Showing papers on "Dengue virus published in 1970"

Observations related to pathogenesis of dengue hemorrhagic fever. 3. Virologic studies of fatal disease.

Abstract: Virologic study of fatal dengue hemorrhagic fever (DHF) is a problem of special importance to an understanding of the pathogenesis of this disease. As opposed to experience in patients surviving DHF, virus isolations from fatal cases are extremely rare, three having so far been reported in the literature.`2 This report summarizes studies on autopsy materials submitted to the SEATO Medical Research Virology Department during the period 1962-64. the body was usually moved into a refrigerator until autopsy permission. The interval between death and autopsy was measured in the first 46 study cases and is shown in Table 1. These cases were all autopsied at the Children's Hospital. Organ sections were placed in separate containers and transferred to the Virus Laboratory on wet ice. They were then frozen and stored at-700 C. Venous blood was obtained from some patients with hemorrhagic fever who subsequently died. Collection of these specimens has been described.' In other instances heart blood was drawn immediately after the patient expired, placed at 40C. and brought to the laboratory. If not already hemolysed, the red cells were separated from serum. Serum was quick frozen in a dry-ice-alcohol bath and stored at-70°C. until tested. Twenty liver specimens were obtained immediately after death by use of Vim-Silverman needle. These tissues were immediately brought to the laboratory on wet ice.

Observations related to the pathogenesis of dengue hemorrhagic fever. II. Antigenic and biologic properties of dengue viruses and their association with disease response in the host.

Abstract: One of the hypotheses invoked to explain the occurrence of different diseases associated with dengue virus infection is that dengue viruses differ in virulence properties. Observations on virologically studied dengue fever and dengue hemorrhagic fever (DHF)\"'8 patients have reasonably established that both of these diseases are associated with dengue viruses of all known antigenic types. The possibility that virus strains within the same type differ in their virulence properties and that these differences might be genetically associated with surface antigen or other readily measured markers has not been examined. This hypothesis was the initiating motivation for this study. Using single lots of mouse immune ascitic fluids, we tested a large number of dengue viruses by a plaque reduction neutralization test and the results were compared with the disease response and geographic origin of virus strains. A few observations on biologic properties of the examined dengue virus strains are included. Plaque reduction test The production of LLC-MK2 monolayers, the techniques of plaque assay and the plaque reduction neutralization test have been given elsewhere.' In all tests, six repli-cate 2 oz. plaque bottles were used. All neutralization tests reported in this paper were performed by incubating serum and virus mixtures at 22-250C. for exactly 60 minutes. Reactions were stopped by dilution of serum-virus mixtures to 1:100 in chilled 0.75% bovine albumin-phosphate buffered saline, pH 7.8-8.0 (BAPS) or 20% heat inactivated agamma calf serum in phosphate buffered saline, pH 7.8-8.9. Residual virus was in-cubated on cell sheets for 90 minutes at 370C. before agar overlay.

Ecology and Control of Dengue Vectors on an Island in the Gulf of Thailand

Abstract: Entomological observations made on Koh Samui during an epidemic of dengue hemorrhagic fever in 1967 indicated that the densities of the populations of the 2 vector species, Aedes aegypti and Aedes albopictus , were directly related to the amount of rainfall during that period. The incidence of dengue virus infections in man and mosquitoes was also highest during the period of greatest precipitation. On Koh Samui A. aegypti was highly endophilic, while A. albopictus was exophilic, and there was very little overlap between the preferred habitats of the 2 species. Significant numbers of both species were observed to be taking multiple blood meals during their individual gonotrophic cycles. Effective control of the A. aegypti was achieved for a period of approximately 10 weeks in a village on the island by treatment of water storage containers with Abate and by ground applications of malathion fog. The results obtained suggest that such control measures would be effective in preventing dengue transmission by A. aegypti in Thailand.

Observations related to pathogenesis of dengue hemorrhagic fever. I. Experience with classification of dengue viruses.

Abstract: Two distinct syndromes associated with dengue virus infection are prevalent in tropical Asia; dengue fever, a benign disease characterized by fever, myalgia, leucopenia and a maculo-papular rash and dengue hemorrhagic fever (DHF), accompanied by fever, shock, hemorrhagic diathesis and a significant mortality.1 The dengue viruses, a group of antigenically related members of the Group B arthropod-borne virus family, are transmitted from man to man by the mosquito, Aedes aegypti. Multiple members of the group are known to be simultaneously transmitted in large urban areas of tropical Asia. Dengue disease syndromes of both types may occur concurrently, DHF usually is restricted to the indigenous population, while dengue fever may occur in both indigenous and non-indigenous residents of an area.\" When dengue hemorrhagic fever was first described in the Philippines, two new dengue viruses, types 3 and 4 were recovered from patients.' Shortly thereafter, dengue strains recovered from DHF patients in Thailand were tentatively designated types 5 and 6.5 As one explanation of the malignant type of dengue fever, it was suggested that dengue viruses had acquired virulence properties.6 A corollary to this hypothesis was that virulence and surface antigen were genetically linked and thus, the \"newer\" types of dengue viruses were the cause of the severe dengue syndrome. The hypothesis that DHF is due to a self-destructive host response has been proposed by Halstead and associates.7 They suggested that some persons are sensitized by their first dengue infection. In such a host the course

