Showing papers on "Dengue virus published in 1983"

Transovarial transmission of dengue viruses by mosquitoes: Aedes albopictus and Aedes aegypti

Abstract: Transovarial transmission of all four dengue serotypes was demonstrated in Aedes albopictus mosquitoes. The rates of such transmission varied with the serotype and strain of virus. In general, the highest rates were observed with strains of dengue type 1 and the lowest with dengue type 3. Surprisingly, despite the use of viral strains of the four dengue serotypes which gave the highest rates with Ae. albopictus, transovarial transmission was observed in Aedes aegypti only with dengue type 1, and then only at a relatively low rate. Five different strains of Ae. aegypti were employed, including one that was known to be relatively susceptible to oral infection with dengue viruses. The findings support the view that Ae. aegypti, while of major importance from the point of view of transmission of dengue to man, may be relatively unimportant in the overall natural history of dengue viruses.

Rapid identification of dengue virus isolates by using monoclonal antibodies in an indirect immunofluorescence assay.

Abstract: Type-specific monoclonal antibodies prepared against the four dengue (DEN) virus serotypes were evaluated for their ability to identify low-passage human and mosquito isolates from Jamaica and West Africa by an indirect immunofluorescence assay. Serotyped human isolates from Jamaican dengue fever patients included 12 DEN-1, two DEN-2, and five DEN-4 viruses. Viruses from West Africa included 84 DEN-2 mosquito strains as well as two DEN-1 and one DEN-2 from humans. Results obtained using the immunofluorescence assay were consistent with virus identifications obtained using the more classical but costly and time-consuming plaque-reduction neutralization test. More viral isolates and higher virus yields were obtained using the C6/36 clone of Aedes albopictus cells rather than LLC-MK2 (monkey kidney) cells. Dengue type-specific monoclonal antibodies detected prototype viral antigens 24-48 hours postinfection in C6/36 cells. This is the first time that monoclonal antibodies have been used to serotype low-passage flavivirus isolates.

Clinical observations on virologically confirmed fatal dengue infections in Jakarta, Indonesia

Abstract: Thirty virologically confirmed cases of dengue infection with a fatal outcome were studied clinically in Jakarta, Indonesia, from 1975 to 1978. All 4 dengue virus serotypes were isolated from fatal cases, but dengue type 3 was responsible for 21 (70%) of these isolates, compared to only 47% of isolates from all cases of dengue infection. The majority (60%) of these 30 cases were males in the 5-9-year age group. Nonspecific signs and symptoms in the fatal cases were no different from those in patients who survived dengue infection, but 70% of the patients with fatal outcome had one or more signs of encephalitis, primarily convulsions and somnolence; 3 of them developed spastic tetraparesis before death and 2 died of an illness clinically compatible with viral encephalitis. Other unexpected observations were that only 63% of the patients had classical dengue shock syndrome with haemoconcentration, thrombocytopenia and shock. A high percentage (80%) had gastrointestinal haemorrhage, and in 9 patients (30%) this was severe enough to cause shock and death. In these 9 cases, the gastrointestinal haemorrhage and haematemesis began before the onset of shock and there was no evidence of haemoconcentration or pleural effusion at any time during hospitalization. According to certain widely accepted criteria, these patients would not be diagnosed as dengue haemorrhagic fever (DHF). But as they made up nearly one-third of the confirmed fatal dengue infections in this study and had massive gastrointestinal haemorrhages with thrombocytopenia, the definition of DHF should be changed to include this type of patient. It is proposed that the disease should be more realistically classified as dengue fever with or without haemorrhage and dengue shock syndrome.

Transovarial transmission of dengue 2 virus by Aedes aegypti in nature.

Abstract: Dengue 2 virus was recovered from three of 123 pools of naturally infected Aedes aegypti larvae (6,200 insects) collected from water containers in Rangoon. The virus was also isolated from two of 76 pools (7,730 mosquitoes) of male Ae. aegypti, collected as larvae and reared in the laboratory to adults. Minimum field infection rates among these two groups of mosquitoes were 1:2,067 and 1:3,865, respectively. Insect pools were inoculated into Toxorhynchites splendens mosquitoes and dengue viral antigen was subsequently detected in headsquash preparations by direct fluorescent antibody technique. Identification of the dengue serotype was done by complement-fixation test. This is the first report of dengue virus isolation from naturally infected mosquito larvae. These findings suggest that transovarial transmission of dengue virus occurs in nature.

