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At least 19 recordsLinked to original sources
PubMed1977

Infections with two dengue viruses in Greece in the 20th century. Did dengue hemorrhagic fever occur in the 1928 epidemic?

From contemporary clinical accounts we hypothesized that the 1928 dengue epidemic in Greece may have been an earlier occurrence of dengue hemorrhagic fiver/dengue shock syndrome (DHF/DSS). To study the possibility that two different dengue viruses may have been involved, serums from 62 Athenians alive during the epidemic were examined for dengue antibodies; 73 per cent showed evidence of prior dengue infection. Monotypic neutralizing antibodies were found to two different dengue viruses, types 1 and 2. A large proportion of the sampled population had evidence of two or more past dengue infections. Since there is no evidence that dengue viruses have been transmitted in Greece since 1928, during the epidemic a very large number of persons immune to one dengue type must have acquired infections with a secon type. The virological criteria for secondary infection DHF/DSS are thus satisfied. Although DHF/DSS is currently restricted to Asia and the Pacific, the Greek oubreak suggests a biological potential for fatal consequences of dengue infections in Caucasians, particularly the elderly.

Adolescent↗
PubMed1976

Replication of dengue viruses in cultures of peripheral blood leukocytes from dengue-immune rhesus monkeys.

Dengue virus of types 1, 2, and 4 replicated reproducibly in cultures of peripheral blood leukocytes from 18 dengue-immune rhesus monkeys but failed to multiple in peripheral blood leukocytes from 25 nonimmune monkeys. Replication was observed at input multiplicity of infection of 0.1 and 0.01 but irregularly at less than or equal to 0.001. Dengue viruses in permissive leukocytes achieved maximal titers on days 2-4 of culture. Viral replication in peripheral blood leukocytes from animals immune to a different type of dengue virus and in animals immune to two or more types of dengue virus was quantitatively similar to that in peripheral blood leukocytes from homotypically immune donors. Dengue virus permissiveness developed between two and three weeks after primary dengue infections. Leukocytes of animals that developed immunity to dengue virus remained permissive to in vitro infection by dengue virus of types 1 and 2 for prolonged periods, but within six months permissiveness to type 4 decreased. Thus an immunological dependence of in vitro dengue virus replication in simian peripheral blood leukocytes was demonstrated.

Animals↗
PubMed1978

The defined antigen substrate sphere system with direct immunohistoperoxidase for detection of soluble dengue antigen in sera of patients with dengue hemorrhagic fever.

The defined antigen substrate sphere system is a simple method for detecting antigen or antibody in the circulation. The technic is based on the coupling of antigen or antibody with Sepharose 4B beads that have been activated by cyanogen bromide. In this study the activated beads were exposed to dengue antigen in the serum from a patient with dengue hemorrhagic fever and then stained with antidengue antibody conjugated with horseradish peroxidase. The positive reaction showed brown beads by light microscopy, whereas the negative reaction gave colorless beads. The authors examined 134 specimens from 91 cases. The results were positive in 53.85%. The dengue antigen appeared in the sera on the day before shock or subsidence of fever. The percentages of sera containing soluble dengue antigen were greatest on the day of shock or subsidence of fever (33.33%) and on the fifth day of fever (28.07%). The highest titers of soluble dengue antigen (1:40 to 1:80) appeared in the sera of patients who had Grade III disease on the day of shock. The dengue antigen appeared most often in sera that had high titers of dengue antibody. It is postulated that this detected dengue antigen may be a part of soluble immune complexes formed during the hyperimmune stage of the immune response, and plays a significant role in the pathogenesis of dengue hemorrhagic fever and shock syndrome.

Antibodies, Viral↗
PubMed1979

Absence of leukocytes permissive to dengue 2 virus in the acute phase of dengue hemorrhagic fever.

