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PubMed1997

Dengue virus infectivity depends on envelope protein binding to target cell heparan sulfate.

Dengue virus is a human pathogen that has reemerged as an increasingly important public health threat. We found that the cellular receptor utilized by dengue envelope protein to bind to target cells is a highly sulfated type of heparan sulfate. Heparin, highly sulfated heparan sulfate, and the polysulfonate pharmaceutical Suramin effectively prevented dengue virus infection of target cells, indicating that the envelope protein-target cell receptor interaction is a critical determinant of infectivity. The dengue envelope protein sequence includes two putative glycosaminoglycan-binding motifs at the carboxy terminus; the first could be structurally modeled and formed an unusual extended binding surface of basic amino acids. Similar motifs were also identified in the envelope proteins of other flaviviridae. Developing pharmaceuticals that inhibit target cell binding may be an effective strategy for treating flavivirus infections.

Amino Acid Sequence↗

PubMed2001

Prenatal transmission of dengue: two new cases.

Dengue is commonly observed in most tropical countries, but its transmission from mother to fetus has not been frequently described. We report two such cases. The first signs of dengue in the infants appeared on the 3rd and 9th days of life. In both, a bacterial infection was suspected initially. In areas where it is endemic, the diagnosis of dengue should be considered in the neonate with signs of bacterial infection. When dengue is suspected in a pregnant woman, laboratory investigation and extended observation of the newborn are advised.

Adult↗

PubMed1997

Antibodies against dengue virus E protein peptide bind to human plasminogen and inhibit plasmin activity.

Both mice and rabbits immunized with dengue virus E protein peptide spanning amino acids 100-119 (D4E) produced antibodies that reacted not only with the D4E peptide itself but also with human plasminogen, as shown by ELISA and Western blot. Sera from dengue virus-hyperimmunized mice and dengue patients also contained antibodies against D4E and plasminogen. Furthermore, such sera all contained plasmin inhibitory activity. Using affinity-purified anti-D4E antibodies and free D4E peptide for competitive inhibition, we demonstrated that the inhibition of plasmin activity was due to anti-D4E antibodies rather than other substances in the sera. Taken together, these results suggest dengue virus E protein amino acids 100-119 are a cross-reactive immunogenic region, and antibodies against this region may interfere with human fibrinolysis.

Animals↗

PubMed2000

Dengue fever in international travelers.

Dengue virus infection is becoming increasingly recognized as one of the world's major emerging infectious diseases. Although only a few systematic studies have been conducted to assess the incidence and clinical course of dengue fever in travelers, it is now possible to estimate risk factors for travelers to areas of endemicity. Dengue virus and its vector, Aedes mosquitoes, benefit from human habitation and travel-related aspects of human behavior. Thus, travelers serve an important double role as potential victims of the disease and as vehicles for further spread of dengue.

Animals↗

PubMed2002

Differing influences of virus burden and immune activation on disease severity in secondary dengue-3 virus infections.

Dengue hemorrhagic fever (DHF), the most severe form of illness following infection with a dengue virus, is characterized by plasma leakage, thrombocytopenia, and hepatic inflammation. The interrelationships among virus burden, immune activation, and development of DHF were examined in 54 children with secondary dengue-3 virus infections participating in a prospective, hospital-based study. DHF was associated with higher mean plasma viremia early in illness and earlier peak plasma interferon-gamma levels. Maximum plasma viremia levels correlated with the degree of plasma leakage and thrombocytopenia. Maximum plasma levels of interleukin (IL)-10 and soluble tumor necrosis factor receptor-II correlated with the degree of thrombocytopenia, independently of viremia levels. Hepatic transaminase elevation correlated with plasma soluble IL-2 receptor levels and not with viremia levels. Quantitative differences in virus burden and host immune responses, and the timing of type 1 cytokine responses, have differing influences on the severity of disease manifestations during secondary dengue-3 virus infections.

Antigens, CD↗

PubMed2006

Parvovirus B19 empty capsids as antigen carriers for presentation of antigenic determinants of dengue 2 virus.

For the production of dengue-vaccine candidates, empty capsids, or virus-like particles (VLPs), of parvovirus B19 that carry dengue 2-specific epitopes were employed as antigen carriers. Two epitopes (comprising amino acids 352-368 and 386-397) of domain BIII of the envelope glycoprotein were chosen to produce recombinant B19 VLPs for immunization of BALB/c mice. Serum samples from immunized mice revealed that recombinant B19 VLPs elicited strong humoral immune responses. In summary, this B19 VLP-vaccine platform produced high (> or =2.0 x 10(5)) anti-dengue 2 titers and robust (< or =1 120) 50%-plaque-reduction neutralization test (PRNT(50)) titers, which effectively neutralized live dengue 2 virus in PRNT(50) assays.