Comparison of P388D1 Mouse Macrophage Cell Line and Human Monocytes for Assay of Dengue-2 Infection-Enhancing Antibodies

Abstract: Tissue culture-adapted dengue 2 virus (DEN 2), strain 16681, exhibits antibody-dependent enhancement of infection (ADE) in P388D1 cells, a mouse macrophage-like cell line. ADE is dependent upon maintaining DEN 2 multiplicity of infection at between 0.1 and 0.001, and can be simply measured in multi-well plastic plates. The assay uses either trypsinized or non-trypsinized P388D1 cells at 5 x 10(5) cells per ml, an appropriate dilution of DEN 2 virus, and a source of antibody, and is most conveniently performed without further washing of stationary cultures, which are incubated in 5% CO2. Trypsinization of P388D1 cells prior to the addition of virus-serum mixtures reduced infection in control cultures thus increasing ADE. When cells were washed after incubation of virus-serum mixtures for 1 hour, a paradoxical increase of infection in cultures exposed to virus plus normal serum was noted, which reduced the sensitivity of the ADE assay. Using human cord blood sera, ADE titers measured in human monocytes and P388D1 cells were closely similar. This convenient and economical assay will facilitate large scale biological and epidemiological studies of dengue virus enhancing antibodies.

Treatment of intracranial dengue virus infections in mice with a lipophilic derivative of ribavirin.

Abstract: Rimantadine, ribavirin, and 6-mercapto-9-(tetrahydro-2-furyl)purine, administered intraperitoneally every 8 h for 7 days starting minutes after virus challenge, had no effect on survival and mean survival time of BALB/c mice inoculated intracranially with dengue virus type 2. In contrast, intraperitoneal treatment with ribavirin 2',3',5'-triacetate, a lipophilic analog of ribavirin, effected significant increases in both mean survival time and survival rate, suggesting that ribavirin 2',3',5'-triacetate may be superior to rabavirin for treatment of viral diseases of the brain.

Serological studies on volunteers inoculated experimentally with a dengue virus strain in 1943.

Abstract: In 1943, a large dengue epidemic occurred in the Osaka district and several samples of dengue virus were isolated from patients with dengue fever by workers in this Institute. These were inoculated into human volunteers to confirm that they were dengue virus. In the present study, serum samples were collected from the volunteers who had been inoculated with dengue virus and were examined serologically. In the neutralization test, all the sera showed a higher titer against dengue type 1 virus (DEN-1) than against the other three types of dengue virus, indicating that the virus strain isolated in 1943 was DEN-1.

Effect of dengue virus infection on Fc-receptor functions of mouse macrophages.

Abstract: Fc-receptor-mediated attachment and ingestion of opsonized sheep erythrocytes (EA) by the macrophages of spleen and peritoneal cavity were studied during dengue virus type 2 (DV) infection of Swiss albino mice. Following intracerebral inoculation, virus antigen could be demonstrated by immunofluorescence in the splenic macrophages from day 4 and in peritoneal macrophages from day 5 post-infection, with a higher number of positive cells discernible on the 7th and 8th days. The virus could be isolated from spleen tissue from day 5. The total number of cells was markedly reduced from day 4 onwards both in the spleen and peritoneal cavity. A loss in the capacity to attach and ingest EA was noticed, the lowest values of attachment index (AI) and phagocytic index (PI) being reached on day 4. At later periods the AI values increased markedly but continued to be significantly less than those in uninfected control mice. The PI values continued to be lower throughout. The dichotomy between the Fc-mediated attachment and ingestion may be a mechanism for prevention of virus infection of macrophages.

Transmission of dengue virus by orally infected Aedes triseriatus.

Abstract: Transmission of dengue type 1 was demonstrated for 3 strains of Aedes triseriatus mosquitoes after oral infection. Rates of infection were similar to those observed in a control strain of Aedes aegypti. Three additional species belonging to the subgenus Protomacleaya (Aedes brelandi, Aedes hendersoni, and Aedes zoosophus) were also susceptible to oral infection with dengue type 1 virus but transmission could not be demonstrated although virus was detected in the salivary glands of infected mosquitoes. Virus transmission was demonstrated for Ae. hendersoni following parenteral infection. The results of this study support the view that non-Stegomyia mosquitoes may become involved in the transmission of dengue virus to humans.

