acids 25 to 89 of 27 dengue 3 viruses were determined by direct sequencing of PCR-amplified products, and the viruses were compared regarding their time of isolation and geographic distribution. Four distinct genotypic groups were discerned at 6% divergence between nucleotide sequences. The first group contained isolates from the South Pacific (1988 to 1992), Singapore (1973) and Indonesia (1973 to 1991). The second group comprised viruses from Asia (1956 to 1989) including the reference strain H-87. The third was composed of one isolate from Thailand (1971), and the fourth included the early strains from French Polynesia (1964 to 1969) and from Puerto Rico (1963). Furthermore, the difference between early and recent strains from the South Pacific was as high as 12.3%. This observation suggests that the recent epidemics in the South Pacific were probably the consequence of the spread of a new variant that emerged from New Caledonia. However, relatedness between nucleotide sequence and disease severity, or between strains from epidemics with mild disease (New Caledonia) and strains from epidemics with severe disease (French Polynesia) could not be demonstrated.

Aedes↗
PubMed1988

Evidence that maternal dengue antibodies are important in the development of dengue hemorrhagic fever in infants.

To establish the role of maternal dengue-specific antibodies in the development of dengue hemorrhagic fever and dengue shock syndrome caused by dengue 2 virus in infants, we examined sera from mothers of infants and toddlers with dengue hemorrhagic fever or dengue shock syndrome and mothers of infants with pyrexia of unknown origin. The mean titers of hemagglutination inhibition, neutralization, and infection-enhancing activities against dengue 2 virus were not statistically different among the three groups. However, among infants who developed dengue hemorrhagic fever/dengue shock syndrome there was a strong correlation between the mothers' dengue 2 neutralizing titers and infant age at the time of onset of severe illness, where no such correlation was found among the other two groups. Furthermore, the actual age at which dengue hemorrhagic fever/dengue shock syndrome occurred in each infant correlated with the age at which maximum enhancing activity for dengue 2 infection in mononuclear phagocytes was predicted. This critical time for the occurrence of dengue hemorrhagic fever/dengue shock syndrome was observed to be approximately 2 months after the time calculated for maternal dengue 2 neutralizing antibodies to degrade below a protective level. In addition, sera of mothers of infants with dengue hemorrhagic fever/dengue shock syndrome enhanced dengue 2 virus infection to a slightly greater degree than did sera from mothers of infants with pyrexia of unknown origin and toddlers with dengue hemorrhagic fever/dengue shock syndrome. These data are consistent with the hypothesis that maternal dengue antibodies play a dual role by first protecting and later increasing the risk of development of dengue hemorrhagic fever/dengue shock syndrome in infants who become infected by dengue 2 virus.

Age Factors↗
PubMed1997

Analysis of a recombinant dengue-2 virus-dengue-3 virus hybrid envelope protein expressed in a secretory baculovirus system.

In a step towards a tetravalent dengue virus subunit vaccine which is economical to produce, highly immunogenic and stable, a hybrid dengue virus envelope (E) protein molecule has been constructed. It consists of 36 amino acids from the membrane protein, the N-terminal 288 amino acids of the dengue-2 virus E protein plus amino acids 289-424 of the dengue-3 virus E protein. It has been engineered for secretory expression by fusion to a mellitin secretory signal sequence and truncation of the hydrophobic transmembrane segment. Using the baculovirus expression system and serum-free conditions, more than 95% of recombinant dengue-2 virus-dengue-3 virus hybrid E protein (rD2D3E) was secreted into the cell culture supernatant in a stable form with multiple features indicative of preserved conformation. The hybrid molecule reacted with a panel of dengue virus- and flavivirus-specific MAbs which recognize linear or conformational epitopes on dengue virions. Human dengue virus-specific antisera also reacted with the protein. The hybrid rD2D3E protein was able to inhibit the in vitro binding of dengue-2 and dengue-3 viruses to human myelomonocytic cells, suggesting that the receptor-binding epitope(s) was preserved. Adjuvant-free immunization with the hybrid protein induced an antibody response to both dengue-2 and dengue-3 virus in outbred mice, comparable in strength to that of individual rD2E and rD3E proteins. Notably, these antibody responses were primarily of the IgG2a and IgG2b isotype. A strong dengue virus cross-reactive T cell response was also induced in the mice, suggesting that dengue virus hybrid E proteins could form the basis of an efficacious multivalent dengue virus vaccine.

Animals↗