Showing papers on "Dengue virus published in 1977"

Dengue viruses and mononuclear phagocytes. I. Infection enhancement by non-neutralizing antibody.

Abstract: Cultured mononuclear peripheral blood leukocytes (PBL) from nonimmune human beings and monkeys are nonpermissive to dengue 2 virus (D2V) infection at multiplicities of infection of 0.001-0.1, but become permissive when non-neutralizing dengue antibody is added to medium. D2V infection occurred in PBL prepared from anti-coagulated but not from defibrinated plasma. Infection enhancement was produced by multiple lots of heterotypic anti-dengue raised in several mammalian species. Homotypic anti-dengue neutralized D2V at high concentrations but enhanced at low concentrations; enhancement end point in one serum was 1:320,000. The infection-enhancing factor was a noncytophilic antibody of the IgG class. D2V infection occurred in the absence of heat-labile complement components but did not occur when complexes were prepared with anti- dengue F(ab)(2). Treatment of PBL with several proteases increased permissiveness to D2V infection by immune complexes but not by virus alone. Two rhesus monkey serums collected 14 days after D2V infection contained an IgG antibody with high-titered enhancing activity but with no hemagglutination-inhibition or neutralizing activity. Virus-antibody complexes are irreversibly attached to PBL within 15 min and completely internalized in 60 min. There was considerable variation in cellular infection in different experiments, however, maximum virus yields usually exceeded 1,000 plaque-forming units per 1 x 10(6) PBL occurring between 2 and 4 days in culture. In vitro antibody-dependent infection of PBL provides a possible model for study of pathogenetic mechanisms in infants with dengue shock syndrome who passively acquire maternal anti-dengue IgG.

Antibody-enhanced dengue virus infection in primate leukocytes

Abstract: DENGUE viruses, types 1–4, are arthropod-borne flaviviruses which cause dengue shock syndrome (DSS) in humans possessing pre-infection antibody, passively acquired or derived from heterotypic infection1. Although the immuno-pathological mechanism of DSS is not fully understood, experimental studies suggest that dengue virus production is immunologically regulated. Monkeys with monotypic immunity to dengue types 1, 3 or 4 viruses, when challenged with dengue 2, had significantly higher levels of circulating virus than did similarly infected susceptible animals2. This may be attributable to the replication of virus in leukocytes. In infected monkeys, virus was frequently recovered from buffy coat cells and from lymphatic tissues3. The role of leukocytes in enhanced infection is further supported by the observation that dengue replicates readily in cultures of peripheral blood leukocytes (PBL) prepared from immune simian or human donors, but poorly or not at all in leukocytes from non-immune hosts4–6. Studies on the immunological specificity of this phenomenon have been hindered by the requirement either for expensive experimental hosts (monkeys) or for human donors with chronologically defined dengue infections. Here we describe the in vitro enhancement of dengue infection in PBL by antibody. This system provides a provisional model for DSS in young infants during primary dengue infections7,8.

Dengue viruses and mononuclear phagocytes. II. Identity of blood and tissue leukocytes supporting in vitro infection

Abstract: Studies were made on the identity of human and monkey mononuclear leukocytes permissive to antibody-enhanced dengue 2 virus (D2V) infection. In cultures of peripheral blood leukocytes (PBL) inoculated immediately after separation, it was concluded that only mononuclear phagocytes support dengue infection. This is based upon observations that D2V-permissive cells were resistant to 1,200 rads, were both plastic adherent and nonadherent, were removed when passed through nylon wool columns in 10 percent fetal bovine serum or 100 percent autologous serum, and were destroyed by incubation with 100 mug/ml particulate silica. On direct immunofluorescence staining, perinuclear dengue antigen was visualized at 24 h, becoming maximal at 60 h. Antigen-containing cells had ample cytoplasm, ruffled cytoplasmic membrane, and 73 percent were actively phagocytic. As further evidence of the infection of mononuclear phagocytes, antibody-enhanced D2V replication was observed in bone marrow cultures from five of five rhesus monkeys, but not in cell cultures of spleen, thymus, or lymph nodes prepared from the same animals. It is hypothesized that dengue virus complexed with non-neutralizing antibody is internalized by immune phagocytosis in a mononuclear phagocyte with a defective virus-destroying mechanism. Dengue permissiveness may depend upon cellular immaturity since bone marrow leukocytes could be infected even when held for 4 days before infection while PBL held for this time decreased in permissiveness. In vitro antibody-dependent infection of mononuclear phagocytes should prove useful as a model for study of immunopathologic mechanisms in human dengue.