Dengue virus-induced cytotoxic factor induces macrophages to produce a cytotoxin.

Abstract: In our earlier studies we have observed that T lymphocytes of dengue type 2 virus (DV)-infected mouse spleen produce a cytotoxic factor (CF). In the present study it has been observed that CF induces mouse spleen and peritoneal macrophages to produce a cytotoxin (CF2) as has been revealed by DEAE-cellulose chromatography. CF2 is produced by an induction process and is present intracellularly as well as leaking out of the cells. CF2 kills most of the macrophages and some of the T cells, as observed with CF. It appears that CF2 is produced to amplify the effect of CF and/or for cooperative action with CF.

Enhancement of dengue virus type 2 replication in mouse macrophage cultures by bacterial cell walls, peptidoglycans, and a polymer of peptidoglycan subunits.

Abstract: The effects of bacterial cell walls, peptidoglycans, and a water-soluble polymer of peptidoglycan subunits on dengue virus type 2 replication in cultured mouse peritoneal macrophages were studied. Pretreatment of macrophage cultures with all of test cell walls isolated from seven bacterial species for 3 days significantly enhanced the virus production in the cultures. Peptidoglycans prepared from four of the above cell walls also exerted the virus production-enhancing effects in a similar manner as the walls. A water-soluble polymer of peptidoglycan subunits which was prepared by treatment of Staphylococcus epidermidis wall peptidoglycan with an interpeptide bridge-splitting enzyme (endopeptidase) also definitely enhanced the virus production in macrophage cultures, although its activity was weaker than that of the original wall and peptidoglycan. Macrophage cultures from athymic nude mice, when treated with cell walls and peptidoglycans of S. epidermidis and Lactobacillus plantarum for 3 days, also showed an increased ability to support dengue virus type 2 replication. The infectious center assay demonstrated that the virus replication enhancement by S. epidermidis cell wall and peptidoglycan was primarily due to an increase in the number of virus-infected cells. This finding did not seem to be in conflict with the observation that macrophages treated with the above cell wall or peptidoglycan phagocytized more latex particles than did untreated macrophages. The conclusions based on the above experiments are that the treatment of mouse peritoneal macrophage cultures with bacterial cell walls and their components increases the take of dengue virus type 2 by macrophages and thus raises the virus production in the macrophage cultures.

Cultivation of mosquito cell lines in serum-free media and their effects on dengue virus replication

Abstract: Seven mosquito cell lines from five species (Aedes aegypti, Ae. albopictus, Ae. pseudoscutellaris, Culex tarsalis, andToxorhynchites amboinensis) were adapted to three kinds of serum-free media (SEM), which were composed of equal volumes of tryptose phosphate broth and of either Leibovitz (L15) medium, Eagle’s minimum essential medium, or Medium 199 with Hanks’ salts. Population growth rates of the cells cultivated in the SMFs were generally slower than those of original cell cultures maintained in conventional media containing bovine sera. A karyological study showed a significant shift to heteroploidy in two of the four cell lines examined. Four SMF-adapted sublines were compared with parental cultures for replication of dengue viruses.Ae. aegypti RML-12,Ae. albopictus C6/36,Ae. pseudoscutellaris AP-61, andTx. amboinensis TRA-171 demonstrated different levels of alteration in virus replication ranging from lower titers (as inAe. albopictus C6/36) to comparable or higher titers (as inAe. aegypti RML-12) when they were simultaneously inoculated with four dengue serotypes.

The problems of Aedes aegypti control in the Americas.

Abstract: The moso o Aedes aeupti, its increasing spread, and difficulties involved in its control, togethc pose one of the most serious public healt problems facing the Americas today. That problem is compounded by the long-term presence of two dengue virus serotypes (dengue-2, isolated in Trinidad in 1952, and dengue-3, isolated in Puerto Rico in 1963) and by the recent arrival of dengue serotypes 1 and 4, which were respectively introduced into the Caribbean in 1977 and 1981. Aedes aeupti is the vector of several arboviral diseases, two of which are important to man and usually occur in epidemic form. These diseases are yellow fever, which is fatal to a significant proportion of its victims, and dengue fever, which is not fatal to most victims, but which sometimes causes hemorrhagic symptoms, shock, and death. The urban-dwelling aegypti, which was introduced into the Americas around the time of the Spanish Conquest by ships coming from Africa, has been responsible for all urban epidemics of these diseases. Over the past five years, the incidence of these aegypti-transmitted diseases in the Amer-

Characterization of the cytotoxin produced by macrophages in response to dengue virus-induced cytotoxic factor.