Patients with primary dengue infection developed dengue 2 virus (D2V) permissive peripheral blood leukocytes (PBL) 2--3 weeks after infection. PBL from healthy individuals with dengue antibody were permissive to D2V in vitro, suggesting that immunologically mediated in vitro D2V permissiveness persists for a relatively long time after recovery from dengue infection. However, PBL obtained from second infection dengue hemorrhagic fever patients did not support D2V growth during the acute phase of illness but did so during convalescence. Leukocytes from dengue-immune patients with typhoid fever or non-dengue viral illness were permissive throughout both acute and convalescent phases of illness although there was tendency for increased permissiveness during convalescence. Acute phase PBL from DHF patients synthesized and secreted dengue neutralizing antibody in culture. Absence of D2V replication in these cultures was strongly, but not completely, correlated with antibody production. Other immunological mechanisms, in addition to antibody, may be operating in vitro or in vivo during acute phase dengue hemorrhagic fever to alter the permissiveness of PBL to D2V infection.

Adolescent↗
PubMed1992

Envelope protein sequences of dengue virus isolates TH-36 and TH-Sman, and identification of a type-specific genetic marker for dengue and tick-borne flaviviruses.

Complementary DNAs were synthesized from the envelope protein genes of two isolates of dengue virus (TH-36 and TH-Sman, previously suggested as possible dengue virus type 5 and dengue virus type 6 respectively) and amplified by the polymerase chain reaction using sense and antisense primers designed from conserved dengue virus gene sequences. The amplified cDNA clones were sequenced in both directions by double-stranded dideoxynucleotide sequencing. Alignment with published dengue virus sequences enabled us to assign these viruses accurately to classified serotypes, confirming that TH-36 and TH-Sman are strains of dengue virus type 2 and dengue virus type 1 respectively. Amino acid changes between the proteins encoded by these two isolates and strains of their respective serotypes may account for the significant antigenic differences observed during previous serological typing of these viruses. Moreover, sequence alignment of flavivirus envelope proteins revealed a hypervariable region, within which members of the dengue and tick-borne virus antigenic complexes show unique peptide sequences. This type-specific hypervariable domain may be useful as a genetic marker for typing dengue and tick-borne flaviviruses.

Amino Acid Sequence↗
PubMed1992

An enzyme-linked immunosorbent assay using a chaotropic agent (sodium thiocyanate) for serotype specific reaction between crude dengue viral antigen and anti-dengue mouse antibody.

An enzyme-linked immunosorbent assay (ELISA) has been developed to detect serotype specific reaction between crude dengue viral antigen and anti-dengue mouse hyperimmunized antibody under the stringent condition in the presence of a Chaotropic agent, sodium thiocyanate (NaSCN), in the reaction mixture of antigen and antibody. Rapidly sedimenting hemagglutinin (RHA) derived from type 2 dengue virus-infected mosquito cell culture fluid reacted to the antibody for both type 2 and type 3 dengue viruses in the ELISA. In contrast, its reactivity was reduced after the addition of NaSCN in the ELISA. Soluble complement-fixing antigen (SCF) derived from type 2 dengue virus-infected mosquito cell culture fluid reacted serotype specifically to anti-dengue type 2 antibody, and was relatively stable for the NaSCN treatment in the ELISA. Anti-type 2 RHA mouse antibody reacted to both type 1 and type 2 dengue viral antigens and its reactivity was reduced after the addition of NaSCN in the ELISA. Anti-type 2 SCF antibody reacted serotype specifically to type 2 dengue viral antigen with and without NaSCN in the ELISA.

Animals↗
PubMed1992

Use of dengue blot in dengue diagnosis: the Malaysian experience.