Animals↗

PubMed2006

Cellular immune activation in children with acute dengue virus infections is modulated by apoptosis.

Apoptosis is an important modulator of cellular immune responses during systemic viral infections. Peripheral-blood mononuclear cell (PBMC) apoptosis and plasma soluble levels of CD95, a mediator of apoptosis, were determined in sequential samples from children participating in a prospective study of dengue virus (DV) infections. During the period of defervescence, levels of PBMC apoptosis were higher in children developing dengue hemorrhagic fever (DHF), the most severe form of illness, than in those with dengue fever (DF) and other, nondengue, febrile illnesses. CD8(+) T lymphocytes made up approximately half of the peak circulating apoptotic PBMCs in DHF and DF. Maximum plasma levels of soluble CD95 were also higher in children with DHF than in those with DF. The level of PBMC apoptosis correlated with dengue disease severity. Apoptosis appears to be involved in modulation of the innate and adaptive immune responses to DV infection and is likely involved in the evolution of immune responses in other viral hemorrhagic fevers.

Adolescent↗

PubMed2004

Modulation of dengue virus infection of dendritic cells by Aedes aegypti saliva.

Dengue virus (DV) is a flavivirus carried by the Aedes aegypti mosquito that causes a spectrum of illnesses in the tropics, including dengue fever, dengue hemorrhagic fever, and dengue shock syndrome. Dendritic cells (DCs) are professional antigen presenting cells recently shown to be permissive for DV, and implicated as the primary targets of initial DV infection. DV is transmitted to human host by infected mosquitoes during a blood meal, but it is currently unknown whether transmission is modified by vector saliva that is also deposited in the host's skin during feeding. Previous studies evaluated only the outcome of DV infection of DCs, and did not address the influence of mosquito saliva. To more fully characterize natural transmission of DV, we evaluated the effects of Ae. aegypti saliva on DV infection of human myeloid DCs. We found that saliva inhibited DV infection in DCs. Moreover, pre-sensitization of DCs with saliva, prior to DV infection, enhanced inhibition. In addition, enhanced production of IL-12p70 and TNF-alpha were detected in DV-infected DC cultures exposed to mosquito saliva. The proportion of dead cells was also significantly reduced in these cultures. These data contribute to the overall understanding of the natural pathogenesis of DV infection and suggest that there is a protective role for mosquito saliva that limits viral uptake by DCs.

Aedes↗

PubMed2006

Development of a live attenuated dengue virus vaccine using reverse genetics.

There are four serotypes of dengue (DEN1-DEN4) virus that are endemic in most areas of Southeast Asia, Central and South America, and other subtropical regions. The number of cases of severe disease associated with DEN virus infection is growing because of the continued spread of the mosquito vector, Aedes aegypti, which transmits the virus to humans. Infection with DEN virus can result in an asymptomatic infection, a febrile illness called dengue fever (DF), and the very severe disease called dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS). Currently, a licensed vaccine is not available. However, a tetravalent vaccine is urgently needed to prevent DF and DHF/DSS, the latter of which occurs predominantly in partially immune individuals. A live attenuated, tetravalent DEN virus vaccine candidate has been generated using reverse genetics that is able to provide immunity to each of the four serotypes of DEN. Attenuation has been achieved by generating recombinant DEN (rDEN) viruses which are modified by deletion or, alternatively, by antigenic chimerization between two related DEN viruses using the following two strategies: 1) introduction of an attenuating 30 nucleotide deletion (Delta30) mutation into the 3' untranslated region of DEN1 and DEN4; and 2) replacement of structural proteins of the attenuated rDEN4Delta30 vaccine candidate with those from DEN2 or DEN3. Attenuation of the four monovalent vaccine candidates has been achieved for rhesus monkeys or humans and an immunogenic tetravalent vaccine candidate has been formulated. The level of attenuation of each dengue vaccine component can be increased, if needed, by introduction of additional attenuating mutations that have been well characterized.

Dengue↗

PubMed1979

Rapid detection of dengue viral antigens by counterimmunoelectrophoresis.

