Showing papers on "Dengue virus published in 1982"

Dengue Virus-Specific and Flavivirus Group Determinants Identified with Monoclonal Antibodies by Indirect Immunofluorescence

Abstract: Monoclonal antibodies produced against the four dengue virus serotypes identified four categories of reactions by immunofluorescence: flavivirus group reactive, dengue complex specific, dengue subcomplex specific (DEN-1, DEN-3), and dengue serotype specific. This is the first time that monospecific antibodies have been available for all of these unique antigenic determinants. Hybridoma cell lines producing dengue type-specific antibodies have been deposited in the Hybridoma Cell Bank of the American Type Culture Collection (Rockville, MD) for general distribution.

Infection enhancement of dengue type 2 virus in the U-937 human monocyte cell line by antibodies to flavivirus cross-reactive determinants.

Abstract: Dengue type 2 virus replication was detected in the U-937 human monocyte cell line when the virus inoculum and the culture medium contained flavivirus antibodies diluted beyond their neutralizing titers. This was in marked contrast to yellow fever virus, which replicated very well in the absence of antibodies; however, 10-fold-higher yields of yellow fever virus could be obtained in the presence of flavivirus antibodies. These infection-enhancing antibodies were obtained from either a dengue type 2 human antiserum or reference hyperimmune obtained from either a dengue type 2 human antiserum or reference hyperimmune mouse ascitic fluid. The infection enhancement phenomenon, previously shown to be due to infection of Fc receptor-bearing cells with virus-antibody complexes, was completely blocked by preincubation of the cells with aggregated gamma globulin. The blocking results suggested an Fc receptor-mediated infection of the U-937 cells as well. A panel of monoclonal antibodies, previously characterized as either virus type specific or flavivirus cross-reactive and with mouse immunoglobulin subclasses G1 and G2a in both categories, were tested for their infection enhancement characteristics. A type-specific neutralizing monoclonal antibody preparation that was diluted beyond its neutralization titer did not cause infection enhancement, nor did low-level neutralizing monoclonal antibodies that were dengue serotype specific by the hemagglutination inhibition test. Only flavivirus cross-reactive monoclonal antibodies caused infection enhancement, irrespective of whether the immunoglobulins were G1 or G2a. These cross-reactive flavivirus determinants may reside at the tips of the glycoprotein projections on the virus particles, enabling the Fc ends of the cross-reactive antibodies attached to these determinants to interact with Fc receptors on susceptible cells.

Demonstration of interference between dengue virus types in cultured mosquito cells using monoclonal antibody probes.

Abstract: Summary Cultured Aedes albopictus cells (clone C6/36), persistently infected (PI) with dengue virus type 1 (dengue-1) were found resistant to superinfection with dengue virus type 3 (dengue-3). This was determined by indirect immunofluorescent (IF) staining of cultures using monoclonal antibody against a dengue-3 type-specific antigen. Dengue-1 PI cultures stained with this antibody 3 days after superinfection with dengue-3 virus (m.o.i. of 2) had dengue-3 antigen in 0.1 to 1.0% of the cells. Control cultures infected with dengue-3 at the same multiplicity contained dengue-3 antigen in greater than 90% of the cells. The resistance to superinfection was not interferon-mediated, and occurred within 20 h after primary infection. In cultures simultaneously infected with two dengue virus types, one virus type was excluded from replication in most cells. A small population of cells was also found (about 1%) that contained type-specific antigen of both dengue virus types.

Dengue-2 vaccine: oral infection, transmission, and lack of evidence for reversion in the mosquito, Aedes aegypti.

Abstract: The dengue-2 vaccine virus (S-1), and its parent virus (PR-159), were compared for their ability to infect orally, to replicate in, and subsequently to be transmitted by Aedes aegypti mosquitoes. The vaccine virus was markedly less efficient in its ability to infect mosquitoes orally. After ingesting infectious bloodmeals containing 3, 7 to 8.2 log10MID50/ml of the respective viruses, 56% (220/396) of the mosquitoes became orally infected with the parent virus contrasted with 16% (66/397) for the vaccine virus. None of the 16 infected mosquitoes transmitted the vaccine virus, while 14% (3/22) of the mosquitoes transmitted the parent virus. The vaccine virus remained temperature-sensitive (restrictive temperature 39 degrees C) after orally infecting and replicating in Ae. aegypti mosquitoes.

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

Abstract: 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.

Immunological enhancement and the pathogenesis of dengue haemorrhagic fever.

Abstract: Laboratory studies have provided evidence that the replication of dengue viruses in preparations of primary peripheral blood mononuclear cells of human or simian origin, or in macrophage-like cell lines of human or murine origin, may be enhanced by sub-neutralizing concentrations of homotypic dengue antibody, by heterotypic dengue antibody, or by antibody against heterologous flaviviruses. The mechanism underlying this phenomenon is discussed in the context of dengue haemorrhagic fever and the dengue shock syndrome.

Evaluation of Toxorhynchites splendens (Diptera: Culicidae) as a bioassay host for dengue viruses.