Antigenic characterization of flavivirus structural proteins separated by isoelectric focusing.

Abstract: Isoelectrofocusing of nonionic-detergent-disrupted flaviviruses separated the envelope glycoprotein of 53,000 to 58,000 daltons and the nucleocapsid protein of 14,000 daltons. The envelope protein and nucleocapsid protein were isolated at isoelectric points of pI 7.8 and 10.3, respectively. The antigenic determinants of St. Louis encephalitis, Japanese encephalitis, and dengue virus envelope and nucleocapsid proteins were examined by solid-phase competition radioimmunoassay. By the appropriate selection of antiserum and competing proteins, it was possible to distinguish type-specific, complex-reactive and flavivirus group-reactive antigenic determinants. The envelope glycoproteins of St. Louis encephalitis, Japanese encephalitis, and dengue viruses were found to contain each of these three classes of antigenic determinants. Most of the determinants on the envelope protein were type specific, some were complex reactive, and a small fraction were flavivirus group reactive. The nucleocapsid protein contained only flavivirus group-reactive antigenic determinants.

Dengue virus infections in Nigeria: a survey for antibodies in monkeys and humans.

Abstract: A retrospective serological survey for dengue immunity was conducted in Nigeria to determine the prevalence of infection in man and non-human primates. Preliminary haemagglutination-inhibition (HI) tests revealed that 63% of persons tested had HI antibodies against one or more of the following flaviviruses: dengue type 1, yellow fever, West Nile and Wesselsbron. Parallel HI and neutralization (N) tests on 179 human sera showed that six of 20 sera (30%) negative for flavivirus HI antibody contained dengue N antibody. This finding emphasized the advantage of the N test over HI in screening for dengue virus immunity. Neutralization tests performed on 1,816 human sera from different geographical locations in Nigeria showed that 45% of Nigerians were immune to dengue type 2 virus. The percentage of immunity in adults aged 20 years and older (51%) was significantly higher than in children (37%) (P less than 0-01). In all four ecological zones sampled, the highest percentage of dengue N antibody was observed in the derived Savannah zone (63%) followed by the rain forest zone (42%). The Southern Guinea savannah and plateau zones had lower percentages of dengue-immune persons. There was a higher prevalence of antibodies in urban (48%) than in rural communities (37%). Tests on dengue-immune sera showed that 35% of such sera contained N antibodies to dengue only or to dengue and one other virus. Therefore, dengue immunity cannot be explained by heterologous cross reactions within the flavivirus group. In addition, evidence of dengue infection was found in monkeys and galagos. 48% of monkeys and 25% of galagos contained dengue N antibody. The presence of specific dengue N antibodies in a few sera suggests that the occurrence of a forest cycle of dengue is possible in Nigeria.

Epidemiological investigations on arbovirus infections at Igbo-Ora, Nigeria.

Abstract: A study of arbovirus infections occurring in Igbo-Ora community was carried out between May and October 1975. Haemagglutination inhibition test performed on seventy-eight human sera showed a high prevalence of antibodies against all the six arboviruses used. Percentage of positive sera were as follows: Chikungunya, (28%); Yellow fever (36%); Dengue type 1 (67%); Dengue type 2 (45%). Prevalence of HI antibodies to West Nile and Wesselsbron viruses were 44% and 59% respectively. Virus isolation studies carried out on 148 blood samples yielded three viruses: Yellow fever, Dengue type 1 and Zika. Antibody conversions to these three viruses were demonstrated in seven persons within the period of study.

