Showing papers on "Dengue virus published in 1988"

Pathogenesis of dengue: challenges to molecular biology

Abstract: Dengue viruses occur as four antigenically related but distinct serotypes transmitted to humans by Aedes aegypti mosquitoes. These viruses generally cause a benign syndrome, dengue fever, in the American and African tropics, and a severe syndrome, dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS), in Southeast Asian children. This severe syndrome, which recently has also been identified in children infected with the virus in Puerto Rico, is characterized by increased vascular permeability and abnormal hemostasis. It occurs in infants less than 1 year of age born to dengue-immune mothers and in children 1 year and older who are immune to one serotype of dengue virus and are experiencing infection with a second serotype. Dengue viruses replicate in cells of mononuclear phagocyte lineage, and subneutralizing concentrations of dengue antibody enhance dengue virus infection in these cells. This antibody-dependent enhancement of infection regulates dengue disease in human beings, although disease severity may also be controlled genetically, possibly by permitting and restricting the growth of virus in monocytes. Monoclonal antibodies show heterogeneous distribution of antigenic epitopes on dengue viruses. These epitopes serve to regulate disease: when antibodies to shared antigens partially neutralize heterotypic virus, infection and disease are dampened; enhancing antibodies alone result in heightened disease response. Further knowledge of the structure of dengue genomes should permit rapid advances in understanding the pathogenetic mechanisms of dengue.

A prospective study of dengue infections in Bangkok.

Abstract: Dengue infections were prospectively studied among 4- to 16-year-old students at a Bangkok school. Blood samples were obtained from 1,757 students in June 1980, before the dengue season, and in January 1981, after the season, and tested for dengue antibodies by the hemagglutination inhibition method. Classrooms were monitored daily for school absences. Fifty percent of the children had antibodies to, and were presumably immune to, at least 1 dengue serotype by the age of 7 years. Most (90/103, 87%) students who became infected by dengue viruses during the study period were either asymptomatic or minimally symptomatic (absent only 1 day). Most (7/13, 53%) of the symptomatic dengue infections (absent with fever for greater than or equal to 2 days) were clinically recognized as cases of dengue hemorrhagic fever which required hospitalization. None of 47 primary dengue infections required hospitalization, whereas 7 of 56 secondary infections did (P = 0.012). Preexistent dengue immunity, as detected by conventional serologic techniques, was a significant (odds ratio greater than or equal to 6.5) risk factor for development of dengue hemorrhagic fever.

Evidence that maternal dengue antibodies are important in the development of dengue hemorrhagic fever in infants.

Abstract: To establish the role of maternal dengue-specific antibodies in the development of dengue hemorrhagic fever and dengue shock syndrome caused by dengue 2 virus in infants, we examined sera from mothers of infants and toddlers with dengue hemorrhagic fever or dengue shock syndrome and mothers of infants with pyrexia of unknown origin. The mean titers of hemagglutination inhibition, neutralization, and infection-enhancing activities against dengue 2 virus were not statistically different among the three groups. However, among infants who developed dengue hemorrhagic fever/dengue shock syndrome there was a strong correlation between the mothers' dengue 2 neutralizing titers and infant age at the time of onset of severe illness, where no such correlation was found among the other two groups. Furthermore, the actual age at which dengue hemorrhagic fever/dengue shock syndrome occurred in each infant correlated with the age at which maximum enhancing activity for dengue 2 infection in mononuclear phagocytes was predicted. This critical time for the occurrence of dengue hemorrhagic fever/dengue shock syndrome was observed to be approximately 2 months after the time calculated for maternal dengue 2 neutralizing antibodies to degrade below a protective level. In addition, sera of mothers of infants with dengue hemorrhagic fever/dengue shock syndrome enhanced dengue 2 virus infection to a slightly greater degree than did sera from mothers of infants with pyrexia of unknown origin and toddlers with dengue hemorrhagic fever/dengue shock syndrome. These data are consistent with the hypothesis that maternal dengue antibodies play a dual role by first protecting and later increasing the risk of development of dengue hemorrhagic fever/dengue shock syndrome in infants who become infected by dengue 2 virus.

Gamma interferon augments Fc gamma receptor-mediated dengue virus infection of human monocytic cells.