Abstract: We have observed earlier that dengue type 2 virus-induced cytotoxic factor (CF) induces macrophages to produce a cytotoxin (CF2) which kills mainly the macrophages, some of the T lymphocytes and has no effect on B-lymphocytes of normal mouse spleen. The findings of the present study show that CF2 is heat-labile, trypsin-sensitive and unstable at acid and alkaline pH. It is a low molecular weight product as it is dialysable, non-sedimentable on ultracentrifugation at 103,500 g for 3 h and passes through 0.22 micron Millipore filter. It is adsorbed onto the target normal mouse spleen cells. The properties of CF and CF2 have been compared.

Effect of experimental dengue virus infection on immune response of the host. I. Nature of changes in T suppressor cell activity regulating the B and T cell responses to heterologous antigens.

Abstract: Summary Dengue virus-infected mice showed a depressed antibody response to polyvinylpyrrolidone (PVP) when compared to controls. In both control and dengue virus-infected animals which were treated with anti-thymocyte serum (ATS) and primed with PVP, there was a heightened antibody response to PVP, suggesting that the anti-PVP response was controlled by T suppressor cells. The increase in the anti-PVP response in dengue virus-infected, ATS-treated animals was found to be similar to that seen in ATS-treated controls. T cells from infected animals could transfer suppression of anti-PVP response to normal mice, whereas the T cells from control animals could not induce significant suppression. The T cells from dengue virus-infected animals which had received 2,4-dinitrofluorobenzene (DNFB) tolerogen could induce in normal mice a significantly higher percentage of tolerance to contact sensitivity to DNFB when compared to the control T cells. The adherent and B cells from both infected and control animals failed to induce significant tolerance. These findings suggested that during dengue virus infection, there is enhanced T suppressor cell activity regulating the B cell response to PVP and T cell response to DNFB.

Plasma membrane-acting drugs inhibit the effect of dengue virus-induced cytotoxic factor.

Abstract: Summary Our earlier studies reported that the cytotoxic factor (CF) produced in the spleen of dengue virus type 2-infected mice killed the lymphoid cells of many species of animals and induced normal mouse splenic and peritoneal macrophages to produce a cytotoxin (CF 2 ). In the present study, it has been observed that pretreatment of target cells with cell plasma membrane stabilizers — 2,4-dinitrophenol, ouabain and reduced glutathione — prevents the cytotoxicity of CF and blocks the production of CF 2 , but does not abolish the cytotoxic effect of the latter. CF thus appears to act on target cells through damage to the plasma membrane.

Temperature-sensitive events during the replication of the attenuated S-1 clone of dengue type 2 virus.

Abstract: Temperature-sensitive events occurring during the replication of the attenuated S-1 clone of dengue type 2 virus were examined. The S-1 clone was more thermolabile than the parent virus at the nonpermissive temperature of 38.5 degrees C. Adsorption experiments in fetal rhesus monkey lung cells revealed an inefficient adsorption of S-1 at 38.5 degrees C compared with the parent virus, suggesting an alteration in a thermolabile virion protein important in adsorption. The production of S-1 viral RNA and antigen occurred at the nonpermissive temperature, which indicated that early events in the replication cycle of S-1 were not affected. Release of infectious virus at 38.5 degrees C was not impaired; however, lower amounts of infectious virus in infected cells at the nonpermissive temperature indicated that maturation of the S-1 clone was suppressed.

Flavivirus infections in Chiang Mai area, Thailand, in 1982.