Virulence and immunogenicity of a temperature-sensitive dengue-2 virus in lower primates.

Abstract: Clones of dengue-2 virus were tested for virulence by inoculation of rhesus monkeys and chimpanzees. Although primates showed no overt signs of illness, inoculation with the parent virus or a subline of a large-plaque clone resulted in a viremia lasting 1 to 7 days. By these criteria, sublines of a small-plaque clone were significantly less virulent and produced little or no viremia in primate hosts. Although they had a substantially reduced viremia, primates inoculated with the small-plaque sublines showed stimulation of complement-fixing, hemagglutination-inhibiting, and neutralizing antibodies. The protection afforded rhesus monkeys 3 months after inoculation with two of the small-plaque sublines was demonstrated by a lack of viremia and a failure to escalate preexisting antibody levels after challenge with the parent virus. Both the S-1 subline and the parent virus had a limited capacity to produce central nervous system pathology in monkeys inoculated intrathalamically and intrathecally. Evidence thus far accumulated for primates indicates that the S-1 subline of dengue-2 virus has potential value as a candidate vaccine virus.

Effect of immunosuppression on dengue virus infection in mice.

Abstract: Mean survival time following intracerebral inoculation of dengue virus was reduced and the titre of the virus in the brain of immunosuppressed mice was markedly increased. A single dose of cyclophosphamide given 24 h after dengue virus i.c. or i.p. substantially reduced the number of antibody forming cells in the spleen. Three doses of dengue virus, each followed by cyclophosphamide 24 h later, produced specific hyporesponsiveness to the dengue virus but not to a heterologous virus (Coxsackie B4), with a reduction in antibody forming cells in the spleen of such animals against dengue virus but not against Coxsackie B4 virus. Adoptive immunity by antiserum was abolished along with increased titres of the virus in the brain of immunosuppressed mice but the protection could be restored by a second dose of antiserum. Pre-treatment of mice with immune or normal spleen cells i.v. or reconstitution of immunosuppressed mice by such cells had no effect. Thus, humoral antibodies play a crucially important role in host defence mechanism in recovery of mice from primary dengue virus infection.

The mosquitoes of Polynesia with a pictorial key to some species associated with filariasis and/or dengue fever.

Abstract: A list of the mosquitoes of Polynesia is tabulated and their dis- tribution outlined. Keys for the identification of adults and larvae of Poly- nesian species are provided, A pictorial key for the recognition of species associated with filariasis and dengue fever is furnished for the use of field workers.

Type 1 dengue with hemorrhagic disease in Fiji: epidemiologic findings.

Abstract: An explosive epidemic of dengue occurred in Fiji between January and July 1975. All laboratory evidence indicated that type 1 dengue was the only prevalent dengue virus. This type had probably not been in Fiji for 30 years and over 70% of the population was susceptible. Aedes aegypti appeared to be the major vector in urban areas, but circumstantial evidence indicated that Aedes rotumae was a vector in at least one remote area. All forms of the clinical spectrum of dengue were seen and reported in all age groups. Overt clinical symptoms tended to be less frequent among children under age 10 and adults over age 30. Approximately 16% of persons reporting dengue-like illness had some type of bleeding associated with their disease with little difference by age, sex, or ethnic group. Epistaxis and gingival bleeding were the most commonly reported and observed hemorrhagic manifestations, but internal bleeding was reported in about 25% of hemorrhagic cases. The proportion of hemorrhagic cases was the same among primary and secondary dengue-infected persons. These and other epidemiologic observations did not support the hypothesis that the hemorrhagic complications seen with dengue occur only in secondary infections.