Abstract: It has been reported that anti-dengue antibodies at subneutralizing concentrations augment dengue virus infection of monocytic cells. This is due to the increased uptake of dengue virus in the form of virus-antibody complexes by cells via Fc gamma receptors. We analyzed the effects of recombinant human gamma interferon (rIFN-gamma) on dengue virus infection of human monocytic cells. U937 cells, a human monocytic cell line, were infected with dengue virus in the form of virus-antibody complexes after rIFN-gamma treatment. Pretreatment of U937 cells with rIFN-gamma resulted in a significant increase in the number of dengue virus-infected cells and in the yield of infectious virus. rIFN-gamma did not augment dengue virus infection when cells were infected with virus in the absence of anti-dengue antibodies. Gamma interferon (IFN-gamma) produced by peripheral blood lymphocytes from dengue-immune donors after in vitro stimulation with dengue antigens also augmented dengue virus infection of U937 cells. IFN-gamma did not augment dengue virus infections when cells were infected with virus in the presence of F(ab')2 prepared from anti-dengue immunoglobulin G. Human immunoglobulin inhibited IFN-gamma-induced augmentation. IFN-gamma increased the number of Fc gamma receptors on U937 cells. The increase in the percentage of dengue antigen-positive cells correlated with the increase in the number of Fc gamma receptors after rIFN-gamma treatment. These results indicate that IFN-gamma-induced augmentation of dengue virus infection is Fc gamma receptor mediated. Based on these results we conclude that IFN-gamma increases the number of Fc gamma receptors and that this leads to an augmented uptake of dengue virus in the form of dengue virus-antibody complexes, which results in augmented dengue virus infection.

Immunization of mice with dengue structural proteins and nonstructural protein NS1 expressed by baculovirus recombinant induces resistance to dengue virus encephalitis.

Abstract: We have constructed a recombinant baculovirus containing a 4.0-kilobase dengue virus cDNA sequence that codes for the three virus structural proteins, capsid (C) protein, premembrane (PreM) protein, and envelope glycoprotein (E), and nonstructural proteins NS1 and NS2a. Infection of cultured Spodoptera frugiperda cells with this recombinant virus resulted in the production of E and NS1 proteins that were similar in size to the corresponding viral proteins expressed in dengue virus-infected simian cells. Other dengue virus-encoded proteins such as PreM and C were also synthesized. Rabbits immunized with the dengue virus protein products of the recombinant virus developed antibodies to PreM, E, and NS1, although the titers were low, especially to PreM and E. Nevertheless, the dengue virus antigens produced by the recombinant virus induced resistance in mice to fatal dengue encephalitis.

Partial Nucleotide Sequence and Deduced Amino Acid Sequence of the Structural Proteins of Dengue Virus Type 2, New Guinea C and PUO-218 Strains

Abstract: Summary The nucleotide sequence and the deduced amino acid sequence for the genes encoding the structural proteins of two strains of dengue virus type 2 (DEN-2) were determined from cDNA clones. The genes for C, prM(M) and E proteins were sequenced for the prototype DEN-2 virus, the New Guinea C strain. Also sequenced were the prM(M) and E genes of PUO-218. This strain of DEN-2 was isolated during 1980 in Bangkok and had received a limited number of laboratory passages. Comparisons of the newly determined sequences with those published for the Jamaica 1409 and Puerto Rico PR-159 (S1 vaccine candidate) strains revealed a close relationship between New Guinea C virus and both the Jamaica and PUO-218 viruses (greater than 96% similarity in nucleotides of the E gene), whereas S1 virus was the most divergent.

Unusual clinical manifestations of dengue virus infection.

Abstract: Four recent cases of dengue fever with severe, unusual clinical manifestations are described Two of these cases had features of fulminant hepatitis and encephalopathy; one of these cases was fatal The two remaining cases showed hepatitis with renal impairment The significance and importance of these unusual manifestations of dengue disease are discussed

Production of interferon alpha by dengue virus-infected human monocytes.

Abstract: Summary Human monocytes appear to be very important in the pathogenesis of dengue infection. They are thought to be the most active sites of virus replication during dengue infection. We have analysed interferon (IFN) production by dengue virus from peripheral blood mononuclear cells (PBMC). IFN activity was first detected at 12 h after infection of monocytes and reached a maximum level by 48 h. Non-adherent PBMC depleted of monocytes did not produce detectable levels of IFN, and did not contain dengue antigen-positive cells after exposure to dengue virus. The IFN produced was characterized as IFN-α by neutralization tests using specific antisera to HuIFN-α, HuIFN-β and HuIFN-γ, and by radioimmunoassay. The culture fluids of dengue virus-infected monocytes, which contained IFN-α, were able to inhibit infection of human monocytes by dengue virus. These results suggest that IFN-α produced by dengue virus-infected monocytes may play an important role in controlling primary dengue virus infection.

Nucleotide sequence of dengue type 3 virus genomic RNA encoding viral structural proteins.