Dengue fever/Dengue haemorrhagic fever (DF/DHF) has been a public health problem in Malaysia with an endemic level of about 7 per 100,000 population per year. In 1990, Malaysia experienced its most severe outbreak of DF/DHF with a record total of 5,590 cases referred to the Division of Virology, Institute for Medical Research (IMR). Of these, 1,880 were confirmed serologically to be DF/DHF. The conventional serological procedure, the Haemagglutination Inhibition (HI) test, for the diagnosis of DF/DHF is cumbersome and causes delay in diagnosis. Another problem associated with the HI test has been that it has often been difficult to obtain a second convalescent serum sample for an accurate diagnosis. This has raised an urgent need to establish a "rapid" test for diagnosis of DF/DHF. As such the authors recently carried out an evaluation of a newly available commercial rapid test, namely, the Dengue Blot Assay (Diagnostic Biotechnology Singapore Pte Ltd). The test is intended for use in laboratory confirmation of dengue virus infection. The evaluation was to determine if the test could be utilised as a routine laboratory test and to establish its sensitivity and specificity. Over 400 samples were tested against the Dengue Blot Assay. Results were checked against an in-house Dengue IgM ELISA and HI assay. Preliminary results indicate that the sensitivity and specificity of the Dengue Blot is satisfactory. Our results also indicate that the Dengue Blot has a useful role to play in a routine laboratory especially since it provides rapid results on single serum samples thereby reducing the workload in a busy diagnostic laboratory.

Dengue↗
PubMed1975

Placental passage of antibodies to Dengue virus in persons living in a region of hyperendemic Dengue virus infection.

Maternal and umbilical cord levels of antibodies to dengue 2 and 3 viruses were compared in 54 matched pairs of specimens from subjects in the Dominican Republic. Dengue infection appeared to be hyperendemic; pregnant women experienced a 6% weekly infection rate. Titers of antibody to dengue 2 and 3 viruses were considerably higher in cord sera than in maternal sera (P smaller than 0.001 and P smaller 0.01, respectively), especially when maternal levels were low. When maternal and cord sera were compared at equal titers of dengue 2 virus, heterotypic antibodies to dengue 1 and St. Louis encephalitis viruses were higher in the cord. These findings could not be directly related to the higher levels of IgG found in cord sera or to the presence of elevated concentrations of IgM. It is concluded that antibody with increased cross-reactivity preferentially crosses the placenta. The presence of such cross-reactive antibody does not appear to sensitize infants to dengue hemorrhagic fever/shock syndrome.

Adolescent↗
PubMed1992

Dengue and dengue hemorrhagic fever.

Hundreds of thousands of dengue cases are reported worldwide each year. Given the difficulty in obtaining full reporting, the actual number of human infections is probably much higher than the number reported. Dengue is usually a nonspecific febrile illness that resolves with supportive therapy but the clinical spectrum ranges from asymptomatic infection through severe hemorrhage and sudden fatal shock. The pathophysiology of the severe forms of dengue may be related to sequential infection with different serotypes, variations in virus virulence, interaction of the virus with environmental and host factors or a combination of these factors. Control of dengue at the present time is dependent on control of the principal vector mosquito, A. aegypti. Efforts to achieve such control are now focusing on community education and action towards eliminating this mosquito's breeding sites near human dwellings. Vaccine development continues, but at present the only way to avoid dengue in an area where it is endemic or epidemic is to use repellents and mosquito barriers. The movement of people to and from tropical areas makes dengue an important differential diagnosis in any patient with an acute illness and history of recent travel to tropical areas. Because of continued infestation of the southeastern United States with A. aegypti, indigenous transmission in the continental United States remains a public health concern.

Dengue↗
PubMed1975

A lipid inhibitor of dengue virus in human colostrum and milk; with a note on the absence of anti-dengue secretory antibody.

Neutralizing activity against dengue virus types 1--4 was observed in milk samples from 5 non-immune and 29 dengue immune women. Anti-dengue activity in milk and colostrum was found only in the lipid component. The inhibitory activity is directed against the virus and not cell surfaces. When immunoglobulin types IgM,IgA, IgG were isolated from colostrum from dengue immune women, no antibody activity was found. Anti-dengue activity in human milk did not decrease over a period of ten months after delivery.