Abstract: Infection by JE virus still constitutes major cause of encephalitis in Chiang Mai Area, although some cases of possible dengue encephalopathy were observed. In spite of many apparent encephalitis cases, infection of vector mosquitoes by JE virus was not demonstrated. Virus isolation from hospitalized patients showed that the principal type of dengue virus circulating in Chiang Mai in 1982 was type 1 virus. Seroepidemiological survey on healthy humans indicated that the northern part of Chiang Mai Province in the region of the Maekong Valley has not yet been invaded so much by dengue viruses, compared with the Chiang Mai Valley, where dengue infection apparently became more prevalent than 12 years ago. The survey also indicated that the spread of JE virus in the study area was not uniform. Survey on vertebrates showed that anti-JE antibodies were highly prevalent among swine, horses, mules, sheep, and dogs. On the other hand, antibody prevalence was low in monkeys, ducks, and sparrows, and was negative among chickens and lizards. IgM-ELISA appeared to help differential diagnosis on JE from dengue even when the HI test did not give positive results.

Gambaran Epidemiologik Virus J.e. di Dua Kecamatan dalam Kotamadya Denpasar pada Tahun 1982

Abstract: An Epidemiological Study of J.E. virus was carried out in 1982 covering two kecamatan namely Badung and Bangli, Denpasar, Bali. Badung is recognized as an endemic area of DHF and suspected J.E, whereas Bangli is endemic of DHF only. Blood samples were collected from 587 children as 1-17 years old and from 220 young pigs while light traps were used for Culex collection in the sorrounding of JE cases. The JE virus transmission rates found are as follows : In Badung and Bangli, the transmission rate among the children was respectively 30% and 2%, while among the young pigs respectively 80% and 64 %. Mixed infections with Dengue virus were found in Badung and Bangli respectively 20% and 0%. As the dominant Culex species were found C. tritaeniorhynchus and C. fuscochepala in Badung and C. tritaeniorhynchus in Bangli.

Dengue haemorrhagic fever--case report.

Abstract: A 29-year-old Dutch tourist of the Caucasian race had to break her return journey from Indonesia as she developed dengue haemorrhagic fever. She appeared to have been infected on Bali. Serological investigation revealed very high antibody titres against dengue virus types 1 and 3 and a moderately high titre against type 4 virus in the serum sample collected two weeks after onset of disease. In the sample taken 14 weeks after onset only more normalized antibody titres against type 1 and type 3 remained detectable. Although during earlier trips to the tropics she never showed signs of dengue fever, the timing of her first infection remains uncertain. The influence of age, race and double infections is discussed with relation to the cause of dengue haemorrhagic fever.

Virological and Epidemiological Studies on Encephalitis in Chiang Mai Area, Thailand, in the Year of 1982 VIII. Summary and conclusion

Abstract: Virological and epidemiological studies performed in Chiang Mai in 1982 could be summarized as follows: (1) Dengue hemorrhagic fever (DHF) cases were observed mainly in Chiang Mai City, while encephalitis cases were observed more widely over Chiang Mai Province. (2) Almost half of the encephalitis appeared to be Japanese encephalitis (JE), although some cases were considered as dengue encephalopathy. (3) Enzyme-linked immunosorbent assay to measure IgM-antibodies against JE antigen helped to differentiate JE from dengue infection. (4) Dengue virus infection apparently become more prevalent in the study area compared with 12 years ago, and type 1 virus was the principal type of the virus circulating in Chiang Mai in 1982. (5) Northernmost part of Chiang Mai Province showed lower prevalence of flavivirus antibodies compared with Chiang Mai Valley. (6) Infection rate of vector mosquitoes with JE virus was low, compared with the number of apparent JE cases, although one-third of swine population possessed IgM antibodies against JE virus, (7) Infection of Hill Tribe People by JE virus remains to be elucidated in future studies.

Brief-Exposure Break-Bone Fever-Reply

Abstract: In Reply.— Drs D'Angelo and Burris raise a point in their case report about group B arbovirus (flavivirus) serology that is well known to arbovirologists but was beyond the scope of our brief review of dengue. That is, while patients with primary flavivirus infections often have a specific antibody response, a heterologous antibody response occurs in secondary infections, which makes infecting virus type identification by hemagglutination inhibition, complement fixation, or virus neutralization virtually impossible. 1 An exception might be tests for neutralizing antibodies with serum from a person for whom the first flavivirus infecting type is well documented. The only reliable way of identifying virus serotype in patients with secondary infections, therefore, is by virus isolation. Virus isolation is accomplished by inoculating serum into mosquitoes or mosquito culture. These techniques, developed and improved during the past ten years, have made dengue virus isolation a relatively easy process. Identification of dengue