Abstract: Complementary DNAs to the 5′ proximal region of the dengue virus type 3 RNA were cloned into bacterial plasmids and the nucleotide sequence of 3,000 bases from the 5′ terminus of the genome were determined by DNA and RNA sequencing methods using dideoxy chain-termination reactions. Comparison of the nucleotide sequence thus obtained with those of other flavivirus genomes revealed significant homology existing in nucleotide sequence of the flavivirus genomes. When we compared amino acid sequence deduced from the nucleotide sequence with those of other flaviviruses, this genome region was found to include sequences encoding three viral structural proteins C, M, and E and a part of the viral nonstructural protein NS1 in this order in addition to the 5′-noncoding sequence. The characteristics and functions of these proteins were discussed based on the deduced amino acid sequences and their hydrophobic profiles. The genetic relationship of flaviviruses was also discussed based on the genetic variation observed in their genomes.

Variation in dengue type 2 viruses isolated in Bangkok during 1980.

Abstract: Dengue type-2 viruses isolated in metropolitan Bangkok during 1980 (Bangkok/80) were characterized by oligonucleotide fingerprinting, restriction enzyme (RE) mapping and antigenic analysis using monoclonal antibody probes. Of 10 isolates analysed by oligonucleotide fingerprinting, nine were very closely related, showing 72.5% to 91.4% oligonucleotide homology. One isolate (D80-141) produced a distinctly different fingerprint (55.7% to 58.0% homology) and was less related to other Bangkok/80 dengue-2 virus isolates than to a 1964 Bangkok isolate (16681). RE mapping conducted on complementary dsDNA prepared from three Bangkok/80 isolates, strain 16681 and the prototype New Guinea C strain confirmed that D80-141 was genetically distinct. On antigenic analysis, only one of 22 monoclonal antibody probes produced against representative 1980 Bangkok dengue-2 isolates, D80-100 and D80-141, was able to distinguish between these virus strains. Monoclonal antibody 47-10/10, prepared using D80-100 virus and directed at the NS1 non-structural glycoprotein, had a significantly lower (100-fold) solid phase radioimmune assay endpoint titre for D80-141 antigen than for D80-100 antigen. By the indirect immunofluorescence assay, 47-10/10 had lower antibody endpoint titres against D80-141, the NGC strain and 13 (12%) of 110 Bangkok/80 isolates than to a control antibody preparation. These results suggest that strain D80-141 represents a second minor topotype of dengue-2 which was circulating concurrently with the major endemic topotype in Bangkok in early 1980.

Heterologous flavivirus infection-enhancing antibodies in sera of Nigerians.

Abstract: Human sera collected from Nigerians were examined for plaque reduction neutralizing and infection-enhancing antibodies against dengue 2, yellow fever, and West Nile viruses. Neutralization tests showed that 17 of 19 sera contained flavivirus neutralizing antibody; 11 were positive to all 3 viruses, 5 to dengue and yellow fever, and 1 to dengue virus only. Two sera had no detectable neutralizing antibody to any of the flaviviruses. Enhancement assays showed that 17 flavivirus neutralizing antibody-positive sera contained infection-enhancing antibodies to dengue 2, and 16 had antibody to yellow fever. Although 11 sera were positive for West Nile neutralizing antibody, 17 enhanced this virus. Heterologous infection-enhancing antibody titers were lower than the homologous ones. Broadly reacting sera and those with high neutralizing antibody titers produced the highest infection-enhancing antibody titers.

Detection of dengue virus type 2 in Aedes albopictus by nucleic acid hybridization with strand-specific RNA probes.

Abstract: A molecular hybridization technique with radiolabeled, strand-specific RNA probes was developed to detect dengue virus type 2 RNA in pools of infected Aedes albopictus mosquitoes. One infected mosquito in a pool of 25 could be detected, corresponding to a dengue virus type 2 titer of 2.75 log10 50% tissue culture infectious doses. Images

T Cell‐Mediated Cytotoxicity against Dengue‐Infected Target Cells

Abstract: A cytotoxic T lymphocyte (CTL) response to dengue virus-infected target cells is described. Effector cells were generated in an in vitro secondary culture and appeared to be T cells possessing both the Lyt 1.1 and Lyt 2.1 surface antigens. A stronger CTL response was noted with the H-2k haplotype compared to H-2d, and H-2 compatibility was required between CTL and target cells. CTL generated showed some cross-reactivity with target cells infected with Japanese encephalitis virus (JEV), another flavivirus, but not with target cells infected with an alphavirus, Sindbis. The significance and importance of these findings are discussed.

Failure of a dengue 1 sub-unit vaccine to protect mice against a lethal dengue virus infection.

Abstract: Mice immunized with DEN-1 pre-matrix protein produced antibody which reacted with dengue virus infected cells and intact virions but failed to neutralize virus in vitro or in vivo. Newborn mice passively immunized with anti-DEN-1 pre-matrix antibody also failed to survive intracerebral infection with 100 LD50 of any dengue virus serotype.

Isolation and characterization of dengue viruses serotype 1 from an epidemic in northern Queensland, Australia.