Counterimmunoelectrophoresis (CIE) was applied to detect dengue viral antigen in an experimental system and in clinical situations. In the experimental system, all four types of dengue viruses (dengue 1 to 4) were detected when tested against rabbit hyperimmune sera. With homologous antibody, antigen could be detected when hemagglutinating titer was as low as 1:20. In clinical situations, 67% of the sera of patients with dengue hemorrhagic fever collected on day 4 after onset of fever were positive by CIE. Antigens could be detected most frequently from day 4 to day 7. In 11% of the cases, antigens were found to persist as long as 38 days. Validity of this detection was confirmed in some cases by immunologic methods. Virtues of CIE are its technical simplicity, rapidity, and economy.

Antigens, Viral↗

PubMed1994

Dengue infection complicated by severe hemorrhage and vertical transmission in a parturient woman.

A Thai woman with a febrile illness was delivered of a healthy infant by cesarean section. The etiology of her 2-day fever was unknown at the time of surgery; results of serology performed later established a diagnosis of dengue infection. Postoperative hemostatic monitoring was not performed. She experienced massive and prolonged (8 days) wound hemorrhage that necessitated multiple transfusions of blood, platelets, and frozen plasma. The newborn became febrile on his 6th day of life. Dengue virus type 2 was isolated from his serum. Although the infant developed marked thrombocytopenia, his illness was brief and uncomplicated. This report emphasizes the hazards of surgical intervention in patients with acute dengue infection. We also believe it to be the first report of vertical transmission of dengue in humans.

Adult↗

PubMed1984

Dengue virus type 2 vaccine: reactogenicity and immunogenicity in soldiers.

A live dengue virus type 2 (dengue-2) vaccine (PR-159/S-1) was tested for reactogenicity and immunogenicity in a placebo-controlled, double-blind clinical trial involving 98 soldiers. Seroconversion rates based on the development of neutralizing antibody to dengue-2 were 90% in 70 recipients with immunity to yellow fever and 61% in 28 vaccinees without such immunity (P less than .01). Peak titers of neutralizing antibody were three times higher in recipients with antibody to yellow fever virus and persisted in most for at least 18 months. Individuals seroconverting to the vaccine virus more frequently experienced systemic symptoms than those who received placebo (P less than .02). Future users of this dengue-2 vaccine may wish to employ immunization schedules that include preliminary immunization against yellow fever and must be prepared to accept mild vaccine-related symptoms in some recipients.

Adolescent↗

PubMed1992

Failure of dengue viruses to replicate in Culex quinquefasciatus (Diptera: Culicidae).

Culex quinquefasciatus (Say) and Aedes aegypti (L.) were parenterally infected with dengue viruses and virus replication was monitored at intervals after infection in each species. Dengue viruses replicated rapidly in Ae. aegypti, reaching a peak titer of 10(6)-10(7) mosquito infectious dose 50 (MID50) per mosquito. In Cx. quinquefasciatus, however, dengue virus replication did not occur. We conclude that this mosquito species is refractory to infection with dengue viruses and, therefore, does not serve as a vector in nature.

Aedes↗

PubMed1998

New procedures to estimate water temperatures and water depths for application in climate-dengue modeling.

Two new approaches have been developed to estimate water temperatures and water depths in containers that commonly are used as breeding sites for mosquitoes, the primary vectors of dengue viruses. These estimates are incorporated in recently developed stochastic simulation models used to describe the daily dynamics of dengue virus transmission in the urban environment. Water temperature estimates are provided through a regression model that includes meteorological variables not previously used; results show that they are significantly better than those used in previous dengue transmission models. Water depth models use a climatic water budget approach which estimates moisture storage within containers. The water depth models are less precise than those developed for water temperature; however, results are superior to those used in previous models. These new approaches should improve estimates of the impact of water conditions on dengue vectors.

Aedes↗

PubMed1999

Vector competence of Aedes notoscriptus (Diptera: Culicidae) for Barmah Forest virus and of this species and Aedes aegypti (Diptera: Culicidae) for dengue 1-4 viruses in Queensland, Australia.

Aedes notoscriptus (Skuse) mosquitoes colonized from Brisbane, Queensland, Australia, were fed on blood suspensions containing either Barmah Forest (BF) virus, dengue virus type 1 (DEN-1), dengue virus type 2 (DEN-2), dengue virus type 3 (DEN-3), or dengue virus type 4 (DEN-4). Ae. notoscriptus was shown to be moderately susceptible to oral infection with BF virus, ID50 = 10(3.3) CCID50 per mosquito, with titers in infected mosquitoes peaking 10 d after infection. BF virus transmission occurred between days 5 and 12, with an average rate of 45% (range, 40-50%). For DEN 1-4, Ae. notoscriptus showed low level susceptibility to oral infection, with maximum head and thorax squash infection rates of 8, 5, 13, and 3%, respectively. Rates of infection were notably higher in a north Queensland strain of Aedes aegypti (L.) used as a positive control, with maximum thorax squash infection rates of 58, 68, 78, and 60% for DEN 1-4, respectively. On the basis of these data, it is concluded that Ae. notoscriptus could act as an efficient vector of BF in urban environments, but it is unlikely to be an important vector of DEN.