Quantitative Aspects of Replication of Dengue Viruses in Aedes Albopictus (Diptera: Culicidae) After Oral and Parenteral Infection

Abstract: Replication of the 4 prototype strains of dengue viruses was studied in male and female Ae. albopictus mosquitoes following intrathoracic infection, and in females following oral infection. Replication was rapid in both sexes and virus titers reached levels of 107 or more mosquito infectious doses50 per insect in females. Titers attained in males were about 5-fold less than in females. Maximum titers occurred several days later in females infected orally as compared with those infected intrathoracically. Virus titers in both sexes declined slowly after reaching their maxima. Replication of 3 nonprototype strains of dengue type 3 also was studied in male and female Ae. albopictus mosquitoes following intrathoracic infection. Replication of each strain appeared to be significantly different than the prototype.

Morphogenesis of Dengue-1 Virus in Cultures of a Human Leukemic Leukocyte Line (J-111)

Abstract: In previous experiments we found that cultures of a human leukemic leukocyte line ( J-111) supported good growth of dengue-1 virus (K. Shiraki and S. Hotta, unpublished data). In this communication we describe results of electron microscopic observations on the infected J-111 cells. Two strains of dengue-1 virus were used: Mouse-passaged Mochizuki strain, and strain 32748 propagated in Aedes albopictus mosquitoes (kindly supplied by Dr. L. Rosen, Pacific Research Section, NIH, Hawaii) (11). The former was in the form of infected mouse brain homogenate, and the latter was of mosquito emulsions

Opportunities for the Future

Abstract: This monograph ends with a lengthy and rather inconclusive discussion on the current status of dengue vaccines for use of man. This emphasis is deliberate: the practical solution of pressing medical problems through prophylaxis or therapy is, after all, an ultimate aim of “basic” and “applied” research on infectious diseases; the inconclusiveness shows how much more needs to be learned.

Definitions and Nomenclature

Abstract: Dengue is the accepted name of an acute infectious disease of man characterized by fever, aches and pains in various parts of the body which may range from mild to excruciatingly severe, generalized rash, lymphadenopathy and leukopenia. Its effects may be debilitating to the point of prostration, but uncomplicated classical (primary) dengue is rarely, if ever, fatal. It is caused by at least four antigenically distinct viruses constituting the dengue subgroup of group B togaviruses (see Section IV on Classification). By definition, they are transmitted to man by mosquitoes of the genus Aedes (Stegomyia). It follows that the occurrence of the disease (and the viruses) is restricted to those geographic areas in which suitable vector species are prevalent or in which, once imported, they can maintain themselves.

An entomological survey on the mosquitoes of Wuvulu Island, Papua New Guinea.

Abstract: An entomological survey in Wuvulu Island, Papua New Guinea, in August 1975 and 1976 shows the presence of six mosquito species: Aedes (S.) hebrideus, AE. (F.) notoscriptus, AE. (V.) lineatus, ? Ae. (L.) dasyorrhus, Culex pipiens fatigans and Armigeres breinli. The medical significance of these mosquitoes is discussed, with special reference to the problem of dengue virus transmission.

Surface Charge of Dengue Virus Hemagglutinins Prepared from Infected Mouse Brains

Abstract: Surface charge of dengue virus hemagglutinin (HA) prepared from infected suckling mouse brains was studied by sucrose gradient electrophoresis. The findings were as follows: (1) Both the slow- and rapid-sedimenting hemagglutinins (SHA and RHA, respectively) prepared after streptomycin treatment of the brain homogenate were distributed broadly within the gradient after electrophoresis, while echovirus type 7 HA which was used as a reference migrated narrowly, suggesting heterogeneity of the surface charge of both dengue HAs. (2) Neuraminidase treatment of dengue HA slightly retarded its migration toward the anode but did not alter the broad distribution. (3) Protamine treatment used for purification of HA from the brain homogenate changed the surface charge from negative to positive.

Immunological sensitization following inapparent infection with dengue virus type 3 in rhesus monkeys.

Abstract: Rhesus monkeys previously given dengue virus type 3, without apparent viremia or antibody response, exhibited a secondary-type response upon reinoculation. These data suggest that monkeys can be immunologically sensitized to dengue virus without detectable antibody production.