Abstract: Toxorhynchites splendens , a nonhematophagous mosquito, was evaluated as a bioassay host for the detection and propagation of dengue viruses. All dengue virus serotypes and strains attained titers in Tx. splendens comparable to those observed for 2 strains of Aedes aegypti . Peak virus titers occurred in Tx. splendens approximately 6 days postinoculation; however, specific fluorescence for all viruses was not observed in 100% of mosquito heads until 12 days postinoculation. A 100% correlation was noted between specific fluorescence in Tx. splendens heads and the recovery of virus from corresponding thoraxabdomens. The volume of inoculum tolerated by Tx. splendens was approximately 5 times greater than that injected into Ae. aegypti . Thus, for a given volume of inoculum, the number of Tx. splendens required for virus assays was appreciably less than that needed for Ae. aegypti . The overall survival rate for Tx. splendens following intrathoracic inoculation with dengue viruses was 92%, compared to 41 and 42% for 2 strains of male Ae. aegypti . These findings imply that Tx. splendens would be more efficient than Ae. aegypti as a laboratory assay host for detecting dengue viruses in blood of infected patients and for use in experimental investigations.

Ultrastructural changes in skeletal muscles in dengue virus‐infected mice

Abstract: Dengue type 2 virus was inoculated intracerebrally in 20 adult swiss albino mice. Thigh muscles were removed after 24 h 3, 5 and 7 days after virus inoculation. Electron microscopic studies of the striated muscles show destruction of myofibrils, rarification of the sarcoplasmic reticulum network and changes in the mitochondria. Aggregates of electron-dense material as well as glycogen particles were also seen in the cytoplasm.

Persistent infection of a nonvector mosquito cell line (TRA-171) with dengue viruses.

Abstract: Dengue viruses often caused an apparent, persistent infection in a cell line derived from a nonvector mosquito, Toxorhynchites amboinensis . The characteristics of the viruses were m

Dengue virus replication in a polyploid mosquito cell culture grown in serum-free medium.

Abstract: A subline of a polyploid cell line (TRA-284) derived from a nonbiting mosquito, Toxorhynchites amboinensis, was adapted to a serum-free medium. The sensitivity of the subline (TRA-284-SF) to all serotypes of adapted dengue viruses was generally comparable to that of Aedes albopictus (C6/36), and DEN 3 viruses replicated to higher titers in TRA-28F-SF cells than in C6/36 cells. The subline was found to be useful for isolation of dengue viruses from human serum, since isolation rates were higher in TRA-284-SF cells than in C6/36 cells. The advantages of using a serum-free medium and mosquito cells for virus isolation are discussed.

Dengue Virus Multiplication in Cultures of Mouse Peritoneal Macrophages:Effects of Macrophage Activators

Abstract: Dengue-2 virus multiplied in cultures of methylcellulose-induced peritoneal macrophages of BALB/c mice. The in vitro-cultivated macrophages from dengue-1 virus-immune mice produced larger amounts of dengue-2 virus than did those from nonimmune controls. The effect of macrophage activators was examined by using nonimmune macrophages. Enhanced virus production was demonstrated in cultures of macrophagges pretreated with phytohemagglutinin (PHA) or bacterial lipopolysaccharide (LPS). The number of virus-infected cells in the pretreated cultures was estimated to be about 0.01% or less of the total macrophages. Continuous treatment of macrophages with PHA before and after virus inoculation brought about the most marked enhancement of dengue-2 virus multiplication. On the other hand, treatment with concanavalin A or pokeweed mitogen showed little effect on the multiplication of the same virus. Treatment with carrageenan, a specific macrophage blocking agent, markedly suppressed dengue-2 virus production in both dengue-1 virus-immune macrophages and LPS-treated macrophages. The indirect fluorescent-antibody (FA) technique revealed dengue-2 viral antigen in the cytoplasm of infected macrophages, and the FA-positive macrophages were more numerous in PHA-treated cultures than in untreated controls. The results obtained are discussed in relation to a possible role of activated monocytes/macrophages in the pathogenesis of dengue hemorrhagic fever.

Dengue-2 vaccine: infection of Aedes aegypti mosquitoes by feeding on viremic recipients.

Abstract: Colonized Aedes aegypti mosquitoes were fed on voluntary recipients of an experimental, live, attenuated, dengue type 2 (PR 159/S-1) vaccine to estimate the frequency of vector infection and the stability of the virus in mosquitoes. Two volunteers were viremic at the time of mosquito feeding, but only two of 114 mosquitoes that took a viremic blood meal became infected with the vaccine virus. Strains of virus recovered from the bodies of the mosquitoes and the volunteer's blood retained the temperature sensitivity and small plaque growth characteristics of the vaccine virus. Dengue viral antigen was not detectable in any of the mosquito heads by direct immunofluorescence and in vitro virus transmission by droplet feeding was not observed. This experiment showed that vector mosquitoes can be infected with vaccine virus by feeding on viremic vaccinees. Furthermore, the virus is sufficiently stable to retain the in vitro growth characteristics associated with the vaccine virus.