Aedes↗

PubMed2000

Hepatic dysfunction in childhood dengue infection.

Hepatic functions of 61 children, diagnosed to have dengue infection (DI), aged 2 months to 12 years comprising 37 cases of dengue fever (DF), 16 with dengue hemorrhagic fever (DHF), and eight with dengue shock syndrome (DSS) were prospectively studied during the acute attack. Hepatomegaly (74 per cent), epistaxis (26 per cent), jaundice (25 per cent), and petechial rashes (18 per cent) were the common clinical manifestations of DI. On admission, levels of serum aspartate transaminase (AST), serum alanine transaminase (ALT) and serum alkaline phosphatase (AP) were raised in 80-87 per cent of children with hepatomegaly (group I) and 81 per cent of cases without hepatomegaly (group II). During the second week of hospitalization the proportion of cases with raised levels of AST, ALT, AP and serum bilirubin increased and the mean levels were significantly higher (p < 0.05) in both the groups. These levels gradually declined over the next 2-3 weeks. All the cases with DSS and DHF had raised AST, ALT and AP levels and the mean levels of these enzymes were significantly higher (p < 0.05) as compared to DF. Our results suggest a transient derangement of liver functions in childhood DI, more so in DSS and DHF, with or without hepatomegaly.

Child↗

PubMed2002

Randomized comparison of oxygen mask treatment vs. nasal continuous positive airway pressure in dengue shock syndrome with acute respiratory failure.

Dengue hemorrhagic fever (DHF) is caused by dengue virus. Patients with DHF grade 3-4, termed Dengue Shock Syndrome (DSS), may develop acute respiratory failure after initial fluid resuscitation. Previously, these patients were treated with oxygen on a nasal cannula, or if necessary with tracheal intubation and mechanical ventilation. In the present prospective randomized study, we compared the effectiveness of oxygen treatment administered by a face mask vs. nasal continuous positive airway pressure (NCPAP). Morbidity, mortality, and supportive treatment was evaluated. Thirty-seven patients with DSS complicated by respiratory failure were enrolled. On admission and after 30 min of treatment, clinical and paraclinical data were obtained. Chest X-ray revealed pleural effusion in 92 per cent and showed interstitial oedema in 33 per cent. After 30 min of treatment the respiratory rate decreased significantly in the NCPAP group (p < 0.05), while SaO2 and PaO2 increased in both groups (p < 0.01). However, subsequently a significant difference of unresponsiveness to treatment between the oxygen mask group and the NCPAP group (13/19 vs. 4/18,p < 0.01) was noted. Complications of NCPAP or oxygen mask treatment were not documented. We conclude that NCPAP is useful in improving the management of acute respiratory failure in children with DHF/DSS in dengue-endemic areas.

Child↗

PubMed2005

Hepatosplanchnic circulatory dysfunction in acute hepatic infection: the case of dengue hemorrhagic fever.

The mechanism of shock in patients with dengue hemorrhagic fever (DHF) has not yet been fully understood. In this study, we investigated the possibility of splanchnic venous pooling as a contributor for circulatory dysfunction in these patients. Ultrasonographic studies of portal vein and inferior vena cava were done in 45 patients with serologically or PCR-confirmed diagnosis of dengue virus infection. The size of portal vein and inferior vena cava, mean blood flow velocity in the right portal vein, and modified portal vein congestion index were compared between patients with dengue fever (DF, n = 20), DHF without shock (n = 14), and dengue shock syndrome (DSS, n = 11) during the toxic stage, convalescent stage, and at follow-up. The portal vein was significantly more dilated in patients with shock (DSS) than DHF without shock and than DF during the toxic and convalescent stages (P < 0.05), but not at follow-up. The change in the size of inferior vena cava followed the opposite trend (not statistically significant). Portal vein blood flow velocity was lower and congestion index was higher in shock cases (DSS) than DHF without shock and than DF at toxic and convalescent stages (P < 0.01). The differences disappeared at follow-up. Hepatosplanchnic venous pooling and/or dysfunction occur and correlate with the severity of circulatory derangement and shock in patients with DHF. The cause(s) and significance of hepatosplanchnic circulatory dysfunction in DHF and possibly other viral hepatic diseases deserve further study.

Adolescent↗