Animals↗
PubMed1975

Dengue virus replication in cultures of peripheral blood leukocytes during the course of dengue haemorrhagic fever.

A preliminary study was made of the ability of cultured human peripheral blood leukocytes (PBL) to support dengue 2 infection. Leukocyte donors, children hospitalized with primary (one case) or secondary dengue infections (12 cases), were studied during the acute and convalescent stages of illness. D2 virus replication occurred infrequently in PBL cultures obtained from children before the 10th day after onset of symptoms (2/23 samples), but frequently thereafter (8/13 samples). The absence of virus permissive cells during the acute stage of illness might be explained by several different mechanisms, including the possibility that permissive PBL are exhausted as the result of a severe dengue infection. An unexpected finding was the appearance of dengue hemagglutination-inhibition antibodies in cultures of PBL obtained from children during the acute stage of secondary dengue infections.

Acute Disease↗
PubMed1992

Epidemiology of dengue and dengue haemorrhagic fever in Malaysia. III. A comparative study of clinical features seen in virologically confirmed cases for periods between 1963-1987--a review.

Dengue fever, Dengue hemorrhagic fever and Dengue shock syndrome within the dengue complex is a sinister disease of great public health importance and continues to ravage children, young adults and the aged in Malaysia. The history of the disease is traced for over the years and the changing pattern of clinical presentation are noted. Various hospital based studies have been compared and the pathognomonic features of the disease in Malaysia are highlighted.

Adult↗
PubMed1978

A rapid fluorescent focus-inhibition test for determining dengue neutralizing antibody and for identifying prototype dengue viruses.

Neutralizing antibody to dengue virus in human and animal sera was assayed by the rapid fluorescent focus-inhibition test (RFFIT). Neutralizing-antibody titers could be detected after only 24 h compared to 5--6 days required by the plaque-reduction test. The RFFIT is more definitive than the conventional complement fixation (CF) or hemagglutination-inhibition (HI) test in identifying prototype dengue viruses, is reproducible, and is applicable to the routine detection of neutralizing antibodies to dengue viruses.

Antibodies, Viral↗
PubMed1979

Demonstration of dengue antibody complexes on the surface of platelets from patients with dengue hemorrhagic fever.

By the direct immunofluorescent technic, dengue antigen, human immunoglobulins, and beta 1C globulin were detectable on the surfaces of platelet suspensions from 48% of patients with dengue hemorrhagic fever. The percentages of positive-staining platelets were not related to the severity of thrombocytopenia, which was marked on the day after the patient developed shock or subsidence of fever. It is suggested that an immunologic mechanism is one of the factors associated with the thrombocytopenia caused by increased platelet destruction.

Adolescent↗
PubMed1992

A model of the transmission of dengue fever with an evaluation of the impact of ultra-low volume (ULV) insecticide applications on dengue epidemics.

We have developed a deterministic susceptible, exposed, infectious, resistant or removed (SEIR) model of dengue fever transmission that enables us to explore the behavior of an epidemic, and to experiment with vector control practices. Populations of both host and vector are divided into compartments representing disease status (susceptible, exposed, infectious, and, for humans, resistant), and the flow between compartments is described by differential equations. Examination of the equilibrium points leads to a formulation of the basic reproduction rate (Z0) of the disease. With a base set of parameters, Z0 = 1.9 and the model realistically reproduces epidemic transmission in an immunologically naive population. Control of adult mosquitoes by ultra-low volume (ULV) aerosols is simulated by an abrupt decrease in vector densities, followed by gradual recovery of the vector population. The model indicates that ULV has little impact on disease incidence, even when multiple applications are made, although the peak of the epidemic may be delayed. Decreasing the carrying capacity of the environment for mosquitoes, and thus the basic reproduction rate of the disease, by source reduction or other means, is more effective in reducing transmission.

Animals↗