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.

https://science.sciencemag.org/content/sci/239/4839/476.full.pdf

Pathogenesis of dengue: challenges to molecular biology

Dengue, a major public health problem throughout subtropical and tropical regions, is an acute infectious disease characterized by biphasic fever, headache, pain in various parts of the body, prostration, rash, lymphadenopathy, and leukopenia. In more severe or complicated dengue, patients present with a severe febrile illness characterized by abnormalities of hemostasis and increased vascular permeability, which in some instances results in a hypovolemic shock. Four distinct serotypes of the dengue virus (dengue-1, dengue-2, dengue-3, and dengue-4) exist, with numerous virus strains found worldwide. Molecular cloning methods have led to a greater understanding of the structure of the RNA genome and definition of virus-specific structural and nonstructural proteins. Progress towards producing safe, effective dengue virus vaccines, a goal for over 45 years, has been made. Images

The dengue viruses.

Molecular evolution and distribution of dengue viruses type 1 and 2 in nature.

The origin, emergence and evolutionary genetics of dengue virus

Gestational trophoblastic disease I: epidemiology, pathology, clinical presentation and diagnosis of gestational trophoblastic disease, and management of hydatidiform mole

Geographic classification of dengue-2 virus strains by antigen signature analysis.

Human chorionic gonadotropin and free subunits' serum levels in patients with partial and complete hydatidiform moles.

A monoclonal radioimmunoassay (RIA) was developed for detection of dengue virus in infected cell culture fluids and blood samples from dengue patients. Antibodies used to construct the RIA were selected on the basis of high binding avidity, the demonstration of synergism in competitive binding assays and empirical trials with different antibody combinations. Optimal binding of all four dengue virus serotypes was achieved by use of a flavivirus group-reactive and a dengue virus complex-reactive antibody as radiolabelled probe. A 'simultaneous sandwich' format and prolonged (18 h) incubation at 37 degrees C yielded optimal results. The limit of sensitivity of the RIA for detection of dengue type 2 virus was 2.7 log10 mosquito 50% infectious doses (MID50). The assay was tenfold more sensitive for dengue type 2 than for dengue types 1 and 3 viruses and 100-fold more sensitive than for dengue type 4 virus. Specificity, assessed using over 500 disease control human sera, was increased by addition of monoclonal anti-tetanus blocking antibodies, resulting in a false positive rate of only 0.2%. Heterologous dengue virus antibodies were shown to inhibit the RIA in assays performed with artificial immune complexes. Acute phase human sera containing 10(4.2) to 10(7.6) MID50 but no detectable antigen by RIA, were also shown to inhibit binding of the homologous dengue virus serotype; this effect was attributed to heterologous antibody from a prior infection. Among 116 viraemic sera from dengue patients, the RIA was positive in 43 to 47% of patients with dengue type 1, 2 or 3 infections but in only 10% of the dengue type 4 cases. Virus was more frequently detected in cases of primary infection (54%) than in cases of superinfection (16%). Despite the limitations imposed by immunological interference, the antigen capture RIA appears useful as a rapid diagnostic technique for dengue surveillance.

Multisite Monoclonal Immunoassay for Dengue Viruses: Detection of Viraemic Human Sera and Interference by Heterologous Antibody

A solid-phase radioimmunoassay (RIA) was developed for the detection of yellow fever (YF) virus in infected cell culture supernatant fluid and clinical samples. The test employed a flavivirus group-reactive monoclonal antibody attached to a polystyrene bead support and a radiolabeled type-specific antibody probe in a simultaneous sandwich RIA format. Optimal assay conditions specified a 16-h incubation at high temperature (45 degrees C). Monoclonal antibody to tetanus toxoid was added to the radiolabeled probe to inhibit nonspecific binding. The sensitivity of the assay for cell culture-propagated virus was 2.0 log10 50% mosquito infectious doses per 100 microliters or 100 pg of gradient-purified virion protein per 100 microliters. Specificity, assessed with human sera from 512 patients with liver diseases other than YF, including acute viral hepatitis, showed a false-positive rate of 0.0 to 0.6%. Sera from experimentally infected rhesus macaques containing greater than 3.0 log10 units/100 microliter of YF virus were positive by RIA. Sera and liver tissue from human patients were found to be positive.

https://jcm.asm.org/content/jcm/23/1/129.full.pdf

L. J. Hill

Papers

Geographic classification of dengue-2 virus strains by antigen signature analysis.

Human chorionic gonadotropin and free subunits' serum levels in patients with partial and complete hydatidiform moles.

Multisite Monoclonal Immunoassay for Dengue Viruses: Detection of Viraemic Human Sera and Interference by Heterologous Antibody

Sensitive and specific monoclonal immunoassay for detecting yellow fever virus in laboratory and clinical specimens.