Induction and Characterization of Delayed-Type Hypersensitivity to Dengue Virus in Mice

Abstract: Delayed-type hypersensitivity (DTH) to dengue virus type 4 in mice is described. The DTH reaction (measured by footpad swelling) was maximal at 24 hr after challenge and was enhanced significantly when mice were pretreated with cyclophosphamide. The response was maximal six days after infection with an immunizing dose of approximately 10(7.3) 50% lethal doses per mouse. Histologic examination of the test footpad showed a predominantly mononuclear cell infiltrate at 24 hr after challenge. fibrin deposition was also noted. DTH reactivity was transferable to normal mice by injection of immune spleen cells but not of immune serum. The DTH reaction was apparently specific for dengue virus type 4 because significantly lower responses were detected when dengue virus types 1-3 and Japanese encephalitis virus were used as challenge antigens in mice infected with dengue virus type 4. The probable importance and significance of these findings in relation to the host immune response and the pathogenesis of dengue virus infection are discussed.

Depressed macrophage functions in dengue virus-infected mice: role of the cytotoxic factor

Abstract: Dengue virus Type 2 (DV) infection causes immunosuppression in mice. Since macrophages are crucial for immune response, we have studied their functions in this condition and report our findings here. It was observed that in DV-infected mice the phagocytosis of neutral-red and latex particles by splenic and peritoneal-cavity macrophages was significantly reduced (P less than 0.001) from Days 3 to 10 after inoculation. Similarly the migration of splenic and peritoneal macrophages on a glass surface was reduced significantly (P less than 0.001) from Days 4 to 10 after inoculation. Pre-treatment of normal mouse spleen cells with DV-induced cytotoxic factor (CF) inhibited the phagocytic and migratory functions in the same way as observed in DV-infected mice. Higher dilutions of CF (10(-3) and 10(-3.7)) did not kill the cells but affected their functions. It was concluded that macrophage functions are affected by killing and metabolic changes in these cells by DV-induced CF, thus producing immunosuppression.

Serological studies on a case of laboratory dengue infection.

Abstract: One of the authors (Y.O.), who had previously been immunized with Japanese encephalitis (JE) vaccine, showed symptoms of typical dengue fever 6 days after accidental infection with a newly isolated dengue type 4 virus strain from a patient with dengue hemorrhagic fever (DHF) in Thailand. His sera were examined by hemagglutination inhibition (HI), complement fixation (CF) and neutralization (N) tests. The JE N antibody titers of his sera were high even on the first day of the illness and remained almost constant during the next year. Antibodies that reacted with dengue viruses were detected from a very early stage of the illness by all three serological tests. In addition, his convalescent phase sera showed high titers against all 4 types of dengue virus. These data suggest that the dengue infection caused secondary stimulation of antigens of flavivirus. Sedimentation analysis of antibodies in Y.O.'s serum (day 9) was carried out and IgM antibody that reacted only with dengue type 4 virus and homologous infecting virus was separated. These findings clearly demonstrated that the laboratory infection of Y.O. was primary dengue infection with dengue type 4 virus.

Fluorescent antibody techniques applied to the identification of dengue virus in infected tissue.

Abstract: We evaluated an indirect fluorescent antibody (FA) method for the detection of dengue virus antigen in infected mouse tissues. The biotin-avidin system [unlabeled antiviral antibody, biotinyl-anti-IgG and fluorescein conjugated avidin D(biotin-avidin system)] theoretically enhances the sensitivity of the FA method by amplifying the number of fluorescein particles attached indirectly to antigen. Using antibody endpoint titers in dengue-infected suckling mouse brain as an assay for sensitivity, we compared this three-step technique with the standard direct and two-step indirect FA techniques. Comparative tests were done on frozen sections of mouse brains with infectivity titers between 4.5 and 8.3 log10 LLC-MK2 cell PFU/g. Antibody endpoint titers with the biotin-avidin system were 2- to 8-fold higher than those obtained with the indirect and direct fluorescent antibody systems. The biotin-avidin system may be useful for rapid postmortem diagnosis of some fatal dengue hemorrhagic fever-dengue shock syndrome cases and perhaps also for early diagnosis of dengue by examination of leukocytes or biopsy material.

Replication of dengue virus in cultured mosquito cells at suboptimal temperature.

Abstract: Cultured Aedes albopictus mosquito cells were infected at optimal (28°) and suboptimal (20°) temperatures with dengue virus type-3 at multiplicities of infection of 2.0 and 0.01. Extracellular and intracellular virus titers were determined over an interval of 6 weeks by fluorescent focus assay using hyperimmune mouse ascities fluid as a source of antibody. Upon infection at a multiplicity of 2.0, cultures at 28° reached peak virus titers in 3 days, while cultures at 20° required 14 days. At a lower infection multiplicity of 0.01, peak titers were reached in 5 days at 28°, but required 3 weeks at 20°. Viral titers maintained after the peak was reached were the same at both infection multiplicities and temperatures tested. At both 28° and 20° A. albopictus cultures became persistently infected with 20-30% of the cells containing immunofluorescent cell-associated viral antigen. These results indicate that the time required to reach peak infectious virus titers for dengue-3-infected A. albopictus cell...