Abstract: Thirteen strains of dengue type 1 were isolated from the lymphocyte fractions of 69 acute phase blood samples collected at Thursday Island Hospital during 1981 and 1982. One further strain of type 1 was isolated from 7 blood samples despatched by air from Cairns Base Hospital during 1982. Four of these Australian isolates representing the beginning, middle, and end of the epidemic were examined by restriction enzyme mapping and were found to be identical for the nine restriction enzymes used. The maps differed from those derived from two Malaysian dengue type 1 strains isolated during the epidemic of 1981-82 in that country. This suggests reliance on serological typing to establish global circulation patterns of epidemic dengue is insufficient and that more specific methods such as genome mapping are useful.

A dot enzyme immunoassay for dengue 3 virus: comparison with the haemagglutination inhibition test.

Abstract: A dot enzyme immunoassay (DEIA) was used to determine the levels of antibody to dengue 3 virus in the acute and convalescent sera of febrile patients with a clinical diagnosis of dengue fever or dengue haemorrhagic fever. The antibody titres were compared with titres determined by the haemagglutination inhibition (HI) test. The results of the study showed that, besides being more simple to perform, the DEIA is in order of magnitude more sensitive than the HI test. Furthermore, the data suggest that it is possible to use a single dilution as a cutoff point to predict with reasonable accuracy, if a patient has had a recent dengue infection. The DEIA test for antibodies to dengue virus is an appropriate technology highly suitable for rapid diagnosis and surveillance in developing countries.

Immunogenic Characterization of the Dengue Virus Specified Nonstructural Glycoprotein GP48 (NV3, Soluble Complement Fixing Antigen)

Abstract: : Efforts have been concerned with mechanisms of the protective immune response to the flavivirus nonstructural protein NS1 and to identification of protective NS1 domains for incorporation into possible future subunit flavivirus vaccines. This report summarizes work performed during the funding period and includes data from experiments initiated in our laboratory as well as from these performed in collaboration with our colleagues in other institutions. Evidence of protective immunity to NS1. We had earlier reported that immunization with yellow fever (YS) NS1 protects mice and monkeys against lethal YF infection and that mice immunized with dengue are similarly protected against this flavivirus. (js)

Presence of receptors for antigen and antibody on dengue virus-induced suppressor T cells and their products

Abstract: Dengue type 2 virus (DV)-induced suppressor pathway consists of a cascade of Ts 1 cell and its product SF, Ts 2 cell and its product SF 2 and the Ts 3 cell which mediates antigen-specific suppression of humoral immune response. The present study was undertaken to investigate if the different constituents of this pathway have complementary receptors. It was observed that the suppressor activities of Ts 1 , SF and Ts 3 were abrogated by binding with anti-DV antibody while those of Ts 2 and SF 2 were abrogated by binding with DV antigen. Thus DV-induced suppressor pathway has a network of idiotype-anti-idiotype-like interactions which maintain the antigen specificity.

Modification and improvement of the haemadsorption immunosorbent technique (HIT) for the detection of dengue IgM antibodies.

Abstract: A modified and improved version of the haemadsorption immunosorbent test (HIT) to detect dengue-specific IgM antibodies is described. No significant differences in titres were noted compared to the original HIT and 62.5% of single sera tested were shown to possess IgM antibodies by the modified HIT, as well as most acute-phase sera from secondary dengue infections. Only one acute-phase serum from primary dengue infection showed the presence of IgM by the modified HIT. A monotypic IgM response to dengue3 virus was observed in one acutephase serum which was subsequently confirmed by virus isolation. Three acute-phase sera from suspected cases of viral encephalitis were shown to possess Japanese encephalitis virus (JEV)specific IgM by the modified HIT. The significance and importance of these findings are discussed.

Absence of cross-reactivity between dengue and human immunodeficiency virus type 1 (HIV-1).

Abstract: An association between malaria, schistosomia­ sis and tropical splenomegaly and human immunode­ ficiency virus type 1 (HIV-1) seropositivity has been observed in Africa1 2. Recently, the cross-reactivity between infection with Schistosoma mansoni and HIV-1 seropositivity was not confirmed in Brazil5. The potential cros-reactivity among other endemic of epidemic diseases in developing countries and HIV-1 has not been investigated as of yet. We studied the possible cross-reactivity between dengue (break bone fever) and HIV-1. In December, 1986 there were 3000 cases of dengue and 10 cases of Acquired Immunodeficiency Syndrome (AIDS) in Ceara State in Northeast of Brazil3 4. We analyzed sera of 89 individuals with dengue in this State (46 males and 43 females; mean age = 32 ± 16 years). All sera were tested by ELISA (Salk Dupont Laboratories) and all of them were negative for HIV-1 antibodies in at least two of three examinations. This result demonstrates that there was no cross-reactivity between dengue and HIV-1 in the investigated Brazilian patients.