Arbovirus Replication in Mosquito Cell Lines (Singh) Grown in Monolayer or Suspension Culture

Abstract: SummarySingh's mosquito cell line derived from larval A. albopictus was grown in spinner cultures with a doubling time of 24-30 hr at 23 or 28°. It was found to be adaptable to various partially defined growth media. The typical chromosome count was 6, with 12 chromosomes appearing in 25% of figures. Infection of the cells with Sindbis virus or type 2 dengue virus at multiplicities of 1 or 2 pfu/cell and maintenance at 28° yielded viral growth cycles similar in timing to those seen in infected vertebrate cells at 37°. Cells chronically infected with Sindbis virus yielded virus at the rate of 1 pfu/cell/-day 7 weeks after infection. Sindbis virus production by cells exposed to actinomycin-D was unaffected by noncytotoxic doses. CPE due to actinomycin occurred at concentrations similar to those affecting vertebrate cells.

Protection against St. Louis encephalitis and West Nile arboviruses by previous dengue virus (types 1-4) infection.

Abstract: Summary Hamsters inoculated with Den-2 virus were shown to survive peripheral challenge with large amounts of WN virus. Dengue types 1, 3, and 4 gave less complete protection than Den-2. Cynomolgus monkeys with probable naturally acquired Den-2 neutralizing antibody were shown to be protected from a persistent viremia following SLE virus inoculation. Serological tests on both hamsters and monkeys were of the expected pattern but did not lead to an understanding of the specific mechanism involved in the cross protection. These results support epidemiological observations of the absence of severe epidemics of JBE, SLE, WN, and other Group B encephalitides in areas with endemic dengue.

Studies on arboviruses in Egypt. II. Contribution of arboviruses to the aetiology of undiagnosed fever among children.

Abstract: Acute blood samples from 120 children, attending the fever hospital in Alexandria and complaining of fever, were collected and examined for haemagglutination-inhibiting (HAI) and complement-fixing (CF) antibodies against the following arbovirus antigens; Sindbis, West Nile (WN), yellow fever, dengue 1, sandfly fever, Quaranfil, Chenuda and Nyamanini. Positive reactions in the acute sera were only detected against Sindbis (4·3%) and WN (4·3%) antigens. The convalescent sera obtained from 48 of these children showed a pronounced HAI titre against WN antigen in 14·6% of them. The same sera showed a lower titre against yellow fever antigen (Asibi strain) which is due to cross-reaction between the two viruses. None of the acute or the convalescent sera showed CF antibodies against Quaranfil, Chenuda or Nyamanini antigens. The convalescent sera were not tested against dengue type 1 antigen. It is suggested that of the known arboviruses in Egypt, WN is the most important from the public health point of view.

Dengue virus plaque development in simian cell systems. I. Factors influencing virus adsorption and variables in the agar overlay medium.

Abstract: Chemical and physical variables influencing the plaquing of all dengue serotypes in two simian cell systems were studied. Calf serum in the nutrient overlay may be replaced by mouse ascitic fluid or bovine plasma albumin when employing the rhesus monkey kidney LLC-MK2 cell system for plaquing all dengue serotypes. Doubling the serum concentration in the overlay had little effect in modifying dengue types 1, 2, 3, and 4 plaque titers. Newborn agamma, 4-week-old and 8-week-old calf serum gave comparable titers with all dengue virus serotypes. Dengue virus titers, plaque size, and development time were unaffected by sodium bicarbonate concentrations ranging from 1.1 to 4.4 mg/ml of overlay. A twofold increase (0.00332 g%) in the amount of either autoclaved or filtered-sterilized neutral red reduced the dengue 2 virus titer as much as 2.2 logs. An increased Mg++ and decreased Ca++ concentration in the overlay medium increased the efficiency of the plaquing system.

Dengue virus plaque development in simian cell systems. II. Agar variables and effect of chemical additives.

Abstract: Dengue type 2 virus, strain New Guinea B, plaqued with equal facility and titer under overlays containing six different grades of commercial agar in the LLC-MK(2) cell system. Doubling the agar volume on LLC-MK(2) cell monolayers increased the plaque development time of dengue type 1, strain Hawaii. Storage of agar at 56 C reduced or totally abolished dengue type 4, strain H-241, plaque titer in LLC-MK(2) cells. The influence of six known virus plaque-enhancing compounds on plaque development of all dengue virus serotypes was studied in two continuous simian kidney cell lines, LLC-MK(2) and Vero. In the absence of any chemical additive, plaque development of all dengue serotypes was more rapid (4 to 10 days) in the LLC-MK(2) line than in the Vero line (6 to 13 days). Increased plaque development time of type 1, strain Hawaii, by pancreatin and plaque-size doubling of dengue types 1 and 4 was the only advantage conferred by the addition of six chemical additives in the LLC-MK(2) cell system. Dengue types 1 and 6 failed to plaque in the Vero cell system unless aided by a plaque-enhancing compound; plaques of dengue types 2, 3, 4, and 5 appeared sooner (2 days) and were increased in plaque diameter. The optimal DEAE concentration for plaquing dengue type 1, strain Hawaii, was 100 mug/ml; plaque development either failed at lower concentrations or was inhibited at higher (200 mug/ml) concentrations.